From US A 4,796,563 there is known such a grating. This grating shows sharp transi- tions between different levels. Therefore, there is a risk of pressure damages on the feet of the animals and risk of collecting animal droppings in comers.

Floor gratings with surfaces divided into sections are known. The sections are divided by beads standing up from the floor surface and dividing this into the sections. It is the purpose of these beads to prevent the animals from slipping and especially it is the intention to prevent that the animals slip when they are about to rise or lay down.

In the known gratings the grating surface within each section may either be plain or curving downwards. Thus, it has been proposed to make the sections curving down- wards at least over a part of the extension of the section. Such a downward curving will ensure that the animals step in the middle of the section. This is an advantage, because it may damage the hoofs of the animals to step on the beads themselves. This will give rise to very large local pressure loads.

However, it appears that the gratings with the projecting beads have a relatively small self-cleaning ability. Because of the projecting beads, animal droppings may be placed in immediate connection with the beads. Since the animals will not step on and around the beads and since relatively sharp edged corners occur, some of the droppings will collect in the corner between the beads and the top side in the individual sections.

Thereby, a relatively large ammonia evaporation from the stable floor will occur.

Furthermore, the beads will give rise to harmful local pressure loads on the animals, when they are lying on the stable floor. When the animal rests with a large weight, a large part of the weight will rest on the raised beads. This gives rise to very strong pressure loads which may cause pressure damages, for example bad blood circulation, bruises, etc.

In certain countries there are requirements for reducing the ammonia evaporation from the stable floor. To fulfil such requirements, it will be necessary to have a stable floor which is self-cleaning to the greatest possible extent, i.e. a stable floor where animal droppings are stepped down in the space between the grating bars by the normal movement of the animals on the stable floor. Such a self-cleaning effect is insufficient with the known stable floors of the kind mentioned in the introduction.

It is the object of the present invention to provide a grating of the kind mentioned in the introduction, where the above-mentioned drawbacks are remedied and which has a self-cleaning ability while at the same time there is no risk of harmful local pressure loads on the animals.

This is achieved according to the present invention with a grating which is character- ised in that the sections at least form elevated areas which are wholly or partly sur- rounded by areas or sections that are at lower levels, that there is a smooth transition between the different levels, that the sections form a check pattern, and that the sec- tions in transverse direction and longitudinal direction of the check pattern are curving downwards and upwards, respectively, against a central section part.

According to a special embodiment, the central section part is substantially plane.

There is a smooth transition between the single sections.

A grating of the kind mentioned in the introduction will usually be made of plastic, and therefore has a relatively slippery surface. Alternatively, the grating may also be made of cast iron.

As the grating has elevated areas distributed over the floor surface, the feet of the ani- mals will be prevented from sliding. When a check pattern is used where the check pattern is alternately upwards and downwards curving, it will be ensured with very great certainty that the feet of the animals do not slide. The feet of the animals will normally be placed in the downwards curving sections. The hoofs of the animals will be prevented from sliding, as they will find support at the smooth transition between such a downwards curving section and an upwards curving section. When the animal lies down or rises, it will thus be able to set off against such a transition to an elevated area or a transition between adjoining sections. As a smooth transition between the individual sections occurs, the animal may also step on the area, where the transition between adjoining sections appear, just as the animal may step on the upwards curving sections. If the sections curving upwards are provided with a non-skid cover, there will be achieved a very safe floor, where the risk of sliding is also avoided, even if the animal steps on the upwards curving sections. However, when the animal stands on the floor, there will be no risk of their sliding, even if their hoofs are on an upwards curving section. The problem with sliding on the grating will occur especially when the animal is about to rise or lay down. In this situation, it will not be a problem, when the hoof of the animal slide a distance over the floor, until it finds a point where it can set off.

As the animal thus in a safe way may step on both the elevated areas or in the down- wards and in the upwards curving sections and in the transition between the individual sections, it will be ensured with very great certainty that animal droppings are stepped down over all of the surface of the grating. As a smooth transition occurs between the individual sections, there will be no risk of collection of animal droppings in corners or at edges at the surface of the grating, thereby giving rise to ammonia evaporation from the surface of the grating.

When the animal is lying on the floor, its weight will be evenly distributed over the whole floor surface. Even though a greater pressure load will occur in the sections which are upwards curving, there will not occur local pressure loads which can give

rise to harmful pressure loads, for example in the shape of the so-called shoulder dam- ages. Because of the smooth transition between the sections, it will also be possible that the body of the animal follows the curvature so that the pressure is distributed substantially over all of the surface without local pressure loads occurring. This will be the case especially if no great difference of height between the lowest and the high- est part of the sections in the upwards curving and downwards curving parts occurs.

Thus, it is preferred to use differences in height between 5 and 40 mm and preferably between 10 and 15 mm. That means that part elevations between 21/2 and 20 mm in the individual sections occur. However, it should be mentioned that the sections do not necessarily have to be symmetrically downwards curving and upwards curving. There may thus occur a greater downwards directed curving and a lesser upwards directed curving. Hereby, it will be easier for the hoofs of the animal to find support in the downwards curving sections while at the same time the risk that the hoofs of the ani- mals slide down the upwards curving parts is reduced.

A suitable size for sections for use in pigsties has turned out to be sections having a substantially quadratic shape with a side length of between 50 and 100 mm. However, it is to be mentioned that the sections may also be rectangular. Furthermore, the sec- tions may be rhombic. Such a rhombic form will occur, when the check pattern is ori- ented with an angle relative to the sides of the grating. Such an oblique orientation is particularly suitable in a pigsty, where the gratings will normally be placed with an orientation corresponding to the orientation in which the animals normally are, for example in sow pens. When such an animal will rise, it will displace the legs away from itself. In order that a sow pressing its legs out from itself during the rising finds support in the best way, the angle relative to the sides of the grating and thereby rela- tive to the longitudinal direction of the sow may preferably be between 15 and 75°, preferably between 30 and 60°, and especially between 40 and 50°. Because the sow will press its legs away from itself under an angle of about 45°, such an oblique orien- tation of the check pattem will cause the sowto support itself approximately perpen- dicularly against a transition between two adjoining sections.

As the grating bars will be oriented in parallel with one of the sides of the grating, and when the check pattern is oriented with an angle relative to the side of the said grating, there is achieved a particularly safe self-cleaning ability. Thus, spaces between grating bars will extend transversely to the transition so that with a particularly great certainty, there is also achieved a stepping down of animal droppings in this area.

Description of the drawing The invention will be explained in more detail hereinafter with reference to the at- tached schematic drawing, in which Fig. 1 shows a perspective view of a grating according to the invention as seen from above, Fig. 2 shows a view of the grating in Fig. 1 as seen from below, Fig. 3 shows a partial view in an enlarged scale of the grating shown in Fig. 1 Fig. 4 shows a partial view of a second part in an enlarged scale of the grating shown in Fig. 1, Fig. 5 shows a view of a further embodiment of a grating according to the invention, Fig. 6 shows a view of a further embodiment of a grating according to the invention, Fig. 7 shows a section through the grating shown in Fig. 5, Fig. 8 shows a section through the grating shown in Fig. 6, Fig. 9 shows a view of a further embodiment of a grating according to the invention, Fig. 10 shows a view of a further embodiment of a grating according to the invention, Fig. 11 shows a section through the grating shown in Fig. 9, and Fig. 12 shows a section through the grating shown in Fig. 10.

In Fig. 1, there is shown a grating 1 intended for use when building up a floor in live- stock stables. The grating comprises an outer substantially rectangular encircling con- sisting of two end sides 2 and two lateral sides 3. At the lateral sides 3, there are teeth 4 comprising downwards directed grooves for use at the mounting of the grating. Be- tween the teeth 4 there are spaces 3 for receiving teeth for an adjoining grating 1. The gratings may thus be used in a known way to make a floor. The gratings comprise grating bars 6 between which there are gaps 7 intended for passage of animal drop-

pings. The grating bars 6 have a surface forming the floor surface on which the ani- mals are placed. The grating comprises sections so that the floor surface appears with different levels. In Fig. 1 elevated sections 8 are seen. Between the elevated sections 8 there are areas 9 which are at a lower level. The transition 10 between a section 8 and the surrounding areas or sections 9 is a smoothly curved transition.

The transition between the different sections is more clearly seen in Figs. 4 and 5. The grating shown in Figs. 1-4 is a kind where elevated sections 8 are completely sur- rounded by the area 9 which is at a lower level. Within the sections 8, the floor surface appears substantially plane just as the floor surface in the area 9 is also substantially plain.

In the embodiment shown in Figs. 1-4, the grating bars 6 are oriented in parallel with the sides of the grating 3. The check pattern formed by the elevated areas 8 is oriented under an angle relative to said grating side. Each of the check areas appears thus with a substantially rhombic appearance.

In Fig. 5 another embodiment is shown where elevated sections 8 are completely sur- rounded by areas 9 which are at the lower level. In this embodiment, the check pattern is oriented in parallel with the sides of the grating 2,3. Each of the check areas 8 thus appear with a substantially rectangular, approximately quadratic, appearance.

In Fig. 6 is seen an embodiment, where sections 8 together with sections 9 form a check pattern. Each of the elevated areas 8 are thus at their comers adjoined to a corre- sponding elevated area, just as each of the individual areas 9 which are placed at a lower level in each corner will adjoin a corresponding area 9 placed at a lower level.

Of the sections shown in Figs. 7 and 8 it is seen how smooth transitions 10 between an elevated section 8 and an area 9 at a lower level occur. In Fig. 8 it is seen that the sec- tions 8 are curving upwards from the outside against a central upper section part which may be substantially plane just as the sections 9 are curving smoothly downwards against the central section parts which are also mainly plane.

The embodiments shown in Figs. 9 and 10 differ from the embodiments shown in Figs. 5-6 in that the formed sections are rhombic. As the same references are used to denote identical or corresponding elements, there will not be given any specific expla- nation in connection with the embodiments shown in Figs. 9 and 10 or the sectional views shown in Figs. 11 and 12. However, it should be mentioned that at the top side of each elevated side 8 in Fig. 12, there may be provided a cover (not shown), which for example is of a rubber material in order to make the upwards curving section safe against slipping.