The present invention relates to an air filter housing having at least one filter chamber for receiving at least one filter unit, an access opening in a side wall of said housing leading to said filter chamber, a door for closing said access opening and a clamping device for holding said at least one filter unit in abutment against a first end wall of said filter chamber.
Filter housings according to the introduction are known from filtering devices for certain laboratories or the like in which there is a risk that the ambient air will be contaminated. In order to prevent air from such environment to leak out, such laboratories often are set under sub-pressure. The function of the filter is to capture all infectious particles or other contaminations, such as bugs or other air carried infectious organisms, in the circulated air. There is thus a risk that the filter unit will contain dangerous contaminations after the filtering device has been in operation. Before changing a filter unit it must therefore be ensured that the possible contaminations captured therein no longer are dangerous to human beings. This is done by letting a decontamination gas pass through the filter unit in order to kill all bacteria or other infectious or contagious organisms or the like. In known filter housings of the kind mentioned in the introduction there is nothing to stop filtered air or contamination gas to reach the region in the filter chamber surrounding the circumferential side walls of the filter unit and thereby there is a risk that the outside of the filter unit will be contaminated by infectious or contagious matter that has escaped being captured in the filter unit. However, since said region is outside the main stream of contamination gas it will take a rather long time before one can be sure that the contamination gas has reached or “leaked” into the whole of this region. It is also a risk that contaminated air or decontamination gas will leak out of the housing if sealings between the doors for the openings giving access to the filters are defective.
An objective of the present invention is to eliminate or at least further reduce the risk for air or gas leaking out through access openings to filter chambers. Another objective is to prevent the region outside the filter unit in the filter chamber from being contaminated, thereby getting rid of the necessity to fill this region with decontamination gas.
This objective is accomplished by an air filter housing having at least one filter chamber for receiving at least one filter unit, an access opening in a side wall of said housing leading to said filter chamber, a door for closing said access opening and a clamping device for holding said at least one filter unit in abutment against a first end wall of said filter chamber, characterised in that, when a filter unit is held by said clamping device, a portion of said clamping device is sealingly in abutment with a circumferential portion of the wall of said housing in the second end of said filter chamber so that air or decontamination gas that has passed through the filter unit can not enter the filter chamber outside of the filter unit. By such a construction double security against dangerous leakage through access openings to filter chambers is achieved.
In a preferred embodiment a circumferential flange projects inwardly from the wall of said housing in the second end of said filter chamber. Further, said clamping device includes a frame which is movable back and forth in a direction from one end of the filter chamber towards the other end and which has a first tubular part having an outer circumference smaller than an inner circumference of said circumferential flange and a second tubular part having an outer circumference larger than said inner circumference of said circumferential flange, and means for moving said frame. The means for moving said frame can to advantage consist of at least three pneumatic cylinders. The pistons of said pneumatic cylinders are preferably spring biased towards a first end position in which the frame is in a clamping position. Said filter housing can to advantage include two filter chambers.
The invention shall now be described with reference to the enclosed Figures, of which;
In
In
Clamping device 8 consists of a frame 10 which is movable back and forth in the flow direction of the air or gas passing through the filter unit F. In the preferred embodiment shown, the means for moving the frame 10 are four pneumatic cylinders 11, of which two are shown in
According to the present invention a circumferential flange 15 is projecting inwardly from the outer wall of the filter housing 1 in the second end of the filter chamber 2. In the operative position of the frame 10, a portion 16 of the frame 10 is in abutment with the flange 15 via a sealing element 17. The sealing element 17, for example an O-ring, can be affixed to flange 15 or frame 10. By this arrangement it is ensured that air or gas that have passed through the filter unit F placed within the filter chamber 2 can not enter the space outside the circumferential wall of the filter unit i.e. the space to the left of flange 15 in
In order to be able to push a filter unit F towards the end wall of the filter chamber 2, i.e. to the left in
In the embodiment shown, the sealing element 17 co-operates with the flange 15. It is of course possible to instead of a flange make the outer wall of the filter housing co-operate with the sealing element, for example by making the portion of the outer wall defining the filter chamber having a smaller diameter than the outer diameter of the tubular part 16. Another possible way is to obtain a seal is to use a sealing lip radially extending from the frame 10 which is sealingly engaged with the outer wall of the filter housing also during the movements of the frame into and out of operative position.
The second filter chamber 3 is constructed the same way as filter chamber 2 and includes also a clamping device similar to the clamping device 10,11 described above.
A lot of modifications of the described embodiment can of course be made without leaving the scope of the present invention. For example, other actuating means than pneumatic cylinders can be used for manoeuvring the frame, such as manual actuated levers or the like, toggle links, etc. Furthermore, other types of sealing elements than O-rings can be used, such as sealing elements having one or several sealing lips. The frame need not be manufactured from two tubular parts affixed to each other but can consists of one piece of material having a L-shaped cross-section. The present invention shall therefore be limited only of the content of the enclosed patent claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE06/50027 | 3/14/2006 | WO | 00 | 2/2/2009 |