Patent GB-588947-A (GB)
Title: Improvements in or relating to control gear for the hydraulic drives of motor vehicles
IPC: B60W10/06
Filed: 1945-02-06
Abstract: 588,947. Motor vehicle driving arrangements. SCHLATTER, G. Feb. 6, 1945, No. 3043. Convention date, Jan. 11, 1944. [Classes 79 (ii) and 79 (v)] A control gear for the hydraulic drive and throttle of a motor vehicle comprises a body supporting radially arranged cylinders which is moved to and fro to vary the gear ratio, and a control piston which is subjected to the pressure of a pump driven from the engine and carries two curved guideways, the latter acting on levers which automatically co-ordinate the gear ratio of the hydraulic drive, the engine speed and the fuel supply in the following sequence, firstly the gear ratio is increased at full engine speed and full fuel supply, secondly the gear ratio is further increased and engine speed reduced at full fuel supply (these two steps corresponding to acceleration from a standstill and changing up gear), thirdly maintaining the gear ratio and the engine speed but decreasing the fuel supply (this step corresponds to running at speed with light load), fourthly changing down gear with increasing engine speed and nil fuel supply, fifthly further changing down gear with full engine speed and nil fuel supply (the fourth and fifth steps corresponding to braking with the engine). The transmission comprises a casing 1, Fig. 1, supporting by means of a pair of cylinders 4 and pistons 3 the body 2 of a hydraulic transmission gear (not shown) of the type in which lateral displacement, e.g., by the pistons.3 moving in the cylinders 4, varies the gear ratio. A pump 12, whose output is proportional to engine speed, delivers oil at low pressure via pipe 19 to the cylinder 20 and also to the pipe 36 which operates the throttle by a spring-pressed piston (not shown), and oil under high pressure via the pipe 22 to the reservoir 23 and also via pipe 24 to the rotary valve 55, 56, Figs. 5 and 7, which valve, according to its position, passes on high pressure oil to one of the pipes 61, 62 and puts the other into communication with the atmosphere, whereby cne or the other of the pistons 3, Fig. 1, is subjected to pressure to vary the gear ratio. The position of the rotary valve 55 is also governed by the relative height of the piston 21, Figs. 4 and 5, moving in cylinder 20, which carries a pair of guideways 28, 29 acting on rollers 39, 31 to move a pair of two armed levers 38, 30, the adjacent ends of which act on the rotary valve 55 by means of pin and slotted link mechanisms 53, 49 and 50, 51. The other arm of lever 30 operates a relief valve 33 in the pressure chamber for the piston 21, and the other arm of lever 38 is acted on by link 80; lever 79, Figs. 1, 4, 5, and rod 72 carrying a connection 72 to the manually operated speed control lever (not shown). The arrangement is such that operation of the manual speed control lever connected to the link 70, rod 72, clutch 78, 79, link 80, lever 38, links 40 and 51, moves the rotary valve 55 to alter the gear ratio, and engine speed as measured by oil pressure from pump 12 acting on the piston 21 is superimposed on the manual control of the rotary valve to give the sequence of operations set out above. The brake pedal is connected to the lever 81, Fig. 1, rod 83, which terminates in a slotted portion 85, Fig. 5, arranged so that on rotation thereof the link 86 depresses the plunger 92 and the valve 91 so admitting high pressure oil from pipe 24 and chamber 26 into pipe 93 which leads to the hydraulic brake system. The brake actuating rod 83 and speed control rod 72 are interconnected through torsion spring 95, lever 94, two armed lever 75, 74 pivoted on an extension of rod 72, torsion spring 76 and spring-pressed clutch members 78, 79 so that on application of the brakes, the links 79, 80, 38, 40 and 51 are moved to rotate the valve 55 to obtain neutral gear in the hydraulic gear transmission.