AIR CLEANING ELEMENT OF THE CARTRIDGE TUBE TYPE

Abstract: A filter element designed to form an air cleaning filter of cartridge tube type, said filter element comprising an essentially planar filter plate (2, 4, 6), one lateral face of which is formed with protruding cells (4) filled with a filter material and which plate is arranged to be bent into tubular shape with the cells (4) being turned inwards, towards the tube axis. The cells (4) are formed with oppositely positioned side faces which, upon bending of the filter plate (2, 4, 6) into the tubular shape, assume a position in abutment against one another so as to form a self-stabilising tubular element (14). The filter plate is formed with a projecting marginal portion (10) arranged, following bending of the filter plate, to be fixed to the outer face (12) of the opposite side edge so that the facing lateral faces of meeting cells abut against one another.

Description: AIR CLEANING ELEMENT OF THE CARTRIDGE TUBE TYPE The present invention relates to an air cleaning element of the cartridge tube type, i.e. of the type consisting of two concentric, perforated tubes, between which there is arranged a filling of active carbon or an equivalent material for cleaning the air flowing through the tube wall. Reference is made herein to the extensively used "air cleaning cartridges", which are typically designed with concentric, finely perforated plate tubes, between which is placed a filling of active carbon in the form of granules which, by dust suction and steam treatment, have been made to agglomerate in such a manner that the material will not give off dust or particulate matter and yet will allow air penetration with a very small pressure drop. Over a number of years, a rather stable pattern of use has been established, according to which small and semi-large air cleaning installations are equipped with a small or large number of cleaning cartridges of the kind referred to and the used cartridges are sent to special- ised, regional renovation centres, where special equipment is used to empty and refill the cartridges with fresh filter material, something that it is almost impossible for the users to do themselves. Correspondingly, some obvious drawbacks with which these cartridges are afflicted, have become acceptable. The users are aware that these cartridges, being standard products, are vulnerable to corrosion, a phenomenon that occurs very easily in the near environments of use of the cartridges. In particularly critical cases, the users accept the high costs of reusable cartridges that comprise expensive plate tubes of so-called stainless steel, whereas plates of galvanised iron-sheet otherwise is the standard material used for this purpose. The users also know that the filter cartridges gradually loose in effi- ciency, not only due to the natural saturation of the filter, but also because the more or less pronounced vibrations, to which the filter material is exposed, cause compaction of the material, creating an empty area of free air passage inside the filter. Moreover, the users know that when required the cartridges need to be sent away for external renovation with consequential considerable expenses. For use in larger filter installations, other types of filters have been developed, though without affecting the relatively rigid pattern of use adopted with respect to the tubular cartridge filters. Thus, EP-A-318 934 discloses a gas treatment system equipped with a bag filter, the filter bags of which are designed with double walls encasing a catalyst material in a cellular structure, wherein the double walls may be joined together with the aid of a quilting technique. Such bags, which can only be factory-produced, are voluminous products to ship, since they may be compressed only slightly, and they are not suitable for use in connection with conventional cartridge filters. The present invention recognises that the drawbacks connected with the conventional use of tubular cartridges may be alleviated in a relatively simple manner, while it also recognises that such tubular cartridges are still useable in filter batteries in a fully advantageous manner . The inventions is based on a study of some of the large filter installations mentioned previously, wherein planar plate supports are used for special filter plate units consisting of cellular, air-permeable sheets of a fibrous material, the cell formations of which hold the granular filter material. Typically, two layers of a polyester fibre web are used, one of which is planar while projecting macro-cell portions are formed in the other layer in a steam-shaping process, which projecting cell portions are filled with the granular filter material prior to the two web layers being joined together. The two webs may then be welded together at the partition areas between the cell formations, and the joining conditions may be adapted to ensure that complete and airtight sealing is obtained in the welded areas whereas each one of the outer webs are elsewhere easily air-permeable . In comparison with PCT/DK97/00416 it has been found that these prior-art filter plates, when modified, are perfectly suitable for use as inserts in cartridge filter tubes, provided they can be inserted in round, i.e. tubular shape. The only condition therefor is that said projecting cells be spaced sufficiently apart in the circumferential direction to allow the filter material to be given a round shape without the inwardly-facing apex portions of the cells substantially colliding with one another. This arrangement offers rather extraordinary advantages with respect to filter renovation and still also as regards the very structure of the cartridge holders, since it becomes possible to completely omit the use of one of said concentric tubes. The subject invention involves a further advancement, which is based on the recognition that said cellu ¬ lar filter plates, when designed in a particular way, may be bent such that they assume a self-stabilising tubular shape, whereby it becomes possible to entirely do away with the use of permanent cartridge tubes. This is due to the fact that the projecting cells in the cellular plate material may be formed with side walls of such a con- figuration that when the cellular plate is bent to and fixed in its round or tubular shape, the side walls will abut one against the other to suit the desired tube diameter in question and in doing so stabilise the corresponding tubular configuration in such a manner that the latter becomes entirely self-supporting when held between opposed end-wall elements. It is at least theoretically possible that the user may himself bend the filter plate elements into the desired round shape, which elements are shipped in the form of compactly stacked flat elements, but it is assumed in accordance with the invention that the bending of the plate elements into their rounded shape as well as the shape-fixation associated therewith should be effected under industrial conditions with the use of for example hot-melt glue to permanent the tubular shape. According to the invention it is thus accepted that the filter elements must be shipped in the form of voluminous, space-requiring tubular units; however, it will still be a considerable advantage that it is possible to completely eliminate the permanent filter tubes mentioned above. In principle, the filter tubes bent to a tubular shape may be used together with permanently applied end pieces in the form of an end-covering disk and an annular end disk, respectively, between which the filter tube is held axially. However, it is realised according to the invention that these very simple accessory pieces could equally well, or better, consist of stationarily mounted parts of the various filter tubes, preferably in the form of simple plate pieces of plastic that are attached to the tube ends in tightly sealed relationship therewith. Accordingly, also these pieces form part of the "disposable unit" that the filter tube is intended to form, and the end pieces should not either be expected to have a particularly long serviceable life. The invention will be described in more detail in the following with reference to the drawings, wherein Fig 1 is a perspective view illustrating the manufacture of a filter plate element for use in a filter cartridge in accordance with the invention, Fig 2 is an end view of said element while being partly bent into its tubular shape, Fig 3 is a perspective view of the element when fully bent to tubular shape, also showing the associated end-covering pieces, and Fig 4 is a lateral cross-sectional view of the filter cartridge in the mounted condition thereof. Fig 1 illustrates a bottom sheet piece of a polyester fibre material wherein have been formed downwardly protruding large-cell or macro-cell depressions 4, which are filled with a suitable filter granules, whereupon an upper covering piece 6 of an identical material is applied on the upper surface of the bottom piece 2 in abutment therewith, and is welded to said bottom piece in the linear areas intermediate the cells 4. The plate material thus produced has the cross- sectional configuration appearing from Fig. 2. The oppositely positioned side faces of the cells 4 are configured such that they project from a thin welding seam 8 while forming between them an angle V, more precisely in such a manner that upon bending of the plate 2, 6 to the desired degree of roundness as illustrated at the right- hand side of Fig 2, said side faces will be juxtaposed, whereby neighbouring cells 4 will assume a position in shape-stabilising abutment against one another. At one of the lateral edges of the blank 2, 6 to be bent the latter is formed with a projecting marginal area 10, which after bending of the blank may be glued to the outer face 12 of the opposite marginal area of the blank, such that lateral contact between meeting cells 4 may be achieved also along this joint area. The tubular blank 14 thus bent and shape-stabilised is shown in Fig 3 together with the end-covering pieces associated therewith, said pieces being in the form of a circular disk 16 and an annular disk 18, respectively, both of which are glued to their respective one of the tube ends. The annular disk 18 is provided with projecting locking pins 20 for co-operation with a bayonet catch 22 on the wall portion 24, Fig 4, on which the filter tube is intended to be mounted. Other fastening means are, however, possible.

Claims: CLAIMS 1. A filter element designed to form an air cleaning filter of cartridge tube type, said filter element comprising an essentially planar filter plate (2, 4, 6), one lateral face of which is formed with protruding cells (4) filled with a filter material and which plate is arranged to be bent into tubular shape with the cells (4) being turned inwards, towards the tube axis, c h a r a c- t e r i s e d in that the cells (4) are formed with oppositely positioned side faces which, upon bending of the filter plate (2, 4, 6) into the tubular shape, assume a position in abutment against one another so as to form a self-stabilising tubular element (14). 2. A filter element as claimed in claim 1, c h a r a c t e r i s e d in that the cells (4) are essentially rectangular and in that in the planar condition of the filter plate (2, 4, 6) , said oppositely positioned side faces of said filter plate form between them an angle (V) which diminishes to essentially zero as the filter plate is being bent to form said tubular element (14) . 3. A filter element as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the abutting, oppositely positioned side faces of adjoining cells (4) are fixed relative to one another. 4. A filter element as claimed in claim 3, c h a r a c t e r i s e d in that the oppositely positioned side faces are glued together. 5. A filter element as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that at one of its side edges said filter plate (2, 4, 6) is formed with a projecting marginal portion (10) , said marginal portion arranged, following bending of the filter plate to form the tubular element (14), to be fixed to the outer face (12) of the opposite side edge so that the facing lateral faces of meeting cells abut against one another. 6. A filter element as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that end pieces (16, 18) are attached to the ends of the tubular element (14) . 7. A filter element as claimed in claim 6, c h a r a c t e r i s e d in that one end piece is attached to an outer free end of the tubular element (14) and is configured as a circular disk, and in that the opposite end piece is attached to the inner end of the tubular element (14) and is configured as an annular disk (18), which may be connected with a wall portion (24) on which the filter element is to be mounted.

Inventors: HOEJMARK JENSEN JOERGEN, HOEJMARK JENSEN, JOERGEN
Applicants: HOEJMARK JENSEN JOERGEN, NORDIFAGRUPPEN AB, HOEJMARK JENSEN, JOERGEN
Application year: 1998
Main classification: B01D46
IPC codes: B01D46