Patent GB-666923-A (GB)
Title: Improvements in cross-bar switches
IPC: H01H67/26
Filed: 1949-07-18
Abstract: 666,923. Cross-bar switches. DEHN, S. G. (Automatic Electric Laboratories, Inc.). July 18, 1949, No. 18865. Class 40 (iv). A cross-bar switch comprises a plurality of vertical bare wires, crossed horizontally by a plurality of metal strips carrying contact blades, one for each vertical bare wire, a first electromagnet being operative to condition a lever to rock a plate, and a second electromagnetic operating the lever so that the plate rocks to bring one of the contact blades into contact with one of the bare wires. Construction and mechanical details.-As shown, ten trunks, each comprising four wires, are each connected to individual bare wires 361 ... 360, Fig. 5, extending vertically across a rigid frame. Lines, to be connected selectively to the trunks, are connected to individual horizontal cross-bars 42, Fig. 9; each line comprises four wires which are connected to insulated metal plates 391 ... 394 from each of which depends ten contacts 401, Fig. 6, opposite the corresponding bare wire of the vertical trunks. Thus each line can have its four wires appropriately connected to the four wires of any trunk by pressing the appropriate depending contacts against the appropriate bare trunk wires. Each group of four depending contacts 401, Fig. 8 (one from each line wire), is associated with an actuating projection 83 which forms part of a plate suspended from hook 469, the hole in the plate through which the hook passes being large enough to permit a limited vertical movement of the plate and projection. Connection between a line and a trunk is effected by the actuation of a plate 81, Fig. 5, which has holes 831, 832 ... in line, with one exception, with the actuating projections associated with the depending contacts so that when the plate is actuated, only one actuating projection is operated to press the contacts against the bare vertical wires; the one exception is that actuating projection associated with the trunk to which connection is to be attempted. Associated with each group of four vertical wires constituting a trunk, is a vertical bar 381 ... 380, Fig. 5; these bars are normally lifted, but a rotatable shaft 69 has cams 581 ... 580 so that each bar in turn is dropped vertically and lifted again. Each bar includes a number of shoulders 611, Fig. 1, in line with the horizontal cross-bar, and these shoulders co-operate with stirrups 621 on the actuating projections 83, so that when the vertical bar drops, the actuating projection 83 drops out of register with the hole in plate 81; if the plate 81 is then actuated, it presses this out-ofregister projection back to cause the associated four depending contacts to connect with the four vertical wires. The cam-shaft 69, Fig. 1, is stepped by the energization and de-energization of a stepping magnet 68 actuating a pawl and ratchet mechanism. Each cam, e.g. 581 lifts a lever 561 to close contacts 601 and allow vertical bar 381 to drop; when the cam is stepped on, the springs of contacts 601 press lever 561 back to its lifted position. Operation when a demand exists on a line for a free trunk.-A demand on a particular line causes the operation of line relay 87, Fig. 15, which attracts its armature 89, Fig. 10A, to the position of Fig. 10B in which the bell-crank lever 91 is lifted, so that it can engage lever 93. Relay 87 completes the circuit of cut-off relay 88 which attracts its armature 90 from the position shown in Figs. 10A, 10B, to that shown in Fig. 10C, thus actuating lever 93 to press-plate 81, Fig. 5, against the actuating projection corresponding to the vertical trunk whose vertical bar is dropped. If the trunk is free, a relay (not shown) across the - ve and + ve lines is energized to earth the C line and stepping magnet 68 is operated and a circuit for slow acting relay 106 is completed. The stepping magnet 68 withdraws the pawl from the ratchet mechanism, and relay 106 actuates and opens contact 108 to become quick release to de-energize stepping magnet 68 which steps on the cam-shaft, thus opening contacts 601 to release relay 106 and dropping the next vertical bar to prepare it for an attempted connection to the next line that has a demand. If, however, this trunk is busy, the closure of contacts 600 will connect earth on the C line to relay 106 and stepping magnet 68, and the stepping magnet rotates the cam-shaft another step, this process being repeated until the bar corresponding to a free trunk is dropped. Adaptation for an incoming trunk call for a particular line.-A separate frame with the appropriate vertical bare wires, vertical bar, contacts and stepping magnet is provided. The bell-crank lever associated with the line and cut-off relay is extended, as shown in Fig. 16A to provide a further link 110 for actuating the plate associated with the separate frame. As shown in Fig. 16A, 16B, the operation of cut-off relay 88, corresponding to a demand on an incoming trunk, causes the plate to be actuated on the separate frame. The operation of the line relay 87 before the cut-off relay 88 corresponding to a demand for an outgoing trunk, actuates the other plate as shown in Figs. 16C, 16D.