GB1016061A - Mine roof support - Google Patents

Abstract

1,016,061. Advancing mine roof supports. DOWTY TECHNICAL DEVELOPMENTS Ltd. April 2, 1964 [April 4, 1963], No. 13356/ 63. Heading F1P. A mine roof support system comprises a series of roof supports 4 each advanceable by an associated jack 7 and each comprising at least one support prop 6, and a valve assembly operable, when a pilot line 18 connected thereto is pressurised, to cause the props 6 of the first support to retract and the jack 7 to advance the first support and when the pilot line pressure is changed a predetermined amount, to open the valve assembly thereby bringing the pilot line into communication with the next support in the series whereby further pressurisation causes advance of the next support. The valve assembly comprises three main valve units A, B, C, a sequenal valve D and a pilot valve E. The main valve unit A is connected by a line 22 to a subsidiary valve assembly 23 including a control valve 24 for each prop 6. Each valve assembly is connected to a supply line 11 through a branch supply line 13, a return line 14 through a branch return line 15, a datum pressure line 19 through a branch line 21 and the pilot line 18 through a group of non return valves 61 which allow the supports to be advanced in both left to right and right to left sequence. In the position of the parts of valve assembly shown the props 6 are set against the roof by hydraulic fluid in their respective pressure chambers 25 and a conveyer advancing jack 8 is operative by pressure fluid supplied from the branch supply line 13, via the main valve C and a line 38. To initiate an advancing operation the left hand portion of the pilot line 18 is pressurised to a value equal to the pressure in the datum pressure line 19 whereby a line 49 connected to the main valves A, B, C is also pressurised. Pressurisation of the line 49 causes the pistons 28, 36, 39 of valves A, B, C to move respectively to the right, left and left. The piston 28 engages a piston valve 29 and maintains it in the position shown; the piston 36 causes connection between a line 31 and the branch supply line 13 thus pressurising lines 32, 33, 34; the piston 39 connects the line 38 to the branch return line 15. The pressurisation of line 32 contracts the conveyer advancing jack 8 and causes the jack 7 to apply an advancing force to the roof support. The pressurisation of the line 33 contracts the props 6. The pressurisation of line 34 acts on the pistons 62 of the prop control valves 24 to open their ball valves 63, so that fluid escapes from the pressure chamber 25 of each prop 6 through the line 22 and valve unit A to the branch return line 15. A line 59 in communication with the pressure chamber 25 is therefore also depressurised and the piston 54 and ball valve 52 of the pilot valve E is thereby allowed to move to the left by the pressure in the datum branch line 21. When the roof support 4 has been fully advanced i.e. the jack 7 is fully contracted the pressure of the pilot line 18 is reduced to half the datum pressure value, whereby the piston 36 of the valve B returns to the position shown so that the lines 31, 32, 33, 34 are re-connected to the branch return line 15 arid the piston 28 of valve A moves to the left causing pressurisation of line 22 which extends the props 6 to reset the support against the roof. When the props are fully pressurised, the build-up of pressure in line 59 moves piston 54 of pilot valve E to the right allowing the ball valve 52 to return to the position shown. The pilot line 18 is then depressurised so that the pressure in datum branch line 21 returns pistons 29, 39 to the positions shown, so that jack 8 re-continues to advance the conveyer. Movement of the piston 39 displaces hydraulic fluid into the lines 56, 58 to thereby move the piston 47 of the sequence valve D to the left where it is maintained by fluid supplied from the datum branch line 21. Pistons 45, 46 and ball valves 42, 43, 44 are also displaced to the left so that line 49 communicates through ball valve 42 with the branch return line 15 and the pilot line 18 communicates through ball valve 43 and non-return valves 61 with the valve assembly of the next roof support which can therefore be advanced by varying the pressure in the pilot line 18 in the same manner described. The sequence valves D of all the valve assemblies may be brought back to the position shown by reducing the pressure in the datum line 21 to zero. In Fig. 5, not shown, the valve assembly is modified and is provided with an additional pilot line for effecting section-by-section advance of the conveyer.