When drifting tunnels and mines a method for mark¬ ing out drill hole patterns on the face of the rock by projecting the image of a slide provided with markings, re¬ presenting the positions of holes to be drilled on a re- duced scale belongs to prior art. It is described in U.S. patent specification No. 3,431,049. This known method ne¬ cessitates a separate direction determining means, a di¬ rection laser, for instance, as a reference in respect of the tunnel direction, as well as comparatively complicated measures for correcting the position of pattern points of a slide to correspond to correct positions of drill holes on the rock surface when projecting the. slide image onto the rock face. This is due to the fact that the face of the rock, after blasts for instance, obtains varying shapes, which seldom or never constitute a substantially plan sur¬ face extending perpendicularly to the optical axis of the projector when projecting the -slide onto the rock surface. Said situation is illustrated by Fig. 1 of the accompanying drawing. One object of the invention is to avoid the above- mentioned drawbacks, in particular the necessity of correct¬ ing the slides used for projecting markings for the drill holes with respect to a variable shape of the rock surface. Said object is attained by utilizing the fact that a projection of a narrow unidirectional light bunch such as and in particular a laser based projection; allows for such a distance of projection as compared with what could nor¬ mally be effected by means of a projector in which represen¬ tation of a pattern is illuminated in its entirety by means of a condensor lens system, that _the light beams represent¬ ing different locations on the drilling hole pattern on the rock surface run substantially parallel to the direction of the tunnel. In ^' its turn, this fact implies that no measures are requred to compensate for irregularities in the rock surface, onto which the drill hole markings are to be pro¬ jected.

In practice, the invention brings about valuable improvement, in that additional work to adjust the shaj.

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of the rock surface after a preceding blasting in order to obtain a correct marking of the drill holes will not be ne¬ cessary, thus allowing for a desired drill hole pattern without any correction of the slide pattern to be project- 5 ed.

The method according to the invention is defined by the accompanying method claims. A device according to the invention for carrying out the method has character¬ istics appearing from the appended claims in respect of a 0 device.

In a preferred embodiment for utilizing the in¬ vention in practice, a device comprising one single light . source, generating a light bunch of substantially parallel light, rays, is mounted, advantageously hanging down from 5 the roof of the tunnel, to be used during a plurality of markings for subsequent drillings and blastings, for ex¬ ample by means of a "remote control box", which, in case the device being equipped with data program.defining diffei ent topic drill hole patterns, obviously -may be arranged 0 for selecting a desired program and marking of a selected drill hole of a pattern. An important advantage of using light beams consisting of unidirectional rays, laser beams in particular, when projecting images corresponding to dri] hole locations is to be seen in the possibility thereby to 5 obtain on the rock wall distinct and easily observable images under varying ambient light conditions and projectic distances. Further, by use of the invention it is made possible that one single laser source - an equipment being rather cost consuming in purchase as well as in use - may ^ be used for the vitally important laying-out of tunnel di¬ rection as well as for the laying-out of drill hole posi¬ tions in a manner superior to prior art. A still further advantage of a device according to the invention having a light source in the form of a laser to generate the light 5 beam is that the device can be used within coal mining in¬ dustry, in which conventional light projection of drill hole is not allowable due to safety rules relating to danger of explosion.

The invention will become more closely

from the following description of a preferred embodiment thereof, considered as illustrating a best mode of the in¬ vention, in- connection with the..accompanying drawing, of which Fig. 1, as mentioned above, for better understanding • of the invention, illustrates a method of the present art for defining a tunnel direction by aid. of a reference laser light beam in connection with marking of drill hole posi¬ tions by means of film slide projection utilizing either a fixed predetermined distance between a lens system .pro- jector and the image plane on or adjacent, respectively, the rock surface or a variable focal distance (zoom) for selecting the ^' focal distance to obtain a drill hole pattern of desired dimension in the image plane, Fig. 2 illustrates ^' a projection of not only the tunnel direction defining beam but the driil hole pattern as well onto the rock wall from such long a distance from the image plane, the rock wall, that unevennesses therein are of very little consequence in the accuracy of the marking out of the holes, and Fig. 3 schematically illustrates a preferred embodiment of a de- vice according to the invention.

In the conventional method illustrated by Fig. 1, a direction defining laser is used for defining the direct¬ ion of the tunnel to be drifted, said laser generating a coherent beam bundle 1 in the direction of the tunnel. To mark predetermined locations of drill holes, a projector

2 projects an image of a slide provided with a small scale drill hole pattern within a space angle ω towards an image plane 3, selected with best possible adaptation to present unevennesses of a rock wall 4, in which holes are to be drilled for further blasting of rock in the tunnel 5. To obtain hole marking images at correct locations of the rock wall 4 when projecting the film slide onto the wall it is requisite, according to well known principles, to correct the markings of the slide, as related to an intended drill hole pattern, with respect to the shape of the rock wall 4. This measure implies not only a time consuming choice of slide pattern amongst a plurality of slides having pattern images approximately adapted to a corresponding number of different shapes of walls, but as well time

culations for correcting, on the rock wall, the position of holes to be drilled relative to corresponding projected hole images.

Fig. 2 illustrates the situation when adapting the method according to the invention by utilizing light bunch¬ es of unidirectional light rays, a laser light beam in particular, for projecting a drill hole pattern image at such large a distance from the rock wall that the light beams for the different holes of the pattern could general- ly be considered as hitting the wall in a direction paralle to the direction of the tunnel and the light beam 1 definin the tunnel direction.

The device according to the invention, in Fig. 2 designated 7, is advantageously mounted close to the tunnel roof 6. So mounted, the device may stay at this location during a plurality of marking and subsequent blasting cycles without being interfered with by intermediate clearing works

Fig. 3 illustrates a preferred embodiment of a de¬ vice according to the invention, said device comprising a laser beam source a. with a collimator b generating a laser beam £ having a direction defining the extension of the tunnel to be drifted. This laser beam then passes a trans¬ parent mirror dl,- through which part of the beam proceeds in an unchanged direction, constituting a direction refer- ence, beam c_ of the device, while part of the laser beam is reflected towards a second mirror d2, which directs this part of the laser beam substantially in the same direction as the reference beam toward the end wall 4 of the tunnel, where the drill holes are to be marked according to pattern The pair of mirrors ^consisting of the mirrors dl -and &2 _f is of the kind well known per se, which, according ^' to well known principles, are adjustable relative to each other to eject a light beam _e in a direction depending on the mutual position of the mirrors dl and d2. In the present situatioi the mirrors dl and d2 are each connected to positioningmean for positioning the mirrors mutually in such a manner that the wall -surface 4 may be scanned by beam e_ which thus, by controlling the positioning of the mirrors, may be directed towards any selected point within a space angle, the maxima:'

size of which is selected with due respect to a smallest desired distance and a largest desired wall surface.

The device comprises attachment -and position ad¬ justing means f_ so as to be steadily mounted at a select¬ ed location and adjusted to present a desired direction of the tunnel direction reference beam c_. A control means 8 for controlling the positioning of the pair of mirrors dl and d2 for directing the beam e in a selected direction for presenting a light spot representing the position of a hole to be drilled comprises, as illustrated, a RAM-memory having a capacity for a large number of drill hole patterns, Further, the control means 8 comprises a micro-computer 1 ■ which is programmed for translating drill hole coordinates present ^' in the memory into a corresponding angle in depend- ence of a present distance between the device and the tunnel end wall, that is, a kind of "electrical zoom", and gene¬ rating a signal controlling the positioning of the mirrors. , • Said positioning is provided for by means of two step motors, represented by block m, one ^* for each mirror, said 5 _> tep motors receiving a corresponding control signal gene¬ rated by a scan signal generator h.

When preparing the marking of drill hole positions according to a programmed pattern, the beam e is being di¬ rected, by actuating the scan signal generator h remotely from ^' a control box _j L, for instance, first to the image j_ of the reference beam £, then to a selected orientation point k at a predetermined distance from point j_, whereby an in¬ formation adequate for determining the present distance from the laser projector device to the rock surface has been fed into the micro-processor 1 of the control means 8. Then, the marking of the drill holes may proceed by actuating the micro-processor 1. to translate the drill hole coordinates of a selected drill hole pattern present in the memory cj into angle valid for the stated distance, thus deviating the beam e_ to a direction of the location of drill holes in wall 4.

By aid of the control box i_ the operator selects a desired hole pattern in the memory g and a forward stepping of points in the pattern, while marking the hole locatjj

by painting or adjusting drilling tools correspondingly.

It is obvious to those skilled in the art, that th control of the beam e_ for light spot- marking of drill posi tions in accordance with a selected pattern may be provide 5 for in a number of other ways, for instance by letting the micro-processor control a continuous scanning, of the patter for instance so as to simultaneously present images of all drill holes of a pattern.

In an embodiment .according to the invention and as

10 an alternative to drill hole patterns programmed in a memo¬ ry of a micro-processor, drill hole patterns in form of dia slides or perforated plates having apertures corresponding to positions of drill holes on a selected scale, in a manner similar to that valid for a projection according to hither-

15 to used methods, however without using an optical lens system for generating a large scale image of a small scale slide. In such an embodiment the beam e_ is, by means of a pair of mirrors or other device for directing a light beam into different directions in accordance with a predetermine 2.0 pattern to scan the dia slide or hole plate, in Fig. 3 sym¬ bolized by block n, light ^' points corresponding to the drill hole pattern being projected onto the rock wall through transparent portions of the dia or holes of the plate, the position of which relative to the exit point of the ray fro 25 the scanning means is being adjusted with respect to the distance to the rock wall.