GB211206A - Improvements in method and machine for folding heavy metal sheets - Google Patents

Abstract

211,206. Marks, E. C. R., (Locomotive Firebox Co.). Nov. 13, 1922. Steam generators. - In a method of bending metal plates or sheets, particularly heavy plates for forming water circulating elements as described in Specification 137,093, [Class 123 (ii), Steam generators], the plate is formed with projections coacting with a mandrel to position the plate and is bent through the action of gravity to conform to the shape of the mandrel by dropping hinged wings thereon. The plate 58 has headed centering pins 59, Fig. 8, at opposite ends and is brought, preferably by a wheeled car, into alignment with the tapered end of a longitudinal groove in the removable head 6 of the mandrel 3,. whereupon the plate is pushed into position over the mandrel. The bending wings, 39, 40, which are connected together by a series of hinge chains 51 and pinching chains 54, are each secured towards each end thereof to one end of a pair of chains 31, 32, the chains 31 being secured at their other ends to a pair of pulleys 25 on the shaft 23, and the chains 32 passing over pulleys- 29 on the shaft 24 and being secured to pulleys on the shaft 23. The shafts 23, 24 are mounted on a pair of overhead beams 7 supported on pillow blocks. Some of the hinge chains carry posts 64, 65, slidable in guides 66<1> in the framing so as to prevent swaying of the wings, which are notched to accommodate them. The wings are raised into horizontal position by a, chain 21 secured at one end to a pulley 22 and at the other end to the rod 18 of a piston 17, which is forced backwards by air or water as controlled by valved pipes 15, 16. The rod 18 has a dog 70 which may be engaged by a latch 71 controlled by a weight 72 so as to maintain the horizontal position of the wings during exhaustion of the cylinder. The latch 71 may then be lifted or tripped to allow the wings to drop by their own weight and bend the plate 58 round the mandrel. For very heavy plates the latch may be disengaged during the initial stroke, the weight of the wings acting against the fluid in front of the piston during exhaustion thereof. The wings may consist of metal plates 41, 42, Fig. 4, with wooden fillers 43, 44, and dovetailed blocks 45, 46, which are secured by screws 47, 48 and provided with interchangeable pinching bars 56, 57. In operation, after the wings have been lowered on to the mandrel, they first swing round the mandrel head and then, towards the end of the operation, act as levers fulcrummed on the pinching chains 54 so as to effect the under-bending as shown in Fig. 4. The pinching chains are adjusted to suit the thickness of the work by nuts on the shanks 52, 53, and are preferably held up by springs when the wings are in their horizontal position. The pinching bars may be out away at 56<1>, 57<1>, Fig. 10, so that one upper end portion of the work terminates in straight inclined portions 75. The pinching chains may be replaced by pinch blocks 78, Fig. 12, hinged at 79 to one of the wings. The hinge chain may be adjustable and arranged diagonally, as shown, or may pass at right angles through the wing plates. In another form the wooden fillers are dispensed with, the metal wing-plates being provided at their inner end with brackets. Mandrel heads of varying shapes may be used. Forms are shown which taper from one end either to the other end or to the centre and a further form which terminates at one end in corrugations. The shaping is effected by using connecting chains 93, Fig. 15, with links 94 of different sizes and shapes so as to conform to the shape of the mandrel-head.