Patent Application
20240240562
The present invention relates to a method and an arrangement for powering holes in mountains through so-called full face reaming. The invention also relates to a full face reaming machine comprising an arrangement according to the invention.
Full face reaming machines, also called FRM machines; Shaft Boring Machines, also called SBM machines and Tunnel Boring Machines, also called TBM machines, relate to machines having in common that they are intended for drilling circular cylindrical vertical or horizontal holes in mountains with a pre-determined diameter, without blasting. As an example, it can be mentioned that by grinding a mountain ahead, a machine forms circular holes or tunnels with a final diameter, typically in sizes of 2-10 m. Conceptually, each of the machine types comprises the following main components: a rotatable front drill head, a control system, a support system for the machine, a propulsion system for the machine, a driving system for feeding the drill head forwards, whereby the machine acts as abutment.
The machine equipment is supported by or rests on a number of hydraulically operated tension shoes or “feet” by means of which a drive machinery, a so-called case, having a diameter that is somewhat smaller than the diameter of the drill head, can gradually be moved forwards in the drilling direction. At the very front of the machinery, a rotatable drill head (drill bit) sits, which has the same diameter as the final hole profile. The drill head is rotatably accommodated in a machine housing at the front part of the machine.
The drill head is provided with a plurality of cutterheads, each of which can comprise separately accommodated cutting means in the form of disc-shaped disc cutters with hard metal bits, alternatively the cutting means can be constituted by so-called studs or the like. Usually, disc cutters are used, which are rotatably mounted via a shaft in a retainer (a so-called saddle or body), which is embedded in the drill head. The disc cutters are usually oriented in groups on a front side of the drill head for efficient grinding of the mountain. The disc cutters usually have a shape resembling an ordinary discus disc. The disc cutters are normally fastened in a shaft at the centre of the disc, and via said saddles they are recessedly mounted on the front side of the drill head. The front part of the machine, which carries the drill is tightened onto the side walls of the tunnel or chute with strong hydraulic cylinders that press on said tension shoes adapted according to the radius of curvature of the hole wall. When the FRM machine is pressed firmly against the hole wall, the drilling is initiated, as the drill head is applied by being pressed against the wall of the drilling front, i.e. the chute or tunnel front wall, with strong force, by means of hydraulic cylinders simultaneously with the drill head being rotated in order for said cutterheads on the rotating drill head to be able to penetrate and grind the surface of the mountain. The rest of the machine stands completely still. The disc cutters of each cutterhead are thereby forced rollingly to press with strong force against the mountain wall. The mountain is ground by the disc-shaped disc cutters into flakes that fall down below the drill head and are passed on to the rear end of the machine via a conveyor, usually in the form of a conveyor belt travelling through the entire machine, wherein it can be transported away by being loaded onto carriages that are driven out of the tunnel or on so-called skip hoists or similar lifts conveying the mountain material out of the chute to ground level.
As the disc cutters are the tools with direct contact with the mountain, they are quickly worn and must be replaced regularly. Replacement of disc cutters not only involves high costs for cutting tools as such, but also results in recurring production stoppage as the machine will occasionally have to be taken out of operation, which affects the overall efficiency of the machine.
As mentioned above, hard metal is included in the disc cutters, the life and performance of which are significantly affected by the cutting speed and load to which the disc cutters are exposed. Exceeding the optimum cutting speed (peripheral speed as m/min) of the hard metal cutters leads to a increased loading and temperatures, resulting in a wear mechanism that is usually characterised by occurrence of plastic deformation, i.e. a change in the shape of the cutting edges of the disc cutters. Undershooting the optimum cutting speed also leads to abnormal wear of the cutters. Usually, the load lies in a contact area between the mountain and TBM cutters of about 300 MPa, and the rolling cutting speed V of the disc cutters against the mountain at between 1.4 to 2.9 m/s (84-174 m/min)
The formula for cutting speed V (m/min) is: π·2r·n wherein
Due to the relatively large diameter of the rotating drill head, it should be understood that for each given revolution speed, the peripheral speed of the disc cutters included in the cutterheads located on the furthest periphery of the drill head during loading against the tunnel front, will operate at relatively high cutting speeds that substantially exceeds the optimum cutting speed (cutting speed>optimum cutting speed), while disc cutters closely connected to the central middle of the drill bit, at loading against the tunnel front, will operate at relatively low cutting speeds, which substantially undershoot the optimum cutting speed. As a result, none of the cutterhead disc cutters located at different radii from the centre of the drill head will operate at optimum cutting speed, which means that the disc cutters on the drill head considered as a whole will be worn prematurely.
In addition to the high cutting speeds occurring at the outer periphery of a drill head, there is an additional problem associated with FRM machines, namely the strong power and moment and holding forces that the machine will have to have in order to be able to drill with large drill heads in terms of diameter. For rotating systems, the mechanical power equals the product of the torque e and the rotational speed w according to the formula:
wherein ω is measured in radians per second (rad/s) and the torque in Newtonmeter (Nm).
It should be understood that the relatively high power required for rotatably driving a drill head with a large diameter in practice restricts the size of the diameter of the holes drilled by an FRM machine, and correspondingly retain the large moment and holding forces necessary for the machine to operate as abutment during the drilling work. Thus, machines for drilling holes with large diameters not only become expensive and complicated, but in practice also difficult to use due to their considerably weight and bulky construction.
It would therefore be desirable to obtain FRM machines that make it possible to drill holes with a large diameter, but which at the same time have a limited power requirement. It is thus desirable to be able to provide inexpensive, compact light-weight FRM machines that can drill holes with large diameters. Moreover, it is desirable to provide FRM machines that can drill mountains of varying quality, also in mountains with many cracks without risk of breakdown or damage caused by large mountain pieces uncontrollably being passed from a drill front.
A first object of the present invention is to obtain a method making it possible to avoid the problems of FRM machines outlined above, and which also makes it possible to perform drilling in a more efficient manner with drill heads with large diameters and with the desired optimum cutting speed of it or the setting of cutting tools included in each cutterhead in a rotatable drill head.
Another object of the invention is to provide an arrangement with an FRM machine that enables this.
A third object of the invention is to provide an FRM machine that comprises such arrangement.
These objects of the invention are obtained by a method of the type indicated in claims 1-9, an arrangement of the type indicated in claims 10-14 and a full face reaming machine (FRM machine) according to claim 15.
The invention is based on the idea that by arranging the drill head in such a manner, a bottom or front in a bore can be drilled sectionally with radially or diameter-wise increasing width or extent by carrying out the drilling work successively like a target board along concentric rings in sections (so-called drill rings) that go from an inner smallest circle to an outer largest circle. As the bore is driven successively after drill rings, the advantage is obtained that it becomes possible to drill large holes in terms of diameter with relatively little power.
In an embodiment of the invention, the cutterheads independently of each other are displaceably moveably accommodated from a retracted condition in the drill conveyable to a protruding mountain-grinding condition from a front side of the drill head simultaneously with the drill head rotating, whereby a front surface in the bore is gradually drilled along concentric rings “drill rings” that go from an inner smallest circle to an outer largest circle by new cutterheads with gradually increasing radius from the centre of the drill head in successive steps progressing in mountain-grinding condition.
In an embodiment of the invention, the drill parameters, which i.a. comprise cutting speed and feeding force or driving speed forwards can be optimized by the revolution speed of the drill head being adjusted (reduced) according to the drill head at each new drill ring with successively increasing processing radius or diameter towards said front of the mountain.
In an embodiment of the invention, a time is determined for each transition from an inner drill ring to a subsequent outer drill ring with a larger radius by measuring the feeding force Ff (N) or the specific cutting force kc (N/mm2) that is applied on a cutterhead in an inner drill ring. As soon as the operating cutterhead in the inner drill ring no longer meets new mountain, the feeding force on the operating cutterhead will decrease to finally essentially cease completely. When the feeding force on the operating cutterhead against the front falls below a pre-determined limit value, a subsequent outer drill ring is activated by one or a plurality of cutterheads for said subsequent outer drill ring with force is applied against the front.
In another embodiment of the invention, the cutterheads are, independently of each other, displaceably moveably accommodated in the drill head by the effect of a linear drive means arranged for each cutterhead and which cutterheads, from a retracted condition in the drill head by means of said linear drive means, are conveyable to a from a front side of the drill head projecting mountain-grinding conditions simultaneously with the rotation of the drill head.
In an embodiment of the invention, each cutterhead is applied in a drill ring by hydraulic force from a hydraulically operating actuator and control included in a linear drive arrangement arranged in a body of the rotatable drill head.
In another embodiment, the arrangement comprises a swivel coupling for transmitting hydraulic flow between the machinery and an actuator and control included in each linear drive arrangement of the rotatable drill head.
In yet another embodiment replacement of a cutterhead from an inner to an outer drill ring can take place by sensing the application pressure against the front via hydraulic pressure sensors arranged in the linear drive arrangement.
In a further embodiment of the invention, wherein the linear drive arrangement is of a non-hydraulically driven type, it is imaginable that the pressure sensor could be constituted by a wire strain sensor, a load cell or similar sensing elements/sensor that can measure occurring stress of material at loading.
In the following, the present invention is described in more detail with reference to the accompanying drawings, in which;
With reference to
As most clearly appears from
The case 6 has a diameter that is somewhat smaller than the diameter of the drill head 11, and which successively is to be moved forwards and rearwards, respectively, relative to the drill head 11. During the drilling work, the front end of the drill head 11 is pressed against a front surface 90 in the bore 5 by means of hydraulic cylinders 16, whereby the tension shoes 4, 4′ in the case serve as abutment.
Also, with reference to
The drill head 11 also has one or a plurality of buckets 4 that let fragmented mountain pass from the front surface 90 to the rear side of the drill head 11. A conveying means for taking away fragmented mountain from the front surface 90 ahead of the drill head 11 is denoted 30. The conveying means 30 comprises a first conveyor (not shown) located behind the drill head 11, by which mountain fragments can be scooped up to a higher level, where the mountain fragments fall down onto a second conveyor travelling along the FRM machine in a rearward direction. Furthermore, the conveying means 30 comprises a framework 33 along which said second conveyor such as a belt conveyor or the like travels rearwards.
Also, with reference to
As shown in
During hole powering, a cutterhead 20:1-20:n, or a group of jointly operating cutterheads, can successively generate each new drill ring with increased radius by being conveyed from the front side 11′ of the drill head 11 and be set in a mountain-grinding or mountain-removing condition against the front surface 90. The force for conveying said cutterheads 20:1-20:n in mountain-grinding condition is obtained from a hydraulically operating actuator and control included in a linear drive arrangement 22:1-22:n arranged for each cutterhead 20:1-20:n. Said hydraulically driven actuator and control 41:1-41:n included in said linear drive arrangements 22:1-22:n are discretely accommodated in the body 12 of the rotatable drill head 11. Consequently, each cutterhead 20:1-20:n or group of cutterheads can hereby for one to form a drill ring B:1-B:n be driven to mountain-removing application against the front surface 90 simultaneously with the rotation of the drill head 11. As the cutterheads 20:1-20:n are successively conveyed for forming drill rings B:1-B:n with an increasingly larger diameter, which in practice means that the mountain-grinding work is only carried out by the one or the smaller group of cutterheads 20:1-20:n that are operating in the outermost drill ring, it should be understood that the power requirement of the FRM machine, also for drilling with considerable hole diameter becomes very low. As to the latter, it should be understood that the other cutterheads of the drill head certainly rotate along the inner drill rings but without meeting any real resistance, while in practice they rotate freely without performing any mountain-grinding work against the front surface in the bore.
As illustrated by double arrows in
With reference to
With reference to
With reference to
“Pilot drilling”—each axially displaceable cutterhead 20:1-20:n in the annular large drilling area B is in a condition retracted in the drill head 11 and thus in a non-mountain-grinding condition relative to the small drilling area A, forming the pilot drilling area. It could be mentioned that in an alternative embodiment of the invention, wherein the pilot drill head for the small drilling area A and the annular outer drill surface B of the drill head 11 is arranged so that they can rotate independently of each other, it is imaginable that only the pilot head is driven rotatably in this initial drilling step. The revolution speed of the drill head 11 is adapted for optimum cutting speed V for the fixed cutterhead 20 of the pilot drill head A (alternatively group of a plurality of cutterheads 20).
“Drilling of an inner first drill ring B1 with each first cutterhead 20:1 in a mountain-removing projecting condition in the drill head 11, wherein they meet the front surface 90”- and wherein each otherwise non-operating cutterhead 20:2-20:n intended for radially outer bores is 11 retracted in the drill head in a non-operating condition. The revolution speed of the drill head 11 is thereby so adapted that the disc cutters 21 included in each first cutterhead 20:1 for forming a first drill ring obtain desirable optimum cutting speed V. When the feeding force Ff on each first cutterhead 20:1 has fallen below a pre-determined level, the control unit 40 initiates transition to a subsequent drill step (step III).
“Drilling of an outer second drill ring B2 with each second cutterhead 20:2 in a mountain-removing projecting condition for obtaining a second drill ring with larger radius”- and wherein each otherwise non-operating second cutterhead 20:3-20:n is retracted in the drill head 11 in a non-operating condition. The revolution speed of the drill head 11 is thereby so adapted that the disc cutters 22 included in each second cutterhead 20:2 for forming a second drill ring obtains desirable optimum cutting speed V. When the feeding force Ff on each second cutterhead 20:2 has fallen below a pre-determined level, the control unit 40 initiates transition to a subsequent drill step (step IV).
Drilling of a last outer drill ring B3 farthest out on the radius, each third cutterhead 20:3 being in a mountain-removing projecting condition to obtain a third drill ring with larger radius”. The revolution speed of the drill head 11 is thereby so adapted that the disc cutters 22 included in each third cutterhead 20:2 for forming a final third drill ring obtains desirable optimum cutting speed V. When the feeding force Ff on each third cutterhead 20:3 has fallen below a pre-determined level, the control unit 40 initiates transition to a subsequent drill step (step IV).
The drilling cycle is completed by all cutterheads 20:1-20:n returning to a non-operating condition retracted in the drill head 11, whereupon the arrangement is ready for a new drilling cycle.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2150660-5 | May 2021 | SE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SE2022/050479 | 5/17/2022 | WO |
