WO2003006791A1

WO2003006791A1 - Rolling rock cutters

Info

Publication number: WO2003006791A1
Application number: PCT/IB2002/002455
Authority: WO
Inventors: Llewellan Anderson
Original assignee: Ag Associates, Llc
Priority date: 2001-07-09
Filing date: 2002-06-27
Publication date: 2003-01-23

Abstract

The invention concerns rolling cutters used in cutter heads for rock breaking surfaces the cutters being designed primarily for use with swinging boom mining machines and having a selection of a number of inserts (3) per row in a number of rows to give a ratio of spacing between inserts to insert penetration suited to a particular rock type. The inserts are preferably arranged in a helical path across the width of the cutter, the spacing of the rows of inserts and the distance between inserts in any row is such that any four adjacent inserts form an approximate rectangle.

Description

ROLLING ROCK CUTTERS

FIELD OF THE INVENTION

This invention relates to cutters used for penetrating rock and more particularly to cutters used on a cutter head in underground rock cutting operations.

BACKGROUND TO THE INVENTION

The cutters find application in mining equipment of the kind described in the complete specification of our South African patent number 99/2714 entitled "MINING MACHINE".

That specification is included in this specification in its entirety by reference.

Generally, that specification describes a mining machine which can be used in underground mining to be remotely controlled for both location and mining operations and having at least one cutter head on the end of a boom rotatable about its end opposite the cutter head. The boom is carried by a beam anchorable at each end and having means for rotating the boom. Either or both the boom and the beam can be extensible.

More specifically, the mining machine consists of a cutter head fitted with rolling cutters. The head is fitted to the forward end of a swinging boom structure. The rear end of the boom is rotatable about an anchorable support formed by a vertically arranged hydraulic actuator with its axis at right angles to the length of the boom. The boom will be mounted on the cylinder of the actuator which will have a hanging wall engaging head and a footwall engaging foot.

A further vertical hydraulic actuator is provided at the front end of the boom so that this end may also be anchored between the hanging and footwalls.

Extending from the actuator in a generally opposite direction to the boom is a telescopic support beam controlled by further hydraulic actuators. The beam and actuators are carried at their ends remote from the actuator by a further pair of vertically operable hydraulic actuators. The actuators are spaced apart on opposite sides of the end of the support beam.

Boom rotating actuators extend from a frame on the support beam and actuators. The actuator or actuators extend along each side of the support beam and may be operably connected to the boom at any particular time. The connection of the actuators to the boom could conveniently be by means of a releasable connection to clevises.

It will be understood that pivotable clevises are provided one on each side of the boom. Each clevis is connected to one of the actuators. One way to bring a clevis and associated actuator into operative effect to rotate the boom in either left hand or right hand direction, is to use a releasable link to connect between the appropriate clevis and the boom. The preferred way is to have the actuators connected to the boom at all times and to have the actuators and clevis positions designed in such a way that either left hand or right hand or from fully left to fully right rotatable directions can be achieved.

The support beam extending actuators are provided singly or in pairs, one or one pair on each side of the beam with the actuators of each pair one above the other. Hinged lashing ploughs could be provided one on each side of the cutter head to facilitate muck removal from the face. An alternative and preferred method is to use a vacuum system in place of the lashing ploughs.

In use the machine is set up in a drive at a stope face with the axis of the support beam set up along the desired direction of cut so that the rolling cutters can be forced into the stope rock face along an arcuate path around the end of the boom by the boom rotating actuators.

To enable this to be done the anchoring hydraulic actuator at the rear of the boom and the actuators at the end of the support beam are extended to anchor between the hanging and footwalls of the stope.

Stepwise advancing of the cutters is effected by extension of the boom or the beam.

Because the operation of the machine described in the above specification involves a different mechanism for rock cutting than that previously known, it is desirable that the different roller cutter and cutterhead design be provided to optimize the use of the machine.

Those skilled in the art of rock cutting using kerf cutters appreciate how chips are formed and how the spacing to penetration ratio influences the formation of chips. The conventional rolling kerf cutter approach to rock cutting which is a two dimensional one, is to locate as many inserts as practical in each of the rows of cutting edges. As these cutters roll under considerable load on the rock face being cut, the rows of edges form kerfs in the rock face, and induce tensile cracks that propagate in adjacent kerfs. This is the basis of chip formation. Once the cracks meet, the rock chips become detached or spall from between the kerfs. The distance between the kerfs, the spacing, is critical as is the edge load that causes the inserts to penetrate into the rock. For any particular rock type, if this spacing to penetration ratio is too large, the cracks generated at each kerf do not connect and the chip will not spall. For any particular rock type, the spacing to penetration ratio is approximately constant.

In the machine briefly described above, the method of operation is the simultaneously sweeping and extending of a boom that supports the cutter head with rolling cutters mounted to it across the rock face to be cut, cutting the rock as it does so. The radius from the arm pivot to the tips of the cutters in contact with the rock increases from a minimum to a maximum dimension depending on the geometry and size of the particular mining machine. If more than two rows of cutters are mounted to the fixed geometry cutter head the cutters would not be contacting the rock at the same time as the arm radius increases during the cutting stroke. For example, if there were four rows of cutters mounted symmetrically about a centerline normal to the direction of motion, the outer two rows of cutters would contact the rock being cut at the minimum arm radius. At the maximum arm radius the inner two rows would be in contact with the rock.

The reason more than one row of conventional kerf cutters is necessary is that gauge cutters and face cutters, because of their geometry and size, cannot be mounted end to end and achieve the required kerf spacing. Two rows of cutters can generally achieve the required kerf spacing over the entire face to enable proper chip formation, if the rock being cut is conducive to a wider spacing for chip formation. For harder and less borable rock types, the kerf spacing required to produce proper chip formation becomes smaller requiring more edges on the cutter. The kerf edge load required also increases for these rock types. There is a bearing and cutter size limitation for any cutter that prevents increasing a number of rows of heavily loaded cutters beyond a practical maximum. For any particular kerf cutter, if the number of button insert rows is increases, the load per row is decreased accordingly so as not to exceed the rated cutter load capacity. This is counter to what is needed to penetrate the harder rock formations where higher than normal edge loading is required. To overcome this anomaly in conventional raise or tunnel boring, additional cutters are strategically positioned about the circular cutter head to decrease the kerf spacing to suit the hard rock to be cut. The total cutter head load increases to accommodate the increased number of cutters while the rated load per cutter remains the same.

After the rolling cutters have completed their arcuate cut the support beam, or the boom, is extended by means of the hydraulic actuators with the actuator at the cutterhead end of the boom released. When the support beam, or boom, has been extended to the required depth of the next cut, the support beam is re- anchored and the arcuate cutting operation repeated using the boom rotating actuators.

This operation is repeated until the support beam, or boom, is fully extended. The beam, or boom, is then retracted by keeping the actuator at the cutterhead anchored while the anchoring actuators are released and the beam, or boom, actuators retracted to move the actuators to a new anchoring position.

OBJECT OF THE INVENTION

It is an object of this invention to provide a rolling cutter and cutterhead which will mitigate the disadvantages set out above.

SUMMARY OF THE INVENTION

According to this invention there is provided a rolling rock cutter with a selection of a number of inserts per row, in a number of rows to obtain a ratio of spacing between inserts to insert penetration suited to a particular rock type. Further features of this invention provide for the selection to give a minimum number of inserts in contact with the rock during use to ensure a load on each insert adequate to penetrate the rock to a desired amount without exceeding the rated load capacity of the cutter or insert. Furthermore, the spacing of the rows of inserts and the distance between inserts in any row is such that any four adjacent inserts form an approximate rectangle, preferably a square or a rhomboid.

The invention also provides for each row of inserts to follow a helical path across the width of the cutter.

Still further features of this invention provide a cutter head comprising a plurality of cutters as defined above and for the cutter head to be mounted on a mining machine described in our patent specification referred to above.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred example of a cutter according to this invention is described below with reference to the accompanying drawings in which:

FIG 1 shows an elevation of a cutter; and FIGS 2 to 5 are details of the cutter.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated a roller cutter consists of a circular cylindrical body 1 supported through bearings (not shown) on a shaft 2 for mounting in a cutter head.

The body 1 carries inserts 3 for penetrating rock and forming rock chips.

The inserts 3 are arranged in rows with each row following a helical path across the width of the body 1. The helix angle is a function of the number of rows and can be small, for a large number of rows, as illustrated at 4 at about 1.5° or much larger for a lesser number of rows of up to about 25°.

In this embodiment there are 10 inserts in each row and the arrangement is illustrated in the details in Figures 2 to 5. Figure 2 shows the spacing indicated at 5 and 6 where the inserts lie with their centers on the corners of a square or rhomboid. For three dimensional rock cutting as is effected in the use of our mining machine described generally and referred to above, the rock chips removed from the working face will be the result of spalling between any four adjacent inserts arranged on such an approximate square or rhomboid. The three dimensional cutting of our mining machine involves a simultaneous sweeping movement around the fixed pivot with an extension of a boom that supports the cutter head. The arrangement of the rows of inserts to follow the helical path ensures the cutter rolls as smoothly as possible from one row of inserts to the next while maintaining the maximum load on the insets in each row, without overloading individual inserts, to obtain maximum spalling of the rock face.

The ratio of spacing of the inserts to penetration under operating conditions has an approximately constant value for any particular rock type. Thus different cutters can be made for use with the different rock types and the invention approaches a design maintaining maximum pressure on each insert by limiting the number of inserts in each row and increasing the number of rows to obtain the desired result for each rock type.

The end view and sections of the cutter head with ten rows of inserts as shown in Fig 1 are shown in Figures 3 to 5. The number of rows and spacing of the inserts will be varied depending on the rock type being cut or on the size of the chip required. This ability to effectively size the chips, width and length, by strategically spacing the button inserts, is also a feature which has not been possible before with conventional kerf cutters where the length of the chip can vary by an order of magnitude. The invention is, of course, not limited to the application on the mining machine described in our patent specification referred to above but can obviously be adapted for use on any other machine operating to cut three dimensionally.

Claims

1. A rolling rock cutter with a selection of a number of inserts per row in a number of rows, to obtain a ratio of spacing between inserts to insert penetration suited to a particular rock type.

2. A rolling rock cutter as claimed in claim 1 in which the selection is made to give a minimum number of inserts in contact with the rock during use to ensure a load on each insert adequate to penetrate the rock to a desired amount without exceeding the rated load capacity of the cutter or insert.

3. A rolling rock cutter as claimed in claim 2 in which the spacing of the rows of inserts and the distance between inserts in any row is such that any four adjacent inserts form an approximate rectangle.

4. A rolling rock cutter as claimed in claim 2 in which the spacing of the rows of inserts and the distance between inserts in any row is such that any four adjacent inserts form an approximate square.

5. A rolling rock cutter as claimed in claim 2 in which the spacing of the rows of inserts and the distance between inserts in any row is such that any four adjacent inserts form an approximate rhomboid.

6. A rolling rock cutter as claimed in any one of the preceding claims in which each row of inserts follows a helical path across the width of the cutter.

7. A rolling rock cutter as claimed in claim 6 in which the helix angle is between 1.5° and 25°.

8. A cutter head comprising a plurality of cutters as defined in any one of the preceding claims.

9. A rolling rock cutter substantially as described with reference to the accompanying drawings.