WO2011047416A1

WO2011047416A1 - Cable bolt

Info

Publication number: WO2011047416A1
Application number: PCT/AU2010/001364
Authority: WO
Inventors: Neville Hedrick
Original assignee: Garford Pty Ltd
Priority date: 2009-10-23
Filing date: 2010-10-15
Publication date: 2011-04-28
Also published as: AU2010310869B2; AU2010310869A1

Abstract

A multi-strand cable bolt (10) has a pitch of at least 250mm such as about 300mm. The cable bolt (10) is formed with a plurality of spaced bulbs (12) having a bent kingwire therein. The bulbs ( 12) preferably each have a length of 180mm to 300mm such as about 250mm. The bulbs (12) preferably have an overall width of from 30mm to 40mm.

Description

TITLE

"CABLE BOLT"

The present invention relates to a cable bolt.

BACKGROUND OF THE INVENTION

In Australian Patent Number 640906 in the name of the present applicant, there is described and claimed a cable bolt provided with a plurality of spaced expanded portions or bulbs and a method and apparatus for the manufacture thereof. The entire disclosure of Australian Patent Number 640906 is incorporated herein by reference.

The cable bolt of Australian Patent Number 640906 is formed of a plurality of strands including a central king wire. In the bulbs the king wire is bent so as to reduce the risk of the king wire being selectively pulled out in use.

It has now been discovered that the effectiveness of the cable bolt can be increased by making the bulb longer than has hitherto been the case.

Typically, the unbulbed cable bolt, as supplied, has a pitch of about 220mm. This means that an outer wire is twisted about the king wire in such manner that it extends around the periphery of the cable bolt every 220mm. It has been found that it is difficult to produce longer bulbs in cable bolts with a 220mm pitch. Simply increasing the length between a pair of clamping jaws only increases the bulb length marginally.

It has now been discovered, surprisingly, that by decreasing the pitch of the cable bolt that longer bulbs can be produced.

In accordance with one aspect of the present invention there is provided a multi-strand cable bolt having a king wire and a longitudinal axis comprising a plurality of spaced apart bulbs in which the king wire is bent in each bulb, wherein the cable bolt has a pitch of at least 250mm.

Preferably, the cable bolt has a pitch in the range from 275mm to 400mm, more preferably from 275 to 320, mm such as about 300mm.

Conventionally, the bulbs have a length up to 150mm. In the cable bolt of the present invention the bulbs preferably have a length in the range from 180mm to 300mm, more preferably as from 225mm to 275mm, such as, about 250mm. This requires the clamping jaws to be spaced apart by a corresponding distance to achieve the desired bulb length. With the decreased pitch of the starting cable bolt, compared to prior art products, the increased bulb length is readily achieved.

Preferably, the bulbs in the cable bolt of the present invention have an overall width in the range from 25mm to 55mm such as from 30mm to 40mm. Further, it has been found that the increased length of the bulb enables the bulb to have an angle preferably in the range from 2° to 9° more preferably from 4° to 6° from the axis of the cable bolt.

It has been found that the provision of a bulb of greater length, than that provided previously, has the advantage of providing the bulb with an increased selective pull out force of the king wire and more resistance to movement under load. This is believed to be because of an enhanced wedging action or greater radial confinement in use of the bulbed cable bolt.

Further, it has been found in use that the longer bulbs of the cable bolt of the present invention are more resilient than the conventional bulbs in that if they are compressed during installation, for example, they have a greater ability to resume a shape close to their original shape than conventional bulbs.

Still further, with conventional bulbs having a length of up to 150mm the overall width of the bulb cannot readily exceed 30mm. Above this width, it has been found, that the wedging effect is reduced so that the selective pull out load is lower and displacement tends to be higher.

A longer bulb in accordance with the present invention has the advantage that it can be produced with an overall width greater than 30mm with a similar angle to a conventional bulb which provides the advantages discussed above. DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawing which is a side elevation of a bulbed multi-strand bolt in accordance with the present invention

In the accompanying drawing there is shown a cable bolt 10 in accordance with the present invention having a longitudinal axis 11. The cable bolt 10 comprises a plurality of cable strands having a pitch of about 300mm.

The cable bolt 10 is formed with a plurality of spaced bulbs 12 at a spacing A- A of about 250mm.

The bulbs 12 have an angle a from the longitudinal axis 1 1 of the cable bolt 10 of about 5° and an overall width B-B of about 35mm.

The angle ά, as shown, extends from the unbulbed cable bolt 10 to the outermost periphery of a bulb 12. Further, the' overall width B-B extends as shown from an outermost lateral extremity of a bulb 12 as shown in the drawing to an outermost lateral extremity of the bulb on an opposite side of the cable bolt 10.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims

1. A multi-strand cable bolt having a king wire and a longitudinal axis, characterised by comprising a plurality of spaced apart bulbs in which the king wire is bent in each bulb; wherein the cable bolt has a pitch of at least 250mm.

2. A multi-strand cable bolt according to claim 1 , characterised in that the cable bolt has a pitch in the range from 275mm to 400mm.

3. A multi-strand cable bolt according to claim 2, characterised in that the cable bolt has a pitch in the range from 275 to 320mm

4. A multi-strand cable bolt according to any one of the preceding claims, characterised in that the bulbs each have a length in the range from 180mm to 300mm.

5. A multi-strand cable bolt according to claim 4, characterised in that the bulbs each have a length in the range from 225mm to 275mm.

6. A multi-strand cable bolt according to any one of the preceding claims, characterised in that the bulbs each have an overall maximum width in the range from 25mm to 55mm.

7. A multi-strand cable bolt according to claim 6, characterised in that the bulbs each have an overall width in the range from 30mm to 40mm.

8. A cable bolt according to any one of the preceding claims, characterised in that the bulbs each have an angle from the longitudinal axis of the cable bolt in the range from 2° to 9°.

A multi-strand cable bolt according to claim 8, characterised in that the bulbs each have an angle from the longitudinal axis of the cable bolt in the range from 4° to 6°.