AU717939B2 - Rock bolt with grout mixing device - Google Patents

Description

S F Ref: 399358

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

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44.

b4 4 4* 4 et 4 4 *4 4**44 e 4 Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: ASSOCIATED PROVISIONAL [31] Application No(s) P04338 The ANI Corporation Limited Level 5, Merlin Centre 235 Pyrmont Street Darling Harbour New South Nales 2000

AUSTRALIA

Mietek Rataj Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Rock Bolt with Grout Mixing Device APPLICATION DETAILS [33] Country

AU

[321 Application Date 23 December 1996 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5815 ROCK BOLT WITH GROUT MIXING DEVICE Field of the Invention The following invention relates to an improved rock bolt and a method of manufacturing a rock bolt.

A known method of installing a resin grouted rock bolt to secure the roof of an underground mine involves drilling a hole to accommodate the bolt and inserting a container of resin into the hole. The bolt is then driven into the hole to puncture the walls of the resin container and mix the resin to secure the bolt in the hole once the resin has set.

Due to the nature of the resin being generally used, the clearance between the outer diameter of the bolt and the diameter of the hole has to be minimised to ensure proper mixing of the resin. Typically, the annulus should not be larger than 3mm. In coal mining, the annulus varies between 1.75mm and 2.0mm where standard 22mm diameter :'"'"bolts are used.

15 However, holes currently being drilled for bolt installation in hard rock mining are "larger as compared to those of coal mining. The annulus in hard rock mining can vary from 5mm to l1mm. Therefore, in hard rock mining, a standard 22mm diameter rock bolt cannot be used as a resin grouted anchor because the resin does not mix properly in the larger annulus. In hard rock mining, it is not generally practical to drill smaller holes 20 due to limitations of the type of drilling equipment in general use. That is, the annulus can generally only be reduced by using a suitable bolt.

Reduction of the annulus by use of a bolt of a larger diameter is not economical and S" is often impractical. Therefore, to improve the mixability of the resin, specifically modified bolts have been prepared.

25 In one instance, the standard 22mm bolt was flattened in three or four places ee creating sections of the bolt called "paddles" having a dimension larger than the bolt S"diameter. These paddles improved the mixing of the resin, but resin voids were created behind the paddles rendering such bolts less efficient.

In another known bolt, a wire spring was attached to the leading end of the bolt.

The spring was attached to the bolt by having one end welded to the bolt and the other end secured to the bolt by adhesive tape. A serious problem with this bolt was that during the installation of the bolt in a drilled hole, while the bolt was being turned, the spring wire created a loop which was subsequently twisted in the direction opposite to the original direction. As a result, instead of pushing the resin to the back of the hole during turning, it pulled the resin down resulting in poor encapsulation of the top part of the bolt. This loop was formed because of the reasonably large clearance between the outside diameter of the bolt and the inside diameter of the spring. The large clearance between the bolt and spring was necessary to enable the spring to slide onto the bolt during the manufacturing process.

[N:\LIBLL]01 173:KEH Another serious problem with this known bolt was that the wire very often broke off the bolt during installation in the rock. It is believed that breakage of the wire was partially attributable to loads from additional resistance from the resin as well as the wall of the bore hole. Where the wire is of a relatively small diameter (typically 3mm) its strength and the strength of the weld is relatively small.

Object of the Invention It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide an improved rock bolt with a grout mixing device.

Disclosure of the Invention There is disclosed herein a bolt comprising first and second ends, the first end comprising external thread to receive a nut and the second end comprising a transverse slot, and a wire inserted into the transverse slot and wound around the bolt toward said first *15 end.

Preferably, the wire comprises two portions, each portion extending from an end of •the slot and being wound around the bolt in the same direction.

Preferably, the wire is affixed to the bolt at spaced intervals therealong.

Preferably, said fixing is by means of welding.

S 20 Preferably, the direction of winding of said wire should be opposite to the intended rotation direction of the bolt. For example, for a left hand rotation installation, the spiral should be right hand wound. This opposite direction of the spiral moves resin which surrounds the bolt in a predrilled hole upwardly toward the deep end of the hole during the mixing process.

25 Preferably, there is no clearance between the wire and the bolt.

Alternatively, clearance can be provided between the wire and the bolt, this clearance being dependent upon the diameter of the bore hole where the bolt is to be installed.

There is further disclosed herein a method of assembling a bolt with a mixing device, the method comprising: forming a slot in the end of a bolt, placing a wire into the slot, and rotating the bolt whilst feeding the wire along the bolt to form a mixing device.

The relationship between the rotation speed of the bolt and the feeding speed will determine the pitch of the wire.

In the situation where the length of wire extends only from one end of the slot and is wound around the bolt, the slot is crimped to affix the wire to the bolt.

In this situation, an alternative is to weld the wire to the bolt at or near the slot.

[N:\LIBLL]01173:KEH There is further disclosed herein a method of forming a bolt with a mixing device, the method comprising: providing a bolt, forming a transverse slot at one end of the bolt, forming a wire into a coil shape, and sliding the wire over the bolt to form a mixing device such that an end portion or intermediate portion of the wire fits into the slot.

The method may also comprise the step of crimping the slot.

Alternatively, rather than crimping the slot, a portion of wire passing out of one end 1 o of the slot can be affixed against the bolt under a portion of wire extending from the other end of the slot and extending around the bolt.

Brief Description of the Drawings Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic perspective view of a rock bolt having a grout mixing device, Fig. 2 is a schematic perspective view of an end portion of a rock bolt having another grout mixing device, and Fig. 3 is a schematic perspective view of an end portion of a rock bolt having another grout mixing device.

20 Description of the Preferred Embodiments In Fig. 1 of the accompanying drawings there is depicted a rock bolt 1 having a •transverse slot 2 formed in the end distal from threaded end 8. A wire 3 is inserted into the slot 2 and wound around the bolt 1 forming a double spring. That is, respective portions of the wire 3 are wound around the bolt 1 in the same direction. The tails of the 25 respective portions of the wire 3 can be affixed at 4 and 5 to the bolt, preferably by welding.

In addition, the wire 3 can be affixed to the bolt at additional locations 6 and 7, preferably by welding. By winding the wire directly to the bolt, the clearance between the wire and the bolt can be controlled, and, if necessary, reduced to almost zero.

By affixing the wire 3 to the bolt 1 in locations 6 and 7 between the ends of the wire, the "free" length of the wire is reduced, thus the chances of creating an unwanted loop of wire during installation are diminished.

Also, by affixing the wire 3 into the bolt 1 by placing a portion of the wire into slot 2, rather than welding provides more security as this portion of the wire is exposed to higher frictional loading than are other parts of the bolt.

End 8 of bolt 1 is threaded to accommodate a nut (not shown) which secures a mine plate (not shown) to the bolt 1. The direction in which the spiral of wire extends about the bolt 1 is to be the opposite to the intended rotation direction of the bolt 1, ie., if the IN:\LIBLL]O1 173:KEH 4 4 bolt is going to be used with a left hand rotation installer, the spiral will be right hand wound. This opposite direction of the spiral is required in order to move the resin upwards during the mixing process.

It should be noted that the number of intermediate fixing points 6, 7 as well as the clearance between the wire 3 and the bolt 1 will depend on the diameter of the bore hole where the bolt is to be installed.

The preferred method of assembly of the bolt is to place a portion of a length of wire into the slot 2 and then rotate the bolt 1 (or rotate the wire) whilst feeding the wire longitudinally along the bolt 1. The relationship between the rotation speed of the bolt and the feed speed will determine the pitch of the spring formed by wire 3.

In Fig. 2 there is schematically depicted an alternative embodiment wherein a single coil of wire 3 is formed. That is, in this case, the wire 3 is placed into slot 2 of bolt 1 and the end of wire 9 is crimped to the bolt 1. That is, the slot 2 is crimped at 10 to prevent the small portion of wire 11 located within slot 2 from straightening while the wire 3 is being pulled down axially. That is, if the portion 11 of wire is not allowed to move, the top part of the coil of wire 3 will not be detached during the installation process.

Another method of affixing portion 11 of wire 3 to the bolt would be by means of welding (not shown). The quality of such a weld in this case is not important as the shear and tensile loadings in this vicinity are limited.

The method of assembly of the rock bolt shown in Fig. 2 can be similar to the method described above in reference to Fig. 1.

Another assembly method may be to preform the wire 3 into the spring shape and slide it over the bolt 1 before securing the ends and intermediate points of the wire to the bolt. An intermediate point is shown at 5 in Fig. 2.

:It should be appreciated that the above described methods of fixing the wire 3 to bolt 1 are preferred. There may be variations to the method of fixing such as different methods of crimping, for example. Also, the end portion 11 might be glued into the slot 2.

In Fig. 3 there is schematically depicted the end portion of a bolt 1 requiring no crimping or welding in the vicinity of slot 2. That is, an end portion 12 of wire 3 is positioned under a portion of the wire which is wound about the bolt 1.

As used herein, the word "comprising" means "including, although not limited to".

Similarly, the word "comprises" means "includes, although is not limited to".

[N:\LIBLL]O 173:KEH

Claims (15)

1. A bolt comprising first and second ends, the first end comprising external thread to receive a nut and the second end comprising a transverse slot, and a wire inserted into the transverse slot and wound around the bolt toward said first end.

2. The bolt of claim 1, wherein the wire comprises two portions, each portion extending from an end of the slot and being wound around the bolt in the same direction.

3. The bolt of claim 1 or claim 2, wherein the wire is affixed to the bolt at spaced intervals therealong.

4. The bolt of claim 3, wherein said fixing is by means of welding.

The bolt of any one of the preceding claims wherein there is no clearance between the wire and the bolt.

6. The bolt of any one of claims 1 to 5, wherein clearance is provided between the wire and the bolt. 15

7. A method of assembling a bolt with a mixing device, the method comprising: forming a slot in the end of a bolt, placing a wire into the slot, and rotating the bolt whilst feeding the wire along the bolt to form a mixing device.

8. The method of claim 7, wherein rotation of the bolt occurs at a speed which is related to the feeding speed to determine the pitch of the wire.

9. The bolt of any one of claims 1 to 7, or the method of claim 8 or claim 9, wherein the slot is crimped to affix the wire to the bolt.

:10. The bolt of any one of claims 1 to 7, or the method of claim 8 or claim 9, wherein the wire is welded to the bolt at or near the slot.

11. A method of forming a bolt with a mixing device, the method comprising: S. providing a bolt, forming a transverse slot at one end of the bolt, forming a wire into a coil shape, sliding the wire over the bolt to form a mixing device such that an end portion or intermediate portion of the wire fits into the slot.

12. The method of claim 11 further comprising the step of crimping the slot.

13. A bolt, substantially as hereinbefore described with reference to the accompanying drawings.

14. A method of assembling a bolt with a mixing device, the method being substantially as hereinbefore described with reference to the accompanying drawings. Dated

15 December, 1997 The ANI Corporation Limited Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [N:\LIBLL01173:JED