US2019966A - Propeller - Google Patents

Description

C. H. HAVlLL Nov. 5, 1935.

PROPELLER Filed June 25, 1934 2 Sheets-Sheet 1 Patented Nov. 5, 1935 UNITED STATES PATENT OFFICE PROPELLER Clinton 11. Havill, East Orange, N. J., assignor to Eclipse Aviation Corporation, East N. 1., a corporation of New Jersey Application June 25, 1934, Serial No. 732,333

9 Claims.

speed may be readily limited irrespective of power,

air density or other conditions to which the aircraft is subjected.

Another object of the invention is to provide, in a construction of the above character, a novel mechanism embodying a normally-circulating fluid system entirely contained within the pro peller thus avoiding all fluid-sealing problems usually inherent in such mechanisms.

A further object is to provide, in a mechanism such as that indicated above and wherein a normally-circulating fluid system carried by the propeller is employed, a novel mechanism whereby the circulation of the fluid is interrupted to permit a build-up of pressure to oppose a further decrease in the pitch of the blades as soon as the speed of rotation of the propeller has attained a predetermined maximum.

A still further object is to provide, in a variable pitch propeller of the above character, a novel centrifugally-governed device for interrupting the circulation of fluid at a predetermined maximum speed of rotation of the propeller.

A further object is to provide, in a variable pitch propeller having a closed circulating fluid system functioning to limit the maximum rate of revolutions of the propeller, a novel arrangement embodying a pump in said system for circulating fluid therein together with connections between a stationary member and a propeller for operating the pump.

Other objects and novel features of the invention will appear more fully hereinafter from the following detailed description when taken in connection with the accompanying drawings, wherein one embodiment of the invention is illustrated.

vIt is to be expressly understood, however, that the drawings are utilized for purposes of illustration only and are not designed as a d'efinitionof fonthis purpose to the appended claims.

the limits of the invention, reference beinghad several views: I Fig. 1 is a side view, partly in section, of a propeller constructed in accordance with the present invention;

Fig. 2 is an enlarged sectional view of a portion of the mechanism shown in Fig. 1, and

Fig. 3 is a vertical sectional view of the propeller shown in Fig. 1.

Referring more particularly to Figs. 1 and 2, a propeller constructed in accordance with the present invention is illustrated therein as being constituted by a rotatable engine shaft or extension 10 thereof 5 and a hub 6 drivably connected thereto as by-means of a driving block 1 but relatively movable longitudinally thereof in response to the thrust exerted by the blades, there being provided a plurality of bearings 8 interposed between 15 the hub and driving block for more readily enabling such movement of the hub. The latter is provided with a plurality of radially-extending sockets 9 adapted to rotatably receive the inner or root ends of propeller blades I 0, there being 20 also provided suitable link mechanisms H interconnecting the blades with a plate member l2 fixedly secured to the propeller shaft, these last named mechanisms being effective to. vary the pitch of the blades during the aforesaid thrust- 25 for the purpose of arresting such movement at 30 certain positions along the shaft in accord-- ance with the degree of thrust exerted by the blades under the existing conditions of operation, there is preferably provided a plurality of resilient members, such as for example coil springs 35 1 [3, arranged in a circle concentric with respect to the shaft and having one end thereof bearing against a plate I 4 secured in any suitable manner to a forward extension l5 of driving block 1,

the other ends of said springs bearing against a 40 cylinder l5 carried by the propeller hub and being provided for a purpose-which will appear more fully hereinafter. It is to be noted that when the parts are in the position shown in Fig. 1, the

pitch of the blades is a maximum, the pitch being 45 gradually reduced during forward movement of the hub relative to the shaft in response to the thrust of the blades, the above mentioned resilient members I3, however, serving to yieldably oppose such movement and to arrest the hub in such a position relative to the shaft that the pitch assumed by the blades will be substantially proportional to the thrust thereof and such as to yield a substantially maximum propeller eiliciency for the conditions of thrust imposed.

One of the features of the present invention resides in the provision of means for limiting the maximum rate of revolutions of the propeller and such means cooperate with the pitch-changing mechanism in such a manner that at a predetermined rate of maximum revolutions, further reduction in the pitch of the blades is prevented. In the form shown, such means are fluid operated and include a normally-circulating cloud fluid system. Preferably, the system is carried entirely by the propeller and includes a suitable gear pump I 6 comprising driving and driven gears l1 and II respectively, the former being suitably driven by a stationary gear ll meshing with an elongated pinion 20. During rotation of the propeller, the gear pump it pumps any suitable fluid such as oil, for example, through conduit 2| which communicates with cylinder ll surrounding the propeller shaft. In this last named cylinder, a circular piston element 22 concentric with the propeller shaft is disposed and such element, as shown, is secured to one end 01' pins 22' and 2|, each of these pins being secured at the other end to the plate l4. As shown more particularly in Fig. 2, a hollow screw 25 secures piston 22 to the pin 23 and the latter is provided with a passage 26 which conveys fluid from the cylinder I! to a fluid reservoir 21 by means of conduit 28 and passages 29 and 30, there being a valvular element II disposed in said last named passage normally per mitting flow of fluid to said reservoir.

In order to conduct fluid from the reservoir 21 back to the pump IS, a conduit 32 communicates with the reservoir through passage 23 and also communicates with a passage 34 provided in pin 24, this last named passage conducting fluid to a return conduit or duct 35 through a hollow member 36 threadedly secured at one end thereof to the pin 24 and slidably received in a suitable aperture 31 in the propeller hub.

With the above named construction, it will be readily perceived that during rotation of the propeller, the pump I6 normally circulatesfluid through passage 2|, cylinder l5, passage 26, conduit 28, passages 29 and 30 to the reservoir 21 and fluid from such reservoir is conducted back to' the pump through 23, 32, 34, I1 and return duct 35. As long as no obstruction is offered to the flow oi fluid, no pressure will be built up in the cylinder l5 sufllcient to oppose relative movement between the cylinder I! carried by the hub and piston 22 carried by the propeller shaft and change in pitch of the propeller blades may be readily efiected.

Upon reduction in pitch of the blades, however, the rate of revolutions of the propeller rises and in order to limit the maximum rate of revolutions in order tosecure maximum propeller and engine efliciency, a centritugally-operable mechanism is provided for obstructing the flow of fluid in the above described. system. As shown, such means comprise the valvular mechanism 3| which is slidably received in a cap 38 carried by the forward portion of the engine shaft, such valvular mechanism being normally urged to the position shown as by means of a spring 39, the compression of which may be varied by adjustment of screw 40. In the position shown, the valve 3| establishes communication between duct 3. and reservoir 21 by reason of the cut-away portion II but as the speed of the propeller increases. this communication is gradually cut of! by outward movement of the valve Si in response to centrifugal force. As

the valve moves outwardly under these conditions, communication between the pump and res- 'der. ll.

ervoir 2! is gradually closed oi! and the pump gradually builds up pressure within cylinder II to offer an increase in resistance to relative movement between the cylinder and piston 22 during a further decrease in the pitch of the blades. 5 This resistance gradually increases until communication between the pump and reservoir 21 is entirely shut on, at which time suflicient pressure will be built up in cylinder I! to prevent a further decreasein the pitch of the blades. A suitable by-pass valve 42 resiliently urged to its seat as by means oi spring 43 serves to bypass the fluid around the valve ii to duct 44 in order to limit the pressure which may be built up in cylin- In operation, thrust-responsive movement of the hub with respect to the propeller shaft effects a reduction in the pitch of the blades through the link mechanisms -H and during such movement of the hub, the cylinder it will be moved to the right with respect to the stationary piston 22. The resilient means I I, as above stated, serve to resiliently oppose such thrust-responsive movement of the hub and in normal operation, the hub will move forwardly and backwardly to decrease and increase the pitch of the blades in accordance with the thrust exerted thereby. The fluid system including the gear pump has a normally-circulating flow of fluid therein until such time as the valve 3| is moved in response to centrifugal force to such a position as to obstruct the circulation of fluid, whereupon pressure built up in cylinder l5 by continued operation of the pump I6 will prevent any further decrease in the pitch of the blades and hence will limit the maximum rate of revolutions of the propeller.

While one form of the invention has been shown and described herein, it is to be understood that the same is not limited thereto but may be embodied in other forms as well known to those skilled in the art. Reference will, therefore, be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a variable pitch propeller having a plu- 45 rality of blades, means including a relativelymovable hub and shaft for automatically varying the pitch of said blades during operation of the propeller, fluid pressure-operated means for limiting the reduction in pitch, and speed-responsive mechanism for rendering operative said fluid pressure-operated means to limit said pitch reduction.

2. In a variable pitch propeller having a plurality of blades, means for automatically varying 56 the pitch of said blades during operation of the propeller, fluid pressure-operated means independent of said pitch-varying means for opposing further movement of said pitch-varying means after the pitch of the blades has reached 60 a predetermined minimum, and centrifugallyoperable mechanism for eflecting the operation of said fluid pressure-operated means to oppose further movement of said pitch-varying means in the direction to reduce the pitch.

3. In a variable pitch propeller having a plurality of blades, means for automatically varying the pitch of said blades during operation of the propeller, fluid pressure-operated means indeo pendent oi. said pitch-varying means for opposing movement of said pitch-varying means, and mechanism operable at a predetermined speed of rotation of the propeller for effecting the operation of said fluid pressure-operated means to 7 4. In a variable pitch propeller having a plurality of blades, means for automatically varying the pitch of said blades during operation of the propeller, means independent of said pitchvarying means and operable to oppose further movement of said pitch-varying means only after the pitch of the blades has reached a predetermined minimum, and means responsive to the speed of rotation of the propeller at said predetermined minimum pitch for effecting the operation of said opposing means.

5. In a propeller of the type having a plurality of blades, and a relatively-movable hub and shaft, the pitch of the blades being automatically varied in accordance with such relative movement responsive to the thrust of said blades, the combination with said propeller, of fiuid pressureoperated means for opposing the pitch-changing operation only after the pitch of the blades has reached a predetermined minimum, and centrifugally-operable mechanism for determining the initiation of operation of said fluid pressureoperated means.

6. In a variable pitch propeller having a plurality of blades, means for automatically varying the pitch of said blades during operation of the propeller, "fluid pressure-operated means independent of said pitch-varying means operative for opposing a further decrease in the pitch of the blades only after a predetermined speed of rotation of the propeller has been attained, and means responsive to centrifugal force and operable at said predetermined speed for rendering operative said fluid pressure-operated means.

7. In a variable pitch propeller of the type having a relatively-movable hub and shaft and means operable during such relative movement to vary the pitch of the propeller, a fluid pressure-operated pitch-limiting mechanism cooperating with said pitch-varying means and embody- 5 ing a normally-circulating fluid system, a pump in said system, and valvular means for interrupting circulation of fluid in said system whereby said pump builds up pressure therein to oppose further change in pitch.

8. In a variable pitch propeller of the typev having a relatively-movable hub and shaft and means operable during such relative movement to vary the pitch of the propeller, a fluid pressureoperated pitch-limiting mechanism cooperating with said pitch-varying means and embodying a normally-circulating fluid system for limiting the reduction in pitch of the propeller, a pump in said system, and means responsive to a predetermined speed of rotation of the propeller for interrupting circulation of fluid in said system whereby said pump builds up pressure therein to oppose a further decrease in pitch.

9. In a variable pitch propeller of the type embodying a plurality of blades and a shaft drivably connected therewith, means for automatically varying the pitch of said blades during operation of the propeller, and means for limiting the reduction in pitch of the blades comprising a normally-circulating fluid system, a pump in said system, and a centrifugally-operable valve mechanism effective at a predetermined'speed of rotation of the propeller for interrupting circulation of fluid in said system whereby said pump builds up pressure therein to oppose a further reduction in pitch.

' CLINTON H. HAVILL.

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