Patent GB-521405-A (GB)
Title: Improvements relating to traffic controlling systems for railways and the like
IPC: B61L5/06
Filed: 1938-11-15
Abstract: 521,405. Controlling railway points. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., VENNING, C. F. D., and CHALLIS, E. W. Nov. 15, 1938, No. 33173. [Class 104 (i)] In a railway traffic control system having an electrically operated point machine, operation of the machine by accidental or extraneous current is prevented by providing a crossprotection relay in series in the point control or control relay circuit adjacent to one of the current supply terminals, this,relay controlling the circuit of the point machine, either directly or indirectly. Fig. 1 shows a lay-out comprising an approach section 2T, points 3 and signal S with a fouling section 3T, a main line exit 4T and a branch exit 6T. Fig. 2 illustrates a corresponding circuit arrangement in which the cross-protection relay 3CPR is adjacent terminal B and in series through usual track relay front contacts 2TR, 3TR, with the parallel normal and reverse windings 3LR(N), 3LR(R) of a point interlocking relay 3LR which controls the point machine circuits. Circuit of normal winding 3LR(N) includes normal contact N of conflicting route contacts 2-6R and a normal contact N of the individual point control device bridging reverse route contact 2-4R in series with a neutral or central contact C of the device. Circuit of reverse winding 3LR(R) includes normal contact N for route 2-4R and reverse contact R of the individual point-control device bridging reverse contact R of route contacts 2-6R and central contact C of the individual point control device. The point machine windings 3NW, 3RW are supplied through contacts N, R of relay 3LR and contacts X opening when an operation of the machine is completed. The contact of relay 3CPR is included in the common return adjacent terminal C. With this arrangement operation of the point machine requires a simultaneous energization of relays 3LR, 3CPR which cannot occur with accidental current. Fig. 3 shows a modified arrangement in which relay 3CPR has slow-release characteristics and is connected adjacent to terminal C in parallel with the windings of relay 3LR, through circuits branched from the normal and reverse supply wires of that relay through reverse and normal contacts respectively. A front contact of relay 3CPR is. included as shown in the control circuit of relay 3LR. In this arrangement relay 3CPR is released as soon as the points have started movement, and to avoid interruption of the movement which would occur if a contact of relay 3CPR were included in the common return of the machine windings 3NW, 3RW, such contact is replaced by a contact of a repeater relay 3CR which is itself controlled by a contact of relay 3CPR so as to pick up when re'ay 3CPR is energized, and remain energized until operation of the points is completed. A further contact of relay 3CR may control circuit between a detector contact device Y and indicator KR. The Specification shows modification to allow the repeater relay to be located in the signal cabin instead of adjacent to the point machine, and to adapt the invention to a power-interlocking system in which the point levers are mechanically interlocked.