WO2004011397A2

WO2004011397A2 - Plug for bore-holes in mining operations

Info

Publication number: WO2004011397A2
Application number: PCT/ZA2003/000100
Authority: WO
Inventors: Stanley Nance-Kivell; Frederick Berrange
Original assignee: Morrison, Ian
Priority date: 2002-07-27
Filing date: 2003-07-24
Publication date: 2004-02-05
Also published as: AU2003260143A8; AU2003260143A1; WO2004011397A3

Abstract

A blasting plug for a mining bore hole has a frustoconical body (10) of a resilient material and a core (14) of a hard material also of fructoconical shape. A screw (20) is provided to draw the core up the body to compress it against the wall of the bore hole. An explosion in the bore hole further forces the core upwards to complete an effective plug for the explosion.

Description

PLUG FOR BORE-HOLES IN MINING OPERATIONS

TECHNICAL FIELD OF THE INVENTION

This invention relates to a plug for blasting operations, for example in mining operations whether underground or surface mining, rock breaking and other similar operations.

BACKGROUND ART.

Rubber or rubber-like plugs have been used in rock-breaking operations for many years and while there is a fair degree of blasting success there are still enough misfires and blasts which expel the plug prematurely, to seek better plugs.

The problem of misfires is particularly bothersome and requires the careful removal of the plug which is time-consuming and dangerous.

It is an object of the present invention to provide a blasting plug which has improved anchorage in a bore hole than conventional plugs and which is easily removed in the event of a misfire.

DISCLOSURE OF THE INVENTION

According to the invention a blasting plug includes a resilient cylindrical body and an element therein which is adapted to deform the body outwardly against the surface of a bore hole sufficiently for the body to form an effective plug during an explosion.

In a preferred form of the invention the inside surface of the body is frustoconical and the element is correspondingly frustoconical and is provided with means for drawing it into the body as to expand agairist the surface of the bore hole. The means may comprise a screw accessible from the outside, for example by a head with a slot for receiving a tool to assist in the rotation of the screw - either for advancing the element in the body to expand the latter or, in the case of a misfire to move the element out of the body so that the plug can be easily and safely removed.

In another form of the invention the means for drawing the element into the body is the explosion itself but it is preferred that the screw is used in addition, thereby providing a more accurate initial location prior to the explosion, and also providing the means for removing the element from the body in the event of a misfire.

It will be appreciated that in the case of a misfire and successful removal of the plug, the plug may be reused.

The body may be manufactured of a soft plastic material while the element should be made from a harder material.

The head of the screw may be provided with a retaining washer which abuts a shoulder of the body during withdrawal of the plug.

The head may include a slot with a bay at right angles so that the tool can be used in either direction.

The body and element may include passages for guides, fuses and cables.

FIRST EMBODIMENT OF THE INVENTION

A first embodiment of the invention is described below with reference to the accompanying drawings in which

Figure 1 is a selected side view of a plug according to the invention •

Figure 2 is a plan view of the resilient body

Figure 3 is an isometric view of a section of the resilient body Figure 4 is an isometric view of the frustoconical element from one side thereof Figure 5 is a similar view of the element from the other side;

Figure 6 is an isometric view of a screw for raising or lowering the frustoconical element; and Figure 7 is a similar view as Figure 6 of an alternative form of screw head.

BEST MODE FOR CARRYING OUT THE INVENTION

In the drawings a blasting plug includes a resilient cylindrical body 10 whose inside surface 12 is frustoconical. An element 14 is movable against the inside surface of the cylindrical body so that when it moves upwardly the cylindrical body expands against the wall 16 of a bore hole.

The element 14 is movable by virtue of a screw 20 which has a head 22 with a cross groove 24 and bay 26 (Figure 6) or spigots 27 (Figure 7) so that the head may be turned with a suitable tool in either direction depending on whether it is required to move the element upwards (for forming a tight plug in the bore hole) or downwards (to relax the cylindrical body in case of a misfire so that the plug may be removed).

The cylindrical body 10 is preferably made from a soft polymeric material ,while the inner element is made from a higher density polymeric material.

The inside surface of the body includes a key ridge 28, which engages a complemental groove 30 in the element 14. On the other side the body has a slot 32 to receive a blasting cable, the element having a corresponding passage 34 for the cable.

Expansion slits 36 are provided in the body to assist the expansion operation.

A washer 38 is mounted on the shaft of this screw to prevent the screw from being pulled out. SECOND EMBODIMENT OF THE INVENTION

A second embodiment of the invention is described below with reference to the accompanying drawings:

Figure 11 is a diagrammatic view of an assembly according to the invention in which the frustoconical element, or wedge, is in its initial position.

In Figure 11 an explosion has taken place below the wedge and it has been forced into the fructoconical body or skirt, to expand it outwardly as shown by the arrows.

Figure 12 shows top and bottom views of the skirt while Figure 13 shows four views of the wedge. It will be noted that the skirt is provided with a guide rail and the wedge has a corresponding groove.

In Figure 14, an assembly is shown inside a bore-hole A comprising a skirt B, a wedge C, a body of sand D and a space E for an explosive charge. As the charge is detonated, the sand is forced upwardly against the wedge which then enters the skirt and forces it to expand to form a tight fit in the bore-hole.

It will be appreciated that the screw arrangement of the first embodiment may also be incorporated into the second embodiment arrangement.

Claims

CLAIMS:

1. A blasting plug characterised in that it includes a resilient cylindrical body and an element therein, the element being adapted to deform the body outwardly against the surface of a bore hole sufficiently for the body to form an effective plug during an explosion.

2. The blasting plug according to claim 1 characterised in that the inside surface of the body is frustoconical and the element is correspondingly frustoconical and is provided with means for drawing it into the body as to expand against the surface of the bore hole.

3. The blasting plug according to claim 2 characterised in that the means comprises a screw accessible from the outside, for example by a head with a slot for receiving a tool to assist in the rotation of the screw - either for advancing the element in the body to expand the latter or, in the case of a misfire to move the element out of the body so that the plug can be easily and safely removed.

4. The blasting plug according to claim 2 characterised in that the means for drawing the element into the body is the explosion itself.

5. The blasting plug according to claim 4 characterised in that the screw of claim 3 is used in addition.

6. The blasting plug according to any of the above claims characterised in that the body is manufactured of a soft plastic material while the element is made from a harder material.

7. The blasting plug according to any of the above claims characterised in that the body and element includes passages for guides, fuses and cables.