Patent GB-237333-A (GB)
Title: Improvements relating to token instruments for railways and the like
IPC: B61L23/24
Filed: 1924-04-22
Abstract: 237,333. Edmonds, C. H. W., Roberts, W. S., Westinghouse Brake & Saxby Signal Co., Ltd., and Railway Signal Co., Ltd. April 22, 1924. Staff, tablet, and ticket systems.-In systems wherein the withdrawal of a staff &c. from an instrument permits the 'setting of the signal from " danger " to " clear," the withdrawal of a token momentarily energizes a stick relay controlling the releasing circuit of a locking mechanism for the signal lever, the energization of the relay being automatically maintained. The usual arrangement is followed whereby removal of a token at one end of a section prevents removal of a token at the other end, return of the token to either instrument allowing a second token to be removed from either instrument, but arrangement is made to prevent return of a token to the issuing instrument so long as the starting signal is in "clear" position. The instrument., Fig. 1, has the usual locking discs 14 rotated by the staff on its removal from or insertion in slot 17 by way of the aperture 16, the front disc having pins 15 adapted to engage the tail 4 of a pivoted lever 1 carrying contacts 10 co-operating with fixed contacts 12. The tail 4 is pivoted to the lever so that closure of contacts 10, 12 occurs on the clockwise movement of disc 14 as a staff is withdrawn, but the tail 4 yields idly against the action of a restoring spring 7 on anti-clockwise movement of the disc when a staff is returned to the instrument. Aperture 16 is obstructed by a vertically sliding rod 22, Fig. 4, which is raised and held by the inward movement of a slide 19 when the signal is at " clear," but is freed to fall under gravity when the slide occupies its normal outward position shown. In its inner position the slide 19 is locked by a member 27 engaging a recess 25, released by the rotary armature 31 of a polarized relay 32, and contacts 34, 35 are bridged by a contact 33 on the slide. Fig. 7 shows the circuit arrangements at one end A of a section, those at the other end (designated B), not shown, being similar. The arrangements comprise the usual polarized locking relay 43, a plunger-operated two-wav switch 71 co-operating with contacts 67, 70 for controlling the circuit of the slide lockrelay 32. a stick-relay 44 controlling contacts 45, 46. an electric lock 57 of known form normally locking the starting signal lever in " danger " position, and an electrically-operated signal reverser having a holding coil 52 and normally closed contacts 53, 54 which are opened by passage of a train over a treadle. The remaining arrangements in Fig. 7 are those usually provided. Assuming the section clear and it is desired to send a train from A to B, current from B actuates relay 43, thus allowing a staff to be removed from A instrument, with consequent closure of contacts 10, 12. This closes a circuit from battery 49 through relay 44, contact 41, wire 55, contacts 53, 54, and coil 52. Contact 45, in shunt with contacts 10, 12, then closes a hold-on circuit so that relay 44 remains energized when contacts 10, 12 open. The slide 19, Fig. 4, is next moved inwards so that contacts 34, 35 are bridged by contact 33. A switch 58 operated by plunger or by the catch handle of the starting signal lever can now close a circuit from battery 59 through the lock 57, thus releasing the starting-signal lever so that the signal may be moved to " clear." The train passing the starting signal de-energizes coil 52 by opening contacts 53, 54, and the signal returns automatically to "danger." Relay 44 is simultaneously de-energized, so that lock 57 is de-energized by opening of contact 46, and the signal lever when returned to normal position is locked there. The slide 19 in its inner position is locked, and can only be released by current from B through polarized relay 32 when the instruments have been brought into phase by insertion of the staff, carried from A, into the instrument at B, and after switch 71 has been moved into engagement with contact 70. If it be desired to cancel departure of a train from A, return of the previously removed staff to A instrument momentarily opens the circuit of relay 44 at contact 41, restoring the apparatus to normal condition. As an alternative to the reverser arrangements shown the relay 44 may be controlled by a track circuit. A modification is described in which the parts 52, 53, 54 are replaced by contacts controlled by the signal lever, the arrangement being such as to prevent the starting signals at both ends of the section from being in " clear " poition simultaneously.