US2094149A

US2094149A - Adjustable pitch propeller

Info

Publication number: US2094149A
Application number: US79898A
Authority: US
Inventors: Gaba Achille Ernest
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-05-15
Filing date: 1936-05-15
Publication date: 1937-09-28
Anticipated expiration: 1954-09-28

Description

Sept. 28, 1%? A. E. GABA ADJUSTABLE PITCH PROPELLER Filed May '15, 1936 INVENTOR ACH ILLE ERNEST GABA ATTO R N EY5 Patented Sept. 28, 1931 UNITED STATES PATENT OFFICE 10 Claims.

vision of improved apparatus for connecting the blade of an adjustable pitch propeller to a r0- tatable propeller hub. The present application is a continuation in part of my copending application Serial No. 757,536, filed December 14, 1934, which issued on September 22, 1936, as United States Patent No. 2,054,810.

In my above-mentioned copending application, an adjustable pitch propeller is described in which propeller blades are received within cylindrical stub branches extending outwardly from a rotatable propeller hub and are secured to the hub by means of a core comprising a pair of interconnected helically threaded cylinders and a stud. The threads of one of the cylinders of the core engages corresponding threads provided in the foot of the propeller blade and the threads of the other cylinder of the core engages threads provided upon a, cylindrical member disposed within the stub branch and extending outwardly from the hub. The stud engages a second set of threads formed in a recess in the propeller blade and is secured to the core.

In the structure described above, the centrifugal force tending to tear the blades from the hub when the assembly is rotating is resisted wholly by the threaded cylindrical member whose threads engage the threads of'the core. The

present invention provides improved apparatus for connecting the blades to the rotatable hub in such a manner that a centripetal force is applied to the propeller blades to offset in part the centrifugal force of the rotating blades and thereby to provide an improved distribution of the forces acting while the propeller assembly is rotating.

In the apparatus of the invention, a substantially cylindricalblade-support member having an outwardly. extending flange adjacent its lower end is rigidly associated with a propeller blade adjacent the foot of the blade, and appropriate means are provided for exerting a force upon the flange of the blade-support member to aid in holoding the blade in operative relation with the The structure of the inventionincludes a main connecting element for connecting the blade to the hub which comprises a threaded stud engaging the propeller blade adjacent the foot thereof and also engaging a threaded inner core secured toand extending outwardly from the hub. The blade-support member is rigidly connected to the stud and to the blade. An outer cylindrical core extending outwardly from the hub and surrounding the blade-support member is provided with an annular cap extending substantially radially inwardly. The relation of the annular cap with respect to the flange of the blade 5 support member is such that the cap'is positioned substantially directly over the flange. A ball or roller bearing is seated against the flange, and spring means seated against the underside of the cap exert a force on the ball or roller bear- 1o ing assembly and through it to the flange of the blade-support member, thereby applying a centripetal force to the blade when the propeller assembly is rotating to aid in holding the propeller blade in operative relation with respect to 15 the hub.

A substantially cylindrical housing member associated with the cap surrounds the foot of the blade. A bushing member associated with the upper end portion of the housing member is 20 adapted to provide a bearing surface against the foot of the blade. A relatively hard ring member associated with the blade advantageously is provided to furnish a bearing surface upon which the bushing acts.

The invention will be better understood from the following description considered in conjunction with the accompanying drawing, in which Fig. l is an elevation, partially in section, showing the relation of the apparatus of the inven- 30 tion to an adjustable pitch propeller assembly;

Fig. 2 is a longitudinal cross section through a structure according to the invention by which a. propeller blade is connected to a rotatable Fig. 3 is a transverse cross section taken substantially along the line 3-3 of Fig. 2; and

Fig. 4 is a cross section through a modified spring assembly.

.A propeller hub I0 is mounted by means 014.40 a plate II and a cap screw II! on a propeller shaft l3. Mechanism I4 for adjusting the pitch of propeller blades is housed within the annular space between the hub and the propeller shaft and in a casing l5, and the entire assembly is nected to the crank shaft of a motor I 6. An outwardly extending cylindric'al'inner core I! is secured to the hub (preferably it is formed integrally therewith) and is provided with helical threads l8 formed on its inner surface. A 50 propeller blade 20, the foot of which is suitably recessed, is positioned adjacent the cylindrical inner core H. A stud 2| provides means for connecting the propeller blade to the hub through the cylindrical con- 45' core I1, and this stud-constitutes the main connecting element between the propeller blade and the hub. The stud 2| is threaded adjacent its upper end portion to engage threads 22 formed in the propeller blade 20 and adjacent its lower end to engage the helical threads l8 of the core IT. The assembly is such that if a turning moment is applied to the stud 2|, the propeller blade will be turned about its longitudinal axis toadjust the pitch of the blade. I

A substantially cylindrical blade-support member 23 is rigidly secured to the blade. The conthe ring member 42 are advantageously formed of very hard steel and are accurately machined to reduce to a minimum the frictional resistance 7 to turning the blade about its longitudinal axis.

ne'ction between the blade-support member and the blade is effected principally through the intermediary of the stud. The upper portion of the blade-support member 23 extends radially inwardly and is provided with threads 24 engaging a section of the helical threads formed on the stud 2| adjacent the point at which the stud enters into engagement with the propeller blade. The blade support member thus in effect becomes a lock-nut on the stud to hold it rigidly in engagement with the blade, the blade, stud,and bladesupport member becoming thereby a solidary structure. A pin 25 extending through the blade, the blade-support member, and the stud locks these three elements in position.

The lower portion of the blade-support member 23 is provided with an annular flange 26 extending radially outwardly beyond the periphery 'of the foot of the blade 20. A ball or roller bearing- 2I is seated against the flange 2., which advantageously constitutes the lower face thereof. An annular ring 28 forms the upper faceaet the bearing.

An outer cylindrical core 30 extending outwardly from the hub Ill surrounds the flange 26 of the blade support member and extends to a point substantially above the flange. Suitable stops 3| engaging the outer cylindrical core 36 and the upper face 28 of ball or roller bearing hold the latter in non-rotatable relation with respect to the outer core 30.

An annular cap 32 extending radially inwardly is secured to the outer cylindrical core 30 by a threaded clamping ring 33 engaging threads suitably formed on the outer cylindrical core. The

annular cap 32 is positioned substantially directly over the flange-26 of the blade-support member.

A series of compression springs 34, seated against the undersurface of the annular cap'32, 1

arelmounted within the space between the cylindrical core 30 and the outer surface of the blade 20 to exert a force upon the upper face of-the ball' or roller bearing and through it upon the flange 26 of the blade-support member to aid in holding the blade in operative relation with respect to the hub. The springs 34 are guided by shafts 35 mounted on the upper face 28 ofthe ball or roller bearing'and extending upwardly into suitably formed recesses 36 in the annular cap 32. The recesses 36 are suificiently deep to allow slight movement of the guide shafts 35 into and out of them.

In place of the compression springs 34 describe above, other means for applying force to the flange 26 of the blade-support member 23 may be adopted. For example, as shown in Fig. 4, a series of dished washers 31 mounted one over the other on the guide shafts 35 to act in the manner of springs may be employed if desired.

A substantially cylindrical housing member 40 extends upwardly from the annular cap 32 and surrounds the foot of theblade 20. A bushing A cylindrical hoop 42' provided with a flange 43 surrounding. the blade foot aids in retaining the ring member 42 in position and in preventing lateral distortion of the blade foot.

An oil-seal 44 is provided adjacent the bushing 4| to lubricate it and to' keep dirt and grit from gaining access to the mechanism. The oil-seal is closed by a ring 45 in threaded engagement with the upper end portion of the cylindrical housing member 4| The apparatus of theinvention is such that an improved distribution of the forces exerted at the foot of the blade when the propeller assembly is in operation is attained. A considerable portion of the centrifugal-force tending to throw the blade from the hub is taken by. the stud 2| and the inner cylindrical core H, but these members are relieved from taking the full magnitude of such forces by virtue of the pressure exerted by the springs 34 on the flange 26 of the blade-support member. The pressure of the springs constitutes a centripetal force acting in opposition to the centrifugal force of the rotating blade. Suppose the-centrifugalforce of the blade has a value F-and the counter-force exerted by the springs 34 'on the blade-supporting member 23 has a value f. The resultant pressure on the screw-thread of the inner core I! will be Ff. The arrangement of the invention thus provides for a better distribution of the stresses encountered in retaining the blade in position, since the threaded inner core I! participates in these stresses only to the extent of the value of F-f, the outer cylindrical core 30 participating therein to the extent'of the'value of 1.

Due to the fact that the coefficient of the friction on the ball or roller bearing is much lower than the coefficient of the friction of the screwthread, the frictional resistance to be overcome in order to cause the blade to turn in adjusting the pitch thereof during flight is made less. If tan 1/1 equals the coefficient of friction of the screw threads, and tan 6 the coeflicient of fricition of the bearing roller, then for a centrifugal force F the frictional resistance F0 on the screw threads is, as pointed out in my above-mentioned copending patent,

(where a is the pitch of the screw threads) whereas with the compensating device of the invention, exerting a centripetal force f, I will have a frictional resistance F0 due to the screw threads amounting only to Fc'=(Ff) cos a tan 1/ and on the ball bearing a frictional resistance fc Of fc= (f) tan 6 tion of the propeller assembly comprising an outwardly extending flange associated with the blade adjacent the lower end thereof and means exerting a downwardly acting force on the flange.

2. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the blade, apparatus for connecting the blade to the hub comprising a main connecting element, and means for relieving the stress imposed on the main connecting element during operation of the propeller assembly comprising an outwardly extending flange associated with the blade adjacent the lower end thereof and spring means exerting a downwardly acting force on the flange:

3. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the blade, apparatus for connecting the blade to the hub comprising a stud secured in the lower end portion of the blade, means connecting the stud to the hub, an outwardly extending flange associated with the blade adjacent the lower end thereof, and means exerting a downwardly acting force on the flange to relieve the stress imposed on the stud during operation 'of the propeller assembly.

4. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the blade, apparatus for connecting the blade to the hub comprising a stud secured in the lower end portion of the blade, means connecting the stud to the hub, an outwardly extending flange associated with the blade adjacent the lower end thereof, and a plurality of springs exerting a downwardly acting force on the flange to relieve the stress imposed on the stud during operation r of the propeller assembly.

5. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the blade, apparatus for connecting the blade to the hub comprising astud' secured in the lower end portion of the blade and engaging with the hub to secure the blade tothe hub and resist the centrifugal force tending to tear the blade from the hub during rotation of the hub, an outwardly extending flange associated with the blade adja-' cent the foot thereof, and means for exerting a centripetal force on the flange during rotation of the hub to relieve the stress imposed by the centrifugal force of the blade on the stud.

6. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the-blade, apparatus for connecting the blade to the hub comprising an inner core extending outwardly from the hub, a stud secured in the lower endportion of the blade and engaging with to the hub comprising an I propeller hub, and

the inner core, an outwardly .extendingflange associated with the blade adjacent the lower end thereof, an outer core extending outwardly from the hub and surrounding the flange, and

means associated with the outer core exerting a downwardly acting force on the flange.

'7. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the blade, apparatus for connecting the blade inner internally threaded core extending outwardly from the hub, a stud secured in the lower end portionof the blade and engaging'with the threads of inner core, an outwardly extending flange associated with the blade adjacent the lower end thereof,

an outer core extending outwardly from the hub and surrounding the flange, an annular cap secured to the outer core, and means bearing against the annular cap and exerting a downwardly acting force on the flange.

8. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the blade, apparatus for connecting the blade to the hub comprising an inner internally threaded core extending outwardly from the hub,

a stud secured in the lower end portion or the blade and engaging with core, an outwardly extending flange associated with the blade adjacent the lower end thereof, an outer core extending outwardly from the hub and surrounding theflange, an annular cap secured to the outer core, and spring means seated against the annular cap and exerting a downwardly acting force on the flange.

9. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable means for adjusting the pitch of the blade, apparatus for connecting the blade to the hub comprising an inner internally threaded core extending outwardly from the hub, a stud secured in the lower end portion of the blade and engaging with the threads of inner core, an outwardly extending flange associated with the blade adjacent the lower end thereof,

, an anti-friction bearing seated on the flange, an

outer core extending outwardly from the hub and surrounding the flange, an annular cap secured to the outer core, and a plurality of springs bearing against the annular cap and exerting a downwardly acting force on the anti-friction bearing.

10. In an adjustable pitch propeller assembly comprising a propeller blade, a rotatable propeller hub, and means for adjusting the pitch of the blade, an outer core extending outwardly from the hub and surrounding the lower end of the blade, an annular cap secured to the outer core, a substantially cylindrical housing member extending upwardly from the annular cap and surrounding the lower end portion of blade, and a bushing associated with the upper end of the housing and providing a bearing surface for the blade.

ACHILLE ERNEST GABA.

the threads of inner