Patent GB-797056-A (GB)
Title: Improvements in or relating to relay controlling apparatus in railway safety systems, for signalling between a vehicle and the track which carries the vehicle
Inventor: MILLER MAX
IPC: B61L1/18
Filed: 1955-12-02
Abstract: 797,056. Railway signalling. SIEMENS & HALSKE AKT.-GES. Dec. 2, 1955, No. 34606/55. Class 105. Equipment for signalling between a railway vehicle and track apparatus comprises a Hall generator fixedly disposed in a gap in a ferromagnetic path and a signal receiver consisting of at least one relay connected to the Hall electrodes and means operable by the vehicle on a predetermined portion or section of the track to modify one or more of the factors controlling the output of the Hall generator, e.g. the strength and direction of the controlling magnetic field or the controlling current. In the first case, the Hall generator may be carried on the vehicle and arranged to interact with a magnetic field disposed on the track or the magnetic field may be carried on the vehicle and the Hall generator be disposed on the track. In the second case the controlling current of the Hall generator on the track may be derived from the track circuit and modified or varied when the vehicle enters the track section. A.C. or D.C. current-may be used for the controlling current. The Hall generator may be formed of a semi-conducting compound of one of the elements boron, aluminium, gallium and indium with one of the elements nitrogen, phosphorous arsenic and antimony having, e.g. a mobility of the electricity carriers higher than 6000 cm. sec.<SP>2</SP>/volt. sec. As shown in Fig. 1, the vehicle carried magnet' comprises pole pieces 1, 2, a soft iron bridge 3, 4 and magnetic pieces 5, 6 forming a gap therebetween accommodating the Hall generator 7 consisting of a thin plate of semi-conducting material with control electrodes 10, 11 extending in contact over the entire horizontal edges, and Hall electrodes disposed on the vertical edges 12, 13, these Hall electrodes being of smaller area than the control electrodes. The control electrodes are supplied with current through a resistor 9 from a battery 8 and a relay 14 is connected to the Hall electrodes 12, 13. Resistance 9 which is large compared with the resistance between the control electrodes tends to keep the control current constant. For supervision of the control current, the winding of a supervisory relay may replace resistor 9. To supervise all closed circuits, the controlling field is sufficiently great to hold the relay 14 operated by the Hall voltage and for this an auxiliary magnet 15 provides additional control flux to that of the vehicle magnet 1, 2, 3, 4. The track magnet is a permanent magnet 16 with soft iron pole pieces 17, 18 having thereon neutralizing windings 19, 20 which are energized, when e.g. the track signal associated with the magnet 16 is at clear, to neutralize the field of the magnet 16 so as not to influence the Hall receiver as the vehicle magnet passes thereover. Relay 14 may be a polarized relay and the magnet 16 must then be so strong as to reverse the controlling field of the Hall generator as the vehicle magnet passes over the permanent magnet 16 when this latter is to be effective. For a relay with an armature having a stable mid position and operable to one off-normal contact or the other by energization of the relay winding by current of appropriate sign, two different signals can be transmitted, by omitting the magnet 15 and arranging the direction of the track magnet in accordance with the desired signal. The polarized relay may be replaced by two parallel connected neutral relays with respective oppositely poled current rectifiers. The permanent magnet may be carried by the train to effect control of the Hall generator assembly 1-14 disposed on the track for e.g. end-of-train signalling, route release, switching-on warning installations or for point-setting from the train. Amplifiers, preferably transistor amplifiers, are connected between the Hall generator and the signal receiver. The invention is also described in connection with axle counting systems, Figs. 2 and 3 (not shown), by reversing the Hall generator control flux as the wheel of an axle passes the main magnet of the generator assembly on the track to divert the main control flux from the Hall generator and allow an oppositely compensating flux to reduce the controlling flux to zero in the Hall generator. If D.C. controlling current is used the signal receivers are disposed immediately adjacent the Hall generator impulse emitters. If A.C. controlling current is used the A.C. output voltage from the Hall generator is stepped up by a transformer and transmitted by lines to rectifiers at the signal box, the output from the rectifiers being fed to the receiving relays to actuate the counting device. For economy in cable a particular frequency of the control current may be allocated to each impulse emitter of a counting point. As shown in Fig. 4, the A.C. control current for the Hall generator 32 disposed on the track, is derived from the track circuit of section 29, the feed to the track being through a reversing switch 28 and a resistor 39 from a mains 27, at one end of the section and the Hall generator 32 being connected through a resistor 40 across the rails at the other end of the section. The control magnetic field is produced by two choke coils 36, 37 fed from the mains 27, through a condenser 38 by which phase equality between the control field and the control current may be adjusted, so that a pulsating unidirectional voltage is set up at the Hall electrodes, the direct current component of which is fed to the track relay 35, the fundamental A.C. component and the harmonics being filtered out by the low pass filter 33, 34, 65. If relay 35 is a polarized relay with armature having a stable mid-position, the position of this relay can be changed when the track is vacant by changing over the switch 28 which results in a reversal of the control current and may be used to indicate the condition of the track section adjacent the insulation joints 30. The windings 36, 37 may alternatively be excited by current fed from the track circuit and the control current may be fed directly from the source 27 through a 90 degree phase shifter. To increase the power supplied to the signal relay 35 two or more Hall generators may be provided in juxtaposition to one another in the same gap in the magnetic circuit or in a plurality of gaps, the corresponding control electrodes being connected together and also the corresponding Hall electrodes, preferably using A.C. controlling current, in which case the control current of each Hall generator may be provided by its respective secondary winding associated with the same primary winding of a transformer fed e.g. from the track circuit, the Hall electrodes of the generators being connected in series. Alternatively all the generators may be connected into the same control circuit, Ó transformer then feeding the signal receiver from its secondary winding associated with several primary windings connected to respective Hall electrodes of the generators. Alternatively, the signal receiver may have as many windings as there are Hall generators.