The present invention relates to a protective board forming part of a packing for cylindrical rolls of wound webs of material, especially paper webs, the packing com¬ prising a sheet- or web-shaped wrapping to be arranged round the circumferential surface of the roll, and said protective board which is adapted to be arranged on at least one of the two opposite end surfaces of the roll in order to absorb blows and impacts and reduce the risk of deforming the web of material, for instance when placing the roll end surface on a rough or uneven surface. Background of the Invention When making paper or other web-shaped materials, the finished web of material is generally wound onto a tubular core of e.g. board and is thus shaped as a cylindrical roll containing a considerable amount of web. The size of each roll may vary within wide limits; for example in case of paper rolls, the roll generally has a length of 1-2 m and a diameter of 1-1.5 m, and the weight may vary between about 1.5 and 5 tonnes. Of course, each roll is of great economic value, and it is therefore important to try to protect the rolls as much as possible during storage and transport to the consumers. It is particularly important to protect the end surfaces of the rolls since even rela¬ tively limited damage to the end surfaces may necessitate discarding large amounts of paper, perhaps even the entire roll, owing to the lateral edges of the web being damaged, which in turn results in the web not fitting into subse¬ quent processing machines, e.g. a printing machine, or being torn therein.

Thus, it is necessary to pack the paper rolls care¬ fully, especially the end surfaces of the rolls. This is normally carried out by winding a paper wrapping round the circumferential surface of the roll, while the end sur¬ faces are protected by circular protective pieces of board

or corrugated fibreboard of essentially the same diameter as the paper roll.

However, it has been found that such pieces of board do not provide sufficient protection of the end surfaces, which results in a relatively large amount of complaints and returned paper rolls owing to damage. The damage arises on the one hand because the end surfaces are sub¬ jected to blows and impacts and, on the other hand, be¬ cause irregularities in the ground, e.g. in the form of loose objects such as stones, may be pressed into and damage the end surface when, during transport and storage, the paper rolls are arranged to stand on one end surface, thereby preventing them from starting rolling. In many cases, a number of rolls are stacked, which means that the load to which the lowermost end surface is subjected will be very great. Moreover, damage may arise if the rolls, which are handled by means of lift-trucks and other me¬ chanical lifting devices, are put down on the ground in a careless manner or even let down at a distance from the ground, which results in the end surface being pressed in. Protective pieces of board or corrugated fibreboard have proved to be unsatisfactory for all these types of damage.

Experiments have been made to use as protective boards hard fibreboards having a thickness of 4-5 mm, but they have proved to be too hard to absorb impacts or take up irregularities in the ground, and too week to carry the load of one or more rolls, when placed on a punctual sup¬ port in the form of e.g. a stone. A local fracture and subsequent pressing-in of the roll will be inevitable. One way of coping with this would be to use thicker and, thus, stronger protective pieces of hard fibreboards which, when placed on a punctual support, could carry the load without any fracture arising. However, such protective pieces would in practice be too expensive and too heavy. It is also in many cases desirable that the packing, after being removed by the receiver, can be burnt in local solid fuel furnaces to make it possible to recover the

calorific value of the packing and avoid any costs of dis¬ posal. As a rule, the protective boards must be divided into small pieces to be supplied to the furnaces, which, at least for comparatively rigid protective boards, can only be effected with great difficulty. In some countries, there are restrictions on burning of board and other products having long fibres, such as paper and cardboard. These materials should preferably be recycled, thereby contributing to the supply of raw material. Such recycling involves great expenses, and the costs are generally higher than the payment for the recycled material. Summary of the Invention

There are three main objects of the present invention. First, the inventive protective board should efficiently be able to protect the end surfaces of rolls of wound webs of material, on the one hand against blows and impacts and, on the other hand, against pressing-in when the rolls are placed on an uneven surface. Secondly, one object of the invention is to provide a protective board which after use, for transport and storage, and removal at the consumer's place can be directly disposed of or, preferably, be burnt, without the national laws which exist in many countries and which stipulate that products containing a certain minimum amount of long fibres of a given minimum length are not allowed to be destroyed or burnt, but that the products must be reused or the fibres be recovered. Thirdly, one object of the invention is to provide such protective boards which are so inexpensive to manufacture that they may be disposed of or burnt without any real loss, i.e. the manufacturing cost should be lower than the cost of hand¬ ling and returning the boards to the supplier. At least these main objects are achieved by means of a protective board according to the characterising clause of claim 1.

A further object of the invention is to facilitate the dividing of the protective board into small pieces after removal of the packing. This object is achieved by means of a protective board according to any one of claims 3-7.

Further description of the Prior Art

US 3,669,255 discloses the use of thick protective boards of various materials to protect the end surfaces of rolls, mentioning materials such as wood, composite card- board, foamed plastic, metal and cermets.

The first object of the invention can of course be achieved by means of all the materials enumerated if the protective boards are made sufficiently thick. The second object of the invention, however, cannot be achieved by means of protective boards of wood, composite cardboard or cardboard of recycled newsprint since these materials con¬ tain too large amounts of long fibres. Both because of the expense and for environmental reasons, none of the other materials is suited for disposable packings which are disposed of or burnt after use. Regarding the third object of the invention, this cannot be achieved by means of pro¬ tective boards of any of the materials mentioned in the US patent specification and having the thicknesses which are necessary to prevent pressing-in of the end surface of a roll when placed on a small stone or the like. This applies especially to cardboard which, although it is a relatively hard material of high density, has low carrying capacity. The high density of cardboard means that e.g. a small stone cannot be "taken up" by local compression of the material. To protect the roll against such damage, there just remains the possibility of making the material so thick that it can carry the roll even when placed on a punctual support, without any local fracture arising. The measures mentioned in col. 3, line 38, indicate this, since the applicant has used cardboard having a thickness of 15-16 mm. Of course, cardboard having such a thickness is exceptionally expen¬ sive to manufacture and cannot, in practice, be used for disposable packings. Brief Description of the Drawing In the drawing

Fig. 1 is a perspective view of a roll of paper and the associated packing,

Fig. 2 is a perspective view of one end surface of the roll of paper, the packing being attached, Fig. 3 is a top plan view of a preferred embodiment of the inventive protective board, Fig. 4 shows the protective board in Fig. 3 divided into pieces, and Fig. 5 is a cross-sectional view of the protective board in Fig. 3. Detailed Description of a Preferred Embodiment of the Invention

A preferred embodiment of the invention will now be described, partly with reference to the accompanying draw¬ ing. Fig. 1 illustrates a paper roll 1 which comprises a web of paper wound on a central tubular core 2 of e.g. board, and a packing consisting of a paper wrapping 3 for protecting the circumferential surface of the roll, and two protective boards 4, 4' for protecting the end surfaces of the roll. The figure is merely schematic, and as a rule use is made of a wrapping 3 of essentially greater length to permit winding a number of turns round the roll of paper. When the wrapping has been wound on the roll of paper and fixed, for example by gluing, the wrapping is in the form of a tube extending a distance beyond the end surfaces of the roll of paper. A protective board is inserted in this tube from each end so as to engage with the end surfaces of the roll of paper, and the end portions of the wrapping are folded and each fixed to one of the protective boards, as illustrated in Fig. 2, the wrapping thereby ensuring that the protective boards are kept in engagement with the end surfaces of the roll of paper. In actual practice, a fur¬ ther protective layer in the form of a paper wrapping, provided with e.g. the manufacturer's trademarks and de¬ scriptions of quality, can be attached to the end surfaces on the outside of the packing, thereby covering the protec- tive boards and the folded wrapping.

The protective board 4, 4' according to the invention is made of a per se known porous or medium hard fibreboard having a density in the range of 100-750 kg/m ³ and a thick¬ ness of 5-12 mm. Preferably, the density amounts to 150-350 Kg/m ³ and the thickness to 5-8 mm.

Such fibreboards are made by short wood fibres, which are suitably obtained from sawdust which is heated or boiled in water and ground so as to release the individual fibres, being mixed with long wood fibres which may derive from e.g. waste paper or papermaking pulp, and water to a stock or pulp. The amount of short fibres in relation to long fibres preferably is in the range of 70-90%, suitably 75-85%, and thus constitutes the main ingredient of the finished fibreboard. The long fibres serve as reinforcement and contribute to holding the material of the board to¬ gether and make the board stronger. To further reinforce the fibreboard, also some sort of binding agent is general¬ ly added to the pulp, e.g. rosin size.

The actual forming of the boards is done by collecting the pulp on a wire and pressing it during simultaneous drainage between a pair or a number of pairs of press rolls. The degree of compressing the pulp determines the density of the finished boards. After forming, the web is dried and cut to boards of any desired size. A fibreboard manufactured as described above and having the composition and dimension as stated, has a plurality of important properties which make it suitable for use as protective board for rolls of paper or other web-shaped materials according to the present invention. Since the main ingredient of the fibreboard is short fibres which can be obtained from sawdust, which normally is a waste material without any particular commercial value and which normally is disposed of or burnt, the boards are inexpensive to manufacture and, regarding the price, they are on a level with the corresponding protective pieces of board or cardboard. Moreover, there are in most countries no restrictions on burning such boards after use. The low

density further implies that the boards have a good pro¬ tective capacity, without necessitating great thickness and causing large consumption of material. For instance, the thickness combined with the porous or medium hard state makes it possible to efficiently absorb blows or impacts. When the roll is placed on an uneven surface or receives a strong blow, the protective board will be compressed local¬ ly, resulting in a local increase of density, without the inside of the protective board being pressed in and dam- aging the roll.

Reference is now made to Figs 3-5 which illustrate a preferred embodiment of the protective board according to the invention. To facilitate dividing of the protective boards into pieces after use and any subsequent burning in a solid fuel furnace, the protective board is formed with fracture lines in the form of shallow grooves 5 on one side of the board. As illustrated in Fig. 3, the grooves are oriented in parallel with each other, and preferably the distance between two neighbouring grooves is 10-30 cm, or suitably about 20 cm. The grooves are preferably 5-15 mm wide and of a depth corresponding to approximately half the thickness of the board, preferably in the range of 35-65% of the thickness of the board. By turning, as shown in Fig. 1, the side of the protective board formed with the frac- ture-indicating grooves inwards to the end surface of the paper roll, the protective effect of the board will not be reduced to any appreciable extent.

Fig. 4 illustrates how a protective board of the type shown in Figs 3 and 5 has, after use, been broken along the grooves into relatively long and narrow pieces which may easily be burnt in a solid fuel furnace. The possibility of manually dividing the protective boards in a simple manner along the grooves serving as fracture lines is, of course, advantageous not only when the boards should be burnt in a solid fuel furnace. By dividing, in a first step, the large protective boards, which as mentioned above may have a dia¬ meter of 1-1.5 m and in some cases even greater, into elon-

gate pieces, it is possible to supply them to a disinteg¬ rating machine, for instance a cutting machine or a mill, so as to further disintegrate the material and, for in¬ stance, burn it in a furnace intended for sawdust or chips. Although the preferred embodiment of the protective board according to the present invention is formed with fracture-indicating grooves on one side, it is, of course, quite possible to form fracture lines in some other op¬ tional manner, for example as perforations, i.e. holes extending wholly or partly through the board and placed along a straight line, or as grooves formed on both sides. The fracture lines can also be oriented in optional direc¬ tions, and it is thus also possible to have intersecting fracture lines. Furthermore, the boards can be manufactured in other ways than by the wet-forming process described above, e.g. by a dry-forming process in which the fibre material is distributed over a moving web together with a binding agent and is hardened during simultaneous compressing and supply of heat. Further, the wrapping need not be made of precise¬ ly paper, but any other flexible sheet- or web-shaped mate¬ rial may be used. Thus, also plastic can be wound round the roll in the axial direction thereof.

Of course, it is also possible to provide the retain- ing of the protective boards on the rolls in some other way than by means of the wrapping as in the embodiment de¬ scribed above. Moreover, protecting only one of the two end surfaces of the roll by means of a protective board accord¬ ing to the invention also lies within the scope of the in- vention.