US3196756A

US3196756A - Roof support assemblies

Info

Publication number: US3196756A
Application number: US314324A
Authority: US
Inventors: Douglas H H Bolton; Michael C Potts
Original assignee: Dowty Mining Equipment Ltd
Current assignee: Dowty Mining Equipment Ltd
Priority date: 1962-10-10
Filing date: 1963-10-07
Publication date: 1965-07-27
Anticipated expiration: 1982-07-27
Also published as: DE1192140B; GB993670A

Description

y 1965 p. H. H. BOLTON ETAL 3,196,7 6

ROOF SUPPORT ASSEMBLIES Filed Oct. '7, 1963 2 Sheets-Sheet 1 E m am HYDRAULIC PRESSURE SOURCE N LINE 1 I PILOT ESSURE sounce SECONDARY PILOT LINE lNvENToRs ua- Pom.- BY am. H-H. BeLTon ATTQQNEY! United States Patent 3,196,756 R0635 SUPPORT ASSEMBLIES Douglas H. H. Bolton, Winchcombe, near Cheltenham, and Michael C. Potts, Prestbury, Cheltenharn, England, assignors to Dowty Mining Equipment Limited, a British company Filed Uct. 7, 1963, Ser. No. 314,324 Claims priority, application Great Britain, 0st. 10, 1952, 38,395/62 16 Claims. (Cl. 92-5) This invention relates to roof support assemblies suitable for use in mines.

The present invention concerns a roof support assembly including a series of fluid-pressure-operated roof supports arranged to advance sequentially, a source of fluid pressure connected to the roof supports for operating the roof supports, a fluid-carrying line along which fluid passes when each roof support undergoes an advancing operation, and incorporates in such an assembly soundproducing means responsive to the fluid pressure in the fluid-carrying line and arranged to emit one sound when the pressure is above a chosen value and a different sound when the pressure is below a chosen value, the values being chosen so that the variation in pressure which occurs in the tluidcarrying line when each roof support undergoes an advancing operation causes a change from one sound to the other.

The sounds may differ in pitch, quality or loudness.

The fluid-carrying line may be that one which carries fluid under pressure from the source to the roof supports or it may be that one which carries the return flow of fluid from the roof supports.

When a fiuid-pressure-operated roof support of the type described in general terms undergoes an advancing operation, a flow of fluid with a consequent drop in pressure will occur in a fluid-carrying line, normally in that line (hereinafter termed the pressure line) which carries the fiuid from the source to the roof supports, this flow being due, for example, to the extension or contraction of a prop which forms part of the roof support or of a jack connected between the roof support and an anchorage such as a conveyor or another roof support. Where the sound-producing means is responsive to pressure in this line, and because the pressure in this line varies at different stages of the operation, one sound will be ernitted before this flow occurs, and pressure in the line is still high, but while the flow is taking place and in consequence pressure in the line has dropped, the other sound will be emitted. When the flow ceases, the pressure will rise again and the first sound will be emitted. Where the fluid-carrying line is a return line connected to each sup- I port, and the sound-producing means is responsive to pressure in the return line, rather than to the pressure in the pressure line, the two sounds will occur alternately as the roof support undergoes an advancing operation due to the variation of flow in the return line. Thus as the roof supports advance successively, the sounds alternate. A distant operator is thereby informed at what stage is the advance, and if the advance halts before the sequence is completed, he can take appropriate action.

After an advancing sequence of the series of roof sup ports has been initiated, interruption of the regular alternation of the two sounds and the continued emission of one sound indicates that the advancing sequence has stopped. If this occurs before the last roof support in the series has advanced, this indicates a fault and the cause of the stoppage can be investigated.

Where the fluid-carrying line is that one which carries fluid from the source to the roof supports, the part of the sound-producing means which emits the said one sound when the pressure is above the chosen value may be rendercd inoperable by the completion of an advancing sequence of the series of roof supports and rendered operable by the initiation of an advancing sequence of the series of roof supports. In these circumstances the part of the soundproducing means which emits the dir erent sound when the pressure is below the chosen value may T31 lain operable after the completion of an advancing sequence of the series of roof supports. When an advancing sequence is not supposed to be taking place, the occurrence of this sound indicates an unwanted loss in pressure in the fluid-carrying line.

One embodiment of the present invention will now be described, by Way of example, with reference to the accompanying drawings, of which,

FZG. 1 is a diagrammatic plan View of mining apparatus, with the hydraulic connections and roof bars omitted,

FIG. 2 is a similar View on a larger scale of part of the mining apparatus showing the hydraulic connections and,

FIG. 3 is a similar view of the warning system in the apparatus, such as the present invention concerns.

The principal parts of the roof support assembly have been disclosed in numerous applications such as the two specifically referred to hereinafter, and need not be described in detail here. It is sufiicient to point out that the coal mining apparatus as a whole includes a conveyor 1 which extends along the working face 2 of a coal mine and acts as a guide means for a coal cutting machine 3. A series of hydraulically-operable roof supports 4 are arranged along the working face 2 and lie on the opposite side of the conveyor l to the Working face 2.

Each roof support 4 includes a ground-engaging sole beam 5 which carries a number, for example three as shown, of hydraulically-operable telescopic props 6 and a roof-engageable bar (not shown) carried by the props 6. Each roof support 4 is connected to the conveyor 1 by a single-acting hydraulically-operable jack 7 anchored to the conveyor 1, and acting to advance the roof support 4- up to the conveyor 1 when properly actuated, and some roof supports 4 (for example every fourth roof support as shown) have a double-acting hydraulically-operable jack 8 for advancing the conveyor 1 relative to the-roof support 4 using the roof support 4 as an anchorage.

.A hydraulic power unit 9, the details whereof that do not concern this invention being omitted, is located at one end of the working face 2 and a main hydraulic pressure line 11 and a hydraulic return line 12 extend from a source it) of hydraulic pressure in the power unit 9 along the working face 2. Each roof support 4 includes a hydraulic control valve 13, many of the details whereof do not concern this invention, hence are not shown, to which the pressure line 11 and return line 12 are connected by

lines

14 and 15 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 providedwith a jack 8 may be so arranged that the jack 8 is urging the conveyor 1 towards the working face 2 continually except when the roof support 4 is being advanced. If desired, however, the control valve 13 of each roof support 4 provided with a jack 8 may be operable to cause the jack 8 to urge the conveyor 1 towards sure 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 13 initially closes the pilot line 17. When the pilotsource 16 is operated to pressurise the pilot line 17, the hydraulic pressure in the pilot line 1'7 acts as a signal to the control valve 13 of the first roof support 4, which then undergoes an advancing operation in the following manner.

(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 4 from the roof.

(c) The jack 7 is caused to advance the roof support 4 up to the conveyor 1.

(d) After support advance has been completed, the jack 7 is caused to cease urging the roof support 4 forwardly, and the props 6 are extended to reset the roof support 4 against the roof.

All such operations are effected automatically, in sequence, and constitute the subject of a companion application. However, they are explained here in order to make clear the need for and the operation of this invention. I

When the roof support 4 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 open the pilot line 17 so that the hydraulic pressure signal is then applied to the control valve 13 of the next roof support 4, which then undergoes an advancing operation. Thus each roof support 4 in turn undergoes an advancing operation.

When the last roof support in the series has completed its advancing operation, its control valve 13 opens the pilot line 17 to a secondary pilot line 18 which therefore becomes pressurised. The secondary pilot line 18 is connected to a control valve 19 on the first roof support 4 and also to the pilot pressure source 16. Pressurisation of the secondary pilot line 18 causes the pilot pressure source 16 to be disconnected from the pilot line 17 so that the pressure in the pilot line 17 is lost. When the conveyor 1 has been advanced a predetermined distance relative to the first roof support 4, the control valve 19 is operated by the extension of the jack 7 to first connect the secondary pilot line 18 to a line 21 and then connect the secondary pilot line 18 to a line 22.

Line 21 is connected to the warning system 23 that constitutes the subject of this invention, and which will be described later, and line 22 is connected to the pilot pressure source 16 in such a manner that pressurisation of line 22 from line 18, following advance of the last roof support and operation of the control valve 19, causes the pilot pressure source 16 to be connected again to the main pilot line 17 so that the series of roof supports 4 begin another sequence of advancing operations, and at the same time the pressure in the secondary pilot line 18 and lines 21 and 22 is lost.

The present application is one of a series to related subject matter, and the basic mining apparatus is further disclosed in some detail in such other applications, not necessary to list here, but particular reference is made to Serial Nos. 282,760, filed May 23, 1963, and 314,132, filed October 7, 1963. This application is directed to the fluid-pressure-operated sound-producing signaling means such as can be readily incorporated in such known roof support assembly.

In accordance with this invention, the warning system 23, shown in detail in FIG. 3 is provided. The warning system 23 includes an electrical A.C. source 24, a main switch 25, and a transformer 26 with

output lines

27, 28. The line 27 is connected to a low pitch bell 29, a counter 31 and a high pitch bell 32. If desired, a series of high pitch bells 33 may be provided at intervals along the working face 2, each of these bells 33 being connected to line 27. The line 28 is connected to three further 4

lines

34, 35, 36 of which

lines

34, 35 are connected to line 37. Line 37 is connected to high pitch bell 32 and high pitch bells 33.

Line 34 includes a manually-operable normally-open switch 33. Line 35 includes a switch 39 and a twoway switch 41. Switch 39 is operated by a pressure transducer 42 responsive to the hydraulic pressure in the main pressure line 11. When the hydraulic pressure in the main pressure line 11 is less than a chosen value, say 2,000 pounds per square inch, the transducer 42 maintains the switch 39 in its open position and, when this pressure is above the chosen value, the transducer 42 closes the switch 39. This chosen value is slightly less than the maximum pressure in the main pressure line 11.

Switch 41 is operated by a pressure transducer 43 responsive to the hydraulic pressure in the secondary pilot line 18. When the hydraulic pressure in the secondary pilot line 18 indicates that an advancing sequence of the series of roof supports 4 is in progress, for example when the pressure is less than 1,500 pounds per square inch, the transducer 43 maintains the switch 41 in the position shown in the drawings, that is to say bringing one side of switch 39 into communication with line 37. When the hydraulic pressure in the secondary pilot line 18 indicates that an advancing sequence of the series of roof supports 4 has been completed, for example when the pressure is greater than 1,500 pounds per square inch, the transducer 43 operates the switch 41 in such a manner that, instead of being in communication with line 37, switch 39 is brought into communication through line 44 with a resetting mechanism in the counter 31.

A line 45 extends from the portion of line 35 between switches 39 and 41 to one side of a switch 46, the other side of which is connected to line 37. Switch 46 is operated by a pressure transducer 47 responsive to hydraulic pressure in line 21. A hydraulic pressure occurs in line 21 just before an advancing sequence of the series of roof supports is about to commence, but is lost at the start of the advance. This pressure may be, for example,

rather more than 1,500 pounds per square inch, the pres sure in the line 21 at other times being negligible. Therefore, when the pressure in line 21 is less than 1,500 pounds per square inch, transducer 47 maintains switch 46 in an open position, and when the pressure in line 21 is greater than 1,500 pounds per square inch, indicating that an advancing sequence is about to begin, transducer 47 closes switch 46.

Line 36 is connected to one side of a switch 48, the other side of which is connected by line 49 to one side of the low pitch bell 29 and connected by line 51 to one side of the counter 31, the other sides of the low pitch bell 29 and counter 31 being connected to line 27. Switch 48 is operated by a pressure transducer 52 responsive to hydraulic pressure in the main pressure line 11. When the hydraulic pressure in the main pressure line 11 is below a chosen value, say 400 pounds per square inch, transducer 52 maintains the switch 48 in a closed position, and when this pressure is above the chosen value, transducer 52 opens switch 48. This chosen value is slightly more than the minimum pressure which occurs in the main pressure line 11 when a roof support 4 is undergoing an advancing operation.

Thus, in operation of the mining appartus, and assuming that no advancing sequence of the series of roof supports 4 is taking place, the hydraulic pressure in the main pressure line 11 will be at its maximum and the secondary pilot line 18 will be pressurised. Therefore switch 39 will be in its closed position and switch 41 will be connecting switch 39 by way of line 44 to the resetting mechanism of counter 31, which is thereby reset to give a zero reading. Switch 43 is in its open position since pressure in the main pressure line 11 is high, and switch 46 is in its open position since warning line 21 is not pressurised. In this condition of the electrical circuit neither the low pitch bell 29 nor the

high pitch bells

32 and 33 operate.

As explained previously, warning line 21 becomes pressurised just before an advancing sequence of the series of roof supports 4 commences. When this occurs, transducer 47 closes switch 46, thereby completing a circuit to the

high pitch bells

32 and 33 which therefore operate. Then, as pilot line 17 is pressurised by the pilot pressure source 16, line 18 is de-pressurised and transducer 43 operates switch 41 to connect switch 39 to line 37. Also line 21 is de-pressurised and transducer 47 opens switch 46. Then the electrical current to the

high pitch bells

32 and 33 is now through switch 41 instead of switch 46, and the

high pitch bells

32 and 33 continue to operate.

As the first roof support 4 undergoes an advancing operation, the pressure in the main pressure line 11 will fall, first to a value vsufficient to cause transducer 42 to open switch 39 and break the circuit to

high pitch bells

32 and 33, and then to a value sufiicient to causetransducer 52 to close switch 48 and complete the circuit to low pitch bell 29 and the counter 31, which both operate. When the roof support has finished its advancing operation, the pressure in the main pressure line 11 will increase to or nearly to its maximum value again. As the pressure increases, the circuit to low pitch bell 29 and counter 31 will be broken and the circuit to

high pitch bells

32 and 33 will be completed.

The same procedure will occur when each roof support 4 undergoes an advancing operation. Therefore, when an advancing sequence of the series of roof supports 4 is taking place, the low pitch bell 29 and the

high pitch bells

32 and 33 operate alternately. If the advancing sequence stops before it has been completed, either one sound will be emitted continually or there will be no sound at alldepending upon the hydraulic pressure in the main pressure line 11.

While each roof support 4 is undergoing an advancing operation, the low pitch bell 29 and the counter 31 may operate more than once. In this case, the counter 31 will be arranged to indicate the advance of each roof support by the receipt of a number of electrical pulses corresponding to the number of times the switch 48 closes during the advance of each roof support 4.

When the last roof support 4 in the series has completed its advancing operation, line 18 becomes pressurised and transducer 43 operates switch 41 to cause switch 39 to be connected to the counter 31 instead of line 37. Thus the counter 31 is reset to Zero and the operation of

high pitch bells

32 and 33 is prevented until another advancing sequence commences.

While no advancing operation is taking place, the low pitch bell 29 remains operable and will give a warning if a serious leak occurs in the main pressure line 11, that is to say if the main pressure falls low enough to cause transducer 52 to close switch 48.

If desired,

high pitch bells

32 and 33 may be operated independently of the hydraulic pressure in the main pressure line 11 and whether or not an advancing sequence is taking place, by manual operation of switch 38. This enables testing of the

bells

32, 33.

Additional low pitch bells which ring at the same time as the low pitch bell 29 may be provided at intervals along the working face if desired, in addition to or in place of the high pitch bells 33.

We claim as our invention:

1. A roof support assembly including a series of fluidpressure-operated roof supports arranged to advance sequently, a source of fluid pressure connected to the roof supports for operating the roof supports, a fluid-carrying line along which fluid passes when each roof support undergoes an advancing operation, and sound-producing means responsive to the fluid pressure in the fluid-carrying line and arranged to emit one sound when the pressure is above a chosen value and a diffierent sound when the pressure is below a chosen value, the values being so chosen that the variation in pressure which occurs in the fluid-carrying line when each roof support undergoes an 6 advancing operation causes a change from one sound to the other.

2. A roof support assembly according to claim 1 wherein the fluid-carrying line carries fluid under pressure from the source to the roof supports.

3. A roof support assembly according to claim 2 wherein including means to render inoperable the part of the sound-producing means which emits the said one sound when the pressure is above the chosen value by the completion of an advancing sequence of the series of roof supports, and to render the same operable again by the initiation of an advancing sequence of the series of roof sup ports.

4. A roof support assembly according to claim 3 including means sensitive to pressure in the fluid-carrying line to maintain operable the part of the sound-producing means which emits the different sound when the pressure is below the chosen value, after the completion of an advancing sequence of the series of roof supports.

5. A roof support assembly comprising a series of fluid-pressure-operated roof supports arranged to advance sequentially, a source of fluid pressure and conduits connecting said source and the several roof supports to effect such advance thereof, said conduits including a pressurized fluid-carrying line along which fluid passes at the time of an advancing sequence, and in which the pressure is difiierent at difierent stages of the sequence, two sound-producing means, and means connected to said fluidcarrying line and subject to pressure therein, and operatively connected to said sound-producing means, said means including devices responsive to pressure in the line above a chosen value to energize one sound-producing means and not the other, and devices responsive to pressure in the line below a chosen value to energize the other sound-producing means but not the one.

6. A roof support assembly according to claim 5, wherein the fluid-carrying line constitutes the same line which carries fluid under pressure from the source to the several roof supports.

7. A roof support assembly according to claim 6, including a secondary pilot line arranged to be pressurized only upon completion of an advancing sequence, said secondary pilot line being operatively connected to the devices for energizing the one sound-producing means to render the one sound-producing means inoperable upon completion of the advancing operation, and to render the same operable upon initiation of an advancing sequence.

8. A roof support assembly according to claim 7, including a further line arranged to be temporarily pressurized immediately before initiation of an advancing sequence, and operatively connected to the devices for energizing one of the two sound-producing means, whereby temporary pressurization of said further line operates a sound-producing means to effect a Warning of the initiation of an advancing sequence.

9. A roof support assembly comprising a series of fluid-pressure-operated roof supports arranged to advance means to produce a sound difiering from the first, a

pilot pressure source, a primary pilot line extending from the pilot pressure source to the several roof supports, and upon passage of pressure initiating advance of each roof support in turn, a secondary pilot line arranged to be pressurized upon completion of an advancing sequence, and connected to the control valve of the first roof support in the series, to actuate said control valve upon pressurization of said secondary pilot line, a line extending from said control valve to the warning system, and a further line extending from said control valve to the pilot pressure source to reconnect the latter through the primary pilot line to the series of roof supports for initiation of a further advance thereof, said warning system also including a first and a second circuit including respectively first and second sound-producing means, and pres: sure-sensitive means operatively connected to the respective circuits to energize the circuit that contains the first sound-producing means during advance of each roof sup.- port, and at that time to deenergize the second soundproducing means, and to energize the second sound-producing means, and to deenergize the first, upon completion of the advance of each roof support.

It A roof support assembly according to claim 9, wherein the pressure-sensitive means include a transducer sensitive to pressure in the secondary pilot line, arranged to close a switch in the circuit of and to render operable the first sound-producing means When no pressure is in the secondary pilot line, another transducer sensitive to pressure in the main hydraulic pressure line and arranged to close a corresponding and normally open switch in 8 l the circuit of and to complete energization of the first sound-producing means when pressure in said line is above a predetermined value, a further transducer sensitive to pressure in, the line between the control valve and the warning system, and operable to closea normally open switch connected in circuit between the two firstrnentioned switches and the first sound-producing means, to provide an alternative circuit forthe latter, and a still further transducer sensitive to pressure in the main hydraulic pressure line to a switch in the second soundproducing means when pressure in that line is below a predetermined value, during advance of a roof support.

No references cited.

SAMUEL LEVINE, Primary Examiner. RICHARD B. WILKINSON, Examiner.

Claims

1. A ROOF SUPPORT ASSEMBLY INCLUDING A SERIES OF FLUIDPRESSURE-OPERATED ROOF SUPPORTS ARRANGED TO ADVANCE SEQUENTLY, A SOURCE OF FLUID PRESSURE CONNECTED TO THE ROOF SUPPORTS FOR OPERATING THE ROOF SUPPORTS, A FLUID-CARRYING LINE ALONG WHICH FLUID PASSES WHEN EACH ROOF SUPPORT UNDERGOES AN ADVANCING OPERATION, AND SOUND-PRODUCING MEANS RESPONSIVE TO THE FLUID PRESSURE IN THE FLUID-CARRYINGING LINE AND ARRANGED TO EMIT ONE SOUND WHEN THE PRESSURE IS ABOVE A CHOSEN VALUE AND A DIFFERENT SOUND WHEN THE PRESSURE IS BELOW A CHOSEN VALUE, THE VALUES BEING SO CHOSEN THAT THE VARIATION IN PRESSURE WHICH OCCURS IN THE FLUID-CARRYING LINE WHEN EACH ROOF SUPPORT UNDERGOES AN ADVANCING OPERATION CAUSES A CHANGE FROM ONE SOUND TO THE OTHER.