US2955663A - Propeller control system - Google Patents

Description

Oct. 11, 1960 BRANDES ETAL 2,955,663

PROPELLER CONTROL SYSTEM Filed Dec. 11, 1956 INVENTORS E0 v I?! Ben/v0.5.5 y P/CH'A'RDA H1250 Afar/2M ATTORNEY A 2,955,663 PRQPELLER CONTROL SYSTEM Roy H. Brandes, Dayton, and Richard A. Hirsch, West Milton, Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Dec. 11, 1956, Ser. No. 627,619

'15 Claims. (Cl. 170-'160.21)

This invention pertains to propellers, and particularly to an improved control system for a variable pitch propeller designed for use with a gas turbine engine.

Heretofore, the tendency of the blades of a variable pitch propeller to move in the decrease pitch direction toward a low angle, or flat pitch position, due to the aero- "dynamic and centrifugal twisting moment forces acting on the blades, has been troublesome. Thus, in previous propeller control systems, means were included to control and limit the rate of pitch change in the decrease pitch direction. The aforesaid means necessarily increases the complexity of the propeller control system, but were considered essential from the safety standpoint. However, in a variable pitch propeller having a mechanical pitch lock, a mechanical low pitch stop, and safety feathering means, the problem of controlling the rate of pitch change in the decrease pitch direction is of little, or no, significance. Therefore, the propeller control system can be simplified. Accordingly, among our objects are the provision of an improved control system for a variable pitch propeller; a further provision of a variable pitch propeller control system including safety feathering means; and the still further provision of a variable pitch propeller control system having governor valve means and a feathering valve means including means for automatically disabling the governor valve means upon operation of the feathering valve means.

atent ICC the torque units so as to increase or decrease propeller Pitch. The distributor valve is controlled by governor valve means which maintain propeller speed substantially constant during the propeller operation in the governing regime. Moreover, during the operation in the governing regime, the pitch change rate is proportional to the amount of off speed. The governor valve can also be manually positioned to operate the propeller in the manually selected blade angle regime and the emergency feathering'regime. The control system also includes a feathering valve assembly which is operable to disconnect the high pressure fluid supply to the distributor valve thereby rendering the governing means ineffective during manual feathering, safety feathering, and automatic feathering operation. At this time, the feathering valve assembly connects the high pressure supply directly to increase pitch chambers of the torque units while connecting the decrease pitch chambers to drain so as to move the propeller blades to the run feathered position.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

The'drawing is a schematic diagram on the propeller I control system of this invention.

The aforementioned and other objects are accomplished in the present invention by having a single high pressure supply conduit for the governor operated distributor valve which conduit can be cut off from the source of high pressure fluid during operation of the feathering valve means. Specifically, the invention relates to an improved control system for a variable pitch propeller of the type disclosed in French Patent 1,173,259, which corresponds to copending application Serial No. 572,348, filed March 19, 1956, and assigned to the assignee of this invention.

Thus, the propeller includesa hub having a plurality. of 1 fluid reservoir containing 'suflicient fluid to completely feather the propeller under all conditions.

Thepitch position of the propeller blades is adjusted by fluid pressure operated motors, or torque units, carried by the propeller hub. The regulator reservoir contains a quantity of fluid, such as oil, and carries a plurality of pumps, which are energized incident to the propeller rotation, for drawing fluid from the reservoir and delivering the fluid under high pressure to a hydraulic control system. The hydraulic control system includes a With particular reference to the drawing, the propeller includes a' hub 10 shown schematically in the drawing. As is conventional, the hub 10 includes a plurality of radially extending sockets, such as the one indicated by numeral'll in the drawing. A propeller blade 12 is journalled for rotation about its longitudinal axis by means of bearings 13 within the socket 11. The propeller blade is shown schematically in the drawing and, thus isshown including an integral cylinder 14 having internal helical splines 15. A piston 16 is disposed for reciprocal movement within the cylinder 14, the piston 16 having external helical splines 17 which mate with the internal helical spline 15 of the cylinder 14. In addition, a piston 16 has internal integral helical splines, not shown, which mate with external helical splines on a reaction member 18 which is integral with the hub 10. Thus, it will be appreciated that upon reciprocation of the piston 16, rotation will be imparted to the propeller blade 12. In

addition, upward movement of the piston 16, as shown in the drawing, will move the propeller blade 12 in the increase pitch direction, andv downward movement of the piston 16 moves the propeller blade in the decrease pitch direction.

'Ihe propeller blade is shown integral with a bevelt'ype sector gear 19 which meshes with a bevel-type master gear 20 supported for rotation in the hub 10 about the horizontal propeller axis. It is to be appreciated that each propeller blade 12 has a bevel-type sector gear meshing with the master gear 20, and the function of the master gear 20 is to coordinate and synchronize the pitch adjustment movement of all the propeller blades mounted in the hub.. Thus, it will be appreciated that the master gear has a predetermined angular position for each and every pitch position of blades 12. In accordance with the teachings of British Patent 798,372, which corresponds to copending application Serial No. 571,523, now Pat. No. 2,882,975, filed March 14, 1956,

in. the name of Richard 'A. Hirsch et al., and assigned 7 to the assignee of this invention, the master gear 20 has associated therewith a mechanical pitch lock designated 4 generally by the numeral 21 and a mechanical low pitch distributor valve for directing the high pressurev fluid. to l stopdesignated, generally by the numeral 22. The construction of the mechanical pitch lock and the mechanical pitch stop, per se, constitute no part of this invention. However, the functional relationship of these safety devices. to the propeller control system is within the scope of this invention. It suflices to say that the mechanical pitch lock 21 is moved into the operating position by a plurality of springs 23 so that the nonrotatable ratchet teeth 24 thereof engage a series of ratchet teeth 25 formed integral with the'master gear 20. When the ratchet teeth 24 engage the ratchet teeth 25 rotation of the master gear in the decrease pitch direction is precluded, although rotation of the master gear in the increase pitch direction is permitted due to the ratchet teeth construction. The mechanical pitch lock is normally maintained in the release position by the application of fluid under pressure to servo chamber 26.

The pitch stop 22 includes a flange element having a plurality of circumferentially spaced lugs 27 thereon which rotate with the master gear 20. The lugs 27 can be engaged by a set of complementary, nonrotatable lugs mounted on an axially movable member 28. The member '28 is engaged by the springs 23 which normally position the lugs of the member 28 in the path of movement of lugs 27. The low pitch stop can be released to permit movement of the blades to a negative pitch position by the application of fluid under pressure to servo chamber 29.

As alluded to hereinbefore, the major components of the hydraulic control system are disposed within a regulator assembly rotatable with the propeller hub. The propeller control system includes a plurality of pumps 30 which are driven incident to the propeller rotation, and are operable to draw fluid from the rotating reservoir and supply the fluid under pressurethrough check valves 31'to high pressure conduit 32. The high pressure conduit 32 communicates with a constant speed, or governor valve assembly, 40 and also with a check valve 33 of the feathering pump and reservoir assembly 34 which is connected to and rotatable with the hub. The propeller control system also includes a feathering valve assembly designated generally by the numeral 35, a solenoid valve assembly designated generally by the numeral 36, and a pitch stop and pitch lock valve assembly 37. High pressure conduit 32 communicates withport 38 of a pressure reducer valve designated generally by the numeral 39. The pressure reducer valve 39 includes a plunger 41 which is biased downwardly as viewed in the drawing by means of a spring 42. It is to be understood that all of the components in the regulator, namely valve assemblies 35, 36, 37 and 40 are subject to centrifugal force in the direction of arrow 4201. Land 42b on the plunger 39 controls a throttling port for .43, which is connected at one side through a restriction 44 to the bottom of the plunger, namely, servo chamber 45. The plunger land 42b throttles the flow of high pressure fluid through port 43 and maintains substantially constant pressure in conduit 47 and passage 46 which pressure may be on the order of 400 psi. The low pressure servo conduit 47 communicates with the pitch lock and pitch stop assembly 37 as shown in the drawing. The low pressure passage 46 communicates with a speed sensitive valve unit designated generally by the numeral 48.

The speed sensitive valve unit 48 comprises a reciprocable sleeve 49 which is biased upwardly by means of a spring 50a. Within the sleeve is a speed sensitive plunger, or piston 50. The piston 50 is subject to the thrust of centrifugal force in the direction of arrow 42a, and a thrust of centrifugal force tends to move the piston 50 upwardly as viewed in the drawing. The lower end of the piston 50 is connected by means of a pin 51 to a lever 52, the other end of which is pivoted at 53 to the housing of the valve assembly 40. The lever 52 and the piston 50 constitute a substantial mass responsive to centrifugal force. The lever 52 is engaged by a spring 54 between the pivot points 51 and 53 and the spring 54 opposes movement of the piston 50 and lever 52 under the thrust of centrifugal force. The piston 50 includes a control land 55 which cooperates with a series of ports 56. The land 55 connects, ports 56 either. to the low servo pressure through the passage 46, or to drain. The ports 56 connect with a passage 57 which communicates with a servo chamber 58 at the lower side of a distributor valve plunger 59.

The distributor valve plunger 59 is positioned hydraulically, and thus includes a differential area piston 60, having a lower area substantially twice the size of the upper area. The upper, or smaller area of the piston 60 is continuously subjected to the low pressure fluid from passage 46. The servo chamber 58'is alternately connected to drain and to pressure by means of a land 55 of the speed sensitive piston 50, and thus, the position of the distributor valve plunger 59 can be controlled. In addition, to maintain the requisite sensitivity, the pressure in servo chamber 58 is cyclically pulsed by a mechanically actuated jitter plunger 61, controlled by a cam 62 and having a conduit 63 connected with the servo chamber 58.

The distributor valve plunger 59 is connected to a lever 64 having intermediate pivot point 65 on the housing of the valve-assembly 40. One end of the lever 64 ispivotally connected to the plunger 59 and the other end of the lever 64 is pivotally connected to the sleeve 49. This arrangement constitutes a closed loop servo'system inasmuch as movement imparted to the distributor valve plunger causes a follow-up movement of the sleeve 49 relative to the originaldisplacement of the speed sensitive piston .50 so that the rate of change of propeller pitch ,is proportional to the amount of off speed. This arrangement accomplishes proportionalized speed governing. The distributor valve plunger 59 includes space lands 66, 67 and 68. An internal passage 69 is formed in the plunger 59 for interconnecting the annular grooves between lands 66, and 67 and the annular groove between lands 68and the piston 60. The annular groove between thelands 66 and 67 communicates with a high pressure supply port 70. This high pressure supply port communicates with conduit 71, which also communicates with the. inlet port 72a of the solenoid valve assembly 36. In addition, the conduit 71 communicates with a passage 72 in the feathering-valve assembly 5. The passage 72 connects with a minimum pressure valve element 73, constituting the plunger 74 which is biased downwardly by means of a spring 75. The high pressure trunk line, or conduit, 32 communicates with a passage 76 of the feathering valve assembly 35 and thence to a port 77 of a shuttle valve 78. With the shuttle valve 78 in the position depicted in the drawing, the port 77 communicates with a port 79 and the bottom side of the minimum pressure valve plunger 74. In addition, the port 79 communicates through a branch passage to the annular groove between the lands on the plunger 74. Thus, when the pressure in conduit 32 exceeds the setting of the minimum pressure valve 74, high pressure fluid will be .spppliedto passage 72 and conduit 71 and thence to the 'supplyports of the distributor valve.

he distributor valve land 67 controls an increase pitch port which communicates with conduit 80. The distributor valve land '68'controls the decrease pitch port whiclrcommunicates with conduit 81. Conduits 80 and '81communicate respectively with increase and decrease pitch chambers 82 and 83 of the torque units. The annular'groove between land 67 and 68 communicates with a drain port 84 which connects with adrain conduit 85. Thus, when the distributor valve plunger 59 moves upwardly, the increase pitch conduit 80 is connected to the drain conduit 85, and the decrease pitch conduit 81 is connected to the high pressure conduit 71. Conversely when the distributor valve plunger 59 moves downwardly, the increase pitch conduit is connected to the high pressure conduit 71, and the decrease pitch conduit is connected to the drain conduit 85.

The'increase pitch conduit'80 includes, or connects with, abranch conduit 86 which connects with a servo chamber 87 associated'with a pressure control valve 88.

The pressure control valve 88 includes aplunger which is biased upwardly by means of a spring 89. -The upper surface of the plunger is subjected to the pressure potential in the high pressure conduit 71 through passage 90. Thus, the pressure control valve regulates the pressure potential available for varying propeller pitch. More particularly, the pressure control valve 88 assures that the pressure potential available for increasing propeller pitch will always exceed the demands of the pitch changing motor. Thus, when high pressure fluid is supplied to conduit 80, it is likewise applied to the servo chamber 87. This high pressure fluid in servo chamber 87 assists the spring 89 .in urging the plunger upwardly so as to close drain port 92. ,The pressure from conduit 71 acts in opposition to the force of spring 89 in servo chamber 87. Thus the pressure control valve will always assure that the requirements of the pitch changing motor during movement in the increased pitch direction will be maintained. l

Particular attention is called to the fact that high pressure fluid is employed 'b0th to increase and decrease propeller pitch. This arrangement enables simplification of the propeller control system, and this arrangement is only permissible since the propeller assembly includes safety devices hereinbefore alluded to. Thus, since the propeller includes a mechanical pitch lock, a mechanical low pitch stop, and a hydraulic low pitch stop to be described, the necessity for controlling the rateof decrease pitch change has been eliminated.

As seen in the drawing, the feed-back gear 20 includes a toothed flange 92a. More particularly, the flange 92a is partially toothed and is engaged by a pinion gear 93 which is connected to a rotary feed-back shaft 94. During a predetermined movement of the propeller blades, the pinion gear 93 engages the toothed portion 92a of the flange so as to rotate the shaft 94. This feed-back shaft 94 is actually only rotated during movement of the blade from the full reverse to a predetermined positive angle, for instance a positive 32.. The feedback shaft 94 extends into the regulator and is formed with a high lead screw 95. The high lead screw engages a nut 96 which is articulated to one end of a lever 97 having an intermediate pivot point 98. The other end of the lever 97 is articulated to a rod 99 which connects with a control shoe 100. The intermediate pivot point 98 is connected to a rod 101, the end of which carries a roller 102 which cooperates with a cam surface 103 formed on the lever 52. In the governing range, when the blades reach a predetermined low angle, for instance 'a positive 20, the rotary feed-back shaft 94 will position the lever 97 by pivoting the same in a clockwise direction about its articulated connection with the rod 9 9so as to move the rod' 101 to the right so that the roller 102 will engage the cam surface 103 at the end and move the piston 50 upwardly. By so doing, the flow of hydraulic fluid to the pitch changing motor in the decrease pitch direction is interrupted thereby establishing a. hydraulic low pitch stop.

Moreover, in accordance with the teachings of the aforementioned copending application Serial No. 572,348, the position of the hydraulic low pitch stop, or in other words the angular position of the propeller blades 12 at which the hydraulic low pitch stop becomes effective, can be varied through a beta follow-up system. The beta follow-up system includes the rod 99 which is connected 'to the control shoe 100, the control shoe 100 riding on a control ring 104. It is to be appreciated that the control ring 104 forms a part of the stationary adaptor assembly about which the regulator. rotates. Thus, the shoe 100 rotates about the control ring 104, and upon axial movement of the control ring 104 axial movement will be imparted to the rod 99. The control ring 104 is connected by a plurality of high lead screws, indicated by numeral 105, to a segmental internal ring s .107, t m dm cc it onw r g r,.. 2y-.Pi11 a gears 106. The condition. control gear has a radial abutment 108 extending therefrom which is. connected to the pilots power lever. The regulator'also includes a feathering control ring 109 and a speed synchronizing ring 110. The feathering control ring is connected'by a plurality of high lead screws designated by the numeral 111 to a pinion gear 111a which meshes with a feathering control gear 112. Similarly, the speed or synchronizing control ring is connected by a plurality of high lead screws designated by the numeral 113 to a pinion gear 114 which meshes with synchronizing control gear 115. Both control gears 112 and 115 have radial abutments extending therefrom through which they may berotated.

The condition control ring 104 also has control shoes 116 and 117 thereon. Control shoe 116 is connected to a rod 118 while control shoe 117 is connected to a rod 119. The rod 118 is pivotally connected to a crank arm 120 for actuating a selector valve 121a. Therod 119 is formed with three discrete cam surfaces 121, 122 and 123. The control ring 110 receives a control shoe 124 which is connected to a rod 125 having a roller 126 thereon. The roller 126 cooperates with the cam surface 127 of a lever 128. The lever 128 has an intermediate pivot at 129 to the casing of valve assembly 40 and the free end thereof engages a combined spring retainer and servo piston 130 for the governor spring 54.

The feathering control ring 109 has a control shoe 131 thereon which is connected to a rod 132 having cam surfaces 133 and 134. The cam surfaces 133, 134, 121, 122 and 123 coact with a pair of cam followers 135 and 136 mounted on a trolley 137 pivotally connected at 138 to a feathering trigger valve plunger 139.'. The plunger 139 is biased downwardly by means of a spring 140, and has a pair of spaced lands 141 and 142. The annular groove between lands 141 and 142, is always in communication with the high pressure passage 76. The land 141 controls a port 143 which is connected with a servo chamber 144 associated with the shuttle valve 78. The shuttle valve 78 includes a plurality of spaced lands 145, 146, 147 and 148 and 149. The shuttle valve 78 is biased upwardly by means of a spring 150. With the shuttle valve 78 in the position depicted in the drawing, land 146 blocks communication between ports 151 and 152, the annular groove between 147 and 148 interconnects passages 76 and 79, and the annular groove between lands 149 and 148 interconnects passages 153 and 154. Under these conditions high pressure fluid is supplied to conduit 71 and the increase pitch conduit 80 communicates with the increase pitch chambers ,82

through passages 153 and 154.

The feathering control valve assembly 35 also includes a decrease loader valve which constitutes a spring biased check valve. Since the pumps 30 normally pro; duce excess flow, the pressure control valve 88 supplies this excess flow to the controlled drain line 85. The controlled drain line 85 communicates with the top side of the decrease loader valve 155. The bottom side of the decrease loader valve 155 communicates'with port 151 and the conduit 156 which communicates with the decrease pitch conduit 81. Thus the decrease loader maintains a predetermined pressure at all times in the decrease pitch conduit 81 and in the decrease pitch chambers 83 as set forth more specifically in the aforementionedcopending applications. However, when the shuttle valve 78 is moved downwardly by pressure fiuid acting on the land 145, conduit 156 is connected to drain through ports 151 and 152, and the connection between passages 153 and 154 is interrupted. In addition, the connection between passages 76 and 79 is interrupted thereby interrupting the supply of high pressure fluid to the conduit 71 and the inlet port 70 of the distributor valve 59. Thus, when the trigger valve 139 is moved upwardly, the shuttle valve is moved downwardly to disconnect the dis-; tributor valve 59 and the speed system or governor valve 50 :from controlof the pitch changing motors. Moreover, at this time the passage 76 is connected directly to the passage 154 and thus high pressure fluid is supplied directly to the increased pitch chambers 82, while the decrease pitch chambers 83 are connected to drain through conduit 81, conduit 156, port 151, and port 152. Consequently, the propeller blades 12 will move to their feathered position.

The trigger valve 139 can be moved upwardly by either movement of rod 132 or rod 119. Thus, if the rod 132 is moved to the left as viewed in the drawing due to move ment of the feathering control ring 109 to the left, the roller 136 will engage the cam surface 134 thereby moving valve plunger 139 upwardly to interconnect passage 76 and port 143. Similarly, the rod 119 can be moved to the right so that the roller 135 engages the cam surface 121 thereby moving the plunger 139 upwardly. However, when the rod 119 is moved to the left so that the roller 135 engages the cam surface 123, movement of the rod 132 to the left so that the roller 136 engages the cam surface 134 will not impart sufficient movement to the trigger valve 139 to actuate the shuttle valve 78. This is known as the feathering block-out during operation in the manually selected blade angle regime, or beta range.

The feathering control ring gear 112 is used to initiate all normal feathering operations, and, thus, may be actuated manually during manual feathering, automatically during takeoff due to automatic feathering mechanism, or automatically during operation in the governing regime when the aircraft is in flight due to a negative torque signal sensing mechanism, as set forth in the aforementioned copending application S.N. 572,348. In addition, the condition control ring gear 107 can be actuated to call for emergency feathering by rotating the gear 107 in the clockwise direction as viewed in the drawing. By this movement, the rod 118 and the rod 99 are simultaneously moved to the right as viewed in the drawing, the rod 99 actuating the roller 102 through the link 97 and the rod 101 to cam the piston 50 upwardly so as to call for an increase in propeller pitch. At the same time, the rod 119 is moved to the right so that the roller 135 engages the cam surface 121 thereby moving the trigger valve 139 upwardly to actuate the shuttle valve 78 and call for an increase in propeller pitch. Thus, under emergency feathering conditions, if for some reason the feathering valve assembly 35 shauld be inoperative, feathering can be accomplished through the governor valve and distributor valve plunger 59.

The only way in which the feathering valve assembly 35 can be rendered inoperative is by failure of the shuttle valve 78 to move from the position it is shown in the drawing wherein ports 77 and 79 are interconnected, and passages 153 and 154 are interconnected, downwardly to a position where the connection between ports 77 and 79 is blocked and the connection between passages 153 and 154 is blocked so that port 77 is connected to passage 154. This inoperativeness could be caused by a failure in the trigger valve 139, since the trigger valve 139 controls the application of fluid under pressure to servo chamber 144 for moving the shuttle valve 78 downwardly against the force of spring 150. Since the shuttle valve 78 only has two positions, as shown in the drawing, namely, one wherein it connects the source of fluid under perssure to the supply port of the servo distributor valve 59, and a second wherein it connects the source of fluid pressure directly with the increase pitch chambers of the pitch adjusting motor, if the shuttle valve 78 does not move from the position shown in the drawing to a position where port 77 is connected with passage 154 upon actuation of the trigger valve 139 during emergency feathering, fluid under pressure will be applied to the increase pitch chamber of the pitch adjusting motorby the servo distributor valve 59.

Automatic feathering during take 011 constitutes a safety mechanism for a multipower plant aircraft. As shown in the aforementioned copending application S.N. 572,348 the feathering control ring gear 112 is positioned by a solenoid which is automatically energized upon failure of an engine during take off to feather the propeller of the failing engine. The solenoid for actuating the feathering control ring gear 112 can also be energized automatically by a negative torque signal mechanism when the aircraft is airborne, as well as by a manual switch controlled by the pilot.

The speed sensitive plunger 50 in combination with the lever 52 and the spring 54 constitute an isochronous governor assembly. That is, the governor assembly tends to maintain propeller speed substantially constant at a predetermined value. However, the force of the spring 54 can be varied by movement of the lever 128 as effected by movement of the control ring which is actuated by the synchronizing ring gear 115. The synchronizing mechanism whereby the speed of the said propeller can be synchronized with that of the master propeller by resetting the governor springs, constitutes no part of this invention.

The solenoid valve assembly 36 includes a casing having disposed therein a reciprocable plunger having space lands 161 and 162. The plunger 160 also includes armatures 163 and 164. As is conventional practice, the solenoid valve is normally spring centered by oppositely acting springs 165 and 166. The land 161 controls a supply of high pressure fluid from supply port 72a through a pressure compensating valve assembly 167 to an increase pitch conduit 168 which connects with a passage 153 of the feathering valve assembly 35. The land 162 controls a port associated with a conduit 169 which connects with the decrease pitch conduit 81. It is noted that the land 162 is of sufiicient width so that the conduit 169 can never be connected to the high pressure conduit 71, but can only be connected to drain. Thus, when the plunger 160 moves to the right, conduit 168 is connected to drain through the compensating valve assembly 167 and the port controlled by land 161, while the fluid required for a decreasing propeller pitch is supplied by the decreased loader valve 155. The solenoid valve plunger 160 is continuously reciprocated during operation in the governing regime. Control of the propeller pitch is effected by varying the dwell in the open position of the plunger 160 so that the net flow to either side of the torque units will be such as to either increase or decrease propeller pitch. Energization of the windings 170 and 171 is controlled by an electronic unit, forming no part of this invention.

The pressure compensating valve assembly comprises a check valve 172 which is connected in parallel with a pressure reducer valve 173, and which maintains a substantially constant pressure in chamber 174 so as to control the rate of flow from the increase pitch chambers to drain through the port controlled by land 161.

The pitch lock and pitch stop control valve assembly 37 includesin addition to the rotary selector valve 121a, a mechanical low pitch stop control valve 175, a mechanical pitch lock control valve 176 and a speed sensitive valve 177. These valve components are of the type disclosed in the aforementioned copending application Serial No. 571,523, and per se, constitute no part of this invention. Suffice it to say that the speed sensitive valve 177 is calibrated to move upwardly at a speed somewhat above the speed setting of the governor valve assembly. Thus, in response to a predetermined propeller overspeed, the valve 177 will move upwardly thereby connecting the servo chamber above valve 176 to drain and permit the spring 180 to move the pitch lock control valve upwardly. When the control valve 176 is moved upwardly by spring 180, the passage 181 is connected to drain through passage 182, and since the passage 181 is connected-to conduit-183 which communicates with the servo chamber 26 of the mechanical pitch lock, the springs 23 will move the ratchet element 24 into engagement with the ratchet element 25 so as to prevent further movement of the blades in the decrease pitch direction. Normally when propeller speed does not exceed a speed setting of the valve 177, the pitch lock is maintained released by the application of the low pressure fluid from conduit 47 through passage 181 to conduit 183.

When the condition control ring gear 107 is moved in the counterclockwise direction as viewed in the drawing, the control ring 104 is movedto the left thereby moving the rod 118 to the left so as to turn the crank arm 120 whereby the selector valve plunger 121a will be rotated in the counterclockwise direction so as to interconnect passage 187a with passage 184 thereby moving the pitch stop control valve- 175 downwardly against the spring 186. When the low pitch stop valve 175 is moved downwardly, low pressure fluid from conduit 47 is admitted to conduit 187 and thence to the servo chamber surrounding the piston 130 so as to reset the governor valve spring 54. Thus, by'resetting the governor valve spring 54 and lever 52 has its cam surface 103 maintained in engagement with the roller 102. Hence, by moving the rod 101 by either the rod 99 or by the feed-back shaft 94, the position of the piston 50 can be controlled so as to select any desired blade angle in the beta range. Simultaneously, low pressure fluid from conduit 47 is admitted to conduit 188 and to the servo chamber 29' of the mechanical low pitch stop to permit movement of the blades below a positive 18 and to the full reverse position.

As alluded to hereinbefore, the present invention also contemplates the use of an electric motor feathering pump which is mounted in the feathering pump and cooling reservoir assembly 34. The pump as designated by numeral 200 is driven by an electric motor 201 through a mechanical connection indicated by a line 202. The controlled drain flow in conduit 85 is supplied to the reservoir. The reservoir 34 is maintained under a slight pressure, i.e., 20 to 30 p.s.i. by having a restrictor 203 in the return line 209. This pressure is maintained in the reservoir and the controlled drain line 85 for supplying the decrease loader valve 155 and to prevent syphoning of the pitch lock release chamber and the pitch stop release chamber. In other words, some liquid is always present in the pitch stop and lock release chambers.

The regulator reservoir and the feathering pump reservoir are interconnected by a conduit designated by the numeral 209, having a restriction 203, one end of the conduit 209 opening to the center of the reservoir 34 which rotates with'the propeller. Thus, the flow of fluid through conduit 209 can only be accomplished when the reservoir34 is full of oil since the oil is normally thrown outward by centrifugal force. However, the incoming pressure oil in conduit 85 will force the cool oil through the conduit 209 and back to the regulator reservoir.

This continuous circulation of oil prevents the oil from becoming dangerously hot.

In addition, the feathering pump 200 can be energized manually by the pilot and automatically under certain conditions such as during automatic feathering and feathering due to the negative torque signal. The feathering pump is used to supply fluid under pressure to adjust the pitch position of the propeller blade when. the propeller is not rotating. In addition, the pump 200 is used to supply pressure when the propeller is rotating so slowly that the pumps 30 develop insuflicient pressure, for instance during the completion of the feathering movement of the blades 12. Thus the pump draws fluid from the reservoir 34, and the outlet of the pump is connected to the check valve 33. The check valve 33 includes a plunger 210 having a sealing land 211 and a damping land 212 which is perforated. The plunger 210 is biased by a spring 213 and a sealing land 21 1 is exposed to the oppositely acting pressures in conduit 71 and the output of the pump 200. Thus, when the pressure in the output of the pump 200 exceeds the combined force of the pressure in conduit 71 and the spring 213, it being remembered that centrifugal force acts upwardly on the plunger 210, the outlet of pump 200 will be connected to the high pressure conduit 32. In addition, the outlet of pump 200 is connected by conduit 214 to a pressure control valve 215. The pressure control valve includes a centrifugally responsive plunger 216 which is acted upon by the output pressure .of the pump 200 as well as a spring biased centrifugally responsive valve 217.. The feathering pressure control valve 215 controls the output pressure of the pump 200, and since the centrifugally responsive element 217 is connected to the pressure control valve 216 through a lever 218, the pressure of the pump 200 is proportion to the speed of the propeller rotation when the propeller is rotating. That is, the pressure outputof the pump 200 is determined by the spring load on element 217 and centrifugal force when the propeller is rotating. ,However, when the propeller is stationary the spring load on the element 217 alone determines the output pressure of the pump 200.

Operation of the propeller mechanism is substantially as follows. During operation in the speed governing regime, propeller pitch is under control of the distributor valve 59. Thus, during propeller over-speeding, the speed responsive piston moves upwardly to connect servo chamber 58 to drain, whereupon the constant low pressure acting on the smaller area of piston 60 will move the distributor valve plunger 59 downwardly. This downward movement of the plunger 59 will move the sleeve 49 upwardly through the link 64 in a follow-up relation so that ports 56 will be closed, by land 55. With the distributor valve 59 moved downwardly, high pressure fluid from conduit 71 is supplied to the increase line while the decrease pitch line 81 is connected to drain. Thus the pitch of the propeller blades will be moved in the increase direction so as to reduce the over-speed.

Conversely when the propeller speed falls below the speed setting of the governor, the piston 50 will move downwardly thereby supplying low pressure fluid through ports 56 to the servo chamber 58 and effecting upward movement of the distributor valve plunger 59. Upward movement of the plunger 59 will result in downward movement of the sleeve 49 in a follow-up manner so as to again close the ports 56. With the plunger 59 moved upwardly the decrease pitch conduit 81 is connected to high pressure fluid while the increase pitch conduit 80 is connected to drain so that the propeller blades will move in the decrease pitch direction thereby permitting propeller to increase its speed.

When the trigger valve 139 of the feathering control valve assembly is actuated by either rod 132 or rod 119, the shuttle valve 78 interrupts the supply of high pressure fluid to the conduit 71 thereby disabling the distributor valve 59 and the governor valve. At this time, the increase pitch chambers are connected directly to the output of the pumps through high pressure conduit 32 and the decrease pitch chambers are connected to drain. This feathering operation is used during manual feathering, emergency feathering, automatic feathering, and negative torque signal feathering. It should be pointed out that the negative torque signal feathering mechanism is of the uncommitted type, whereas the automatic, manual and emergency feathering systems are of the committed type. Emergency feathering means feathering by actuating the control ring gear 107 to manually position the governor pilot valve and the trigger valve of the feathering valve assembly. Thus, emergency feathering will only be used when the solenoid for actuating the feathering control ring gear 112 is inoperative for any reason, such as a failure of the electrical power supply system of the aircraft.

In the beta range, the condition control ring gear 107 is manipulated manually by the pilot to position the roller 102 with respect to the cam surface 103, it being realized that the cam surface 103 is maintained in engagement with the roller 102 by virtue of increasing the load on the spring 54 through the piston 130 which is actuated by the fluid controlled by the rotary selector valve 121a. At this time, if the rod 101 is moved to the left, thereby calling for a decrease pitch movement of the blades, the piston 50 will move downwardly so as to supply low pressure fluid to the servo chamber 58 moving the distributor valve 59 upwardly. This will cause the application of pressure fluid to the decrease pressure chambers while the increase pitch chambers are connected to drain. When the angle selected by the pilot has been obtained by the blades, the feed-back mechanism comprising sector gear 92, pinion gear 93, and the rod, or shaft, 94 will reposition the roller 102 through rod 101 and link 97 so as to interrupt further application of pressure fluid to the torque units. Thus in the beta regime any specific angle between the full reverse angle and the low positive pitch stop angle of 20 can be selected by the pilot.

During emergency feathering, as alluded to hereinbefore, the rod 99 is moved to the right thereby camming the piston 50 upwardly through link 97, rod 101 and roller 102 so as to effect downward movement of the distributor valve plunger 59. At the same time, the rod 119 is moved to the right so as to effect upward movement of the trigger valve 139 through the trolley 137, the roller 135 and the cam surface 121. However, if for some reason the shuttle 78 should fail to operate, nevertheless high pressure fluid will be directed to the increase pitch chambers of the torque units to increase propeller pitch by the distributor valve 59. However, if the feathering control valve 35 is working properly, the shuttle valve 78 will disable the governor valve by cutting off the supply of high pressure fluid thereto.

From the aforegoing it is readily apparent that the present invention provides a simplified hydraulic control system for a variable pitch propeller, the simplification being possible by virtue of incorporating the various safe- -ty devices for preventing movement of propeller blades to a dangerously low angle upon a malfunction.

While the embodiment of the present invention as disclosed herein constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in a beta range, and feathering operation, the combination including, fluid pressure operated means for adjusting propeller pitch, a source of fluid under pressure, first valve means operable to control said pitch adjusting means during propeller operation in the regimes of constantspeed and the beta range, second valve means serially connected between said source of fluid under pressure. and said first valve means and operable to control said pitch adjusting means during feathering operation of said propeller, first means operable to actuate the second valve means to initiate feathering operation of said propeller, manually operable means for selectingthe regime of propeller operation, and means operable during propeller operation in the beta range for preventing actuation of the second valve means by operation of said first means.

-2. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in a beta range, and feathering operation, the combination including, fluid pressure operated means for adjusting propeller pitch, a source of fluid under pressure, first valve means operable to control said pitch adjusting means during propeller operation in the regime of constant speed and the beta range, second valve means serially connected between said source of fluid under pressure and said first valve means and operable to con- 12 trol said pitch adjusting means during feathering operation of said propeller, said second valve means including a valve element having a pair of interconnected cam followers for positioning the same, a pair of independently movable cams engageable with said cam followers, first means operable to move one of said cams to position said valve element and actuate the second valve means to initiate feathering operation of said propeller, manually operable means for selecting the regime of propeller operation, and means operable during propeller operation in the beta range to move the other cam and render said one cam inoperative to position said valve element and thereby prevent actuation of the second valve means by operation of said first means.

3. The combination set forth in claim 2 wherein said pair of interconnected cam followers are mounted on a trolley, and wherein said trolley is pivotally connected to said valve element.

4. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in a beta range, and feathering operation, the combination including, fluid pressure operated means for adjusting propeller pitch, a source of fluid under pressure, a servo actuated distributor valve for controlling the flow of fluid to and from said fluid pressure operated means during propeller operation in the regimes of constant speed and the beta range, a governor pilot valve connected between said source of fluid pressure and said servo actuated distributor valve for controlling the position thereof, manually operable means to position said governor pilot valve to select any blade angle in the beta range during propeller operation in said beta range, feedback operated means connected with said propeller for repositioning said governor pilot valve when the selected blade angle has been attained during operation in said beta range, a feathering valve serially connected between said source, said servo actuated distributor valve and said fluid pressure operated means, said feathering valve having a first position wherein it connects said source of fluid under pressure with said distributor valve and a second position wherein it interrupts the connection between said source and said distributor valve and establishes a direct connection between said source and said pitch adjusting means, first means operable to effect movement of said feathering valve from said first position to said second .position to initiate feathering operation of said propeller, manually operable means for selecting the regime of propeller operation, and means operable during propeller operation in the beta range for preventing movement of said feathering valve from said first position to said second position by operation of said first means.

5. The combination set forth in claim 4 including spring means normally maintaining said feathering valve in said first position, servo means operable to move said feathering valve to said second position, and a trigger valve connected between said source and said servo means for controlling the actuation thereof.

6. The combination set forth in claim 5 including a pair of interconnected cam followers for positioning said trigger valve, and wherein said first means comprise a first cam engageable with one of said cam followers for positioning said trigger valve to interconnect said source and said servo means.

7. The combination set forth in claim 6 wherein the means operable to prevent actuation of the feathering valve by operation of said first means during propeller operation in the beta range comprises a second cam engageable with the other of said cam followers for rendering said first cam inoperative to actuate said trigger valve.

8. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in beta. range. and feathering operation, the combination including, power operated means for adjusting propeller, pitch, first control means operable to control the pitch adjusting means during propeller 0poration in the regimes of constant speed and the beta range, second control means serially connected with said first control means and said power operated means and operable to control normal feathering operation of said propeller, first means operable to actuate said second control means to initiate normal feathering operation of said propeller, manually operable means for selecting the regime of propeller operation, and means operable during propeller operation in the beta range for preventing actuation of said second control means by operation of said first means.

9. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in a beta range, and feathering operation, the combination including, fluid pressure operated means for adjusting propeller pitch, pressure developing means energized incident to propeller rotation, first valve means for controlling the flow of fluid under pressure from said pressure developing means to said pitch adjusting means during propeller operation in the regimes of constant speed and the beta range, second valve means serially connected between said pressure developing means, said first valve means and said pitch adjusting means for controlling the flow of fluid therebetween during normal feathering operation of said propeller, a normal feathering control to actuate said second valve means to initiate normal feathering operation of said propeller, manually operable means for selecting the regime of propeller operation, and means operable during propeller operation in the beta range for preventing actuation of said second valve means by operation of said normal feathering control.

10. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in a beta range, and feathering operation, the combination including, fluid pressure operated means for adjusting propeller pitch, a source of fluid under pressure energized incident to propeller rotation, first valve means for controlling the flow of fluid between said source of fluid under pressure and said pitch adjusting means during propeller operation in the regimes of constant speed and the beta range, second valve means serially connected between said source, said first valve means and said pitch adjusting means, said second valve means having a first position wherein it connects the source of fluid under pressure with said first valve means and a second position wherein it interrupts the connection between said source and said first valve means and establishes a direct connection between said source and said pitch adjusting means to effect normal feathering operation of said propeller, a normal feathering control operable to move said second valve means from said first position to said second position, manually operable means for selecting the regime of propeller operation, and means operable during propeller operation in the beta range for disabling said normal feathering control.

11. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in a beta range, and feathering operation, the combination including, fluid pressure operated means for adjusting propeller pitch, a source of fluid under pressure energized incident to propeller rotation, first valve means for controlling the flow of fluid between said source of fluid under pressure and said pitch adjusting means during propeller operation in the regimes of constant speed and the beta range, second valve means serially connected between said source, said first valve means and said pitch adjusting means, said second valve means having a first position wherein it connects the source of fluid under pressure with said first valve means and a second position wherein it interrupts the connection between said source and said first valve means and establishes a direct connection between said source and said pitch adjusting means to effect normal feathering operation of said propeller, a normal feathering control operable to move said second valve means from said first position to said second position, and an emergency feathering control operable to move said second valve means from said first position to said second position to initiate emergency feathering of said propeller.

12. The combination set forth in claim 11 including spring means normally maintaining said first valve means in said first position, servo means operable to move said second valve means to said second position, and a trigger valve connected between said source of fluid under pressure and said servo means for controlling the actuation thereof.

13. The combination set forth in claim 12 including a pair of interconnected cam followers for positioning said trigger valve, and wherein said normal feathering control comprises a first cam engageable with one of said cam followers for positioning said trigger valve, wherein said emergency feathering control comprises a second cam engageable with the other of said cam followers for positioning said trigger valve.

14. In a variable pitch propeller having several regimes of propeller operation including constant speed operation, operation in a beta range, and feathering operation, the combination including, fluid pressure operated means for adjusting propeller pitch, a source of fluid under pressure, a servo actuated distributor valve for controlling the flow of fluid between said source of fluid to pressure and said pitch adjusting means in the regimes of constant speed and the beta range, a governor pilot valve connected between said source of fluid under pressure and said servo actuated distributor valve for controlling the position thereof, a feathering valve serially connected between said source, said distributor valve and said pitch adjusting means, said feathering valve having a first position wherein it connects said source with said servo distributor valve and a second position wherein it interrupts the connection between said source and said distributor valve and establishes a direct connection between said source and said pitch adjusting means for controlling the flow of fluid therebetween during feathering operation of said propeller, a normal feathering control operable to move said feathering valve from said first position to said second position to initiate normal feathering operation of said propeller, and an emergency feathering control operable to move said feathering valve from said first position to said second position and simultaneously position said governor pilot valve so as to effect movement of said distributor valve to a position calling for propeller feathering whereby if the feathering valve fails to move from said first position to said second position upon actuation of the emergency feathering control said distributor valve will initiate emergency feathering operation of said propeller.

15. The combination set forth in claim 14 including first cam actuated means for controlling the position of said governor pilot valve, second cam actuated means for controlling the position of said feathering valve, and wherein said emergency feathering control includes operatively interconnected means for simultaneously operating said first and second cam actuated means.

References Cited in the file of this patent UNITED STATES PATENTS Hirsch Sept. 4, 1956

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