US2097599A - Cellular structure - Google Patents

Description

Nov.2 1937. 4 J. PAVLECKA 2,097,599

STRUCTURE Patented Nov. 2, 1937 CELLULAR s'raUc'rUan John Pavlecka, Detroit, Mich.

Application December 31, 1934, Serial No. 759,816 Renewed July 20, 1937 17 Claims. ((71. 244-124) My present invention presents a cellular structure utilizing the principle of interlocked cells as first disclosed in my co-pending application Serial No. 651,494, filed January 13th, 1933, and relates more particularly to structures having an irregular shape such'as wings of aircraft. The present application is a continuation in part of said copending application.

The-object of my invention is to devise an airfoil or similar structure that is light and strong under all conditions of loading, and that is easy to fabricate and assemble. An important object of my invention is to present a. sheet metal structure in which most of the usual riveting is eliminated whereby cost of fabrication is reduced, failure due to faulty workmanship obviated, and reduced air resistance achieved due to smooth exterior surface.

Another object and novelty disclosed through 20 this invention resides in that the exterior envelope or shell of asheet metal structure having an irregular contour is made to cooperate to an equal extent with internal bracing in stress carrying.

vention resides in forming an irregular closed structure, such asa wing, of a series of oddshaped cells or spars, which cells when integrated will yield the exact predetermined contour and will maintain it permanently due to transverse bulkheads incorporated in the cells. I

The manner in which these objects are ma rialized will now be described with reference to the drawing which forms an integral part of this specification, and in which Fig. 1 represents-a perspective view of the wing panel of an airplane, disclosing in transverse cross-section the shell and the diagonal bracing therefor as formed by two rows of triangular 40 cells within the airfoil contour, in the foreground. and showing a fragmented view of the interior of the wing further on along its span with reinforcing bulkheads therein.

Fig. 2 is a transverse cross-section through th wing of an airplane in which but .one row of cells. is employed to provide the exterior shell and the interior truss webbing, and a panel of sheet material to complete the shell. Fig. 3 represents the fore portion of a wing in transverse cross-section disclosing a construction analogous to that in Fig. 2 except for the manner of attaching the panel which provides one side of the shell, and shows stiffened bulkheads in the cells. I

All three structures as shown are characterized,

A still further novelty realized through this inthe shell.

is to be reproduced and maintained closely. The

structures are assembled essentially of a number of tubular cells or spars of any suitable or desirable shape, triangular shape or a modification of it being preferred and is represented in all three embodiments. The. generally triangular cells extend lengthwise of the structure and have each one web-hereinafter referred to asthe chord web-and one or two sides that are normally straight; the chord web of each cell provides one link or section in the exterior shell of the structure and for that reason is formed to a more or less oblique curvature as pertainingfor instance, to an airfoil at the particular location of the cell in it; theone or both sides of each cell form diagonal truss webbing in the interior of the structure. The chord web and the sides of each cell meet in at least two profiled apices, both of them at the chord web, and the cells are disposed parallely in such a manner that each two associated cells form a groove, a socket or a sheath between them with their apices; a substantially rigid strut is inserted in each groove, socket or sheath. In the preferred embodiments as illustrated, the cells are conjoined through the instrumentality of these rigid struts, the apices of the cells at their chord webs being transversely serrated and intermeshed withqthe apices of the associated cells whereby all the cells thusly intermeshed into a continuous row will constitute one side, either the top or the bottom, of the structure, and the struts, tubular or'prismatic, one of which is thrust in each sheath formed by two associated cells, interlock these cells into unity.

Referring now exclusively to Fig. 1, the wing assembly which-it represents is distinguished in that its whole exterior shell is constituted by the chord webs of two rows of generally triangular tubular cells, one on the ventral side comprising the cells I to 4, and the otheron thev dorsal side made up of the cells 5 to I; the cells in both of the rows alternate with and are complementary to each other whereby the sides I! and I3 of each two opposite abutting cells jointly form a diagonal truss web of double thickness in the interior of The two rows of cells forming the dorsal and the. ventral sides of the structure are integrated into the exact shape of the airfoil the leadingand the trailing portions ofwhich are provided by the particular, generally triangular, profile of the nose and the tail cells I and 4 respectively, while the intermediate cells 2, 3, and 5 to 'I collectively furnish the main body of the structure which becomes a coherent unit both mechanically and functionally,

To this end, the upright cells I to 4 as well as the inverted cells 5 to I have their two apices at their chord webs transversely serrated, and the full apcx portions I4 of each cell are intermeshed with the full apex portions I8 of the associated cells in the corresponding row, and rigid struts 8 are inserted one in each sheath formed by each pair of intermeshed cells. The serrations of the cells are alternate lengths of their apex portions cutout to a predetermined depth and staggered lengthwise in such a manner that the full apex lengths I4 and I6 of each cell will be opposite to and accommodated by the serrated lengths of the associated cells.

A feature of special importance resides inthe manner in which the two inverse rows of cells on the dorsal and the ventral sides are conjoined into unity; this is accomplished through the instrumentality of the fore and aft cells I and 4 respectively, in the ventral row; these two cells are interlocked in their apices not only with the associated cells 2 and 3 therein, but, moreover, with the end cells 5 and I in the dorsal row. This interlocking of two inversely opposite yet complementary rows of cells is achieved readily by profiling the apex of one of each two cells from the two rows at each end, as the apex I5 of the cell 1 and the apex I'I pertaining to the cell 4; by profiling is meant imparting the cell with a groove beyond its normal shape, such as the triangular groove of the apices I5 and H which corresponds to the shape of the struts I; the profile grooved apices I5 and II are transversely serrated and intermeshed with the normal apices of the associated cells I and 4, respectively. The dorsal row of cells 5 to I is thus tied up with the ventral row I to 4 firmly, without the use of any exterior means and without additional weight outside of that of the stress members that do the interlocking. In certain embodiments, for reasons of greater rigidity or because of a large number of cells in each row, further joining means may be employed if required, such as riveting each pair of opposite abutting cells together in their sides I2 and I3, as disclosed in 'my above cited parent application.

The cells I to I run from the root of the wing in the foreground to its very tip or its proximity in case there is a separate fairing piece at the tip, and they may be either of constant crosssection or of tapering proportions, thereby producing a wing of uniform or tapered aspect, respectively.

The cells are fabricated of sheet material of suitable properties and thickness by bending or rolling up a strip of the material into a triangular elongated box spar that will fit into a particular place in the assembly, the closing seam of the edges 9 being either welded or riveted by rivets I 0.

The rigid struts 8 may be either solid rods, hollow sections or tubing of suitable profile, the triangular shape being best suited to the natural shape of the apices of the triangular cells. In order to retain these struts in' place in the sheaths, screws II are driven into them through the shell of the structure at any number of points.

The function of the struts 8 is by no means limited to interlocking the cells and to conjoining the two rows of them into unity; being 10- cated immediately underneath the shell of the structure they provide excellent stress members, particularly in bending at the points of anchorage or suspension of the structure, in that they are constrained against failure by the firm hold that the cells have on them. .7

The cells in an airfoil or any other structure of the above type are not true' triangles, their chord webs being arched to a varying degree, and are, therefore, unstable as-to their shape under surface loading orin flexing. In-order to assure an unchangeable contour for the structure, means in the form of transversebulkheads are incorporated in its interior at strategic points where stresses are concentrated, as atthe hinges I8 and I9 for the aileron or at the points of anchorage or suspension of the structure. The bulkheads are made up each of a series of individual diaphragms 20, one in each cell and conforming to the shape of the cell closely except in the corners-and being secured in place as by rivets 2| Bulkhead diaphragms intermediate of those shown may be employed, particularly in the nose cell I, if desired.

Fig. 2 represents a structure derived from a number of cells in all ways analogous to those in the previous case, only one row however being made use of, which is preferably the row forming the dorsal side in the case of an airfoil. The cells 22 to 26 are serrated in their apices at the chord web, intermeshed and interlocked by means of the struts 8 as in the structure of Fig. 1. The extreme cells 22 and 26 provide the leading and the trailing portion of the airfoil, respectively,

and are interlocked with the associated cells 23 and 25 on the dorsal side, but instead of being tied up with cells intermediate of those on the dorsal side, they are secured to the abutting sides of the associated cells, as by rivets 3|. The shell of the airfoil on the ventral side is completed by the panel 21 which extends lengthwise. throughout the whole extent of the cells 23to 25, or any portion of it, and transversely spans the chord width between the extreme cells 22 and 26, and between these cells contacts with the continuous apices 28 of the cells 23 to 25; in each of these apices is deposited one strut 29' which corresponds to the interlocking struts 8 on the dorsal side. A number of screws 30 which penetrate into the struts 29 through the apices 28 are employed to retain both these struts and the panel 21 detachably in place. Aside from their function as retaining stringers the struts 29 serve the same purpose as the struts 8, Le, as stress members.

The sides of the cells 23 to 25 are shown as provided with reinforcing and stiffening means in the form of flanged perforations 38; this feature can be employed in any structure of my invention, such as the one in Fig. 1, with the advantage of increased resistance to failure and reduced weight.

Fig. 3 presents a modification of the embodiment of Fig. 2 which resides primarily in the manner of securing the panel H of sheet material to the extreme cells at the nose and tail end of the structure. The panel H is secured to the continuous apices of the intermediate cells as in Fig, 2, except at its fore and aft ends, of which this figure shows the former one; at these ends the panel H is not secured to the cell 33 as it is to the cells 23 and 25 in Fig. 2, but is provided, instead, with the profiled sheath 42 all along its fore end, and the aft end likewise. This sheath is formed by rolling the edge of the panel up and over and welding or riveting it by rivets 36 to theinward side of the panel. The sheath 42 is serrated transversely, similarly as the apex portions of the nose cell 34, and is intermeshed and interlocked with the apex portion of this cell at the dorsal side by the. strut 39.

Similarly as in the structure of Fig. l, transverse bulkheads consisting of individual diaphragms are incorporated in this embodiment, and means for stiffening them are made use of in this case flanged perforations 40 analogous to the perforations 88 in the diagonal webbing of Fig. 2 are shown. Any other means, such as corrugations, embossed ribs or riveted lattices may be substituted for the perforations 38 and 40.

I claim: I

1. A structure comprising, a series of individual tubular cells of sheet material extending lengthwise of the structure, each of said cells having its own chord web and two sides meeting in three apices, two of said apices at said chord web being transversely serrated and the third apex being continuous, said cells being intermeshed in said serrated apices thereof whereby said chord webs provide a portion of the exterior surface of the structure, a number of struts, certain of said struts interlocking each two intermeshed apices of said cells and others of said struts being disposed in said continuous apices of said cells, a panel or panels of sheet material providing the remaining portion of the exterior surface of the structure, said panel or panels being secured detachably to said struts in said continuous apices of said cells.

2. A structure comprising, one upright and one inverted row of tubular cells extending lengthwise of the structure, said cells having each one chord web and two side webs meeting in at least two well-defined apices, both of them at said chord web, said two apices at said chord web being transversely serrated and said cells ineach row being intermeshed in said serrated apices whereby they jointly provide an exterior shell and a series of webs of double thickness in said shell, a number of struts, each of said struts interlocking the two intermeshed apices of said cells, and means at the transverse ends of the structure for conjoining said two rows of cells into unity.

3. A structure having an irregular profile contour comprising, a series of tubular cells of sheet material extending lengthwise of the structure, each of said cells having one chord web and two sides meeting in three apices, two of said apices at said chord web being transversely serrated, said chord web of each cell being shaped to provide a particular section of said profile contour, said cells being intermeshed in said serrated apices thereof whereby said chord webs will jointly provide one side of the structure, a number of struts, each of sa d struts interlocking two intermeshed apices, a panel of sheet material contacting with the third of said apices of the cells and providing the other side of the structure, said panel having a transversely'serrated sheath at each transverse end thereof, and two terminal cells, one of said cells providingeach transverse extremity of the structure, said terminal cells abutting onto the last of the aforesaid series of cells and having each two apices thereat transversely serrated, intermeshed and interlocked, one apex with said last cell of the series and the other with said sheath of said panel.

4. A structure comprising, one upright and one inverted row of tubular cells of sheet material extending lengthwise of the structure, said cells having a generally triangular shape with at least two well-defined apices per cell, said two rows of cells being interposed to complement each other, the cells in each row providing jointly one exterior surface of the structure and having the two apices thereof at said surface transversely serrated and intermeshed, a terminal cell at each transverse extremity of the structure, each of said terminal cells having two apices transversely serrated and intermeshed, one apex with one cell from both aforesaid rows, and a number of struts, each of said struts interlocking two intermeshed apices in the structure.

5. A structure comprising, a number of tubular cells of sheet material extending lengthwise of the structure and having each two sides and one chord web meeting in three apices, said cells being abutted one onto each other inversely whereby all upright cells provide the surface on one side of the structure with said chord webs thereof and all inverted cells intermediate thereto provide the surface on the other side, one tubular cell constituting each transverse extreme end of the structure, said upright and saidinverted cells having two apices thereof at their chord webs transversely serrated and intermeshed with the apices of the corresponding associated cells, each of said extreme cells having likewise two apices serrated and intermeshed, one apex with an upright and the other with aninverted cell, and a number of struts, each of said struts interlocking two intermeshed apices in the structure.

6. A wing structure comprising, a series of tubular cells of sheet material extending lengthwise of the structure, each of said cells having one chord web and two sides meeting, in three apices, said chord web of each cell being shaped to fit into a particular location in the airfoil profile contour of the wing, said cells having each two apices thereof at said chord web transversely serrated and intermeshed with the apices of the associated cells in said series whereby all of said cells therein will jointly provide the dorsal side of the wing; another series of tubular cells intermediate of and complementary to aforesaid series providing the ventral side of the wing with the chord webs thereof and being intermeshed in apices thereat, one tubular. cell at the leading and another one at the trailing edge of the wing,

from the series on the dorsal and one cell on the ventral side of the wing, and a number of struts.

each of said struts interlocking two intermeshed apices in the wing.

7. In a structure, a number of tubular cells of -a number of struts, each of said struts interlocking two intermeshed apices in the structure, and a plurality of longitudinally spaced diaphragms of sheet material in said cells, said diaphragms in each cell being coplanar with the diaphragms in the other cells whereby said diaphragms will jointly form a number of bulkheads inthe structure.

8. In a structure, a number of tubular cells of iii sheet material extending lengthwise of the structure, said cells having chord webs and sides meeting in a number of apices, each of said cells having two apices at said chord web thereof transversely serrated and intermeshed with the apices of the associated cells whereby said chord webs of all cells jointly provide the exterior surface of the structure and said sides of each two abuttin cells form a web in the interior. thereof, a number of struts, each of said struts interlocking two intermeshed apices in the structure; and a plurality of longitudinally spaced diaphragms of sheet material in said cells, said interior webs and said diaphragms being formed with means recessing from their plane for stiffening said sheet material thereof.

9. A structure having a curvilinear profile integrated of a plurality of individual tubular spars,

said spars having a substantially triangular shape and being abutted one onto each other in inverse relation thereby forming jointly a shell and a series of inclined double webbed trusses intersecting each other at said shell, a number of linear members disposed as stress elements at the intersections of said trusses, and means for interlocking said spars into unity through the instrumentality of said linear members.

10. A structure integrated of a plurality of individual tubular spars, said spars jointly defining a portion of the exterior of the structure, means complemental to said spars abutting thereon and providing the remaining portion of the exterior of the structure, rigid strutsdisposed as stress members in the interior of the structure, and means for conjoining said spars and said complemental means into unity through the instrumentality of said struts.

11. A structure integrated of a plurality of individual tubular spars, said spars jointly defining a portion of the exterior of the structure, a panel of sheet material, said panel contacting said spars and providing the remaining portion of the exterior of the structure, rigid struts disposed as stress members in the interior of the structure, and means for conjoining said spars into unity and conjoining said panel with said spars through the instrumentality of said struts.

12. A composite airfoil structure comprising, a plurality of substantially triangular tubular spars disposed alongside of one another in inverse relation to form the airfoil shell and a series of continuous diagonal double webbed trusses within said shell, and a number of linear stress members lodged between said series of trusses and said shell, said spars being integrated into unity through the instrumentality of said stress members.'

13. An airfoil structure integrated of a plurality of individual tubular spars, one row of said spars defining a portion of the exterior of the airfoil and another row of said spars complemental to said first row defining the remaining portion of the exterior of the airfoil, said two rows of spars jointly forming a series of double webbed trusses within the airfoil, rigid struts disposed at and along said trusses, means for joining the two rows of 'spars together, and means for conjoining said spars in each row through the instrumentality of said struts.

14. An airfoil structure integrated of a plurality of individual tubular spars, one row of said spars defining a portion of the exterior of the airfoil and another row of said spars complemental to said first row defining the remaining portion of the exterior of the airfoil, said two rows of spars jointly forming a series of double webbed trusses within the airfoil, rigid struts disposed at and along said trusses, and means for conjoining said two rows of spars with each other into unity and for conjoining said spars in each row through the instrumentality of said struts.

15. A structure comprising, a plurality of individual tubular spars of sheet material each having at least two pointed apices and being serrated in said apices, said spars being disposed alongside of one another whereby each two adjoining spars form a double webbed truss and said serrated apices thereof intermesh to form joint- 1y a substantially triangular sheath at and along said truss, a number of linear members having a triangular cross-section conforming to that of said sheaths, said members being inserted in said sheaths to interlock said spars relatively immovably.

16. A structure comprising, a plurality of individual tubular spars of sheet material each having at least two outwardly profiled apices and being serrated in said apices, said pars being disposed alongside of one another whereby each two adjoining spars form a double webbed truss and said serrated apices thereof intermesh to form a generally polygonal sheath at and along said truss, a number-of linear members having a polygonal profile conforming to that of said sheaths, said members being inserted in said sheaths to interlock said spars relatively immovably.

17. A structure comprising, a plurality of individual tubular spars of sheet material having a triangular cross-section and each having two of the apices thereof serrated, said spars being disposed alongside of one another alternately in inverted spars.

JOHN PAVLECKA.

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