CA2448230A1 - Cutterhead for a rock cutting machine - Google Patents

Abstract

The invention concerns a cutterhead for a rock cutting machine which operate s in a three dimensional manner with a swinging extendable boom carrying a cutterhead moving in an arcuate path with the cutterhead designed to have al l cutters effective throughout a cutting operat0on. The operation extends through a plurality of cuts and the cutterhead has a pair of bases which are linked together and to the boom, each supporting a plurality of cutters, and driven by independent piston and cylinder assemblies operating in unison.</S DOAB>

Description

CUTTERHEAD FOR A ROCK CUTTING MACHINE
FIELD OF THE INVENTION
This invention relates to cutterheads used for penetrating rock and more particularly to a cutterhead used in underground rock cutting operations.
BACKGROUND TO THE INVENTION
The cutterheads 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 CONFIRMATION COPY

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 cutterhead to facilitate muck removal from the face. An alternative 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 kerts. 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 kert 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 kert 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.

5 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 boom is extended by means of the hydraulic actuators with the actuator at the cutterhead end of the boom released. When the 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 boom is fully extended. The boom is then retracted by keeping the actuator at the cutterhead anchored while the anchoring actuators are released and the boom, actuators retracted to move the anchoring actuators to a new anchoring position.
More than two rows of cutters are frequently necessary and mounted to the fixed geometry cutter head. In this assembly the cutters would, in use, not be contacting the rock at the same time as the boom radius increases during the cutting stroke. For example, if there are 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 boom radius.
At the maximum boom radius the inner finro rows would be in contact with the rock.
This is illustrated in Fig1 of the accompanying drawings.
OBJECT OF THE INVENTION

It is an object of the present invention to provide a cutterhead in which the difficulty of the kind above set forth is at least to a large extent avoided.
SUMMARY OF THE INVENTION
According to this invention there is provided a cutterhead for a rock cutting machine operating in a three dimensional manner comprising a rigid base carrying a plurality of rolling rock cutters with the base linkable to a second equivalent base to ensure even distribution of the working load on the cutters with the bases pivotally mountable on separate parallel thrust piston and cylinder assemblies for an extensible boom of a mining machine.
Further features of this invention provide for the cutters to be mounted in pairs and for there to be a plurality of pairs of roller cutters mounted inclined to each other on each base.
The invention also provides for each base to have a pair of links pivotally supported at one end to a common pivot with the other end of each link pivotally anchorable to the boom on anchors spaced longitudinally apart along the axis of the boom with these anchors common to corresponding links from an equivalent base.
Yet further features of this invention provide a mining machine cutterhead assembly comprising an extensible boom with a pair of thrust piston and cylinders and cutterhead bases pivotally mounted on these assemblies and linked to the boom as above defined.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of this invention will become apparent from the following description of one example of the cutterheads and cutterhead assemblies mounted on a mining machine as illustrated in Figure 2 to 4 of the accompanying drawings.
In the drawings:
Figure 1 illustrates the prior art;
Figure 2 illustrates a similar view showing the invention; and Figure 3 and 4 illustrate separate sets of details.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure 1 the operating end 1 of a mining machine as set forth in the specification of our earlier patent referred to above is shown.
The frame 2 of the mining machine has pivotally supported at its forward end 3 on an extensible boom 4. The boom 4 is swingable by a pair of piston and cylinder assemblies 5.
The boom 4 is extensible by means of thrust piston and cylinder assemblies 6 which operate in unison. The boom carries a rigid base 7 which supports the plurality of pairs of rolling rock cutters 8. These rolling rock cutters are mounted on a fixed radius relative to the axis of swing of the boom 4.
Referring now to Figure 2 the frame 10 of the mining machine carries the same kind of boom 11 as described above with thrust piston and cylinder assemblies 12.
There is a pair of bases 13 and 14 each of the pair supporting two pairs of roller rock cutters 15 and 16. The detail in Figure 3 shows the layout of the cutters and 16.

g Each base 13 and 14 is pivotally mounted to its respective thrust piston on a centerline extending between the finro pairs of cutters 15 and 16.
Each base 13 and 14 has one end of a pair of links 17 and 18 pivotally mounted on a common anchor 19 or 20. The links are splayed outwardly and the free ends of the links 17 are pivotally mounted on a common anchor 21 and those of links 18 are similarly mounted on anchor 22.
The anchors 21 and 22 are spaced apart along the forward end of the axis of the booms 11. Anchor 21 is able to slide in a closely contained manner with respect to anchor 22 to enable lateral swing loads to be adequately countered.
This system of links and separate bases enable each cutter to share an equal amount of the operational load applied through the thrust piston and cylinders as the boom 11 is driven forward and swept around its arc of operation.
The detail of Figure 4 shows how the peripheries of all of the cutters follow the different radii of curvature along which the cutterheads move as the boom is extended. In this way the most effective chip formation can take place between the cutters with consequent efficient penetration into the rock being cut.
It will be appreciated that other linkages and slides can also be designed to effect the desired distribution of the load on the cutters during use.

Claims (7)

1. A cutterhead for a rock cutting machine operating in a three dimensional manner comprising a rigid base carrying a plurality of rolling rock cutters with the base linkable to a second equivalent base to ensure even distribution of the working load on the cutters with the bases pivotally mountable on separate parallel thrust piston and cylinder assemblies for an extensible boom of a mining machine.

2. A cutterhead for a rock cutting machine as claimed in claim 1 in which the cutters are mounted in pairs.

3. A cutterhead for a rock cutting machine as claimed in claim 1 or 2 in which there are a plurality of pairs of roller cutters mounted inclined to each other on each base.

4. A cutterhead for a rock cutting machine as claimed in any one of the preceding claims in which each base has a pair of links pivotally supported at one end to a common pivot with the other end of each link pivotally anchored to the boom on anchors spaced longitudinally apart along the axis of the boom.

5. A cutterhead as claimed in claim 4 in which the anchors are common to corresponding links from an equivalent base.

6. A mining machine cutterhead assembly comprising an extensible boom with a pair of thrust piston and cylinders and including a cutterhead as claimed in any one of the preceding claims.

7. A mining machine cutterhead assembly substantially as described with reference to Figures 2 to 4 of the accompanying drawings.