Patent GB-981624-A (GB)
Title: Mining apparatus
Inventor: THOMAS DAVID GURNEY ARNOLD
IPC: E21D23/14
Filed: 1962-04-17
Abstract: 981,624. Advancing mine roof supports. DOWTY TECHNICAL DEVELOPMENTS Ltd. April 16, 1963 [April 17, 1962], No. 14755/62. Heading F1P. A series of hydraulic mine roof supports 1 arranged to be automatically advanced towards the working face 2 in a predetermined sequence by an automatic advance control 8 responsive to signals obtained from the preceding support in the sequence is provided with override means 11 for causing the automatic advance control 8 to omit a failed roof support from the sequence and safety means 12 arranged to indicate a predetermined number of selections of the override means. The safety means may indicate a predetermined number of selections of the override means corresponding to a predetermined number of failed supports randomly situated in the sequence (Fig. 2) and/or adjacently situated in the sequence (Fig. 3). Each roof support 1 is connected to a conveyer 3 by an hydraulically operated jack 7 and comprises a floor beam carrying two or more hydraulically operable props 5 surmounted by a roof beam 6. The automatic advance control 8 is operative to control a series of electro-hydraulic valve assemblies (not shown) each associated with a roof support. When a support is automatically selected for advance the associated props 5 are collapsed, the jack 7 associated therewith is contracted to advance the support towards the conveyer 3 and the props 5 are extended to support against the mine roof. When a roof support fails the automatic advance of the roof supports 1 will stop until the override means 11 is manually operated, which operation simultaneously temporarily closes a switch 52 in a circuit constituting part of the safety means 12. The circuit (Fig. 2) comprises a number of parallel connected electrical relay solenoids N/4 V/2, V/4 each connected through a pair of relay contacts between a line 15 and a line 14, and the line 15 and a line 16. Each relay solenoid is further connected in sequence to one of a number of lines 19 adapted to be connected by a rotary arm 18 to one side of a relay W/3. The position of the arm 18 determines the number of random supports which can fail before further operation of the override means is prevented. In operation a reset switch 51 is operated to close a line and open the line 14 which energizes relay solenoid N/4 and ensures that all the other relay solenoids are in the de-energized condition. Subsequent closure of switch 52 due to operation of the override means 11 de-energizes relay N/4, energizes relay O/4 and prepares relay P/4 for energization when the override means is again actuated. Hence the relays are energized in sequence due to operation of the override means until relay solenoid W/3 is also energized Contacts W1, W2, W3 associated with relay W/3 operate a warning device and prevent operation of the advance control 8 and the override means Il. Another part of the safety means shown in Fig. 3 indicates when two adjacent roof supports have failed. The circuit of Fig. 3 comprises three relays A/2, B/2, C/2 and two switches PS and SS sensitive to failure of the roof supports. In normal operation switches PS and SS make and thereby energize relay B/2 through contact A1. Subsequent failure of a support necessitates operation of switches 52, 54 associated with the override means which thereby energizes relay C/3, de-energizes relay B/2 and lights a warning lamp 21. The now open contact B2 prevents operation of the override means should the next support also fail. Specification 959,492 is referred to.