GB2488624A

GB2488624A - Filter element

Info

Publication number: GB2488624A
Application number: GB1121285.9A
Authority: GB
Inventors: Sergei Botov
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-12-09
Filing date: 2011-12-09
Publication date: 2012-09-05
Anticipated expiration: 2031-12-09
Also published as: GB201121285D0; GB2488624B

Abstract

A polymer filter element (101) is provided for the removal of contaminants from a fluid, the filter element comprises a polymeric blend comprising from 2% to 30% by wt. of a poly (chloroalkylene). Preferably the polymeric blend further comprises a further thermoplastic of a given weight, such as a polyester, polyamide and polyalkylene. A further invention discloses a polymer filter for the removal of contaminants from a fluid comprising: (i) a filter inlet (150, 151) for the ingress of unfiltered fluid into a chamber (105); (ii) a filter outlet (200) for the egress of filtered fluid from a chamber (106) for the receipt of filtered fluid; (iii) a polymer filter element (101) located in the fluid flow path between the chamber for the receipt of unfiltered fluid and the chamber for the receipt of filtered fluid. The polymer filter element comprising: (a) a first portion (107) having a first permeability to contaminants; (b) a second portion (108) having a second permeability greater than the first permeability, and (c) a valve (110) associated with the second portion and being operable according to a threshold pressure. Advantageously the polymer filter element may be used in fluid filtration to filter fuel and oil in automotive vehicles.

Description

Filter elements and filter The present invention relates to a polymer filter for the filtration of fluids (especially, but not exclusively liquids, such as fuel and oil) and polymer filter elements for use in such filters.

Conventional filter elements for use in fluid filtration, in particular, filtration of fuel and oil in automotive vehicles are made from paper. Once used, such filters cannot be readily cleaned for re-use, Por can they be readily recycled so the spent filter elements are typically disposed of as waste, for example, on landfill sites.

It has therefore been proposed to make filter elements from plastics materials, such as those described in U55256284 and USS1B2O1S. US5695638 discloses the use of a filter element of polyacetal and US622l242 discloses the use of a polyester filter element. 0S2002/0033365 and tJS55474Bl disclose filter elements made from sintered high density polyethylene.

It is an object of the present invention to provide an improved and/or alternative filter element.

In accordance with a first aspect of the present invention, there is provided a polymer filter element for the removal of contaminants from a fluid, the polymer filter element preferably comprising a polymeric blend comprising from 2% to 30% by wt. of a poly(chloroalkylene) The polymer filter elements of the first aspect of the present invention have been found to be effective filter for oil, automotive fuel and hydraulic fluid.

The poly(chloroalkylene) may comprise a poly(chloroêthylene) . The chloroethylene groups may comprise 1, 2, 3 or 4 chlorine atoms, and each chloroethylene group may be the same or different.

The poly(chloroalkylene) may, for example, be provided by polyvinyl chloride, chlorinated polyvinyl chloride, plasticized polyvinyl chloride, unplasticized polyvinyl chloride or related polymer, or a copolymer in which all or substantially all, that is, more than 90% by weight of the copolymer is derivable from chlorohydrocarbon monomer units.

It is preferred that at least 50% by weight (and preferably at least 80% by weight and more preferably at least 90% by weight) of the poly(chloroalkylene) is provided by group X having the general structure (i) below wherein A, B, E and 0 are H or Cl provided that at least one of A, B, E and D is Cl.

Structure(i) is A E Each repeat group X in the polymeric blend may be mutually the same. For example, the repeat group X may always be a -CH2--CHC1--repeat group. Alternatively, the polymeric blend may comprise repeat groups X of mutually different structure. For example, the polymeric blend may comprise two or more of the repeat groups -CH2-CHC1-, -CH2-CC12-, -CHC1-CHC1-, -CHO1-CC12-and -CC12-CC12-.

The repeat group X content pf the polymeric blend may substantially be provided, for example, by polyvinyl chloride (PVC) or chlorinated polyvinyl chloride (CPVC). It has been found that polyvinyl chloride and its related derivatives produce efficient filters. This is of importance in that PVC and derivatives are common waste products that may be recycled. The filter element of the present invention is not limited to one using recycled materials; virgin materials may be used, such as Evipol-SH, -EP and -EEl polymers (Ineos Vinyls, Runcorn, UK) Those skilled in the art will realize that the poly(chloroalkylene) may comprise impurities or defects, such as the presence of unchiorinated branch groups (such as methyl, ethyl and butyl), carbonyl groups and unsaturated carbon-carbon bonds. For example, a polyvinyl chloride, chlorinated polyvinyl chloride, plasticized polyvinyl chloride, unplasticized polyvinyl chloride or related polymer may comprise up to 5% (and preferably up to 1%) by weight of groups having a structure other than a chloroethylene structure (chloroethylene meaning -CH2-CHC1-, -CH2--CC12--, -CHC1-CHC1--, -CHC1-CC12-or -CC12-CC12-).

It is preferred that the polymeric blend comprises from 2% to 20% by weight of the poly(chloroalkylene), preferably from 2% to 15%, more preferably from 3% to 12%, further more preferably from 4% to 12% and most preferably from 8% to 12% by weight of the poly(chloroalkylene) It is preferred that the polymeric blend comprises from 60 to 98% (preferably from 70 to 95%, more preferably from 80 to 90% and most preferably from 80 to 85%) by weight of a further thermoplastic.

It is preferred that the further thermoplastic comprises one or more of poly acrylonitrile butadiene styrene, acrylic, celluloid, cellulose acetate, a polyester (such as poly ethylene vinyl acetate, a polyacrylate and a terephthalate [e.g. polybutylene terephthalate, polyethylene terephthalate and polycyclohexylene dimethylene terephthalate], polyhydroxyalkanoates), poly ethylene vinyl alcohol, fluoroplastics (for example, polyfluorotetraethylene (PTFE)), polyacetal, polyacrylonitrile, polyamide (such as nylon), polyamide-imide, polyaryletherketone, polybutadiene, polybutylene, , polycarbonate, polyketone, polyethylene, polyetheretherketone, polyetherimide, polyethersul fone, polyethylenechlorinates, polyimide, polylactic acid, polymethylpentene, polyphenylene oxide, polyphenylene sulfide, polyphthalamide, polypropylene, polystyrene and polysulphone.

It is preferred that the further thermoplastic comprises one or more of a polyamide, a polyester (such as a terephthalate) and a polyalkylene. The polyamide may be a nylon, such as nylon 6,6. The polyalkylene may be polypropylene or polyethylene, for example. The polyalkylene terephthalate may be polyethylene terephthalate. The polyalkylene may be a high density or a low density polyalkylene. Examples of high density polyethylenes include HMA 014, HMA 025 and HMA 035 (Exxon Mobil Corporation).

Examples of low density polyethylenes include LL6101, LLG201 and LDIOOAC (Exxon Mobil Corporation).

The filter element may be a substantially porous structure.

It is preferred that the mean pore size is between 10 to 20 microns. It is preferred that at least some of the pores are sufficiently small so as to inhibit passage therethrough of particles having a largest dimension of 5xrn. It is preferred that the filter comprises pores having a pore size of about 3im.

It should be understood that the filter element of the present invention may be an inherently physically stable, shaped body.

The filter elements may also comprise from 2 to 10% by weight of a compatilising agent. The compatibilising agent enables blending of the poly(chloroalkylene) with the further thermoplastic (if present) It is preferred that the filter element of the first aspect of the present invention is made from granules of a poly(chloroalkylene), such as a poly(chloroethylene) Examples of a poly(chloroalkylene) include polyvinyl chloride, chlorinated polyvinyl chloride, plasticized polyvinyl chloride, unplasticized polyvinyl chloride or related polymer. It is preferred that said granules are heated. It is also preferred that the granules are subject to a raised pressure to aid formation of the filter element.

The granules may be subject to raised pressure prior to, simultaneous with or subsequent to heating, It is further preferred that the filter element is made using a mould.

It is especially preferred that the filter element is made by: (i) providing a mixture comprising granules of a poly(chloroalkylene), such as a poly(chloroethylene); (ii) introducing said mixture into a mould; (iii) subjecting the mixture to a raised pressure to form a filter element precursor body; and (iv) heating the filter element precursor body.

It is preferred that the mixture provided in step (i) comprises a further thermoplastic such as those listed above. The mixture may also comprise a liquid. The liquid may be present up to 5% by weight of the weight of the mixture, more preferably up to 2%, and further more preferably from 0.02 to 1%. The liquid has been found to ease removal of the filter element from the mould.

The mixture may also comprise from 2 to 10% by weight of a compatilising agent. The compatibilising agent enables blending of the poly(chloroallcylene) with the further thermoplastic (if present) In accordance with a second aspect of the present invention there is provided a filter comprising a filter element in accordance with the first aspect of the present invention and a filter housing for accommodating the filter element for use.

In accordance with a third aspect of the present invention, there is provided there is provided a method of making a filter element, said method comprising: (i)providing a mixture comprising a plastics material; (ii) introducing said mixture into a mould; (iii) subjecting the mixture to a raised pressure to form a filter element precursor body; and (i) heating the filter element precursor body.

The method of the third aspect of the present invention is a preferred method of making the filter element of the first aspect of the present invention.

The mixture may comprise a liquid. The liquid may be present up to 5% by weight of the weight of the mixture, more preferably up to 2%, and further more preferably from 0.02 to 1%. The liquid has been found to ease removal of the filter element from the mould.

It is anticipated that step (iv) may remove some or all of the liquid from the filter element precursor body. For example, some of the fluid may be retained.

It is preferred that the mixture comprises from 2% to 30% by wt. of a poly(chloroalkylene), such as a poly(chloroethylene). The chloroethylene groups may comprise 1, 2, 3 or 4 chlorine atoms, and each chloroethylene group may be the same or different.

The poly(chloroalkylene) may, for example, be polyvinyl chloride, chlorinated polyvinyl chloride, plasticized polyvinyl chloride, unplasticized polyvinyl chloride or related polymer, or a copolymer in which all or substantially all, that is, more than 90% by weight of the copolymer is derivable from chlorohydrocarbon monomer units.

It is preferred that at least 50% by weight (preferably at least 80% by weight and more preferably at least 90% by weight) of the poly(chloroalkylene) is provided by group X having the general structure (i) as shown above in relation to the first aspect of the present invention, wherein A, B, E and D are H or Cl provided that at least one of A, B, E and D is Cl.

Each repeat group X may be mutually the same. For example, the repeat group X may always be a -CH2-CHC1-repeat group.

Alternatively, the mixture may comprise repeat groups X of mutually different structure. For example, the mixture may comprise two or more of the repeat groups -CH2-CHC1-, -CH2--Cd2-, -CHC1-CHC1-, -CFIC1-CC12-and -CC12-CCI2--.

The repeat group X may substantially be provided, for example, by polyvinyl chloride (PVC) or chlorinated polyvinyl chloride (CPVC) . It has been found that polyvinyl chloride and its related derivatives produce efficient filters. This is of importance in that PVC and derivatives are common waste products that may be recycled. The filter element of the first aspect of the present invention and the method of the third aspect of the present invention are not limited to the use of recycled materials; virgin materials may be used, such as Evipol-SH, -EP and -EH polymers (Ineos Vinyls, Runcorn, UK) It is preferred that the mixture comprises from 2% to 20% by weight of poly(chloroalkylene), preferably from 2% to 15%, more preferably from 3% to 12%, further more preferably from 4% to 12% and most preferably from 8% to 12% by weight of polychloroalkylene.

It is therefore preferred that the mixture comprises from 2% to 20% by weight of group X, preferably from 2% to 15%, more preferably from 3% to 12%, further more preferably from 4% to 12% and most preferably from 8% to 12% by weight of group x.

It is preferred that the mixture comprises from 60 to 98% (preferably from 70 to 95%, more preferably from 80 to 90% and most preferably from 80 to 85%) by weight of a further thermoplastic.

It is preferred that the further thermoplastic comprises one or more of poly acrylonitrile butadiene styrene, acrylic, celluloid, cellulose acetate, a polyester (such as poly ethylene vinyl acetate, a polyester (e.g. polybutylene terephthalate, polyethylene terephthalate and polycyclohexylene dimethylene terephthalate] and a polyacrylate), poly ethylene vinyl alcohol, fluoroplastics (for example, polyfluorotetraethylene (PTFE)), polyacetal polyacrylonitrile, polyamide (such as nylon), polyamide-imide, polyaryletherketone, polybutadiene, polybutylene, polycarbonate, polyhydroxyalkanoates, polyketone, polyester, polyethylene, polyetheretherketone, polyetherimide, polyethersulfone, polyethylenechlorinates, polyimide, polylactic acid, polymethylpentene, polyphenylene oxide, I0 polyphenylene sulfide, polyphthalamide, polypropylene, polystyrene and polysuiphone.

Examples of low density polyethylenes include LL61O1, LL62O1 and LD100AC (Exxon Mobil Corporation).

It is preferred that the mixture further comprises from 2 to 10% by weight of a compatilising agent. The compatibilising agent enables blending of the poly(chloroalkylene) with the further thermoplastic (if present) The plastics material (such as the polyvinyl chloride, chlorinated polyvinyl chloride, plasticized polyvinyl chloride, unplasticized polyvinyl chloride or related polymer or further thermoplastic) may be supplied in step (i) in a granular form. The granules may have a mean largest dimension of from 0.1mm to 1mm and preferably from 0.2 to 0.6mm. It is anticipated that in many circumstances the mixture will comprise granules of different sizes. For example, several granular sizes of PVC may be used to make-up the PVC component of the mixture (if PVC is present) If a poly(chloroalkylene) such as polyvinyl chloride, chlorinated polyvinyl chloride, plasticized polyvinyl chloride, unplasticized polyvinyl chloride or related polymer is used in the present method, it is preferred that such material is provided in a granular form in step (i) . It is preferred that the mean largest dimension of said granules of the poly(chloroalkylene) is from 0.2 to 0.8mm, and preferably from 0.2 to 0.6mm.

If a further thermoplastic is provided, then it is preferred that it is provided in step (i) in granular form. The mean largest dimension of the granules of the further thermoplastic may be from 0.2 to 1mm and preferably from 0.3 to 0.8mm.

Step (iv) may comprise heating the filter element precursor body to a maximum temperature of 120°C, more preferably to a maximum temperature of from 80°C to 110°C. It is preferred that step (iv) is performed at ambient pressure i.e. not under reduced or increased pressure.

In step (iii), the material may be under compression for from 0.2 to 1.0 seconds, more preferably from 0.2 to 0.6 seconds and most preferably from 0.3 to 0.5 seconds. It has been found that the application of pressure over a shàrt timescale is beneficial to the formation of filter elements with suitable pore sizes that enable the filter elements to be used as oil and fuel filters.

The maximum compressive force applied in step (iii) is preferably from 10kW to 1000kW, more preferably from lOkN to lOOkN and most preferably from lOkN to 150kW. In certain circumstances, in particular for the production of larger filter elements, a maximum compressive force of from 3OkN to SOOkN (and more preferably from 30kW to l5OkN) may be preferred.

The mould determines the shape of the filter element precursor body. One or more of the surfaces of the mould which, in use, comes into contact with the mixture comprising a plastics material may have a low surface energy. A low surface energy may be provided by a substrate that has been coated with a material that provides a low surface energy. Alternatively, a substrate cf a material that provides a low surface energy may be used. Materials that provide a low surface energy include polytetrafluoroethylene (PTFE, such as Teflon®) . Surfaces with a low surface energy may be formed by coating a substrate with a silane or polytetrafluoroethylene (PTFE, such as Teflon®) -The mould may be shaped so as to form a cylindrical filter element precursor body.

The mould may also be provided with one or more end-fitting casting elements to prevent egress of mixture from the mould once the filter element precursor body has been formed in step (iii) -This is important if the mould containing the filter element precursor body is physically removed from an apparatus so that the mould-precursor element ensemble can be put into an oven or the like to perform step (iv).

The method may further comprise providing a tamper for compressing the mixture in step (iii) . The tamper may comprise a tamping head for contacting the mixture and a means for urging the tamping head into compressive contact with the mixture. The means for urging the taming head into compressive contact with the mixture may comprise a piston.

It is preferred that the piston is electrically driven. This facilitates the tamping head to be brought into contact with, and removed from, the material quickly. Such rapid movement has been found to be beneficial to the formation of filter elements. It has been discovered that certain other pistons (for example, a hydraulic driven piston) do not facilitate the rapid movement of the tamping head. The tamping head may have an annular shape. This is of particular benefit in the manufacture of filter elements for oil or fuel filters.

The method may further comprise providing a return mechanism for urging the tamping head away from the mixture in the mould. Such a return mechanism may comprise a bias means, such as a spring. A helical spring may conveniently be used, for example. When the tarnping head is urged into compressive contact with the material the return mechanism acts so as to try to urge the tamping head away from the mixture in the mould. Once the force urging the tamping head into contact with the mixture in the mould is removed, the return mechanism urges the tamping head away from the mixture.

The method may further comprise providing a ccnveyor for moving said mixture comprising a plastics material towards the mould. The conveyor may comprise a screw conveyor. A screw conveyor has been found to provide an effective mechanism for moving mixtures having the consistency of paste towards the mould.

The method may further comprise providing a receiver for guiding the mixture into the mould. The receiver may be placed adjacent the mould. The receiver may flare outwardly, and, for example, may have a funnel like portion. The receiver may receive the mixture from the conveyor, if present.

The method may comprise providing a plurality of moulds. The method may further comprise providing a transporter for moving the moulds into a position in which material may be delivered into the moulds.

The method of the third aspect of the present invention may be used to make the filter element in accordance with the first aspect of the present invention.

Conventional filter elements are provided with a material having essentially the same permeability to particles. Such filter elements are typically used in filters having an inlet for the introduction of unfiltered fluid and an outlet for the egress of filtered fluid. During normal operation, fluid passes through the filter element, removing particles from the fluid. Under certain circumstances, fluid does not readily pass through the filter element and pressure builds-up on the unfiltered side of the device. This pressure build-up may occur, for example, because the filter element is blocked, the vehicles is operating at high speed or the fluid is more viscous than during normal operation (e.g. at start-up of a vehicle) . Such pressure build-up in a filter can be dangerous and so filters are often provided with valves which are operable at a threshold pressure to allow unfiltered fluid to flow from the fluid inlet to the fluid outlet without passing through the filter element. This means that unfiltered fluid is transmitted out of the filter, and this may be damaging to the machinery to which the unfiltered fluid is transmitted.

The present invention provides a filter element that mitigates the problems of conventional filter elements mentioned above.

In accordance with a first aspect of the present invention there is provided a filter element for the removal of contaminants from a fluid, the filter element comprising: (1) a filter inlet for the ingress of unfiltered fluid into a chamber for the receipt of unfiltered fluid; (ii) a filter outlet for the egress of filtered fluid from a chamber for the receipt of filtered fluid; (iii) a polymer filter element located in the fluid flow path between the chamber for the receipt of unfiltered fluid and the chamber for the receipt of filtered fluid, the polymer filter element comprising: (a) a first portion of the polymer filter element having a first permeability 3pm -3Opm to contaminants present in the unfiltered fluid, (b) a second portion of the polymer filter element having a second permeability 3Oprn -4Opm to contaminants present in the unfiltered fluid, the second permeability being greater than the first permeability, and (c) a valve associated with the second portion, the valve being operable so that, below a threshold pressure level in the chamber for the receipt of unfiltered fluid, the valve inhibits transmission of fluid from the chamber for the receipt of unfiltered fluid to the outlet via the second portion of the polymer filter element, and, above a threshold pressure in the chamber for the receipt of unfiltered fluid, the valve permits transmission of fluid from the chamber for the receipt of unfiltered fluid to the outlet via the second portion of the polymer filter element.

The valve may be operable from the first to the second valve state by the application of a force greater than a threshold force.

In the filter element of the first aspect of the present invention, the filter element comprises two portions of differing permeabilities. The valve is associated with the second portion of the filter element, the second portion of the filter element having a greater permeability than the first portion. During normal operation of the filter element, fluid passes through the first portion of the filter element, thereby filtering the fluid. During normal operation, the valve is closed and so fluid cannot pass through the valve and the second portion of the filter element.

Under certain circumstances, the first portion of the filter element may not operate effectively. For example, if the fluid is cold and viscous, it may not adequately pass through the first portion of the filter element. Likewise, if the first portion of the filter element becomes blocked, fluid may not adequately pass through the first portion of the filter element. This may cause the pressure in a filter, of which the filter element forms a part, to increase. When a certain pressure is reached, the force acting on the valve is greater than a threshold force, and the previously-closed valve is opened to permit fluid flow through the valve and through the second portion of the filter element. This reduces the pressure in the filter, therefore decreasing the chance of the filter exploding. Furthermore, the fluid is also filtered before it reaches the cutlet of a filter of which the filter element forms a part.

In accordance with a second aspect of the present invention, there is provided a filter for the removal of contaminants from a fluid, the polymer filter comprising: (i) a filter inlet for the ingress of unfiltered fluid into a chamber for the receipt of unfiltered fluid; (ii) a filter outlet for the egress of filtered fluid from a chamber for the receipt of filtered fluid; (iii) a polymer filter element located in the fluid flow path between the chamber for the receipt of unfiltered fluid and the chamber for the receipt of filtered fluid, the polymer filter element comprising: (a) a first portion of the polymer filter element having a first permeability 3pm -3Opm to contaminants present in the unfiltered fluid, (b) a second portion of the polymer filter element having a second permeability 3Opm -4Opm to contaminants present in the unfiltered fluid, is the second permeability being greater than the first permeability, and (c) a valve associated with the second portion, the valve being operable so that, below a threshold pressure level in the chamber for the receipt of unfiltered fluid, the valve inhibits transmission of fluid from the chamber for the receipt of unfiltered fluid to the outlet via the second portion of the polymer filter element, and, above a threshold pressure in the chamber for the receipt of unfiltered fluid, the valve permits transmission of fluid from the chamber for the receipt of unfiltered fluid to the outlet via the second portion of the polymer filter element.

The filter element used in the filter of the second aspect of the present invention may be the filter element of the first aspect of the present invention.

The valve may conveniently be located on the side of the second portion facing or forming the chamber for the receipt of filtered liquid. Alternatively, the valve may conveniently be located on the side of the second portion facing or forming the chamber for the receipt of unfiltered liquid.

The filter element may be arranged so that, when the valve is open, fluid may pass from the chamber for the receipt of unfiltered fluid, through the second portion of the filter element, before passing through the valve to the chamber for the receipt of filtered fluid.

Alternatively, the filter element may be arranged so that, when valve is open, fluid may pass from the chamber for the receipt of unfiltered fluid, through the valve, before passing through the second portion of the filter element and into the chamber for the receipt of filtered fluid.

For the avoidance of confusion, it is hereby stated that the following statements apply to both the filter element of the first aspect of the present invention and the filter of the second aspect of the present invention.

It is preferred that the first portion of the filter element has a first permeability to particles present in an unfiltered fluid and the second portion of the filter element has a second permeability to particles present in an unfiltered fluid, the second permeability being greater than the first permeability. This is often conveniently achieved by the first and second portions of the filter element having a porous structure, the pores of the second portion of the filter element being larger than the pores of the first portion of the filter element.

It is preferred that the filter element is a filter for the filtration of liquids, such as a fuel, oil or hydraulics fluid filter.

The valve may comprise a slit valve. Advantageously, the valve may comprise a valve member which is biased into sealing engagement with a valve seat. The valve member is movable away from the valve seat by a pressure in the chamber for the receipt of unfiltered fluid that is above the threshold level (corresponding to a force above a threshold value in relation to the filter element of the first aspect of the present invention) so that the sealing engagement is broken, permitting fluid flow from the chamber for the receipt of unfiltered fluid to the outlet via the second portion of the filter element.

The filter element may comprise a substantially tubular structure, such as a hollow cylindrical structure. The first portion may be provided by the substantially tubular structure. The second portion may be provided by a covering or capping structure. The covering or capping structure may be in the form of a disk.

It is preferred that the smallest particles that may be removed from the fluid by the first portion of the filter element are smaller than the smallest particles that may be removed from the fluid by the second portion of the filter element. For example, the smallest particles that may be removed by the first portion of the filter element may have a largest dimension of about Spin. In this case, it may be desirable for the smallest particles that may be removed by the second portion of the filter element to have a largest dimension of about l5.tm.

Reference to the smallest particles that may be removed by a portion of the filter element refers to the filter element in its initial, clean operating state. A dirty or partially blocked filter will obviously inhibit passage therethrough of particles which it may have permitted to pass when in a clean state.

The filter element may be provided with a cavity between the second portion of the filter element and the valve. Such a cavity may be formed by a cover placed in sealing engagement with the second portion of the filter element.

The filter element may be inherently physically stable.

The first portion and the second portion of the filter element may be provided by a filter element body. The filter element body may be made from plastics material. The filter element body may, for example, be made from a polyethylene as described in US5547481 or in US2002/0033365.

The filter element may be a filter element in accordance with the first aspect of the present invention. The filter element may be made in accordance with the method of the third aspect of the present invention.

The present invention is now described by way of example only with reference to the following figures of which: Figure 1 is a schematic side view of an apparatus used to make an embodiment of a polymer filter element; Figure 2A is a cut-away view of a mould and the tamping portion of the apparatus of Figure 1; Figure 2B is a side-on view of a part of the apparatus of Figure 1; and Figure 3 is a schematic cross-section through an embodiment of a polymer filter comprising a polymer filter element.

Figure 1 shows a schematic representation of an apparatus used to make an embodiment of a polymer filter element. The apparatus is denoted generally by reference numeral 1001.

The apparatus is now briefly described with reference to Figure 1. The apparatus comprises a chute 1002 into which a mixture comprising a plastics material may be fed. The chute 1002 guides the mixture into a screw conveyor 1003. The electrically powered screw conveyor moves the mixture into a mould lOOSa via a receiver 1007 which acts as a funnel to direct the mixture to the mould. Mould 1008a is one of four moulds mounted on a turntable platter 1010 driven by turntable motor 1011, but only two of the moulds (1008a, lOOSb) are shown for the purposes of clarity. The turntable platter 1010 is rotated by the turntable motor 1011 to move respective moulds into (and out of) the mixture-receiving position underneath the end of the screw conveyor 1003.

Mould lOOSa is shown in Figure 1 as being in the mixture-receiving position. An indexing pin 1012 engages with a locking hole (reference numeral 1029 in Figure 2a) in the turntable platter 1010 to prevent unwanted movement of the turntable platter 1010 once a mould is located in the mixture-receiving position. An indexing pin driver 1013 causes the indexing pin to engage with the locking hole.

When in the mixture-receiving position, the mould 1008a is aligned with a tamper 1004 that is used to compress the mixture in the mould 1008a to form a filter element precursor body. Once the mixture in a mould has been compressed, the indexing pin 1012 is withdrawn to permit rotation of the turntable platter 1010, moving an empty mould into the mixture-receiving position and moving the mould containing the filter element precursor body into an unloading position.

The operation of the apparatus is controlled by control panel 1015.

The structure of the moulds 1008a, 1008b and the portion of the apparatus associated with tamping will now be described in more detail with reference to Figures 1 and 2a. Figure 2a shows a cut-away diagram of the tamper 1004, with a mould 1008a in a mixture-receiving position. The mould 1008a comprises a cylindrical outer wall 1031 and a cylindrical inner piece lOO9a. At the lower end of the mould lOOSa, an annular end-piece 1030 extends between the outer wall 1031 and the inner piece lOO9a. The inner piece lOO9a, outer wall 1031 and end-piece 1030 form a receptacle for the receipt of the mixture comprising a plastics material. The surfaces of the inner piece lOO9a and the outer wall 1031 that come into contact with the mixture have been coated with a low energy material (in this case, polytetrafluoroethylene). This low energy material helps resist adhesion of the mixture and any subsequently-produced filter element to the walls of the mould 1008a. The lowermost part of the inner piece 1009a locates in a cavity 1028 in the turntable platter 1010 provided for accurate and convenient siting of a mould.

Once the mixture has been delivered to the mould 1008a via the receiver 1007, the mixture may be compressed. The tamper 1004 comprises a cylindrical tamping member 1006 which is provided with an annular tamping head 1022. The tamping member 1006 and tamping head 1022 are sized so that they may be received in the gap between the mould inner piece lOO9a and the mould outer wall 1031. The electrically-operated piston 1020 engages with the tamping member 1006 and urges the tamping head 1022 into compressive contact with the material in the mould 1008a.

The apparatus is provided with a return mechanism in the form of a helical spring 1025 mounted around a cylindrical insert 1026. When the tamping member 1006 is urged towards the mould lOOBa, the lower end of the helical spring 1025 abuts against the upper surface of lip 1027 provided on the mould inner piece 1009a. The upper end of the helical spring 1025 abuts against the tamping member 1006. As the tamping member 1006 is urged further downwards the helical spring 1025 becomes more compressed, increasing the force in the 10-spring 1025. Once the piston 1020 is retracted, the compressed spring 1025 urges the tamping member 1006 away from the mould 1008a. The cylindrical insert 1026 is provided to support the spring 1025.

The tamping member 1006 is provided with two fill-level pins 1023a, 1023b which protrude through fill-level slots 1024a, 1024b respectively provided in cylindrical body 1005. This arrangement may also be seen in Figure 2B. Referring to Figure 2A, during compression, the tamping member 1006 is moved onto the mixture. The displacement of the tamping member 1006 is dictated primarily by the amount of mixture in the mould lOOSa. The position of the fill-level pins 1023a, 1023b are indicative of the amount of mixture in the mould 1008a, and (referring to Figure 2B) the position of the fill-level pin l023a relative to the scale 1032 provided on the body 1005 permits the user to verify that the correct amount of mixture has been loaded into the mould lOOSa.

The cylindrical body 1005 is sized so that it may abut against the end of the mould outer wall 1031.

The piston 1020 is associated with a piston cover 1021. The piston cover is cylindrical and sized to that it may abut against cover 1005.

Those skilled in the art will realize that the gaps shown in Figure 2a between different elements of the apparatus have, in many cases, been exaggerated for the purposes of clarity.

The true gaps between elements are, in many cases, smaller than those shown.

Those skilled in the art will realize that the moulds 1008a, 1008b are not part of the apparatus in accordance with the present invention.

The operation of the apparatus of Figure 1 will now be described in further detail with reference to Figures 1, 2A and 2B.

An empty mould 1008a is in a mixture-receiving position. The turntable is looked in this position by indexing pin 1012 which is inserted into locking hole 1029.

A mixture comprising a plastics material is formed by mixing 10% by weight of granules of polyvinyl chloride (PVC), 80% by weight of granules of polyethylene terephthalate (PET), 8-9% by weight of a commercially available compatibilising agent and 0.02-2% by weight of a liquid (typically an organic acid). The compatibilising compound facilitates the blending together of PET and PVC. Examples of such oompatibilising agents include modified polyolefins ("Elvaloy", "Fusabond", "Surlyn" and "Elvanol" agents from DuPont) and styrenio block copolymers ("Styrolux" and "Styroflex" from BASF) . Other compatibilising agents of interest are polycaprolactones (such as the TONE P-767 and P-787 polycaprolactones from Dow Chemical Company) . Also of particular interest are the block-graft copolymers disclosed as compatibilisers in Polymer, Vol. 37, No. 17, August 1996, page 3871-3877 (Braun et al.). Chlorinated polyethylenes have also been recognized as having compatibilising properties in a PVC/high density polyethylene mixture.

The liquid essentially acts as a lubricant to reduce the likelihood of material sticking to the mould. Examples of liquids which may conveniently be used are organic acids, such as acetic acid.

IS The liquid content is so small that the mixture has a powdery, granular consistency. The mixture is delivered via chute 1002 to the screw conveyor 1003. The screw conveyor transfers the mixture to mould 1008a, via a receiver 1007.

It is desirable to use the mixture shortly after preparation; leaving the mixture to stand may result in the liquid evaporating. Once the appropriate amount of mixture had been delivered to the mould 1008a, the mixture may be compressed. Piston 1020 contacts tamping member 1006 and urges tamping head 1022 into the gap between the mould inner piece lOO9a and the mould outer wall 1031. The tamping head 1022 is urged into compressive contact with the mixture in the mould lOO8a, and the mixture is compressed to form a filter element precursor body. The piston is then withdrawn, and the return mechanism provided by the helical spring 1025 ensures that the tamping member is retracted from the mould lOO8a.

The maximum force applied during the compression stroke is of the order of 50-lOOkN. The mixture is under compression for a period of about 0.5 seconds. The piston is electrically actuated. It has been found that a hydraulically-actuated piston may be used but applies a force over a longer timescale, the resulting filter element being less satisfactory than if an electrically-actuated piston is used.

The indexing pin 1012 is then removed from the locking hole 1029 and the turntable rotated so that an empty mould (not shown) is located in the mixture-receiving position and mould 1008a, containing the filter element precursor body, being moved to an unloading position. The mould 1008a is then removed from the turntable platter 1010 and placed in an oven (not shown) so that the filter element precursor body may be heated. The filter element precursor body is heated to 100°C and kept at 100°C for 20 minutes. The temperature is then reduced to 60°C and kept at 60°C for 30 minutes. The temperature is then reduced to 40°C and kept at 40°C for 30 minutes. The temperature is then reduced to 20°C, and kept at 20°C for 40 minutes. The filter element may then be removed from the mould; this process includes removing the end-piece 1030 from the filter element.

It is expected that the heating process removes substantially all of the liquid from the filter element.

The size of the pores in the filter element may be varied by varying the relative proportions of PVC and PET used. The size of the pores may also be varied by varying the size of the granules of PVC and PET used, the smaller the granules the smaller the pores in the filter element.

Those skilled in the art will realize that the apparatus of Figure 1 is merely exemplary. It may be more efficient to provide a conveyor belt or the like with many moulds which are subsequently filled with paste. The filled moulds may then be moved to a tamping station provided with one or more tampers. Once tamped, the filter element precursors may be moved to a heating station where the filter elements precursors are heated to remove some or all of the fluid (if initially present) . Such an apparatus may be substantially automated.

The method described above may be readily adapted in order to change the properties of the filter element. For example, changing the composition of the plastics material can be used to change the properties of the filter element. For example, increasing the mean maximum dimension of the PVC granules used in the mixture gives rise to an increase in pore size. An increase in pore size has been observed when one replaces 0.5mm PVC granules in a mixture with 0.8mm PVC granules.

The method described above with reference to Figures 1, 2A and 2B describes the manufacture of a tubular portion of a polymer filter element. As described below, an embodiment of the polymer. filter element may typically comprise a tubular portion (the manufacture of which has been described above) and a disk-shaped cap portion. The disk-shaped cap portion may be made using the same general apparatus and method as described above, but using a different mould. Those skilled in the art would also realize that a different tamper head (having a circular end shape) would also be required. The disk-shaped cap portion may have a different permeability to particles than the cylindrical portion. This may be achieved S by the cap portion having a different (typically greater) mean pore size than the cylindrical portion. As explained above, this may typically be achieved by using polymer granules of different size and/or by varying the proportion of PET and PVC.

Figure 3 shows a schematic cross-section through an embodiment of a polymer filter comprising a filter element in accordance with the present invention. The polymer filter (in this case, an oil filter generally denoted by reference numeral 100) comprises a polymer filter element 101 disposed within a housing 102. The space between the filter element 101 and the housing defines a chamber 105 for the receipt of unfiltered fluid. Six inlets (only two of which are labeled using reference numerals 150, 151) are provided to allow unfiltered fluid into the chamber 105. The inlets 150, 151 are provided by holes formed in an annular inlet plate 152.

The polymer filter element 101 provides a filtration barrier between the chamber 105 for the receipt of unfiltered fluid and a chamber 106 for the receipt of filtered fluid. Egress of fluid from the chamber 106 is via outlet 200 for the egress of filtered fluid. Polymer filter element 101 is mounted in sealing engagement with an annular plate 170.

A helical spring 120 is provided to urge the polymer filter element 101 into sealing engagement with the annular plate so that unfiltered fluid cannot readily pass to the outlet 200 without passing through the polymer filter element 101.

The polymer filter elements is provided with two portions, first portion 107 and second portion 108. First portion 107 is provided by a cylindrical tube of plastics material made as described above with reference to Figures 1, 2a and 2b.

The first portion 107 is porous and the pore size is such that particles having a greatest dimension of less than about 5pm are able to pass through the filter (particles having a greatest dimension of about 5pm or greater are not able to pass through the filter) . The second portion 108 is generally disk-shaped. The second portion 108 is porous and the pore size is such that particles having a greatest dimension of less than about 15pm are able to pass through the filter (particles having a greatest dimension of about 15pm or greater are not able to pass through the filter) . A valve 110 is provided on the lower face of second portion 108. The valve 110 comprises a valve member 111 urged (under normal operating conditions) into engagement with a valve seat (not shown) [and therefore into a non-transmissive position] by a valve spring 112. A cavity 113 is in the flow path between the second portion 108 of the filter element 101 and the valve 110. The cavity 113 is formed by the placement of a disk-shaped cover 115 against the second portion 108 of the filter element. A sealing member 114 is provided to seal the disk-shaped cover 115 so that fluid may only pass into the chamber 106 for the receipt of filtered fluid via the second portion 108 and the valve 110.

The outlet 200 is provided with a threaded neck 210 for attachment to a corresponding threaded feature on the equipment with which the filter will be used. The filter is also provided with an annular sealing gasket (not shown) which forms a seal when the filter is mounted for use so that unfiltered fluid does not leak from the filter.

The operation of the filter will now be described. Under normal operating conditions (i.e. when the filter is operating normally) the pressure in the chamber 105 for the receipt of unfiltered fluid is below a threshold value. In this case, fluid passes from the chamber 105 for the receipt of unfiltered fluid to the chamber 106 for the receipt of filtered fluid via first portion 107 of filter element 101.

Fluid does not pass into the chamber 106 for the receipt of filtered fluid via second portion 108 because valve member 111 is urged into engagement with the valve seat so that fluid may not pass through the valve.

Under certain operating conditions, the pressure in the chamber 105 for the receipt of unfiltered fluid will exceed a threshold value. This may happen, for example, if the first portion 107 of the filter element 101 becomes blocked.

In a vehicle engine, pressure may increase when the fluid to be filtered (either oil or fuel) is cold and therefore viscous. High acceleration in a vehicle may also lead to increased pressure in the filter. When the pressure in the chamber 105 is above a threshold pressure, valve member 111 is urged away from the valve seat and fluid may pass through the second portion 108 into the chamber 106 via the valve 110. Even though the filtration provided by second portion 108 is not as good as that provided by first portion 107, the filter element of the fourth aspect (and the filter of the fifth aspect) of the present invention provides better performance than the conventional alternative which is to have a bypass valve that allows unfiltered fluid to be transmitted to an outlet without passing through any filter element.

Once the pressure in chamber 105 falls below the threshold value for keeping the valve 110 open the valve 110 closes and the only way for fluid to pass to the outlet is via the first portion 107 of the filter element 101.

The pore size of the first and second portions of the polymer filter element may be chosen to suit the particular use of the filter. The first portion of the filter element was made from a mixture of 10 wt% polyvinyl chloride, SOwt% polyethylene terephthalate, 8-9% compatibilising agent and 0.02-2% liquid. The second portion of the polymer filter element was made from a similar mixture, using granules of pvc and PET with a larger diameter.

The polymer filter 100 is arranged to be a polymer oil filter. Those skilled in the art will realize that the polymer filter of the present invention may be applied to the removal of contaminants from any fluid.

The first and second portions of the polymer filter element 101 are described as being made from a blend of vc and PET.

Other, well-known methods may be used to make polymer filter elements from plastics materials. For example, USS547481 discloses a method for the manufacture of filter elements from polyethylene. US5547481 also discloses how pore size in the filter element may be controlled, for example, by the use of small particles of polytetrafluoroethylene. The teaching of US5547481 may be used to manufacture both the first and second portions of the polymer filter element 101.

t3S2002/0033365 also discloses how filter elements may be made from plastics materials using the so-called "sintering" technique. t3S2002/0033365 also discloses how the pore size of such a filter depends on the size of the particles or granules that are used to make the filter. The teaching of US2002/0033365 may also be used to manufacture both the first and second portions of the filter element 101.

Those skilled in the art will realize that the filter element of the present invention may be made from materials other than plastics. For example, the first and second portions of the filter element may be made from paper (cellulose), the first and second portions of the filter element having mutually different pore sizes.