GB2279320A

GB2279320A - A convolutely wound tapered drum

Info

Publication number: GB2279320A
Application number: GB9312776A
Authority: GB
Inventors: Peter Johnson; John E Ingham; Kenneth Tinsley; Steven J King; John Mason; Neil Hyde; Graham Harwood; Eric Siddall; Geoffrey Lindley; David Moss; Alan Swinglehurst; John K Weatherhead; Michael Atentyk; Garreth Whitford; Terrence Hadfield; Christopher T Harlin; Kenneth Atkinson; Frederick J Wood
Original assignee: Bowater Packaging Ltd
Current assignee: SCA Packaging Britain Ltd
Priority date: 1993-06-21
Filing date: 1993-06-21
Publication date: 1995-01-04
Anticipated expiration: 2013-06-21
Also published as: IE940506A1; GB2279320B; GB9312776D0

Abstract

A tapered drum 10 is formed from a plurality of convolutely wound, discrete lengths of material, eg kraft paper 20, which are impregnated with adhesive and then wound onto a tapered mandrel (50 Figure 2). Once the tapered drum has been wound, the ends are trimmed with a knife and a portion is severed from the wider end of the drum 10, inverted, positioned over the narrower end of the drum and bonded to the drum side wall 12 to form an anti-locking collar 8. To ensure that the paper 20 is convolutely wound, without crumpling or folding, a pressure roll (52, Figure 2) having a taper corresponding to that of the mandrel is provided to press the impregnated paper 20 against the mandrel. This ensures that the lengths of paper 20 are not skewed while being applied to the mandrel 50. The discrete lengths of paper may be obtained by severing a continuous web of paper (26, Figure 2). The mandrel may be contractable to release the wound drum, and a cover sheet may be wound onto the mandrel prior to winding the lengths of material. <IMAGE>

Description

A TAPERED DRUM This invention relates to storage drums of the type formed from lengths of laminating material, such as kraft paper, wound onto a mandrel in the presence of an adhesive binder.

Cylindrical drums of the above type are well-known and may be wound from a single length of laminating material.

Where, say, a seven-ply laminate is required, a length of laminating material equal to about seven circumferences of the winding mandrel are used. The laminating material is commonly impregnated with adhesive before being wound on the mandrel, but for an initial length equal to one circumference of the mandrel. This prevents the mandrel from becoming contaminated with adhesive.

It has been proposed to manufacture a tapered drum, since such a drum requires less space in which to be stacked empty than do cylindrical drums. One proposals was to form a flat laminated sheet, in the shape of a part-annulus, to bend the sheet around on itself to form the required frustoconical configuration and then to sew the two edges of the sheet together. The resulting tapered drum has a line of weakness along the seam, which can fairly easily be split through rough handling.

It has also been proposed to wind a relatively thin length of laminating material helically onto a tapered mandrel. By "helically" is meant with a constant winding pitch. However, a tapered drum made this way is also relatively weak, having a large number of circumferential seams, and the laminating material, being helically wound and therefore not conforming exactly with the tapered mandrel, may have a tendency to crumple or fold as it is laid on the mandrel.

The present invention seeks to overcome these disadvantages and accordingly provides a tapered drum formed from a plurality of convolutely wound, discrete lengths of laminating material bound to one another by an adhesive. By "convolutely" is meant wound in such a way as to conform exactly with the tapered surface of the drum.

The invention also provides a method of manufacturing a tapered drum comprising convolutely winding a plurality of discrete lengths of laminating material onto a tapered mandrel and binding the lengths of laminating material together with an adhesive. Again, the convolute winding ensures that the laminating material conforms to the surface of the mandrel and prevents the formation of folds or creases, which may weaken the end product.

Finally, the invention provides apparatus for the manufacture of a tapered drum comprising a tapered mandrel, means for convolutely winding a plurality of discrete lengths of laminating material on the mandrel and means for binding the length of laminating material to one another with an adhesive.

Preferably, the drum includes an anti-locking collar which prevents adjacent empty drums in a stack from sticking to one another. The drum is provided with a conventional base and/or lid.

For reasons of strength, it is preferred that the discrete length of laminating material from which the drum is formed be equidistantly distributed around its circumference.

To prevent the mandrel from being contaminated with adhesive, the method according to the invention preferably includes winding a preshaped cover sheet onto the mandrel, prior to winding the lengths of laminating material. These lengths may then be impregnated with adhesive before being wound onto the mandrel. Alternatively, precoated paper may be used, for example activated by heat. The adhesive may be an extruded thermoplastic, a water-based adhesive such as polyvinyl acetate, polyvinyl alcohol, starch, sodium silicate, etc., a solvent-based adhesive or a hot-melt adhesive.

The convolute winding of the lengths of laminating material causes the direction of winding, although it may begin perpendicular to the mandrel's axis, to turn through an angle for each length of material. That in, the material tracks across the mandrel towards its wider end. Thus, if the discrete lengths of laminating material are rectangular, the end result is a drum having irregular ends.

Accordingly, the method preferably includes trimming each end of the drum once it has been wound. Preferably, a portion of the drum at its wider end is severed from the drum, inverted, threaded onto the drum from its narrower end and then bonded to the drum to form an anti-locking collar.

Preferably, the apparatus according to the invention comprises means for advancing a continuous length of laminating material from a roll and means for severing the continuous length into the said plurality of discrete lengths.

To ensure good adhesion between the lengths of laminating material, the apparatus preferably includes a tapered pressure roll to press the said lengths onto the tapered mandrel. The taper of the pressure roll allows its circumferential speed to match that of the mandrel at all points of contact, thus ensuring that the laminating material is not skewed when applied to the mandrel.

The present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a diagrammatic sectional view of a drum according to the invention, in which the taper is exaggerated; and Fig. 2 is a schematic representation of the apparatus of the invention.

Fig. 1 illustrates a tapered drum 10 according to the invention. The drum 10 includes a tapered side wall 12, a conventional lid 14 having a depending skirt 16 and a conventional base 18, held in place by an annular insert 20.

The insert 20 and drum base 18 are held in place by an adhesive. Of course, the drum base may be formed by any one of a number of conventional manufacturing techniques. The base may consist of laminated fibre board, steel, plastics, composite material or any combination of the foregoing. The drum base 18 may be secured to the tapered side wall 12 by any one of the following, amongst other means: by means of a chimb band holding the drum end in position, the chimb being formed of metal, plastics or laminated fibre board; by bonding the drum side wall 12 directly to the base 18; by forming the side wall 12 at its base, with or without a chimb band, in order to facilitate easier, or more mechanically strong, joins between side wall 12 and base 18; or, substantially as illustrated, by stitching, stapling or gluing a thick annular ring at the base on the inside of the side wall 12, to support and/or be glued to the base 18 placed inside and above the thick annular ring.

The top end of the tapered side wall 12 may be worked in any one of a number of conventional ways. Thus, the top may be: simply a straight-forward, severed end of the tapered side wall 12; formed to give the top of the drum more rigidity and/or to enable the lid to be fitted or located more securely; fitted with a chimb band, the chimb band being formed of metal, plastics or laminated fibre board; or slotted or perforated to allow a lid to locate into the slots or perforations. Where the top of the side wall 12 is fitted with a chimb band, the chimb band may be formed to give the top of the drum more rigidity and/or to enable the lid to be fitted or located more securely. If the top chimb band is formed into a bead, this may be on the inside or the outside of the drum. Where the bead is on the outside of the drum such as for the Bowater "Supercask", as described in U.K.Patent No...., good nesting of empty drums can be achieved.

The lid 14 may be made from laminated fibre board, steel, plastics, composite material or any combination of the foregoing. The lid may be: designed to lip over the drum's side wall or top chimb, for location; designed to locate on the top of the side wall and to have an outer skirt to drop down outside the side wall, substantially as illustrated; or designed to be a tight "plug" fit on the inside of the tapered side wall 12, and either designed simply to lie within the drum, or to progress over the top of the side wall and/or to continue in a skirt down the outside of the drum.

The lid may be secured to the drum by a closure ring which closes over the lid and top chimb, or tightens over the lid and side wall. The closure ring may simply be a strap or may be formed into a suitable profile to grip the lid, top chimb and/or side wall. The closure ring may be tightened by a lever-action toggle, a latch, a bolt or a buckle. The material of the closure ring and tensioning device may be laminated fibre board, steel, plastics, composite material or any combination of the foregoing.

Alternatively, a "plug" lid may have a securing device which tightens the lid against the inside of the side wall. This may include wedges or grippers acting against the inside of the side wall. Furthermore, virtually any lid could be held in position by the use of adhesive tape and/or by cooperating perforations in the drum's side wall and the lid which could allow the use of tag-type seals.

The apparatus upon which the tapered drum sidewall for this invention can be laminated is illustrated in fig. 2.

A continuous length of laminating material, 20, in this case kraft paper is fed from the left of the figure from a reel (not shown), past a guillotine 26. From the area immediately after the guillotine 26, either sheets cut from the reel, or pre-cut sheets, of laminating material are fed over a glue coated roller 42 on to a mandrel 50. Successive pre-cut sheets, or multiple sheets sheared from the reel by the guillotine 26 enable multi-ply laminations to be built up on the mandrel 50.

By means of suitable adjustments in the timing of the paper feed in relation to the paper speed through the machine, and the mandrel 50 surface speed, it is possible to obtain an equidistant distribution of say six sheets around the circumference of the drum sidewall 12.

Adhesive is transferred from the surface of the glue roll 42 on to the lengths of paper passing through the apparatus. These lengths of paper pass between the glue roll 42 and an application roll 44 which can be raised or lowered, to co-operate with the glue roll. In its lowered position, the application roll 44 presses the advancing lengths of paper 20 on to the glue roll 42, thereby ensuring their coating with adhesive.

The final portion of the apparatus is the mandrel 50, and a co-operating pressure roll 52. The mandrel 50 is tapered, and so is the pressure roll 52. The ratio of the circumference of the mandrel 50 and the pressure roll 52 is equal at all points of contact between the two rolls. This enables the surface speeds of the mandrel 50, and the pressure roll 52 to be matched at all times. The pressure roll 52 may be raised out of contact with the mandrel 50 to enable the laminated tapered sidewall to be removed from the mandrel 50.

The first stage in winding a tapered sidewall is the inclusion of a lining sheet to cover the mandrel 50, before the addition of further, glued plies. The lining sheet is applied to a row of vacuum holes in the mandrel 50, from the front of the machine, with the winding machine stationary.

The winding operation then commences with the lowering of the pressure roll 52, the rotation of the mandrel 50, and the addition of the further glued plies.

Although not illustrated in fig. 2, the apparatus includes three knives which may be brought into the proximity of the mandrel 50, once the drum has been formed, so as to trim the ends of the drum and to severe a portion of the drum at its wider end. The mandrel 50 is designed as an expandable mandrel, with the drum being wound thereon when in its expanded state. To facilitate removal of the drum, when formed, the mandrel is contracted, thus allowing the drum to be slid off the narrow end of the mandrel. The portion which is severed from the wider end of the drum is then inverted, threaded onto the narrower end of the drum and bonded to the drum side wall 12, so as to form an antilocking collar 8, as illustrated in fig. 1.

It will of course be appreciated that the present invention has been described above purely by way of example and that modifications of detail may be made without departing from its scope.

Claims

1. A tapered drum formed from a plurality of convolutely wound, discrete lengths of laminating material bound to one another by an adhesive.

2. A drum according to claim 1 including an anti-locking collar.

3. A drum according to claim 1 or claim 2 in which the said discrete lengths are equidistantly spaced around its circumference.

4. A method of manufacturing a tapered drum comprising convolutely winding a plurality of discrete lengths of laminating material onto a tapered mandrel and binding the lengths of laminating material together with an adhesive.

5. A method according to claim 4 including winding a cover sheet onto the mandrel prior to winding the lengths of laminating material.

6. A method according to claim 5 wherein the said lengths are impregnated with adhesive before being wound on the mandrel.

7. A method according to any one of claims 4-6 including trimming each end of the drum once it has been wound.

8. A method according to claim 7 in which the trimming includes severing a portion of the drum at its wider end, which portion is then inverted, threaded onto the drum from its narrower end and then bonded to the drum to form an anti-locking collar.

9. Apparatus for the manufacture of a tapered drum comprising a tapered mandrel, means for convolutely winding a plurality of discrete lengths of laminating material on the mandrel and means for binding the lengths of laminating material to one another with an adhesive.

10. Apparatus according to claim 9 including means for advancing a continuous length of laminating material from a roll and means for severing the continuous length into the said plurality of lengths.

12. Apparatus according to claim 9 or claim 10 including a tapered pressure roll to press the said discrete lengths onto the tapered mandrel.

13. A tapered drum substantially as described herein with reference to the accompanying drawings.

14. A method of manufacturing a taper drum substantially as described herein with reference to the accompanying drawings.

15. Apparatus for the manufacture of a tapered drum substantially as described herein with reference to the accompanying drawings.