GB481007A - Pressure varying device for hydraulically controlled change speed gear clutches - Google Patents

Abstract

481,007. Controlling change - speed gearing. KEGRESSE, A. June 2, 1937, No. 15351. Convention date, June 10, 1936. [Class 80 (ii)] A pressure-varying device for hydraulic change-speed clutches in an automatic changespeed gear is mounted in the pipe line, connecting the pump to the change-speed gear, and comprises a fixed cylinder with ported walls for the passage of the fluid and enclosed in a chamber, a ported sleeve adapted to rotate on said cylinder and operated manually from the driving position and a cylindrical valve sliding in the interior of said cylinder and moved by the pressure of the fluid against the action of a spring. A control handle mounted on the steering column moves over a graduated sector plate and is connected to an arm 8, Fig. 3, on a ported sleeve 10 rotatable over a cylinder 14 fixed in a casing 9. The sleeve 10 has ports 30 adapted to register with ports 31 in cylinder 14, and also has a large port 32, Figs. 3, 5, adapted to uncover ports 33, 34, Figs. 3, 6, in the cylinder 14. Between the sleeve 10 and casing 9 is an annular chamber 12 with an outlet 13. Within the cylinder 14 is slidable a piston 15 loaded by a calibrated spring 19, and having holes 17. and an external groove 16, a stop for the piston being provided at 18. A valve 20 in the end of the casing 9 is held on its seat by a spring 21 and an outlet 23 is provided in connection with this valve. Liquid under pressure enters at 24 and is conveyed through 25 to the gear-change mechanism. The sleeve 10 is adapted to be held in different positions for neutral, first, second, &c. speeds by a spring plunger 26. When the control lever is at neutral, the ports 30, 31 register and liquid passes from 24 to 13, no pressure being produced in conduit 25. If the lever is moved to " first " position the ports 31 are no longer uncovered and the fluid pressure increases and forces back the piston 15 to uncover the port 33 to produce the pressure in conduit 25 necessary to shift the gear to first speed. When the lever is moved to " second " the sleeve 14 is rotated so that the large opening 32 uncovers only a part of opening 33 but the whole of opening 34. The piston is now moved further to the right to close opening 33 and uncover opening 34 thus giving a higher pressure than for first speed so as to bring in second speed. For third speed when both the openings 33, 34 are partly covered by the edge of port 32, the pressure rises rapidly and ultimately opens the valve 20, the pressure then being at the maximum to give third speed. Whatever the position of the control lever, the working will be automatic through a certain range, but by further rotation of the control lever, beyond " third " the sleeve 10 is brought to a position intermediate that for third speed and that in which the openings 33, 34 are entirely closed, and the gear changing becomes fully automatic, in which the duration of the transmission on each of the speeds is adjustable by moving the lever. The control also gives a degree of pre-selectivity.