AU2005100072B4 - Hardened plate fixing system - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Applicant(s): BRIAN INVESTMENTS PTY LTD Invention Title: HARDENED PLATE FIXING SYSTEM The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 HARDENED PLATE FIXING SYSTEM F1 SField of the Invention 00 The present invention relates to a fixing system for a hardened plate.

SBackground of the Invention Plates of hardened material, such as steel and steel alloys, are often used to minimise the effect of wear on structural elements of a piece of equipment. Often, these hardened plates are called wear plates because the material of the plate is selected for its resistance to wear. Examples of equipment which use wear plates includes hoppers, bins and chutes used in rock handling equipment and in an ore processing plant. This sort of equipment can be exposed to wear in the form of sliding and/or gouging abrasion. The wear plates act as a sacrificial element so that the plates are worn rather than the structural element of the equipment. The plates can be readily exchanged once worn, thus extending the life of the working equipment.

Recently, harder materials have been used to form a wear plate. Such a harder wear plate is a sheet of very hard material (such as a steel alloy having a Brinell hardness of approximately 500 HB) which is attached to the surface of the equipment which would otherwise be subject to wear. It is possible to perform cutting, welding, drilling and machining operations on such steels, however the difficulty of such operations increases with the hardness of the material. For H:\mcamp\keep\speci\P55339 HARDENED FIXING PLATE INNOV.doc 3 example, when drilling steel of this hardness a tungsten i carbide drill bit is usually required, and the feed and speed rates of the drill bit need to be carefully O selected, thus requiring complex expensive drilling C' 5 machinery.

Figure 1 shows a cross sectional view of a wear plate Swith a hole 12 for fixing the wear plate 10 to a structural element (not shown) according to a known system. The surface 14 on the wear plate 10 is exposed Ci to wear. Therefore, the opposing surface 16 will abut the structural element. In this system, a standard counter sunk bolt 18 as shown in Figures 2 and 3 is provided. The counter sunk bolt 18 has an externally threaded shaft 20 which extends from a frusto-conical head 22. The head 22 is provided with a hexagonal hole 24 for receiving an Allen key to hold or turn the bolt 18 during fastening etc.

Obviously, the structural element would be provided with a hole for receiving the shaft 20 of the bolt 18. The hole 12 in the structural element could be either an internally threaded hole to threadingly engage the thread on the shaft 20, or could merely be a throughway such that a nut (not shown) can be threaded onto the shaft The hole 12 in the wear plate 10 is shaped to allow the bolt 18 to be recessed with respect to the wear surface 14. Accordingly, the hole 12 comprises a first cylindrical portion 26, a frusto-conical portion 28 and a second cylindrical portion 30. The first and second cylindrical portions 26, 30 are dimensioned to receive H:\mcamp\keep\speci\P55339 HARDENED FIXING PLATE INNOV.doc 4 the head 22 and the shaft 20 of the bolt 18, respectively. It should be noted that the frustoconical portion 28 is dimensioned to compliment the frusto-conical shape of the head 22. Furthermore, as shown in figure 2, the half-opening angle 0 of the frusto-conical head 22 is The bolt 18 is recessed to minimise the amount of wear which the bolt head 22 will experience. This is at a price to the wear plate 10 because the recessing of the head 22 leaves a void in the cylindrical portion This in turn allows material to catch on the wall of the cylindrical portion 30 which increases wear around the hole 12.

Due to the properties of the material used in the wear plates 10, forming the hole 12 is an expensive and time consuming process. Generally, the hole 12 can be created in at least two drilling operations using a small drill bit to create the second cylindrical portion and a larger drill bit with a conical tip to create both the first cylindrical portion 26 and the frustoconical portion 28.

Summary of the Invention According to one aspect of the present invention, there is provided a fastener element comprising a frusto-conical head and a threaded shaft, wherein at least the frustoconical head is hardened to a Brinell hardness of at least 300 HB.

Kirstie/keep/retype/P55339 retype claims 22/06/2005 5 Preferably, the half opening angle of the frusto-conical head is within the range of 50 to 200.

Preferably, the head has a wearing surface remote from the threaded shaft, the wearing surface being continuous such that when a nut is tightened onto the shaft the bolt is prevented from rotating by friction between the conical side of the head and the abutting surface.

Preferably, the fastener element further comprises a shoulder between the head and the shaft, the shoulder having a diameter larger than the outer diameter of the shaft and smaller than the smallest outer diameter of the head.

According to a second aspect of the present invention, there is provided a fastener element comprising a frustoconical body and an internally threaded hole extending through the body and substantially parallel to the centre line of the cone shape, wherein the body is hardened to a Brinell hardness of at least 300 HB.

Brief Description of the Drawings In order for the invention to be more easily understood, embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1: is a cross section of a wear plate according to a prior art fixing system; Figure 2: is an elevation view of counter-sunk bolt which is used in conjunction with the wear plate of figure 1; Kirstie/keep/retype/P55339 retype claims 22/06/2005 6 Figure 3: is a plan view of the counter-sunk bolt of figure 2; Figure 4: is a schematic cross section view of a first embodiment of a fixing system invention; Figure 5: is a cross section view of the wear plate of figure 4; Figure 6: is of an elevation view of an embodiment of a bolt according to the present invention used in the fixing system of Figure 4; Figure 7: is a plan view of the bolt of figure 6; Figure 8: is a bottom view of the bolt of figure 6; Figure 9: is a schematic cross section view of a second embodiment of a fixing system; Figure 10: is a cross section of an elevation of a retainer of the fixing system as shown in figure 9; Figure 11: is a bottom view of the retainer of figure Figure 12: is a schematic plan view of four wear plates; Figure 13: is a schematic plan view of a wear plate of figure 12; Figure 14: is a side elevation of an alternative embodiment of a bolt according to the present invention; Figure 15: is a cross sectional side elevation of a retainer according to the present invention, with a coating applicable to fastener elements of the present invention; and Figure 16: is a schematic representation of the retainer of figure 15 in use.

Kirstie/keep/retype/P55339 retype claims 22/06/2005 7 Detailed Description of the Preferred Embodiments Figure 4 shows a schematic cross sectional view of a fixing system 50 according to one embodiment. The fixing system 50 fixes a first element, such as a wear plate 52 to a second element, which may be a structural element 54 such as the wall of a hopper or the bin of a earth moving truck. The wear plate 52 has a first surface 56 which is exposed to wear, and a second surface 58 which, in use, abuts the structural element 54. The structural element can be, for example, the wall of the hopper or ore bin.

The wear plate 52 is made of a wear resistant material having a Brinell hardness of at least 300 HB. Typically BISALLOY 500 TM or similar is used, which has a typically Brinell hardness of 500 HB.

A bolt 62, having a head 64 and a threaded shaft 66, is used to secure the wear plate 52 to the structural element 54. The threaded shaft 66 extends through a hole 68 in the structural element 54. A nut 70 is threaded onto the shaft 66 to fix the wear plate 52 to the structural element 54. It will be appreciated that additional nuts and/or washers may be used in combination with the nut 70. Alternatively, the hole 68 in the structural element 54 may be internally threaded to engage the threaded shaft 66. In this alternative, the head 64 of the bolt 62 may be provided with, for example, a hexagonal hole to allow the bolt 62 to be rotated.

Kirstie/keep/retype/P55339 retype claims 22/06/2005 8 As shown in figure 5, the wear plate 52 is provided with a hole 60 which is frusto-conical in shape such that the diameter of the opening on the first surface 56 is larger than that on the second surface 58. The hole can easily be formed in the material of the wear plate 52 using, for example, a plasma cutter or an oxyacetylene cutter. Where a plasma cutter is used, the hole 60 may be formed by inclining the head of the plasma cutter an angle corresponding with the half opening angle of the desired frusto-conical shape for the hole 60 and then rotating the head of plasma cutter about the centre line for the hole The hole 60 may be formed such that the cut is made from the second surface 58 toward the first surface 56.

Cutting in this manner minimises the exposure of the first surface 56 to heat during cutting which may result in deterioration of the wear plate 52 material.

Forming the known wear plate 10 as shown in figure 1 involves separate equipment to perform the cutting operation and the drilling operation. This would obviously involve significant handling time in transferring the plate from a cutting station to a drilling station. In addition, the drilling operation would take at least approximately 10 minutes per hole and could take up to 30 minutes including set up time.

As discussed above, drilling the hole 12 requires the use of special drill bits. In addition, a coolant fluid must be used to remove heat generated during the drilling operation.

A plasma cutter can be computer numerically controlled, allowing the cutting and hole-forming operations to be Kirstie/keep/retype/P55339 retype claims 22/06/2005 9 performed at the same station. Using a plasma cutter, the hole 60 can be created in approximately 10 seconds.

These time savings will ultimately result in significant cost savings.

In one alternative, the circumferential surface 65 of the head 64 may be provided with at least partly radially protruding ramps (not shown) which engage the wear plate 52 about the hole 60 as the head 64 is inserted into the hole 60. During the working life of the fixing system 50, the ramps resist any unintended rotational movement of the bolt 62 within the hole Alternatively or additionally, where a plasma cutter is used to create holes 60, the cutting operation will often result in grooves being formed on the surface of the cut. These grooves can engage, for example, the head 64 of the bolt 62 and provide resistance to any unintended rotational movement of the bolt 62 within the hole 60. Corresponding grooves could be formed on the head 64 of the bolt 62.

Figures 6 to 8 show the bolt 62. The head 64 of the bolt 62 is also frusto-conical in shape to compliment the shape of the hole 60. The half opening angle a of the conical frustum in each of the hole 60 and the head 64 is, in this embodiment, 15. However, it will be appreciated that the angle a would be greater than or equal to about 5" and usually less than or equal to about 20. Angles larger than 200 will work, but are less desirable. The head 64 is machined and hardened such that it resists wear. In addition, the top surface 72 of the bolt 62 is substantially flat.

Kirstie/keep/retype/P55339 retype claims 22/06/2005 10 The process of forming the bolt 62 may involve through hardening (that is, quenching and tempering) of at least the head 64.

It is noted that cutting the hole 60 may leave imperfections in the surface forming the hole 60. To alleviate problems that may arise from the bolt 62 from not seating correctly in the hole 60 due to these imperfections, the half opening angle of the conical frustum of the hole 60 may be slightly greater than the half opening angle a of the head 64 of the bolt 62. The difference may be about 1 20 or less. This will allow the base of the head 64 to engage with the base of the hole 60 first. Slight deflection of the hole surface/head will allow for an increase in the area of contact as the nut 70 threaded on the bolt is tightened.

Furthermore any gap left will be relatively small and is likely to be filled with fines from the inside of the bin/hopper which will act as a cement further increasing holding ability of bolt 62.

To assemble the fixing system 50, the holes 60, 68 are aligned and the shaft 66 is inserted through both holes 60, 68. The nut 70 is then threaded onto the shaft 66 and tightened. The head 64 becomes wedged in the hole 68 as the nut is tightened. Because the half opening angle a of the conical frustum of each of the hole and the head 64 is shallow, the friction between the head 64 and the wear plate 52 rises rapidly. This friction is sufficient to prevent the bolt 62 from rotating as the nut 70 is rotated to tighten/loosen the clamping force.

Kirstie/keep/retype/P55339 retype claims 22/06/2005 11 As shown in figure 4, the depth of the frusto-conical head 64 is preferably approximately equal to the thickness of the wear plate 52 about the hole Furthermore, as shown in figure 4, when the fixing system 50 is assembled the top surface 72 of the bolt 62 is substantially flush with the first surface 56 of the wear plate 52.

The fixing system 50 of the present invention is advantageous over the existing fixing systems for hardened plates because the method of forming the hole in the plate is considerably easier and requires less expensive equipment. The new bolt of the present invention is just as effective in fastening the hardened plate and can be used with the new hole in the hardened plate of the present invention.

In figure 9, a fixing system 150 according to a second embodiment is shown. The fixing system 150 fixes a first element, such as a wear plate 152, to a second supporting or structural element 154. The wear plate 152 has a first surface 156 which is exposed to wear, and a second surface 158 which, in use, abuts the structural element 154.

A hole 160, of frusto-conical shape, is provided in the wear plate 152. The diameter of the opening on the first surface 156 is larger than that on the second surface 158. The fixing system 152 includes an retainer 162 having a frusto-conical shape which complements that of the hole 160. The retainer 162 may be selected to have a depth equal to the thickness of the wear plate Kirstie/keep/retype/P55339 retype claims 22/06/2005 12 152. An internally threaded hole 164 extends through the retainer 162. The same slight difference in angles between the head of the bolt and the hole may be employed with the nut and the hole to alleviate problems caused by imperfections in the surface of the hole.

To fix the wear plate 152 to the structural element 154, a bolt 170, having an externally threaded shaft 172, is inserted through a hole 168 in the structural element 154. The thread on the shaft 172 engages the internal thread of the retainer 162. The retainer 162 is drawn into the hole 160 in the wear plate 152 as the bolt 170 is threaded into the retainer 162.

The friction force between the retainer 162 and the wear plate 152 increases with the tensile force along the shaft 172. Thus, as the bolt 170 is tightened the friction force will prevent the retainer 162 from rotating.

As shown in figure 10, the half opening angle 0 of the conical frustum in each of the hole 160 and the head 162 is, in this embodiment, 15. However, it will be appreciated that the angle 3 will usually be in the range of 5" to Figures 10 and 11 show a cross section view and bottom plan view of a retainer 262 according to another embodiment. In this embodiment, the internally threaded hole 264 is offset with respect to the centre of the retainer 262. In some cases, the hole 168 in the structural element 154 may not line up with the hole 160 in the wear plate 152. The retainer 162 can be rotated Kirstie/keep/retype/P55339 retype claims 22/06/2005 13 prior to engagement with the bolt 170, thus aligning the centre of the holes 160, 162.

It will be appreciated that the threaded shaft 172 may be longer than the combined thickness of the wear plate 152 and the structural element 154. Accordingly, once the fixing system 150 is assembled, the threaded shaft 172 may protrude from the top surface 166 of the retainer 162. The protruding portion will wear away until the threaded shaft 172 and the retainer 162 are flush at the top surface 166.

Figure 12 is a plan view showing schematically four wear plate 52 "tiled" together over a structural element (not shown). Figure 13 is a plan view of one such wear plate 52. As shown in figure 13, there are three types of holes in the wear plates 52. The first, a complete hole 360 provided within the wear plate 52; a second, half hole 362 provided on an edge of the wear plate 52; and, a third, quarter hole 364 provided on an edge of the wear plate 52. As shown in figure 13, two half holes 362 can be aligned to receive either the head 64 of a bolt 62 or a retainer 162. Similarly, four quarter holes 364 can be aligned to receive either the head 64 of a bolt 62 or a retainer 162. While not shown in the figures, a half hole 362 and two quarter holes 364 may be aligned.

It will be appreciated that variations of wear plates 52 can be formed. For example, wear plates 52 may be formed having any combination of complete holes 360, half holes 362 and quarter holes 364 as required.

Furthermore, it will be appreciated that, where wear Kirstie/keep/retype/P55339 retype claims 22/06/2005 14 plates 52 having half holes 362 and/or quarter holes 364 are used, it will be necessary to provide lateral support to prevent the wear plates 52 separating. Such lateral support may be provided by complete holes 360 and/or external supports. The location and number of the complete holes 360 would be determined by the lateral support required, and the shear stress applied to the shafts 72, 172 of the bolts 70, 170 within those complete holes 360.

An example of one method of forming individual wear plates 52 can be described in connection with the wear plates 52 shown in figure 13, as follows: 1. providing a large plate of hardened material; 2. forming nine holes in the large plate using, for example, a plasma cutter; 3. cutting the large plate along two orthogonal lines which intersect the holes to form four wear plates 52, each having a complete hole 360, two half holes 362 and a quarter hole 364.

Obviously, other combinations of holes and cuts, and the number of wear plates 52 formed can be created as desired. It will be appreciated that some allowance for loss of material may be required when cutting the plate through the holes formed in step 2 of the method described above. Thus, for example, the size and/or shape of the holes formed in step 2 may need to be adjusted.

In the embodiment shown in figures 9 and 10, the internally threaded hole 164 in the retainer 162 extends Kirstie/keep/retype/P55339 retype claims 22/06/2005 15 through the retainer. Alternatively, the hole 164 may be a blind hole such that the bolt 170 only extends part way into the retainer 162. In this alternative embodiment, a hexagonal hole, for example, may be provided which extends into the retainer 162 from the top surface 166. Accordingly, an Allen key may be inserted into the retainer 162 to assist preventing the retainer 162 from rotating during assembly of the fixing system 152. This embodiment of the retainer is useful where an externally threaded stud is fixed to the structural element and inserted through the hole 160 to perform the role of the bolt 170.

Referring to Figure 14 a variant of the bolt shown in Figure 6 is shown. In this variant bolt 462 has a shoulder or step 402 between the head 464 and the threaded pull shaft 466. The step 402 is typically sized to fit within the hole 68. This allows for a larger sized bolt head and step which is more resistant to shearing forces.

Referring to Figures 15 and 16, which show a variant retainer 162. The variant retainer 162 is the same as retainer 162 except it has a hard plastic coating 502.

As seen in Figure 16 as the clamping force is applied to the retainer it causes the plastic 502 to flow into the hole 68 as indicated by 504. This provides a seal through the hole 68. The same coating can also be applied to bolt 162 or 462 so that the respective coating can also flow into the hole 68 in the supporting element 154. This is useful where materials having a high sulphide content exposed to water. This can produce an acidic liquid that if it flows through the Kirstie/keep/retype/P55339 retype claims 22/06/2005 16 hole 68 it can damage the supporting structure and/or components behind the supporting structure.

It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the scope of the invention. For example, the fixing system may be used in applications where access to the bolt head can be impeded during the service life of the bolt. Furthermore, the hardened plate may be other material.

Throughout this specification, except where the context requires otherwise due to express language or necessary implication, the words "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense; that is, to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Kirstie/keep/retype/P55339 retype claims 22/06/2005

Claims (5)

1. A fastener element comprising a frusto-conical head and a threaded shaft, wherein at least the frusto-conical head is hardened to a Brinell hardness of at least 300 HB.

2. A fastener element as claimed in claim 1, wherein the half opening angle of the frusto-conical head is within the range of 50 to 200.

3. A fastener element as claimed in either claim 1 or 2, wherein the head has a wearing surface remote from the threaded shaft, the wearing surface being continuous such that when a nut is tightened onto the shaft the bolt is prevented from rotating by friction between the conical side of the head and the abutting surface.

4. A fastener element as claimed in any one of the preceding claims, wherein the fastener element further comprises a shoulder between the head and the shaft, the shoulder having a diameter larger than the outer diameter of the shaft and smaller than the smallest outer diameter of the head.

5. A fastener element comprising a frusto-conical body and an internally threaded hole extending through the body and substantially parallel to the centre line of the cone shape, wherein the body is hardened to a Brinell hardness of at least 300 HB. Dated this 22nd day of June 2005 BRIAN INVESTMENTS PTY LTD By Its Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia. Kirstie/keep/retype/P55339 retype claims 22/06/2005