AIR FILTER

Abstract: An air filter with a housing, which comprises at least one wall with one or more openings through which air can pass, such that the openings are covered by a filter element, the said filter element being held in a holding frame fitted into the housing, comprising projections or catches to engage the edge of the elements.

Description: AIR FILTER The invention relates to air filtration, for example air conditioning units, ventilating units and the like. One known form of air filter unit comprises a so-called header containing filter cells. The frame is generally trapezoidal as seen in plan, having an open front and a solid relatively smaller rear wall. The side walls are open, and the filter elements or cells are located in the side wall frames; each filter cell is made up of a filter media located with a frame; the element can be made of pleated paper and the frame of cardboard. Each cell is urged against the side wall, with a sealing gasket maybe present in between. It is one object of the invention to provide a filter unit which is both simpler to make and install, and which is more efficient in use. In one aspect the invention provides that part of the holding frame which faces the side surfaces of the filter element, at least in part, is provided with one or more projections which extend into the side or other surfaces of the filter element. In another aspect the invention provides an air filter which with little assembly effort allows a secure joint to be made between the housing and the holding frame. This object is achieved by providing the holder with catch elements, which engage with correspondingly designed detents on the holding frame. The projections project into the side surfaces of the filter element to provide a good seal. Together with the filter element, the projections form a barrier which prevents the unfiltered atmosphere from reaching the clean air side. The assembly of the filter element and its holding frame is simple and no additional sealing means are needed at the points where the projections engage with the filter element. Since no adhesive joint is needed between the filter element and its holding frame, these two components can also be easily separated and recycled separately. In one preferred embodiment of the invention, the filter element is formed from a flat sheet section folded transversely to its longitudinal extension to form filter laminations, which are joined by means of strips of glue or the like nuining along the length of the sheet section, the strips of glue being positioned at the edges of the filter element and making a sealing contact with the projection or projections. In such a filter, the projection can extend into the filter element as far as the strip of glue near the edge of the filter element. The distance of the glue strip from the associated end side of the filter element can therefore be made no larger than the height of the projection. At their free ends beyond the glue strip, the individual filter laminations are urged down by the projection and clamped between it and the glue strip. In this way a secure airtight joint between the filter element and its holding frame is achieved. Air can no longer leak through to the clean air side. Clearly, in addition to the glue strips at the edges, other glue strips can be provided further inside the filter element. It is preferable, however, for the glue strips at the edges, which are responsible for forming the sealing joint, to be made thicker. Preferably the projections extend continuously along the longitudinal direction of the filter element side to ensure that the entire side surfaces of the filter element are sealed along their whole length. The projections, which taper from the point of their attachment to the holding frame towards the filter element, are designed like swords or fins. With such a geometry, it is then easy to push them into the associated surfaces of the filter element. One preferred embodiment of the holding frame comprises four profile sections positioned at right-angles to one another, each being substantially U-shaped in section and consisting of a connecting section with two webs attached thereto spaced apart, such that the connecting section rests against the end side surfaces of the filter element and the webs against the walls of the filter element, and the connecting section carries the projection or projections. The four profile sections may be joined together in one piece or connected together as separate pieces to form the holding frame, preferably by clip joints. The U-shaped cross-section of the profile sections holds the filter element securely. In this, the projection on the connecting section engages with the side surfaces of the filter element at the predetermined points. For preference, the projections are formed in one piece with the profile sections. To enable the holding frame to be fitted into a filter housing, the holding frame is provided with supporting elements on its outside facing away from the end side surfaces, which co-operate with matching elements on the filter housing, the said supporting elements being arranged close to the projections so that they will also serve to hold and stabilise the projections in their engagement with the side surfaces of the filter element. To fit a filter element, according to the invention, the holding frame with the filter element in it need only be inserted in the housing and clipped into place with a single hand movement, which brings the catch elements into active engagement with the detents. The holding frame is then securely held in the housing. With this type of attachment, the holding frame is also always in a predetermined position relative to the housing. The seal between the housing and the holding frame remains fully effective at all times. The exchange and replacement of the filter element is also considerably simplified. When laden with particles, the filter can be released from its attachment with a single hand movement. A new filter can then be inserted. With the air filter according to the invention, the exchange procedure takes very little time. This is an advantage, especially with large air-conditioning units, where numerous filters often have to be exchanged. Furthermore, during its release the filter is shaken very little, so trapped particles will not fall off and find their way into the air duct on the clean air side behind the filter element. According to a preferred embodiment of the invention it is provided that the catch elements are formed in one piece on the housing, on opposite sides of the holding frame. The frame can then be inserted first into the catch element or elements on one side of the frame, and then clipped into the catches on the opposite side. With this type of attachment, secure clamping of the holding frame is possible. If the catch elements are formed as fins extending almost along the whole length of the associated side of the holding frame, and the fins comprise an abutment ramp inclined in the direction of the insertion movement of the holding frame, then the holding frame will be aligned over a large section along one side. It can then be reliably positioned over a sealing strip on the housing. The abutment ramp on the fins ensures that they can move accurately into the detents formed as recesses. A preferred design of the invention provides that the housing comprises a bottom and a cover section connected to one another by the walls provided with openings, the bottom and cover sections are of trapezoid shape so that the walls are at an angle relative to one another, the walls are connected at the back by a back wall and at the front by a front wall, and the said back and front walls carry the catch elements. A filter according to the invention, consisting of a filter element and its holding frame, which can be fitted into the housing, is characterised by the presence on the holding frame of detents which co-operate with correspondingly designed catch elements on the housing. It is important that the holding frame is individualised, so that exchange with the wrong type of holding frame cannot take place. This avoidance of the risk of confusion is an important factor for operational safety. For this purpose, it can be provided that the holding frame, on its side surface facing the catch elements, has longitudinal grooves which form the detents. The grooves can for example form the catch joint together with the aforementioned fins. It is also possible that several catch elements are provided on housing, which engage with a groove on a side surface of the holding frame. In one design for a holding frame the filter element is surrounded by horizontal and vertical profile sections of the holding frame, the profile sections are connected together in a one-piece profile which is connected at its ends by a connector to form a closed frame, and the profile sections are at least in part provided with the detents. The holding frame with its detents can also be made from a single piece. For assembly, the profile strand forming the holding frame is folded around the filter element. Here, it can be provided that the connector to join the ends of the profile strand is in the form of a clip component with catch projections, such that the catch projections snap into openings of the holding frame. This enables the holding frame to be assembled rapidly and accurately. The filter element can be held securely and firmly in the holding frame if the holding frame is assembled from the profile sections, which are U-shaped in cross-section and consist of a connecting section to which are attached webs parallel to one another and some distance apart, the connecting section is provided with the detents on its outside facing away from the webs, and the edge of the filter element is fitted into the holding space surrounded by the connecting section and its webs. The filter element will then be held between the two webs, and will rest with its end surface against the connecting section. The detents, which are on the side of the connecting section facing away from the filter element, remain easily accessible. The holding frame can be produced as a plastic injection-moulded component. For this, it could also be injection-moulded directly onto the filter element. It is also conceivable that the profile strand for the holding frame could be extruded. To seal the holding frame against the housing, a seal may be formed or applied as foam to the holding frame, which is pressed around the opening in the wall. The seal will be held in place by the engagement between the catch elements and the detents in their locating positions on the housing. The seal could be formed as a sealing Up on the holding frame, or applied as foam to form a separate sealing bead. If two holding frames are joined together by a hinge axis around which they can swivel, then the holding frames can be folded over one another. This gives a single unit which can be easily assembled and dismantled. If the particle-loaded sides of the filter elements are laid against one another by this swivelling mechanism, fall-out of dust particles and their penetration through to the clean air side is reliably prevented. Other features of the invention are set out in the dependant Claims. In order that the invention may be well understood it will now be described in greater detail with reference to the accompanying diagrammatic drawings in which Figure 1 is a perspective exploded view of one filter element and a profile section of a holding frame of one embodiment of the invention; Figure 2A to 2C show a profile strand for a holding frame, consisting of several profile sections shown in various views. Figures 3A to 3C show a connector for the profile shown in Figures 2A to 2C. Figure 4 shows a detail of the profile of Figures 3 A to 3C ; and Figure 5 shows in section a filter housing of the invention. Figure 1 shows a filter element 10 consisting of filter paper folded to form individual filter laminations 11 which are essentially parallel. The front and rear filter laminations provide side surfaces 13a which extend parallel to the plane of the drawing. At right- angles to the side surfaces 13a there are side surfaces 13b. The side surfaces 13b are formed by the ends 12 of the filter laminations 1 1. The filter element 10 thus forms a substantially square body which separates a clean air side 25 from a working atmosphere side 26 in a filter unit. To produce this filter element 10, glue strips 17 are apphed parallel to one another on the filter paper in the longitudinal direction. When the individual filter laminations 1 1 are formed by folding, they stick to one another along the glue strips 17. In the drawing of Figure 1, for the sake of simplicity only two glue strips 17 are shown. These two glue strips 17 are positioned in the area of the side surfaces 13b. To enable the filter element 10 to be fitted into the filter unit, a holding frame 20 is provided. The drawing shows only part of the said holding frame 20, namely a profile section 21. The profile section 21 is substantially U-shaped in cross-section, and is formed from a connecting section 32 and two side webs, 31. The webs 31 are distanced further apart at their points of connection to the connecting section 32 than at their free ends. The webs 31 and the connection section 32 create a holding space 34 for the filter element 10. The filter element 10 can be inserted into this holding space 34 along its side surface 13b. The webs 31 contact the wall 16 of the filter element 10, and the connecting section 32 contact with the side surface 13b. Since the two webs 31 are set at a slight angle relative to one another, the filter element 10 is clamped in place. A projection or fin 33 is present on the connecting section 32 to face the filter element 10. The projection 33 extends longitudinally along the profile section 21. It is V- shaped in cross-section, tapering from its base at the connecting section 32 towards its free end. The projection 33 engages with the side wall 13b by penetrating into the filter element 10 along a horizontal contact line 15 as far as the glue strip 17. This engagement bends the ends 12 of the filter laminations 11. Depending on the condition of the glue strip material 17, the projection 33 may also penetrate into the glue strip 17. The height of the projection 33 is dependant on the distance from the glue strip 17 to the side wall 13b. The filter laminations 1 1 fold over against one another at their free ends, to produce a sealing contact between the connecting section 32 and the side wall 13b. This simple measure ensures that no atmospheric air from the working atmosphere side 26 can pass unfiltered to the clean air side 25. The height of the projection 33 above the connecting section 32 is preferably at least equal to the distance between individual filter laminations 11 to ensure that each filter lamination 1 1 will be bent down far enough to he over the end 12 of the next adjoining filter lamination 1 1. In the same way. the vertical side surfaces 13a are covered by profile sections 22. The projection 33 engages in the side surface 13a to form a seal. The upper horizontal side surface 13a is also gripped by a profile section 21. The individual profile sections 21 can be made separately and joined together by connectors, or it may be a one-piece component could be used as the holding frame 20. As shown in Figures 2A to 2C the individual profiles 21, 22 are joined together. For simplicity, the profile sections 21 are shown shortened. Between the individual profile sections 21, 22, cut-outs 29 are provided in the form of rectangular slots. At these, a profile section 21 can be folded over against a profile section 22. If the profile sections 21, 22 are folded against one another at all these slots 29, a closed holding frame 20 will be formed. The drawing of Figure 2b shows that the slots 29 extend across the full width of the profile strand. A continuous seal 24 is formed as a sealing Up to seal the holding frame 20 against the housing of a filtration unit. (A corresponding contact surface must be provided on the housing). Figure 2 shows that the seal 24 is positioned at the transition zone between the connecting section 32 and the lower web 31. Supporting elements 23 are formed on the back of the connecting section 32. The supporting elements 23 extend in the form of continuous grooves on the back side of the profile sections 21, 22 to co-operate with corresponding fittings on the housing into which the holding frame is inserted. These fittings support and stabilise the projections 33 so that they are held securely against the sealing element 10. At the same time, the supporting elements 23 and the projections of the housing serve to fix the holding frame 20 and hold it in place. With a definite mounting of this type, the seal 24 is also pressed against the housing in a predefined position. With this connection technique assembly is particularly simple, since it is only necessary to cUp the holding frame 20 into the housing. To close the holding frame 20 firmly, openings 28 are provided at the ends of the profile strand. The catch projections 44 of a connector 40 (Figures 3A to 3C and 4) can be snapped into these openings. Figure 3A shows that the connector 40 consists of two shanks 41, 42 at right-angles to one another. The shanks 41, 42 comprise catch projections 44 provided with ramps 45. The detailed design of such a catch projection can be seen more clearly in Figure 4. Figures 3B and 3C show the connector in views from behind and from above. Two catch elements 44 are used per shank. To assemble the connector 40 on the holding frame 20, the catch projections 44 are placed against the openings 28 in the profile strand. The connector 40 can now be pushed onto the holding frame 20, when the catch projections will be pushed sideways by their deflection ramps against the openings 28. When the ramps have passed through the openings 28, the catches engage with the connecting sections 32 of the profile sections 21, 22. Figure 5 shows one embodiment of assembled filter unit. The waUs 1 13 are connected together by a bottom and a cover section 116. At the front, the housing has a front waU 1 10. At the back, the two waUs 113 are connected to a back waU 1 14. The back wall 1 14 consists of two partial back waUs 114a and 1 14b set at an angle to one another. Catch elements 115b are positioned on the two part back waUs 1 14a and 114b, projecting into the housing. Catch elements 115a are also provided on the front waU 10. The catch elements 115a, 115b are formed as vertical fins running along the front waU 10 and the part back waUs 114a, 114b. The catch elements 1 15a, 115b serve to hold filter cassettes in place. The filter cassettes comprise a holding frame 120. In the area of the catch elements 115a, 115b, the holding frame 120 is provided with a vertical groove directed longitudinally. The grooves serve as detent elements 123. A filter element is held in place in the frame 20. The holding frame 120 and its filter element cover an opening 1 13a in the waU 1 13. This separates the air exhaust side from the clean air side. A seal 24 is present to prevent leak points where the holding frame 120 rests against the waU 113. The seal 124 is in the form of a sealing Up, a hoUow sealing section or a sealing bead, and is formed in one piece on the holding frame 120. As is shown in Figure 5 the seal 124 rests against the back side of the wall 113. The distance aUowed between the catch elements 115a, 1 15b and the back side of the waU 1 13 is selected that the seal element 124 will always be pressed sufficiently firmly against the waU 1 13. This results in the reUable prevention of leakage. For fitting into a ventilation system, the housing has a flange 1 1 1 which projects to the side, beyond the front waU 1 10. At the back, recesses 112 are formed in the flange 1 1 1. Sealing elements can be fitted into these recesses 1 12, by means of which the housing is sealed in place. As Figure 5 also shows, two geometricaUy identical housings are connected together. Depending on the air entry cross-section required, as many housings as desired can be connected in series. It is also possible to connect them in a series along the direction of the plane of the drawing. With such an arrangement the air required can be drawn through the opening in the front wall 110. The particles to be separated out are captured by the filter elements. The filtered air can then pass into the air duct behind the filter element, through the openings 113a in the waUs 113. The profile strand for the holding frame 120 is co-extruded from a plastic material. It is also conceivable that the strand could be made as an injection-moulded component. The connector 144 too is an injection-moulded component. To fit the holding frame 120 with its fitted filter element into the open housing shown in Figure 5, the holding frame 120 is first placed with one profile section 121 against the catch element 115b on the part back wall 1 14,114b. The holding frame 120 can then be moved towards the waU 113 by a manual movement to the side. In this, the profile section 122 sUdes in the area of the front wall 10 past the catch element 1 15a. The catch element 1 15a, provided with an abutment ramp, deflects the profile section 122 sUghtly outwards until the catch element 115a snaps into the detent 123. Now, the holding frame 120 is securely held in the housing. Dismantling is carried out in the same way. For this, the holding frame can easily be extracted again from its locked position between the catch element 1 15a and the detent 123. The invention is not limited solely to the design features illustrated in the drawings. The folded paper filter can be replaced by a foam filter or any other filter element could be used. The projection 33 also need not extend continuously along the longitudinal direction of the profile sections 21 , 22. Instead several projections obhque to the connecting section 32 could be provided, each displaced relative to the others. Such a design would also aUow the formation of a seal between the filter element 10 and the connecting section 32. Two holding frames 20, which are fitted adjacent to each other in the housing, could be hinged to one another along the back waU 14. A hinge axis would then be formed along the adjacent edges of the holding frames 20. This would simplify both the assembly and the dismantling of the filter consisting of filter elements and their holding frames 20. During dismantling, the filters with their particle-laden front sides could be folded together, and this would ensure that during extraction from the housing, no particles could faU out of the filter elements and reach the clean air side. To hinge the holding frames 20 together, they could be joined by a strip. It is also conceivable to have a one-piece joint, for example in the form of a film hinge.

Claims: CLAIMS 1. An air filter unit comprising a frame, a filter element being received vvitbin the frame wall to present an air filtration surface, wherein the filter element and the facing waU of the frame are engaged by a projection received in a recess. 2. A unit according to Claim 1 , wherein a holding frame (20) faces the side surfaces (13a, 13b) of the filter element (10) and is provided at least in part with one or more projections (33) which project into the side surfaces (13a, 13b) of the filter element (10). 3. A unit according to Claim 1 or 2, wherein the filter element (10) consists of a flat sheet section folded transversely to its length to form individual filter laminations joined together by means of lines of adhesive (17) extending in the longitudinal direction of the sheet section, and lines of adhesive (17) are positioned at the edges of the filter element (10) and are in sealing contact with the projection or projections. 4. A unit according to any preceding Claim, wherein the projections (33) extend substantially continuously in the longitudinal direction of the associated side surfaces (13a, 13b) of the filter element (10). 5. A unit according to any preceding Claim, wherein the projections (33) taper from their base towards the filter element (10). 6 A unit according to any preceding Claim, wherein the holding frame (20) comprises four profile sections (21, 22) located at right angles to one another, the profile sections (21,22) have an essentiaUy U-shaped cross-section with a base section (32) and two side webs (31), the connecting section (32) being in contact with the end side surfaces (13a, 13b) of the filter element (10) and the webs (31) in contact with the walls (16) of the filter element (10), the projections (33) being present on the base section (32). 7. A unit according to Claim 6, wherein the profile sections (21 ,22) are made of a plastic or plastic composite material and are formed together in one piece, 8. A unit according to any preceding Claim, wherein the holding frame (20) is adapted to be fitted into a filter housing, the holding frame (20) comprises supporting elements (23) on its outer side facing away from the end side surfaces (13a, 13b) which co-operate with correspondingly shaped fittings (115a,115b) on the filter housing, and the supporting elements (23) are positioned close to the projection or projections (33). 9. A unit according to any preceding Claim, wherein the filter element (10) is a paper filter with folded laminations (1 1) lying one behind the other and the projections (33) have a height substantiaUy equal to the distance between individual folds. 10. A unit according to any preceding Claim, including catch elements (115a, 115b) which engage with correspondingly shaped detents (23) on the holding frame (120). 11. A unit according to Claim 10, wherein the catch elements (1 15a) are formed in one piece on the housing, on opposite sides of the holding frame (120). 12. A unit according to Claim 10 or 1 1, wherein the catch elements (1 15a) are formed as fins extending over nearly the whole length of the associated side of the holding frame (120), and are inclined in the direction of the insertion movement of the holding frame (120). 13. A unit according to any of Claims 10 to 12, wherein the housing (120) comprises a bottom and a cover section (116), which are connected together by the waUs (113) provided with openings (113a), the bottom and cover sections (116) are of trapezoidal shape, so that the waUs (113) Ue a an angle to one another, the waUs (113) are connected together at the back by a back waU (1 14) and at the front by a front waU (110), and the front waU (110) and the back waU (1 14) support the catch elements (115a). 14. A unit according to any of Claims 10 to 13, wherein the holding frame (120) comprises detents (123) to engage with correspondingly shaped catch elements (115a) of the housing. 15. A unit according to Claim 14, wherein the holding frame (120) has longitudinaUy directed grooves in its side surface facing the catch elements (115a) which constitute the detents (123). 16. A unit according to Claim 14 or 15, wherein the filter is surrounded by horizontal and vertical profile sections (121,122) of the holding frame (120), the profile sections (121,122) are connected together in one piece to form a continuous section joined at its ends by a connector (140) to produce a closed frame, and the profile sections (121, 122) are provided at least in part with the detents (123). 17. A unit according to Claim 16, wherein the connector (140) which joins the ends of the continuous section comprises a cUp with detent lugs, adapted to engage in apertures (128) in the holding frame (120). 18. A unit according to any preceding Claim, wherein a seal (124) is formed or apphed as a foam on the holding frame (120), which is pressed against the opening (1 13a) in the waU (1 13). 19. A unit according to any preceding Claim, wherein two holding frames (120) are connected together so as to swivel about a hinged axis.

Inventors: ROEHE WERNER, SCHULZ RAINER, ROEHE, WERNER, SCHULZ, RAINER
Applicants: MCLEOD RUSSEL HOLDINGS PLC, ROEHE WERNER, SCHULZ RAINER, ROEHE, WERNER, SCHULZ, RAINER
Application year: 1997
Main classification: B01D46
IPC codes: B01D46