Patent GB-1235872-A (GB)
Title: Self-advancing pit-prop systems
IPC: E21D23/14
Filed: 1968-05-31
Abstract: 1,235,872. Fluid logic and switching circuits. BERGWERKSVERBAND G.m.b.H. May 31, 1968 [June 14, 1967], No.26170/68. Heading F1P. Each of a plurality of self-advancing mine roof support 501 to 510, Fig. 3, arranged along the working face 500a has a known device for sensing when the unit has space to advance and has known control means e.g. hydraulic rams for releasing the unit from a braced roof supporting condition, advancing it and resetting at the end of advance and the control means for each unit is connected in a pneumatic logic system which associates each unit except the two end units with at least one adjacent unit on each side so as to form a succession of overlapping groups of units with n units in each group, (n being at least three) and successive groups having (n-1) units in common, the logic system acting to control all the units so that throughout the overlapping groups during the period while the control means of an inner unit of a group is operable or of any single inner unit respectively belonging to two or more non-successive groups are operable the control means of the outer units of the group or groups containing the advancing unit or units are locked against operation. The logic system for each of three units I, II, III, Fig. 2, may unit II comprises an input line 204 for receiving a signal from a sensor indicating room to advance, a dominant input store 201 having its input side connected by a line 205 to the output 206 of a inhibit output store 202 in series with store 201 and having its inhibit side connected through an OR gate 203 by lines 208, 209 to the outputs 106, 306 of output stores 102, 302 of units I, II; lines 208, 209 having branch lines leading to OR gates on the inhibit side of the output stores of units (not shown) to the left and right of units I, II. The output 206 of store 202 is also connected by lines 211, 212 to OR gates 103, 303 of units I, III. In operation and assuming the feelers (not shown) of all three units and possibly one or two on both sides, indicate room to advance then or prepare to advance signal will appear in all three lines 104, 204, 304 but in practice one signal say that in line 204 will be initiated first in time and this will be transmitted through stores 201, 202 to line 206 to produce locking signals in lines 211, 212 which will pass through OR gates 103, 303 to the inhibit input of output stores 102, 302 thereby arresting the prepare to advance signals at the signal input at 102, 302. The signal in line 214 is transmitted through a line 205 which thus cancels signal in 204 whilst signal at 206 is transmitted through a line 214 and triggers the prop unit II advance and reset control means. Finally a return signal in a line 213 leading from the reset prop unit to the OR gate 203 is transmitted to the inhibit input 207 of output store 202 whereby signal in lines 206, 211, 212 is cancelled. The flow resistance of say line 211 is less than that of line 212 whereby the signal in inhibit input line 307 is cancelled before that in line 107 whereby the command advance signal appears in the output line 306 and simultaneously there appear locking signals in lines 209 leading to OR gates 103, 203 thus providing signals in lines 107, 207 which inhibit stores 102, 202 and thus prevent access of signals to 106, 206. The order of advance of the several units is determined of the resistances in the lines connecting the outputs of stores 102, 202, 302 with the OR gates of the neighbouring units. The units 501 to 510 are arranged in successive overlapping groups of three units successive groups having two units in common and the units are connected in the logic circuit as already described. As shown only units 503 to 508 have room to advance and as soon as units 505, 508 advance they lock units 504, 506 and 507, and also 509 even though it is not prepared for advance. At the end of advance of 505, 508, units 504, 506, 507, 509 are unlocked and units 504, 507 advance thereby locking units 503, 505 and 506, 508. At the end of advance of 504, 507 units 503, 506 advance and in doing so lock units 502, 504 and 505, 507 whilst units 501, 508, 509, 510 are unlocked but none are prepared for advance.