Patent GB-253996-A (GB)
Title: Improvements in and relating to bending machines for assembling wire grid or the like material
IPC: B21F45/00
Filed: 1925-03-24
Abstract: 253,996. British Thomson-Houston Co., Ltd., and Kingwell, K. F. March 24, 1925. Making metal fabrics.-Wire grid and like material, made for example by machines as described in Specifications 210,565 and 237,005, particularly for use in forming a bank of electrical resistances, is bent alternately in opposite directions into zig-zag form by releasable pairs of jaws rotatable with a carriage about the bending point and co-operating with a fixed pair of releasable jaws, the material being fed into position where the part to be bent is in line with the centres on which the jaws rotate, and the folds being assembled on rods on the carriage and separated by spacers fed thereto between each fold. A grid having long loops a<1>, Fig. I,. for receiving the tappings from sections of the resistance, wide loops b<1>, c<1>, and intermediate narrow loops, is folded by rotating the assembled portion so as to twist the leg e connecting the assembled and unassembled portion through 90‹ and then again rotating so as to twist the leg f through 90‹ into the position shown in Fig. 2, the folds being separated by washers g consisting of an insulating washer such as mica between two metal washers, which at an intermediate stage are pushed over insulating rods a, b, c removably mounted on the carriage. A section of the material is placed over the insulating rods and over blades 5, 5<a> projecting from a carriage 4, Fig. 4, traversable on rails 3 on a table 2 which is rotatably mounted on a pillar 1. The rods mav have distance-pieces m, Fig. 8, to suit the size of the bank. Jaws 6, which are spaced by a handle 9, are slidable in a guide 12, which by either of a pair of connected levers 17 and a clutch 16 is secured either to the pillar 1 or to the table. The jaws are moved into or out of contact with the work by a lever 14, which is connected by a link to counterweighted slidable bars 20<a> carrying a bracket 20 in which the jaws 7. 8 with handles 10, 11 are mounted. the jaws 7 are mounted rigidly with the bracket 20 and the jaws 8 are slidable in a sleeve rotatably mounted therein and formed with an arm 26 having slots 26<a>, 26<b> at its lower end. The jaws 8 are held in their lower position in the bracket, Fig. 4, by a catch 32 against the action of springs 31. The end 8<a> of the jaws carries a spring-pressed pin 28 engaging a spring-raised pin 27 on the arm 26. When the lever 17 is moved to lock the guide 12 to the pillar, Fig. 4, the locking bar 34<a> of a pair of spring-raised locking bars 34a, 34<b> carried by the table is raised so as to engage the slot 26a and thus lock the arm to the table. The table is then rotated until the arm 26 engages the stop 35 on the bracket 20. The jaws 8 during this motion rotate with the table and twist the legs e through an angle of 90‹ plus substantially twice the amount required to allow for the spring in the wire. Towards the end of this motion the spring pin 27 comes over a gap in the flange 27a and is pushed down by the spring pin 28, the arm being then brought to rest against the shoulder on the flange at an angle of 90‹ from its initial position. The table is at the same time locked by a spring-stop 36. At this stage washers which have been placed behind the spring clips 39<c>, Fig. 15, on the spring-pressed ends 39a of hollow-ended rods 39 are pushed by the rods over the spring-pressed latches n<2>, Fig. 14, on the conical ends of members n removably mounted on the insulating rods and the fabric is pressed back to the extent of the depth of a fold. For this purpose the rods are mounted in a carriage 37, Figs. 4 and 8, pushed forward on rails 38, the final movement being given by a hand-operated pinion 40 on the carriage in engagement with a fixed rack 41. Slotted plates may be inserted temporarily every few folds so as to keep the guides and rods parallel in the event of malformation of the grid. After the washers are applied the jaws 8 are unclamped and the catch 32 released to allow the springs 31 to with. draw the jaws and also free the arm 26 at this end. The lever 17 is then depressed to secure the jaw guide 12 to the table and to release the lower end of the arm 26, which is then returned to its central position. The table and jaws 6 are now rotated through 90‹ to complete the fold: whereupon after clamping the jaws 6, 7 the lever 14 is operated to withdraw them from the work. During this motion the jaw shank 8<a> engages a projection 30 and is pushed into its forward position. The material is now fed forward in a channel guide 43 by pawls 46 on tubes 44 operated by a pedal 49 through a lever 47 and the carriage 4 is at the same time pushed to the other end of the rails by a rod 48 connected to the lever 47. The pawls are brought into operative position by rods 57, Fig. 12, inside the tubes through pins 59 thereon passing through slots 60 in the tubes. The rods are traversed by the lever 47 through pins 59a passing through slots in the tubes 44, which are frictionally held in guides 44<a> so that they do not move until the pawls are in action. After the next section has been fed forward the jaw 6 is freed and returned by hand to the angular position of Fig. 4. In forming the second fold the table is rotated in the reverse direction. Duplicate sets of washercarrying rods 39 and carriage traversing rods arranged at opposite sides of the machine are used for every alternate fold. Winding and reeling.-The grid material is carried by a drum on a rotatable table 64, Fig. 5<A>, which is rotated during the feed to relieve strain thereon by a ratchet lever 61 slotted to engage a roller 73 on a block 77 which is secured to a slidable rod 66 carried frictionally in bearings 58. A rod 57a connected to the lever 47 is connected to a lever 71 carried by the rod 66, so that during the feed a bar 68, which is connected by links to the framing and to a spring- controlled pivoted block 69 attached to the ends of a brake band 74, is pushed down by the lever 71 so as to release the brake. The rod 57a then pulls the rod 66 forward to operate the ratchet lever.