GB2184959A

GB2184959A - Applying adhesive to sheet material

Info

Publication number: GB2184959A
Application number: GB08600222A
Authority: GB
Inventors: Anthony John Sissons; Reginald Robert Green
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-01-07
Filing date: 1986-01-07
Publication date: 1987-07-08
Also published as: GB8600222D0

Abstract

Sheet material is contacted with a uniform fine surface layer of adhesive on an applicator cylinder (3), which layer has been formed by metering a coarse layer with a metering cylinder (15) rotating in the same sense as the applicator cylinder. Adhesive is removed from the metering cylinder (15) by doctor means which preferably takes the form of a cylinder (21) frictionally engaging and driving the metering cylinder. The invention has particular application to the application of cold set adhesive, especially PVA, to the flute tips of a corrugated sheet during the manufacture of corrugated paper. <IMAGE>

Description

SPECIFICATION Apparatus and Method of Applying Adhesive to Sheet Material The present invention relates to the application of adhesive to sheet material and provides an apparatus and method for that purpose. It has particular, but not exclusive, application to corrugators, i.e. machines for the production of corrugated paper.

In the manufacture of corrugated paper, it is necessary to cause a flat liner sheet to adhere to the flute tips of a corrugated sheet already backed with a flat liner sheet whereby the corrugated sheet is sandwiched between the liner sheets. Usually, the backing sheet is simultaneously caused to adhere to the flute tips of a second liner-backed corrugated sheet to provide a double sandwich arrangement.

The corrugator operates at relatively high velocity, for example 200 metres per minute, and it is necessary to apply adhesive to the flute tips whilst the liner-backed corrugated sheet is travelling at such velocity. Conventionally, adhesive is applied by a rotatable applicator cylinder upon which a surface layer of adhesive is applied by a rotatable pick-up cylinder passing through a bath of adhesive.

The thickness of adhesive on the applicator cylinder is controlled by a doctor blade located between the adhesive-supply and sheet-engaging stations of the cylinder.

The said conventional arrangement is satisfactory for providing adhesive layers of conventional thickness (i.e. about 0.01 inch) on the applicator cylinder but cannot be used for providing layers of less than about 0.006 inch. This limitation does not present any problem when using the starch-based adhesives which are conventionally used in the manufacture of corrugated paper. However, when such adhesives are used, the sandwich arrangement must be heated in order to set the adhesive. This heating takes place on steam tables and not only consumes energy but also limits the operating speed of the corrugator.

Cold set adhesives, especially polyvinyl acetate (PVA), suitable for use in the preparation of corrugated paper have been available for some years. The use of cold set adhesives would make it possible to reduce, and possibly eliminate, heating of the sandwich arrangement and thereby provide a significant saving in energy consumption and enable the corrugatorto be operated at higher speeds. However, the potential saving in energy consumption has been outweighed by the additional cost of the cold set adhesives, which are about five times as expensive as starch-based adhesives. The additional expense of the cold set adhesives would be offset to some extent by the use of smaller quantities of adhesive but, as mentioned above, the conventional adhesive applicator is not capable of applying a surface layer of less than about 0.006 inch.

It is an object of the present invention to provide an adhesive applicator which can be used in a corrugator to apply adhesive at a thickness of less than 0.006 inch and preferably of about 0.002 inch. This object has been achieved by the provision of a rotatable metering cylinder to remove adhesive from the coarse surface layer provided by the pickup cylinder to provide a uniform fine surface layer of adhesive. However, it will be appreciated that the invention is not limited to the use of a pick-up cylinder or to the manufacture of corrugated paper.

According to the present invention, there is provided apparatus for applying adhesive to sheet material, said apparatus comprising a rotatable applicator cylinder for supplying a surface layer of adhesive to a sheet-engaging station, means for applying a coarse surface layer of adhesive to said applicator cylinder at an adhesive-supply station; a rotatable metering cylinder located between said adhesive-supply station and said sheet-engaging station and rotatable in the same sense as the applicator cylinder to engage said coarse surface layer to remove adhesive and leave a uniform fine surface layer of adhesive on the applicator cylinder; and doctor means for removing adhesive from the metering cylinder.

The invention also provides a method of applying adhesive to sheet material, which method comprises contacting the sheet material with a surface layer of adhesive on a rotating applicator cylinder wherein the adhesive is applied to the applicator cylinder as a coarse layer and subsequently adhesive is removed from said coarse layer by a metering cylinder rotating in the same sense as the applicator cylinder to leave on the applicator cylinder a uniform fine surface layer of adhesive with which the sheet material is contacted.

It is preferred that the method of the invention is conducted using apparatus of the invention.

Usually, the means for applying the adhesive to the applicator cylinder will be a rotatable pick-up cylinder which transfers adhesive from an adhesive bath to the applicator cylinder. Preferably, the pickup cylinder is rotatable in the opposite sense to the applicator cylinder.

In order to provide for adjustment of the thickness of the fine surface layer left on the applicator cylinder by the metering cylinder, the metering cylinder usually will be adjustable to vary the gap between the two cylinders. For this purpose, the metering cylinder may be journalled in a bearing housing slidable in a guide but continuously pressed in the direction of the guide into contact with an adjustment cam. Suitably, the bearing housing can be pressed against the cam by the piston of a pneumatic cylinder.

In the present preferred embodiment of the invention, the doctor means comprises a cylinder rotatable in the opposite sense to and engaging the metering cylinder. In such an arrangement, the metering cylinder advantageously is driven by the doctor cylinder. The metering cylinder preferably has a resiliently deformable outer circumferential surface and, in this case, it is especially preferred that the doctor cylinder has a rigid outer cylindrical surface which serves to resiliently deform said outer surface of the metering cylinder at the zone of contact of the cylinders.

In an alternative arrangement, the doctor means can comprise a stationary doctor blade of conventional design. In this case, it is presently preferred that the metering cylinder should have a rigid outer circumferential surface.

Usually, the applicator cylinder will be of greater diameter than the metering cylinder and, if present, the pick-up and/or doctor cylinders.

Advantageously, the metering cylinder diameter is of the order of twice that of the said other cylinders.

The metering cylinder usually will also be fractionally shorter than the other cylinders by, for example, about 0.5 inch.

Usually, the applicator cylinder, metering cylinder and, if present, pick-up cylinder will be driven independently of each other. The applicator cylinder usually will be driven at an angular velocity such that the circumferential speed matches exactly the linear speed of sheet material passing in contact with the applicator. Where the linear velocity of the sheet material changes, for example during start up of a corrugator, the angular velocity of the applicator cylinder can be controlled by a tachogenerator by impulses supplied by the sheet feed drive. The angular velocity of the metering cylinder usually will be adjustable as required over a substantial range, for example, zero to 500 r.p.m.

When present, the pick-up cylinder usually will be adjustable over a limited range of, for example, 200 to 240 r.p.m. In use, the coarse layer deposited on the applicator cylinder usually will be of the order of 0.01 inch and the metering cylinder will reduce the thickness of that layer to below 0.005 inch, especially to about 0.002 inch.

As mentioned previously, the apparatus and method of the invention have particular application to the production of corrugated paper and to the use of cold set adhesives, especially PVA.

The following is a description, by way of example only and with reference to the drawing, of a presently preferred embodiment of the invention.

The single figure of the drawing is a side view (with the nearest side wall omitted) of the operating side of an adhesive applicator for use in a corrugator.

Referring to the drawing, apparatus in accordance with the invention comprises a pair of laterally spaced side walls of which the far side wall 1 is shown but the near side wall is omitted. The walls are connected at their corners by cylindrical supporting members 2. Beyond the wall 1 and not visible in the drawing are located the drive mechanisms for the apparatus (see below).

An applicator cylinder 3 is journalled in a pair of bearing housings 4 attached to the respective side walls. The cylinder 3 is made of steel and has a sand-blasted surface. The shaft of the cylinder extends through the far wall 1 and is driven by a belt and pulley arrangement by a variable speed impulse tachogenerator controlled drive responsive to impulses from the main motor of the corrugator so that the circumferential velocity of the cylinder exactly matches the linear speed of paper through the corrugator. The cylinder rotates in the direction of arrow A.

An idler cylinder 5 is journalled in a pair of bearing housings 6 attached to the respective side walls to support a liner-backed corrugated sheet (not shown) immediately prior to contact with the applicator cylinder 3. Alternative fixing holes 7 are provided in the side walls in order to facilitate alternative positioning of this idler cylinder.

A pneumatic cylinder 8 also is journalled in a pair of bearing housings 9 mounted on the respective side walls. The diameter of the cylinder 8 is adjustable by varying the air pressure within the cylinder. It is provided in order to ensure contact of the flute tips of the corrugated paper with the applicator cylinder 3 and also to remove any creases or other irregularities in the corrugated paper.

Adhesive is applied as a coarse surface layer to the applicator cylinder 3 by a pick-up cylinder 10 journalled in a pair of bearing housings 11 attached to the respective side walls. The bearing housings are capable of limited forward-rearward movement in respective guide tracks 12 and the housing can be positioned at any point along those tracks by means of locating bolts 13. The shaft of the pick-up cylinder 10 extends through the far wall 1 where it is driven by a belt and pulley arrangement by a manually controllable variable speed drive. As indicated by arrow B, the drive is in the opposite sense to that of the applicator cylinder 3. Like the applicator cylinder, the pick-up cylinder is made of steel with a sand-blasted circumferential surface.

The pick-up cylinder 13 passes through an adhesive bath 14. The adhesive is continuously circulated through the bath by means of a pump (not shown).

The thickness of the adhesive surface layer on the applicator cylinder 3 is metered by a metering cylinder 15 which isjournalled in a pair of bearing housings 16. These bearing housings are slidably mounted in guides 17 secured to the respective side walls. The housings 16 bear against respective eccentrics 18 whereby the spacing of the metering cylinder 15 from the applicator cylinder 3 can be adjusted by manual rotation of the eccentric. In order to maintain the spacing constant, each housing 16 is pressed against the respective eccentric 18 by a piston 19 of a pneumatic cylinder 20. The metering cylinder 15 is formed of rubber having a shore hardness of about 30.

Metering cylinder 15 is driven by frictional contact with a steel doctor cylinder 21 which is journalled in a pair of bearing housings 22 carried by the respective side walls. The shaft of cylinder 21 extends through the far wall 1 where it is driven buy a belt and pulley arrangement from a variable speed drive. The direction of the drive of doctor cylinder 21 is indicated by arrow C and the resultant rotation of the metering cylinder 15 is indicated by arrow D.

The circumferential surfaces of the cylinders 15 and 21 overlap whereby there is a zone of contact over which the doctor cylinder 21 deforms the metering cylinder 15 thereby both driving the metering cylinder and removing adhesive from that cylinder.

In a typical arrangement, the applicator cylinder is 14-3/4 inches by 84-3/8 inches; the pick-up cylinder 10 is 7-1/2 inches by 84-3/4 inches and the metering cylinder 15 and doctor cylinder 21 are both 6 inches by 84-3/4 inches. The gap between the pick-up cylinder 10 and the applicator cylinder 3will usually be maintained at about 0.01 inch and the gap between the metering cylinder 15 and the applicator cylinder 3 will usually be maintained at about 0.002 inch. The angular velocity of the metering cylinder 3 will usually provide a circumferential speed of about 200 metres per minute, the pick-up cylinder 10 is adjustable in the range 200 to 240 r.p.m. and the doctor cylinder 21 is adjustable from zero to 500 r.p.m.

In use, the bath 14 contains PVA adhesive which is transferred by the pick-up cylinder 10 to form a coarse (about 0.01 inch thick) layer on the applicator cylinder 3. The metering cylinder 15 removes adhesive from the coarse layer to leave a uniform fine (about 0.002 inch thick) layer of adhesive on the applicator cylinder 3. Some of the removed adhesive falls directly back into the bath 15 and some is removed from the metering cylinder 15 by engagement with the doctor cylinder 21. Adhesive is transferred to the flute tips of a continuous linerbacked sheet feed passing over the idler cylinder 5 to contact the applicator cylinder 3. After passage between the applicator cylinder 3 and the pneumatic cylinder 8, the corrugated sheet is pressed against a liner sheet feed thereby sandwiching the corrugated sheet between two liner sheets. If desired, a second liner-backed corrugated sheet to which PVA adhesive has been applied by an identical applicator apparatus is pressed into contact with the backing liner thereby producing a double sandwich arrangement.

It will be appreciated that the invention is not restricted to the particular details described above and that numerous modifications and variations can be made without departing from the scope of the invention as defined in the following claims. In particular, the rubber metering cylinder 15 could be replaced by the steel doctor cylinder 21 (which then becomes the metering cylinder) and a conventional doctor blade provided to remove adhesive from the cylinder 21.

Claims

1. Apparatus for applying adhesive to sheet material, said apparatus comprising a rotatable applicator cylinder for supplying a surface layer of adhesive to a sheet-engaging station; means for applying a coarse surface layer of adhesive to said applicator cylinder at an adhesive-supply station; a rotatable metering cylinder located between said adhesive-supply station and said sheet-engaging station and rotatable in the same sense as the applicator cylinder to engage said coarse surface layer to remove adhesive and leave a uniform fine surface layer of adhesive on the applicator cylinder; and doctor means for removing adhesive from said metering cylinder.

2. Apparatus as claimed in Claim 1 wherein said means for applying adhesive is a rotatable pick-up cylinder for transferring adhesive from an adhesive bath to the applicator cylinder.

3. Apparatus as claimed in Claim 2 wherein said pick-up cylinder is rotatable in the opposite sense to the applicator cylinder.

4. Apparatus as claimed in any one of the preceding claims wherein the position of the metering cylinder is adjustable to vary the gap between said cylinder and the applicator cylinder and thereby the thickness of the fine adhesive layer left on the applicator cylinder.

5. Apparatus as claimed in Claim 4 wherein the cylinder is journalled in a bearing housing slidable in a guide and is continuously pressed in the direction of the guide into contact with an adjustment cam.

6. Apparatus as claimed in Claim 5 wherein the piston of a pneumatic cylinder acts on the bearing housing to press said housing into contact with the adjustment cam.

7. Apparatus as claimed in any one of the preceding claims wherein the doctor means comprises a cylinder rotatable in the opposite sense and engaging the metering cylinder.

8. Apparatus as claimed in Claim 7 wherein the metering cylinder is driven by the doctor cylinder.

9. Apparatus as claimed in Claim 7 or Claim 8 wherein the metering cylinder has a resiliently deformable outer circumferential surface.

10. Apparatus as claimed in Claim 7 wherein the metering cylinder has a resiliently deformable outer circumferential surface, the doctor cylinder has a rigid outer circumferential surface and said outer surface of the metering cylinder is resiliently deformed at a zone of contact of the said cylinders.

11. Apparatus as claimed in any one of Claims 1 to 6 wherein the doctor means comprises a stationary doctor blade.

12. Apparatus as claimed in Claim 11 wherein the metering cylinder has a rigid outer circumferential surface.

13. Apparatus as claimed in any one of the preceding claims wherein the applicator cylinder is of greater diameter than the metering cylinder and, if present, the pick-up and/or doctor cylinders.

14. Apparatus as claimed in Claim 13 wherein the diameter of the metering cylinder is of the order of twice the diameter of the said other cylinders.

15. Apparatus as claimed in any one of the preceding claims wherein the coarse surface layer is about 0.01 inch thick and the fine surface layer is less than 0.005 inch thick.

16. Apparatus for applying adhesive to sheet material substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

17. A corrugator including as an adhesive applicator, apparatus as claimed in any one of the preceding claims.

18. A method of applying adhesive to sheet material which comprises contacting the sheet material with a surface layer of adhesive on a rotating applicator cylinder wherein the adhesive is applied to the applicator cylinder as a coarse layer and subsequently adhesive is removed from said coarse layer by a metering cylinder rotating in the same sense as the applicator cylinder to leave on the applicator cylinder a uniform fine surface layer of adhesive with which the sheet material is contacted.

19. A method as claimed in Claim 18 wherein the thickness of the coarse layer is about 0.01 inch and the thickness of the fine layer is less than 0.005 inch.

20. A method as claimed in Claim 19 wherein the thickness of the fine layer is about 0.002 inch.

21. A method as claimed in any one of Claims 18 to 20 wherein the adhesive is applied by apparatus as claimed in any of Claims 1 to 17.

22. A method as claimed in any one of Claims 18 to 22 wherein the sheet material is a liner-backed corrugated sheet for use in the manufacture of corrugated paper.

23. A method as claimed in any one of Claims 18 to 22 wherein the adhesive is PVA.

24. A method of applying adhesive to sheet material substantially as hereinbefore described with reference to the drawing.