US2694458A

US2694458A - Rotor blade construction

Info

Publication number: US2694458A
Application number: US196149A
Authority: US
Inventors: Emerson W Stevens
Original assignee: Bell Aircraft Corp
Current assignee: Bell Aircraft Corp
Priority date: 1950-11-17
Filing date: 1950-11-17
Publication date: 1954-11-16
Anticipated expiration: 1971-11-16

Description

Nov. 16, 1954 E. w. STEVENS ROTOR BLADE CONSTRUCTION 2 Sheets-Sheet 1 Filed NOV 17, 1950 INVENTOR. Emerson M/ Steve/75 BY ATTORNEYS Nov. 16, 1954 E. w. STEVENS ROTOR BLADE CONSTRUCTION 2 Sheets-Sheet 2 Filed NOV. 17, 1950 Jnnen tor [me/"5012 14/ Stevens Qu n, Ma

Gttorncgs United States Patent Office 2,694,458 Patented Nov. 16, 1954 ROTOR BLADE CONSTRUCTION Emerson W. Stevens, Snyder, N. Y., assignor to Bell Aircraft Corporation, Wheatfield, N. Y.

Application November 17, 1950, Serial No. 196,149

Claims. (Cl. 170-159) This invention relates to hollow metal rotor blades, and more particularly to an improved rotor blade construction for use in rotary wing aircraft and the like.

The present invention is especially applicable to relatively large rotor blades wherein the problems of vibration and flexing are more severe; and one of the objects of the invention is to provide a blade of the character aforesaid which is of improved fatigue life and practically impervious to fungi, rot and moisture absorption, as well as being adapted to take gun fire damage to some degree without disastrous results.

Another object of the invention is to provide a blade construction as aforesaid which may be readily and inexpensively fabricated of easily formed standard type component parts.

Another object of the invention is to provide an improved blade as aforesaid which comprises a novel fabrication of structural elements eliminating highly stressed connection areas and providing improved overall structural strength.

Another object of the invention is to provide a blade as aforesaid which is free from welds or unreinforced perforations, or other stress raising arrangements in areas of substantial blade stress.

Another object is to provide an improved blade constituting multi-cell type construction elements which may be individually penetrated by bullets or shell fragments or the like without disastrous results.

Other objects and advantages of the invention will appear from the specification hereinafter.

In the drawing:

Fig. l is a fragmentary top plan view of the root end portion of a blade of the invention;

Fig. 2 is a composite fragmentary top plan view of intermediate and tip end portions thereof;

Fig. 3 is a section, on an enlarged scale, taken along line III-III of Fig. l; and

Fig. 4 is a fragmentary composite section, on a large scale, taken along line IV-IV of Fig. 2.

As shown in the drawing, the blade of the invention is illustrated to comprise a metal nose element in the form of a metal extrusion member sectioned as illustrated in Figs. 34 to comprise a typical airfoil nose contour and consisting generally of top and bottom surfaces interconnected by chordwise spaced web portions 11-12. The element 10 runs lengthwise of the leading edge of the blade, and is preferably uniformly dimensioned throughout its length and designed and selected as to weight so as to assist in bringing the overall center of gravity of the blade forwardly to the desired chordwise position. Abutting the rear web 12 of the nose section 10 is a box section structure 14 comprising a pair of positionally opposed channel section metal members 15-16. Similar

box section structures

18 and 22 comprising positionally opposed channel section elements 19-20 and 23-24, respectively, are arranged alongside and successively to the rear of the box section 14 and the box section 18; the members 23-24 in turn mounting in lapped relation at their trailing edge portions upon a trailing edge strip 25 (Fig. 3) which may also be conveniently fabricated in the form of a metal extrusion strip.

The channel section elements 15-16-19-20-23- 24 are connected at their positions of abutting continuity by means of suitable metal-to-metal cement, and the members 15-16 are similarly connected to the extrusion 10 where they abut the web portion 12 thereof,

and the members 23-24 are similarly connected to the trailing edge strip 25 at positions of overlapping thereof. Thus, the box sections 14-18-22 combine with the nose section 10 to provide a multi-cell base structure which may be readily fabricated to the desired airfoil sectional contour simply by suitable shaping of the element 10 and selection of suitably dimensioned channel members forming the box sections of the unit. Skin elements such as are indicated at 30-30 are then applied over the top and bottom surfaces of the framing cell structure and integrally connected thereto as by any suitable metal-to-metal adhesive; the nose element 10 being illustrated at 32-32 as being recessed atits top and bottom surfaces so as to receive the skin plates 30-30 in flush relation thereon. Similarly, the skin plates 30-30 overlap and are. cemented to the trailing edge strip 25; thus firmly bonding the structure together. 1 As illustrated in Figs. 1 and 3, the root end portion of the blade may be effectively reinforced if required in. the neighborhood of the rotor hub attachment connection by means of root

doubler metal sheets

34, 36, 38, 39, which are shaped to lap over the skin and to build up a laminar structure the sheets of which are cemented together by suitable metal-to-metal adhesive. Thus, as shown in Figs. 1-3, the laminar structure may be provided of progressively increased thickness at the root end of the blade and of maximum thickness in the re gion of the clevis bolt connection of the blade .to the rotor hub. For this purpose the nose element 10 and the skin and reinforcing sheet elements are apertured to receive a sleeve 40 which also extends at its opposite ends through apertured portions of a clevis bracket 42 constituting the hub-to-root connection device. A bolt. (not shown) slip-fits through the sleeve 40 to take th connection loads during service.

Thus, it will be appreciated that the

channel section elements

15, 16, 19, 20, 23, 24 are fabricated in conjunction with the nose element 10 and trailing edge strip 25 to provide a novel airfoil base fabrication; the flange portions of the channel members being arranged so that each line of junction between oppositely paired channel flanges as indicated for example at 46 (Fig. 3) registers against a solid flange portion of the adjacent abutting channel flange. Consequently, the channel elements of one box section cooperate in novel manner .to reinforce the lines of junction between the channel elements of the next adjacent box section, and the completed structure is therefore of improved strength while being of utmost simplicity. An abrasion-resistant leading edge cover sheet of steel or the like is preferably cemented over the leading edge of the blade as indicated at 50 to guard the blade against impact damage during service. Supplemental reinforcement elements such as indicated at 52 may be cemented in place as shown in Fig. 3 to further brace the blade against loads, as may be required.

Thus, it will be appreciated that by simple constructional processes the channel sectioned elements are relatively assembled so as to provide box sectioned structural cells interiorly of the blade, such as provide maximum strength against failure due to damage for example as by gun fire penetration of the individual cells. In such event due to the construction of the cells they are not materially reduced in strength, and in most cases the blade would be suited to continued operation until opportunity may be found for repair of the blades. Whereas, only one specific form of the construction has been shown and illustrated herein it will be understood that the invention is not so limited but that various changes may be made therein without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. A hollow rotor blade comprising a multi-cell base structure shaped externally to airfoil contour form, said base structure comprising a plurality of cells extending longitudinally of the blade in side-by-side relation, one of said cells comprising an integral hollow metal extrusion having a surface portion forming the shape for the leading edge portion of the blade and terminating rearwardly thereof in a transverse web portion, a second cell adjacent said one cell web portion comprising opaeaasrss positely paired channel sectioned metal members disposed in oppositely faced relation to define a box-sectioned shaped cell, the remaining of said cells similarly comprising oppositely faced channel sectioned members disposed to define corresponding box sectioned .cell formations terminating in a trailing edge strip portion, said extrusion and said channel members being cemented together at positions of abutting continuity, and said base structure being covered by sheet metal skin elements cemented thereto so as to overlap the junctions between said cel 2, A hollow rotor blade comprising a multi-cell base structure shaped externally to airfoil contour form, said base structure comprising a plurality of cells extending longitudinally of the blade in side-by-side relation, one of said cells comprising a generally tubular member having a surface portion forming the shape for the leading edge portion of the blade and terminating in a rear wall portion extending spanwise .of the blade, the cell adjacent said .one cell comprising oppositely paired channel sectioned metal members disposed in'oppositely faced relation to define a box-sectioned shaped cell, the re.- maining cells similarly comprising oppositely faced channel sectioned members disposed to define corresponding box-sectioned cell formations terminating in a trailing edge strip portion, said tubular member rear wall portion and said channel members being cemented together at positions of abutting continuity with the channel members of each cell bearing against a channel member of both adjacent cells, and said base structure being covered cells extending longitudinally .of the blade inside-by-side relation, one of said .cells comprising a generally tubular shaped extrusion member having a surface portion forming the base for the leading edge portion of the blade and terminating in a rear fiat wall portion, the cell next adjacent said one cell comprising oppositely paired channel sectioned metal members disposed in oppositely faced relation to define a box sectioned shaped cell, the remaining of said cells each similarly comprising oppositely faced channel sectioned members disposed to define corresponding box sectioned cell formations, said tubular member and said channel members being cemented together at positions of abutting continuity with a channel member in each cell overlapping both channel members of an adjacent cell, and said base structure being covered by sheet metal skin elements cemented longitudinally of the blade in side-by-side relation, said cells each comprising oppositely paired channel sectioned metal members disposed in oppositely faced relation to define a box sectioned shaped cell, the channel members of adjacent cells being arranged in abutting continuity with the junction between channel members of the same cell registering with a solid flange portion of an adjacent cell channel member, said channel members being cemented together at positions of abutting continuity, and said base structure being covered by sheet metal skin elements cemented thereto so as to overlap the junctions between said cells.

5. A hollow rotor blade comprising a multi-cell base structure shaped externally to airfoil contour form, said base structure comprising a plurality of cells extending longitudinally of the blade in side-byv-side relation, one of said cells comprising an integral hollow metal extrusion having a surface portion forming the shape for the leading edge portion of the blade and terminating rearwardly thereof in a transverse web portion, a second cell adjacent said one cell web portion comprising oppositely paired channel sectioned metal members disposed in oppositely faced relation to .define a box sectioned shaped cell, the remaining of said cells similarly comprising oppositely faced channel sectioned members disposed to define corresponding box sectioned cell formations terminating in a trailing edge strip portion, said extrusion and said channel members being cemented together at positions of abutting continuity, said base structure -being covered by sheet metal skin elements cemented thereto so as to overlap the junctions between said cells, a clevis bracket provided adjacent the root end of said blade, said extrusion being apertured adjacent the root end thereof, a sleeve extending through said bracket and said aperture, and a sheet metal laminar reinforcing structure over said skin elements, said reinforcing structure being of maximum thickness in the region of said clevis bracket and of progressively decreased thickness from the root end to the tip end and the leading edge to the trailing edge of the blade.

References Cited in the file of this patent N TED TAT S PA E TS Number Name Date 397,767 Wells Feb. 12, 1889 1,287,613 Basquin Dec. 17, 1918 1,565,153 Hubert Dec. 8, 1925 1,785,543 Dornier Dec. 16, 1930 1,842,736 Stout Jan. 26, 1932 1,846,256 Havill Feb. 23, 1932 1,930,285 Robinson Oct. 10, 1933 2,183,158 Bennett Dec. 12, 1939 2,410,609 Pecker Nov. 5, 1 946 2,469,480 Sikorsky May 10, 1949 2,568,230 Gluhareff Sept. 18, 1951 2,580,363 Schmitt Dec. 25, 1951 FOREIGN PATENTS Number Country Date 625,778 Great Britain July 4, 1949