Patent GB-620425-A (GB)
Title: Improvements in or relating to power operated hydraulic actuators
IPC: F15B17/00
Filed: 1946-10-11
Abstract: 620,425. Fluid-pressure brakes. BENDIX AVIATION CORPORATION. Oct. 11, 1946, No. 30442. Convention date, Dec. 22, 1945. [Class 103 (i)] In pneumatically-operated hydraulic master cylinder units, particularly for operating brakes, an end plate of the pneumatic cylinder has an internally-threaded boss into which screws the hydraulic master cylinder. The system shown is such as described in Specification 550,450 in which the control valve of the pneumatic cylinder is operated by a manually-operated master cylinder 16. According to Fig. 1, the pneumatic cylinder of the unit comprises cylindrical members 94, 100 to which is secured by bolts 96 end plates 98, 102. The end plate 98 has a boss 104 threaded at 106 into which screws the master cylinder 14 formed of a length of conventional tubing and secured by a lock-nut 128. The pipe-lines 24 which lead to the brakes 18 are connected to the cylinder- 14 by a fitting 136 provided with a bleeder valve 140. The pneumatic cylinder is divided by a partition 70 into chambers for tandem pistons 56, 58 connected by a tubular rod 68. The pistons are connected by a pin 112, rod 30 and a pin at 114 to the master piston 32. Normally, as described in Specification 620,407, a ball-valve 82 is normally unseated by a forked member 88 which then abuts on a washer 110 to provide communication of' the master cylinder and pipe-lines through the piston and a port 86 with a reservoir 80. When the piston 32 is operated, the valve 82 seats. to close this communication. The manual master cylinder 16 is connected by passage 22 to a space between two pistons, one of which, 28, acts directly through the rod 30 on the master piston 32 and the other of which 36 operates the control valves 40, 74 of the pneumatic cylinder 12. The piston chambers 60, 62 of cylinder 12 are constantly connected to a vacuum source by pipe 64 and the piston chambers 52, 54 are connected together through the piston-rod 68 and by pipe 50 to the valve chamber 44, thence normally through the aperture in diaphragm 38 to chamber 46 and the pipe 48 to the. vacuum source. Pressure applied by the manual master cylinder 16 to the piston 36 causes the diaphragm to seat on the valve 40 to cut off the vacuum source from piston chambers 52, 54 and by opening the valve 74 to admit air from the atmosphere to valve chamber 44 and thus to these piston chambers, thus operating the pistons 56, 58, 32 to apply the brakes. A fast application valve, as described in Specification 620,408, comprises a diaphragm 63 mounted in the partition 70 and having the left-hand chamber connected by passage 67 to piston chamber 54 and the right-hand chamber by passages 63, 65 to valve chamber 44. If in an application the pressure in the right-hand chamber rises more rapidly than that in the left-hand chamber, the diaphragm lifts a valve 61 to admit air directly to chamber 54. In a modification, there is only one pneumatic piston, the valve is mounted upon the end plate to which the master cylinder 14 is secured and the manual master cylinder 16 is connected directly to the master cylinder 14 immediately behind the piston 32 so that no reservoir such as that shown at 80 is necessary.