GB616954A - Improvements relating to variable speed power transmission - Google Patents

Abstract

616,954. Controlling change-speed gear. FORD MOTOR CO., Ltd. Sept. 25, 1946, No. 28660. Convention date, Oct. 27, 1945. [Class 80 (ii)] In a three-speed gear mechanism in which first speed is obtained by a hydraulic coupling, and second and third speeds by hydraulic governor-controlled fluid clutches which cut out the hydraulic coupling and drive through a multiple planetary gearing, a reciprocating valve is provided, which, on excess travel opens the third speed clutch supply to exhaust and thus provides second speed for acceleration purposes. The change-speed gear of Specification 615,175 is modified by the provision of a piston valve 62 mounted for vertical movements in the gear casing 56. The valve 62 has a bore 64 open at the lower end and in communication with an annular groove 81 at the upper end, and is movable axially by a cam 69 on a shaft 71 rotated by the levers 73 or 74, coupled to the accelerator and a manual control respectively. Movement of the valve is opposed by a spring 63 which bears at its lower end on a perforated disc 65 secured in the gear casing. The end of the valve can also bear on a second spring 82 when approaching full travel. The pressure chamber 43 of the fluid pump communicates through a passage 76 with an annular groove 75 and thence to a passage 77 leading to the third speed clutch conduit as shown in Fig. 4, which represents the conditions within the normal travel of the accelerator. Increased travel results in the valve covering the passage 76, and the passage 77 being connected to exhaust through the groove 75 and passage 78, which disengages the third speed clutch. Still further travel of the accelerator causes the valve to overcome the additional resistance of the spring 82 and aligns the groove 81 with the passage 76, thus connecting the pressure chamber directly with exhaust, which, providing the pump speed is not sufficient to enable it to overcome the loss, will result in disengagement of both clutches. The valve thus provides a " kick-down " shift from third to second and from second to first speeds providing the road speed is lower than a predetermined maximum, a higher speed than which would prove detrimental to the engine.