Patent GB-961225-A (GB)
Title: Hydraulically operated advancing roof support systems
Inventor: PHILLIPS JOHN
IPC: E21D23/14
Filed: 1961-06-12
Abstract: 961,225. Hydraulic apparatus. ELECTRO-HYDRAULICS Ltd. Sept. 12, 1962 [June 12, 1961], No. 21175/61. Heading F1P. Means for automatically operating hydraulically operated self-advancing mine roof supporting systems having a plurality of support units comprises solenoid-operated valves for controlling the supply of hydraulic fluid to each support unit and the advancing means thereof, and means whereby the valves are selected for operation by uniselectors. Each support unit may be as described in Specification 949,674 and comprises two frames 1, 1a, Fig. 1, which can be advanced relative to one another by a ram 5, each frame having a pair of props 3, 4, 3a, 4a interconnecting a roof bar 2, 2a and a floor skid. The props are operated by fluid from a high pressure line 9 under the control of valves 10, 10a, each valve having a solenoid operated pilot valve 23, 23a controlling main valves 15, 20, 15a, 20a. The ram 5 is supplied with low pressure fluid from a line 12 under the control of a valve 13 and high pressure fluid from the line 9 under the control of a valve 11, each valve 11, 13 having solenoid operated pilot valves 25, 27 controlling main valves 24, 26. When solenoids SOL RH and SOL LH are de-energized, high pressure fluid is supplied to the props through main valves 15, 15a and one-way valves 17, 17a, 18, 18a maintain the props in their supporting positions. Operation of solenoid SOL RH or SOL LH actuates its valves to connect its associated props to a tank line 14 to lower its roof bar; the circuit includes means to ensure that both roof bars are not lowered at the same time. With a roof bar lowered, the solenoids of the valves 11, 13 can be operated either to connect the low pressure line 12 to the full area side of the ram 5 and the annular area side to tank or to connect the full area side to tank and the annular area side to the high pressure line 9 to advance a frame. A number, e.g. 120, of support units as described above may be arranged in ten groups A to K, each group having twelve support units 1 to 12 and an electrical circuit having uniselectors US1, US2, Fig. 2 is provided to control the advancing movements of the units so that only one unit is advanced at a time, the units being advanced sequentially. Further uniselectors MS1, MS2 are also provided to enable manual actuation to be effected, a main switch 30 being movable to automatic or manual positions. Each uniselector has two banks of contacts and a pair of wiper arms coupled together, one bank and one wiper selecting a support unit and the other bank and wiper controlling a light in a panel 50 to indicate which unit has been selected to be advanced. At the commencement of an advancing operation, the support frames are extended to support the roof with the left-hand frame of the support unit Al foremost and the ram 5 fully extended. The unit adjacent unit A1 has its ram 5 nearly fully extended and so on until the ram of the unit K12 which is fully closed. With the ram of unit Al fully extended, a switch S1 is closed to energize a relay A/1 to close its contacts and energize solenoid SOL Ram LP and disconnect the low pressure supply to the full areaside of the ram. When the pressure at that side of the ram drops to near zero, a switch P S3 closes and, since a contact RHB of a switchS3 is closed when its right-hand frame is in its rear position, solenoid RH is energized to actuate valve 10 to connect the props 3, 4 to tank. As the pressure drops in the props, the left-hand contacts of a switch PS1 open and the right-hand contacts close to make a holding circuit for relay A/1 to ensure the completion of the advancing movement. A switch S4 is closed when the roof bar 2 of the frame 1 has been lowered to energize solenoid SOL Ram HP which operates valve 11 to connect the high pressure line 9 to the annular area side of the ram 5 which pulls the right-hand frame 1 forward in advance of the left-hand frame using that frame and a conveyer as anchorages. After the ram 5 is fully closed, solenoid SOL RH is de-energized for high pressure to be supplied to rams 3, 4 to raise the roof bar, the pressure in the props operating switch PS1 to open the holding circuit for the relay A/1 which results in de-energizing SOL Ram LP to actuate valve 13 reconnecting the lowpressure line 12 to the full area side of the ram 5. Operation of valve 13 causes a striker to actuate a switch S2 and an impulse to operate a coil 36 to move the wiper arm 32 of uniselector one step so that the above sequence of operations may be repeated for the adjacent support unit A2 when its ram is fully extended. The piston rod 8 of each ram is connected to a coal conveyer to which a plough is attached and the low pressure applied to the full area side of the rams urges the conveyer and plough towards the coal face so that the conveyer is pushed into the position occupied by the coal as the plough passes. When the conveyer has been moved so that the ram of unit Al is fully extended its switch is closed to instigate an advancing movement of its frame. After all the units 1 to 12 in group A have been advanced, a coil 54 is operated to advance the wiper arm 40 of uniselector US2 from contact A to contact B so that the units 1 to 12 of group B are then sequentially advanced, the operation continuing until the last unit K12 has been advanced whereupon the wiper arm 32 of uniselector US1 is returned to contact 1 in preparation of a further advancing movement. The wiper arms 32, 40 are coupled to wiper arms 43, 46 which co-operate with banks of contacts B2, B4 to illuminate lamps 1 to 12, A to K so that the operation of the support system can be followed. Other uniselectors MS1, MS2 having banks of contacts B5, B6, B7, B8 can be operated when the master switch 30 is moved to the manual position so that the advancing of the units is under manual control. In another embodiment, the master switch 30 has a third, monitor position and an impulse unit to successively stop the wiper arms of the uniselectors so that the circuit can be tested, the polarity of the circuit to the uniselectors being reversed and rectifiers being provided to prevent the support units being actuated. If a unit is faulty, the wiper arms of the uniselectors are held to indicate the faulty unit. Specification 961,226 is referred to.