Patent GB-620408-A (GB)
Title: Power device for hydraulic pressure systems, more particularly for operating brakes
IPC: F15B17/00
Filed: 1946-06-25
Abstract: 620,408. Fluid-pressure brake systems. BENDIX AVIATION CORPORATION. June 25, 1946, No. 18979. Convention date, Oct. 22, 1945. [Class 103 (i)] In a fluid-pressure-operated power unit such as described in Specification 580,468 and comprising a control valve for the power cylinder, controlled by a manually-operated hydraulic master cylinder, and including a second master cylinder operated by the power cylinder and connected to brakes or other device to be operated, the control valve and the second master cylinder are arranged at opposite ends of the unit and the fast application valve which is adapted to connect one of the piston chambers of the power cylinder to the atmosphere or other pressure source separately from the control valve is arranged within that piston chamber. As shown, a cylinder 12 divided by a fixed partition 14 contains tandem pistons 16, 18 connected by a tubular rod 20 and operating by a rod 26, the piston 28 of a hydraulic master cylinder 36 connected to brake cylinders 34. The master cylinder 36 is normally connected to a reservoir 42 by a passage 38 through the piston. The piston chambers 50, 54 are constantly connected to a vacuum source by a pipe 92 and ports 90, 94. The control valve comprises a diaphragm 82 carrying the seat 98 of a vacuum valve 64 connected by a rod to an application valve 62 adapted to connect the valve chamber 86 to atmosphere through chamber 104. Normally, the valve 62 is seated and diaphragm 82 is held away from valve 64 by spring 100 so that valve chambers 84, 86 are connected and as these chambers are respectively connected to the vacuum pipe 92 and to the piston chamber 48 by pipe 88 and piston chambers 48, 52 are connected by the rod 20, all these chambers are normally under vacuum. The diaphragm 82 is operated by the pedal-operated master cylinder 74 acting through pipe 72 and chamber 68 on a piston 66. The pressure in chamber 68 also acts on a piston 76, the rod 76<SP>1</SP> of which thus transmits the pressure in the master cylinder 74 directly to the pistons 16, 18 and thus to the brakes. When the master cylinder 74 is operated, the diaphragm 82 seats on the valve 64 and opens valve 62 to admit air to chamber 86, and thence to the piston chambers 48, 52, thus operating the pistons and master cylinder 36. The increase in volume of chamber 68 due to the piston 76 following-up the movement of pistons 16, 18 tends to return the diaphragm 82 to the lap position. Further, since the diaphragm 82 is subject to the same pressure differential as the pistons 16, 18, the pressure applied to the master cylinder 74 is proportional to that applied to the brakes so that the braking pressure is indicated to the operator. The fast application valve which may be as described in Specification 597,890, comprises chambers 114, 116 formed in the partition 14 and divided by a diaphragm 118 connected to a valve 110. Chambers 114, 116 are respeetively connected to valve chamber 86 by pipe 122 and to piston chamber 52 by passage 120. Thus, if in a brake application the pressure rise in chambers 52 and 116 lags behind that in chambers 116, 86 and 48, the valve 110 is unseated to admit air directly to chamber 52 by passage 108.