Patent GB-867706-A (GB)
Title: Hydraulic locking devices for controlling the spacing between two members
IPC: B64D11/06
Filed: 1959-07-23
Abstract: 867,706. Adjustable links. PORTER, P. L. July 23, 1959, No. 25374/59. Class 80 (3). [Also in Group XXV] An hydraulic locking stay, intended for controlling the tiltable back-rest of a seat and comprising a cylinder 10 divided into two chambers 18, 20 by a piston 16 having a tubular piston rod 15 containing a spring-loaded gland 28 forming a reservoir 32 in the rod for replenishing fluid in the chambers and a locking valve 24 which permits flow between the chambers during adjustment of the position of the piston and when closed prevents flow to lock the piston, is characterized by a check valve 25 which can be opened only when the locking valve is open and when closed prevents flow between the reservoir and the chambers. The piston and cylinder are urged apart telescopically by a counterbalancing spring 22. The check valve member 25 is mounted in a valve body 122 which is screwed into the piston 16 and also forms a seat for the locking valve member 24, and has an enlarged portion 25a fitting with restricted clearance in the body 122 to allow flow between the reservoir 32 and the chambers 18, 20 when the valve member is raised from its seating 26, in the form of a resilient 0-ring. The check valve member also comprises an intermediate portion 25b, which controls the rate of flow between the chambers 18 and 20 through radial ports 74, 75 in the piston rod when the valve 24 is open, and a cylindrical extension which reaches to the valve member 24 to actuate the latter. An operating rod 34 extends from outside the device through the gland 28 and fits into a socket 35 in the check valve member 25, and a diametrical pin 38 fixed in the rod cooperates with a cam surface 36 fixed in the hollow piston rod so that rotation of the operating rod causes it to shift axially and move the check valve member 25 and locking valve member 24 axially to unseat the latter. The check valve is opened only after a substantial movement of the valve member 25, initial movement thereof merely reducing the pressure of the member against the resilient 0-ring seat 26. Relative rotation of the piston rod 15 and the cylinder 10 is prevented by a diametrical pin 44 carried by the piston rod in sliding engagement with a pair of slots 40 (Fig. 1) in an extension 42 of the cylinder. The amount by which the stay may be contracted is determined by a stop sleeve 45 which is rotatably mounted on the cylinder extension and has a pair of diametrically opposite stepped slots 46 providing corresponding pairs of shoulders 48, 50, 52 for engagement by the pin 44. A detent 54 releasably holds the sleeve in any of its operative positions. In'a modification (Fig. 7, not shown). the reservoir 32 is supplemented by an annular communicating chamber surrounding a portion of the hollow piston rod exterior of the cylinder 10 and closed at one end by a slidable spring- loaded annular piston. The operating rod 34 may be removed, during assembly of the stay, and replaced by a filling nozzle which, when inserted, opens the check and locking valves to allow the chambers 18 and 20 to be filled with hydraulic fluid under pressure, the valves closing as the nozzle is withdrawn and the check valve preventing the fluid from flowing out of the chambers.