Patent GB-935751-A (GB)
Title: Improvements relating to conveyor systems
Inventor: BARR ARTHUR ERNEST
IPC: G05D1/02
Filed: 1958-11-24
Abstract: 935,751. Inductive signalling. ELECTRIC & MUSICAL INDUSTRIES Ltd. Nov. 16, 1959 [Nov. 24, 1958; July 16, 1959], Nos. 37812/58 and 24419/59. Class 40 (5). [Also in Group XXX] In a conveying system in which driverless vehicles are controlled and steered in response to alternating signals received from a route defining conductor or leader cable, the conductor is divided into sections or blocks and a signalling system controls the energization of each section to maintain a clear section between vehicles. Each vehicle has two sensing coils 1, 2, Fig. 1, in which currents are induced by the magnetic field produced by current flow in the conductor and these signals are amplified 3, 4 and control relays 5, 6 which operate a steering mechanism 7. The arrangement acts to maintain an equal pick-up of signal in each coil. The sum of the amplifier signals is also applied to a relay 8 which energizes when the sum exceeds a set value and if a further relay 11 is operated the vehicle drive motor 10 is started and the brakes removed by a solenoid 9. Relay 11 is operated when the vehicles drive battery voltage is above a predetermined minimum, if the safety bumper switch 20 and gear interlock switch 21 are correctly positioned and a start button 22a has been depressed. The relay may also be controlled by additional stop and start circuits influenced by the signalling system. The route is defined, Fig. 3, by conductor sections A, B, C, &c., which may be energized under the control of switching units AB, BC, &c. from the source of alternating current CS. The presence of a vehicle approacha junction, e.g. between sections A and B, is signalled to the associated switching unit AB by the pick-up of a signal produced by an oscillator 40 on the vehicle which is transmitted to the switching unit via coil 13 on the vehicle and coil Zb positioned alongside the route. The signal is amplified ATb, Fig. 4, and operates relay RLSB which locks over contact RLSB1, if the section in advance of the next section (section C) is free and de-energized relay RLB is energized via contacts RLSB2 and RLC4 and locked over contact RLB1. Section B is thus energized over contact RLB3 and section A is de-energized by contact RLB5 and the vehicle proceeds into section B. If, due to occupancy of section C, relay RLB cannot operate, current flowing through coil LA which is connected in series with the supply to section A induces a signal in coil 14 on the vehicle which releases the relay 11 and brings the vehicle to a halt and the information that a vehicle is waiting at the junction AB is stored in the switching unit AB by the locked-up condition of relay RLSB. When section C is free relay RLB energizes and current is switched to section B which in flowing around the loop SB at the commencement of the section induces a signal in coil 15 on the vehicle which is amplified and restarts the vehicle by operating relay 11. Route selection is controlled by a coding switch 42 on the vehicle which controls which of the transmission coils 13 or 17 is energized from the oscillator 40. These coils co-operate, e.g. at the junction of section D and diverging sections E and F with coils Ze and Zf respectively connected to switching units DE and DF controlling the energization of sections E and F. The coding switch has route information stored therein at the commencement of a journey and acts in accordance with this information under the control of counter pulses produced in coil 43 on the vehicle as it passes over-energized markers (not shown) positioned alongside the route whereby at appropriate points on the route the oscillator output is switched to either the left or righthand coils or the vehicle is brought to a halt by de-energizing relay 11. At approach sections to diverging or converging junctions the energization of a section may be inhibited by occupancy of sections other than that in advance of the next section.