GB795874A - A new or improved control for hydraulic servo mechanism - Google Patents

Abstract

795,874. Hydraulic control for vehicle clutches or brakes. GIRLING, Ltd. Aug. 13, 1956 [May 11, 1955], No. 13610/55. Class 69 (2). [Also in Groups XXIV and XXXIV] In an hydraulic system in which a pump supplies liquid to one or more slave cylinders, which may operate a vehicle clutch or brake, the supply of liquid is controlled manually through a spring and a valve, the valve being sealed against leakage by a diaphragm. In one form, liquid from a pump 24 passes via a pipe 23, the manually operated valve 12, a chamber 16, a pipe 30, and another pipe 32, to a tank 33. The valve is in the form of a sleeve having a recess 21 and a shoulder 18 which engages an abutment 19. When a pedal 44 is depressed, a spring 27 is loaded and gradually closes the gap between the faces 18, 19 and the pressure in the pipe 23 increases until it is sufficient to open a spring- loaded valve 35, thereby connecting the pump delivery to a pipe 39 leading to a slave cylinder. The depression of the pedal causes a plunger 25 to force liquid which is inside the valve 12 through a port 42, passages 41, 32, and a chamber 31, to the tank. If the pump fails and the pedal is depressed, the valve 35 remains in the position shown in Fig. 1 and the liquid inside the valve 12 is forced through the port 42, passages 41, 39, and an annular groove 38, and operates the slave cylinder. A diaphragm 17 seals the piston and a second diaphragm 14 may be provided and is subjected to the pressure of the liquid in the pipe 30 via a pipe 30<SP>1</SP>. The second diaphragm balances the force on the diaphragm 17. In another embodiment, the diaphragm 14 is replaced by a spring located on the outside of the diaphragm 17. In a further embodiment (Fig. 10), for operating a clutch, the valve is in the form of a plunger 98 operating in a bore 90. The pump delivers to an inlet 93 and liquid returns to the tank from an outlet 94. The slave cylinder is connected between the pump and the port 93. A spring 107 balances the pressure on the diaphragm 96. An axial bore 109 and radial ports 110 connect a chamber 95 with the outlet 94. When the pedal is released, liquid passes through the inlet 93, the chamber 95, ports 110, and the bore 109 to the outlet 94. When the pedal is depressed, a head 100 on the valve engages the end of the bore 90 and the pressure in the pipe between the pump and the valve increases and operates the slave cylinder connected to the clutch.