WO2005044542A1

WO2005044542A1 - Method and device for print embossing surfaces

Info

Publication number: WO2005044542A1
Application number: PCT/CH2004/000659
Authority: WO
Inventors: Daniel Suhm
Original assignee: Daniel Suhm
Priority date: 2003-11-05
Filing date: 2004-11-01
Publication date: 2005-05-19

Abstract

The invention relates to a method and a device for introducing an embossed design (14) having a precise contour onto a surface (15) of a body (16) that is made of meltable material by means of a sonotrode (1).

Description

METHOD AND DEVICE FOR PRINTING SURFACES

The invention relates to an apparatus and a method for pressure embossing surfaces of thin materials.

Various methods and the devices used for this purpose are known from the prior art, which are used to join meltable plastic films.

For example, EP 0 242 480 B1 shows a device which is used for the ultrasonic welding of flat materials made of thermoplastic material. The contact surfaces used for actual welding have projections and depressions which are designed in such a way that molten material is distributed as uniformly as possible. The device is suitable for closing the tube body after filling.

German patent DE 100 27 735 shows a thin-walled container, as well as a method and a device for its production. The thin-walled container is made of a flexible base material that is coated with a thin layer that can be welded with ultrasound. The container is held together by welding lines.

The object of the invention is to show a method and a device which is suitable for the pressure embossing of a surface of a film made of meltable material, or for the simultaneous joining of several layers of films.

Many packages are made from meltable plastic, known as thermoplastic. Thin-walled boxes or other containers are made, for example, by folding a punched-out folding sheet. Since these materials are difficult to glue, one possibility is to join them by ultrasonic welding. Devices are known from the prior art which are suitable for producing linear connections. A sonotrode, which is operatively connected to the areas to be connected, is used to introduce sound energy into the materials to be connected. The sonotrode is designed in such a way that the vibrations are introduced as optimally as possible into the materials to be connected and there is no uncontrolled melting in the area of the interface between the sonotrode and the materials to be connected. By coupling the sound energy into the connecting materials, the aim is that the sound energy is converted as optimally as possible in the area of the contact surfaces of the materials to be connected into frictional energy, so that the material of the parts to be connected melts and connects. The aim of the conventional methods is primarily to connect layers of material.

Packaging made of meltable plastic is now labeled by printing in a separate step using conventional processes using color. To date, however, no methods have been known by means of which plastic films can be easily and nevertheless high-quality embossed and printed. For this reason, markings embedded in a surface of a material to be inscribed with a certain depth have hitherto not been known or are very difficult to produce. The disclosed invention includes a method that is used for high-quality, deep-effective labeling of surfaces of thin plastic films. In a special embodiment, the method is used for labeling and embossing, or respectively labeling and joining, of a plurality of layers of plastic film.

The invention uses a sonotrode on which the character or logos to be applied are applied in the area of an end face. The one or more characters or logos protrude over the end face like an embossing stamp and have one or more active areas which serve to transmit sound energy into a surface. The several end faces can have different levels from one another, which leads to the fact that different amounts of energy are transmitted in the areas that protrude further. This creates the possibility that only one embossing print is applied in one area and at the same time an overlay of several layers superimposed on the embossing print can be achieved. Depending on the area of application, the active surfaces are set in vibration by means of a sonotrode in such a way that they vibrate essentially parallel and / or perpendicular to the surface to be machined.

The sonotrode is configured in one or more parts in such a way that the sound energy is concentrated in the area of the active surfaces, the active surfaces vibrating perpendicularly or parallel to the longitudinal axis of the sonotrode. In contrast to the methods known from the prior art, in the described invention the sonotrode is designed in such a way that melting occurs primarily between the at least one active surface of the sonotrode and the surface of a meltable material. In contrast to a pure joining method, the entire cross-sectional area of a sonotrode is generally not used in the invention described here, but only active surfaces provided for this purpose and immediately adjacent side surfaces. The The method described is optimized so that, depending on the process control, the base material of the surface to be processed is not displaced laterally, but with a certain depth effect. As a result of the shear forces introduced into the base material, even with a thicker base material it is achieved that no negative material accumulations occur on the surface. The surface of the body to be shaped becomes primary and accurate in contour only in the effective area of the active surfaces of the sonotrode. An uncontrolled melting of the adjacent surface, as would result from a conventional process, can therefore occur. can be avoided because the surrounding material has a supporting effect. This explains the high quality that can be achieved by means of the method according to the invention. The method according to the invention is suitable for introducing high-quality embossments even in relatively thick base materials.

In one embodiment of the invention, which is suitable for continuous, ribbon-shaped printing, respectively embossing and / or joining, a sonotrode with an actively or passively driven wheel with a tread is preferably used, the tread for embossing and, if necessary, simultaneous joining of several Layers of a base material can be used.

The sonotrode is preferably driven by means of a conventional electronic ultrasound generator which is operatively connected to a sonotrode via a converter (booster). The force required for the forming is generated by means of a pressing device. Depending on the field of application, the sound waves are oriented longitudinally or transversely.

In order to be able to process boxes and boxes, for example, a device is proposed in which the sonotrode is designed in the form of pliers with two active surfaces facing each other. The active surfaces are advantageously arranged such that they are parallel to each other when opening and closing, so that a uniform pressure distribution results. At least one of the two active surfaces is provided in order to have an embossing shape which is used to emboss a surface of a meltable material. The sonotrode is preferably designed in such a way that the vibrations of the active surface are supported by the pincer-shaped design.

If necessary, the sonotrodes used are designed in several parts, so that the active surface that can be used for an embossing print can be replaced easily, completely or in some areas. For this purpose, a preferred embodiment of the sonotrode has a separation point arranged essentially parallel to the active surface. Different active surfaces can be created using a dovetail guide or an equivalent means that does not negatively affect the transmission of sound energy.

A preferred embodiment of a sonotrode has a first and a second region arranged one behind the other in the longitudinal direction, both of which have essentially the same maximum length but a different maximum width. The first and / or second area are arranged one behind the other and merge into one another. The transition region is designed in such a way that it serves to concentrate sound waves towards an active surface which is arranged on an end face of the second region. There is a threaded hole opposite the active surface, which is used for the active connection of the sonotrode to a sound generator. If large embossing is desired, the sonotrode is preferably designed in several parts or the embossing is applied in several parts. The form of oscillation of the sonotrode is preferably selected such that melting occurs primarily in the interaction area between the at least one effective surface of the sonotrode and the surface of the material to be processed, and the material is effectively displaced.

The invention offers the possibility of introducing fonts and logos into the surface of a body without distortion. Light-collecting plastics are known from the prior art, which collect the ambient light that strikes your surface and emit it again at corners and edges. Plastics of this type are manufactured and sold by Bayer AG, Leverkusen, under the name USA ^® . The invention is suitable for providing surfaces of a body made of light-collecting plastic with an embossing according to the invention, so that the embossing begins to shine as collected ambient light emerges along the corners and edges of the embossing. For this purpose, the effective or side surfaces of the embossing are preferably arranged at a certain angle to the surface of the body, so that an optimal luminosity is achieved and this can be perceived by an observer. Sonotrodes that can be used for this purpose are preferably designed in such a way that the active surfaces and the side surfaces adjoining them are arranged at an angle to the end surface of the sonotrode. Special effects can be achieved if the body made of light-collecting plastic is provided with a thin, opaque coating which is locally pierced by the embossing according to the invention. At least one wall of the embossing can have a refractive surface structure if required.

The depth of an embossing preferably correlates with the thickness of a film to be processed or the width of the embossing. The depth of the embossing is preferably greater than the thickness of the film a factor of 0.1 to 2. A factor of 2 means a relief-like protrusion on the back of the film. Other values are possible depending on the embodiment.

Using a preferably used ultrasound device, a high-frequency oscillation is introduced into the surface of the body to be processed under relatively low static pressure by means of the sonotrode. The ultrasonic vibrations are preferably introduced into the interface in the form of shear waves. The frequencies used are typically in the range from 20 kHz to 50 kHz. The amplitude size is in the range of 5 to 40 μm. Depending on the application, other values are possible.

Embodiments of the invention are explained in more detail with reference to the following figures. It shows schematically and simplified:

1 shows a first embodiment of a sonotrode;

2 shows a second embodiment of a sonotrode with an exchangeable active surface;

3 shows detail D from FIG. 2;

4 shows a device with an upper and a lower sonotrode;

5 detail F from FIG. 4;

6 shows a device with a coating film;

7 shows an embossing device; ,

8 shows a third embodiment of a sonotrode;

9 shows a detail E from FIG. 7;

Fig. 10 shows a fourth embodiment of a sonotrode and a male.

FIG. 1 shows a first embodiment of a sonotrode 1 in a perspective view with a first, thick area 2 and a second, thinner area 3 with a front area 4. The front area 4 has active surfaces 5 which are arranged in a projecting manner and the word “Mo- del Prime Pac ". The active surfaces 5 here consist of the same material as the sonotrode 1, preferably steel, titanium, brass or a similar material. The active surfaces 5 are preferably formed by material removal, for example by milling, lasering, etching or another suitable Process so that the active areas are arranged 0.05 mm to 1.5 mm above depending on the area of application. Other values are possible if required. The sonotrode 1 is used to impress the lettering "Model Prime Pac" formed by the active areas 5 into a surface made of meltable material ( see following figures 3). The active surfaces 5, 24 are designed in such a way that the best possible embossing is achieved with a precise typeface. Depending on. The desired result can of course be used with differently shaped active surfaces, for example cross, circular, star, polygonal or concave and / or convex. Inverse configurations are possible. Instead of one or more large-area active surfaces 5, 24, these can also be designed, for example, as a multiplicity of conical, spherical, cylindrical or pyramid-shaped, regularly or irregularly arranged elevations, which overall give the impression of a typeface or logo.

FIG. 2 shows a multi-part sonotrode 1 with a thicker first region 2 and a thinner second region 3. In the embodiment shown, the second region 3 is constructed in several parts and has a holder 6 which serves to hold an exchangeable end region 4 with active surfaces 5.

FIG. 3 shows detail D from FIG. 2. In the embodiment shown, the operative connection between the holder 6 and the stimulating area 4 is formed by means of a dovetail-shaped groove 7 and a correspondingly designed wedge 8. The groove 7 is designed so that it can be pulled together by means of screws 9, so that the wedge 8 is clamped. Other active connections that do not adversely affect sound transmission are possible.

In the embodiment shown, the active surfaces 5 have different levels, ie they protrude differently beyond an end surface 10 of the end region 4. A first segmented active surface 5.1 projects less far beyond the end surface 10 than a second active surface 5.2. The result of this is that more energy is introduced into a surface to be machined in the area of the second active area 5.2 above than in the area of a first active area 5.1. It can thereby be achieved that the second active surface 5.2 can be used, for example, for joining a first with a second plastic film while simultaneously embossing by means of the second active surface 5.1. If necessary, the invention is suitable as a tamper-evident seal to counter possible counterfeiting and to be able to clearly determine the origin of a product. For this purpose, characteristic features 23 (markings) are introduced at a defined location, which is only known to the manufacturer, and which, for example, are not visible or are very difficult to see by the eye. Since the precision of an embossing that can be achieved with the method according to the invention is very high, the active surfaces 5 themselves or their arrangement with respect to one another can be used as an originality seal.

FIG. 4 shows an embossing device 11 for printing embossing one or printing embossing and joining a plurality of layers 16, 17 from a meltable material. A first upper sonotrode 1, which largely corresponds to the sonotrode shown in FIG. 2, has an active surface 5 which is used to introduce a one- or multi-part figurative and / or character-shaped embossing 14 into a surface 15 of a first, upper plastic film 16 meltable plastic is used by penetrating the active surface (s) 5 and adjacent side surfaces 24 into the surface 15 and displacing the base material in a depth-effective manner. The method according to the invention can be used to process films of different thicknesses and properties. The thickness of a film to be processed is typically between 0.05 and 5 mm. Other values are possible depending on the application. If necessary, the side surfaces 24 are also designed as active surfaces.

A second lower sonotrode 18, which is aligned with respect to the upper first sonotrode 1, serves as a counterpart or an abutment. Depending on the embodiment, a support surface 13 corresponding to the active surface 5 also has concave or convexly arranged or designed active surfaces (not shown here) which are suitable for supporting the embossing 14 on the top. The axial, lateral and transverse direction of oscillation of the sonotrode 1, or the active surfaces 5, are indicated by three arrows 19, 20, 21.

Figure 5 shows a detail of the embossing 14 (detail F from Figure 4) in an enlarged view. The embossing 14 has a rear wall 32 arranged essentially parallel to the surface 15 of the body 16 and side walls 33 arranged essentially vertically to the rear wall 32. In certain embodiments, the side walls 33 of the embossing 14 are arranged inclined to the surface 15. In extreme cases, the embossing 14 has no rear wall 32, since the side walls open into one another. The rear wall 32 and / or the side walls 33 abut one another directly or are connected to one another via further edge surfaces (chamfers, curves). These measures are particularly advantageous for embossing in light-collecting plastics (see FIG. 9), since they can have a positive influence on the light emission. The rear wall 32 and / or the side wall 33 can have an additional surface structure in the form of linear, punctiform regular or irregularly arranged elevations or depressions or be coated at least in regions. The embossing 14 here has a first and a second depth t1, t2. The first depth is chosen so that the embossing 14 is visually clearly visible. The second depth t2, on the other hand, is selected such that the upper and lower plastic films 16, 17 are connected directly or indirectly to one another in the region of the second depth t2 by the embossing 14. The rear wall 32 and the side walls 33 can be designed to be smooth or rough (refractive), depending on the optical impression to be achieved.

Instead of an embossing 14, which contains one or more large-area depressions 34, an embossing 14 can also be formed, for example, as a plurality of conical, spherical, cylindrical or pyramid-shaped, regularly or irregularly arranged elevations, which overall give the impression of a Play typeface or logos.

FIG. 6 shows a further embodiment of the invention in which a plastic film 16 is provided with an embossing 14 by means of a one-piece sonotrode 1. The active surface 5 of the sonotrode 1 has the shape of the lettering "Model Prime Pac" in the example shown. In order to provide the plastic film 16 with the embossing 14, the active surface 5 of the sonotrode 1 is axial (z) and / or lateral (x) and / or transversal (y) vibration, then the multi-part active surface 5 is pressed against the surface 15 of the plastic film 16 by moving the sonotrode 1 essentially in a vertical direction (-z) towards the surface 15 of the plastic film 16 until that the active surfaces 5 have penetrated into the surface 15. Depending on the field of application, there is alternatively the possibility to support the active surface 5 first on the surface 15 and only then to set it in vibration, depending on the size, the depth and the qualitative requirements of the order of 0.1 to 5 seconds. Other times are possible. After a cooling time, the sonotrode is removed from the surface surface 15. In the embodiment shown, a counter surface 25 of a counter body 26 serves as an abutment.

The invention offers the possibility of introducing a film into all or part of the embossing 14, which, for example, produces a special optical effect. Metallic, shiny foils (for example gold-shining) are suitable, which are introduced between the active surface 5 of the sonotrode 1 and the surface to be machined. A foil strip 28 unrolled from a supply roll 27 is deflected by deflection rolls 29, 30 between the active surface 5 of the sonotrode 1 and the surface 15 to be embossed. When processing, this is in the area of Foil tape 31 located in the active surfaces 5 is introduced into the embossing and operatively connected to the surface 15. If the process control is adjusted accordingly, it is also possible to print or emboss materials that are not or only poorly meltable.

Figure 7 shows an embossing device 35 in a perspective view. The embossing device 35 has a sonotrode 1 which is operatively connected to an electronic ultrasound generator 36 and a converter 37. The ultrasound generator 36 and the converter 37 serve to drive and transmit vibrations to the sonotrode 1. An active surface 5 of the sonotrode 1 is used for pressure embossing and simultaneous local fusing of an inner and an outer plastic film 38, 39 of a box 40. The ultrasound generator 36 is attached to a stand 45, which in turn is operatively connected to a support surface 46. The support surface 46 serves as an abutment when embossing the two plastic films 38, 39. The sonotrode 1 is arranged to be displaceable in the longitudinal direction (axially), so that the plastic films 38, 39 can be clamped between the active surface 5 of the sonotrode and the support surface.

Figure 8 shows a third embodiment of a sonotrode 1 in a perspective view. The sonotrode 1 is essentially rotationally symmetrical and is used here to introduce an ornamental embossing 14 into a surface 15 of a body 16 made of light-collecting plastic (eg USA ^® ). Figure 8 shows detail E in an enlarged view.

FIG. 9 shows detail E from FIG. 8. On the one hand, part of the embossing 14 in the surface 15 of the body 16 can be seen. In the end region, the sonotrode 1 has second, in addition to the first active surfaces 5 arranged essentially perpendicular to a longitudinal axis 44 of the sonotrode 1 Active surfaces 47, which are arranged at an angle α with respect to the longitudinal axis 44. This angle α is transferred to the embossing 1 4 during embossing. In addition to the first and the inclined second active surfaces 5, 47, side surfaces 24 can be seen in the illustrated embodiment, which laterally close the active surfaces 5, 47. This configuration ensures that the embossing 14 always has the same embossing width 48 regardless of the immersion depth of the sonotrode. The active surfaces 5, 47 and the side surfaces 24 are arranged in such a way that light collected in the film 16, which emerges through the embossing 14, is emitted in the direction of a viewer, so that the impression is given that the embossing is illuminated. The angle α is preferably chosen so that the most direct light possible is achieved. Depending on the embodiment, the active surfaces 5, 47 are not curved or are curved in one or two spatial directions. Since light preferably emerges in the region of irregularities, the active surfaces 5, 47 and the side surfaces 24 of the sonotrode can escapes, the active surfaces 5, 47 and the side surfaces 24 of the sonotrode 1 can be provided with a suitable regular or irregular surface structure, for example in the form of grooves, ribs, knobs, etc., which have a low height compared to the embossing and which is transferred to the embossing during the embossing process. One embodiment of the sonotrode 1 does not have a first active surface 5 arranged perpendicular to the longitudinal axis 44, in that the inclined active surfaces 47 open into one another directly along an edge or are connected by a rounding.

FIG. 10 shows a fourth embodiment of a sonotrode 1 with a die 49 (embossing stamp) which interacts with a support 50 with a depression 51, which serves as a patrix during the stamping process of a film 16. In the perspective view shown, the individual parts are shown so that the essential areas are visible. The individual objects are therefore not aligned with each other. The recess 51 serving for the male part is larger than the female part 49, so that the base material of the body 16 is pressed into the recess 51 in a plasticized manner during an embossing process. In addition to an actual embossing 14, a protruding relief is created on the back of the body 16. Using the described method, it is possible not only to produce embossing, but also reliefs that protrude over a material surface.

Claims

1 ; Method for providing a surface (15) of a body (16) made of fusible plastic with a contour-accurate embossing (14) with the following method steps: a) positioning the body (16) on a counter surface (25); b) periodic deflection of at least one active surface (5, 24, 47) projecting over an end face (10) of a sonotrode (1); c) bring the excited active surface (5) into active connection with the surface (15) of the body (1 6) made of meltable plastic (1 6, 40), so that the base material of the body (1 6) has a precise contour in the region of the at least one active surface (5, 24, 47) begins to melt as a result of the periodic deflection; d) pressing the at least one active surface (5, 24, 47) against the surface (15) so that the active surface (5) sinks into the surface (15); e) removing the sonotrode (1) or the at least one active surface (5, 24, 47) from the surface (15) of the body (16).

2. The method according to claim 1, characterized in that the at least one active surface (5, 24, 47) is deflected at a frequency of 20 kHz to 50 kHz.

3. The method according to any one of the preceding claims, characterized in that the amplitude with which the at least one active surface (5, 24, 47) of the sonotrode (1) is deflected is 5 to 40 μm.

4. The method according to any one of the preceding claims, characterized in that the at least one active surface (5, 24, 47) is in contact with the body (16) for 0.1 to 5 seconds.

5. The method according to any one of the preceding claims, characterized in that a first with a second plastic film (16, 17, 38, 39) are connected to the embossing process.

6. The method according to any one of the preceding claims, characterized in that the embossing (14) is introduced into a body (16) made of light-collecting plastic.

7. The method according to any one of the preceding claims, characterized in that a foil (31) is inserted between an end face (10) of the sonotrode (1) and the body (16) when embossing (14).

8. embossing (14) in a surface (15) of a body (16) made of fusible material, characterized in that the embossing (14) is produced by the method according to one of the preceding claims.

9. embossing (14) according to claim 8, characterized in that the embossing has at least one side wall (33).

10. Embossing according to claims 8 or 9, characterized in that the embossing has a coherent or several individual depressions.

1 1. Embossing according to one of the claims 8 to 10, characterized in that at least one wall (32, 33) of the embossing (14) has a light-refracting surface structure.

1 2nd embossing according to one of the preceding claims 8 to 1 1, characterized in that the at least one side wall (33) of the embossing (14) includes an angle α to the surface (15) of the body (16)

13. Embossing (14) according to one of the claims 8 to 12, characterized in that the depth (tl, t2) corresponds at least to the embossing (14) 0.05 to 2 times the thickness of the body (1 6)

14. Sonotrode (1) for use in a method according to claims 1 to 8, characterized by at least one active surface (5) which can be used for introducing a contour-accurate embossing (14) into a surface (15) of a body (16) 1 5. Sonotrode (1) according to claim 14, characterized by a holder (6) and an exchangeable end region (4) with at least one active surface (5).