Patent GB-447866-A (GB)
Title: Improvements in or relating to railway and like signalling systems
IPC: B61L1/16
Filed: 1935-09-13
Abstract: 447,866. Railway signalling systems. STANDARD TELEPHONES & CABLES, Ltd., GRIFFITHS, J. B., and BROWN, A., 63, Aldwych, London. Sept. 13, 1935, No. 25448. [Class 105] Railway signals or points are controlled by a single apparatus which counts the axles entering and leaving a section as they pass over only two normally closed treadle contacts at each end of the section, the axles being counted in or out according to the direction of travel, and the arrangement is such that a wheel travelling slowly enough for a reverse movement off the treadle to be possible is counted both in and out if such reverse movement occurs. The Figure shows only the control arrangements for the axle-counting apparatus SAC Counting-in is effected when the normally closed line to terminal " In " is broken and counting-out when the normally closed line to the terminal " Out " is broken. Overlapping treadles X, Y, X<1>, Y<1> are provided at each end of the section. With a wheel entering at the left-hand end of the section the treadle X first opens its contact to drop the relay A ; next the treadle Y opens its contact to drop the relay B and thereafter the treadle X is freed to re-energize the relay A and finally the treadle Y is freed to re-energize the relay B. The relays A, B being overlappingly dropped in that order de-energize a relay AB a contact ab3 of which then opens the line to the terminal " In " to effect a counting-in. The dropping of the relay A opens contact a1 thereby de-energizing the relay AB and so when shortly afterwards the relay B drops and opens its contact b1 a back contact ab2 of the relay AB is already closed and therefore a relay BA remains energized over its stick contact ba1 the relay AB remains de-energized by contact b2 being open when the contact a1 re-closes. If the wheel passes first over treadle Y and then over treadle X the relays B, A are overlappingly dropped in that order and de-energize the relay BA (the relay AB being stuck up over a back contact ba2) and thus a counting-out will be effected by the line to the terminal " Out being opened at contact ba3. The other end of the section is provided with similar relays A<1>, B<1> controlling relays AB<1>, BA<1>, which through contacts ab<1>3, ba<1>3 effect counting- out and counting-in respectively. In order that a wheel moving on to a treadle and then reversing may be properly counted in and out there are provided slow-acting relays AR, BR, AR<1>, BR<1> which are de-energized when the wheel reaches the treadles but only drop. f the wheel remains for a sufficient time on the treadles. Normally therefore these relays AR, BR, AR<1>, BR<1> do not exercise any control but if an entering wheel is moving very slowly over the treadles X, Y, the relay AR will drop and open its front contact arl, but as the quickacting relay AB will already have closed its back contact ab4, which is in parallel with contact ar1, there will not be, at this time, any opening of the line to the terminal " Out." If, however, the wheel reverses and backs out then, when the treadle X is freed, the relay AB will lift before the relay AR lifts and thus the back contact ab4 will open before the front contact arl closes and thus the line to the terminal " Out " will be opened to effect a counting-out. Specification 412,620 is referred to.