Abstract:
A laser source for use in providing a laser beam for industrial operations in an industrial plant. The laser source selectively providing a first laser beam at a first outlet having relatively high power and lower beam quality and a second laser beam at a second outlet having relatively lower power and higher beam quality. The laser source including an optical path selector device for selectively transmitting a first laser beam along a first or second optical line toward respective first and second outlets. The second optical path having an optical amplification unit for changing the first laser to the second laser. An industrial plant including at least a first laser source selectively controls the first laser source to provide the first and the second lasers to predetermined laser processing stations. A second laser source may be used and controlled to provide a first or second laser to an alternate laser processing station on a failure of another laser source.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to laser sources and in particular to laser sources of the type adapted for industrial processes, such as welding, brazing and cutting operations on metal materials. 
       BACKGROUND 
       [0002]    Many kinds of laser sources have been developed in the past and are presently available in the market in order to satisfy various needs in the field of industrial processes and in particular in the field of processes on metal materials. In general, different processes (such as welding, brazing and cutting of metal materials), different degrees of precision in the process and different characteristics of the materials being processed (such as a different values of the thickness of a metal sheet to be welded or to be cut) require different characteristics of the laser beam in order to ensure optimum results. For some of these processes, the quality level of the laser beam may be lower, whereas for other applications the quality of the beam must be higher. 
         [0003]    In the present description, and in the following claims, by the term “quality” of the laser beam means the ability of the laser beam to be focused into a very small spot, so as to give rise to a high power density at the laser spot. The quality of the laser beam defined in this manner is commonly represented by the value of a parameter called BPP (“Beam Parameter Product”), measured in millimetres per milliradiant (mm.mrad) corresponding to the product of one half of the divergence angle of the laser beam by the beam diameter at its narrowest portion (beam waist). The quality of the laser beam is higher when the value of BPP is lower. Therefore, different industrial applications may require the use of laser beams with values of the BPP parameter much different from each other. Similarly, also the power of the laser beam may be varied, as a function of the specific applications. 
         [0004]    In many laser sources of known type, it is possible to vary the quality and the power of the laser beam to a very limited extent, with no possibility however of modifying the characteristics of the laser beam significantly. For this reason, at present it is often necessary to use different laser sources for performing different industrial operations. 
         [0005]    On the other hand, it would be desirable to have a single “universal” laser source, which may be easily adapted depending upon the nature of the industrial operation to be performed and/or the nature of the materials to be processed. 
         [0006]    Among the various types of laser sources which have been already developed and are presently available on the market, diode laser sources and laser sources with active optical fibres are worth to be mentioned here in particular. The latter type comprises optical fibres in which an “active” material is dispersed (typically a rare earth material) which has the ability of amplifying a light beam by exploiting the principle of stimulated emission. Typically the active optical fibre is “pumped” with a laser beam generated by a diode laser source. In general, sources with active optical fibres generate a higher quality of the beam with respect to diode laser sources, while causing a loss of power due to the dispersions within the optical fibre. 
         [0007]      FIG. 3  of US 2014/0177038 shows a laser device with dual brilliance, having a fibre-integrated optical beam switch, able to switch the laser beam between two optical fibres, one of which is connected to a first outlet, the other optical fibre being connected to an ytterbium fibre oscillator, which provides a fibre output with a radiation having a higher brilliance. 
       SUMMARY 
       [0008]    The object of the present invention is that of providing a laser source able of selectively generating laser beams with characteristics which are significantly different from each other, so that it can be used in industrial applications which are also much different from each other. 
         [0009]    A further object of the present invention is that of achieving this purpose with a laser source having a simple and efficient structure. A further object is that of providing a system with a plurality of devices, cells or stations for laser processes, which make use of one or more laser sources of the above indicated type in an advantageous and efficient manner. 
         [0010]    In view of achieving these objects, the present invention provides a laser source comprising:
       a laser beam generating unit, including one or more diode laser sources, for generating a first laser beam,   an optical amplification unit, including at least one amplifier module adapted to receive laser light derived from said first laser beam emitted by said generating unit and to emit a second laser beam at its output having a higher beam quality and a lower power value with respect to said first laser beam coming from said generating unit, and   a laser beam switching and addressing optical unit, interposed between said generating unit and said optical amplification unit, said switching and addressing optical unit including:   an inlet for receiving said first laser beam coming from said generating unit,   a first optical line for forwarding said first laser beam to a first outlet of said laser source,   a second optical line for forwarding said first laser beam towards said at least one amplifier module of said optical amplification unit, and   an optical path selector device interposed between said inlet and said first and second optical lines, for directing said first laser beam coming from said generating unit selectively towards:   said first optical line, so as to generate the emission of a laser beam of a relatively higher power and a relatively lower quality at said first outlet of said laser source,       
 
         [0019]    or towards
       said second optical line, so as to generate the emission of a laser beam having a relatively lower power and a relatively higher quality at a second outlet of said laser source.       
 
         [0021]    Preferably, said optical amplification unit includes a plurality of amplifier modules arranged in parallel, having respective inlets supplied in parallel by said second optical line and respective outlets connected to optical lines converging towards said second outlet. 
         [0022]    Due to the above indicated features, the invention provides a single laser source which has a first outlet and a second outlet separated from each other, which are selectively activated for emitting laser beams having characteristics which differ significantly, depending upon the specific application of interest. 
         [0023]    It is thus possible, for example, to implement a process cell in an industrial plant having a single laser source for performing at this cell processes of different nature within a same working cycle and/or in order to enable a future introduction of a new working cycle within the same cell, without requiring a replacement of the laser source and/or in order to use the same laser source for example for performing different processes at a same working cell or for performing different processes in different working cells, or for acting as dedicated source at a first working cell and as a back-up source at another working cell. 
         [0024]    According to a preferred embodiment, the above mentioned laser&#39;s beam generating unit is a unit comprising a plurality of diode laser sources, as already indicated above, whereas each amplifier module of said optical amplification unit comprise at least one active optical fibre, of the type containing an active material (such as ytterbium) able of amplifying the laser beam which enters into said module, coming from said generating unit through said second optical line of said switching and addressing optical unit. 
         [0025]    Also in the case of the above mentioned preferred embodiment, said optical path selector device is preferably constituted by a mirror movable between a first operative position and a second operative position in which the laser beam coming from said generating unit is directed respectively towards said first optical line and towards said second optical line. In a first solution, the mirror does not intercept the laser beam coming from the generating unit when it is at its first operative position, thereby enabling the laser beam of proceeding further towards the first optical line, whereas in its second operative position the mirror intercepts the laser beam and reflects the same towards the second optical line. In one variant, the mirror intercepts the laser beam in both its operative positions but assumes different orientations at said positions, so as to reflect the laser beam respectively towards said first optical line and towards said second optical line. 
         [0026]    The movement of the optical path selecting mirror is controlled by an actuator device of any known type, preferably having electric actuation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Further features and advantages of the present invention will became apparent from the description which follows with reference to the annexed drawings, given purely by way of non limiting example, in which: 
           [0028]      FIG. 1  is a diagram of an exemplary embodiment of a laser source according to the present invention; 
           [0029]      FIG. 2  is an enlarged portion of  FIG. 1 ; 
           [0030]      FIG. 3  is an alternate enlarged portion of  FIG. 1 ; 
           [0031]      FIG. 4  is an alternate enlarged portion of  FIG. 1  showing an example of an active optical fibre and Bragg recticles inside of an exemplary amplifier module; 
           [0032]      FIG. 5  is a schematic diagram of an example of an industrial plant using a single laser source; and 
           [0033]      FIG. 6  is a schematic diagram of an alternate example of an industrial plant using two laser sources according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    With reference to the drawings, numeral  1  generally designates a laser source for use in industrial processes, in particular on metal materials. The laser source illustrated herein can be used for example in an industrial cell in which operations of various types are performed, such as laser welding operations, laser brazing operations and/or laser cutting operations. 
         [0035]    Many of the components forming part of the embodiment described herein are shown in the annexed drawings only diagrammatically, since each of them, taken alone, can be made in any known way. The deletion of these details of construction from the drawings renders also the latter simpler and easier to understand. 
         [0036]    According to the invention, the laser source  1  comprises a laser beam generating unit, generally indicated by reference numeral  2 . The generating unit  2  comprises a plurality of a diode laser sources  20  constituted in any known way. The laser light coming out from the diode laser sources  20  is guided into optical fibres  21  which merge into a fibre combiner  22 , which is also of a type known per se, whose output is connected to an optical fibre  3 . 
         [0037]    In an actual embodiment, the generating unit  2  is able to generate a first laser beam within the optical fibre  3  having a power in the order of 6 kW and a beam quality corresponding to a BPP value in the range of 50 mm.mrad. 
         [0038]    Naturally, the configuration of the generating unit  2  which is diagrammatically shown in  FIG. 1 , and visible at an enlarged scale also in  FIG. 3 , is provided herein purely by way of example, while it is well understood by the skilled men in the art that this generating unit can be made according to any of the configurations of presently known diode laser sources. 
         [0039]    Downstream of the generating unit  2 , the laser source  1  according to the present invention comprises a single laser beam shifting and addressing optical unit  4 . With reference also to  FIG. 2 , unit  4  comprises an inlet constituted by a connector  40  to which the optical fibre  3  coming from the generating unit  2  is connected. Connector  40  connects optical fibre  3  to an optical fibre  41  which is at the inlet of unit  4 . An optical interface  42 , of any known type, transmits the laser beam coming from the generating unit  2  through the optical fibres  3  and  41  within a free space S provided inside the casing of unit  4 , in which the laser beam freely propagates. 
         [0040]    Within space S at the inside of unit  4  there is arranged an optical path selector device, which in the example illustrated herein is constituted by a mirror  43 . In the illustrated example, mirror  43  is movable parallel to itself between a first operative position (shown by dotted line in  FIGS. 1, 2 ) and a second operative position (shown by undotted line). 
         [0041]    In the first operative position of mirror  43 , this mirror does not intercept the laser beam coming from the generating unit, so that the laser beam can proceed freely towards a first optical line, generally indicated by reference  44 , which ends at a first outlet U 1  (see  FIG. 1 ) of the laser source according to the invention. In its second operative position, mirror  43  intercepts the laser beam coming from the generating unit and reflects the same towards a second optical line, generally indicated by reference  45 . 
         [0042]    As already indicated in the foregoing, as an alternative to the arrangement which is shown diagrammatically herein for mirror  43 , it is possible to provide an arrangement in which the mirror is simply caused to oscillate between a first operative position and a second operative position, so that in both these positions the mirror intercepts the laser beam coming from the generating unit and reflects the beam in the direction of two different optical lines. 
         [0043]    Again with reference to  FIG. 2 , numeral  46  designates an actuator of any known type, preferably an electrically controlled actuator, adapted to drive the movement of mirror  43  between its two operative positions. When the mirror  43  is in its first operative position (shown by dotted line) in which it does not intercept the laser beam coming from the generating unit along a direction S 0 , this beam proceeds further within free space S along a direction S 1  (constituting the extension of direction S 0 ) until it enters into an optical interface  47 , through which the laser beam is guided into an optical fibre  48 . The optical fibre  48  ends at a connector  49  through which it is connected to another optical fibre  481  which ends at a connector  482  (see  FIG. 1 ) which constitutes the first outlet U 1  of the laser source  1  according to the present invention. 
         [0044]    Again with reference to  FIG. 2 , when mirror  43  is in its second operative position (shown by undotted line) the laser beam coming from the generating unit along direction S 0  hits mirror  43  and is then reflected along a direction S 2  towards the second optical line  45 . 
         [0045]    In the case of the specific embodiment shown herein by way of example, the second optical line  45  comprises a fixed mirror  451  which reflects the laser beam coming along direction S 2  into a direction S 3 . The laser beam which proceeds along direction S 3  meets in sequence a plurality of fixed semi-reflecting mirrors  452  and a terminal fixed mirror  453  which is totally reflective. The semi-reflective mirrors  452  are configured in such a way that the laser beam which hits them is in part reflected into a direction S 4  and in part proceeds beyond the mirror, along the direction S 3 . The terminal mirror  453  reflects the portion of light which has passed beyond all the semi-reflective mirrors  452 . The beam portions reflected along directions S 4  are guided through respective optical interfaces  454  into a plurality of optical fibres  5  at the outlet of unit  4 . 
         [0046]    With reference again to  FIG. 1 , the optical fibres  5  lead the laser light to the inlets of a plurality of amplifier modules  60  of an optical amplification unit  6 . Each of the amplifier modules  60  has a configuration of the type diagrammatically shown in  FIG. 4 , which is known per se, comprising “active” optical fibres  61  where particles of active materials (ytterbium in the specific case illustrated herein) are dispersed, which have the ability of amplifying the laser source by exploiting the principle of stimulated emission. 
         [0047]    Also according to a technique known per se, the active optical fibres  61  extend between two Bragg reticules  62 ,  63  arranged at the input and at the output of each module  60  and respectively connected to the inlet optical fibre  5  and an outlet optical fibre  64 . The optical fibres  64  merge into an optical fibre combinator  65  whose outlet is connected through an optical fibre  66 , a connector  67  and another optical fibre  68  (see  FIG. 1 ) to a connector  69  constituting a second outlet U 2  of the laser source  1  according to the invention. 
         [0048]    The active optical fibres  61  of the amplifier modules  60  are optically pumped with laser light coming from unit  4  and derived from the diode laser sources  20  and give rise to a laser beam at the second outlet U 2  having characteristics which are different with respect to the laser beam made available at the first outlet U 1 . In particular, the passage through the active fibres  61  implies a loss of power (such as in the order of 30% approximately), but increases the beam quality, i.e. the ability of the beam to be focused into a very small spot. In the actual exemplary embodiment, the laser beam available at the outlet U 2  has a power of 4 kW and a BPP value in the order of 3 mm.mrad. 
         [0049]    As already indicated, in the foregoing description and in the annexed drawings the details of construction relating to the illustrated components have not been provided, since they can be made in any known way and the deletion from the drawings render the latter simpler and easier to understand. 
         [0050]    According to a technique which also is known per se, all the functions of the laser source are controlled by an electronic control unit (not shown in  FIGS. 1-4 ) to which a human-machine interface of any known type is associated. 
         [0051]      FIG. 5  diagrammatically shows an example of an industrial plant making use of a laser source according to the invention. The illustrated example refers to the case of a plant for production of motor-vehicles, comprising a plurality of laser processing cells or stations R 1 , R 2 , R 3 , R 4 . For example, the plant comprises a station R 1  in which a laser brazing operation is performed (a typical case is that of the operation for connecting a roof to a body of a motor-vehicle), a station R 2  where a laser welding operation is performed on a component (such as a structure of a motor-vehicle door), a station R 3  where a laser cutting operation is performed, such as an operation for forming an aperture in a wall of the motor-vehicle body, and a station R 4  where a laser remote welding operation is performed, i.e. a welding operation where the laser head is kept spaced away from the welding area. 
         [0052]    At each processing station there is provided a processing equipment making use of a laser beam. For example, the equipment may comprise one or more multi-axis manipulating robots, each provided with a laser head connected by an optical fibre to the laser source. Also by way of example, to each cell or station there is associated an electronic control unit E 1 , E 2 , E 3 , E 4 . A supervisor electronic unit E communicates with the electronic units E 1 , E 2 , E 3 , E 4 . 
         [0053]    Brazing, welding, cutting, remote welding processes imply the use of a laser beam with increasing quality (the lower quality being required for brazing and welding, whereas the higher quality is required for cutting and remote welding). 
         [0054]    In the plant of  FIG. 5  there is illustrated a laser source according to the invention which has been described above, with the two outlets U 1 , U 2  connected, by means of optical distributors D 1 , D 2  of any known type to optical fibres f 1 , f 2 , f 3 , f 4  which transmit a respective laser beam to the equipment provided at the respective processing station or cell. 
         [0055]    An electronic unit ES for controlling the selector device  43  of the laser source  1  activates either outlet U 1  or outlet U 2  of source  1  based on signals coming from supervisor E, so as to perform operations at cells R 1 , R 2  or at cells R 3 , R 4 . 
         [0056]    Still more advantageously, two sources  1  according to the invention may be provided one of which, for example, is dedicated to one or more cells R 1 , R 2  and the other one being dedicated to one or more cells R 3 , R 4 . This solution is diagrammatically shown in  FIG. 6 , where two sources  1  according to the invention each have one of the two outlets U 1 , U 2  connected to a cell R 1  and the other one connected to a cell R 4 . The optical fibre at the inlet of each cell is connected to two optical fibres coming from two different sources by means of three-ways connectors C 1 , C 2 . 
         [0057]    Supervisor E controls the electronic unit ES of the sources so that normally the laser source on the left side has its outlet U 1  activated for supplying cell R 1 , whereas the other source  1  has its outlet U 2  activated for supplying cell R 4  with a laser beam of a higher quality. 
         [0058]    However, in the case of failure of one source, the other source can be temporarily used for supplying the cell whose source has a failure, after shifting the respective selector. This can be useful for example when a failure on the source of cell R 4  justifies an interruption in the process at cell R 1  in order to use the source of R 1  as a back-up source for R 4 . 
         [0059]    The illustrated diagrams are purely given by way of example, the configuration and arrangement of the cells and the associated laser sources being clearly variable at will, according to the needs of the specific applications. 
         [0060]    The source according to the invention can be also associated to a single processing cell for transmitting laser beams of different characteristics to different laser devices provided at the same cell, in order to perform different laser operations within the same cell. 
         [0061]    Naturally, while the principle of the invention remains the same, the details of construction and the embodiments may widely vary with respect to what has been described and illustrated purely by way of example, without departing from the scope of the present invention.