AU2019246893A1

AU2019246893A1 - Polymer Locking Plug

Info

Publication number: AU2019246893A1
Application number: AU2019246893A
Authority: AU
Inventors: Jeffrey Bruce Phillips
Original assignee: Rise Mining Developments Pty Ltd
Current assignee: Rise Mining Developments Pty Ltd
Priority date: 2018-11-28
Filing date: 2019-10-11
Publication date: 2020-06-11

Abstract

A locking plug (10) for blocking a drill hole, the plug comprising an elongate plug body (12) comprising an angled wedge-shaped recess (18) provided in an external cylindrical surface of the body (12), a front locating (10) aperture (22) and a rear locating aperture (24) respectively being provided in the recess and angled into the plug body. The plug (10) further comprises a wedge-shaped locking member (20), made from a resilient plastics material, received in the wedge-shaped recess (18), and having a front locating lug (26) received in the front locating aperture (22) of the recess (18), and a rear locating lug (28) received in the rear locating aperture of the recess. The front locating lug is bent to bias the front of the wedge-shaped locking member inwards towards the body of the plug so that it is seated in the recess. isol C.l Fiue Figure 7 Figure 8

Description

“POLYMER LOCKING PLUG”

Field of the Invention

The present invention relates to a locking plug made from suitable polymer materials and relates particularly, although not exclusively, to such a plug used to prevent broken or jammed longhole rods in production blast holes from falling out.

Background to the Invention

Broken or jammed longhole rods in production blast holes or ‘upholes’ are a common problem in the underground mining industry. Broken or jammed drill rods have the potential to fall out of drill holes without warning, presenting a serious safety hazard to personnel and equipment in an underground mine. In order to prevent broken or jammed drill rods from falling out of drill holes into an area where personnel might be working some way of blocking the hole is required. These drill holes are upholes, i.e. holes that are vertical or near vertical overhead in an underground mine, which is the typical drilling and blasting configuration for underground hard rock ore production.

The drill holes are drilled with percussion button drill bits, which can reduce in diameter considerably due to resharpening, and in some instances may also increase in size slightly due to differing drill bit manufacturers’ sizes for the same “nominal” size, or due to the type of ground that is being drilled. Additionally percussion drill holes tend to spiral somewhat when being drilled, creating considerable surface roughness on the inside of the hole. Any method of blocking these holes needs to cater for these differences and inconsistencies in hole size.

Prior art methods of blocking drill holes include grouting the hole in order to lock the jammed drill rods in place, or plating over the drill hole exit with a rock bolt. Neither method is very satisfactory as a solution to the problem of broken or jammed drill rods. Grouting is expensive and time-consuming, and plating over has been proved inadequate to withstand the force of a falling drill rod. In each instance the drill rig has to be removed from the drilling location, and other equipment brought in to carry out the grouting or plating, adding further disruption and cost to those solutions. Another solution, described in a paper presented at the 2017 AusIMM Underground Mining conference,¹ is the Long Hole Plug or LHP, which is the subject of International Publication No. WO2017/079808 A1. The LHP is a safety system designed to be mechanically anchored at the bottom end (or collar) of the drill hole.

The LHP consists of two components that cooperate to decelerate the forces generated from falling drill rods: (i) a cone section, and, (ii) a slotted tube. The LHP is installed using percussion and is held in place by the slotted tube component. When a rod falls and strikes the cone section, it drives the cone section into the slotted tube which behaves like an expansion shell anchor, by transferring the axial forces from the falling drill rod horizontally into the rock mass. The LHP was demonstrated to be strong enough to absorb the impact and prevent the drill rod from entering the working area. However, disadvantages of the LHP are that it is quite expensive, is not easy to install, and, at 40kg for the 102mm model, is very heavy for a single operator.

Various kinds of stemming plugs are in use in mining blasting operations. For example, US 2008/0236434 A1 discloses a mechanical stemming apparatus comprising a base piece in the form of a cylindrical body, a central piece in the form of a cylindrical-base cone, and two lateral wedge pieces and four supporting pivots, which together form a main cylindrical body with an outer diameter less than the borehole diameter. Following detonation of an explosive, the gases generated violently move up the base piece, without moving the lateral wedge pieces, which allows the central piece to press the lateral wedge pieces against the borehole or blast hole wall. At the same time, the lateral wedge pieces are pressed against the central piece, thus preventing the upward displacement of the central piece, and causing a total mechanical stemming of the borehole or blast hole. This stemming plug is ¹ https://www.mesafe.com.au/wp-content/uploads/2018/Q8/ausimm uqops2Q17 lonq-holepluq.pdf accessed 20 November 2018 designed for use in downholes (i.e. open pit blasting) and requires gravity for the lateral wedge pieces to engage the wall of the blast hole. Therefore this arrangement would not work in upholes in underground mining, because the lateral wedge pieces would not engage the wall of the drill hole and would simply fall away.

The present invention was developed with a view to providing a single-use, locking plug that is inexpensive, lightweight, and easy to install in upholes.

References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere.

Summary of the Invention

According to one aspect of the present invention there is provided a locking plug for blocking a drill hole, the plug comprising:

an elongate plug body of substantially cylindrical shape having a front end and a rear end, the plug body having an angled wedge-shaped recess provided in an external cylindrical surface of the body, a front locating aperture and a rear locating aperture respectively being provided in the recess and angled into the plug body;

a wedge-shaped locking member, made from a resilient plastics material, adapted to be received in the wedge-shaped recess of the plug body, and having a front locating lug at a front of the wedge-shaped locking member adapted to be received in the front locating aperture of the recess, and a rear locating lug at the rear of the wedge-shaped locking member adapted to be received in the rear locating aperture of the recess wherein, in use, when the front locating lug is bent and inserted into the front locating aperture and the rear locating lug is inserted into the rear locating aperture of the recess the front locating lug acts to bias the front of the wedge-shaped locking member inwards towards the body of the plug so that it is seated in the recess.

Preferably the wedge-shaped recess is one a plurality of wedge-shaped recesses provided in the external cylindrical surface of the body. In one embodiment four wedge-shaped recesses are provided in the body, two front recesses provided on diametrically opposite sides of the plug body, closer to the front end of the plug body, and two rear recesses provided on diametrically opposite sides of the plug body, closer to the rear end of the plug body. Preferably the two front recesses are on a diametrical axis that is orthogonal to a diametrical axis on which the two rear recesses lie, so that viewed end-on the four recesses are symmetrically located, at 90° to one another, about the circumference of the cylindrical plug body.

Preferably the wedge-shaped recess comprises a first substantially planar surface formed at an acute angle with respect to a central longitudinal axis of the plug body, and a second substantially planar surface formed substantially at right angles to the first substantially planar surface. Typically the front locating aperture is located in the first substantially planar surface adjacent a front of the recess, and extends at an acute angle into the first substantially planar surface.

Advantageously the rear locating lug is recessed into the rear of the wedgeshaped locking member wherein, in use, when the rear locating lug is received in the rear locating aperture of the recess, and the wedge-shaped locking member is forced inwards towards the body of the plug the rear locating lug is subject to a bending moment rather than a shear force. Preferably the rear locating aperture of the recess is located in the second substantially planar surface, spaced from the first substantially planar surface wherein, in use, when the rear locating lug is received in the rear locating aperture, it acts to bias the rear of the wedge-shaped locking member outwards away from the body of the plug to interact with a wall of the drill hole during installation.

The wedge-shaped locking member preferably comprises an outer curved surface and an inner planar surface. Typically both the front locating lug and the rear locating lug in their rest condition have one side arranged coplanar with the inner planar surface of the wedge-shaped locking member. Typically both the front locating lug and the rear locating lug are bent at an acute angle with respect to the inner planar surface, when the locking plug is installed in a drill hole, and the front locating lug and the rear locating lug are inserted in the front locating aperture and the rear locating aperture respectively. Preferably the outer curved surface of the wedge-shaped locking member is ribbed, to increase friction between the wedge-shaped locking member and the wall of the drill hole. Preferably the wedge shaped member is made of a higher friction material than the plug body. Preferably a low friction material and surface finish is provided on the plug body and inner planar surface of the wedge-shaped locking members, so that the body of the plug may move relatively unhindered by friction under load. Preferably the plug body is made from a low friction, high strength, engineering plastic material.

Advantageously a disconnection mechanism is provided so that upon withdrawal of an installation rod from a connection end of the plug body a disconnection force is applied to the plug body, and therefore a preload onto the plug, to immediately and positively compress each wedge-shaped locking member between the plug body and a wall of the drill hole.

Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Likewise the word “preferably” or variations such as “preferred”, will be understood to imply that a stated integer or group of integers is desirable but not essential to the working of the invention.

Brief Description of the Drawings

The nature of the invention will be better understood from the following detailed description of several specific embodiments of the locking plug, given by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a side perspective view of a first embodiment of a locking plug in accordance with the present invention;

Figure 2 is a top perspective view of the locking plug of Figure 1 with the wedge-shaped locking members removed;

Figure 3 is a top plan view of the locking plug of Figure 1;

Figure 4 is a partially transparent side perspective view of the locking plug of Figure 1 with the wedge-shaped locking members removed;

Figure 5 is a top perspective view of one of the wedge-shaped locking members of the locking plug of Figure 1;

Figure 6 is a bottom perspective view of the wedge-shaped locking member of Figure 5;

Figure 7 is a side elevation of the wedge-shaped locking member of Figure 5 as it would appear when assembled in the locking plug of Figure 1;

Figure 8 is a side perspective view of a second embodiment of a locking plug in accordance with the present invention;

Figure 9 is a top perspective view of one of the wedge-shaped locking members of the locking plug of Figure 8; and,

Figure 10 is a bottom perspective view of the wedge-shaped locking member of Figure 9.

Detailed Description of Preferred Embodiments

A first embodiment of a locking plug 10 for blocking a drill hole in accordance with the invention, as illustrated in Figures 1 to 7, comprises an elongate plug body 12 of substantially cylindrical shape having a front end 14 and a rear end 16. The plug body 12 has an angled wedge-shaped recess 18 provided in an external cylindrical surface of the body 12. In this embodiment, the recess 18 is one a plurality of wedge-shaped recesses 18 provided in the external cylindrical surface of the body 12. Four such recesses 18 are provided in the body 12, two of the recesses 18a and 18b provided on diametrically opposite sides of the plug body 12, closer to the front end 14 of the plug body, and two more of the recesses 18c and 18d provided on diametrically opposite sides of the plug body 12, closer to the rear end 16 of the plug body 12. The front two recesses 18a and 18b are on a diametrical axis that is orthogonal to a diametrical axis on which the rear two recesses 18c and 18d lie. Therefore when viewed end-on, as shown in Figure 3, the four recesses 18 are symmetrically located, at 90° to one another, about the circumference of the cylindrical plug body 12. This arrangement negates the possibility of all of the wedges aligning with shear structures in the rock mass. This is advantageous because if the plug did not have this feature, and happened to align with shears in the rock mass, then it may be compromised by lack of grip due to that alignment. The offset ensures that in any shear conditions, the shear can at most only affect one set of wedge-shaped locking members 20 (see below).

As can be seen most clearly in Figures 2 and 4, a front locating aperture 22 and a rear locating aperture 24 are respectively provided in each recess 18, and angled into the plug body 12.

The locking plug 10 further comprises a wedge-shaped locking member 20, as shown in Figures 5 to 7, made from a resilient plastics material, and adapted to be received in the wedge-shaped recess 18 of the plug body 12. A front locating lug 26 is provided at a front of the wedge-shaped locking member 20 and is adapted to be received in the front locating aperture 22 of the recess 18, and a rear locating lug 28 is provided at the rear of the wedgeshaped locking member 20 and is adapted to be received in the rear locating aperture 24 of the recess 18. In use, when the front locating lug 26 is bent and inserted into the front locating aperture 22 and the rear locating lug 28 is inserted into the rear locating aperture 24 of the recess 18 the front locating lug 26 acts to bias the front of the wedge-shaped locking member 20 inwards towards the body 12 of the plug 10 so that it is seated in the recess 18.

Preferably the wedge-shaped recess 18 comprises a first substantially planar elliptic surface 30 formed at an a acute angle with respect to a central longitudinal axis of the plug body 12, as can be seen most clearly in Figures 2 and 4, and comprises a second substantially planar elliptic surface 32 formed substantially at right angles to the first substantially planar elliptic surface 30. In this embodiment the front locating aperture 22 is located in the first substantially planar elliptic surface 30 adjacent a front of the recess 18, and extends at an acute angle into the first substantially planar elliptic surface 30.

Advantageously the rear locating lug 28 is recessed into the rear of the wedge-shaped locking member 20 wherein, in use, when the rear locating lug 28 is received in the rear locating aperture 24 of the recess 18, and the wedge-shaped locking member 20 is forced inwards towards the body 12 of the plug 10 the rear locating lug 28 is subject to a bending moment rather than a shear force. Preferably the rear locating aperture 24 is located centrally in the second substantially planar elliptic surface 32 at a rear of the recess 18, spaced from the first substantially planar elliptic surface 30 wherein, in use, when the rear locating lug 28 is received in the rear locating aperture 24, it acts to bias the rear of the wedge-shaped locking member 20 outwards away from the body 12 of the plug 10 to interact with a wall of the drill hole during installation, even when the wall of the hole is rough and varies in diameter over a large size range.

The wedge-shaped locking member 20 preferably comprises an outer curved elliptical surface 34, as can be seen most clearly in Figures 1 and 5, and an inner planar elliptical surface 36, as can be seen most clearly in Figures 6 and 7. Typically both the front locating lug 26 and the rear locating lug 28 in their rest condition have one side arranged coplanar with the inner planar elliptical surface 36 of the wedge-shaped locking member 20. However, in use, when the locking plug 10 is installed in a drill hole, with the front locating lug 26 and the rear locating lug 28 are inserted in the front locating aperture 22 and the rear locating aperture 24 respectively, both lugs will be bent at an acute angle with respect to the inner planar elliptical surface 36, as shown in Figure 7.

Preferably the outer curved elliptical surface 34 of the wedge-shaped locking member 20 is ribbed, as shown in Figures 1, 5 and 7, to increase friction between the wedge-shaped locking member 20 and the wall of the drill hole. Preferably a low friction material and surface finish is provided on the plug body 12 and inner planar elliptical surface 36 of the wedge-shaped locking members 20, so that the body 12 of the plug may move relatively unhindered by friction under load. The locating lugs 26, 28 allow the plug body 12 to move rearward under load yet the wedge-shaped locking members 20 remain stationary, by allowing both the front and the rear locating lugs to slide easily from the locating apertures. In this way, as the body 12 is forced rearwards under load the wedge-shaped locking members wedge more tightly against the wall of the drill hole to lock the plug 10 in position. The angle of the front locating lug 26 is particularly important, since it must provide both a biasing action and a releasing action during the wedging movement.

Preferably the plug body 12 is made from a low friction material, for example, a high strength engineering plastic, such as acetal. Preferably the wedgeshaped locking members 20 are made from a firm, semi-flexible polymer material, such as harder polyurethanes or softer nylons. The wedge-shaped locking members 20 are designed so that they can be manufactured in any one of a number of ways:

1. 3D printed for prototypes and small volume production

2. Conventionally moulded in polyurethane or similar for medium volumes, and

3. Injection moulded using polyurethane or suitable nylon type materials for high volume production.

In the case of injection moulding the wedge-shaped locking members 20 would likely need to be cored to reduce volume and cooling time, and therefore cost, so material choice would be more critical to ensure both the strength of the now cored material, and the resilience of the locating lugs to still provide the biasing action required.

Figures 8 to 10 illustrate a second embodiment of the locking plug 40 which is substantially identical to the first embodiment 10, except that in this case the wedge-shaped locking members 50 are cored. As can be seen most clearly in Figures 8 and 9, in this embodiment the outer curved elliptical surface 54 of the wedge-shaped locking member 50 is cored. In other respects the locking plug 40 is substantially identical to the first embodiment, and therefore the like parts are identified using the same reference numerals and will not be described again.

In use, during installation, the locking plug 10, 40 would be pushed up the drill hole with an installation rod into close proximity to, or even abutting, the jammed or broken drill rod, using the same drill rig that is already in location. Viewed from the front end of a correctly sized plug 10 or 40, (see Figure 3) it is apparent that as the plug initially enters the drill hole the wedge-shaped locking members 20 will follow in a compressed state. The front of each wedge-shaped locking member 20 is retained closely adjacent to the plug body 12 by the biasing action provided by the front locating lug 26. This ensures that upon entry the outer diameter of the plug 10, 40, with wedgeshaped locking members 20, remains smaller than the inner diameter 42 of the drill hole, shown in broken outline in Figure 3.

Once inside the drill hole, the rear of each polymer wedge-shaped locking member 20 is supported by the second substantially planar elliptical surface 32 at the rear of the respective wedge-shaped recess 18 in the body 12 of the plug, as it is pushed up the drill hole. Therefore, once the plug 10, 40 is inserted into the collar of the drill hole, the wedge-shaped locking members 20 will only have freedom of movement in one direction, i.e., to move forwards relative to the body 12 of the plug. Typically this would only occur upon completion of installation. When the plug 10, 40 is in its final installed position, the wedge-shaped locking members 20 will remain stationary, but in relative terms, the body 12 of the plug eases backward, down the drill hole, either under load or under its own weight. As the plug body 12 eases backward, the inner planar elliptical surfaces of the wedge-shaped locking members 20 slide over the first substantially planar elliptical surfaces 30 of the recess 18, forcing the wedge-shaped locking members 20 into greater engagement with the wall of the drill hole. The greater the load on the plug body 12, the more tightly the wedge-shaped locking members 20 become wedged between the plug body 12 and the wall of the drill hole. A disconnection mechanism can be provided so that withdrawal of the drill jig installation rod provides a disconnection force, and therefore a preload onto the plug, to immediately and positively compress the wedges between the plug body and the wall of the drill hole, much like installation of a “pop rivet”.

Advantageously the level of preload can be easily adjusted by altering the design of a connection end of the plug body. For example, a client wants a preload of approximately 500kg. The plug can be designed to have a disconnection mechanism comprising an O-ring, located within a gland inside the connection end at the base of the plug as can be seen in Figure 4 in dotted line (O-ring not shown). The O-ring forms an interference fit with a thread on the end of the installation rod when it is inserted in the connection end of the plug. The disconnection force can be adjusted by using different strength, (duro 70 or 90) or different sized O-rings. Alternatively, when machining the plug body some plastic can be left inside the connection end as an interference object. The important point is that the disconnection mechanism can be tailored to whatever disconnection force is required by the client to satisfactorily preload the plug.

The wedge-shaped locking members 20 act as a one-way brake, ratcheting the plug 10, 40 up the drill hole as it is pushed up. In its final installed position the plug does not allow the broken or jammed drill rods to fall any significant distance. In this way the plug 10, 40 prevents any kinetic energy from developing, and the task is less onerous than that of the Long Hole Plug. Falling drill rods in a drill hole are known to punch through rock bolt plates with ease. The Long Hole Plug needs to be engineered for this considerable force, whereas the plug 10, 40 does not, since being located close to the rods there is little momentum built-up by the rods should they fall.

Note: the plug 10, 40 is a single-use plug, and so is not made to be, nor should it be, removed under any circumstances since it would be dangerous to do so. As mining progresses, normal practice is that the jammed or broken rods and plug would be blasted out with the stoping operations in the mine, and recovered and disposed of during ore recovery and haulage. At that time, the locking plug’s task would be complete.

Now that preferred embodiments of the locking plug have been described in detail, it will be apparent that the described embodiments provide a number of advantages over the prior art, including the following:

(i) It is simple and inexpensive to manufacture.

(ii) It is easy to install as a single-use, disposable product.

(iii) It is lightweight; typically under 3kg for a 102mm sized plug.

(iv) It does not require any additional installation equipment other than the drill rig which is already at the location.

(v) It has a high load capacity. Initial testing gives a minimum 12 tonnes resistance with four wedge-shaped locking members in a 102mm hole.

(vi) It has minimum parts, and uses the spring-loaded properties of the resilient polymer material to bias the wedge-shaped members into the desired positions.

It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention. For example, in the described embodiments both the recesses and wedge-shaped locking members are elliptical in shape; however this is not essential, and these components may be of any suitable shape. Therefore, it will be appreciated that the scope of the invention is not limited to the specific embodiments described.

Claims

1. A locking plug for blocking a drill hole, the plug comprising:

2. A locking plug as defined in claim 1, wherein the wedge-shaped recess is one of a plurality of wedge-shaped recesses provided in the external cylindrical surface of the body.

3. A locking plug as defined in claim 2, wherein four wedge-shaped recesses are provided in the body, two front recesses provided on diametrically opposite sides of the plug body, closer to the front end of the plug body, and two rear recesses provided on diametrically opposite sides of the plug body, closer to the rear end of the plug body.

4. A locking plug as defined in claim 3, wherein the two front recesses are on a diametrical axis that is orthogonal to a diametrical axis on which the two rear recesses lie, so that viewed end-on the four recesses are symmetrically located, at 90° to one another, about the circumference of the cylindrical plug body.

5. A locking plug as defined in any one of claims 1 to 4, wherein the wedgeshaped recess comprises a first substantially planar surface formed at an acute angle with respect to a central longitudinal axis of the plug body, and a second substantially planar surface formed substantially at right angles to the first substantially planar surface.

6. A locking plug as defined in claim 5, wherein the front locating aperture is located in the first substantially planar surface adjacent a front of the recess, and extends at an acute angle into the first substantially planar surface.

7. A locking plug as defined in claim 1, wherein the rear locating lug is recessed into the rear of the wedge-shaped locking member wherein, in use, when the rear locating lug is received in the rear locating aperture of the recess, and the wedge-shaped locking member is forced inwards towards the body of the plug the rear locating lug is subject to a bending moment rather than a shear force.

8. A locking plug as defined in claim 7, wherein the rear locating aperture of the recess is located in the second substantially planar surface, spaced from the first substantially planar surface wherein, in use, when the rear locating lug is received in the rear locating aperture, it acts to bias the rear of the wedge-shaped locking member outwards away from the body of the plug to interact with a wall of the drill hole during installation.

9. A locking plug as defined in claim 1, wherein the wedge-shaped locking member preferably comprises an outer curved surface and an inner planar surface.

10. A locking plug as defined in claim 9, wherein both the front locating lug and the rear locating lug in their rest condition have one side arranged coplanar with the inner planar surface of the wedge-shaped locking member.

11. A locking plug as defined in claim 10, wherein both the front locating lug and the rear locating lug are bent at an acute angle with respect to the inner planar surface, when the locking plug is installed in a drill hole, and the front locating lug and the rear locating lug are inserted in the front locating aperture and the rear locating aperture respectively, allowing the wedgeshaped locking member to move unimpeded relative to the body of the plug to take-up the load.

12. A locking plug as defined in claim 9, wherein the outer curved surface of the wedge-shaped locking member is ribbed, to increase friction between the wedge-shaped locking member and the wall of the drill hole.

13. A locking plug as defined in claim 1, wherein the wedge shaped member is made of a higher friction material than the plug body.

14. A locking plug as defined in claim 9, wherein a low friction material and surface finish is provided on the plug body and the inner planar surface of the wedge-shaped locking members, so that the body of the plug can move relatively unhindered by friction under load.

15. A locking plug as defined in claim 1, wherein the plug body is made from a low friction, high strength, engineering plastic material.

16. A locking plug as defined in any one of the preceding claims, wherein a disconnection mechanism is provided so that upon withdrawal of an installation rod from a connection end of the plug body a disconnection force is applied to the plug body, and therefore a preload onto the plug, to immediately and positively compress each wedge-shaped locking member between the plug body and a wall of the drill hole.