GB2423540A

GB2423540A - Core drills and cutting discs

Info

Publication number: GB2423540A
Application number: GB0506012A
Authority: GB
Inventors: Mario Halbeisen
Original assignee: Marcrist International Ltd
Current assignee: Marcrist International Ltd
Priority date: 2005-02-24
Filing date: 2005-03-24
Publication date: 2006-08-30
Also published as: GB2423537A; GB0503803D0; GB0506012D0

Abstract

A core drill comprises a tubular body having a closed end adapted to be fitted to a drill and an open end with an annular face substantially normal to the longitudinal axis of the body, at least one drill segment fixed to the annular face, the at least one segment having at least one through passage (9) extending through the thickness of the wall of the tubular body to permit cooling fluid to pass between the inside and the outside (10) of the tubular body. The through passage may comprise at least one aperture passing through the segment. Alternatively, the segment may have at least one notch or groove formed in one of its edges, the notch or groove co-operating with the annular face to provide the through passage. The notch or groove may be of part circular or triangular cross-section. The through passage may extend substantially radially of the tubular body or at an angle to a radius through the wall of the tubular body to assist fluid flow. A cutting disc is also disclosed having fluid passages 23, 24, 25.

Description

CUT11NG TOOLS

Field of the Invention

The present invention relates to cutting tools provided with means to improve the flow of cooling fluid, and in particular to core drills and cutting discs.

Background to the Invention

The action of core drills and cutting discs, especially those used for cutting rock and masonry, is essentially the same: cutting segments consisting of abrasive material held in a carrier matrix are moved through the material being cut, either in a circular cutting path, in the case of core drills, or in a straight path, in the case of cutting discs. Tradition- ally, diamond-tipped core drills are cooled with water fed to the diamond tips from the centre of the drill. When a core drill is being used, it removes material previously occupy- ing an annular space in the material, leaving a pillar of material that can be subsequently removed. Cooling water is forced into the drill at the end remote from the cutting face and passes over the outside surface of the pillar, over the cutting segment and emerging from the hole being drilled. The flow path of the cooling water therefore passes over both the inside surface and the outside surface of the drill body. The water flow not only cools the diamond tips but also assists debris removal, flushing it out of the hole.

Cutting discs may also be provided with a flow of cooling water, and this will need to be fed equally to both faces of the cutting disc to ensure uniform cooling.

When the flow is insufficient or is interrupted, heat builds up rapidly at the cutting edges. As a consequence, drilling or cutting speed can be significantly reduced and/or segment wear increased substantially. In extreme cases the segments can begin to glaze.

If so, heat builds up to the point where segments can begin to melt and ultimately become detached.

Moreover, when certain materials are being drilled or cut, it is possible that the slurry at the drilling or cutting edge is more viscous than the cooling water or is otherwise more resistant to flow than the cooling water. This builds up a back-pressure which can be sufficient to interrupt water flow. The water does not then flow past the cutting edge and the segments are no longer cooled.

There are therefore a number of factors that can accumulate to such an extent that drilling or cutting performance is reduced and segment wear increased. Ultimately, the core drill or cutting disc can fail completely.

Typical symptoms of an inadequate water supply are uneven wear of the segment, excessive wear, segment glazing, segment loss and core drill destruction. Segments can be inspected to monitor wear. Rounding of the cutting edge on the inside or outside can be a strong indication of inadequate water supply on the inside or outside respectively.

This is indicated in Figures 2 and 3. It is clear that measures need to be taken to minimise the occurrence of these problems.

In US Patent 4,739,844 a series of cut-outs are provided around the periphery of the cutting face of a core drill between the cutting segments and in US Patent Application US 2002/0112895 a series of spiral grooves in the external surface of the drill body help carry away slurry from the cutting segments, which have external grooves leading to the spiral grooves.

Summary if the Invention

According to the present invention, there is provided a cutting tool having a sup- port body rotatable about an axis and carrying at least one cutting element having a cut- ting face directed away from the support body, the at least one cutting element having at least one through passage extending laterally thereof relative to the cutting face to permit cooling fluid to pass between opposed side faces of the cutting member.

In one embodiment of the invention, a core drill comprises a tubular body having a closed end adapted to be fitted to a drill and an open end with an annular face substan- tially normal to the longitudinal axis of the body, at least one cutting element fixed to the annular face, the at least one cutting element having at least one through passage extend- ing through the thickness of the wall of the tubular body to permit cooling fluid to pass between the inside and the outside of the tubular body.

In another embodiment of the invention, a cutting disc comprises a circular metal support body with the cutting element or elements mounted on the periphery thereof so as to extend radially outwardly of the body with the or each through passage extending normally to the plane of the support body.

The through passage may comprise at least one aperture passing through the cut- ting element. Alternatively, the cutting element may have at least one notch or groove formed in an edge thereof, the notch or groove cooperating with the support body to define the through passage.

The notch or groove may be of any cross-sectional shape, for example partcircular or triangular.

The through passage may extend substantially radially of the tubular body or at an angle to a radius through the wall of the tubular body to assist fluid flow, in the case of a core drill.

While the cooling fluid will typically be water, it will be understood that in some circumstances it may be desirable to use instead a flow of air or other cooling gas.

The cutting element could be in the form of a continuous member extending around the support body, but will typically be in the form of shorter segments.

An additional benefit of the provision of apertures passing through the segment is that, as the segments wear down to the level of the aperture or apertures, the segment becomes divided into two or more smaller segments. Ideally, for best cutting action in some circumstances, a drill or cutting disc would be provided with a larger number of shorter segments, but attaching these would be difficult. A similar effect is achieved by causing the individual segments to sub-divide as they wear down in use.

Brief Description of the Drawings

The invention will now be described with reference to the drawings, in which: Figure 1 is a cross-section of a typical core drill showing the coolant path; Figures 2 and 3 are schematic diagrams showing segment wear; Figure 4 shows improved flow paths in a core drill in accordance with the present invention; Figures 5a, 5b and 5c illustrates possible variants on the form of through passages; Figure 6 shows a perspective view of a segment with notches or grooves; Figure 7 illustrates a cutting disc in accordance with the invention; and Figure 8 is an enlarged view of one cutting element of the disc shown in Figure 7.

Detailed Description of the Illustrated Embodiments Referring first to Figure 1, a typical core drill 1 comprises a tubular core body 2 having a closed end with a fitting 3 adapted to co-operate with a driver (not shown) and an open end presenting an annular face to which are attached one or more cutting seg- ments 4. The drill is illustrated in use, drilling into solid material 5 so as to make an annu- lar cut and leave a pillar 6 connected to the bulk of the material being drilled. The pillar can subsequently be removed.

Cooling fluid, usually water, is pumped into the closed end of the tubular body through an inlet port 7. The fluid flows over the pillar and over the inside face of the tu- bular body, as indicated by a series of arrows 8. When it reaches the cutting face of the drill, the fluid is forced over the segments between their cutting faces and the end of the hole being cut by the drill. It finally emerges out of the hole, passing over the outer sur- face of the tubular body in the process. Problems associated with this fluid flow path have been discussed above and Figures 2 and 3 show schematically the sort of segment wear 1 5 that is indicative of poor fluid supply.

Referring now to Figure 4, this is identical with Figure 1 in all respects except that the segment(s) are provided with through passages 9 enabling the fluid to pass through the segment(s). In this way, cooling fluid passing along the inside surface of the body can pass not only over the cutting surface of the segments, as normally, but also through the segment(s) into the annular space 10 between the outer face of the body and the inner surface of the hole being drilled without being dependent on gaps between the base of the hole and the cutting faces of the segments.

With this construction, there is less of a tendency for the build up of a back pres- sure and the problems of reduced fluid flow as compared with the prior art discussed above.

Figures 5a, 5b and 5c illustrate some exemplary forms for the through passages.

For example, the passages may be formed at the edge of the segment by one or a pattern of notches or grooves extending the full thickness of the segment. These notches may be of any convenient shape such as semi-circular or triangular, as shown at 11 and 1 2. Al- ternatively, holes 1 3 may penetrate the segment in a variety of patterns and number, as illustrated in Figure 5. Combinations of grooves, notches and apertures are also possible, the number and arrangement being selected to suit the circumstances, such as the viscos- ity of the cooling fluid, the size of drill and the type of material being drilled.

Figure 6 shows an example of segment where a notch or groove 14, 1 5 is formed on opposed sides of the segment. One of the notches 14, 1 5 co-operates with the annu- lar face of the tubular body to define a semicircular cross-section through passage for cooling fluid. The other notch opposes the cutting face and can assist in debris removal and/or can provide additional pathways for cooling fluid.

Although the through holes may be formed radially through the wall of the body, they may be inclined at an angle to encourage flow of cooling fluid through the segment from the inside to the outside.

Referring now to Figures 7 and 8, a cutting disc in accordance with the invention comprises a steel support disc 20 having the periphery thereof divided by inwardly di- rected slots 21 in conventional manner. A cutting segment 22 is mounted on the circum- ferential edge of the support disc 20 between each adjacent pair of slots 21. Each seg- ment 22 is typically formed from a mixture of metal powder and diamond grit, com- pressed and sintered, and is attached to the edge of the support disc by welding or braz- ing, for example by laser welding. The segments are moulded so as to have V-shaped grooves 23, 24 and 25 in the cutting face and the underside respectively. In the case of the groove 25 in the underside, this forms with the rim of the support disc 20 a triangular aperture through the segment from one side to the other. Each of the grooves 23-25 serves to allow the passage through the segment of cooling fluid, while also serving to sub- divide the segment cutting surface for greater cutting efficiency. The groove 25 serves this function when wear of the segment, while obliterating the outer grooves 23 and 24, reaches its top, effectively dividing the segment into two.

The invention therefore provides an improved core drill or cutting disc with en- hanced provision for cooling and which does not suffer from the problems discussed above in connection with known core drills or cutting discs. In addition, the life of a cut- ting tool incorporating the measures provided by the invention is prolonged.

Claims

1. A cutting tool having a support body rotatable about an axis and carrying at least one cutting element having a cutting face directed away from the support body, the at least one cutting element having at least one through passage extending laterally thereof relative to the cutting face to permit cooling fluid to pass between opposed side faces of the cutting member.

2. A cutting tool according to Claim 1, wherein the through passage comprises at least one aperture passing through the cutting element.

3. A cutting tool according to Claim 1, wherein the cutting element has at least one notch or groove formed in an edge thereof, the notch or groove co-operating with an edge of the support body to provide said through passage.

4. A cutting tool according to Claim 3, wherein said notch or groove is of part circular cross-section.

5. A cutting tool according to Claim 3, wherein said notch or groove is of tn- 1 5 angular cross section.

6. A cutting tool according to any preceding claim, in the form of a core drill comprising a tubular body having a closed end adapted to be fitted to a drill and an open end with an annular face substantially normal to the longitudinal axis of the body, at least one drill segment fixed to the annular face, the at least one segment having at least one through passage extending through the thickness of the wall of the tubular body to permit cooling fluid to pass between the inside and the outside of the tubular body.

7. A cutting tool according to Claim 6, wherein said through passage extends substantially radially of said tubular body.

8. A cutting tool according to Claim 6, wherein said through passage extends at an angle to a radius through the wall of said tubular body to assist fluid flow.

9. A cutting tool according to any of Claims 1 to 5, in the form of a cutting disc comprising a circular metal support body with the cutting element or elements mounted on the periphery thereof so as to extend radially outwardly of the body with the or each through passage extending normally to the plane of the support body.

10. A core drill substantially as herein described with reference to the draw- ings.