Patent GB-486301-A (GB)
Title: Improvements in or relating to control devices for variable ratio transmissions
IPC: F16H61/00
Filed: 1936-11-30
Abstract: 486,301. Controlling variable speed gearing; fluid-pressure servomotor-control systems. ROBIN, L., and ROGGEN, M. VAN. Nov. 30, 1936, No. 32778. Convention date, Nov. 29, 1935. [Class 80 (ii)] [Also in Group XXIX] A conjoint speed- and accelerator-pedalresponsive control for a vehicle change-speed gear, preferably of the continuously-variable type, comprises a hydraulic governor 48, developing a pressure responsive to enginespeed in a conduit 11, provided with a leakagevalve 26, the degree of opening of which is varied by the engine accelerator-pedal 2, acting on the valve through a lever-system, which can be adjusted by a manual button 35 to vary the transmission ratio with which the accelerator-pedal acts on the valve. The control may also be responsive to the vehicle service- or hand-brake, operating additional leakage-valves 50 or 51, and to the resisting torque. An additional leakage-valve 53, controlled by a button 54, provides manual means for compensating for oil-temperature variation, or thermostatic valves may be provided for this purpose. In operation the engine works at maximum power, speed changes of the vehicle being produced in the gearing rather than in the engine, the accelerator-pedal being provided with a supplementary gear-controlling stroke beyond its full-throttle position. Reverse and a zero-ratio position may be included in the range of the gear, which may form its own main-clutch, or a separate servo-operated mainclutch may be provided. The hydraulic governor comprises a gear-pump 8, which may be the lubricating-pump of the engine, pressure from which acts on a piston 5, which is connected to the change-speed lever 1 either directly, or through a follow-up hydraulic servomotor 21. The latter acts through a floating lever. 22, connected at its mid-point to the change-speed lever 1 and servomotor 21, and at its ends, respectively to the piston 5 and slide-valve 23 controlling the servomotor 21. Pressure for the servomotor 21 is derived from a hydraulic accumulator 14, supplied from a separate gearwheel pump 10, through a cut-off valve 13, operated by the accumulator. A pressure-relief valve 12 is provided. In the form shown in the Figure, the gear provides only forward speedratios, the pistons 5 and 21 being single-acting and loaded by springs 7, 25 respectively, in the leftward direction towards lower ratios and the initial zero position shown. Thus, operation of any of the leakage-valves 26, 50, 51, 53 as by the accelerator-pedal, brakes or manual control tends to restore the change-speed lever 1 to lower speed positions or to its initial position, whilst speed increase at the pump 8 moves the lever to the right to high-speed positions. The leakage-valve 51 may be arranged to limit the range of automatic movement of the piston 5 and so of the change-speed lever 1, by being connected to its control member 49 (e.g. leading to the vehicle brakes) through a floating lever, centrally pivoted to the piston-rod of the servomotor 21. Thus when the stroke of the piston 5 exceeds that determined by the setting of the control 49, the leakage-valve 51 opens and opposes further rightward movement of the piston 5. In a modification, Fig. 2 (not shown), both pistons 5 and 21 are double acting, the change-speed lever 1 being movable to the left of the initial zero position for reverse. In this case the leakage-valve 51 acts to cut off the pressure supply to either operative face of the control piston 5, when the pre-set range is exceeded. In both forms the variable leversystem between the accelerator-pedal 2 and the leakage-valve 26 includes a rod 31, one end of which is connected to a floating lever 43, centrally pivoted to a rod 27, operating the valve 26, whilst its other end is movable by the button 35 along a curved slot 33 in a lever 29, mounted on a fixed pivot 30, and actuated through a spring 37 by a lever 28, also pivoted at 30, and directly linked to the acceleratorpedal 2. The position of the end of the rod 31 along the slot 33 determines the extent of movement the valve 26 receives from the pedal 2. The lower end of the lever 29 operates the engine-throttle 3 through a rod 47, and the arrangement is such that the valve 26 and throttle 3 are operated together until the throttle is nearly or fully opened, whereafter the lever 29 is arrested by a fixed stop 39, and continued downward movement of the accelerator-pedal has no further effect on the throttle, but causes the spring 37 to yield and permit the upper end of the lever 28 to act on the leakagevalve 26 through a rod 41, pivoted to the upper end of the floating lever 43. This supplementary range of the accelerator-pedal thus controls the change-speed gear, and an additional throttle opening may be provided towards the end of such movement, by a projection 45 on the lever 28. In a modification, Fig. 4 (not shown), the floating lever 43 is omitted and the rod 41 operates the leakage-valve 50 or 51. In order to prevent stalling of the engine on starting and undesired racing of the engine when running, the conduit leading to the leakage-valves may include a centrifugallyoperated safety-valve, Fig. 2 (not shown), which itself allows leakage at idling speeds thereby lowering the ratio for starting ; cuts-off the leak normal speeds ; and completely closes the conduit to the leakage valves 50, 26 at excessive speed, thereby causing rapid movement of the piston to the high-speed position and preventing racing. In Fig. 2 (not shown), the leakage-valve 53 is omitted, the manual button 54 acting on the leakage-valve 26 through a floating lever, connected at its opposite ends to the button 54 and rod 27, Fig. 1, and at its mid-point to the valve 26. The Specification as open to inspection under Sect. 91 states that the governor may be pneumatic or centrifugal. This statement does not appear in the Specification as accepted.