CONNECTION METHOD USING A LASER TRANSMISSION BONDING TECHNOLOGY, AN APPARATUS FOR BONDING AS WELL AS A PART MADE OF A LASER TRANSMISSIVE BONDED FIRST PLASTIC PART AND A SECOND PLASTIC PART

Abstract

A method for connecting first and second plastic parts by a laser transmission bonding wherein the first plastic part absorbs laser light and the second plastic part is made of transparent plastic. The method includes the following steps: positioning the first plastic part in a first tool, positioning the second plastic part in a second tool so that the first plastic part and the second plastic part are spaced from each other thereby preventing mutual heat exchange between the parts, directing laser light through the second plastic part onto a connection zone of the first plastic part whereby the first plastic part is heated at least within the connection zone, after heating the first plastic part, moving the second plastic part into contact with the first plastic part, so that the second plastic part is firmly bonded to the first plastic part.

Claims

1. A connection method for connecting a first plastic part and a second plastic part to each other by means of a laser transmission bonding technology wherein the first plastic part absorbs laser light and the second plastic part is made of transparent plastic, wherein the connection method comprises the following steps: S1 positioning of the first plastic part in a first tool, S2 positioning of the second plastic part in a second tool so that the first plastic part retained by the first tool and the second plastic part retained by the second tool are spaced apart from each other thereby preventing mutual heat exchange between the first and the second plastic parts, S3 directing laser light through the second plastic part onto a connection zone of the first plastic part whereby the first plastic part is heated at least within the connection zone, S4 after heating the first plastic part, moving the second plastic part into contact with the first plastic part, so that the second plastic part is firmly bonded to the first plastic part.

2. The connection method according to claim 1, comprising the further step: switching off the laser light after heating up the first plastic part and pushing the second plastic part against the first plastic part while no light enters the first plastic part.

3. The connection method according to claim 1, comprising the further step: pushing the second plastic part against the first plastic part while laser light is directed through the second plastic part onto the connection zone at the same time.

4. The connection method according to claim 1, wherein the laser light is directed to the connection zone in at least two stages in step S3 in which (a) a first stage has a laser light intensity so that the first plastic part is heated up and/or plasticized to support a shape adaptation of the first plastic part for tolerance compensation, and (b) the laser light intensity is adapted in a second stage so that the material of the first plastic part is melted within the connection zone of the first plastic part.

5. The connection method according to claim 1, in which the first plastic part is made of thermoplastic material.

6. The connection method according to claim 1, in which the second plastic part is a plastic film having a thickness in the range of 10 .Math.m to 10 mm.

7. The connection method according to claim 2, wherein the laser light is directed to the connection zone in at least two stages in step S3 in which (a) a first stage has a laser light intensity so that the first plastic part is heated up and/or plasticized to support a shape adaptation of the first plastic part for tolerance compensation, and (b) the laser light intensity is adapted in a second stage so that the material of the first plastic part is melted within the connection zone of the first plastic part.

8. The connection method according to claim 2, in which the first plastic part is made of thermoplastic material.

9. The connection method according to claim 2, in which the second plastic part is a plastic film having a thickness in the range of 10 .Math.m to 10 mm.

10. The connection method according to claim 3, wherein the laser light is directed to the connection zone in at least two stages in step S3 in which (a) a first stage has a laser light intensity so that the first plastic part is heated up and/or plasticized to support a shape adaptation of the first plastic part for tolerance compensation, and (b) the laser light intensity is adapted in a second stage so that the material of the first plastic part is melted within the connection zone of the first plastic part.

11. The connection method according to claim 3, in which the first plastic part is made of thermoplastic material.

12. The connection method according to claim 3, in which the second plastic part is a plastic film having a thickness in the range of 10 .Math.m to 10 mm.

13. The connection method according to claim 4, in which the first plastic part is made of thermoplastic material.

14. The connection method according to claim 4, in which the second plastic part is a plastic film having a thickness in the range of 10 .Math.m to 10 mm.

15. The connection method according to claim 5, in which the second plastic part is a plastic film having a thickness in the range of 10 .Math.m to 10 mm.

16. An apparatus for connecting a first plastic part and at least one second plastic part by means of laser transmission bonding technology by means of a connection method according to claim 1, which has the following features: a first tool adapted for retaining the first plastic part made of light absorbing material, a second tool adapted for retaining a second plastic part being a plastic film and having a thickness in the range of about 10 .Math.m to 10 mm, a laser light source adapted to direct laser light through the second plastic part onto the first plastic part so that the first plastic part is heated by the laser light and a moving construction adapted to move the first and the second tool relative to each other to push the second plastic part against the heated first plastic part.

17. The apparatus according to claim 16, in which the laser light source can be switched on and off in a defined manner so that the first and the second plastic parts are pushed against each other with laser light entering the second plastic part at the same time or with no laser light entering the second plastic part at the same time.

18. A part made of a first plastic part and at least one second plastic part wherein the second plastic part is a plastic film having a thickness in the range of 10 .Math.m to 10 mm and the first plastic part and the at least one second plastic part are connected by means of a laser transmission bonding technology by means of a connection method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The embodiments of the present disclosure are described in detail with respect to the accompanying drawing. It shows:

[0035] FIG. 1 an embodiment of the apparatus for laser transmission bonding of a first and a second plastic part in which the first end and the second plastic parts are spaced apart to each other,

[0036] FIG. 2 the apparatus of FIG. 1 in which the first and the second plastic parts are in bonding contact by pushing the first and the second plastic part against each other,

[0037] FIGS. 3a and 3b are embodiments of the apparatus for laser transmission bonding of a first and a second plastic part in which the lower tool bearing the absorptive part may be laterally movable between a heating position and a joining position with a transparent second part, and

[0038] FIG. 4 a flowchart of an embodiment of the connection method for connecting the first and the second plastic part by laser transmission bonding to each other.

DETAILED DESCRIPTION

[0039] FIG. 1 shows an embodiment of an apparatus 1 for connecting a first plastic part A and at least one second plastic part B. The first plastic part A is adapted to absorb light, in particular laser light. The absorbed laser light is transformed into thermal energy within the plastic material of the first plastic part A. Therefore, the first plastic part A is also denoted as an absorber.

[0040] Typical material examples for plastic laser light absorbing material are thermoplastic materials or the like adapted for laser transmission welding.

[0041] The second plastic part B may be made of a transparent plastic material. The transparency of the second plastic part is used to direct laser light through the second plastic part B onto the first absorbing plastic part A.

[0042] According to an embodiment of the second plastic part B, it may be made of a plastic film. The plastic film may have a thickness in the range of 10 .Math.m to 10 mm.

[0043] According to a further embodiment of the material choice of the second plastic part B, it may be made of a non-transparent plastic film. The non-transparent plastic film B may have a thickness in the range of 10 .Math.m to 10 mm.

[0044] Furthermore, the above mentioned transparent film may have different physical properties. According to one alternative, the film may constitute a membrane. A membrane allows for a transport of material and/or energy through the membrane or through individual parts of the membrane. Additionally, the membrane is used to separate certain parts or substances from each other. According to another embodiment of the film, the membrane may be adapted to transform or absorb or transfer energy or forces acting onto the film or membrane.

[0045] If a non-transparent plastic film B is used as the second plastic part, the first plastic part A will be exposed to laser light with no second non-transparent plastic part positioned on top of the first plastic part A or within the laser light beam directed onto the absorber A. Accordingly, thermal heat will be stored in the first plastic part A in a similar way as in a laser transmission welding procedure. After the laser light has heated the first plastic part A in a preferred connection zone 50, the non-transparent film may be used as the second plastic part B will be pushed against the first plastic part A. The fused plastic material of the connection zone 50 in the first plastic part A may bond to the non-transparent plastic film to form a connection between the first A and the second plastic part B. To this end, the fused material of the connection zone 50 of the first plastic part A solidifies in close contact to the second plastic part B.

[0046] As shown in FIGS. 1 and 2, the first plastic part A is retained by a first tool 10. Within the first tool 10, the first plastic part A is clamped, mounted, held by vacuum or releasably fixed according to known techniques.

[0047] The second plastic part B is retained by a second tool 20. According to an embodiment of the second tool 20, a vacuum holder may be provided holding the second plastic part B. To this end, the second tool 20 may have several suction heads 22. The suction heads 22 generate a vacuum on a respective opening 24. The second plastic part B is placed over this opening 24 and blocks the opening 24. Thereby, the second plastic part B is releasably retained by the second tool 20.

[0048] Further, a laser light source 30 is mounted on the second tool 20. The laser light source 30 denotes any qualified light construction to guide light to the second tool 20. Thus, the laser light source 30 may comprise a fiber bundle, a laser bank (not shown), at least one laser diode of brick is (not shown), individual light guides or the like.

[0049] The laser light source 30 may provide laser light 32 which may be directed through a waveguide 40 to the first plastic part A. The laser light 32 may be focused by the waveguide 40 to the connection zone 50 of the first plastic part A or absorber A.

[0050] After the first plastic part A is positioned in and retained by the first tool 10, and the second plastic part B is positioned in and retained by the second tool 20 (see steps S1 and S2, FIG. 3), the first part A and the second part B are positioned in a certain distance d to each other (see FIG. 1). The distance d may be large enough to prevent heat transfer between both plastic parts A, B. In spite of the distance d, the plastic retained parts A, B are oriented in such a way to each other that the laser light 32 exiting the waveguide 40 may meet the connection zone 50 of the first plastic part A. Due to the laser light 32 absorbed by the plastic material within the connection zone 50, the material of the connection zone 50 is heated or fused dependent on the intensity of the laser light 32. It has to be noted that the second plastic part B is a transparent plastic part B or a transparent or a non-transparent plastic film B.

[0051] The heated material within the connection zone 50, either it is fused or softened, is thereby enabled for shape adaptation of the first plastic part A. The shape adaptation or tolerance compensation will be used when the first plastic part A and the second plastic part B are moved into contact with each other. The first plastic part A and the second plastic part B may be pushed against each other until the material within the connection zone 50 has solidified. (Step S4).

[0052] The material of the first plastic part A within the connection zone 50 may be heated while the first plastic part A and the second plastic part B are arranged at the distance d from each other. Before reducing the distance d and pushing the first plastic part A and the second plastic part B against each other, the laser light 32 heating the material in the connection zone 50 is switched off. The plastic parts A, B are pushed against each other and held in close contact so that the first plastic part A bonds to the second plastic part B within the connection zone 50.

[0053] According to another embodiment, the laser light exposure of the connection zone 50 may be continued while the first plastic part A and the second plastic part B are pushed against each other. After a certain time of contact between parts A, B the laser light 32 is switched off and the plastic material within the connection zone 50 solidifies. In this bonding alternative, the second plastic part B is transparent.

[0054] For realizing the movement of the first 10 and the second tool 20 relative to each other, electric or pneumatic or hydraulic moving means are provided. Such constructions are generally known in the art.

[0055] According to a further embodiment as exemplarily shown in FIG. 3, the material of the first plastic part A within the connection zone 50 may be heated by the laser light 32 while the first plastic part A is arranged below the laser light source, e.g. the exit end of the waveguide 40. The second plastic part B to be connected with the heated plastic part A is arranged at a remote location (see FIG. 3a). This arrangement allows for an individual preparation of the parts to be connected. This may be helpful, the parts A and B require different environmental conditions like temperature, humidity, radiation the like. Furthermore, the part B may be protected from ambient or corrosive impacts while heating part A.

[0056] After part A was sufficiently heated within the connection zone 50, the heated part A is moved relative to part B. The relative movement of the parts A and B is indicated by the motion arrow in FIG. 3b). The movement either of part A (as shown), or of part A and B, or of part B only is carried out by known driving techniques, e.g. electric, pneumatic or hydraulic drives. Furthermore, the movement of the parts A, B is realized on a linear or a curvilinear path or a combination thereof.

[0057] After the above part movement is completed, part A and part B are arranged in a joining position as shown in FIG. 3c). In this arrangement, the second part B may be retained by a vacuum source or the like at an upper tool 60. For joining parts A and B together, the parts A and B are relatively moved to contact each other in the connection zone 50. This movement may be carried out by the upper tool 60. During contact of parts A and B within the connection zone 50, the parts A and B are joined or bonded to each other.

[0058] The thermal energy stored in the connection zone 50 is sufficient to create a reliable connection or bonding between the first and the second plastic parts A, B.

[0059] According to a further embodiment, the second plastic part B is a plastic film. The plastic film has a thickness in the range of 10 .Math.m to 10 mm.

[0060] Furthermore, the plastic film may be made of a thermoplastic material.

[0061] Dependent on the light intensity used to expose the connection zone 50, the plastic material of the first plastic part A is heated or plasticized, or it is fused within the connection zone 50. Based on the laser light treatment, the thermal energy stored within the material of the connection zone 50 is sufficient for bonding the plastic film B to the first plastic part A. In at least some implementations, it is preferred to switch of the laser light 32 before contacting and bonding the first plastic part A and the plastic film B.

[0062] Based on the above bonding method, a bonded part is produced from a first plastic part A and a second plastic part B, which may be a plastic film as defined above.