The invention concerns a device for cleaning the tread band of vehicle wheels, comprising a ramp having two inclined planes arranged at a distance from each other, one for driving the vehicle on and the other for driv- ing it off. Two rollers are arranged in the space between the upper ends of the inclined planes, in approximately the same horizontal plane and with their axes at right angles to the ramp. At least one of the rollers is driv¬ en, and a rotary brush and means for supplying cleaning fluid are provided between the rollers.

It has been proven that the grip of a tyre is reduced considerably when a layer of tarmac, oil, salt, etc. is deposited on the tread surface during normal use. These deposits have a particularly negative influence on the grip of the tyre and hence the handling of the vehicle in winter. Salt is mainly used to keep main roads clear of ice and snow. This salt will deposit on the tread of the tyre, and when leaving a main road for a minor road the gri will be reduced considerably. Together with oil and tarmac residue, this will considerably reduce the ability of the tyre to get a grip on the road surface. It is therefore recommended that the tyres are cleaned regular¬ ly.

At present this is done by using a spray can containing a liquid solvent and flushing it off with water. Firstly, spray cans are expensive, secondly, all use of spray cans is unsuitable with respect to the environment, and third- lY _r the solvent can be harmful to the user, e.g. allergy sufferers. In addition this cleaning is time-consuming and difficult to perform without getting dirty, not to mention that the vehicle has to be moved in order to access the entire tread.

For instance, the Norwegian patent no. 142 388 discloses a device for cleaning the tread on car tyres. This device comprises a ramp.with inclined planes for driving on and off, a space between the inclined planes, in which space two rollers are arranged at approximately the same hori¬ zontal plane, and which rollers are mounted at right angles to the ramp. One of the rollers is driven and a rotary brush is arranged between the rollers. The axes of the rollers are parallell, and it has become apparert that during operation the wheels of the vehicle will be displaced, or "wander", to one side of the ramp. The wheels will tend to wander if the air pressure in the tyres is not equal, if the wheels are not properly aligned, if the vehicle is unevenly loaded, etc.. On the whole, very little is needed to make the wheels wander either way along the rollers.

The known device also includes a tub of cleaning fluid into which th tyre is dipped during the cleaning opera- tion. After a short period of operation the fluid will be useless due to accumulation of various impurities.

The present invention proposes to provide an improved device for cleaning tyre treads, avoiding the above-men- tioned disadvantages and obtaining further advantages.

According to the invention, this is achieved by a device as described above, characterized in that the rollers are given a slight inclination in opposite directions, so that they from an upright V-shape.

Other characteristics are given in the dependent claims.

Devices are described above are arranged in pairs, so that both wheels or the same axis can be cleared simulta¬ neously. As the rollers in each device form an upright V-shape, the wheels are subjected to a slight lateral

force striving to move the wheels towards the apex of the V. Irrespective of any differences between the two wheels, e.g. unequal air pressure, they will always strive to¬ wards an equilibrium point. Under no cirmumstances will they begin to wander out over the edge of the rollers.

If the axes of the rollers converge in the horizontal plane, towards the centre of the vehicle ot be treated, as stated in claim 2, a further enchancement of the ten- dency of the wheels to wander towards the middle of the rollers is achieved.

An embodiment of the invention will now described by way of example, with reference to the accompanying shematic drawings, in which:

Fig. 1 is an overall plan view of one embodyment of the invention;

Fig. 2 is a cross-section taken along line II-II in Fig. 1;

Fig. 3 is a lateral view of the device shown in Fig. 1.

The device comprises a ramp made up of an inclined plane

(2) , e.g. for driving on, and another inclined plane (3) for driving off. As shown in fig. 3, the inclined planes (2, 3) are arranged with their upper ends facing each other and at a certain distance from each other. Between the two planes (2, 3) a frame (4) is provided, which supports two rotatable rollers (5, 6) . The rollers are driven by a motor (7) , preferably an hydraulic motor, by means of chains or belts (8, 9) .

Between the rollers (5, 6) a brush (10) is arranged, which is being driven by one of the rollers (6) by means of a chain or belt (11) . Such an arrangement will make the brush rotate in the same direction as the rollers.

However the brush can also be driven by other means. Instead of driving the brush (10) with a belt (11) of its own, the belt (9) driving the rollers can be laid around a pulley (16) , which is indicated with dotted lines in fig. 1, over a belt-tensioning device (not shown) . The brush will the rotate in the opposite direction of the wheel (15) . It is important that the rollers (5, 6) are rotated in the same direction, e.g. in the direction of the arrow Pi in fig. 3, so that the wheel (15) of the vehicle rotates in the direction of the arrow P, provid¬ ing this is the direction of rotation of the wheel when the vehicle is driven forwards. As far as the front wheels are concerned, this is a necessity. Should the wheel be driven in the opposite direction, the alignment of the wheels will cause them to move laterally and to come off the rollers (5, 6) . As shown in fig. 2, two nozzles (12, 13) supplying cleaning fluid are placed at the bottom of the frame (4) . These nozzles are directed at an angle towards the middle of the frame, so that the spray from the nozzles will cover the entire width of the ramp. The reason for this is to make sure that the fluid is applied evenly, regardless of the tread gauge. Obvious¬ ly, the tread gauge will vary, within limits, between different types of vehicles.

As shown in fig. 2 the two rollers (5, 6) are supported on the frame (4) with the axes (5 ¹ , 6') inclined in oppo¬ site directions, so that the two rollers are arranged in slight V-shape. As explained above, a vehicle wheel will move towards the centre of the device. The angle of the axes (5 ¹ , 6*) is exaggerated in fig. 2. An angle of 1- 2° will probably suffice.

The device operates as follows. A wheel pair of a vehicle is driven up on an arrangement consisting of two devices according to the invention. Each device is started by means of signal device (14) , e.g. a microswitch or a photocell. The motor (7) is held stationary while the

vehicle is driven onto the ramp, so that both rollers (5, 6) are locked. When the wheel is sitting on the rollers, the motor is started, driving both rollers (5, 6) in the same direction. The brush (10) , being dirven by one of the rollers (6) via a chain (11) , will rotate in the same direction as the rollers, but at a higher speed.

A pump (not shown) will supply the nozzles (12, 13) with cleaning fluid, showering the tyre (15) as it is being brushed by the brush (10) . The cleaning cycle is con¬ trolled by a time relay. If required, additional .nozzles can be arranged to flush the tyre with water upon comple¬ tion of a cleaning cycle. After each cycle, the motor will stop, locking the rollers (5, 6) , enabling the vehi- cle to be driven off the device and allowing the next wheel pair to be rolled onto the ramp and cleaned.

The known devices are provided with one freely rotatable roller, requiring the vehicle to drive on and off the ramp from one directin only. This means that the vehicle must be turned and reversed onto the device, in order to clean the other wheel pair.

The invention is not limited to the example shown in the drawings or the embodyment described above. For instance, the two inclined nozzles, (12, 13) can be replaced by nozzle, which can be moved towards the tyre by means of e.g. a worm-driven holder, controlled by a sensor.