Patent GB-657623-A (GB)
Title: Molding machine for bank strips suitable for telephone switch banks
IPC: H04Q1/16
Filed: 1948-02-26
Abstract: 657,623. Moulding strips suitable for automatic telephone switch-banks. STANDARD TELEPHONES & CABLES, Ltd. Feb. 26, 1948, No. 5714. [Class 87 (ii)] [Also in Group XXII] Bank strip bodies, e.g. for automatic telephone switch-banks, with terminal pins secured therein are made by feeding a number of wires intermittently through a moulding unit in which bank strip bodies of thermoplastic material, e.g. polystyrene, are injection-moulded on to the wires, means being provided to feed previously moulded bank strips away from the moulding unit. The wires are cut to leave projecting ends on the bank strips. The general form of the underside of a bank strip is shown in Figs. 59, 64, the bank strip comprising the insulating frame 331, 332, 336, with panel 330, moulded on wires constituting terminal or selector pins 115. The wires are flattened at 342 to key with the moulding material. Grooves 333 in the panel receive a set of wires disposed transversely of those constituting the pins 115 and the two sets of wires are connected electrically at their exposed crossing points in diagonal slots 337 in the panel. The slots 337 are grouped in pairs which, taken together, cross all of the grooves. Specifications 634,873, [Group XXXIX], and 657,622, [Group XXII], are referred to as describing respectively the bank-strip body form and the welding apparatus for welding the longitudinal wires to the transverse pins. Wire reel rack. The wires 110, which form the terminal or selector pins 115 are supplied on reels 100, Fig. 1, supported by pairs of spools 101 on shafts 102, the wires being led over double grooved sheaves 109 to pass intermittently through a moulding machine in which the bodies of the bank strips are moulded thereon and the wires cut to form the terminal or selector pins 115. The moulding machine has a heavy frame comprising four posts 121, Fig. 2, and a base 122, the posts 121 being connected at their upper ends by a top frame number 123 carrying a stationary upper ram 124. A vertically slidable lower ram 125 is mounted in the lower part of the frame and is actuated by a fluid pressure cylinder. The wires 110, Fig. 8, extend above a space between two arms 127 of a plate 128 and through a tension and guide device comprising upper and lower rollers 131, 136. These rollers are grooved and have spacers at intervals so that the wires are guided in spaced groups. The plate 128 has side guides on its upper surface for a wire gripper and feed slide 153, Fig. 9, which may be reciprocated by fluid-pressure operated pistons, one at each side of the plate 128. A support or bed 165 forming part of the lower ram and extending the full length of the press has its left-hand end located slightly below the plate 128, which plate is guided by vertical pins 168, Fig. 16, so that it may have limited vertical movement relatively to the support 165. The bed 165 is thus adapted to pick up the plate 128 after slight upward movement. The plate 128 forms one end of a frame and is connected by the side bars of the frame to a plate 173, Fig. 10, which advances pairs of previously formed bank strip bodies and has cutting means for separating at each operation two bank strip bodies and selector pins 115 therein from a string of such bodies. The plate 173 is guided similarly to the plate 128 for limited vertical movement relatively to the right-hand end of the bed 165. The wires 110 are gripped in the slide 153 for the feed movement by clamping plates 176, Fig. 16, which are moved endwise to grip the wires, by cam heads 184 actuated by bell cranks coupled to the piston rods which reciprocate the slide 153. Thus the operation of these piston rods first clamps the wires and then advances the slide 153 to feed the wires through the machine. On the return stroke of the piston rods, the wire clamps are opened. Wire gripping means on the plate 128, similar to the feed clamps, prevent rearward movement of the wires during the return stroke of the wire feed-slide 153. The wires can be fed only when the lower ram 125 is in its lower position. At the rear of the cutting device on the plate 173 is a reciprocating carriage 203, Fig. 10, actuated by rods 214 coupled to the wire gripping and feed slide 153 at the rear end of the press, and provided with multiple pawls 212 mounted in pawl carriers 211, these pawls in their forward movement advancing the previously moulded bank strips with wires embedded therein, and positioning a fresh length of the wires in the moulding device. On the return movement of the carriage 203 and wire gripping slide 153, the pawls wipe over the freshly moulded bank strips and the wire gripper slide 153 moves freely along the stationary wires to take up position ready for a fresh advance of wires and of the bank strips which have been moulded thereon. Retrograde movement of the bank strips, during return of the carriage 203 is prevented by pawls 276, Fig. 9. Wire-cutting apparatus.-Cutting blades 226, Fig. 10, carried by a plate 225 mounted in a recess at the discharge end of the plate 173 co-operate with blades 237 carried by a cross beam 230 which is guided for vertical movement relatively to the plate 173, when the beam strikes a bumper 231 at the end of upward movement of the lower ram 125 together with the bed 165 and plate 173. At each operation of the press two bank strips are moulded on the wires, and the blades 237 cut-out short lengths of wire between the leading bank strip and the second, and between the second bank strip and the string of following bank strips. The short pieces of wire removed by the cutters fall through openings 227. The upper blades 237 work through a pressure plate 239 urged by spring pressure 235 and shaped to engage the bank strips and wires to hold them firmly in position during the cutting operation. Moulding apparatus.-The moulding apparatus is located at the central zone of the bed 165. A lower mould section 255, Fig. 12, is mounted in a plate 251, Fig. 9. Combs 265 extend across the wires 110 at the rear and forward edges of the mould section and a comb of less depth is mounted midway between these to ensure accurate positioning of the wires in the mould. Co-operating dies 282 at the rear end of the plate 251 deform the wires so that they will key with the moulded material, on advance to the moulding position. The upper mould section 285 is fixed in an upper plate 286, the upper and lower mould sections being maintained in register by guide pins, projecting upwardly from the plate 251. The plastic material is injected into the moulds through a nozzle 317 communicating with an inlet 315 and a number of discharge passages so that there is simultaneous injection into the moulds at a number of points. Provision is made at 380, 381 for the circulation of cooling fluid for the moulds. Fig. 20, which is a crosssection on the line 20-20 of Fig. 9 shows the disposition of the passages, the sprue being held by the keying of the material with the ends of pins 327 carried in the plate 310. Ejector pins 260 which project into the lower mould are supported by a beam 257 whose ends project under the side members 171 of the frame mounting the plates 128, 173 and carrying the wire gripping and cutting mechanism. The beam 257 is normally carried by the lower ram 125, and the tops of the ejector pins 260 are then flush with the bottom of the moulds. The arrest of the beam 257 by the fixed pins 258 near the end of the descent of the ram causes the ejector pins to enter the lower mould as the ram completes. its downward movement. In operation, the lower ram rises to close the mould parts and at the end of the upward movement of the ram the wires are cut at two positions thus cutting off two individual bank strips. The wire gripping carriage 153 and bank strip feeding carriage are then run back to rearmost position and a charge of plastic material injected into the mould. The lower ram is then lowered accompanied by both mould sections, the upper mould section being stripped from the sprue formed in the mould passages, during this movement, as the sprue is keyed to the ends of the pins 327. The downward movement continues until the stops 305 engage the plate 300 and strip the sprue from the ends of the pins 327. The moulded bank strip meanwhile remains in the lower mould section and is ejected therefrom by the pins 260 as the lower ram nears the end of its downward movement. The bank strip remains suspended by the wires as the lower mould completes its downward movement and the wire feeding and bank strip feeding carriages are then actuated to discharge the previously severed bank strips, and to advance the last moulded bank strips to the cutting position.