US3228302A

US3228302A - Roof support assembly

Info

Publication number: US3228302A
Application number: US283796A
Authority: US
Inventors: Bolton Douglas Herbert Hewlett
Original assignee: Dowty Mining Equipment Ltd
Current assignee: Dowty Mining Equipment Ltd
Priority date: 1962-06-07
Filing date: 1963-05-28
Publication date: 1966-01-11
Anticipated expiration: 1983-01-11
Also published as: DE1188022B; GB991009A

Description

Jan. 11, 1966 H. H. BOLTON ROOF SUPPORT ASSEMBLY 2 Sheets-Sheet 2 Filed May 28, 1963 J i .L

lNVENTOR DOUGLA H. H. BOLTON ATToQN EY United States Patent C) 3,228,302 ROOF SUPPORT ASSEMBLY Douglas Herbert Hewlett Bolton, Winchcombe, near Cheltenham, England, assignor to Dowty Mining Equipment Limited, Ashchurch, near Tewkesbury, England, a British company Filed May 28, 1963, Ser. No. 283,796 Claims priority, application Great Britain, June 7, 1962, 22,113/ 62 4 Claims. ((31. 91-189) This invention relates to roof support assemblies such as include fluidepressure-operated props.

The present invention provides a roof support assembly including a series of fiuid-pressure-operated advanceable roof supports, a source of fluid pressure for operation of the roof supports and means for automatically advancing the roof supports in a predetermined sequence, each roof support including a fluid-pressure-operated extendable and contractable prop having safety means operable by the extension of the prop to, or nearly to, its maximum length to stop an advancing sequence. By such provision, unless each roof support is extended sufiiciently to properly support its roof area, the advance of further roof supports is halted automatically until some appropriate action is taken. This prevents skipping an area of inadequate support, through lack of warning thereof, and compels corrective action before the automatic sequence can be resumed.

The safety means may include a valve which, when operated, prevents fluid under pressure from reaching subsequent roof supports in the series. The valve, when operated, may cause fluid under pressure from the source to leak away to a region of lower pressure.

The safety means may include a lost-motion connection having two parts which move relatively to each other as the prop extends and contracts, the lost-motion connection being so connected to the valve that as the prop reaches or nearly reaches its maximum length the lostmotion is fully used up and the valve is operated. Each part of the lost-motion connection may be in the form of a chain-link, one sliding within the other.

The present invention also provides a fluid-pressureoperated exten-dable and contractable prop including safety means operated by the extension of the prop to, or nearly to, its maximum length to indicate such an extension. The safety means may include a fluid-flow control valve, which may be operated by a lost-motion connection as described above.

During normal operation the prop is first contracted from its normal roof-supporting condition preparatory to undergoing an advance. Its construction, the subsequent advance of its roof support, and the normally ensuing extension of the prop to reset it in the advanced position against the roof are all accomplished automatically by pressure fluid controlled by mechanism that in its details is not a part of this invention, but which includes conduit means which in part lead from the control valve assembly of one roof support to the control valve assembly of the next roof support in the series, and which becomes pressurized by the completion of an advancing operation of the one roof support and the satisfactory resetting of the prop thereof securely against the roof. The lost-motion connection opens the safety valve of the roof support in the event that roof support reaches substantially its full extension without resetting securely, and the pressure fluid that normally would reset the prop of the roof support leaks away through the thus-opened safety valve to a region of lower pressure, wherefore the conduit means leading to the next roof support in the series is not pressurized, and thus the advancing operation of the next roof support is not initiated. Advance of this next and all subsequent roof supports is prevented until the one roof ice support is arranged by the operator to set securely against the roof. The present invention is concerned, in such a system, with the automatic means for halting an advancing sequence until the condition that produced the insecure setting of the one roof support has been cured.

One embodiment of the present invention will now be 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 of the mining apparatus showing the hydraulic connections,

FIGURE 3 is a similar view, partly in section, of one of the props, 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 acc mpanying 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 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 hydraulically-operable 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 hydraulicallyope'rable jack 8 for advancing the conveyor 2 relative to the roof support 4-.

The mining apparatus also includes a hydraulic power unit '9 which has a main pressure source 19 from which a hydraulic pressure supply line 11 and a hydraulic return line 12 extends along the working face 2. Each roof support 4' includes a hydraulic control valve assembly 13 to which the pressure line 11 and return line 12 are connectedby

branch lines

14 and 15 respectively. The control valve assembly 13 of each roof support 4 is connected to its props 6, jack 7 and jack 8 (if provided). The control valve assembly 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 assembly 13 causes the following operations to take place, automatically and 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. I

(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 valve assemblies 13is caused by a hydraulic pilot system. The power unit' 9 includes a source 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' assembly of each roof support 4 in turn. Each control valve assembly initially closes the pilot line 17. When the pilot source 16 is operated to pressurise the pilot 17, the hydraulic pressure in the piiot line 17 acts as a signal to the control valve assembly 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 assembly 13 is caused to open the pilot line so that the hydraulic pressure signal is then applied to the control valve assembly 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 State-s 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 non-return 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 pivotall'y-mounted 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 suflicient hydraulic pressure in a line 73 to cause the piston rod 71 to lift the valve member 66 olf 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 15 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 onto 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 non-return valve 89. A lifter rod 91 can be moved to lift the valve member 84 off its seat 86, as the jack 7 becomes fully contracted, 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 rig-ht 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 conveyor advancing 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 in 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 spring-operated 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 jack-contracting 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 fully contracted, 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 83. The line 88 is therefore brought into communication with the main supply line 11 through the branchv 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 non-return valve 89, restrictor 56 and non-return 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 satisfactory 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 is 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. The present invention adds to such a system a safety valve that will automatically interrupt the automatic continuation of its advance in the event any prop in the series cannot be extended far enough to reset securely against the roof, until such time as the operator takes steps to insure that such prop will adequately bear its share of the loading. The present invention therefore concerns such automatically operable safety means incorporated in such a system for effecting automatically sequential advance under fluid-pressure control.

During the operation of this mining apparatus, it may happen that when one of the roof supports 4 has advanced, its props 6 may become fully extended and yet not support the roof. For example, the roof support may have advanced to a position where there is a hole in the roof. If this happens, it is desirable that, in the interests of safety, some action should be compelled, to which end stoppage of the sequence of operations should automatically take place.

In accordance with this invention, at least one of the props 6 of each roof support 4 is constructed as shown in FIGURE 3. The prop 6 includes a base 18 carrying an outer cylinder 19 in which is slidably mounted an inner cylinder 20. One end of the inner cylinder 20 projects from the outer cylinder 19 and carries a head 21. The head 21 includes a conduit 22 connected to the corresponding control valve assembly 13 and communicating with the pressure chamber 23 of the prop. The control valve assembly 13 controls the supply of hydraulic fluid to, and return of hydraulic fluid from, the pressure chamber 23 via the conduit 22 and thus controls extension and contraction of the prop.

The conduit 22 also communicates with a chamber 24 in the head 21, which chamber 24 is normally prevented from communicating with a further conduit 25 in the head 21 by a valve-closure member 26 which is resiliently urged against a valve seat 27 in the chamber 24 by a spring 28 housed in the head 21. The conduit 25 connects to a low pressure region, such as the return line 12.

The valve-closure member 26 is secured to a stem 29 which is connected to a chain-link 31. This chain-link forms one part of a lost-motion connection whose other part is formed by a second chain-link 32 secured to the base 18. The chain-link 31 can slide in the chain-link 32. Other lost-motion means might be employed instead of the form shown.

The innermost end of the inner cylinder 20 carries a stop 33 which includes a sealing assembly (not shown) to prevent loss of fluid between the outer cylinder 19 and the inner cylinder 20 from the chamber 23. The outer cylinder 19 carries a stop 34 at its end remote from the base 18. Maximum extension of the prop occurs when the stop 33 engages the stop 34. The stop 34 also acts as a bearing for the inner cylinder 20 as it slides relatively to the outer cylinder 19. In normal operation of the prop, the prop does not extend to its maximum length and the chain-

links

31, 32 slide one within the other. If

the prop should nearly reach its full extension, the lower end of the link 31 will engage the upper end of the link 32 so that the lost-motion is fully used up and further extension of the prop will cause the link 32 to pull the link 31 away from the head 21, thus unseating the valveclosure member 26 from the seat 27 and bringing the chamber 24 into communication with the conduit 25. Since the conduit 25 is connected to the return line 12, and as conduit 22 will be in communication with the pressure line 11 at this stage of operation, the pressure in the pressure line 11 will be lost into the return line 12 and the advancing sequence will stop. Thus thevalve 26, 27 and the lost-motion connection forms a safety means which indicates that a prop in a roof support is fully extended, and in consequence the advancing sequence is stopped.

The stoppage of the advancing sequence may be detected by the method and apparatus described in United States Patent Application Serial No. 282,396, filed May 22; 1963, and the location of the fully extended prop can be determined by apparatus such as is described in United States application Serial No. 282,412, filed May 22, 1963.

If desired, instead of the

valve

26, 27 being operated to exhaust the pressure line 11 into the return line 12, it may be arranged that the

valve

26, 27 operates to shut 011 the pressure line 11 from subsequent roof supports in the series and therefore stop the advancing sequence.

In the mining aparatus described, the means for automatically advancing the roof supports is all-hydraulic. If the means for automatically advancing the roof supports includes an electrical circuit then, instead of being provided with the

valve

26, 27 at least one prop in each roof support may include electrical means which are actuated by the extension of the prop to, or nearly to, its maximum length to cause the advancing sequence to stop. The electrical means may include two contacts, one carried by the outer cylinder and the other carried by the inner cylinder, which contacts engage one another when the prop is fully, or nearly fully, extended.

I claim as my invention:

1. A roof support assembly for mines, including a series of advanceable roof support-s, a source of fluid pressure, conduit means connecting said source with the several roof supports, each roof support including at least one two-part fluid-pressure-operated prop extensible into roof-supporting disposition and contractible from such disposition, jack means arranged to advance each support while the prop is contracted, a control valve assembly individual to each roof support and connected between said conduit means and said prop, and operable to contract the prop upon initiation of the advancing operation of its roof support, and to extend the same against the roof at completion of such operation, each control valve assembly including means responsive to the attainment of a predetermined roof-setting pressure in its prop to send a signal by way of said conduit means to the control valve assembly of the next roof support In the series, to initiate an advancing operation thereof, a normally closed valve at each prop, interposed in said conduit means, and means interengageable between the two parts of each prop upon extension of such prop beyond its normal limit during resetting, and operatively connected to said valve to open the same in such event, and thereby to prevent the sending of the initiating signal to the next roof support.

2. A roof support assembly as in claim 1, wherein the conduit means includes a pressure supply conduit connected to the prop and a return conduit to a low pressure region, said valve being carried by one part of the prop and located intermediate the prop and such low pressure region, and the valve-opening means includes an element connected directly to the other part of the prop and connected by a lost-motion connection to the valve, of an efl ective length somewhat less than the full extension of the prop, to open the valve in the event the prop extends beyond a predetermined limit.

3. A roof support assembly including a source of fluid pressure and a series of advanceable roof supports, each roof support having at least one fiuid-pressure-operated contractible and extensible prop operable to extend the support against a roof and a fluid-pressure-operated jack operable to advance the support, each roof support also including a control valve assembly controlling the supply of fluid under pressure from the source to the prop and the jack, each control valve assembly being operable to cause its roof support to undergo an advancing operation in which the prop is contracted from a roof-supporting condition, the support is advanced by the jack, and the prop is extended to a roof-supporting condition, each control valve assembly responsive to the attainment of a predetermined roof-supporting fluid pressure in the prop, as the prop is extending, to cause the operation of the control valve assembly of the next roof support in the series, and each prop including a valve operated by the extension of the prop substantially to its maximum length to prevent said predetermined roof-supporting fluid pressure from being attained.

4. A roof support assembly for mines, including a series of advanceable roof supports, a source of fluid pressure, conduit means connecting said source with the several roof supports, each roof support including at least one two-part fluid-pressure-operated prop extensible into roofsupporting disposition and contractible from such disposition, jack means arranged to advance each roof support while its prop is contracted, a control assembly individual to each roof support and including valve units connected between said conduit means and its prop, and operable to contract the prop upon initiation of the advancing operation of its roof support, and to extend the prop at completion of such operation, a connection between the control assemblies of the several roof supports, for transmission of a signal from one such assembly, upon completion of its advancing operation, to the next assembly, to initiate an advancing operation of the latter, each control assembly including means responsive to the attainment of a predetermined roof-setting pressure in its prop, to transmit a signal by way of said connection to the control assembly of the next roof support in the series, to initiate an ad vancing operation thereof, means in said conduit means, normally inactive, but operable to prevent operation of the signal-transmitting means, and means interengageable between the two parts of each prop upon extension of such prop beyond its normal limit during resetting, and operatively connected to said transmission-preventing means to actuate the latter in such event.

References Cited by the Examiner UNITED STATES PATENTS 1,108,952 9/1914 Wales 911 1,905,065 4/1933 Scholl. 2,753,036 7/1956 Joy 248-356 2,826,165 3/1958 Adelson 911 3,148,591 9/1964 Sheesley 91-1 FOREIGN PATENTS 1,201,174 12/1959 France. 1,033,612 7/1958 Germany. 1,123,640 2/1962 Germany.

843,354 8/1960 Great Britain.

SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner.

Claims

1. A ROOF SUPPORT ASSEMBLY FOR MINES, INCLUDING A SERIES OF ADVANCEABLE ROOF SUPPORTS, A SOURCE OF FLUID PRESSURE, CONDUIT MEANS CONNECTING SAID SOURCE WITH THE SEVERAL ROOF SUPPORTS, EACH OF SUPPORT INCLUDING AT LEAST ONE TWO-PART FLUID-PRESSURE-OPERATED PROP EXTENSIBLE INTO ROOF-SUPPORTING DISPOSITION AND CONTRACIBLE FROM SUCH DISPOSITION, JACK MEANS ARRANGED TO ADVANCE EACH SUPPORT WHILE THE PROP IS CONTRACTED, A CONTROL VALVE ASSEMBLY INDIVIDUAL TO EACH ROOF SUPPORT AND CONNECTED BETWEEN SAID CONDUIT MEANS AND SAID PROP, AND OPERABLE TO CONTACT THE PROP UPON INITIATION OF THE ADVANCING OPERATION OF ITS ROOF SUPPORT, AND TO EXTEND THE SAME AGAINST THE ROOF AT COMPLETION OF SUCH OPERATION, EACH CONTROL VALVE ASSEMBLY INCLUDING MEANS RESPONSIVE TO THE ATTAINNMENT OF A PREDETERMINED ROOF-SETTING PRESSURE IN ITS PROP TO SEND A SIGNAL BY WAY OF SAID CONDUIT MEANS TO THE CONTROL VALVE ASSEMBLY OF THE NEXT ROOF SUPPORT IN THE SERIES, TO INITIATE AN ADVANCING OPERATION THEREOF, A NORMALLY CLOSED VALVE AT EACH PROP, INTERPOSED IN SAID CONDUIT MEANS, AND MEANS INTERENGAGABLE BETWEEN THE TWO PARTS OF EACH PROP UPON EXTENSION OF SUCH PROP BEYOND ITS NORMAL LIMIT DURING RESETTING, AND OPERATIVELY CONNECTED TO SAID VALVE TO OPEN THE SAME IN SUCH EVENT, AND THEREBY TO PREVENT THE SENDING OF THE INITIATING SIGNAL TO THE NEXT ROOF SUPPORT.