Patent GB-1331397-A (GB)
Title: Fluid pressure actuator
IPC: F16F9/44
Filed: 1972-02-07
Abstract: 1331397 Adjustable seats CORTE & COSSO S A S 7 Feb 1972 [10 Feb 1971] 5577/72 Heading A4J [Also in Divisions E2 F2] A fluid pressure actuator comprises a cylinder 1 in which a piston 9 slides, a hollow spindle 8 attached to the piston and projecting through one end of the cylinder fluid tightly, the piston defining two opposite chambers A, B for fluid under pressure, a control rod 20 within the hollow spindle and operable from the outside, the rod 20 acting on an axially movable plunger 21 within the spindle 8, and having a head 23 which supports an annular sealing ring 25 in an annular groove in the plunger 21, the sealing ring with an adjacent end of the spindle 8 forms a transfer valve control communication between the opposite chambers of the cylinder through the interior of the spindle, the head 23 and the sealing ring 25 being surrounded by an axially displacable cup 27 which defines with the end of the spindle an annular orifice 29 of adjustable cross-section through which fluid passes between the two chambers A, B, through the transfer valve and the interior of the spindle and a screw 28 for adjusting the axial position of the cup 27 to adjust the cross-section of the orifice 29 and thus the velocity of displacement of the piston when the transfer valve is opened by manual operation of the control rod, the transfer valve formed by the enlarged head of the plunger and the sealing ring being biased automatically towards the closed position by the pressure acting in one of the chambers of the cylinder. The sealing ring 25 prevents flow of fluid through the orifice 29 and holds the piston in any predetermined position. To vary this position, the control rod 20 is depressed to release the ring from the end of the spindle, the orifice then communicates with the interior of the spindle 8 and fluid flows between chamber A and B, to equalise the pressure but owing to differences in effective areas of opposite sides of the piston the piston moves until the orifice is again closed by raising the rod 20 at the predetermined position of the piston. The orifice is maintained closed by the spring 26 and fluid pressure on the head. The piston 9 has a recess 11 in which fits a hollow  nub 12 screwed on to a threaded end part 13 of the spindle 8 to secure the piston to the spindle and pushing the piston against a collar 14 secured to the spindle by a resilient ring 16 engaging in a groove in the spindle. Between the collar and the piston is a sealing ring 17. The spindle has apertures 19 adjacent the collar whereby the bore of the spindle communicates with the chamber A. The plunger 21 has two grooves for sealing rings 22 and the head is biased towards the end of the spindle by the spring 26 abutting the head and a bottom wall of the cup 27. The cup is mounted on the head of the screw 28 which screws into the bottom well of the nut whereby rotating the spindle moves the nut axially and adjusts the orifice 29 to control the rate of fluid flow through an annular space 30, a radial orifice 31 in the nut 12 a recess 11 in the piston communicating with the chamber B. The nut is adjusted by depressing the piston so that it is adjacent cylinder wall 1a and so that a portion of the screw 28 fits non-rotatably in an end of a tube 2 in the cylinder. The spindle 8 is then rotated and raises or lowers the nut 12 and with it the piston or the screw to vary the size of the annular orifice 29.