METHOD FOR CONNECTING WORKPIECES, AND ASSEMBLED OBJECT

Abstract

Two workpieces 30, 40 are joined by means of ultrasound. First, a workpiece 30 with at least one energy direction sensor 31 and a second workpiece 40 are provided. The workpieces are brought into contact with each other in such a way that the energy direction sensor 31 comes into contact with a first surface 41 of the second workpiece 40. Ultrasonic vibrations are then introduced into one of the workpieces 40 via a working surface 11 of a sonotrode 10. A sonotrode 10 is used, which has a contour with contact lines 12 on the working surface 11. The sonotrode 10 is positioned with respect to the first workpiece 30 in such a way that the contact lines 12 run transversely to the energy direction generator 31.

Claims

1.-25. (canceled)

26. A method for joining workpieces by means of ultrasound, comprising the steps of: providing a first workpiece with at least one energy direction generator; providing a second workpiece; bringing the first and the second workpiece into contact in such a way that the energy direction generator comes into contact with a first surface of the second workpiece; and introducing ultrasonic vibrations into one of the workpieces via a working surface of a sonotrode, wherein a sonotrode is used which has a contour with contact lines on the working surface, and wherein the sonotrode is positioned with respect to the first workpiece in such a way that the contact lines run transversely to the energy direction generator.

27. The method according to claim 26, wherein the working surface of the sonotrode is brought into contact with a second surface of the second workpiece opposite the first surface.

28. The method according to claim 26, wherein a sonotrode is used in which the working surface is circular and the contact lines are arranged in a star shape on the working surface.

29. The method according to claim 28, wherein a sonotrode is used in which the contact lines are formed on a rib between two depressions.

30. The method according to claim 29, wherein the cross-section of the rib in a plane perpendicular to the radial direction r of a welding area remains constant in the radial direction.

31. The method according to claim 29, wherein the rib is V-shaped in cross-section in a plane perpendicular to the radial direction and/or wherein the distance H between the contact lines and a base of the recesses is 0.1 mm to 1.5 mm.

32. The method according to claim 26, wherein the contact lines have a distance a of 0.1 mm to 2.5 mm from one another.

33. The method according to claim 26, wherein the energy direction generator is designed as a circumferential elevation and/or wherein the energy direction generator is in particular trapezoidal in cross-section and has a con-tact surface for connection to the second workpiece, the contact surface being designed in particular to be flat and having a width and the energy direction generator having a height perpendicular to the contact surface, and the width of the contact surface corresponding at least 5 times the height of the energy direction generator.

34. The method according to claim 26, wherein the contact lines run at an angle β of 90° to the energy direction generator.

35. The method according to claim 26, wherein the ultrasonic vibrations are introduced as torsional vibrations, as longitudinal vibrations or as a combination of torsional and longitudinal vibrations.

36. The method according to claim 26, wherein workpieces of different material are provided as first and second workpieces.

37. The method according to claim 36, wherein the first workpiece consists of HDPE at least in the region of the energy direction transmitter and the second workpiece has LDPE at least on the first surface.

38. The method according to claim 26, wherein the first workpiece is a spout for a packaging and the second workpiece is a packaging material.

39. A method comprising the steps of: providing a first workpiece with at least one energy direction generator; providing a second workpiece; bringing the first and the second workpiece into contact in such a way that the energy direction generator comes into contact, in particular, with a first surface of the second workpiece; and introducing ultrasonic vibrations into one of the workpieces via a working surface of a sonotrode, wherein ultrasonic vibrations are introduced into the first or the second workpiece in the region of the energy direction generator in at least one sound introduction point, and in that, starting from the sound introduction point, melting of the material of at least one of the workpieces takes place as far as a welding zone which is spaced apart from the sound introduction point.

40. The method according to claim 39, wherein the first workpiece is a spout for a packaging and the second workpiece is a packaging material.

41. A composite article having a first and a second workpiece, wherein the first and second workpieces are joined to one another by means of ultrasonic welding, and wherein the first workpiece has an energy direction generator on a side that faces the second workpiece, wherein the article has, on the second workpiece, in a region along the energy direction generator, acoustic introduction impressions which are spaced apart from each other and separated from each other by welding lines and which extend transversely to the energy direction generator.

42. A composite article comprising a first and a second workpiece, wherein the first and the second workpiece are connected to each other by means of ultrasonic welding and wherein the first workpiece has, on a side facing the second workpiece, an energy direction sensor which has, in cross-section, a contact surface for connection to the second workpiece, wherein the contact surface is in particular flat and has a width and the energy direction generator has a height perpendicular to the contact surface, wherein the width of the contact surface is at least 5 times the height of the energy direction generator.

43. The article according to claim 41, wherein the article is a package and the first workpiece is a spout and the second workpiece is a packing material.

44. The article according to claim 16, wherein the first workpiece has a first plastic material and wherein the second workpiece has, on its side facing the first workpiece, a second plastic material which is different from the first plastic material.

45. The article according to claim 41, wherein the second workpiece is a laminate and the sound introduction impressions extend substantially through an uppermost layer of the laminate.

46. A workpiece for the production of a composite article from the workpiece and a second workpiece, wherein the workpiece has, on a side which can face the second workpiece, an energy direction generator which has, in cross-section, a contact surface for connection to the second workpiece, wherein the contact surface is, in particular, flat and has a width and the energy direction generator has a height perpendicular to the contact surface, wherein the width of the contact surface is at least 5 times the height of the energy direction generator.

47. The workpiece according to claim 46, wherein the second workpiece is a spout for a packing.

48. A method for joining workpieces of different material, wherein a first workpiece has a first degree of crystallization at least in the region of an interface facing the second workpiece, a second workpiece has a second degree of crystallization at least in the region of an interface facing the first workpiece, which degree of crystallization is different from the first degree of crystallization, wherein at least one of the workpieces is subjected to torsional vibrations at a sound introduction surface and the workpieces are thereby bonded to one another.

49. The method according to claim 48, wherein a torsional vibration with an amplitude of at least 40 micrometers is introduced in the region of the sound introduction surface.

50. The method according to claim 48, wherein the first degree of crystallization is between 10% and 60% and the second degree of crystallization is between 60% and 90%.

51. The method of claim 50, wherein the first workpiece comprises LDPE at least in the region of the interface with the second workpiece, and wherein the second workpiece comprises HDPE at least in the region of the interface with the first workpiece.

52. A composite article comprising a first and a second workpiece, wherein a first workpiece has a first degree of crystallization at least in the region of an interface facing the second workpiece, a second workpiece has a second degree of crystallization at least in the region of an interface facing the first workpiece, which degree of crystallization is different from the first degree of crystallization, wherein the workpieces are joined to one another by a welded joint between the interfaces produced by means of torsional ultrasonic vibrations.

53. The article of claim 52, wherein the first degree of crystallization is between 10% and 60% and the second degree of crystallization is between 60% and 90%.

54. The article of claim 53, wherein the first workpiece comprises LDPE at least in the region of the interface with the second workpiece and wherein the second workpiece comprises HDPE at least in the region of the interface with the first workpiece.

Description

[0056] The invention is explained in more detail below in embodiment examples and on the basis of the drawings. They show:

[0057] FIG. 1: A perspective view of a sonotrode according to the invention with a holder for workpieces.

[0058] FIG. 2: A side view of the arrangement from FIG. 1 in an exploded view.

[0059] FIG. 3: Perspective view of a sonotrode according to the invention from the working surface.

[0060] FIG. 4: A side view of a sonotrode according to the invention.

[0061] FIG. 5: A cross-section through a sonotrode according to the invention along a longitudinal axis of the sonotrode.

[0062] FIG. 6: A view of the working surface of a sonotrode.

[0063] FIG. 7: An enlarged view of the section A from FIG. 6.

[0064] FIG. 8: An enlarged section of two workpieces, which are exposed to the working surface of a sonotrode in perspective view.

[0065] FIG. 9: A cross-sectional view in a radial plane through a sonotrode according to the invention and workpieces according to the invention.

[0066] FIG. 10: A side view of the working surface of a horn according to the invention in the enlarged section B from FIG. 5.

[0067] FIG. 11: A perspective view of a section of the working surface of a sonotrode.

[0068] FIG. 12: A sectional view of a spout connected to a packing material in a plane perpendicular to an energy direction generator.

[0069] FIG. 13: A sectional view of a spout connected to a packing material along an energy direction generator.

[0070] FIGS. 14a and b: An illustration of an alternative embodiment of an energy direction generator with an alternative shape of a support.

[0071] FIGS. 15a and b: An illustration of the energy direction generator of FIGS. 14a and 14b in perspective form and in cross-section.

[0072] FIGS. 16a and b: A representation of a support and a support surface of an anvil in a first embodiment.

[0073] FIGS. 17a and b: A representation of a receiving surface of an anvil according to a second embodiment, and

[0074] FIG. 18: A graphical representation of the bonding parts for workpieces with the same and with different crystalline parts.

[0075] FIG. 1 shows a sonotrode 10 and a receptacle 18 in perspective view. Between the sonotrode 10 and the receptacle 18 two workpieces in the form of a packaging material foil 40 and a spout (not shown in FIG. 1, see FIG. 2) are shown. The horn 10 and the holder 18 can be moved relative to each other in a manner known per se, so that the workpieces can be clamped between them. For this purpose, the sonotrode can be fixed in a machine frame, which is adjustable with a drive, typically a pneumatic drive or an electromechanical drive.

[0076] The sonotrode 10 is set into ultrasonic vibrations in a manner known per se. For this purpose, an ultrasonic generator and an ultrasonic converter are provided (not shown in FIG. 1), which are known to the person skilled in the art. The sonotrode 10 is set into torsional oscillations in a direction of oscillation S about its longitudinal axis L. The ultrasonic generator and the ultrasonic converter are known to those skilled in the art. In addition, longitudinal oscillations in longitudinal direction L can be present.

[0077] In operation, welding is performed in a manner known per se. For example, ultrasonic oscillations of 20, 30 or 35 kHz are generated. The oscillations are typically generated by a converter with piezoelectric elements known per se.

[0078] FIG. 2 shows an exploded view of the arrangement according to FIG. 1. The first workpiece in the form of a spout 30 and the second workpiece in the form of a foil of packing material 40 are arranged between the sonotrode 10 and the receptacle 18.

[0079] FIG. 3 shows a sonotrode 10 in perspective from its working surface 11. The working surface 11 is circular. Within the annular working surface 11 is a recess 17. The recess 17 forms a clearance for a contour of the spout 30. Contact lines 12 are arranged on the working surface 11 in a radial direction relative to the longitudinal axis L. The contact lines 12 extend from the longitudinal axis L to the working surface 11. The contact lines 12 extend from an inner edge of the working surface 11 to an outer edge of the working surface 11.

[0080] FIGS. 4 and 5 show the sonotrode 10 in a side view and in a cross-section along the longitudinal axis L of the sonotrode 10. In the side view it can be seen that the working surface 11 has a contoured surface in the form of a Hirth serration. FIG. 5 also shows the recess 17 for the spout 30 (not shown in FIG. 5).

[0081] FIG. 6 shows a detailed view of the working surface 11 of the sonotrode 10. The contact lines 12 are formed by ribs 13 which extend in radial direction r from the longitudinal axis L of the sonotrode 10.

[0082] FIG. 7 shows an enlarged view of the section A of FIG. 6. The ribs 13 extend in radial direction r and have the contact lines 12 on their uppermost point. The cross-section through the ribs 13 in a plane perpendicular to the radial direction r is constant over a welding area 15. The welding area 15 designates the area in which the working surface 11 of the horn 10 can come into contact with the packing material 40 in an area adjacent to an energy direction generator 31 at the spout 30 (see FIGS. 8 and 9).

[0083] FIG. 8 shows an enlarged section of a portion of the sonotrode 10, the spout 30, and the packing material 40.

[0084] The pourer 30 has a flange 33 to which the packing material 40 is to be connected. An energy direction sensor 31 is provided on the flange 33 on the side 32 facing the packing material 40. The energy direction generator has a triangular cross-section in a manner known per se.

[0085] The energy direction sensor has a height of typically 0.3 mm.

[0086] The packing material 40 has a first surface 41 which is directed towards the pouring spout 30 and in particular towards the side 32 of the flange 30. A second surface 42 of the packing material 40 is directed towards the working surface 11 of the horn.

[0087] Thereby, the contact lines 12 of the working surface 11 of the sonotrode 10 run along the second surface 42.

[0088] The sonotrode 10 is positioned with respect to the pouring spout 30 such that the contact lines 12 intersect at sound introduction points 43 at a right angle with the energy direction generator 31. The energy direction sensor 31 is arranged on the flange 33 in a circular circumferential manner. The welded-together pouring spouts 30 and packing material 40 together form a packing 20, a section of which can be seen in FIG. 8. Typically, this packaging is food packaging, e.g. beverage packaging. However, packaging for other products, in particular liquids or bulk materials, is also conceivable.

[0089] FIG. 9 shows an illustration similar to FIG. 8 in a transverse section. The horn 10 is with its working surface 11 and its contact lines 12 in contact with the second surface 42 of the packaging material 40. The packaging material 40 contacts with the first surface 41 the pouring spout 30 in the area of the energy direction generator 31.

[0090] FIG. 10 shows an enlarged section of the working surface 11 of the horn according to section B in FIG. 5. The working surface 11 is provided with a structuring similar to a Hirth serration. As a result, ribs 13 with a V-shaped cross-section are present on the working surface 11. The tip of the V-shaped ribs forms the contact lines 12. A recess 14 with a base 16 is formed between the ribs. The height of the recess, i.e. the distance H between the contact lines 12 and the base 16 is 0.6 mm. The distance a between two adjacent contact lines 12 is 1 mm in the example shown.

[0091] FIG. 11 shows a perspective view of a section similar to FIG. 10. In FIG. 11 it can be seen that the cross-section of the ribs 13 in the radial direction r does not change substantially. On the other hand, the shape and in particular the width of the recesses 14 and their base 16 change between the individual ribs 13. The angle a between two legs 19 of the ribs 13 is 60°.

[0092] FIG. 12 shows a section through a layer of a packing material 40 which has been welded onto a spout 30. The cut is made in a direction perpendicular to the energy direction sensor 31, i.e. in a direction analogous to the cut shown in FIG. 9. The energy direction sensor 31 is still recognizable, but somewhat flattened compared to the original shape (see FIGS. 8 and 9). There is a continuous and uniform weld between the packing material 40 and the pouring spout 30.

[0093] The packaging material 40 has an aluminum layer 48 and a cardboard layer 47, which are enclosed on both sides by an LDPE layer 46. As FIG. 12 shows, the aluminum layer 48 is not damaged. The lower LDPE layer 49 is intimately bonded to the material of the spout 30, which in the example shown is HDPE.

[0094] FIG. 13 shows a cross-section through an article comprising a pourer 30 and a packing material 40 along the energy director. Again, it can be seen that the central aluminum layer 48 is undamaged. Sound injection impressions 45 are discernible on the second surface 42 of the packing material 40, which was facing the horn 10. The sound injection impressions 45 substantially penetrate the top layer 46 of LDPE and extend nearly to the cardboard layer 47. The bottom LDPE layer 49 is intimately bonded to the dispenser 30 in weld zones 44. The weld zones 44 extend between the sound injection impressions 45.

[0095] FIGS. 14a and 14b show a perspective view of a weld of a packaging material 40 to a spout 30 in a second embodiment. Similar to the embodiments described above, the spout 30 is placed with its flange 33 on a receptacle 18. The receptacle 18 has a contact surface 21 for the flange 33. The contact between the spout 30 and the packaging material 40 takes place in the area of an energy direction generator 31 (see FIG. 14b). Similar to the foregoing, the horn 10 has a recess 17 for receiving a threaded portion of the spout 30. As in previous embodiments, the working surface 11 of the sonotrode 10 is provided with contact lines 12 (see FIG. 14b).

[0096] The contact surface 21 of the receptacle 18 is provided with a corrugation 19.

[0097] FIGS. 15a and 15b show enlarged representations of the flange 33 of the spout 30 and in particular of the energy direction sensor 31. The energy direction sensor 31 is formed as a circular contour on the flange 33. The energy direction sensor 31 has a flat circular contact surface 34 on which the packaging material 40 is placed and welded. In cross-section, the energy direction sensor is trapezoidal with rounded side flanks.

[0098] The contact surface 34 is annular and has a width b of 1 mm in the radial direction. In a direction perpendicular to the contact surface 34, the energy meter 31 has a height h of 0.1 mm. Due to the flat and relatively wide contact surface 34, penetration of the energy directing transmitter 31 into the packaging material 40 (see FIG. 14b) is prevented or at least minimized.

[0099] FIGS. 16a and 16b show a first embodiment of a corrugation 19 on the contact surface 21 of a receptacle 18. In the embodiment example according to FIGS. 16a and 16b, the corrugation 22 is formed similarly to the contact lines 12 of the horn 11 according to FIGS. 10 and 11, in particular with comparable angles a between legs and comparable height H between a base and the tip of the ribs. In contrast to the corrugation of the sonotrode, a further, smaller corrugation is provided between two adjacent ribs 23 in the valley bottom in order to compensate for different heights due to the circular geometry.

[0100] FIGS. 17a and 17b show an alternative embodiment of a support surface 21 of a receptacle 18. The ribs 23 are connected here with U-shaped valleys. Here, too, smaller ribs are provided to compensate for different heights between two adjacent ribs 23. The angles and dimensions correspond in each case as in the embodiment according to FIGS. 16a and 16b to the angles and dimensions of the associated sonotrode.

[0101] FIG. 18 shows graphical representations of tests for welding joining partners with different materials.

[0102] FIG. 18 above shows the joint between two identical plastic parts made of LDPE. FIG. 18 below shows the joining of different plastics, one part made of LDPE and one part made of HDPE. The two left-hand columns show the amorphous and crystalline proportions of the joining partners. It can be seen from this that in the lower illustration according to FIG. 18, the amorphous and crystalline portions in the two joining partners (left LDPE, right HDPE) are different.

[0103] With a longitudinally applicable amplitude of 30 μm, a sufficiently good bond with a bond content of 65% can be achieved in a bond between LDPE and LDPE (upper illustration) due to the relatively high, equal amorphous content. When the amplitude is increased to 40 μm, an almost complete bond is obtained.

[0104] In contrast, with an amplitude of 30 μm, a bond of only 20% can be achieved when LDPE is bonded to HDPE (lower illustration). This is not sufficient. However, by increasing the amplitude to 40 μm, a compound content of almost 100% can be achieved here as well. Such an amplitude can be achieved in particular with the torsional initiation described above without impairing sensitive joining partners.