GB1012460A - Constant speed reciprocable hydro-pneumatic retarding device - Google Patents

Abstract

1,012,460. Hydro-pneumatic shock absorbers. J. KIRSCH. Feb. 7, 1963, No. 4990/63. Heading F2S. A unidirectionally constant speed hydropneumatic retarding device comprises a main cylinder 12 having reciprocably mounted therein a longitudinally bored piston 14 extending through the open end of the cylinder and containing a floatingly mounted free piston 16 which divides the bore into a lower pneumatic chamber 26 and a middle hydraulic chamber 24 separated from an upper hydraulic chamber 22 by the head 40 of the piston 14 which includes a cup-shaped sleeve valve member 94 responsive to the flow of fluid in one direction to control the area of ports 80 interconnecting upper and middle hydraulic chambers to thereby maintain the speed of the cylinder 12 constant in that direction. The pneumatic chamber 26 is filled with compressed air or nitrogen through a charging fitting 50 and the hydraulic chambers 22, 24 are filled through a port 25 in the end 23 of the cylinder closed by a threaded plug 27. In operation the cylinder 12 is secured to the movable part of, e.g., a press, and the piston 14 is secured to a stationary part thereof so that in the extended position an annular shoulder 43 on the piston is in close proximity to an annular shoulder 34 on the cylinder 12, and the floating piston 16 is forced by the compressed gas in the chamber 26 close to the casing 66 of the valve 94. When the cylinder 12 moves down on to the piston, hydraulic fluid is forced from the upper chamber 22 through ports 76, 80 in the casing 66 and ports 98, 104 in the valve 94 to the middle chamber 24 to thereby move the floating piston down and compress the gas in the lower chamber 26. A spring 90 maintains the ports 80, 98 aligned. When the cylinder 12 is released the floating piston is urged upwardly by the compressed gas in the chamber 26 and expels hydraulic fluid back into the upper chamber 22 through the port 104, the flow therethrough causing a pressure drop thereacross whereby the valve 94 moves to decrease the area of the ports 80 and thus reduce the flow of fluid to the upper chamber 22. In another construction the valve is reversed and therefore provides a regulated flow of fluid at a constant rate during the retracting stroke and free flow during the extending stroke.