TECHNICAL FIELD The present invention relates to a device and a method for manufacturing of concrete tile bonnets showing a collar at least at one end by extrusion of a crude concrete mass onto pallets, which are conveyed past an extrusion unit and which then are conveyed to a hardening device where the crude tile bonnets are hardened. BACKGROUND TECHNIQUES

Hitherto, tile bonnets showing a collar at one end have been manufactured piece by piece by pressing concrete mass between two forms of which the lower form then constituted the upper side of the tile bonnet and the upper form constituted its under side. Piece by piece manufacturing of tile bonnets like that is effected with low capacity per manufacturing unit and is very personnel intense which results in high prices for manually pressed tile bonnets.

Tile bonnets not showing any collar at one end on the other hand have been manufactured by extrusion in the same way as standard roofing tiles. However, when applying extruded tile bonnets the ridge gets a less attractive fish-scale like appearance. In addition, it proved to be difficult to attach these tile bonnets to each other in an adequate way and to prevent water from penetrating when a gale is blowing. DESCRIPTION OF THE INVENTION The object of the present invention is to achieve a device complete with a method for manufacturing of tile bonnets according to the preamble not showing the disadvantages of hitherto known devices and manufacturing methods. The object is achieved with a device in which concrete mass is extruded onto pallets which are conveyed past an extrusion unit and which is characterized in that it comprises a cross roll unit arranged after the extrusion unit and comprises a cross roll which is rotary

around an axle extending along the direction of motion of the pallets. The cross roll is movable in a course above the pallet in contact with the crude extruded upper side of the tile bonnet imparting an upper side to the tile bonnet with a mainly uniform profile and at one end of the tile bonnet a collar protruding from the upper side.

The cross roll is designed with a profile in longitudinal direction matching the desired corresponding profile of the tile bonnet. Possible irregularities which result from the extrusion may be adjusted by cross roll¬ ing which partly involves the distribution of concrete mass between different parts of the tile bonnet but partly may involve that certain surplus materials are removed during cross rolling. In addition to that the cross rolling imparts a desired profile to the tile bonnet both in its cross- direction and in its longitudinal direction the cross rolling even imparts a tighter surface layer to the tile bonnet on its upper side. The cross roll may be compulsory rotating with a periphery speed higher than its motion speed in the course passing the upper side of the tile bonnet which results in better removal of materials and a better tile bonnet surface but also lessens the risks for the crude concrete mass to cling to the cross roll and give an inferior surface to the tile bonnet.

In order to achieve a preforming of the crude tile bonnet before cross rolling the extrusion unit may comprise at least one in vertical direction moving packing block which in its lower position imparts an upper side to the tile bonnet with a mainly uniform profile and which in its upper position imparts to the tile bonnet a material elevation protruding from its upper side. It lies within the scope of the invention to arrange a collar at either end of the tile bonnet that is formed on the pallet when passing under the extrusion unit.

Further features concerning the present invention are evident from the description to the drawings subsequently and from the claims. DESCRIPTION TO THE DRAWINGS The invention is described subsequently as an example of an embodiment in connection with the enclosed drawings .

Figure 1 shows a complete machine according to the invention in a view seen from one long side. Figure 2 shows in a side-view and enlarged the principal parts of one part of an extrusion and packing unit that is an integral part of the machine.

Figure 3 shows the extrusion unit according to figure 2 seen in the direction towards the outlet end of the unit.

Figure 4 shows the end of the machine according to figure 1 with a cross-rolling unit seen in a view in the direction towards the extrusion direction.

Figure 5 shows a cross roll that is an integral part of the cross-rolling unit.

Figure 6 shows the cross roll according to figure 5 seen in a half view towards the right end of figure 5.

Figure 7 shows the cross roll according to figure 5 in a longitudinal section.

Figure 8 shows a pallet for tile bonnets in a longitudinal section.

The machine for manufacturing of tile bonnets according to the invention as shown in figure 1 comprises a frame 1 with a conveying track 2 upon which the pallets 3 are fed in the direction of arrow A on the figure from a feed track for pallets, not shown in the figure, to an extrusion and compact unit 4, hereafter referred to as extrusion unit, in which a crude concrete mass is applied to and compacted upon the pallets 3. From the extrusion unit 4, the pallets with the applied concrete mass are conveyed to the cross-rolling unit 5 in which the upper side of the tile bonnet is established with its final

configuration. The pallets 3 with the ready-configured crude tile bonnets then are conveyed forward to hardening on conveying tracks not shown in the figure.

The extrusion unit 4 comprises a hopper 4.1, shown symbolically with dash dotted lines in figure 2 which is filled with concrete mass that is fed downwards onto the pallet 3 by means of a feed roll 4.2 provided with a driving member and an extrusion roll 4.3. The rotary direction of the rolls is indicated by the arrows B and C in figure 2. A stationary packing block 4.4 is arranged in the direction of motion of the pallet 3 followed by a packing block 4.5 that is movable in vertical direction. When extruding a tile bonnet upon a pallet 3 the movable packing block 4.5 is at first in its upper position at the same time as a heightening 3.1, arranged on the pallet 3 as seen in figure 8, passes the packing block 4.5. That results in that the crude tile bonnet is provided with a material heightening on its in direction of motion front end. As soon as the heightening 3.1 of the pallet 3 has passed the packing blocks 4.4,

4.5 the movable packing block 4.5 is lowered to its lower position and then provides the crude tile bonnet an even thickness across its remaining surface. When the following pallet 3 arrives edge to edge with the previous to the extrusion unit 4 the movable packing block 4.5 again will be heightened to its upper position, whereupon the work cycle will be repeated.

The cross-rolling unit 5 as shown in figure 4 comprises a cross roll 5.1 which is rotary around an axle extending along the longitudinal direction of the machine, i. e. in the direction of extrusion of the tile bonnets. The cross roll 5.1 may simultaneously be caused to rotate and to perform a movement from one side of the pallet 3 to its other side as the surface of the cross roll 5.1 is in contact with the upper side of the extrud¬ ed crude tile bonnet. In a preferred embodiment the cross roll 5.1 has an appearance as is evident from figures 5-7 which, however, not implies that the invention is limited

to a cross roll 5.1 with this appearance. As is evident from those figures, the cross roll 5.1 shows a mainly cylinder-shaped mantle surface 5.2 designed as connected plane sections in the shape of facets and on one side a cup-shaped rotary symmetrical surface 5.3. The cylinder- shaped facet surface 5.2 is intended to form the main body of the tile bonnet whereas the cup-shaped surface 5.3 is intended to form the collar of the tile bonnet at the heightening 3.1 of the pallet 3. The cross roll 5.1 shows further on its under side a ring-shaped section 5.4 extending from the facet surface 5.2 intended to form a notch in the upper side of the tile bonnet for interaction with a collar of an adjacent tile bonnet when laying a ridge. It has shown to be favourable to let the cross roll 5.1 rotate with a speed leading to a sliding between the surface of the cross roll 5.1 and the surface of the tile bonnet. The surface of the cross roll 5.1 then is able to rotate both with and against its motion over the tile bonnet. The object of partly shaping the cross roll 5.1 with facet surfaces, partly causing it to rotate with a periphery speed and direction that results in sliding against the surface of the tile bonnet is to prevent crude concrete mass from to cling to its surface and deteriorate the appearance of the surface.

Yet it lies within the scope of the invention to let the cross roll 5.1 roll freely in its course past the upper side of the crude tile bonnet on pallet 3.