Patent GB-990837-A (GB)
Title: Roof support assembly
Inventor: POTTS MICHAEL CHARLES
IPC: E21D23/16
Filed: 1963-04-05
Abstract: 990,837. Advancing mine roof supports. DOWTY MINING EQUIPMENT Ltd. March 25, 1964 [April 5, 1963], No. 13715/63. Heading F1P. A fluid pressure operated roof support assembly comprises a series of advanceable roof supports 4 arranged in groups, each group being controlled by an associated manually or remotely operated safety valve 16 whereby the roof supports in any selected group may be prevented from advancing while allowing the advance of the roof supports in another group. Each roof support 4 is controlled by an associated valve assembly 12 connected by a branch supply line 13 to a supply line 11 and by a branch return line 15 to a return line 14. A pilot line 17 is connected between each of the valve assemblies 12 of a group and to the safety valves 16 disposed between the groups. Each safety valve 16 controls one of the two adjacent groups of supports depending on whether the supports of a group are to be advanced from left to right or visa-versa. Operation of a safety valve 16 pressurises through a branch line 18 the pilot line 17 up to the valve assembly 12 of the first support of the group. Pressurisation of the pilot line 17 causes each support of the group to undergo, in turn, an advancing operation. Fig. 3 shows the valve assembly 12 of a roof support having a double-acting jack 8 for advancing a conveyer (not shown) and a jack 7 for advancing the support up to the conveyer. The valve assembly 12 comprises valve units A, D and E controlling respectively the supply of hydraulic fluid for extending the jack 8, contracting the jacks 7 and 8, and extending the support props 6. In those roof supports without a jack 8, valve units A and B and lever 32 are omitted. In the conveyer advancing condition of each valve assembly 12 a lever 32 is moved in an anti-clockwise direction either manually or by pressurisation of a line 65 connected to the valve unit B and is held in the anti-clockwise position by a spring latch 66 to thereby maintain valve A open, whereby the conveyer advancing jack 8 is supplied with fluid through lines 11, 13 and 23. To advance the first support of a group, the appropriate safety valve 16 is operated whereby the upper left hand portion of the pilot line 17 is pressurised. Pressurisation of line 17 releases the latch 66 and operates on a valve unit C to cause clockwise movement of the lever 32 and a lever 33. As a result valve unit A closes thereby cutting off the supply to the jack 8 and valve unit B opens to allow fluid to pass from the jack 8 to the return line 14. At the same time valve unit C closes and valve unit D opens thereby connecting the contracting sides of the jacks 7 and 8 through a line 24 to the branch supply line 13. Pressurisation of line 24 also pressurises a line 69 thereby causing the valve unit F to open whereupon the props 6 retract, the fluid therein passing via a non-return valve 29, a line 28 and the valve F to the branch return line 15. The jack 7 then advances the support towards the conveyer until a trip 63 on the jack 7 opens a re-setting valve 53 so that a line 58 is pressurised whereby valve unit F closes and fluid passes through a non-return valve 59, a restrictor 26 and a non- return valve 27 to extend the props 6. The pressure build-up in a line 43 which occurs after the props have re-set is arranged to displace the piston 39 of a pilot valve 35 whereby the pilot line 17 is pressurised up to the valve assembly 12 of the second roof support of the group. In this way, each roof support in the group is advanced in turn. The valve assemblies 12 can be operated manually by appropriate operation of their levers 32, 33, 34. The props 6 are provided with a pressure relief valve 31.