GB634583A - Method of making airfoils - Google Patents

Abstract

634,583. Making parts of aircraft. GOODYEAR AIRCRAFT CORPORATION. May 16, 1947, No. 13211. Convention date, Nov. 26, 1946. [Classes 83 (ii) and 83 (iv)] Angular bending; stretching; stamping.- A step in a process for making an airfoil and more particularly a leading edge for a helicopter blade comprises applying a longitudinal tension to a blank so as to tension it strongly, but below its elastic limit and then gripping the tensioned blank at closelyspaced areas and applying additional stress to permanently bend the blank therebetween. A blank 1 of sheet stainless steel, formed with holes 2 and slits 3 is bent longitudinally to U-shape in cross-section and placed in a tensioning and bending device. This comprises a pair of heavy members pivoted at 7, connected on one side of the pivot by a pressure cylinder 6 and at the other side formed as jaws with portions 8 adapted to be tightly clamped on to the blank, suitable filler blocks being placed within the blank. From each jaw extends an elongated channel-member 9 having at its outer end a plate 11 secured by bolts 12 to a clamp 13 or 14 adapted to grip the ends of the blank. The blank is placed in the device in the position shown in dotted lines in Fig. 3, the clamps 13 and 14 are tightened and the bolts 12 turned so as to put the blank under a tension which never exceeds and is preferably ten to twenty per cent below the elastic limit. The clamps 8 are then tightened on to the work and the jaws move apart so as to stretch a short length of the blank to beyond the yield point and give it a permanent bend as indicated in full lines in the Fig. 3. By turning the jaws over and arranging the pivot at the end as shown in Fig. 4, the blank is given another bend in the reverse direction near its other end. The bent blank is then trimmed as indicated by the full lines 16 in Fig. 5, so that the curved bottom part is shorter than the top, formed by straight upper edges 15 which are then bent at right angles along the line 15a to form a flange by which the blank is clamped by a member 18 within a channelled member 17. By supporting the member 17 by a number of clamping frames 21, a former 20 may be slowly forced down into the blank so as to draw it to the required final form, after which the ends are cut square and the flange removed.