US2514477A

US2514477A - Variable pitch propeller

Info

Publication number: US2514477A
Application number: US598791A
Authority: US
Inventors: Maurice E Cushman
Original assignee: Curtiss Wright Corp
Current assignee: Curtiss Wright Corp
Priority date: 1945-06-11
Filing date: 1945-06-11
Publication date: 1950-07-11
Anticipated expiration: 1967-07-11

Description

y 1950 M. E. CUSHMAN 2,514,477

VARIABLE PITCH PROPELLEB Filed June 11, 1945 4 Sheets-Sheet 1 INVENTOR J/auricefl (mime/z ATTORNEY y 1950 M. E. CUSHMAN 2,514,477

VARIABLE PITCH PROPELLER Filed June 11, @945 4 Sheets-Sheet 2 y 1950 M. E. CUSHMAN 2,514,477

VARIABLE PITCH PROPELLER Filed June 11, 1945 4 Sheets-Sheet 3 c; I A INVENTOR .flfburz'cel'. (us/2111a]:

ATTO R N EY July 1, 1950 M. E. cusHMAN 2,514,477

VARIABLE PITCH PROPELLER Filed June 11, 1945 4 Sheets-sheet 4 3 n renter .J/aur/refif ('us/zrllmz Gttomcg Patented July 11, 1950 VARIABLE PITCH PROPELLER Maurice E. Cushman, Verona, N. J assignor to Curtiss-Wright Corporation, a corporation of Delaware Application June 11, 1945, Serial No. 598,791

Claims.

This invention relates to variable pitch propellers, and more particularly to a hub and blade shank construction in which the blade centrifugal force is employed to counteract the blade centrifugal twisting moment.

In variable pitch propellers, the blade centrifugal twisting moment which tends to cause the blade to rotate so as to bring the blade surface into the plane of rotation, causes the pitchchanging mechanism to be heavily loaded, requiring mechanism heavier than would be required if the moment could be neutralized in some manner. Also, the power requirements in increasing pitch must be relatively high to over- ,come the twisting moment, and the speed at which changes may be effected depends upon such moment and the available power. Thus by neutralizing the twisting moment, more rapid changes in pitch could be effected with the same power.

It is accordingly one object of the present invention to neutralize the blade centrifugal twisting moment in a variable pitch propeller throughout a wide range of pitch adjustment.

Another object of the invention is to provide, in a variable pitch propeller, having a pitchchange mechanism, means for compensating the blade centrifugal twisting moment, in order to relieve the pitch-changing mechanism of the necessity for overcoming such twisting moment.

A further object of the invention is to provide in a variable pitch propeller, means for compensating the blade centrifugal twisting moment within the blade socket throughout the complete blade angle range.

The above and other novel features of the invention will appear more fully hereinafter from the following detailed description, when taken in conjunction with the accompanying drawings. It is expressly understood, however, that the drawingS are for illustrative purposes only, and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings wherein similar reference characters refer to like part throughout the several views:

Fig. 1 is a sectional view of a propeller hub, the section being taken on a line passing through the rotational axis of the hub and the axis of one of the blades;

Fig. 2 is a transverse section taken through the blade socket substantially on the line 2-2 of Fig. 1;

Fig. 3 is a transverse section taken through the blade socket substantially on the line 3-3 of Fig. 1;

Fig. 4 is a transverse section taken through the base of the blade socket substantially on the line 4-4 of Fig. 1;

Fig. 5 is a diagrammatic view centered about a roller such as is shown in Figs. 1 and 3, to show the forces and axial movement of the blade within its socket in response to the pitch-changing of the blade;

Fig. 6 is a fragmentary, sectional view of a modified blade socket, the section being taken through the blade axis; and

Fig. 7 is a sectional detail of Fig. 6, taken on the line 1-1.

Referring to the drawings and more particularly to Fig. 1, there is illustrated a propeller hub with one of its blade sockets shown in detail. The hub, generally indicated at I0, is drivably connected to and supported from the end of the engine crank shaft l2 or other driving shaft as the case may be. On the opposite end of the hub is a pitch-changing mechanism contained within the housing M. The hub is provided with two or more integral blade sockets such as [6 the axis of which, in the present construction, intersects with the hub axis. Within the socket I6 is positioned the shank of a propeller blade IS, the same being rotatable within the socket for the purpose of changing the blade pitch angle. The blade is journaled in the socket by means of outer and

inner roller bearings

20 and 22. The inner bearing engages an outward flange 24 on the inner end of the blade shank I8, and slidably bears against an annular sleeve bearing surface 28 provided for this purpose between the bearing 22 and the cylindrical socket side wall 26. The outer bearing 20 includes a retaining ring 30, screwthreaded in the end of the socket l6, and contains as a part thereof the roller raceway 32. The other raceway 34 of the bearing 29 is arranged around the cylindrical wall 36 of the blade shank l8 and is adapted to axially slide with respect thereto, there being provided an annular bearing sleeve 38 for this purpose. A suitable packing for retaining the lubricant in the hub socket I6 is employed and consist of an annula channel section cup washer of rubber-like material 40 held in place by a two-piece packing retaining ring 42. The cup washer is held in engagement with the retaining ring 30 and the blade shank I8 by meansof expanding and contracting garter springs 44 and 46, respectively.

For the purpose of compensating the blade centrifugal twisting moment, which causes the blade to tend to turn within its socket to bring the blade surface into the plane of rotation of the propeller, face cams 48 are employed to cause the blade centrifugal force to provide a turning moment in opposition to the blade centrifugal twisting moment. The cams 48 are arranged segmentally around the inner face of the ring 52, while the ring abuts against the retaining ring 30, and is splined against rotation as at 54. In the form shown three identical cams are shown, each one occupying a segment of 120 degrees. Facing the cam surfaces, and spaced therefrom inwardly, is a thrust bearing 56 seated against the shoulder formed by the shank flange 24. The thrust bearing has a plane face 58 between which and the cams are positioned rollers 58, one roller being provided for each cam face.

In order to position said rollers with respect to the shank of the propeller blade there are provided radially extending bosses or trunnions 60, one for each roller, each of which forms in effect a means for circumferentially holding said rollers in their proper position. Each of the bosses is somewhat oval in shape (see Fig. the major axis thereof being arranged circumferentially and being of a diameter to closely match the internal bore 62 of each of the rollers. The minor axis, extending in an axial direction, is reduced sufficiently to permit the roller mounted thereon to move axially in response to stresses and strains, without transmission of any load by the rollers to the trunnions. The rollers are retained upon the stud by a threaded nut 64, the roller 58 being annularly recessed as at 66 to in eifect countersink the nut.

To transmit pitch-changing movement to the blade shank from the pitch-changing motor contained within the housing I4, the hub is provided with a boss 58 extending upwardly into each of the blade sockets, the boss being positioned at the base of each socket and being coaxial with the axis of the blade and the socket. Journaled on the boss 68 is a sleeve having splines I2 interengaging with splines 14 on the inside wall of the inner end of the blade shank. The sleeve 18 is provided with an integral sector beveled indexing gear 16 adapted to engage a gear 18 drivably connected to the pitch-changing mechanism contained within the housing l4. The sleeve 70 is journaled upon the boss 68 through anti-friction bearings 80, the bearings being retained upon the boss 68 and sleeve III by threaded castellated retaining rings 82 and 84, respectively.

The blade shank is urged outwardly in its socket by means of a series of resilient. alternately reversed dished washers 88, the washers bearing against the end of the boss 68 and an annular internal shoulder 88 arranged on the inside wall of the blade shank I8.

The structure thus far described requires for assembly purposes, that the cam ring 52, retaining ring 38 and the rings associated with the

bearings

56 and 20 be split in halves as will be well understood in the art. If it be desirable to avoid such procedure a modified form such as illustrated in Figures 6 and '7 may be employed, wherein the shoulder 24 is replaced by a separate continuous shoulder ring I24. The shoulder ring is secured in place upon the blade shank by means of a two-piece ring I38 bearing in part upon complemental shoulders I32 and I34 on the -shank and shoulder ring respectively, and by a ring nut I36 threaded on the shoulder ring I24 and bearing against an annular recess I38 in the end of the shank I8.

In the modification shown, the blade shank is retained in position by a spring washer I40 bearing against a shoulder I42 in the socket, and a ball thrust bearing I44. The spring washer and ring nut I38 are retained against displacement by a locking ring I48, provided internally with a sleeve-like flange I41 containing thereon splines 14' for coasting with pitch-changing mechanism as is disclosed in Fig. 1. The remainder of the modification includes a thrust bearing I48 having a plane bearing surface I50 engaging rollers I58, which in turn engage the cam ring 52 splined in the socket IS. The rollers are retained in radial and circumferential position by an integral stem I59 extending through axial slots I62 of a circumferential width corresponding to the stem diameter. A look ring Hi4 having U-shaped slots I65 is adapted to engage an annular groove I66 in the end of the roller stem (see Fig. '7). A spring ring I88 lying in an annular groove in the inside wall of the shank limits the movement of the lock ring against displacement from its proper position.

In operation, it will appear that as the blade shank I8 is rotated by the pitch-changing mechanism to the position shown in Fig. 1, the rollers 58, being carried on the studs 68, are caused to travel upon their respective cam surfaces 48, thereby displacing the rollers axially inwardly of the socket. The rollers in turn engage the plane surface 50 of the thrust bearing 56 and thereby move the bearing axially, forcing the shank of the blade axially inwardly of the socket against the centrifugal force of the blade. The centrifugal force of the blade acting upon the rollers 58 and the socket retained cam faces 48 sets up a moment, tending to cause the rollers to move (see Fig. 5) to the right, the degree of which moment depends upon the shape of the cam. Since the blade centrifugal force is divided among three rollers, the moment set up by each roller and its associated cam is one-third of the total moment.

The unbalanced force or component Fr set up by these forces acting at an angle to one another tends to move the roller to the right. The rollers in turn transmit this force to their respective trunnions 60, and tend to offset the blade centrifugal twisting moment such as is indicated by the vector which vector is the force exerted by the moment at the radius of the roller from the blade axis, each roller taking one-third of the moment. If

the component Ft tending to move each roller to the right is equal and opposite to the force then no turning moment exists at'the indexing gear 16, and the pitch-changing mechanism may effect pitch-change in either direction, with equal resistance, the resistance being limited. to the friction of the parts. Under such circumstances. the pitch-changing mechanism may be lightened since no heavy loads are imposed during actual pitch-changing in either direction and the gear is relieved of the static load otherwise present due to the blade centrifugal twisting moment. Since the circumferential component of force Ft at the cam is in direct proportion to the centrifugal force produced by the blade, and the blade centrifugal twisting moment Q is likewise directly proportional to centrifugal force, it is possible by selecting a proper cam pitch to neutralize the turning forces completely and unburden the pitch-changer therefrom. The twisting moment resulting from centrifugal force may diifer at different pitch settings, and to compensate for such changes, it is only necessary to vary the contour of the cam so that at all settings, the turning forces are neutralized. Each cam has been shown as 120 degrees in length so that full pitch-changing from feathering to reverse pitch may be compensated for. Since the cam ring 52 is splined in place in the socket, it will readily appear that the ring may be easily changed for another in the event blades having difiering characteristics should be installed, it being possible to change blades by the mere removal'of the outer retaining ring 30.

Although one embodiment and a modification of the invention have been illustrated and described, it is to be understood that the invention is not limited thereto. For example, where various roller thrust bearings are shown with cylindrical rollers it will appear obvious that tapered rollers Or other forms of anti-friction rollers may be employed if desirable, and the length of the cams and number thereof may be varied to suit the conditions as may exist. Also any of the constructional details or their equivalents of either modification may be readily applied to the other. Various other changes may be made in the details of construction and arrangement of parts, as well known by those skilled propeller blade, a blade having a shank positioned in said socket, opposed retaining shoulders on said socket and shank, thrust rollers engaging saidopposed shoulders, means for flxing one of said shoulders against rotation relative to one of said socket and shank and means.

for mounting the other rotatably with respect to the other of said socket and shank, means for fixing the axis of said rollers about the circumference of said other of said socket and shank, one of said shoulders having inclined cam faces for engaging each of said rollers whereby rotation of said shank relative to said socket produces relative movement therebetween axially of the shank, a boss forming a part of said hub and extending into the base of said socket, antifriction bearing means rotatably arranged on said boss, a drive member borne on said bearing means having driving engagement with the inner end of said shank, and means coaxial with and within the said hub for rotating said driving member.

3. In combination, a propeller hub having a socket for receiving the shank of a variable pitch propeller blade, a blade having a shank positioned in said socket, opposed retaining shoulders on said socket and shank, thrust rollers engaging said opposed shoulders, means for fixing one of said shoulders against rotation relative to one of in the art, without departing from the spirit of the invention. Reference will therefore be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In combination, a propeller hub having a socket for receiving the shank of a variable pitch propeller blade, a blade having a shank positioned in said socket, opposed retaining shoulders on said socket and shank, thrust rollers engaging said opposed shoulders, means for fixing one of said shoulders against rotation relative to one of said socket and shank and means for mounting the other rotatably with respect to the other of said socket and shank, one of said shoulders having inclined cam faces for engaging each of said rollers whereby rotation of said shank relative to said socket produces relative movement therebetween axially of the shank, a boss forming a part of said hub and extending into the base of said socket, anti-friction bearing means rotatably arranged on said boss, a member borne on said bearing means having driving engagement with the inner end of said shank, and means coaxial with and within said hub for rotating said driving member.

2. In combination, a propeller hub having a socket for receiving the shank of a variable pitch said socket and shank and means for mounting the other rotatably with respect to the other of said socket and shank, a flange aifixed to the said other of said socket and shank, anti-friction thrust bearing means between the I said other shoulder and flange, one of said shoulders having inclined cam faces for engaging each of said rollers whereby rotation of said shank relative to said socket produces relative movement therebetween axially of the shank, a boss forming a part of said hub and extending into the base of said socket, anti-friction bearing means rotatably arranged on said boss, a member borne on said bearing means having driving engagement with the inner end of said shank, and means coaxial with and within said hub for rotating said driving member.

4. In combination, a propeller hub having a socket for receiving the shank of a variable pitch propeller blade, a blade having a shank positioned in said socket, opposed retaining shoulders on said socket and shank, thrust rollers engaging said. opposed shoulders, means for fixing one of said shoulders against rotation relative to one of said socket and shank and means for mounting the other rotatably with respect to the other of said socket and shank, means for fixing the axis of said rollers about the circumference of the said other of said socket and shank, a flange afiixed to the said other of said socket and shank, antifriction thrust bearing means between the rotatable shoulder and flange, one of said shoulders having an inclined cam face for engaging each of said rollers whereby rotation of said shank relative to said socket produces relative movement therebetween axially of the shank, a boss forming a partof said hub and extending into the base of said socket, anti-friction bearing means rotatably arranged on said boss, a member borne on said bearing means having driving engagement with the inner end of said shank, and means coaxial with and within said hub for rotating said driving member.

5. In combination, a propeller hub having a socket for receiving the shank of a variable pitch propeller blade, a hollow blade shank in said socket, a concentric boss in the base of said socket and integral with said hub, pitch-changing means pivotaliy mounted upon said boss and splined to said blade shank, a cam ring carried by and keyed to said socket at its outer end and opposed by an annular bearingiace on said shank adjacent its inner end, rollers bearing against said cam ring and annular bearing face, and radial pins on said shank cooperating with said rollers for fixing the axes of said rollers circumferentially with respect to said shank, said rollers having a circular aperture into which said pins extend, and said pins being substantially oval in cross section with the major axis of the oval extending the diameter of said aperture circumferentially of the shank, whereby said rollers are confined against relative circumferential movement and permitted axial movement limited by the diiference between the major and minor axes of said oval.

MAURICE E. CUSHMAN.

REFERENCES CITED The following references are of record in the file of this patent:

Number 15 Number 8 UNITED STATES PATENTS Name Date Barbarou Aug. 1, 1933 Ratier Aug. 8, 1933 Lougheed Sept. 11, 1934 Coates Nov. 5, 1935 Blanchard Mar. 3, 1936 Landrum June 25, 1940 Qemeny Feb. 25, 1941 Moore May 5, 1942 Anderson Mar. 19, 1946 Hoover Aug. 19, 1947 FOREIGN PATENTS Country Date Sweden Mar, 2, 1939 Great Britain Oct. 16, 1930 Great Britain June 8, 1938 France Apr. 4, 1924 France Apr. 7, 1934