GB2076446A

GB2076446A - Borehole plug

Info

Publication number: GB2076446A
Application number: GB8111908A
Authority: GB
Original assignee: Thermoplast & Apparatebau GmbH
Current assignee: Thermoplast & Apparatebau GmbH
Priority date: 1980-04-17
Filing date: 1981-04-15
Publication date: 1981-12-02
Also published as: FR2480850A1; GB2076446B; DE3014834A1; BE888407A; FR2480850B1; DE3014834C2

Abstract

An expandable plug for a bore- hole, particularly for bore-holes to be filled under pressure to consolidate rock in the underground mining of coal, comprises a hollow flexible plug section 16 at the opposite ends of which are provided with valve blocks 12, 14 each of which comprises a non-return valve 60, 62, 68,70. The non-return valves are both aligned in the same direction of through-flow and the valve 68, 70 which is situated downstream in the through-flow direction has a pretensioning such that it allows the passage of fluid from the plug section when the internal pressure in the plug section reaches a predetermined value. When the plug is inserted in a bore-hole, a foamed material is pumped into the plug through the valve 60, 62 and the pretensioning of the valve 68, 70 at the other end of the plug allows the build up of pressure within the hollow plug section 16 which expands to fill and seal the bore-hole. As the internal pressure increases further, the valve 68, 70 opens to allow the passage of further foamed material through the plug. <IMAGE>

Description

SPECIFICATION Plug for a bore-hole The invention relates to a plug for a bore-hole, particularly for bore-holes to be filled under pressure to consolidate rock in the underground mining of coal.

To achieve consolidation of rock in underground coal mining, bore-holes are drilled into the rock in accordance with a known procedure and these bore-holes are filled under pressure with foamed material. Dowel-shaped metal plugs are used for this purpose, which plugs, acting as a connection for a feed line or feeding device, are inserted into the bore-hole and which, after the foamed material pressed into the borehole has hardened, are removed again if possible.

The known dowel-shaped metal plugs are designed in the form of expanding plugs. The dowel or plug is first introduced into the bore-hole in its unexpanded state whereupon the plug is then forced apart in a second operation, for example by screwing in an expander, in order to seal the bore-hole tight.

Bore-hole plugs of this type are relatively costly to construct and manipulation of the plugs also calls for a relatively great amount of work.

The object underlying the invention is therefore to provide a bore-hole plug which, while having at least the same effectiveness, can be manufactured and handled more cheaply.

This object is achieved in that two oppositely lying ends of a hollow flexible plug section are each provided with a valve block, that each valve block contains a non-return valve, that the two non-return valves have the same direction of throughflow, and that the valve which is situated downstream in the throughflow direction is subjected to a pretensioning which limits the internal pressure of the plug section.

A bore-hole plug of this type is relatively simple and cheap to manufacture, special operations no longer being required to expand the bore-hole plug in the bore-hole after the plug has been introduced into the bore-hole. Only the feed line or filling device is connected and the foamed material under pressure is introduced. In this case the hollow flexible plug section expands first in order to seal the bore-hole, whereupon the valve situated downstream opens when a predetermined pressure is exceeded and allows the foamed material to flow into the now sealed bore-hole.

With the known bore-hole plugs it was desirable, not only for cost reasons, for the borehole plug inserted in the bore-hole to be removed again if possible, after the foamed material pressed into the bore-hole had hardened. As these known bore-hole plugs were made of metal, there was actually a danger that the boring head of the mining equipment would be damaged or even destroyed during subsequent coal mining by mining equipment striking against the plug left in the bore-hole. Even though it was therefore desirable for the bore-hole plug to be removed again from the bore-hole, which involved further expenditure of work, this was not always successful so that the mining equipment was endangered.

The bore-hole plug according to the invention is suitable for also overcoming this problem in an advantageous manner and, as a result, for achieving at the same time a further improvement with regard to the object of reducing the work involved.

An advantageous solution of the invention resides actually in that at least one chamber-like or box-like main body of the valve blocks is made of plastics material.

As a result, the bore-hole plug can be left in the bore-hole without endangering the mining equipment because the plastics material does not constitute a danger to the boring heads. At the same time this removes the necessity for the work involved in removing the bore-hole plugs from the bore-hole.

Further advantageous embodiment of the invention are obtained from the subsidiary claims.

The invention is described in more detail with the aid of the following description of an exemplary embodiment illustrated in the drawing.

In the drawing: Fig. 1 shows a partially cut-away side view of a bore-hole plug according to the invention prior to introduction into the bore-hole, and Fig. 2 shows a view of the bore-hole plug corresponding to Fig. 1, after introduction of the bore-hole plug and after expansion of the flexible plug section.

The bore-hole plug, which is generally designated by reference numeral 10, comprises a plug section 1 6 which is inserted between two valve blocks 12 and 14 and which is in the form of a rubber tube or hose which is resistant to high pressure and the diameter of which, in the unloaded state, is slightly smaller than the diameter of the bore-hole to be sealed, which diameter can be, for example, 45 mm.

The two valve blocks 1 2 and 14 consist of main bodies 1 8 and 20, respectively, which are substantially dynamically balanced relative to the axis of the rubber tube and which are penetrated by central channels 22 and 24, respectively. On the side facing the plug section 16, the main bodies 18 or 20 comprise a tubular section 26 or 28 which is provided with an internal thread 30 or 32 and into which is screwed the end of a tubular distance piece 38 which is provided with a corresponding external thread 34 or 36 and which serves to keep the two valve blocks 1 2 and 1 4 apart by a predetermined distance in which the plug section 1 6 is stretched or extended so that it can be easily inserted into the bore-hole by means of a feeding pipe or tube.The end sections 44 or 46 of the tubular plug section 1 6, which are overlapped by clamping sleeves 48 or 50 formed on the main bodies 18 and 20, are drawn on to the outer faces 40 and 42 of the tubular sections 26 or 28.

The two valve blocks 2 and 14 are designed differently with regard to the valve arrangement depending on the provided direction of throughflow. When the bore-hole plug 10 is inserted into the bore-hole to be sealed, the foamed material which is to be fed into the borehole must be pressed through the bore-hole plug 10 into the bore-hole. For this purpose a feed line 52 is connected to the valve block 12 which is adjacent to the mouth of the bore-hole. The main body 18 is for this purpose provided, in its end section directed away from the plug section 16, with an internal thread 54 on the inner end of which there is formed a shoulder 56 which surrounds a valve opening 59. A seal 58 is located on the shoulder 56.Downstream in the throughflow direction, i.e. the direction of the other valve block 14, there is formed on the other side of the valve opening 58 a conical valve seat 60 associated with which is a valve ball 62 which is forced against the valve seat 60 by a compression spring 64. The compression spring 64 is supported on the end of the distance piece 38 inserted in the main body 18.

A valve opening 66 is also provided in the valve block 14 situated downstream, a valve seat 68 being formed again on the downstream side of the said valve opening 66, that is on the side directed away from the distance piece 38, a valve ball 70 which is forced against the valve seat 68 by a compression spring 72 being associated with the said valve seat 68. The compression spring 72 is supported on a nipple 74 which is screwed into an internal thread 76 formed on that end section of the main body 20 which is directed away from the plug section 1 6.By adjusting the nipple 74 it is possible to vary the action of the spring 72, the force of which is in any case greater than the force of the spring 64 in the valve block 12, in order that the plug section 1 6 may first be expanded during the initial state of introduction of the pressurized foamed material, before the latter can flow out into the bore-hole. The nipple 74 is provided with a bore 78 to allow passage of the foamed material into the bore-hole.

In order that the material which flows into the bore-hole plug 10 via the valve block 1 2 and its valve opening 58 and at the plug first into the distance piece may expand the plug section 16, the distance piece 38 is provided with a plurality of openings 80.

The bore-hole plug 10 described has a relatively simple construction and can be manufactured cheaply. Handling is very simple because the bore-hole plug 10 must be pushed forward into the bore-hole only with the correct side, i.e. with the valve block 14, whereupon then only the line for feeding the pressurized foamed material still needs to be connected and removed again after the bore-hole has been filled.

With the exception of the valve springs 64 and 72 and the valve balls 62 and 70, the bore-hole plug 10 described is made exclusively of a material which offers no appreciable resistance at all to the mining equipment so that the latter is no longer endangered by the said bore-hole plug.

Claims

1. An expandable plug for a bore-hoie, comprising a hollow flexible plug section each end of which is provided with a valve block containing a non-return valve, the two non-return valves having the same direction of throughflow, and the valve which is situated downstream in the throughflow direction having a pretensioning such that it allows the passage of fluid from the plug section when the internal pressure in the plug section reaches a predetermined value.

2. A plug according to Claim 1, wherein the plug section has a tubular shape.

3. A plug according to Claim 1 or Claim 2, wherein the two valve blocks are connected by a rigid spacer which extends through the plug section.

4. A plug according to Claim 3, wherein the spacer is in the form of a tubular section which connects the valve blocks and the wall of which is provided with openings.

5. A plug according to any one of the preceding Claims, wherein both valves are biassed in the closing direction, and that the closing tension of the valve which is situated upstream in the throughflow direction is less than the closing tension of the valve situated downstream.

6. A plug according to any one of the preceding Claims, wherein the closing tension of the valve situated downstream in the throughflow direction is adjustable.

7. A plug according to any one of the preceding Claims, wherein the valve block which is situated upstream in the throughflow direction is provided with a coupling or connection for a pressure medium feed line.

8. A plug according to any one of the preceding Claims, wherein the valves are in the form of ball valves.

9. A plug according to any one of the preceding Claims, wherein at least one chamber-like or boxlike main body of the valve blocks is made of plastics material.

10. A plug according to Claims 3 and 9, wherein the spacer is made of plastics material.

11. An expandable plug for a bore-hole, substantially as herein described with reference to the accompanying drawings.