IT202000003970A1 - 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. Pi? in particular, the invention lends itself to being applied also to TTIr welding, that is the welding through infrared welding (? Through-Transmission Infrared welding?) of two plastic components, one of which is transparent, and it will be? detailed here referring to this particular application case, which? given purely as an example and not? to be understood in no way as limiting the scope of application of the present invention. For example, such a production technique? 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 beams of laser light and leads 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 reflective and tapered light guide in a convergent manner in such a way as to concentrate the laser light beam, and make it the most? homogeneous as possible.

Summary of the invention

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

This and other objects are fully achieved according to the present invention thanks to a laser welding apparatus having the characteristics defined in the attached claim 1 and to a laser welding process having the characteristics defined in the attached claim 4.

Advantageous embodiments of the invention are specified in the dependent claims.

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 laser light. of stationary optical fibers each having one end? entrance and one end? exit, in which the ends? input are suitable to receive the beam of laser light and the ends? output are positioned so as to convey the beam of laser light towards one or more? plastic bodies to be welded. The equipment also comprises a system of selective orientation of the laser light beam, interposed between the laser light source and the plurality of of stationary optical fibers, suitable to sequentially send the laser light beam coming from the laser light source on the extremities? input of stationary optical fibers. The selective orientation system includes a galvanometric head designed to deflect the laser light beam in two directions and scan the ends? of entry of the plurality? of stationary optical fibers.

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 features and advantages of the present invention will be more apparent. clearly from the detailed description that follows, given purely by way of non-limiting example, with reference to the attached drawings, in which:

figure 1? a two-dimensional diagram of a laser welding apparatus not forming part of the present invention;

figure 2? an exploded perspective view of the laser welding apparatus of figure 1; figure 3? a two-dimensional diagram of a laser welding apparatus not forming part of the present invention;

figure 4? an exploded perspective view of the laser welding apparatus of figure 3; figure 5? a two-dimensional diagram of a laser welding apparatus not forming part 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 an embodiment of the present invention.

Detailed description

With initial reference to Figures 1 and 2, a laser welding apparatus 10 comprises at least one laser light source 12, at least a first optical focusing device 14, a selective orientation system 16 of the laser light beam, a second optical device of focus 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 adapted to generate 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? generation of the laser light beam does not? limiting for the purposes of implementing the present invention.

In one embodiment, the laser light source 12 may be be used continuously. According to an alternative embodiment, the laser light source 12 can be switched off and on 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 known per se), to allow focusing of the laser light beam B, arriving from the laser light source 12, on a specific IP entry point belonging to a surface of the selective orientation system 16.

The selective orientation system 16? 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 with precision to at least one target entry point DP 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 a rotating drum or a variable inclination mirror system, or an optical transmission system, such as a 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 that connects the ends? stationary optical fibers input 20.

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

According to an alternative embodiment to the one 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 ends. input of the stationary optical fibers 20, and enters the stationary optical fibers 20 without any aid of further optical elements.

In a first embodiment, the selective orientation system 16 can? comprising 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 end. input 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 end? outlet 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 extremity? output OE1 of the selection optical fiber 20a sequentially aligns with each of the respective ends? IE input of the plurality? of stationary optical fibers 20. In this way, the movement of the mobile support 26 allows the position of the objective point DP to be varied at will, orienting the beam of laser light B, so as to sequentially illuminate the plurality of optical fibers. of stationary optical fibers 20 through their respective ends? IE input.

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 end? input 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 extremity? outlet OE1 lies in an off-center position with respect to axis z1 on the second base 26b of the mobile support 26. In this way, during the rotation of the mobile support 26, the end? output OE1 of the selection optical fiber 20a sequentially aligns with each of the respective ends? IE input of the plurality? of stationary optical fibers 20.

In a further embodiment (not shown), the selective orienting device 16 can? understand more? of a selection optical fiber 20a, for example two selection optical fibers 20a. In such further embodiments, the ends? inputs IE1 of each selection optical fiber 20a are positioned on the first base surface 26a of the mobile support 26 and receive a beam of laser light B from a respective laser light source 12, and the ends? output 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 ends? output OE1 of the two or more? selection optical fibers 20a can be arranged at radial distances differentiated from the longitudinal axis z1.

In a further embodiment, the selective orienting device 16 can? oscillate along a plane or translate along a line, or perform a combined motion between the previous ones, depending on the spatial distribution of the extremities? stationary optical fibers input 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 extremity? OE1 of one or more? selection optical fibers 20a describes a cylinder or a cone, depending on the orientation of the outlet portions OE1, whereby the ends? of the stationary optical fibers 20 are arranged in a circular configuration.

According to another embodiment (not shown), the 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? controlled in an oscillating or translating way to bring the position of the target point DP of the laser light beam B to affect the extremities? input IE of the stationary optical fibers 20 according to a predetermined sequence.

In another embodiment, the selective orientation system 16 can be include 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 elements. of lateral support surfaces 30. On the lateral support surfaces 30? placed at least one reflective surface 32. The adjustable 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 ends. IE input of the plurality? of stationary optical fibers 20 in a sequential manner.

The adjustable support 28 can? have a single reflecting 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 ends? input 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 can? have a shape of a right prism with a polygonal base, with lateral support surfaces 30 each having 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 orienting device 16 can? comprising 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 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. Pu? an optical fiber 19 is provided to convey and guide the LASER B radiation towards the selective orientation device 16.

According to the invention (Figures 6 and 7), the selective orientation device 16 comprises a galvanometric head 34, capable of deflecting the laser light beam B in two directions, and of scanning the extremities. IE input of the plurality? of 20 stationary optical fibers desired. The galvanometric heads and their modalities? of operation are known in the art and therefore will not be described in detail here. In particular, the galvanometric head 34 can? sequentially direct the beam of laser light B on different ends? input IE of the stationary optical fibers 20, following a predetermined pattern, for example programmed.

The stationary optical fibers 20 may have the respective ends? input IE constrained to a connection surface 22, while the respective ends? output OE can be linked to a light guide element 24. In particular, the perimeter described by the ends? input IE of the stationary optical fibers 20 on the connecting surface 22 pu? be predefined in accordance with the selective orientation system 16. In fact, the extremities? inputs 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, by itself? known, can? comprising a metal block forming a through trench 36 with reflecting and facing walls.

Trench 36 can? extend along a profile to be welded, and d? of such shape as to concentrate the beam of laser light B exiting from the extremities? OE output of the plurality? of stationary optical fibers 20 along the perimeter of the profile to be welded.

Similarly to the perimeter described by the ends? input IE of the stationary optical fibers 20, the perimeter described by the ends? output 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 apparatus according to the present invention can be increased. to vary. In particular, ? can 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, can a plurality be arranged? 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.

Sar? now described the operation of the apparatus illustrated in Figures 1 and 2.

A laser light beam B is generated by the laser light source 12 and sent, after focusing through the first optical focusing device 14, to the IP entry point on the first surface 26a of the mobile support 26. At this point? localized the extremity? input IE1 of the selection optical fiber 20a. The beam of laser light B propagates in the selection optical fiber 20a from its extremity. input IE1, and is conducted to the? end? output OE1. At the same time, the movable support 26 rotates around its axis z1. In this way, the end? output OE1 is sequentially aligned from time to time with each of the extremities? IE input of the respective plurality? of stationary optical fibers 20. Consequently, the beam of laser light B strikes from time to time each of the respective ends? IE input. From here on, the beam of laser light B is transported by the selectively struck stationary optical fiber 20 up to its respective extremity. OE output. 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 focus area? variable depending on the optical characteristics of the beam and of the light guide or trench 36.

Instead, the operation of the apparatus illustrated in Figures 3 and 4 is described below.

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. On this surface? a reflecting surface 32 is placed, 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 device focusing optic 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. Therefore, the beam of laser light B hits each of the extremities sequentially from time to time. IE input 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 up to its respective extremity. output OE. 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 FIGS. 1 and 2,? preferably present in the embodiment of figures 3 and 4.

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

In a further embodiment, the power of the laser light source 12? adjustable in intensity, between a minimum and a maximum value, according to a predetermined or programmable law, in order 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, up to a minimum of one, the number of laser light sources, with consequent savings both on the cost of installing the equipment and on the cost of maintaining it.

Furthermore, the smaller number of laser light sources leads to a reduction in the electrical power requirement for carrying out the process, with consequent savings on the operating cost of the equipment.

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

Various aspects and embodiments of the laser welding apparatus and process have been described. It is meant that each embodiment can? be combined with any other embodiment. Furthermore, without prejudice to the principle of the invention, the embodiments and the details of construction can 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 (5)

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 one end input (IE) and one extremity? exit (OE), in which the ends? input (IE) are suitable for receiving the beam of laser light (B) emitted by said source and the ends? output (OE) are positioned so as to convey the beam of laser light (B) towards one or more? bodies of plastic material to be welded; a selective orientation system (16) of the laser light beam (B), interposed between the laser light source (12) and the plurality of of stationary optical fibers (20), adapted to sequentially send the laser light beam (B) coming from the laser light source (12) on the extremities? input (IE) of the plurality? stationary optical fibers (20); characterized by the fact that the selective orientation system (16) includes a galvanometric head (34) able to deflect the laser light beam (B) on two directions and scan the ends? input (IE) of the plurality? of stationary optical fibers (20). 2. Laser welding equipment according to claim 1, wherein the galvanometric head (34) sequentially directs the laser light beam (B) on different ends. input IE of the stationary optical fibers (20), following a predetermined pattern, for example programmed. 3. Laser welding equipment according to claim 1 or 2, wherein the stationary optical fibers (20) have respective ends. entrance (IE) constrained to a connection surface (22), while the respective ends? outlet (OE) are constrained to a light guide element (24). 4. Laser welding process using a laser welding apparatus (10) according to any one of the preceding claims. 5. Laser welding method according to claim 4, wherein the laser light source (12) is pulsed or adjusted in intensity. according to a predetermined or programmable law.