GB2494918A

GB2494918A - Thermal laminator

Info

Publication number: GB2494918A
Application number: GB201116515A
Authority: GB
Inventors: Andy Wah Yiu Chan
Original assignee: TIKO CORP Ltd
Current assignee: TIKO CORP Ltd
Priority date: 2011-09-23
Filing date: 2011-09-23
Publication date: 2013-03-27
Also published as: JP2013116624A; GB201116515D0

Abstract

A laminator with improved thermal performance has a heating chamber 20 holding two pairs of laminating rollers 22, 23, 24, 25 between which sheet material 29 is fed along a planar path 28. The two rollers on each side of the path have a respective heating element 32, 33 and thermal conductor bar 34, 35. The thermal conductor bars are disposed between the pairs of rollers on opposing sides of the path to one another, and spaced apart from the heating elements so as to be primarily heated by radiant energy. Heat shields 26, 27 are disposed on opposing sides of the path to one another, each having a concave surface 56, 57 extending about the two rollers on each side of the path and directing radiant to energy toward the rollers. The heat shields are spaced apart from the respective heating elements they enclose within a cavity bounded by the heat shields and outer surfaces of the rollers.

Description

THERMAL LAMINATOR

Technical field

The present invention relates to laminators for performing hot lamination.

Background of the Invention

Thermal laminators are commonly used to bond one or two layers of film to a sheet of material to form a laminate. The film is covered in a thin adhesive resin coating which is fused by heat while the opposing sides of the pouch are pressed together, so that after coaling a permanent bond is produced between the film and the sheet * item. * * . * .*

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* 10 The thermal performance of laminators is a critical aspect of their design. In ** particular, the temperature of the laminating rollers must be precisely controlled.

Before lamination, the adhesive resin coating gives the film a high degree of opacity, but following proper curing and lamination the film becomes transparent. Inadequate * heat can therefore produce a defective lamination in which the adhesive layer retains some haze or opacity, or lack of adhesion On the other hand, excessive heat may aflow the lamination to be wrinkled, bubbled and deformed or, by excessively softening the film, the sheets can tend to curl and thereby become more readily caught in the rollers and jam the machine. Dea'ing with components at excessively high temperatures also shortens the life of the elements of the machine, or else requires more costly heat mitigation measures. Additionally, the operating efficiency must be reasonable and, to avoid testing the patience of users, the pre-heating time must be as short as possible without compromising manufacturing cost.

Fig. 1 illustrates the construction of a prior art laminator in which the laminating chamber comprises two pairs of hot rollers 12a/12b, 13a/13b with the film and sheet 10, 11 being fed sequentially between the first pair and second pair of rollers along a path 18, thus providing a two-stage compression and heating process, One roller 12a, 13a of each pair is substantially enclosed in a metallic heat shield 15, which also serves to locate a heating element 16 between the rollers 12a, 13a, the element 16 extending longitudinally with the rollers. Thermal conductor bars 17 are formed on the edges of the element 16 adjacent opposing sides of the path 18. Drawbacks of this arrangement are that the heat is not transferred efficiently to the rollers, and at high heating rates local overheating can occur, such as on the heating bars 17. It is therefore an object of the present invention to seek to provide a laminator with improved thermal performance, or more generally to provide an improved thermal laminator. * . * . *

Disclosure of the Invention

According to one aspect of the present invention there is provided a laminator for * . sheet material, comprising: first and second pairs of substantially parallel rollers which define a planar path extending tangentially to the rollers, along which path the sheet material is fed between the rollers of each pair, the two railers on each side of the planar path comprising first and second sets of rollers respectively; two substantially parallel heating elements, the heating elements being disposed on opposing sides of the path to one another, each extending alongside the rollers of a respective one of the first and second sets; two substantially parallel thermal conductor bars, the thermal conductor bars being disposed between the pairs of rollers on opposing sides of the path to one another, and spaced apart from the heating elements, each extending alongside the rollers of a respective one of the first and second sets, and two heat shields, the heat shields being disposed on opposing sides of the path to one another, each heat shield extending about the rollers of a respective one of the first and second sets to define a respective cavity, each cavity substantially enclosing a respective heating element, each cavity being further bounded by outer surfaces of the rollers of a respective one of the first and second sets and one of the thermal conductor bars, and wherein each heat shield is spaced apart from the respective * heating element. * * * * .*

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* By providing a laminator with a heating chamber according to the invention, heat from the elements is transferred to the rollers more efficiently, allowing high heating * * rates during pre-heating for a reduced waiting time, without localised overheating 15 and its consequent problems 5$*S

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Preferably the heating elements are tubular. Preferably axes of each of the heating elements lie in a plane orthogonal to the planar path and equidistant from the axes of each of the rollers.

Preferably first and second spaces between the rollers of the first and second sets are bounded by parallel planes tangential to the rollers of each set, and each heating element projects into a respective space.

Preferably each thermal conductor bar is radiantly coupled to a respective element.

Preferably the thermal conductor bars are hollow. Preferably two sides of the thermal conductor bars are tapered in cross section, from a wider portion adjacent the path to a narrower portion that extends between the rollers of the first and second sets respectively. Preferably the two tapered sides include a concave outer surface facing the adjacent rollers. Preferably the wider portion comprises a concave outer surface.

Preferably the heat shields comprise a substantially concave inner surface that extends about the rollers of the first and second sets respectively. The concave inner surface may be parabolic in cross section, with the heating element disposed proximate a locus of the parabolic surface.

Preferably the planar path extends substantially horizontally in use and the sheet material exits from an exit side of the second pair of rollers, the heat shields further .* comprise upper and lower flanges positioned on the exit side of the second pair of S.....

* rollers and spaced from the path, each flange being arranged axially along a respective roller and in close proximity to an exterior surface of the respective roller for preventing * the material from passing between the roller and respective flange; wherein the lower :... 15 flange has a surface facing the planar path which extends upwardly from the exit side * toward a longitudinal edge of the lower flange.

Preferably the rollers of the first and second sets project from a mouth of the respective heat shiejd extending about them, the dimension of the mouth parallel to the planar path being smaller than the maximum dimension of the concave inner surface parallel to the planar path.

This invention provides a laminator which is effective and efficient in operational use, which may be economically constructed and which addresses drawbacks in the thermal performance of laminators of the prior art. In particular, heat is transferred to the rollers more efficiently, allowing high heating rates for a short pre-heating time.

Avoiding localised overheating also allows a higher, more uniform operating temperature to be achieved and allows a higher throughput speed for the sheet material.

Brief Description of the Drawings

Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Figure 1 is a schematic cross-sectional view through the heating chamber of a prior art * :" 10 laminator, Figure 2 is a schematic cross-sectional view through the heating chamber of a laminator according to an embodiment of the invention, and * * "* Figure 3 is a partly sectioned pictorial illustration of the heating chamber of Fig. 2. * .

Description of the Preferred Embodiments

Referring to Figs 2 and 3 of the drawings, a laminator includes a heating chamber 20 including an inlet pair of rollers 22, 23 at the inlet side 30 and an outlet pair of rollers 24, 25 at the outlet side, both pairs of rollers being generally enclosed by heat shields 26, 27. A planar path 28 extends tangentially to the rollers 22-25. As the rollers 22-25 turn, sheet material 29 (such as a film and sheet to which the film is to be bonded) is fed from the inlet side 30 along the path 28 between the rollers 22-25 of each pair to exit from an exit side 31 of the rollers. For ease of reference, the two rollers on each side of the planar path 28 may be referred to as comprising first and second sets of rollers, each set comprising one rofler from each of the first and second pairs of rollers. The first set comprises the rollers 22, 24 on one side, and second sets comprise the rollers 23, 25 on the other side of the path 26. Within each of the heat shields 26, 27 is a respective heating element 32, 33 and thermal conductor bar 34, 35. The heating chamber 20 may include members 45 to which longitudinally opposing ends of the rollers 22-25, heating element 32, 33, thermal conductor bars 34, 35 and heat shields 26, 27 are connected.

The rollers 22-25 may be of like dimension and arranged with their longitudinal axes substantially parallel. In this manner a plane 36 orthogonal to the planar path 28 is equidistant from the axes of each of the rollers 22-25. In the preferred embodiment shown, the path 28 is horizontal in use. The rollers 22-25 may be solid metallic bars(or of another material with similar relatively high heat capacity) surrounded by a cylindrical layer of silicon rubber.

The two like heating elements 32, 33 may be disposed, like the rollers 22-25, generally symmetrically relative to the planes 26 and 36. The heating elements 32, 33 are disposed alongside respective ones of the rollers 22-25, on opposing sides of the path 28 to one another. The heating element 32 is adjacent roller 22 and roller 24 of the first set, and likewise element 33 lies adjacent both rollers 23 and 25 of the second set. The elements 32, 33 may be tubular, for instance quartz tubes. The axes of the elements 32, 33 may lie in plane 38, equidistant from the rollers of the respective set. The dashed line in Fig. 2 represents a plane 40 parallel to the planar path 28 and tangential to the rollers 23, 25 of the second set. A space 41 is shown between the rollers 23, 25, bounded by the planar path 28 and the plane 40. The heating element 33 may project into this space 41, with the element 32 likewise projecting into the corresponding space 42.

The two thermal conductor bars 34, 35 are made of metal, such as aluminium. The thermal conductor bars 34, 35 are of like form and may also be disposed generally symmetrically relative to the planes 28 and 36, on opposing sides of the path 28 to one another and between the inlet pairs of rollers 22, 23 and the outlet pair of rollers 24, 25. The thermal conductor bar 34 extends alongside the rollers 22, 24 of one of the first set, while thermal conductor bar 35 extends alongside the rollers 23, 25 of one of the second set. The thermal conductor bars 34, 35 extend adjacent to and spaced from a respective one of the elements 32, 33. The thermal conductor bars ". : 34, 35 are metallic and are radiantly coupled to respective ones of the elements 32, * ** 33 by providing the spaces 41,42 through which radiant energy can flow directly. As the thermal conductor bars 34, 35 are spaced apart from the heating elements they are heated by radiant and convective heat transfer, not by conductive heat transfer.

The thermal conductor bars 34, 35 serve to moderate the temperature of the sheet * S * *.* material as it passes between the first and second pairs of rollers and to prevent the sheet material from being deflected too far from the path 18, as depending upon the sheet material composition it may have a tendency to curl up when passing from the first pail of rollers 22, 23. The thermal conductor bars 34, 35 may be hollow and include a base 46 connected to a tip 47 by sides 48, 49 disposed either side of the plane 36. The sides 48, 49 taper from the base 46, which is relatively wider, toward the narrower tip 47. The two tapered sides 48, 49 include respective concave outer surfaces 50, 51 facing the adjacent rollers. Each tip 47 may protrude between the rollers of a respective set, while the bases 46 lie adjacent the planar path 28 and include opposing concave outer surfaces 52, which minirnises the opportunity for the sheet material to come into contact with the conductor bars 34, 35.

The heat shields 26, 27 may be formed from metal, as from aluminium extrusions and disposed on opposing sides of the path 28 to one another. A upper heat shields 26 extends about the rollers 22, 24 of the upper, or first set, and a Pike lower heat shield 27 extends about the rollers 23, 25 of the lower, or second set. Each heating element 32, 33 is disposed in a respective cavity 54, 55 bounded by one of the heat shields 26, 27, the outer cylindrical surfaces of the two rollers of each set, and one of the thermal conductor bars 34, 35. The heat shields 26, 27 may comprise respective substantiatly concave inner surfaces 56, 57 that extend about the upper and lower rollers of each pair. The concave inner surface 56, 57 may be parabolic n ".: cross section, with the heating elements 32, 33 disposed proximate a locus 157 of the parabolic surface for directing radiant energy toward the rollers.

Upper and lower flanges 58, 59 may be formed integrally with the heat shields 26, 27 and positioned on the exit side 31, spaced from the path 28. The flanges are 58, 59 ... 15 arranged axially along a respective roller of the outlet pair 24, 25 in close proximity to an exterior surface of the respective roller 24, 25. This prevents the material 29 from passing between the rollers 24, 25 and respective flange 58, 59. The lower flange 59 has a surface 60 facing the planar path 28 which extends upwardly from the exit side 31 of the rollers toward a longitudinal edge 61 of the lower flange 59. This surface 60 serves to guide the leading edge of the sheet material 29 as it exits the heating chamber 20, limiting its possible sagging deflection below the path 28.

The rollers 22, 24 of the first set project through a mouth 62 of the heat shields 26, with the rollers 23, 25 of the second set likewise projecting through a mouth of the heat shield 27. The concave inner surfaces 56, 57 may have a re-entrant form, such that the dimension 63 of the mouth 62 parallel to the planar path 28 is smaller than the maximum dimension 64 of the concave inner surface 56, 57 parallel to the planar path 28. In this manner the heat shields 26, 27 serve to efficiently direct the heat toward the rollers 22-25, while retaining a substantial amount of the energy within the chamber 20. Heat loss may be further restricted by a covers 70 extending over the upper heat shield 26, and by insulation (not shown). Compared to known designs, a single element 32, 33 is able to more efficiently heat the two adjacent rollers of each set and less heat is "lost" to the heat shields 26, 27 by conduction, and to the thermal conductor bars 34, 35.

Aspects of the present invention have been described by way of example only and it ". : should be appreciated that modifications and additions may be made thereto without * .* departing from the scope thereof. * . * * * * S.

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Claims

<claim-text>CLAIMS: 1. A laminator for sheet material, comprising: first and second pairs of substantially parallel rollers which define a planar path extending tangentially to the rollers, along which path the sheet material is fed between the rollers of each pair, the two rollers on each side of the planar path comprising first and second sets of rollers respectively; two substantially parallel heating elements, the heating elements being disposed on opposing sides of the path to one another, each extending alongside the rollers of a respective one of the first and second sets; * . . * *s two substantially parallel thermal conductor bars, the thermal conductor bars * : * being disposed between the pairs of rollers on opposing sides of the path to * E one another, and spaced apart from the heating elements, each extending alongside the rollers ala respective one of the first and second sets, and * two heat shields, the heat shields being disposed on opposing sides of the path to one another, each heat shield extending about the rollers of a respective one of the first and second sets to define a respective cavity, each cavity substantially enclosing a respective heating element, each cavity being further bounded by outer surfaces of the rollers of a respective one of the first and second sets and one of the thermal conductor bars, and wherein each heat shield is spaced apart from the respective heating element.</claim-text> <claim-text>2. The laminator of claim 1 wherein the heating elements are tubular.</claim-text> <claim-text>3. The laminator of claim 1 or claim 2 wherein axes of each of the heating elements lies in a plane orthogonal to the planar path and equidistant from the axes of each of the rollers.</claim-text> <claim-text>4. The laminator of any one claims 1 to 3 wherein first and second spaces between the rollers of the first and second sets are bounded by parallel planes tangential to the rollers of each set, and each heating element projects into a respective space.</claim-text> <claim-text>5. The laminator of any one claims 1 to 4 wherein each thermal conductor bar is radiantly coupled to a respective element.</claim-text> <claim-text>6. The laminator of any one claims 1 to 5 wherein the thermal conductor bars are * * hollow. *e. * S SS</claim-text> <claim-text>7. The laminator of any one claims 1 to 6 wherein two sides of the thermal conductor bars are tapered in cross section, from a wider portion adjacent the S. * S*.path to a narrower portion that extends between the rollers of the first and * S second sets respectively.6. The laminator of claim 7 wherein the two tapered sides include a concave outer surface facing the adjacent rollers.9. The laminator of claim 8 wherein the wider portion comprises a concave outer surface.10. The laminator of any one claims 1 to 6 wherein the heat shields comprise a substantially concave inner surface that extends about the rollers of the first and second sets respectively.11. The laminator of any one claims I to 10 wherein the concave inner surface is parabolic in cross section, with the heating element disposed proximate a locus of the parabolic surface.12. The laminator of any one claims 1 to 11 wherein the planar path extends substantially horizontally in use and the sheet material exits from an exit side of the second pair of rollers, the heat shields further comprise upper and lower flanges positioned on the exit side of the second pair of rollers and spaced from the path, each flange being arranged axially along a respective roller and in close proximity to an exterior surface of the respective roller for preventing the material from passing between the roller and respective flange; wherein the * lower flange has a surface facing the planar path which extends upwardly from the exit side toward a longitudinal edge of the lower flange. S. *13. The laminator of any one claims 1 to 12 wherein the rollers of the first and *5ss..* second sets project from a mouth of the respective heat shield extending about them, the dimension of the mouth parallel to the planar path being smaller than * the maximum dimension of the concave inner surface parallel to the planar path.</claim-text>