GB1305845A - - Google Patents

Abstract

1305845 Hydraulic transmission control VERLINDE SA 17 June 1971 28422/71 Heading F2D [Also in Division G3] A control circuit for controlling the displacement of a variable stroke pump 2, and for controlling the direction of rotation of a motor 26, comprises a main two-way distributer 6, having a spool valve movable in response to fluid supplied to one of two chambers 6d and 6e, an auxiliary pump 3 connected to said chambers through an auxiliary two way distributer 22, its spool valve movable by a rod 21 attached to a lever 9 and a further control distributer 20 connecting the output of the auxiliary pump 3 to either side of a piston 11a, connected to a rod 11b for varying the displacement of the pump 2. With the control lever 9 in a neutral position the main pump 2 is at its minimum displacement position, and the auxiliary distributer 22 connects the output of pump 3 through a throttle valve 33a to a reservoir 10. A brake 8 on the motor is automatically actuated by the resultant low pressure in the line leading thereto, shown as broken lines. On movement of lever 9 in one direction the spool valve 7 in the control distributer 20 is moved and causes the output from pump 3 to move piston 1la and so increase the pump displacement. Simultaneously the spool valve of auxiliary distributer 22 is moved and causes pressure to be applied to either of chambers 6e and 6d through lines 35 or 34 respectively and so the output from pump 2 (not now zero) is applied to the motor 26. The brake 8 on the motor is automatically released when the pressure in the line leading to it increases (i.e. when distributer 22 starts feeding lines 34 or 35). Valves 31 and 23 limit the pressures in the main and hydraulic circuits respectively. In the movement of piston 11a by the result of movement of the spool valve 7 the distance which the piston moves (and hence the amount the pump is varied) is dependent on the degree of movement of the lever 9 since the piston and valve are interconnected by a lever 17 which causes the valve to close on movement of the piston dependent on the position of the lever 9. A unit 27 may be included to aid the returning of the distributer 6 to its neutral position upon the lever 9 being returned to its neutral position. The lever 9 may be operated manually or automatically. The auxiliary pump 3 acts additionally as a make-up pump.