Dual filter vacuum cleaner apparatus

Details Dual filter vacuum cleaner apparatus Dual filter vacuum cleaner apparatus

2000-07-14

2003-04-15

Moore, Chris K. (Department: 1744)

Brushing, scrubbing, and general cleaning

Machines

With air blast or suction

C015S347000, C055S488000

Reexamination Certificate

active

06546592

ABSTRACT:

TECHNICAL FIELD
The present invention relates to improvements in the filter arrangements used in vacuum cleaners, and in particular to improvements in the filter arrangements used in hand held battery operated vacuum cleaners.
BACKGROUND OF THE INVENTION
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.
SUMMARY OF THE INVENTION
According to a first preferred embodiment of the present invention there is provided a dual filter arrangement for a vacuum cleaner. The dual filter arrangement is effective for filtering particles of dust and debris from an airflow passing through the vacuum cleaner. The dual filter comprises a coarse pre-filter and a fine primary filter which is located rearwardly of the pre-filter in the direction of flow of the airflow.
Clearly, the pre-filter will prevent a proportion of the particles of dust and debris entrained in the airflow from reaching the primary filter and thus will reduce the blocking of the primary filter. Furthermore, the use of a coarse pre-filter means that the sizes of particles reaching the primary filter will be of more uniform diameter than if the pre-filter was not present, because all particles reaching the primary filter will have diameters less than the diameter of the pores in the pre-filter. It has been found that particulate material of more uniform diameter is more resistant to binding than particulate material of greatly varying diameter. This further reduces the tendency of the primary filter to become blocked because the particulate matter incident on it is less inclined to bind together to form the conglomerated masses of dust and debris particles which are responsible for the blocking up of the filter. In this way, the majority of particles of dust or debris incident on the primary filter will fall away from the surface thereof and can be collected.
Preferably, the diameter of the pores of the pre-filter is set at a substantially uniform value, preferably at a value within the range 0.75 mm to 1.75 mm and in particular a value of 1 mm. It would generally be expected that using such large diameter pores would not deflect particulate matter of smaller size, such as average sized dust particles from the airflow. However, the pre-filter with an array of substantially uniform diameter pores with a diameter set at a value within this preferred range serves to deflect a significant amount of particles of dust and debris picked up in a standard manner by a vacuum cleaner and entrained in an airflow passing through it irrespective of the particle size. When the particles entrained in the airflow hit the pre-filter, their momentum is reduced or eliminated and the airflow is often insufficiently strong to recapture such particles which then fall out of the airflow and can be collected. This significantly reduces the volume of particulate material which reaches the primary filter and so will reduce blocking of the primary filter further.
The primary filter comprises a concertina shaped arrangement of a fine filter material in order to provide a high surface area and low volume primary filter. It is preferred that the primary filter comprises a frame comprising two opposing arrays of arms and that the concertina shaped arrangement of fine filter material is supported between opposing pairs of the arms. This support for the fine filter material enables more inexpensive and flexible fine filter material to be used because the filter material is supported in the concertina formation and so does not have to maintain this formation due to its own rigidity. In a preferred arrangement, the opposing arrays of arms are each arranged to form a corrugated or zig-zag formation and so are conveniently positioned to support the entire length of the opposing sides of a strip of filter material folded into a concertina formation. To further increase the surface area of the primary filter without increasing its volume it is preferred that additional pieces of fine filter material are located between adjacent arms of the arrays of arms. To ease manufacture,

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