Improvements in or relating to adjustable hydraulic mine props or the like

摘要

737,748. Hydraulic pit props. EISENWERK WANHEIM GES. June 6,1952 [June 9, 1951], No. 14355/52. Class 20 (2). In a hydraulic pit prop, a relief valve 10 which an overload allows pressure fluid to flow from the lower cylinder 3 to the upper pistonlike part 1, is held against its seating by the fluid pressure and by the additional force of a spring 13 and is moved positively therefrom by a spring-loaded piston 9 located within the piston 2 of the upper part 1. As shown, a sleeve 4 is movably located within the piston 2 and is surmounted by a screwed cap 5, a spring 6 being located between the cap 5 and piston 2. A piston cylinder 9 is movably disposed in the sleeve 4 and is integral with a tube 8 providing a passage for the pressure fluid into the cap 5 and through holes therein to the inside of the upper part 1. A relief valve cone 10 inside the piston cylinder 9 is held against the bottom of the tube 8 by a spring 13 and is guided by a valve rod 11 passing through a passage in the closure base 12 of the cylinder 9. A spring 14 serves to push the cylinder 9 downwardly relative to the head 7 of the sleeve 4. A rod 15 connected to the valve cone 10 passes through the tube 8 and cap 5 and is secured to one end of a lever 19 manually operable by means of a rod 18. On increase of pressure within the lower cylinder 3, the piston cylinder 9 is pressed upwardly against the spring 14, the valve cone 10 being pressed more strongly on to its seat until projections 17 on the rod 15 engage the inside of the cap 5 when further upward movement of the cone 10 with the piston cylinder 9 is prevented. Continued upward movement of the cylinder 9 forces the cone 10 from its seating against the pressure of the spring 13, thereby allowing fluid to flow from the lower cylinder 3 through the closure base 12 and tube 8 to the upper part 1 until the force of the spring 14 again exceeds the fluid pressure in the cylinder 3. To remove the prop the rod 18 is actuated to first lift the valve cone 10 off its seat, the lever 19 finally engaging the cap 5 to depress the cap 5 and sleeve 4 against the spring 6 to provide a large passage for fluid flow and thus to enable a rapid sinking of the upper part 1.