Patent GB-471105-A (GB)
Title: Improvements in or relating to control mechanisms for gear boxes
IPC: F16H61/02
Filed: 1935-12-24
Abstract: 471,105. Controlling change - speed gearing. CHAMBERS, W. E., and LONDON PASSENGER TRANSPORT BOARD. Dec. 24, 1935, No. 35662. [Class 80 (ii)] Relates to means for preventing the abuse of gear boxes of the Wilson type by drivers throwing the transmission into reverse instead of applying the vehicle brakes. To go into reverse, it is necessary to bring a change lever 29, Fig. 5, to neutral, and to press in a button 32, which is not so easy as to disengage the drive and brake the vehicle. The struts 16, Fig. 2, for second, third, and fourth speeds are biassed, as is usual, by springs (not shown) to the "out" position clear of the busbar (not shown) which rises to engage and lift a selected strut. These struts are put in by energizing selectively solenoids 23a, 23b, 23c, Fig. 3, which act to thrust pins 24a right of Fig. 2. But the struts 161, Fig. 1, for reverse and first speed are biassed to the "in" position so that in the event of failure of current, these two struts 161 are both engaged by the rising bus-bar, and since they cannot both pass an interlocking sectional bar device 18, Fig. 4, like that described in Specification 370,442, the result is no drive or neutral. A neutral may also be produced by a blind strut additional. To engage first speed, a solenoid 23, Fig. 3, of the reverse train is energized which pulls a pin 24, Fig. 1, left against a bias spring 26 so that the strut 16<1> of the brake of the reverse train is caused to follow the pin left by a spring (not shown) so that the strut 16<1> of the first speed train is left in the " in " position where it is biassed by the spring 26 of the inert solenoid 23<1>, Fig. 3, opposite the first speed train. The rising busbar then throws in the first speed. To throw in reverse, the solenoid 23<1> is energized so that the strut 16<1> of the reverse is held in by the spring 26 of the inert solenoid 23. Fig. 5 shows the control lever 29 in firstspeed position so as to bridge terminals 60, Fig. 8, supplying current to the solenoid 23. A cam 34, Figs. 5 and 7, carried by the lever 29 is in position to block the passage of the stem 32a of the button 32 which must be pressed in alternatively to bridge contacts 30 and so energize the solenoid 23<1> to bring in reverse, as is apparent from Fig. 8. To bring in second speed, four contacts 62, Fig. 8, are bridged. This energizes not only the solenoid 23a, which moves the selected strut 16 of Fig. 2 to the "in" position, but also energizes both solenoids 23, 23<1> simultaneously, so that the biassed-in struts 16<1> of Fig. 1, are both held "out." Similarly when the quadruple contacts 63 and 64, Fig. 8, are bridged to energize solenoids 23b, 23c for third and fourth speeds respectively. Thus when second, third or fourth speed is in, the reverse is out by electrical connection and it is not possible to engage reverse except by bringing the lever 29 to neutral before pressing in the button 32. The four sets of contacts 60, 62, 63, 64 for the forward speeds are bridged selectively, one at a time, by the lever 29 moved to the four corners 1, 2, 3, 4 of a gate shown in Fig. 7. The lever 29 carries two dogs 69, 69a which are engaged alternatively with two double rocker switches 65, 65a whch carry bridging contacts 31. Spring bolts 70 bias the lever 29 to neutral. A master switch 37, Fig. 8, renders it possible for the solenoids to be energized only at such time as the executive pedal (not shown) is depressed to raise the bus-bar. The pedal preferably opens a valve to admit compressed air to a slave unit to depress the bus-bar against springs, as described in Specification 402,794, and in Fig. 8 is shown a main pneumatic switch 3S which ensures that the circuit cannot be completed on starting the engine until there is sufficient air pressure in a supply reservoir.