GB781643A - Mobile system of mine roof support - Google Patents

Abstract

781,643. Mine roof supports. KLOCKNERBERGBAU VICTOR-ICKERN AKT.-GES. Aug. 10. 1954 [April 12, 1954], No. 23190/54. Class 20(2) In a fluid pressure actuated mine roof support system a pressure pipe 9, Fig. 1. and a return flow pipe 10 are connected to groups of props 3 constituting individual support frames 1, 2 adapted for alternate advancing movements by operation of horizontal piston and cylinder unit 5 connected between pairs of frames 1, 2, the connection between each of the groups of props 3 and the pipes 9, 10 being made by means of a reversing valve 8 and a differential pressure safety valve 7. The safety valve 7 comprises a poppet valve 20 formed on a piston having three portions 19a, 19b and 19c, Fig. 4 slidably mounted in a chamber in a valve housing 23 having portions 22a, 22b and 22c of different diameters. The chamber 22c is connected to a passage 33 which communicates with the pressure pipe 9 by way of the reversing valve member 8 and a bore 29. The chamber 22c also communicates through a restricted passage 21 with a bore 28 to which the associated group of props is connected. The eross-sectional areas F', F<SP>2</SP>, F<SP>3</SP> and F<SP>4</SP>, and the crosssectional area of the passage 21 are so proportioned that in the event of loss of pressure in the pressure pipe 9, the poppet valve 20 will close to seal the prop cylinders connected to the bore 28 against loss of pressure and the valve 20 will remain open as long as the pressure in the pipe 9 does not fall below a predetermined value at a rate in excess of a predetermined rate. The reversing valve member 8 consists of a rotatable conical plug 24 having a bore 24a which can be positioned to place the prop cylinders in communication with the pressure pipe 9 or may be rotated through 90 degrees to the position shown in Fig. 4 in which the bore 24a completes a passage from the prop cylinders connected to the bore 28 to the return flow pipe 10. The plug 24 is forced against its seat by the resultant of forces acting in opposition against the conical surface of the plug and the annular surface K<SP>2</SP>. A spring 36 maintains the seal of the conical surface of the plug in the event of a complete failure of pressure. Specifications 750,293 and 781,644 [hoth in Group XXIX] are referred to.