International patent application WO 90/12532 discloses a vacuum cleaner construction, which uses a rotating filter. Due to the rotation of the filter, dust and similar material sucked in does not remain of the surface of the filter, but is thrown off and remains on the bottom of the receptacle.

The filter construction of the aforementioned vacuum cleaner is, in principle, a vertically corrugated cylinder. Figure 1 in the accompanying drawings shows a schematic cross-section of such a filter. As can be seen, the filter 1 comprises a corrugated outer surface, with alternating points 2 and bottoms 3 of the pleats.

Generally the filter works well, but it is possible for certain materials to begin to collect in the bottom folds of the pleats, thus blocking part of the filter surface and consequently naturally leading to a reduction in suction power. The material causing the blockage is marked with the reference number 4.

The present invention is intended to alleviate the aforesaid problem. The solution is achieved in the manner stated as characteristic in the accompanying Claims.

In the following, the invention is examined in greater detail with reference to the accompanying drawings, in which: Figure 1 shows a filter solution according to the state of the art; Figure 2 shows a general view of a vacuum cleaner, in connection with which the invention is applied ; Figures 3a-3c show cross-sections and a top view of one filter solution according to the invention; and Figures 4-7 show certain forms of the filter according to the invention, which differ from the embodiment of Figure 3.

The solution of the state of the art according to Figure 1 has been described above, and will therefore not be dealt with in greater detail here.

Figure 2 shows a cross-section of the construction of an exemplary vacuum cleaner, in which the invention can be applied. Thus, inside the body 100 of the vacuum cleaner, which can particularly have a more or less cylindrical shape, is fitted a motor 103, which, with the aid of suitable vanes, rotates to create an airflow, which in a conventional manner enters through duct 101 and exits through duct 102. The arrows illustrate the main path of the airflow. The airflow is directed from the lower part of the casing through a central suction duct 104 to a duct 107 in the middle of the casing, and from there out. The filter construction 1 is attached, using suitable attachment means 105, to the lower end of the suction duct 104. In this particular solution, the suction motor 103 rotates the filter through a shaft arrangement 106. Obviously, these particular constructions achieve only one practicable total construction. It is equally possible to use constructions too.

As stated, the filter construction shown in Figure 2 has always been shaped as a vertical cylinder. In the cylinder, there has been a pleated circumference according to Figure 1. Thus, the surface area of the filter has been increased.

However, this has also resulted in the drawback referred to above, especially when sucking in fine, damp dust. The centrifugal force created by rotation has been simply insufficient to overcome the retaining and other forces holding the material in the bottom of the folds. This is, of course, partly because the folding of the circumferential surface always causes various air vortices, with an often unpredictable effect.

Figures 3a and 3b show a cross-section and top view (3b) of one solution to the problem affecting the state of the art. Thus, in this case, the basic filter component is manufactured from two cylindrical filter"tubes"11 and 12, which join in the upper part to form a single duct 13, from which the air flows forwards.

This solution has a large filter surface, though perhaps the best suction result is achieved by making some surfaces of the cylinders 11 and 12, for example, the innermost, of a material impermeable by air. Nothing also prevents the filter being made of more than two tubular cylinders. If desired, the suction surface of the cylinders can be pleated, to increase the filter surface.

Figure 3c in turn represents an adaptation of the form of the filter construction of Figure 3a. The outer cylinder 12 is now spread to form a cone, which creates a freer flow in the space between parts 11 and 12.

Figures 4 and 5 show cross-sections of types of filters analogous to that of Figure 3a, which has a large filter surface, but no shapes in the surface, in which material could begin to collect.

Thus, the filter 1 in Figure 4 is formed from several disc-like filter components 14, which are joined together by disc-like intermediate components 15 of a smaller diameter, which are of a material that, as such, may, or may not, have filter properties. In the latter case, the purpose is only to move air from one part to the next.

Figure 5 in turn shows a construction closely resembling a round concertina.

The filter discs 14, which above were essentially of an even size over their entire length, or rather width, now taper towards their outer edges. In other respects, the principle is identical to the previous cases.

In the embodiment shown in Figure 6, a basic frame is formed of disc-like elements 16, which can be, for example, of a plastic material. These are supported on a spindle 18, into which the filtered air flows from the holes shown and from there exits from the vacuum cleaner, according to the principles described above. A filter fabric 17 is now stretched to form a mat supported by the discs 16, which if necessary can be held in place, for example, using suitable springs or similar, which retain the fabric in place in the shape shown.

The material itself can also, as such, be elastic.

In practice, the suction keeps the filter material more or less in the shape shown in Figure 6. When the suction diminishes or ends, the material mat returns to its original shape between the discs 16, possibly forming an outwardly convex shape, so that the filter material will tend to clean itself, without requiring any other special measures.

It is obvious that the discs 16 need not be of a solid material, but that, for instance, some peg-like protrusions can be used to support the fabric 17.

Figure 7 shows how the filter unit 1 is installed inside a surrounding cylindrical wall 19. This is intended to guide the airflow. In addition, one or several vanes 20 are installed on the intake side of the airflow and are rotated by being set on the shaft of the filter unit 1, or are else rotated by a separate power source. If necessary, the flow tube 19 can also be utilized in the installation. The rotation speed is regulated as desired in a suitable manner, for instance, by using gears. The vane construction causes changes in the flow, which are intended to favourably affect the operation of the filter unit and especially to prevent its becoming blocked. Depending on the situation, this construction can be used especially to accelerate the rotational flow.

In all the embodiments described above, the base construction of the filter can also be exploited as a filter surface, if this is sensible. If desired, adaptations increasing the filter surface can also be made in the base. On the other hand, the base constructions of the filter can clearly also be of a solid material, essentially impermeable by air, if this achieves greater power.

Obviously the shape, as such, has little effect on the filter. The construction can be used to affect the size of the filter surface very greatly. The filter surface can be increased, as has been described in many places above, by making pleats or similar in the filter material. It is also possible to use, for example, a material, which has fibres, that may be long, on its outer surface. The material's electrical properties can also be exploited. The most important point is, however, that no angles or shapes must be left in the filter, which could result in the material being sucked in collecting on the surface, at least under certain conditions. This is achieved by mainly rounding the surfaces in the direction of rotation.

Described above are certain embodiments, in which the filters have an essentially even size from top to bottom vertically (cf. Figure 2), under operating conditions. This need not necessarily be the case in practice. The filter can equally well broaden/narrow from one end to the other, if this is of any benefit.

This refers especially to Figure 3c. The operating position is otherwise not limited to a vertical position, instead, if necessary, the filter unit can also be essentially horizontal.

In terms of the invention, the manufacturing material is of no significance, only provided it meets the filtering, durability, and other desired properties set for it.

The filter construction can be adapted in many ways, without deviating from the basic idea of the invention and the protection of the accompanying Claims.

Thus, one variation comprises a filter construction formed by a spiral structure, instead of disc-like filter components. The spiral construction can be used to direct forces other than a purely centrifugal force on the filter. These forces acting in other directions will help to keep the filter clean.

It is also possible to add suitable protrusions, vanes, to the surfaces of the filter, which will allow the rotation of the filter to be exploited to create airflows in a specific direction and of a specific size. The vanes can be located either on the surfaces through which air is sucked, or possibly on the surfaces that are essentially impermeable by air. The shape and number of the vanes are selected in individual cases to create the desired effect.