GB2227694A

GB2227694A - Mine roofbolts

Info

Publication number: GB2227694A
Application number: GB9000870A
Authority: GB
Inventors: Maurice Richard Stokes
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-01-25
Filing date: 1990-01-15
Publication date: 1990-08-08
Anticipated expiration: 2010-01-15
Also published as: GB2227694B; GB9000870D0; GB8901547D0

Abstract

A mine roofbolt or foundation bolt comprises a length of metal reinforcement bar 10 with a driving head 12 at one end. So that the driving head 12 can be provided on the metal bar otherwise than by screwthreading, a generally annular head element 12 is swaged down onto the unmachined surface of the bar 10. An adhesive may be used to aid the securement of the head to the bar. <IMAGE>

Description

Mine roofbolts.

The invention relates to mine roofbolts and the like which are used for example to reinforce the roof strata in a mine in those areas where the roof strata requires reinforcement for reasons of safety. Mine roofbolts are generally lengths of steel reinforcing bars of the kind commonly used as reinforcement in concrete structures and foundations. When used as mine roofbolts, the bars are forced into pre-drilled holes in the rock strata which have been filled with a resin mixture or a cementitious material acting as an appropriate adhesive. However, before being forced into the pre-drilled holes, the bars are each provided with a driving head by means of which the bar can be rotated and forced into the pre-drilled hole.

One particular kind of reinforcing bar which is available for making mine roofbolts etc. is one which has a ductile core and a relatively hard skin. However, the provision of a driving head on this kind of bar is a problem. For.example, if the driving head is in the nature of a hexagonal nut screwthreaded on a threaded end portion of the bar, the application of the screwthread to the bar involves the machining away of the relatively hard skin and this may considerably weaken the bar in that region. The invention has for its object to at least alleviate this problem.

According to one aspect of the invention, a method of making a mine roofbolt or the like involves the step of swaging onto the surface of a portion of reinforcement bar a generally annular driving head element. The driving head element may be heated before being fitted on the bar prior to swaging. The method may involve the use of an adhesive, to create a strong joint between the interior of the driving head element and the surface of the bar. The external dimensions of the driving head element may be reduced during the swaging operation to those required for fitting said driving head in an appropriate driving tool.

Alternatively, a final machining operation may be required to bring the driving head to the required size after said driving head has been secured on the reinforcement bar by the swaging step.

According to a further aspect of the invention, there is provided a mine roofbolt or the like constituted by a length of reinforcement bar onto a surface of a portion of which a driving head element has been swaged. Preferably, the driving head element will have been secured on the surface of the bar with the aid of an adhesive. The driving head element may have an external configuration adapted for engagement with a driving tool.

In order that the invention may be fully understood and readily carried into effect, the same will now be described by way of example only, with reference to the accompanying drawings, of which:- Figure 1 is an exploded perspective view which illustrates the inventive method of making a mine roofbolt, and Figure 2 is a sectional view through an end portion of the roofbolt.

Referring now to the drawings, the mine roofbolt there illustrated has two parts, that is to say a length of reinforcement bar 10 and an annular driving head element 12, the latter being of noncircular outline shape so that it can be fitted into an appropriatt driving tool. In the illustrated embodiment the head element is shown to be fitted on one end of the bar (but in some instances it may require to be located soiae way along the bar). Although the driving head element has been shown to be of square outline shape by way of example, it will be understood that it may well be of hexagonal outline shape or indeed of any other preferred non-circular shape.

As shown, the length of reinforcement bar is of the kind having a plurality of ridges 14 formed along its length so that they key into whatever medium the bar is set, which in the case of a mine roofbolt will be a resin mixture or a cementitious material used to fill pre-drilled holes formed in the roof strata requiring reinforcement. A further feature of the bar but one which is not visible in the drawing is that it has a ductile core and a relatively hard skin.

As indicated by the chain-dotted lines in Figure 1, the roofbolt has been made by a method involving the step of swaging the generally annular driving head element onto the unmachined surface of an end portion of the bar. The full strength of the bar has therefore been retained throughout the full length of the bar.

Various modifications may be made. For example, although in the illustrated embodiment the driving head element has been constituted. by a standard internally threaded nut this is not essential. The driving head element could be constituted by a generally annular element having a plain bore because it is thought that the swags of said element onto the unmachined surface of the bar will provide an adequate joint between the interior of the driving head element and the surface of the bar. However, to create a stronger joint between the driving head element and the bar it would be quite feasible to use a suitable adhesive, for example that available under the trade mark ARALDITE. In the illustrated embodiment, the swaging operation has been such as to bring the external dimensions of the driving head element to those required for fitting to a driving tool (not shown). However, a final machining operation could be carried out to bring the driving head to the required size after it has been secured on the reinforcement bar by the swaging operation.

Although the invention is primarily concerned with the production of roofbolts for use in reinforcing mine roof strata, such a bolt may find other uses, for example in civil engineering for use as a foundation bolt. When used in civil engineering, such a bolt may be set into wet concrete during the casting of a reinforced concrete body or foundation. Alternatively, a hole may be drilled for the reception of the bolt which may then be set in a resin mixture or a cementitous material acting as a suitable adhesive.

Claims

CLAIMS:

1. A method of making a mine roofbolt or the like, the method including the step of swaging onto the surface of a portion of reinforcement bar a generally annular driving head element.

2. The method claimed in claim 1, including the step of heating the driving head element before it is fitted on the bar prior to swaging.

3. The method according to either one of the preceding claims, including the use of an adhesive to create a strong joint between the interior of the driving head element and the surface of the bar.

4. The method according to any one of the preceding claims, including the reduction of the external dimensions of the driving head element during the swaging operation to those required for fitting said driving head in an appropriate driving tool.

5. The method according to any one of claims 1 to 3, including a final machining operation to bring the driving head to the required size after said driving head has been secure on the reinforcement bar by the swaging step.

6. A mine roofbolt or the like constituted by a length of reinforcement bar onto the surface of a portion of which a driving head element has been swaged down.

7. A mine roofbolt or the like according to claim 6, in which the driving head element has been secured on the unmachined surface of the bar with the aid of an adhesive.

8. A mine roofbolt or the like according to either one of claims 6 and 7, in which the driving head element has an external configuration adapted for engagement with a driving tool.

9. A method of making a mine roofbolt or the like, substantially as hereinbefore described with reference to the accompanying drawings.

10. A mine roofbolt or the like which has been made by a method according to any one of claims 1 to 5 or claim 9.

11. A mine roofbolt, substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.