A method and a tool for forming such convexities are known from the Applicant's own Norwegian patent no. 302 505 and Norwegian patent application no. 19984531. The latter is corresponding to international patent application no. PCT/N097/00080.

The main object of the invention according to the above publications is, as in the case of the present invention, to allow convexities to be formed across a larger area of a plate than that which is possible with methods and tools according to prior art.

Such a plate with convexities across a large area such as e. g. the entire plate may as an example be used as a mounting plate in e. g. shop interiors, or as a support for floors, the plate with convexities ensuring appropriate spacing between e. g. a wooden floor and a concrete floor. In the case of such an application, heat may be introduced by blowing air in through the gaps formed between the convexities in the plate. The gaps distribute air well. The plates may be used as a sound absorbing wall where, as an example, two such walls may be arranged with insulation in between, the purpose of the convexities being to disperse the reflected sound. The plates may also be used as a light shade, where a light source is fitted on the back of the plate and the plate has the effect of diffusing the light, providing indirect lighting from e. g. a wall or a ceiling; as an acoustic ceiling plate; or for anchoring of reinforcement bars, where the plate may form a connection between several reinforcement bars and maintain the correct spacing between these; as decorative panels on walls or ceilings, or optionally for other decorative purposes, e. g. as a lamp shade; and as a hinged joint, where convexities formed along the respective side edges of two plates are placed into engagement with each other and a hinge pin is threaded through the convexities.

Plates formed in the above manner have a high strength to thickness ratio.

According to the above publications, a method is provided in which the plate body is inserted between two halves of a tool. The tool halves are brought together and co- operate to stamp out a first set of convexities in a first direction relative to the main surface of the plate body and a second set of convexities in another, opposite direction relative to the main surface of the plate body. The convexities are formed along a straight line across the plate body between two of the side edges of the plate body.

What is novel and special according to NO 19984531 is that the plate body is held to ensure that its main surface maintains its orientation, and each convexity in the first set of convexities is stamped out with a length that when measured from one side of the convexity at a point by the main surface of the plate body to the other side of the convexity at a point by the main surface of the plate body, essentially corresponds to the length of each convexity in the second set of convexities stamped out.

Achieving an equal length for the convexities on either side of the plate is important in order to ensure that the plate does not arch after the stamping has been carried out, but maintains its essentially plane configuration.

According to NO 19984531, the method is implemented in a tool comprising a first and a second tool half, the tool halves having a plurality of protuberances arranged in a straight line and separated by a plurality of interspaces. The protuberances on the first tool half fit into the interspaces on the second tool half and vice versa. What is novel and special about this tool is that it is equipped with a surface that lies in the dividing plane of the tool when the tool halves have been brought together fully. When the tool halves are brought together all the way, a workpiece is retained on this surface. The protuberances have a length that when measured from a point in the dividing plane of the tool over the top of the protuberance to a point in the dividing plane on the opposite side of the protuberance, is equal to the corresponding length across the protuberances on the second tool half.

In order to maintain the plane configuration of the plate and avoid bending of the plate, it is important to hold the plate exactly in the dividing plane of the tool.

According to the above publications, the invention is realized by means of a tool in which the lower tool half is fixed and the upper tool half travels vertically down towards the lower tool half, in the same way as a punching (stamping) tool. In this manner, one line of convexities is stamped out at a time. Clearly, it is also possible for several lines of convexities to be stamped out at the same time using a tool with several sets of protuberances. Such a tool is highly suited for the production of smaller quantities of the above type of plate.

However, this tool has proven to be too inefficient for production of larger quantities of this type of plate. Thus the present inventor has developed a more efficient method of producing plates of this type and a more efficient tool for use in this production. It is not possible by the known method to produce plates with breaks, i. e. portions having no convexities, in the row of convexities.

The invention is characterised by the characteristics that appear from the characterising part of the appended independent claim. The dependent claims describe advantageous embodiments of the invention.

The invention will now be explained in greater detail with reference to the enclosed drawings, in which: Figure 1 shows a plate produced in accordance with the present invention; Figure 2 shows a cutout of the plate in Figure 1; Figure 3 shows a cross section through the cutout in Figure 2; Figure 4 shows a longitudinal section through the cutout in Figure 2;

Figure 5 shows a rolling machine in accordance with the invention; Figure 6 shows the rollers and the plate in Figure 5 separately; Figure 7 shows a longitudinal section through the rollers and the plate in Figure 6; Figure 7b shows a cutout of Figure 7; Figure 8 shows an alternative construction of the rollers for production of a plate having a different pattern; Figure 9 shows two sets of rollers and a plate having yet another pattern; and Figure 10 is a perspective view of a section through part of the plate in Figure 6.

Figure 1 shows a plate 1 generally comprising a first side face 2a and a second side face 2b on the opposite side of the first side face 2a. As can be seen more clearly from the cutout in Figure 2, the cross section in Figure 3 and the longitudinal section in Figure 4, areas 3 have been stamped out from this plate 1 in a first direction, so that the areas 3 form a curved surface at a distance from the first side face 2a. Other areas 4 have been stamped out from the plate 1 in an opposite direction, forming a second curved surface at a distance from the second side face 2b, so that the areas 3 and 4 end up alternating in a row 5 across the plate (see Figure 1). Several such rows 5 may be provided, with separation, defining areas 6 in between, which areas 6 lie in the plane main portion 2 of the plate.

Between each area 3 and 4 there are openings 7 for insertion/introduction of e. g. hooks, bolts, wire, cords, cables, pipes, air, heat etc.

The alternating areas 3 and 4 are formed with alternating short and long lengths.

Thus the areas 3a have a greater length than the areas 3b, and likewise the areas 4a have a greater length than the areas 4b. NO 19984531 describes how a plate formed in this

manner may be used as a mounting board. Reference is made to this application for further information on how to achieve this.

The stamped-out areas 3 and 4 may have an optional cross sectional shape, e. g. edged as shown, or circular.

Figure 5 shows a rolling machine for production of a plate having convexities as specified above. In the case shown, the machine consists of a machine bed 10 on which is placed a roller support 11 carrying a lower roller 12 and an upper roller 13. Tables 14 and 15 are provided upstream and downstream of the rollers for guiding a plate 1.

Figure 6 shows a cutout of the rollers 12 and 13 and the plate 1. In the rollers 12 and 13 there are recesses 16 and raised parts 17. The recesses 16 in the roller 12 coincide with the raised parts 17 of the roller 13, and the recesses 16 in the roller 13 coincide with the raised parts 17 of the roller 12. In the areas around the recesses and the raised parts there is a surface 18 on the roller 12 and a surface 19 on the roller 13. Between them, the surfaces 18 and 19 define the thickness of the plate in the areas around the convexities 3 and 4.

Figure 7 shows a longitudinal section through the rollers 12 and 13 and the plate 1. In the cutout in Figure 7 b, there is shown a detail of the roll-nip between the rollers 12 and 13. Here it can be seen that a raised part 17 on the roller 12 goes into a recess 16 in the roller 13. Between the raised part and the recess, there is a clearance 23. The clearance 23 defines the thickness of the plate material in the convexity 3 that is formed by the interworking of the raised part 17 and the recess 16.

Along the longitudinal axes of the rollers there is little or no clearance between the raised parts 17 and the recesses 16, so that e. g. a raised part 17 on the roller 12 and the nearest raised part 17 on the roller 13 located closest to each other in the roll-nip pass each other with little or no clearance. This

causes a cutting action against the plate, which separates the material in the convexity from the remainder of the plate material, leaving the convexity protruding up from the plate as a curved strip, thus forming the opening 7.

Between the rows 5 of convexities 3 and 4 the plate material may be rolled somewhat thinner than in the convexities 3 and 4. This is particularly important in the areas 6 adjacent to the convexities 3 and 4 in the axial direction of the rollers, in order to prevent the plate from curving. The rolling in this area must be such that the rolling-induced extension of the areas 6 in the direction of rolling corresponds to the extension of the plate in the areas of the convexities 3 and 4, in the direction of rolling, which extension is caused by the buckling of these convexities. Although not shown here, there may obviously also be an area with no convexities along the edge of the plate, for instance to provide room for the plate to be placed in a frame (not shown).

Figure 8 shows the rolling of a plate where the convexities 3 and 4 extend continuously across the width of the entire plate. In this case, there is no need to roll the plate in the area 20 between the convexities, as this will have no effect on the curving of the plate 1.

Figure 9 shows rolling of a plate where the rows of convexities 3,4 extend in the direction of rolling. Moreover, two sets of rollers are shown. Here, the first stage of rolling is carried out by rollers 12 and 13. This rolling constitutes a partial formation of the convexities 3 and 4, i. e. the plate material is pushed out of the main plane of the plate, and the plate material is cut to form openings 7. In the next rolling stage, which takes place between rollers 21 and 22, the convexities are pushed all the way out of the main plane of the plate 1.

In the second rolling stage, there is lateral clearance between the recesses and raised parts on opposite rollers, to ensure that these do not touch. Here, the convexities are stamped out without the rollers touching.

Figure 10 illustrates the fact that the plate material between the convexities 3 and 4 has been rolled so as to be thinner than that of the convexities 3 and 4, thus thickness y is less than thickness x.

Both the size and length of the convexities, as well as the length of the interspaces, may be varied in dependence on the area of application.

By rolling the pattern of convexities into the plate instead of using the stamping method of e. g. NO 19984531 it becomes possible to achieve a substantially higher production rate and more uniform product quality. It will also be possible to roll/mill long bands of plate material that may optionally be coiled after rolling in order to facilitate storage and transport.

Although the invention has been illustrated by means of examples showing convexities in two opposite directions in the plate, it is also possible to produce plates having convexities in only one direction relative to the main plane of the plate.