US3228300A

US3228300A - Mining apparatus

Info

Publication number: US3228300A
Application number: US282396A
Authority: US
Inventors: Potts Michael Charles; Bolton Douglas Herbert Hewlett
Original assignee: Dowty Mining Equipment Ltd
Current assignee: Dowty Mining Equipment Ltd
Priority date: 1962-05-25
Filing date: 1963-05-22
Publication date: 1966-01-11
Anticipated expiration: 1983-01-11
Also published as: GB991007A; DE1189504B; GB991012A; FR1356892A; DE1176087B; FR1356891A; US3217603A

Description

Jan. 11, 1966 M. c. POTTS ETAL 3,228,300

MINING APPARATUS 2 Sheets-Sheet 1 Filed May 22, 1963 FIG].

SEQUENCE STOPPAGE HYDRAULIC CONTROL VALVE INDICATOR PRESSURE SOURCE HYDRAULIC PRESSURE SOURCE IN E'hToKS Mia/M L C. 7 07 73 DooSLAs H-H- B./ T Y M M,

Jan. 11, 1966 M. c. PoTTs ETAL MINING APPARATUS 2 Sheets-Sheet 2 Filed May 22, 1963 M/Cl/AEL a PZ T DOUGLAS H. H. BOLTON 3 BY ATTORN at United States Patent 3,2285% MlNlNG APPARATUS Michael Charles Potts, Presthury, Cheltenham, and Douglas Herbert Hewlett Bolton, Winchconihe, near Cheltenharn, England, assignors to Dowty Mining Equipment Limited, Ashchurch, near Tewkeshury, Gloucester, England, a British company Filed May 22, 1963, Ser. No. 282,3% Claims priority, application Great Britain, May 25, 1962, 2il,l98/62 8 Claims. (til. 91-1) This invention relates to roof support assemblies for use in mines.

The roof support assembly with which this invention is concerned includes a series of roof supports distributed along the working face of a mine, and each including one or more props extendable by fluid pressure against the roof to support the same, and contractible in like manner. During normal operation the prop is first contracted from its normal roof-supporting condition preparatory to undergoing an advance. Its contraction, its subsequent advance, its normally ensuing extension to reset it in the advanced position against the roof, and the transmission of a signal to the next-to-be-advanced roof support, are all accomplished automatically by fluid pressure controlled by mechanism that in its details is not a part of this invention. There may be some failure to follow the normal sequence of operations, from one cause or another, and if this occurs the sequence of operations ceases. Since the series of roof supports extends for quite a distance along the working face, whereas the operator is stationed at one end of the series and is unable to observe any stoppage, it is important that he be advised, immediately and automatically, so that he can take necessary steps promptly, leading to correction of the cause of failure and resumption of the automatic operation of the system. The present invention is concerned, in such a system, with indicating means automatically operable to indicate a stoppage to the operator, actuated, in the form shown herein, by the existence of a predetermined pressure in a pressure line that is part of the system, for more than a predetermined period of time, whenever the series of roof supports is undergoing an advancing sequence.

The indicating means may indicate the existance of a maximum pressure in the pressure line for more than the predetermined time when the series of roof supports is undergoing an advancing sequence, or it may indicate the existence of a predetermined low pressure in the pressure line for more than the predetermined time when the series of roof supports is undergoing an advancing sequence.

The support advancing means may include a hydraulic pilot line connected to a control valve of each roof support in turn, said control valves each closing the pilot line before an advancing sequence commences, being actuated by receipt of a hydraulic-pressure signal in the pilot line from the previous support in the series, to cause its roof support to undergo an advancing operation and opening the pilot line to next support upon completion of the advancing operation of its own roof support.

When the indicating means is of the type to indicate existence of the maximum pressure in the pressure line for more than the predetermined period of time, the absence of a pressure in the pilot line may be arranged to render the indicating means inoperative.

The indicating means may include a device responsive to pressure in the pressure line, the device being arranged to actuate an electrical circuit, including an indicating device, when the pressure reaches the predetermined value.

One embodiment of the present invention will now be 3,2233% Patented Jan. 11, 1966 ice described, by way of example, with reference to the accompanying drawings, of which,

FIGURE 1 is a diagrammatic view of mining apparatus, 'but with the hydraulic connections and roof bars omitted,

FIGURE 2 is a similar view on a larger scale showing the hydraulic connections,

FIGURE 3 is a diagrammatic view of the stoppage indicating means, and

FIGURE 4 is a diagrammatic view of the hydraulic control valve assembly of a roof support.

With reference to FIGURES 1 and 2 of the accompanying drawings, mining apparatus includes a conveyor 1 extending along the working face 2 of a coal mine and a cutter 3 which passes along the working face 2 and is situated between the Working face 2 and the conveyor 1. The conveyor 1 acts as a guide means for the cutter 3. The mining apparatus also includes a roof support assembly located on the opposite side of the conveyor 1 to the cutter 3 and working face 2. The roof support assembly includes a series of roof supports 4 arranged along the working face 2,. Each roof support 4 includes a groundengaging sole beam 5 carrying three hydraulicallyoperable telescopic props 6, and the three props 6 carry a roof beam (not shown). Each roof support 4 is connected to the conveyor 1 by a hydraulically-operable jack '7 for advancing the roof support 4 towards the conveyor 1, and every fourth roof support 4 has a further hydraulically-operable jack 8 for advancing the conveyor 1 relative to the roof support 4.

The mining apparatus also includes a hydraulic power unit 9 which has a main pressure source 10 from which a hydraulic pressure line 11 and a hydraulic return line 12 extend along the working face 2. Each roof support 4 includes a hydraulic control valve 13, details of which will be given later, to which the pressure line ill and return line 12 are connected by lines 14 and respectively. The control valve 13 of each roof support 4 is connected to its props 6, jack 7 and jack 8 (if provided). The control valve 13 of each roof support provided with a jack 8 is so arranged that the jack 8 is urging the conveyor 1 towards the coal face continually except when the roof support 4 is being advanced. Actuation of the control valve 13 causes the following operations to take place in sequence:

(a) The jack 8 (if provided) is caused to cease pushing the conveyor 1 forwardly,

(b) The props 6 are contracted to release the roof support from the roof,

(c) The jack 7 is caused to advance the roof support up to the conveyor 1,

(d) After support advance has been completed, the jack 7 is caused to cease urging the roof support forwardly, the props 6 are extended to reset the roof support against the roof and the jack 8 (if provided) is caused to resume pushing the conveyor 1 forwardly.

Actuation of the control valves 13 is caused by a hydraulic pilot system. The power unit 9 includes a source which in FIGURE 2 is designated 16, of hydraulic pressure for the pilot system, and a pilot line 17 extends from the pilot source 16 and passes through the control valve 13 of each roof support 4 in turn. Each control valve initially closes the pilot line 17. When the pilot source 16 is operated to pressurise the pilot line 17, the hydraulic pressure in the pilot line 17 acts as a signal to the control valve 13 of the first roof support 4. This roof support 4 undergoes an advancing operation, as described above and when the roof support has been satisfactorily reset against the roof, the satisfactory resetting being sensed by the attainment of a desired hydraulic pressure in the props 6, the control valve 13 is caused to 3 open the pilot line so that the hydraulic pressure signal is then applied to the control valve 13 of the next roof support, which then undergoes an advancing operation.

Thus each roof support in turn undergoes an advancing operation. The hydraulic circuit relating to the advancing sequence is described in United States application Serial No. 282,760, filed May 23, 1963, and in United States application Serial No. 355,769, filed March 30, 1964.

The operation of the valve assembly 13 of each roof support 4 will now be described with reference to FIG- URE 4. The valve assembly 13 of a roof support 4 with a double-acting jack 8 includes six valve units A, B, C, D, E and F. Valve unit A controls the supply of hydraulic fluid to the jack 8 in a jack-extending sense and is connected to the branch supply line 14 and to a line 53 leading to the jack 8. Valve unit B is connected to the line 53 and to the branch return line 15.

Valve unit D controls the supply of hydraulic fluid to the jack 7 and jack 8 in a jack-contracting sense and is connected to the branch supply line 14 and to a line 54 leading to the jacks 7 and 8. Valve unit C is connected to the line 54 and to the branch return line 15.

Valve unit E controls the supply of hydraulic fluid to the props 6 and is connected to the branch supply line 14 and to the props 6 through a line 55 including a restrictor 56 and a non-return valve 57. Valve unit F controls the release of hydraulic fluid from the props 6 and is connected to a line 58 leading from the props 6 and to the branch return line 15. The line 58 includes a nonreturn valve 59, and a pressure relief valve 61 is connected in parallel with the valve unit F between the line 58 and the branch return line 15.

The valve units A and B are associated with a pivotallymounted lever 62 which is connected to a similar lever 63 associated with the valve units C and D. The levers 62 and 63 coordinate the action of valve units A, B, C and D. In those roof supports without a double-acting jack 8, valve units A and B and lever 62 are omitted. The action of valve units E and F are coordinated by a pivotally-mounted lever 64. The levers 62, 63 are ganged to one another as shown by the connection 60.

The valve assembly of each roof support 4 includes a pilot valve 65 which, before an advance of the roof support begins, closes the pilot line 17. The pilot valve 65 includes a valve member 66 urged towards a valve seat 67 by a spring 68, and also includes a piston 69 carrying a piston rod 71. The piston 69 can be moved against the force exerted by a spring 72 by a sufiicient hydraulic pressure in a line 73 to cause the piston rod 71 to lift the valve member 66 off the valve seat 67. The line 73 is connected to line 55. The piston rod 71 has a bore 75 which, when the piston rod 71 is not engaging the valve member 66, brings one side of the valve member 66 into communication with the branch return line 15. When piston rod 71 engages the valve member 66, the valve member 66 closes the bore 75.

Four non-return valves 76 are connected in the pilot line 17 to enable the roof support to be caused to undergo an advancing operation by the receipt of a signal along pilot line 17 from the adjacent left hand roof support or from the adjacent right hand roof support. A small restrictor 74 is connected in the pilot line 17 across pilot valve 65 to ensure that pressure cannot be trapped in the portion of pilot line 17 between valves 76 and valve unit C by providing a leak to the branch return line through the bore 75 in piston rod 71.

A prop resetting valve 83 is associated with the support-advancing jack 7. The resetting valve 83 includes a valve member 84 urged by a spring 85 into a valve seat 86 to isolate the chamber 87 of the jack 7 from a line 88 connected to valve unit F and to line 55 through a nonreturn valve 89. A lifter rod 91 can be moved to lift the valve member 84 oif its seat 36, as the jack 7 becomes contracted to the full extent intended, by a trip 93 carried by the piston rod 94 of the jack 7.

FIGURE 1 shows the cutting machine 3 traveling from left to right along the working face 2. After the cutting machine 3 has passed the first few roof supports 4 in the series, it is necessary to advance the conveyor 1 in front of these roof supports 4 and then to advance the roof supports 4. Each roof support 4 having a conveyoradvancing jack 8 is operated to cause the jack 8 to apply an advancing force to the conveyor 1, the roof support 4 being set against the roof and acting as an anchorage. This is achieved by pivoting lever 62 is an anticlockwise direction to open valve unit A and thus pressurizing the line 53 and the pushing side of jack 8. This movement of the lever 62 may be caused by manual operation of lever 62 or by pressurization of a hydraulic line 95 connected to valve unit B. The line 95 may be connected through a manually or remotely controlled valve to the main supply line 11. After the lever 62 has been pivoted in the anticlockwise direction to cause the jack 8 to be pressurized in the conveyor-advancing sense, a springoperated latch 96 holds the lever 62 in this position. The anticlockwise movement of lever 62 causes a similar movement of lever 63, but such movement does not change the state of valve units C and D from that shown in FIGURE 4. The latch 96 is connected to the pilot line 17 in such a manner that pressurization of the pilot line 17 releases the latch 96 so that valve unit A closes and returns lever 62 and consequently lever 63 to the position in FIGURE 4.

When the first portion of the conveyor 1 has been advanced, as shown in FIGURE 1, the roof supports 4 can then be advanced. The source 16 is operated to pressurize the pilot line 17 and hence a hydraulic pressure signal is sent along line 17 to the first roof support 4. Referring now to FIGURE 4, the hydraulic pressure signal reaches the roof support through the portion of line 17 shown in the upper left-hand part of FIGURE 4. The hydraulic pressure signal releases the latch 96 and operates on valve unit C to cause clockwise movement of levers 62 and 63. As a result, valve unit A closes, valve unit B opens, valve unit C closes and valve unit D opens. Thus the pushing or jack-extending side of jack 8 is connected to the branch return line 15, and the jackcontracting sides of the jacks 7 and 8 are connected through the line 54 with the branch supply line 14. The conveyor-advancing jack 8 is not actually connected to the conveyor 1 but merely pushes against the conveyor 1 when applying an advancing force to it. Therefore, at this stage, the jack 8 contracts and takes no part in advancing the support.

Line 54 is also connected by a line 99 to valve unit F, and the pressurization of line 54 causes the valve unit F to be opened to bring the line 58 into communication with the branch return line 15, thus releasing the hydraulic pressure in the props 6 and so releasing the roof support 4 from the roof. The jack 7 then contracts and advances the roof support 4 towards the conveyor 1 with the conveyor 1 acting as an anchorage.

When the jack 7 is contracted to the full extent intended, or in other words when the roof support is fully advanced up to the conveyor 1, the trip 93 on the piston rod 94 of the jack 7 engages the lifter rod 91 and opens the resetting valve 33. The line 38 is therefore brought into communication with the main supply line 11 through the branch supply line 14, now-open valve unit D, line 54, jack 7 and resetting valve 83. The pressure in line 88 acts upon valve unit F to close it and then passes through nonreturn valve 89, restrictor 56 and nonreturn valve 57 to extend the props 6 and so reset the roof support 4 against the roof.

The hydraulic pressure in line 88 is also present in line 73. When the props 6 have been extended to give a statisfactory roof-supporting force, as evidenced by a buildup of pressure in line 73 to a predetermined value, this value of pressure is arranged to operate on the piston 69 and to open pilot valve 65. Thus the portion of the pilot line 17 between the control valve 16 and the first roof support 4 is brought into communication with the portion of the pilot line 17 between the first roof support and the second roof support (that is the portion of the pilot line 17 in the lower left portion of FIGURE 4) with the result that the hydraulic pressure signal in the pilot line 17 reaches the second roof support in the series and causes it to undergo an advancing operation. In this way, each roof support in the group in advanced in turn.

If it is desired to operate the valve assembly 13 manually, this can be done by manually operating levers 62, 63, 64.

The mechanism so far described is not conventional, but is known, and has associated with it various mechanisms and controls, of which the present invention is one. This invention adds to the hydraulically operated basic system for automatic sequential advance of the roof supports a means to indicate a stoppage in an advancing sequence, as a result of some fault or abnormality; for it is most important that the operator be warned so that he can take necessary corrective or precautionary measures at once, leading eventually to correction of the fault and resumption of the automatic sequential advance of the roof supports in the series. Absent such warning, the mine roof lacks support as near as possible to the working face. If the roof supports do not advance when they should, operation of the cutter 3 and the conveyor 2 may have to be stopped immediately, and thus it is important, in carrying out the mining operation safely, that a stoppage in an advancing sequence should be brought to the attention of an operator soon as possible.

While an advancing sequence is taking place, the pressure in the main pressure line 11 will fluctuate as the various props and jacks are operated in the sequence, and maximum pressure, if attained at all during an advancing sequence, will only be attained for short periods. The pressure in the pressure line 11 will only be able to build up to and remain at maximum pressure, during an advancing sequence, if the advancing sequence stops before it is completed, for example by reason of a fault in a roof support or an obstruction preventing the advance of a roof support.

In accordance with this invention, a sequence stoppage indicating means 18 includes a pressure gauge 19 which is connected to the main pressure line 11 so as to indicate the pressure in it. The pressure gauge 19 has a pointer 21, which forms a movable contact in an electrical circuit. A fixed contact 22 is located in the pressure gauge 19 at a position which corresponds to the position of the pointer 21 when the pressure in the pressure line 11 is the maximum. The electrical circuit also includes a battery 23 and an audible and/ or visual warning device 24 which includes a conventional false start time delay and relay so that the device 24 is only actuated if the circuit is closed for more than a predetermined period of time, for example thirty seconds.

A hydraulic-pressure-operated electrical switch 25, biased to open, is also included in the electrical circuit and is connected to the pilot line 17 by a hydraulic line 26, so that a pressure in the pilot line 117 will be transmitted to the switch 25 so as to close it.

When no advancing sequence is taking place, there is no pressure in the pilot line 17 and therefore switch 25' is open and the warning device 24 cannot be operated even though the pressure in the pressure line illl may be maximum for a considerable time.

When an advancing sequence is taking place, the pilot line 17 is pressurized and this pressure is transmitted along line 26 to close switch 25. Each time the pressure in the pressure line 11 reaches the maximum, the pointer 21 engages the contact 22 and completes the circuit. However, temporary attainments of maximum pressure which may occur in the pressure line 11 during an advancing sequence will not cause the closure of the circuit since the time delay device at 24 permits closure only if the maximum pressure persists for more than the pre determined period of time.

The warning device 24 only operates if, during an advancing sequence, the pressure in the pressure line 11 remains at maximum for more than the predetermined period of time. As explained above, this can only happen if the advancing sequence stops before it is completed and, therefore, the operator is warned of such an event.

If the power unit 10 fails or a serious leak occurs in the hydraulic circuit, an advancing sequence may stop. Such a leakage will cause the pressure in the main pressure line 11 to fall to and remain at a low value. The pressure in the pressure line 11 may fall to such a low value for short periods during an advancing sequence, for example when the props 6 are being reset, and, therefore, only a low pressure for more than a predetermined period of time will indicate failure of the hydraulic system by leakage or failure of the power unit 10.

The pressure gauge 19 includes a contact 27 which is engaged by the pointer 21 if the pressure line 11 falls below a predetermined value. The contact 27 is connected to the warning device 24 by a connection which bypasses the switch 25. Therefore, the circuit to the warning device 24 will be completed eace time the pressure in the pressure line falls to the predetermined low value, but due to the delay included in the device at 24, the Warning device 24- will only operate if the low pressure is present for more than the predetermined period of time.

The operation of the warning device 24 by the occurrence of low pressure in the pressure line 11 is independent of the switch 25, that is to say if low pressure occurs for more than the predetermined period of time, the warning device 24 will operate whether an advancing sequence was in progress or not.

We claim:

1. A roof support assembly including a series of fluidpressure-operated advanceable roof supports, a source of fluid pressure, a conduit connecting said source with each roof support, each roof support including at least one fluid-pressure-operated prop to which said conduit is connected, and a fluid-pressure-operated means to advance it also connected to said conduit, and a control valve assembly individual to each roof support and operable to supply pressure fluid from such source to cause its roof support to undergo an advancing operation, each control valve assembly being arranged to send a signal to the control valve assembly of the next roof support, to initiate advance thereof, upon completion of the advance of its own roof support, a Warning device including a pressuresensitive means operatively connected to said conduit, and operable by departure of pressure therein from its normal range fluctuation occurring during an advancing operation, to indicate interruption of such operation, and time delay means operatively connected to said indicating means to delay its indication during such normal pressure fluctuations, but effecting such indication in the event of a continuing abnormal pressure in said conduit.

2. A roof support assembly including a series of fluidpressure-operated adva'nceable roof supports; a main source and a pilot source of fluid pressure; a main pressure conduit pressurized from said main source and operatively connected to the several roof supports to effect their advance; each roof support including at least one fluid-pressure-operated prop to which the main pressure conduit is connected, and a control valve operable to cause its roof support to undergo an advancing operation; a pilot pressure conduit operatively connected between the pilot pressure source and the control valves of the several roof supports in sequence; each control valve being arranged to send a fluid pressure signal along the pilot pressure conduit from its own roof support to the control valve of the next roof support, upon completion of the advancing operation of its own roof support, to initiate an advancing operation of the next roof support; a warning device connected to the main pressure conduit and operable by departure or pressure therein from its normal range of fluctuation occurring during an advancing operation, to indicate interruption of such advancing operation; and means operatively connected to said warning device to delay its indication during normal pressure fluctuations, but eifecting such indication in the event of a continuing abnormal pressure in the main pressure conduit.

3. A roof support assembly as in claim 2, wherein the warning device includes pressure-sensitive means shiftable under the influence of pressure in the main pressure conduit, from a null position towards a maximum position, but arranged to remain between such positions under the influence of normal pressure fluctuations in said main pressure conduit during an advancing operation, and a warning signal arranged for operation by said pressuresensitive means upon its reaching its maximum position under the influence of maximum pressure in the main pressure conduit occurring as a result of stoppage of an advancing operation.

4. A roof support assembly as in claim 3 wherein the delaying means is operatively interposed between the pressure-sensitive means and the Warning signal, to delay operation of the latter unless the pressure-sensitive means remains in its maximum position for a predetermined period of time.

5. A roof support assembly as in claim 3, wherein the Warning device includes means operable by the pressuresensitive means when the latter is in its null position, and arranged to operate the warning signal when the pressure sensitive means remains for a predetermined period of time in its null position.

6. A roof support assembly as in claim 5, wherein the delaying means is operatively interposed between the last- 8 mentioned means and the Warning signal, to prevent actuation of said signal during momentary movement of the pressure-sensitive means to its null position.

'7. A roof support assembly as in claim 2, including a connection from the pilot pressure conduit to the Warning device, said warning device including a pressure gauge movable from a 'null position towards a maximum position by pressure in the main pressure conduit, an electrically operable warning signal, an electric circuit including a switch closable by the pressure gauge in its maximum position, and also including the time delay means and the warning signal, and a switch in said circuit biased to open, but arranged to be closed by pressure in the pilot pressure conduit.

8. A roof support assembly as in claim '7, the circuit also including a switch arranged to be closed by the pressure gauge when the latter is in its null position, and a by-pass connection from said latter switch directly to the time delay means and the warning signal, by-passing the pilot-pressure'operated switch, to energize the warning signal by the pressure drop in the main pressure conduit when no advancing operation is occurring.

References Cited by the Examiner UNITED STATES PATENTS 758,819 5/1904 Callum 340-227 2,749,536 6/1956 Sperling 20083 2,959,156 11/1960 Dreptin 91-l 3,045,627 7/1962 Eek 73407 SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner.

Claims

1. A ROOF SUPPORT ASSEMBLY INCLUDING A SERIES OF FLUIDPRESSURE-OPERATED ADVANCEABLE ROOF SUPPORTS, A SOURCE OF FLUID PRESSURE, A CONDUIT CONNECTING SAID SOURCE WITH EACH ROOF SUPPORT EACH ROOF SUPPORT INCLUDING AT LEAST ONE FLUID-PRESSURE-OPERATED PROP TO WHICH SAID CONDUIT IS CONNECTED, AND A FLUID-PRESSURE-OPERATED MEANS TO ADVANCE IT ALSO CONNECTED TO SAID CONDUIT, AND A CONTROL VALVE ASSEMBLY INDIVIDUAL TO EACH ROOF SUPPORT AND OPERABLE TO SUPPLY PRESSURE FLUID FROM SUCH SOURCE TO CAUSE ITS ROOF SUPPORT TO UNDERGO AN ADVANCING OPERATION, EACH CONTROL VALVE ASSEMBLY BEING ARRANGED TO SEND A SIGNAL TO THE CONTROL VALVE ASSEMBLY OF THE NEXT ROOF SUPPORT, TO INITIATE ADVANCE THEREOF, UPON COMPLETION OF THE ADVANCE OF ITS OWN ROOF SUPPORT, A WARNING DEVICE INCLUDING A PRESSURE SENSITIVE MEANS OPERATIVELY CONNECTED TO SAID CONDUIT AND OPERABLE BY DEPARTURE OF PRESSURE THEREIN ITS NORMAL RANGE FLUCTUATION OCCURING DURING AN ADVANCING OPERATION, TO INDICATE INTERRUPTION OF SUCH OPERATION, AND TIME DELAY MEANS OPERATIVELY DURING SUCH NORMAL PRESSURE MEANS TO DELAY ITS INDICATION DURING SUCH NORMAL PRESSURE FLUCTUATIONS, BUT ABNORMAL PRESSURE IN SAID CONDUIT.