The present invention relates to a cleaning device using suction for collecting dirt in a dirt container, to a suction nozzle for such a device and to a method carried out by such a device.

Background of the invention

When it comes to cleaning of indoor and outdoor areas, there are two basic methods, which are primarily used for collecting dirt in the form of particles and smaller items from substantially horizontal surfaces of these areas.

The first method consists in sweeping the dirt directly into a dirt container, the bottom part of which forms a dustpan. The use of this method puts a limit to the size of the dirt container because all the dirt must be swept into the container and therefore the dirt layer within the container can only be as high as the sweeping brush(es) is/are able to lift up the dirt. This method is not used very often in machines for outdoor cleaning where, typically, there is a large volume of dirt, because this means that the dirt container must be emptied very often which, in turn, results in a low efficiency of the sweeping procedure.

In the second method, the dirt is sucked into the dirt container, often by means of a rotating suction wheel creating a vacuum within the dirt container, which is connected to a suction nozzle through a suction hose. During cleaning, the orifice of the suction nozzle is moved across the surface to be cleaned. Basically, the larger the vacuum formed within the dirt container and/or within the suction hose, the larger the airflow and vacuum are created within the suction nozzle and the larger items can be lifted up from the surface by the suction nozzle and sucked into the dirt container. In general, however, the generation of a larger vacuum also results in a larger noise level created by the vacuum-generating means. The process of generation of a vacuum and a sufficiently large airflow within the suction nozzle demands a substantial amount of energy and not all small mobile machines are able to provide the necessary energy for doing this. Because of a limited airflow, many systems have difficulties lifting up items with high densities relative to their external volume, such as round stones and shifting sand. It is known in the art to improve the capability of the suction nozzle to lift up dirt from the surface by compensating for the insufficient airflow by means of a horizontally arranged cylinder brush inside the suction nozzle. This cylinder brush is arranged in the rear part of the suction nozzle sweeping in a forward direction so that the dirt is swept directly into the oncoming airflow for being lifted through the suction hose and into the dirt container.

In order to optimise the effect of using such a cylinder brush, it must be placed relatively far ahead relative to the oncoming airflow, typically directly beneath the opening of the suction hose into the suction nozzle. This means, however, that the gap between the brush and the front edge of the suction nozzle is relatively small, and the suction nozzle is easily blocked. Thus, because of the small space between the cylinder brush and the front edge of the suction nozzle, the suction nozzle may have problems handling items such as wet leaves, which have a large volume relative to their weight. The same small space also means that the machine may have difficulties picking up burger trays, plastic trays and the like. The rate at which the suction nozzle can be moved over the surface to be cleaned is therefore limited by the rate at which the cylinder brush can sweep such items into the airflow. Alternatively, more energy may be used to generate a larger vacuum and airflow within the suction nozzle for better lifting up the items from the surface and sucking them through the suction hose into the dirt container. In this relation, the design of the suction nozzle is very important. For instance, the airflow inside the suction nozzle gets longer time to lift up the items into the airflow if the distance between the front edge of the suction nozzle and the connection of the suction hose to the suction nozzle is increased. It is also known that the efficiency of the suction nozzle can be improved by creating an opening along the rear edge of the suction nozzle, so that two airflows - one oncoming (from the front) and one from behind - are created within the suction nozzle, which, so to speak, gives the items two chances for being lifted up into the suction hose. Still, high airflow velocities through the openings in the front and rear edges of the suction nozzle are needed, if items such as round stones and shifting sand are to be lifted up. Such high velocities are typically obtained by reducing the height of these openings. The use of low openings along the front and rear edges of the suction nozzle causes the vacuum within the suction nozzle and/or the dirt container to increase. Due to the smaller cross-sectional area of the openings and, thereby, an increased resistance to the airflow through the openings, however, the velocities of the airflows within the suction nozzle and the suction hose decreases. This means that the machine may have difficulties lifting the items through the suction hose and into the dirt container.

If the suction nozzle is moved across the surface to be cleaned too fast and therefore too many items are not lifted by the oncoming airflow, it may have at least two consequences. Firstly, the airflow from behind has less time to lift up the items. Secondly, the items which are not lifted up and which are too large to leave the suction nozzle through the opening along the rear edge of the suction nozzle will aggregate and eventually block the airflow, resulting in a reduction or complete elimination of the suction efficiency of the machine. Thus, the relation between the air velocity within the suction nozzle and the ground speed of the machine is important for ensuring that all items are lifted up by the suction nozzle.

It is a generally known problem that it is difficult to obtain optimally functioning sweeping and suction systems for small mobile machines because of the many influencing factors, such as the vacuum, the air velocity within the suction hose and the suction nozzle and the ground speed. In particular, items having small external surface to weight ratio are known to challenge known systems when it comes to be sucked or lifted up into the dirt container.

Brief description of the invention

It is an object of the present invention to provide a cleaning device, in which the above-mentioned disadvantages of similar devices known in the art are removed or at least significantly reduced. The present invention relates to a cleaning device for cleaning indoor and/or outdoor areas, said cleaning device comprising a suction nozzle being connected to a dirt container through a suction hose and a vacuum-generating means, such as for instance a suction wheel, for generating a vacuum within the dirt container and/or within the suction hose, wherein, when a vacuum is generated within the dirt container and/or within the suction hose and the nozzle orifice is placed against a surface to be cleaned, dirt in the form of particles and smaller items can be lifted up from the surface by the suction nozzle and sucked into the dirt container through the suction hose, and wherein at least one air inlet channel is arranged within the periphery of the nozzle orifice in such a way that, when a vacuum is generated within the dirt container and/or within the suction hose and the nozzle orifice is placed against the surface to be cleaned, an airflow is caused to enter the suction nozzle through the air inlet channel in a direction, which is substantially parallel to the surface to be cleaned and substantially tangential to the opening of the suction hose into the suction nozzle, whereby a whirlwind is formed within the suction nozzle, which whirlwind continues at least partly through the suction hose to the dirt container, and wherein the suction nozzle is designed to have a front side being designed so that one or more substantially parallel oncoming airflows enter the suction nozzle through and/or under the front side when a vacuum is generated within the dirt container and/or within the suction hose and the suction nozzle is moved with the front side first across a surface to be cleaned. It has surprisingly been shown that the formation of a whirlwind within the suction nozzle and at least part of the suction hose as described above results in a significant increase in the suction efficiency of the cleaning device, i.e. in its ability to lift up especially smaller items from the surface to be cleaned and suck them into the dirt container. It has furthermore been proved that this improvement is at least partly caused by the fact that, when using such a whirlwind effect, the suction power is concentrated around the centre of the whirlwind.

This means that all of the air is sucked into the suction hose from a relatively small area at the bottom of the whirlwind rather than from the full area of the nozzle orifice, which is more or less the case in cleaning devices known in the art. The rotation of the air combined with the fact that the air within the suction nozzle is sucked along the surface towards the centre of the whirlwind results in significantly higher air velocities within the suction nozzle relative to the surface to be cleaned, which in turn increases the ability of the airflow to lift up particles and small items, even those with a small external surface relative to the weight, from the surface and into the suction hose.

Thus, particles and smaller items on the part of the surface covered by the nozzle orifice are caught and lifted by the rotating airflow, sucked into the whirlwind and into the suction hose.

The best results are obtained when the whirlwind effect is combined with an intake into the suction nozzle of oncoming airflows like known from other cleaning devices known in the art.

In an embodiment of the invention, the cleaning device further comprises a plurality of air inlet channels arranged to create airflows into the suction nozzle in directions, which are substantially parallel to the surface to be cleaned and substantially tangential to the opening of the suction hose into the suction nozzle, which air inlet channels are preferably distributed along the all other sides of the suction nozzle than the front side.

The use of a plurality of air inlet channels distributed along the periphery of the nozzle orifice results in a stronger whirlwind effect and, thereby, in a better suction efficiency.

In an embodiment of the invention, the cleaning device further comprises one or more air inlet channels arranged in a side wall and/or a top of the suction nozzle in such a way that, when a vacuum is generated within the dirt container and/or within the suction hose and the nozzle orifice is placed against a surface to be cleaned, an airflow is caused to enter the suction nozzle through the air inlet channel in a direction, which is inclined against the nozzle orifice and substantially tangential to the opening of the suction hose into the suction nozzle.

The strength of the whirlwind effect can be improved even more by adding more air inlet channels than there is room for along the periphery of the nozzle orifice. When placed in a sidewall or the top of the suction nozzle, the air inlet channels should be inclined against the orifice since, as mentioned above, all of the air is sucked into the suction hose from the bottom of the whirlwind. In order to obtain the maximum "push" to the whirlwind, these air inlet channels may furthermore be directed towaids points slightly within the periphery thereof.

In an embodiment of the invention, the cleaning device further comprises one or more movable, preferably rotatable, brushes placed at least partly in front of the suction nozzle, which bmshes are arranged to sweep dirt towaids the front side of the suction nozzle, i.e. into the one or more airflows entering the suction nozzle through and/or under the front side. The efficiency of the cleaning device may be further improved by combining the whirlwind effect with the use of brushes similar to what is the case for other cleaning systems known in the art.

In an embodiment of the invention, the cleaning device is a self-propelled road sweeper.

A road sweeper constitutes a preferred embodiment of the cleaning system according to the invention primarily for outdoor use.

In an embodiment of the invention, the cleaning device is a vacuum cleaner.

A vacuum cleaner constitutes a preferred embodiment of the cleaning system according to the invention primarily for indoor use.

In an aspect of the invention, it relates to a suction nozzle for being connected to a dirt container of a cleaning device through a suction hose, said suction nozzle having one or more air inlet channels causing airflows entering the suction nozzle through those air inlet channels, when a vacuum is generated within the dirt container and/or within the suction hose and the nozzle orifice is placed against a surface to be cleaned, to have directions, which are substantially tangential to the opening of the suction hose into the suction nozzle, whereby a whirlwind is formed within the suction nozzle, which whirlwind continues at least partly through the suction hose to the dirt container, and wherein the suction nozzle is designed to have a front side being designed so that one or more substantially parallel oncoming airflows enter the suction nozzle through and/or under the front side when a vacuum is generated within the dirt container and/or within the suction hose and the suction nozzle is moved with the front side first across a surface to be cleaned.

In an aspect of the invention, it relates to a method for obtaining an improved suction efficiency of a cleaning device comprising a suction nozzle being connected to a dirt container through a suction hose and a vacuum-generating means, such as for instance a suction wheel, for generating a vacuum within the dirt container and/or within the suction hose, said method comprising the steps of - generating a vacuum within the dirt container and/or within the suction hose, whereby dirt in the form of particles and smaller items can be lifted up from a surface by the suction nozzle and sucked into the dirt container through the suction hose - placing the nozzle orifice against the surface to be cleaned forming a whirlwind within the suction nozzle, which whirlwind continues at least partly through the suction hose to the dirt container wherein the whirlwind is formed by providing the suction nozzle with one or more air inlet channels arranged so that the airflows entering the suction nozzle through those air inlet channels have directions, which are substantially tangential to the opening of the suction hose into the suction nozzle, and wherein the suction nozzle is designed to have a front side being designed so that one or more substantially parallel oncoming airflows enter the suction nozzle through and/or under the front side when a vacuum is generated within the dirt container and/or within the suction hose and the suction nozzle is moved with the front side first across a surface to be cleaned. Thus, the invention not only relates to a complete cleaning device as described above but also to a suction nozzle for such a cleaning device, for instance for replacement of an existing suction nozzle not falling within the scope of the present invention, and to the method carried out by such a cleaning device. The drawing

In the following a few embodiments of the invention are described in more detail in the following with reference to the drawing, of which is a perspective view of a road sweeper according to an embodiment of the invention, is a partly cross-sectional view of the road sweeper showed in Fig. 1, is a perspective view of the sweeping and suction unit of the road sweeper showed in Figs. 1 and 2, is a bottom view of the sweeping and suction unit showed in Fig. 3, is a bottom view of the suction nozzle of the sweeping and suction unit showed in Fig. 3, is similar to Fig. 5 a with the exception that indications of the directions of the airflows into and through the suction nozzle have been added, is a bottom view of the front part of the road sweeper of Figs. 1 and 2 with indications of the directions of the airflows into and through the suction nozzle thereof, is a perspective view of the suction nozzle of the sweeping and suction unit of Fig. 3 with indications of the directions of the airflows into and through the suction nozzle, Fig. 8a is a cross-sectional view of the suction nozzle of the sweeping and suction unit showed in Fig. 3, Fig. 8b is similar to Fig. 8a with the exception that indications of the directions of some of the airflows into and through the suction nozzle have been added, and

Fig. 9 is a perspective view of a suction nozzle according to another

embodiment of the invention.

Detailed description of the invention

Fig. 1 is a perspective view of a road sweeper 1 according to an embodiment of the invention, primarily designed for removing leaves, stones, paper, branches, plastics, grass, sand, dirt and other particles and small items, i.e. for outdoor use. The illustrated road sweeper comprises a dirt container 2 placed at its rear end and a sweeping and suction unit 3 arranged at its front end. The illustrated sweeping and suction unit 3 comprises two rotating brushes 6 and a suction nozzle 4, the latter being connected to the dirt container 2 through a suction hose 5.

In the illustrated embodiment, the suction nozzle 4 is provided with a number of wheels 13. In other embodiments of the invention, the suction nozzle 4 can be designed to slide against the surface to be cleaned, i.e. without wheels 13. In other embodiments, the sweeping and suction unit 3 can be replaced with a suction unit, i.e. with a suction nozzle 4, suction hose 5 and dirt container 2 but without any brushes 6.

Fig. 2 is a partly cross-sectional view of the road sweeper 1 showed in Fig. 1. This illustration further shows a suction wheel 7 arranged within the dirt container 2 for generating a vacuum therein. It is also shown, how the suction hose 5 passes through the road sweeper for connecting the dirt container 2 and the suction nozzle 4 to each other. In the illustrated embodiment, the suction nozzle 4 is provided with a bottle flap 9 for letting items into the suction nozzle 4, which are too large to pass under the front edge of the suction nozzle 4. In other embodiments, there may be no such bottle flap 9.

Furthermore, it is indicated in this figure how the airflow within the suction nozzle 4 and at least a part of the suction hose 5 forms a whirlwind 8 as described in further detail below.

Fig. 3 is a perspective view of the sweeping and suction unit 3 of the road sweeper 1 showed in Figs. 1 and 2 further illustrating the arrangement of the brushes 6 and the suction nozzle 4 relative to each other.

Fig. 4 is a bottom view of the same sweeping and suction unit 1 , in which a plurality of air inlet channels 10 are arranged within the periphery of the nozzle orifice. Figs. 5a and 5b are bottom views of the suction nozzle 4 alone. The only difference between the two figures is that in Fig. 5b a number of arrows are added to indicate the paths and directions of airflows 1 1 , 12 entering the suction nozzle 4 along the surface to be cleaned, when a vacuum is generated within the dirt container 2 and the orifice of the suction nozzle 4 is placed against this surface.

Similarly to the function of other suction nozzles 4 known in the art, a plurality of substantially parallel airflows 12 are sucked into the suction nozzle 4 from the front thereof. In other embodiments, there may be only one broad airflow 12 entering the suction nozzle 4 from the front side. These airflows 12 from the front typically carry a certain amount of dirt and small items swept into the airflows 12 by brushes 6 arranged in front of the suction nozzle 4, if such brushes 6 are present in the given embodiment.

A plurality of tangential airflows 1 1 enter the suction nozzle 4 through the air inlet channels 10 illustrated in Figs. 4 and 5a. The term "tangential airflow" is used because the air inlet channels 10 are arranged in such a way that the airflows 1 1 entering the suction nozzle through the air inlet channels 10 all have directions, which are substantially tangential to the opening of the suction hose 5 into the suction nozzle 4. This means that all these tangential airflows 11 contribute to forming and strengthening a whirlwind 8, which begins near the surface to be cleaned and continues into the suction hose 5 towards the dirt container 2.

The rotation of the whirlwind 8 can be clockwise or anticlockwise depending on the design of the suction nozzle 4. The formation of the whirlwind 8 results in larger air velocities within the suction nozzle 4 relative to the surface to be cleaned and increases the ability of the cleaning device 1 to lift up particles and small items from the surface and suck them into the suction hose 5 and further into the dirt container 2.

The illustrated suction nozzle 4 is designed with a permanent opening along its front side allowing particles and smaller items to be sucked into the suction nozzle 4. Heavier items such as stones are typically lifted up and sucked into the whirlwind 8 and the suction hose 5 only after the suction nozzle 4 has been placed above the item.

Larger items, such as plastic bottles and the like, which are too large to enter the suction nozzle 4 through the permanent opening along the front side thereof, may be allowed to enter the suction nozzle 4 by opening a bottle flap 9 arranged at the front of the suction nozzle 4. Obviously, in embodiments comprising such a bottle flap 9, the suction nozzle 4 must be designed with a sufficient internal height to allow such items to pass through the suction nozzle 4 to the suction hose 5. As described above, the air inlet channels 10 direct the entering airflows 11 , 14, 15 so that they contribute to forming and strengthening a whirlwind 8 within the suction nozzle 4 continuing into the suction hose 5. Depending on the size of the suction nozzle 4, the incoming tangential airflows 1 1, 14, 15 can be directed towards points within and/or outside the periphery of the opening of the suction hose 5 into the suction nozzle 4. The optimal number and size of the air inlet channels 10 depends on the size of the suction nozzle 4 and on the available vacuum and airflow into the dirt container 2 generated, for instance, by a suction wheel 7. If, for instance, there are too many air inlet channels 10 and the rotational velocity of the whirlwind 8 becomes too high, heavier items can be thrown out of the whirlwind 8 inside the suction nozzle 4 before they are sucked into the suction hose 5.

Thus, the optimisation of the efficiency of the ability of the cleaning system 1 to lift up particles and smaller items and suck them through the suction hose 5 into the dirt container 2 is a complicated matter, which in each individual case involves a number of tests taking into account a large number of characteristics of the cleaning system 1, such as for instance: characteristics of the suction wheel 7 (flow, vacuum)

the diameter and length of the suction hose 5

the dimensions (length, width and height ) of the suction nozzle 4

the height of the opening along the front side of the suction nozzle 4 the number, sizes and positions of the air inlet channels 10 In some embodiments, the sides and rear part of the suction nozzle 4 are arranged to slide against the surface to be cleaned. In order to reduce the wear on the suction nozzle 4, this means that either at least a part of the suction nozzle 4 must be produced from a suitable wear-resistant material or the suction nozzle 4 must be provided with runners made of such a material. In other embodiments, like the ones illustrated in the present figures, the suction nozzle 4 is provided with wheels 13 in order to reduce the friction against the surface to be cleaned as well as the wear on the suction nozzle 4. In such embodiments, there will inevitably be a certain gap between the suction nozzle 4 and the surface to be cleaned. Fig. 6 is a bottom view of the front part of the road sweeper 1 with indications of the directions of the airflows 8, 1 1 , 12 into and through the suction nozzle 4 thereof. Fig. 7 is a perspective view of the suction nozzle 4 with indications of the directions of the airflows 8, 11, 12 into and through the suction nozzle 4. Figs. 8a and 8b are cross-sectional views of the suction nozzle 4 with and without indications of the directions of some of the airflows 8, 1 1 , 12 into and through the suction nozzle 4 and further into the suction hose 5, respectively.

Fig. 9 is a perspective view of a suction nozzle 4 according to another embodiment of the invention, which is further provided with air inlet channels for tangential airflows 14, 15 entering the suction nozzle 4 through the side and the top thereof, respectively. Apart from being tangential to the opening of the suction hose 5 into the suction nozzle 4 like the directions of the previously described tangential airflows 1 1 , the directions of these tangential airflows 14, 15 also comprise a downward directed component because the air entering the suction nozzle 4 through these air inlet channels must move down to the surface to be cleaned before it can be sucked into the whirlwind 8 from the bottom thereof as described above.

Tangential airflows 14, 15 entering the suction nozzle 4 through the side or top thereof rather than along the surface to be cleaned can be used for strengthening the whirlwind 8 and increasing its rotational velocity, which can be advantageously if it is difficult to find sufficient space for the necessary air inlet channels 10 along the periphery of the nozzle orifice. In order to obtain an improved strengthening effect of these auxiliary tangential airflows 14, 15, the can be directed to meet the whirlwind 8 at points slightly within the periphery thereof. List of reference numbers

1. Road sweeper

2. Dirt container

3. Sweeping and suction unit

4. Suction nozzle

5. Suction hose

6. Rotating brush

7. Suction wheel

8. Whirlwind flow of air leaving suction nozzle

9. Bottle flap

10. Air inlet channel for tangential airflow

11. Tangential airflow into suction nozzle

12. Airflow into suction nozzle from the front thereof

13. Wheel for suction nozzle

14. Tangential airflow entering through side of suction nozzle

15. Tangential airflow entering through top of suction nozzle