In order to i ncrease t he o uttake r ate o f o re a nd r educe m ining c osts, t he m ining industry has recently started to use so-called long-hole production methods to an increasingly larger extent. Through careful control of the course of the drilling equipment, the borehole, and thereby also the explosive, can be positioned in a way in relation to the ore body that allows a maximum profit on production of the ore to be gained from the point of view of blasting. In contrast, an incorrect or less precise positioning of the explosive will give an inefficient blast, resulting in poorly fragmented stone and unacceptable amounts of unusable stone in the extracted ore.

To enable especially precise directional drilling in rock for blast hole drilling, for example, a drill support in the form of a so-called"coil-tubing"is used, which means that instead of using a series of conventional rigid joinable drill tubes a flexible jointless drill tube is used with a proximal and a distal end. The flexible drill support is unreeled from a spool and fed successively into the borehole. To form a drill string, a continuous bottom hole assembly (BHA), which includes a drill machine, is fastened at the distal end of the drill support. A percussion unit in the form of a fluid-pressure activated hammer or similar reciprocal mass is arranged on the drill machine to apply a drill bit fastened to the drill machine axially against the opposing rock surface. The bottom hole assembly (BHA) usually also comprises some kind of positioning device, so-called measurement while drilling (MWD). A driving f luid intended f or t he m otors i ncluded in the BHA is I ed via a passage extending through the drill support. The rock cuttings are transported through secondary passages in the drill support away from the worked area and out of the borehole with the used driving fluid.

In order to continuously switch the contact points of the drill bit studs and to make them work on uncut rock, the drill machine must be indexed or gradually rotated around its axis between each blow of the drill bit. This is normally achieved by rotating or twisting the flexible drill support with a means of indexing situated outside the borehole. Known are also bottom hole assemblies on which the indexing means forms an integrated part, which, seen from the direction of drilling, is located after the rock drill and designed to provide a stepped rotation of the entire rock drill around its main axis.

The means of i ndexing comprises u sually a rotating fluid m otor of m ud type a nd motor-driven valve arrangement with which the rock drill located at the front of the rig can be turned or indexed a certain number of degrees between each stroke. In operation, a drive fluid comprising a mixture of water or a suspension of bentonite clay in water flows through the motor, which in turn drives the said indexing means.

To enable directional control of the drill bit inside the borehole, there is a steerable motor arranged in the BHA that conveys motion through a universal joint or other suitably flexible part so that the drill bit can take on different angles relative to the drill support. The said BHA normally constitutes a fluid activated motor in the form of a so-called mudmotor that, like the other motors in the BHA, is supplied with a driving fluid via a passage extending through the drill support.

A special type of drill rig combination is known that performs the directional drilling described above. Such drill rig combinations comprise partly a carrier that normally can be driven and a controllable arm system pivot mounted to the carrier, partly a bottom hole assembly of the type described above and carried by the arm system. The drill rig also carries a rotating drum from which the flexible drill tube can be wound on and off.

Even though the use of drill rig combinations with flexible drill strings enables the drilling of non-linear holes and precise control of the BHA's drill bit through the rock, it should be understood that the positioning of the drill bit during the initial stage of the drilling is often decisive to how the borehole subsequently follows a given course in the rock. More precisely, this is due to, among other things, the possibility of controlling the BHA's drill bit in curved courses is not only limited by the total length of the BHA but also the resistance of the drill bit to bending or its stiffness. By improving the possibility to control the course of the drill bit in the rock already in the initial stage of drilling, unnecessary drilling in non-ore-bearing rock can be avoided and the drilling can be more precisely controlled directly to the ore-bearing bodies in the rock.

One object of the present invention is therefore to provide a drill rig combination of the type described above that considerably improves the possibility of controlling the BHA's drill bit in a certain course through the rock and in particular a drill rig combination that offers a more precise positioning of the drill bit during the initial stages of the drilling process. A second object of the invention is to achieve a drill rig combination that offers a general improvement in the degree of movement possible for the BHA carried by the drill rig so that the transport of the rig as well as the drilling process in confined galleries and tunnels is made easier. Furthermore, it is a third object of the invention to achieve a drill rig combination for drilling that allows the BHA to be manoeuvred within a large range, which, for example, can include working directions that are vertically upward, downward or horizontally forward. That is to say to cover as large a working area as possible on the rock face, which, where appropriate, can be said to constitute a concave confining surface facing the drill rig.

The said objects of the invention can be achieved with a drill rig combination exhibiting the distinctive features and characteristics specified in claim 1.

The knowledge that forms the basis of the invention is that a more precise control of the drill bit course in the rock can be obtained partly through the drill rig and the pivoting arm

system it carries, partly through choosing and designing the BHA is such a way that the possibility of precisely directing and positioning the drill bit against the rock face during the initial stage of the drilling process is considerably improved. Even if the present type of drill rig combinations are normally equipped with systems that allow the drill bit to be controlled during the drilling operation, it should be understood that these systems provide only limited control in the rock for the drill bit and thereby also the drill string. It should be understood that a drill rig combination with improved possibility to start drilling from a correct initial position facilitates an efficient control of drilling in ore-bearing rock.

A drill rig combination as described in the claims also offers an improved degree of movement to facilitate drilling in confined galleries and tunnels.

The following is a description of the invention with references to attached drawings, where fig. 1 shows a vertical cross section through a gallery and the drilling operation with a drill rig combination according to the invention, fig. 2 to fig. 4 show the BHA included in the drill rig combination in fig. 1 in various working positions and fig. 5 shows a plan view of a control for the BHA.

Designated on the drawings generally with the number 1 is a driveable drill rig employed in tunnel driving in a gallery. The drill rig 1 has a chassis 2 that carries a boom 3, which at its rear end is pivot-mounted with a pin 4 on a boom bracket 5. Between lugs 6 on the boom 3 and boom bracket 5 respectively is arranged a means of driving 7 in the form of a hydraulic ram, with which the boom can be swung relative to the boom bracket around the pin 4 and shaft that is parallel with respect to the surface 8 on which the rig is resting. Even if it is not shown in the figures, it should be understood that the boom 3 in a known manner can be telescopic and formed by a number of parts sliding longitudinally relative to each other, whereby achieving extending and contracting in a suitable hydraulic manner by a means of driving acting between the parts.

At the front end of the boom 3 is a boom head 9, the first end of which is pivot mounted around a transverse pin 10 for swinging in the same plane as the boom. A feed beam 12 is slide mounted to a second end of the boom head 9 by means of a control element 11, which includes, amongst other things, a guide, for making linear movements relative to the boom 3. The swinging movement of the feed beam 12 around the joint pin 10 is controlled with a driving means 13, in this case a dual-action hydraulic cylinder acting between the boom head 9 and the feed beam 12. The linear movement of the feed beam 12 relative to the boom 3 is controlled with a driving means 14 in the form of a dual-action hydraulic cylinder acting between the feed beam and the boom head 9.

The feed beam 12 supports a long, mainly cylindrical, bottom hole assembly (BHA), generally designated 15, which, while forming a drill string, exhibits a drill bit 16 at its front end and at its rear end a drill support in the form of a flexible jointless drill tube 17 that also

offers a connection to a source for supplying a driving fluid to the BHA and a passage for leading away the drill cuttings. The bottom hole assembly 15 comprises actually in a known manner a percussion tool, a positioning device or a so-called"measurement while drilling" (MWD), a c ontrol d evice i n t he form o f a motor for i nclining o r s etting t he p osition o f the assembly, an indexing device and a drill machine with said drill bit.

Through the movement of the arm sections 3,12 described above relative to each other and the choice of suitable joints for them, a high degree of mobility is obtained with many settings so that the feed beam 12 and thereby also the BHA 15 it supports can be manoeuvred within a working range between the alternative working modes as is shown with dashed a nd d otted I ines i n fig. 1 i n t he case w hen a s eries of b oreholes i s b eing d rilled.

Referred to are also the alternative working modes that are illustrated in fig. 2 to fig. 4, whereby in said order is. shown examples of working directions for drilling vertically upwards, horizontally forwards and vertically downwards.

It should be understood that when carrying out drill operations with the type of BHA 15 referred to here, the feed beam 12 is used principally for supporting the BHA 15 when the driveable drill rig 1 is moved between various workplaces and when the BHA via its moveable arm sections 3,12 is manoeuvred in different directions and working positions in a way shown in fig. 1 for example. Meanwhile, the feed beam 12 is used principally during the initial stage of a drilling operation in that the feed beam hereby is partly used to safeguard a precise control and positioning of the BHA 15.

For this reason in the front end section of the feed beam 12 is arranged means of guiding 18 the BHA 15 and a means 19 of application against the rock face, which means can be in the form of a centre point or similar. Since the function of the feed beam 12 as a support for the BHA 15 essentially ceases once the BHA has drilled into the rock, the guides 18 are so arranged that they can be manoeuvred between an active position supporting the BHA and an inactive position, which should be understood after a closer look at fig. 5.

Referring to fig. 5, each guide means 18 comprises two moveable jaws 20 that when moved to an active position together in a supporting manner can receive and support the periphery of the BHA at the same time as the same is allowed to slide along its axis and thereby into the borehole. Once the BHA has been inserted far enough in the borehole that the wall of the hole that is formed in itself provides sufficient support, the jaws 20,20'can be moved away from each other and thereby take a non-supportive position.

As is evident from the drawing figures, the rear end of the drilling rig chassis 2 carries a drum 21 on which the flexible drill tube 17 is wound. As the BHA 15 drills into the rock, the flexible drill tube 17 is unwound from the drum 21. With the help of guides 22 for the drill tube 17 in the form of a number of suitably located guide wheels, the drill tube can be conveyed between the drum 21 and the BHA 15 in a smooth and adaptable manner. On the

rear end of the feed beam 12, and therefore in the area of the connecting point between the BHA 15 and the distal end of the flexible drill tube 17, is arranged a means of guiding 23, which also constitutes a means of driving for feeding out the flexible drill tube 17 from the drum 21 and feeding in the same into the borehole together with the BHA 15. As is evident from the drawing figures, this driving means 23 comprises a set of diametrically opposing wheels that are arranged to receive the flexible drill tube 17 between them and drive the same forward in coordination with the drill tube periphery.

To make the axially reciprocating drill bit 16 studs continually act on unworked rock, the drill bit must be indexed or rotated in suitable steps around the drill axis in conjunction with each blow. As was described above, this takes place through currently known technique by means of a rotating arrangement situated outside the hole or via an indexing means integrated in the BHA, which, seen from the direction of drilling, is located after the rock drill and designed to provide a stepped rotation of the entire rock drill around its main axis.

In our own pending patent application no. SE 0104217-5 is shown and described a new type of fluid-driven down-hole rock drill which hereby is incorporated as a reference in the present application. Contrary to known down hole assemblies in which the drill bit is rotationally fixed but axially limited in movement in a type of percussion drill in the down hole drill housing, the drill bit in the said patent applied for bottom hole assembly is both rotationally and axially limited in movement in the housing. More precisely, the drill bit is mounted rotationally fixed but axially limited in a bit sleeve, which in turn is supported in a rotating mounting in a housing included in the down-hole rock drill. A ram included in the bottom hole assembly is arranged to impact on the neck of the drill bit, a valve is arranged to control the reciprocating motion of the ram, wherein the valve alternately applies pressure and relieves pressure in a chamber with a piston surface that when under pressure drives the ram forward. One interesting feature of this drill machine, unlike conventional BHAs in which, as said above, the respective units, including the means of indexing the drill, are arranged in line after each other in the direction of drilling, is that some of the drive fluid used to activate the percussion ram is diverted to drive a rotating sleeve arranged on the bit sleeve with axial booms. The said booms, constituting the limits of a number of chambers, form part of rotating pistons that turn the rotating sleeve to and fro to index the bit sleeve and thereby also the drill bit. This means of rotation is so synchronised with the movement of the ram that indexing is performed when the drill bit is in its rearmost end position or more precisely when it moves back away from the rock surface.

Since a separate unit in the BHA for indexing the drill machine is no longer needed in this embodiment, the BHA will be considerably shorter than currently known units, which has the advantage that the force applied via the flexible drill support is concentrated very close to the working area of the drill bit. Not least, this considerably reduces the risk of the

"stick-slip"phenomenon. That is to say, the bottom hole assembly acts like a torsion spring instead of the drill bit being indexed evenly between blows from the percussion unit. Thanks to the shorter bottom hole assembly, it should be understood that controlling the drill bit with small curve radii is also facilitated and that only very little application force on the rock face is lost on the way to the drill bit, even when the drill support diverts at a very small curve radius.

Besides the mobility and manoeuvrability given to the sections of the arm system described above including the boom 3 and feed beam 12, as one step in further improving the manoeuvrability of the bottom hole assembly 15 in confined tunnels and galleries and thereby also the positionability of the bottom hole assembly drill bit during the initial stages of the drilling, the feed beam 12 has been given a length that is essentially adapted to the relatively short bottom hole assembly 15 that is shown and described in the aforesaid patent application.

In accordance with the principles of the invention the combination of a manoeuvrable arm system with relatively short both rotating and lengthwise adjustable feed beam and a bottom hole assembly of the type shown and described in SE 0104217-5, a drill rig combination allowing a more precise positioning of the drill bit during the initial stages of the drilling operation. As the drill bit in the aforesaid patent application is rotating and axially limited in movement in a housing in the drilling machine, a bottom hole assembly with limited longitudinal movement is manufactured. Thanks to the means of driving the rotation of the drill bit around its axis of rotation being fluid activated like the means of driving the included percussion unit, the two can easily be synchronized to each other so that the indexing or rotation takes place when the drill bit is withdrawn into the bottom hole assembly or in an inactive position on its way from the rock face. The risk of so-called"stick-slip"can hereby be avoided.

Referring to fig. 3, the chosen length of the feed beam 12 in all essentials in this described embodiment of the invention is based on the distance B between a plane A, which, extending from the contact surfaces of the means of application 19 at the front end of the feed beam 12, cuts at right angles the longitudinal axis of the feed beam and the contact points of the driving means 23 acting on the periphery of the flexible drill tube 17. More precisely, the distance between the said parts is so chosen in relation to the length of the principally cylindrical part that forms the main part of the bottom hole assembly 15, that a certain limited axial allowance for movement, designated C in fig. 3, is always guaranteed for the bottom hole assembly when the same is at rest on the feed beam 12.

In this part the chosen allowance for movement for the maximum expected roughness or unevenness of the rock surface against which the drill bit 16 is to be applied should be limited as the rock face, at least in extreme cases, can come into contact with the

drill bit already when the feed beam is applied to the rock face via the application means 19.

This applies even if the bottom hole assembly is in its rearmost withdrawn position in the feed beam 12. To prevent this happening, the present invention suggests that the axial allowance for movement is chosen in the interval 10% to 50% of the total length of the bottom hole assembly, preferably 20% of the total length of the assembly.

The present invention is not limited to the above description and as illustrated in the drawings but can be changed and modified in a number of different ways within the framework of the idea of invention specified in the following claims.