Patent GB-974388-A (GB)
Title: Shock absorber for pipe-line supports
IPC: F16L3/217
Filed: 1962-03-06
Abstract: 974,388. Spring suspensions. GRINNELL CORPORATION. March 6, 1962 [March 13, 1961], No. 8549/62. Heading F2S. A sway brace, e.g. for supporting a steam pipe 22 from a structure 16, includes an hydraulic shock-absorber unit 4 comprising a cylinder 7 and a piston 21, the two sides of which communicate with each other through conduits 8, 10 and a valve unit 30, the latter providing a main fluid passage with restrictions 88, 102 to control the resistance offered to normal slow rates of relative movements between the piston 21 and the cylinder 7 and a pressure-responsive valve 34 which is responsive to shocks above the normal rate to effect a further restriction of fluid transfer. Vertical bores 72, 74 in the valve unit 30, leading respectively through branch bores 68, 70, adjustable needle valves 86, 88 and 100, 102, and vertical bores 82, 95, connect the pipes 8, 10 to a central compartment 44 in a bore 32 for the valve 34 and provide the main fluid passage for normal movements of the pipe system, a parallel fluid by-pass passage being formed by the vertical continuations of the bores 72, 74 which lead through end chambers 40, 42 of the bore 32 and are interconnected by a horizontal conduit 106 having an adjustable needle valve 112 the restricted passage of which is much less than that of the orifices 88, 102 of the needle valves 86, 100. The valve piston 34, having a reduced diameter centre portion 46 between lands 36, 38 which divide the bore 32 into the centre and end compartments 44 and 40, 42, has end portions 46, 48 which locate springs 50, 52 for biasing the piston 34 into its central position, the springs being adjustable for balance by means of plugs 54 which threadedly engage the ends of the bore 32. Excess and make-up fluid flows to and from a reservoir 2 through a conduit 14 leading to the centre chamber 44. For shocks which cause more than the normal rate of relative movement pressure differentials build up between the end compartments 40, 42 to move the piston 34 either to the right or left according to the direction of relative movement between the piston 21 and the cylinder 7 so that one or other of the outlet ports 84, 96 of the conduits 82, 95 which open into the centre compartment 44 is covered and the main fluid passage is closed, flow of fluid between the opposite sides of the piston 21 then only being able to take place through the bypass passage 106 and the more restricted passage of the needle valve 112 which offers much stiffer resistance to shock movement. The springs 50, 52 return the valve 34 to its central position after the shock has subsided. The pipe 22 is connected to the rod 20 of the piston 21 by means of a turnbuckle 24 and a universal joint 26, the cylinder 4 being connected to the stationary structure 16 by means of a universal joint 18. In a modification the needle valves in the main fluid passage are replaced by restricted ports of permanent size. In a further modification the by-pass is omitted, the lands 36, 38 during heavy shocks only partially covering the restricted ports of permanent size so that at no time are the latter completely blanked off.