GB723845A - Improvements in or relating to liquid pressure servo-motor systems - Google Patents

Abstract

723,845. Fluid-pressure servomotors; hydraulic transmissions. AUTOMOTIVE PRODUCTS CO., Ltd. Oct. 20, 1953 [Nov. 11, 1952], No.28412/52. Classes 69 (2) and 136. In a liquid pressure servomotor system including a double-acting servomotor 10 and a control valve 16 therefor, the control valve, when in its neutral position, connects each end of the servomotor to one of a pair of passages 31, 32 leading from a source of liquid pressure such as the accumulator 38, a non-return valve 34 or 35 being provided in each of the passages to prevent flow of liquid from either end of the servomotor cylinder 11 through the passages and thus lock the servomotor in any position to which it is set. The control valve 16 has a pair of circumferential grooves 17, 18 separated by a land 19, and a pair of diametral passages 22, 23 permanently connected by an axial bore 21 closed at both ends. The grooves 17, 18 are always in communication with passages 28, 29 leading to opposite sides of the servo-piston 12, and in the neutral position shown, are also in communication with circumferential grooves 25, 26 leading to the passages 31, 32 respectively. On movement of the valve 16 to either side of the neutral position, the grooves 17, 18 are cut off from the respective grooves 25, 26 and connected to grooves 24, 27 respectively, the latter due to the passages 21, 22, 23 and a connection 37 being permanently connected to a low-pressure reservoir 41. The accumulator 38 is supplied by a pump 40, the delivery of which is passed back to the reservoir 41 by a cut-out valve 42 when the accumulator pressure reaches a predetermined upper limit, the valve 42 restoring the connection to the accumulator at a predetermined lower limit of pressure. A follow-up connection may be provided between the valve 16 and the servomotor. The effective areas at opposite sides of the piston are equal.