This invention relates to a rock drilling machine. More particularly, it concerns a rock drilling machine comprising a drill portion with a drill bit and an associated gear and driving motor, a string portion and also pipes and lines for supply of drilling fluid and power.

During rock drilling, it is common for a drill bit to be connected to a drill string extending through a borehole onto a support device at the outside of the borehole. In order to achieve cutting, it is necessary to displace the drill string into the borehole using a substantial force.

In this context, the term support device implies a piece of equipment disposed at the opening of the borehole and structured in a manner allowing it to at least displace a string portion within the borehole, or to rotate the string portion about a central axis thereof, or to be provided with equipment for control and supply of power to the drill portion and the string portion.

The axial displacement force must be able to overcome the force required to displace the very string portion and drill portion within the borehole and, additionally, to apply sufficient axial force to the drill bit of the drill portion in order for cutting of mass to take place.

Upon drilling from a lower-lying portion onto, for example, the bottom of a higher- lying water reservoir within which at least a part of the borehole may assume an approximately vertical direction, a substantial share of the weights of the drill portion and the string portion may be transmitted to the support device. Experience goes to show that the required axial force used on the string portion may limit the size of the diameter and the length of the borehole that can be drilled by means of prior art drilling devices.

The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art.

The object is achieved in accordance with the invention and by virtue of the features disclosed in the following description and in the subsequent claims.

A rock drilling machine comprising a drill portion with a drill bit and an associated gear and driving motor, a string portion and also pipes and lines for supply of drilling fluid and power is provided, the drilling machine of which is characterized in that the string portion, at a distance from the drill bit, is provided with a self-driven reamer with a reamer bit, a gear and a driving motor.

By disposing a self-driven reamer in the string portion, the diameter of a borehole may be increased substantially without having to increase the thrust force of a support device. The reamer, which is connected to the string portion, follows the string portion within the borehole, the string portion being provided, in a manner known per se, with components for directional control of the drill bit.

The reamer, which takes up torque from the reamer bit, may be structured so as to supply an axial force to the drill bit and to take up torque from the drill bit via the string portion. By so doing, the support device may be relieved fully or at least to a substantial degree.

The reamer may be provided with at least one support shoe which is clampable against the borehole, and which is axially displaceable relative to the string portion, the support shoe of which is structured in a manner allowing it to form a counter support when the rock drilling machine is displaced into the borehole.

Pipes and lines for supply of drilling fluid and power may be flexible at least over a portion of the length of a borehole. By so doing, the rock drilling machine may be displaced in a remote controlled manner into the borehole by entraining hoses and cables from, for example, reels at the outside of the borehole.

A rock drilling machine according to the invention allows for drilling of relatively long boreholes having diameters larger than one metre, and without the use of a conventional drill string extending to the outside of the borehole. This significantly reduces the required extent of equipment transport, oftentimes in rugged terrain, and typically by means of helicopter. The work associated with construction and

dismantling of the pipe string is made redundant, and the opening of the borehole may also be disposed at locations where a support device is difficult to place, such as under water.

In the following, an example of a preferred embodiment is described and is depicted in the accompanying drawings, wherein :

Fig. 1 shows a sketch of a rock drilling machine according to the invention during drilling in a substantially vertical borehole;

Fig. 2 shows, in larger scale, a sketch of a reamer, partly in section, wherein the reamer support shoes are extended, whilst the reamer is being displaced forwards; and

Fig. 3 shows the same as in fig. 2, but here the support shoes are retracted whilst the support shoes are being displaced onto their starting position.

In the drawings, reference numeral 1 denotes a rock drilling machine located within a borehole 2, wherein the rock drilling machine 1 comprises a drill portion 4 and a string portion 6.

The drill portion 4 comprises a drill bit 8 and a stabilizer 10, a support bearing 12, a gear 14 and a motor 16 and also a directional control device 18.

The string portion 6 comprises auxiliary modules 20, which include hydraulic pumps, a power transducer and instruments (not shown). Moreover, and besides pipe lengths 22, the string portion 6 is provided with a navigation module 24, a centering module 26 and a self-driven reamer 28.

The components 8, 10, 12, 14, 16, 18, 20, 22, 24 and 26 are of a design and mode of operation known per se and will not be described in further detail herein.

The reamer 28 comprises a housing structure 30 provided with a front connector 32 for connection to a pipe length 22. A motor housing 34 is disposed behind the front connector 32, the motor housing of which is connected to a rear portion 38 of the reamer 28 by means of guide rails 36. The rear portion 38 is formed with a rear connector 40 structured in a manner allowing it to be connected to a string portion (not shown), or to pipes and lines 42 for supply of drilling fluid and power. A protective pipe 44 extends in the forward direction forward from the rear portion 38.

A reamer bit 46 is disposed in a rotatable manner at the front connector 32 and is driven, via a gear 48, by motors 50 located within the motor housing 34. Electric power is supplied to the motors via pipes and cables 42. A feeding frame 52 is supported in an axially displaceable manner on the guide rails 36. The feeding frame 52 is displaced back and forth within the reamer 28 by hydraulic guide cylinders 54.

Four support shoes 56 are disposed in a radially displaceable manner in respective support cylinders 58 within the feeding frame 52. The support cylinders 58 are structured in a manner allowing them to displace their respective support shoes 56 between a retracted, inactive position - see fig. 3, and an extended, active position - see fig. 2.

A telescopic pipe 64 is connected to the feeding frame 52 and is displaceable along the motor housing 34 and the protective pipe 44. Seals 66, here in the form of bellows seals, are disposed at the end portions of the telescopic pipe 64.

Upon initiating drilling with the drilling machine 1, the drill bit 8 and the reamer 28 are started. The directional control device 18 is set on the basis of information from the navigation module 24.

Upon pressurizing the support cylinders 58, the support shoes 56 of the reamer 28 are displaced outwards against the wall of the borehole 2, see fig. 2.

Then, the displacement cylinders 54 displace the reamer 28 and thus the rock drilling machine 1 inwards during the cutting of material.

When the feeding frame 52 has been displaced to its end position within the reamer 28, the support cylinders 58 are disengaged, whereby the support shoes 56 no longer press against the wall of the borehole 2, see fig. 3. Then, the guide cylinders 54 displace the feeding frame 52 to its starting position within the reamer 28.

While the support shoes 56 are disengaged, the rock drilling machine is held in place by increasing, for example, the contact pressure exerted by the centering module 26 or the directional control device 18 against the wall of the borehole 2. The feeding sequence is repeated for further displacement of the rock drilling machine 1.