WO1998028127A1

WO1998028127A1 - Manufacture of corrugated board

Info

Publication number: WO1998028127A1
Application number: PCT/GB1997/003505
Authority: WO
Inventors: Peter White
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 1996-12-20
Filing date: 1997-12-19
Publication date: 1998-07-02
Anticipated expiration: 1999-06-20
Also published as: GB9626620D0; AU5330398A

Abstract

A double backer machine for joining a single-faced corrugated web to at least an additional liner, with the aid of an applied adhesive, comprising a pair of opposed conveyor belts (14, 16) which convey between them the material (10-12) to be joined, the lower belt 16 being supported by a table and the upper belt (14 ) being urged downwards by air pressure, and including a dielectric heating device (30, 32, 34) arranged to produce radiation which passes through the material so as to heat and at least partially set the adhesive.

Description

: Manufacture of Corrugated Board

2

3 This invention is concerned with double backing devices used in

A the manufacture of corrugated board . A double backer joins a s single-faced corrugated web, comprising a liner and an attached

6 corrugated medium, to at least one further liner so that the corrugated

7 medium is sandwiched between two liners and adheres to both. A a double backer can also, for example, be used to join two similarly 9 orientated single faced corrugated webs together with a liner so as to ιo form a double corrugated board. ii Double backers have conventionally consisted of a series of i2 heated steam chests along which the material is conveyed by a belt

: which urges the material downwards onto the stream chests with the aid

I* of air pressure above the belt. The single faced web usually lies above i5 the additional liner, which runs in contact with the steam chests. The i6 adhesive joining the additional liner to the corrugated medium is set by i7 the heat conducted to it from the steam chests. is According to one aspect of the present invention, a double backer i comprises a pair of opposed conveyor belts which convey between

20 them the material to be joined, the lower belt being supported by a table

2i and the upper belt being urged downwards by air pressure, and 2 includes a dielectric heating device arranged to produce radiation which 3 passes through the material so as to heat and at least partially set the 4 adhesive. The dielectric heating device preferably operates in the radio 5 frequency band, but could alternatively, for example, be at microwave 6 frequency. In either case, the energy passes readily through at least one of the belts and has its most significant heating effect on the water 8 content in the adhesive and to a lesser extent on the moisture in the added liner and corrugated medium. In a preferred arrangement the 0 heating device comprises a number of electrodes powered by an i appropriate generator and positioned so that energy fields between the 2 electrodes cross through the material being joined. The electrodes may 3 all lie on one side of the material, preferably in the air pressure chamber 4 above the upper belt, but as an alternative the arrangement may involve 5 electrodes situated above and below the material. 6 In a conventional double backer, there is a risk of the steam 7 chests distorting as they heat up, and that can be a factor in the 8 corrugated board becoming warped. The present invention allows the 1 lower belt to run along a perfectly flat table which is not prone to

2 distortion since it is not heated to any significant extent by the dielectric

3 energy. Since the material being joined by a double backer according to A this invention is conveyed by opposed belts, rather than running

5 frictionally along a stationary surface, it is subject to a more reliable and

6 even tractive force. In a conventional system it is usual to provide a

7 traction unit downstream of the double backer, but such a unit can be β dispensed with in a double backer according to the present invention, with consequent cost and space savings. ιo Each of the belts is preferably porous so as to allow moisture from ii the adhesive to pass through and to be extracted, for example, at the i2 side edges of the belts, as well as from the main surfaces of the belts is during their return runs. i4 An example of a double backer according to this invention is i5 shown in the accompanying drawing. This shows two single faced webs i6 10 and 1 1 (exaggerated in size for the purpose of illustration) and a i bottom liner 12 being fed between belts 14 and 16 which pass around is various pulleys as shown. Each single faced web comprises a liner i9 joined to an underlying corrugated medium. Before entry to the double

20 backer, the bottom crests of the corrugated mediums are coated with

2i adhesive by any well-known form of adhesive applicator. Thus the two

22 single faced webs and the additional liner 12 will be joined together by

23 the double backer to form double corrugated board. Alternatively, one

2 of the single faced webs may be omitted if what is required is single

25 corrugated board.

26 The belts 14 and 16 have opposed horizontal runs in order to

27 convey the material 1 0-1 2 horizontally and to join the components 8 together. A double corrugated board web 18 is thus produced and

29 passes from the left-hand end of the double backer. 0 The upper and lower belts 14 and 16 (together with the material i 10-12), upon commencing their horizontal travel, initially pass through a 2 radiation-attenuating duct comprising upper and lower walls 20 and 22 3 before entering the region of an air pressure chamber 24 in which air pressure urges the upper belt downwards while the lower belt is 5 supported by a table (not shown). Beyond the air pressure chamber 24 6 the belts are again arranged to pass through a radiation attenuating duct 7 comprising upper and lower walls 26 and 28. The ducts 20,22 and 26,28 8 are intended to prevent any significant escape of RF energy from the chamber 24.

It will be understood that the air pressure chamber 24 has side walls extending downwards to positions close to the side edges of the upper belt 20.

Ducts (not shown) are provided at the edges of both of the belts to draw away moist air in the region of the pressure chamber 24.

7 In the arrangement shown, a dielectric energy field is produced by a upper electrodes 30, located in the air pressure chamber 24, in cooperation with staggered lower electrodes 32. Alternatively, as already mentioned, all the electrodes may be located in the air pressure

: chamber 24, close enough to the upper belt to ensure that the energy

2 fields extending between them pass through the material 10-12. With the arrangement shown, in which the electrodes 32 are

14 below the table supporting the lower belt, it will be understood that the is table would be of a material through which the radiation can readily

:β pass. i7 A power generator 34 for powering the electrodes is situated is above the air pressure chamber 24. Air pumped into the chamber 24 to i produce the required air pressure (for example about 0.5 pounds per

20 square inch) passes first through the generator so as to cool the latter.

2i By way of example, the heating device formed by the electrodes

22 30,32 may operate at a frequency of 27.12 MHZ, which is in the radio

2 frequency range and is available (though not necessarily the best) for

24 this purpose. The power supplied to the electrodes by the generator

25 may, for example, be of the order of 250kW. Suitable equipment for this

26 purpose is available from Radyne Ltd. of Wokingham, UK, which is a

27 subsidiary of Inductotherm Inc., USA.

∑^β The following modification may be made. One or both of the belts

2 may be omitted, and the material to be joined may be pulled through the 0 field of the dielectric heating device by a separate or integral traction 3i unit. The traction unit may comprise a belt or a pair of opposed belts. In 2 the case of a single belt, vacuum may be applied through apertures in the belt to grip the adjacent liner.

34 35 36

Claims

CLAIMS:

3 1. A double backer machine for joining a single-faced corrugated web to at least an additional liner, with the aid of an applied

5 adhesive, comprising a pair of opposed conveyor belts which convey e between them the material to be joined, the lower belt being supported 7 by a table and the upper belt being urged downwards by air pressure, a and including a dielectric heating device arranged to produce radiation 9 which passes through the material so as to heat and at least partially set ιo the adhesive.

1 1 i2 2. A machine according to claim 1 , in which the heating i3 device comprises a number of electrodes positioned so that energy i4 fields between them pass through the material being joined.

15 i6 3. A machine according to claim 2, in which some of the i7 electrodes lie above the upper conveyor belt and others lie below the is lower conveyor belt.

19 0 4. A machine according to any one of claims 1 to 3, in which i at least one of the conveyor belts is porous so as to allow moisture from 2 the adhesive to pass through. 3 4 5. A machine according to claim 4, including means for drawing away moisture from the edge of the porous belt or belts. 6 7 6. A machine according to any one of claims 1 to 5, in which 8 electrodes, or at least some of them, which comprise the heating device 9 lie in an air pressure chamber above the upper conveyor belt, and air 0 blown into the pressure chamber passes through a power generator i which powers the electrodes so as to cool the generator. 2 3 7. A double backer machine for join ing a single-faced corrugated web to an additional liner with the end of an applied adhesive, comprising a conveyor belt or a pair of opposed conveyor 6 belts arranged to pull the material to be joined through the field of a 7 dielectric heating device which is arranged to heat and at least partially 8 set the adhesive.