WO2005014213A1

WO2005014213A1 - Wire saw

Info

Publication number: WO2005014213A1
Application number: PCT/IB2004/002518
Authority: WO
Inventors: Martin Walter Powell; Rudolf Olivier
Original assignee: Anglo Operations Limited
Priority date: 2003-08-06
Filing date: 2004-08-05
Publication date: 2005-02-17

Abstract

One aspect of the invention concerns a wire saw (10) comprising a core wire (12), abrasive beads (14) spaced apart on the core wire and a flexible, typically elastomeric material such as rubber moulded over the core wire between the beads. This elastomeric material has a non-circular outer cross-sectional shape defined by relatively thick zones in which the radial extent of the material overlying the core wire is relatively great and intermediate zones, between the first zones, in which the radial extent of the material is zero or relatively small. In the preferred embodiments, the elastomeric material moulded about the core wire between the beads defines a generally polygonal outer cross-sectional shape. The polygonal shape includes sides (30, 34) which, at central positions on those sides, are located close to or at an outer surface of the core wire. Other aspects of the invention concern a method of moulding the elastomeric material and the mould itself.

Description

"WIRE SAW"

BACKGROUND TO THE INVENTION

THIS invention relates to a wire saw.

Conventionally wire saws consist of a length of core wire carrying spaced apart, abrasive beads, typically including diamond or a hardmetal such as tungsten carbide. The beads are typically held in place on the core wire by rubber which lines the core wire between the beads and which extends over the ends of the ferrules on which the abrasive material is located in the beads. The wire is formed into an endless loop and is driven longitudinally against a material, such as rock, which is to be cut. The driving machine is moved continuously to keep the saw under tension with the result that the abrasive beads cut a slot through the material. During the cutting action flushing water or other liquid is introduced into the slot both to cool the saw and to assist in removal of the cuttings.

There is a constant demand to increase cutting speeds. An increase in cutting speed requires that the flushing liquid be capable of cooling the saw and removing the cuttings at a faster rate, which in turn implies a requirement for a greater flow of flushing liquid to convey the cuttings.

Another requirement is acceptable longevity of the saw. For optimum working life, the abrasive beads should be concentrically mounted with respect to the core wire, since this ensures that the beads will wear uniformly about their circumferences.

The present invention seeks to provide a wire saw which addresses these requirements. SUMMARY OF THE INVENTION

According to the present invention there is provided a wire saw comprising a core wire, abrasive beads spaced apart on the core wire and a flexible material moulded over the core wire between the beads, the flexible material moulded over the core wire between the beads having a non- circular outer cross-sectional shape defined by relatively thick zones in which the radial extent of the material overlying the core wire is relatively great and intermediate zones, between the first zones, In which the radial extent of the material is zero or relatively small.

In the preferred embodiments, the flexible material moulded over the core wire between the beads as defines a generally polygonal outer cross- sectional shape. Preferably the polygonal shape defined by the flexible material includes sides, typically three or six, which, at central positions on those sides, are located close to or at an outer surface of the core wire. The flexible material defining the polygonal shape may have a thickness of 0,1mm or less at central positions on the sides of the polygonal shape.

In modified embodiments, a flexible sleeve, typically a coiled element of spring steel, may be located about the core wire between the beads and the polygonal shape defined by the flexible material includes sides which, at central positions on those sides, are located close to or at an outer surface of the sleeve.

The invention includes within its scope embodiments in which the flexible material moulded over the core wire between the beads has a sinuous outer profile defined by alternating relatively thick zones and intermediate zones. In one particular embodiment, the flexible material has eight relatively thick zones and eight intermediate zones. In this case the relatively thick zones may have outer extremities lying on a circle centred on the centre of the core wire, and the radial extent of the flexible material may be zero in some intermediate zones and greater than zero in other intermediate zones. The invention envisages embodiments in which the beads include longitudinally extending shoulder portions and shoulder portions of flexible material are moulded over the shoulder portions of the beads, each shoulder portion of the flexible material having a generally polygonal, possibly square, outer cross-sectional shape.

At central positions, sides of the polygonal shape of the shoulder portions of the flexible material will be located close to or at the outer surface of the shoulder portions of the beads.

The invention also envisages embodiments in which, once again, the beads include longitudinally extending shoulder portions and shoulder portions of elastomeric material, typically or circular cross-section, are moulded over the shoulder portions of the beads, the shoulder portions of flexible material in these embodiments including indentations or recesses therein formed by inward projections on a mould used to mould the elastomeric material, the indentations or recesses extending inwardly to positions close to or at outer surfaces of the shoulder portions of the beads.

According to another aspect of the invention there is provided a method of moulding flexible material onto an assembly comprising a core wire and abrasive beads spaced apart along the length of the core wire, thereby to form a wire saw in which flexible material is moulded over the core wire between the beads, the method including the step of using a mould shaped to ensure centralisation of the core wire in the flexible material.

According to yet another aspect of the invention there is provided a mould for moulding flexible material onto an assembly comprising a core wire and abrasive beads spaced apart along the length of the core wire, thereby to form thereby to form a wire saw in which flexible material is moulded over the core wire between the beads, wherein the mould is shaped to ensure centralisation of the core wire and beads relative to the mould. In the method and mould, the mould will be shaped to mould flexible material to a polygonal cross-section over the core wire between the beads and to approach or contact an outer surface of the core wire, and also to have surfaces or inwardly extending projections or pins which closely approach or locate against outer surfaces of ferrules of the beads which present longitudinally extending shoulders.

Other features of the invention are described below or set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now fee- escribed in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a side elevation of a section of a wire saw according to this invention;

Figure 2 shows a longitudinal cross-section of the section of wire saw seen in Figure 1 ;

Figure 3 shows a cross-section at the line 3-3 in Figure 1 ;

Figure 4 shows a cross-section at the line 4-4 in Figure 1 ;

Figure 5 shows a longitudinal cross-section of a section of wire saw according to a second embodiment of the invention;

Figure 6 shows a perspective view of another embodiment of the invention;

Figure 7 shows a side view of the embodiment of Figure 6; Figure 8 shows a cross-section at the line 8-8 in Figure 7;

Figure 9 shows a side view of another embodiment of the invention;

Figure 10 shows a cross-section at the line 10-10 in Figure 9;

Figure 11 shows a side view of another embodiment of the invention; and

Figure 12 shows a cross-section at the line 12-12 in Figure 11.

DECRIPTION OF THE ILLUSTRATED EMBODIMENTS

Figures 1 to 4 illustrate a section of wire saw 10 according to a first embodiment of the invention. The wire saw 10 has a steel wire core 12 of twisted, multi-strand construction. The wire core 12 carries spaced apart abrasive beads 14 at regular intervals along its length. The beads 14 are conventional and are shown diagrammatically to include a steel ferrule 16 carrying an abrasive element 18. In this embodiment, the abrasive element 18 comprises a diamond-impregnated matrix but in other embodiments, other suitable abrasive materials may be used.

As illustrated each ferrule presents shoulder portions 20 on opposite sides of the abrasive portion. As is also illustrated, the inner surfaces of the shoulder portions are flared at 22 to allow the core wire 12 to flex.

The beads 14 are anchored on the core wire 12 by a flexible material 23, in this case an elastomer such as rubber, is moulded over the core wire in regions 24 between the beads 14 and also over the shoulder portions 20 in shoulder regions 26 close to the abrasive elements 18. In practice, the rubber will also enter any clearance between the inner surfaces of the ferrules 16 and the core wire 12 as well as infiltrating the core wire between the strands thereof. Those skilled in the art will be familiar with the moulding and vulcanisation procedures used to mould the rubber in position, as well as with the bond promoting agents which are incorporated in the rubber and possible pre- treatment of the metal components, prior to vulcanisation, to improve the quality of the bond between the rubber and metal components.

In conventional practice, the rubber which is moulded about the core wire in the regions 24 between the beads 14 has a circular cross-section. Similarly, the rubber which is moulded over the shoulder portions 20 of the ferrules 16 of the beads 14 in the shoulder regions 26 has a circular cross-section. As indicated previously, this gives rise to the problem of ensuring that the core wire 12 is centrally, axially located in the rubber material in the regions 24, and that the beads are accurately centralised.

According to the present invention, the rubber in the regions 24 between the beads has a non-circular outer cross-sectional shape. In the embodiments depicted in Figures 1 to 10, the rubber has a polygonal outer cross-section. In the embodiment of Figures 1 to 4, the rubber has a generally triangular cross-section in the regions 24, as will be apparent from Figure 3 which shows that the rubber 29 has the external shape of an equilateral triangle with flat sides 30 and rounded comers 32.

It will be understood that the mould used to mould the rubber material will have, when closed, a corresponding triangular internal shape in regions between the beads 14. The dimensions of the mould are such, when the mould is closed, that the sides of the mould approach the outer surface of the core wire 12 very closely, to the extent that the when demoulding takes place, the rubber at central positions on the sides may have a thickness of only 0,1mm or even less. The sides of the mould may even touch the core wire. Thus it will be understood that the mould itself, when closed about the core wire in preparation for moulding, ensures that the core wire is centrally and axially located. Thus it will be understood that in the polygonal, in this case triangular, shape of the rubber, there are relatively thick zones adjacent the corners 32 in which the radial extent of the rubber is relatively great, and intermediate zones adjacent the positions 30 where the radial extent of the rubber is zero, when the sides of the mould touch the core wire or, in any event, relatively small compared to the rubber in the relatively thick zones.

Further according to the invention, the rubber in the shoulder regions 26 also has a generally polygonal cross-section. In this embodiment, the rubber has a generally square cross-section in the regions 26, as will be apparent from Figure 4 which shows that the rubber 29 has the external shape of a square with flat sides 34 and rounded corners 36. In these regions the mould has a corresponding, generally square cross-section. The mould dimensions in these regions are such that the sides of the mould approach the shoulder portions 20 of the ferrule very closely, to the extent that the when demoulding takes place, the rubber in these areas may have a thickness of only 0,05mm or even less.

Once again, there may even be contact between the sides of the mould and the shoulder portions 20 of the ferrules. Thus the mould itself, when closed about the shoulder portions of the ferrules in preparation for moulding, ensures that the ferrules, and hence the beads 14 themselves, are centrally and axially located.

The polygonal, in this case triangular, cross-section of the rubber in the regions 24 of the wire saw is considered to be a major advantage of the invention. The rubber in these regions has a smaller cross-sectional area than would be the case in the conventional arrangement where the rubber has a circular cross-section, as indicated by the broken line 40 in Figure 3. There is accordingly a greater cross-sectional area available to accommodate the flow of flushing fluid and cuttings when the saw is in use. As a result of the increase in area available for fluid and cutting flow it is expected that a wire saw incorporating this feature will allow greater cutting speeds to be achieved. A further advantage arises from the fact that the wire saw is normally twisted manually before being applied to a workpiece which is to be cut, or inserted into a slot in that workpiece. The twist applied to the wire saw in the regions 24 causes the corners 32 of the rubber to assume a spiral configuration. It is envisaged that this feature will also allow for an increase in the rate at which fluid and cuttings can flow and, accordingly, for an increase in overall cutting speed.

The accurate, axial centralisation of the core wire in the regions 24 and of the beads 14 is also considered to be advantageous. Particularly in the case of the beads 14, centralisation and resultant concentricity between the beads and the core wire will ensure that as the wire saw wears during use, the outer, operative surfaces of the beads will wear uniformly about their full circumferences. Even wear is also promoted by the centralisation of the core wire itself in the moulded rubber.

Figure 5 shows a modified embodiment of the invention. Here the core wire 12 has protective, flexible sleeves in the .form of coiled spring steel elements 50 located about it in the inter-bead regions 24. This configuration would typically be used when the wire saw is used to cut particularly abrasive material. Once again, the rubber in these regions has a triangular shape in cross-section. The dimensions of the mould in these regions will be chosen such that the flat sides of the mould approach the elements 50 very closely, or even contact them, as described above.

As an alternative to the use of a mould which has a polygonal cross-section at the shoulder regions 26 to ensure centralisation of the beads 14, it is also within the scope of the invention for the mould to carry pins or other projections or formations which will contact the shoulder regions 20 of the ferrules when the mould closes, once again ensuring centralisation of the beads in the mould and hence concentricity of the beads and the core wire. This is exemplified in Figures 6 to 8 in which the shoulder regions 26 have a circular cross-section. Indentations or dimples left by inwardly projecting mould formations which ensure centralisation of the beads are indicated by the reference numeral 60.

In each embodiment described above, it will be understood that it is the shape of the mould which gives rise to the desirable centralisation of the core wire and beads.

Figures 9 and 10 illustrate a further embodiment in which the rubber in the regions between the beads has a hexagonal cross-section rather than the triangular cross-section of the earlier embodiments. As in the earlier embodiments, central regions of the flat sides 70 of this polygonal cross- section are very close to or at the outer surface of the wire core 12. As before the thickness of the material in these regions will typically be 0,1mm or less.

As in the earlier embodiments, it will be understood that the mould once again ensures centralisation of the core wire in the rubber. It will furthermore be understood that in each case the mould will include surfaces which, when the mould is closed, very closely approach or contact the surface of the core wire such that the moulded material has the thickness as discussed above.

The space occupied by the hexagonal cross-section rubber of Figures 9 and 10 can be even less than that occupied by the triangular cross-section of the earlier embodiments, and it is accordingly envisaged that flow of flushing fluid for cooling and cutting removal can be further enhanced.

As will be apparent from Figure 9, this embodiment is similar to that of Figures 6 to 8 in that the mould carries pins or projections at positions corresponding to the shoulder regions 26 which will closely approach or contact the shoulder portions of the ferrules of the abrasive beads when the mould is closed. As before this ensures that the ferrules, and hence the beads themselves, are accurately centralised. The shoulder regions 26 are circular in cross-section as in Figures 6 to 8, but it will be understood that the polygonal cross-sectional rubber shape in the shoulder regions could equally well be used in other embodiments.

Figures 11 and 12 illustrate a further embodiment in which the rubber moulded over the core wire is again non-circular. However in this case the rubber has a sinuous outer profile defined by peaks 80 and troughs 82 rather than the polygonal shape of the embodiments described above. Referring to Figure 12 in particular it will be appreciated that the rubber is, as in the earlier embodiments, composed of relatively thick zones, in this case adjacent the peaks 80, where the radial extent of the rubber is relatively great and intermediate zones, in this case adjacent the troughs 82, where the radial extent of the rubber is relatively small. In the troughs 82.1 , the radial extent of the rubber is in fact zero, i.e. the relevant surfaces of the mould actual touch the core wire when the mould is closed. In the other troughs, the radial extent of the rubber is relatively small but greater than zero, i.e. the rubber does have a finite thickness.

In Figure 12 it will be noted that the troughs 82.1 are generally radially oriented while the other troughs are not. Although an arrangement in which all troughs are radially orientated might be considered desirable, it has been found by the applicant that there are inherent difficulties in machining a mould having the appropriate shape to create such a configuration.

Like the earlier embodiments, the embodiment of Figures 11 and 12 allows both for centralisation of the core wire and for enhanced flow of flushing fluid, particularly when twisted in use, as described above.

Figure 11 shows indentations or dimples 84, similar to those described above in relation to the embodiments of Figures 6 to 8 and 9 and 10, left by mould pins that serve to centralise the beads. It will however be understood that the polygonal rubber shape described in relation to Figures 1 to 4 could also be used to achieve such centralisation. -li¬

lt will of course be understood that centralising the core wire and simultaneously centralising the beads ensures not only that these components are centralised but also that they are in concentric alignment with one another.

Although specific mention has been made of moulded rubber, it should be understood that the invention includes in its scope other flexible, moulded materials. The material may for instance be a moulded polymer, typically a suitable plastics material, possibly injection moulded.

Claims

1.

A wire saw comprising a core wire, abrasive beads spaced apart on the core wire and a flexible material moulded over the core wire between the beads, the flexible material moulded over the core wire between the beads having a non-circular outer cross-sectional shape defined by relatively thick zones in which the radial extent of the material overlying the core wire is relatively great' and intermediate zones, between the first zones, in which the radial extent of the material is zero or relatively small.

2.

A wire saw according to claim 1 wherein the flexible material moulded over the core wire between the beads as defines a generally polygonal outer cross-sectional shape.

3.

A wire saw according to claim 2 wherein the polygonal shape defined by the flexible material includes sides which, at central positions on those sides, are located close to or at an outer surface of the core wire.

4.

A wire saw according to claim 3 wherein the polygonal shape has three sides each of which, at a central position on the side, is located close to or at the outer surface of the core wire.

5.

A wire saw according to claim 3 wherein the polygonal shape has six sides each of which, at a central position on the side, is located close to or at the outer surface of the core wire.

6.

A wire saw according to any one of claims 3 to 5 wherein the flexible material defining the polygonal shape has a thickness of 0,1mm or less at central positions on the sides of the polygonal shape.

7.

A wire saw according to claim 2 wherein a flexible sleeve is located about the core wire between the beads and the polygonal shape defined by the flexible material includes sides which, at central positions on those sides, are located close to or at an outer surface of the sleeve.

8.

A wire saw according to claim 7 wherein the sleeve comprises a coiled element.

9.

A wire saw according to claim 8 wherein the coiled element is of spring steel.

10.

A wire saw according to any one of claims 7 to 9 wherein the polygonal shape has three sides each of which, at a central position on the side, is located close to or at the outer surface of the sleeve.

11. A wire saw according to any one of claims 7 to 9 wherein the polygonal shape has six sides each of which, at a central position on the side, is located close to or at the outer surface of the sleeve.

12.

A wire saw according to any one of claims 7 to 11 wherein the flexible material defining the polygonal shape has a thickness of 0,1mm or less at central positions on the sides of the polygonal shape.

13.

A wire saw according to claim 1 wherein the flexible material moulded over the core wire between the beads has a sinuous outer profile defined by alternating relatively thick zones and intermediate zones.

14.

A wire saw according to claim 13 wherein the flexible material has eight relatively thick zones and eight intermediate zones.

15.

A wire saw according to claim 13 or claim 14 wherein the relatively thick zones have outer extremities lying on a circle centred on the centre of the core wire, the radial extent of the flexible material is zero in some intermediate zones and greater than zero in other intermediate zones.

16.

A wire saw according to any one of the preceding claims wherein the beads include longitudinally extending shoulder portions and shoulder portions of flexible material are moulded over the shoulder portions of the beads, each shoulder portion of the flexible material having a generally polygonal outer cross-sectional shape.

17.

A wire saw according to claim 16 wherein, at central positions, sides of the polygonai shape of the shoulder portions of the flexible material are located close to or at the outer surface of the shoulder portions of the beads.

18.

A wire saw according to claim 16 or claim 17 wherein the shoulder portions of the flexible material have a square cross-section.

19.

A wire saw according to any one of claims 1 to 15 wherein the beads include longitudinally extending shoulder portions and shoulder portions of flexible material are moulded over the shoulder portions of the beads, the shoulder portions of flexible material including indentations or recesses therein formed by inward projections on a mould used to mould the flexible material, the indentations or recesses extending inwardly to positions close to or at outer surfaces of the shoulder portions of the beads.

20.

A wire saw according to claim 19 wherein the shoulder portions of the flexible material are circular in cross-section.

21.

A method of moulding flexible material onto an assembly comprising a core wire and abrasive beads spaced apart along the length of the core wire, thereby to form a wire saw in which flexible material is moulded over the core wire between the beads, the method including the step of using a mould shaped to ensure centralisation of the core wire in the flexible material.

22.

A method according to claim 21 including the step of using a mould shaped, when closed, to mould flexible material in a polygonal shape over the core wire between the beads.

23.

A method according to claim 22 including the step of using a mould including surfaces which, when the mould is closed, locate close to or against an outer surface of the core wire or of a protective sleeve on the core wire between the beads.

24.

A method according to claim 23 including the step of using a mould shaped, when closed, to mould flexible material in a hexagonal or triangular shape over the core wire between the beads.

25.

A method according to any one of claims 21 to 24 wherein the abrasive beads of the assembly include longitudinally extending shoulder portions, the method including the step of using a mould shaped, when closed, to mould shoulder portions of flexible material over the shoulder portions of the beads with each shoulder portion of flexible material having a generally polygonal outer cross-sectional shape.

26.

A method according to claim 25 including the step of using a mould including surfaces which, when the mould is closed, locate close to or against outer surfaces of the shoulder portions of the beads, thereby to ensure centralisation of the beads.

27.

A method according to any one of claims 21 to 24 wherein the abrasive beads of the assembly include longitudinally extending shoulder portions, the method including the step of using a mould formed with inwardly extending projections or pins which, when the mould is closed, closely approach or contact the shoulder portions of the beads, thereby to ensure centralisation of the beads.

28.

A mould for moulding flexible material onto an assembly comprising a core wire and abrasive beads spaced apart along the length of the core wire, thereby to form thereby to form a wire saw in which flexible material is moulded over the core wire between the beads, wherein the mould is shaped to ensure centralisation of the core wire and beads relative to the mould.

29.

A mould according to claim 28 wherein the mould is shaped, when closed, to mould flexible material in a polygonal shape over the core wire between the beads.

30.

A mould according to claim 29 wherein the mould includes surfaces which, when the mould is closed, locate close to or against an outer surface of the core wire or of a protective sleeve on the core wire between the beads.

31.

A mould according to claim 30 wherein the mould is shaped, when closed, to mould flexible material in a hexagonal or triangular shape over the core wire between the beads.

32.

A mould according to any one of claims 28 to 31 wherein the abrasive beads of the assembly include longitudinally extending shoulder portions, the mould being shaped, when closed, to mould shoulder portions of flexible material over the shoulder portions of the beads with each shoulder portion of flexible material having a generally polygonal outer cross- sectional shape.

33.

A mould according to claim 32 including surfaces which, when the mould is closed, locate close to or against outer surfaces of the shoulder portions of the beads, thereby to centralise the beads.

34.

A mould according to any one of claims 28 to 31 wherein the abrasive beads of the assembly include longitudinally extending shoulder portions, the mould being formed with inwardly extending projections or pins which, when the mould is closed, closely approach or contact the shoulder portions of the beads, thereby to centralise the beads.