WO2008097143A1

WO2008097143A1 - Air filter housing

Info

Publication number: WO2008097143A1
Application number: PCT/SE2007/050063
Authority: WO
Inventors: Cédric LANCIEUX
Original assignee: Camfil AB
Current assignee: Camfil AB
Priority date: 2007-02-05
Filing date: 2007-02-05
Publication date: 2008-08-14
Anticipated expiration: 2009-08-05
Also published as: EP2125155A4; EP2125155A1

Abstract

The invention relates to an air filter housing (1) comprising a filter body (9) and a tube (10) connecting the up-stream side of the filter body to the downstream side thereof, said tube passing through the wall (13, 14) of the filter housing at one or more locations. According to the invention said tube (10) is permanently and air-tightly secured to the wall (13, 14) of the filter housing (1) at each location where it passes therethrough.

Description

Air filter housing.

TECHNICAL FIELD

The present invention relates to an air filter housing comprising a filter body and a tube connecting the up-stream side of the filter body to the downstream side thereof, said tube passing through the wall of the filter housing at one or more locations.

BACKGROUND OF THE INVENTION

In order to create clean air within a room, outside air is delivered to the room via air filters and also exhausted from the room via air filters. Some of the exhausted air is usually recirculated. The amount of air delivered to the room is depending on the necessary level of cleanness of the air and is generally between twenty to four hundred times the volume of the room per hour. The air filters are contained within filter housings generally made of painted steel, stainless steel, aluminium or plastic materials. The connection between the filter and the filter housing must be leakproof so that all outside air and/or recirculated air passes through the filter and also the connection between the filter leading to or from a filter housing must of course also be leakproof. The inlet filter or filters are mounted in the ceiling of the room and the exhaust filter or filters are mounted in a wall near the floor of the room.

The inlet filter has a tube of plastic material leading from the inside of the filter housing at a location upstream of the air filter body, which is mounted in the housing in a leakproof manner, to a location within the mouth of the filter housing downstream of the air filter body. Such a tube can be used for measuring the pressure drop over the filter and is also needed in certain cases for leak test equipment that needs an upstream connection. In Figure 1, a part of a known filter housing H containing a filter body B and a tube T is schematically shown. As is evident from this Figure the tube T passes through the wall of the filter housing H at two locations I and II. The tube T is at these locations attached to the housing by connections C comprising nuts, special screw and gaskets. At the downstream end of the tube T, a plug P is closing the opening thereof. In order to ensure leak-tightness of the connections C, the mounting thereof must be done very carefully and is therefore time consuming. Furthermore, after full assembly of the filter housing it is not in practice possible to tighten these connections.

When a leak test is to be performed, the operator removes the plug P and connects the tube T to a further tube leading from the filter housing in the ceiling of the room to a test equipment placed on the floor. In order to avoid contamination from the air upstream of the filter, said further tube is sealed by a plug in the floor end thereof which is removed just before said further tube is connected to the test equipment. However, it has been shown that there is a risk that the operator pull too hard on the tube T so that it is removed or loosened from the screw tightening the connection C so that a leak occur. If such a loosening or removal takes place, there is not enough space between the filter body B and the housing H to admit access to the connection C so that such a leak has to be dealt with by plugging the connection C with silicone gel or the like. This leads to a situation when the filter no longer can be used for leak testing.

A further problem is that since the tube is of flexible material it can be pinched in the piece outside of the filter housing, i.e. the piece between the two connections C. Since there is no access to said piece of tube when the filter housing has been mounted in the ceiling such a pinched piece can not be repaired or replaced. The objective of the present invention is to improve an air filter housing of the above-mentioned type so that the drawbacks discussed above are eliminated.

SUMMARY OF THE INVENTION

This objective is accomplished by an air filter housing comprising a filter body and a tube connecting the up-stream side of the filter body to the downstream side thereof, said tube passing through the wall of the filter housing at one or more locations, characterised in that said tube is permanently and air-tightly secured to the wall of the filter housing at each location where it passes therethrough. By permanently securing said tube there is no longer any risk for leakage at locations where said tube passes through a wall of the filter housing.

In a preferred embodiment, said tube is made of two parts, a first part of rigid material and a second part of plastic material attached to the downstream end of the first part in an air-tight manner. Preferably the first part of the tube is made of stainless steel. The tube has preferably such a length that the downstream end of the first part of said tube is located downstream of the filter body. To advantage, said tube is welded to the filter housing and a downstream end portion of said first part of said tube is perpendicular to the direction of an air flow through the filter.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described with reference to the enclosed Figures, of which; Fig. 1 schematically shows a part of an air filter according to prior art with a front wall of a filter housing removed,

Fig. 2 schematically shows an air filter housing according to a preferred embodiment of the present invention mounted in the ceiling of a room,

Fig. 3 schematically shows a part of the filter housing in Figure 2 with a front portion of the housing removed, and

Fig. 4 schematically shows a view of the filter housing in Figure 3 taken along line IV-IV in Figure 3.

DESCRIPTION OF EMBODIMENTS

In Figure 2, an air filter housing 1 is schematically shown mounted in the ceiling of a clean room. A duct 2 leads out-side air and recirculated air into the filter housing. The filter housing 1 is attached to the ceiling 3, usually made of concrete, by four screws 4 or the like, of which two are shown in Figure 2. The screws 4 having outer threads in the lower end portions thereof co- operating with nuts 5 for enabling adjustment of position of the filter housing. Furthermore, the clean room has a false ceiling 6, the plane of which shall be coincident to the plane of the mouth of the air filter housing. Said false ceiling is sealed to a flange projecting out from the mouth of the filter housing 1. If the mouth of the filter housing is not flush with the false ceiling 6, the position thereof is adjusted by manipulating the nuts 5.

The filter housing comprises an upper part 7 and a lower part 8, in which a filter body 9 (not shown in Figure 2) is supported. A grid (not shown) for directing the flow of air from the filter into the room is also supported in the lower part 8 near the mouth of the filter.

The air filter housing so far described and its components including the filter body is of conventional design and could be any known air filter suitable for clean room application.

The air filter housing also includes a tube 10 according to the present invention which connects the upper part 7 being located upstream of the filter body 9 with the downstream end of the filter housing 1. This tube 10 consists of a first part 11 and a second part 12. The first part 11 is made of rigid material and has an upper end passing through a side wall 13 of the upper part 7 of the filter housing 1. In its upper part the first part 11 of the tube 10 is curved and passes from the side wall 13 of the upper part 7 of the filter housing through a bottom wall 14 of the lower part 8 passing along a side of the filter body 9, as can be seen in Figure 3. The second part 12 is a plastic tube.

The first part 11 of the tube 10 is permanently attached to side wall 13 and bottom wall 14 of the filter housing. The permanent connection between the fist part 11 and the respective wall 13,14 of the filter housing should also be air-tight so that no "dirty" air from the upstream portion of the filter housing can leak into the clean room, i.e. all air should pass through the filter body 9. The permanent connection is preferably made by welding but could also be made by soldering or gluing.

Furthermore, in order to enable change of the second part 12 of tube 10 without having to dismount the filter body 9, the first part 10 is extended beyond filter body 9 in the downstream direction. Moreover, the first part 11 is curved so that a downward end portion thereof is extended in a direction perpendicular to the flow of air through the filter, as best seen in Figure 4. If an operator pulls the second part 12 out of the filter housing in order to couple the free end of the second part to a test equipment, the pulling force will thereby be directed perpendicular to the portions of the first and second parts that are connected to each other. The risk that the first and second parts 11, 12 will disengage from each other is therefore greatly reduced compared to a case when the pulling force act on portions of the first and second parts that are connected to each other and directed in a downward direction.

When the permanent connection between walls 13,14 of the filter housing 1 and the first part 11 of tube 10 is a weld, which is preferred, the material in the first part 11 of the tube 10 should preferably be compatible with the material in the filter housing from a welding point of view. Thus, if the filter housing 1 is made of metal, the first part 11 should also be made of metal. In such a case, the first part 11 should to advantage be made of stainless steel in order to prevent the creating of rust. Thus, if the filter housing is made of plastic also the first part 11 should be made of plastic.

By a "permanent connection" is in this application meant a connection or join which can not be broken without at the same time damage the tube 10 or a wall of the filter housing. Such a connection can resist a force of at least 50N.

The described embodiments can of course be modified within the scope of the present invention. If₅ for example, the connection between the pressure drop tube is connected or joined to the walls of the filter housing by soldering or gluing, the material of the tube need not be compatible with the material in the filter housing from a welding point of view. The downstream end portion of the first part of the tube need not exactly be perpendicular to the vertical air flow direction but can form an angle of 0-20 degrees to the horizontal. In such a case, the angle between the two straight portions of the first part of the pressure drop tube is preferably greater than 90 degrees. The scope of the invention should therefore only be limited by the content of the enclosed patent claims.

Claims

1. An air filter housing (1) comprising a filter body (9) and a tube (10) connecting the up-stream side of the filter body to the downstream side thereof, said tube passing through the wall (13,14) of the filter housing at one or more locations, characterised in that said tube (10) is permanently and air- tightly secured to the wall (13,14) of the filter housing (1) at each location where it passes therethrough.

2. An air filter housing according to claim 1, wherein said tube (10) is made of two parts, a first part (11) of rigid material and a second part (12) of plastic material attached to the downstream end of the first part in an air-tight manner.

3. An air filter housing according to claim 2, wherein the first part (11) of the tube (10) is made of stainless steel.

4. An air filter housing according to claim 2 or 3, wherein the downstream end of the first part (11) of said tube is located downstream of the filter body (9).

5. An air filter housing according to claim 2, 3 or 4, wherein said tube (10) is welded to the filter housing (1).

6. An air filter housing according to any of claims 1-5, wherein a downstream end portion of said first part (11) of said tube (10) is inclined in relation to the direction of an air flow through the filter housing (1).

7. An air filter housing (1) according to claim 6, wherein said downstream end portion of said first part (11) of said tube (10) is inclined 90 degrees in relation to the direction of an air flow through the filter housing (1).