GB517190A - Improvements in or relating to servomotors - Google Patents

Abstract

517,190. Fluid-pressure servomotors. BOSCH GES., R. (formerly BOSCH AKT-GES., R.). July 22, 1938, No. 21762. Convention date, July 22, 1937. [Class 135] A fluid-pressure servomotor comprises a double-acting power piston 7, Fig. 1, working in a rotatable valve sleeve 5 in a fixed casing 1. The sleeve 5 has two bores 6, 6 communicating with pressure-fluid supply pipes 3, 3 and cooperating with oblique grooves 13, 13 on the surface of the piston 7 which is connected by a rod 8 to, for example, the control rod of a fuel injection pump. The grooves 13, 13 in the piston are connected by longitudinal grooves 14, 14 to the two ends of the piston respectively so that a rotary movement of the valve sleeve 5 by, for example, a governor actuating the arm 10, will supply more pressure fluid to one end of the piston and less to the other which results in a longitudinal "follow-up" movement of the piston to equalise the pressures at the two ends. Leakage bores 16 are provided in end covers 9 of the sleeve 5 to allow of, and at the same time to damp, the movement of the piston. In a modified arrangement the control sleeve 5 is omitted and parallel oblique control edges are provided at the ends of the piston member which co-operate with inlet and exhaust ports at each end in the fixed cylindrical casing, the piston member being rotated to control the supply of pressure fluid to one or other end of the piston and moving longitudinally to "follow-up." In another arrangement, Fig. 3, grooves 45a, 45b on the surface of the piston between the two working chambers are provided which are in communication with said chambers through passages 46, 47 and are controlled by longitudinal movement of a valve sleeve 33, actuated, for example, by a governor capsule B. The valve'controls the supply of pressure fluid from supply passages 43, 42, 44 to move the piston to "follow-up" the movement of the valve.