Patent GB-860833-A (GB)
Title: Pneumatic control apparatus for change speed gears of motor vehicles
IPC: F16H61/02
Filed: 1958-07-31
Abstract: 860,833. Change-speed control. LANCIA & C. FABBRICA AUTOMOBILI-TORINO S.p.A. July 31, 1958 [Aug. 3, 1957; Oct. 22, 1957], No. 24749/58. Class 80 (2). A pneumatic change-speed control system for use in a motor car comprises a handoperated preselector lever acting through a cam to condition valves which, on disengagement of the car main clutch, admit compressed-air to servomotors establishing a desired ratio. As shown, a preselector lever 31 slides a cam bar 30 to condition valves 24 ... 27 so that when a main clutch pedal 32 is depressed, compressed - air from a source 33 is admitted through a valve 42 to a pipe 34 and a main clutch disengaging servomotor 35 which, when it has reached its clutch-disengaged position, opens a valve 35 f to pass compressed-air through a check valve 68, a pipe 37 and the preselected open valve(s) 24 . . . 27 to servomotors 22, 23, thereby rendered operative for establishment of a desired forward ratio in the change-speed gear. The servomotors 22, 23 each comprise a central piston 22e fast with a striker fork 4, 5 and supporting slidably on plungers 22c, pistons 22f, 22g in cylinders 22a, 22b. The arrangement is such that when compressed-air is admitted to both the cylinders 22a, 22b of each servomotor, the piston 22e is moved to its central, neutral, position, but.when compressedair is admitted to one only of the cylinders the piston 22e is pushed into the other. The pistons 22e are normally held looked in ratio established or neutral position by detent pins 62b biased by springs 67 to engage holes 22p therein. Depression of the main clutch pedal 32 admitting compressed-air to the pipe 34, as described, also admits air through a pipe 66, 64, 65 to cylinders 62, 63 containing piston 62a connected to the detents 62b thereby moved against the bias of their springs 67 to a disengaged position, so that the servomotor pistons 22e are free to slide. The preselector valves 24 ... 27 include vent holes 24d through which compressed-air is exhausted when the associated servomotor cylinder is not operative. Reverse in the change-speed gear is established directly by opening a valve 29 on movement of the preselector lever 31, to admit compressed-air from the source 33 to a pipe 43 leading to a servomotor 28. The check valve 68 prevents the immediate exhausting of compressed-air from the servomotors 22, 23 when the main clutch is re-engaged following establishment of a ratio, in order that full engagement of the ratio establishing positive clutches in the change-speed gear may be obtained while the main clutch slips during take-up of drive. The change-speed gear shown comprises a constantmesh gear having a driving shaft 6, a countershaft 8 and a driven shaft 7, with axially slidable double positive clutch sleeves 2, 3 actuated by the striker forks 4, 5. Reverse is established when an idle gear 20 is slidden by the servomotor 28 to engage a gear 21. In a modification, Fig. 2 (not shown), the preselector valves 24 . . . 27 do not supply compressed-air directly to the servomotors 22, 23, but are instead connected to pneumatic relays which are themselves opened on depression of the main clutch pedal to establish a desired ratio. As modifications, the main clutch may be controlled by direct mechanical actuation of the pedal 32, the clutch disengaging servomotor 35 then being omitted, and the cam 30, shown as a linearly moving bar, may be a rotary cam.