CA1139144A - Apparatus for forming tubular filter elements - Google Patents
Apparatus for forming tubular filter elementsInfo
- Publication number
- CA1139144A CA1139144A CA000382434A CA382434A CA1139144A CA 1139144 A CA1139144 A CA 1139144A CA 000382434 A CA000382434 A CA 000382434A CA 382434 A CA382434 A CA 382434A CA 1139144 A CA1139144 A CA 1139144A
- Authority
- CA
- Canada
- Prior art keywords
- filter screen
- fibres
- mass
- cylindrical filter
- core
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Filtering Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Apparatus for forming a tubular filter element comprising a cylindrical filter screen, and a central core centrally mounted in and spaced from the filter screen. An annular filter screen extends between the core and the cylindrical filter screen so as to provide a base of a container providing a moulding space otherwise defined by the core and the cylindrical filter screen. A duct for delivering a dispersion of fibres in liquid is provided peripherally around the top of the moulding space for accumulating a tubular mass of the fibres in the moulding space while the liquid is drained through;
the screens. Means for applying pressure to the dispersion throughout its introduction into the moulding space is provided and a reciprocable imperforate screen is provided in sliding contact with the cylindrical filter screen for progressively uncovering the cylindrical filter screen as a mass of fibres builds upwards along the moulding space from the annular filter screen. The apparatus packs the fibres in circumferential direction more uniformly than is possible with prior techniques providing high filtering efficiency and a capacity to withstand high differential pressures.
Apparatus for forming a tubular filter element comprising a cylindrical filter screen, and a central core centrally mounted in and spaced from the filter screen. An annular filter screen extends between the core and the cylindrical filter screen so as to provide a base of a container providing a moulding space otherwise defined by the core and the cylindrical filter screen. A duct for delivering a dispersion of fibres in liquid is provided peripherally around the top of the moulding space for accumulating a tubular mass of the fibres in the moulding space while the liquid is drained through;
the screens. Means for applying pressure to the dispersion throughout its introduction into the moulding space is provided and a reciprocable imperforate screen is provided in sliding contact with the cylindrical filter screen for progressively uncovering the cylindrical filter screen as a mass of fibres builds upwards along the moulding space from the annular filter screen. The apparatus packs the fibres in circumferential direction more uniformly than is possible with prior techniques providing high filtering efficiency and a capacity to withstand high differential pressures.
Description
~L39~4 This application is a divisional of C~anadian Patent Application Seridl No. 319,636 filed January 15, 1979.
This invention relates to apparatus for forming tubular filter elements.
Canadian Patent No. 1,077,864 issued May 20, 1980 to the present applicant and entitled "Filter Elements For Gas or Liquid and Methods for Makin~ Such Elements" describes a method of forming a filter element which comprises dispersing a mass of fibres in a liquid to form a slurry, draining the liquid throu~Jh a lilter surlace on whicll tllc Libres collect while an apertured sheet of supporting material is located at a selected distance above the filter surface, so that the fibres build up from the filter surface -through the apertures in the supporting ma-terial to a predetermined distance above the supporting material, removing the collected fibres containincJ
the sheet oE supporting material Erom the Eilter surface, and bonding the fibros to one another and to the supportincJ material by means of a synthetic resin.
One aspect of -the present invention is based on further ~0 experiments that demonstrate unexpectedly satisfactory results if, in the aforesaid method, the shee-t of supporting material is omitted or, iE provided, is located substantially in contact with the filter surface so that the sheet of supporting material becomes moulded into one surface of the filter element. The invention results in the production of a particularly efficient fibrous filter that is very economical to manufacture.
According to the present invention, a method of forming a filter element is disclosed and which comprises dispersing a mass of fibres in a liquid to form a slurry, applying -~.
~L~3~
the dispersioll under ~ressure to a f.i:Lter surface so that the fibres collect as a layer covering the Eilter surEace while the liquid passes throuc~h the filter surface, and bonding the fibres in the collectecl mass of fibres, after drying to one another by means oE a synthe-tic resin. A sheet of material that is to provide a support :Eor the filter element may be mounted in contact with at least a portion of the filter surface so that the support sheet becomes moulded into one surface of the collected mass of fibres. ~rhus~ when the supL~ort sheet, wllich may L~e pl^ovi(le(l by vei-y fine nlesh material, is removed, the fibres are found to have pene-trated through the support sheet leaving their outer surface flush with the outer surface oE the support sheet, which mcly be a .Laye:r of expanded metal. :[n the past, in the case of cy:Lindric.~ .ilter elements, these have :required the acldit:ion oE a separate support sheet to (I:ive~ strength, but the p~esent mouldincJ nlethod enables the filter cylinder and support sheet to be produced as an integral part in one opera-tion wlth precision, saving time and labour.
The present invention relates to apparatus for forming a compacted mass of fibres comprising a cylindrical filter screen, a central core centrally moun-ted in and spaced from the filter screen, an annular filter screen ex-tending between the core and the cylindrical f:ilter screen so as to provide a base of a container providing a moulding space otherwise defined by the core and the cylindrical filter screen, a duct for delivering a dispersion of fibres in liquid peri-pherally around the top of the moulding space for accumulating a tubular mass of the fibres in the moulding space while the 1~3~
liquid is drained throucJh the scre~ens, means for receiving -the drained liquicl ancl removing it from the vicinity of the screens, means for applying pressure to the dispersion throughout its introduction into the moul~ing space, and a reciprocable imperEorate screen in sliding contact with the cylindrical filter screen for progressively uncovering the cylindrical filter screen as a mass of fibres builds upwarcls along the moulding space from the annular filter screen, -the imperforate screen thereby increasing the area of the filter L0 screen through which the li~uid can drain as the mass of fibres accumulates.
In general, it is desirable to make -the apertures and open area of the support sheet as large as possibLe. ~lowever, it is difficult to specify the~ largest aper-t-lre that can be used. The smallest aperture at presen-t contemplated is 0.25 mm diame-ter. tlowever, it must be~ remenlbered that certain fibres, such as potassium polytitanate, e.g., potassium clititanate, have a diameter of 0.5 microns and length of up to 0.15 mm and these can penetrate apertures of 0.25 mm and smaller.
In the case of the fil-ter surEace, expanded metal with narrow flat strips between overlapping elonqated apertures, an aperture size of 0.75 mm by 0.5 mm has been found to be practical. This yives a good surface finish. 1 mm by 0.75 mm will of course give a somewhat rougher Einish.
Other practical examples or rigid supports have had apertures of 2.8 mm by 0.8 mm providing an open area of 26%
of the area of the support sheet, and 43 mm by 20 mm with an open area of 83%. In general it has been found that the support sheet results in a very small flow restriction, of the order ~:~3~
of 1~ -to 2~ of the total ~low.
In a modification of the aEoresaid method, the support sheet consists of a rigid ~oam or sintered material thereby eliminating the necessity Eor -the use of the very fine mesh material in the production of the filter element.
When, as in the aforesaid prior specification, the binder is used not only to boncl the fibres bu-t also to the support sheet, this may be, for example, silicone, polyurethane, expoxy or phenolic resin. ~eat cured resins arc preferred though air drying resins can be used. The weight of -the resin binder depends on the strength required. Generally the weight of the binder is no more than 100% of the weight of the fibres.
It has been found that the use of pressure in the method according to the invention results in a majori-ty of the fibres beiny disposed so that they are directed, in some measure, approximately in parallel with Otle atlOther . '['tli5 gives particularly aclvantacJeous results, whether or not a support sheet is used. ~ccording to a further aspect of the invention, therefore, a filter element comprises a mass of ibres compacted together and bonded to one another wi-th a synthetic resin, a majority of the Eibres being disposed so that -they are directed, in some measure, approximately in parallel with one another.
In order that the invention may be clearly understood and readily carried into efEect, exan)ples of the invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is a sectional elevation of part of a filter element;
Figure 2 is an enlargement of a portion of Figure l;
1~L3~
Fic~ure 3 is a sectiorla:L el.evatioll of part of another filter element;
Figure 4 is a diagralll showinq appa.ratus for manufacturing a filter element;
Figure 5 is a sectional elevation o~ a detail of the apparatus of Figure 4;
Figure 6 is similar to Fic~ure 5 bu-t relates ta a different phase in the operation O e the apparatus;
Figure 7 is a sectional elevation of a further filter element; and Figures 8 to 18 show portions of various sealing arrangements ~ for the ends of filter elements.
; The portion o:E the fil-ter element shown in Fi~ures 1 and
This invention relates to apparatus for forming tubular filter elements.
Canadian Patent No. 1,077,864 issued May 20, 1980 to the present applicant and entitled "Filter Elements For Gas or Liquid and Methods for Makin~ Such Elements" describes a method of forming a filter element which comprises dispersing a mass of fibres in a liquid to form a slurry, draining the liquid throu~Jh a lilter surlace on whicll tllc Libres collect while an apertured sheet of supporting material is located at a selected distance above the filter surface, so that the fibres build up from the filter surface -through the apertures in the supporting ma-terial to a predetermined distance above the supporting material, removing the collected fibres containincJ
the sheet oE supporting material Erom the Eilter surface, and bonding the fibros to one another and to the supportincJ material by means of a synthetic resin.
One aspect of -the present invention is based on further ~0 experiments that demonstrate unexpectedly satisfactory results if, in the aforesaid method, the shee-t of supporting material is omitted or, iE provided, is located substantially in contact with the filter surface so that the sheet of supporting material becomes moulded into one surface of the filter element. The invention results in the production of a particularly efficient fibrous filter that is very economical to manufacture.
According to the present invention, a method of forming a filter element is disclosed and which comprises dispersing a mass of fibres in a liquid to form a slurry, applying -~.
~L~3~
the dispersioll under ~ressure to a f.i:Lter surface so that the fibres collect as a layer covering the Eilter surEace while the liquid passes throuc~h the filter surface, and bonding the fibres in the collectecl mass of fibres, after drying to one another by means oE a synthe-tic resin. A sheet of material that is to provide a support :Eor the filter element may be mounted in contact with at least a portion of the filter surface so that the support sheet becomes moulded into one surface of the collected mass of fibres. ~rhus~ when the supL~ort sheet, wllich may L~e pl^ovi(le(l by vei-y fine nlesh material, is removed, the fibres are found to have pene-trated through the support sheet leaving their outer surface flush with the outer surface oE the support sheet, which mcly be a .Laye:r of expanded metal. :[n the past, in the case of cy:Lindric.~ .ilter elements, these have :required the acldit:ion oE a separate support sheet to (I:ive~ strength, but the p~esent mouldincJ nlethod enables the filter cylinder and support sheet to be produced as an integral part in one opera-tion wlth precision, saving time and labour.
The present invention relates to apparatus for forming a compacted mass of fibres comprising a cylindrical filter screen, a central core centrally moun-ted in and spaced from the filter screen, an annular filter screen ex-tending between the core and the cylindrical f:ilter screen so as to provide a base of a container providing a moulding space otherwise defined by the core and the cylindrical filter screen, a duct for delivering a dispersion of fibres in liquid peri-pherally around the top of the moulding space for accumulating a tubular mass of the fibres in the moulding space while the 1~3~
liquid is drained throucJh the scre~ens, means for receiving -the drained liquicl ancl removing it from the vicinity of the screens, means for applying pressure to the dispersion throughout its introduction into the moul~ing space, and a reciprocable imperEorate screen in sliding contact with the cylindrical filter screen for progressively uncovering the cylindrical filter screen as a mass of fibres builds upwarcls along the moulding space from the annular filter screen, -the imperforate screen thereby increasing the area of the filter L0 screen through which the li~uid can drain as the mass of fibres accumulates.
In general, it is desirable to make -the apertures and open area of the support sheet as large as possibLe. ~lowever, it is difficult to specify the~ largest aper-t-lre that can be used. The smallest aperture at presen-t contemplated is 0.25 mm diame-ter. tlowever, it must be~ remenlbered that certain fibres, such as potassium polytitanate, e.g., potassium clititanate, have a diameter of 0.5 microns and length of up to 0.15 mm and these can penetrate apertures of 0.25 mm and smaller.
In the case of the fil-ter surEace, expanded metal with narrow flat strips between overlapping elonqated apertures, an aperture size of 0.75 mm by 0.5 mm has been found to be practical. This yives a good surface finish. 1 mm by 0.75 mm will of course give a somewhat rougher Einish.
Other practical examples or rigid supports have had apertures of 2.8 mm by 0.8 mm providing an open area of 26%
of the area of the support sheet, and 43 mm by 20 mm with an open area of 83%. In general it has been found that the support sheet results in a very small flow restriction, of the order ~:~3~
of 1~ -to 2~ of the total ~low.
In a modification of the aEoresaid method, the support sheet consists of a rigid ~oam or sintered material thereby eliminating the necessity Eor -the use of the very fine mesh material in the production of the filter element.
When, as in the aforesaid prior specification, the binder is used not only to boncl the fibres bu-t also to the support sheet, this may be, for example, silicone, polyurethane, expoxy or phenolic resin. ~eat cured resins arc preferred though air drying resins can be used. The weight of -the resin binder depends on the strength required. Generally the weight of the binder is no more than 100% of the weight of the fibres.
It has been found that the use of pressure in the method according to the invention results in a majori-ty of the fibres beiny disposed so that they are directed, in some measure, approximately in parallel with Otle atlOther . '['tli5 gives particularly aclvantacJeous results, whether or not a support sheet is used. ~ccording to a further aspect of the invention, therefore, a filter element comprises a mass of ibres compacted together and bonded to one another wi-th a synthetic resin, a majority of the Eibres being disposed so that -they are directed, in some measure, approximately in parallel with one another.
In order that the invention may be clearly understood and readily carried into efEect, exan)ples of the invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is a sectional elevation of part of a filter element;
Figure 2 is an enlargement of a portion of Figure l;
1~L3~
Fic~ure 3 is a sectiorla:L el.evatioll of part of another filter element;
Figure 4 is a diagralll showinq appa.ratus for manufacturing a filter element;
Figure 5 is a sectional elevation o~ a detail of the apparatus of Figure 4;
Figure 6 is similar to Fic~ure 5 bu-t relates ta a different phase in the operation O e the apparatus;
Figure 7 is a sectional elevation of a further filter element; and Figures 8 to 18 show portions of various sealing arrangements ~ for the ends of filter elements.
; The portion o:E the fil-ter element shown in Fi~ures 1 and
2 may be part of the wall oE a cylindrical :ilter element although i-t can equally well be regarded as part o~ a disc, sheet or conical or frus-to conical cylindrical shape (for example closecl at one end as shown in F`igure 7). A similar me-thod may also be used for the production of concave or convex discs. The bulk 1 of the filter element comprises fibre :` :
material; for example, glass, ceramic, synthetic fibres, asbestos, mineral wool, organic or silicate fibres. Raw borosilicate microEibre is a preferred material. For cartridge : type filters to be used in liquid filtration, cellulose, wool, synthetic polymer (e.g. polypropylene and acrylic) fibres, and combinations of these, also such combinations containing a portion of borosilicate microfibre can very advantageously :~: be used. These combinations can also be used for gas filtration.
Both faces of the fibre mass 1 have an apertured suppor-t sheet 2 moulded thereto so that the fibrous mass penetrates through ; ----' ' ' ' :
' ~1~13~
the aper-tures in the sheets to present surfaces tha-t are flush with the outer surfaces of the sheets (Figure 2). Each support sheet consists of an apertured or open pore ri~id material such as a perforated, expanded or woven material which, in turn, may be of metal, phastics, ~lass or ceramic. Expanded metal is a preferred material.
The filter element of Figure 3 is simi:Lar to that of Figure 2, but only one support sheet 2 is used. Where one support sheet is used, this is ~enerally located on the downstream 10 side of the fibres. This not only cJives strength where it is required but does not reduce the inlet surface area of the filter, thereby increasing the dirt holding capacity. For low pressure use as for example in vacuum systems, the SUppOl^t sheet can be of comparatively light cons-truction but, when usec:l in a high pressure syst.em, either with cJas or liquicl, the support sheet can be of lleavier construction.
In a further example consisting of a cylindrical ~ilter element, no support sheet is used. This example COllSiS ts of a tube made from raw borosilica-te microfibre moulded by pressure 2~0 : formin~ into the cylindrical shape by a method as described below with reference to Figures 4 to 6. The moulded tube is then dipped into a solution oE resin in a solvent so as t:o : impregnate the Eibrous material and is -then heat cured. By using a method as described below a filter element without any support sheet can be constructed with very advantageous properties. For example such filter elements 54 mm long, 44 mm outside diameter and 34 mm inside diameter have been constructed and tested to give the following characteristics:
., f~
V.O.P. UlJI~S~ LO~ ~p p O.D.T.
~ bclr NM~I bar bar % w/w ___ _ __, _ 9'3.999 7.0 45 .069 7.0 15.0 99.97 7.0 45 .06~ 3.0 27.0 99.90~7.0 48 .035 3.0 25.0 99.80~7.0 52 .035 3.0 21.0 99.80~7.0 50 .035 ~.0 35.0 In the above table p is the operatinc~ test pressure, L\p iS -the pressure loss across the filter below ancl O.D.T. is the ratio L0 of the oven clried total wei-ltlt of resin to tl~e fibre conten-t of the filter element. The binder used in all the filter elements represen-ted in the above table was a silicone resin, which is preferred, but many other binclers carl be llsecl-to give comparative test results. 'rhe highest res~ content wll:ictl is in the :la~t tabulated examEjle, is 35'~ but this can be raisecl as h:iclll as 100 while still prov:kling ~aL:isl.lctory chalacteristics. Ilowever, 25~ has been ~oulld adlnirably satis~actory t`or most aE)E)lications.
The effect Oll performance of varying the wall thickness of an unsupported tubular filter element is shown i.n the following table relating to a larger element 200 mm long, 66 mm outside diameter and 54 mm inside diameter For sampLe (a) but 46 nlnl inside ~ meter Lor ~xa~ le (b):-SAMPI.E D.O.P. FLOW ~p p O.D.T
_% MN~/II bar bar % w/w (a)99-99 306 .017 4.2 16.0 (b)99.999 107 .017 4.2 16.0 In the above table the pressure p is a gauge pressure above atmospheric pressure while L~p, of course, is a pressure differential.
113~L4 The above table shows that it is effectively only the flow capacity and efficiency that is affectecl by the increase in wall thickness. In practice, it is thought that about 3 mm will prove to be a lower limit for the wall thickness.
The good results, exempliEied by the above tables, are believed to arise from the packing pattern of the fihres that arise as a result of a methocl of manufacture such as described below with reference to Figures 4 to 6. This packing pattern results from the fibres lying in some measure more uniformly L0 in a circumferential direction round the Lilter elelne~nt, than is possible with known vacuum methods which display a totally random packing pattern. The more regular packing in the filter elements of the invention does not detract from their eEEiciency.
A}though the fil-ter elelllent describe(~ immediateLy above have no rigid support shee-t, they can be provi~led with an inner, outer, or both inner ancl ou~t~r lay~r oE woven or non-woven Elexible material to improve -the hanclling characteristics. Such a layer can be inc~rporated during the manuEac-ture of the filter element ; by a method as described below. The fibres would generally ~:
penetrate through an aperture or pore structure of the flexible material. Moreover ln the case of a filter element with a slngle rigid suuport sheet as shown in Figure 3, the opposi-te face of the fibrous structure can be provided with a layer of flexible material.
Simple, unsupported tubular filter elements as described above may be formed with a variety of surface patterns for example circumferential or longitudinal grooves, to increase the surface area.
Figure 4 shows diagrammatically apparatus for forming : ,' a tubular filter ~lelllent. When this apparatus is in operation, water and borosilicate miel~o~i~res are fecl into a blending tank 31. ~Iydrochloric or sulphuric acid is added until the pH value reaches 2.~ to 3.5. Borosilicate microfibres are found to disperse more readily at this value. It has also been found that the fibres disperse more readily if the solu-tion temperature is increasecl to about 35C. The quality of the fibres that are used depends on the grade of the filter elemen-t that is to be used. rrhe fibre to water ratio (by weight) is generally 0.05% but can vary between 0.01~ and 0.5~. A binder such as colloidal silica may be introduced into the slurry at this stage. It has been found advantageous to use this type of binder to impart adclitlonal streng-th prior to resin impregnation.
The final dispersion is eE~Eectecl by a mecllanical ac~i-tator 32 and takes about 15 minutes.
With valves 33 allcl 34 cLosed ancl valve 35 open, a pump 36 transfers the dispersion to a pressure vessel 37. The precise quantity transferred depends on the fibre/water ratio and the size of the filter element to be produced.
Next the valve 35 is closed and the valve 33 is opened to adrnit compressed air to the pressure vessel 37. Generally the pressure used is 3.5 bar. 'I'his top prcssure is the forming pressure and can be varied according to the efficiency required.
The efficiency can be varied within a ranye, e.g., 99.9~ to 99.999~, usiny the same fibre blend. The forming pressure may be as low as 0.3 bar, bu-t a pressure of 3.5 bar has been found highly satisfactory with the ,fibre blend adjusted to suit the required efficiency.
The next step is to open the valve 34 -to enable the _g_ . .
~:~3~
dispersion to LLow into a molllclLncJ rig 38 shown in detail in Figures 5 and 6. The mouldincJ ric) includes inner and outer vertical cylinders 39 40 defininy a space 41 through whieh the dispersion can flow into a cylindrica~ mouldinc~ spaee 42 defined between a fine mesh screen 44 supported by a maehined perforated cylinder 45 and a core 43 when in the position of Figure 5. Yigures 4 and 5 show the filter element being moulded as a unit with an outer rigid cylinclrical support sheet 2 but it will be appreciated tha-t for a simple borosilica-te mircofibre filter tube this can be omitted. Alternatively of course an inner support sheet can be moulded into the inside surface of the tube eithe~r insteacl o~ or as an adclition -to the outer sheet 2. The bottom of the moulclirlcJ space is eovere(l by a fine mesh sereen 46. A reciproca~:le slee~ve 47 is moullted to slide outside the eylinder 40 and perEoratecl c~ylindcI^ 45.
With the core ~3 and sleeve 47 in the positions shown in F'igure 5 the water drains away throuc~h the screen 46 and lower end oE the screen 44 into a tank 48 (FicJure 4) while the mass of fibres becJin to build up in the moulding space 42.
After all the fibres have accumulated in the moulding spaee the air pressure is maintained so as to remove residual water from the fibres and so dry the ~ormed Lilter. The valve 34 is then elosed. Durinc3 the moulding process a pump 49 continuously pumps the water from the tank 48 to a holding tank 50 ~rom which the water is recycled.
Finally the core 43 is removed to enable the formed filter element to be removed from the rig 38. The process can then be started once more. As an example i-t has been found that the time taken to moulcl a tubular filter element 250 mm 1~l3~
lon~, 65 null outside di~ t~l with a wall thickness oC 10 mm takes ayproximcltely one~ minute. 'I'he formed fil-ter element is removed to a hot air dryer for final drying and is then resin impregnated and oven cured to harden the resin.
Particularly in the case of long Eilter elements, e.g., over 50 mm, it has been found desirable progressively to raise the sleeve 47, substantially at the same rate that the height of the fibre mass increases, in order -to maintain an uninterrupted flow of the dispersion -to the poin-t where the mass of fibres is building up. The movemen-t oE the sleevc 47 then terminates as shown in Fiyure 6.
The core 43 is formed wi-th an upper por-tion 51 of reduced diameter. This is to enable an additional internal layer of fibrous filter material to be added to the ~ilter mate~idl formed in the mouldlng space 42, by Eeecting a further dispersion through the cylinder 39 into a mouldinq space S2 (FicJure 6) between the moulding space 42 and the core portlon Sl when the core 43 is lowered. The water from the new layer escapes through the fibres in -the space 42. The new layer may be of higher or lower efficiency than the tubular element formed in the space 42. This arrangement enables a filter element of c~raded de~nsity to be produccd ~s part or un integr.ll process.
Investigations have shown that the fibres in a finished filter element produced by the method described above with reference to Figures 4 to 6 are predominantly layered in planes perpendicular to the direction in which the dispersion flows into the moulding space. Lt has further been found that the the same packing pattern arises -throughout -the range of forming pressures that can be used effectively in practice. Advantages ~13~
of this packin-J pattern appear from -the results -tabulated above.
For some ap~lications of the invention, where cellulose fibres or combinations of cellulose fibres with borosilica-te fibres are used, A melamine or phenolic resin binder may advantageously be used Eor the bonding material. Cellulose when bonded with melamine resin is approved as being suitable for potable water and sanitary conditions. Phenolic resin is preferred for higher temperature work. The combination of cellulose fibres wi-tll other fibres provides economies both in regard to cost and production time, good flow characteristics and chemical resistance, and controlled selection of pore size by blending difEererlt fibre materials with cellulose. It has been found that by blending 20'~ borosilicate microibre wi.th 80 cellulose by weight the production tinle Eor the E:ilter can be reduced by 30~. Ln this case whe~n the fluicl is water the pressure drop (~p) across the Eilter was 0.15 bar with a flow rate of 16 litres per minute. With a weiqht to weight ratio of 50%, Ap was found to be 0.15 bar with a Elow rate oE 22 litres per minute. The glclss fibre size (diameter) was 3.8 to 5.1 microns and the cellulose a bleached sof-twood kraft. The bonding material, e.g. melamine resin, phenolic resin or other synthetic resin, can be a~plie~ in one of three difEerent ways.
Firstly, by forming a mass of fibres in a moulding rig such as shown in Figures 5 and 6, then impregnating the mass after drying by dipping in a resin solution and curing the resin in an oven. Secondly, by preparing the cellulose fibre and separately mixing the borosilicate fibre with a resin solution, bringing`the two mixtures together, forming the mass under , pressure in the mouldincJ ri~J ancl curincl the mass~ Thirclly, all the fibres and resin solution can be mixed in a single tank, passed to the mouldiny rig, the mass beiny subsequently eured.
~ eylindrieal filter element for liquid filtration haviny a eombination of fibres as described above may have an outside diameter of 64 mm, a wall thickness of 18 mm and various lengths, sueh as 250 mm. No support sheet is necessary for many uses but ean be added when necessary. lrhe Eilter is preferably arranyed for flow from outside to inside the cylinder to give grea-ter surfaee area ~or eollection ol dirt. 'l'~-~is ared ean be inereased by forming lonyitudinal or eircumferential yrooves in -the outside surfaee of the eylinder.
Instead oE usincJ a coMpressecl clas to apply ~ressure to the slurry in the moulclin~ ricl, a hydr.l-llie pump lll,ly L)e used, this pump being arran~Jecl to withclraw the slurry From tl~e ~lenclillq tank and force it into tlle moulclirlcl riLcl.
Tubular or cylindrical ~iL-ter e:lements made in aeeordanee with the inven-tion may be mounted in a variety of Eil-ters, in partieular those shown in l;`icJures 5, 6, 7 and 13 in the aforesaid speeifieation. ~s in tha-t speeiEieation, also the ends of the eylindrieal filter elemen-ts may be fitted into end eaps in a variety oE ways. ~ueh ways are shown in FicJures 8 to 17 of the present speeifieation.
Figures 8 to 13 show eases where the end of a eylindrieal, unsupported filter elemen-t 10 is fitted into an end eap 11 using a gasket seal 21 (Figure 8), a double taper seal 13 (Figure 9), an outside taper seal 14 (Fiyure 10~ an inside taper seal 15 (Figures 11 and 12) and a double taper flange seal 16 (Figure 13).
For a eylindrieal filter element with an inside support sheet 17 an outside taper seal 14 (l;`i~lure l4) may be used. F`or an outside suppor-t sheet 18 (~igure :L5) an inside taper seal 15, or a single taper flange seal 19 (Figure 16) may be used. In the case of a filter element having insid~ and outside support sheets 20, 21 (l~ligure 17) a (Jasket seal 12 (Figure 17) can be used. In all forms of the Filter element constructed according to the invention, an open pore ~ilter layer of sleeve, as shown in Figures 12 and 17, can be used if required to act as a pre-filter or as an after-filter to drain coalesced liquids. This layer or sleeve C.lll be all open ~ore plastic or metal foanl or a layer or layers of non-woven material such as felt. As a further alternative the filter element can be dip sealed into end caps as shown in FicJure 6 ol- the aforesa:id specification.
~'igure 18 shows an arran{Jealllent similar to Figllre 15 with an internal supportincJ spring 2~ in place of any inside support sheet.
Fil-ters made in accordance with the invention can be usecl Eor either yas or liquid ~Eiltra-tion. The efEiciency can be as hiyh as 99.99998% when testecl as ss 4400 or can be produced with a micron rating in various stages between 1 and 50 microns.
A further method of increasing the efficiency of the moulded filter material is by compressincJ the material whi:Le being resin impre~Jnated and cured.
A further material that can be used for the support sheet is a rigid metal foam. The fibres can be moulded directly onto such Eoam so that they pene-trate only so far into the thickness of the foam sheet, but the fine mesh screen 44 can be eliminated in this process because the foam sheet i-tself provides the filter surface through which the water is drained. The same -~I~L3~
method can be used in the case of the aforesaid sintered SuppQrt sheet. rt'he same me-thod can also be used with foam consisting of plastics material, which may be flexible or semi-rigid. However, very advantageously a rigid polyvinyl chloride coated plastic foam can be used.
Among the many possible uses of the EiLter according to the invention are the removal oE oil from compressed air, pre-filtration, aeration, vacuum filtration, liquid filtration, air sterilisation and for pneumatic silencing.
,, ~ 20 ~
. :
~ :
~ -15-; ~ ;J
' : ' , .
'
material; for example, glass, ceramic, synthetic fibres, asbestos, mineral wool, organic or silicate fibres. Raw borosilicate microEibre is a preferred material. For cartridge : type filters to be used in liquid filtration, cellulose, wool, synthetic polymer (e.g. polypropylene and acrylic) fibres, and combinations of these, also such combinations containing a portion of borosilicate microfibre can very advantageously :~: be used. These combinations can also be used for gas filtration.
Both faces of the fibre mass 1 have an apertured suppor-t sheet 2 moulded thereto so that the fibrous mass penetrates through ; ----' ' ' ' :
' ~1~13~
the aper-tures in the sheets to present surfaces tha-t are flush with the outer surfaces of the sheets (Figure 2). Each support sheet consists of an apertured or open pore ri~id material such as a perforated, expanded or woven material which, in turn, may be of metal, phastics, ~lass or ceramic. Expanded metal is a preferred material.
The filter element of Figure 3 is simi:Lar to that of Figure 2, but only one support sheet 2 is used. Where one support sheet is used, this is ~enerally located on the downstream 10 side of the fibres. This not only cJives strength where it is required but does not reduce the inlet surface area of the filter, thereby increasing the dirt holding capacity. For low pressure use as for example in vacuum systems, the SUppOl^t sheet can be of comparatively light cons-truction but, when usec:l in a high pressure syst.em, either with cJas or liquicl, the support sheet can be of lleavier construction.
In a further example consisting of a cylindrical ~ilter element, no support sheet is used. This example COllSiS ts of a tube made from raw borosilica-te microfibre moulded by pressure 2~0 : formin~ into the cylindrical shape by a method as described below with reference to Figures 4 to 6. The moulded tube is then dipped into a solution oE resin in a solvent so as t:o : impregnate the Eibrous material and is -then heat cured. By using a method as described below a filter element without any support sheet can be constructed with very advantageous properties. For example such filter elements 54 mm long, 44 mm outside diameter and 34 mm inside diameter have been constructed and tested to give the following characteristics:
., f~
V.O.P. UlJI~S~ LO~ ~p p O.D.T.
~ bclr NM~I bar bar % w/w ___ _ __, _ 9'3.999 7.0 45 .069 7.0 15.0 99.97 7.0 45 .06~ 3.0 27.0 99.90~7.0 48 .035 3.0 25.0 99.80~7.0 52 .035 3.0 21.0 99.80~7.0 50 .035 ~.0 35.0 In the above table p is the operatinc~ test pressure, L\p iS -the pressure loss across the filter below ancl O.D.T. is the ratio L0 of the oven clried total wei-ltlt of resin to tl~e fibre conten-t of the filter element. The binder used in all the filter elements represen-ted in the above table was a silicone resin, which is preferred, but many other binclers carl be llsecl-to give comparative test results. 'rhe highest res~ content wll:ictl is in the :la~t tabulated examEjle, is 35'~ but this can be raisecl as h:iclll as 100 while still prov:kling ~aL:isl.lctory chalacteristics. Ilowever, 25~ has been ~oulld adlnirably satis~actory t`or most aE)E)lications.
The effect Oll performance of varying the wall thickness of an unsupported tubular filter element is shown i.n the following table relating to a larger element 200 mm long, 66 mm outside diameter and 54 mm inside diameter For sampLe (a) but 46 nlnl inside ~ meter Lor ~xa~ le (b):-SAMPI.E D.O.P. FLOW ~p p O.D.T
_% MN~/II bar bar % w/w (a)99-99 306 .017 4.2 16.0 (b)99.999 107 .017 4.2 16.0 In the above table the pressure p is a gauge pressure above atmospheric pressure while L~p, of course, is a pressure differential.
113~L4 The above table shows that it is effectively only the flow capacity and efficiency that is affectecl by the increase in wall thickness. In practice, it is thought that about 3 mm will prove to be a lower limit for the wall thickness.
The good results, exempliEied by the above tables, are believed to arise from the packing pattern of the fihres that arise as a result of a methocl of manufacture such as described below with reference to Figures 4 to 6. This packing pattern results from the fibres lying in some measure more uniformly L0 in a circumferential direction round the Lilter elelne~nt, than is possible with known vacuum methods which display a totally random packing pattern. The more regular packing in the filter elements of the invention does not detract from their eEEiciency.
A}though the fil-ter elelllent describe(~ immediateLy above have no rigid support shee-t, they can be provi~led with an inner, outer, or both inner ancl ou~t~r lay~r oE woven or non-woven Elexible material to improve -the hanclling characteristics. Such a layer can be inc~rporated during the manuEac-ture of the filter element ; by a method as described below. The fibres would generally ~:
penetrate through an aperture or pore structure of the flexible material. Moreover ln the case of a filter element with a slngle rigid suuport sheet as shown in Figure 3, the opposi-te face of the fibrous structure can be provided with a layer of flexible material.
Simple, unsupported tubular filter elements as described above may be formed with a variety of surface patterns for example circumferential or longitudinal grooves, to increase the surface area.
Figure 4 shows diagrammatically apparatus for forming : ,' a tubular filter ~lelllent. When this apparatus is in operation, water and borosilicate miel~o~i~res are fecl into a blending tank 31. ~Iydrochloric or sulphuric acid is added until the pH value reaches 2.~ to 3.5. Borosilicate microfibres are found to disperse more readily at this value. It has also been found that the fibres disperse more readily if the solu-tion temperature is increasecl to about 35C. The quality of the fibres that are used depends on the grade of the filter elemen-t that is to be used. rrhe fibre to water ratio (by weight) is generally 0.05% but can vary between 0.01~ and 0.5~. A binder such as colloidal silica may be introduced into the slurry at this stage. It has been found advantageous to use this type of binder to impart adclitlonal streng-th prior to resin impregnation.
The final dispersion is eE~Eectecl by a mecllanical ac~i-tator 32 and takes about 15 minutes.
With valves 33 allcl 34 cLosed ancl valve 35 open, a pump 36 transfers the dispersion to a pressure vessel 37. The precise quantity transferred depends on the fibre/water ratio and the size of the filter element to be produced.
Next the valve 35 is closed and the valve 33 is opened to adrnit compressed air to the pressure vessel 37. Generally the pressure used is 3.5 bar. 'I'his top prcssure is the forming pressure and can be varied according to the efficiency required.
The efficiency can be varied within a ranye, e.g., 99.9~ to 99.999~, usiny the same fibre blend. The forming pressure may be as low as 0.3 bar, bu-t a pressure of 3.5 bar has been found highly satisfactory with the ,fibre blend adjusted to suit the required efficiency.
The next step is to open the valve 34 -to enable the _g_ . .
~:~3~
dispersion to LLow into a molllclLncJ rig 38 shown in detail in Figures 5 and 6. The mouldincJ ric) includes inner and outer vertical cylinders 39 40 defininy a space 41 through whieh the dispersion can flow into a cylindrica~ mouldinc~ spaee 42 defined between a fine mesh screen 44 supported by a maehined perforated cylinder 45 and a core 43 when in the position of Figure 5. Yigures 4 and 5 show the filter element being moulded as a unit with an outer rigid cylinclrical support sheet 2 but it will be appreciated tha-t for a simple borosilica-te mircofibre filter tube this can be omitted. Alternatively of course an inner support sheet can be moulded into the inside surface of the tube eithe~r insteacl o~ or as an adclition -to the outer sheet 2. The bottom of the moulclirlcJ space is eovere(l by a fine mesh sereen 46. A reciproca~:le slee~ve 47 is moullted to slide outside the eylinder 40 and perEoratecl c~ylindcI^ 45.
With the core ~3 and sleeve 47 in the positions shown in F'igure 5 the water drains away throuc~h the screen 46 and lower end oE the screen 44 into a tank 48 (FicJure 4) while the mass of fibres becJin to build up in the moulding space 42.
After all the fibres have accumulated in the moulding spaee the air pressure is maintained so as to remove residual water from the fibres and so dry the ~ormed Lilter. The valve 34 is then elosed. Durinc3 the moulding process a pump 49 continuously pumps the water from the tank 48 to a holding tank 50 ~rom which the water is recycled.
Finally the core 43 is removed to enable the formed filter element to be removed from the rig 38. The process can then be started once more. As an example i-t has been found that the time taken to moulcl a tubular filter element 250 mm 1~l3~
lon~, 65 null outside di~ t~l with a wall thickness oC 10 mm takes ayproximcltely one~ minute. 'I'he formed fil-ter element is removed to a hot air dryer for final drying and is then resin impregnated and oven cured to harden the resin.
Particularly in the case of long Eilter elements, e.g., over 50 mm, it has been found desirable progressively to raise the sleeve 47, substantially at the same rate that the height of the fibre mass increases, in order -to maintain an uninterrupted flow of the dispersion -to the poin-t where the mass of fibres is building up. The movemen-t oE the sleevc 47 then terminates as shown in Fiyure 6.
The core 43 is formed wi-th an upper por-tion 51 of reduced diameter. This is to enable an additional internal layer of fibrous filter material to be added to the ~ilter mate~idl formed in the mouldlng space 42, by Eeecting a further dispersion through the cylinder 39 into a mouldinq space S2 (FicJure 6) between the moulding space 42 and the core portlon Sl when the core 43 is lowered. The water from the new layer escapes through the fibres in -the space 42. The new layer may be of higher or lower efficiency than the tubular element formed in the space 42. This arrangement enables a filter element of c~raded de~nsity to be produccd ~s part or un integr.ll process.
Investigations have shown that the fibres in a finished filter element produced by the method described above with reference to Figures 4 to 6 are predominantly layered in planes perpendicular to the direction in which the dispersion flows into the moulding space. Lt has further been found that the the same packing pattern arises -throughout -the range of forming pressures that can be used effectively in practice. Advantages ~13~
of this packin-J pattern appear from -the results -tabulated above.
For some ap~lications of the invention, where cellulose fibres or combinations of cellulose fibres with borosilica-te fibres are used, A melamine or phenolic resin binder may advantageously be used Eor the bonding material. Cellulose when bonded with melamine resin is approved as being suitable for potable water and sanitary conditions. Phenolic resin is preferred for higher temperature work. The combination of cellulose fibres wi-tll other fibres provides economies both in regard to cost and production time, good flow characteristics and chemical resistance, and controlled selection of pore size by blending difEererlt fibre materials with cellulose. It has been found that by blending 20'~ borosilicate microibre wi.th 80 cellulose by weight the production tinle Eor the E:ilter can be reduced by 30~. Ln this case whe~n the fluicl is water the pressure drop (~p) across the Eilter was 0.15 bar with a flow rate of 16 litres per minute. With a weiqht to weight ratio of 50%, Ap was found to be 0.15 bar with a Elow rate oE 22 litres per minute. The glclss fibre size (diameter) was 3.8 to 5.1 microns and the cellulose a bleached sof-twood kraft. The bonding material, e.g. melamine resin, phenolic resin or other synthetic resin, can be a~plie~ in one of three difEerent ways.
Firstly, by forming a mass of fibres in a moulding rig such as shown in Figures 5 and 6, then impregnating the mass after drying by dipping in a resin solution and curing the resin in an oven. Secondly, by preparing the cellulose fibre and separately mixing the borosilicate fibre with a resin solution, bringing`the two mixtures together, forming the mass under , pressure in the mouldincJ ri~J ancl curincl the mass~ Thirclly, all the fibres and resin solution can be mixed in a single tank, passed to the mouldiny rig, the mass beiny subsequently eured.
~ eylindrieal filter element for liquid filtration haviny a eombination of fibres as described above may have an outside diameter of 64 mm, a wall thickness of 18 mm and various lengths, sueh as 250 mm. No support sheet is necessary for many uses but ean be added when necessary. lrhe Eilter is preferably arranyed for flow from outside to inside the cylinder to give grea-ter surfaee area ~or eollection ol dirt. 'l'~-~is ared ean be inereased by forming lonyitudinal or eircumferential yrooves in -the outside surfaee of the eylinder.
Instead oE usincJ a coMpressecl clas to apply ~ressure to the slurry in the moulclin~ ricl, a hydr.l-llie pump lll,ly L)e used, this pump being arran~Jecl to withclraw the slurry From tl~e ~lenclillq tank and force it into tlle moulclirlcl riLcl.
Tubular or cylindrical ~iL-ter e:lements made in aeeordanee with the inven-tion may be mounted in a variety of Eil-ters, in partieular those shown in l;`icJures 5, 6, 7 and 13 in the aforesaid speeifieation. ~s in tha-t speeiEieation, also the ends of the eylindrieal filter elemen-ts may be fitted into end eaps in a variety oE ways. ~ueh ways are shown in FicJures 8 to 17 of the present speeifieation.
Figures 8 to 13 show eases where the end of a eylindrieal, unsupported filter elemen-t 10 is fitted into an end eap 11 using a gasket seal 21 (Figure 8), a double taper seal 13 (Figure 9), an outside taper seal 14 (Fiyure 10~ an inside taper seal 15 (Figures 11 and 12) and a double taper flange seal 16 (Figure 13).
For a eylindrieal filter element with an inside support sheet 17 an outside taper seal 14 (l;`i~lure l4) may be used. F`or an outside suppor-t sheet 18 (~igure :L5) an inside taper seal 15, or a single taper flange seal 19 (Figure 16) may be used. In the case of a filter element having insid~ and outside support sheets 20, 21 (l~ligure 17) a (Jasket seal 12 (Figure 17) can be used. In all forms of the Filter element constructed according to the invention, an open pore ~ilter layer of sleeve, as shown in Figures 12 and 17, can be used if required to act as a pre-filter or as an after-filter to drain coalesced liquids. This layer or sleeve C.lll be all open ~ore plastic or metal foanl or a layer or layers of non-woven material such as felt. As a further alternative the filter element can be dip sealed into end caps as shown in FicJure 6 ol- the aforesa:id specification.
~'igure 18 shows an arran{Jealllent similar to Figllre 15 with an internal supportincJ spring 2~ in place of any inside support sheet.
Fil-ters made in accordance with the invention can be usecl Eor either yas or liquid ~Eiltra-tion. The efEiciency can be as hiyh as 99.99998% when testecl as ss 4400 or can be produced with a micron rating in various stages between 1 and 50 microns.
A further method of increasing the efficiency of the moulded filter material is by compressincJ the material whi:Le being resin impre~Jnated and cured.
A further material that can be used for the support sheet is a rigid metal foam. The fibres can be moulded directly onto such Eoam so that they pene-trate only so far into the thickness of the foam sheet, but the fine mesh screen 44 can be eliminated in this process because the foam sheet i-tself provides the filter surface through which the water is drained. The same -~I~L3~
method can be used in the case of the aforesaid sintered SuppQrt sheet. rt'he same me-thod can also be used with foam consisting of plastics material, which may be flexible or semi-rigid. However, very advantageously a rigid polyvinyl chloride coated plastic foam can be used.
Among the many possible uses of the EiLter according to the invention are the removal oE oil from compressed air, pre-filtration, aeration, vacuum filtration, liquid filtration, air sterilisation and for pneumatic silencing.
,, ~ 20 ~
. :
~ :
~ -15-; ~ ;J
' : ' , .
'
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for forming a compacted mass of fibres comprising a cylindrical filter screen, a central core centrally mounted in and spaced from the filter screen, an annular filter screen extending between the core and the cylindrical filter screen so as to provide a base of a container providing a moulding space otherwise defined by the core and the cylindrical filter screen, a duet for delivering a dispersion of fibres in liquid peripherally around the top of the moulding space for accumulating a tubular mass of the fibres in the moulding space while the liquid is drained through the screens, means for receiving the drained liquid and removing it from the vicinity of the screens, means for applying pressure to the dispersion throughout its introduction into the moulding space, and a reciprocable imperforate screen in sliding contact with the cylindrical filter screen for progressively uncovering the cylindrical filter screen as a mass of fibres builds upwards along the moulding space from the annular filter screen, the imperforate screen thereby increasing the area of the filter screen through which the liquid can drain as the mass of fibres accumulates.
2. Apparatus according to Claim 1, in which the core is formed along its length with portions of different diameters, each portion having a length as long as the cylindrical filter screen, the core being longitudinally adjustable in position relative to the cylindrical filter screen to vary the volume of the moulding space by bringing different portions of the core into register with the cylindrical filter screen.
3. Apparatus according to Claim 2, including vertical concentric ducts for delivering dispersion of different constitutions to the top of the moulding space and arranged for one mass of fibres to be built up between the cylindrical filter sleeve and a core portion of larger diameter and a lining of another mass of fibres to line said one mass by being built up between that mass and a core portion of smaller diameter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000382434A CA1139144A (en) | 1978-01-23 | 1981-07-23 | Apparatus for forming tubular filter elements |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2559/78A GB1603519A (en) | 1978-01-23 | 1978-01-23 | Filter elements for gas or liquid and methods of making such filters |
| GB2559/78 | 1978-01-23 | ||
| CA000319636A CA1121285A (en) | 1978-01-23 | 1979-01-15 | Filter elements for gas or liquid and methods of making such filters |
| CA000382434A CA1139144A (en) | 1978-01-23 | 1981-07-23 | Apparatus for forming tubular filter elements |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139144A true CA1139144A (en) | 1983-01-11 |
Family
ID=27166047
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000382434A Expired CA1139144A (en) | 1978-01-23 | 1981-07-23 | Apparatus for forming tubular filter elements |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1139144A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115646092A (en) * | 2022-11-23 | 2023-01-31 | 汇舸(南通)环保设备有限公司 | Gas self-guiding desulfurization equipment for ship tail gas purification |
-
1981
- 1981-07-23 CA CA000382434A patent/CA1139144A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115646092A (en) * | 2022-11-23 | 2023-01-31 | 汇舸(南通)环保设备有限公司 | Gas self-guiding desulfurization equipment for ship tail gas purification |
| CN115646092B (en) * | 2022-11-23 | 2023-07-21 | 汇舸(南通)环保设备有限公司 | Desulfurizing equipment for purifying tail gas of gas self-guiding ship |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4360433A (en) | Filter elements for gas or liquid | |
| US5129923A (en) | Oil coalescing filter and filtering process | |
| DE2713033C2 (en) | Method of manufacturing a filter element | |
| US5232595A (en) | Deep bed filter, method of manufacture of a filter layer and a filter module | |
| US4052316A (en) | Composite coalescing filter tube | |
| US4102785A (en) | Inside-to-outside flow filter tube and method of using same | |
| EP0106908B1 (en) | Multilayer filter material, process for making it and its use | |
| CA1063946A (en) | Continuous production of tubular modular filter elements using nonwoven webs from thermoplastic fibers and products | |
| JP6265544B2 (en) | Filter media | |
| US3261473A (en) | Glass fiber cartridge filters for drycleaning solvent filtration | |
| DE69316647T2 (en) | FILTER ELEMENT AND METHOD FOR THE PRODUCTION THEREOF | |
| GB1558823A (en) | Composite coalescing filter tube and method of manufacturethereof | |
| EP0648524A1 (en) | Filter cartridge construction | |
| JP2008518770A (en) | Improved high strength, high capacity filter media and structure | |
| JP2010284649A (en) | Nanofiber filter medium | |
| AU2003210565A1 (en) | Nanofiber filter media | |
| CA1139144A (en) | Apparatus for forming tubular filter elements | |
| EP0695573A1 (en) | Cartridge filters | |
| CA1284772C (en) | Filter media | |
| DE60026420T2 (en) | Heat-resistant material and filter made from it | |
| WO2002020126A2 (en) | Production of filters containing reactive material | |
| KR102621800B1 (en) | Nanofiber filter and preparation method thereof | |
| CA1103175A (en) | Inside-to-outside flow filter tube and method of manufacturing same | |
| JP2670116B2 (en) | Method for producing molded adsorbent and suction molding die used therefor | |
| DE4036551A1 (en) | Vehicle engine spin-on-filter - comprises cellulose and/or glass fibre, wool, propylene], etc., bound with plastic to form pores converging in flow direction |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20000111 |