Patent GB-445262-A (GB)
Title: Improvements in or relating to preselective change-speed gearing
IPC: F16H3/091
Filed: 1934-07-05
Abstract: 445,262. Variable - speed gearing. ROBOT GEARING, Ltd., 39, New Broad Street, London, RAILTON, R. A., Brooklands Track, Byfleet, Surrey, and SAMPIETRO, A. C., Rapallo, Genoa, Italy. July 5, 1934, No. 19824. [Class 80 (ii)] Preselective change-speed gearing comprises a pair of nested friction-clutches 26, 27, geared to a countershaft 32 through gear-pairs 30, 31 and 33, 34, and a double synchromeshed positive-clutch 39, splined to the driven shaft 37, for clutching thereto the wheel 33, or the driven wheel 36<1> of a third pair 35, 36. The positive clutch is always closed before the friction clutch. The end-wheel 35 is loose on the countershaft but is clutched thereto in all four forward speeds, by a splined wheel 43, which, for reverse, is slid forwardly, taking along with it, by its double helical teeth, a compound idler on a separate countershaft and having spur teeth, which mesh with an end-wheel 50. Both the friction and positive shifter-elements 22, 86 are controlled by connecting them to preselected members of pairs of elements which are moved towards and away from each other at each depression and release of an executive pedal secured to a rockshaft 54, Fig. 6. The double frictionclutch 26, 27 is operated through radial levers 15, urged in either direction of engagement from a dead-centre neutral position, by three telescopic spring - extended links 18, connecting the inner ends of the levers, which latter are controlled by rocking the shifter-member 22. The executive rockshaft 54, Figs. 6 and 9, carries an arm 57, which has segmental toothed engagement with a pivoted arm 59, whereby depression of the executive pedal causes the arms 57, 59 to rock towards each other, whereupon lateral projections 60, 61 thereon, bring the shifter-member 22 to the neutral position. Pivoted with vertical play on the shifter-member 22, is a spring- loaded pawl 67, which, under control of a preselector cam shaft 70, Fig. 3, can be urged into engagement with single ratchet-teeth 65, 63, Fig. 9, on either of the arms 57, 59, to determine which arm shall pick-up the shifter-member when the arms move apart on release of the control pedal. The controlmember 86 of the synchromesh clutch 39 is secured to a rail 85, Fig. 3, on which slide members 87, 88, which are moved towards and away from each other by turning a cam disc 83 having cam-slots 84, engaging pins 87<1> projecting from the members 87, 88, the cam disc being turned backwards and forwards by a link-connection with the rockshaft 54, Fig. 6, of the executive pedal. The closing movement of the members 87, 88 neutralizes the shifter-member 86 and the direction of movement of the latter when the members 87, 88 open, is determined by a cam 95, on the preselector cam-shaft 70, and engaging through a spring plunger 93, a rocker 91, pivotally carried by the shiftermember 86. The rocker 91 is pressed against the cam 95 by a light spring 94, and has hooked ends which are selectively engaged with the members 87 or 88 by the cam 95. The reverse shifter-member 100 is operated by a lever 102, pivoted thereto and having a slot engaged by the pin 87<1> of the member 87. During changes for all forward speeds, the lever 102 swings idly as the member 87 moves to-andfro, but in reverse, a stop 107 on the preselector cam-shaft 70 obstructs forward movement of the free upper end 105 of the lever 102 and engages reverse. The preselector camshaft 70 is turned by a small handle, through bevel-gearing 73 and a toothed segment 72, loose on the rail 85. The cam-slots 84 in the disc 83, have an initial idle concentric part so that the synchromesh clutch 39 opens after and closes before the friction clutch 26, 27.