Patent GB-937902-A (GB)
Title: Improvements in or relating to apparatus for detecting vehicles
IPC: G08G1/02
Filed: 1960-09-21
Abstract: 937,902. Retractive switches; control of motors. BOWSER INTERNATIONAL Ltd. (Bowser Inc.). Sept. 21, 1960, No. 32501/60. Classes 38 (3) and 38 (5). [Also in Group XXV] Apparatus for detecting vehicles, particularly for controlling the operation of a gate or barrier 14, comprises two treadle electric switches 20a, 20b disposed in close proximity to one another, a third electric switch 66a connected in series with the second treadle electric switch, means connected for energization through the second and third switches, and a time delay relay connected for energization through the first switch and controlling the operation of the third switch. Each treadle switch comprises two metal bars 28, 30 (Fig. 3) separated by an insulating strip 32 formed with a plurality of openings, and is encased in a hard rubber strip 24 disposed in a metal channel 22 so that passage of a vehicle wheel deforms the bars 28, 30 into contact through the openings. The switches 20a, 20b (Fig. 5) are located beneath a rigid actuating plate 40 loosely connected by bolts 42 to a base-plate 36 so that a wheel approaching from the left first encounters and depresses the edge 46 to actuate the switch 20a and then depresses the remaining part of the plate 40. As the wheel encounters the right-hand edge 48, the switch 20a opens, and as the wheel leaves the plate the switch 20b also opens. The control circuit for the motor 60, which drives a reciprocating crank arm assembly to effect cyclical raising and lowering of the gate, is shown in Fig. 6. The closing of switch 20a energizes a time delay relay 66 powered by a transformer 50 through a switch 78, the relay being designed to close the switch 66a after a delay of 50-80 milliseconds. Providing that the vehicle is travelling sufficiently slowly, the switch 20b will be closed when the switch 66a is closed, and these two switches complete an energizing circuit for relays 62, 64, the former closing the switch 62a of the motor 60 to commence gate opening movement and the latter closing a switch 64a to complete a holding circuit for the two relays. Relay 64 also opens switch 64b. When the gate has opened 10 degrees to 15 degrees, it moves the switch 78 to contact 82, and as it approaches its fully open position it opens a switch 72 to de-energize relay 62 and thus stop the motor. When the front wheels of the vehicle pass over an exit treadle 20 a switch 84 closes and energizes relay 70, thereby opening switch 70a to de-energize relay 64, and shifting switch 70b. Switch 64b also closes. As the front wheels leave treadle 20, the switch 84 opens and deenergizes relay 70, thus closing switch 70a and causing switch 70b to return to its illustrated position. Relay 68 is now energized and closes its hold-in switch 68a and a switch 68b. As the rear wheels of the vehicle pass over treadle 20 the relay 70 is again energized and, by closing its switch 70b, establishes a hold-in circuit for itself via contact 82, switch 68a, switch 64b, contact 92 and switch 68b, and also closes an energizing circuit for the relay 62. The gate now begins to close, and when it approaches its fully closed position it moves the switch 78 back to contact 80 and closes switch 72. Movement of switch 78 de-energizes the relays 62, 68 and 70, and thereby stops the gate motor and places the system in readiness for another complete cycle of operations. U.S.A. Specification 2,842,876 is referred to.