IT201800005899A1 - Equipment for laser welding of plastic materials and related procedure. - Google Patents

Description

DESCRIPTION of the invention entitled:

"Equipment for laser welding of plastic materials and related procedure"

DESCRIPTION

The present invention generally relates to an apparatus for laser welding of plastic materials and a related laser welding process.

Technical field

Possible applications of the present invention include, but are not limited to, welding, cutting, etching of plastic materials, in particular polymers. More specifically, the invention lends itself to being applied also to TTIr welding, that is the welding by means of infrared crossing ("Through-Transmission Infrared welding") of two plastic components, one of which is transparent, and will be detailed here with reference to this particular application case, which is given purely by way of example and is not to be understood in any way as limiting the scope of application of the present invention. For example, such a production technique is used in the production of optical groups for automobiles.

Known technique

Laser welding apparatuses are known which are provided with a number n of laser light sources which emit a respective number of laser light beams. A plurality of optical fibers receives these laser light beams and conducts them along a line, called welding profile, defined on two bodies to be welded. Before reaching the profile to be welded, the laser light beam is passed through a reflecting and tapered light guide in a convergent manner in such a way as to concentrate the laser light beam, and make it as homogeneous as possible.

Summary of the invention

Objective of the present invention is to realize a laser welding equipment of the type described above which allows to reduce the costs of installation, maintenance and use of the same and of the related laser welding process.

This and other purposes are fully achieved according to the present invention thanks to a laser welding equipment having the characteristics defined in the attached independent claim 1 and to a laser welding process having the characteristics defined in the attached independent claim 13.

Advantageous embodiments of the invention are specified in the dependent claims, the content of which is to be understood as an integral and integral part of the following description.

In summary, the invention is based on the idea of realizing an apparatus for laser welding of plastic materials, comprising at least one laser light source capable of emitting a laser light beam, a plurality of stationary optical fibers each having an input end and an output end, in which the input ends are adapted to receive the laser light beam and the output ends are positioned so as to convey the laser light beam towards one or more bodies of plastic material to be welded, characterized by furthermore comprising a selective orientation system of the laser light beam, interposed between the laser light source and the plurality of stationary optical fibers, able to sequentially send the laser light beam coming from the laser light source onto the input ends of the stationary optical fibers. According to another aspect, the invention proposes a laser welding process as defined in claim 11.

The selective orientation system can comprise a mobile support, for example rotating, or translating or oscillating, which incorporates one or more selection optical fibers. Alternatively, the selective orientation system can comprise a reflecting system, with mirrors controlled in a rotating or translating manner.

Thanks to such an architecture of the selective orientation device, it is possible to reduce the costs of installation, maintenance and use of a laser welding apparatus of the type described above and of the laser welding process related thereto.

Brief description of the drawings

Further characteristics and advantages of the present invention will become clearer from the following detailed description, given purely by way of non-limiting example, with reference to the attached drawings, in which:

Figure 1 is a two-dimensional diagram of a laser welding apparatus according to an embodiment of the present invention;

Figure 2 is an exploded perspective view of the laser welding apparatus of Figure 1; figure 3 is a two-dimensional diagram of a laser welding apparatus according to a further embodiment of the present invention;

Figure 4 is an exploded perspective view of the laser welding apparatus of Figure 3; Figure 5 is a two-dimensional diagram of a laser welding equipment according to another embodiment of the present invention; and Figures 6 and 7 are respectively a two-dimensional diagram and a perspective view of a laser welding apparatus according to a still different embodiment of the present invention.

Detailed description

With reference initially to Figures 1 and 2, a laser welding apparatus 10 according to an embodiment of the present invention can comprise at least one laser light source 12, at least one first optical focusing device 14, a selective beam orientation system 16 of laser light, a second optical focusing device 18 (optional), and a plurality of stationary optical fibers 20 arranged between the selective orientation system 16 and a light guide element 24.

The laser light source 12 comprises a device suitable for generating a beam of coherent light radiation, that is a beam of laser light B, by means of a diode laser light generation system, known per se (not shown). In particular, the specific mode of generation of the laser light beam is not limiting for the purposes of the implementation of the present invention.

In one embodiment, the laser light source 12 can be used continuously. According to an alternative embodiment, the laser light source 12 can be switched off and on again in a pulsed manner or according to predetermined or programmable switch-off and switch-on times, or modulated according to a predetermined or programmable law.

The first optical focusing device 14 comprises at least one lens or a system of lenses (not shown in detail and per se known), to allow focusing of the laser light beam B, arriving from the laser light source 12, on one specific IP entry point belonging to a surface of the selective orientation system 16.

The selective orientation system 16 is a system with mixed optical-mechanical components, capable of receiving a beam of laser light B from at least one IP entry point on one of its surfaces and directing it precisely on at least one target DP entry point of the stationary optical fibers 20.

In particular, the selective orientation system 16 can include a reflection system, such as a mirror system, or a movable, oscillating, rotating or translating mechanism, such as for example a rotating drum or a system of mirrors with variable inclination, or even an optical transmission system, such as for example one or more optical fibers.

In the example illustrated in Figure 1, the selective orientation system 16 receives from an input point IP the laser light beam B generated by the laser light source 12 and exits from the first optical focusing device 14 and sends it to a objective point DP belonging to a surface 22 which connects the input ends of the stationary optical fibers 20.

The second optical focusing device 18, optional, can comprise at least one lens or a system of lenses (not shown in detail and per se known), to focus the beam of laser light B, arriving from the selective orientation system 16 of laser light 12, on the target point DP at the inlet of the stationary optical fibers 20.

According to an alternative embodiment to that illustrated in Figure 1, the optical focusing device 18 can be omitted. According to this variant, the laser light beam leaving the selective orientation system 16 propagates towards at least one target point belonging to a surface 22 which connects the input ends of the stationary optical fibers 20, and enters the stationary optical fibers 20 without any use of additional optical elements.

In a first embodiment, the selective orientation system 16 can comprise a movable support 26 having a first base or side 26a and a second base or side 26b, opposite. The selective orientation system 16 comprises at least one selection optical fiber 20a, having a respective input end IE1 positioned on the first base 26a of the mobile support 26 so as to receive the laser light beam B exiting from the first optical focusing device 14 , and a respective output end OE1 positioned on the second base 26b of the mobile support 26. The movement of the mobile support 26 can be controlled in such a way that the output end OE1 of the selection optical fiber 20a sequentially aligns with each of the respective input ends IE of the plurality of stationary optical fibers 20. In this way, the movement of the mobile support 26 allows the position of the target point DP to be varied at will, orienting the laser light beam B, so as to sequentially illuminate the plurality of stationary optical fibers 20 through their respective input ends IE.

In particular, as shown in Figure 2, the movable support 26 can be mounted in such a way as to rotate around its axis z1, and the selection optical fiber 20a can be mounted so that its input end IE1 lies on the axis of rotation z1, in this example at the center of the first base 26a of the mobile support 26, and its outlet end OE1 lies in an off-center position with respect to the axis z1 on the second base 26b of the mobile support 26. In this way, during the rotation of the movable support 26, the output end OE1 of the selection optical fiber 20a sequentially aligns with each of the respective input ends IE of the plurality of stationary optical fibers 20.

In a further embodiment (not shown), the selective orientation device 16 can comprise more than one selection optical fiber 20a, for example two selection optical fibers 20a. In such further embodiments, the input ends IE1 of each selection optical fiber 20a are positioned on the first base surface 26a of the mobile support 26 and receive a laser light beam B from a respective laser light source 12, and the output ends OE1 of each selection optical fiber 20a can be positioned on the second base surface 26b of the mobile support 26 in such a way as to be angularly equidistant on the same circumference centered on the longitudinal axis z1 of the mobile support 26. Alternatively , the output ends OE1 of the two or more selection optical fibers 20a can be arranged at different radial distances from the longitudinal axis z1.

In a further embodiment, the selective orientation device 16 can oscillate along a plane or translate along a line, or perform a combined motion between the previous ones, as a function of the spatial distribution of the input ends of the stationary optical fibers 20.

In the example of Figures 1 and 2, in which the selective orientation device 16 performs a rotation around the axis z1, the beam of laser light B exiting from the end OE1 of the one or more selection optical fibers 20a describes a cylinder or a cone, depending on the orientation of the output portions OE1, whereby the input ends of the stationary optical fibers 20 are arranged in a circular configuration.

According to another embodiment (not shown), the input ends of the stationary optical fibers 20 can be arranged according to a linear configuration, and consequently the movement of the selective orientation device 16 is controlled in an oscillating or translating way to bring the position of the target point DP of the laser light beam B to strike the input ends IE of the stationary optical fibers 20 according to a predetermined sequence.

In another embodiment, the selective orientation system 16 may comprise a rotating mirror system 16.

The rotating mirror system 16, according to an embodiment shown in Figures 3 and 4, comprises an orientable support 28, having a plurality of lateral support surfaces 30. At least one reflecting surface 32 is placed on the lateral support surfaces 30. orientable support 28 can rotate around its longitudinal axis z2. In this way, during the rotation of the support 28, the angle at which the laser light beam B hits the reflecting surface 32 changes. Consequently, the laser beam reflected from the reflecting surface 32 hits the input ends IE of the plurality of fibers stationary optics 20 in a sequential manner.

The adjustable support 28 can have a single reflective surface 32 and be moved in a controlled and coordinated manner with the emission of the laser light beam B from the source 12 to illuminate the input ends of the stationary optical fibers according to a predetermined or programmable sequence.

In the particular embodiment illustrated in figures 3 and 4, the orientable support 28 may have the shape of a right prism with a polygonal base, with lateral support surfaces 30 each provided with a reflecting surface 32 parallel to the longitudinal axis z2. Alternatively, the adjustable support 28 can have the shape of a truncated pyramid with a polygonal base, so that the lateral support surfaces 30 are not parallel to the longitudinal axis z2.

In a further embodiment (illustrated in Figure 5), the selective orientation device 16 can comprise a rotating block provided with two optically facing reflecting surfaces, which comprise a flat reflecting surface 17a and a reflecting surface with a parabolic profile 17b. The rotating block allows you to sequentially direct the laser beam inside the stationary optical fibers. The reflecting surface with parabolic profile 17b allows to focus the laser beam inside the stationary optical fibers, obtaining a good coupling efficiency. An optical fiber 19 can be provided to convey and guide the LASER B radiation towards the selective orientation device 16.

In a further embodiment (illustrated in Figures 6 and 7), the selective orientation device 16 can comprise a galvanometric head 34, capable of deflecting the laser light beam B in two directions, and of scanning the input ends IE of the plurality of stationary optical fibers 20 desired. Galvanometric heads and their operating modes are known in the art and therefore will not be described in detail here. In particular, the galvanometric head 34 can sequentially direct the laser light beam B on different input ends IE of the stationary optical fibers 20, following a predetermined pattern, for example programmed.

The stationary optical fibers 20 can have their respective input ends IE constrained to a connecting surface 22, while the respective output ends OE can be constrained to a light guide element 24. In particular, the perimeter described by the input ends IE of the fibers stationary optics 20 on the connecting surface 22 can be predefined in a manner concordant with the selective orientation system 16. In fact, the input ends IE of the stationary optical fibers 20 can be arranged, for example, in a circle, along a polygon, along a curve , along a straight line or in the form of a matrix.

The light guide element 24, per se known, can comprise a metal block that forms a trench 36 passing through with reflecting and facing walls. The trench 36 can extend along a profile to be welded, and is of such shape as to concentrate the laser light beam B exiting from the output ends OE of the plurality of stationary optical fibers 20 along the perimeter of the profile to be welded.

Similarly to the perimeter described by the input ends IE of the stationary optical fibers 20, the perimeter described by the output ends OE of the stationary optical fibers 20 on the light guide element 24 follows the shape of the trench 36.

In further embodiments, the number of components of the laser welding equipment according to the present invention can vary. In particular, it is possible to use a plurality of variously displaced laser light sources 12, although the present invention advantageously allows to reduce the number of laser sources to a minimum. Similarly, a plurality of first optical focusing devices 14 and optionally second optical focusing devices 18, stationary optical fibers 20 and selection optical fibers 20a, selective orientation systems 16 and light guide elements 24 can be provided.

The operation of an embodiment of the present invention will now be described, as illustrated in Figures 1 and 2.

A beam of laser light B is generated by the laser light source 12 and sent, after focusing through the first optical focusing device 14, to the entry point IP on the first surface 26a of the mobile support 26. In this point the end is located. input IE1 of the selection optical fiber 20a. The beam of laser light B propagates in the selection optical fiber 20a from its input end IE1, and is conducted up to the output end OE1. At the same time, the movable support 26 rotates around its axis z1. In this way, the output end OE1 is sequentially aligned from time to time with each of the input ends IE of the respective plurality of stationary optical fibers 20. Consequently, the laser light beam B hits each of the respective IE input end. From here on, the laser light beam B is transported by the selectively struck stationary optical fiber 20 to its respective output end OE. The beam of laser light B then enters the trench 36 of the light guide element 24, and is concentrated each time on a restricted area of the profile to be welded, in such a way as to locally heat the plastic material and weld it. The width of the focusing zone is variable depending on the optical characteristics of the beam and of the light guide or trench 36.

Instead, the operation of a further embodiment of the present invention is described below, as illustrated in Figures 3 and 4.

A beam of laser light B is generated by the laser light source 12 and sent, after focusing through the first optical focusing device 14, to the entry point IP on a lateral surface 30 of the orientable support 28. A surface is placed on this surface reflector 32, which reflects the beam of laser light B, as a function of the angle of incidence of the same on the reflecting surface 32. The beam of laser light B, once reflected by the reflecting surface 32, is therefore focused by the second optical focusing device 18. At the same time, the orientable support 28 rotates around its longitudinal axis z2. In this way, the beam of laser light B hits the reflecting surface 32 with a varying angle of incidence, and is consequently reflected towards a different point. Thus, the laser light beam B hits sequentially each time each of the input ends IE of the respective plurality of stationary optical fibers 20. From here on, the laser light beam B is transported by the selectively struck stationary optical fiber 20 until at its respective OE outlet end. The beam of laser light B then enters the trench 36 of the light guide element 24, and is concentrated each time on an area of the profile to be welded, in such a way as to locally heat the plastic material and weld it. The second optical focusing system 18, optional for the embodiment illustrated in Figures 1 and 2, is preferably present in the embodiment of Figures 3 and 4.

In one embodiment, the laser light source 12 can be turned off when the selective orienting device 16 is in a configuration whereby no laser light beam B can reach the trench 36, and can be turned on again when the selective orienting device 16 is in a configuration whereby at least one laser light beam B can reach one of the stationary optical fibers 20. In particular, the laser light source 12 can be switched off in the time period in which the selective orientation device 16 is in a configuration whereby the laser light beam B is reflected or conveyed to a point which is not on an input end IE of any of the stationary optical fibers 20.

In a further embodiment, the power of the laser light source 12 is adjustable in intensity, between a minimum value and a maximum value, according to a predetermined or programmable law, so as to be able to obtain a better energy yield and adjust the intensity. of the radiation of the laser light beam B as a function of the demand for the materials to be welded.

An apparatus for laser welding according to the present invention and the laser welding process relating thereto have numerous advantages with respect to the prior known art. In fact, thanks to the use of a selective orientation device, it is possible to reduce the number of laser light sources to a minimum of one, resulting in savings both on the cost of installing the equipment and on the cost of maintaining it.

Furthermore, the lower number of laser light sources leads to a reduction in the demand for electrical power for the implementation of the procedure, with consequent savings on the cost of operating the equipment.

The possible possibility of adjusting the power or even activating the laser light source only in a pulsed manner contributes to a further reduction in the operating costs.

Various aspects and embodiments of the laser welding equipment and process have been described. It is understood that each embodiment can be combined with any other embodiment. Furthermore, without prejudice to the principle of the invention, the embodiments and construction details may be widely varied with respect to what has been described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention as defined. in the attached claims.

Claims (14)

CLAIMS 1. Apparatus for laser welding (10) of plastics, comprising: at least one laser light source (12) capable of emitting a laser light beam (B), a plurality of stationary optical fibers (20) each having an input end (IE) and an output end (OE), in which the input ends (IE) are adapted to receive the laser light beam (B) emitted by said source and the output ends (OE) are positioned so as to convey the laser light beam (B) towards one or more bodies of plastic material to be welded; characterized in that it also comprises a selective orientation system (16) of the laser light beam (B), interposed between the laser light source (12) and the plurality of stationary optical fibers (20), suitable for sequentially sending the beam of laser light (B) coming from the laser light source (12) on the input end (IE) of the plurality of stationary optical fibers (20). Laser welding equipment according to claim 1, wherein the selective orientation system (16) comprises: a movable support (26) having a first side (26a) and a second side (26b) opposite the first, and at least one selection optical fiber (20a) mounted on the movable support (26) and having an inlet end (IE1) positioned on the first side (26a) of the mobile support (26), so that the inlet end (IE1) can receive the laser light beam (B) exiting the light source laser (12), ed an output end (OE1) positioned on the second side (26b) of the mobile support (26), in such a way that during the movement of the mobile support (26), the output end (OE1) of the selection optical fiber ( 20a) directs the laser light beam (B) sequentially to the input end (IE) of the plurality of stationary optical fibers (20). 3. Laser welding equipment according to claim 2, in which the movable support (26) is rotatable around an axis (z1), and in which the output end (OE1) of the selection optical fiber (20a) is decentralized with respect to the axis (z1), so that during the rotation of the mobile support (26) the output end (OE1) of the selection optical fiber (20a) directs the laser light beam (B) sequentially on each of the respective input ends (IE) of the plurality of stationary optical fibers (20). 4. Laser welding equipment according to claim 2 or 3, comprising at least two selection optical fibers (20a) and a corresponding number of laser light sources (12), where the input end (IE1) of each optical fiber of selection (20a) is positioned on the first side (26a) of the mobile support (26) and receives a laser light beam (B) from a respective laser light source (12), and the output ends (OE1) of each fiber selection optics (20a) are positioned on the second side (26b) of the mobile support (26) at different radial distances from the longitudinal axis (z1). 5. Laser welding apparatus according to claim 1, wherein the selective orienting device (16) is mounted in an oscillatable manner along a plane or is mounted in a translatable manner along at least one direction, or is mounted in such a way as to be able to perform a motion combined oscillation and translation. Laser welding apparatus according to claim 1, wherein the selective orienting device (16) comprises a reflective system (16), having a pivotable support (28) in a controlled manner and at least one reflective surface (32), mounted on the orientable support, adapted to receive the laser light beam (B) coming from the laser light source (12) and to reflect it on the input ends (IE) of the plurality of stationary optical fibers (20) according to a predetermined or programmable sequence. Laser welding apparatus according to claim 6, wherein the pivotable support (28) is rotatable about an axis of rotation (z2) and the reflective system (16) comprises a plurality of reflective surfaces (32) which are mounted on the orientable support (28) in different angular positions around the rotation axis (z2) and each have a predetermined or adjustable orientation with respect to the rotation axis (z2). Laser welding equipment according to claim 7, wherein the orientable support (28) has the shape of a prism. Laser welding equipment according to claim 7, wherein the swiveling support (28) has the shape of a truncated pyramid, whereby the at least one reflecting surface (32) is not parallel to the axis of rotation (z2) of the support swiveling (28). Laser welding apparatus according to claim 1, wherein the selective orientation system (16) comprises a block rotating around a given axis (z1) and having a flat reflecting surface (17a) and a parabolic profile reflecting surface ( 17b), facing the flat reflecting surface (17a) and able to focus the laser light towards the stationary optical fibers (20). 11. Laser welding equipment according to claim 1, wherein the selective orientation system (16) comprises a galvanometric head (34) adapted to deflect the laser light beam (B) in two directions and scan the input ends (IE ) of the plurality of stationary optical fibers (20). 12. Laser welding equipment according to claim 1, wherein the selective orientation system (16) comprises a block rotating around a given axis (z1) and having one or more optical components suitable for directing and focusing the laser light towards stationary optical fibers (20). 13. Laser welding process using a laser welding apparatus (10) according to any one of the preceding claims. Laser welding method according to claim 12, wherein the laser light source (12) is pulsed or adjusted in intensity according to a predetermined or programmable law.