Patent GB-1123975-A (GB)
Title: Hydraulically-operated advancing mine roof supports
Inventor: CARNEGIE JAMES
IPC: E21D23/26
Filed: 1964-10-12
Abstract: 1,123,975. Advancing mine roof supports. DOWTY ELECTRICS Ltd. Oct. 8, 1965 [Oct. 12, 1964], No.41628/64. Heading F1P. Each hydraulic fluid operated mine roof support 4, Fig. 2, of a series of sequentially advanced supports is provided with potentiometers 83, 84, Fig. 3, responsive to extension of a support advancing jack 7 and to fluid-pressure within the props 6 forming the support 4 and each support also includes a switch 79 which when closed by fluid-pressure in a signal line 18 leading from the adjacent support in the series just having been advanced completes the circuit between the potentiometers 83, 84 and meters 76, 77 through leads 78, 81, 82 extending along the supports 4. Each support 4 has a valve block 12 connected by branch lines 13, 15 to main supply and return lines 11, 14 respectively connected to a primary pressure source 10. The signal line 18 is fed from a source 16 and leads to a group of non- return valves 35 to 38 at each support 4 in turn and a control line 19 supplied from a source 17 is connected through a brand line 21 to one side of the piston 55 of an unlocking valve 39 and through a branch line 22 to one side of the piston 66 of a prop resetting valve 57; the valves 39, 57 being repeated in the block 12 of each support 4. Every fourth support has in addition to jack 7, a doubleacting conveyer advancing jack 8. The valve assembly also includes units A, D and E controlling respectively the supply of hydraulic fluid for extending jack 8, contracting jacks 7, 8 and setting the support props 6. In the conveyer advancing condition of each valve block 12 a lever 32 is moved anti-clockwise either manually or by pressurization of a line 71 connected to unit B and is held by a spring catch 72 whereby the jack 8 is supplied through lines 11, 13 and 23. When the first support 4 in the series is to be advanced, line 18 is pressurized, valve 35 opens to admit pressure to a line 42 which releases latch 72 and operates on a unit C to cause clockwise movement of a lever 33 and lever 32 connected thereto resulting in valve unit A closing and cutting off the supply to jack 8 and valve unit B opening to connect the jack 8 to return line 14. At the same time valve unit C closes and unit D opens thereby connecting the contrasting sides of jacks 7, 8 through a line 24 to the supply line 13. Pressurization of line 24 also pressurizes a line 30 thereby causing valve unit F to open whereupon prop pressure is relieved past a non-return valve 29 to the return line 15. Jack 7 then advances the support 4 towards the conveyer until a trip 67 on the jack 7 opens the resetting valve 57 so that a line 62 is pressurized from line 24 to close valve unit F whereon pressure fluid passes through non- return valves 63, 27 to reset the props 6. The pressure build-up in a line 49 which occurs after the props are reset displaces a piston 45 of a control valve 41 to open the same and pressurize the signal line 18 leading to the next support in the series to be advanced. Pressurization of the second line 18 and a line 43 connected thereto closes valve unit D thereby returning the interconnected units A, B, C, to their neutral positions. Solenoid 84 is of the rotary type whereas solenoid 83 comprises a helical strip 86 threaded through the vented end of jack 7.