Method and device for the manufacture of perforated films or foils

Abstract

A device for the manufacture of perforated films or foils comprises a means (5) for the perforation of the film or foil (2), as well as a means (19) for crimping the edges of the thusly produced holes. By crimping the edges, the holes are fixed after having been opened. Punching tools for cutting the perforation out of the film or foil are not required. Rather, the desired hole is first created as a puncture, or as a cut, and is then widened. During the crimping operation, the material bent out of the plane of the film or foil is fixed in place in such a manner that it will not close the pierced hole again.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of European Patent Application No. 06 006 503.4, filed on Mar. 29, 2006, the subject matter of which, in its entirety, is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a method and to a device which can be used for the manufacture of perforated films or foils.

Frequently, films or foils, for example plastic films, metal foils or plastic film/metal foil laminates are provided with a number of holes, in which case the holes frequently should have only a small hole diameter. Basically, various methods have been known for the manufacture of perforated films or foils.

Document DE 299 08 254 U1 discloses the manufacture of perforated films or foils with the use of two contra-directionally rotating rollers, between which the film to be perforated is passed. The rollers are provided with teeth having cutting edges that form short tears that are more or less widened by the wedge shape of the teeth.

Referring to this method, no material is removed from the film or foil. There is the risk that the formed tears will mostly close again if the film exhibits elastic properties.

Furthermore, referring to document DE 39 06 573 A1, a method for punching very small holes in a film web or a tubular film has been known, in which case the film web is guided over a plunge-cut roller. The plunge-cut roller is provided with strips of needles, whereby the needles puncture the film web when the strips of needles are guided radially outward by an eccentric guide.

Document JP 2001 001 007 A discloses a method for the manufacture of a perforated metal foil with the use of a profiled roller and an elastic support. The metal foil that is to be perforated is placed on the elastic support, across which the profiled roller is rolled. As a result of the exerted pressure, sections of the elastic support penetrate cutouts of the roller and thus separate sections of foil, thus removing them from the foil. This is a punching process.

Furthermore, thin metal sheets, e.g., metal foils that are not too thin, can be pierced by means of piercing dies, in which case each piercing die is associated—on the other side of the foil—with a cutting plate having a cutting opening that forms a cutting gap with the piercing die.

As the thickness of the metal sheet or of the foil decreases, this method is limited because the cutting gaps must be narrower than the thickness of the foil. If the foils are too thin, it is hardly possible to obtain adequate tool life quantities. In addition, considering very small hole diameters of, e.g., 100 μm, it can hardly be ensured that all piercing dies (e.g., several hundred or several thousand) find their associate holes in the cutting plate.

Considering this, the object of the invention is to provide a method with which perforated films or foils can be manufactured in a simple and economical manner.

SUMMARY OF THE INVENTION

This object is achieved in accordance with the method of Claim 1:

Referring to an inventive method, first holes are produced in the film, e.g., in that the film or foil is pierced at several locations. Then, the edges of the resultant holes of the film or foil are compressed. As a result of this measure, it is achieved that short film or foil tags or film or foil flaps projecting from the edges of the hole will not re-close the hole that has formed. Rather, these tags or flaps are deformed in such a manner that they, even if they were to slightly relax in an elastic manner, could no longer close the resultant hole.

This method is suitable for metal foils and plastic films, or for plastic film/metal foil laminates, such as, for example, metal-coated plastic films, or metal foils having a plastic coating, paper having a metal coating, paper having a plastic coating, or varnished films or foils of different materials. The thickness of the film or foil may vary within wide limits. The method is particularly suitable for process films or foils having a thickness of a few tens of micrometers, for example, 50 μm. The film or foil may be provided with holes having a diameter of less or greater than the thickness of the film or foil. For example, an aluminum foil having a thickness of 50 μm can be pierced with holes having a diameter of 100 μm. While the hole is initially opened during the step of piercing the foil, the hole is fixed during the step of crimping of the edge. As a result of this, the shape of the hole may be maintained or modified, depending on process management. The shape of the hole can largely be fixed or even be left to incidental process influences.

The produced holes may essentially be round or polygonal or have an irregular form. The shape of the hole can be affected by the cross-sectional configuration of a needle-like tool for piercing the film or foil, and/or—if said tool does not have a circular cross-section—can be affected by the alignment of the cross-section of the tool relative to the advance direction of the film or foil. In addition, the shape of the hole can be affected by the way the edges of the hole are crimped.

Preferably, the holes are produced with needle-like tools that have a tip and a conically enlarging section. After the tip has through the preferably non-moving film or foil, the tool is further moved in axial direction, whereby the resultant hole is widened. The thusly displaced material forms flaps or tags which project from the film or foil. During the crimping operation, these flaps or tags are pressed against the reverse side of the film or are pressed into said reverse side. The resultant hole edges are relatively smooth. They essentially consist of former surface parts of the film or foil that has been pulled into the hole. Likewise, the reverse side of the film or foil is mostly smooth due to the crimping operation.

Another object of the invention is to provide a device for the manufacture of perforated films or foils. An appropriate device comprises means for puncturing the film or foil, as well as means for the preferably non-moving or, optionally, moving support of the film or foil during the piercing operation. Furthermore, a means for crimping the edges of the generated holes is provided. The means for the compression of the edges of the generated holes permits a fixation of the holes that have been produced by a piercing process, so that said holes cannot involuntarily close. The holes are fixed as to their form and diameter.

The means for piercing the film or foil preferably is a tool having a longitudinal working part with a tip with—extending therefrom—a progressively enlarging cross-section of the working part. Considering this, the working part has—at least in part, or even in full, a conical configuration. The increase in diameter of the working part—in the direction extending from the tip—may be linear, progressive or degressive or degressive-progressive-degressive (s-shaped), or otherwise. The tip of the working part may be configured as a point or as a cutting edge. If it is a pointed tip, the tip consists of a spherical section or a similarly configured surface area having a very small radius. If the tip is configured as a cutting edge, the working part terminates in a straight or curved edge that creates a small cut in the film or foil during the piercing operation, said cut being widened by the working part. In order to produce a hole, the tool can perform a linear back and forth movement in axial direction. However, it is also possible to mount the tool or several tools to a rotating machine element, e.g., a roller, in order to perforate a passing film or foil. In that case, a support means for the film or foil is not necessary. Then the support means, e.g., may also be an air cushion.

By designing the tip as a cutting edge and by aligning the cutting edges relative to the material transport direction of the film or foil, for example, along said film or foil, the position of the flaps or tags created on the film or foil by the piercing tools can be fixed in a manner favorable for the subsequent crimping operation in order to push the flaps or tags back onto the reverse side of the film or foil, however, not into the pierced hole.

The working part of the tool may have a circular cross-section, a knife-type cross-section, a polygonal cross-section or another cross-section. Knife-type and polygonal cross-sections permit the targeted fixation of the positions of tags or flaps that have initially formed on the hole edge. A knife-type cross-section, e.g., is a narrow two-corner cross section (two corners and edges bent away from each other) or a triangular or polygonal cross-section having at least one very acute angle (e.g., a narrow rhombus).

The working part may have a section with a constant cross-section. This is advantageous when the size of the pierced hole is to be independent of the stroke width of the tool. If the piercing operation is restricted to the conical section of the working part, the stroke width can be used to control the hole size.

When it is perforated, the film or foil is placed on the means for supporting it, for example, a support table. Preferably, this table is provided with openings into which move the needles or other tools. Preferably, the openings have a diameter that is clearly greater than the diameter of the working part associated with the respective opening. Preferably, the diameter has a size that prevents a cutting gap from forming. The annular space between the working part and the wall of the opening has a width that is greater than the thickness of the film or foil in order to prevent the hole edges that have been pierced in the opening from being pinched.

The means for crimping the edges of the holes has preferably two elements with pressure surfaces, between which the film or foil is pressed. The elements may be arranged so that they can be moved in linear direction or so that they can be rotated. Furthermore, the elements can optionally be designed in a stiff or even flexible manner. For example, they may represent a stiff or an elastic support, an associate stiff or flexible stamp, as well as represent stiff or flexible rollers.

In order to continuously move the film or foil or intermittently consistent with the cycle of the piercing movement of the needle-like tools, a transport device is preferably provided. The transport device may, at the same time, be the means for crimping the edges of the produced holes in a modular unit. For example, two rollers, which intermittently advance the film or foil and between which the film or foil is moving, may at the same time crimp the edges of the holes. Also, clamping jaws that compress the film or foil may periodically clamp the film or foil in place and intermittently advance the film or foil.

Details of advantageous embodiments are obvious from the claims, the drawing or the description. The drawings illustrate exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration, partially in section, of a device for the perforation of a film or foil;

FIG. 2 is a schematic view of a section, on an enlarged scale, of the device in accordance with FIG. 1, before the production of a hole;

FIGS. 3 and 4 are a schematic illustration, vertically in section, of the device in accordance with FIG. 2 in different stages during the production of a hole;

FIG. 5 is the device in accordance with FIGS. 2 through 4, after the production of the hole;

FIG. 6 is the part belonging to the device in accordance with FIG. 1, for crimping the hole edges, before crimping the hole edges;

FIG. 7 is the device part in accordance with FIG. 6, while crimping the hole edges;

FIG. 8 is an illustration of the hole, in vertical section, of the film or foil with the produced perforation, after crimping;

FIG. 9 is a side view of a section of the working part of the tool for the production of a hole; and,

FIGS. 10 to 14 are various configurations of the tip and of the cross-section of the working part in accordance with FIG. 9, viewed in the direction onto the tip.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic illustration of a device 1 that is used for the perforation of a film or foil 2 that is guided as a film or foil web through the device 1. The film or foil 2 is wound, e.g., on a roll 3 which is supported by a pull-off device 4 and is driven to rotate, in a specified manner if necessary. The pull-off device 4 may act as the transport device for the intermittent movement of the film or foil 2. Alternatively, not specifically illustrated claws or rollers may be provided which advance the film or foil 2 in an intermittent manner.

The device 1 comprises a means 5 for piercing the film or foil 2. Referring to the present exemplary embodiment, the means 5 comprises a support means designed as a lower tool 6. The latter is designed as a perforated plate, in which case the film or foil 2 preferably slides across the flat upper side of said plate. The upper side of the perforated plate represents a support surface 7 for the film or foil 2.

Furthermore, the means 5 comprises an upper tool 8 with a tool guide plate 9 having a preferably flat underside. The tool guide plate 9 forms a gap together with the support surface 7. The tool guide plate 9 has openings 10, opposite which openings 11 in the lower tool 6 are provided. The diameters of the openings 10, 11 may be the same or may be different from each other.

In addition, the upper tool 8 has a head holding plate 12 which holds the heads 13 of needle-like tools 14 used for piercing the film or foil. The tools 14 comprise, for example, a cylindrical shaft 15 that extends into the openings 10 and is guided in these in a sliding manner. Extending from the shaft 15 is a working part 16 having a diameter that is preferably substantially smaller than the diameter of the opening 11. The working part 16 is preferably a straight section that extends in longitudinal direction relative to the shaft 15 and terminates via a conical section 17 in a tip 18 (FIG. 2).

As indicated in FIG. 2, the head holding plate 12 and the tool guide plate 9 are supported, so that they can be moved relative to each other, in which case the tool holding plate 9 is elastically tensioned against an abutment away from the head holding plate 12. The head holding plate 12 is connected to a not specifically illustrated drive which is designed to impart a back-and-forth movement as indicated by an arrow in FIG. 1. The travel is large enough so that, on the one hand, the tool guide plate 9 can lift off the film or foil and that, on the other hand, the working parts 16 of the tools 14 can pierce the film or foil 2.

Furthermore, the device 1 comprises a means 19 for crimping the film or foil 2 in order to fix the produced holes in position. Referring to the exemplary embodiment in accordance with FIG. 1, this means 19 consists of a stationary element 20 and a movably arranged element 21, which have, on their sides that face each other, preferably flat pressure surfaces 22, 23. Whereas the element 20 is preferably arranged in a stationary manner next to the preferably also stationary lower tool 6, or is a part thereof, the element 21—as indicated by an arrow in FIG. 1—can be moved toward the element 20 and away therefrom. The element may be arranged in a rigid or resilient, for example, spring-biased manner and/or be connected to the head holding plate 12 or to its own drive. Alternatively, it is not only possible to move the two elements 20, 21 toward each other and away from each other but to additionally move them in the advance direction of the film or foil 2 and in a back-and-forth oscillating manner, in order to intermittently advance the film or foil 2.

For example, the device 1 is used for the perforation of plastic films or metal foils, for example, aluminum foils, or for the perforation of laminate films or foils that consist of plastic material, metal or even of other materials. Preferably, said device is used for the perforation of films or foils of a material that can be plastically deformed. To achieve this, the head plate 2 holds appropriate tools 14 in several rows, which extend preferably across the entire width of the film or foil 2, or at least across the width of the area that is to be perforated. The tools 14 of the individual rows (for example, ten rows) can be offset with respect to each other, or they may be arranged in another pattern.

Using the device 1 in accordance with FIG. 1, the film or foil 2 is perforated in the following manner:

As illustrated by FIGS. 1 through 6, the film or foil 2 is placed in the gap between the upper tool 8 and the lower tool 6, as well as between the elements 20 and 21. The end of the film or foil 2 is grasped by the pick-off device 4. The film or foil 2 is supported by the support surface 7, which, consequently, forms a means 24 for supporting the film or foil 2 during the subsequent piercing operation.

In order to perform the piercing operation or the piercing step, the head plate 12 is moved in the direction toward the lower tool 6 until the tool guide plate 9 clamps the film or foil 2 against the support surface 7. FIG. 2 shows this mode.

While the plate 9 supports the film or foil 2 the head plate 12 is moved further downward, so that the tip 18 pierces the film or foil 2, as illustrated by FIG. 3. A puncture hole is formed, said hole being widened by the conical section 17 when the tool 14 continues to move downward into the opening 11. Preferably, in so doing, the tool 14 is moved far enough for he cylindrical section of the working part 16 to enter the hole 25 now created in the film or foil 2. The film or foil material that is forced out of the hole 25 hangs downward in the form of a tag or flap 26 into the opening 11 and thus forms an edge 27 of the hole 25 (FIG. 4).

In this state, the hole 25 is completely open. The upper tool 8 is again moved away from the lower tool 6, whereby, as illustrated by FIG. 5, the working part 16 and the tip 18 are first moved out of the hole 25, and the tool guide plate 9 is lifted off the film or foil 2. In so doing, said plate carries the film or foil 2 somewhat along, so that the film or foil is also lifted off the support surface 7. Optionally, this operation can be aided by injecting air (pressurized air) in the opening 11 or in separate blow openings that extend through the support surface 7.

As long as the film or foil 2 between the support surface 7 and the tool guide plate 9 is released, said film or foil is advanced by one step, which, for example, is as large as the length of film or foil detected by the tool 5, said length being measured in film or foil transport direction (in FIG. 5, from left to right). The perforated parts of the film or foil 2 thus arrive between the pressure surfaces 22, 23 of the elements 20, 21. Referring to FIG. 6, this is shown by the just opened hole 25. Now the elements 20, 21 are moved toward each other in such a manner that the pressure surfaces 22, 23 clamp the film or foil 2 between them. In so doing, the flaps or tags 26 are crimped. FIG. 8 shows an optional method as to how to this may be achieved. The tags 26 are cramped and folded onto the reverse side of the film or foil 2 that had been positioned on the support surface 7 when the hole 25 was opened. In so doing, the tags 26 are plastically deformed at least to such an extent that they will not move back into the cross-section of the hole 25. They may also be pressed flat against the reverse side of the film or foil. There, they may be positioned loosely or they may be cemented to the reverse side or cold-welded thereto. It is possible to aid the pressing operation by additional measures, for example, by the application of ultrasound to at least one of the elements 20, 21, by the application of heat or by material fixing agents, for example, fixing varnishes or adhesive varnishes that are to be applied to the reverse side of the foil or film around the holes 25.

FIGS. 9 and 10 show a first embodiment of the tool 14 as can be used for the perforation of the film or foil. In so doing, the working part 16 is essentially cylindrical, whereby the section 17 forms a circular cone having a rounded tip 18. FIG. 10 shows the working part 16 of the tool 14, with a view on the tip 18.

Alternatively, the tip 18 have a different configuration as shown by FIGS. 11 through 14, in particular. Referring to FIGS. 11 and 12, the tip 18 is configured as a cutting edge, whereby the cutting edge may be relatively short (FIG. 11) or may be long enough so that it corresponds approximately to the diameter of the working part 16 (FIG. 12). In the latter case, the section 17 has a knife-type cross-section, which, beginning on an end-side cutting edge, gradually terminates in the circular section of the working part 16.

As shown by FIG. 13, the tip 18 may also have a pyramid shape in section 17. The cross-section of section 17 thus is bordered by a polygonal configuration, at least in some parts. As shown by FIG. 14, it is also possible to design the section 17, as well as the remaining part of the working part 16, in a polygonal configuration, for example, in triangular, square or rectangular configuration. In this, way non-round holes 25 can be produced.

The means for piercing the film or foil can be, as illustrated, a needle-like tool 14 or also any other means suitable for piercing the film or foil 2, such as, for example a sharp air jet or water jet, miscellaneous fluids or pressure waves generated therein, flexible elements or the like. The means for crimping the edges of the produced holes may be rigid, flat or non-flat surfaces provided on appropriate elements, or may also be non-concrete means, such as, for example, fluids or pressure waves generated in fluids.

A device for the manufacture of perforated films or foils comprises a means 5 for the perforation of the film or foil 2, as well as a means 19 for crimping the edges 27 of the thusly produced holes 25. By crimping the edges 27 or the tags 26 of film or foil material, the holes 25 are fixed after having been opened. Punching tools for cutting the perforation out of the film or foil 2 are not required for the production of the holes 25. Rather, the desired hole 25 is first created as puncture, or as a cut, and is then widened during the perforating operation. During the crimping operation, the material bent out of the plane of the film or foil is fixed in place in such a manner that it will not close the pierced hole again.

LIST OF REFERENCE NUMBERS

• 1 Device
• 2 Film or foil
• 3 Roll
• 4 Pull-off device
• 5 Means
• 6 Lower tool
• 7 Support surface
• 8 Upper tool
• 9 Tool guide plate
• 10, 11 Openings
• 12 Head holding plate
• 13 Heads
• 14 Tools
• 15 Shaft
• 16 Working part
• 17 Section
• 18 Tip
• 19 Means
• 20, 21 Element
• 22, 23 Pressure surfaces
• 24 Means
• 25 Hole
• 26 Tag
• 27 Edge

Claims

1. Method for the manufacture of perforated films or foils (2), whereby holes (25) are first produced in the film or foil (2), and whereby the edges (27) of the resultant holes (25) in the film or foil (2) are crimped.

2. Method in accordance with claim 1, characterized in that the holes (25) are produced with needle-like tools (14).

3. Method in accordance with claim 1, characterized in that the film or foil (2) is guided between two clamping elements (6, 9) and is clamped between said elements in order to be pierced.

4. Method in accordance with claim 1, characterized in that, in order to produce the holes (25), pierced holes are first produced, and that said holes are subsequently widened.

5. Method in accordance with claim 1, characterized in that, while crimping the edges (27) of the holes (25), material present on the film or foil (2) is folded and pressed against said film or foil.

6. Device for the perforation of films or foils (2), comprising a means (5) for producing holes in the film or foil (2), and a means (19) for crimping the edges (27) of the produced holes (25).

7. Device in accordance with claim 6, characterized in that the device comprises a means (7) for supporting the film or foil (2) during the piercing operation.

8. Device in accordance with claim 6, characterized in that the means (5) for piercing the film or foil (2) is a tool (14) having a longitudinal working part (16) with a tip (18), whereby the cross-section of the working part (16) enlarges extending from said tip.

9. Device in accordance with claim 8, characterized in that the working part (16) is configured as a needle.

10. Device in accordance with claim 8, characterized in that the tip (18) is a punctiform tip.

11. Device in accordance with claim 8, characterized in that the tip (18) is configured as a cutting edge.

12. Device in accordance with claim 8, characterized in that the working part (16) has a circular cross-section.

13. Device in accordance with claim 8, characterized in that the working part (16) has a knife-type cross-section.

14. Device in accordance with claim 8, characterized in that working part (16) has a polygonal cross-section.

15. Device in accordance with claim 8, characterized in that the working part (16) has a section with a constant cross-section.

16. Device in accordance with claim 8, characterized in that the means for supporting the film or foil (2) has a support surface (7) which is provided with openings (11) that are associated with the tool (14) for producing the holes (25).

17. Device in accordance with claim 16, characterized in that each of the openings (11) has a diameter which is greater than the diameter of the working part (16) associated with the opening (11).

18. Device in accordance with claim 6, characterized in that the means (19) for crimping the edges (27) of the holes (25) comprises a first element (20) with a pressure surface (22) facing the underside of the film or foil (2) and comprises a second element (21) with a pressure surface (23) facing the upper side of the film or foil (2), and further comprises a drive means for moving the two elements (20, 21) in a controlled manner toward each other and away from each other.

19. Device in accordance with claim 6, characterized in that the film or foil (2) is associated with a transport device (4) in order to intermittently move the film or foil through the device (1).

20. Method for the manufacture of perforated films or foils (2), whereby holes (25) are first produced in the film or foil (2) by means of a tool (14) which has a longitudinal working part (16) with a tip (18), extending from which the cross-section of the working part (16) enlarges, in that the tool (5) carries out a linear back and forth movement in axial direction, the stroke width of said movement being used for the adjustment of the hole size, and whereby the edges (27) of the previously formed holes (25) of the film or foil (2) are crimped.

21. Device for the perforation of films or foils (2), comprising a tool (14) for piercing the film or foil (2), whereby the tool (5) for producing the holes in the film or foil (2): performs a linear back and forth movement in axial direction, the stroke width of said movement being used for the adjustment of the hole size, and has a longitudinal working part (16) with a tip (18), extending from which the cross-section of the working part (16) enlarges, and comprising a means (19) for the subsequent crimping of the edges (27) of the produced holes (25).