EP 1 340 528 B12510152025303540455055Description?[0001] The present invention relates to a filtering massin sheet form for an air filter for an enclosed space, par-ticularly for a motor vehicle cabin.?[0002] Filters are known which are installed at ventila-tion systems of enclosed spaces in order to filter the ex-ternal air that enters the enclosed spaces; this is the case,for example, of motor vehicle cabins, or of buildings usedfor living or for work.?[0003] Very commonly, such filters comprise a filteringmass in sheet form, which is inserted in a pleated or flatarrangement in a supporting frame, and currently the fil-tering mass is substantially produced according to twotypes.?[0004] A first type of filtering mass consists of a sheetformed by fibers of different materials, such as for exam-ple polyester, polyamide, polypropylene, pure or mixedtogether, providing what is known as "nonwoven fabric",or also by cellulose fibers, either substantially pure ormixed with fibers of materials such as the ones citedabove, providing what is known as "filter paper".?[0005] The materials and fibers currently used are ref-erenced respectively hereinafter as "standard-?type ma-terials" and "standard fibers".?[0006] The fiber mat meant to constitute the sheet offiltering mass is subjected, after forming, to impregnationin order to give it the necessary mechanical consistencyand any other characteristics, such as for example fire-resistant and antibacterial properties, and is finally sub-jected to finishing operations.?[0007] With this type of filtering mass, filters are pro-duced which are known as "particulate filters" becausethey are capable of retaining exclusively particulate mat-ter.?[0008] If it is also necessary to retain unwanted gase-ous substances, a second type of sheet of filtering massis currently used which is constituted by an intermediatelayer of carbon granules enclosed between two layers ofstandard fibers, which ensure particle retention, while theintermediate layer of carbon granules retains the gase-ous substances.?[0009] This second type of sheet of filtering mass, how-ever, has drawbacks, such as a high cost and the gen-eration of high load losses; moreover, carbon granulescan break away and be dispersed into the environment.?[0010] Filter masses, as set forth in the preamble ofclaim 1, are known from the document Patent abstractof Japan Vol. 011, No. 369 (C-?461), 2 December 1987& JP 62 140614 A and from WO 01/66223A and US-?4904 343. Document US 3 769 144 discloses a quiltedfabric containing high surface area carbon fibers.?[0011] The aim of the present invention is to provide afiltering mass in sheet form for an air filter, which is ca-pable of retaining both particulate matter and undesirablegaseous substances, has a low cost, generates limitedload losses and cannot cause contamination.?[0012] This aim is achieved by a filtering mass in sheetform for an air filter for an enclosed space, particularly amotor vehicle cabin, according to the invention com-posed of elements made of standard-?type materials nor-mally used to form filtering masses and carbon elementsrendered active for the absorption of gaseous substanc-es, characterized in that it comprises at least one layercomprising said elements which are made of pure stand-ard-?type materials and pure active carbon in the form offilament and woven so as to form an actual fabric in whichthe filaments made of pure standard-?type materials andthe pure carbon filaments are arranged, respectively, aswarp and weft filaments.?[0013] Further characteristics and advantages of theinvention will become better apparent from the descrip-tion of some preferred but not exclusive embodimentsthereof, illustrated only by way of non-?limitative examplein the accompanying drawings, wherein:?Figure 1 is a view of a portion of a sheet of filteringmass with a single layer of elements in fiber form;Figures 2 to 5 are views of portions of different sheetsof filtering mass with two layers of elements in fiberform;Figure 6 is a view of a portion of a sheet of filteringmass with a single layer of fabric formed by elementsin filament form;Figure 7 is a view of a portion of a sheet of filteringmass with a layer of fabric formed by elements infilament form and a layer of elements in fiber form;Figure 8 is a view of a portion of a sheet of filteringmass with three layers of elements in fiber form.?[0014] The embodiments of figures 6 and 7 are com-prised within the scope of the claims.?[0015] The embodiments of the other figures are there-fore deemed, in the context of the claimed invention, toconstitute examples which are useful for understandingsuch invention.?[0016] With reference to Figure 1, the reference nu-meral 1 designates a portion of a sheet of filtering masswhich comprises a single layer of elements in the formof fibers of materials normally used in the manufactureof filters which, as mentioned, are referenced herein asstandard fibers, are shown in thin lines and are designat-ed by the reference numeral 2; these fibers are mixedwith carbon fibers, shown in thick lines and designatedby the reference numeral 3, which are generally obtainedfrom vegetable or synthetic polymers, activated for theadsorption of gaseous substances by means of knownprocesses.?[0017] All the fibers comprised in this embodiment, aswell as the fibers comprised in the other embodimentsdescribed hereinafter, may have any length and may beobtained in any manner, for example by breaking up fil-aments as regards the carbon fibers, which obviously,regardless of how they are obtained, are always activatedfor the adsorption of gaseous substances.?[0018] The mat that leads to the formation of the de-1 2
