WO1998003769A1

WO1998003769A1 - A disc cutter

Info

Publication number: WO1998003769A1
Application number: PCT/AU1997/000455
Authority: WO
Inventors: Richard Andre Willoughby; Xing Sheng Li; Halim Gurgenci; Zhiqiang Guan
Original assignee: The University Of Queensland; Commonwealth Scientific And Industrial Research Organisation; Pasminco Australia Limited
Priority date: 1996-07-17
Filing date: 1997-07-17
Publication date: 1998-01-29
Also published as: CA2261003A1; AUPO106896A0

Abstract

A disc cutter (23) for a rock working machine, the disc cutter (23) having a hard metal cutting ring (11) attached to a hub (12) characterised in that the hub (12) has a footing portion (14) formed of hard metal to support the cutting ring (11).

Description

TITLE A DISC CUTTER FIELD OF THE INVENTION This invention relates to a disc cutter and particularly relates to a disc cutter for a rock working machine including machines used in underground mining and for tunnel boring.

BACKGROUND ART

Rock working machines are used in underground mines to excavate rock, or other materials such as ore, coal and the like, and have a rotary head of about the diameter desired for the amount of excavation required.

The rotary head has a surface on which a number of disc cutters are located. Each disc cutter has a cutting ring mounted to a hub, the hub being mounted to a shaft.

The rotary head is pushed hard up against the rock face and rotated which places an enormous force onto the disc cutters which in turn cut grooves in the rock face. The enormous force also fractures the rock allowing it to be excavated.

The amount of radial force on the disc cutter varies depending on the type and hardness of the rock to be excavated, but a typical peak force is about 100 tonnes. The cutting rings on many conventional disc cutters are made from steel . The steel rings blunt very quickly in abrasive rock and become uneconomical due to the downtime of the machine during replacement of the disc cutters. An attempt has been to simply place a tungsten carbide ring on a conventional steel hub. In practice it was found that the tungsten carbide ring broke or cracked making it unsuitable for use on a rock working machine.

The present invention is directed to a disc cutter which can use a hardmetal, such as a tungsten carbide ring, attached to a ferrous metal hub characterised in that the hub contains a hardmetal footing to support the ring. OBJECT OF THE INVENTION It is an object of the invention to provide a disc cutter which may overcome the abovementioned disadvantages or provide the public with a useful or commercial choice.

In one form, the invention resides in a disc cutter for a rock working machine, the disc cutter having a hardmetal cutting ring attached to a hub, characterised in that the hub has a footing portion formed of hardmetal to support the cutting ring.

It has now been found that the incidence of breaking or cracking of the tungsten carbide ring can be significantly reduced if the ring is supported on a hardmetal footing rather than supported directly on a non-hardmetal (such as ferrous metal) hub. While not wishing to be bound by theory, it appears that the interface stress between the ring and the hub interface is reduced to below a critical level by providing a hardmetal footing. While the entire hub can be formed of hardmetal, it is preferred that the hub has a main body portion formed from a non-hardmetal with only the footing portion formed of hardmetal. The footing portion is typically annular to support a continuous cutting ring. There are also significant cost savings, aε; the disc cutter of the invention, having the hardmetal cutting ring, outperforms any conventional disc cutter with a steel cutting ring, and also outperforms any disc cutter having a tungsten carbide ring on a plain metal hub, because of the reduction in breaking or cracking of the ring due to the ring/hub interface stresses.

The disc cutter of the invention is cheaper and easier to manufacture as much of the hub can be formed from conventional ferrous metal, with only a footing portion of the hub formed from hardmetal. Further, should the disc cutter become worn or damaged, it is only necessary to replace the hardmetal cutting ring.

The disc cutter can be used as a cutting tool on a rock working machine. The term "rock working" is meant to include, but not be limited to, tunnel boring, raise boring, mine shaft excavation, ore recovery in mines, coal recovery, and surface excavation and cutting. The term rock working is not limited to tunnelling or mining, and the disc cutter can also be used to cut grooves, channels and the like in almost any type of solid material. Of course, in soft materials such as coal, a normal steel cutting ring would be sufficient, and the disc cutter according to the invention would typically be used with a machine for excavating harder types of rock, or a solid where hard rock portions are likely to be encountered (for instance in tunnelling).

The term "hardmetal" is known in the art and includes metal alloys such as carbides, and cemented carbides such as tungsten carbides and cobalt cemented tungsten carbides. Throughout the specification and claims the term "hardmetal" is also meant to include non metal materials which have the same hardness as the above materials; and an example of such a non metal material is a ceramic.

It is preferred that the hard metal ring has a hardness of HV3 of 900 or more. A cemented tungsten carbide ring formed of tungsten carbide and cobalt is suitable. A suitable tungsten carbide ring is one having over 80% and preferably about 87% of tungsten carbide in a cobalt binder. Such a ring has a hardness HV3 of 1070, a density of 14.2g/cm and a stiffness (Youngs Modulus) of GPa 450. The hub can be a more or less standard-type hub used on conventional disc cutters. The hub is rotatably attached to a non-rotating shaft containing roller bearings such that the ring and the hub can be rotated together. The hub has a main body portion formed from conventional material which usually comprises steel or ferrous metal such as cast iron, and which is adapted to be mounted to the shaft. The hub has a peripheral side wall and the peripheral side wall is provided with a footing portion which can extend about the hub and on which the cutting ring is supported. The footing portion is formed from hardmetal and it is found that this arrangement minimises breaking or cracking of the hardmetal ring when attached to a non-hardmetal hub.

The footing portion may be formed of a hardmetal which is identical to or different to the hardmetal of the cutting ring; but it is preferred that the footing portion has a stiffness similar or greater to that of the hardmetal ring. Thus, the footing portion may also be formed from tungsten carbide, and while the footing portion should be harder than the main body portion of the hub, it is not necessary for the footing portion to be of the same hardness as the cutting ring.

The cutting ring may have a substantially planar inner portion and a rounded or otherwise curved outer cutting portion. It is preferred that the inner portion and the footing portion mate together to allow distribution of the load. It is envisaged that if the inner portion is not planar, it should be of a configuration to complement the shape of the footing such that the outer ring can mate with the footing portion. The hub can be formed with the hardmetal footing portion and the non-hardmetal main body portion by a CIC process which is a known cast-in-carbide process. In this process, the hardmetal (for instance tungsten carbide) is metallurgically bonded to the nodular cast iron base. Alternatively, the footing portion can be formed separately and fitted to the main body portion.

In order to prevent the cutting ring from rotating relative to the hub, one or more clamp rings may be provided. Clamp rings are known in the art and clamp on one or both sides of the cutting ring to prevent the cutting ring from slipping on the hub. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will be described with reference to the following drawings in which Figure 1 is a view of a disc cutter according to an embodiment of the invention.

Figures 2A - 2G show various alternative shapes of the hard metal cutting ring.

Figure 3 is a perspective view of the disc cutter of Figure 1.

BEST MODE Referring to Figure 1, there is shown a disc cutter 10 having a hardmetal cutting ring 11 and a hub 12 which has a main body portion 13 formed from a non- hardmetal material, and an annular peripheral footing portion 14 formed from hardmetal. Support rings 15, 16 provide side support to the hardmetal ring 11. Clamp rings 28,29 are provided on the outside of the support rings 15,16 to securely hold the support rings and the hardmetal ring 11 in position.

Hub 12 has a more or less conventional design for disc cutters and includes a bore to allow the hub to be mounted to a shaft in the usual manner. Hub 12 has a main body portion 13 which is formed from conventional cast iron or steel. The main body portion has an inner wall 17 and an outer wall 18. Inner wall 17 is made entirely of the conventional ferrous metal hub material

(i.e. cast iron or steel) and is not formed from hardmetal . In the outer wall is a radial, annular, integrally formed footing portion 14 which is formed from hardmetal. In Figure 1, footing portion 14 is formed from 75% tungsten carbide and 25% cobalt binder. The footing portion has a hardness HV3 750, a density of 13g/cm³ and a stiffness of GPa 450.

The footing portion is cast integrally with the conventional main body portion 13 using a cast in carbide (CIC) process which is known. The process forms the composite hub having the main body portion and the footing portion where the hard metal footing portion is metallurgically bonded to the main body portion. A transition zone of about 5mm extends between the two materials, and over the transition zone, the properties gradually change from tungsten carbide to cast iron or steel. It is however envisaged that the footing could be formed separately and fitted into a corresponding recess on the main body portion. Footing portion 14 has a first area of lεirger cross-section 19 which is within the periphery of outer wall 18 of the main body portion, and has a sescond extending or proud area 20 of smaller cross-section. The footing thereby presents a pair of upstanding shoulder portions 21, 22.

Cutting ring 11 is formed from tungsten carbide and the composition is 87% tungsten carbide and 13% cobalt binder. The cutting ring has a hardness HV3 1070, a density of 14.2g/cm and a stiffness of greater than GPa 450. The cutting ring 11 has a domed upper portion 23, a substantially straight lower edge area 24, and a flat base portion 25.

The width of base portion 25 is substantially the same as the width of the extending second area 20 of footing portion 14.

Support rings 15, 16 function to prevent cutting ring 11 from slipping over its footing portion 14. Support rings 15, 16 have substantially straight clamping faces 26, 27 which are dimensioned to press against the shoulder portions 21, 22 of footing portion 14 and also against the lower edge area 24 of cutting ring 11.

Two clamp rings 28,29 are provided to clamp the support rings 15,16 and the hardmetal ring 11 in place. The clamp rings are pressed into grooves 30,31 machined on the hub 13. The clamp rings are split rings to facilitate attachment of the rings onto the hub.

Figures 2A - 2G illustrate some variations to the cross-section of the cutting ring.

The disc cutter according to the invention allows a disc cutter to be produced which has an extremely hard-wearing cutting ring having a reduced tendency to break or crack under the enormous compressive loads placed on it and on the hub. This is achieved by supporting the hardmetal ring on a footing which is also formed from hardmetal while the main body of the hub is formed from conventional cast iron or steel. While it may be possible to manufacture a hub entirely of hardmetal to provide the same reduced tendency for the cutting ring to break, this would be considerably more expensive to manufacture than the hub described above. As well, the cutting ring can be made proportionally smaller, and particularly can have a smaller base width without increasing the risk of fracture of the ring under compressive loads. The enormous loads on the smaller base width can be supported and distributed by the footing portion. When the cutting ring does become worn, it can be simply replaced and there is no need to replace the hub of the disc cutter.

It should be appreciated that various other changes and modifications may be made to the embodiment described without departing from the spirit or scope of the invention.

Claims

CLAIMS :

1. A disc cutter for a rock working machine,, the disc cutter having a hardmetal cutting ring attached to a hub characterised in that the hub has a footing portion formed of hardmetal to support the cutting ring.

2. The cutter of claim 1, wherein the footing portion is annular to support a continuous hardmetal cutting ring.

3. The cutter of claim 2, wherein the remainder of the hub is formed of conventional non-hardmetal material.

4. The cutter of claim 3, wherein the cutting ring is formed from ceramics and/or carbides.

5. The cutter of claim 4, wherein the footing portion is formed from ceramics and/or carbides and has a stiffness similar to or greater than that of the cutting ring.

6. The cutter of claim 5, wherein the cutting ring has a hardness of at least HV3 900.

7. The cutter of claim 6, wherein the cutting ring is formed of at least 80% tungsten carbide in a cobalt binder.

8. The cutter of claim 7, wherein the footing portion is formed of at least 80% tungsten carbide in a cobalt binder.

9. The cutter of claim 8, wherein the cutting ring has a planar inner portion which mates with a planar upper portion of the footing portion to εillow distribution of the load.

10. The cutter of claim 9, wherein the hub is formed with the hardmetal footing portion by a cast in carbide process.

11. The cutter of claim 10, wherein the cutting ring is held in place by at least one clamping ring.