In many known vacuum cleaners a motor powered either by a mains electricity supply or a battery pack, which may be rechargeable, rotatingly drives a fan. The fan generates an airflow within which particles of dust and debris to be collected by the vacuum cleaner become entrained. The airflow generally enters the vacuum cleaner via an inlet nozzle and passes through a filter so that particles of dust and debris entrained in the airflow are removed from the airflow by the filter and are collected in a collecting chamber. A problem with this type of vacuum cleaner is that after some use the pores of the filter can become blocked by particles of dust and debris which tend to bind together to form relatively large conglomerations. Once the filter becomes blocked the airflow through it is reduced and the suction power of the vacuum cleaner is reduced.
In its simplest form the filter can be a piece of woven polyester material supported in a frame and located between a collecting chamber and the fan. Such a simple filter will filter out the majority of particles of dust and debris from the airflow drawn into the fan, some of which particles then drop into the collecting chamber. However, such simple filters do tend to become blocked relatively quickly and can be ineffective to filter out smaller particles of dust and debris from the airflow.
Improved filters are known in which the filter comprises an accordian-like or “concertina” of filter material, in order to increase the surface area of the filter while not taking up too much space within the vacuum cleaner. However, these can also become blocked through use and the folds in the concertina of filter material provide crevices in which conglomerations of particles of dust and debris can accumulate. In such filters the filter material has to be made of materials which maintain their shape once folded, which can increase the expense of the filter material used, particularly if a fine filter is required.
It is important that the filter arrangement used in the vacuum cleaner is effectively sealed within the housing of the vacuum cleaner so that none of the airflow within which dust and debris is entrained leaks around the sides of the filter. It is desirable that all the airflow through the fan passes through the filter so that all the particles of dust and debris entrained in the airflow are filtered out and collected in a collecting chamber. Such a seal for a filter will have to be effective throughout the lifetime of the vacuum cleaner and may have to withstand regular disassembly of the parts of the vacuum cleaner surrounding it in order that the collecting chamber can be emptied, and possibly so that the filter itself can be cleaned.
In some vacuum cleaners the filter is regularly removed from the housing of the vacuum cleaner so that it can be cleaned. In such vacuum cleaners it is desirable to be able to remove and replace the filter easily and without reducing the strength of any seal between the filter and components of the vacuum cleaner surrounding it. However, the need for the user to physically handle the filter element to clean same is a drawback.
A first aspect of the present invention seeks to overcome some of the problems discussed above by providing a filter arrangement for a vacuum cleaner which is less vulnerable to blocking by particles of dust and debris. A second aspect of the present invention seeks to overcome some of the disadvantages discussed above by providing a high surface area and low volume filter in which relatively inexpensive, flexible, fine filter material can be used. A third aspect of the present invention seeks to overcome some of the problems discussed above by providing a filter arrangement with improved sealing to adjacent components. A fourth aspect of the present invention seeks to overcome some of the disadvantages discussed above by providing a releasable fixing arrangement for a filter arrangement within a vacuum cleaner which is easy to operate and maintains a good seal around the filter arrangement when the arrangement is fixed within the vacuum cleaner.