Patent GB-232737-A (GB)
Title: Improvements in electric signalling apparatus
IPC: B66B19/06
Filed: 1924-03-04
Abstract: 232,737. Dale, W. B., Hopkinson, R. A., and Hopkinson & Co., Ltd., J. March 4, 1924. Mine signalling systems; Order apparatus.-In apparatus of the type wherein a pointer is moved step-bystep over a dial by an electromagnet and is returned to zero by the first impulse of a subsequent signal, means are provided for preventing the rebound of the pointer when returned to its zero position. A pointer a is moved over a dial b on the down-stroke of the pawl d by a ratchet wheel c. Depression of the signalling key 10 closes the circuit of a magnet g and also the coil 18 of a release magnet s through the contacts 17, 16, 20. Energization of the magnet g causes the attraction of an armature f which is pivoted at h and raises the pawl d. The release magnet s attracts the armature r which swings a pivoted lever 5 to raise a pawl i and allow the wheel c, which has been set by a previous signal to return to its zero position. The pawl d is also'raised by the lever 5 when the magnet s is energized. The armature r also swings a catch p into the path of a latch o on the wheel c to prevent the rebound of the pointer a after its return to zero. When the signalling key 10 is released, the armature f is released and a spring e causes a downstroke of the pawl d and a movement of the pointer a through one step. Over-running of the, ratchet wheel c is prevented by a weighted catch v which is moved into the path of a second ratchet wheel u by a projection y on the pawl d'. When the release magnet s is operated the projection y is moved over a recess 6 and the catch v is moved clear of the ratchet wheel u by a weight x. The operation of the release magnet s is dependent upon a time limit switch 16., 17 which, if the signalling impulses are sent with sufficient rapidity, is held open by the action of a series of diaphragms 12. The contact 16 is carried by a lever 40 which is pivoted at h and is mechanically connected to the diaphragms 12. When the key 10 is first operated the armature f is attracted to operate the lever 40 and open the contacts 16, 17 air being expelled from the diaphragms 12 through a non-return valve 13. The contacts remain open until sufficient air has leaked past the valve 15. The release armature r is maintained by a hold-on coil 19 on the release magnet, s after the contacts 16, 17 are opened. The release magnet coil 18 may be energized independently by the. switch 20. When an important signal is given, such as the signal " 3 " (open), a dial 21 is illuminated. A pin 32 energizes a latch 23, when the pointer occupies a position corresponding to the signal, and releases a weighted arm 24 to operate a contact 27 through a connecting rod 26. The contact 27 co-operates with a contact 28 mounted on the lever 40 of the time limit switch when this is in the closed position. A circuit is thus closed through the contacts 27, 28 to a coil 29 on a magnet 30. The armature 31 closes the contacts 32, 33 which are in circuit with the lamp which illuminates the dial 21. When the armature 31 is attracted, a hold-on coil 34 is energized to maintain the lamp alight until the circuit is broken at the contacts 35. The pointer, when released, is returned to its zero position by the spring 7. The force of the spring is communicated to the ratchet c bv a chain j connected to a scroll-plate k, the shape of which ensures an equal pull in each signalling position of the pointer.