AU2009273761B2

AU2009273761B2 - A method of encasing a yielding rock bolt shaft

Info

Publication number: AU2009273761B2
Application number: AU2009273761A
Authority: AU
Inventors: Neville Hedrick
Original assignee: Garford Pty Ltd
Current assignee: Garford Pty Ltd
Priority date: 2008-07-25
Filing date: 2009-07-24
Publication date: 2014-07-31
Anticipated expiration: 2029-07-24
Also published as: PE20110526A1; KR20110036827A; WO2010009506A1; CL2011000130A1; AU2009273761A1

Abstract

A method of encasing a solid shaft (10) to be used in a yielding rock bolt which comprises passing a de-bonding sheath (18) through a mechanical feed means (14) and feeding the de-bonding sheath (18) onto the shaft (10). The shaft (10) is preferably mounted into an externally threaded end (12) which engages with a threaded stopper (16).

Description

WO 2010/009506 PCT/AU2009/000938 "A METHOD OF ENCASING A YIELDING ROCK BOLT SHAFT" BRIEF DESCRIPTION OF THE INVENTION 5 The present invention relates to a method of encasing a yielding rock bolt shaft. FIELD OF THE INVENTION In International Patent Application Number WO 2004/055327 there is described and claimed a yielding rock bolt comprising a shaft which is arranged to be inserted into a 10 rock body. The yielding rock bolt of Patent Application Number WO 2004/055327 preferably comprises a debonding sheath mounted about the shaft to prevent the shaft from bonding to other material such as resin. In placing a debonding sheath over the shaft of a yielding rock bolt difficulties have been 15 encountered. For example, it is known to use manual methods to place a debonding sheath over a shaft of a yielding rock bolt but this has proved to be time consuming and labour intensive. Further, the sheath may be damaged during the process of fitting. Any damage to, or 20 malfunction of, the sheath undermines the function of the sheath in preventing bonding of the shaft with resin or other material. The present invention attempts to overcome at least in part the aforementioned disadvantages of the prior art.

I

WO 2010/009506 PCT/AU2009/000938 SUMMARY OF THE INVENTION In accordance with the present invention there is provided a method of encasing a shaft, to be used in a yielding rock bolt, with a debonding sheath, which comprises mounting 5 the shaft securely, passing the debonding sheath through mechanical feed means and feeding the debonding sheath onto the shaft. DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the 10 accompanying drawings, in which: Figure 1 is a perspective view of a shaft used in production of a yielding rock bolt; Figure 2 is a perspective view of a means to sheathe a shaft in accordance with the 15 method of the present invention; Figure 3 is a perspective view similar to figure 2 showing a means to cut a debonding sheath encasing a shaft in accordance with the method of the present invention; 20 Figure 4 is a perspective view showing the fitting of a means to fix to a debonding sheath in position on a shaft in accordance with the present invention; and Figure 5 is a perspective view of a shaft fitted with a debonding sheath and fixed in accordance with the present invention. 2 WO 2010/009506 PCT/AU2009/000938 DESCRIPTION OF THE INVENTION In the drawings, there is shown a solid metal shaft 10 having two ends, one with a threaded portion 12. The shaft 10 is placed on a preformed channel, not shown, with a 5 stopper 16 at a distal end and a means to sheathe disposed at a proximal end, as shown in figure 2. The stopper 16 may be adjusted in position longitudinally and fixed at a suitable position required for the length of the yielding rock bolt produced. Yielding rock bolts can vary in length depending on the environmental conditions in which they are used. Typical examples are 1.8m, 2.4m and 3m in length. Further, the stopper 16 contains a 10 threaded aperture arranged to receive and engage the threaded portion 12 of the shaft 10. In the present invention a preferred embodiment of a mechanical feed means comprises a plurality of laterally disposed adjacent rollers 14 (in this case, two rollers) arranged to receive the shaft 10. Each roller 14 is generally cylindrical in shape with an annular, and 15 transversely arcuate circumferential groove 20 extending around an outer circumference thereof as illustrated in figure 2. The rollers 14 are so arranged that a longitudinal axis of the shaft 10 forms a centre point of a recess formed by opposed adjacent grooves 20. Further, the grooves 20 contain a plurality of transverse ribs 22 which, in use, aid in gripping a debonding sheath 18 between the rollers 14. The dimensions of the adjacent 20 grooves 20 are complementary to an outer profile of the debonding sheath 18. The debonding sheath 18 may be manufactured from, but is not limited to, a plastics material such as polyethylene piping. In use, opposed rollers 14 are powered to rotate at equal known speeds in opposite 3 WO 2010/009506 PCT/AU2009/000938 directions. The debonding sheath 18 is fed between the rollers 14 and received into the grooves 20. The debonding sheath is then gripped by ribs 22 and thereby urged onto an end of the shaft 10 disposed between the rollers 14 as illustrated in figure 2. In an embodiment of the present invention the rate of rotation of the rollers 14 is proportional 5 to the length of the debonding sheath 18 passing between the rollers 14 and may be used to measure and thereby control the length of debonding sheath 18 used in any application. A bulk supply of sheathing material may be positioned near the rollers 14, or further removed, in a spool arrangement to provide a constant supply for mass production. 10 Once the debonding sheath 18 encases the shaft 10 to a desired length it is immobilised by braking the rollers 14. A means to cut is then initialised to sever the debonding sheath 18 as shown in figure 3. In the illustrated embodiment of the present invention the means to cut is in the form of a guillotine blade 24 arrangement which is arranged to be activated by any suitable means. Other embodiments may use a different means to cut 15 such as a rotating blade, a toothed edge or a heat source. Further, other embodiments may include a variety of programmable motion sensors to bring the means to sheath and the means to cut into mechanical or electronic communication whereby an appropriate length of debonding sheath 18 is automatically 20 severed by the blade 24. Lastly, as shown in figures 4 and 5, a fixing means is applied to the sheath 18. A preferred embodiment of the present method uses a crimping sleeve 26 as the fixing means. The sheath 18 and the crimping sleeve 26 are correctly positioned on the shaft 10 4 WO 2010/009506 PCT/AU2009/000938 before a lateral force is applied to the crimping sleeve 26. Flanged side sections 28 upon the crimping sleeve 26 are thereby formed and result in a constant compressive force firmly fixing the sheath 18 to the encased shaft 10. 5 Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. 5

Claims

2. A method according to claim 1, characterized in that a longitudinal axis of the shaft forms a centre point of a recess formed by a pair of opposed adjacent grooves.
3. A method according to claims 1 or 2, characterized in that the grooves contain a plurality of transverse ribs which aid in gripping the debonding sheath.
4. A method according to any one of the preceding claims, wherein the adjacent rollers are powered to rotate at equal speeds in opposite directions.
5. A method according to claim 4, characterized in that the rollers are immobilized by being braked once the shaft has been encased. AMENDED SHEET . IPENAU 6 Received 1 September 2010
6. A method according to any one of the preceding claims, characterized in that the shaft is solid and has two ends, one of the ends being provided with an externally threaded portion.
7. A method according to claim 6, characterized in that the shaft is engaged with a stopper containing a threaded aperture which receives and engages the threaded portion of the shaft
8. A method according to claim 7, wherein the stopper is adjusted in position longitudinally and fixed at a position appropriate for a length of the yielding rock bolt produced.
9. A method according to any one of the preceding claims, characterized in that the debonding sheath is severed by cutting means after the shaft has been sheathed.
10. A method according to any one of the preceding claims, characterized in that fixing means is affixed to the sheath after the shaft has been encased so as to fix the sheath to the shaft.
11. A method according to claim 10, characterized in that the fixing means is a crimping sleeve which applies constant compressive force to the encased shaft. AMENDED SHEET IPENAU 7