GB2174025A - A cutting tool - Google Patents

Abstract

A cutting tool for mounting on a machine for excavating rock or mineral, comprising a tool body (1) securable in a tool holder (not shown) and passage means (5, 6) for feeding hydraulic fluid to a cutting bit (4). At least a portion of the cutting bit is of relatively hard and porous material. <IMAGE>

Description

SPECIFICATION A cutting tool This invention relates to cutting tools which, in use, are mounted on cutter heads provided on excavating orturning machines.

In particular, although not exclusively, the present invention relates to rock or mineral cutting tools which, in use, are mounted on rotary cutter heads provided on excavating or mining machines.

It is known for hydraulic fluid, usually water, to be fed through a passage provided in the tool body, to a discharge orifice sited in the vicinity of a cutting tip or edge provided on the leading portion ofthe tool body.

Usually, the cutting tip or edge is constituted by a cutting bit of relatively hard material, as for example, tungsten carbide, inserted into the cutting tool body.

During the cutting operation a jet offluid discharging from the orifice tends to cool the cutting bit, provide lubrication and removes fine debris from the cutting zone. The result is that the cutting efficiency of the tool tends to be prolonged. Also, the amount of airbourne dustgenerated during the cutting operation tends to be suppressed.

Unfortunately, the known cutting tools tend to sufferfrom the disadvantagesthatthe use offluid is wasteful as only a small proportion oftheflow is effectively used forthe above purposes. The jet tends to impinge on only a portion ofthe exposed surface area ofthe cutting bit thereby subjecting the bit to relatively high thermal gradients and to thermal shock when the jet's flow path is interrupted due to debris movement. Thus, the operational life of cutting tools provided with hydraulic fluid discharge jets tend to be less than expected.

An object of the present invention is to provide a cutting tool which tends to overcome or reduce the above mentioned disadvantages.

According to the present invention a cutting tool for mounting on a machine for excavating material comprises atool body securable in a tool holder, and passage means forfeeding hydraulicfluidto a cutting bit mounted on the tool head, at least a portion of the cutting bit being of relatively hard and porous material Preferably, the porosity of the cutter bit is graduated through the matrix ofthe bit to promote graduated flowthroughthematrixtendingtoreducetempera- ture gradients within the cutting bit.

Advantageously, the cutting bit may comprise laminated layers of materials of different relative hardness or porosity.

Two embodiments ofthe present invention will be described with reference to the accompanying drawings, in which: Figure lisa longitudinal section taken through one form of rotary cutting tool; and Figure 2 is a longitudinal section takenthrough a second form of rotary cutting tool.

Figure 1 illustrates a rock or mineral cutting tool for mounting on a rotary cutter head of an excavating or mining machine. The cutting tool comprises a body 1 having a generally rectangular shank portion 2 and a head portion 3 provided on its leading or cutting portion with a cutting bit 4 of relatively hard porous material. The cutting bit 4 defines a leading cutting edge 9. In use, the shank is mounted in one of a plurality of similartool holders (not shown) carried on the rotary cutter head. When mounted in the tool holderthe shank extends substantially radially ofthe cutter head, the cutting direction of the tool being tangential tothe shank.

Passage means constituted by intersecting passages Sand 6 are provided in the tool bodyforfeeding pressurised hydraulic fluid, as for example, water, from asource (notshown) provided inthetool holder and engaged in a mouth 7 to passage 5, the passage 5, 6feeding the hydraulic fluid to the porous cutter bit 4.

Thus, in use, hydraulic fluid is discharged from the exposed surface area of the cutter bit into the cutting zone around the cutting tool. Atapered outlet 8 from passage 6 ensures substantially all the porous cutting bit is fed with hydraulic fluid ensuring adequate flow.

The flow of hydraulic fluid tends to cool substantially the whole matrix ofthe cutting tiptherebytending to prolong the efficient cutting life of the cutter tool.

In some embodiments the porosity ofthe cutter bit is graduatedthrough the matrix ofthe bit to promote graduatedflowthroughthematrixtendingto main- tain a uniform temperature gradientwithin the cutting bit. Theflowthrough the cutting bit is graduated such that a relatively largerflow occurs in portions ofthe bit which tend to becomehotestduring cutting. The relatively cooler portions ofthe bit have less flow.

In other embodiments of the invention the cutting bit is made up of layers of materials having different relative hardness and different relative porosity.

Figure 2 shows a second embodiment of cutting tool for mounting on a rotary cutter head of an excavating mining machine. The cutting tool comprises a body 11 having a generally circulartapered shank 12 and a head portion 13 provided on its leading or cutting portionwith acutting bitl4ofrelatively hard porous material.The cutting bit 14 defines a leading cutting tip 19. In use, the shank is sealably mounted in one of a plurality ofsimilartool holders (not shown) carried on the rotary cutter head. When mounted in the tool holder the longitudinal axis ofthe cutting tool is inclined to the radial direction of rotary cutting head.

Passage means constituted by intersecting passages 15 and 16 are provided in the tool body for feeding pressu rised hydraulic fluid, as for example, water, from a source (not shown) provided in the tool holder and engaged in a mouth 17 to the passagelS, the passages 5, 6feedingthe hydraulic fluid to the porous cutter bit 14. Thus, in use, hydraulic fluid is discharged from the exposed surface area of the cutter bit into the cutting zone around the cutting tool.

Atapered outlet 18fromthe passage 16 ensures substantially all the porous cutting bit is fed with hydraulic fluid ensuring adequate flow. The flow of hydraulic fluid tends to cool substantiallythe whole matrix of the cutting tip thereby tending to prolong the efficient cutting life of the cutter tool.

In some embodiments the porosity ofthe cutter bit is graduated through the matrix ofthe bit tending to maintain a uniform temperature gradient within the cutting bit. The flow th rough the cutting bit is graduated such that a relatively largerflow occurs in portions ofthe bit which tend to become hottest during cutting. The relatively cooler portions of the cutting bit have less flow.

In other embodiments ofthe invention the cutting bit is made up of layers of materials having different relative hardness and different relative porosity.

Claims (4)

1. Acutting tool for mounting on a machine for excavating or cutting material, comprising a tool body securable in a tool hoider, and passage means for feeding hydraulic fluid to a cutting bit mounted on the tool head, at least a portion ofthe cutting bit being of relatively hard and porous material.

2. Atool as claimed in claim 1, in which the porosity of the cutter bit is graduated through the matrix ofthe bit to promote graduated flow through the matrix tending to reduce temperature gradients within the cutting bit.

3. Atool as claimed in claim 1 or 2, in which the cutting bit may comprise laminated layers of materials of different relative hardness or porosity.

4. A cutting tool for mounting on a machinefor excavating rock or mineral, substantially as described herein and substantially as shown in Figure 1 or Figure 2 ofthe accompanying drawings.