GB764194A - Hydraulic pit props - Google Patents

Abstract

764,194. Hydraulic pit props. DEUTSCHE KOHLENBERGBAU-LEITUNG. June, 25, 1954 [June 25, 1953], No. 18697/54. Class 20(2) [Also in Group XXIX] A hydraulic pit prop which may be set to a high initial pressure by means of relatively low pressure working fluid, has a piston rod 3 carrying spaced piston heads 5, 6 and 8 which work in corresponding pressure chambers 11, 12, 13 defined in a cylinder 1 by spaced partition walls 9 and 10 through which the piston rod 3 passes in sealed relationship. In the arrangement of Fig. 1 pressure fluid is admitted through a pipe 16, control valve 17 and pipe 18 to the pressure chamber 13 and it passes to the pressure chambers 11 and 12 through a hollow portion of the piston rod 3 and radial bores 7 therein: Air from the chambers 11, 12 and 13 is exhausted through a pipe 14 to a discharge pipe 20. The pipe 18 communicates with the pipe 14 through an excess pressure valve 19 and may be placed in communication with the discharge pipe 20 through a pipe 21 by appropriately positioning the valve 17. The cylinder 1 constitutes the upper portion of a prop, telescopically adjustable within a tubular lower prop portion 22 enabling the prop to be adapted to any thickness of coal seam. The cylinder 1 is secured in adjusted position by a bolt 23 passed through holes 24 in the portion 22. In a modification, Fig. 2 (not shown) the cylinder 1 constitutes the power portion of the prop telescopically arranged within an exchangeable upper tubular portion 22 having a retaining bolt 23 which may be engaged selectively in holes 24 in the tubular portion 22. The pressure fluid flows from the tube 18 directly into a hollow piston rod 3 and air exhaust inserts are provided in the walls of the chambers 11, 12, 13. In the embodiment of Fig. 4 the cylinder 1 constitutes an upper prop member telescopically arranged within a lower tubular prop member 22. The upper part of the cylinder 1 which constitutes a collecting space 32 for pressure medium, has a cover in which a hand pump 26, suction valve 27, obturator valve 28 and excess pressure and release valve 29 are arranged. The piston rod 3 abuts the bolt 23 which may be selectively engaged in holes 24. A system is shown in Fig. 3 wherein props C<SP>1</SP>, C<SP>11</SP>, according to the invention, are incorporated in a lagging frame having two-part caps a and a lower runner rail b. The props are connected to a supply pipe 16 and discharge pipe 20. The lagging frames may be advanced by pressure cylinders arranged at the rear end of the frames.