US2645295A

US2645295A - Self-adjusting propeller blade

Info

Publication number: US2645295A
Application number: US38304A
Authority: US
Inventors: Doussain Robert; Bousson Robert; Perrier Louis
Original assignee: Office National dEtudes et de Recherches Aerospatiales ONERA
Current assignee: Office National dEtudes et de Recherches Aerospatiales ONERA
Priority date: 1947-07-12
Filing date: 1948-07-12
Publication date: 1953-07-14
Anticipated expiration: 1970-07-14

Description

y 4, 1953 R. DOUSSAIN EI'AL 2,645,295

V SELF-ADJUSTING PROPELLER BLADE Filed Ju ly 12,1948 4 Sheets-Sheet 1 INVENTORS WW y 1 1953 R. DOUSSAIN EFAL 2,645,295

' SELF-ADJUSTING PROPELLER BLADE Filed July 12, 19.48 4 Sheets$heet 2 Fig.1.

InZ/en fars:

WW,WMVMFM July 14, 1953 Rbo'ussm ETAL 2,645,295 SELF-ADJUSIING PROPELLER BLAJ JE Filed July 12, 1948 v N 4 Sheets-Sheet a INVENTORS M y 5 R. pdus'sAm EI'AL 2,645,295

'- SELF-ADJUSTING PROPELLER BLADE Filed July 12, 1948 4 Sheets-Sheet 4 'mvmrons: {2 a BY flow V Patented July 14, 1953 2,645,295 SELF-ADJUSTING PROPELLER BLADE Robert Doussain, Vitry-sur-Seine, Robert Bousson', Lyon, and Louis Perrier, Seto, France, as-

signors to Office National dEtudes et de Recherches Aeronautiques, Paris, France, a company of France Application July 12, 1948, Serial No. 38,304

;In France July 12, 1947 p 3 Claims. (01.170-16056) This'in'vention relatesto screw propellers and has for its object a system of articulation permitting the blade to take, for each speed of rotation, the best appropriate inclination corresponding at each moment to the resultant of the bending moments due to aerodynamic and centrifugal forces, wherefore it is possible to make the blade lighter in weight, and decrease the reactions on the hub due to aerodynamic and centrifugal forces so that the hub may, in turn, be made considerably lighter in weight, while doing'away with vibrations and flutter, as wellas with stresses due to centrifugal force in the articulations of the blade.

The applicants have already proposed, in their patent application Serial No. 745,360 for improvements in an Articulation Mounting and Its Application to Screw Propellers With Oscillating Blades, a system of articulation allowing of the blades to orient themselves freely, without subjectingthe articulations to the stresses due to centrifugal force. They have found, however, that with the system of articulation proposed the blades are likely to vibrate or flutter, in certain operational conditions.

The present invention has for an object to provide means whereby the blade, while orienting itself freely and its articulations being free from the stresses due to centrifugal forces, may behave at every instant like a rigid blade.

According to the invention, each blade is mounted on an articulation permitting the blade to orient itself freely at least about one axis and more particularly about two perpendicular axes forming a universal joint, means being provided, on one hand, for relieving the articulations from the stresses due to centrifugal forcesand, on the other hand, for subordinating the parameters of position of the articulation to the law of varia-- tionof pitch, in such a way that, for every pitch position of the blade, the inclination of the latter is determined in one and the same way and that the blade behaves like a rigid blade.

' As the pitch of the blade is determined according to the conditions of operation, it follows that, according to the invention, the. inclination of the blade is determined automatically according to the said conditions and, consequently,.,following the resultant of centrifugal and aerodynamic forces.

' Circumferential guiding elements are provided for imparting convenient inclinations to the blade for each pitch of the same, said guiding elements being arranged for operation through angles varying from 0 to 360%, or merely from 0 to 2 to simplify the construction. Said guiding elementsmay not be used for. certain pitches of the blade, so as to render the latter free for operation in pre-selected working conditions.

The guiding may be arranged to be effective only at rest or else at lower speeds, the blade remaining freely pivoted at greater speeds. Of course, the law of subordination of the guiding. system to the pitch variation will be determined by a preliminary calculation, account being taken of the aerodynamic characteristics of the propeller utilized, as well as of the conditions of utilization of the aeroplane.

The advantage of the construction according to the invention are as follows: a i I (a) All vibrations or flutter may be eliminated since, during pitch variation, the blade can be guided so as to be rigidly supported in each pitch position.

(b) The blade may be straight and, therefore, does not present the constructional difficulties of a blade set off with respect to its hub.

(c) It is possible to utilize the same type of blade for different applications, by merely modifying the servo-control of the blade.

(d) The guidage may be not employed for cer- V tain pitches and the blade may be renderedfree for operation in preselected working conditions. (e) The'initial position of the guiding system may be adjusted at rest or in operation; The invention will be more clearly understood by referring to the accompanying drawings which show the preferred embodiment (of which Fig:

l is a good illustration) of apparatus designed according to the invention and in which:

Fig. l is a sectional view, taken on the line I-I of Fig. 1a., of a variable pitch propeller showing the swivel mounting of one blade only, and the blade guiding means designed according to the invention for rigidly supporting the blade for an angular displacement about its longitudinal axis varying from 0 to 360.

Fig. 1a represents a transverse section taken on the line Ia-'-Ia of Fig. 1.

Fig. 2 is a view similar to that of Fig. 1, showing a modification in which the blade guiding means is effective through an angle varying from 0 to 120.

Fig. 3 is a detail view showing a device for changing the initial angular position of the guided on a lateral projection 2a of ablade carrying member 2 by means of a retaining ring 3. The blade carrying member 2 is mounted toose cillate about a ball joint 4 supported by a central tubular member 20 to which the change of, pitch is transmitted from aworm gear (not 7 shown) by means of a helical worm wheel II and a nut l2, which on the other hand, connects the lower portions 5a of a hollow socket member 6 with the wheel ll, these lower portions 6a traversing, each with a certainamount of play, a corresponding slot 2b provided in the lateral projection 2a of blade-carrying member 2. The unit constituted by wheel H, socket member Gand central tubular member, 20 is ro 'tatably mounted in hub l by means'of a nut 8 and the thrust bearings 9 and H]. The space left between the inner face of the spherical upper portion 61) of socket 6 and the outer surface of blade-carrying member 2 is completely filled by a rubber body 5 which adheres to this outer surface of member 2. mounted in tubular member 29 and connected with blade-carrying member 2 in such a way as to transmit to the latter the pitch'change motion from tubular member 26, while permitting the unit constituted by blade 1, blade'carrying member 2 and 2a and locking ring 3, to orient itself freely. It is easy to see that this arrangement allows the pitch adjustment of the r tatable and free tiltable blade whereby the confined rubber body 5, which is substantially incompressible, acts. as a thrust bearing. adapted to relieve the Cardan joint l3 from centrifugal force in each position of the blade;

The guiding means for supporting the bladein each pitch position comprises, in the example shown, a system of three annular guiding

elements

11', 18,19, mounted on hub 7 so as to concentrically surround the blade carrying member 2. Each'guidingrelement has an upper sloping surface, the disposition and length of which, as well as the precise degree of inclination, being determined in accordance with the desired pitch adjustment of the propeller blade and the conditions by which free swivelmovements of the latter are accomplished. A ring I4 is mounted to rotate with the lateral projection 2a of blade carrying member 2, said-ring having three shafts 15' disposed at 120 fromone another and receiving each a roller [Br Each of these rollers is rolls on .the'inclined surface of one of the guiding elements ll, i8 and [9, the shafts t having, of course, different lengths. In this way, there is obtained a guiding of the blade throughout an angular displacement of about 360, the guiding elements ll, 18' and I9 supporting the blade in each adjusted pitch position, whereby the blade has, for instance, substantially the same tilted position which it-would have freely taken without the help of guiding means such as the elements. ll, 18 and I9.

In the example shown in Fig.- 2, the/general construction is similar to that of Fig. 1, theonly difference being in that the blade is arranged for an angular displacement not exceeding 120; thispermits of using'a singleguiding, element A Carda-n joint is is 0 4 I! on which each of the inclined guiding surfaces ensuring a rigid support of the blade, occupies one third of the circumference. In this example, the shafts l5 are, therefore, of equal length. i v

In Fig. 3 is shown by way of example an arrangement for changing at any time the angular position of the guiding surfaces. This adjustment may be made either on starting or during flight. It will be apparent that the guiding elements [7, l8, l9, are here shown as being carried by a ring gear 24 rotatably mounted on the'outer end of hub l. A worm gear 23, disposed in a stationary casing which may be secured to or formed as part of hub 1, is arranged to mesh with ring gear 24 whereby actuation of worm gear 23 will adjust the angular position of the guiding elements l1, 18, I 9 with respect to the position of the propeller blade.

In the examples of Figs. 1 and 2 the stresses due to centrifugal force, are absorbed: by the rubber body 5 of variable shape and constant volume. a

In the example shown inFig. 4 the rubber body is eliminated and theguiding element 21 pcsitioned on the side of the rollers opposed'to that directed toward the hub. Of course, more than one guiding element may be used, the only difference from the previous constructions (Figs;

l and 2') being inthat here the particular ,device for absorbing the stresses due to centrifu gal force is eliminated and replaced by the guide ing surfaces which subordinate the inclinations of the blade to its pitch and, consequently to speeds.

As hereinabove stated, the invention is not limited to the particular constructions, norto the particular applications, described and shown; for changes may be made thereih-withoutsubstantially departing from the invention hereof,- in particular with a view to accommodating the same to propelling members in aeroplanes,v helicopters and rotating-wing machines, windmills,

4 air-blowing machines, compressors, etc/. the in:-

vention being intended to bejdefined in the accompanying claims. I

Having thus described our inventionwejclaimz 1. A variable pitch propeller comprising a-hub,

a plurality of blades, socket members mounted,

on said hub for rotation around axese radially with respect to the axis of t e l ih b blade carrying members engaged withsaid socket member for rotation therewith to different pitch positions and each carrying one of said blades, a Ca-rdan joint connecting each said socket member with the corresponding blade carrying.

member, said Cardan joint transmitting rotational movement from the socket member to the blade carrying member while permittingfree" swivel movement of the latter, thrust means ink ity of shafts projecting from the blade carry ing member, a roller journaled on each shaft, and inclined guiding surfaces mounted on-tthe socket member and-disposed along. arcsof-circles centered on the longitudinal axis ofv the socket member, said rollers running on said guiding.

surfaces.

. 5' 2. A variable pitch propeller according to claim 1 in which there are, for each blade, three shafts bearing rollers spaced 120 apart around the longitudinal axis of the blade carrying member and three corresponding annular concentric inclined guiding surfaces.

3. A variable pitch propeller according to claim 1 in which the guiding surfaces are mounted on the socket member for rotation with respect to said member about the longitudinal-axis thereof, and which includes control means between said surfaces and member operative to displace angularly said surfaces with respect to said member.

ROBERT DOUSSAIN. ROBERT BOUSSON. LOUIS PERRIER.

Number 5 2,121,345 2,163,482 2,241,786 2,275,053 2,3 64,871 10 2,365,214 2,394,460 2,457,815

Number 15 131,419 805,178

Date

Name Hafner June 21, 1938 Cameron June 20, 1939 Loth et a1. May 13, 1941 Reissner et a1. Mar. 3, 1942 Reissner Dec. 12, 1944 Reissner Dec. 19, 1944 Martinotti Feb. 5, 1946 Green Jan. 4, 1949 FOREIGN PATENTS Country Date Great Britain Aug. 14, 1919 France Apr. 17, 1936