Patent GB-576513-A (GB)
Title: Improvements relating to control apparatus for railway signals
IPC: B61L5/18
Filed: 1944-04-15
Abstract: 576,513. Railway signals. WESTING- HOUSE BRAKE & SIGNAL CO., Ltd. April 15, 1944, No. 6982. Convention date, May 29, 1943. [Class 105] A control apparatus for railway signalling comprises two electromagnets with their armatures jointly controlling a signal device, the electromagnets being energized from a reversible supply, in which one electromagnet has means for locking or retaining its armature in the unoperated position when supplied with current of one polarity (normal) but not when supplied with current of the other polarity (reverse), the armature of this electromagnet, or the locking means therefor, controlling the supply of current to the other electromagnet so that it is always of fixed polarity whatever the polarity supplied to the first electromagnet. The electromagnets may operate contacts for the control of the signal but, in the arrangements shown, the two armatures Al, A2 are connected to a common link 16 for the operation of a signal spectacle 20. As shown in Fig. 1, the electromagnet M1 has a polar armature P1 formed by a permanent magnet 5 pivoted at 6 with poles N, S as marked. When the control switch PC is moved to its lower position (normal) the current flow in the windings 12, 13 of magnet M1 gives a flux such that the polar armature P1 moves to the full line position shown, thereby locking the armature A1 against movement, whereas the armature A2 of the other magnet M2 is operated thereby moving the spectacle 20 to display the Y aspect. The, circuit is from battery B1, contact 22 of control switch PC in its lower position, wire L1, winding 13 of magnet M1, contact 8/10 of the polar locking armature P1 in the full line position shown, windings 14, 15 of magnet M2, rectifier 24, wire 25, winding 12 of magnet M1, wire L2, and contact 26 of control switch PC in its lower position, back to battery B1. With the control switch PC in its upper (reverse) position the current flow is at first from battery B1, contact 22 in its upper position, wire L2, winding 12 of magnet M1, wire 25, rectifier 27, wire 23, contact 10/8, winding 13 of magnet M1, wire L1, and contact 26 back to battery B1. This sets up a flux in magnet M1 such that the polar armature P1 moves to the dotted position whereby the locking of armature A1 is released and this armature therefore rises ; the polar armature P1 moreover moves its contact 8 to close the contact 8/11 whereby the current from winding 12, wire 25, rectifier 27, now passes to windings 14, 15 of magnet M2, wire 28, contact 11/8, winding 13 of magnet M1, and contact 26 back to battery. With both armatures A1, A2 attracted the spectacle 20 displays the G aspect. " Flashing of the red " during the change-over is prevented by the slow-release characteristic of the magnet M2 due to the rectifiers 24, 27 providing a circuit for the decay-flux current and it will be noted that the current in the windings 14, 15 of magnet M2 is always of the same polarity. In the arrangement shown in Fig. 5 the contacts to ensure unidirectional current in the magnet M2 are operated by the armature A1 of magnet M1 and this armature A1 is retained in its unoperated condition by means of a neutralizing winding 49, when the control switch PC is in its left-hand position (normal). With control switch PC at the left hand (normal), the circuit is from battery B1, wire L1, winding 13 of magnet M1, back contact 39/40 of armature Al, winding 14 of magnet M2, neutralizing winding 49 of magnet M1, winding 15 of magnet M2, rectifier 24, wire 25, winding 12 of magnet M1, wire L2, and control switch PC at left-hand back to battery. When control switch PC is put to the right hand (reverse) the circuit is at first from battery B1, control switch PC at the right hand, wire L2, winding 12 of magnet M1, wire 25, rectifier 27, back contact 40/39, winding 13 of magnet M1, wire L1, and control switch PC at the right hand, back to battery. The armature A1 is attracted since the neutralizing winding 49 is not now in circuit and thereupon closes front contact 38/39 whereby the current from winding 12 of magnet M1, wire 25, rectifier 27, now passes to winding 14 of magnet M2, winding 49, winding 15 of magnet M2, front contact 38/39 of armature A1, winding 13, wire L1, and control switch PC at the right hand, back to battery. It will be noted that the windings 12, 13, 49 of magnet M1 are now additive and that the current in the windings 14, 15 of magnet M2 is always of the same polarity. An arrangement is described in which the retention of the armature A1 of the magnet M1 in its unoperated position is effected by means of a permanent magnet when the control switch is put to the position (normal) for setting the spectacle to the Y aspect, Figs. 3 and 4 (not shown).