Bocjl Corp. v. United States, (1951)

Full title: BOCJL CORP. et al. v. UNITED STATES

Court: United States Court of Federal Claims

Date published: Oct 2, 1951

100 F. Supp. 600 (Fed. Cl. 1951)

Opinion

No. 48816.

October 2, 1951.

William H. Parmelee, Pittsburgh, Pa., for plaintiffs. Almon S. Nelson, Washington, D.C., and William G. Young, Pittsburgh, Pa., were on the brief.

Arthur Raisch, Detroit, Mich., with whom was Asst. Atty. Gen. Holmes Baldridge, for defendant. T. Hayward Brown and E.R. Weisbender, Washington, D.C., were on the brief.

Before JONES, Chief Judge, and LITTLETON, WHITAKER, MADDEN and HOWELL, Judges.

The Court, having considered the evidence, the report of Commissioner Hayner H. Gordon, and the briefs and argument of counsel, makes the following

Special Findings of Fact

1. This is a patent suit for infringement of United States letters patent No. 2,257,126, entitled "Propeller", issued September 30, 1941, to Arthur G. Rindfleisch, assignor, and Bocjl Corporation, trustee, both plaintiffs herein, on an application filed in the Patent Office on January 27, 1936.

A copy of the patent in suit and a copy of the Patent Office file wrapper and contents thereof which materialized into the patent in suit are a part of the record in this case, having been received in evidence as plaintiffs' exhibit 1 and defendant's exhibit 1.

Title

2. Bocjl Corporation, one of the plaintiffs herein, is a corporation duly organized and existing under and by virtue of the laws of the State of Delaware, having its principal place of business at Pittsburgh, Pennsylvania; plaintiff Brooke L. Jarrett is a citizen of the United States, residing at Sewickley, Pennsylvania, and plaintiff Arthur G. Rindfleisch is a citizen of the United States, residing at Chicago, Illinois.

3. Prior to the issuance of letters patent No. 2,257,126, Arthur G. Rindfleisch, by an assignment in writing and recorded in the United States Patent Office, sold, assigned, and transferred the entire right, title, and interest, in and to the invention to the Bocjl Corporation to hold as trustee in accordance with the terms of an agreement in writing between plaintiffs Rindfleisch and Jarrett, this agreement being incorporated in the assignment by reference. This agreement is in evidence as plaintiffs' exhibit 2-A.

The plaintiffs are the sole owners of the entire right, title, and interest in the patent in suit.

Propulsion of Airplanes

4. An ariplane is propelled through the air by the rotation of one or more propellers which are driven by internal-combustion engines. In general, a propeller consists of a hub mounted on an engine shaft and having two or more blades extending radially from the hub. These blades are set at an angle (called the pitch angle) with reference to the axis of the engine shaft upon which they are mounted, so that, as the propeller rotates, it bites into and screws itself through the air, advancing as it turns and pulling the airplane with it. The higher the pitch angle the farther the propeller will advance through the air for each revolution. Also the higher the pitch angle, the greater the forward thrust of the propeller and the greater will be the power demanded from the engine to maintain the propeller at a given speed.

The returning effort required to operate the propeller at any given speed can be altered by changing the pitch of the propeller blades.

5. In the operation of an airplane more power is required during take-off and climb than under normal flight conditions. In this respect the airplane is rather similar to the automobile. As internal-combustion engines employed in automobiles are more efficient and produce more power at a relatively high speed range, it has become common usage to provide the automobile with different gear ratios for starting, climbing, and traveling on the level. These same conditions apply to the internal-combustion engines in airplanes, and this has led to the development and use of what is known as the variable pitch propeller. In take-off or climb the propeller blades are set at a low pitch angle so that the engine is not unduly overloaded. When, however, the airplane has completed its climb and assumes level or cruising flight, the pitch angle is then increased so that the airplane travels a greater distance through the air for each revolution of its propellers. This is analogous to an automobile starting and climbing a hill with the gears in first or second, and then after the top of the hill is reached and the road becomes level, shifting into high.

In the earlier phases of development of the variable pitch propeller, propellers were devised in which the blades had two positions, i.e., low pitch and high pitch. These were manually controlled by the pilot, and permitted selection of a low pitch angle for take-off and climb and a high pitch angle for cruising.

A subsequent stage in propeller development resulted in the adoption of power mechanism for altering the pitch angle of the propeller blades, the power mechanism shifting the blades automatically in accordance with the power demanded by the propeller. Such a structure finds a rough analogy in the automatic transmission systems now in use on automobiles. It is to such an automatic variable pitch propeller that the patent in suit is directed in part.

6. The automatic pitch control mechanism referred to in the previous finding is in general controlled by a speed-responsive device known as a governor. In mechanisms in which the pitch angles are automatically changed by hydraulic mechanism and to which type the patent in suit is particularly directed, the operation is as follows:

Assuming that the pilot sets his throttle and propeller controls for 2,300 R.P.M., and then changes the attitude of the aircraft from level flight to a dive, the engine would tend to pick up speed as a result of the decreased load on the engine brought about by the dive. The governor responds to the resulting change in engine speed and actuates the hydraulic pitch-regulating mechanism that moves the blades to a higher angle. An increase in blade angle requires an increase in engine power output, and consequently the engine and propeller return to the on-speed or constant speed condition. If the pilot should now change the attitude of the aircraft from a dive into a climb, the engine would tend to lose speed as a result of the increased load on the engine brought about by the climb. The governor responds to the resulting change in engine speed and actuates the pitch-regulating mechanism to move the propeller blades to a lower angle or pitch. A decrease in the blade angle or pitch requires less engine torque and consequently the engine and propeller would again return to the on-speed position.

7. When an airplane is in flight and engine failure occurs, the propeller of the dead engine usually continues to rotate. This rotation, which is caused by the flow of air over the propeller blades, is called windmilling, and will cause rotation of the dead engine. If the engine failure is due to the breakage of any internal members of the engine, the engine might not only be severely damaged but might grind itself to pieces. Even if the engine failure is caused by ignition breakdown, breakage of gasoline or oil lines, and the engine rotates without damage, the windmilling propeller consumes power that is being produced by the other engines in driving the plane through the air.

If the engine failure is of such a nature that the engine jams and the propeller ceases to rotate or windmill, the propeller, with its blades set at an angle with respect to the air stream, will still consume power.

In order to overcome these difficulties, various methods have been devised for "feathering" the propeller. Feathering consists of changing the pitch angle of the blades until the blades are substantially parallel with the hub axles and with the air stream through which the propeller is moving. By feathering a propeller in case of engine failure of any kind it will both stop rotation of the dead engine and impose a minimum power demand upon the remaining engines.

The Patent in Suit

8. The Rindfleisch patent in suit, after discussing the desirability and the superior performance of the automatic variable pitch propeller and the desirability of full feathering the propeller in an emergency, states as the objects of his invention:

"The primary object of my invention is to provide a propeller construction which is variable and automatically controllable by a governing mechanism which is regulated by the rotative speed of the propeller during the various maneuvers of the aircraft, or by an increase or decrease in the engine power, or both.

"A further object is to provide an isolated independent fluid pressure and control system for operating automatically the pitch changes of the propeller.

"A further object is to provide automatic means for full feathering the propeller.

"A further object is to provide emergency means controlled by the pilot for full feathering the propeller.

"A further object is to provide manual control means for changing the pitch of the propeller.

"A further object is to provide novel means for attaching and supporting the propeller blades on the hub."

In order to simplify the explanation of the embodiment selected by Rindfleisch as illustrative of his invention, Figs. 2, 3, 5, and 6 of the patent, with the reference numerals removed and explanatory legends added, are hereinafter referred to.

Fig. 3 is a view looking down upon the propeller blade and its associated structure. This blade, as is the corresponding blade underneath, is so mounted in the propeller hub as to be capable of rotation about its own axis. Such rotation is obtained by means of a link that connects the movable nosepiece of the mechanism to a crank arm at the hub of the propeller. As shown in this figure, when the nosepiece moves axially to the left with respect to the engine casing, the link will rotate the propeller blade toward an increased pitch position.

Fig. 2 is substantially the same as Fig. 3 but with the various parts shown in cross-section. A plate is fixed to the forward end of the crankshaft and this plate carries extending outwardly a fixed cylindrical member which, together with the plate, forms a concentric reservoir for the hydraulic fluid which is utilized to change the pitch of the propeller blades. This fluid is normally placed under pressure during the rotation of the propeller by means of two oppositely disposed gear pumps, one of these pumps being shown in Fig. 2 and both being shown in the cross-section view (Fig. 5). These pumps are driven by shafts extending rearwardly to a point adjacent the front of the engine crankcase. The rear ends of these shafts are provided with gears which mesh with a fixed gear mounted at the front end of the engine crankcase, so that, as the propeller rotates, the pumps will be driven and will build up pressure in the hydraulic fluid. This pressure is kept at a constant value by means of the spring-controlled relief valve which discharges back into the reservoir.

Still referring to Fig. 2, the central concentric cylinder is fixed and has operating within it a piston which, when hydraulic fluid is admitted behind it, pushes the nosepiece forwardly. An annular pitch control piston is mounted to slide upon the fixed cylinder containing the feathering piston. When hydraulic fluid is admitted behind the pitch control piston this causes the pitch angle of the propeller blades to increase. If pressure upon hydraulic fluid behind this piston is released so that the fluid can flow back to the reservoir the inherent centrifugal force acting upon the propeller blades will act to decrease the pitch of the blades. The small central cylinder and its co-acting piston function only to full feather the propeller, i.e., to place the propeller blades edge on with respect to the air stream.

9. Control of the hydraulic fluid is next referred to. This is best shown in Figs. 5 and 6, reproduced herewith, and which are cross sections, respectively, as indicated by 5. . . .5 and 6. . . .6 of Fig. 2 of the patent in suit. Referring to Fig. 5, the pitch-control governor is shown at the upper right of this figure and comprises a weight carried on the upper end of a pivoted arm. When the propeller is rotating, centrifugal force tends to urge this weight outwardly against the tension of a restraining spring, the outer end of which is fixed to the governor arm, the inner end being fixed to a pin in a right-angled arm which is also mounted on the same pivot as the governor arm. An eccentric cam is adjustable with reference to the right-angled arm carrying the inner end of the spring, and by rotation of this cam the tension on the governor spring can be altered. The position of the cam and the tension of the governor spring are under control of the pilot by a mechanism which will be subsequently described.

Referring next to the right-hand portion of Fig. 6, a rocker arm is pivoted coaxially with the governor arm and is fixed thereto. This rocker arm operates upper and lower poppet valves. When the propeller and its associated centrifugal governor are "on-speed", that is, when the tension on the governor spring is equal and opposite in amount to the centrifugal force, this rocker arm is in a neutral position as shown in Fig. 6, and both of the poppet valves are closed.

10. If it is now assumed that the attitude of the airplane changes from level flight to climb, and assuming a fixed throttle position with the engine, the torque on the propeller would increase, thus tending to slow it down. When this occurs, the pitch control governor weight will move inwardly and the rocker arm will open, the upper poppet valve thus venting the pitch control cylinder to the reservoir and permitting the blades to assume a flatter pitch position due to the effect of centrifugal force on the blades. The pitch of the blades being thus reduced, the torque or load on the propeller will be reduced and cause the propeller to increase speed. As soon as the propeller arrives "on-speed", again equilibrium will be established between the governor weight and its controlling spring and both poppet valves will again be closed.

If it is next assumed that the plane assumes a descending attitude instead of climb or level flight, and the throttle position still remains fixed, the propeller will tend to overspeed. This in turn will cause the governor weight to move outwardly and will open the lower right-hand poppet valve, which in turn will admit hydraulic fluid under pressure to the pitch-control cylinder. This will cause the nosepiece of the propeller mechanism to move outwardly and thus increase the pitch of the propeller blades to a point where the torque demanded by the propeller from the engine is such as to bring the governor weight and its opposing spring once more into equilibrium. When this happens, the rocker arm will again assume a neutral position, and the propeller will again be "on-speed."

By means of this mechanism the servomotor, consisting of the annular movable cylinder and its fixed piston, automatically controls the pitch of the propeller under various flight conditions. The Rindfleisch patent indicates a speed in horizontal flight of about 2,000 R.P.M.

The patent does not state any range within which the R.P.M. of the engine can be varied by the eccentric cam that controls the tension of the governor spring. The weight of the centrifugal governor ball, the tension and length of the adjustable governor spring, and the eccentricity or shape of the cam are factors that are capable of being varied by those skilled in the art to meet any given situation.

11. The eccentric cam that controls the tension of the governor spring is mounted on a shaft driven by a gear train mounted within the mechanism. The driving end of this gear train consists of a star wheel, carried upon the propeller structure and shown at the upper right-hand portion of Fig. 3. When the pilot desires to change the setting of the cam and the resultant tension of the governor spring, he operates a control within the cockpit, which pushes upwardly a lever marked "governor adjustment" in the lower right-hand portion of Fig. 3. This lifts a detent into a position where the star wheel is rotated one tooth per revolution of the propeller shaft as long as the detent is held in by the pilot. This type of control, while inconvenient in that it rotates the cam only in one direction, is operable to obtain any desired cam setting.

12. Reference is next made to the automatic and full-feathering features of the Rindfleisch disclosure. Both of these are independent and separate from the automatic pitch control described in the previous findings.

Both automatic and manual feathering are obtained by the centrally located feathering piston shown in Fig. 2. Hydraulic pressure in this separate servomotor will cause the nosepiece of the propeller mechanism to move farther to the left than the pitch-control servomotor, a lost motion arrangement being provided for this purpose.

Automatic feathering is provided by means of a feathering control governor which for symmetry and balance is mounted diametrically opposite the pitch-control governor, as shown in Fig. 5. This governor acts against a spring which the patent specification states is set to maintain a neutral governor position at 500 R.P.M. The feathering control governor operates a rocker arm which, in turn, engages two poppet valves similar in construction to and also symmetrically arranged directly opposite the two poppet valves previously described in connection with the automatic pitch control operation. The feathering poppet valves are shown in the left-hand portion of Fig. 6.

13. During normal flight and when the propeller is turning over at a rate above the setting of the feathering control governor, this governor arm is maintained in an outward position due to centrifugal force, and the top poppet valve is held open. As this is of importance in connection with manual full feathering, the following is quoted from the specification with reference to this valve: "* * * the valve 72 is open, thus forming an unobstructed passage between the full feathering cylinder and the reservoir. The full feathering piston moves with the controllable pitch cylinder in its cycle of operation, and this vent to the reservoir permits free movement of the full feathering piston." [Italicization supplied.]

If an engine fails and the failure is of such a nature that the pistons tend to seize and slow down the propeller below 500 R.P.M., the feathering governor moves inwardly, opening the lower poppet valve (Fig. 6) and closing the top one, thereby admitting hydraulic fluid to the feathering cylinder. Because of its extra length, the piston therein will then move the nose of the mechanism sufficiently far to the left, as shown in Fig. 2, to completely feather the propeller blades.

14. If an engine equipped with an automatic pitch control such as disclosed by the patent in suit cuts out, and its failure is due to such conditions as interruption of the ignition system or lack of gasoline, etc., instead of a type of failure such as would tend to slow down the propeller materially, the propeller will begin to windmill, tending to slow down somewhat due to the frictional resistance of the dead engine which it now drives. Such tendency of the propeller, however, will cause its governor to readjust the blades to a decreased pitch position which, in turn, will tend to make the propeller windmill at a faster R.P.M. Windmilling speeds of an automatic pitch control propeller operating with a dead engine under these conditions will not depart materially from the normal operative speed of the propeller, and automatic full feathering cannot take place.

15. Manual full feathering, as taught by the patent in suit, is based upon the use of a reservoir or accumulator, located upon the airplane, in which hydraulic fluid is stored under pressure. The patentee describes the use of a hand pump for obtaining this pressure but says any equivalent means, such as a pump driven by an electric motor, could be used for this same purpose.

In order to full feather the propeller in an emergency, the pilot opens a valve located in the cockpit of the airplane, thereby supplying fluid under pressure to the pipe shown in the lower right-hand portion of Fig. 2. This hydraulic fluid is fed into a hollow central opening in the crankshaft of the engine by means of an annular groove and passes through the center of the crankshaft through a hall check-valve and into the feathering cylinder where under a specific set of conditions it acts to full feather the propeller.

16. If the emergency is of the nature described in finding 14, with the propeller windmilling at approximately its normal operative speed, admission by the pilot of the hydraulic fluid, stored under pressure in the airplane, to the full-feathering cylinder will not cause the propeller blades to assume the full-feathered position. At this time the R.P.M. of the propeller is well above the 500 R.P.M. taught by the patent for the operation of the feathering governor, and the upper left-hand poppet valve is open, giving an unobstructed or free vent from the full-feathering cylinder to the reservoir, which is, in turn, open to the atmosphere and thus at atmospheric pressure. With such unobstructed passageway it would not be feasible to build up sufficient pressure in the full-feathering cylinder to feather the propeller. In this situation the full-feathering servomotor would not only have to exert sufficient power to full feather the blades but, in addition, would have to overcome the inherent tendency of the blades to flatten their pitch in this particular kind of emergency.

17. If, however, the emergency is of the character referred to in finding 13, in which the propeller slows down below 500 R.P.M., the automatic full-feathering control takes over. Manual full feathering may then be used to assist the automatic full feathering.

The only other type of emergency in which manual full feathering could be utilized is one in which either some portion of the engine breaks or the pistons seize to such a degree that the engine and propeller actually stall. In such case the automatic full-feathering governor would act to close the passageway between the full-feathering cylinder and the reservoir but no pressure would be obtained from the gear pumps located in the propeller hub which, under these conditions, would be stationary.

Under this particular set of conditions the pilot could then admit hydraulic fluid under pressure to the full-feathering cylinder and manually full feather the propeller.

18. Manual full feathering under all emergency conditions might be provided by partially obstructing the passage through the upper left-hand poppet valve (Fig. 6) back to the reservoir, and by providing large pipes and openings from the tank on the airplane to the full-feathering cylinder, but such change would be contrary to the teachings of the patent, which indicate an unobstructed passage to the reservoir to permit free movement of the full-feathering piston during the normal pitch-control operations of the Rindfleisch mechanism.

It might also be possible to change the weight of the automatic full-feathering governor or its spring so that, instead of operating at 500 R.P.M. it would operate at some higher speed. This, however, would also be contrary to the teachings of the patent, in that if the governor is set to operate at a higher speed, the propeller might become automatically full-feathered whenever the pilot "idles" his engine.

The manual full-feathering structure of the Rindfleisch patent is operable, but only during a particular kind of emergency such as has been referred to above.

19. In the Rindfleisch structure of the patent in suit the propeller, if full-feathered, either automatically or manually, cannot be returned to operative position while in the air but must be reset while on the ground by applying a sufficient turning effort to the blades to restore them to their original position. Such turning effort would have to be sufficient to discharge the hydraulic fluid from the full-feathering cylinder against the spring tension of the relief valve and back into the reservoir.

The automatic full-feathering and the manual full-feathering mechanisms are separate and distinct from the automatic pitch control of the patent in suit. The automatic full-feathering system could be rendered inoperative or have its function entirely removed by fastening the full-feathering governor weight in its outermost position, and the manual full feathering would be rendered inoperative by the expedient of either not filling the pressure reservoir located on the airplane or blocking off the pipe leading from this reservoir to the propeller mechanism. The removal of these accessories from the Rindfleisch construction would in no way interfere with the operation of the automatic pitch-control mechanism.

In the Rindfleisch mechanism the reservoir and the servo cylinders for pitch control and full feathering are all mounted concentrically in the mechanism forward or in advance of the hub of the propeller. By such concentric mounting and by the fact that two diametrically mounted pumps are utilized to place the hydraulic fluid under pressure, and that the two governor elements of the mechanism are also diametrically mounted with respect to each other, the patent teaches a construction in which all of the various elements are so located as to be in balance during the normal rotation of the propeller.

20. The charge of infringement in this suit is based upon the use of the invention of the patent in suit as defined in claims 8, 25, 26, 27, and 31. These claims are paraphrased in subsequent findings 53-58, in connection with their application to the alleged infringing structures and their validity in connection with the prior art. Certain of these claims refer to the Rindfleisch structure as "a propeller unit" and others refer to a portion of the Rindfleisch mechanism as "a blade-actuating unit." These phrases, when interpreted in the light of the complete disclosure of the patent in suit, are definitive of a unitary mechanism which carries in it its own supply of hydraulic fluid to operate the pitch changes so that the fluid system is completely isolated from the remainder of the airplane. This is of importance due to the fact that various antifreeze solutions could be used in such a structure.

These terms do not mean necessarily that the propeller unit or the blade-actuating unit can be entirely preassembled and then subsequently mounted upon the propeller shaft.

21. Rindfleisch conceived his invention in September 1935 and constructively reduced the same to practice by filing in January 1936 the patent application that matured into the patent in suit. There is no record that the plaintiffs in this case ever issued any licenses under the patent in suit or that they have manufactured, sold, or used any propellers of the type embodied in the patent in suit.

The Alleged Infringing Structure

22. Within a period of six years preceding the filing of the petition in this case the United States, without the license or consent of plaintiffs, had manufactured or used an automatic pitch-control propeller known as the aeroprop. A description of the construction of this propeller and five sheets of drawings accompanying the same are in evidence as plaintiffs' exhibits 5 and 4-a to 4-e, inclusive, respectively, and form a part hereof by reference.

Two forms of the aeroprop have been manufactured or used, the form shown in plaintiffs' exhibit 4-a being of the nonfeathering type, and the form shown in plaintiffs' exhibits 4-b, 4-c, and 4-d is of the full-feathering type.

The nonfeathering and feathering types of the aeroprop are similar with the exception of certain additional parts included in the full-feathering construction.

23. The aeroprop consists of two essentially separate assemblies which are —

1. A hub, with attached blades and pitch change units mounted in driving relation on a conventional propeller shaft, and

2. A regulator unit, mounted on a rearward extension of the hub and behind the blade sockets.

Each pitch change unit comprises a piston and cylinder located in the root of the blade. These pistons are pushed inwardly or outwardly in the hub through controlled hydraulic pressure supplied by the regulator. The movement of the pistons is converted into turning action on the blades by means of helical or twisted splines.

One spline member is mounted solidly onto the hub; the piston has a skirt with internal and external splines, the internal splines mating with the hub splines and the external splines of the piston in turn meshing with internal splines of a cylinder that is connected directly to the blade.

Outward movement of the pistons increases the pitch setting of the blades while inward movement decreases the pitch setting.

As shown in the accompanying drawing entitled "non-feathering aeroprop," an equalizing bevel gear that meshes with segmental gears attached at the inner end of each propeller blade, coordinates the movement of the blades so that all of them will change pitch to exactly the same degree.

Hydraulic fluid under pressure is simultaneously supplied either to the inner ends

or outer ends of the pistons by means of passageways which are under the control of a centrifugal governor located in the regulator unit.

24. The regulator devices are contained in a circular housing which is mounted on the propeller hub and directly to the rear of the same, i.e., between the propeller hub and the engine crankcase. This housing as shown in the accompanying drawing rotates as a unit with the propeller hub, and its hollow interior forms a reservoir for the hydraulic fluid. A gear pump shown at the lower right-hand portion of the drawing is fixed within the circular housing. This gear pump as it rotates with the housing is driven by means of a stationary gear located adjacent to and fixed to the front end of the engine crankcase. This pump provides pressure for the hydraulic fluid, the pressure being kept at a predetermined value by means of a pressure control valve located adjacent the pump.

The hydraulic fluid under pressure is fed to a combined centrifugal governor and valve mechanism which is indicated on the drawing by the legend "governor."

25. The basic element of the governor mechanism consists of what is known as a spool valve. It is thus named because it resembles a spool in that it is cylindrical in shape and its outer ends are of larger diameter than the central portion. This spool valve, which is located radially with respect to the axis of rotation of the propeller shaft, is capable of movement along its axis. The hydraulic fluid under pressure is fed to its reduced central portion, each of its enlarged ends normally covering the passageways leading respectively to the inner and outer ends of the pitch-changing pistons.

The spool valve being mounted off center, with respect to the axis of rotation of the propeller, is subjected to centrifugal force against a spring. When the governor is "on-speed" the passageways leading to the pitch control pistons are both closed by the inner and outer ends of the spool valve. If, however, the propeller tends to speed up because of a reduced load, centrifugal force will move the spool valve outwardly, uncovering the passageway leading from the outer ends of the pitch control pistons, thus venting them to reservoir pressure and at the same time placing the passageways that lead to the inner ends of the pitch control pistons in connection with the hydraulic fluid under pressure. This will cause the pistons to move outwardly, thereby increasing the pitch of the propeller sufficient in amount to restore the propeller to normal speed, at which time the spool valve will again assume the "on-speed" position.

26. The "on-speed" position of the governor spool valve occurs when the centrifugal force tending to move the spool valve outwardly is balanced by the spring's resisting such movement. The "on-speed" setting of the governor unit is under control of the pilot within a certain speed range.

As shown in the drawing, the spool valve and the governor spring are adjacent to each other and have their lower ends connected with a flat bar. The end of this bar nearest the engine rests upon a fulcrum, this being in such a position that when centrifugal force acts to throw the spool valve outwardly, the spring is also compressed. This fulcrum point may be adjusted toward or from the spring, thereby altering the effect of the spring tension in the governor unit. This is accomplished from the pilot's compartment by the pilot's governor control.

This is in the form of a lever connected by linkages and gear mechanism to a recessed ring located in the regulator compartment. The fulcrum for the governor rides in this recess as the governor mechanism rotates with respect to the ring. Movement of the pilot's governor control lever acts to shift this ring fore and aft along the axis of the propeller shaft, thereby changing the fulcrum point of the bar connecting the lower end of the spool valve and the spring.

27. In the feathering type of aeroprop the same elements that have just been described in connection with the nonfeathering type of propeller are all present. In addition, and as shown in the accompanying drawing, entitled "feathering aeroprop," there is mounted on the front end or forward end of the propeller hub a reservoir or accumulator in which during normal operation hydraulic fluid is stored under pressure. Such fluid is maintained under pressure even though the propeller is not revolving and the plane is standing on the ground.

An assemblage of parts consisting of springs, valves, etc., best known as a feathering unit, is mounted, as shown in the drawing, in the lower portion of the regulator unit. When the pilot desires to full feather the propeller he moves the combined governor and feathering control fully to the end of its quadrant, advancing the axial ring which controls the governor fulcrum to the left in such a position that the governor spring assists centrifugal force in opening the spool valve and permitting the pump pressure to increase the pitch of the blades. As this occurs, the propeller tends to slow down, thereby decreasing the pump pressure. In the meantime, however, a trip on the feathering unit is also actuated by the movement of the control ring to the left.

Without going into the details of this feathering unit, which is quite complicated, it is sufficient for the purposes of this case to state that when the pump pressure decreases due to the slowing down of the rotation of the propeller, the feathering unit will then permit hydraulic fluid under pressure from the accumulator to act

against the lower faces of the pitch-changing pistons and full feather the propeller. When this occurs, the remaining fluid in the reservoir is sealed off by the feathering unit and remains under pressure for unfeathering the propeller, which is accomplished by the pilot moving his control in the opposite direction.

Prior Art and Knowledge

28. The following prior art was available to the public prior to the Rindfleisch date of conception (September 1935) of the subject-matter which materialized into the patent in suit:

Patents ------------------------------------------------------------------------- Country | Patentee | Number | Defendant's exhibit --------------------|--------------|-------------|----------------------- United States ..... | Walker ..... | 1,374,787 | 15 Do ............. | .... do .... | 1,374,786 | 2 Do ............. | McCauley ... | 1,550,550 | 18 Do ............. | Hele-Shaw .. | 1,723,617 | 19 Great Britain ..... | .... do .... | 250,292 | 38 United States ..... | Squires .... | 1,878,011 | 3 France ............ | Ballu ...... | 775,507 | 8, 8-A, 8-B, 8-C United States ..... | Lilley ..... | 1,894,047 | 4 Do ............. | Caldwell ... | 1,893,612 | 24 Great Britain ..... | Salmon ..... | 134,258 | 37 -------------------------------------------------------------------------

Publication

Hele-Shaw article entitled "The Variable Pitch Air Screw" published July 1928, in the Royal Aeronautical Society Journal (defendant's exhibit 43).

The following United States patents were issued on application filed in the Patent Office prior to the Rindfleisch date of conception:

-------------------------------------------------------------------------- Patentee | Number | Issued | Filed | Defendant's | | | | exhibit -------------|-------------|----------------|---------------|------------- Havill ..... | 2,019,966 | Nov. 5, 1935 | June 25, 1934 | 31 Waseige .... | 2,181,985 | Dec. 5, 1939 | Apr. 25, 1939 | 5 Bace ....... | 2,013,647 | Sept. 10, 1935 | Oct. 24, 1933 | 29 Mader ...... | 2,205,625 | June 25, 1940 | Aug. 12, 1935 | 7 --------------------------------------------------------------------------

Of the patents listed above, the following represent prior art considered by the Patent Office during the prosecution of the Rindfleisch application which materialized into the patent in suit: United States patent to Walker (1,374,787); United States patent to Havill; United States patent to Bace; and British patent to Salmon.

The patents and printed publication herein set forth by exhibit numbers are made a part of this finding by reference.

29. United States patent to Caldwell et al., No. 2,174,717, was issued October 3, 1939, on an application filed August 4, 1936.

The parties have stipulated that the multiposition controllable pitch propeller shown and described in the F.W. Caldwell et al. United States patent No. 2,174,717 was conceived by the patentees on May 16, 1935, reduced to practice and flight-tested on June 30, 1936; that the patentees were diligent throughout the entire period between the date of conception and the date of reduction to practice and flight-test in reducing the propeller to practice, and that the propeller was full-feathered and unfeathered in flight on a single engine plane; that only one such propeller was made, and subsequent to June 30, 1936, the structure of the propeller was modified.

It was not stipulated, however, that the original conception or reduction to practice described or used fluid other than engine lubricating oil derived from the engine which drives the propeller. The present construction used by United Aircraft Corporation, assignees of patent 2,174,717, is shown in a stipulated exhibit, a book entitled "Hydromatic Quick-Feathering Propellers, Service Manual No. 140C," published by the Hamilton Standard Propellers Division of United Aircraft Corporation, East Hartford, Connecticut, February 1, 1946, 2d Edition, August, 1947, which is in evidence as defendant's exhibit 46.

It was further agreed that the pump shown in the patent and referenced 157, was, in the aforesaid propeller, an electric motor-driven pump controlled by a manually operated electric switch in the cockpit of the plane; that British patent cited in the second column, line 15 of page 3 of the Caldwell patent should be British patent 470,284 (U.S. patent 2,204,640), and that the blueprint in evidence as defendant's exhibit 47 is a clearer showing of the automatic valve 152, Fig. 9 of the Caldwell patent (2,174,717) drawings.

The parties still further agreed that although the Caldwell application which matured into patent 2,174,717, filed August 4, 1936, was copending with the Rindfleisch application filed January 27, 1936, which matured into the Rindfleisch patent in suit, no interference was declared between the Rindfleisch and Caldwell applications.

The Caldwell patent 2,174,717; a book entitled "Hydromatic Quick-Feathering Propellers"; the blueprint, and copy of United States patent 2,204,640 (defendant's exhibits 45, 46, 47, and 48) are in evidence and form a part of this finding by reference.

30. The two United States Walker patents (defendant's exhibits 15 and 2) are related since they both issued as a result of one original application and are therefore considered together.

These patents disclose a variable pitch propeller in which the pitch of the blades is adjusted or changed by means of an electric motor incorporated in the hub mechanism of the propeller. This electric motor is capable of either increasing or decreasing the pitch of the blades, and its operation is controlled by means of a centrifugal governor fixed on some portion of the aircraft. This governor operates to alternately close an electrical circuit through two contacts, one to increase pitch and the second to decrease pitch. Current is fed from these contacts to the rotatable portion of the propeller and the motor therein by means of two slip rings.

These patents also disclose an independent switch mechanism for manually controlling the pitch of the propeller, and the structure is of such a nature that the propeller may be full-feathered with this manual control.

These patents do not disclose any hydraulic or fluid pressure system operating through servomotors to control propeller pitch, and the automatic mechanism such as the centrifugal governor is not incorporated as a unit and does not rotate with the propeller structure.

31. United States patent to McCauley (defendant's exhibit 18) discloses a hydraulically operated system in which fluid pressure is used to operate a pair of fixed servomotors. Piston rods extend forwardly from the servomotors and engage a slidable member on the rotating axis of the propeller shaft, which is in turn connected by linkage to the propeller blades to alter their pitch when the pistons in the servomotors operate. The patent suggests the use of the oil pump of the engine as the source of hydraulic pressure, thereby indicating the use of engine oil as the hydraulic fluid, although the patent also states that the pressure fluid may be supplied from a source independent of the engine. The operation of the servomotors is controlled by manually operated valves. This disclosure does not teach the use of a hydraulic system in which the servomotors are incorporated in the propeller structure and rotate therewith, and no mechanism is disclosed which will function to automatically adjust the pitch of the propeller in accordance with the power demands of the propeller.

32. The Hele-Shaw references, United States patent No. 1,723,617 (defendant's exhibit 19); the related British patent of Hele-Shaw No. 250,292 (defendant's exhibit 38), and the article on the Hele-Shaw propeller from the publication "The Royal Aeronautical Society Journal" for July 1928, Vol. 32 (defendant's exhibit 43), all disclose propeller pitch-adjusting mechanism which is hydraulically operated.

As disclosed in the accompanying drawing of Fig. 1 of the United States patent to Hele-Shaw, the hydraulically operated mechanism for effecting pitch change adjustments is located in the rotating hub of the propeller, but the fluid is supplied from a special variable output pump mounted with and operated by the aircraft engine, the output of which is controlled by a speed-responsive device on a stationary part of the airplane. Connections between the pump and the hydraulic mechanism on the propeller are made through three separate lines. This propeller does not have a self-contained operating unit or a unit having an isolated and independent fluid system in the hub. Manual means comprising a lever is provided by which a manual adjustment of the pitch position of the propeller blades may be effected. This manual operation is accomplished by a direct manual application of force which is not at all dependent upon operation of the fluid pressure system. The disclosure of the manual means is such that it is questionable whether an operator could exert sufficient force to move the propeller blades to a feathered position. The British patent, however, suggests that instead of the manual connection of levers directly controlled by the pilot, the pilot could actuate a hand pump which, in turn, through another cylinder would actuate this mechanism to move the propeller blades into a feathered position. Another Hele-Shaw patent, No. 1,829,930, was a file reference.

33. United States patent to Squires (defendant's exhibit 3) shows a propeller for aircraft having a plurality of blades, the angle of which can be changed. This is done by providing the blades at their roots with worm gearing, and this, in turn, is actuated by a sliding collar on the shaft of the hub which is connected by linkage to a control wheel in the pilot's cockpit. There is nothing in this patent which discloses either hydraulic operation or automatic operation, the propeller being adjusted manually by the pilot in the cockpit.

34. The French patent to Ballu (defendant's exhibit 8; translation, 8-A, and enlarged drawings 8-B and 8-C) relates to a propeller structure involving adjustable pitch blades operated by a hydraulic system including a servomotor for moving the blades, a pump for creating pressure, and a centrifugal governor for controlling the operation of the servomotor in accordance with the speed of the propeller. The drawings of the patent relating to the present issue are too intricate and involved to reproduce in this finding and, for clarity, have been photostatically enlarged and are defendant's exhibits 8-B and 8-C.

The servomotor consists of a series of rotary vanes associated with fixed vanes and constructed as a unit. As shown in Fig. 16 (defendant's exhibit 8-B) rotation of the movable vanes is obtained by feeding hydraulic fluid under pressure into spaces on either side of the movable vanes. These spaces, together with the movable vanes, are the mechanical equivalent of a cylinder with a piston operating in it. Thus, as oil is fed on one side or the other of the movable vanes and withdrawn from the opposite side, the vanes will rotate. These vanes carry a beveled gear which meshes with gears at the roots of the propeller blades, thus altering their pitch. Fig. 16 of the drawings is defective, in that it does not correctly show the location of the passageways through the center of this device for operation of the servomotor, and defendant's exhibit 8-C shows in red a modification of these passageways suggested by defendant's expert witness as necessary in order to make this device properly operate.

35. The flow of oil from the pump to and from the servomotor is controlled by means of a slide valve extending through the center of the hub and concentrically with the pump located therein. This slide valve, depending upon its position, either permits fluid to be fed in or exhausted from either side of the servomotor, and when in neutral position closes off the inlet and outlet ports of the servomotor. The position of this slide valve is regulated by a centrifugal governor which acts against a spring. A manual control is provided for the pilot by means of which he can adjust the tension of this spring and thereby control governor operation. When the governor is "on-speed" as selected by the pilot, the passageways to the servomotor are blocked and the pitch of the propeller blades is held in a fixed position. If the propeller speed decreases, the governor will function to admit hydraulic fluid to the servomotor in such manner as to decrease the pitch of the blades until the governor is again "on-speed." The reverse operation takes place should the propeller speed increase.

36. The pump which is supposed to produce the pressure for the operation of the servomotor is located in the center of the axis of rotation of the propeller hub and just to the rear of the propeller blades. The pump piston consists of a cylindrical member which operates within a concentric cylinder. The piston reciprocates along the

axis of the propeller and is resiliently connected through springs to a cam device which causes the pump piston to move to the right as shown in the drawing, defendant's exhibit 8-B, creating space within the cylinder and then moving to the left under the urge of the springs. The inlet of this plunger pump has a cut-away opening in the side of its cylinder and its piston. The inlet valve to the pump is carried in the head of the piston or plunger, and the outlet valve is a ball check-valve at the end of the pump cylinder. As disclosed, the entire system is full of fluid and no reservoir is present.

Inasmuch as the operation of the pump plunger changes the volumetric capacity of the system each time it performs a stroke, and the system is completely full of fluid, such a system is inoperative unless either the fluid passageways cut through the various metal portions of the mechanism yield or bulge or the hydraulic fluid is capable of being compressed.

Liquids in general are substantially incompressible unless they contain occluded air or gas, and in the present instance a compressible liquid would tend to defeat control of the propeller pitch by the hydraulic servomotor.

37. The defendant's skilled expert Lane suggested a form of pump to overcome the volumetric changes of capacity in the system which in the present disclosure make the pump ineffective. This pump structure is shown in a sketch made by the witness (defendant's exhibit 51). This sketch shows a piston arrangement in which a so-called "dummy rod" is used so that no volumetric change will take place in the system. It also shows a rearrangement of the pump valves to permit use of the dummy rod.

There is no satisfactory evidence as to how the ordinary person skilled in the art could reconstruct the mechanism of Ballu in order to make the same operative or as to how such person could incorporate the "Lane" pump and valves into the Ballu structure.

The French patent to Ballu has no fluid reservoir, no reservoir located within the hub, and does not teach manual full feathering. Even though the pilot's control of governor spring tension were made of sufficient scope to entirely remove tension upon the governor spring, as the pitch of the propeller increases, it would at the same time slow down, with a consequent reduction in the hydraulic fluid utilized to increase the pitch. (In this connection, it is noted that both the patent in suit and the full-feathering propeller of the Government have an independent supply of hydraulic fluid under pressure to accomplish full feathering.)

38. United States patent to Lilley (defendant's exhibit 4) discloses a variable pitch propeller having an independent hydraulic fluid system carried entirely by the propeller structure. This structure consists of a pair of propeller blades mounted in a hub and adjustable as to pitch by means of a linkage which, in turn, is actuated by a pair of servomotors. These are supplied with hydraulic fluid from a pair of pumps. When the pumps operate in one direction the pitch is increased, and when they are operated in the opposite direction the pitch is decreased.

These pumps, which rotate with the propeller, are located in a casing fixed to the forward end of the crankcase just behind the hub of the propeller and are driven by a pair of beveled gears, either of which may be held stationary by means of a brake. The direction of rotation of the pumps, and hence the increase or decrease in pitch of the propeller, is controlled by a rod leading to some place on the plane. When this rod is operated in one direction, one of the beveled gears is locked against rotation, and when the rod is moved in the other direction the other beveled gear is similarly locked. The only suggestion of the method of control for operation of this device is operation of the brakes by the pilot.

39. United States patent to Caldwell No. 1,893,612 (defendant's exhibit 24) discloses a variable pitch propeller in which fluid pressure against a piston of the servomotor located concentrically within the shaft of the propeller, acts to increase the pitch of the propeller blades, and the rotation of the blades in their sockets in the hub caused by centrifugal force is relied upon to decrease the pitch. The fluid pressure for operating the pitch-increasing servomotor is supplied by a pump mounted on the engine which obtains oil from the engine sump. Thus, the faster the engine tends to run and the more pressure it supplies through the pump, the greater will be the increase of pitch of blades. A pressure regulator introduced between the pump and the servomotor consists of a spring-actuated tapered valve which allows a bleed-off of oil back to the engine sump. The tension of the spring controlling this valve may either be adjusted by the pilot or controlled by a centrifugal governor. This patent does not disclose an independent fluid system in which all of the parts are mounted within the hub of the propeller nor does it disclose a reservoir within the hub or governor control system mounted within the hub, a pump driven by the propeller, or controlling means located within the rotatable propeller unit.

40. The British patent to Salmon (defendant's exhibit 37) discloses a mechanism for varying the pitch of a propeller which is mounted on the forward end of the propeller shaft in advance of the propeller. This mechanism consists of a concentric or coaxial piston, the piston rod at its forward end carrying a side-projecting rod which is connected by a mechanism, not disclosed, to rotatable blades for altering their pitch as the piston moves. The piston is urged to the rear of its cylinder by means of a spring in which position it holds the blades in decreased pitch position.

At the front end of this device is an independent propeller that drives an oil pump for the purpose of supplying hydraulic pressure to the rear of the piston to increase the pitch of the main propeller. The auxiliary propeller and its associated pump are operated by the movement of the airplane through the air, and the oil pressure thus produced is therefore dependent upon the speed of the plane. A bypass valve controls leakage or bypassing of the fluid pressure from the rear of the piston to the front end thereof, which acts as a reservoir. The position of this bypass valve is controlled by means of a centrifugal governor acting against a spring, the tension of which is under control by the pilot. The functioning of this structure is well defined by claim 1 of the British patent reading as follows: "1. Automatically controlling variable pitch propellers used on aircraft, by means of an oil or other fluid pump, the speed of which is caused automatically to change with the speed of the aircraft, under the action of the air, substantially as described."

This patent is directed to a device in which the speed of the airplane functions in controlling the propeller pitch, and it does not disclose a propeller for an airplane having a predetermined rotative speed or any pump means operated directly and entirely through rotation of the main propeller or any means for driving the fluid pressure pump by rotation of the main propeller.

41. United States patent to Havill (defendant's exhibit 31) was a file wrapper reference. Because of the importance of this patent, Fig. 1 is reproduced herewith. This patent discloses a variable pitch propeller, the pitch of the blades being under the control of several interacting forces. As shown in the accompanying drawing, the structure consists of a propeller hub fixed on an elongation of the engine shaft so as to rotate with the same but having a limited axial movement. As the propeller hub moves to the rear or toward the engine (to the left in the accompanying figure) the blades are caused to assume a maximum pitch position. The propeller hub is normally urged to this rearward position by means of a series of springs 13 concentrically located with respect to the engine shaft and forward of the propeller hub. As the propeller rotates, thrust of the blades and centrifugal force acting upon them tend to move the hub forward and to decrease or flatten the pitch. There are therefore existent in this structure two opposing forces, i.e., the springs which tend to increase the pitch and the effect of thrust and centrifugal force which tend to oppose the springs and decrease the pitch.

42. A third controlling force is superimposed upon the two opposing forces just mentioned. This consists of a servomotor operated by hydraulic fluid and under control of a centrifugal governor. The fluid pump for obtaining pressure to operate the hydraulic control system is shown at 17 in Fig. 1, this being driven by a planetary gear 20. The gear 20 meshes with a stationary internal ring gear 19 fixed to the front of the engine, and as the propeller rotates the pump delivers oil to an annular concentric cylinder 15 fixed to the forward end of the slidable propeller hub. An annular piston is fixed to the forward end of the structure so that when the propeller hub moves forwardly the volume of the annular cylinder is reduced.

The oil fed to this cylinder from the pump is bled out of the cylinder and returns to the reservoir 27 through a passageway 29. This passageway is provided with a spool-type centrifugal valve 31 having a reduced portion 41. This spool-type valve is located off center of rotation of the propeller so that it is subjected to centrifugal force which tends to push it radially outward (downwardly as shown in the annexed figure). Outward movement of this valve is opposed by a governor spring 39 which is capable of adjustment when the propeller is not operating. A pipe line from the cylinder back to the reservoir is provided with a relief valve which can be set to adjust the maximum fluid pressure in the system.

43. The operation of the Havill fluid system is as follows: When the speed of rotation of the propeller is such that the spool valve has its reduced portion in line with the return passageway 30 back to the reservoir, the system is open and little, if any, pressure will exist in the annular cylinder or servomotor, the oil flowing therethrough and returning to the reservoir. If, however, the speed of the propeller tends to increase, centrifugal force will cause the spool valve to move radially outward and to gradually close off the outlet port 30, thereby causing pressure in the cylinder to build up. The piston being fixed and the cylinder being relatively moveable thereto, will move rearwardly (to the left, as shown in Fig. 1), thereby rotating the propeller blades in a pitch-increasing direction. As the pitch angle of the blades is increased, the R.P.M. of the engine will decrease and the governor valve 31 will then move radially inward and seek an equilibrium position. The centrifugal valve

in Havill is the watchdog of the propeller and engine R.P.M.

44. Havill discloses an automatic constant speed propeller which embodies an independent or self-contained fluid system in which the fluid motor and the reservoir are concentric and are located in a member secured to the forward end of a propeller shaft in advance of the hub of the propeller. The pump of Havill which supplies the fluid is located within the hub of the propeller, and Havill has speed-responsive means within his structure for operating a valve for controlling the flow of fluid from the pump through the motor.

45. United States patent to Waseige (defendant's exhibit 5) discloses a mechanical system for adjusting the propeller blade pitch. The basic elements consist of four epicyclic gear trains spaced along the propeller shaft between the propeller hub and the crankcase housing of the engine. Each of these gear trains is provided with an outer cylindrical surface, the rotation of which may be stopped or locked by means of a surrounding brake band. (This system of control resembles closely the old Ford planetary gear-shift mechanism.)

The braking elements may be operated manually to effect a pitch adjustment of the propeller blades. In addition, there is provided an automatic speed-responsive system for controlling the operation of the brake elements. The speed-responsive system may be adjusted manually and thereby set for different speeds of operation. The direct manual control for the brake elements and automatic speed-responsive control are separate from and do not form a part of the propeller unit. These control elements are mounted on the aircraft and do not rotate with the propeller unit or form a part of the propeller unit.

46. United States patent to Bace (defendant's exhibit 29), a file history reference, discloses a variable pitch propeller, the pitch of which is controlled by a centrifugal governor mounted in the nose of the propeller at the front of the hub. This governor, the speed of which may be adjusted by the pilot, controls a slide valve within the hub of the propeller which, in turn, controls distribution of fluid pressure to movable vanes or servomotors located at the root of each blade. There are two channels running through the engine shaft, one an inlet and the other an outlet passageway for the hydraulic fluid. The hydraulic fluid is applied to either one side or the other of the movable vanes forming the servomotor.

The specification makes no reference as to the source of the hydraulic fluid or its source of pressure. It is evident, however, from the disclosure of the drawings that it comes from some pressure device located on or adjacent the engine. The source of fluid pressure is not contained in the propeller construction nor is any reservoir for hydraulic fluid present in the propeller construction.

47. United States patent to Mader (defendant's exhibit 7) is primarily concerned with a control system for variable pitch propellers in which the speed-responsive means of a pitch-changing mechanism is interconnected with the throttle control of the engine. The Mader disclosure relative to the constructional details of a variable pitch propeller mechanism is merely diagrammatic in character.

Fig. 1 of the patent is reproduced herewith. This figure diagrammatically illustrates a pressure pump and a governor-controlled spool valve for feeding pressure fluid to either end of a servomotor, which in turn is connected through a rod to vary the pitch of propeller blades.

This patent, while disclosing the interconnection of a throttle valve with a pitch-changing mechanism, does not teach those skilled in the art how to incorporate into a rotating propeller hub the various elements diagrammatically shown or how the parts should be arranged to obtain balance in the propeller hub as the device rotates.

48. United States patent to Caldwell et al., No. 2,174,717 (defendant's exhibit 45) was issued October 3, 1939, on an application filed August 4, 1936. The Rindfleisch application which materialized into the patent in suit was filed on January 27, 1936, and issued September 30, 1941. These two applications were thus copending in the Patent Office from August 4, 1936, until October 3, 1939, the Rindfleisch patent application having been filed some five months prior to the Caldwell et al. application.

The Patent Office declared no interference between these copending applications.

49. In accordance with the stipulation of the parties set forth in finding 29, the propeller structure shown and described in the Caldwell et al. patent, now under consideration, was conceived on May 16, 1935, reduced to practice by actual construction and flight-testing on June 30, 1936, and the patentees were diligent throughout the entire period between the date of conception and the date of reduction to practice. The Rindfleisch date of conception was September 1935, with a constructive reduction to practice by filing his application January 27, 1936.

The structure disclosed in the Caldwell et al. patent, together with certain slight modifications referred to in the next finding, represents knowledge and invention by the Caldwell et al. patentees prior to Rindfleisch.

50. The structure of the Caldwell et al. patent (defendant's exhibit 45) cannot be reproduced in connection with this finding because of its complexity. This patent discloses a variable pitch propeller for aircraft in which fluid under pressure is admitted to the rear side of a double-walled hollow piston for increasing pitch during constant-speed operation. For decreasing pitch during constant-speed operation the structure depends upon the centrifugal twisting effect upon the blades.

Fig. 9 of the Caldwell patent shows the use of engine oil taken from the sump and supplied under pressure by a pump which the patent states "may be the pump which supplies lubricating oil to the engine." The oil under pressure passes through a distributor valve that is controlled by a governor which is driven by the engine. The oil passes from this distributor valve into the center of the propeller shaft, and from there to the cylinder in the propeller hub. If the engine tends to over-speed, the governor will feed fluid under pressure into the cylinder, push the piston forward, and increase the pitch angle of the blades through the operation of suitable cams and gears. If the engine is under speed, the governor will act to release pressure fluid from the piston, and the centrifugal force acting upon the blades will rotate them on their axes so as to reduce their pitch angle. The pump, the engine sump, and the governor were all mounted on the engine, as shown in the Caldwell patent and in the actual construction which formed the reduction to practice.

51. In feathering the propeller, fluid under high pressure was used. This was obtained by means of a pump shown at 156 in Fig. 9 of the Caldwell et al. patent. While there shown as a hand-operated pump, in the actual construction an electric motor-driven pump was used, controlled by a manual electric switch in the cockpit. This pump drew oil from the sump, raised the same to a high pressure sufficient to operate a spring-controlled valve which would cut off the fluid line from the governor. This high pressure oil then flowed forward through the propeller shaft into the cylinder with its operating piston, which then increased the pitch angle of the blades to the feathered position.

For unfeathering, a still higher pressure was utilized which raised a spring-controlled valve located in the propeller hub from its seat and permitted the high pressure oil to flow forward into the front end of the nose of the propeller hub. Because the area on the back or inner side of the piston which was exposed to this high pressure was less than the area on the front or outer side of the piston, the piston moved the blades to a decreased pitch position. Drain passageways were provided for draining the pressure fluid back to the stationary sump.

The structure of the Caldwell et al. patent is similar to that of the Hele-Shaw patent, in that the servomotor for adjusting the pitch of the blades is located in the rotating parts of the propeller but the pump and speed-responsive device for controlling the flow of hydraulic fluid therefrom to the servomotor are mounted on a stationary part of the airplane. The governor of Caldwell et al. is capable of being adjusted by the pilot.

The Caldwell et al. construction does not disclose a self-contained operating unit having an isolated and independent fluid system in the hub or having a speed-responsive control device or reservoir located within such unit.

Validity and Infringement

52. The patent in suit is directed to a constant-speed propeller mechanism assembled into a unitary structure for mounting upon the engine shaft. Such unitary assembly includes the pitch-changing linkage mechanism, a servomotor for actuating the same, a reservoir for the hydraulic fluid, a pump for placing the same under pressure, a speed-responsive means, together with suitable valve mechanism, for controlling the circulation and pressure of the hydraulic fluid. In such self-contained isolated construction the use of engine oil for pressure is avoided, nor is it necessary to arrange for mounting upon the engine or other fixed portions of the airplane such devices as governors, pumps, and piping to carry oil pressure into the rotating portion of the propeller, which features are prominent in several of the prior art patents.

In general, the accused constant-speed propeller construction of the Government is similar to that of the patent in suit and while individual parts of the Government structure are specifically different as to location and arrangement, the accused structures possess the same elements of the patent in suit, arranged in the same general way to produce the same results.

Claims 8, 25, 26, 27, and 31 are in suit. In the following findings these claims are paraphrased for convenient consideration.

53. Claim 8 is paraphrased below:

Claim 8

(1) A propeller unit for an aircraft having a predetermined rotative speed,

(a) an independent fluid system wholly within said unit,

(b) speed-responsive means in said system to maintain said predetermined propeller speed by varying the pitch of said propeller blades, and

(2) means for manually full feathering said propeller.

The group of elements (1)(a) and (b) in this claim is directed to a hydraulically actuated constant-speed propeller, the function of this combination of elements being to control the pitch of the propeller in accordance with the speed thereof. Element (2) of this claim is directed broadly to means for manually full feathering the propeller, which is for a separate and distinct function. The constant-speed propeller functions independently of and in the same manner that it would without the manual feathering means, and the manual feathering means functions independently of and in the same manner that it would without the constant-speed mechanism.

The combination of constant-speed propeller mechanism and manual feathering mechanism is old, as shown in Hele-Shaw (finding 32) and the Caldwell et al. patent No. 2,174,717 (findings 48, 49, 50 and 51). The only alleged improvement expressed in this claim resides in making the fluid system independent, and elements (1)(a) and (b) of this claim are disclosed in the Havill patent.

The terminology of this claim is applicable to the type of Government structure in which manual full feathering is utilized (finding 27). This claim, however, is directed to a group of elements between which there is no cooperative function, and the claim is invalid as an aggregation.

54. Claim 31 is next referred to and is paraphrased as follows:

Claim 31

A propeller for airplanes comprising

(1) a hub,

(2) blades on the hub movable on the hub through a varying range of pitch angles,

(3) a propeller mounting with respect to which the hub rotates,

(4) a pump within the hub,

(5) cooperating means on the hub and mounting for positively driving the pump upon rotation of the propeller.

(6) a fluid reservoir within the hub,

(7) a fluid pressure motor means within the hub to which the pump supplies fluid,

(8) a distributing valve in the hub for controlling the flow of fluid from the pump through the motor.

(9) speed-responsive means within the hub for operating the distributing valve, and

(10) means for transmitting motion from the motor means to the propeller blades to vary the pitch angle thereof.

The terminology of this claim is applicable to both the feathering and nonfeathering forms of the Government structure.

The terminology of this claim is equally applicable to the United States patent to Havill (findings 41-44). It is to be noted that in Havill the off-center governor element, with its reduced portion which functions as a distributing valve to control the flow of hydraulic fluid to Havill's servomotor, is identical in construction and function to the defendant's governor-distributor valve.

In view of Havill, this claim is invalid.

55. The remaining claims 25, 26, and 27, are more detailed in phraseology and are directed to specific locations of the various elements. For an interpretation of these claims, reference is made to the Patent Office file wrapper history of the Rindfleisch application which matured into the patent in suit.

These claims were inserted in the Rindfleisch application by an amendment dated July 17, 1937, in response to a rejection of certain claims by the Patent Office on prior art, including a patent to Schmitthenner. Rindfleisch canceled original claim 3, as amended, this claim specifying a variable pitch propeller having "an independent fluid system wholly within the structure of the propeller, pumps in said system, a hub structure, propeller blades rotatable on said hub structure, a cylinder and piston in said fluid system, automatic means operable on said fluid system and controlled by the speed of said propeller for causing relative movement between said cylinder and piston, and said movement imparting rotation to said blades for changing their relative pitch angle." This claim specified the basic elements but not their detailed location.

In connection with the presentation of present claims 25, 26 and 27 before the Patent Office the remarks included in connection with them in order to differentiate them from the prior art patent to Schmitthenner, stated as follows: "In the Schmitthenner patent No. 1,957,183, the fluid pressure system is disposed between the propeller and the source of power. This not only makes a complicated arrangement, but is an undesirable arrangement for aeroplane work because there is too long an overhang of the propeller shaft between the bearings of the engine and the propeller. Applicant's arrangement permits the propeller to be just as close to the engine as it is now, avoiding any overhang of undesirable length and concentrating the control unit in the nose of the propeller entirely beyond the hub." (Page 55, file wrapper and contents, defendant's exhibit 1.)

56. Claim 25 is paraphrased below:

Claim 25

A variable pitch propeller unit comprising

(1) a shaft,

(2) a hub fixed on the shaft,

(3) adjustable blades on the hub,

(4) a blade-actuating unit secured to the hub and shaft assembly at the forward end of the shaft, said unit comprising members constituting

(a) a concentric reservoir and

(b) expansible chamber fluid pressure motor,

(c) pump means in said unit operated directly and entirely through the rotation of the propeller for circulating fluid through the motor and reservoir,

(d) valve means in said unit for controlling such circulation, and

(e) speed-responsive means for controlling the valve.

The phraseology of this claim is not readable upon defendant's structure because defendant's blade-actuating unit is not secured to the hub and shaft assembly at the forward end of the shaft but is located at the rearward end between the propeller and the front end of the crankcase. The defendant's valve means which controls the oil circulation to the servomotors, and the speed-responsive means for controlling the valve, are also positioned between the propeller and the engine instead of being located "at the forward end of the shaft."

57. Claim 26 is paraphrased as follows:

Claim 26

A variable pitch propeller unit comprising

(1) a shaft,

(2) a hub fixed on the shaft,

(3) adjustable blades on the hub,

(4) a blade-actuating unit secured to the hub and shaft assembly at the forward end of the shaft, said unit comprising members constituting

(a) a concentric reservoir and

(b) expansible chamber fluid pressure motor,

(c) pump means in said unit driven entirely through the rotation of the propeller for circulating fluid through the motor and reservoir,

(d) valve means in said unit for controlling such circulation,

(e) speed-responsive means for controlling the valve, and

(5) manually adjustable means for independently actuating the valve. [Italicization supplied.]

This claim is substantially identical with claim 25 with the exception that it contains the additional element which has been indicated above by italicization. Element (5) of this claim has reference to the adjustable cam means which controls the tension on the governor spring.

For the reasons stated with respect to claim 25, the phraseology of claim 26 is likewise not applicable to the Government structures.

58. Claim 27 is paraphrased as follows:

Claim 27

An attachment for operating the blades of an adjustable pitch propeller, comprising

(1) a member adapted to be secured to the forward end of a propeller shaft in advance of the hub of the propeller, said member supporting

(a) a reservoir,

(b) an expansible chamber fluid pressure motor, said member also carrying

(c) a pump driven entirely by the rotation of the adjustable pitch propeller, and

(d) valves for circulating fluid through the reservoir and motor, and

(e) means for transmitting motion from the motor to the adjustable blades of the propeller to which the unit is attached.

This claim expresses limitations with respect to the various parts of the pitch-controlling structure being located in advance of the hub of the propeller, and the phraseology of this claim is not readable upon the Government structures.

59. Claims 8 and 31 are invalid, and none of the claims in issue is infringed.

Conclusion of Law

Upon the foregoing special findings of fact, which are made a part of the judgment herein, the court concludes that, as a matter of law, plaintiffs are not entitled to recover, and the petition is therefore dismissed.

Judgment is rendered against plaintiffs for the cost of printing the record herein, the amount thereof to be entered by the clerk and collected by him according to law.

JONES, Chief Judge.

This is a patent suit. The plaintiffs claim that certain propellers used by the Government are an infringement of a propeller patent owned by the plaintiffs.

The case is largely factual and will be discussed briefly since our findings practically dispose of the issues.

Application for the patent in suit, entitled "Propeller" and known as the Rindfleisch patent, was filed January 27, 1936, and letters patent were issued September 30, 1941. Plaintiffs are the sole owners.

Propeller blades are set at an angle, called the pitch, so that the rotating propeller bites into or screws itself through the air, advancing as it turns and pulling the airplane with it. The higher the pitch angle of the blade, the farther the propeller will advance through the air per revolution and the greater the engine power required to keep the propeller rotating at a given speed. If the pitch is lowered less power is required.

As in most kinds of mobile machinery more power is required during the take-off and climb than under normal flight conditions. In automobiles the problem is met by shifting gears. In airplanes the problem has led to the development of the variable pitch propeller, in the take-off or climb the propellers being set at a low pitch angle so as not to overload the engine. When the cruising level has been reached the pitch angle is increased so as to get greater speed and distance.

The prior art exemplifies a gradual development, starting with only two pitch angles, high and low, manually controlled by the pilot and finally reaching the stage of the automatic variable pitch propeller, hydraulically operated and controlled by a speed-responsive device known as a governor.

When the engine, or one of the engines, fails, the associated propeller continues to rotate due to the flowage of air over the propeller blades. This is called windmilling. If the engine failure is due to jamming or internal breakage the engine might grind itself to pieces or cause other damage, or waste the power of other engines.

This problem has led to various prior art methods of "feathering" the propeller, which is simply a method of changing the pitch angle of the blades until the blades are substantially parallel to the hub axis at which point the flow of air will not cause the blades to continue in motion.

The stated purpose of the patent in suit is as follows:

"The primary object of my invention is to provide a propeller construction which is variable and automatically controllable by a governing mechanism which is regulated by the rotative speed of the propeller during the various maneuvers of the aircraft, or by an increase or decrease in the engine power, or both.

"A further object is to provide an isolated independent fluid pressure and control system for operating automatically the pitch changes of the propeller.

"A further object is to provide automatic means for full feathering the propeller.

"A further object is to provide emergency means controlled by the pilot for full feathering the propeller.

"A further object is to provide novel means for attaching and supporting the propeller blades on the hub."

A simplified explanation of the Rindfleisch patent is set out in detail and illustrated in finding 8. It provides for propeller blades that are capable of rotation about their own axes, which rotation is obtained by links connected with a movable nosepiece, the fore and aft movement of which increases or decreases the pitch position of the blades. This motion is obtained by hydraulic pressure from a self-contained reservoir of fluid, which is placed under pressure by gear pumps, driven by a shaft attached to the crank case in such a way as to be operated when the propeller is in motion.

The hydraulic pressure, which acts against a piston in the nosepiece, is controlled by a governor that consists of a weighted arm responding to centrifugal force which varies with propeller speed, and which acts against a restraining spring. Control of the hydraulic fluid and operation of the governor are described in findings 9 and 10. The automatic and manual full-feathering operation are fully described in findings 12 to 19, inclusive.

The invention in suit was conceived by Rindfleisch in September 1935 and constructively reduced to practice by filing his patent application in January 1936.

The record in this case does not show that the plaintiffs ever issued any licenses under the patent in suit, nor that they ever manufactured, sold or used any propellers of the type embodied in such patent.

The claims of the patent in suit when measured by the prior art subsequently discussed are indicative that the patent is in no sense a pioneer but is directed merely to structural location and arrangement of individual parts already known in the art. The claims, in the light of the specifications and the prior art, must be rather narrowly construed. See Yates v. Jones, 4 Cir., 176 F.2d 794.

Within the six-year period immediately preceding the filing of plaintiffs' petition the defendant, without any license from or consent of the plaintiffs, had manufactured or caused to be manufactured, and used, an automatic, pitch-controlled propeller known as the aeroprop. These are the alleged infringing structures. An illustrated description of these structures together with their purposes and points of similarity and dissimilarity may be found in findings 22 to 27, inclusive.

At the time of the conception (September 1935) of the invention which later materialized into the patent in suit, there was available to the public in the way of prior art, numerous patents relating to the subject matter of the patent in suit. These are described in findings 28 to 51, inclusive.

The July 1928 issue of the Royal Aeronautical Society Journal contained an article entitled "The Variable Pitch Air Screw." This article and other references contained in finding 32 disclose propeller pitch adjusting mechanism hydraulically operated. The Caldwell patent No. 2,174,717, used as a basis for the disclosure of a prior invention, was conceived May 16, 1935, reduced to practice with diligence and flight-tested on June 30, 1936. This invention featured a propeller that was full feathered and unfeathered in flight. It apparently, however, did not have a self-contained reservoir and did not use fluid, except lubricating oil from the engine which drives the propeller. (See finding 29.)

The two Walker patents (finding 30), issued by the United States, disclose a variable propeller in which the pitch of the blades is adjusted by means of an electric motor incorporated in the hub mechanism of the propeller. The pitch of the blades is increased or decreased by means of a centrifugal governor. There is also an independent switch mechanism by which the pitch of the propeller may be manually controlled. These patents do not disclose a hydraulic or fluid pressure system.

The McCauley patent (finding 31) discloses a hydraulic pressure system in which oil pumps are suggested as the source of hydraulic pressure, but it does not teach the use of hydraulic pressure which would automatically adjust the pitch in accordance with the needs of the propeller.

The Hele-Shaw references (finding 32) disclose a hydraulic mechanism for adjusting change of pitch, the mechanism being attached to the propeller. No self-contained reservoir is disclosed.

A patent to Caldwell, No. 1,893,612 (finding 39), discloses a variable pitch propeller, the variation being brought about by fluid pressure controlled by a centrifugal governor or by the pilot. Lubricating oil from the engine is used as the source of hydraulic pressure.

The patent (British) to Salmon describes a variable pitch propeller (set out in finding 40), the functioning of the structure being defined in the patent as follows: "1. Automatically controlling variable pitch propellers used on aircraft, by means of an oil or other fluid pump, the speed of which is caused automatically to change with the speed of the aircraft, under the action of the air, substantially as described." This patent discloses a self-contained reservoir.

The Havill patent, application filed June 25, 1934, and letters patent issued November 5, 1935, is important in that it discloses a variable pitch propeller, the angle or pitch of the blades being determined by several interacting forces. The servomotor is operated by hydraulic fluid under control of a centrifugal governor. The patent discloses an automatic constant-speed propeller with a fluid reservoir. The patent is described in detail in findings 41 to 44, inclusive.

The Waseige patent (finding 45), the Bace patent (finding 46), and the Mader patent (finding 47), each discloses automatic and manually controlled propeller pitch adjustment mechanism.

Claims Nos. 8, 25, 26, 27, and 31 are involved in this suit.

Claim No. 8 is directed to a hydraulically actuated constant-speed propeller with the elements combined in such a way that the pitch of the propeller is controlled in accordance with its speed, and also claims a means for manually full-feathering the propeller.

The combining of a constant-speed propeller mechanism and a manually feathering mechanism is shown in the Hele-Shaw and the Caldwell patents. The terminology of this claim is applicable to the type of Government structure which utilizes manual full feathering.

The record is clear that the addition of the manual full feathering means to the Rindfleisch propeller having a predetermined rotative speed produces no conjoint result. The manual full feathering propeller operates in the same old way to produce full feathering of the propeller under certain conditions and the governor-controlled variable pitch propeller operates in the same old way to produce predetermined engine or propeller speed. They do not act in concert. Claim 8 is void because it is a mere aggregation of old elements each of which functions in the same old way and which do not cooperate to produce a conjoint result. We quote from the opinion in Lincoln Engineering Co. v. Stewart-Warner Corp., 303 U.S. 545, 549, 58 S.Ct. 662, 664, 82 L.Ed. 1008: "* * * The mere aggregation of a number of old parts or elements which, in the aggregation, perform or produce no new or different function or operation than that theretofore performed or produced by them, is not patentable invention. And the improvement of one part of an old combination gives no right to claim that improvement in combination with other old parts which perform no new function in the combination."

The phraseology in Claim 25 is set out and its basis outlined in findings 55 and 56.

When the wording of this claim is laid alongside defendant's structure it will be found that the construction and arrangement are different. The defendant's blade-actuating unit is not secured to the hub and shaft at the forward end, but is located in the rear end between the propeller and the forward end of the crank case. The defendant's valve means which operates to control the oil circulation to the servomotors, as well as the means for controlling the valve, are placed between the propeller and the engine instead of at the forward end of the shaft.

Claim 26 is substantially the same as Claim 25 with the exception that Claim 26 contains the additional element described by the following language: "manually adjustable means for independently actuating the valves." The quoted language refers to the valve means in the unit for controlling the circulation of the fluid through the motor and reservoir. This part of the claim has reference to the adjustable cam means which controls the tension on the governor spring. For the reasons stated in connection with Claim 25 the phraseology of Claim 26 is not applicable to the Government structure.

As set out in finding 58, the terms of Claim No. 27 are also not applicable to the Government structure.

The terms of Claim 31 are applicable to both the feathering and nonfeathering forms used in the Government structure. They are also equally applicable to the United States patent to Havill as shown in findings 41 to 44, inclusive. The means of controlling the flow of hydraulic fluid to Havill's servomotor is almost identical in construction and in its function with the defendant's governor-distributor valve. The claim is invalid view of the prior art as disclosed in the Havill patent.

For the reasons stated herein and as further set out in detail in our findings, Claims 8 and 31 are invalid, and the record does not show infringement of any of the claims in issue. The petition is dismissed.

HOWELL, MADDEN, WHITAKER and LITTLETON, Judges, concur.