METHOD FOR LAMINATED A HOT-MELTED ARTICLE BY MEANS OF ULTRASOUND AND LAMINATED DEVICE FOR CARRYING OUT THE METHOD

Description

TECHNICAL FIELD

[0001] The present invention relates to an improved ultrasonic rolling process for a hot-melt article. The invention also relates to a rolling device for implementing said process.

[0002] The invention finds an advantageous application in the field of joining two hot-melt articles, for example presented in the form of strips or sheets.

[0003] Splicing is a well-known technique among those skilled in the art, primarily used to join two strips or sheets of a hot melt product. For example, splicing joins the end end of a sheet from one reel to the beginning end of a sheet from a second reel to form a single continuous product. Lamination is used to achieve a perfect splice, free of edges or ridges at the joint between the two sheets. PRIOR STATE OF TECHNOLOGY

[0004] In the current state of the art, it is known to use a sonotrode to perform ultrasonic rolling operations on a hot-melt article, consisting for example of two joined strips or sheets.

[0005] For the splicing operation, the two layers are stretched and overlapped. These two layers are then held in position and simultaneously cut and welded using a sonotrode-type welding cutting tool, for example. This cutting / welding operation allows, for example, the joining of the end end of the first layer to the starting end of the second layer.

[0006] The weld and cutting area is slightly deformed by partial flattening, forming a kind of beak with fragile and precarious strength. The next step involves rolling this beak to complete the butt joint. Once rolled, the two layers are fused to form a single part. Rolling is performed, for example, by moving the sonotrode along the weld and pressing it against the weld.

[0007] Another splicing technique involves overlapping two hot-melt sheets and directly rolling, using a sonotrode, the overlap area to merge the two sheets into a single article.

[0008] Regardless of the technique used, the visual and tactile qualities of the resulting rolling can be significantly improved, as can the speed of said rolling, and therefore the yield.

[0009] Indeed, there are adhesion constraints between the sonotrode and the part being rolled, as well as constraints on the part's displacement as the sonotrode passes through it. These constraints, on the one hand, limit the sonotrode's movement speed and, on the other hand, can lead to damage to the part. For example, when rolling a weld between two hot-melt sheets with a density of 80 g / m², and using a sonotrode with a frequency between 20 kHz and 50 kHz, the sonotrode's movement speed cannot exceed 30 millimeters per second.

[0010] Document US2014 / 0311654 describes a method for welding two hot-melt articles by rolling, using ultrasound and a sonotrode, according to the preamble of claim 1. DESCRIPTION OF THE INVENTION

[0011] One of the aims of the invention is to provide an improved ultrasonic lamination process for a hot-melt article, enabling the visual and tactile qualities of the resulting lamination to be improved.

[0012] Another objective of the invention is to provide a high-speed rolling process, enabling in particular a considerable improvement in the efficiency of a prior art butting device.

[0013] To this end, a process for rolling a hot-melt article by ultrasound and by means of a sonotrode has been developed, remarkable in that it consists of carrying out the rolling operation by moving the sonotrode in the plane of the hot-melt article to be rolled, with said sonotrode resting on a strip suitable for conducting the vibrations generated by the sonotrode, positioned between said sonotrode and the hot-melt article to be rolled.

[0014] In this method, the lamination is performed across the belt, with the sonotrode resting on it. The belt facilitates the transfer of the forces required for lamination while eliminating the pressure exerted by the article as it passes over the sonotrode (the bulge effect in front of the sonotrode). Furthermore, the belt holds the article in position, particularly in the area to be laminated, ensuring optimal lamination.

[0015] The lamination of the hot-melt article is carried out through said strip in such a way that there is no degradation of said article. Naturally, said strip is sufficiently thin to prevent any loss of amplitude and frequency power of the sonotrode. The invention thus makes it possible to obtain better visual and tactile qualities of the lamination obtained, since the displacement of the article is eliminated, and said lamination is carried out without direct contact between the sonotrode and the hot-melt article.

[0016] According to the invention, the coefficient of friction between the strip and the sonotrode is less than the coefficient of friction between the article to be rolled and the sonotrode.

[0017] Thus, lamination can be performed at high speed. Indeed, the belt also eliminates the adhesion stresses of the sonotrode on the article. There is no phenomenon of the article being pushed back in front of the sonotrode.

[0018] For example, when rolling a weld between two hot-melt sheets with a density of 80 g / m², and using a sonotrode with a frequency between 20 kHz and 50 kHz, the speed of the sonotrode with the rolling process according to the invention is on the order of 300 millimeters per second, representing a rolling speed and efficiency ten times greater than the current state of the art. The coefficient of friction between the sonotrode and the part being rolled is 0.25, while the coefficient of friction between the sonotrode and the strip is 0.1.

[0019] According to particular embodiments, the strip consists of a strip of plastic material, or a strip, such as a strip of paper or glass fabric for example, impregnated or coated with a coating with a low coefficient of friction with the sonotrode, such as polytetrafluoroethylene for example.

[0020] The invention also aims to provide a device for rolling a hot-melt article using ultrasound by means of a sonotrode. The rolling device comprises a sonotrode positioned directly above the hot-melt article to be rolled, movable relative to the article and within the plane of said article.

[0021] According to the invention, the rolling device comprises a belt, suitable for conducting the vibrations generated by the sonotrode, positioned between the sonotrode and the article to be rolled. The sonotrode is movable between a rest position in which it is not in contact with the belt, and a rolling position in which it rests on the belt to perform the rolling operation itself.

[0022] This laminating device therefore allows for optimal lamination, with the visual and tactile qualities of said lamination being significantly improved.

[0023] According to the invention, the coefficient of friction between the strip and the sonotrode is less than the coefficient of friction between the article to be rolled and the sonotrode, so that the rolling is carried out at high speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features and advantages of the invention will become clear from the description given below, which is by way of example and not limitation, with reference to the accompanying figures in which: there figure 1 is a schematic representation illustrating, from the side, the positioning of the strip before rolling, between the article to be rolled and the sonotrode, in an overlapping butt joint operation; the figure 1a is a schematic representation similar to that of the figure 1 representing the process according to the invention in a butt-jointing operation by cutting and welding; the figure 2 is a schematic representation similar to that of the figure 1 representing the rolling operation itself, with the sonotrode resting on the strip; the figure 2a is a schematic representation similar to that of the figure 1a representing the rolling operation itself; the figure 3is a schematic representation similar to that of the figure 1 illustrating the result of the rolling process according to the invention; the figure 3a is a schematic representation similar to that of the figure 1a illustrating the result of the rolling process according to the invention; the figure 4 is a schematic representation illustrating in perspective a rolling device according to the invention, arranged in a splicing installation of two hot-melt sheets. DETAILED DESCRIPTION OF THE INVENTION

[0025] The invention relates to a rolling method and device (6) for carrying out high-speed ultrasonic rolling using a sonotrode (2) of a hot-melt article (1).

[0026] With reference to figures 1, 2 And 3, article (1) hot meltable to be rolled is for example made up of two overlapping hot meltable sheets (3, 4), intended to be joined by an ultrasonic rolling operation.

[0027] With reference to figures 1a, 2a And 3a, and 4 article (1) hot meltable to be rolled can for example also consist of two hot melt sheets (3, 4) joined by the cutting and welding technique, the weld area of ​​which must be joined to eliminate the beak and perfect the joining.

[0028] According to the invention, and with reference to Figures 1 and 1a , to carry out the lamination of the hot-melt article (1), it is necessary to position at the level of the area to be laminated, a strip (5) suitable for conducting the vibrations generated by the sonotrode between said sonotrode (2) and said article (1).

[0029] The band (5) may consist of a band (5) of plastic material, or of a band (5) of material, such as paper or glass cloth for example, or any other suitable material.

[0030] It is clear that the thickness of the tape (5) must be adjusted according to the characteristics of the sonotrode (2). Indeed, the tape (5) must be sufficiently thin to prevent any loss of amplitude and frequency power from the sonotrode (2). A person skilled in the art will, of course, be able to adapt the thickness of the tape (5) according to the sonotrode (2) being used. Crucially, the tape must not impede the transmission of vibrations generated by the sonotrode (2).

[0031] Advantageously, the strip (5) exhibits a very low coefficient of friction with the sonotrode (2), which can be made of titanium, aluminum, or steel. For example, the strip (5) may be impregnated or coated with a material such as polytetrafluoroethylene. The key point is that the coefficient of friction between the strip (5) and the sonotrode (2) is lower than the coefficient of friction between the part (1) to be rolled and the sonotrode (2). Indeed, the lower the coefficient of friction, the higher the speed at which the sonotrode can move.

[0032] For example, the sonotrode (2) used in a preferred embodiment of the invention consists of a sonotrode (2) having a frequency between 20 kHz and 50 kHz, and the polytetrafluoroethylene impregnated paper strip (5) used has a thickness between 0.1 and 1 millimeter.

[0033] The paper strip (5) is impregnated with polytetrafluoroethylene by dispersion on its face intended to be in contact with the sonotrode (2). This polytetrafluoroethylene-impregnated paper strip (5) has excellent thermal resistance, an extremely low coefficient of friction with the sonotrode (2), in particular on the order of 0.04 for a steel sonotrode (2), as well as excellent friction strength.

[0034] With reference to figures 2 and 2aThe rolling operation is performed with the sonotrode (2) resting on the belt (5). The rolling is carried out through said belt (5). In this way, the belt (5) allows the transfer of the forces necessary for rolling while eliminating the adhesion stresses of the sonotrode (2) on the article (1), and the displacement of said article (1) as the sonotrode (2) passes over it. Furthermore, the belt (5) helps to hold the article (1) in position during rolling, particularly in the area to be rolled, for optimal rolling performance.

[0035] With reference to figures 3 and 3a , we obtain a lamination whose visual and tactile qualities are optimal because the lamination is carried out without direct contact between the sonotrode (2) and the hot-melt article (1).

[0036] The friction between the sonotrode (2) and the band (5) is very clearly reduced, and there is no repulsion effect of the article (1) on the passage of said sonotrode (2), so that it is possible to considerably increase the speed of movement of the sonotrode (2).

[0037] With reference to the figure 4 The invention takes the form of a laminating device (6), for example, implemented in a device for joining two hot-melt webs (3, 4) to form a single article (1). The joining device is notably associated with a textile machine, for example, using unwinding reels. The device thus makes it possible to join the end end of a first hot-melt web (3) from a first unwinding reel with the initial end of a second hot-melt web (4) from a second unwinding reel.

[0038] The splicing device includes, for example, a cutting / welding unit designed to perform cutting and welding operations in combination with a counter-support element.

[0039] Once the cutting / welding operation is completed, the weld zone, marked by a beak or rim, is moved to the rolling device (6) according to the invention. The rolling device (6) comprises a sonotrode (2) positioned opposite the heat-fusible article (1) and movable relative to the article (1) and transversely to said article (1), particularly along the weld. The sonotrode (2) is movable, for example, along a rail (7), in a manner known in the prior art. A counter-support element (8), such as a flat surface, is arranged, in a known manner, opposite the sonotrode (2), behind the article (1) to be rolled.

[0040] The laminating device (6) further includes arrangements suitable for positioning the strip (5) between said sonotrode (2) and the article (1) to be laminated so that the laminating is carried out with the sonotrode (2) resting on said strip (5), and through it.

[0041] The arrangements take the form, for example, of a support base (9) from which extend two arms (10) positioned on either side of the area to be laminated, each receiving one end of the strip (5). The two arms (10) are arranged to position the strip (5) between the weld area and the sonotrode (2), substantially resting on the weld area.

[0042] As can be seen from the above, the invention provides a method and a device for high-speed rolling (6) using a sonotrode (2) which makes it possible to considerably increase the efficiency of a splicing device while improving the visual and tactile qualities of the resulting rolling.

Claims

1. Ultrasonic laminating process using a sonotrode (2) for a thermofusible article (1) consisting of two thermofusible layers (3, 4) which are either overlapping and intended to be joined by the ultrasonic laminating process, or already joined by a cutting-welding technique, characterized in that it consists of positioning a strip (5) capable of conducting the vibrations generated by the sonotrode between the sonotrode (2) and the article to be laminated (1) by means of arrangements in the form of a support base (9) from which two arms (10) extend, positioned on either side of the area to be laminated and each receiving an end of the strip (5), the two arms (10) being arranged to position the strip (5) between the welding area and the sonotrode (2), substantially resting on the welding area, and to perform the laminating operation by moving the sonotrode (2) in the plane of the thermofusible article (1) to be laminated, with said sonotrode (2) resting on the strip (5), the coefficient of friction between the strip and the sonotrode being lower than the coefficient of friction between the article to be laminated and the sonotrode.

2. Laminating process according to claim 1, characterized in that the strip (5) consists of a plastic strip (5).

3. Laminating process according to claim 1, characterized in that the strip (5) consists of a strip (5) impregnated or coated with a coating having a coefficient of friction with the sonotrode lower than the coefficient of friction between the article to be laminated and the sonotrode.

4. Laminating process according to claim 3, characterized in that the coating is polytetrafluoroethylene.

5. Laminating process according to claim 3, characterized in that the impregnated or coated strip (5) consists of a glass fabric strip (5).

6. Laminating process according to claim 3, characterized in that the impregnated or coated strip (5) consists of a paper strip (5).

7. Laminating device (6) for a thermofusible article (1) by ultrasound and using a sonotrode (2), for implementing the process according to any one of claims 1 to 7, said sonotrode (2) being positioned in line with the thermofusible article (1) to be laminated, and movable relative to the article (1) and in the plane of said article (1), characterized in that the laminating device (6) comprises a strip (5), capable of conducting the vibrations generated by the sonotrode, positioned between said sonotrode (2) and the article (1) to be laminated, the coefficient of friction between the strip and the sonotrode being lower than the coefficient of friction between the article to be laminated and the sonotrode, and said sonotrode (2) being movable between a rest position in which said sonotrode (2) is not in contact with the strip (5), and a laminating position in which said sonotrode (2) is in contact with the strip (5) to perform the laminating operation as such, and in that the laminating device (6) comprises arrangements capable of positioning the strip (5) between the sonotrode (2) and the article to be laminated (1) in the form of a support base (9) from which two arms (10) extend, positioned on either side of the area to be laminated and each receiving an end of the strip (5), the two arms (10) being arranged to position the strip (5) between the welding area and the sonotrode (2), substantially resting on the welding area.