Patent GB-730675-A (GB)
Title: Apparatus and process for forming helices from metal strips, rods, bars, tubes and the like
IPC: B21D11/06
Filed: 1952-12-15
Abstract: 730,675. Bending. CYRIL BATH CO. Dec. 15, 1952 [Dec. 17, 1951], No. 31736/52. Classes 83 (2) and 83 (4). A method of forming metal strip into an annular contoured body such as a section of a hollow conical frustum comprises bending the strip into helical form over a die mounted on a turntable, cutting off the required portion of the helix, bringing the ends together and butt - welding them. A machine for forming the helix comprises a base 1 on which is mounted firstly a turntable 2 carrying a former D, F and a means 72 for clamping one end of the strip and secondly a reversible piston and cylinder assembly 8 provided with a work-gripping or toolholding head 35 which is movable vertically and is also rotatable. The turntable is bolted to a ring gear 4 driven from a motor 7 through reduction gearing 6 and a pinion 5. Also rotatably mounted on the base is a plate 14 carrying guideways 13 along which a carriage 19 is slidable under the control of a piston operating within a double-acting cylinder 9 clamped to the guideways. Vertically movable in the carriage 19 by means of a double-acting cylinder 24 is a support 20 within which is mounted a horizontal shaft 28 to which is secured a holder 35 having jaws 36. The shaft 28 is rotatable by a rack 30 operated by another double-acting cylinder and the holder 35 carried by the shaft may be locked in any position of rotation by teeth 60 engageable by a manually actuated detent 61. The jaws 36 may be closed to grip the work or a tool by ramps 38 along which they slide under the action of a carrier 37 operated by another double-acting cylinder device. The rotational and vertical movements of the holder 35 may be positively controlled by the pressure cylinders either manually or automatically through cams on the turntable 2 or the cylinders may be allowed to act as dashpots, leaving the head free to follow the movements of the former. In one method of forming a helix, the strip is clamped at one end to the turntable, at the other end is gripped by the jaws 36 and the table is rotated so that the strip is bent under tension around a helical face F on the former D, the movements of the head 35 being conditioned to the pitch of the helix and the angle of the face F. If the final annular device is required to be bowed out of the general plane of the device, the pitch of the helix will be non-uniform. Instead of the work being bent under tension, the gripping jaws 36 may carry a tool such as 65 conforming to the cross-section of the forming face F3 in order to press the strip around the former D3 as shown in Fig. 10. Alternatively both methods may be used together, the work being stretched by the cylinder device 9 through the jaws 36 and pressed against the former by a tool 65 carried by a similar cylinder assembly 100 mounted at right-angles to the assembly 8, as shown in Fig. 4. The Figure also shows a modification in which the longitudinal travel of the workgripping holder 35 is increased by mounting the cylinder assembly 8 on a carriage 87 which is itself movable along a base 81 by another double-acting cylinder device 88.