Patent GB-753598-A (GB)
Title: Improvements in or relating to transmission systems
Inventor: STEADMAN CLIFFORD STUART
IPC: F16D37/02
Filed: 1953-12-10
Abstract: 753,598. Change-speedgearing. SMITH & SONS (ENGLAND), Ltd., S. Dec. 3, 1954 [Dec. 10, 1953], No. 34376/53. Class 80(2) Gearing for motor vehicles giv ing automatic changes between three ratios from the engine flywheel 5 to the output shaft 14 comprises a first slippable clutch 13 giving direct drive and a second slippable clutch 16 giving alternatively low-speed drive through a one-way clutch 25 on intermediate-speed drive on engagement of a dog clutch 33 provided with balking means preventing engagement except at synchronism, the automatic control means being such that, when operating to change from low to intermediate speed, clutch 13 is simultaneously fully engaged, and clutch 16 partially disengaged, so as to produce synchronism of the dog clutch parts without interruption of power flow to shaft 14, and clutch 13 is disengaged and clutch 16 again fully engaged only when the dog clutch 33 has engaged. As shown in Fig. 1, clutches 13, 16 are of magnetic-powder type with energizing windings 8, 9, and the gearing also provides emergencylow and reverse speeds. Clutch 13 drives shaft 14 direct and clutch 16 drives a hollow shaft 17 geared at 18, 19 to a lay-shaft gear cluster 29, 21, 36. Gears 29, 21 mesh with gears 30, 22 loose on shaft 14, gear 30 being connectable through the dog clutch 33, with balking ring 32, to shaft 14 while gear 22 is connected through one-way clutch 25 to a member 26 which is free on shaft 14 but which is normally connected, for forward drive, by clutch teeth to a gear 27 splined on shaft 14 and controlled by a manual yoke 35. As shown, gear 27 occupies a neutral position. If moved left it is clutched to member 26, while if moved right to mesh with gear 36 it provides emergency-low speed (with clutch 16 engaged) and if moved further right it meshes with a gear 37 driven from gear 36 to give reverse drive (with clutch 16 engaged). Engagement of dog clutch 33 is effected by energization of a spring-loaded solenoid 70, Fig. 5, the movement of which also controls a change-over switch GS1. The electric circuit, Fig. 5, includes various relays A, B... which operate switches A1, B1..., battery 86, engine-driven dynamo 77, voltage regulator 79, ignition switch 87, governor switch 95 responsive both to vehicle speed and throttle position, switch TS1 which opens on opening of throttle, switch N which is closed only in neutral, and switch RN which is opened only in reverse emergency-low or neutral. With the vehicle at rest with engine idling (switch 87 closed) and yoke 35 positioned for normal forward drive (switch RN closed), relays X, Y, A, G are energized, thus switch A1 is open, isolating the clutch windings 8, 9. On opening the throttle, TS1 opens, A de-energizes, A1 is closed and winding 9 is energized from dynamo 77 to engage clutch 16 and give free-wheel low-speed drive, while winding 8 is energized through resistance 90 sufficiently to counteract leakage flux from 9 so that clutch 13 is inoperative. When vehicle speed and throttle position are such as to require change to intermediate speed, contacts 94, 96 of switch 95 separate, X, G de-energize and C energizes. Thus, A1 is now connected to battery 86, either direct via switch 89 which opens at predetermined engine suction, or through resistance 88. Solenoid 70 energizes via C1 tending to engage 33, and B energizes. Thus, winding 8 energizes to fully engage clutch 13 and winding 8 is de-energized, though clutch 16 remains partially engaged due to leakage from 8. The dog-clutch parts quickly reach synchronism, whereupon 33 engages, GS1 changes over, de-energizing D, B. Thus, 9 is now energized to fully engage 16, giving intermediate speed, while 8 is partially engaged via resistance 90 to counteract leakage from 9 so that clutch 13 is inoperative. When speed and throttle are such as to require change to top speed, contacts 94, 97 of switch 95 engage, de-energizing Y. Thus B energizes, 8 energizes to engage clutch 13, giving direct drive, while 9 is partially energized via resistance 93 to counteract leakage from 8. During change down from intermediate to low speed, i.e. when 94 again contacts 96, X energizes, C and 70 de-energizes, A energizes and A1 opens, so that 13, 16 are both disengaged to allow easy disengagement of 33. Closure of either a manual switch LO or a switch KD operated by kick-down of accelerator, provided a switch 100, which opens only at high vehicle speed, is closed, causes relay E to be energized, de-energizing B and energizing C so that intermedi- . ate-speed is engaged and remains engaged so long as E is energized. A switch TS2 opens at small throttle openings to reduce excitation of winding 8.