Patent GB-563470-A (GB)
Title: Improvements in or relating to press tools for working a strip or web of metal
IPC: B21D11/08
Filed: 1942-05-11
Abstract: 563,470. Stretching and upsetting. SALT, D. F. May 11, 1942, Nos. 6326/42 and 2665/43. [Class 83 (iv)] In a press of the kind comprising a pair of jaws 12, 17 each having parts collectively forming a gripping surface for the work, such parts being adapted to move relatively to compress or stretch the metal between such parts in its own plane, the said parts are so constructed that the degree of compression or stretch is not the same all over the area. affected, thus producing curvature of the work in the plane of the part gripped. The lower jaw 12 is fixed to the base 11 of the press and the upper jaw 17 is secured by a bolt 18, Fig. 3, to a ram 15, pressed up by a spring 23 and moved down by a lever 21, cam 20 and adjustable abutment 19 of the ram. Except for the securing means the jaws are identical and each has two parts 37, Figs. 4 and 5, with gripping faces 43 arranged between stepped plates 34 fixed in the gap of a C-shaped support 31. The parts 37 are supported by a pad 38, lever 26 and preloaded spring 28 and separated by a work-supporting wedge 39 pressed between them by a spring. The inclined stop faces 35, 36 on the plates 34 are not parallel with the corresponding faces on the parts 37 so that in use, after these parts have gripped the work and begin to move, against the action of the springs 28, relative to the plates 34, the inclined faces 35, 36 engage first at the rear of the parts 37 and a greater degree of compression is effected towards the rear, thus producing a bend of the work in the plane of the work-part held between the jaws, e.g. the web of an angle bar. This action may be increased by forming a recess 33 in the lever 26 below the rear of the pad 38. In a modification, the parts 37 have each one inclined face engaging a corresponding face on a plate 34 and an inner face engaging a central wedge carried by the pad 38. In another modification, adapted to stretch the work, the parts 37, Fig. 7, have similar inclined faces, but the inner faces engage a fixed wedge 52, while the outer ones engage wedges 53 carried by the pad 38. In another modification, the parts 37 and plates 37 have parallel engaging faces and the relative movement of the parts 37 is obtained by levers 60, Fig. 8. In each of these modifications there is a wedge 39 and, as in the first construction, the interengaging inclined faces are not parallel. In another modification, a lower jaw 61, Fig. 9, is fixed to a base 64 having a pillar 66 on which the upper jaw 65 is moved by a head 70 and returning spring 69. Both jaws have rectangular recesses and in each are arranged two sets of plates 74, Figs. 10 and 11, one set being separated from the other by a rubber pad 76, and all resting on inclined bases or on pivot bars 72, which may be adjustable'to and from each other. In use, the pressure first causes the jaws to grip the work then compress it in its own plane and as this bends, e.g. owing to the resistance of a flange f along its edge, the plates move by different amounts, the curvature of the gripping faces being such as to separate the lines where grip occurs as the action progresses and to allow for the resultant increase in thickness of the work. The plates 74 may vary in size so as to interleave slightly. In another modification, the recesses in the jaws 61, 65 are cylindrical and contain a pair of wedges 79, Figs. 14, 15, carrying a pair of interdigitated parts 78 pressed apart by springs 80, 81 to engage the cylindrical wall of the recess. In use the pressure causes the pieces 78 to grip the work and then compress it, being free to turn to follow differences of compression as the work bends. The jaws 61, 65 may be mounted with the gripping parts 74 adjacent the frame 10 or the jaws may have gripping parts 74 at each side, one set being larger than the other. The lever 21 may engage an adjustable stop to limit the amount of compression of the work.