Patent GB-560194-A (GB)
Title: Improvements relating to hydraulic damping devices
IPC: B64D5/00
Filed: 1942-06-05
Abstract: 560,194. Hydraulic shock-absorbers. TECALEMIT, Ltd., and LE CLAIR, C. C. S. June 5,1942, No. 7714. [Class 108 (iii)] An hydraulic damping device of the piston- and-cylinder type comprises a hollow header 2 or 5 at each end of the cylinder 1 having a valve-controlled passage communicating with the interior of the cylinder, the passages in the two headers being connected by a transfer conduit 59, while the piston-rod 18 projects through one end of the cylinder for connection to an anchorage or to the member whose movments are to be damped, resilient means being provided for compensating for the differential action of the piston 50, and /or for the effect of temperature changes in the liquid, by maintaining the liquid under pressure. As shown, each of the upper and lower headers 2, 5 contains similar damping-valve arrangements consisting of a valve-seat 37a or 37 having holes 38a or 38, a flat valve 40a or 40 pressed by an adjustable spring 41a or 41 on to the seating 39a or 39 to close a passage leading into the upper or lower end of the cylinder, and a further flat valve 47a or 47 pressed by a light spring 49a or 49 to close the holes 38a or 38. The springs 41a, 41 are such that when the valves 40a, 40 are seated, little or no load is applied by the springs, whereas when the valves are fully lifted, maximum resistance is offered to the flow of liquid. The operating piston 50 of cup-form, slidable in the cylinder 1, is fitted at the bottom end of a tube 18 constituting the piston-rod, which is slidable in a cup 4 fixed in the upper header 2. The device is particularly applicable for damping the movements of a member oscillatably mounted on an aircraft fuselage and to which one end of a tow rope is secured, a forked member 26 fixed to the upper end of the tube 18 being pivotally connected to a fixed part of the aircraft and a forked member 30, fixed to the lower header 5, being pivotally attached to the oscillatable member. In operation, on extension of the device, the piston 50 forces liquid from the cylinder 1, past the valve 40a, through the conduit 59 and back into the other part of the cylinder 1 through the holes 38 in the valve-seat 37 and past the valve 47. Owing to the difference in area of the annular spaces above and below the piston 50, the volume of liquid displaced above the piston is less than that entering the cylinder below the piston. This deficiency is compensated for by a spring-pressed accumulator piston 9 which displaces the necessary quantity of liquid from an inner tube 6 into a passage 35 in the bottom header 5 and then through the holes 38 in the valve-seat 37 to that part of the cylinder 1 below the piston 50. On compression of the device, the valve 40 restricts the flow of liquid and the excess liquid displaced below the piston 50 passes to the tube 6 through the passage 35 forcing the accumulator piston 9 towards the header 2. The piston 9, which places the liquid under pressure and also compensates for temperature changes therein, is acted on by a number of springs 13 separated by cup-shaped members 14, 14a, 17, 17a, slidable in the tube 6. The liquid volumecompensator may be external to the main cylinder. As the device is usually filled with liquid under high pressure supplied through the nipple 34, a spring-loaded, liquid-relief valve 63 is fitted to the valve-box 58. The damping valves 40a, 40 may be replaced by resilient discs each anchored at its centre and free at the edge.