The invention relates to spools, in particular spools to carry elongated metal elements. The invention further relates to a method of preventing corrosion of elongated metal elements coiled on such spools.

Background of the invention.

Elongated elements such as metal wire and steel cord are conveniently wound on metal, plastic or cardboard spools or reels for storage and for transport to the customers.

When metal spools are used, in many cases corrosion either on the spools itself or on the metal wire coiled on these spools is observed.

The application of an expensive corrosion protection layer can help to avoid the corrosion on the spool. However, a discoloration of the wire is still observed when this kind of spools is used.

On the other hand, spools completely made of cardboard can be considered. Such spools are however characterised by a limited strength, unless hard and thick cardboard is used. These spools further have the drawback that they have a short life-time.

In order to avoid corrosion, wire coiled on the conventional spools has to be stored inside a warehouse under severe conditions of humidity and temperature.

Other precautions can be taken, for example by providing a packing unit with silicagel dessicant and/or a humidity indicator.

In many cases, all these precautions do not seem to be satisfactory, especially not when the spools are exposed to large temperature variation, for example during transportation.

Summary of the invention.

It is an object of the invention to provide spools which are sturdy and resistant to damage and which do not cause a discoloration or corrosion of the wire wound on it.

It is another object to enable the re-use of the great mass of existing metal and plastic spools.

The discoloration of metal wire coiled on conventional spools is ascribed to the condensation of moisture on the wire surface.

It has been observed that particularly wire wound at relatively high temperature is very sensitive to corrosion and discoloration.

The wire is wound in layers on the spool. Each such layer comprise a number of adjacent windings. Air is enclosed within the mass of wire wound on the spool.

Further, it has been observed that the layers of wire located at the innermost part of the wound material suffers most from corrosion and discoloration.

This can be explained as : Since the wire is wound at the spool at relatively high temperature, for example at 50 °C, the wire will cool down to ambient temperature.

The layers of wire located at the innermost of the wound material cool only slowly.

As the temperature decreases, the pressure will also decrease and as a consequence the moisture content will increase.

Consequently, the concentration of moisture will be the highest at the innermost of the wound material, i. e. the places that keep the highest temperature for the longest time.

The layers of wire located at the innermost are therefore the most sensitive to discoloration and rust formation.

According to this invention, a spool comprising a central portion and two flanges is provided. The central portion and the flanges of the spool are made of a non-absorbing material, such as metal or plastic.

The above mentioned problem of avoiding corrosion and discoloration of the wire coiled on a spool is solved by applying a moisture absorbing material on the spool.

The central portion of the spool is thereby at least partially covered with this moisture absorbing material. The said central portion and/or the flanges of the spool is/are thereby at least partially covered with the moisture absorbing material.

Preferably, the central portion of the spool is covered with the moisture absorbing material.

Possibly, also the inner sides of the flanges are covered with the moisture absorbing material.

As moisture absorbing material any material with a sufficiently high moisture absorbing capacity can be used, such as any material comprising cellulose or equivalent fibers.

Preferred material is for example paper, quilted paper, cardboard or corrugated cardboard.

The material may further comprise a water absorbing resin or gel.

Conditions such as the relative humidity, the temperature at which the elongated metal element is coiled, the conditions at which the coiled spools are stored and transported determine the minimum requirements the moisture absorbing material has to meet and the amount of moisture absorbing material that is necessary to avoid the discoloration and corrosion of the elongated metal element.

Preferably, the moisture absorbing material has a water absorbing capacity of at least 10 g/m2, more preferably the water absorbing capacity of the moisture absorbing material is higher than 20 g/m2. The water absorbing capacity is defined as the amount of water that paper or cardboard can absorb. To determine the water absorbing capacity, the surface of a defined paper or cardboard area is covered with water and after a given time, its increase in weight is determined by the weight difference.

The paper or cardboard preferably has a thickness of at least 0.1 mm, more preferably the thickness of the paper or cardboard is higher than 0.2 mm, for example 0.5 mm or 2 mm.

The use of thicker protection layers or protection layers with a higher water absorbing capacity leads to the absorption of potentially penetrating air after rupture of the package material wrapped around the spool. In this way thicker cardboard or cardboard with a higher water absorbing capacity is leading to a more robust corrosion protection.

The moisture absorbing material does not only soak up the moisture of the air enclosed in the layers of the coiled material most closely to the central portion of the spool, it also absorbs the moisture of the air enclosed in the more outer layers of the coiled material.

In addition to the moisture absorbing material, a corrosion inhibiting material can be applied on the spool, preferably on the central portion of the spool or around the moisture absorbing material.

A suitable corrosion inhibitor is benzothiazole.

More details about corrosion inhibitors can be found in EP 0 845 548 A1.

In a preferred embodiment, strips, such as paper or cardboard strips, impregnated with a corrosion inhibitor are applied on the spool, they are for example wrapped around the central portion of the spool or around the moisture absorbing material.

During the winding of the wire, the inhibitor is heated and evaporated and is distributed over the wire, while the cardboard or paper absorbs the moisture of the enclosed air.

Although spools according to the invention can be of importance for the winding of all material that is sensitive to the action of moisture and

corrosion, these spools are in particular suitable for elongated metal elements such as metal wire, metal cord, bead wire, hose wire, steel cord or steel strips.

The spools according to the invention are sturdy and resistant to damage. They may carry substantial quantities and weights of metal wire.

After the wire is unwound, the moisture absorbing material can be removed, and the spool can be re-used by applying again moisture absorbing material on the spool.

As a result, the present invention makes the re-use of the great mass of existing metal or plastic spools possible.

According to a second aspect of the invention, a packing unit is provided.

The packing unit comprises at least one spool according to the invention with an elongated metal element wound on it and a package material, preferably a watertight package material, wrapped around the coiled spool or spools.

According to a third aspect of the invention, a method of preventing the discoloration and corrosion of wire coiled on a spool is provided.

This method comprises the steps of -providing a spool comprising a central portion and flanges, said central portion and said flanges being made of a non-absorbing material ; -applying a moisture absorbing material on said central portion and/or on said flanges.

In a subsequent step the elongated metal element is coiled or wound on the spool.

The method may further comprise the step of applying a corrosion inhibiting material on the spool before the elongated metal element is coiled on the spool.

The moisture absorbing material is preferably applied shortly before and more preferably just before the winding of the elongated metal element on the spool.

When thicker moisture material or material with a high moisture absorbing capacity is used, the time period between preparing the spool and winding the elongated element on the spool is less critical.

Another possibility comprises the application of a moisture absorbing material protected by a water resistant film which evaporates during the winding of the elongated material because of the wire temperature.

Still another possibility comprises the application of a moisture absorbing material covered with an adhesive strip. The adhesive strip is then removed just before the start of the take up of the elongated metal element.

Preferably, after the wire is coiled on the spool, the moisture absorbing material has no direct contact with the surrounding air, so that the absorbing material absorbs the moisture of the air enclosed in the layers of wound material and not-or only to a limited extent-the moisture of the surrounding air.

By using spools according to the present invention, the storing conditions of the coiled metal element are less severe.

It is not longer a requirement to store the spools at warehouses with expensive air-conditioning installations in order to keep the temperature and the relative humidity low.

Even exposure to large temperature variations, for example during transportation or during storing, have no longer a detrimental effect.

Brief description of the drawings.

The invention will now be described into more detail with reference to the accompanying drawings wherein -FIGURE 1 and FIGURE 2 are illustrations of two types of spools according to this invention.

Description of the preferred embodiments of the invention.

Referring to figure 1, a spool 10 comprises a central portion 12 and two flanges 14.

The central portion 12 is preferably cylindrical and can be made of metal or plastic. This central portion 12, however, may be made of any other material that has a sufficiently high strength.

The flanges 14 are preferably made of plastic or steel and are provided with a circumferental edge. They may be reinforced by radial ribs.

The flanges may further be provided with fastening means so that they can be fastened to and removed from the central portion of the spool.

By these fastening means, the spools can be assembled by fixing the flanges to the central portion, even when this central portion has wire wound on it over its full width.

The central portion is covered with a moisture absorbing cardboard sheet 16 over its full width.

Instead of covering the full width of the central portion, one or more smaller cardboard strips may be wrapped around the central portion of the spool.

In addition to the moisture absorbing material applied on the central portion 12, the inner sides of the flanges 14 can be covered with a moisture absorbing material.

Bead wire was wound on the spool and the spool with the wire wound on it was stored in a warehouse at normal conditions during some weeks.

After this storing period, no corrosion or discoloration has been observed on the unwound wire.

Figure 2 shows another embodiment of a spool according to the invention. A cardboard sheet 16 is wrapped around the central portion 12 of the spool. Additionally, a strip 18 impregnated with benzothiazole is wound around the cardboard.

In another embodiment more than one strip 18 impregnated with benzothiazole are wound around the cardboard.