GB2150038A

GB2150038A - Filtration apparatus

Info

Publication number: GB2150038A
Application number: GB08330452A
Authority: GB
Inventors: William Allison
Original assignee: NORTHERN IND SYSTEMS ENGINEERI
Current assignee: NORTHERN IND SYSTEMS ENGINEERI
Priority date: 1983-11-15
Filing date: 1983-11-15
Publication date: 1985-06-26
Also published as: GB8330452D0

Abstract

Filtration apparatus comprises an elastomeric and tubular filter element penetrated by a plurality of apertures produced in the element wall by laser energy. The element is cleaned by backwashing which opens out the apertures to release solids. The apertures taper in the normal direction of flow.

Description

SPECIFICATION Improvements relating to filtration This invention relates to filtration and more particularly to filtration apparatus, a filter element therefor, and a method of producing such an element.

According to a first aspect of the invention there is provided filtration apparatus comprising a filter element penetrated by a plurality of apertures produced in the material of the filter element by laser energy.

According to a second aspect of the invention there is provided a filter element penetrated by a plurality of apertures produced in the material of the element by laser energy.

The invention also provides a method of producing a filter element comprising using laser energy to produce a plurality of apertures in the material of the element.

In the filtration apparatus of the invention, filtration is effected through a filter element which is penetrated by a plurality of apertures produced by laser energy and sized to filter out solid materials which it is desired to remove, We have found that laser energy is an extremely effective way of producing the filter element as it allows holes of the required cross-sectional size to be produced quickly and accurately and allows the production of filter elements at low cost.

The hole size produced by the laser is dependent on the power thereof, the time of action of the laser on the material of the element, and the nature of this material.

Typical, but non-limiting parameters employed for the laser are as set out below: 1) Max. power output 100W.

2) Wave length 10.6 microns 3) Overall beam diameter at exit aperture 8.5 mm.

4) Pulse Frequency Up to 5000 Hz.

5) Gas consumption a) Helium 60 litres per hour b) Nitrogen 9 ,.

c) Carbon Dioxide 6 A suitable laser is an electrox 80W continuous wave, CO2 pulsed laser, although other pulsed lasers may of course be used.

Typically the hole size in the filter element will be from 20-1000 microns depending on the nature of material to be filtered, and can be even lower. In fact, the hole size produced by the laser may be sufficiently small that the filtration apparatus may be used as air purification apparatus, i.e. for filtering fine particulate matter from air.

The filter elements may be produced by supporting a blank of a suitable material and moving the material relative to a laser which is fired at the appropriate time to produce the required pattern of apertures in the material. The aperture may be arranged in aligned or staggered rows or any other required pattern. The number of apertures/unit area will depend on the particular application of the filter element.

The profile of the apertures produced by the laser is of interest. Depending on the material of the element, the power of the laser and the time of application of the laser, the aperture may be of uniform cross-section along its length or alternatively may be narrow away from the side of the material at which the laser energy was applied. In this latter case the filter element is arranged in the filtration apparatus such that fluid flows from the wider to the narrower end of the aperture. In this way, particulate matter may enter the wider end of the aperture but is prevented from exiting through the narrower end of the aperture due to the lesser cross-sectional size thereof. This embodiment is of particular interest in the case where the filter element is an elastomeric membrane, as discussed below.

A wide range of materials may be used for the filter element, for example metals such as stainless steel. The invention is however particularly applicable to filter elements of elastomeric material, e.g. neoprene. Such elastomeric filter elements are particularly useful in the filtration apparatus described and claimed in European Patent Specification No. 0 069 528A, the disclosure of which is to be understood as being incorporated herein.

Briefly such appartus comprises a layer of porous elastomeric material mounted to be expandable on the application of fluid pressure to one side thereof, a filtration inlet and a filtration outlet respectively on opposite sides of said layer, and a fluid inlet through which an expansion fluid may be supplied to the opposite side of the layer to that to which fluid is supplied to expand said layer to remove collected solids. In a preferred embodiment of such apparatus, the elastomeric material is in the form of a sleeve mounted on a porous tubular former.

The use of a laser for producing the porous elastomeric material for the above apparatus has a number of advantages. Firstly, the methods previously used involved either the use of glass microspheres in the casting of the elastomer, which microspheres were subsequently removed to leave apertures in the elastomer, or alternatively the use of needles or the like to produce the aperatures in elastomeric sheet. The former method had the disadvantage that the microspheres would not be of uniform size, thereby leading to different sized aperture in the sheet. In the latter method, the needles or the like merely pierced the elastomer without removal of material so that, the elastomer had to be stretched to open the apertures and allow fluid to pass therethrough. In contrast, the use of a laser allows the production of apertures of a uniform size which, because the laser actually removes material, are open in the relaxed condition of the elastomer.

The use of apertures which narrow in diameter in the direction of fluid flow is particularly useful in this construction of apparatus since expansion of the layer (and thus the apertures) by use of the expansion fluid (eg gas) allows any material trapped in the aperture to be 'blown' out by the expansion fluid.

Claims

1. Filtration Apparatus comprising a filter element penetrated by a plurality of apertures produced in the material of the filter element by laser energy.

2. Apparatus as claimed in claim 1 wherein the filter element is of an elastomeric material.

3. Apparatus as claimed in claim 2 wherein the elastomeric material is mounted to be expandable on the application of fluid pressure to one side thereof, a fluid inlet and a fluid outlet are respectively provided on opposite sides of said layer, an expansion fluid inlet is provided on the same side of the layer as the fluid outlet whereby the layer may be expanded to remove collected solids.

4. Apparatus as claimed in claim 3 wherein the elastomeric material is a sleeve and is mounted on a porous tubular former.

5. Apparatus as claimed in any one of claims 1 to 4 wherein the apertures in the filter element taper along their length.

6. Filtration Apparatus substantially as hereinbefore described.

7. A filter element penetrated by a plurality of apertures produced in the material of the element by laser energy.

8. A filter element substantially as hereinbefore described.

9. A method of producing a filter element comprising using laser energy to produce a plurality of apertures in the material of the element.

10. A method of producing a filter substantially as hereinbefore described.