FR2698286A1 - Filter element, its manufacturing process and apparatus for implementing this process. - Google Patents

Abstract

A cylindrical metal filter element (34) is connected to a plastic end cap (31) by means of a heating method (24, 26). This allows the filter element thus formed to be recycled and avoids the problems encountered when welding metal end caps on cylindrical metal filter media. The connection can be made in the presence of an inert or reducing atmosphere.

Description

The present invention relates to filter elements and more

  in particular, filter elements in which the

  filter media are metallic.

  Many filter elements use filter media that are metallic, such as stainless steel mesh, stainless steel fibers, or stainless steel powders. There are also filter media made of other metals. such as bronze or aluminum In use, these filter media can be shaped in a tubular configuration (for example cylindrical) pleated or non-pleated, and are incorporated in a housing which defines a

  fluid path through the filter medium.

  These media make it possible to carry out filtration in extremely dangerous environments, for example at extreme temperatures in the presence of highly corrosive fluids or in the presence of highly viscous fluids. Stainless steel exhibits in particular excellent mechanical and corrosion resistance properties and it can be cleaned

  and re-used repeatedly.

  In order to allow these filter media to be incorporated into the housing and to define the required flow path, these metal media are provided with metal end caps which cover the ends of the medium, which cooperate with the conjugated parts. contained in the

  housing and which define the necessary flow path.

  These metal end caps are attached to the metal middle by means of a welding, soldering or bonding process to form a filter element These caps

  however have a number of disadvantages.

  When a welding process is used, the metal medium often requires mechanical deformation or reinforcement during the fixing of the metal end caps This can damage the medium or create debris In addition, after fixing the end caps made of metal, the filter element may require cleaning and passivation In addition, the metal end caps cannot be easily removed to allow recovery and / or cleaning of the medium In addition, the filter elements are heavy and when welding is used, non-flow zones can be created at the junction between the end caps and the filter medium, which zones interfere with the flow of the filtrate or with the flow of materials In addition, the metal end caps are not flexible and therefore do not deform easily to adapt to different conditions. tolerances

  when encased in a case.

  According to a first aspect of the invention, a filter assembly is proposed comprising a metal filter medium and a support made of a polymeric material connected to an edge of the

filter medium.

  According to a second aspect of the invention, a method of manufacturing a filter element is proposed comprising bringing an edge of a metallic filtering medium into contact with a support made of a polymeric material and then heating the filtering by means of an induction heating process in order to cause the melting of at least part of said support and then the insertion of the edge of the filter medium into the molten support

  in order to connect the edge and the support.

  According to a third aspect of the present invention, an apparatus is provided for connecting a polymeric support to a metal filtering medium, comprising a base having a surface for supporting a support, a heating device supported by said base for heating at least an edge of a metal filter medium, means for producing an inert or reducing atmosphere in the area of said edge such that when said edge of the filter medium comes into contact with the support in a predetermined arrangement, the edge is inserted into the holder when the

  support was melted by the heated filter medium.

  Plastic end caps such as polypropylene or polyester are known, primarily for use with filter media

  plastic, as described in document WO 85/05286.

  However, proposals are also being made to use these end caps with media.

  metallic For example, the United Kingdom patent of Great

  Brittany GB-A-1,151,592 describes the use of polyurethane materials for metallic cap media

  The patent for the United Kingdom of Great Britain GB-

  A-680211 describes the use of synthetic thermosetting resins with media including gauze

  metallic The patent of the United States of America US-A-

  4,819,722 describes the connection of a metal screen to a polypropylene end cap. The patent of the United Kingdom of Great Britain GB-A-1,208,567 describes a filter medium including metallic elements and a protective cap. 'end in

polyurethane.

  The plastics from which the end caps described or the end cap described are produced have melting points of between approximately 1500 C and 2500 C (for polypropylene, between 1550 C and 1650 C and for polyester , between 2250 C and 2550 C) This places an upper limit on the temperature of the environment in which these filters can be used. Although metal filter media can withstand much higher temperatures, the plastic end caps require much lower temperature limits For environments with higher temperatures, metal end caps have been used with

problems highlighted above.

  Certain plastics available have higher melting points (for example greater than 3400 ° C.) but they have not made it possible to connect end caps made of these materials successfully to metallic media. There is also the problem that even with low melting polymeric materials such as polypropylene or polyester in which, when connected to metallic filter media by heating the media and when the media are of significant size, which requires longer heating of the media, surface deterioration of the media may be

caused by this heating.

  According to a fourth aspect of the invention, there is provided a filter element comprising a metal filter medium and a support made of a polymeric material connected to an edge of the

  filter medium in an inert or reducing atmosphere.

  According to a fifth aspect of the present invention, there is provided a method of manufacturing a filter element comprising placing a metallic filter medium and a support made of a polymeric material in an inert or reducing atmosphere, heating '' at least one edge of the filter medium in order to melt the support then the insertion of the heated edge of the filter medium in the molten polymer material

  of the support in order to connect the filter medium and the support.

  According to a sixth aspect of the invention, an apparatus is proposed for connecting a polymeric support to a metal filtering medium, comprising a base comprising a surface for supporting a support, a heating device supported by said base for heating at least an edge of a metal filter medium, means for producing an inert or reducing atmosphere in the area of said edge such that when said edge of the filter medium comes into contact with the support in a predetermined arrangement, the edge is inserted in the support when the support has been melted

  by the heated metal filter medium.

  The following is a more detailed description of

  certain embodiments of the invention presented by way of example, reference being made to the appended drawings in which: FIG. 1 is a schematic cross-sectional view of a mounting assembly making it possible to connect end caps in a plastic material to a filter medium of metallic material; Figure 2 is a schematic side elevational view partially in section of a mounting assembly for testing the tensile strength of the connections between the end caps and the filter medium of filter elements prepared using the 'assembly assembly of Figure 1; and Figure 3 is a cross-sectional view of an assembly for removing the end caps of prepared filter units using the assembly of the

figure 1.

  In the exemplary embodiments of the invention, end caps prepared from three different materials are connected to media made from three different materials by means of a connection method which will described The filter elements thus manufactured are tested as to their bubble point, as to their integrity and as to their tensile strength The integrity of the filter elements after re-use is also tested by means of a removal of the caps end and a new fitting of end caps before test These various characteristics

  are now described in detail.

  End caps are made from three different materials: polypropylene, polyester and

polyetheretherketone (PEEK).

  Polyproplylene is a commercial class polypropylene distributed by Exxon Corporation under the brand name ESCORENE (PP 1074) This material has a melt index of The melt index is a means of assessing viscosity, a low value indicating a high viscosity and by

  therefore greater resistance to creep.

  Polyester is a commercially available polyester distributed by Exxon Corporation under the brand name CELANEX 1700 A.

  It has a fusion index of 5.

  PEEK is distributed by Imperial Chemical Industries under the designation 450 G However, other classes of PEEK are available from HERE which may be suitable for use in the process which will be described For example, there are classes of PEEK 150 GL 300 , 450 GL 30, 150 CA 30 and 450 CA 30 which may be suitable The designation GL indicates that the PEEK comprises a glass fiber reinforcement of 30% by volume and CA indicates the presence of a carbon fiber reinforcement of 30% by volume Class 150 has a viscosity

lower than class 450.

  The strain temperatures of these classes are

  presented in Table 1 below.

TABLE 1

  PEEK CLASS DEFORMATION TEMP TEST PRESSURE

  450 G 1600 C 18 bars GL 30 3000 C 18 bars 450 GL 30 3150 C 18 bars 150 CA 30 3000 C 18 bars 450 CA 30 315 C 18 bars The "deformation temperature" in Table 1 is the temperature at which the class of Designated PEEK Deforms Significantly The "pressure" is a standard test pressure at which the strain temperature of the PEEK is measured.

MATERIALS OF THE MEDIA

  Three materials are used for the filter medium: porous sintered stainless steel, lattice of sintered woven stainless steel wire and a steel fiber matrix

  stainless fine crisscrossed sintered.

  Media made of porous sintered stainless steel

  are those distributed by Pall Corporation under the PSS brand.

  These media are produced by sintering a pre-alloyed stainless steel powder. No binder is used during the manufacturing process, which avoids any increase in the carbon content. The sintering is carried out without any pressure in order to avoid reductions. permeability The medium is highly porous, up to a volume of 50% of pores, and it fully retains the properties of

  corrosion and temperature resistance of the alloy.

  The PSS is classified according to its extraction capacity measured by means of a modified OSU F 2 yield determination test which uses standard AC dust in water, the extraction yield being determined by means of a count. of particles These capacities are expressed for a range of values P A value 5 is the ratio of the number of particles having a size greater than a given size in the dust / water mixture applied to the support by comparison with the number of particles of the same size or larger contained in the dust / water mixture leaving the medium The class of PSS PH presents

  a capacity of 15 micrometers for P 3 = 100 (99%).

  The lattice of sintered woven stainless steel wires used is that distributed by Pall Corporation under the brand name RIGIMESH The medium consists of a lattice of woven stainless steel wires whose class has been raised by sintering This allows obtain a very resistant material,

  wires being effectively welded at their intersections.

  The sintering process also ensures the integrity of the size

  pores under difficult operating conditions.

  The RIGIMESH has an extraction capacity which is measured in terms of diameter of the largest hard spherical particle which crosses the medium under specified test conditions This diameter is an indication of the largest opening made in the element The class of

  RIGIMESH RMA has a capacity of 45 micrometers.

  The fine crisscrossed stainless steel fibers sintered in the media are those distributed by Pall Corporation under the brand name PFM This is a matrix of randomly crisscrossed fine metallic fibers which are sintered to

  weld the fibers together at their contact points.

  Up to 85% of the volume consists of interconnection voids The PFM is classified by reference to its extraction capacity as measured by means of a modified OSU F 2 yield determination test which uses test dust fine AC in oil, the extraction yield being determined by means of a particle count. The capacities are expressed for a value, (or for P values), which value is the ratio of the number of particles of which the size is greater than a given size in the dust / oil mixture before filtering by comparison with the particles having the same size or a larger size in the dust / oil mixture after filtering The class of PFM has a capacity of 22 micrometers for a IB value of

(99%).

  In all cases, the filtering medium is shaped according to a tube (for example a cylinder) which can be continuous or which can include a welded edge The filtering medium can

be pleated or not pleated.

CONNECTION PROCESS

  The connection between the end caps and the media is made using the mounting assembly shown in Figure 1 The mounting assembly comprises a generally cylindrical base 20 having an upper surface 21 from which protrudes a rod guide 22, its axis being coaxial with the axis of the base 20 The base

  and the guide rod 22 are made of nylon.

  The external curved surface of the base 20 is provided with an annular groove 23 which contains a heating inductor

  water cooled 24 from a high frequency induction machine 25.

  The machine 25 has a maximum power of 3 k W and it is controlled by a potentiometer with 10 turns 26 making it possible to adjust the power output between O and 100% The HF machine has an on / off switch 35 which controls the duration of the heating It includes a timer 36 by means of

  which the duration of the heating can also be controlled.

  A passage 27 opens at a lower surface 28 of the base 20 in a transverse passage 29 which emerges at diametrically opposite sides of the guide rod 22 towards the lower end of the guide rod 22 Le

  passage 27 is connected to a source of argon 30.

  The upper surface 21 of the base 20 as well as the guide rod 22 are configured so that an end cap 31 can be threaded on the guide rod 22 and can rest on the upper surface 21, an internal surface 32 of the end cap 31 being generally

horizontal.

  The guide rod 22 also guides an annular guide weight 33 which rests on the upper end of a cylindrical filter medium 34 whose lower end rests on the internal surface 32 of the end cap 31 The weight is

  4 kg but any other suitable weight can be used.

  A two-part collar or slit ring 37 is fixed to the filtering medium 34 at its lower end and it has an annular lower surface 38 provided with four studs spaced equiangularly 39 The upper surface 21 of the base 20 is provided with four equi-angularly spaced recesses 40 in radial alignment with the pads 39 The pads 39 and the recesses 40 together control the penetration depth of the filter medium 34 inside the end cap 31 in a manner which will be described below -after this depth is 1.5 mm although it can be varied as necessary to ensure a specific penetration of the filter medium 34 to

  inside the end cap 31.

  In use, the mounting assembly operates as follows. First of all, an end cap 31 is placed on the upper surface 21 of the base 20 The filter medium 34 is placed on the end cap and the slit ring 37 is fixed around the filter medium 34, the pads 39 coming into contact with the surface 21 in order to fix the axial position of the slit ring 37 on the filter medium 34 The slit ring 37 and the filter medium 34 are then turned together until

  that the pads 39 are aligned with the recesses 40.

  The guide weight 33 is then placed on the upper end of the filter medium 34. The argon source 30 is then started and the HF machine 25 is started for a predetermined period, with power and predetermined current, depending on the materials involved This is discussed in more detail below The HF machine 25 heats the edge of the medium 34, which melts the end cap 31 When the end cap 31 is melted, the guide weight 33 forces the end of the filter element 34 into force inside the end cap 31 The penetration depth is controlled by the studs 39 which enter

  contact with the bases of associated recesses 40.

  The use of inert atmosphere has the very significant advantage that it prevents surface deterioration of metallic media during the joining process. For example, when the end cap is made of PEEK, it can, as indicated above , it may be necessary to heat the end cap up to a temperature well above 3000 C and possibly up to 400 C or even 5000 C, in order to carry out the joining process At these temperatures, metallic media can suffer from surface deterioration such as oxidation which can adversely affect

filter characteristics.

  Even if the end cap 31 is made of a material having a low melting point, the reducing atmosphere has the advantage of reducing or eliminating any surface deterioration of the metallic media which could occur when elements of large dimensions are hooded, due to the considerable time during which these media must be heated to allow a connection of the cap

end.

  Of course, the atmosphere does not necessarily have to be made up of argon and it can be made up of

  any other suitable gas or gas mixture.

  The atmosphere can also be a reducing atmosphere such as hydrogen or a mixture of hydrogen in argon (5% hydrogen in argon, by volume), which not only prevents deterioration surface such as oxidation but which also removes all oxides or carbon impurities present during the process

end cap.

  When the HF machine 25 is stopped, the source of argon 30 is cut off The guide weight 33 is then removed and the slot ring 37 is removed The attached end cap 31 and the filter medium 34 are then removed and the steps are repeated in order to connect a second end cap 31 to

  the other end of the filter medium 34.

  It may be necessary to dry the PEEK and polyester end caps before treatment in order to remove any absorbed moisture The PEEK 31 end caps may require 3 hours of drying at 1500 C and the polyester end caps 31 may require 10 hours of drying at 1210 C Dried end caps 31 must be used within three hours of drying

  to avoid moisture absorption before assembly.

  The power output of the HF 25 machine and the duration of the power output must be adjusted to take into account the materials of the end cap 31 and the medium 34 When using high power for a short time , the medium 34 quickly reaches the desired temperature to melt and penetrate the end cap 31 without absorbing a significant amount of heat This is due to the very local area of the induction, namely only the surface of the medium 34 which is adjacent to the heating inductor 24 The polymeric end cap 31 is not heated directly by the heating inductor 24 since heat can only be induced in conductive materials Similarly, the mounting assembly who is

  made of nylon is not affected by induction heating.

  If greater heat penetration is required, then a longer duration allows the heat to propagate by conduction. However, when the desired temperature is reached, significantly more heat is absorbed and the

  medium 34 needs more time to cool.

  Table 2 below gives the power and duration for the various combinations of cap materials

  and medium materials presented by way of example above.

  It will be appreciated that other powers and durations may be necessary for other combinations of materials of

  cap and middle material.

TABLE 2

  CAP MATERIAL MEDIA POWER (%)

  (all registered trademarks) Polypropylene PSS (PH) 40 Polypropylene Rigimesh (RMA) 60 Polypropylene PFM 20 60 Polyester PSS (PH) 50 Polyester Rigimesh (RMA) 60 Polyester PFM 20 60

PEEK PSS (PH) 50

PEEK Rigimesh (RMA) 60

PEEK PFM 20 60

  TIME (s) (approx) 1 5 1 5 1 7 1 7 1 1 It can be seen that the longest heating time is necessary for the PEEK end caps 31 used in conjunction with the 34 RIGIMESH filter media or in PFM It is possible to reduce this time to approximately 18 seconds by using 80% of the nominal power but the reduced time generally does not allow the PEEK to creep uniformly in the filter medium 34 It may be possible to overcome this disadvantage by means of a

  easy-creep PEEK class of the type discussed above.

  It will of course be appreciated that the geometry of the heating inductor 24 and that the number of its turns are chosen so as to obtain optimum performance The geometry of the heating inductor 24 must closely follow the profile of the sample A space as low as possible between the heating inductor 24 and the end cap 31 is preferably to obtain the highest efficiency by increasing the concentration of the flux Since the flux generated is proportional to the number of turns in the heating inductor , it is desirable to wind as many turns as possible for the given area of the upper surface 21 while maintaining an internal diameter compatible with the desired coupling with the

middle 34.

BUBBLE POINT TEST

  The filter elements prepared as described above using the combinations of Table 2 are tested for the integrity of their connection using a bubble point test In such a test, the filter element is submerged in a bath isopropyl alcohol ("IPA") so as to wet all the pores A pressure is then applied to the interior of the structure and the pressure required for the first air bubble or initial air bubble to appear on the surface exterior of

the item is saved.

  For porous media only, the bubble point (i.e.

  i.e. the pressure at which the first air bubble or initial air bubble appears) is related to the pore size of the medium If the connection between the end caps 31 and the medium 34 leaves spaces or passages which are larger than the size of the middle pores, then the integrity of the element is compromised. The bubble point test results for the element configurations in Table 2 are equivalent to or better than those obtained for elements with caps

  metal end caps welded to metal media.

INTEGRITY TEST

  The bubble point test described above is a measure of the integrity of the seal between the end cap 31 and the filter element 34 However, it does not constitute an accurate simulation of the actual operating condition of a filter element In order to better simulate these conditions, it is necessary to maintain a significant pressure difference on the filter elements at a high temperature The integrity of the seal after repeated replacement of the caps

  end 31 is also tested in this way.

  In order to conduct such a test for the filter elements described above, a sample of a filter element of each of the types described above is processed in the following manner First, after an initial end cap , the end caps 31 are removed and the filter element 34 is provided with new end caps 31 which are then removed and replaced by other new end caps 31 The surface of the filter medium 31 is sealed using a shrink tubing of the type distributed under the registered trademark

  EM 52 101 6 by Egerton Power Products.

  Each filter element is then maintained at a given temperature presented below in table 3 by means of a pressure difference between the inside and the outside of the filter element, as presented in the

Table 3 below.

TABLE 3

  DIFFERENCE TEMPERATURE HOOD COMBINATION

/ PRESSURE MEDIA

  PEEK / Rigimesh 2320 C 9.0 bar Polyester / PFM 1540 C 4.5 bar Polypropylene / PSS 100 C 3.2 bar After the temperature / pressure test for 24 hours, all the filter elements are tested for bubble point as described above It is found that they all have bubble points equivalent to or greater than those obtained for elements comprising welded metal end caps

to metal media.

TENSILE TEST

  Some of the filter elements produced as presented by way of example above are tested in order to determine the load which must be applied to the end cap 31 along the direction of the axis of the filter element in order to cause a failure in the filter element This failure is either a failure of the cap 31 itself or a failure of the seal located between the end cap

31 and the filter medium 34.

  The tests are carried out using the assembly assembly of FIG. 2 This assembly comprises two couplings 41 arranged coaxially with respect to the axis of the filter element and cooperating respectively with the end caps 31 of the element of filter Each coupling 41 comprises a slot retaining ring 42 which receives the associated end cap 31 and which has a flank 43 which cooperates with the peripheral edge of the internal surface 32 of the associated end cap 31 Each retaining ring slot 42 is connected to a fastening element 44, which in turn is connected to the load The load is applied along the common axes of the

  couplings 41 and the filter element.

  The results of this test are presented in Table 4

following.

TABLE 4

COMBINAISOQNL

HOOD / MEDIA

  Polypropylene-PSS Polypropylene-PSS Polypropylene-Rigimesh Polypropylene-Rigimesh Polypropylene-PFM Polypropylene-PFM Polyester-PSS Polyester-Rigimesh

PEEK-PSS

RESISTANE

TRACTION

k N TONS

, 02 0.51

4.33 0.44

3.43 0.35

3.83 0.39

.30 0.54

7.41 0.76

7.93 0.81

, 73 0.58

11.86 1.21

TYPE OF FAILURE

SEALED HOOD

* r * * *

RE-USE OF ELEMENTS

  The stainless steel filter media 34 can be chemically cleaned without affecting the PEEK or polypropylene end caps 31 Thus, these filter elements can be cleaned and re-used as is known in the art. polyester end 31 can be cleaned but they have a reduced range of chemical compatibility compared to hooded elements

PEEK and polypropylene.

  In addition, the end caps 31 can be removed and replaced with new end caps. The polyester end caps 31 can be dissolved 100% by chemicals. The polypropylene end caps 31 can be removed. by fusion and combustion The PEEK 31 end caps cannot be

  easily removed either chemically or by combustion.

  All end caps can, however, be removed using the following procedure which uses a modified form of the mounting assembly of Figure 1 This modified mounting assembly is shown in Figure 3 and parts common to it. assembly of Figure 1 and assembly of Figure 3 are given the same indexes

  for reference and are not described in detail.

  The assembly of Figure 3 omits the guide rod 22 and the guide weight 33 The argon inlet passage 27 therefore emerges at the upper surface 21 of the base 20 A cylindrical enclosure 45 closed at its upper end comprises an open lower end which fits onto the upper surface 21 of the base in order to constitute a chamber intended to enclose a filter element. In use, an end cap 31 of an element of

  filter is placed on the upper surface 21 of the base 20.

  The enclosure 45 is then placed on the element and it is

  fitted onto the upper surface 21.

  The argon source 30 is then turned on in order to fill the enclosure 45 with argon in order to purge any air contained in the enclosure 45 by evacuating it through the evacuation 46 The HF machine 25 is then switched on for a time sufficient to melt the seal between the end cap 31 and the filter medium 34, after which it is cut off The inert atmosphere again has the role of preventing any deterioration of the surface of the medium filter 34 The argon source 30 is then cut and the enclosure 45 is removed. The end cap 31 can then be separated from the filter medium 34, if necessary by being dislodged using an appropriate tool. The procedure is then repeated for the other

end cap 31.

  After the end caps 31 have been removed, the new end caps can be connected to the filter medium 34, as described above with reference to FIG. 1 As discussed above during the INTEGRITY TEST, this reconnection can be achieved without adversely affecting the bubble point performance of the filter element After the end caps 31 have been removed, small deposits of polymer may remain, particularly on pleated media This does not affect the end cap provided that the same type of end cap in

polymer be used.

  It will be appreciated that materials other than those described

  above can be used For example, polyether-

  sulfone (PES) can be used In addition, the configurations of the end caps 31 and of the filter media 34 can be other than those described above. The end caps 31 can be in the form of adapters or domed end caps, the shape of the mounting assembly of Figure 1 being adapted accordingly. The constructions described above with reference to the drawings have a certain number of advantages. These are as follows: 1 The use of an inert or reducing atmosphere reduces or prevents any surface deterioration of the metallic medium, particularly at temperatures and / or during the connection of large filter media to end caps. 2 The end caps 31 can be fixed firmly to the filter media 34 without mechanical deformation or reinforcement of the medium This avoids possible damage (as measured by means of a test of

  bubble point) and / or the creation of debris during manufacture.

  3 The filter media 34 can be fully passivated and cleaned before fitting the end caps

  since no metal welding process is necessary.

  4 The end caps 31 can be removed from the filter media 34, which makes it possible to recover the media, or to clean them and replace them with new caps

end 31.

  The filtering media 34 can be better cleaned without removing the end caps because a reinforcement of the edges of the media is eliminated and thus

the item can be recycled.

  6 Molding the plastic caps 31 consumes less work than machining from a solid material and thus the plastic end caps

are less expensive.

  7 Molded plastic end caps are inherently less expensive than machining from solids because less material is used. 8 Since the plastic end caps 31 are lighter than similar stainless steel end caps, the weight of the filter element is reduced. 9 The design removes dead areas (of no flow) at the junction of the end caps 31 and the filter media 34 This prevents any blockage of the flow of the filtrate which would otherwise lead to the maintenance and stagnation of the water. inside the filter media 34 of some

  quantities of filter fluid (or cleaning materials).

  The end caps 31 are inherently flexible and thus can be adapted to take into account manufacturing tolerances between the filter element and

an associated box.

  11 A given injection molded end cap can be used for more than one type of filter element since a specific size of the recesses or means of

  positioning is not required for the assembly process.

  It will be appreciated that the invention can be applied to any cylindrical filter medium or to any filter medium made of metal. This includes filter media made of metals other than bronze or aluminum. Any edge of these media can be connected to a polymer end cap, as described above with reference to the drawings Of course, the connection must not be an end cap and the connection can be constituted by any support in polymer Any suitable thermoplastic material can be used for the end caps 31 or for any other support and these materials are in practice

  selected in relation to the conditions of use.

  The element does not need to be heated as described above, it can be heated in any suitable way, for example by one of the following ways: 1 Heating the entire metal element up to a temperature of for example around 2600 C then insertion of an edge of the medium into a support (which can itself be preheated). 2 Heating of the metal element then insertion of

  the element in a partially molten support.

  3 Heating the metal element using a

microwave source.

  4 Connection of the element and the support using a rotational welding technique.

  Heating of the metal element directly or using infrared radiation then insertion of the element into the support (which can itself be preheated).

Claims (16)

  1 filter element characterized in that it comprises a filter medium (34) made of metal and a support (31) made of a polymeric material connected to an edge of the filter medium   (34) by means of an induction heating process.   2 Filter element characterized in that it comprises a metal filtering medium (34) and a support (31) made of a polymeric material connected to an edge of the filtering medium   in an inert or reducing atmosphere.   3 filter element according to claim 1 or 2, characterized in that the support is an end cap (31) and said filter medium (34) is cylindrical, one end of the filter medium (34) being connected to the cap end (31).   4 Filter element according to any one of   Claims 1 to 3, characterized in that the cap   end (31) is polyester, polypropylene or polyetheretherketone. Filter element according to any one of   Claims 1 to 4, characterized in that the filter medium   (34) is constituted by a sintered metal powder or by a woven wire mesh or by fine intertwined metallic fibers. 6 A method of manufacturing a filter element, characterized in that it comprises the placement of a metallic filter medium (34) and a support (31) made of a polymeric material in an inert or reducing atmosphere, the heating at least one edge of the filter medium (34) in order to melt the support (31) then inserting the heated edge of the filter medium (34) in the molten polymer material of the support (31) in order to connect the filter medium (34) and support (31).   7 A method of manufacturing a filter element, characterized in that it comprises bringing an edge of a metallic filter medium (34) into contact with a support (31) made of a polymeric material and then heating the filter medium by means of an induction heating process (24) in order to cause the melting of at least part of said support (31) and then the insertion of the edge of the filter medium (34) into the support   melted in order to connect the edge and the support (31).   8 Method according to claim 6, characterized in that said heating is an induction heating method (24).   9 Method according to claim 7 or 8, characterized in that it comprises bringing said edge of the filter medium (34) into contact with said support (31), the application of a force (33) which pushes the support (31) and the filter medium (34) towards each other and then inductively heating the filter medium (34) so that said force (33) pushes the edge   filter medium (34) in the molten support (31).   Method according to any one of claims 6 to   9, characterized in that it further comprises controlling the depth of insertion of the filter medium (34) into the support (31) so that said depth is a predetermined depth which is less than the thickness of the support (31) to insertion point level.   11 Method according to any one of claims 6 to   , characterized in that said support is an end cap (31) and said filter medium is cylindrical, a   end of the filter medium (34) forming said edge.   12 Method according to any one of claims 6 to   11, characterized in that it comprises the melting of a support (31) connected to a filtering medium (34), the removal of the support (31) from its state of connection with the filtering medium (34) then connecting another support (31) to the metal filter medium (34) in the same manner as connecting said first support mentioned (31).   13 Apparatus for connecting or disconnecting a polymeric support (31) to a metal filter medium (34), characterized in that it comprises a base (20) having a surface (21) for supporting a support (31) , a heater (24) supported by said base (20) for heating at least one edge of a metal filter medium (34), means (27, 29, 30, 32) for producing an inert atmosphere or reducing in the area of said edge so that when said edge of the filter medium (34) comes into contact with the support (31) in a predetermined arrangement, the edge is inserted into the support (31) when the support (31) was melted   by the heated metal filter medium (34).   14 Apparatus for connecting a metal filter medium (34) or disconnecting from a metal filter medium (34) a polymeric support (31), characterized in that it comprises a base (20) comprising a surface (21) for supporting a support (31), an induction heater (24) supported by said base (20) for heating the metal filter medium (34) such that when an edge of the medium filtering (34) comes into contact with the support (31) according to a predetermined arrangement, said edge is inserted into the support (31) when the support (31) has been melted by the medium   heated metal filter (34).   Apparatus according to claim 13, characterized in that said means for producing an inert or reducing atmosphere comprises a passage (27, 29) formed in said base (20) for supplying an inert or reducing gas up to   inside the filter medium (34).   16 Apparatus according to claim 13 or 14, characterized in that said heating device is a device for induction heating (24).   17 Apparatus according to any one of claims 13   to 16, characterized in that the filtering medium (34) is cylindrical, said edge being formed by one end of said support (34) and a guide being provided, which comprises an elongated rod (22) which projects relative to said base (20) and which extends through the interior of a cylindrical filter medium (34) thus supported, said guide guiding the filter medium (34) so that said edge comes into contact with said support (31) according to said predetermined position.   18 Apparatus according to any one of claims 13   to 17, characterized in that a means (33) is provided for pushing an edge of a filter medium (34) to bring it into contact with a support (31) supported by said base (20) in order to push said edge in the support (31) when the support (31) has been   melted by the filter medium (34).   19 Apparatus according to claim 18, characterized in that said pushing means comprises a weight (33) intended to come into contact with an edge of said filter medium (34) opposite to said edge of the filter medium (34) which comes into contact with the support (31).   Apparatus according to any of claims 13   to 19, characterized in that means (37, 38, 39, 40) are provided for limiting the depth to which the filter medium (34) is inserted into the support (31) when the support (31) has been   melted by the filter medium (34).   21 Apparatus according to claim 20, characterized in that the filter medium (34) is cylindrical and one end of said medium (34) forms said edge, said limiting means comprising a collar (37) intended to be fixed to the filter medium cylindrical (34), said collar (37) having a surface (38) which, in use, is adjacent to said support bearing surface (21) of the base (20), the collar (37) comprising on said surface (38 ) a plurality of studs (39) in radial alignment with a corresponding number of cooperation recesses (40) formed in said base surface (21), the collar (37) being fixed to the filtering medium, said studs (39) coming into contact with said base surface (21) in order to fix the axial position of the collar (37) along the filter element (34), the collar (37) being then able to be rotated so that said studs ( 39) are aligned with said recesses (40), the studs s (39) penetrating said recesses (40) when the support (31) is melted by the filter medium (34) and when the edge of the filter medium (34) penetrates into the support (31), the studs (39 ) coming into contact with the recesses (40) after the filter medium (34) has penetrated into the support (31) to a predetermined depth so as to determine said depth.