US2974729A - Controllable pitch propeller - Google Patents

Description

March 14, 1961 w. B. VOISARD CONTROLLABLE PITCH PROPELLER 2 Sheets-Sheet 1 Filed July 30, 1958 FIG-1 INVENTOR. WALTER B. VOISARD ATTORNEYS March 14, 1961 w. B. VOISARD 2,974,729

CONTROLLABLE PITCH PROPELLER Filed July 30, 1958 2 Sheets-Sheet 2 INVENTOR. WALTE R B. VOI SAR D ATTORNEYS 2,974,729 CONTROLLABLE PITCH PROPELLER Walter B. Voisard, Dayton, Ohio, assignor to McCauley Industrial Corporation, Dayton, Ohio, a corporation of New York Filed July 30, 1958, Ser. No. 751,912

11 Claims. (Cl. 170-,-160.32)

This invention relates to controllable pitch propellers for aircraft. 1 The invention has particular relation to a propeller control system of-the type wherein a hydraulic motor responsive to engine speed is arranged to urge the propeller blades in the direction to reduce their pitch against the biasing force ofa control spring urging the blades to-" wards a maximum pitchposition, which may be full feathered position or whatever other maximum pitch' position is desired.

In a propeller control system of this type, wheneverthe hydraulic pressure fails or is otherwise insufilcient to counterbalance theforce of the control spring, the spring will automatically move the blades to their maximum pitch position unless some provision is made to the contrary.- This may be a desirable result for a feathering propeller in the event of engine failure in flight, since it will automatically feather the propeller upon such failure of the hydraulic control pressure. It is less desirable, however, if the same action occurs when the engine is shut off with the plane on the ground, since this means that the next time the engine is subsequently started, it must be done against the load created by having the propeller blades in their maximum pitch position in which they offer maximum resistance to turning over the engine.

It is a primary object of the present invention to provide a novel, simple and effective stop mechanism for incorporation with a propeller control system of the type outlinedabove which isso constructed and arranged that it will oiier no interference to operation of the control system when the plane is in flight, but when the engine is shut ofi while the plane is on the ground, it will hold the blade in a desired low pitch position facilitating restarting of the engine.

It is particularly an object of the invention to provide a stop mechanism as outlined-above-which is independent of the engine speed but is responsive to acceleration and deceleration of the engine irrespective of the actual engine speed.

A further object of the invention is to provide a stop mechanism as outlined above wherein a latching member is mounted in the rotary hub structure and is normally biased to a latching position wherein it will engage a fixed stop to block movement of the piston in the direction to increase blade pitch beyond an intermediate position corresponding to --a relatively low pitch, and wherein an inertia weight responsive to deceleration of the engine is effective to move this latching member to a release position to provide for feathering of the propeller.

It is also an object of the invention to provide a stop mechanism as outlined above which is of such structure and operating characteristics that all the moving parts thereof may be mounted within the hydraulic motor component of the propeller control system and will therefore be immersed in hydraulic fluid during use for maintained lubrication as well as-protection against corrosion and other damage.

; Additional objects and advantages of the invention will 2,974,729 Patented Mar. 14, 196 1 ice be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings- Fig. 1 is a partially diagrammatic view generally in axial section through an airplane hub structure constructed in accordance with the invention;

Fig. 2 is an enlarged fragment of Fig. 1 showing parts of the stop mechanism in section and in the relative positions which they occupy when the propeller is being feathered;

Fig. 3 is an enlarged view taken as indicated by the line 3-3 of Fig. 2;

when the propeller is accelerating or blocked in interforward end of the engine shaft 12. The hub 10 carries piston rod 23 to the interior of the cylinder 20 from the usual pump 40 and reservoir 41 through the line 42v and Fig. 4.is a fragmentary section on the line 4-4 of Fig. 3 on a reduced scale; and

Fig. 5 is a fragmentary view similar to Fig. 3 but show ing the parts in the relative positions which they occupy mediate pitch position.

Referring to the drawings, which-illustrate a preferred' embodiment of the invention, Fig. 1 shows at 10 the hub of an airplane propeller which is secured at 11 to the the mountings 13 for the roots of the propeller blades indicated diagrammatically at 15, and the mountings 13 are rotatable on the hub 10 to change the pitch of the blades.-

Fig. 1 also illustrates diagrammatically at 16 a counterweight such as should be attached as at 17 to each blade" mounting in such manner as to overcome thecentr'ifugal' twisting movement of the blade.

The system for controlling the pitch of the blades 15. includes a hydraulic motor comprising a cylinder 20; which is mounted on the front end of the hub 10 as by bolts 21 to form a portion of the rotary hub structure The complementary piston 22 in cylinder 20 is secured on' the forward end of a hollow piston rod 23, as by bolts 24, J

and the piston 22 includes a tubular sleeve 25 which forms an extension of the piston rod 23. The piston rod 23 is connected by a link 26 with each of the blade mountings} 13 in such manner that when the piston 22 is at its limitposition of movement outwardly of the cylinder 20, to the position.

The low pitch stop for the piston 22 limiting its movement outwardly of the cylinder 20 is formed by a flange. portion 30 of the hub 10 which projects radially inwardly beyond the inner wall of the cylinder. The piston 22 is continually biased in the direction to increase the bladej pitch by one or more control springs 33 mounted in thehub structure between the piston 22 and the guide flange 35 at the rearward end of thehub 10 through which the piston rod 23 extends for reciprocation with the piston.- The force opposing the spring 33 to urge the piston 22 in P the direction to decrease pitch is provided by hydraulicfluid supplied through the hollow crank shaft 12 and the transfer bearing 43.

A governor 44 and governor valve 45, which may be of conventional construction, control the pressure supply,

to the cylinder 20 in accordance with engine speed to change the blade pitch as required to maintain the engine speed constant. Thus so long as the engine speed is below the control speed for which the governor is set, the pressure fluid will be supplied to cylinder 20 to maintain the piston 22 in the minimum blade'pitch position- When-; ever the engine speed rises above the control speed, the.

- thecylinder and thus to increase the blade pitch until .the

resulting increased load has slowed down the engine to the control speed range.

If the engine should fail in flight, or if the hydraulic fluid supply should fail for any other reason such as a broken oil line, the resulting rapid loss of pressure in cylinder 20 will allow the spring 33 to move the piston 22 all the way to its maximum or feather pitch position. Similarly feathering can be initiated by the pilot by shifting the governor valve 45 through the manual control 46-47 to its feather position wherein it connects the cylinder 20 directly with the reservoir 41 and thus relieves the entire hydraulic force opposing the control spring 33. However, the same result will occur when the engine is shut off with the plane on the ground and the hydraulic fluid leaks back to the reservoir. This would mean that the blades would be in maximum pitch position when the engine is to be started again, which would offer the maximum resistance to rotation of the engine shaft, and it is this result which the present invention prevents by the provisions of a stop mechanism assuring' that the blades remain in a relatively low pitch position after the engine is shut oflf.

Referring to Figs. 1-2, a stop member in the form of a stud 50 is mounted in the inner or forward end wall of the cylinder 20 as by screws 51, and this stud may be tubular as shown for decreased weight. The stud 50 is proportioned for telescoping engagement with the hollow piston rod 23 when the piston moves inwardly of the cylinder, and an annular shoulder 52 near the base of the stud 50 forms the feather pitch stop for inward movement of the piston and is in position for direct engagement by the forward end of the sleeve portion 25 of the piston. The stud 50 is provided with a through slot 53 which extends throughout the major portion of its length beyond the stop 52. The outer or rearward end face 55 of the stud 50 is therefore in two sections, and these sections form a shoulder which acts as an intermediate pitch stop for the piston 22 and which is utilized selectively for this purpose as now described.

An inertia Weight 60 in the nature of a flywheel is rotatably mounted on the piston sleeve 25 as by a ball bearing 61. This weight 60 includes a hub portion 62 which is directly mounted on the bearing 61 and is connected by a relatively thin radially extending web portion 63 with the outer portion 60 in order to provide the major proportion of the weight of this member at the maximum radial distance from the axis of the piston sleeve 25 while reducing to a practical minimum the overall weight of this member as a whole. The hub portion 62 of the member 60 is provided with opposed slots 64 which receive the ends of a radially arranged bar 65 as shown in Fig. 4, and the piston sleeve 25 is provided with opposed slots 66 which receive this bar 65 therethrough. A snap ring 67 holds the bar 65 in place in the slots 64.

As illustrated in Figs. 3 and 5, the slots 66 cooperate with the bar 65 to limit the rotational movement of the weight 60 on the sleeve 25 to a small angular range shown as about 45. This movement, however, is sufiicient to move the bar 65 into and out of alignment with the slot 53 in the stud 50. Thus in assembling the cylinder and piston, the parts are so aligned that when the weight 60 is at its limit of counterclockwise rotation as viewed in Fig. 3, the bar 65 will be aligned with the slot 53 for free entry therein upon movement of the piston to the left in Fig. 2, and this is the release position of the weight 60 and bar 65. When the weight 60 is rotated in clockwise direction on the sleeve 25 to its other limit position established by the bar 65 and slots 66, the bar 65 will be aligned with the end face 55 of the stud 50 for engagement thereon to block further movement of the piston to the left in Fig. 2, and this is the latching position of the weight 60 and bar 65 as shown in Fig. 5.

In the arrangement of the parts as viewed in Fig. 3, the direction of rotation of the hub structure is counterclockwise. It willtherefore be seen that the inertia forces effective on the weight 60 will urge it in clockwise direction to a retarded position establishing the latching position of the bar when the propeller is accelerating, but will urge the weight 60 in counterclockwise direction to an advanced position locating the bar 65 in its release position when the propeller is decelerating. In addition, a torsion spring 70 is mounted beneath the sleeve 25 and the weight 60 for urging the weight 60 in clockwise direction towards its latching position.

The inner end 71 of the spring 70 is received in one of the slots 66 and held in place axially by a snap ring 72, and the outer end 73 of the spring 70 is received in one of a plurality of bores 74 in the hub 62. The spring 70 should be of such force that it will hold the weight 60 in the latching position of the bar 65 when the hub is stationary or rotating at a constant positive speed but should be insufiicient to prevent movement of the weight 60 to, the release position of bar 65 whenever the hub is decelerating. These conditions are readily achieved by winding the spring 70 to the desired tension while assembling the parts and then inserting the end 73 thereof in the proper selected bore 74.

The stop mechanism of the invention will have no effect on the normal operation of the airplane in flight. More specifically, the propeller will increase or decrease pitch as required by the governor, but this variation will ordinarily be within a relatively low angular range, for example from 9'to 26. The stud 50 will be proportioned in accordance with this normal range so that its end face 55 would be engaged by the bar 65 at a slightly greater pitch, for example 30. Therefore, while the weight 60 will during normal operation move the bar 65 back and forth between its latching and release positions, the blade pitch will not increase sufiiciently to permit the bar 65 to reach the stud face 55.

If on the other handa condition should develop during flight which requires feathering of Y the propeller, the feathering operation is initiated by moving the control 47 to its feathering position in which it shifts the valve 45 to the position connecting the interior of the cylinder 20 directly with the reservoir 41 in order to effect completereliefof the pressure supply in the cylinder. The spring 33 will therefore be free to move the piston inwardly of the cylinder, and the propeller will immediately begin to decelerate, due both to the increase in pitch as well as to the fact that the motor will normally be cut off in conjunction with feathering. Deceleration of the hub will produce an inertia force effective on the weight 60 in the direction to move the bar 65 to its release position in alignment with the slot 53, and therefore the piston will be free to move to its full feathered position established by the stop shoulder 52.

Unfeathering of the propeller in flight may be accomplished by moving the control handle 47 out of its feathering position and then turning the engine over with the usual starter. As soon as sufficient pressure is built up in this way to move the piston away from stop 52, the propeller will begin to windmill, and the resulting rapid pressure build-up will move the piston back to low pitch position. The bar 65 will have no effect on this operation, since it will simply slide through the slot 53 until it is clear of the stud 50.

As noted, while it is desired in accordance with the invention that the propeller be free to feather when the engine is shut off and the hydraulic pressure is relieved in flight, it is also desired that feathering be prevented when the engine is shut off while the airplane is on the ground. Under these conditions, the control handle 47 is retained in the position causing the hydraulic fluid to be continuously supplied to the cylinder 20, and the control system will therefore retain the propeller at minimum pitch, with the piston 22 in contact with the stop 30, until the engine is completely dead. Furthermore, this pressure will remain effective for an appreciable intervahnamelya minute or more, until it is finally lost as 5 a result of gradual leakage ofthehoil back to the reservoir.41.'

During the above operation while the engine is decelerating, the inertia force on the weight 60 will retain the bar 65 in its release position, but thisis not significant because the piston is held on its low pitch stop as just described. However, when the engine is completely dead, there will be no more inertia force on the weight 60, and the spring 70 will therefore be able to return it to the latching position of the bar 65. This return movement will take place before the pressure supply in the cylinder has leaked away, and therefore when the spring 33 is finally able to move the piston inwardly of the cylinder, the bar 65 will be in latching position to engage on the stud face 55 and thereby to block further movement of the piston beyond the intermediate pitch position thus established.

The invention accordingly providesa stop mechanism ofiering a variety of important practical advantages. It is simple to construct and install, it requires a minimum of maintenance, and it is independent of engine speed and: responsive only to acceleration and deceleration of the engine. It is also simple to proportion the working parts, and particularly the stud 50, to establish whatever intermediate pitch position is desired for a particular operating range for the propeller, and it is not a serious disadvantage if such position be within the operating range. it should also be noted that the operating parts are not limited to installation within the cylinder 20 so long as the operating principles of the invention are maintained, but the illustrated arrangement does offer the special advantage that all the moving parts are located within the hydraulic pitch control motor where they are constantly immersed in oil and thus kept thoroughly lubricated as well as protected against corrosion and possible interference by weather conditions such as icing which could affect them if they were in an exposed location. All these advantages are provided in the invention without aiiecting the normal operation of the control system with which it is used.

Cross reference is made to my copending application Serial No. 827,963, filed July 17, 1959, and assigned to the same assignee as this application.-

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a stationary cylinder and a movable piston, means connecting said piston with said supporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston inwardly of said cylinder, means including a line connected with said cylinder for supplying hydraulic pressure fluid to member supported on said hub structure for movement relative thereto betweena release position oifering no resistance to the movement of said piston and a latching position blocking said piston from movement inwardly 5 structure for biasing said latching member to said latch ing position to block inward movement of said piston beyond said intermediate position when said drive engine is shut ofi while said pressure fluid is being supplied to said cylinder, inertia means mounted on said hub structure for movement relative thereto in response to deceleration of said hub structure, and means connecting said latching member with said inertia means for causing said latching member to move against said biasing means to said release position in response to said movement of said inertia means to provide for feathering of said propeller when said pressure fluid supply is relieved by operation of said valve means.

2. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a' stationary cylinder and a movable piston, means connecting said piston with saidsupporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston inwardly of said cylinder, means including a line connected with said cylinder for supplying hydraulic pressure fluid to said cylinder to move said piston against said control spring, selectively operable valve means in said line for relieving said pressure fluid supply, a stop mechanism for selectively blocking increase in the pitch of said blades beyond a predetermined low pitch including a latching member supported on said piston for movement relativethereto between a release position ofien'ng no resistance to the movement of said piston and a latching position blocking said piston from movement inwardly of said cylinder beyond a position corresponding to said predetermined low blade pitch, means connected between said latching member and said hub structure for biasing said latchingmember to said latching position to block inward movement of said piston beyond said intermediate position when said drive engine is shut ofl? while said pressure fluid is being supplied to said cylinders, inertia means mounted on said hub structure for movement relative thereto in response to deceleration of said hub structure, and means connecting said latching member'with said inertia means for causing said latching member to move against said biasing means to said release position in response to said movement of said inertia means to provide for feathering of said propeller when said pressure fluid supply is relieved by operation of said valve means;

3, In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a stationary cylinder and a movable piston, means connecting said piston with said supporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston inwardly of said cylinder, means including a line connected with said cylinder for supplying hydraulic pressure fluid to said cylinder-to move said piston against said control spring, selectively operable valve means in said line for relieving said pressure fluid supply, a stop mechanism for selectively blocking increase in the pitch of said blades beyond a predetermined low pitch including a latching member supported on said hub structure for rotational movement relative thereto between a release position oifering no resistance to the movement of said piston and a latching position blocking said piston from movement inwardly of said cylinder beyond a position corresponding to said predetermined low blade pitch, means .con-

nected between said latching member and said hub structure for biasing said latching member to said latching position to block inward movement of said piston beyond said intermediate position when said drive engine is shut off while said pressure fluid is being supplied to said cylinder, inertia means mounted on said hub structure for movement relative thereto in response to deceleration of said hub structure, and means connecting said latching member with said inertia means for causing said latching member to move against said biasing means to said release position in response to said movement of said inertia means to provide for feathering of said propeller when said pressure fluid supply is relieved by operation of said valve means.

4. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a stationary cylinder and a movable piston, means connecting said piston with said supporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston inwardly of said cylinder, means including a line connected with said cylinder for supplying hydraulic pressure fluid to said cylinder to move said piston against said control spring, selectively operable valve means in said line for relieving said pressure fluid supply, a stop member in said cylinder for limiting movement of said piston in the direction of increase the pitch of said blades beyond an intermediate position corresponding to a predetermined low pitch, a latching member supported on said piston for movement relative thereto between a release position with respect to said stop member offering no resistance to the movement of said piston and a latching position for engagement with said stop member locking said piston from movement inwardly of said cylinder beyond said intermediate position, means connected between said latching member and said hub structure for biasing said latching member to said latching position to block inward movement of said piston beyond said intermediate position when said drive engine is shut off while said pressure fluid is being supplied to said cylinder, inertia means mounted on said hub structure for movement relative thereto in response to deceleration of said hub structure, and means connecting said latching member with said inertia means for causing said latching member to move against said biasing means to said release position in response to said movement of said inertia means to provide for feathering of said propeller when said pressure fluid supply is relieved by operation of said valve means.

5. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a stationary cylinder and a movable piston, means connecting said piston with said supporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston in- Wardly of said cylinder, means including a line connected with said cylinder for supplying hydraulic pressure fluid to said cylinder to move said piston against said control spring, selectively operable valve means in said line for relieving said pressure fluid supply, a stop member in said cylinder for limiting movement of said piston in the direction to increase the pitch of said blades beyond an intermediate position corresponding to apredetermined low, pitch, an inertia .weight: mounted on-said 'pistonfor oscillating movement between advanced and retarded positions in response to deceleration and acceleration respectively of said hub structure, a latching member supported on said inertia weight for movement therewith between a release position corresponding to said advanced position of said weight and out of line with said stop member and a latching position corresponding to said retarded position of said weight and in line with said stop member for engagement therewith, and means connected between said piston and said weight biasing said weight to said retarded position to eifect blocking of inward movement of said piston beyond said intermediate position by said latching and stop members when said drive engine is shut off while said pressure fluid is being supplied to said cylinder.

6. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a stationary cylinder and a movable piston having a hollow piston rod, means connecting said piston with said supporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston inwardly of said cylinder, means including a line connected with said cylinder and means responsive to the operation of said drive engine for supplying hydraulic pressure fluid to said cylinder to move said piston against said control spring, a stud mounted on the inner end wall of said cylinder in position for telescoping engagement with said piston rod upon movement of said piston inwardly of said cylinder and including a shoulder adapted to form a stop for said piston, a latching member for said piston, means mounting said latching member on the inner face of said piston for movement relative thereto between a release position out of line with said shoulder of said stud and a latching position overlying said shoulder for engagement therewith, said stud being proportioned for engagement by said latching member with said shoulder upon movement of said piston to an intermediate low blade pitch position adjacent said limit position, means connected between said latching member and said piston for biasing said latching member to said latching position to block inward movement of said piston beyond said intermediate position when said drive engine is shut 011? while said pressure fluid is being supplied to said cylinder, inertia means mounted on said piston for movement relative thereto in response to deceleration of said hub structure, and means connecting said latching member with said inertia means for causing said latching member to move against said biasing means to said release position in response to said movement of said inertia means to provide for feathering of said propeller when said pressure fluid supply is relieved.

7. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a stationary cylinder and a movable piston having a hollow piston rod, means connecting said piston with said supporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston inwardly of said cylinder, means including a line connected with said cylinder and means responsive to the operation of said drive engine for supplying hydraulic pressure fiuid to said cylinder to move said piston againstsaid control spring, a stud mounted on-the inner end W811 of said cylinder in position for telescoping engagement with said piston rod upon movement of said piston inwardly ofsaid cylinder, said stud having a transverse slot therethrough extending substantially the full length thereof, a latchingmember for said piston, means mounting said latching member on the inner face of said piston for movement relative thereto between a release position in line with said slot and a latching position overlying the end face of said stud for engagement therewith, said stud being proportioned for said engagement by said latching member upon movement of said piston to an intermediate low blade pitch position adjacent said limit position, means connected between said latching member and said piston for biasing said latching member to said latching position to block inward movement of said piston beyond said intermediate position when said drive engine is shut ofl whilesaid pressure fluid isbeing supplied to said cylinder, inertia means mounted on said piston for movement relative thereto in response to deceleration of said hub structure, and means connecting said latching member with said inertia means for causing said latching member to move against said biasing means to said release position in response to said movement of said inertia means to provide for feathering of said propeller when said pressure fluid supply is relieved.

8. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor within said hub structure including a stationary cylinder and a movable piston having a hollow piston rod, means connecting said piston with said supporting means to decrease the pitch of said blades in response to movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to movement of said piston inwardly of said cylinder, a control spring arranged to bias said piston inwardly of said cylinder, means including a line connected with said cylinder and means responsive to the operation of said drive engine for supplying hydraulic pressure fluid to said cylinder to move said piston against said control spring, a stud mounted on the inner end wall of said cylinder in position for telescoping engagement with said piston rod upon movement of said piston inwardly of said cylinder and including a shoulder adapted to form a stop for said piston, a flywheel mounted on the face of said piston for relative advanced and retarded rotational movement coaxial therewith in response to the inertia resulting from deceleration and acceleration respectively of said hub structure, a latching member mounted on said flywheel, means limiting said movement of said flywheel between an advanced release position wherein said latching member is out of line with said shoulder and a retarded latching position I wherein said latching member overlies said shoulder for engagement therewith, said stud being proportioned for said engagement by said latching member with said shoulder upon movement of said piston to an intermediate low blade pitch position adjacent said limit position, and means connected between said flywheel and said piston for biasing said flywheel to said advanced position to block inward movement of said piston beyond said intermediate position when said drive engine is shut ofi while said pressure fluid is being supplied to said cylinder.

9. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a hydraulic motor-within said hub structure comprising a cylinder and a relatively movable piston assembly including a hollow piston rod, means connecting said motor with said supporting means to decrease the pitch of said blade in response to relative outward movement of said piston assembly and said cylinder and to increase said blade pitch to feathered position in response to relative inward movement of said piston assembly and said cylinder, a control spring urging structure, a latching member carried by said flywheel,

a stop mounted on said hub structure for limiting relative inward movement of said cylinder and said piston assembly by engaging said latching member, means limiting said movement of said flywheel between an advanced release position wherein said latching member is out of line with said stop and a retarded latching position wherein said latching member overlies said stop for engagement therewith, said stop being located for said engagement by said latching member upon relative movement of said piston assembly and said cylinder to an intermediate low blade pitch position, and means biasing said flywheel to said advanced position to block relative inward movement of said piston assembly and said cylinder beyond said intermediate position when said drive engine is shut off while said pressure fluid is being supplied to said cylinder.

10. In a control system for the blades of an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a relatively movable cylinder and piston forming a hydraulic motor within said hub structure, means connecting said motor with said supporting means to decrease the pitch of said blades in response to relative movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to relative movement of said piston inwardly of said cylinder, acontrol spring urging relatively inward movement of said piston and said cylinder, means including a line connected with said cylinder for supplying hydraulic pressure fluid to said motor to cause relative movement of said piston and said cylinder against said control spring, selectively operable valve means in said line for relieving said pressure fluid supply, a flywheel mounted in said hub structure for rotational movement about the axis of said hub structure, cooperating means carried by said flywheel and said hub structure establishing a limit position for said rotational movement of said flywheel in the direction opposed to the direction of rotation of said hub structure, means connected between said flywheel and said hub structure for biasing said flywheel to said limit position, complementary latch means on said hub structure and said flywheel arranged for latching engagement in said limit position of said flywheel blocking said piston and cylinder from relative inward movement beyond an intermediate position corresponding to a predetermined intermediate blade pitch position, and said flywheel and said biasing means being proportioned to provide for rotational movement of said flywheel against said biasing means away from said limit position in response to deceleration of said hub structure to prevent engagement of said latch means and thereby to provide for feathering of said propeller when said pressure fluid supply is relieved by operation of said valve means.

11. In a control system for the blades or" an adjustable pitch propeller having a drive engine, the combination of a rotary hub structure including adjustable supporting means for said blades, a relatively movable cylinder and piston forming a hydraulic motor within said hub structure, means connecting said motor with said supporting means to decrease the pitch of said blades in response to relative movement of said piston outwardly of said cylinder and to increase said blade pitch to feathered position in response to relative movement of said piston inwardly of said cylinder, a control spring urging relatively inward movement of said piston and said cylinder, means including a line connected with said cylinder for supplying hydraulic pressure fluid to said motor to cause relative movement of said piston and said cylinder against said control spring, selectively operable valve means in said line for relieving said pressure fluid supply, a flywheel mounted in said hub structure for rotational movement about the axis of said hub structure, cooperating means carried by said flywheel and said hub structure for establishing first and second limit positions for said rotational movement of said flywheel, means connected between said flywheel and said hub structure for biasing said flywheel oppositely to the direction of rotation of said hub structure to said first limit position, complementary latch means on said hub structure and said flywheel arranged for relative release in said second position of said flywheel and for latching engagement in said first limit position of said flywheel blocking said piston and cylinder from relative inward movement beyond an intermediate position corresponding to a predetermined intermediate blade pitch position, and said flywheel and said biasing means being proportioned to provide for rotational movement of said flywheel against said biasing means to said second limit position in response to deceleration of said hub structure to provide for feathering of said propeller when said pressure fluid supply is relieved by operation of said valve means.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATESPATENT OFFICE CERTIFICATION er CORRECTION Patent No, 2 9741 729 March 14L 1961 Walter B. Voisard I It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 7, line 38 for locking read blocking line 66 for "connected read connecting Signed and sealed this 15th day of August 19610 (SEAL) Attest: ERNEST W, SWIDER DAVID L LADD Attesting Officer Commissioner of Patents

Images