GB803820A - Improvements in and relating to hydraulic pit props - Google Patents

Abstract

803,820. Hydraulic pit props. DOWTY MINING EQUIPMENT, Ltd. July 19, 1956 [July 19, 1955], No. 20899/55. Class 20(2) A telescopic hydraulic pit prop comprises a detachable section, such as an extension 32 at the head of the prop, of longitudinally divided parts 33 held together transversely with respect to the axis of the prop by fastening means, such as bolts 42, 43, which may be released when the prop has been fully retracted under roof load so that the parts 33 may be separated from each other, as by driving a wedge between them through slots 45 or 46, to release the main part 10 of the prop. The extension 32 is formed with a socket by which it is connected to a spigot 30 at the upper end of the main part 10 of the prop. Holes 36, 37 receive a bolt which secures the extension on the spigot. The invention is applicable to a mine roof supporting structure in which the props cannot be freed by tipping them about their lower ends, and also to single hydraulic props. The prop comprises a ram tube 11 within a pressure tube 10, the lower end of the ram tube 11 being closed by a plug 22 having a U-shaped packing ring 23 held thereon by a spacer ring 24 and retaining ring 25. The pressure cylinder is closed at its base by a plate 12 having a convex surface 13 with a central spigot 14 intended for loose locating engagement in a base member of a roof supporting framework of the kind having a roof bar carried by the props. The upper end of the cylinder 10 has a gland ring 15 which retains a flexible wiper ring 16, a spacer ring assembly 17 and a bearing insert 19. A fluid connection socket 20 is fixed to the lower end of the cylinder 10. A filling and/or bleeding tube 27 extends from the plug 22 to a socket 28 in a collar 26 which carries the spigot 30.