COMPRISING SUCH A DEVICE

Field of the Invention

The invention relates to a device for the fastening of wear members according to the preamble of claim 1. The invention also relates to a system according to the preamble of claim 11.

Background of the Invention

In the fastening of wear members to frames/supporting

structures, e.g., wearing plates in steep slopes or shafts for the handling of rock masses, ores, etc., bolts are usually utilized. A problem that then arises is that the bolt head either protrudes or is countersunk in the surface of the wear member that is subjected to wear, in the description below denominated inside. The disadvantage of this is that all projecting items or pits/recesses in the inside of the wear member entail a hotbed for increased wear compared with surrounding surfaces of the wear member.

A further problem is to be able to guarantee the securing of the wear member to the supporting structure as the wear proceeds until the critical limit is reached, when the wear member has to be replaced.

A further problem in the fastening of wear members by means of bolts is that the tightening of the bolts to the correct torque usually has to be made from the inside of the steep slope/shaft, since the access from the outside, i.e. the side not subjected to wear, often is limited because of supporting structures, stays, vicinity to rock, etc. Yet a problem is that, in the case of the conically shaped mounting holes in the wearing plate, the holes usually have a rough surface because of they being cut by water, which entails that a bolt having a corresponding conical surface cannot be tightened to the correct torque via the bolt head, since friction arises between the conical surfaces. This entails that the bolt does not rotate sufficiently to allow tightening to the correct torque.

By US 2007/0258791 Al, a fastening system for the fastening of hard sheet-metal plates is known. According to this document, the problem of the fastening of wearing plates is solved by providing bolts having a conical bolt head or utilizing conical nuts .

Summary of the Invention An object of the invention is to provide a device for the fastening of wear members by means of which the above

mentioned disadvantages are entirely or partly obviated.

An additional object of the invention is to provide a system comprising a device for the fastening of at least one wear member to a supporting structure.

Preferred embodiments of the invention are described in the dependent claims.

Brief Description of the Drawings

The invention is described in more detail below, reference being made to the accompanying drawing, in which

- Fig. 1 is a partially sectioned side view of a device according to the invention for the fastening of a wear member to a supporting structure,

- Fig. 2 is an enlarged detailed view of the encircled area in Fig. 1,

- Fig. 3 is an enlarged detailed view of the encircled area in Fig. 1, which shows the angle a of a transition between a sleeve and an unthreaded portion as well as the cone angle β, and

- Fig. 4 is a schematic view that, by a schematically shown line, illustrates the critical wear limit of a traditionally fastened wearing plate (to the left) and of a wearing plate fastened by the device according to the invention (to the right), respectively.

Description of Preferred Embodiments

In the description, the claims and in the drawings below, there is shown a fastening device according to the invention intended to co-operate by means of an appurtenant nut for the fastening of at least one wear member to a supporting

structure by the fact that the fastening device is run through suitably shaped mounting holes aligned with each other in the wear member and as well as in the supporting structure. It is, however, evident to a person skilled in the art that the mounting hole in the supporting structure may consist of a threaded hole.

In Fig. 1, there is shown the fastening of a wear member 20 in the form of a wearing plate to a supporting structure 30 by means of a fastening device 1 according to the invention. As seen in Fig. 1, the fastening device 1 comprises a head 2 and a shank 3 having an unthreaded portion 4 closest to the head, which via a transition 10 transforms into a threaded portion 5, as seen in the direction from the head. It should be mentioned that the head may consist of a usual hex head drive as well as a head intended for a hex key; six point socket (Torx®), or the like. The unthreaded portion 4 is provided with an indication of fracture 6 in the vicinity of the head. The indication of fracture 6 is usually in the form of a notch, the bottom of which, as seen in the cross-section of the unthreaded portion, is in the form of a truncated cone, the tip of which is directed toward the threaded portion.

The purpose of the indication of fracture is to cause the material of the shank 3 to be sheared off when the desired tightening torque has been achieved. This is achieved by adaptation of the depth and shape of the notch to the desired tightening torque.

Even if an indication of fracture 6 is defined in the

description and claims, it is evident to a person skilled in the art that it is possible to cut the fastening device 1 at the indication of fracture 6 in case the tightening torque is not sufficient to shear off the head 2. If so, the cutting of the fastening device 1 should be made on a level with the wear member 30 so that an even and smooth surface is obtained between the cut off surface of the fastening device 1 and the wear member 30. Furthermore, as seen in Figs. 1 and 2, a holed sleeve 8 is arranged to be slipped onto the shank 3 in connection with the fastening of the wearing plate. The sleeve 8 has an outer conical surface having a cone angle β of approx. 4 to 25°, preferably approx. 8°, as defined in Fig. 3, which is intended to fit in a corresponding conical mounting hole in the wearing plate .

The sleeve has also a step 9 that is arranged in the hole, and more precisely at a part of the sleeve that is directed toward the threaded portion of the shank, which step, in the

tightened state of the fastening device, abuts against the transition 10. The transition 10 has an angle a of 90° or less but larger than 5° in relation to the longitudinal direction of the unthreaded portion 4, and the step 9 of the sleeve 8 has a corresponding angle, as defined in Fig. 3. The step 9 is formed by a diameter reduction of the hole and a corresponding diameter increase of the unthreaded portion 4.

It should be mentioned that the transition 10 in the sleeve 8 alternatively may be provided by drilling or milling in such a way that the transition gets the shape of a radius. The tangent of the radius formed in such a way should, however, have the above defined angle where the diameter of the

transition is the smallest.

Upon tightening of the fastening device according to the invention, it is provided that the securing force, which is mediated by the fastening device via the transition, the step and the sleeve, for the fastening of the wearing plate 20 to the supporting structure 30, will be placed at the bottom of the mounting hole in the wearing plate, and not as in an ordinary bolt, at the surface/inside of the wearing plate. This means that, by varying the length of the unthreaded portion of the shank and thereby the distance of the

transition/step to the indication of fracture 6, i.e., the inside of the wearing plate, the quantity of material that is allowed to be worn away from the wearing plate up to the critical wear limit can be varied. Furthermore, there should be a small gap between a lower end 12 of the sleeve 8, which end is situated against the

supporting structure 30, upon correct tightening torque of the fastening device 1, so that the sleeve does not bottom/abut against the supporting structure, i.e., the sleeve should be somewhat shorter than the thickness of the wear member.

However, an upper end 13 of the sleeve 8 should always be on a level with the inside (wear surface) of the wearing plate, when the fastening device is tightened to the correct torque.

More precisely, upon the tightening of the fastening device, the sleeve 8 will extend along the unthreaded portion 4 of the shank 3 up to at most the indication of fracture 6, and upon the achievement of the correct tightening torque, the head 2 is sheared off on a level with the indication of fracture 6, an almost smooth surface being provided between the fraction surface of the shank 3, the upper end 13 of the sleeve 8, and the inside of the wearing plate 20. The smooth surface

achieved in this way in the fastening of wearing plates entails that there are no pits or projecting parts on the inside/wear surface that may act as a hotbed for wear.

In a preferred embodiment, the angle a of the transition in relation to the longitudinal direction of the unthreaded portion 4 amounts to 10-90°, preferably approx . 45°.

Furthermore, the shank 3 has, after the transition 10, as seen toward the threaded portion 5, a cylindrical portion 11 having essentially the same diameter as the threaded portion, and the sleeve has a corresponding cylindrical portion 14.

The unthreaded portion 4 has preferably a circular cross- section and the hole in the sleeve 8 has a corresponding circular cross-section, there being a suitable play between the surfaces . The critical wear limit should be at a suitable distance from the transition/step so that there remains enough material of the sleeve 8/unthreaded portion 4 for providing reliable securing of the wear member 30. By the fact that it is only the surfaces of the step 9 and the transition 10 that abut against each other and where friction arises upon the

tightening of the fastening device 1, these surfaces can be made with a suitable surface finish, whereby the tightening torque can be accurately determined.

Furthermore, by forming the fastening device 1 in the above mentioned way, it is guaranteed that the fastening of the wearing plate 20 to the supporting structure 30 is equally strong irrespective of the wear of the wearing plate until th critical wear limit is reached.