GB1600374A - Filter elements and their manufacture - Google Patents

Description

(54) FILTER ELEMENTS AND THEIR MANUFACTURE (71) I, DEREK ALEXANDER FINCH, a British subject, of 15, Coworth Road, Sunningdale, Berkshire, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of manufacturing filter elements and to filter elements so manufactured.

Commonly filter elements are fabricated from a number of component parts which include a panel of filter medium, which often is of a pliable nature, and a supporting frame work to which or within which the filter medium is mounted and which principally serves to afford rigidity to the combination.

According to one aspect of the present invention there is provided a method of manufacturing a filter element, which comprises pouring, dispensing, printing, spraying or brushing onto the surface of one or more selected portions of a porous or permeable filter medium to a solidifiable liquid to fill the interstices. and to coat the matrix or fibres, of the medium in said portions, and causing or allowing said liquid to solidify to provide for the filter medium an integral frame and/or reinforcement which does not project substantially beyond said surface.

According to another aspect of the present invention there is provided a method of manufacturing a filter element which comprises applying to an upwardly facing surface of one or more selected portions of a porous or permeable filter medium a viscous solidifiable liquid which on heating initially becomes less viscous or a powder which fuses on heating, heating the applied liquid or powder to cause it to become sufficiently mobile to permeate through a portion of the body of said medium adjacent said surface and subsequently causing or allowing the liquid to solidify to provide for the medium an integral frame and/or reinforcement which does not project substantially beyond said surface.

Any filter medium may be employed in the present invention although it will be appreciated that those which do not possess inherent rigidity are particularly suited to the present invention. Examples of suitable filter media are plastics foams such as polyester, polyether or polyurethane, paper and cardboard, woven or non-woven cloth, metal or plastics mesh, cotton wool, fibre glass wool, a sheet of randomly orientated fibres, preferably synthetic, bonded together by an adhesive, preferably a synthetic resin adhesive, or a sheet of fibre glass strands either randomly orientated or arranged in a particular manner. Any two or more of these may be used in combination.

Clearly it is advantageous if the characteristics of the solidifiable liquid are so chosen that the heating step serves both to reduce the viscosity of the liquid and to cause it to harden.

Embodiments of the present invention will now be described, by way of example, with reference to the single sheet of the accompanying drawings in which Figures I to 4 show in perspective view different configurations of filter elements having integral frames produced by the method of the present invention.

To produce a rectangular filter element 1 having an integral peripheral frame 2 as shown in Figure 1, a rectangular panel of porous filter medium 3 is placed inside a flat shallow tray (not shown) having internal dimensions corresponding to those of the panel and which has previously been sprayed with a release agent. At a dispensing station capable of providing a stream of viscous epoxy resin casting mixture through a nozzle of approximately 3/8" in diameter, the mixture is applied or piped around the periphery of the panel there to form a bead.

The action of applying the resin is similar to that of icing a cake except that it is preferred in the method of the invention to move the panel of filter in the tray relative to a stationary dispenser.

One or more trays each containing a panel of filter medium with a peripheral bead of resin mixture are then placed in a warm oven. When heated by the oven the resin mixture initially becomes more mobile and permeates down through the thickness of the peripheral portion of the panel under the influence of gravity and of capillary attraction. Although some migration in the horizontal direction does occur the effect is generally small and insignificant. When the resin reaches the boundary of the filter medium it there comes into contact with the juxtaposed areas of the sides and bottom of the tray and adopts the configuration thereof. The resin subsequently polymerises on further heating and the panel of filter medium is thus provided with a rigid integral epoxy resin frame having three surfaces which are coplanar with the surface of the filter element, the side and bottom surfaces being moulded by the tray and the upper surface being defined by resin which has adhered to the upper surface of the panel after the resin had been caused to flow. The trays are then removed from the oven and the filter elements so formed removed from the trays. For most purposes the filter elements are usable withont any further processing, although in some cases it is desirable to machine the cured resin.

The above-described simple peripheral rectangular frame is sufficient where neither dimension of the element exceeds 12". For larger sizes or where additional reinforcement is required, additional lines of beading may be applied to the surface of the element in a lattice or other pattern.

The resin mixture preferably comprises an epoxy resin, a hardener and one or more fillers such as wood-flour, finely ground mineral particles or finely chopped fibres such as glass fibres.

Where the filter element to be produced is of corrugated form, as exemplified by the element 4 shown in Figure 2, the tray should also be of corresponding corrugated form and the panel of filter medium retained in the tray by a corrugated plate (not shown) also having a form corresponding to that of the tray but of dimensions which are slightly less than those of the tray in order to allow for the application of the resin bead to the periphery of the panel to form a frame 6. An element 7 of L-shaped section as shown in Figure 3, is produced by the use of a corresponding tray and plate in the same manner as described for the embodiment of Figure 2. The panel of filter medium is denoted by the reference 8 and the frame by 9.

To produce a cylindrical element 16 (Figure 4) having an annular reinforcement 11, 12 at each end, the resin mixture must first be applied to one of the end faces of a previously-formed cylinder 13 of filter medium and the mixture heated with the cylinder 13 in an upright position before the other end is treated in a similar way. An annular ring (not shown) may, if desired, be placed against one of the cylindrical surfaces adjacent to the end face, or against each of the cylindrical surfaces, in order to perform the same moulding function as the tray.

The above-described production methods avoid the need to produce the separate frame and then to secure the panel therein; they also avoid the need for positioning the periphery of the element within a closed or nearly closed mould.

Any suitable solidifiable liquid may be employed. For example it may be a plastics material in a molten or plastisol state, a curable liquid resin, a liquid derived by heating a powder to fuse it and which solidifies on cooling or a solution or dispersion of a solid material, for example an adhesive, in an evaporable liquid. Filled epoxy resins are preferred.

The solidifiable liquid may be applied to the filter medium, with or without the aid of jigs or masks, by any suitable method such as by brushing, spraying, dispersing, printing or pouring, the last method being suitable for the application of a powder.

WHAT I CLAIM IS: 1. A method of manufacturing a filter element, which comprises pouring, printing, spraying or brushing on to the surface of one or more selected portions of a porous or permeable filter medium a solidifiable liquid to substantially fill the interstices, and to coat the matrix or fibres, of the medium in said portions, and causing or allowing said liquid to solidify to provide for the medium an integral frame and/or reinforcement which does not project substantially beyond said surface.

2. A method as claimed in Claim 1, wherein said liquid is a viscous liquid whose viscosity is initially reduced by heating, the liquid is poured or dispensed onto the surface of said selected portions and the liquid is then heated to reduce the viscosity of the liquid, thus allowing it to permeate through the filter medium.

3. A method of manufacturing a filter element which comprises applying to an upwardly facing surface of one or more selected portions of a porous or permeable filter medium a viscous solidifiable liquid which on heating initially becomes less viscous or a powder which fuses on heating,.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (20)

**WARNING** start of CLMS field may overlap end of DESC **. the mixture is applied or piped around the periphery of the panel there to form a bead. The action of applying the resin is similar to that of icing a cake except that it is preferred in the method of the invention to move the panel of filter in the tray relative to a stationary dispenser. One or more trays each containing a panel of filter medium with a peripheral bead of resin mixture are then placed in a warm oven. When heated by the oven the resin mixture initially becomes more mobile and permeates down through the thickness of the peripheral portion of the panel under the influence of gravity and of capillary attraction. Although some migration in the horizontal direction does occur the effect is generally small and insignificant. When the resin reaches the boundary of the filter medium it there comes into contact with the juxtaposed areas of the sides and bottom of the tray and adopts the configuration thereof. The resin subsequently polymerises on further heating and the panel of filter medium is thus provided with a rigid integral epoxy resin frame having three surfaces which are coplanar with the surface of the filter element, the side and bottom surfaces being moulded by the tray and the upper surface being defined by resin which has adhered to the upper surface of the panel after the resin had been caused to flow. The trays are then removed from the oven and the filter elements so formed removed from the trays. For most purposes the filter elements are usable withont any further processing, although in some cases it is desirable to machine the cured resin. The above-described simple peripheral rectangular frame is sufficient where neither dimension of the element exceeds 12". For larger sizes or where additional reinforcement is required, additional lines of beading may be applied to the surface of the element in a lattice or other pattern. The resin mixture preferably comprises an epoxy resin, a hardener and one or more fillers such as wood-flour, finely ground mineral particles or finely chopped fibres such as glass fibres. Where the filter element to be produced is of corrugated form, as exemplified by the element 4 shown in Figure 2, the tray should also be of corresponding corrugated form and the panel of filter medium retained in the tray by a corrugated plate (not shown) also having a form corresponding to that of the tray but of dimensions which are slightly less than those of the tray in order to allow for the application of the resin bead to the periphery of the panel to form a frame 6. An element 7 of L-shaped section as shown in Figure 3, is produced by the use of a corresponding tray and plate in the same manner as described for the embodiment of Figure 2. The panel of filter medium is denoted by the reference 8 and the frame by 9. To produce a cylindrical element 16 (Figure 4) having an annular reinforcement 11, 12 at each end, the resin mixture must first be applied to one of the end faces of a previously-formed cylinder 13 of filter medium and the mixture heated with the cylinder 13 in an upright position before the other end is treated in a similar way. An annular ring (not shown) may, if desired, be placed against one of the cylindrical surfaces adjacent to the end face, or against each of the cylindrical surfaces, in order to perform the same moulding function as the tray. The above-described production methods avoid the need to produce the separate frame and then to secure the panel therein; they also avoid the need for positioning the periphery of the element within a closed or nearly closed mould. Any suitable solidifiable liquid may be employed. For example it may be a plastics material in a molten or plastisol state, a curable liquid resin, a liquid derived by heating a powder to fuse it and which solidifies on cooling or a solution or dispersion of a solid material, for example an adhesive, in an evaporable liquid. Filled epoxy resins are preferred. The solidifiable liquid may be applied to the filter medium, with or without the aid of jigs or masks, by any suitable method such as by brushing, spraying, dispersing, printing or pouring, the last method being suitable for the application of a powder. WHAT I CLAIM IS:

1. A method of manufacturing a filter element, which comprises pouring, printing, spraying or brushing on to the surface of one or more selected portions of a porous or permeable filter medium a solidifiable liquid to substantially fill the interstices, and to coat the matrix or fibres, of the medium in said portions, and causing or allowing said liquid to solidify to provide for the medium an integral frame and/or reinforcement which does not project substantially beyond said surface.

2. A method as claimed in Claim 1, wherein said liquid is a viscous liquid whose viscosity is initially reduced by heating, the liquid is poured or dispensed onto the surface of said selected portions and the liquid is then heated to reduce the viscosity of the liquid, thus allowing it to permeate through the filter medium.

3. A method of manufacturing a filter element which comprises applying to an upwardly facing surface of one or more selected portions of a porous or permeable filter medium a viscous solidifiable liquid which on heating initially becomes less viscous or a powder which fuses on heating,.

heating the applied liquid or powder to

cause it to become sufficiently mobile to permeate through a portion of the body of said medium adjacent said surface and subsequently causing or allowing the liquid to solidify to provide for the medium an integral frame and/or reinforcement which does not project substantially beyond said surface.

4. A method as claimed in Claim 3, wherein after application the solidifiable liquid or powder rests on said surface until heated.

5. A method as claimed in any preceding claim, wherein one or more further surfaces of said element adjacent the surface onto which the solidifiable liquid is applied are juxtaposed against a surface which provides a boundary to contain the mobile solidifiable liquid until it solidifies.

6. A method as claimed in Claim 5, wherein the medium is placed in a tray of a configuration such that resin permeating through a face of the medium comes into contact with the tray and is moulded thereby.

7. A method as claimed in any preceding claim, wherein the liquid is applied around the periphery of the medium.

8. A method as claimed in any preceding claim, wherein the liquid is a curable liquid plastics composition.

9. A method as claimed in Claim 8, wherein the curable liquid plastics composition contains an epoxy resin.

10. A method as claimed in Claim 8 or 9, wherein said composition also contains a hardener.

11. A method as claimed in Claims 8, 9 or 10, wherein said composition also contains a filler so chosen as to impart or allow sufficient viscosity in the liquid phase, mobility in the heated phase and mechanical strength in the solid phase.

12. A method as claimed in any preceding claim, wherein the filter medium comprises a plastics foam.

13. A method as claimed in any one of Claims 1 to 10, wherein the filter medium comprises or incorporates a woven or nonwoven cloth.

14. A method as claimed in any one of Claims 1 to 10, wherein the filter medium comprises or incorporates a sheet of randomly orientated synthetic fibres bonded together by a synthetic resin adhesive.

15. A method as claimed in any one of claims 1 to 10, wherein the filter medium comprises or incorporates a sheet of glass fibre strands either randomly or nonrandomly orientated.

16. A method as claimed in any preceding claim, wherein the solidifiable liquid and the medium are so chosen as to ensure permeation of the liquid by capillary attraction.

17. A method as claimed in Claim 3, or any one of Claims 4 to 16 when appendant thereto, wherein the liquid is solidifiable by the action of heat and is caused to solidify by prolonging the same heating step that initially renders it less viscous.

18. A method as claimed in any preceding claim, wherein said selected portions to the surface of which the solidifiable liquid is applied on in the form of a lattice thus providing, when the liquid has solidified, a reinforcement for the medium.

19. A method as claimed in Claim 1 or 3 and substantially as herein described.

19. A method of manufacturing a filter element substantially as hereinbefore described with reference to any one of Figures 1 to 4 of the accompanying drawing.

20. A filter element when manufactured by a method as claimed in any of Claims 1 to 19.