GB2141373A

GB2141373A - Direct moulding of foam filter

Info

Publication number: GB2141373A
Application number: GB08315832A
Authority: GB
Inventors: Peter Graham Guinea
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-06-09
Filing date: 1983-06-09
Publication date: 1984-12-19
Also published as: GB8315832D0; GB2141373B

Abstract

A method of foam filter production eg an air-filter for an automobile engine comprises the steps of injecting a porous foam filter ingredient material into a mould and allowing the material to expand, cool and form a skin, and selectively removing the skin to expose the internal pore configuration. Wire or plastics reinforcement may be incorporated.

Description

SPECIFICATION Foam filter moulding This invention relates to foam filter construction and is particularly concerned with a method or process for the direct fabrication of a foam filter, minimising, or even entirely obviating, intermediate intricate steps of assembling discrete components parts to achieve an integral or integrally formed filter construction.

A component assembly type foam filter construction is described in my co-pending UK Patent Application No 8222402 and a method for producing such a filter is described in my co-pending UK Patent Application No The present invention is concerned with a fabrication process for a foam filter in which different density foam materials, together with a reinforcing element or layer and peripheral seals can be integrally formed in a "one-shot" injection moulding process, using a form of 'open-cast' mould.Such a process enables considerable manufacturing cost savings to be achieved and affords the prospect of a straightforward and simple, yet reliable, manufacturing process, which will achieve a consistent product quality and make foam filter manufacture, with its inherently high raw materials costs (associated with the cost of synthetic plastic material ingredient), competitive with other well known, highly developed filter constructions, such as impregnated or waxed paper filter construction.

This in-ention is also concerned to obviate the use of expensive metal moulds, which need to be precision machined and thus involve heavy tooling instrument costs. A foam filter construction according to the invention may be fabricated with a relatively cheap and simple open mould, which may itself be fabricated of synthetic plastics material.

According to the invention a method of foam filter production comprises the steps of injecting a molten foam filter ingredient material into a mould and allowing the material to cool and form an expanded porous body with an external skin, and selectively removing the skin to expose the internal pore configuration.

Prior to injection of moulding material, on or more reinforcing elements are positioned in the mould so that, in the subsequent injection of moulding material, the or each reinforced element is integrally moulded into the substrate of the foam filter body itself.

Conveniently, the or each reinforcing element takes the form of individual metal or synthetic plastics wire or rod or alternatively a wire mesh or grid. Any of these reinforcing elements can be loosely positioned in the mould priorto injection of synthetic plastics material.

In a particular embodiment of the invention, an annular ring configuration foam filter is produced by injecting synthetic plastics material ingredient direct into an open annular mould tray and allowing the material to cool and form an outer skin while the internal porosity is developed by chemical reaction associated with the cooling of the material.

An abrading or cutting tool, such as a knife or rotating wheel or drum, is then selectively applied to the outer periphery and/or inner periphery of the annular filter body, if neccessary during the cooling stage itself, for example as the mould is rotated and the material is injected, to expose over desired regions the developed or developing pore structure, leaving selected outer peripheral skin areas as barriers or deflectors.

The foam filter construction according to the invention finds particular application in an automobile internal combustion engine air filter.

By using a controlled form of injection, the density of the foam injected into the mould can be varied to achieve a varying porosity in the "cured" condition.

Moreover, twin or multiple injection heads can be applied simultaneously or selectively, alternately or sequentially, to inject different foam material ingredient(s) into the mould, which can cure independently, but which are heat fusion bonded to one another and form an overall integral foam body assembly.

There now follows a description of a particular embodiment of the invention, by way of example only, with reference to the accompanying drawing, which shows diagrammatically and schematically, in part-sectioned and part cut-away from, the direct injection of a foam filter in particular one suitable for an automobile internal combustion engine.

Referring to the drawing, a disc or plate shaped open mould tray 31 is mounted up on a shaft 32 arranged for both rotation and axial movement to raise and lower the mould with respect to a synthetic plastics injection moulding machine 35. The latter incorporates one or more injection nozzles 36 disposed at one or more stations about the mould tray 31 for injection of hot molten synthetic plastics material into an annular recess 34 in the mould tray 31.

The annular recess 34 invorporates a lower depending recess 33 which forms a peripheral annular end seal in the finished filter.

The injection of synthetic plastics moulding material is timed to form a sufficient discharged volume which when cooled, and with the associated chemical curing reaction completed, will form an expanded upstanding porous foam body with the required foam density, with an outer impermeable membrane or skin. The latter is selectively abraded or cut away by one or more rotating wheels or drums 38, the or each of which is selectively engageable with the inner and/or outer periphery of the rotating open mould tray 31.

It will be ppreciated that, as the mould tray 31 rotates and material is injected from the station on the periphery of the unit at which the injection moulding machine 35 is arranged, so the annular recess in the mould tray 31 will be filled; thereby forming a complete closed annular ring, which expands upon moving into a hollow drum or cylinder of foam filter material 20. Thus the axial depth may be varied by adjusting the dimensions of the recess 34 and the volume of molten foam filter material injected there into.

Prior to the injection step, reinforcing material 37 for example in the form of individual elements of metal or synthetic plastics wire or in the form of a metal or synthetic plastics mesh or grid may be inserted into the recess 34 of the mould tray 31 -for example an upstanding annular ring of synthetic plastics mesh may be loosely positioned in the recess 34, approximately centrally in the thickness or radial depth thereof to form an internal reinforcing element for the foam when injected therearound and in the finished annular filter body forming a reinforcing element for the sealing rib 33.

Hot fluid jets of gas or liquid may be applied to the mould and filter material during formation of the filter in order to achieve a desired local cured surface finish and internal porosity. Moreover, in the injection machine 35 itself, material ingredient(s), operating and injection temperature and other conditions may be selectively variable to vary the density of foam produced across the filter body.

Synchronization of rotation and axial movement of the mould tray 31, the abrading cutter(s) 38 and the injection machine 35 may be achieved automatically by computer control methods and the manufacturing step linked to an assembly and transfer conveyor.

Optionally, the assembled filter may be packaged in situ, for example by bagging or vacuum sealing in heat stretchable plastics film which shrink-wraps the finished filter in a sealed condition.

For packaging and transit the filter may be compressed or folded into a desired compact configuration without suffering any damage, particularly when the reinforcing element is present to promote the restoration of shape of the filter when the packaging constraint is removed. Thus considerable savings in packaging costs can be achieved as compared with known filter constructions, in particular paper elements - which are relatively delicate and fragile in terms of handling, packaging and transit and typically require elaborate cardboard paper or card packaging boxes or cartons for each individual filter.

Manufacturing reference information and/or promotional matter may be integrally moulded with or otherwise applied to the foam by impression or colour.

Claims

1. A method of foam filter production comprising the steps of injecting a molten foam filter ingredient material into a mould and allowing the material to cool and form an expanded porous body with an external skin, and selectively removing the skin to expose the internal pore configuration.

2. A method of foam filter production, as claimed in Claim 1,wherein priorto injection of moulding material, one or more reinforcing elements are positoned in the mould so that, in the subsequent injection of moulding material, the or each reinforcing element is integrally moulded into the substrate of the foam filter body itself.

3. A method of foam filter production, as claimed in Claim 2, wherein one or more reinforcing elements take the form of individual metal or synthetic plastics wire or rod or alternatively a wire m#sh or grid.

4. A method of foam filter production, as claimed in Claim 3, wherein one or more of the reinforcing elements are loosely positioned in the mould prior to injection of synthetic plastics material.

5. A method of foam filter production, as claimed in any of the preceding Claims, wherein foam filter annular ring configuration is produced by injecting synthetic plastics material ingredient direct into an open annular mould tray and allowing the material to cool and form an outer skin while the internal porosity is developed by chemical reaction associated with the cooling of the material.

6. A method of foam filter production, as claimed in Claim 5, wherein an abrading or cutting tool, such as a knife or rotating cutter or arbor wheel or drun, is selectively applied to the outer periphery and or inner periphery of the annularfilter body, if necessary during the cooling stage itself as the mould is rotated and the material is injected, to expose the internal developed or developing pore structure;

7. A method of foam filter production, substantially as herein before described with reference to, and as shown in, the accompanying drawing.

8. Afoam filter produced by the method according to any of the preceding claims.