US2868303A

US2868303A - Propeller auxiliary power control

Info

Publication number: US2868303A
Application number: US378096A
Authority: US
Inventors: Chester M Jedrziewski
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1953-09-02
Filing date: 1953-09-02
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13

Description

Jan. 13, 1959 c. M. JEDRZIEWSKI PROPELLER AUXILIARY POWER CONTROL AUX. M070 "m l i 4 m m M 3 M u 2 p d INVENTOR CHESTER l4. \JElNiZ/E SK/ gym 7% 6 m U 6 4 a 7 k Z 3W 4 M Z r W w/ W u mw 5 E 0 7% u o 6 a mfw m 0 476 F .0 2 2 005/ w u 9 M m $0 a U Mn cam E! ZZ d,

United States Patent PROPELLER AUXILIARY POWER CONTROL Chester M. Jedrziewski, Roekville, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application September '2, 1953, Serial No. 378,096

19 Claims. Cl. 170160.2)

This invention relates to improved propeller control mechanism and particularly to an improved power supply system for power actuated pitch control mechanism.

An objectof this invention is a light and eflicient fluid supply system for a hydraulically actuated propeller.

A further object is mechanism by which a pump of small capacity is utilized for normal pitch changesand an auxiliary pump is automatically connectedin parallel with said small pump for larger or more rapid pitch changes.

A still further object is mechanism under the control of the governor for increasing the volume of fluid supply when the governor reaches a predetermined off speed position.

A further object is the provision, in a governor having contacts closable by movement of the governor to supply governing power, of means for supplying governor power while the contacts are open.

A still further object is an improved propeller governing system. i

Other objects and advantages will be. apparent from the specification and claims, and from the accompany ing drawings which illustrate what is now considered to be the preferred embodiment of the invention. 1

Fig. l is a somewhat schematic end view of the propeller control mechanism including a schematic wiring diagram.

Fig. 2 is a schematic side view showing the hydraulic control mechanism and the pitch changing mechanism.

Fig. 3 is a partial wiring diagramiilustrating how the wiring diagram of Fig. 1 may be changed for operation of the governor switch in both directions.

In the drawings which illustrate a mechanical construction which is now considered the preferred form of the invention, a propeller of the type shown in application 84,305, filed March 30, 1949, by John E. Anderson is utilized. Reference may be made to that application for a more complete description of the propeller and its control. In general the propeller comprises a control unit indicated generally at rotatably supported on bearings on the propeller unit indicated generally at 12. The control unit it includes a bearing sleeve 14 which is telescoped with and supported on an axial projection 16 on the hub 18 of the propeller 12 The sleeve 14 is secured in position on the hub and held against axial or rotational movement thereon, as more fully described in the above-mentioned application.

The propeller may be of any type utilizing hydraulic fluid for pitch changing and preferably having the propeller pitch changing motor carried by and rotating with the propeller. In the preferred form, the pitch changing motor comprises a piston mounted in a cylinder 34 and by means of cam slots 36 and cam rollers, not shown, turns a connecting gear 35 geared to the propeller blades 40 to thereby change the propeller blade pitch. Oil may be selectively directed to either side of the pitch changing mechanism by means of conduits 42 and 44. The propeller is secured to a propeller or engine shaft 46 supported'in the usual manner by hearings in the engine 190 or engine nose. For further details 'of these propeller constructions, reference may be made to Patent No. 2,477,868of George W. Forman, filed April 17, 1946, and issued August 2, 1949. Reference may also be made to Patent No. 2,371,873 of Erle Martin, issued March 20', l945, for a further disclosure of a suitable type of propeller for use with the control of this application. As this type of propeller is now well known, further detailed description thereof is believed to be unnecessary.

Hydraulic fluid is led from the control mechanism to the propeller through the conduits 42 and 44 in the propeller hub. Conduit 42 leading into the hub outside of propellershaft 46 and through suitable connections such as shown in Patent No. 2,477,868, is led to the forward side' of piston 32. Fluid may also be led through conduit 44 in the hub to the interior of the propeller hub and the space to the rear or inboard side of piston 32 Suitable means such as a gasket 48 prevents flow of oil inboard along the propeller shaft, the propeller surrounding' the outboard end of the propeller shaft closes the outboard end against the loss of oil in the outboard direction. Oil from the control mechanism is directed into a groove 54 on the inside of sleeve 14, which when assembled on hub projection 16, is in hydraulic communication with conduit 42. Oil may also be led from the control unit into groove 64 formed in the interior of bearing sleeve 14. Groove 60, when assembled on the hub projection 16, is in hydraulic communication with the conduit 44."

The control unit 10 comprises a main casting 74 which supports all of the various control elements, including the governor valve indicated generally at 76, the scavenge pump, indicated generally at 78, the main pump and its connections indicated generally at 30, the auxiliary pump and motor indicated generally at 82, the various valves and their controls, to which reference will be made hereinafter, and the oil reservoir, indicated generally at 84. The various control elements are preferably separate units bolted or otherwise removably secured to the main casting' A hearing sleeve 86 is secured in main casting '74 and serves to rotatably support the entire control system onthe bearing sleeve 14 which is secured as previously described on the hub projection 16. Bearing sleeve 86 is provided with a bearing metal such as babbitt on its inner diameter and inboard face which provides a bearing surface cooperating with the outer surface of bearing sleeve 14 to provide a suitable running joint between the stationary control unit and the rotating propeller unit.

' Four

grooves

88, 90, 92 and 94 are provided in the outer surface of bearing sleeve 86 and, like the grooves in the interior of sleeve 14, are prevented from leaking by means of suitable 0 ring gaskets. Suitable passages lead from groove 94 through sleeve 86 and other pas sages lead from groove 88 through sleeve 86. Suitable passages'lead from grooves 88 and 94 to the governor valve which being thus connected with the propeller pitch changing mechanism controls the flow of oil to and from the pitch changing mechanism. The main and auxiliary pumps are connected in parallel and their output is led to groove 92. Various passages in the main casting connect with groove 92 to deliver the output of the main and auxiliary pumps to the low pressure relief valve, indicated generallyat 96, high pressure relief valve, indicated generally at 98, and to the governor valve 100. A passage 102 connects the auxiliary pump 104, driven by auxiliary motor 106 withpassage 92. As will be explained later, this auxiliary pump and motor are used to provide pressure fluid to assist the main pump, and also to provide pressure fluid when the propeller is not r'otati'ng and the main pump is consequently idle.

. v3 r Suitable check valves'354, 356 are placed in the output line of the auxiliary'and main pumps to assist in preventing bleeding of oil through these pumps when they are idle or otherwise inoperative.

A main sump or reservoir is formed at one side of the main casting 74 of the'control unit which is the lower side when the control unit is in its normal upright position, by means of a curved, tro'u'gh like cover 108 secured to the lower portion of main casting 74. The main pump 80 is enclosed by the cover 108 and comprises a gear pump 116 driven through gear 118 by a gear 120 formed on an upstanding flange 122 on the inboard side of sleeve 14 secured to rotate with the propeller. Pump 116 has an inlet 124 located near the bottom of the reservoir. This inlet, however, is spaced from the bottom of the reservoir a greater distance than inlet 126 leading to auxiliary pump 104 so that in the event of failure of the propeller to change pitch due to lack of oil it may still be possible to feather the propeller by means of the auxiliary motor which can still pump oil if the lack of oil is caused by the level falling just below the inlet to the main pump.

As stated above, oil from main pump 116 is led to passage 92 and thence to the governor valve 100 from where it is directed in the usual manner by the governor to the proper side of the pitch changing motor to maintain constant propeller speed by varying the propeller pitch. The governor is driven from gear 120 by gear 136 and a pair of bevel gears as shown in Fig. 2. The governor comprises the .usual' flyweights 140 opposedby a speeder spring whose tension may be adjusted in a well known manner from the pilots cockpit. Pressure 'oil is also lead through passage 144 to solenoid actuated feathering valve 146 and solenoid actuated reversing valve 148 which are normally closed. Actuation of the feathering valve will direct pressure fluid through conduit 150 to the underside piston 152 on the lower side of governor valve 100 to thereby raise the governor valve 100 and connect pressure fluid with groove 88 and the pitch increasing side of the piston 32 of the pitch changmg motor.

Actuation of the reversing valve will direct pressure fluid from the passage 144 to passage 154 leading to'a piston 155 on the top of the governor valve 100 thereby forcing the pilot valve down to direct pressure fluid from groove 92 into groove 94 and thence to the pitch reducing side of the piston 32 in the pitch changing motor.

Pressure oil is also led from the passage 92 to the front face of plunger 156 of relief valve 96 which is urged into closed position by spring 158. The relief setting of relief valve 96 is normally determined by the capacity of spring 158 but may be increased by leading oil under pressure to the backside of plunger 156. This is accomplished by a shuttle valve 160, one side of which is connected with the reversing valve 148 and piston 155 on the governor valve 100 and the other side of which is connected with the groove 88 leading to the pitch increasing side of the pitch changing motor. Hence, whenever the reversing valve is opened or whenever pressure fluid is being led to the pitch increasing side of the pitch changing motor, the capacity of the relief valve 96 is increased to thereby increase the pressure output of the main pump. Shuttle valve 160 moves under the predominant pressure acting thereon to connect that predominant pressure with the rear of the plunger 156.

Groove .92 is also connected with a high pressure relief valve 98 which serves to limit the ultimate pressure attainable by the main pump. Both relief valve 96 and 98 discharge directly into the main sump or reservoir, relief valve 96discharging through conduit 161.

Gears 162 of scavenge pump 78 are driven by gear 120 and serve to remove oilthat may collect in the drainage area 166 and force it into the reservoir, 84 to keep thedrainage area free from an accumulation of oil .4 and maintain reservoir 84 under a pressure determined by the reservoir relief valve indicated generally at 170: Pump 78 may pump both oil and air to maintain the reservoir pressure. y I

The main casting 74 has projections 186 extending from one side thereof and forming a slot between than. A lug fixed on theefzgihe nose extends to a position be tween said pro ections and acts to prevent rotation of i the control unit with the propeller while permitting it to move axially and radially with the propeller.

In normal constant speed operation the governor 76 operating valve 100 controls the flow of oil through pas sages 42, 88, 44 and 94 to maintain constant propeller speed by varying the propeller" pitch. Shuttle valve 160 is maintainedin the position shown in Figure 1 to ap= ply pressure back of relief valve plunger 156 whenever pressure-oil is introduced to the pitch increasing side of the pitch changing motor, scavenging pump 162 serving to keep drainage area 1'66 free from the accumulation of oil and to maintain a predetermined pressure in reservoir 84.

It has been customary to utilize continuously rotating pumps such as main pump to supply all the hydraulic fluid for changing pitch during constant speed opera; tions. During the major portion of the constant speed.

1 operation, only a small quantity of hydraulic fluid is r= qulred but during extreme operations such as rapid throt tle changes, the entire capacity of the main pump is utilized. Hence the main pump had to be large enough to supply fluid at a rate suflicient to provide the rapid pitch change necessary for these extreme operations. Hence, during the major portion of the time the main pump was pumping an excess of fluid which caused undue heating and a waste of power.

In the present invention applicant has provided means by which the normally stationary auxiliary pump 104 may be utilized to assist the main pump during extreme operations thus permitting a material reduction in the size of the main pump with a consequent reduction of power required and a reduction in the resultant heat of the oil.

A normally open switch 351 having contacts mounted on spring arms is mounted in the governor housing in a position to be actuated by the rod 352 which in turn is actuated by the pilot valve Whenever the governor exceeds a preselected overspeed condition. The rod 352 may be suspended in the switch housing and normally spaced at its lower end from the governor valve 100 or it may be constructed as shown as an integral extension of the valve 100. The upward movement of the valve 100 thus serves to close the switch 351. Closing of the switch 351 will energize hold-in coil 311 and energize the auxiliary motor to start the auxiliary pump 104 and assist the main pump 116, thus supplying the additional fluid necessary to give a pitch change rapid enough to avoid any excessive overspeeding.

In general, it is not necessary to have as rapid a pitch reduction as a pitch increase as the underspeeding which will call for a pitch reduction does not produce dangerous conditions. However, if desired, another switch could be provided as shown in Fig. 3 which would be actuated by the governor valve when it approaches its extreme underspeed position which switch could be placed in parallel with switch 351 to energize the auxiliary motor 106 and operate the pump 104 to assist the main pump 116 in pitch reducing movements.

The above mechanism connected with the auxiliary motor 106 does not interfere with the utilization of this auxiliary motor for feathering, unfeathering and, if desired, reversing and unreversing operations as will he explained below. v When it is desired to feather the propeller, feather but ton 192 in the control compartment of the airplane is I "1192'depressed. This Will -also opeir feathering valvei146, .energize tfeatheringr'solenoid 204*andholding coil 311 cclosingswitch 313 for auxiliarypumpmotor 1'06,.and operate auxiliary pump .104to supply fluid in addition :to that being supplied by the (main pump and to, if neces- :tsary, continue to supply fluid after the main pump has ceased operation due to stopping of the propeller. Hold- ,ing coil 202 is inseries with a cut-out switch 206 which a is actuated by the pressurefluid changing the propeller ;pitch. Opening of feathering valve'146 allows pressure ufluid from grooves 92 and passage .144 to enter conduit 150 and act on the underside of piston 152. to lift governor valve100 which will direct fluidfrom the groove 92 to 'groove88 and the pitch increasing side of the pitch changingmotor. Lifting of the governor valve 100 by the piston l52 will actuate rod-352 to close switch 351 and provide a second path for electricity for'hold-in coil 311 for auxiliary pump switch 313. Pressure oil in groove i88will move shuttle valve 160to the position shown to put pressure oil back-of plunger 156 of relief valve% andwill move shuttle valve 208 from the position shown to .thelower end of its cylinder to thereby connect the pressure cut-out switch with the pitch increasing side of the pitch changing motor. When the pitch changing motor has reached its limit of movement determined by stops, not shown, the'pressure. at the pitch increasing side .of the pitch changing. motor will increase creating a pressure surge which will open thepressurecut-out switch releasing the holding coil.202 and permitting springs 300 to-return the featherbutton 192 to its off position as.-

shownin Figure 1. Return of the feather button 192 to its off position .will break thecircuit through contact .200 to hold-in coil 311 and will break the circuit through contact 193 to the feathering solenoid 204 thus permitting the governor to return under the influence of the speeder spring to an unders peed condition thus opening switch 351 to de-energizehold-in coil 311 thus stopping the auxiliary motor.

To unfeather the propeller from its non-rotating feathered positionpbutton 192 is pulled to the left as viewed inFigure 1, closing contacts 302, 304, 306and 308 to thereby energize holding coil 310 closing switches 318 and 318a, energizing holding coil 311 and consequently energizing auxiliary pump motor 106 and reversing solenoid 312 thus opening reversing valve 1443. Operation of auxiliarypump motor 106 will supply auxiliary fluid in the same manner as described for feathering, except that it must supply all the fluid at the beginning of the operation as the main pump 116 then does not operate and it will assist the main pump after the propeller starts to rotate. Opening of reversing valve 148 will allow pressure fiuid from groove92 and passage 144 to enter passage '154 and act on theupper surface of piston 155 to thereby force the governor valve 101? down and admit pressure fluid from groove 92 to 94 and hence to the pitch decreasing side of the pitch changing motor. Pressure'fluid in passage 154 will move shuttle valve 160 to apply pressure fluid back of plunger 136 of relief valve 96 to thereby increase the available pressure. Pressure in groove 94 will move shuttle valve 208 to the position shown in Fig. 1 thereby connectingthe pitch decreasing sideof the pitch changing motor with the pressure cutout. switch 206. The pressure cut-out switch, however, is not utilized to stop the unfeathering operation as this is accomplished by electrical contacts on the propeller blade shank. When the propeller blade has reached a predetermined position in itspitch reducing movement the current in holding coil 310 is broken by an insulating segment 314 thus releasing holding coil 310 allowing spring 316 to return switch 318 to an off or neutral position thus breaking the current to reversing solenoid 312 and auxiliary motor 106. The plunger which cooperates with holdingcoil 2 is so far out of the holding coil when button 192 isin unfeather position that holding coil 202 has no affect. Button 192 is held out manually for unfeathering rand may be? released' at any timeaafter I. the

trol. As in the feathering operation the switch is returned to its neutral position by springs 300 after his released. Reference may be had to application Serial No. 32,244 of Martin and McCarthy, filed June 10, 1948 for a more complete description of the construction. and operation .of'the insulatingand conducting segments on the'blade 18. It will be sufiicient to state here that by means of a brush, insulated from, and held in fixed position on the propeller hub an electric circuit may becompleted by being con ducted to ground through conducting

segments

328 and 330 and the propeller blade and hub. The brush and segments are arranged :so that the brush will be approximately at the position indicated byF when the propeller is feathered at the position indicated by L. P. when the propeller is at its low pitch stops and at R when the propeller is in its reversed pitchposition. It will thus .be apparent that even if switch .knob 192 is held in the un feather position whenconducting segment 330 contacts the brush, the circuit will again be broken by insulating segment 332 before the propeller reaches its low pitch stop. This will prevent the propeller from going into reverse pitch while unfeathering because the pressure level maintained by relief valve '96 alone, when not backed up. by pressure from reversing valve 148, is notsufiicient to overcome the low pitch stops.

In order to reverse the propellerpitch, switch320 is first closed and then reverse-unreverse switch 322 is moved into the reverse position which is the lower position as viewed in Figure 1. Closing of these switches will energize reversing solenoid 312 and holding coils 324 and 326. Energizing holding coil 324 will close switchs 334 and 336. Closing switch 334 will be effect short circuit switch 322 so as to maintain holding coils 324 and 326 energized independent of the position of switch '322.

Energizing holding coil 326 will close switch 338 which will in effect short circuit switch 320 so as to maintain holding coils 324, 326 energized independent of the position of switch 320. Energizing holding coil 326 will also close switch 354 to start the auxiliary pump in operation. The closing of switch 336 has no immediate 'elfect, but prepares the circuit for unreversing which will'be described later. After passing through

switches

320, 322 and holding coils 324, 326 the current passes through switch340 to ground. Switch 340 is normally held closed by spring 342. Energizing the reversing solenoid 312 will produce the same hydraulic action as in unfeathering. As in unfeathering, governor valve is forced down so as to connect groove 92 with groove 94 and direct fluid to the pitch reducing side of the pitch changing motor. It is to be understood that as is usual in this double'acting type of control, each time pressure fluid is conducted to one side of the pitch changing motor, the opposite side of the motor is connected to drain or the reservoir to permit fluid to flow from one sideof the motor as it is introduced to the other side.

Switches

320 and 322 remain in the closed position just described as long as it is desired to have the propeller remain in the reversed pitch position and the propeller is maintained in that positionby the fluid from the main pump and the auxiliary pump being continuously directed to the pitch reducing side of the pitch changing motor, thereby forcing the propeller against the reverse pitch or pitch limiting stops not shown. If the reversing operation is to be continued for any appreciable length of time,it may be desirable to disconnect the auxiliary pump and allow the propeller to be held in reverse pitch by the main pump alone. This can be accomplished by inserting a switch 356 in the line between the switch 354 and the auxiliary motor 106'which switch' may i 338, it has no immediate effect. I the unreverse position will also close a circuit to prepare when it reaches a selected underspeed position.

be manually operated or if desired may be automatically operated by a mechanism such as a second blade switch reversed to its unreversed position, the position shown in Figure 1, which will de-energize solenoid 312 and close valve 148. In the unreversed position of switch 322 the current will be conducted through switch 336 which is still maintained closed by holding coil 324 and will energize feathering, or increase pitch, solenoid 204. Switch 320 is then opened, but as it short circuited by switch Placing switch 322 in holding coil 344 for action when the circuit is completed through contact 330. Energizing increase pitch solenoid 204 will cause actuation of the governor valve 100 in the same manner as was described in the feathering operation closing switch 351 to energize the auxiliary pump and motor.

nect groove 92 with groove 80 and apply pressure fluid The governor valve 100is moved to conto the pitch increasing side of the pitch changing motor and thus move the blades 18 from reverse pitch through zero pitch to increased pitch position. After the blade pitch has been increased to a pitch somewhat above the pitch defined by the low pitch stops, brush 346 will make contact with conducting segment 330, which will energize holding coil 344 to thereby open switch 340. Opening switch 340 will break the ground connection of holding coils 324 and 326 thus de-energizing them. Springs 348 and 350 will now open

switches

334 and 338 and deenergize increase pitch solenoid 204, closing valve 146 and thus opening switch 351 and returning the governor valve 100 to governor control.

As has been indicated above, the switch actuated by the rod 352 may be arranged so as to be actuated both when the governor reaches a selected overspeed position and Fig. 3 illustrates a wiring diagram showing how such a switch may be fitted into the above-described structure. The rod 352 is attached to the pilot valve 100 for actuation in both directions in accordance with the position of the pilot valve. As in the single switch of Fig. 1, there may be lost motion provided between the governor valve 100 and the rod 352, or the lost motion may be between the rod and the switch or even in the switch itself. A lost motion equivalent to 50 R. P. M. above and 50 R. P. M. below the onspeed position has been found to be satisfactory. Shoulders 360 and 362 on the rod 352 are effective to acuate the switches upon movement of the rod. Upward movement of the rod 352 will cause shoulder 360 to close switch 351 and operate the auxiliary motor 106 as described above.

Shoulder 362 will be moved downward on underspeed and when the governor reaches a selected underspeed condition will close the switch 364 to energize line 366. A switch 368 connects line 366 with holding coil 311 to close switch 313 and actuate the auxiliary motor 106. Switch 368 is closed by a solenoid holding coil 370 which is controlled by a blade switch 372 mounted on one of the propeller blades 40. Blade switch 372 has a conducting portion 374 which will keep holding coil 370 energized and switch 368 closed except near the reverse and feathered positions where insulating segments 376 and 380 will fbreak the circuit through hold-in coil 370 allowing switch 368 to open. Hence, during the normal operating range,

whenever the propeller reaches a preselected underspeed condition, switch 364 will close and switch 368 will operate the auxiliary motor 106. Line 366 is also connected through switch 318a to the hold-in coil 311.so

that, when the propeller reaches a feathered position and .stops rotating, thus causing the the governor to stop rotating, and assume an underspeed position closing switch v364, although switch 364 will be closed, it will not operate the auxiliary motor 106 because both switch 318a and 368 will be open.

When it is desired to unfeather, button 192 is pulled giving two parallel connections to coil 311 or the con-.

nection of line 366 with switch 318a may replace the connection between contact 308 and switch 318a. The connection between contact 308 and coil 310 will of course remain as shown in Fig. 1. In feathering the propeller the connections between contact 200 and the holding coil 311 may be allowed to remain as shown in Fig. 1 or may be removed relying entirely upon the closing of switch 351 by the movement of the governor incident to operation of the feathering solenoid if desired. It will of course be apparent that operation of the feathering solenoid 204 will, through the resulting movement of pilot valve 100, close switch 351. Operation of the reversing solenoid 312 will, through the resulting action of the governor valve 100, close switch 364, which switches- 351 and 364 can be-utilized for the feathering and reversing actions.

In reversing, actuation of reversing solenoid 312 by placing switch 322 in reverse position will close switch 364 and, switch 368 being closed, will actuate the auxiliary motor to assist in reversing. Just before the reverse pitch position is reached, insulating segment 376 will come under brush 346 to de-energize coil 370 and allow its spring to open switch 368 to stop the auxiliary motor 106. The propeller may then be held in reverse pitch position through the action of the reversing solenoid 312 by main pump 116.

In unreversing, the feathering solenoid 204 actuated by moving switch 322 to unreverse position will act to move the governor to close switch 351 and energize coil 311 energizing the auxiliary motor. The de-energization of the feathering solenoid 204 by the opening of switch 336 when coil 344 is energized through contact 330 to open switch 340 and break the ground to coil 324, will of course release the governor to open switch 351 when the propeller speed returns to within 50 R. P. M. of the governor speed setting and the propeller will be returned to governor control. It will be apparent that the governor actuated switches 351 and 364 can be utilized not only for boosting oil flow during governor control but may also be used in the operations outside of the governor range for feathering, unfeathering, reversing and unreversing.

If desired, contact strip 374 may be shortened so as to extend from adjacent the reverse position to only slightly beyond the low pitch position in the governor range so as to limit the use of the auxiliary motor to pitch increasing movements during governoroperations. The switch 368 being open in the governing and feathering ranges and being closed only in the reverse range, and switch 318a being closed only in the unfeathering operation, the switch 364 will not be effective to energize the auxiliary motor for pitch reduction in the governing range. Use of switch 364 in operating the auxiliary motor 106 for pitch reduction would therefore be limited to reversing and to unfeathering.

The propeller has been described in connection with a pressure cut-out switch 206 but if desired a suitable timing mechanism may be substituted for the cut-out switch which mechanism instead of operating on a pressure surge, will operate to disconnect the auxiliary motor after a predetermined elapsed time.

The timer may be used to measure the elapsed time from the time energy is supplied to the auxiliary motor for feathering and may also be used to measure the elapsed time from the supplying of energy to the auxiliary motor for reversing, being substituted for the cut-out switch in the first instance and for-the manually actuated switch 356 in the second instance.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. In combination with a hydraulic governor having a valve controlling the flow of fluid from a source of fluid pressure to a device to be controlled, an auxiliary source of fluid pressure, a conduit connecting said auxiliary source with said governor valve, a check valve in said conduit preventing flow fromsaid governor valve toward said auxiliary source, said conduit being continuously open for flow from said auxiliary source to said governor valve, means actuated by said governor valve, when, in its governing operation, it reaches a predetermined olfspeed position, for supplying additional fluid from said auxiliary source to said governor valve in parallel with said first mentioned source.

2;. A. device as claimed in claim 1 including means .for

de-energizing said auxiliary source while the governor is flow of fluid from said pump to said outlet, a normally inactive fluid pump connected in parallel with said continuously operating pump, means actuated by said governor, when in its governing operation it reaches a predetermined oif speed position, including means for actuating said inactive pump, for supplying fluid to said outlet.

4. A control for an adjustable pitch propeller com prising, a fluid pump actuated by rotation of said propeller, a speed responsive governor controlling the flow of fluid from said pump to said propeller to control the pitch thereof, a source of fluid pressure connected in parallel with said pump, an electric switch, means connected with said governor for actuating said switch when the governor in its governing operation reaches a predetermined off speed position, and means responsive to operation of said switch for energizing said source to supply fluid from said source to said propeller.

\ 5. A device as claimed in claim 4 in which the means responsive to operation of said switchincludes an electric motor and a pump actuated thereby.

6. A control for a hydraulically actuated controllable pitch propeller having a fluid reservoir and a pump connected with said reservoir for drawing fluid therefrom and continuously operated by rotation of said propeller for continuously supplying hydraulic actuating fluid under pressure during operation of said propeller, a governor for controlling the application of said fluid to said propeller for controlling the pitch thereof, a second normally inactive pump connected with said reservoir for drawing fluid therefrom, and means connected with said second pump and actuated by said governor when it reaches a selected off speed position in its governing operation to actuate said second pump and supply fluid in parallel with said continuously operating pump.

7. In combination with a feathering type controllable pitch propeller having means for supplying fluid from a first source of fluid pressure for feathering and unfeathering said propeller independent of propeller rotation, a governor for said propeller, a second source of fluid under pressure, means for supplying fluid from said second second source through said governor to said propeller during normal governed speed operation, and means responsive to a selected ofl? speed condition of said propeller for automatically supplying additional fluid under pressure during governed operation from said feathering and unfeathering supply.

8. A device as claimed in claim 7 in which said first source of fluid pressure comprises an electrically driven pump and the means responsive :to a selected ofispd condition includes a switch actuatedby said governor.

9. A device asclaimed in claim 8 in which saidsecond source of fluid under pressure includes a pump-operated continuously by rotation of said propeller and the pro- -peller includesa common sump for both pumps.

10. A device as claimed in claim 8 including a manually actuated switch for controlling said source of fluid pressure for feathering andunfea'thering connected in parallel with said governor actuated switch.

11. A hydraulic governor having a reciprocating valve for controlling fluid flow, switch means actuatable by said valve adjacent the limit of its reciprocation, a normally de-energized source of fluid pressure connected with said governor and controlled by said switch, said valve being movable incident to the governing action of said governor to actuate said switch and energize said source and manually controlled means for moving said valve to actuate said switch and energize said source.

12. In combination with a controllable pitch propeller, a :first source of fluid pressure energized by rotation of said propeller, a governor valve controlling the application of said fluid to said propeller, a second source of .fiuid presusre independent of rotation of said propeller, connected in parallel with said first source, means actuated by said governor valve when it reaches a predetermined oifspeed position for supplying .fluid from said second source to assist said first source in governing said propeller.

13. A governor, driving means for said governor, a main pump continuously driven by said governor driving means, means continuously directing the output of said pump to said governor, a second pump, driving means for said second pump independent of said main pump driving means, means including a check valve connecting the outlets of said pumps, said check valve preventing flow from said main pump to said second pump and opened by an excess of pressure from said second pump over the pressure of said main pump and connecting said second pump with said governor in parallel with said first pump and means controlled by said governor controlling said second pump driving means.

14. A device as claimed in claim 13 wherein said governor controlled means includes switch means connected with said governor and actuated thereby for controlling the operation of said second pump driving means.

15. In combination, an engine driven hydraulically actuated controllable pitch propeller, a main pump continuously actuated by rotation of said propeller, a governor valve having an onspeed position and oifspeed positions, means connecting said pump with said valve and means connecting said valve with said propeller, said governor valve controlling the flow of fluid between said pump and said propeller to vary the propeller pitch and control the engine speed, a second normally inoperative pump, electric motor means for operating said second pump, a switch connected with said electric motor, means connected with said governor for actuating said switch to energize said motor when the governor, while governing, reaches a predetermined ofi'speed condition, means connecting said second pump with said valve in parallel with said main pump.

16. Governor control means for a controllable pitch propeller comprising a governor valve for directing fluid under pressure to said propeller, a normally de-energized electrically driven pump for supplying fluid under pressure to said valve, governor actuated switches for energizing said pump, means connected with said governor for closing one of said switches and energizing said pump when the governor reaches a predetermined overspeed condition, and closing another of said switches and 'energizing said pump when the governor reaches a predetermined underspeed condition, and additional means for supplying fluid to said governor for governing said propeller between said oifspeed conditions.

17. In combination with a governor having an onspeed position and having governor-controlled electrically-actuated means for supplying speed correcting forces on opposite sides of said onspeed position, said governor having a dead band at and adjacent the onspeed position of said governor in which said electrically actuated means are inoperative, and means controlled by said governor for supplying speed correcting forces in said dead band independent of said electrically actuated means.

18. In combination with a controllable pitch propeller, a first source of fluid pressure energized by rotation of said propeller, a governor controlling the application 'of said fluid to said propeller, a second source of fluid pressure independent of rotation of said propeller, connected in parallel with said first source, means actuated -by said governor when it reaches a predetermined offerning range into a special purpose range and actuating -said means actuatable by said governor to supply fluid 'to move said propeller in said special purpose range.

1.9. Control means for a controllable pitch propeller having a governed range of pitch change and a special purpose range outside of said governed range, compris ing a source of energy, a speed responsive governor controlling the application of said energy to said propeller for controlling the pitch changing movements of said propeller in the governed range, a second source of energy for actuating said propeller in said special purpose range when the propeller is not rotating, means actuated by said governor in its governing action when it reaches a predetermined ofispeed position for controlling the sup ply of energy from said second source to said propeller in parallel with said first source, means for disabling said governor and moving it to one extreme limit of its travel to actuate said governor actuated means and supply en ergy from said second source for moving said propeller in said special purpose range.

References Cited in the file of this patent UNITED STATES PATENTS 2,229,058 Dicks Ian. 21, 1941 2,402,065 Martin June 11, 1946 2,413,439 Drake Dec. 31, 1946 2,545,684 Carson Mar. 20, 1951 2,611,440 Haworth et al Sept. 23, 1952 2,653,668 Anderson Sept. 29, 1953 FOREIGN PATENTS 132,433 Australia May 3, 1949