GB654270A - Improvements in installations for feeding hydraulic servo-motors - Google Patents

Abstract

654,270. Hydraulic brakes. SERVO-FREIN DEWANDRE SOC. ANON. Jan. 9, 1948, No. 763. Convention date, Oct. 20, 1947. [Class 103 (i)] [Also in Group XXIX] In a hydraulic braking system comprising a normally continuously-running pump 1, a liquid tank 2, a pipe circuit 3, 5, 7 that feeds a servomotor steering-device 4, such as that described in Specification 654,269, [Group XXIX], and a pipe 8 that is led off the pipe 3 by way of a non-return valve 13 to feed a servomotor braking device 12 such as that described in Specification 640,542, a shut-off valve 6 is interposed in the pipe 5 which is arranged to be operated by the brake pedal 21 in conjunction with a piston 15 in a cylinder 10 connected to the pipe 8 at a point intermediate the valve 13 and the servomotor brake device 12. Passage 19 in the shut-off valve 6 is normally open to allow the pump 1 to circulate liquid without resistance through circuit 3, 5, 7 and back to the tank 2. Depression of pedal 21 to operate the brakes by actuation through rod 26 of a distributer valve in the servomotor device 12 simultaneously through rod 24 and spring connection 22 shuts off the valve 6 so that pressure is built up on the pump side thereof, which is transmitted through valve 13 and pipe 8 to the device 12. When, however, a certain pressure has been attained in pipe 8, the piston 15 in cylinder 10 is moved to the left against spring 17 to re-open the passage 19. So long as the pedal 21 is kept depressed the spring 22 will ensure that if the pressure to the right of piston 15 falls below a certain value, the valve 6 will again be shut, and the pressure above the non-return valve 13 will be restored to a value that is required to operate the device 12. In the system shown in Fig. 2, the shut-off valve 32, 33, 34 is not controlled in any way by the brake pedal 21 and the passage 33 is normally kept open by the pressure of liquid acting under the piston 30 in the cylinder 28 which forms a hydraulic accumulator. In the event of the pressure dropping, the piston is pressed down by the spring 31, thus closing the passage 33 so that liquid is pumped through the non-return valve 13 until the piston 30 has been raised again to re-open the circuit. The steering servomotor device 4 may be omitted from the system.