Sealing tool for sealing a plastic film

Abstract

The invention relates to a sealing tool (2) for sealing a plastic film (9) with a sealing tape (21) made of an electrically conductive material, the width (26) of the sealing tape (21) being 2 mm to 1000 mm, the length (25) of the sealing tape (21) being 2 mm to 2000 mm and the thickness (27) of the sealing tape (21) being 0.1 mm to 4 mm, and the largest surfaces (22, 23) of the sealing tape (21) being penetrated by a large number of voids (52), wherein the sum of the cross-sectional areas of the recesses (52) in a cross-sectional plane oriented parallel to the largest surface (22, 23) is at most 50% of the area of the largest surface (22, 23).

Description

Technical Field

[0001] The invention relates to a sealing tool for sealing a plastic film. Background Art

[0002] The basic principle of such a sealing tool is known from US Pat. No. 4,010,063 A. Summary of the invention

[0003] The object of the present invention is to provide a sealing tool with which thin-walled plastic films can be sealed.

[0004] This object is achieved for a sealing tool of the type mentioned at the outset in that the sealing tool comprises a sealing strip made of an electrically conductive material, wherein the width of the sealing strip is 2 mm to 1000 mm, the length of the sealing strip is 2 mm to 2000 mm and the thickness of the sealing strip is 0.1 mm to 4 mm, and wherein the maximum surface of the sealing strip is penetrated by a large number of gaps, wherein the sum of the cross-sectional areas of the gaps in a transverse plane oriented parallel to the maximum surface is at most 50% of the area of ​​the maximum surface.

[0005] Known sealing strips are strip-shaped and have a length that is much greater than their width. Furthermore, the thickness of the sealing strip is many times smaller than its length. As a result, the flexibility of the sealing strip in the sealing surface, in particular in the sealing plane defined by the largest surface of the sealing strip, can be selected so that at least slight thickness deviations of the plastic film to be sealed can be compensated by the sealing strip and any flexible supports for the sealing strip. The geometry of the sealing strip can be simplified, in particular by a cube, wherein variants of the sealing strip can also have a curved course in at least one plane, in particular in the sealing plane.

[0006] With a sealing strip whose width is at least 5% of the length of the sealing strip, thin-walled plastic films can also be welded to one another without the sealing seam being damaged even when small tensile forces are introduced into the product formed by the welded plastic films (the product can be, for example, a tubular bag). More precisely, a wide sealing seam is formed by the geometry of the sealing strip according to the invention, wherein a favorable distribution of tensile forces is also ensured for thin-walled plastic films. In order to ensure a heat distribution that is as uniform as possible in such a wide sealing strip and to achieve an energy-efficient operation of the sealing strip, a large number of recesses are introduced into the largest surface of the sealing strip that determines the contact surface with the plastic film and thus the sealing surface or sealing plane. These recesses extend from the largest surface of the sealing strip facing the plastic film through the sealing strip to the largest surface of the sealing strip facing away from the plastic film. Purely by way of example, the recesses are cut out of the sealing strip during the production of the sealing strip by a suitable separation method, in particular from the group of laser cutting, water jet cutting, punching, etc. As an alternative, the sealing strip can be produced by a photochemical process, in particular using etching technology, or by an electrolytic structuring process.

[0007] In order to ensure the advantageous function of the sealing strip, it is provided that the sum of the cross-sectional areas of the gaps in a transverse plane oriented parallel to the maximum surface is at most 30% of the area of ​​the maximum surface. For a sealing strip designed in a square shape, the area of ​​the maximum surface is generated by the product of the length and the width. For a sealing strip designed in a rectangular shape, the sum of the cross-sectional areas of the gaps is directly determined for the maximum surface, and for a curved maximum surface or a three-dimensionally shaped maximum surface, the projection of the gaps into the transverse plane is suitable for determining the sum of the cross-sectional areas. It is preferably provided that the sum of the cross-sectional areas of the gaps is at least 10%, particularly preferably at least 20%, of the area of ​​the maximum surface of the sealing strip.

[0008] The recesses can have different geometries from one another and thus also different areas. Preferably, provision is made for the recesses to be identically shaped and identically oriented.

[0009] Advantageous developments of the invention are the subject matter of the dependent claims.

[0010] The cross-sectional area of ​​the largest gap is expediently at most five times the average cross-sectional area of ​​the gaps. It is assumed that the average cross-sectional area of ​​the gaps is determined by adding the cross-sectional areas of all gaps and dividing by the number of gaps. Accordingly, the cross-sectional area of ​​the largest gap should be selected such that it is at most five times the average cross-sectional area determined in this way. This ensures that the sealing strip is not provided with gaps that would lead to larger surfaces in the sealing gap, into which no heat input and thus no sealing would occur.

[0011] Advantageously, the longest extension axis, which accounts for at least 50% of the gap, is oriented at an angular interval of 70 to 110 degrees relative to the longest edge of the sealing strip or to a section of the longest edge of the sealing strip that is directly adjacent to the corresponding gap. In principle, the gap in the largest surface of the sealing strip can have very different geometric shapes, such as circular, oval, square or rectangular. Preferably, it is provided that the gap has a maximum extension along a spatial direction oriented parallel to the largest surface, wherein this maximum extension determines the extension axis. This extension axis is oriented at an angular interval of 70 to 110 degrees relative to the longest edge of the larger surface of the sealing strip relative to this longest edge in the case of a sealing strip formed in a cubic manner. For the case of a partially curved sealing strip, it is provided that the extension axis is oriented at an angular interval of 70 to 110 degrees relative to the following section of the longest edge of the sealing strip, which has the smallest spacing relative to the gap.

[0012] In a further development of the invention, it is provided that the longest extension axes of the recesses are oriented parallel to one another and transversely to the longest edge of the sealing strip. It is assumed that the largest surface of the sealing strip is of rectangular design.

[0013] In one embodiment of the invention, it is provided that the recesses are arranged at the same spacing along the longitudinal direction of the sealing strip and / or along the transverse direction of the sealing strip. Such a regular arrangement of the recesses can result in advantageous uniform deformation characteristics for all sections of the sealing strip. This applies in particular when the recesses all have the same geometry. It can thereby be achieved that the spacing between the recesses is the same both along the longitudinal direction of the sealing strip and along the transverse direction of the sealing strip.

[0014] It is preferably provided that the recess is slit-shaped with a transverse extension which is at least twice the longitudinal extension. It is preferably provided that the recess has a rectangular cross section, wherein it can additionally be provided that the corners of the cross section are rounded. The transverse extension is the extension oriented parallel to the width of the preferably rectangular sealing strip. The longitudinal extension is the extension oriented parallel to the longest edge of the preferably rectangular sealing strip and thus also parallel to its length.

[0015] As an alternative, the object of the invention for a sealing tool of the type mentioned at the outset is achieved in that the sealing strip is made of an electrically conductive material, the sealing strip has a first contact region for making electrical contact with a first electrode at a first end region and a second contact region for making electrical contact with a second electrode at a second end region, and the sealing strip is provided with at least one gap from the group of a through hole, a cutout, a meandering section in a heating region formed between the first contact region and the second contact region, so that the distance between the first contact region and the second contact region is less than the length of the electrical path between the first contact region and the second contact region. The distance between the first contact region and the second contact region is the shortest straight line extending between the first contact region and the second contact region. The length of this straight line is less than the length of the electrical path that electrons must cross in order to reach the second contact region from the first contact region when an electric current flows through the sealing strip. The number, geometry and arrangement of the gaps introduced into the heating region play a decisive role here, because these gaps determine the path of the electrons and thus the length of the electrical path. The through hole in the heating region is a gap that is completely bordered by the material of the sealing strip. The perforation of the heating zone is a cut into the sealing strip, which extends from the edge area of ​​the sealing strip and is not completely surrounded by the material of the sealing strip. The meander-shaped cut is formed by a linear gap, which is optionally completely or incompletely surrounded by the material of the sealing strip and has at least one bend and / or at least one curve in its course, so that the first section of the gap before the bend or curve and the second section of the gap after the bend or curve determine an angle of at least 90 degrees, preferably at least 120 degrees, particularly preferably at least 150 degrees and in particular at least 180 degrees. It is particularly advantageous if the meander-shaped cut has a plurality of bends and / or curves, wherein the bends or curves that follow one another are each formed in opposite directions.

[0016] Preferably, provision is made that a first heating region section and a second heating region section adjoining thereto are arranged along the distance between the first contact region and the second contact region, wherein the first heating region section has a first resistance and wherein the second heating region section has a second resistance which is equal to or greater than the first resistance. It is thereby possible that when an electric current flows through the sealing strip, the second heating region has a higher temperature than the first heating region section due to its greater resistance. This is the case in particular when the length extensions of the first and second heating regions along the distance between the first contact region and the second contact region are the same.

[0017] In a further development of the invention, it is provided that the first heating region segment has a first arrangement of recesses which determines a first resistance, and that the second heating region segment has a second arrangement of recesses which determines a second resistance which is equal to or greater than the first resistance. To determine the resistance, the ohmic resistance of the respective heating region segment is used as a basis and reference is made to the extension of the respective heating region segment along the distance between the first contact region and the second contact region, so that the resistance per unit of length is described therewith.

[0018] In another embodiment of the invention, it is provided that the first heating region segment has a first average cross section in a transverse plane oriented transversely to the spacing between the first contact region and the second contact region, and that the second heating region segment has a second average cross section in the transverse plane that is equal to or smaller than the first average cross section. The average cross section for the respective heating region segment is formed as the sum of all individual cross sections of the respective heating region segment that are determined along the spacing between the first contact region and the second contact region, in particular with the same spacing distance, and is then referred to the length extension of the heating region segment. The differences between the average cross sections of the respective heating region segments can be attributed to different width extensions of the respective heating region segments along a spatial direction transverse to the spacing and / or to different numbers and sizes of recesses in the respective heating region segments.

[0019] It is suitable that the sealing strip is made of a metal material, in particular a stainless steel material. Thus, the requirements for the sealing strip in terms of temperature resistance, electrical conductivity and mechanical resistance can be met in an advantageous manner. This is particularly applicable when the sealing strip is made of a stainless steel material.

[0020] In another embodiment of the present invention, it is provided that a solid support body, in particular a cubic support strip, is assigned to the sealing strip, which has a support surface, wherein one of the two largest surfaces of the sealing strip rests on the support surface. It is provided, for example, that the support body is made of a metal material, such as aluminum or steel, as a support strip and is provided for clamping into a welding device. The task of the support body is to introduce the force necessary for the implementation of the sealing process, which is provided by the welding device, for example, by means of a corresponding actuator, into the sealing strip as evenly as possible in order to obtain a uniform weld seam for the plastic films to be connected to each other. Purely by way of example, the support strip is constructed in a cubic shape and has a length that at least substantially corresponds to the length of the sealing strip. The width of the support body is equal to or greater than the width of the sealing strip. The height or thickness of the support body is typically equal to or greater than the width of the support body.

[0021] Advantageously, a rubber-elastic and / or electrically insulating intermediate layer is arranged between the support surface and the sealing strip. The intermediate layer, which can be made of a rubber-elastic silicon material, for example, serves to compensate for possible slight unevenness of the plastic films to be welded to one another. Furthermore, the intermediate layer ensures electrical insulation between the sealing strip and the support strip with a suitable material selection, in particular when using silicon. Preferably, provision is made that the intermediate layer at least almost completely covers the support surface formed on the support body and for the placement of the sealing strip.

[0022] In a further development of the invention, it is provided that the largest surface of the sealing strip facing away from the support strip is covered by a temperature-resistant separating film and / or the support body is penetrated by at least one cooling channel, which is oriented in particular parallel to the support surface. The temperature-resistant separating film is, for example, a glass-fiber-reinforced film coated with PTFE (polytetrafluoroethylene), for which it is necessary to prevent the plastic film to be welded from adhering undesirably to the sealing strip. In addition, the temperature-resistant separating film also serves to reduce wear on the sealing strip and / or to achieve temperature compensation within the sealing surface defined by the sealing strip and / or to unify the surface pressure acting on the plastic film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Advantageous embodiments of the invention are shown in the accompanying drawings.

[0024] Figure 1 A sealing device having a sealing tool and a counter tool arranged opposite the sealing tool is shown, wherein the sealing tool comprises a support body and a sealing strip;

[0025] Figure 2 A top view of a first embodiment of a sealing strip is shown;

[0026] Figure 3 Shown is the Figure 2 A cross-sectional view of a sealing belt;

[0027] Figure 4 A second embodiment of a sealing strip having a substantially rectangular shape is shown; and

[0028] Figure 5 A third embodiment of a sealing strip having an essentially rectangular outer shape is shown. DETAILED DESCRIPTION

[0029] exist Figure 1 The sealing device 1 shown only schematically in FIG. 1 comprises a sealing tool 2 and a counter tool 3 arranged opposite the sealing tool. A power supply 4 is assigned to the sealing tool 2, which is connected to a sealing strip 21 belonging to the sealing tool 2 via an infeed line 5 and an outfeed line 6. Purely by way of example, it is provided that the counter tool 3 is fixed in a fixed position on a frame (not shown), which is symbolically represented by a support element 11 arranged on the lower side 10 of the counter tool 3. It is also provided that the sealing tool 2 is accommodated on a frame (not shown) in a linearly movable manner and that an actuator (not shown) supported on the frame is assigned to the sealing tool 2, which actuator can cause a vertical movement of the sealing tool 2 relative to the counter tool. During such a vertical movement of the sealing tool 2, the distance between the sealing tool 2 and the counter tool 3 changes, wherein this distance is also referred to as a working gap 12, into which two plastic films 9 oriented parallel to each other can be introduced, purely by way of example, which are to be welded with the sealing device 1.

[0030] The sealing tool 2 comprises, by way of example, a cuboid support body 31 having a support surface 32 which is, by way of example, flat and faces the counter tool 3. The support surface 32 carries an intermediate layer 33 which, by way of example, is produced as a film layer of a rubber-elastic silicone material with a constant thickness and which partially covers the support surface 32. Furthermore, it can be provided that the support body 31 is penetrated by cooling channels 35 which are preferably oriented parallel to the support surface 32 and are indicated only by dashed lines.

[0031] As a purely exemplary cuboid-shaped counter tool 3, a plate-shaped pressure pad 8 is arranged on the upper side 14, which can be made of a rubber-elastic silicone material in the same way as the intermediate layer 33. The plastic film 9 for carrying out the sealing process can be laid on the pressure pad 8 and, by means of a vertical approach movement of the sealing tool 2 while the working reservoir 12 is reduced, the plastic film is uniformly loaded with pressure, which is introduced into the sealing tool 2 by an actuator (not shown). In addition, the current is conducted from the power supply 4 via the feed line 5 and the discharge line 6 through the sealing strip 21, whereby the sealing strip 21 and the plastic film 9 heat up, thereby causing the desired sealing process.

[0032] The sealing belt 21 is in accordance with Figure 1 The illustration with its longest edge 24 extends in the horizontal direction and is accordingly fixed at the end to a sealing strip holder 34, which in turn is fixed to the support body 31. For example, the sealing strip holder 34 is screwed into the support body 31 and is provided with an insulating washer 36 in order to ensure that the sealing strip 21 is received electrically insulated relative to the support body 31.

[0033] If it can be Figure 2 As shown in the diagram ( Figure 2 Shown in accordance with Figure 1 2 ), the length 25 of the longest edge 24 is approximately 2.5 times the width 26. In mutually opposite end regions 28, the sealing strip 21 is provided with four bores 29, which are penetrated by sealing strip holders 34, which are designed as screws, for example, when the sealing strip 21 is mounted on a support body 31.

[0034] Furthermore, the mutually oppositely oriented largest surfaces 22, 23 of the sealing strip 21 are penetrated by a plurality of recesses 52 in the middle section 51. The recesses 52 are arranged, for example, at equal width intervals 55 in the direction of the width 26 of the sealing strip 21. Furthermore, the recesses 52 are arranged at equal length intervals 56 in the direction of the length 25 of the sealing strip 21. It is further provided that the recesses 52 are arranged with respect to Figure 2 The illustrations are arranged row by row and the rows arranged adjacent to one another are arranged offset by half their width spacing 55 .

[0035] The slit-shaped gaps 52 each have Figure 2, which is oriented purely by way of example at a right angle to the longest edge 24 of the sealing strip 21. Here, too, the condition is satisfied that the axis of extension 53 is oriented transversely to a section of the longest edge 24 which is arranged at a minimum distance 54 from the respective recess 52. Some of the recesses 52 are arranged purely by way of example in such a way that they penetrate the longest edge of the sealing strip 21 in the manner of a cutout. This arrangement of the recesses 52 is not absolutely necessary to ensure the function of the sealing strip 21, but increases the elasticity of the sealing strip 21 in the direction of the longest edge 24. The transverse extension 58 of the recess 52 has an extension which is a multiple of the longitudinal extension 57 of the recess 52.

[0036] If it can be done by Figure 3 As can be seen from the illustration of , the thickness 27 of the sealing strip 21 is significantly smaller than the length 25 and the width 26 and is, purely by way of example, approximately 1.5% of the length 25 of the sealing strip 21 .

[0037] Said in Figure 4 The sealing strip 61 shown in FIG. 1 has a substantially rectangular shape and is manufactured purely by way of example as a metal strip made of a stainless steel material. Figure 4 As can be seen from the purely exemplary illustration of the sealing strip 61, the sealing strip 61 has a first contact region 70 and a second contact region 71 at opposite end regions, each of which is provided for connection to an electrode, not shown in detail, of a sealing tool, which is also not shown in detail. A heating region 73 extends between the two contact regions 70, 71, which are arranged at a distance 72 from each other. The heating region 73 has, purely by way of example, two differently designed heating region sections 74, 75. As can be seen from Figure 4 As can be seen from the illustration of , the first heating region section 74 adjoins the first contact region 70 and extends to a second heating region section 75. The second heating region section then extends to a further heating region section which is designed in the same manner as the first heating region section 74 and is therefore also referred to as a further first heating region section 74.

[0038] By way of example, it is provided that the first heating region section 74 has a total of three transverse slits 77 which are arranged symmetrically with respect to a central axis 76 oriented parallel to the spacing 72 and which extend from the central axis 76 in the direction of the respective longest edge 64, but each at a spacing relative to the respective longest edge 64. The transverse slits 77 are arranged purely by way of example at the same spacing along the central axis 76. It is further provided that a notch 79 is formed which is aligned symmetrically with respect to the central axis with respect to the transverse slit 77 and which each starts from the longest edge 64, but which does not extend all the way to the central axis 76. The transverse slits 77 and the notch 79 achieve that the electrons which are provided on the first contact region 70 and which are to reach the second contact region 71 have to travel a large number of detours, so that the electrical resistance for the first heating region section 74 is much greater than the electrical resistance of a strip-shaped sealing strip which has the same length as the first heating region section.

[0039] The second heating region segment 75 adjoins the first heating region segment 74 along the central axis 76 and has a smaller number of transverse slits 77 and perforations 79 than the first heating region segment 74 and therefore has a lower electrical resistance than the first heating region segment 74. If it is assumed that the first heating region segment 74 and the second heating region segment 75 have the same length extension in the direction of the central axis 76, the ohmic resistance of the first heating region segment 74 is therefore greater than the ohmic resistance of the second heating region segment 75.

[0040] A further, different heating region segment, which is designed in the same way as the first heating region segment 74 , adjoins the second heating region segment 75 .

[0041] Symbolically in Figure 4 , two current paths 80 are shown, by means of which it should be shown that the length of the two current paths 80 is much greater than the spacing 72. By means of the different number and arrangement of transverse slits 77 and cutouts 79, it is achieved that the current density in the sealing strip 61 is greatest in the region of the two first heating region sections 74, so that a greater heat development also occurs there than in the second heating region section 75, which has a lower current density due to the smaller number of transverse slits 77 and perforations 79.

[0042] Sealing tape 81 Figure 5The third embodiment shown in the figure differs from the second embodiment of the sealing strip 61 in the design of the second heating area section 95 of the heating area 93, while the remaining areas of the sealing strip 81 are constructed in the same manner as in the sealing strip 61, so that the same figure marks are used for this purpose and a repeated description is omitted.

[0043] Compared to the first heating region segment 74, the second heating region segment 95 has a smaller width 86, whereby a sealing seam geometry predetermined on the customer side can be realized, for example, with the sealing strip 81. Despite this smaller width 86 of the second heating region segment 95, it is necessary to provide the second heating region segment 95 with transverse slits 97 and cutouts 99 in order to adapt the cross section in the second heating region segment 95 that is effective for the flow of current to the cross section of the first heating region segment 74 that adjoins the second heating region segment 95 on both sides and that is effective for the flow of current.

[0044] exist Figure 5 The embodiment shown in FIG. 8 thus has the object of ensuring a substantially uniform temperature distribution during operation of the sealing band 81 despite the greatly varying geometry of the heating region segments 74 , 95 .

Claims

1. A sealing tool (2) for sealing a plastic film (9) with a sealing tape (21) made of an electrically conductive material, wherein the width (26) of the sealing tape (21) is 2 mm to 1000 mm, the length (25) of the sealing tape (21) is 2 mm to 2000 mm and the thickness (27) of the sealing tape is 0.1 mm to 4 mm, and wherein the maximum surface (22, 23) of the sealing tape (21) is penetrated by a large number of gaps (52), wherein the sum of the cross-sectional areas of the gaps (52) in a transverse plane oriented parallel to the maximum surface (22, 23) is at most 50% of the area of ​​the maximum surface (22, 23).

2. The sealing tool (2) according to claim 1, characterized in that The cross-sectional area of ​​the largest voids (52) is at most five times the average cross-sectional area of ​​the voids (52).

3. The sealing tool according to claim 1 or 2, characterized in that: The longest extension axes (53) which constitute at least 50% of the recesses (52) are oriented at an angular interval of 70 to 110 degrees relative to the longest edge (24) of the sealing strip (21) or to a section of the longest edge (24) of the sealing strip (21) which is directly adjacent to the respective recess (52).

4. The sealing tool (2) according to claim 1, 2 or 3, characterized in that: The longest extension axes (53) of the recesses (52) are oriented parallel to one another and transversely to the longest edge (24) of the sealing strip (21).

5. The sealing tool (2) according to any one of the preceding claims, characterized in that The recesses (52) are arranged at equal spacings along the longitudinal direction (25) of the sealing strip (21) and / or along the transverse direction (26) of the sealing strip (21).

6. The sealing tool (2) according to any one of the preceding claims, characterized in that The recess (52) is designed in a slot-like manner with a transverse extension (58) which is at least twice as large as the longitudinal extension (57).

7. A sealing tool (2) for sealing a plastic film (9) with a sealing tape (61; 81) made of an electrically conductive material, the sealing tape having a first contact area (70) for making electrical contact with a first electrode at a first end area, and a second contact area (71) for making electrical contact with a second electrode at a second end area, and the sealing tape having at least one gap (77, 79; 97, 99) from a group such as a through hole, a cutout, or a meandering section in a heating area (73) constructed between the first contact area (70) and the second contact area (71), so that the distance (72) between the first contact area (70) and the second contact area (71) is smaller than the length of the electrical path (80; 100) between the first contact area (70) and the second contact area (71).

8. The sealing tool (2) according to claim 7, characterized in that A first heating area segment (74) and a second heating area segment (75; 95) adjacent thereto are arranged along a spacing (72) between the first contact area (70) and the second contact area (71), wherein the first heating area segment (74) has a first resistance and wherein the second heating area segment (75; 95) has a second resistance that is equal to or greater than the first resistance.

9. The sealing tool (2) according to claim 8, characterized in that The first heating region segment (74) has a first arrangement of gaps (77, 79) defining a first resistance, and wherein the second heating region segment (75; 95) has gaps (77, 79; 97, 99) of the second arrangement.

10. The sealing tool (2) according to claim 7 or 8, characterized in that The first heating area segment (74) has a first average cross-section in a transverse plane oriented transversely to the interval between the first contact area (70) and the second contact area (71), and the second heating area segment (95) has a second average cross-section in the transverse plane that is equal to or smaller than the first average cross-section.

11. Sealing tool (2) according to any one of the preceding claims, characterized in that The sealing strip (21; 61; 81) is made of a metal material, in particular a stainless steel material.

12. Sealing tool (2) according to any one of the preceding claims, characterized in that The sealing strip (21; 61; 81) is assigned a solid support body (31), in particular a cuboid support strip, which has a support surface (32), against which one of the two largest surfaces (22, 23) of the sealing strip (21; 61; 81) rests.

13. The sealing tool (2) according to claim 12, characterized in that A rubber-elastic and / or electrically insulating intermediate layer (33) is arranged between the supporting surface (32) and the sealing strip (21; 61; 81).

14. The sealing tool (2) according to claim 12 or 13, characterized in that The largest surface (22) of the sealing strip (21; 61; 81) facing away from the support body (31) is covered by a temperature-resistant separating film and / or the support body (31) is penetrated by at least one cooling channel (35) oriented in particular parallel to the support surface (32).

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