A PLANT FOR PROCESSING BY CUTTING MATERIAL WITH THE AID OF A LASER BEAM

Abstract: A laser cutting plant includes a cutting head guidable in two directions, to which a laser beam is taken via three mutually perpendicular tubes (2, 4, 14) in sealed connection to each other and containing two deflection mirrors (22) for the beam. The laser beam unit is stationary. The mirrors are carried by the respective tube (4, 14) via flat throats (24) moving in longitudinal slits (21) in the connecting tubes (2, 4), said slits being covered by two opposing and resiliently engaging lips (31).

Description: TITLE A plant for processing by cutting material with the aid of a laser beam. TECHNICAL FIELD The invention relates to a plant of the kind disclosed in the preamble to the appended claim 1. BACKGROUND ART Laser technology is well suitedfor cutting, e.g. cloth, plastic sheets, plate or fibre particle boards, since, inter alia, the cutting laser beam can be made very narrow and energy-intensive, whereby material waste will be very small. For such cutting processing, it is suitable to arrange a work table for the material. A first slide can be displace- ably arranged along the table and extend transverse the table. A second slide can be displaceably arranged on the first slide for displacement along the first slide, i.e. across the table. By controlled displacement of the two slides the second slide can be caused to find an arbitrary point on the table. Such controlled displacement can be provided by conventional technology with the aid of numerical control, i.e. the driving means of the slides are controlled with the aid of a programmed computer. It is already known in plants of the kind mentioned in the introduction to mount the laser unit directly on the second slide, it thus being achieved that the beam can be easily enclosed along the short distance between the unit and the material to be cut. The exposed beam between the casing and material is so short that an operator can hardly come against and be injured by the beam. Since the laser unit can have a mass of about 400 kg, and since in plants of the kind in question it is desirable to have a cutting speed which is as high as possible in the plane of the table, it will be understood that the plant is subjected to large stresses due to the mass of the laser unit when the direction and rate of travel of the second slide are changed. For reasons of precision and strength, such a known plant must therefore be implemented very robustly and it will therefore be very expensive. The cutting speed • J ^Q can hardly be made larger than some few m/min even so. The laser unit has therefore been placed stationary relative the table, the "weightless" laser beam being deflected in¬ stead to desired points on the table with the aid of deflec- 3 ^ 5 tion mirrors, the beam path then being enclosed in a tele¬ scopic-type tube system, cf SE 347 680. The tube system serves the purpose of preventing the operator from being injured by the laser beam, it thus preventing direct contact with the beam and constitutes a dazzle shield so that eye 20 injuries are avoided. Furthermore, the system can serve to prevent dirtying the mirrors which are placed in the tube system. Telescopic tube systems have been found to be substantially 25 unusable, at least with relatively large cutting table sur¬ faces, e.g. 2 x 3 m, and cutting speeds in the order of mag¬ nitude of 1 m/s. Amongst the reasons for this is that it is very difficult 30 to get a telescope sufficiently rigid when fully extended, since only the outer sections of the telescope can be support ed. It is indeed possible to utilize telescopic tube sections for the telescope which have very great lengths relative their diameter and are also provided with long guides. How- 35 ever, this results in special difficulties with the second telescopic tube in the direction of the ray path, since it must carry a deflection mirror at the connection with the first telescopic tube. This mirror will then be outside the edge of the table by a telescopic section length. In order to be able to operate this mirror without vibration, which is particularly difficult since the sections of the first telescopic tube tend to hook into each other, the seco slide would need to be provided with a support carrying the mirror in question at a distance from the table correspondin to a telescopic section length. In turn, this results in further weight problems. Furthermore, the varying and periodical friction occurring in telescopic tubes would make the use of numerical control impossible, at least for a plant working at such a high spee since every frictional resistance must be compensated for in the calculation of the control pulses to the driving means of the slide. Another disadvantage with a telescopic tube system is that the air therein is pumped in and out, and dust would be deposited onto and fused into the mirrors. One object with the invention is to remove the mentioned drawbacks in known laser cutting plants which have a tube system through which the laser beam path extends. DISCLOSURE OF INVENTION The invention relates to a plant of the implementation appa¬ rent from the following main claim. Each tube is suitably assigned a pair of elastic lips in mutual resilient engage¬ ment along the axial slit in the tube to cover the slit. The part of the mirror holder extending through the slit is suitably cuneiform in order to part the lips. The second mirror holder which is rigidly mounted in relatio to the second slide for deflecting the laser beam to the table, is suitably connected to a third tube, which contains a focusing lens for the beam at its end remote from the second holder. The first tube is suitably closed off at its end remote from the laser unit. The second tube is suitably closed off at its end remote from the first mirror holder. The third tube suitably has an opening for the departing beam at its end which is remote from the second mirror holder. It is thus possible to introduce a pure gas into the first tube in the vicinity of the laser unit, and this pure gas can then flow through the first tube, the second tube and out through the third tube, thus preventing combustion gases or particles from the processed material coming into contact with the deflection mirrors or coming into the laser beam path. The mirror holder is suitably implemented such that gas can freely pass the holder in the tube, thus substan¬ tially avoiding local pressure variations in the tube as a result of displacing the holder. If so desired, the pure gas can of course be flushed through each tube separately. The laser unit may include a CO,, laser, for example, which sends coherent light having a wavelength somewhat greater than /u . Laser power, e.g. in cutting cloth, may attain some hundreds of watts, the beam having a diameter of say 6-15 mm. Plexiglas may be used as the tube material for this wavelength, but it should be quite clear that almost any kind of material may be used for the tubes, since they are primarily intended to serve as touch protection , The mirror holders may include a pipe coil through which a cooling fluid, e.g. a cooling liquid, can be passed for cooling the mirror. Alternatively, the pure gas can be utilized as coolant for the mirrors. The invention is defined in the following patent claims. An embodiment of the invention will now be described in detail in the following with reference to the accompanying drawing. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described in detai with reference to the accompanying drawing, on which Figure 1 is a schematic horiεontal view of a plant in accord¬ ance with the invention, it being imagined that this view is taken along the line I-I in Figure 2, Figure 2 is a vertical view of the plant according to Figure taken along the line II-II in Figure 1, Figure 3 is a section along the mirror holder connections between two tubes denoted in Figure 1 by Ilia and IIlb, Figure U is a section taken along the line IV-IV in Figure 3, Figure 5 is a section taken along the line V-V in Figure 3, Figure 6 is a section taken along the line VI-VI in Figure 3 and Figure 7 illustrates an evacuation nozzle surrounding the opening of the tube facing the material which is to be cut. PREFERRED EMBODIMENT In Figures 1 and 2 there is shown a work table 7 provided at its sides with guide rails 12 and 13 for a first slide 8, which " has grooves 18 and 19 on its underside for the rails 12 and 13, respectively. The first slide 8 extends over the entire width of the table 7, and has on its upper side a pair of guide rails 10 and 11 for a second slide 9, which is guided by a pair of unillustrated guide grooves for travel along the rails 10 and 11. The table 7 is carried by a frame denoted by the numeral 20. A laser unit 1 is illustrated in Figure 1 and is disposed stationary in relation to the table 7. As will be seen from Figures 1 and 2, the laser unit 1 is adapted to send a beam 50 extending parallel to the surface of the table 7, at one 6 side of the table and at the side of, or above the second slide 9. The beam 50 extends coaxially through a first tube 2, which is disposed stationary in relation to the table 7. The tube 2 has an axial slit on the right-hand side of the tube 2 in the plane of the Figure in Figure 1. In tube 2 there is a mirror holder with mirror, generally de¬ noted by Ilia. The mirror deflects the beam 50 so that it extends out through the slit in the tube 2 and coaxially into a connecting tube 4, which is mounted on the first slide 8 with the aid of holders 17. The tube 4 also has an axial slit,diεposed on its underside in Figure 1. A further mirror holder and mirror generally denoted by Illb is disposed in the second tube 4 such that the beam 50 can be deflected downwards through the axial slit of the tube and coaxially into a third tube 14 containing a focusing lens 16 for the beam, and which at its lower portion has an opening 15 for thefocused laser beam. The opening 15 is arranged close to the material laid up on table 7 for cuttin At its remote end the tube 2 is closed by a cover 3, and in a corresponding % way the tube 4 is closed by a cover 40 at its remote end. As will be seen from Figure 5, the slit 21 of tubes 2, 4 is covered by a pair of elastic lips 31, which are attached to the tube and are in mutual resilient engage¬ ment opposite the slit 21. The mirror holder denoted by Ilia and Illb in Figures 1 and 2 is more closely illustrated in Figures 3, 4 and 6. The mirror holder III includes a head 23 on which a mirror 22 is adjustably mounted, the mirror being generally kept at an angle of about 45 to the incident beam 50, such that the mirror deflects the beam 50 out through the tube slit 21. The mirror holder head 23 is carried by a shank portion 24, the width of which is suited to the width of the slit 21 for travel along the slit. The edges of the shank portion 24 are given a plough shape for easily parting the lips 31. In its turn, the shank portion 24 is carried by a foot part 37 tightly sealing against the connecting tube 4, (14). An OMPI opening 25 is arranged in the shank portion and foot part of the mirror holder to allow free passage for the deflected beam 50 and possibly a gas introduced into the tubes. A ducting coil 26 is arranged in the mirror holder, e.g. for carrying cooling liquid for cooling the mirror 22. When, for example, the tube 4 of the first slide 8 is moved relative the tube 2, the shank portion 24 of the mirror hold will move along the slit 21 of the tube 2 and by reason of its plough shape move the lips 31 apart, said lips either sealing against each other or against the longjsides of the shank portion 22, due to their elasticity. The laser beam will therefore extend entirely enclosed from the unit 1 to the opening 15 of the third tube 14 irrespective of the ove ments of the slides 8, 9 and thereby the movements of the tubes 4, 14 relative the unit, and the enclosure is so com¬ plete that an operator cannot unintentionally come into contact with the laser beam 50. The enclosure provided by the tubes, lips and mirror holders is further such that a protective gas can be introduced, e.g. at the gas inlet 41 adjacent the laser unit 1, with a small excess pressure and without too much leakage such that it flows to the tube 2, through the mirror holder denoted by III at the junction between tubes 2 and 4, through the tube , through the mirro holder III at the junction between tubes 4 and 14, through the tube 14 and out through the opening 15. To advantage, the table 7 can be made. rom expanded metal, honeycomb material or the like, and a vaccum source may be connected to the underside of the table. If the table is made from expanded metal or the like, the risk of damage to the table from the laser beam is reduced, and material debris can fall down through the interstices in the table surface. If a vaccum source is connected to such a table, both par- tides of material and combustion gases may be easily removed With a plant in accordance with the invention, dimensioned in correspondencewith the plant in which the laser unit is movably mounted, cutting speeds in the order of magnitude of 1 m/s can be easily achieved. As will be seen from Figure 7, the opening of the tube 14 is surrounded by a suction box 41 having an annular slit 42, The box 41 is evacuated via a conduit 43, the evacuation of smoke etc. being enabled via the slit 42 and conduit 43. t OMPI

Claims: CLAIMS 1. A plant for processing by cutting material with the aid of a laser beam, including a work table (7) on which the mate rial is intended to be placed, a first slide (8) guided for movement along the table (7), a second slide (9) guided for movement along the first slide (8) across the table (7), a laser unit (1) adapted stationary relative the table (7), a first tube (2) rigidly mounted substantially parallel to the table and extending above the surface of the table to one side thereof substantially in the traveling direction of the first slide, the beam (50) of the laser unit (1) being directed through said first tube (2), a second tube (4) which is rigidly mounted on the first slide (8) and extends transverse the traveling direction of said first slide (8), a first deflection mirror (22) disposed in the first tube to deflect the laser beam (50) so that it is directed through the second tube (4), and a second deflection mirror (22) disposed in the second tube (4) for deflecting the beam (50) towards the work table, the first and second tubes being arranged in mutual communication during travel of the first and second slides (8, 9), c h a r a c t e r i z e d in that the first tube (2) has an axial slit, in that the first mirro is carried by a first holder (Ilia) carried by the second tube (4) and extending through the axial slit (21) of the first tube (2), the holder having a bore through which the beam deflected by the first mirror (22) extends, in that the second tube has a second axial slit (21), and in that the second holder for the second deflection mirror is rigidly mou ed on the first slide (9) and extends through the slit (21) of the second tube (4), the second holder (Illb) having a bore through which the beam (50) deflected by the second deflection mirror (22) extends towards the surface of the table. 2. A plant as claimed in claim 1, c h a r a c t e r i z e d in that each tube (2, 4) is assigned a pair of elastic lips (31) resiliently engaging against each other and against the appropriate holder (Ilia, Illb) for screening off the slit m question. nv°τ 10 3. A plant as claimed in claim 1, c h a r a c t e r i z e d in that a third tube (14) is connected to the second holder, this third tube preferably containing a focusing element (16) for the laser beam at its end facing away from the holder. 4. A plant as claimed in claim 3, c h a r a c t e r i z e d in that the third tube (14) has at its free end an evacua¬ tion nozzle (41, 42) adapted for enabling evacuation of generated smoke. 5. A plant as claimed in claim 4, c h a r a c t e r i z e d in that the nozzle is annular and surrounds the opening of the third tube (14). OMPI *- *

Inventors: KNUTSSON LARS GUNNAR, KNUTSSON, LARS, GUNNAR
Applicants: KNUTSSON G ING AB, INGENJOERSFIRMA G. KNUTSSON AB
Application year: 1983
Main classification: B23K26
IPC codes: B23K26