GB988222A - Improvements in or relating to fluid circuit control means - Google Patents

Abstract

988,222. Locks. H. J. HARRIS. July 7, 1961 [July 8, 1960], No. 23956/60. Heading E2A. [Also in Divisions F1 and F2] Control means for a fluid-actuated locking device comprises a one-way valve between an operating device and an actuator, the valve being arranged to retain fluid in the actuator; a valve for releasing fluid from the actuator; and a key-operated device for actuating the fluid release valve. As embodied in a system for immobilizing a vehicle having internal shoe brakes, 14 is a ram for expanding the brake shoes filled with fluid from a pedal-or hand-lever-operated master cylinder 22 through the pipe 21; by reason of the non-return valve 23, the ram remains locked "on" unless fluid can escape through the pipe 26, the valve means 11, and the pipe 28, to the reservoir 24. The valve means 11 comprises two spring- biased piston valves 34, 35 in a housing 31. In order to pass from pipe 26 to pipe 28 fluid must traverse the passages 36, 41, 42, 43, 51, 53; as shown the ball valves 37, 44 respectively prevent communication between the passages 36, 41 and 43, 51. In order to release the ram 14 a suitably worded key must be inserted in the barrel 57 of a locking device 55 and rotated to move the plungers 63, 64 a pre-determined amount to the left as shown in the Fig. 1; by means of fluid links through the pipes 65, 66 the piston valves 34, 35 are also moved into such positions that the land 68 on the valve 34 raises the ball 37 and the passages 36, 41 are placed in communication through the annular groove 46, while the land 69 on the valve 35 raises the ball 44 and the passages 43, 51 are placed in communication through the annular groove 49. If the piston valves are moved too far, as by use of the wrong key, the balls drop off the lands 68, 69 into grooves 47, 50. If the valve means 11 is housed within the brake drum, the brakes cannot be released by cutting any exposed pipe. The system may be part of or additional to the vehicle brake system which may be hydraulic, pneumatic or mechanical. As described, a two-worded key is used but the key may have any number of words in connection with a corresponding number of plungers and piston valves. The system may be used to maintain a safe door locked in which case the valve means is used to monitor the action of a dead bolt.