GB2286362A

GB2286362A - Producing corrugated board

Info

Publication number: GB2286362A
Application number: GB9401415A
Authority: GB
Inventors: Christopher Mark Ward
Original assignee: SCM Container Machinery Ltd
Current assignee: SCM Container Machinery Ltd
Priority date: 1994-01-22
Filing date: 1994-01-22
Publication date: 1995-08-16
Anticipated expiration: 2014-01-22
Also published as: GB9401415D0; GB2286362B

Abstract

A heat transfer system for producing double wall or tri-wall corrugated board in which a single faced board is carried past a series of hotplates (10, 21) with glue applied to the tips of the corrugations so that a liner sheet may be bonded thereto there being a series of gas filled vessels (12, 23) disposed above the single-faced board to press the combined board down evenly and firmly onto the hotplates (10, 21) as it passes through the system. The system comprises two successive sections (A, B,) in the first of which the hotplates (10) are disposed beneath the web of material (28) and in the second of which the hotplates (21) are arranged above the web (30). In each section the gas filled vessels (12, 23) are disposed on the opposite face of the web (28, 30) to press it firmly against the hotplates (10, 21). If required, a further single-faced board (25) may be introduced between the first and second sections (A, B) and between the already-formed board and the hotplates. By this system, glued surfaces in the single or double faced board are fully bonded by uniform contact with the hotplates. <IMAGE>

Description

A HEAT TRANSFER SYSTEM THIS INVENTION concerns a heat transfer system wherein a continuous web of material is to be transported across the surface of one or more hotplates where the web is subjected to an elevated temperature for a predetermined period.

Particularly, though not exclusively, the invention is concerned with corrugating machinery in which, in one example, socalled single faced board with glue applied to the exposed tips of a corrugated sheet is brought together with a liner sheet which is thus bonded to the glued tips to form a double faced board, and the composite board is carried beneath a conveying belt past a bank of hotplates which assist in the bonding of the liner to the corrugated tips of the single faced board.

British patent No. 2233935 describes a system which is characterised by means imposing a load on the face of the web remote from the hotplates to maintain contact with the latter, the load applying means including at least one flexible bag containing a fluid medium thus, by contact to press the web of material against the hotplates thereby to conform to the surface of the latter irrespective of any undulation thereof to ensure even heat transfer.

Hotplate surfaces may become distorted owing to their elevated temperature and so it is essential if uniform heat transfer is to be achieved to ensure that the moving web of material conforms exactly to any undulation which may occur in the heated surface without excessively compressing the material in any particular region.

The extension of this technology is to provide a heat transfer system in cases where a double or triple-walled corrugated web is to be produced, or any substrate which is of sufficient thickness that the heat transfer from one face of the substrate is insufficient at or in the region of the opposite face thereof.

An object of the present invention is to provide a heat transfer system in which adequate heat is transferred to all parts of the depth or thickness of a moving substrate thus to ensure complete and substantially uniform heat transfer during passage through the system.

According to the present invention, there is provided a heat transfer system in which a continuous web of material is carried past a series of hotplates, there being means imposing a load on the face of the material remote from the hotplates to maintain contact between the material and the latter, the load applying means including a flexible or resilient surface which, by contact, presses said material against the hotplates thereby to conform to the surface of the latter irrespective of any undulation thereof; characterised in that the system comprises at least two successive sections in the first of which the hotplates are disposed against one face of the continuous web of material, and in a second of which the hotplates are arranged in contact with the opposite face thereof, there being, in each section, at least one flexible or resilient surface adapted to impose a load on the face of the material remote from the hotplate or plates.

The invention is particularly applicable to the production of double wall or so-called "tri-wall" corrugated board. In the former there are two fluted sheets bonded to an intermediate flat sheet with a further pair of flat sheets on the outer or opposite faces of the two fluted sheets such that the laminated structure comprises three flat sheets and two fluted sheets. In the latter, the laminated structure comprises four flat sheets and three fluted sheets in alternate superimposed relationship.

In GB 2233935, a single faced corrugated sheet with glue applied to the tips of the corrugations is introduced continuously into a heat transfer system together with a liner sheet which is thus bonded to the tips of the corrugations as the composite web passes through the machine. In this case, the liner is introduced into the system beneath the glued tips of the corrugated single faced board then directed over the surface of a bank of hotplates while a flexible or resilient surface presses firmly down on the single faced sheet to cause bonding between the liner and the glued tips, the glue being cured by the elevated temperature provided by the hotplates.

An embodiment of the present invention will be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation of a heat transfer system provided in two separate sections in accordance with the invention; Fig. 2 is an enlarged view of a part of the first section, indicated by the arrow A; and Fig. 3 is an enlarged view of a part of the second section, indicated by the arrow B.

Referring now to the drawings, there is provided a machine in which a series of hotplates 10 is arranged on the bed of the machine and operated at elevated temperature. In one example, a single faced board with its exposed tips lowermost and coated with glue is introduced beneath a conveying belt 11 together with a liner sheet y which is arranged to travel at the same speed as the single faced board across the hotplates 10 and, as can be seen singly in Fig. 2, a series of flexible vessels in the form of inflated air sacks 12 is provided to press the single faced board down into intimate contact with the liner (and the latter with the hotplates 10) as it passes over the hotplates 10 to ensure curing of the glue irrespective of any undulation of the heated surface due to distortion as a result of the elevated temperature.

In the second section of the machine generally illustrated at 20 a bank of hotplates 21 is provided above the line of the travelling web and beneath it is provided a series of air sacks 23 and a driven conveying band 24. At this point, a further single faced board 25 may be introduced via a series of feed rolls generally indicated at 26, and passing through a glue unit 27 whereby glue is applied to the lowermost exposed tips of the corrugated sheet of the single faced board. This is joined with the already formed double raced board 28 to form a double wall laminated structure. In this case, the glue to be cured is disposed above the single faced board entering the second section 20 of the machine and so it is appropriate for the heated surfaces to be disposed uppermost above the continuous web whereby the maximum heat transfer can be achieved.

Referring now to paragraph 3, just like in the first section of the machine, the air sacks 23 are provided beneath each hotplate to press the continuous web firmly against the hotplates to ensure adequate heat transfer to cure the glue. In this example, there issues from the machine a double wall corrugated web 30 comprising three liners and two corrugated sheets formed into a laminate as illustrated in Fig. 3.

The machine may be adapted to produce a so-called triwall web comprising three superimposed corrugated webs with flat liners between them and further liners forming the outer surfaces as illustrated in Fig. 4. In this case, a double wall structure may be formed in the first section of the machine and combined with a further single faced web in the second section.

Several laminae may be assembled using this system in which the heated surfaces are disposed in series below and above the continuous web respectively so that the heated surfaces are closest to the glue to be cured in the appropriate section. In all conventional machines of this general kind the heated surfaces have been disposed only on one side of the continuous web and the web speed has had to be reduced as appropriate to ensure adequate heat transfer and curing of the glue. In the present invention, it is envisaged that by alternating the position of the heated surfaces to comply most closely with the glue to be cured, the production speed may be maximised whilst ensuring adequate and substantially uniform heat transfer to all parts of the continuous web where glue is to be cured or other heat treatment is to be provided.

It will be noted that beneath (or above) each air sack 12 whose degree of inflation may be controlled individually or collectively, there is provided a system of chain links 28 to provide a universally flexible skid plate between the surface of the air sack 12 and the adjacent conveying band 24 or other travelling web.

As can be seen clearly from Figs. 2 and 3, on the side of each air sack 12 opposite to the moving web there is provided a supporting framework 29 to provide a reaction surface against which the air sack 12 may bear.

It is not intended to limit the invention to the above example only. For example, the air sacks 12 may be replaced by liquid-containing vessels in which the internal pressure may be preset or adjustable accordingly. Air or other gas inflated vessels are preferable since they are more readily controlled as to the pressure imposed upon the moving web. One such resilient surface can comprise an array of individually spring-loaded shoes in sliding contact with the web itself or with a flexible skid plate or the like interposed between the shoes and the web. In another alternative arrangement, the gas or liquid filled bags may be replaced by any flexible or resilient single or composite surface adapted to conform to any undulation in the web or the hotplate surfaces.

Across the width of the machine several such vessels may be provided to ensure an adequate load on the continuous web to hold it firmly against the hotplate surfaces irrespective of any undulation thereof as the web travels through the machine.

Claims

1. A heat transfer system in which a continuous web of material is carried past a series of hotplates, there being means imposing a load on the face of the material remote from the hotplates to maintain contact between the material and the latter, the load applying means including a flexible or resilient surface which, by contact, presses said material against the hotplates thereby to cause the material to conform to the surface of the latter irrespective of any undulation thereof; characterised in that the system comprises at least two successive sections in the first of which the hotplates are disposed to be contacted by one face of the continuous web of material, and in a second of which the hotplates are disposed to be contacted by the opposite face thereof, there being, in each section, at least one flexible or resilient surface adapted to impose a load on the face of the material remote from the hotplates.

2. A heat transfer system according to Claim 1, wherein the load applying means comprises a series of flexible vessels containing a fluid medium.

3. Apparatus according to Claim 2, wherein the load applying means comprises a series of gas-inflated sacks.

4. A heat transfer system according to Claim 1, wherein, in the first section, the hotplates are disposed against the lower face of the continuous web of material, and in the second section the hotplates are disposed against the upper face thereof.

5. A heat transfer system according to any preceding claim, including one or more stationary skid plates disposed between the load applying means and the continuous web of material.

6. A heat transfer system according to Claim 5, wherein the or each skid plate comprises a series of interconnected individual members, together providing a universally flexible surface.

7. A heat transfer system according to Claim 6, wherein the or each skid plate comprises a series of chain links interconnected to extend across the entire lower surface of the load applying means.

8. A heat transfer system according to Claim 2, wherein on the side of each fluid containing vessel opposite the moving web of material there is provided a supporting framework to provide a reaction surface against which the vessel may bear.

9. A heat transfer system according to Claim 2, wherein the load applying means comprises a series of liquid-containing flexible vessels.

10. A heat transfer system according to Claim 3, wherein the pressure of gas within the or each sack is adjustable.

11. A heat transfer system according to Claim 1, wherein the flexible or resilient surface of the load applying means is comprised by an array of individually resilient shoes adapted to bear directly or indirectly upon the continuous web of material.

12. A heat transfer system according to Claim 2, wherein across the width of the continuous web of material several such vessels are provided to ensure an adequate load on the entire width of the web to hold it firmly against the hotplate surf aces across the width thereof.

13. A heat transfer system according to Claim 1, including means between said at least two successive sections, for introducing a further continuous web of material to be bonded to the first mentioned continuous web of material, the further web being introduced between the first web and the hotplate surfaces in the second section.

14. A heat transfer system according to any preceding claim, in which a conveyor belt is disposed between the load applying means and the continuous web of material to transport the latter through the system.

15. A heat transfer system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.