GB2065069A - Winding mandrels - Google Patents

Abstract

The winding surface of a mandrel for use in the winding of relatively impermeable sheet material is provided with a plurality of shallow depressions such that on pressing the sheet against the surface so as to express air from at least some of the depressions, a partial vacuum is created therein effective to retain the sheet in contact with the surface for at least long enough to permit initiation of the winding operation. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the winding of sheet materials According to the present invention, the winding surface of a mandrel for use in the winding of relatively impermeable sheet material is provided with. a plurality of shallow depressions such that on pressing the sheet against the surface so as to express air from at least some of the depressions, a partial vacuum is created therein effective to retain the sheet in contact with the surface for at least long enough to permit initiation of the winding operation.

The depressions may be formed directly in the winding surface of the mandrel orinthe surface of a sleeve installed thereon, the latter approach being suitable for applying the invention to existing mandrels. The invention includes such sleeves. However, a sleeve is not essential because in some cases, it is satisfactory to simply apply a strip of perforated material to partofthe mandrel surfaceraswill be described later.

In many cases, where relatively readily deformable plastics sheet is to be wound, the sheet will be retained on the surface of the mandrel following only the application of simple hand pressure. However, where it is not so retained and this will usually be due to an inadequate seal between the sheet and the margins of the depressions, it is a simple matter to wet the surface of the mandrel or of the sheet with water. Relatively shallow depressions may be used, depths in the range 0.1 to about imm being satisfactory. The fact enables the use of a relatively narrow strip of perforated material such as paper to provide the depressions for an existing mandrel. If the strip covers, say up to 25% of the mandrel circumference, that may well be sufficient. The strip can be stuck on with adhesive, or possibly just by use of water.

The resulting temporary seal will normally be enough to initiate winding and, of course, water is unlikely to cause any damage to either the mandrel or to the sheet itself.

Furthermore, even if any of the sheet is damaged the damage will be strictly limited to one relatively small end portion of the sheet. In the context of the amount normally wasted by a faulty start-up, such very limited damage is usually perfectly acceptable.

The invention will now be described very briefly by way of example and with reference to the accompanying drawing which is a perspective view of part ofa mandrel for use in winding vinyl wall covering materials into rolls.

In the figure, an aluminium mandrel 1, of diameter 20cm, has machined into its surface a plurality of spaced-apart depressions 2, of diameter 1cam. The depressions have a maximum depth of about 0.2mm and are of near-rectangular cross-section, as shown at3.

The mandrel was used to make rolls from a vinyl sheet material about 0.25mm thick. It was found that moistening the mandrel surface with water, followed by manually pressing the end of the vinyl material onto the wetted surface firmly enough to expel some air from at least some of the depressions across the width of the mandrel an axial direction was enough to cause the material to be retained on the surface for several minutes. This was certainly long enough to permit winding to be initiated. The vinyl material was not significantly damaged by the operation.

Satisfactory depressions were also achieved by the use of a drill bit ground to give a shallow conical profile to the depressions. Similarly satisfactory results were achieved by using a disposable perforated paper strip, which was stuck to the mandrel across the whole of its width and around about 25% of it circumference. This approach has the advantage of cheapness, of course, and it is not essential to stick the paper on very firmly.

In fact, there are advantages is not doing so; the mere use of water to achieve temporary attachment has the benefit of also assisting the sheet material to seal against the mandrel and strip for at least long enough to start winding. Separation on unwinding is not a problem, since the strip may well simply fall off.

1. A mandrel for use in the winding of relatively impermeable sheet material having a plurality of shallow depressions formed in the winding surface thereof such that on pressing the sheet against the surface so asto express air from at least some of said depressions, a partial vacuum is created therein effective to retain the sheet in contact with the surface for at least long enough to permit initiation of the winding operation.

2. A mandrel according to Claim 1 wherein the depressions are formed directly in the winding surface thereof.

3. A mandrel according to Claim 1 wherein the depressions are formed in a sleeve fitted to the winding surface.

4. A mandrel according to claim 1 wherein the depressions are constituted by perforations in a strip of sheet material at least temporarily attached to part of the mandrel surface.

5. A sleeve having the depressions of claim 1 and for fitting to an existing mandrel.

6. A method of initiating the winding of relatively impermeable sheet material on a mandrel, the method including the steps of providing the winding surface of the mandrel with the depressions of Claim 1, applying an end portion of the sheet material thereto with sufficient pressure to express air from at least some of said depressions so as to cause the sheet two be retained on the mandrel, followed by rotating the mandrel about its axis to form a roll of sheet material thereon.

7. A method according to Claim 5 including the step of moistening the sheet prior to applying it to the surface of the mandrel.

8. A method according to claim 6 or claim 7, including the further step of providing the depressions by at least temporarily attaching to part of the mandrel surface a strip of perforated sheet material.

9. A mandrel substantially as hereinbefore described with reference to and as illustrated by the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to the winding of sheet materials According to the present invention, the winding surface of a mandrel for use in the winding of relatively impermeable sheet material is provided with. a plurality of shallow depressions such that on pressing the sheet against the surface so as to express air from at least some of the depressions, a partial vacuum is created therein effective to retain the sheet in contact with the surface for at least long enough to permit initiation of the winding operation. The depressions may be formed directly in the winding surface of the mandrel orinthe surface of a sleeve installed thereon, the latter approach being suitable for applying the invention to existing mandrels. The invention includes such sleeves. However, a sleeve is not essential because in some cases, it is satisfactory to simply apply a strip of perforated material to partofthe mandrel surfaceraswill be described later. In many cases, where relatively readily deformable plastics sheet is to be wound, the sheet will be retained on the surface of the mandrel following only the application of simple hand pressure. However, where it is not so retained and this will usually be due to an inadequate seal between the sheet and the margins of the depressions, it is a simple matter to wet the surface of the mandrel or of the sheet with water. Relatively shallow depressions may be used, depths in the range 0.1 to about imm being satisfactory. The fact enables the use of a relatively narrow strip of perforated material such as paper to provide the depressions for an existing mandrel. If the strip covers, say up to 25% of the mandrel circumference, that may well be sufficient. The strip can be stuck on with adhesive, or possibly just by use of water. The resulting temporary seal will normally be enough to initiate winding and, of course, water is unlikely to cause any damage to either the mandrel or to the sheet itself. Furthermore, even if any of the sheet is damaged the damage will be strictly limited to one relatively small end portion of the sheet. In the context of the amount normally wasted by a faulty start-up, such very limited damage is usually perfectly acceptable. The invention will now be described very briefly by way of example and with reference to the accompanying drawing which is a perspective view of part ofa mandrel for use in winding vinyl wall covering materials into rolls. In the figure, an aluminium mandrel 1, of diameter 20cm, has machined into its surface a plurality of spaced-apart depressions 2, of diameter 1cam. The depressions have a maximum depth of about 0.2mm and are of near-rectangular cross-section, as shown at3. The mandrel was used to make rolls from a vinyl sheet material about 0.25mm thick. It was found that moistening the mandrel surface with water, followed by manually pressing the end of the vinyl material onto the wetted surface firmly enough to expel some air from at least some of the depressions across the width of the mandrel an axial direction was enough to cause the material to be retained on the surface for several minutes. This was certainly long enough to permit winding to be initiated. The vinyl material was not significantly damaged by the operation. Satisfactory depressions were also achieved by the use of a drill bit ground to give a shallow conical profile to the depressions. Similarly satisfactory results were achieved by using a disposable perforated paper strip, which was stuck to the mandrel across the whole of its width and around about 25% of it circumference. This approach has the advantage of cheapness, of course, and it is not essential to stick the paper on very firmly. In fact, there are advantages is not doing so; the mere use of water to achieve temporary attachment has the benefit of also assisting the sheet material to seal against the mandrel and strip for at least long enough to start winding. Separation on unwinding is not a problem, since the strip may well simply fall off. CLAIMS

1. A mandrel for use in the winding of relatively impermeable sheet material having a plurality of shallow depressions formed in the winding surface thereof such that on pressing the sheet against the surface so asto express air from at least some of said depressions, a partial vacuum is created therein effective to retain the sheet in contact with the surface for at least long enough to permit initiation of the winding operation.

2. A mandrel according to Claim 1 wherein the depressions are formed directly in the winding surface thereof.

3. A mandrel according to Claim 1 wherein the depressions are formed in a sleeve fitted to the winding surface.

4. A mandrel according to claim 1 wherein the depressions are constituted by perforations in a strip of sheet material at least temporarily attached to part of the mandrel surface.

5. A sleeve having the depressions of claim 1 and for fitting to an existing mandrel.

6. A method of initiating the winding of relatively impermeable sheet material on a mandrel, the method including the steps of providing the winding surface of the mandrel with the depressions of Claim 1, applying an end portion of the sheet material thereto with sufficient pressure to express air from at least some of said depressions so as to cause the sheet two be retained on the mandrel, followed by rotating the mandrel about its axis to form a roll of sheet material thereon.

7. A method according to Claim 5 including the step of moistening the sheet prior to applying it to the surface of the mandrel.

8. A method according to claim 6 or claim 7, including the further step of providing the depressions by at least temporarily attaching to part of the mandrel surface a strip of perforated sheet material.

9. A mandrel substantially as hereinbefore described with reference to and as illustrated by the accompanying drawing.