Patent GB-1252133-A (GB)
IPC: G05D1/02
Filed: 1968-11-04
Abstract: 1,252,133. Track apparatus. AMERICAN CHAIN & CABLE CO. Inc. 4 Nov., 1968 [2 Nov., 1967], No. 52155/68. Heading B7N. [Also in Division H4] In an automatic guidance system for selfpropelled vehicles in which an energized electrical conductor connected in a closed circuit defines a guide path for the vehicles in cooperation with sensing means on the vehicles which cause the vehicles to be directed along the conductor, the conductor is provided with decision points at which the conductor is separated into first and second portions interconnected by electrical bridging means, means being provided for selectively connecting one of said first and second conductor portions to the circuit on the reception of a selecting signal from a vehicle approaching a decision point. General description.-A typical guide path 20, Fig. 1, for vehicles used in warehouses, etc., comprises stopping points 1, 2, 3 and includes an intersection I and a diverging point II where the vehicles can move in one of two paths 21, 22 converging at III. The wire 20 is energized by an oscillator 23 at a frequency of, for example, 2 KHz. Each vehicle, Fig. 3, includes a programmer by which an operator selects a destination and sensors 30 which control the steering motor. A permanent magnet 31 operates reed switches on the track which with a transmitting coil 32 control the path selection. A pick-up coil 33 stops the vehicle if it is closer than a predetermined amount to a preceding vehicle and sensors 34, 35 read signals at predetermined positions along the track to guide the vehicle along the shortest path and stop it at a predetermined destination. Operation at decision points.-A vehicle approaching an intersection I along conductor 50, Fig. 4, opens a normally closed monostable switch 51 i.e. a reed switch on the track cooperating with magnet 31, to operate a bi-stable switch 56 to energize by-pass circuit 52 and deenergize portion 54. Thus only path 50 is energized and as the vehicle passes the intersection a normally open monostable reed switch 55 is operated to reset the bi-stable 56 and deenergize by-pass 52 so that current flows through the normal path 54. Similarly, when a vehicle approaches the intersection along conductor 53 a normally closed monostable switch 57 opens to operate bi-stable 59 to energize by-pass circuit 58 until the vehicle has passed the intersection when the normally open monostable 60 is energized to return the path 50 to normal. The bi-stable devices 56, 59 are monostable reed switches with a holding circuit 63. At a point of divergence II a vehicle travelling along conductor 67, Fig. 5, changes over a two-way reed switch 65 if the coil 32, Fig. 3, is energized. Normally conductor 66 is energized but operation of switch 65 de-energizes conductor 66 and energizes conductor 68. The switch 65 will remain in this position until returned by a signal of opposite type from a following vehicle. A resistor 67a prevents short-circuiting during switching. At a point of convergence III, Fig. 6, the conductor 76 is normally energized so that a vehicle following the by-pass conductor 68<SP>1</SP> will pass through to the main path 77. If a vehicle approaches along path 72b the magnet 31 will actuate bi-stable device 75 to de-energize conductor 76 and energize conductor 81. When the vehicle has passed the point of convergence a monostable device 82 is momentarily operated to short-circuit the holding circuit of bi-stable device 75 and re-energize the position 76. Contact between successive vehicle is prevented by coils 85, Fig. 7, which one energized behind the vehicle by a reed switch 86 with a holding coil of the type described, which is operated by the magnet 31 as the vehicle passes. The energization of a coil 85 is sensed by the coil 33 on a following vehicle to stop it. As the leading vehicle moves past the device 86 the magnet 31 momentarily operates a switch 89 which shorts the holding coil of the preceding switch 86 to deenergize the corresponding coil 85. At an intersection I, Fig. 8 (not shown) bi-stable devices 86 controlling coils 85 are provided on both paths and a device 86 controls a coil 85 both in its own path and in the intersecting path. Similarly, devices 86 and coils 85 are provided at diverging and converging paths, Figs. 9 and 10 (not shown).