Patent GB-771498-A (GB)
Title: Supervisory circuit arrangement for axle counters in railway safety systems
IPC: B61L1/16
Filed: 1954-11-09
Abstract: 771,498. Railway signalling systems. SIEMENS & HALSKE AKT.-GES. Nov. 9, 1954 [Nov. 9, 1963], No. 32462/54. Class 105. A supervisory circuit for axle counters in railway signalling systems has a closed circuit supervisory relay U1 and a counting test relay Pm1 which are open circuited on passage of one or more axles over the counting points and produce a disturbance signal if one of these relays has not operated. As shown, axle counters are used having two counting motors Z1, Z2, acting on a differential gear to open a contact mz at the commencement of the counting operation and to return it to its initial position only when the number of axles counted out equals the number counted in. When the first axle passes the entrance counting point the pulse transmitters J1, J2 are actuated and normally closed contacts i11 and i21 associated with the transmitters open to de-energize the relay U1 which breaks its holding circuit at front contact u11. Front contacts i12 and i22 close to operate the motor Z1 and the contact mz is opened in the holding circuit of a section " occupied " signal relay Fz which relay at front contact #z1 breaks its holding circuit and the relay can only now be picked up again when the in and out axle counting operation has been correctly completed. To this end a supervisory test relay PU1 is now picked up over back contacts fz2, u12 to test whether relay Fz has fallen off and relay PU1 is held over its front contact pull. As the motor 21 moves, it oscillates the contact mk1 which in the position shown charges the capacitor e12 over winding a of relay pm1 which picks up and in the other position contact mk1 discharges the capacitor C12 through winding b of relay pm1 and this relay is held during the counting operation. At front contact pm11 relay U1 is picked up, contact pu12 being closed and at the end of the counting operation relay U1 is held over contacts i11, i21 and u11. While contact mz is open relay FZ remains dropped away giving a "section occupied " signal and relay PU1 remains picked up. Relays U2, Pm2 and PU2 function in the same manner as relays U1, Pm1 and PU1 when the axles pass over the exit counting point J3, J4 and if the counting in and counting out are equal contact mz is again closed and relay fz picks up over front contact pu15 and pu25. Should motor Z1 fail to operate after release of relay U1, this relay cannot pickup again over contacts pmll and pu12 and contact u13 opens the energizing circuit of a disturbance relay S to drop this relay which opens its holding circuit at contact s1. At contact s2 a section clearing relay Fm is de-energized and drops off. Should motor Z1 operate, thereby oscillating contact mk1 and relay U1 fail to drop away, relay S is de-energized at contact pm13, this being prevented during normal operation by front contact pu14 so that any defects prevents subsequent clearing of the section and at front contact s3 an alarm lamp SL is energized and the defect can be observed before the train leaves the section. In a modification, relay pm1 may be energized by the current from the secondary winding of a transformer through which intermittent current passes on operation of the contact mk1. In another modification, the capacitor C12 is charged under the action of alternate axles and discharged through the relay Pm1 under the action of the following axles by means of a cam disc on the shaft of the counting mechanism which alternates a changeover contact mechanism.