Patent GB-131106-A (GB)
Title: Improvements in Electric Selectors, particularly for Automatic Telephone Systems.
IPC: H01H67/12
Filed: 1918-07-03
Abstract: 131,106. Western Electric Co., (Western Electric Co.). July 3, 1918. Automatic exchange systems and apparatus.- The brushes of a selector are moved rectilinearly in two directions perpendicular to each other by means of a single driving-mechanism, which moves in one direction only. The steps moved in one direction may be of different length from the steps moved in the other direction. The terminal bank consists of ten superposed structures, each comprising a metal backing and multiple contact strip in the form of a kind of fabric of which bare wires form the warp and insulating strips form the woof. The bare wire is passed over and under the insulating strips in such a way as to leave portions of the wire exposed to form the contact surfaces engaged by the brushes. Construction of selector and side-switch; brush operating-mechanism. The brushes 50, Fig. 1, which are moved upwards to select a level 5 and then horizontally to select a set of terminals in that level, are mounted in a carriage 51 rigid on a shaft 52 slidable in guide-members 53, 54 on a base-plate. A notched bar 56, engaged by the pawl 57 carried by the armature 58 of a magnet 59, is normally locked to the shaft 52 by the engagement of a projection 91 on a collar 62 on the shaft with a notch 63 in the bar 56, as shown in Figs. 1 and 2. The first set of impulses through the masnet 59 therefore raises the shaft 52 and brushes 50 to the desired level, each impulse raising the bar 56 through two teeth of the bar. At the end of the impulses, a magnet 65 is energized and by means of pawl 67 and ratchet 68 moves a cam-plate 74 one step. The cam-plate is provided with a projection 80 controlling the side-switch 82, 83 and with cam surfaces 73, 75 engaging a roller 70 carried by a lever 71 pivoted on a rod 95. When the cam-plate is moved one step, the camsurface 73 moves the roller 70 and lever 71 outwardly so that the part 88 of the lever acts on the collar 63 (see Fig. 2) on the shaft 52, causing the projection 91 to disengage the notched bar 56 and a projection 92 to engage a notch in a, fixed bar 94. The shaft 52 is thus locked against further movement by the notched bar 56, which when it is again operated by the stepping-magnet 59,. acts through the boil-crank lever 100 to move the brushes 50 horizontally. In order that the second set of steps (except the first of that set) given to the bar 56 may be shorter than the first set of steps, a bracket number 96, pivoted on the rod 95, is formed with a lug 97 which normally projects through an opening 98, Fig. 3, in the armature 58 of the stepping-magnet 59. When the cam-plate is moved into its second position and the lever 71 is moved outwardly, the member 96 is moved by a spring 99, Fig. 1, until the lug 97 engages the( side of slot 98 and, when the armature is attracted by the first impulse of the second series, the lug 97 passes under the armature and prevents the latter from moving fully back into its original position. Thus, while the first, impulse of the second series moves the bar 56 a distance equal to two of its teeth, succeeding impulses will move it a distance of one tooth only. The brushes 50 are thus moved horizontally to engage the desired set of terminals. After the second series of impulses the magnet 65 is repeatedly energized as described later and moves the camplate 69 further steps to adjust the side-switch. In its last step but one, the roller 70 engages the cam-surface 77 and is moved inwardly, causing the lever 71 to withdraw a detent from the bar 56 and thus restore the selector to normal. The width of the contact surfaces of the terminal bank is such that two selectors, arranged on opposite sides of the bank, may engage the same set of contacts, as shown at 37, 38, Fig. 8. Construction of terminal bank. The multiplecontact strip is in the form of a kind of fabric comprising ten sets of bare wires 8, 9, 10, Fig. 11, forming the warp, and notched insulating strips 12, 13, 14, 15 forming the woof. The bare wires pass over one and under two of the strips as indicated in Fig. 11, the upper portions 20 forming the contact surfaces engaged by the brushes. The upper portions of the three wires 8, 9, 10 are displaced laterally, so as to be engaged by three displaced brushes 50, as shown in Fig. 8. The multiple contact strip is secured to a metal supporting plate 23, Fig. 8, by insulating material arranged to insulate the fabric from the plate but to leave exposed the portions 20 of the wires. The plate 23 is provided with an extended portion 24 at one end, the wires being passed through notches in a fanning plate 29 and then looped over to form terminals for connecting to other circuits. A series of ten plates 23 are secured adjustably and horizontally in frame members 6, the terminals 20, Fig. 11, being on the underside of the plate so as to protect them from dirt. Circuit arrangements. When a calling line is extended to the group selector shown in Fig. 12, the line relay 115 and slow-release relay 123 are energized in the usual manner. The line relay also energizes a test relay 124 which locks up over a circuit including contact 127, which is opened at the first horizontal movement of the brushes. The first set of selecting-impulses is repeated by the relay 115 through the relay 131 to the stepping-magnet 59, which moves the brushes to the desired level. When the impulses cease, the relay 131 opens the circuit of the magnet 65, which moves the side-switch and cam-plate 69 into their second position, in which the toothed bar 56 is disconnected from the shaft 52, the stepping- magnet being energized intermittingly over contact 136, until an idle trunk is found when the test relay 124 de-energizes and open-circuits the stepping-magnet 59 and the side-switch magnet 65, which moves the cam-plate and side-switch into their third position, in which the calling and called lines are connected, relay 142 being energized by relay 123. At the end of the conversation, relay 123 opens the circuit of the magnet 65, which moves the cam-plate into its fourth position, in which the selector is restored as previously described. The opening of contact 150 then de-energizes magnet 65 again and moves the camplate into its fifth position, and thence into its sixth position, which is equivalent to its normal position.