AU693500B2

AU693500B2 - Cone for a bolt

Info

Publication number: AU693500B2
Application number: AU12252/95A
Authority: AU
Inventors: Peter Gilmour Fuller
Original assignee: JJP GEOTECHNICAL ENGINEERING P
Current assignee: Jjp Geotechnical Engineering Pty Ltd
Priority date: 1994-02-15
Filing date: 1995-02-14
Publication date: 1998-07-02
Anticipated expiration: 2015-02-14
Also published as: AU1225295A

Description

*t Regulation 32(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: S. S Invention Title: CONE FOR A BOLT The following statement is a full description of this invention, including the best method of performing it known to us:- CONE FOR A BOLT Field The present invention relates to the field of fastening or tensioning devices, such as bolts, bars, wires, cable bolts, rock bolts, and other similar devices used in support, reinforcement and/or securing applications. The present invention particularly relates to a part of an end fitting arrangement for such securing or fastening devices. In a very particular form, the present invention relates to a cone, and is suitable for use as a part of an end fitting for the cable bolt disclosed in the present applicant's co-pending application No.

PCT/AU92/00369.

Background Art Reference is made to Figure la of PCT/AU92/00369, which is shown as Figure 1 in this application. There is shown, in a bore hole 4, an end portion of a cable bolt 6 to which there is applied a one piece nut 8 and a collar 5 which serves to support a plate 7 and the earthen material 2. The one piece nut is threaded directly to a threaded cable bolt. The one piece nut 8 has axial slots oo" 21 to allow only part of the end section 20 to be radially compressed against the S. cable. This compression occurs as the nut is threaded onto the cable and as the nut is rotated into a complementary tapered opening 22 in the collar 5 used in association with plate 7. It has been found, however, that the one piece nut is relatively expensive to manufacture. Therefore there has developed among some users of the cable bolt technology disclosed in the above PCT application a tendency to use a standard nut without end section 20 fitted to the end of a cable bolt. Furthermore, the relatively limited inward movement available to the 25 nut due to the termination of the slot proximate the hexagonal nut portion has been found to limit the load capacity of the end fitting.

US 4,633,540 and US 5,230,589 discloses, as shown in Figures 2, 3, 4, and 5 of the present application, a mine roof bolt 10 having a shank 12 made up of steel strands 14, and which utilizes a two piece cone or plug Referring to Figure 2, the plug 20 has outer frusto-conical surfaces 22 which are designed to mate with the inner frusto-conical surface 24 of collar 26.

2 Figure 4 shows one piece of the plug 20, and more clearly shows a series of "serrations or knurls" 30 which are designed to "bite" into wires 14 of shank 12 as the plug and collar are forced onto the shank 12.

Figure 5 illustrates a part of an alternative plug 32, which has a different type of knurl 34 formed in a diamond pattern resulting from diagonally oriented serrations. The diamond serrations are said to improve torsion and tension properties as the bolt is installed and used within a rock formation. It is clear from the US specifications that there is no thread formed on the cable bolt prior to nor during fitting of the two piece plug 20, as the grooves shown in Figures 4 and 5 are not formed in a manner which can be threaded directly onto the shank 12 of the cable bolt.

In use, the two piece plug 20 as shown in Figure 2 is inserted into the collar 26, but around the bolt. In this initial position, the two piece plug 20 only contacts the collar 26 on two lines. The lines are somewhere between the extremities of the gap 28 as shown in Figure 3 of the two pieces. As the collar 26 and plug 20 are pressed on to the end of the bolt 10 and load is applied to the end of the cable, the collar 26 and two piece plug 20 move into the position as shown in Figure 2. A relatively low load is required for this initial locking process to occur. It is from this initial locking position that more contact is made circumferentially between the outer surface 22 of the two piece plug 20 and the inner surface 24 of the collar 26. The application of a further load results in little, if any, further movement between the two piece plug and the collar.

S' Figure 3 shows, in sectional view, the relative position of the plug and collar under a loaded and ins'alled condition. It can be seen that the plug 25 becomes circular within the collar as the outer surface 22 of plug 20 is brought into more contact with the inner surface 24 of collar 26 as a result of more load being applied and resulting in the plug and collar becoming more locked.

During this locking process, the downward movement of the collar 26 (Figure 2) also serves to cause the two piece plug 20 to "bite" into the cable bolt. As the two piece plug is made of a relatively hard steel, the serrations or knurls on the inner surface of the two piece plug 20, serve to bite into the outer surface of the bolt. This biting action serves to form a series of areas of contact between the 3 plug 20 and the outer surface of the bolt 10. It is through this biting action that load is transferred from the collar through the plug 20 and to the bolt 10. As the plug 20 is pressed on to the bolt 10 and essentially locked in axial position on the bolt 10, it is considered to have relatively limited application as an end fitting for bolts, cables, rods and other devices because once installed, it is not possible to tighten the end fitting against a plate by rotation of the plug 20 or collar 26 on the bolt 10. It is therefore considered extremely difficult to obtain a predetermined tensioning of the end fitting as disclosed in the US specifications.

Australian patent application 35348/93 provides an equivalent disclosure to US 5,230,589 Object of Invention An object of the present invention is to alleviate at least one disadvantage of the prior art.

Another object of the present invention is to provide a cone for an end fitting which is relatively less expensive and/or easier to manufacture than existing bolt end fittings.

:Yet another object of the present invention is to provide an alternative end fitting for a bolt, cable, rod or other type of fastening device.

Summary of Invention The present invention is predicated on the realisation that a cone having at least a portion thereof being relatively deformable can be used for fastening purposes on an end fitting of a securing or fastening device, such as a bolt. The cone may also be provided separate from the nut. The cone may be further 25 used in conjunction with a standard nut and a collar.

It has also been discovered that during deformation of the cone member of the present invention onto a bolt or threaded end portion, the deformed cone (with or without the aid of the nut) can serve as a load bearing end fitting.

The cone of the present invention may be threaded or not threaded or may have an inner diameter which is substantially smooth.

A number of advantages accrue from the cone of the present invention, such as: 4 the provision of a separate nut, cone and or collar enables the materials and properties of anyone or all of these components to be optimised on the basis of price and or performance; a separate cone may be made to work over substantially its full length (or parts thereof), rather than just the front part of its length (as with the one piece cone/nut) resulting in a relatively higher load capability; a cone without thread or at least having an inner diameter which is substantially smooth enables the cone, in use, to be radially squeezed and it may work separately from the nut; a non-thread cone can be used on any bolt/cable end provided the diameter is appropriate; and/or for relatively high load capacity applications which would ordinarily require a long nut, the present invention allows a relatively short nut to be used in conjunction with the cone. This may be more cost effective.

15 Although the present specification uses the term bolt, other load bearing or tensionable devices are intended to be encompassed such as cables, cable :bolts, rods, reinforcing, nails, fastening devices, support members, shafts, ropes, o °*strands, wires, bars, structural and/or mechanical members and other securing type of devices whether made of metal, wood, plastic or composite material.

Furthermore, the present specification uses terms such as fix, fixture, fit, and fitting, other like terms are also to be encompassed such as secure, fasten, anchor, place, attach, connect, couple, join, engage, affix, moor, adhere, belong, relate, and other terms which impart a relationship between the bolt and an associated fitting capable of having load placed thereon. Thus, although the 25 preferred embodiment disclosed relates primarily to the fastening of metal bolts, S and the use of a deformable metal cone, the present invention is not to be so limited. Further, the frusto-conical shape allows 3D confinement of the cone.

Operation could be 2D such as a square or rectangular cross section tapered cone or 3D with a triangular cone.

An embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a one piece nut and cone as disclosed in PCT/AU92/000369; Figures 2, 3, 4, and 5 show a two piece plug as disclosed in US 5,230,589; Figures 6a and 6b illustrate forms of cone in accordance with the present invention; Figure 6c shows an alternative cone in accordance with the present invention; and Figure 7 illustrates one form of cone of the present invention in use.

Figure 6a shows one form of the cone in accordance with the present invention in perspective view. The cone 100 is generally frusto-conical in shape, although it may be of any shape depending upon its application. For example, the cone may be a ring-like (eg. cylindrical) member which, in use, is appropriately deformed. The outer surface 101 is preferably tapered for fitment of the cone into a corresponding frusto-conical opening provided in a collar (not shown). The cone has slot(s) 102 which serve to facilitate radial movement, S deformation and/or compression of the cone when being installed around a bolt.

There may be one or any number of slots.

The angle of the taper of surface 101 is preferably approximately 7 degrees, although this can vary dependent upon the application for which the S cone is used.

The cone preferably has a fillet 103 which serves to hold the cone together as one piece. This fillet 103, upon deformation of the cone around a bolt, is adapted to be also distorted and in such a way that it does not hinder the 25 ability of the cone to deform. The fillet 103 may be provided in one or more of the slot(s) 102, and in any number and disposed anywhere along the slot(s) 102. Figure 6a shows the fillet 103 proximate the top of one of the slot(s) 102, and this has been found to be relatively satisfactory in experimental use.

The inner diameter 104 of the cone is preferably a diameter sufficient to provide a clearance fit over the particular diameter bolt used in a given situation.

This inner diameter may also vary dependent upon the particular application.

Figure 6b shows in side elevation view, the cone according to the present invention. However, in this Figure the fillet 103 is provided proximate the bottom of one of the slot(s) 102. There may be one or more fillets per slot.

Figure 6c shows one alternative embodiment, namely a generally rectangular cone shape. This cone may also be generally triangular or any other shape as is desired. It is the deformability of at least part of the cone around the bolt which is of importance. The cone may be one piece or two or more pieces as shown in Figure 6c.

Figure 7 shows, in somewhat similar style to Figure 1, the cone of the present invention in use. Like numerals in the Figures are used to denote like elements.

In use the present cone is adapted, due to its preferably one piece form, to fit snugly against the inner surface of the collar 5. Unlike prior art arrangements, the outer surface 101 of the present cone is adapted to contact 15 the inner surface of the collar 5 at at least several points, and most preferably almost over the whole of the surface 101. As the nut 8 is tightened by rotary movement, the cone is squeezed between the bolt and the collar, the slot(s) 102 becoming slimmer or even becoming negligible, and the deformation of the collar occurring at least proximate and/or over the bolt threads. Thus it can be seen that the bolt threads, in part, serve to deform the inner surface of the cone of the present invention. In this regard, the bolt is preferably of a relative hard material, and of sufficient hardness to deform the cone. This is unlike the prior art, where the cone deforms the bolt.

In another alternative form the cone may be placed on a threadless bar or S 25 bolt having a relatively rough or roughened surface. Deformation of a cone about such a bar or bolt enables load transfer as described with the threaded bolt embodiment.

In yet a further alternative, the cone is provided separate from the nut.

This enables the materials of the cone, collar, nut and/or bolt to be optimised.

This gives rise to a number of alternative embodiments available within the scope of the present invention. For example, in addition to or as an alternative, the collar and or nut may also be rendered either totally or partially deformable to further facilitate load transfer.

The bolt may be provided with groove(s) or ridge(s) instead of a thread as noted above.

Once the deformation, preferably of the cone, has been accomplished, it has been found that the cone also serves to transfer load applied on the collar to the bolt and its inner and outer wires. In fact, in tests, the nut may be removed after the installation of the cone, and it has been found that the cone will carry and transfer load applied to the collar without the nut in place on the bolt.

The use of the collar tends to confine the cone 100. It has been found that this confinement serves to create a radially inward force on the cone and in turn on the bolt which serves to alleviate failure of the threads, and thus serves to increase the load capacity transferred to the bolt. Thus, for example in a mining application, with a threaded cable bolt as the rock or earth 2 moves 15 down onto plate 7 and the collar 5, this creates a downward force on the cone and nut and particularly on the thread of the bolt. The collar, due to its frustoconical shape, serves to transform some of the downward force to a radial inward force. The inward force serves to squeeze the cone onto the outer wires of the cable bolt, and in turn the outer wires squeeze onto the inner wires of the bolt. In this way substantially all wires of the bolt carry load. It is preferable to have the inner and outer wires stretch substantially to the same degree under load in order to maximise bolt load capacity of the end fitting.

The cone 100 may be made threaded or unthreaded, and may be rolled, machined, rough cast, forged or sintered. An unthreaded cone is preferred, as S 25 premature locking of threads is avoidable if only the nut is threaded. The cone S• may be made from a deformable steel or any other material as is appropriate to the particular situation. For a steel cone, as would generally be used in a mining application, a relatively mild steel having characteristics of 1020 or 1030 grade are suitable. An alloy may also be used.

It has also been found that the smaller or more deformable the fillet 103, the more room is provided for the cone to be squeezed and thus engage the bolt. The size and nature of the fillet needs to be balanced by the preference to 8 have, in the case of more than one slot, slots having a relatively even gap. This relative uniformity of gap serves to alleviate the probability of one side of the cone deforming more than another side of the cone due to uneven closure of the gaps. Such uneven deformation may reduce the loading capability of an end fitting.

o o

Claims

1. A fastening device for fastening an end portion of an elongate member, the fastening device comprising: a cone device adapted to be fitted to the elongate member; a collar device adapted to receive the cone device; a nut member including an inner threaded portion; wherein the nut member is adapted to be threadingly engaged with the elongate member to drive the cone device into the collar device thereby forcing the cone device into contact with the elongate member, and wherein the cone device is formed of a deformable material of substantially lower hardness than the elongate member.

2. A fastening device as claimed in claim 1, wherein the cone device has an inner surface which is substantially smooth.

3. A method for forming an end fitting on an end portion of an elongate member, method comprising: placing a collar device and a cone device on the end portion of the elongate member; engaging a nut member onto the end portion of the elongate member; :rotating the nut member until the cone device is driven into the collar device, thereby forcing the cone device into contact with the elongate member; wherein the cone device is formed of a material of substantially lower hardness than the elongate member such that under sufficient pressure, in the region where the cone device comes into contact with the elongate member, the cone device is deformed and the elongate member remains substantially undeformed.

4, A method as claimed in claim 3, wherein after deformation of the cone, the cone becomes at least partially load bearing. A method as claimed in claim 3, wherein the cone member is plasticly deformed. D6AI this 7th day of May 1998 JJP GEOTECHNICAL ENGINEERING -PTY LTD WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHOHN VICTORIA 3122 AUSTRALIA DOC 20 US847791.WPC ABSTRACT The present invention relates to a cone used in conjunction with fastening or tensioning devices. The cone as disclosed has at least a portion thereof being made of deformable material. The cone may be provided separate from a nut used on the fastening or tensionirng devices. The cone may also have a substantially smooth inner diameter. *oo o ii~i ~t