AIR CLEANING ELEMENT OF THE FILTER CARTRIDGE TYPE

Abstract: In filter cartridge batteries for air cleaning it is customary to use a filter material such as active carbon housed between concentric, perforated carrier pipes. There are certain problems with respect to renovation of the filters, and according to the invention it has been found that in this respect it is advantageous to use a single filter pipe, against which there is placed an up-rounded element of a known, planar and cellular filter insert material, which can be changed out as a unitary element and be supported without any opposed filter pipe. The cellular filter plates should be adapted in size according to the length and perimeter of the filter pipes, and in piled condition they are well suited for compact packaging for shipment. At their side edges they may have projecting web portions which enable the user to round up the plate element with overlapping and to join the edges e.g. with the use of double sided adhesive taps for fixation of the element in the relevant tubular shape.

Description: AIR CLEANING ELEMENT OF THE FILTER CARTRIDGE TYPE. The present invention relates to a tubular air cleaning element for use in ventilation systems and of the type con- sisting of two concentrical , perforated tubes, between which there is arranged a filling of active carbon or a corresponding material for cleaning of the air flowing through the pipe wall. Reference is here made to the extensively used "air cleaning cartridges", which are typically designed with con- centrical, finely perforated plate pipes, between which there is a filling of active carbon in the form of a granulate which, by dust suction and a steam treatment has been brought to agglomerate in such a manner that the material will not dust or sift and yet allow an air penetration with a very small pressure drop. Through many years, a rather stable application pattern has been established, whereby small and semi large air cleaning installations are equipped with these cleaning cartridges in the required small or large number, and the used cartrid- ges are sent to specialised, regional renovation centres in which, with the use of special auxiliaries, the cartridges are emptied and refilled with fresh filter material, which is almost impossible for the users to do themselves. Correspondingly, an accept pattern has been established with respect to some obvious drawbacks of these cartridges. The users are aware of the fact that the cartridges as standard products are vulnerable to corrosion, which occurs very easily in the relevant near environments. In particularly critical cases, the users accept the costs of reusable cart- ridges made with expensive plate tubes of so-called stainless steel. The users also know that the filter cartridges gradually loose their efficiency, not only due to the natural saturation of the filter, but also because the filter material, due to more or less pronounced vibrations, will sink together and thereby leave a filter area with free air passage. Moreover, the users agree to the need of the cartridges, according to requirements, having to be dispatched for external renovation with associated noticeable costs. For use in larger filter installations, other types of filters have been developed, though without affecting the relatively rigid application pattern with respect to the tube cartridge filters. Thus, EP-A-318,934 discloses a gas treat- ing system with a bag filter, the filter bags of which are confectioned with double walls encasing a catalyst material in a cell structure provided by a kind of quilt joining of the double walls. Such bags, which can only be factory produced, will be very expensive in shipping, as they can be compressed to a low degree only, and they will not be suitable for use in connection with conventional cartridge filters. With the present invention it has been recognised that it is possible, in a relatively simple manner, to make improve- merits with respect to the drawbacks connected with the conventional use of the tube cartridge filters, while it is also recognised that this filter type is still usable in filter batteries in a fully advantageous manner. The invention is based on a study of some of the said larger filter installations, in which there is used planar plate supports for special filter plate units consisting of cellular, air permeable sheets of a fibrous material, in the cell formations of which the granular filter material is deposited. There is used, typically, two layers of a polyester fibre web, of which one is planar, while the other, by steam shaping, is formed with projecting macro cell portions which, prior to the two webs being joined, have been filled with the granular filter material. A subsequent welding together of the two webs may then be effected at the partition areas be- tween the cell formations, and in that connection it is possible to provide full and airtight sealing in the joining areas, while each of the outer webs are otherwise left easily air permeable. In connection with the invention it has been found that these known filter plates, modified as required, are perfectly suited for use in round, cartridge like filter units, in particular when modified such that the joining areas between the outer webs are sufficiently broad to enable a rounding up of the filter plate to a cylindrical shape without the projecting cell formations hereby colliding substantially with each other, but rather forming an inwardly almost fully closed and thus highly effective filter face. In practice, this will be a question of an adaptation of the width of the welding areas, but still the result will be that the filling of the filter granulate between the concen- trical walls of the fibre webs will act stiffening on the filter plate when, in rounded shape, this plate is placed in a filter cartridge tube, supported solely by this tube, i.e. without any requirement as to an inner cartridge tube at all. In that the granulate is already dustfree enclosed within the cells, the outer cartridge tube may consist of a coarsely perforated tube, and in connection with the invention it is found advantageous to use a plastic tube structured as "stretch metal", i.e. a large meshed, netlike tube, which provides for minimum air resistance and is also inexpensive and almost totally corrosion proof. Moreover, from the beginning the granulate is filled into the cells with good packing, such that there will be no noticeable aftersinking in the material, i.e. the cartridge filter will not exhibit the otherwise associated drawback with respect to decreasing efficiency. It is easy for the user to effect a filter renovation by means of the purchased filter plates, which can be shipped in compact, piled condition. The used filter plates or tubes can normally be disposed of to a local refuse disposal plant. Thus, the invention provides for filter cartridges, which are directly usable in already existing filter systems and show a row of marked advantages. DE-C-34 15 425 discloses thin filter plate materials that are zig-zag folded as the sides of an accordion bellow and are intended to be mounted in up-rounded shape between perforated walls of e.g. a fuel filter. These filter plates, which can be stored and shipped in compressed pleaded form, are from the beginning adapted solely for being mounted in rounded condition in fuel filter holders, and they have had no in- fluence on the application pattern in connection with the more voluminous ventilation air filters. In the following the invention is described in more detail with reference to the drawing, in which: Fig. 1 is a perspective view of a cellular filter plate; Fig. 2 is a top view thereof, shown in a rounded state; and Fig. 3 is an exploded perspective view of a filter cartridge according to the invention. The filter plate 2 shown in Fig 1 is, in principle, of a known design, consisting of a planar, fibrous and air permeable rear web layer 4 and a fully corresponding front web layer 6, which is only shaped with cell -like bulgings 8 that are filled with active carbon. The two webs 4 and 6 are joined by flat welding along the outer edges and along the areas between the cells 8 in such a manner that these welding zones are not air permeable. Thus, a throughflow of air can only occur through the cells 8, whereby all passing air will be cleaned by the active carbon in these cells. The filter plate shown is easily bendable in the welding zones between the cells 8, and at the right hand side edge 10 it is provided with an adhesive which, when the plate is rounded up, can be joined with the rear web 4 at the opposite side edge of the plate member. Then the cylinder thus formed may be inserted into a cartridge tube 12, Figs. 2 and 3, which is closed by an end cap 14. Preferably the tube consists of an coarsely perforated plastic net, while also the end caps are made of corrosion proof plastic. It will be appreciated that a renovation operation can very easily be effected in situ and by the user. The filter plates 2 should not necessarily be provided with the adhesive 10, as the user may easily apply a double sided adhesive tape or use other suitable adhesives, primarily for ensuring tightness of the edge joint. As apparent from Fig. 2, a certain distance should exist between the cells 8 in the transverse direction, such that the rounding up may be effected without too heavy resistance from the cell tops as these are brought together. The relevant filter plates, which are non-stretchable, should be made with such a side distance between the cells 8 that these will not prevent a rounding to the actual diameter, to which also the width of the plate should be rather accurately adapted.

Claims: C L A I M S : 1. An air cleaning element of the filter cartridge type, in which a filter material such as active carbon is enclosed between an outer and an inner cylinder wall, which are perfo- rated for enabling the passage of air therethrough, characterized in that one of said cylinder walls in known manner is constituted by a perforated support tube, while the opposed cylinder wall is constituted by surface portions of a cellular plate body, which is rounded up to suit the support tube, and the cells of which are in known manner filled with the said filter material, such a filter plate body here being used in a rounded shape in association with the support tube, such that the active cylindrical filter element as a whole can be renovated by a changing out of the rounded plate body. 2. An air cleaning element according to claim 1, characterized in that the perforated support tube forms an exterior support for the rounded plate body as mounted inside the tube, the filter material filled cells of the plate body having their inwardly facing surface portions located closely juxtaposed as a result of the rounding up of the plate body. 3. An air cleaning element according to claim 1, characterized in that the perforated, cylindrical support tube as well as associated end cap means are made of corrosion proof plastic material, the support tube preferably being made as a large meshed net body 4. A filter element for use in an air cleaning element according to claim 1, characterized in that it is constituted by a bendable filter plate of the type comprising two layers of an air permeable web, of which at least one is provided with outbulging cell portions holding an active filter material, said filter plate having a length dimension corresponding to the axial length of a cartridge filter tube and a width corresponding to such a perimeter of the plate in rounded up and edge joined condition that it is mountable in support connection with said filter tube, preferably with the cells bulging inwardly towards the tube axis. 5. A filter element according to claim 4, characterized in that the cell portions are locted with such a mutual spacing in the lateral direction that their top portions meet when the element is rounded to a tubular shape with the cells bulging inwardly. 6. A method of renovation of an air filter of the filter cartridge type in a ventilation system, characterized in that a non-stretchable and suitably sized, cellular filter plate element is formed into a tubular shape by rounding up and edge joining of the plate element, preferably with projecting cell portions facing inwardly, this plate tube being arranged in support connection with a perforated cartridge holder tube .

Inventors: JENSEN JOERGEN HOEJMARK, JENSEN, JOERGEN, HOEJMARK
Applicants: JENSEN JOERGEN HOEJMARK, JENSEN, JOERGEN, HOEJMARK
Application year: 1997
Main classification: B01D46
IPC codes: B01D46