US2382835A - Load-carrying member - Google Patents

Description

M. WATTE'R LOAD CARRYING MEMBER Aug 14, 1945.

Filed Feb. 20, 194';

a N ENTOI K Mich-gel Waiter.

. fi a i V 3 .2 1s 9 m ATTORNEY Y Aug. 14, 1945.

M. WATTER LOAD CARRYING MEMBER Filed Feb. 20, 1945 2 Sheets-Sheet 2 INV ENTOR A TTORNE Y 23, Michael Watter Patented Aug. 14, 1945 LO AD CARRYING- MEMBER Michael Watten, Philadelphia, Pa., assignor to Edwardl G Budd Manufacturing Company,,, Philadelphia, Pa, a corporation of Pennsyl- Vania ApplicationlFebruaryr 20, 1943,, SeriaPNo. 476,534

5 Claims.

The invention relates to alload-carryin'gz member or girder, such as is particularly adapted for use as the rib of an: airfoil; particularly where such rib is required to-carry heavy loading.

It is among the objects oi theinvention to provide sucha ribhaving a high strength-weight ratio; and whichcan: be readily" fabricated out of light gauge" sheet metal, such as high-tensile stainless-steel:v

To accomplish these obj ectsthe rib structure is so designed as topermit certain of the strength members thereof; as the chords, while conforming generally to the curved contour of the'ainfoil in whichtherib is to be used, to'be made oi parts of rectilinear'form, in which-form these parts can bereadily made of the desired crosssection by simple draw-rolling ofa strip of the sheet metal.

It is quite diflicult to form angle or channel sections of stainless steel, for example; of the gauge requiredi'n such chords; was to give the exact contour ofthe airfoil; It is desirable for maximum strength that the chords lie as close-to the marginal contour as-possible. Ihe' difficulty is avoided and the last-mentioned desirable feature is attained by the invention by making the chords in-rectilinear'sections joined atthei'r meeting ends to form the full'lengthchords.

A web plate or an extension thereof is used according to the invention to form" the marginal cap stripcontour" forming portions of the rib. Between the chords the web plate is reinforced by a transversely corrugated" sheet and for balance the chords are of composite construction, parts located on oneside of the web and parts on the other. The chord" elements located on the side of the web plate'rei'nforced by the corrugations are further provided toprevent distortion of the ends of the corrugations under load, since these chord elements are secured to the corrugations and tothe'web plate, thus tying the parts strongly together. To facilitate assembling of thesechord elements and to stiffen the-chord structure still further one ofthese elements secured to the corrugations has a freely projecting portion, preferably for added stiffness, a flange portion projecting laterally of the web plate" and secured to the web-plate by a second element secured to the flange and the web plate andbrid'ging the ends of the corrugations.

Other and further objects and advantages and the manner in which they are'attained will become apparent from the following detailed descripti'on' when read in connection with the'drawings forming apart hereof.

iii

In the drawings, Fig. l is a; chordwise sectional: view: thnoug an airfoil showing the ribs of the invention em;-

bodied therein,

Figs 2 is a similar sectional view: on; an: en;- larged scale showing thernose' end ofithe ribz.

Fig; 3' is a sectional view of the nose: portion of the rib taken substantially-along the line.3r-3 of Fig.2;

Fig; 4 is anenlarged fragmentary-perspective view; with parts broken away, of? the lowenportion of the rib showing'the'joint: between; abut;- ting rectilinear chord: sections; as: seen. looking in the direction indicated by the arrowsat" the end of t'he section line-'4 -4 of?1 -i'g..1; and;

Fig. dis a vertical sectional'viewthrough; the rib on substantially the. same scale as Fig. 4, taken substantially aIong'tIie Iine'E -S': of Fig: "1, part of the web-:being broken away.v

In the embodiment-oi the invention selected for illustrationthe load-carrying member on girder is shown comprising a main strength rib :of? an airfoil l0; such as=thehorizonta1 stabilizer: of an aircraft, althoughit will be understood that" the novel features thereof may be useful in: other relations.

Referring to Fig. 1 the airfoili I0 is: shown: as having a' convexlyr curved top and bottom and embodiesa nose portion I i an intermediate spar l2 and a rear spar l3} theseparts being strongly interconnected by a strong" rib; designated generally by Hi; and otherribs' spaced from the-rib l4" and from each other, but not shown herein extend chordwise of the wing. A suitable trailing edge'portion' not shown' i's secured t'o therear spar to complete the airfoil section;

The outer marginal contour of the rib l'kl ccnforms generally to the curvature or the airfoil.

In the nose portion, it extends outwardly 'tothe skin, and-the nose skin sheet, as l5; directly-'overlaps and is securedtothe marginal portion of the rib in this region. Rearwardl'y' of the nose; the marginal portions of the rib, while conforming generally to the contour of the airfoil; are inwardly offset to receive thereinforcedskinblanket l6; l6; and topass under the chords of the spars l2 and l-3' and be secured'theret'o: In the region between the nose and the rearspar I? the skin blanket comprises a skin sheet l 6- stifi"enedby*an inner reinforcing structure; designated-generally by I6 to which are secured a series of c1ips; as

H" which, in turn, have their inner portionsoverlap the marginal portions of" the rib, and are secured thereto in the overlap: The-skin sheet l6 at the iront is secured by a splice'plat'e, see

nose region, see Figs. 2 and 3, Where the web.

plate extends substantially to the skin, its margin is reinforced by angles l8 and I9, the outer arms of which lie parallel to the skin sheet l and are interconnected to each other and to the skin sheet by an overlying flat strap 20.

Rearwardly of the nose portion the margins of the web plate I! are formed by separate top and bottom cap strip extensions 2| and 22, see Fig.

5, flanged in their outer margins, as at 23 so as to give them greater strength and stiffness. As shown in Figs. 1 and 2, the forward ends of these extensions are outwardly offset to overlap both the nose web plate and the angular reinforcement, and are secured, as by spot welding, to both. These forward offset ends, as 2| and 22, may comprise separately formed pieces, as shown, overlapping and secured to the forward ends of the cap strip extensions 2| and 22.

As shown in Fig. 5, the cap strip extensions 2| and 22 have a wide overlap inwardly with the main body of the web plate I! and are strongly secured thereto so as to form, in effect, an integral part of the web plate as a whole, by numerous spot welds in the overlap.

To give the web plate the characteristics of a strong load-carrying beam or girder, it is reinforced adjacent its top and bottom margins by chord membersdesignated generally by 24 and 25. Between the chord members and to give the web plate great stiffness against buckling, it is reinforced by a vertically corrugated sheet or sheets 26 spot welded through the contiguous corrugations tothe web plate H. For convenience of manufacture, the corrugated sheet 26 may be built up in'sections with vertical overapping joints, as indicated at 21, in full lines in Fig. 4 and in dotted lines in Fig. 1. In the nose portion, see Fig. 3, the corrugated sheet extends outwardly close to the marginal angle l9 and the chord parts 33, 34 later to be described as being located on the corrugated side of the web, are discontinued through the .nose portion.

The chords 24 and 25 are of composite construction for convenience of manufacture and, to provide a substantially balanced construction on opposite sides of the plane of symmetry of the web, parts of the chords are located on opposite sides of the web plate I1, as clearly appears in Figs. 4 and 5. The chord parts on each side of the web plate are preferably located close to the contoured margins of the web plate but since this would ordinarily require that they be bent to conform to the curvature of the airfoil a special construction is provided.

Since it is desired to manufacture them of angular or channel form sections for strength and stiffness, to so bend them, particularly when made of high-tensile stainless steel, would require difficult bending operations.

Accordingly, to avoid this bending, and still attain the advantage of having the chords as a whole conform nearly to the contour of the margins of the web and be located relatively close to said margins, the chords are preferably built up ,of rectilinear sections, having their ends secure- 1y joined together to form, in effect, a continuous chord member from end to end of the rib.

As shown in Fig. 1, the chord parts overlapping the flat side of the web plate I! are each, both the top and bottom parts, built up of three rectilinear sections 28, 29 and 30. As shown, these sections consist of shallow outwardly facing channels strongly spot welded to the double thickness metal formed by the overlap of the body of the web plate l1 and its marginal extensions or cap strips 20, 2|. The ends of the sections may abut, as shown, in the joint between sections 29, 30 shown in detail in Fig. 4, the abutting ends being overlapped by a junction strip 3| strongly welded to the adjacent ends of the sections, The joint may be additionally stiffened by an angle 32 welded to the junction strip 3|. The junction strip, as 3|, may be extended, as shown, through the entire length of the intermediate section 29, and into overlapping engagement with the forward section 28, as shown, for example, at the top of Fig. 1.

All the joints between the sections may be made in this way or, as shown at 32' in Fig. 1, the joint may. be made by cutting away the inside flange of one of the channel sections as 29, and stopping the strip 3| short of the end of channel 29 and lapping the bottom of the end of the channel section 28 directly over the bottom of the end of the channel 29 and spot welding them together in the overlap. Additional angle stiffeners, as 3|, could also be applied, if desired, to this type of joint. 1

Certain of the chord parts on the opposite side of the rib are similarly constructed in rectilinear sections joined together at their ends. They flank the margins of the corrugated sheet reinforcement and are secured thereto and to the web plate IT. This securing of thechord parts to the margins of the corrugations prevents the distortion of the side walls of the corrugations under load and adds materially to the stiffness of the rib structure.

As shown in Figs. 4 and 5 the chord parts on this corrugated sheet side of the rib are preferably fabricated, for each the-top and bottom chords 24 and 25, out of two longitudinally extending channel members 33 and 34. Channel member 33 is in rectilinear sections, and has one of its side walls as 35 arranged slightly beyond the margin of the corrugated sheet 26, and of widened construction and flanged in its margin. This member can readily be secured to the contiguous corrugations, after the corrugated sheet 26 has been spotwelded to the web plate IT, by inserting. a spotwelding electrode through the ends of the corrugations.-

'After the member 33 is so secured in place it is further stiffened and rigidly tied to the web plate extensions 2|, or 22, by the channel member 34 which has a wide side Wall as 36, also flanged in its margin and directl welded to the adjacent plate extension and its bottom wall adjacent its shallow side wall in overlapping relation with and spotwelded to the side wall 35 0f the member 33. The laterally projecting double thickness flange so produced adds materially to the stiffness of the chord and the entire rib structure. As indicated in Fig. 4, the longitudinal sections of the member 33 may be joined by lap strips 3| and angle reinforcements 32, in a manner similar to the joinder of the sections 29 and 30 of the chord parts onthe opposite side of therib. Channel member 34, because-it is more readily bent by reasonof its right angular relation, to the web plate of the rib, may be made continuous over the various longitudinal sections of member 33.. Accordingly, no lap strips are required, or shown, in connection with this memher. It is understood, however, if difficulty in bending it at the joints should be encountered, it may very well be constructed in longitudinal sections and joined in the manner indicated in connections with the sections 28, 29, 30 and 33.

At the extreme nose portion the channel sections 28 may have their bottom walls offset and overlapped over the marginal angle l8 and spotwelded thereto, as shown in Fig. 2. For greater strength in this nose region the top and bottom channel section portions 28 of the chords may be reinforced, as shown in Figs. 2 and 3, by a flanged channel reinforcement 31 spotwelded thereto.

From the foregoing detailed description, it will be seen that a very strong and rigid rib construlction readily fabricated from sheet metal parts and readily joined by spotwelding has been provided. However, it will be understood that the specific construction described is merely by way of illustration and that changes and modifications would readily occur to those skilled in the art. Such changes and modifications are intended to fall within the scope of the appended claims.

What is claimed is:

1. An airfoil rib comprising a web plate having a marginal portion conforming to the curved contour of the airfoil, a vertically corrugated stiffener sheet secured to said Web plate and terminating short of the marginal portion thereof, a composite chord member secured to the web plate and its corrugated reinforcement including an angular member extending longitudinally along a margin of the corrugated sheet and secured thereto, and having an arm projecting in a direction away from the web, and another longitudinally extending member secured to said arm and to the web plate.

2. A load-carrying member comprising a chord and a web plate having a marginal portion extending beyond the chord, the web plate inside said marginal portion being reinforced by a transversely corrugated sheet secured thereto, the chord comprising an angular member extending longitudinally along a margin of the corrugated sheet and secured thereto, and having a freely projecting portion beyond the margin of said sheet and a second longitudinall extending mem-' ber interconnecting said freely projecting portion and the web plate.

3. A load-carrying structure having a curved outer edge, as an airfoil rib, comprising in combination, a web having marginal cap-strip portions conforming to the curved outer edge contour, and chordal members adjacent each edge, each chordal member including a series of rectilinear pieces secured to the web and secured together at their juxtaposed ends adjacent the outer edge.

4. A load-carrying structure having a curvilinear outer edge, as an airfoil rib, comprising in combination, a plate web, a cap strip overlapping said :plate Web interiorly and conforming to the curvilinear contour at its outer edge, and a chordal member secured to the overlapping portion of the web and cap strip, said chordal member including a series of rectilinear elements secured together at their juxtaposed ends adjacent the outer edge.

5. A load-carrying structure having opposite curvilinear outer edges, as an airfoil rib, comprising in combination, a plate web, cap strips overlapping the plate web and secured thereto at their inner edges, the cap strips at their outer edges conforming to the required contour for carrying the load, a segmental chord secured to each cap strip adjacent its inner edge, the chord segments being rectilinear and spliced to adjacent segments, a corrugated strut sheet secured to the plate web opposite said cap strips and chords and occupying the zone of and between the chords, further segmental chords secured over the outside of the strut sheet at the ends and opposite the first chords, and chordal strips secured to said cap strips over the ends of said strut sheet, the chordal strips and the second said chords being secured to ether.

MICHAEL WATTER.

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