US2388879A - Blade structure for aircraft sustaining rotors - Google Patents

Description

Nov. 13, 1945. P. H. STANLEY BLADE STRUCTURE FOR AIRCRAFT SUSTAINING ROTORS Filed Feb. 19, 1942 skeleton of novel form,

arranged in a novel in horizontal section;

.and Figure 4 is an elevational view of oneof the rib elements employed in.

'apertured lug I Patented Nov. is, 1945 UNITED STATES PATENT. OFFICE] BIEADE STRUCTURE SUSTAINING ROTOBS' rain 11'. swim. to Antogiro Co Pa., a corporation Huntingdon Valley, Pa, assignor mpany of America,

of Delaware Philadelphia,

Application February 19, 1942, Serial at. 431,410.

sustaining 3 Claims. (01. ale-is) as sponge rubber, is molded to define the airfoil contour .of the blade, the body of said material having embedded therein a reinforcing structural as is more fully described hereinafter.

One of the general objects of the invention is to simplify the structure and fabrication of a blade of this type, in order to make practicable manufacture of rotor blades from molded cellul'ar material. I

More specifically, the invention has in view the provision of means, especially structural elefrom twelve to fifteen ments, arranged to provide eifective strength and reinforcement, notwithstanding the formation of the blade from relatively light cellular material,

such as expanded or sponge rubber.

In accordance with another aspect of the invention, the structural skeleton of the blade is maintaining a desirable cross sectional weight balance in the blade, this being of importance for dynamic and aerodynamic reasons which need not be considered in detail herein.

How the foregoing and other objects and advantages are attained will appear more fully from the following description, referring to the accompanying drawing, in which Figure 1 is a somewhat diagrammatic plan view of a blade constructed in accordance with this invention, an intermediate portion of the blade being broken out, and certain parts being shown Figure 2 is a sectional 2-2 of Figure 1; 1

Figure 3 is a fragmentaryhorizontal sectional view of the nose portion of the blade, this view illustrating a short'piece of the spar in plan;

view taken on the line manner not only achieving the foregoing purposes but, at the same time,

'l'may serve for cooperation with a drag pivot, but the blade mounting preferably also includes a pivot (not shown) the flapping pivot providing freedom for swinging movementof the blade in a direction generally transvers its mean rotative path of travel.

It may be mentioned that the blade, as broken out in Figure 1, is greatly shortened as compared with the usual plan form,,in accordance with-which the blade length is commonly equal to times the chord; dimension.

At spacedintervals along the "spar partial ribs 8 are. provided, each of these ribs preferably having a foot 8 or the like adjacent the nose of the blade and adapted to cooperate with 'a nose strip It, said strip-being secured to the ribs, as by welding. As seen in Figure 2, the sectional shape of the nose strip I0 is such as to define a portion of nose of the blade. V

In accordance with'the invention, the blade is built up by placing ture described-above introducing the molding material in a fluid or plastic state, the entire blade thus being molded as a unit, with the structural skeleton embedded therein. A best seen in Figure 2, the contour the airfoil contourof the of the molded material toward the nose of the. blade constitutes a continuation of the nose contour provided by the strip i0.

Known processes for curing or vulcanizing the plastic material may be employed, so asto produce an integral structure reinforced by the spar, ribs-8 and nose piece l0. By the employment of cellular or expanded molding material, a. relatively lightweight blade may be obtained, which blade, however, further has considerable strength because of the structural skeleton embedded therein. In this connection, it is pointed out that the ribs 8 not only project forwardly of the spar so as to support the nose'strip, but also project rearwardly so as to effectively carry the'centrifugai load set up during rotation and transmit the same from the molded material to the spar.

Examination of the drawing will further show that each of the 'ribs 8 is not only provided with apertures ll, periphery,.as indicated at II, to provide surfaces which, when projected on the mean plane of the blade, are of appreciably extended area; In this blade may be secured to the rotative hub. Lug the axis of the spar.

the skeleton strength struc.. in a suitable mold and then.

but is further flangedaround the.

1 Referring further to the nose strip to, is pointed out that the arrangement thereof as herein disclosed is of particular advantage since i the strip serves as an eiifective protection for the nose of the blade (which is of importance in preventing damage), and at the same time said strip further is highly effective in ballasting the blade to maintain the desired forward location oi the sectional center of gravity. Since the strip it is l and retaining the molded material and for stifat the forwardmost point of the cross sectional contour, the ballasting may be achieved with a minimum of weight,

Although the material 01 which the blade is molded may be of a variety of diflerent types, varying in elasticity, resilience and porosity, prelerably the material is considerably expanded (having considerable voids) and, additionally, has at least that degree of resilience which will avoid damage to the blade under the influence oi the normal flexing which takes place in operation.

- I claim:

1. For an aircraft sustaining-rotor, a substantially elongated aeroform blade comprising a single main spar extending along the major axis of the blade and having a pivotal connection device at its root end so that the entire centrifugal load of the blade is carried through the root end of said single spar, molded material surrounding the spar and in large part defining the aeroioil contour, a tough leading edge strip of channel so form running along and substantially defining the nose of the aerofoil substantially throughout the length or the molded material, and a plurality of transverse members secured to the spar at in- 5 tervals therealong, extending forwardly within said molded material and secured to said leading edge strip and transferring the centrifugal load on said strip to said spar, while iorming with said spar and strip a unified structure for supporting iening the blade as against bending in the mean plane thereof to an appreciable greater extent than in the flappin direction.

2. A construction according to claim 1, wherein said transverse members are of generally" platelike formation from the spar to the leading edge strip and flanged at the points 01' connection to r the spar and the strip, said leading edgestrip being of relatively heavy material as compared .to said molded material, thereby bringing the sectional center of gravity of the blade forward to the desired location.

3. A construction according to claim 1 in which I said transverse members have laterally projecting flanges embedded in the molded material and serving to reinforce the molded material as against torsional deformation about the axis of the spar.

PAUL H. STANLEY.

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