AU2002300343B8 - Cable Bolt - Google Patents

Description

S&F Ref: 600322

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: DYWIDAG-Systems International Pty Limited 25 Pacific Highway Bennett's Green New South Wales 2290 Australia Mieczyslaw Stanislaw Rataj Spruson Ferguson St Martins Tower,Level 31 Market Street Sydney NSW 2000 (CCN 3710000177) Cable Bolt ASSOCIATED PROVISIONAL APPLICATION DETAILS [33] Country [31] Applic. No(s) AU PR7139 [32] Application Date 20 Aug 2001 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5815c Cable Bolt Field of the Invention The present invention relates to mining equipment, and in particular relates to a rock bolt, in the form of a cable bolt, for securing the roof of a mine.

Background of the Invention A known method of installing a cable bolt (sometimes called a strand bolt) to secure the roof of an underground mine involves drilling a hole in the mine roof to accommodate the cable bolt and inserting a resin filled cartridge into the hole. The cable bolt is then driven into the hole to puncture the resin cartridge. The cable bolt is rotated to mix the resin so as to secure the upper end of the cable bolt in the hole once the resin has set.

To provide adequate anchorage of the cable bolt within the resin, the cable bolt as depicted in Figure 1 of the accompanying drawings has previously been proposed.

The leading end of the cable bolt 10 is provided with three to four bulbous deformations 11 which are successively spaced by approximately 250 millimetres. The bulbous deformations 11 are formed by local axial compression of the cable, buckling the individual wires forming the cable so as to form a cage-like arrangement with voids formed between the individual wires. The purpose of the bulbous deformations 11 is to provide a physical anchor for the cable bolt within the resin 20, preventing tension loads applied to the cable via the mine plate 50 and barrel and wedge fastening assembly 51 from pulling the cable bolt through the resin 52. The bulbous deformations 11 are also to assist in mixing of the resin during rotation of the cable bolt The resin is, however, typically only mixed in the immediate vicinity of the bulbous deformations 11, and resin formed between successive bulbous deformations 11 remains poorly mixed. Due to the viscosity of the typical polyester resins utilised in the resin cartridges, the voids formed in the bulbous deformations are not sufficiently penetrated by resin to create a solid mass, leaving large voids within the bulbous deformations. Further, as a result of mixing of the resin only effectively occurring between the exterior surface of the cable bolt and the wall of the rock hole 60, resin which does penetrate into the bulbous deformations may be poorly mixed and hence may not set to a solid consistency.

With voids and/or soft material being located within the bulbous deformations 11, axial tension applied to the cable bolt 10 tends to cause the bulbous deformations 11 [R:\LIBLL] I 3413.doc:TCW to collapse, leaving a generally cylindrical outer surface in the resin encased portion of the cable bolt, allowing for the cable bolt to be pulled from the resin at a reduced load.

This problem is further exacerbated with multi-layer type cable bolts which are comprised of 19 to 21 thin wire filaments arranged in successive annular layers, leaving relatively small gaps between individual wire filaments when provided with a bulbous deformation. It is particularly difficult to ensure that such relatively small gaps become filled with resin as set out above, typically when such resin is of a relatively thick and viscous consistency.

Object of the Invention It is an object of the present invention to overcome or at least substantially ameliorate at least one of the above problems.

Summary of the Invention There is disclosed herein a cable bolt comprising: a cable having first and second ends and a bulbous deformation formed adjacent said first end, and a wire attached to said cable and spirally extending about said cable from adjacent said bulbous deformation toward said cable second end.

Typically, a first end of said wire is secured to a ring secured to said cable adjacent said bulbous deformation.

Typically, a second end of said wire is secured to a second ring secured to said cable.

Preferably, said second ring is sized so as to provide a barrier restricting, in use, flow of resin along said cable bolt toward said cable second end.

Typically said wire is welded to said first and second rings.

Brief Description of the Drawings Preferred forms of the present invention will now be described by way of examples with reference to the accompanying drawings, wherein: Fig. 1 is a schematic cross sectional view of a prior art cable bolt installation.

Fig. 2 is a schematic side elevation view of a cable bolt installation utilising preferred cable bolt of the present invention.

Fig. 3 is a fragmentary side elevation view of the cable bolt of the installation of Fig. 2.

[R:\LIBLL] 13413.doc:TCW Detailed Description of the Preferred Embodiment With reference to Figures 2 and 3, a cable bolt 100 has a cable 101 having first and second ends 101a and 10b. A bulbous deformation 102 is formed in the cable 101 adjacent the first end 101a in much the same manner as described above.

Rings 103, 104, here in the form of crimped ferrules, are secured to the cable at each opposing end of the bulbous deformation 102. The ring 103 positioned at the cable first end 101 a serves primarily to protect the welded end surface of the cable from fraying whilst compressing the cable in forming the bulbous deformation 102.

The ring 104 also serves to locally stabilise the cable 101 whilst forming the bulbous deformation 102, but is primarily provided as an attachment point for a wire 105 which is attached to the cable 100 via the ring 104 and spirally extends about the cable from the ring 104 adjacent the bulbous formation 102 toward the cable second end The wire accordingly takes the general appearance of a spring. The opposing end of the wire 105 is attached to the cable by way of a further ring in the form of a washer 106. A further ferrule 107 is crimped on to the cable 101 and holds the washer 106 in place.

The ends of the wire 105 are typically welded to the ring 104 and washer 106 respectively, however any suitable means of attaching the wire to the cable 101 may be utilised as desired. Whilst a circular wire is depicted in Figures 2 and 3, any suitable cross section of wire may be utilised.

In use, the cable bolt 100 is installed into a rock roof hole 60 in the usual manner. One or more resin cartridges are first installed into the hole 60 and pushed to the top of the hole using a resin inserter in the usual manner. The cable bolt 100 is then driven into the hole 60, puncturing the resin cartridges. The cable bolt 101 is rotated by the typical installation machinery by way of the drive head 108 welded to the cable second end 101b so as to mix the resin 52. The spiral wire 105 acts to assist in mixing the resin, and particularly to pump the resin toward the cable first end 101a and in particular toward the bulbous deformation 102. To ensure the spiral wire pumps the resin toward the bulbous deformation 102 rather than extracts it down the hole, the cable bolt is to be rotated in the appropriate direction. For a left handed spiral, the cable bolt should be rotated with "right handed" rotation installation machinery. In practice, the spiral will be wound in the appropriate direction to suit the machinery available.

The pumping of the resin 52 toward the bulbous deformation 102 increases the pressure in the resin and acts to push the mixing resin into the voids formed in the bulbous deformation to ensure that mixed resin substantially fills the voids, setting to [R:\LIBLL] 13413.doc:TCW form a solid mass preventing the bulbous deformation 102 from collapsing upon the application of a tensile load, allowing it to serve as an anchor as intended.

Whilst the wire 105 itself will also assist in anchoring the cable bolt 100 within the resin, its primary purpose is to mix and pump the resin during installation. Upon high loads being experienced by displacement of rock surrounding the hole 60, the wire 105 will potentially be displaced from its attachment by the crimped ferrules 104, 107, however given that its primary purpose has been fulfilled, this will not be of any particular detriment.

The washer 106 is sized so as to provide a barrier which restricts flow of the io resin down past the end of the wire 105 and toward the cable second end 101b, as is apparent from Figure 2.

Once the resin has been mixed, a mine plate 50 and wedge and barrel assembly 51 is assembled on to the cable bolt adjacent the cable second end 101b, and a grout tube 53 inserted through the mine plate 50 and into the annular cavity defined between the cable bolt 100 and the wall of the rock hole 60. The bolt is then pretensioned in the usual manner to the required preload, and grout injected through the grout tube 53 to post grout the portion of the hole 60 between the resin encased upper portion and the opening of the hole.

Whilst the embodiment depicted has only a single bulbous deformation 102 and spiral wire 105, it is envisaged that two or more bulbous deformations might be formed toward the cable first end, with a spiral wire extending downwardly from adjacent each of the bulbous deformations.

The person skilled in the art will appreciate other possible modifications and variations from the cable bolt particularly described.

[R:\LIBLL] 13413.doc:TCW

Claims (6)

1. A cable bolt comprising: a cable having first and second ends and a bulbous deformation formed adjacent said first end, and .a wire attached to said cable and spirally extending about said cable from adjacent said bulbous deformation toward said cable second end.

2. The cable bolt of claim 1, wherein a first end of said wire is secured to a ring secured to said cable adjacent said bulbous deformation.

3. The cable bolt of either one of claims 1 and 2, wherein a second end of said wire is secured to a second ring secured to said cable.

4. The cable bolt of claim 3, wherein said second ring is sized so as to provide a barrier restricting, in use, flow of resin along said cable bolt toward said cable second end.

The cable bolt of either one of claims 3 and 4, wherein said wire is welded to said first and second rings.

6. A cable bolt substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings. Dated 29 July, 2002 DYWIDAG-Systems International Pty Limited Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [R:\LIBLL] 13413.doc:TCW