This invention relates to a vacuum cleaner, which consists of a dust container con taining filters w ith respective different flow s, and above these an air control space containing control housings, and above these a central housing and an underpres sure space and above this a suction unit and the suction unit engine all these spaces being in mutual communication.

The purpose of the invention is to provide a vacuum cleaner of a new type, in which the filters can be cleaned with the desired effect even while the vacuum cleaner is in operation.

The vacuum cleaner of the invention is characterised in that the control space contains control valves for the air flow, by means of which the air flow in ordinary use is directed through the suction opening in the dust container to the exhaust air open ing in the suction unit, in the manner indicated by the arrows, and in that the control valves have closing means which by opening one valve t the outside air and clos ing the other valve, directs the air flow in the dust container under underpressure in the filter partly from the normal flow direction into the opposite flow direction.

The filters of the vacuum cleaner are automatically cleaned, yielding a better result than manual cleaning. Using the vacuum cleaner is reasonable in terms of ecology, since the use of clean filters reduces the energy consumption and disposable filters can be abandoned. The use of the vacuum cleaner makes cleaning easier. Clean filters are crucial in terms of the operation of the vacuum cleaner. In ordinary use of the vacuum cleaner, the filters are gradually clogged and become less serviceable, and eventually practically inoperative when used over a long period of time. The vacuum cleaner of the invention has automatic operation and continuous alternate cleaning of the filters, so that the filters are never clogged and remain clean. A vacuum cleaner requires at least two filters and at least one dust container. The cleaning

effect is proportional to the amount of opposite air reaching the filter. When maxi- mum cleaning performance is desired for the filter the entire air flow within the vacuum cleaner is directed at the cleaning stage to one single filter with opposite flow.

In this exemplifying case, part of the air flow of four filters is directed to the cleaning of one filter, whereby the amount of air relative to the f iler area is multiplied at the cleaning stage compared to ordinary vacuum cleaning. When the suction opening of the dust container is completely closed the air flow in its totality is directed to the cleaning of the filters.

The desired cleaning effect can be defined with regard to the purpose of use and the requirements. The cleaning controls of the vacuum cleaner be manual!) used if necessary or they cart be programmed with the cleaning function starting automatically by electric means or starting under the joint effect of die suction air, underpressure and pressure differences in the air. The cleaning effect of the vacuum cleaner is determined by the cleaning time and the division of the air quantit in the vacuum cleaner for different functions. One single filter can be cleaned, and then the cleaning efficiency is maximal. On the other hand if the air available for cleaning the filers is divided between several filters in the vacuum cleaner, the cleaning efficiency per filter will be reduced. The cleaning efficienc ₎ can be raised without increasing the power of the suction engine by increasing the number of filters and control housings per filter. At the same time, the filter area is kept constant. In practical operation, this involves reducing the size of the filter·- « he cleaning of the filters takes a few seconds for each filter. Unlike previous v acuum cleaners this vacuum cleaner has the advantage of allowing cleaning of the filters while the vacuum cleaner is being used. The vacuum cleaner has the additional advantage of providing high cleaning performance for each filter owing to the fact that the vacuum cleaner has a separate flow tunnel and a separate closing means controlling the air flow for each of the filters. Up till now. problems hav e been caused by the fact that existing vacuum cleaners have not yielded the desired cleaning result due to the lack of sufficiently effective means for cleaning the filters.

The invention is described below by means of an example n nh reference to the accompanying drawings, which show vacuum cleaner in section. In the figures, filters 2 and the control housings 3 of the vacuum cleaner are al igned. However, in reality, the>· form 90° sectors which describe the cylindrical periphe?} of the vacuum cleaner in section.

The vacuum cleaner consists of a dust container 1 containing filters 2, and above these a control space 3 including control housings 3a. 3b. 3c 3d and above these a central housing 4 and an underpressure space, and above this a suction unit 5 and the suction unit engine 6. Said spaces 1. 3. 4. 5 intercommunicate. Control space 3 contains control valves 7. 8 for the air flow , by means of which, in ordinary use, the air flow is directed through a parti} or completely closabic _Mi ction opening 9 in the dust container 1 to an exhaust air opening 10 in dust container 1, indicated by arrows 9a. 9b. 9c. the control valves having closing means. winch by opening valve 7a to the outside air and closing valve 8a. directs the air flow in the dust container under underpressure in the filter partly from the normal flow direction 9a, 9b, 9c into the opposite flow direction 1 1.

If the air opening in the dust container 9 closes is closed momentarily, the air flows to the filter cleaning in its totality. The closing valves 7 and 8. for instance, are closed by means of springs, and should the suction opening 9 of the container be closed under underpressure valve 7 opens and valve 8 closes. When the suction opening of the dust container is opened the underpressure re\ ailing in the space sinks and the springs return closing valves 7 and 8 to their normal position.

An electric control sensor is also activated by underpressure. If one single filter at a time is cleaned the foulest filter is each time selected for cleaning under the effect

of underpressure given that the most clogged filter generates the highest underpressure in the control housing. The filter is cleaned and the dust sinks into dust con tainer 1. The location of suction unit 5 is not necessarily immediately above the central housing 4. but may as well be anywhere else and the unit can be connected to the central housing 4 with a hose or a pipe. Control housing 3 may also be located outside the control space provided that it can be connected to the control space with a pipe or a hose or in any other manner.

The exhaust air opening 10 can be connected to valve 7a, for instance, which has underpressure, and thus regular and controlled air circulation is achieved.

To replace any external connection closable by-pass tunneb 12 (indicated by a bro- ken line) can also be mounted between suction unit 5 and the control housings, as described above. This prevents pollution or dust from entering the filters from the outside foul and/or dusty air. Filtered and clean air circulates inside the vacuum cleaner. At the same time, suction opening 9 is kept partly or completely closed.