GB880619A - Improvements in and relating to electrical control means for transmission gearing - Google Patents

Abstract

880,619. Change-speed control. SELFCHANGING GEARS Ltd. March 4, 1960 [March 6, 1959; Dec. 14, 1959], Nos. 7885/59 and 42454/59. Class 80 (2). A change-speed gear control circuit in a motor car &c. comprises an output driven generator supplying current to a transistor circuit which is operative either to effect automatic shifts of ratio or alternatively to prevent undesired or unsafe selection or establishment of a ratio. In one form, an alternating generator 20, the Figure (7885/59), driven by the output shaft of a change-speed gear in a motor car or rail car, supplies current through a rectifier 22 to two transistors T3, T4 forming a bi-stable flip-flop arrangement, the transistors being connected between positive and negative D.C. lines 11, 23 and the transistor T3 transmitting current prior to energization by the alternator 20, increasing the output speed ultimately applying such a potential to the base of the transistor T3 that it ceases to transmit current and the transistor T4, hitherto inoperative, instead transmits current, thus energizing the second coil of a relay 3S. Switches 381, 382 are then operated by the relay 3S to de-energize a relay 2 actuating a valve in a pneumatic or fluid pressure second ratio establishing servo means, and instead energize a solenoid 3 controlling a similar valve and servo means to establish the third ratio in the gear. Another pair of transistors T5, T6 in a similar bi-stable flip-flop arrangement acts through a relay 4S to control switches 4S1, 4S2 effecting energization of the relay 3 and a relay 4 establishing direct drive in the gear. A handoperated switch 5 closes a contact 10 for automatic ratio shift between second, third and fourth ratios, and is moved to positions 6 ... 9 to establish reverse, first, second or third ratios. The switch 5 is de-energized when the motor car &c. is stationary and the throttle pedal is released, depression of the pedal moving a switch 13 to earth a live contact 14 connected through one coil of a relay 2S to the positive line 11. A switch 2S1 is closed by the relay 2S to connect the switch 5 to a line 12 and the negative line 23 of the D.C. circuit, one transistor T2 of a further bi-stable flip-flop transistor circuit T1, T2, similar to those described above, transmitting current when the output driven generator 20 rotates at a sufficiently high speed to energize the second coil of the relay 2S, which holds the switch 2S1 closed irrespective of throttle pedal position. A resistor R6 is cut-in by a switch 2S3 similarly operated by the relay 2S to prevent " hunting." Depression of the accelerator pedal also actuates a switch 15 which cuts out series resistors R7 ... R9 in the circuit between the rectifier 22 and the bi-stable flip-flop transistor circuits, to adjust the output speeds at which ratio shifts are effected in dependence upon throttle pedal position. In the event of a failure of the signal source, e.g. the generator 20, a step-up transformer 24, 26 transmits a pulse of current to a further bistable transistor circuit T7, T8 which energizes a relay WS to open contacts WS1 and close contacts WS2, so that the switch 5 can be moved to its position 9 for manual establishment of the third ratio. Stabilization of the D.C. voltage is obtained by transistors T9, T10 and a rectifier 27. In a modification, accidental establishment of reverse while a vehicle is moving forwardly is prevented by an alternator 9, Fig. 2, feeding through a rectifier 19 to a bi-stable flip-flop transistor circuit T1, T2 of which the transistor T1 normally transmits current, operation of the generator applying a potential to the base of. the transistor T1 which becomes inoperative so that the transistor T2 instead transmits current to a relay 23 which closes a switch 24 and thereby energizes a relay 13. The circuit is shown applied to a reverse gear 1, Fig. 1, in a railway locomotive in which an alternator 3 secured on the gear case is connected to a control unit 12 and a relay 13. A displaceable core 15 within the relay 13 is loaded by a spring 16 to lie clear of a hand-controlled forward-reverse gear-shift lever 17. When the relay 13 is energized, the core 15 is displaced into the path of the lever 17, and establishment of reverse is prevented. Specifications 802,272 and 820,395 are referred to.