US2313326A - Propeller having an automatically variable pitch - Google Patents

Description

March 9, 1943. D. SENSAUD DE LAVAUD I 2,313,326

normal: mvme AN AUTOMATICALLY VARIA LE rrrcu Filed Jan. 31, 1939 s Sheets-Sheet} YINVENTOR WAKM ,TGMWM 'ATTORNEY March 1 D. SENSAUD DE LAVAUD 2,313,326

PROPELLER HAVING AN AUTOMATICALLY VARIABLE PITCH Filed Jan. .31, 1939 s Sheets-Sheet 2 .pmvcmon .'s| a v ATTORNEY I I Mud! D. SENSAUD DE LAVAUD I 2,313,326

PROPBLLB: HAVING AH AUI'OIATICALLY VARIABLE PITCH v1mm Jan; 31. 1939 3 Sheets-Sheet s aM/re/ s IVS 7w 0514mm Patented Mar. 9, 1943 PROPELLER. HAVING AN AUTOMATICALLY VARIABLE rrrcn Dimitri Sensaud do l'lavaud, Paris, France Application January 31, 1939, Serial No. 253,719

' In France November 8, 1938 '5 Claims.

which act upon the blades of a propeller having an automaticallyvariable pitch.

Another object ofthe invention is to provide an automatically variable pitch propeller which is simple in construction and highly eflicient.

A further object is to provide novel means for controlling automaticallythe pitch of the blades of a propeller, which means can be easilyadjusted in accordance with the structural peculiarities of the vehicle and propeller withwhich it is employed.

The above and further objects and novel features will more fully appear from the detailed description when the same is read' in connection with the accompanying drawings. It is to be expre'ssly understood, however, that the drawings are for purposes of illustration only and are not intended as a definition of the limits of the invention, reference for this latter purpose being had to the appended claims.

In the drawings, wherein like reference char acters refer to like'parts throughout the several views,

Fig. 1 is a front view, partly in section and partly diagrammatic, of a propeller blade and mounting therefor which is employed with the present invention;

Fig. 2 is a view which is primarily sectional with parts broken away and with parts in elevation of one embodiment of the inventionwherein the nub has shifted angularly through a small distance;

Fig. 3 is a vector representation of certain forces acting upon a propeller as produced by-the means shown in Fig. 2;

Fig. 4 is a front view in elevationof a variable pitch propeller embodying the present invention; and

Fig. 5 is a side view in elevation of said propeller.

Theiorm oi the invention illustrated in the accompanying drawings, by way of example, comprises means for aiding in the automatic adjustment of the pitch of the blades of a propeller such as an aeroplane propeller; The latter is provided, for example, with two blades, each of which is angularly movable about an axis which is angularly disposed relative to the axis of the blade, the axis of pivotal movement being in spaced relation to the axis of rotation of the propeller. When the axis of angular movement and of rotation are projected upon a plane parallel to them both, the projections are not necessarily perpendicular to one another but are preferably mutually inclined at an angle slightly less than 90. The novel adjusting member employed with this propeller is constituted by resilient adjustable means which exert a radial thrust upon each of the blades when the latter are at rest, and which exert a tangential, or approximately tangential, thrust upon each of said blades when the latter have angularly shifted from the rest position, thus producing a torque which tends to increase the angle through which the blade has moved.

In the'diagrammatie form shown in Fig. 1, a propeller blade mounting is illustrated. which is similar to that shown'in my Patent No. 1,943,2l0, and which comprises a pair of blades I, each of which are rigidly secured by means of a socket member 2 to. a torsion or pivot rod 3, the axis of which is angularly disposed relative to that of the blade. Rod 3 is fixed at=the inner end thereof to'a suitable sleeve member (not shown) in any suitable manner, such as that illustrated in the tached to and preferably integral with a hub (not shown). The latter is keyed in a conventional manner to a driving shaft having an axis 0 perpendicular to the plane of the figure. The axis of rod 3 is'at adistance a from that of the driving shaft. In a plane containing the axis of one of the rods 3 and parallel to the axis 0, the axis of rod 3 is preferably inclined relative to a projection of axis 0 upon said plane at an angle diifering slightly from or at right angles to said projection.

If one of the blades were moved axis of its torsion rod 3 through an angle of 360, the neutral longitudinal axis of the blade would describe a cone of revolution and a point on said axis would describe a circle, e. g., circle la (Fig. 1). When the blades are rotating about the axis of rotation O of the driving shaft, certain forces mentioned below act upon each blade causing a pivotal or angular movement thereof about the axis of the respective torsion rod, thereby varying the pitch ofv the blade under certain operating conditions.

During rotation of the propeller, each blade is subjected to the followingtorques:

crease the pitch;

3. A. return torque produced by the torsion of the rod;

4. A torque or natural torsion tending to hold the blades at a minimum pitch; and

5. Devices which are responsive to the thrust of the blade on the'hub are provided for assisting about the Y the pivoting of the blade after the pivoting has commenced, the devices therefore producing a fifth torque which actsupon the blade.

It hasbee'n found dimcult to obtain thus a perfect pitch control because, in addition to the fact that no two propellers can be made exactly alike, the aerodynamic features of'the particular aircraft upon which the propeller is mounted have an eflect upon the operation of the propeller. Consequently, novel means are provided for producing an additional torque, which means can be adjusted to compensate for the individual characteristics of the particular propeller and of the particular craft upon which the propeller is mounted.

In the embodiment shown in Fig. 2, the root or base 2 of blade I is shown in a position occupiedafter having rotated through a small angle from a rest position.

The root 2 of the blade, because of the strains acting thereon, exerts a lateral thrust upon a hub 20 (Fig. 2) by means of lugs 8, 6', having, for example, rounded heads I, I, the latter being in contact with bearings 8, 8' which are rotatably mounted upon the hub. In equilibrium position the points Ofcontact between heads I, 1' and bearings 8, 8' are on lines joining the centers of bears 8, 8' with the center of root 2. As a result, the reactions exerted by bearings 8, 8' on lugs 8, 6' are directed through the center of said root and apply no turning torque thereto. However, as soon as the blade has rotated slightly around the axis of rod 3, turning root 2 slightly, for example, in a clockwise direction, as viewed in Fig. 2, the axes of lugs 8, 6' no longer pass through the contact points of heads I, I and-bearings 8, 8', and said axes no longer coincide with the lines joining the centers of bearings 8, 8' and the center of root 2. As a result, any lateral force applied to root 2 in the direction of bearings8, 8' produces reactions from bearings 8, 8' which are directed eccentrically relative to the root center, thereby producing clockwise torques, the latter tending to further displace the root 2 in a clockwise direction. Therefore, the thrust on the root or base 2 tends to increase the angle through which the blade has moved, and thus produces the above-mentioned fifth torque.

Novel means are provided for producing an additional correcting torque comprising two adjacent cylinders 9, 9', the axes of which extend radially of the base 2. In each of the cylinders is a piston i2 which is urged toward the base 2, i. e., toward the inner extremity of the cylinder by suitable resilient means such as spring washers ii. The thrust of the washers is communicated to the base 2 by means of a driving rod or intermediate member II which engages the base 2 and the piston l2, for example, in ball and socket joints l5 and 10 respectively.

when thepropeller is at rest, it is in such a predetermined position that the rod I4 is normal to the base 2, that is, the axis of the rod extends radially of the base. However, when the blade angularly shifts from the initial position, the

driving rod ll takes an oblique position relative to the root and transmits thereto the thrust of washers II. This thrust produces a torque which acts on the root, as will be explained with reierence to Fig. 3.

In Fig. 3, assume AB to represent the axis of rod I4, and T to represent the thrust acting normally to the base 2. When the latter angularly shifts a slight amount the rod ll will assume a direction.

PQ at an angle a to AB. The thrust of washers 13 now becomes if cos a If T acts at the point Q it produces a tangential thrust t thereupon which can be expressed:

10 This thrust produces the correcting torque.

Transposing t into terms of T, o and a it is found, considering o to-be the center of base 2, that b=90 -(a+c) therefore T i v, H a sin (a-l-o) I Since the radius 013 of the b'ase'is much greater than the length AB of the connecting rod, it is seen that angle a is also much greater than angle cand thus sin (ac) w .005 G is approximately equal to si 2 003 a moves from the initial position. The torque correctlng means can be so designed whereby the thrust t varies in a predetermined manner, thus producing at all times a desired correcting eifect. Suitable means for varying the compression of the resilient means II are provided comprising'a threaded cap it upon each of the cylinders. By angularly moving the cap the position thereof axially relative to the cylinder can be varied and thus the compression of the spring can be adjusted.

When the blade root 2 is in inoperative position, i. e., when said blade is in equilibrium position and has not been laterally or angularly displaced, the

axes of driving rods I4, I! are coincident with the axis of blade 2. As a result, the forces exerted upon said rods by resilient washers I! are directed through the axis or root 2 and produce no turning torque on said root. Similarly,'the reaction of bearings 8, 8' to lateral thrust exerted on said root in the direction of said-bearings by lugs 6, 8' is directed through the axis of said root, also producing no turning torque. Howevenduring rotation of the propeller, the blade root 2 is given an angular displacement, for example, in a clockwise direction, as viewed in Fig. 2, and is also subjected to a lateral thrust in an upward direction, as viewed in said figure. As a result of the angular displacement of the blade, the

axes of driving rods ll are displaced relative to es the center of root 2 and apply a clockwise turning torque to said root. Similarly, the equilibrium position of lugs 6, 6' is disturbed so that the lateral thrust on root .2 produces eccentric reactions from bearings I, if, said. reactions also applying a clockwise torque to the root 2. Thus. the provision of applicant's novel lug and bearing arrangement produces one additional torque, and the provision of the novel resilient washer and rod structure'produces another additional torque 78 when the blade is in operation and has been displaced by the aerodynamic and centrifugal forces.

stead of employing spring washers i3 it is possible to use a suitable coil spring or a plurality of superposed coil springs. Further, instead'of hav ing two torque correcting devices 9, 9' any desired number can be used. Various changes in the design and arrangement of the parts can be made without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art. For a definition of the limits of the invention, reference will be had primarily to the appended claims.

What is claimed is:

1. In a variable pitch propeller, a plurality of blades, a torsion rod for each blade, a hub including' means for mounting each torsion rod, the

axes of said rods being in spaced relation and oblique, relative to the axis of rotation of the hub, means for exerting a torque upon each of said blades, each of the last named means being operable after the blade to which it is operatively connected has angularly moved about the axis of its respective torsion rod from a predetermined position, said torque being in response to a lateral displacement of each blade upon the hub, one or more intermediate members for each one of said blades, and resilient means for urging each interdriving shaft, a hub operatively connected to said shaft, means uponsaid hub for mounting each of said rods, the axis of said shaft and rods being non-intersecting, means responsive to a lateral displacement of each blade upon the hub for assisting a pivotal movement of the blades after said movement has begun from a predetermined position of the blades, means for exerting a resilient torque upon each of said blades, and means for adjusting the last named means, said resilient torque acting upon each blade being variable in a predetermined manner in response to .the angulsr movement of the blade from a predetermined position.

3. A variable pitch propeller comprising blades supported so as to be pivoted about the longitudinal axes thereof and to be laterally displaced from a predetermined equilibrium position by the forces set up when said propeller is rotated in a fluid medium, torsion rods for supporting said blades and for resisting the pivotal movement thereof from said equilibrium position, control means connected to eachofsaid blades, each of said control means comprising a spring mounted to exert a force in the direction of the blade, and a rigid member connected at one end to said spring and at the other end to said blade adjacent the periphery of the latter, said member being radially disposed relative to said blade when the latter is in equilibrium position and being rendered eccentric relative to said blade by the pivotal displacement of the latter whereby said spring applies a torque to. said. blade'tending to increase any pivotal displaceznentthereof from equilibrium position, and means adapted to convert the lateral displacement oi the blades into a turning torque applied to said blades, the latter torque tending to further increase the pivotal displacement of said blades from said equilibrium position.

4. In a variable pitch propeller comprising one or more blades supported so as to be pivoted and laterally displaced from a predetermined initial equilibrium position relative to the hub thereof by the forces set up when said propeller is rotated in a fluid medium, resilient supporting members 'for said blades, said members having axes laterally displaced from and obliquely disposed to the members opposing the angular and lateral disto further angularlydisplace said blades from' placements of said blades relative to the hub, means adapted to convert the lateral displacement of said blades into a turning torque tending said equilibrium position, and control means for each of said'blades, each of said control means comprising resilient means mounted on said hub to exert a force in the direction of the blade, and

a rigid member connected at one end to said resilientmeans and at the other end to said blade adjacent the periphery oithe latter, said member being radially disposed relative to said blade when the latter is inequilibrium position and assuming an eccentric position relative thereto when said blade is pivotally displaced whereby upon pivotal displacement said resilient means applies a torque to said blade tending to increase said pivotal displacement. v

5. In apparatus of the class described, a plurality of pivot rods, 2. blade secured to each rod,

the axis of each of said rods being inclined relativeto the axis of the blade secured thereto, a driving shaft, a hub operatively connected to said shaft, means upon said hub for mounting each of said rods, the axes of said shaft and rods being non-intersecting, means responsive to lateral displacement of each blade upon the hub I "an eccentric position relative thereto when said blade is pivotally displaced whereby upon pivotal displacement said resilient means applies a torque to said blade tending to increase said pivotal displacement. V

DIMITRI SENSAUD on LAVAUD.

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