AU2780400A - Method and apparatus for forming rock anchor - Google Patents

Description

P/00/0011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Address for service in Australia: Invention Title: Industrial Rollformers Pty Ltd CARTER SMITH BEADLE Level 10, 189 Kent St Sydney NSW 2000 Australia Method and Apparatus for Forming a Rock Anchor Details ofAssociated Provisional Application: PP9963 filed 23 April 1999 The following statement is a full description of this invention, including the best method of performing it known to us The present invention relates to an apparatus and a method for manufacturing a rock anchor. More particularly, the present invention relates to an apparatus and a method for manufacturing a rock anchor of the type that comprises or includes a cable having a plurality of strands and at least one enlarged portion in which the strands of the cable are spaced apart from one another.

Rock anchors and rock bolts (the terms are frequently used interchangeably) are used to stabilise underground cavities formed in mining operations. Rock anchors are typically inserted into holes drilled in the side and/or roof of an underground mine. The hole is then filled with a hardenable material, such as cement or synthetic resin, which acts to hold the rock anchor in place. A plate may be attached to the end of the rock anchor, which plate is held in position against the wall or roof of the mine to assist in stabilising the wall or roof.

.o.o S 15 Rockanchors may be broadly classified into two different types: one type in which the rock anchor includes a rod-shaped anchor element, such as a steel rod or pipe, and the other type in which the rock anchor includes a cable or tendon made from a plurality of strands.

Rock anchors made from cables or tendons, such as steel cable made of a number of strands helically wound around a central strand, are particularly useful in applications requiring long anchors. These types of rock anchors have a degree of flexibility, which allows them to be used in areas where the mine provides restricted space by virtue of being able to bend the rock anchor as it is inserted into the bore hole.

It is known to provide rock anchors made from cables or tendons with enlarged portions or bulbous portions that have been formed by separating the strands in the cable or tendon from each other. The purpose of forming the enlarged portion or bulbous portion is to improve the adhesion between the hardening material and the rock anchor. Furthermore, the hardening material also penetrates GWN:DMA:#31022.PRV 17 April 2000 into the space between the strands and when it has set a mechanical connection between the strands and the hardening material is also formed.

Australian patent no. 640,906 (AU-B-46215/89) in the name of Garford Pty Ltd describes an apparatus for manufacturing a rock anchor from a cable, which apparatus comprises at least two first clamp means. Each of the first clamp means comprise an hydraulic ram bearing a plate arranged to clamp the cable against an opposed plate. The apparatus also comprises a cable displacement means for displacing the cable longitudinally relative to the first clamp means after a bulbous portion has been formed in the cable. The cable displacement means comprises a second clamp means arranged to grip the tendon for longitudinal displacement of the tendon. This apparatus suffers the disadvantage of requiring at least two hydraulic rams, and, in most embodiments, more than two hydraulic rams, which require regular maintenance.

It is an object of the present invention to provide an improved apparatus and a method for manufacturing a rock.

In a first aspect, the present invention provides an apparatus for manufacturing a rock anchor of the type including or comprising a cable having a plurality of strands and at least one enlarged portion in which the strands are spaced apart from one another, the apparatus comprising feeding means for feeding the cable, a first holding means which allows the cable to pass therethrough in a forward direction and which holds the cable and substantially prevents the cable from moving in a reverse direction when a force tending to move the cable in the reverse direction is applied to the cable, a second holding means for selectively clamping and unclamping the cable and wherein the first holding means and the second holding means are movable relative to one another.

Preferably, the first holding means comprises a wedging apparatus. The wedging apparatus of the first holding means may comprise a first wedging means GWN:DMA:#31022.PRV 17 April 2000 4 4 having a passageway therein through which the cable can pass and a plurality of second wedging means defining a passageway therebetween through which the cable can pass, wherein when the cable moves in a reverse direction, at least one wedging surface of at least one of the second wedging means interacts with at least one wedging surface of the first wedging means to thereby reduce the size of the passageway such that the second wedging means engage tightly with the cable to prevent further travel of the cable in the reverse direction.

The first holding means. preferably comprises a block having an aperture therethrough, a wall or walls of the aperture defining a least one wedging surface, and a collet comprising at least two collet pieces, wherein the collet has a passageway therethrough and at least one of the at least two collet pieces has a wedging surface that engages at least one wedging surface of the aperture.

Preferably, the collet is substantially frusto-conical in shape and the aperture of the .i 15 block is of a generally complementary frusto-conical shape. The generally complementary frusto-conical surfaces of the collet and aperture act as the wedging surfaces in this arrangement.

The first holding means may further comprises an abutment means that is biased to hold the wedging surfaces of the second wedging means in contact with the at least one wedging surface of the first wedging means. If a collet is used, the oeo• abutment means may contact an end surface of the collet to hold the collet in contact with the wedging surface(s) of the aperture. The abutment means suitably comprises a plate. The biasing means is preferably a spring.

The second holding means may comprise a wedging apparatus that may include a third wedging means and at least one fourth wedging means, the at least one fourth wedging means defining a passageway through which the cable can pass, and a selectively actuable biasing means to cause respective wedging surfaces of the third and fourth wedging means to interact to reduce the size of the passageway to thereby tightly engage the cable to prevent movement of the cable through the GWN:DMA:#31022.PRV 17 April 2000 second holding means. The selectively actuable biasing means may comprise an hydraulic cylinder or a pneumatic cylinder.

The second holding means preferably comprises a collet arrangement in which the third wedging means defines a substantially frusto-conical surface and the at least one fourth wedging means comprises a collet having a plurality of collet pieces defining the passageway through which the cable can pass, the collet being generally frusto-conical, with frusto-conical surfaces of the third wedging means and the collet defining complementary wedging surfaces. The plurality of collet pieces define a passageway through which the cable can pass. An end of one of the third or fourth wedging means may butt against a second abutment means whilst an end of the other of the third or fourth wedging means bears against or is in contact with the selectively actuable biasing means.

oooo 15 Preferably, the apparatus of the present invention further comprises a frame for mounting the first and second holding means, the frame enabling relative movement of the first and second holding means towards and away from each other.

Preferably, the first and second holding means are biased away from each other by biasing means, such as a spring. The biasing means suitably also biases the second wedging means into position with the first wedging means.

The feeding means advantageously comprises a pinch roller arrangement.

Such arrangements are well known in the art of feeding cables from spools or reels and need not be described further. The feeding means preferably are selectively operable to allow the cable to be fed through the forming apparatus at an appropriate time.

In a second aspect, the present invention provides a method for manufacturing a rock anchor of the type including or consisting of a cable having a plurality of strands and at least one enlarged portion in which the strands are spaced apart from one another, the method comprising providing an apparatus as described GWN:DMA:#31022.PRV 17 April 2000 with reference to the first aspect of the present invention, feeding a cable through the first holding means and the second holding means, clamping the cable in the second holding means and initiating relative movement between the first and second holding means to decrease the distance there between, wherein the cable is clamped by the first holding means and forming the enlarged position by continuing the relative movement together of the first and second holding means.

In operation of the apparatus of the present invention, the feeding means feeds a cable, for example, from a spool or reel of cable, through the first holding means and through the second holding means. When the cable has passed through to a sufficient extent to enable the correct position of the bulbous position, the feeding means is stopped and the selectively actuable biasing means is actuated to ,.thereby close the passage in the fourth wedging means. As a result, the fourth wedging means, and hence the second holding means, tightly grips the cable and the S" 15 cable is prevented from moving in either direction through the second holding means. The selectively actuable biasing mans continues to operate and this then o causes the second holding means to move relatively towards the first holding means. The cable wants to move in the rearwards direction but this causes the second wedging means, and hence the first holding means, to securely grip the cable and thereby prevent substantial movement of the cable in the rearwards direction.

Consequently, the cable is securely held or clamped by both the first and second holding means. As the first and second holding means continue to move relatively closer to each other, the strands of the cable move apart to form the bulbous portion.

When the bulbous portion has been formed, the selectively actuable biasing means is released. This results in the first and second holding means moving relatively away from each other. The first holding means allows the cable to move therethrough in a forwards direction and the second holding means releases the cable. The feeding means may then be activated to feed more cable to the apparatus and to move the bulbous portion out of the apparatus.

GWN:DMA:#31022.PRV 17 April 2000 In some embodiments, it may be advantageous to twist the cable to assist in unravelling the strands. Accordingly, in another embodiment, the first holding means and/or the second holding means may be adapted to rotate.

It may also be possible to place a spacing element over a centre strand of the cable to hold the outer strands in a spaced-apart relationship. In this regard, steel cables are commonly formed from a centre strand having a number of outer strands (typically, six outer strands) twisted around the centre strand. Accordingly, in a further embodiment, the method of the present invention includes the steps of forming the enlarged portion such that the outer strands of the cable become spaced apart from the centre strand whilst the centre strand is minimally displaced, and •placing a spacing element about the centre strand.

The present invention will now be further described with reference to a preferred embodiment as shown in the attached Figures. In the Figures:: Figure 1 shows a cross-sectional side elevation view of an apparatus in accordance with the present invention in which the second holding means is in an open position; Figure 2 shows the apparatus of Figure 1 with the second holding means :°•oo o clamped onto the cable; and Figure 3 shows the apparatus of Figure 2 as it forms the enlarged portion of the rock anchor.

Turning to Figure 1, the apparatus 10 of the present invention includes a frame 12 that carries first holding means 14 and second holding means 16. First holding means 14 comprises a fixed block 18 that is fixedly mounted to frame 12.

Fixed block 18 has a frusto-conical aperture 20 formed therein. The first holding means 14 further comprises a first collet piece 22 and second collet piece 24 that, GWN:DMA:#31022.PRV 17 April 2000 8 when together as shown in figure 1, define a generally frusto-conical outer surface that is complementarily shaped to mate with the frusto-conical surface of the aperture 20 in fixed block 14. The collet pieces 22, 24 define a collet that has a passage 26 therein, which passage allows the cable 28 to pass therethrough.

A slideable plate 30 is slideably mounted to frame 12 and the front surface of slideable plate 30 bears on rear surfaces of collet pieces 22, 24 to thereby hold the collet pieces 22, 24 in aperture 20. A spring 32 is used to biased the slideable plate into contact with the rear surfaces of the collet pieces 22, 24.

As can be seen from Figure 1, slideable plate 30 has an opening 31 therein to allow the cable 28 to pass therethrough.

The second holding means 16 comprises bearing members 34, 36. Collet 15 pieces 38, 40 having generally frusto-conical outer wedging surfaces are provided to interact with a complementary shaped wedging surface 42 of wedging member 44. Wedging member 44 has an aperture 46 therein to allow the cable to pass therethrough. A slideable plate 48 that is also biased by spring 32 is in contact with the forward surfaces of collet pieces 37, 39 and this assists in retaining the collet 20 pieces 37,39 in position.

*00o Wedging member 44 is connected at its rear end to an hydraulic cylinder which is partly shown at reference number 50. Hydraulic cylinder 50 is preferably a double actuable hydraulic cylinder that can be powered to open and powered to close.

Figure 1 shows the apparatus 10 set up to enable feeding of the cable 28 through the apparatus. In particular, the cable 28 is fed from a spool or reel (not shown) by a pinch roller arrangement. The pinch roller arrangement may be of any type known to the person of skill in the art to suitable for feeding a cable from a reel or spool and need not be described further. Accordingly, the pinch roller GWN:DMA:#31022.PRV 17 April 2000 arrangement is not shown in Figure 1. The cable 28 passes through the aperture 26 defined between collet pieces 22, 24 and thereafter passes through the second holding member, which is in the open position in Figure 1.

As will be appreciated from Figure 1, the first holding member, in including a collet defined by collet pieces 22, 24, allows the cable 28 to pass through in the forward direction as shown by the large arrow 52. If there is any snagging or friction between the cable 28 and the walls of aperture 26, this snagging or friction will tend to move the collet defined by collet pieces 22, 24 to the right (as drawn) against the action of biasing spring 32 and this movement will result in an enlargement of aperture 26. However, if the cable starts to move to the left (as 4i*" drawn), friction between the cable 28 and the walls of aperture 26 will cause the

(I

collet to also move to the left, which because of the arrangement of the frustoconical wedging surfaces of the collet pieces 22, 24 and aperture 20 will result in the size of the passage 26 decreasing. As a result, the cable will be tightly gripped or clamped by the collet defined by collet pieces 22, 24 and this will prevent movement of the cable in the rearward direction.

Once the cable 28 has passed through the apparatus 10 to an extent such that the correct position for formation of an enlargement is reached, the second holding means is then operated to close and clamp onto the cable 28. This is shown in Figure 2. In Figure 2, hydraulic cylinder 50 has been actuated such that the cylinder expands and pushes wedging means 44 to the left. As a result, frusto-conical wedging surface 42 contacts the complementary shaped surfaces 38, 40 of respective collet pieces 37, 39. This forces collet pieces 37, 39 to move radially inwardly and clamp tightly onto cable 28. As a result of this, cable 28 is immobilised by the second holding means 16.

Continued actuation of the hydraulic cylinder 50 tends to push the cable 28 to the left. This causes the collet defined by collet pieces 22, 24 to tightly grip or GWN:DMA:#31022.PRV 17 April 2000 clamp the cable and prevent further movement of the cable through the first holding means in the reverse direction.

The cable 28 is now firmly clamped at two places by first holding means 14 and second holding means 16. Continued actuation of the hydraulic cylinder causes the second holding means 16 and sliding plate 48 to move against the force of biasing spring 32. In otherwords, the distance between the first holding means 14 and second holding means 16 is reduced. As the cable 28 is firmly held at two positions by first holding means 14 and second holding means 16, the portion of cable 28 intermediate first holding means 14 and second holding means 16 begins to enlarge to form an enlarged portion 54 as shown in figure 3.

Once the external dimensions of the enlarged portion 52 reached the desired size, hydraulic cylinder 50 is retracted. This initially causes cable 28 to be pulled through first holding means 14 (it being appreciated that the cable 28 is still free to move to the right through first holding means 14). Once the cylinder 50 has been retracted such that sliding plate 48 is at its rearmost position, the wedging means 44 is retracted from the wedging surfaces of collet pieces 37, 39. The collet pieces 37, 39 are preferably biased, for example by springs, such that the no-load position of collet pieces 37, 39 of collet pieces 37, 39 is retracted away from the cable (as is shown in Figure Once the collet pieces 37, 39 of the second holding means are in their retracted position, the feeding means is then activated to feed the cable and i the enlarged portion through the aperture in the second holding piece.

*oooo If desired, further enlarged portions may be made in different parts of the cable to provide a rock anchor having a plurality of enlarged portions. The apparatus may also be enclosed with a cable cutting means to cut the rock anchor to the correct size.

As variations of the embodiment described above, it may be possible to impart twist onto the cable. This may be suitably achieved by arranging for either GWN:DMA:#3 1022.PRV 17 April 2000 11 the collet defined by collet pieces 22, 24 to be rotated or by arranging for the collet defined by collet pieces 37, 39 to be rotated. It may also be possible to include the placement of a spacer ring on the central wire in the enlarged portion. This spacer ring may be inserted manually by an operator or automatically.

The method of the present invention provides an effective apparatus for forming rock anchors of the type described. The apparatus has only a small number of moving parts that require regular maintenance.

The apparatus shown in figures 1 to 3 may comprise the entire apparatus for forming the rock anchors. Alternatively, the apparatus shown in figures 1 to 3 may comprise a sub-unit of a larger machine having a plurality of such forming portions therein.

15 Those skilled in the art will appreciate that the invention described herein may be susceptible to variations and modifications other than those specifically described. It will be appreciated that the present invention should be taken to include all such variations and modifications that fall within its spirit and scope.

*oo o GWN:DMA:#31022.PRV 17 April 2000

Claims (27)

1. An apparatus for manufacturing a rock anchor of the type including or comprising a cable having a plurality of strands and at least one enlarged portion in which the strands are spaced apart from one another, the apparatus comprising feeding means for feeding the cable, a first holding means which allows the cable to pass therethrough in a forward direction and which holds the cable and substantially prevents the cable from moving in a reverse direction when a force tending to move the cable in the reverse direction is applied to the cable, a second holding means for selectively clamping and unclamping the cable and wherein the first holding means and the second holding means are movable relative to one another.

2. An apparatus as claimed in claim 1 wherein the first holding means 15 comprises a wedging apparatus. .ooo

3. An apparatus as claimed in claim 2 wherein the wedging apparatus of the Sfirst holding means comprises a first wedging means having a passageway therein through which the cable can pass and a plurality of second wedging means defining a passageway therebetween through which the cable can pass, wherein when the cable moves in a reverse direction, at least one wedging surface of at least one of the second wedging means interacts with at least one wedging surface of the first wedging means to thereby reduce the size of the passageway such that the second wedging means engage tightly with the cable to prevent further travel of the cable in the reverse direction.

4. An apparatus as claimed in any one of claims 1 to 3 wherein the first holding means comprises a block having an aperture therethrough, a wall or walls of the aperture defining at least one wedging surface, and a collet comprising at lest two collet pieces, wherein the collet has a passageway therethrough and at least one of GWN:DMA:#31022.PRV 17 April 2000 13 the at least two collet pieces has a wedging surface that engages at least one wedging surface of the aperture.

An apparatus as claimed in claim 4 wherein the collet is substantially frusto- conical in shape and the aperture of the block is of a generally complementary frusto-conical shape.

6. An apparatus as claimed in any one of claims 1 to 5 wherein the first holding means further comprises an abutment means that is biased to hold the wedging surfaces of the second wedging means in contact with the at least one wedging surface of the first wedging means.

7. An apparatus as claimed in claim 6, when appended to claim 4 or claim S.wherein the abutment means contacts an end surface of the collet to hold the collet 15 in contact with the wedging surface(s) of the aperture. oooo

8. An apparatus as claimed in claim 6 or claim 7 wherein the abutment means Scomprises a plate.

9. An apparatus as claimed in claim 8 wherein the plate is biased by one or Smore springs. i"

10. An apparatus as claimed in any one of claims 1 to 9 wherein the second "holding means comprises a wedging apparatus that include a third wedging means and at least one fourth wedging means, the at least one fourth wedging means defining a passageway through which the cable can pass, and a selectively actuable biasing means to cause respective wedging surfaces of the third and fourth wedging means to interact to reduce the size of the passageway to thereby tightly engage the cable to prevent movement of the cable through the second holding means. GWN:DMA:#31022.PRV 17 April 2000 14

11. An apparatus as claimed in claim 10 wherein the selectively actuable biasing means comprises an hydraulic cylinder or a pneumatic cylinder.

12. An apparatus as claimed in claim 10 or claim 11 wherein the second holding means comprises a collet arrangement in which the third wedging means defines a substantially frusto-conical surface and the at least one fourth wedging means comprises a collet having a plurality of collet pieces defining a passageway through which the cable can pass, the collet being generally frusto-conical, with frusto- conical surfaces of the third wedging means and the collet defining complementary wedging surfaces.

13. An apparatus as claimed in any one of claims 10 to 12 wherein an end of one of the third or fourth wedging means butts against a second abutment means whilst an end of the other of the third or fourth wedging bears against or is in contact with the selectively actuable biasing means.

14. An apparatus as claimed in any one of the preceding claims further comprising a frame for mounting the first and second holding means, the frame enabling relative movement of the first and second holding means towards and away from each other. •co.

An apparatus as claimed in any one of the preceding claims further comprising biasing means for biasing the first and second holding means away from oooo• each other.

16. An apparatus as claimed in claim 15 wherein the biasing means comprises one or more springs.

17. An apparatus as claimed in claim 15 or claim 16, when appended to claim 9, wherein the biasing means also biases the plate. GWN:DMA:#31022.PRV 17 April 2000

18. An apparatus as claimed in any one of the preceding claims wherein the first holding means and/or the second holding means are adapted to rotate.

19. An apparatus as claimed in any one of the preceding claims wherein the feeding means comprises a pinch roller arrangement.

An apparatus as claimed in any one of the preceding claims wherein the feeding means is selectively operable to allow the cable to be fed through the apparatus at an appropriate time.

21. A method for manufacturing a rock anchor of the type including or consisting of a cable having a plurality of strands and at least one enlarged portion in which the strands are spaced apart from one another, the method comprising providing an apparatus as claimed in any one of the preceding claims, feeding a 15 cable through the first holding means and the second holding means, clamping the o :cable in the second holding means and initiating relative movement between the first and second holding means to decrease the distance therebetween, wherein the Scable is clamped by the first holding means and forming the enlarged position by continuing the relative movement together of the first and second holding means.

A method as claim in claim 21, wherein the first holding means comprises a first wedging means having a passageway therein through which the cable can pass i and a plurality of second wedging means defining a passageway therebetween through which the cable can pass, wherein when the cable moves in a reverse direction, at least one wedging surface of at least one of the second wedging means interacts with at least one wedging surface of the first wedging means to thereby reduce the size of the passageway such that the second wedging means engage tightly with the cable to prevent further travel of the cable in the reverse direction and the second holding means comprises a wedging apparatus that include a third wedging means and at least one fourth wedging means, the at least one fourth wedging means defining a passageway through which the cable can pass, and a GWN:DMA:#31022.PRV 17 April 2000 selectively actuable biasing means to cause respective wedging surfaces of the third and fourth wedging means to interact to reduce the size of the passageway to thereby tightly engage the cable to prevent movement of the cable through the second holding means, wherein the method comprises the steps of feeding a cable through the first holding means and through the second holding means, stopping the feeding means, actuating the selectively actuable biasing means to thereby reduce the size of the passageway in the fourth wedging means such that the fourth wedging means and hence the second holding means tightly grips the cable to thereby prevent the cable from moving in either direction through the second holding means, continuing actuation of the selectively actuable biasing means to cause the second holding means to move relatively towards the first holding means whereby the second wedging means and hence the first holding means securely grips the cable to prevent substantial movement of the cable in the rearward direction through the first holding means, and continuing said movement of the 15 second holding means relatively towards the first holding means to form the at least .oo. one enlarged portion.

23. A method as claimed in claim 23 further comprising releasing the selectively actuable biasing means after the at least one enlarged portion has been formed.

-24. A method as claimed in any one of claims 21 to 23 further comprising .0.0. causing the first holding means and/or the second holding means to rotate to twist the cable to assist in unraveling the strands. 060:

25. A method as claimed in any one of claims 21 to 24 further comprising forming the enlarged portion such that outer strands of the cable become spaced apart from a centre strand whilst the centre strand is minimally displaced, and placing a spacing element about the centre strand.

26. An apparatus for forming a rock anchor substantially as hereinbefore described with reference to the accompanying drawings. GWN:DMA:#31022.PRV 17 April 2000 17

27. A method for forming a rock anchor substantially as hereinbefore described with reference to the accompanying drawings. DATED: 17 April 2000 CARTER SMITH BEADLE Patent Attorneys for the Applicant: Industrial Rollformers Pty Ltd *o S 2 *g GWN:DMA:#31022.PRV 17 April 2000