Patent GB-556581-A (GB)
Title: Improvements in or relating to railway signal and/or points control equipment
IPC: B61L19/06
Filed: 1941-12-02
Abstract: 556,581. Railway route-setting systems. STANDARD TELEPHONES & CABLES. Ltd., BROWN, A., and MARSHALL, T. A. Dec. 2, 1941, No. 15489. [Class 105] In a railway route-setting system using multiposition switches as described in Specification 496,495 each circuit which controls the drive of a switch is made independent of other control circuits with which it has a point or portion in common in order to avoid any feedback (improperly operating, for example, the drive of another switch) which might occur during route-setting operations. Fig. 2 shows a typical layout comprising 16 routes numbered as in the left-hand column of Fig. 4 which tabulates the routes, their switches (1 to 4) and switch-positions, together with the interlocking between the routes. The Specification also gives a diagram showing each of the routes separately. Fig. 5 shows conventionally the circuit diagram for the sequence switches providing the required interlocking for all the routes in accordance with the table of Fig. 4. In this a circuit from supply Bf6 passes over the wiper contact of cam BB of switch No. 3 (3BB) to cams BB, BC of switch No. 2 (2BB, 2BC) which, in conjunction with cams 4BB, 4BC control the setting of routes 3A, 3B, 14B and 6. Providing a cam such as 3BB in common with the control circuits of a number of routes is a convenience in practice which provides one of the common points referred to above. Fig. 6 shows the control circuits of switch No. 1 only. The Specification gives a diagram partly extracted from Fig. 5 showing the cams 3 BB, 2 BB, 2 BC combined with the usual arrangement (corresponding but not agreeing with Fig. 6) in which all the route-control circuits involving a switch (e.g. No. 1) converge on a single .relay controlling the operation of the switch and providing a second common point, and explains how with such arrangement the unwanted feed-back might occur. Other conditions under which the feed-back may occur are referred to. The switches described are of rotary type driven from a continuously rotating motor under control of clutch and lock magnets. The windings of the clutch magnet may serve as the switch control relay referred to above or a separate magnet-controlling relay may be used. As described, the unwanted feed-back is avoided by providing a separate control relay or relay winding 1Z<SP>1</SP>R, 1Z<SP>2</SP>R, 1Z<SP>3</SP>R, Fig. 6, for each route controlled by the switch in place of a single relay common to all the routes. Fig. 6 also shows additional switch cams and wipers involved in the control together with the selective hand-operated panel switches 1R, 3AR, 3BR, 3CR, 3DR, 5R, 6R, 14BR, for each of the routes involving control by switch No. 1, and the circuit for setting route 3A by operation of panel-switch 3AR to reverse position is traced from supply Bf6 over cams 3BB, 2BB, 4BB, panel switch 3AR, cams 1BI, 1BK to control relay winding 1Z<SP>1</SP>R causing operation of the switch. This circuit is closed over wiper H of cam 1BK only when the switch is in home position, but the circuit of winding 1Z<SP>1</SP>R is maintained' closed when arm 1BK moves from home bv a contact 1 Z<SP>1</SP>R2 of relay 1Z<SP>1</SP>R bridging cam 1BK and wiper H. Relay 1Z<SP>1</SP>R thus remains energized until its circuit is broken at cam 1BI when the switch reaches the position corresponding with route 3A. When this occurs a proving relay 1ZCR is energized the contacts of which effect the setting of points and clearing of signals for the selected route. In practice, setting a selected route may involve the passage of a cam past a circuit-breaking position for another route already set. To avoid corresponding deenergization of the latter route ZCR relay, the break effected by a cam is made to occupy say one-fifth of a second and the ZCR relays are slow-release with a time lag of say half a second. Where necessary to avoid too many contacts of a ZCR relay, a relief relay 1ZCPR may be used, the contacts of which control the points and signals. To ensure that only one switch may be moving at a time, the specification gives a circuit diagram in which the lock and clutch magnets of the different switches are arranged in parallel between the positive and negative leads, fed from opposite ends, which include contacts so disposed that when the magnets of any switch are operating the contacts open to break the positive lead for all other switch magnets to the right, and the negative lead for all other magnets to the left. When a route has been set it can be restored and the switches returned to home position only by restoring the corresponding panel switch to normal. The Specification gives a diagram and description of the restoring operation.