GB861046A - Improvements in or relating to hydraulically operated pit-props - Google Patents

Abstract

861,046. Valves. BOSCH G.m.b.H., R. Aug. 26, 1957 [Aug. 29, 1956], No. 26796/57. Class 135. [A An hydraulic pit-prop comprising two telescoping parts 1, 2, Fig. 1, defining a pressure chamber 36 has a pressure relief valve comprising a cone - shaped closure member 42 mounted within a cup spring 47 which is retained between an abutment 51 and sealing ring 50 on the end of a bush 38, the spring 47 also acting as the closure member of an inlet and release valve. To set the prop, pressure fluid is introduced through an inlet 18, bores 22, 33, 30 in the head 9 of the part 2 to displace the cup spring 47 from its seating 48 against the action of a spring 46, so that fluid may enter the pressure chamber 36 to extend the prop. At the same time fluid is forced from an annular chamber 35 into the pressure chamber 36 via bores 34, 30. Excess pressure in chamber 36 acts on the cup spring 47, plate 39 and closure member 42 until the shaft 41 of the member 42 abuts a control member 28 so as to unseat the member 42 and allow fluid to escape between it and the plate 39, and through holes 40. Spacing discs 54 are inserted to vary the depth of the control member 53. To lower the prop, fluid is forced into an inlet 23 to depress the control member 28, shaft 41 and closure member 42. Further movement displaces the cup spring 47 from its seating 48 when a pin 45 on the shaft 41 engages the bush 38. A guide ring 11 is lubricated by fluid from an annular groove 14 and slot 12. In Fig. 2, the bush 38 is replaced by a sleeve 66 with two conical seating surfaces 67, 68 and the pin 45 by a washer 84 and spring 85, an additional bore 86 being provided for relieving pressure in the chamber 36. In the embodiment of Fig. 3, a filter 115 of sintered material is provided in this bore and an additional double cup spring 100 is added between the sleeve 95 and a rigid ring 99 so as to press the sleeve 95 on its seat 88. In the embodiment of Fig. 4, the pressure relief valve may be incorporated in a housing 124 secured to the upper part 122 of the prop and opened to collapse the prop by means of a tube 146 which can be detachably positioned over a pin 145 and canted to cause a plate 142 to move a shaft 129 against its spring 141 unseating a closure member 130, further movement causing a ring 131 to unseat the cup spring 136 allowing fluid to flow from the pressure chamber 121 via a pipe 125 and bores 148 into the storage chamber 123.