Rock-cutting machines

[57] ABSTRACT

The invention provides a rock cutter which uses high pressure water jets. The jets are emitted from nozzles carried by pressure intensifiers which are mounted on a head that is movable along a frame. The nozzles are movable with the pressure intensifiers and the jets emitted by the nozzles cut slots in the rock face.

Claims, 6 Drawing Figures

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PATENTED 0K311974

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PATENTED DEC 311974

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PATENTED DEC311874 3,857.516

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PATENTED0EC311974

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PATENTED 0EC311974

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3,857,516 to carry out the other operations as will be described. Slidably carried by the frame 12 is a head 20 carrying a plate 21 on which is mounted a pair of pressure intensifiers 22. Each intensifier comprises a power cylinder 24 and an ejector cylinder 26 the latter being connected via an outlet tube 28 to a nozzle 30. The cylinders 24 and 26 being subject to very high pressures, as will be described, are of extremely robust construction. A hand operated jack screw 31 (see FIG. 2) is provided to move the plate 21 on the head to adjust the location of the nozzles 30 relative to the stope face.

The head 20 is slidably mounted on a pair of longitudinally extending slide beams 32. Movement of the head 20 is effected by means of a pair of chains 34 which are driven by a pair of sprocket wheels 36 at one end of the frame 12 and which passes over a pair of idler sprocket wheels 38 at the other end of the frame 12. The idler sprocket wheels 38 are carried by an idler shaft 40 mounted in bearings in housings 41. The sprocket wheels 36 are carried by a drive shaft 42 mounted in bearings in housings 44. A reversible hydraulic motor 46 is connected to drive the drive shaft 42 and is controlled by the valve 18. Traversing limit valves 48 are provided adjacent each end of the stroke of the head 20 to cause the latter to reverse its direction of movement. Buffers or shock absorbers 50 are provided at the ends of the frame 12 in case the head 20 should tend to overrun its path.

The intensifiers 22 are shown in section in FIG. 4. Within the power cylinder 24 there is a power piston 52. A co-axial extension 54 to the power piston 52 is slidably and sealably fitted to the ejector cylinder 26 and its free end 56 forms an ejector piston. A conduit 58 passes through the end wall 60 of each of the power cylinders 24. The two conduits 58 lead to a directional control valve 62 which is carried in a housing 63 mounted on the head 20. This valve 62 is connected to power and drain conduits 64 and 66 and is arranged so that one of the power cylinders 24 is connected to the hydraulic power source and the other is connected to drain save in the initial position in which both are connected to drain. The exhaust sides of the two power cylinders 24 (ie that part of each cylinder which is on the side of the power piston remote from the end walls 60) are connected together by a short conduit 68 so that as one piston 52 is advanced (ie moved away from the end wall) the other piston is forced by the exhausting fluid to retract. Means to compensate for any leakage of this exhausting fluid is provided. Care must be taken that this device does not overcompensate and overfill the exhaust sides of the power cylinders.

The ejector cylinders 26 are each supplied with water under low pressure. This water is fed in through a bore 70 passing through the power piston 52 and its extension 54. A one way valve 72 prevents reverse flow of water through this bore 70. The bore of a tube 74 carried by the piston 52 forms a continuation of the bore 70. This tube 74 passes through an opening in the end wall 60 and is sealed thereto by seals 76. The free end of the tube 74 is received within an end tube 78 which is of sufficient length to accomodate the movement of the tube 74. Teed off this end tube 78 is a water conduit 80. The two conduits 80 lead to the valve housing 63 where they are joined together and are connected to a water supply conduit 82.

Also contained within the end tube 78 is an hydraulic valve 84 having a movable detector member 86 which

ROCK-CUTTING MACHINES

SUMMARY OF THE INVENTION

This invention relates to cutters particularly but not exclusively for cutting rock.

According to one aspect of the invention there is provided a cutter comprising means adapted to be fixed at least temporarily in position, a nozzle operatively connected to the fixed means and being movable relative thereto and generator means carried by the fixed means and operatively connected to and movable together with the nozzle and being adapted to supply fluid under pressure to the nozzle so that the latter can emit a high velocity jet.

Preferably the fixed means comprises a preferably movable frame and a head carrying the nozzle and being carried by and movable along the frame. The head preferably also carries the generator means. The generator means preferably comprises a piston and cylinder device (hereinafter called the ejector device) discharging through the nozzle. The means to actuate the generator preferably comprises a power piston and cylinder device connectable to a source of hydraulic pressure. The effective area of the power piston is preferably substantially greater than that of the ejector piston 25 and may be between twelve and twenty-four times this size preferably between fifteen and eighteen times the size and preferably approximately seventeen times this size.

The power piston is preferably single acting and actu- ³θ ates one ejector piston but it may be a double acting piston actuating two ejector pistons respectively on forward and return strokes.

The ejector cylinder is preferably connected to the nozzle through a pipe movable to adjust the location of ³⁵the nozzle. Means are preferably provided for moving the head along the frame. The moving and fixed means may vary with the length of the cut that it is intended to make. The fixed means may be a pair of rails and the head a carriage running along the rails. In this case the ⁴⁰moving means may be a motor carried by the carriage and adapted to propel the latter along the rails. Where the fixed means is a movable frame, the moving means may comprise an elongated hydraulic or pneumatic jack or it may comprise a chain or the like connected to the head and to means for advancing the chain so that the head is thereby advanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rock cutter of the invention,

FIG. 2 is a plan of the rock cutter at the stope face, FIG. 3 is a view in the direction of arrow 3 in FIG. 2, FIG. 4 is an enlarged detail section of the intensifiers, FIG. 5 is a view similar to FIG. 2 of a modified rock ⁵⁵cutter of the invention, and

FIG. 6 is a section through the intensifier used therein.

DESCRIPTION OF DIFFERENT EMBODIMENTS 60 OF THE INVENTION

Referring now to FIGS. 1 to 4, a rock cutter 10 of the invention comprises a frame 12 which is mounted on levelling jacks 14 and provided with spragging jacks 16 so that it may be firmly located in position adjacent to a stope face. A valve arrangement 18 is carried by the frame and this serves to control the jacks 14 and 16 and

3,857,516 runs along the tube 74. When the piston 52 is at the forward end of its stroke, the member 86 will be free of the tube 74 and will cause a signal to be passed to the valve 62 to reverse the hydraulic flows to the intensifiers 22.

Each outlet tube 28 is of shallow Z-shape. It has a flange 88 at its inner end. A locking gland nut 90 screwed into the end wall of the ejector cylinder locks the outlet tube in any set or desired position.

Lugs 91 are provided on the frame for the attachment of chains which, by means of winches (all not shown), may be used to move the frame within the stope.

It will be noted that the effective area of the power piston 52 is substantially greater than that of the ejector cylinder and is preferably approximately 17 times that area. The pressure of the oil supplied to the power cylinder 24 is of the order of 300 bars and therefore the pressure of the water is slightly less than seventeen times this amount. The preferred diameter of the jet in the nozzle 30 is 0.6 mm while the range of convenient diameters is 0,4 mm to 1,2 mm. The period required to complete one stroke of the pistons is 2,5 seconds. The speed of movement of the head at present is up to 1 metre per second. The preferred length of traverse of the head 20 is such that the stroke of the ejector cylinder can be synchronized with the traversing stroke of the head. The nozzle is made of a wear resisting material such as a cemented carbide.

In operation, the machine is set up at the stope face 92 and is located between the hanging and footwalls 94 and 96 by the jacks 14 and 16. The outlet tubes are arranged at the correct angular position and locked by nuts 86. The position of the plate on the head 20 is adjusted by the jack screw 31 so that the nozzles 30 are the correct distance from the stope face 92. The head is caused to traverse and during this traverse a jet is emitted from one of the nozzles. On completion of a traverse, the head is moved in the reverse direction and the other nozzle 30 emits a jet. After a number of passes a slot of up to 2 inches depth may be formed in granite or 1 inch in quartzite. The width of the slot will be of the order of 1 to 2 millemetres. The setting of the outlet tubes 28 is such that two slots may be formed or that both jets act to form a single slot. When used in deep gold mines, the pressure to which the rock is subjected by the thousands of feet of rock thereabove is such that rock will spall out from the stope face when the slot is cut and it will probably be unnecessary for a pair of slots to be cut. For coal mining and other low level mining on the other hand, at least two slots are necessary and the material between these slots must be broken out.

A modified cutter 110 of the invention shown in FIG. 5 comprises a frame that includes end pieces 112 and 114 carrying spragging and levelling jacks 116 and 118 and being connected together by elongated guides 120. The guides 120 are comprised by a pair of piston rods which each carry intermediate its ends a piston (not shown). Cylinders 122 respectively slide on these pistons. The cylinders 122 are connected together at their ends by cross-members 124. A bracket 126 forming a head spans the cylinders 122 and carries a double acting pressure intensifier or jet generator 128 in such manner that it, the jet generator 128, can be fixed thereon in angularly adjusted positions. The bracket or head 126 can be located at either end of the cylinders 122.

Referring now to FIG. 6, the pressure intensifier or jet generator 128 comprises a body 130 formed with a 5 central hydraulic power cylinder 132 and on either side thereof two smaller ejector cylinders 134. A double acting power piston 136 fits the power cylinder 132 and carries two piston rods 138 which fit the ejector cylinders 134 respectively to provide ejector pistons there10 for. The diameter of the piston face of the power piston 136 is four times that of the ejector piston 138 so that the area of the piston face is fifteen times that of each ejector piston. Hydraulic connections 140 and 142 enter into the sides of the power cylinder 132. A valve 15 controlled water inlet 144 enters and a water outlet 146 leaves each of the ejector cylinders 134. The water outlets each lead to a nozzle 148 having a 1 millimetre bore so as to eject a very fine jet.

The two hydraulic connections 140 and 142 are re20 spectively connected to hydraulic lines (not shown) which lead to a directional control valve that connects the lines alternatively to a motor driven hydraulic pump and to drain. Both the water inlets 144 are connected via a one way valve to a water line that leads to 25 a source of water supply. The pump is designed and arranged to supply hydraulic fluid at such a pressure and volume that the piston 136 traverses the power cylinder 134 between 0,5 and 1,0 seconds and the water jet is ejected from the nozzles at a pressure of the order of ³θ 3 to 10 kilobars.

If desired the nozzles may be connected as described in the first embodiment hereof.

We have found that the first above described apparatus provides a very satisfactory rock cutter for deep ⁵ level gold mining. However it may also be used for any other type of mining. Furthermore the cutters may be used in applications other than as a rock cutter. For example with some modifications (mainly of the frame) it may be used for cutting any other material such as paper, plywood, and plastic. A particularly advantageous use of the cutter is for cutting asbestos.

It will be seen that with the arrangements herein described the means for providing the very high pressure of the water, i.e., the intensifier, is fixed relative to the ³ nozzle when the machine is in use. Both the intensifier and nozzle are mounted on the head and are moved relative to the material being cut. It will be appreciated therefore that there is no necessity for providing high ₅₀ pressure moving seals which would be required if the nozzle were to be movable relative to the intensifier. By avoiding this requirement the presently acute problem of how to provide such seals is obviated.

It will also be noted that the distance of the nozzles ₅₅ from the rock face is easily adjustable so that optimum spacing can be effected in operation. It will be appreciated that here too, the intensifier and nozzle move as one during the adjustment.

The invention is not limited to the precise construc6Q tional details herein described and illustrated. For example the intensifiers may be arranged so that jets are emitted over part only of the traverse of the head. Usually this will take place in such a way that a number of slots will be cut by the jets emitted from one nozzle dur65 >ⁿS ^a traverse in one direction. In the return traverse, the intensifiers will be caused to act in such a manner that the jets will act on those parts of the rock face which were not treated during the previous traverse. In

3,857,516 this way one or two continuous slots will be formed after two traverses.

Also if desired the water inlet to the ejector cylinders may be through a conduit co-axial with the high pressure outlets from these ejector cylinders. Suitable nonreturn valves would have to be used in such an arrangement.