AU723113B2 - Bulb forming machine - Google Patents

Description

P/00/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION 00 0 0* *0#0 .9 0 0 0 00 90 0 000 0 .8 0 0008 00 0 STANDARD PATENT Name of Applicant: ROCK ENGINEERING (AUST) PTY LTD LES MOLNAR Actual Inventor(s): Address for service is: WRAY ASSOCIATES 239 Adelaide Terrace Perth, WA 6000 Attorney code: WR Invention Title: "Bulb Forming Machine" Details of Associated Provisional Application No(s): P05303 The following statement is a full description of this invention, including the best method of performing it known to me:- The present invention relates to a machine for forming rock anchors for use in stabilising rock faces and ceilings, for use in particular in the mining industry.

Rock in a rock face or ceiling is generally anchored by boring a hole of required depth into the rock to be stabilised and then introducing a cable bolt assembly into the hole. The cable bolt assembly typically includes a strand or strands formed of a plurality of wires of steel, usually with bulbous portions (hereafter referred to as bulbs) disposed at intervals along the length thereof. This strand and its bulbs are inserted into the hole and are fixed therein by a cement grout which is introduced along the length of the hole under pressure and allowed to 10 set. A plate or the like may then be placed in contact with the rock face to .9 additionally secure surface rock if required. Typically the overall diameter of the strand is in the order of 15 mm (actually the industry standards are 0.5 inch o (12.7 mm) 0.6 inch (15.2 mm) and 0.7 inch (18 mm), any of which may be employed as required), and the strand is normally formed of seven wires of steel of equal diameter. In this respect there is normally a central wire around which the remaining six wires are wound in a spiral configuration to achieve close packing of the wires in a hexagonal configuration, as viewed in cross-section.

9• Previous techniques for forming the bulbs have included grasping and twisting the strand with two spaced apart sets of jaws. This technique results in the 20 peripheral wires being displaced radially to form the bulb, while the central wire is undeflected. This type of bulb is referred to in the trade as a "birdcage".

Australian patent specification 46215/89 describes a bulb forming machine having two sets of jaws each formed by opposed plates, and each having hydraulic rams to operate the opposed plates to clamp a strand at spaced apart locations therealong, and a hydraulic ram arranged to force one set of jaws toward the other set of jaws, and so form the bulb in the strand.

It is an object of this invention to provide an improved bulb forming machine to that described in patent specification 46215/89.

-3- In accordance with the invention there is provided a bulb forming machine for forming a bulb in a strand as hereinbefore described, said bulb forming machine having an input end for feeding input strand, and an output end for discharging strand with a bulb formed therein; said bulb forming machine having a first clamping means located adjacent said output end, for clamping said strand; a second clamping means spaced from said first clamping means and located between said first clamping means and said input end, for clamping said strand; and means for displacing said clamping means toward each other in the axial direction of said strand to form said bulb; wherein said second clamping means includes one way clamp means through which said strand may pass from said input end to said output end (forward direction), but which rigidly clamps said strand to prevent said strand from moving in an opposite direction (reverse *direction).

The means for displacement of the clamping means is most conveniently a hydraulic ram means, as indeed is the means of operating the first clamping means, simply because such hydraulic operation is most effective.

0. The means for displacement may act on one or both clamping means to achieve axial compression of the strand. However to minimise capital costs it is preferred for the means for displacement to act on only one of the clamping 20 means.

In one form the one way clamp means may comprise a collet type jaw.

Specifically, in a preferred arrangement, the one way clamp means is most conveniently formed from an externally cone shaped sleeve divided into two or more separable segments, and housed within an internally cone shaped sleeve.

The externally cone shaped sleeve includes a central bore running therethrough of a diameter less than the nominal diameter of the strand, with the central bore preferably including gripping means for gripping the strand.

-4- The gripping means may include tooth means or a roughened surface, but most preferably includes radial ridges located along the central bore. The segments should be urged toward each other for reliable operation of the clamp means.

In a preferred form of the invention, the first clamping means may include a set of jaws arranged to clamp around the strand. For most efficient gripping the jaws should have a recessed surface to match the overall diameter of the strand, within which the strand is accommodated and gripped. This increases the surface area acting on the strand for gripping purposes. To minimise the force required from the hydraulic ram means that closes the set of jaws and holds the strand, while the means for displacement is forming the bulb, the jaws preferably should also have gripping means for gripping the strand. These may be of o similar configuration to the gripping means utilised in the central bore in the cone shaped sleeve.

The gripping surfaces of the one way clamp means and the first clamping means 15 are preferably hardened in order to prolong the life of these parts. Any suitable hardening technique, such as nitriding or some other case hardening method, may be employed for this purpose.

ea The means for displacement preferably acts on the first clamping means. Most preferably, each jaw of the set of jaws are slidably located on the piston of 20 hydraulic ram means that operates the jaws to clamp the strand, and the means for displacement acts on the jaws; causing them to slide on their respective pistons as the bulb is formed. In this manner the hydraulic ram means that operates the jaws to clamp the strand can be fixed to the base plate on which the machine is assembled, and is not subject to movement of its hydraulic connections which would otherwise occur if the entire first clamping means was moved by the means for displacement.

In order to assist in an understanding of the machine of the invention, the operation of a preferred embodiment will now be described. In operation, the bulb forming machine accepts a length of strand fed in its input end. While the strand could be manually fed, it is preferred that the strand is fed by any suitable mechanical means such as being driven by a pinch roller and idler wheel arrangement. The strand passes through the one way clamp means (second clamping means) unimpeded until it reaches the first clamping means, whereupon the first clamping means is operated to grip the strand. The means for displacing the clamping means toward each other is operated, drawing the first and second clamping means relatively together. As the strand is clamped in the first clamping means, the operation of the means for displacing the clamping means attempts to force the strand in the reverse direction in the one way clamp means, whereupon the one way clamp means grips the strand and prevents any further reverse movement. As further force is brought to bear by the means for :displacing the clamping means, a bulb is formed in the strand.

Once the bulb is fully formed, the first clamping means may be operated to 15 release the strand, the means for displacing the clamping means is returned to the original unactuated position and the strand may be fed further through the machine to a position where it is desired to form the next bulb.

The bulb forming machine of the invention, in utilising the one way clamp means for the second clamping means, obviates the need to have a set of jaws with 20 hydraulic ram means to grip the strand, and so saves capital costs and simplifies operation of the machine.

q** Thus, also in accordance with the invention there is provided a method of forming a bulb in a strand for forming a rock anchor, said method comprising: feeding said strand in a forward direction through one way clamp means to a first clamping means, said one way clamp means being adapted to allow said strand to pass freely therethrough in said forward direction but rigidly clamping said strand to prevent said strand from moving in an opposite reverse direction; clamping said strand with said first clamping means; displacing said first clamping means and said one way clamp means toward each other in the axial -5/1 direction of said strand to form said bulb in said strand in a position between said first clamping means and said one way clamp means; and releasing clamping action of said first clamping means and feeding said strand in said forward direction to discharge said bulb beyond said first clamping means.

Preferably in the step of displacing said first clamping means and said one way clamp means toward each other, said first clamping means is urged in a reverse direction toward said one way clamp means, while said one way clamp means remains in a stationary position.

Preferably in the step of displacing said first clamping means and said one way clamp means toward each other, said one way clamp means is urged in a forward direction toward said first clamping means while said first clamping means remains in a stationary position, or alternatively, preferably in the step of displacing said first clamping means and said one way clamp means toward each other, both said first clamping means and said one way clamp means are S 15 urged toward each other.

Preferably said one way clamp means includes a collet type jaw.

Preferably said one way clamp means is formed from an externally cone shaped Ssleeve divided into two or more separable segments, and housed within an a internally cone shaped sleeve, the externally cone shaped sleeve including a central bore running therethrough of a diameter less than the nominal diameter of the strand.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

The invention will now be described in the following description of one specific A4, embodiment thereof, made with reference to the drawings in which: -6- Figure 1 is a plan view of a bulb forming machine according to the embodiment, showing a strand being fed; Figure 2 is a plan view of the, showing a bulb being formed in the strand; Figure 3 is a side elevation of the bulb forming machine of Figure 1; Figure 4 is a side elevation of the bulb forming machine of Figure 2; Figure 5 is an isometric projection of a part of the one way clamp means; and Figure 6 is an isometric projection of a part of the first clamping means.

0• 10 The embodiment is a bulb forming machine indicated generally at 11 for forming a bulb 13 and a strand 15. Referring to Figures 3 and 4, the bulb forming machine 11 is assembled on a base plate 17, and has an input end indicated generally at 19 and an output end indicated generally at 21.

.l The bulb forming machine 11 has a first clamping means in the form of a hydraulically actuated pair of jaws 23, located toward the output end 21, which jaws are best seen in Figures 1 and 2. Each jaw 23 is mounted for sliding movement in the axial direction of the strand 15 on a piston 25, the piston being housed in a cylinder 27 for hydraulic actuation. When pressure is applied to the cylinders 27, the pistons 25 are pushed out, allowing the pair of jaws 23 to engage the strand 15. The cylinders 27 are mounted to the base plate 17, and braced by a bearing plate 29 which is firmly secured to the base plate 17. An aperture 31 is provided in the bearing plate 29 to allow the formed bulb 13 to pass through. In addition, the spacing between the pair of jaws 23 when the piston 25 and cylinder 27 is at rest is sufficient to allow the bulb 13 to pass therethrough.

-7- The bulb forming machine 11 has a second clamping means in the form of a one way clamp means indicated generally at 33, located toward the input end 19 of the bulb forming machine 11. The one way clamp means 33 is in effect a collet type jaw which comprises an externally cone-shaped sleeve which is divided into three separable segments 35, which are housed within an internally coneshaped sleeve 37. There is a 3 minute difference in the angle of the internally cone-shaped sleeve 37 and the angle formed by the segments 35 of the externally cone-shaped sleeve, with the angle of the segments 35 of the externally cone-shaped sleeve being more acute so that the segments 35 make initial contact at the narrower end of the sleeve 37, which prevents the segments binding within the sleeve 37.

A backing plate 39 having an aperture to allow passage of the strand 15, covers the wider end of sleeve 37, and supports a compression spring 41 which biases the segments 35 to a seating position within the sleeve 37, as shown in Figures 2 and 4. As can be seen, the three segments 35 together form a frusto-conical sleeve, there being an axial aperture therethrough, through which the strand may pass from the input end 19 to the output end 21. The aperture through the segments 35 is of a commensurate diameter to the diameter of the strand although each segment 35 does not prescribe a full 1/3 arc, enabling the 20 effective diameter of the aperture to be less than the diameter of the strand when the segments are arranged together without any space between their adjacent edges. The internal surface of the aperture is provided with gripping means in the form of radial ridges 42 having a pitch of 1 mm and a height of 0.7 mm, which when the strand 15 is forced in a reverse direction, will grip the strand 15 around its circumference, and prevent the strand from moving in a reverse direction through the one way clamp means 33. An external circumferential recess 43 provides space to accommodate urging means in the form of an O-ring to urge the segments 35 toward each other, and so facilitate operation of the one way clamp means 33.

A spacer 46 is further provided between the backing plate 39 of the second -8clamping means 33 and the bearing plate 29. The spacer 46 is generally in the form of a cylindrical sleeve through which the strand 15 extends and of sufficient diameter to allow the bulb 13 to the formed therein during operation of the bulb forming machine, as is best seen in Figures 1 to 4. The spacer 46 acts to retain the compression spring 41 against the segments 35 of the one way clamp means 33.

The bulb forming machine 11 also includes means for displacing the clamping means towards each other, in the form of hydraulic ram means indicated generally at 44. The hydraulic ram means 44 has a housing 45 which supports therein a piston 47. The piston 47 has an axial bore 49 of sufficient diameter to receive the bulb 13, extending therethrough. The piston 47 is arranged to act on the pair of jaws 23, when the jaws 23 have clamped the strand 15, and pushed the jaws 23 along the dove tail track formed in each piston 25. This pushing of the pair of jaws 23 causes the bulb 13 to be formed in the strand 15, after the segments 35 have clamped the strand.

Referring to Figure 6, one of the jaws 23 is shown. The jaw 23 has an axial recess 51 of radius commensurate with the radius of the strand 15, which also S. includes gripping means in the form of radial ridges 53, which also have a pitch of 1 mm and a height of 0.7 mm. A dovetail extrusion 54 extends along underneath the jaw 23 along the length thereof, and is received in a S"complementary shaped track (not shown) in the each piston Each jaw 23, and each segment 35 are case hardened, in order to improve the wear resistance of the steel from which they are formed. It may also be desirable to case harden the dovetail track in the piston As can be seen in Figures 1 and 3, the piston 47 includes a threaded portion on which are received a pair of nuts 57 which act as lock nuts, to set the travel of the piston 47, and hence the amount of deflection of the wires in the strand when forming the bulb 13.

-9- Referring now to Figures 1 and 2, the bulb forming machine 11 includes a pair of pinch rollers 59, which are hydraulically driven, in order to advance the strand through the bulb forming machine 11. It will be understood that the pinch rollers 59 may be omitted if the bulb forming machine is to be used manually.

A counter wheel 61 provides a signal input to a programmable logic controller, for measuring the distance that the strand travels into the bulb forming machine 11. This feature is utilised if automated control of the bulb forming machine 11 is required.

Finally, the bulb forming machine 11 includes a cylinder mount bracket 63, to 10 which is mounted the hydraulic ram means 44, and a top cover plate which rigidly secures to the mounting bracket 63, the bearing plate 29, and the external casing of sleeve 37, for structural rigidity of the machine.

In operation, a strand is fed into the input end 19 of the bulb forming machine, and driven through the one way clamp means 33 the segments 35 and a p o 15 compression spring 41 together yielding against the advancing strand 15, and allowing the strand to pass until the strand reaches the pair of jaws 23, as best seen in Figure 3. The spacer 46 acts to locate the backing plate 39 as the compression spring 41 is compressed thereagainst through the pressing of the Ssegments 35 of the one way clamp means 33 thereon. At this stage, the S 20 cylinders 27 can both be actuated, to allow the pair of jaws 23 to grip the strand With the strand 15 firmly gripped by the pair of jaws 23, the piston 47 of the hydraulic ram means 44 is caused to advance and push the pair of jaws 23 toward the one way clamp means 33. The jaws 23 are caused to slide along the dove tail connection with piston 25, and as this occurs, the wires of the strand are deflected outwardly to form the bulb 13, as shown in Figure 4.

Once the bulb 13 has been formed, the piston 47 is then retracted, as are pistons 25. The pair of jaws 23 are caused to move toward the output end 21 along the dove tail track in their respective pistons 25 to return to the position shown in Figures 1 and 3, by a jaw retractor plate (not shown) which is attached to the piston 47, and extends fingers to the other edge of the jaws 23 to pull them along the dove tail track. It will be understood that alternative means for retracting the jaws toward the output end 21 could include tensioning springs or the like.

At this point in time, the bulb forming machine 11 is ready to form another bulb, once the strand 15 has been further advanced through the bulb forming machine 11. As will be understood, the formed bulbs 13 are passed out through the bore 49 and the piston 47, at the output end 21 of the machine.

It should be appreciated that the invention is not limited to the embodiment described herein. In particular, it will be understood that in another embodiment, rather than having the means fordisplacing the clamping means toward each other acting solely on the first clamping means, the means for displacing the clamping means towards each other may act on the housing containing the one 15 way clamp means. In order to do this, the internally cone-shaped sleeve 47

C*°

would form a part of a piston in a cylinder, which would be hydraulically actuable.

The invention provides a machine in which fewer hydraulic cylinders are required than that disclosed in patent specification 46215/89. In addition, the 20 gripping parts of the embodiment which are prone to wear and need periodic replacement, are smaller than those shown in patent specification 46215/89.

Particularly, the segments 35 are not as difficult to machine as a set of jaws, resulting in a saving in the cost of consumable parts.

Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.

Claims (15)

11- The CLAIMS defining the invention are as follows: 1. A bulb forming machine for forming a bulb in a strand for forming a rock anchor, said bulb forming machine having an input end for feeding input strand, and an output end for discharging strand with a bulb formed therein; said bulb forming machine having a first clamping means located adjacent said output end, for clamping said strand; a second clamping means spaced from said first clamping means and located between said first clamping means and said input end, for clamping said strand; and means for displacing said clamping means toward each other in the axial direction of said strand to form said bulb; wherein 10 said second clamping means includes one way clamp means through which said o. strand may pass from said input end to said output end (forward direction), but S-which rigidly clamps said strand to prevent said strand from moving in an S" opposite direction (reverse direction). 2. A bulb forming machine as claimed in claim 1 wherein said means for 15 displacement of the clamping means includes hydraulic ram means. S.i 3. A bulb forming machine as claimed in claim 1 or 2 wherein said means of operating the first clamping means includes hydraulic ram means. 4. A bulb forming machine as claimed in any one of the preceding claims wherein said means for displacement acts on both clamping means to achieve axial compression of the strand. A bulb forming machine as claimed in any one of claims 1 to 3 wherein said means for displacement acts on only one of the clamping means. 6. A bulb forming machine as claimed in any one of the preceding claims wherein said one way clamp means includes a collet type jaw. 7. A bulb forming machine as claimed in any one of the preceding claims -12- wherein said one way clamp means is formed from an externally cone shaped sleeve divided into two or more separable segments, and housed within an internally cone shaped sleeve, the externally cone shaped sleeve including a central bore running therethrough of a diameter less than the nominal diameter of the strand. 8. A bulb forming machine as claimed in claim 7 wherein said central bore includes gripping means for gripping the strand. 9. A bulb forming machine as claimed in claim 8 wherein said gripping means includes tooth means. 10 10. A bulb forming machine as claimed in claim 8 wherein said gripping means includes a roughened surface. o• a 11. A bulb forming machine as claimed in claim 8 wherein said gripping "means includes radial ridges located along the central bore.

12. A bulb forming machine as claimed in any one of claims 7 to 11 wherein urging means are provided to urge said segments toward each other for reliable operation of the clamp means.

13. A bulb forming machine as claimed in claim 12 wherein said urging means comprises a circumferential tension spring extending around said separable segments of said externally cone shaped sleeve, and contained in a circumferential recess.

14. A bulb forming machine as claimed in any one of the preceding claims wherein said first clamping means includes a set of jaws arranged to clamp around the strand. A bulb forming machine as claimed in claim 14 wherein said jaws have a recessed surface to match the overall diameter of the strand, within which the -13- strand is accommodated and gripped.

16. A bulb forming machine as claimed in claim 15 wherein said jaws have gripping means for gripping the strand.

17. A bulb forming machine as claimed in claim 16 wherein said gripping means includes tooth means.

18. A bulb forming machine as claimed in claim 16 wherein said gripping means includes a roughened surface.

19. A bulb forming machine as claimed in claim 16 wherein said gripping means includes radial ridges located along the central bore. i S 10 20. A bulb forming machine as claimed in any one of the preceding claims wherein said means for displacement acts on the first clamping means. Se o00•. S21. A bulb forming machine as claimed in any one of the preceding claims wherein each jaw of the set of jaws is slidably located on the piston of hydraulic op• ram means that operates the jaws to clamp the strand, and the means for displacement acts on the jaws, causing them to slide on their respective pistons as the bulb is formed.

22. A method of forming a bulb in a strand for forming a rock anchor, said method comprising: feeding said strand in a forward direction through one way clamp means to a first clamping means, said one way clamp means being adapted to allow said strand to pass freely therethrough in said forward direction but rigidly clamping said strand to prevent said strand from moving in an opposite reverse direction; clamping said strand with said first clamping means; -14- displacing said first clamping means and said one way clamp means toward each other in the axial direction of said strand to form said bulb in said strand in a position between said first clamping means and said one way clamp means; releasing clamping action of said first clamping means and feeding said strand in said forward direction to discharge said bulb beyond said first clamping means.

23. A method of forming a bulb as claimed in claim 22 wherein in the step of displacing said first clamping means and said one way clamp means toward each other, said first clamping means is urged in a reverse direction toward said one way clamp means, while said one way clamp means remains in a stationary S•position. o

24. A method of forming a bulb as claimed in claim 22 wherein in the step of *displacing said first clamping means and said one way clamp means toward b 15 each other, said one way clamp means is urged in a forward direction toward said first clamping means while said first clamping means remains in a stationary I :position. A method of forming a bulb as claimed in claim 22 wherein in the step of displacing said first clamping means and said one way clamp means toward 20 each other, both said first clamping means and said one way clamp means are urged toward each other.

26. A method of forming a bulb as claimed in any one of claims 22 to wherein said one way clamp means includes a collet type jaw.

27. A method of forming a bulb as claimed in any one of claims 22 to wherein said one way clamp means is formed from an externally cone shaped sleeve divided into two or more separable segments, and housed within an Sinternally cone shaped sleeve, the externally cone shaped sleeve including a central bore running therethrough of a diameter less than the nominal diameter of the strand.

28. A bulb forming machine substantially as herein described with reference to the drawings.

29. A method of forming a bulb substantially as herein described with reference to the drawings. Dated this Twentieth day of March 2000. ROCK ENGINEERING (AUST) PTY LTD Applicant Wray Associates Perth, Western Australia Patent Attorneys for the Applicant 9•