GB1261110A - Improvements in or relating to fluidic logic controlled hydraulic mine roof support systems - Google Patents

Abstract

1,261,110. Fluid logic switching circuits. GULLICK DOBSON Ltd. March 13, 1970 [March 26, 1969], No. 15839/69. Heading F1P. Each of a plurality of sequentially operated self-advancing hydraulic mine roof support units arranged in line and comprising three pairs of hydraulic legs 10 Fig. 1 connected at the base 10a to a hydraulic ram 11 whereby the legs when released from the roof are advanced and then reset has a control box (9) Fig. 3 (not shown) including pneumatic fluid logic element-actuated valves A1 to A5 Fig. 4 for controlling the hydraulic fluid; the elements being in a switching circuit that provides at the completion of advance of any one support unit except the last a signal which is transmitted along a line 32 to the next unit in line to initiate the advance thereof. Valve A1 connects a hydraulic supply line 34 Fig. 2 to lines 28, 27, 28 a valve 16 and a line 12 to the pulling side of ram 11 whilst fluid in a branch 24 controls valve 15 in the hydraulic supply and exhaust line 14, 26 connecting the front pair of legs (only one of which is shown) with valve A4. Line 24 is also connected to a corresponding valve 15 for the rear and middle pair of legs; all three valves 15 being in circuit connection with a common valve A4 which is normally vented to 33. The front legs valve 15 is further controlled by the valve A3 and the remaining two valves 15 are both controlled by the valve A5. Valve A2 which is normally vented to 33 serves to supply hydraulic fluid to the pushing side of the ram. In operation and on pushing a start button B1 the output of an OR gate A directs the output of a bi-stable switch D to the control input of an OR gate F which then actuates valve A1 resulting in all three pairs of props 10 being lowered by venting of fluid through valves 15, A4 and being advanced by ram 11. Switch D also transmits a pulse to one of two control inputs of an AND gate E and when the other input receives a pulse from an advance complete sensor S1 the output of gate E is transmitted in part to one of four control inputs of an OR gate J which then actuates valve A4 thereby supplying hydraulic fluid through open valves 15 to the underside of all three pairs of props to re-set the same. When the resetting is complete a sensor S2 sends a pulse to one control input of an AND gate H which also received the remainder of the output from E; the H output being in part transmitted through the line 32 to the next support unit and in part transmitted through a restrictor R or OR gates C, B to the reset side of switch D which latter by virtue of restrictor R is not reset until after the switch D of the next support unit is set. A stop button B2 when pushed resets switch D which thus de-energizes gate F and vents valve A1 and thus arrests prop and ram motion. A button B3 operates OR gate J which actuates valve A4 and the button also operates an OR gate L which actuates the valve A3 to open the front legs valve 15 resulting in raising of said front legs; the middle and rear legs being unaffected since the corresponding valves A5, 15 are closed. A button B4 also operates gate L which actuates valve A3 to open front legs valve 15 which legs are lowered under gravity. Buttons B5, B6 respectively serve to raise and lower the rear and middle legs. B7 allows retraction of the ram without lowering the legs whilst a button 8 allows extension of the ram after all legs are reset.