GB2190008A - Improvements relating to filters - Google Patents

Abstract

A filter has an adjustable size chamber containing a resilient porous filter medium whose effective pore size is altered by adjusting the chamber size to squeeze the medium. The medium may be a plurality of rubber or resilient plastics balls, and they may be graded in size and/or hardness so that the filter becomes progressively finer towards the outlet end. Alternatively the medium may be open-cell foam material.

Description

SPECIFICATION Improvements relating to filters This invention relates to filters.

Most filters have a set mesh size which cannot be altered, or at least not unless the assembly is partially dismantled and one element exchanged for another.

Another problem is cleaning. Most filters can be cleaned to a certain extent by backwashing, but this does not guarantee complete removal of all deposits.

The alternative is again to take the filter apart and laboriously clean a fine pore screen or equivalent element.

It is the aim ofthis invention to provide a filter where the effective mesh size can be readily altered without any dismantling, and one which is also simple and straightforward to clean.

According to the present invention there is provided a filter comprising an enclosure of adjustable size with an inlet and outlet and containing a resilient porous mass providing interstices through which fluid can pass when flowing from inlet to outlet and whose porosity is variable by adjustment of size of the enclosure.

In one preferred form the mass is a plurality of discrete bodies whose closest packing leaves said interstices.

The i nte rstice sizeis a Itera ble by adjusting the volume of the enclosure. In particular, as that is reduced, so the bodies are squeezed and deformed to increase the packing density and reduce the size of the fluid passages.

Conveniently, the bodies are balls of rubber or resilient plastics material. They may be of uniform size, orthey may be non-uniform. In the latter case, the larger ones may be disposed adjacent the inlet while the smaller ones are adjacent the outlet, with perhaps graduated sizes in between. Thus, the filterwill first stop large particles and then progressively smaller ones as a suspension advances through the filter.

There may also be differences in resilience. In particular, the harder balls may be disposed adjacent the inlet while the softer ones are adjacent the outlet, again perhaps with graduated ones in between. If they are all ofthe same size, then with no pressure applied thefilterwill be uniform throughout. But asthey are squeezed, so the interstices nearthe outletwill be restricted more than those near the inlet and the effect will be to trap coarse particlesfirstand then progres sivelysmallerones. As the pressure on the balls increases so the differential between the interstices adjacent the inlet and outletwill also increase.

These balls of different character may be separated by coarse mesh screens so that when the enclosure is opened forcleaning the balls can be keptseparate and replaced correctly.

In anotherform the mass may be formed by at least one block of open cell foam. When there are two or more such blocks, they may have different cell structure and be arrangedforfluidtoflowthrough them in sequence.

The shape ofthe enclosure may take many different forms, but the simplestwill probably be a cylinder with one of the circular end walls movable axially into the cylinder to compress the resilient balls. It will be preferred to have either the inlet orthe outlet in this movable end wall,with the outletorthe inlet respectively in the opposite end wall.

There is a tendency for a body or mass, when squeezed by such a movable wall, to compress more in the region ofthatwall than elsewhere. Thus, even with a uniform mass of balls or block offoam, a suitably graduated filter may be obtained by having theoutletwall asthemeansbywhichthevolume Is varied.

For cleaning the filter otherthan by backwashing, the movable wall is conveniently made entirely removable and the resilient mass maythen be taken outandwashed. Fortheballs,atumbling action should help remove all traces of deposits. If cleaning by backwashing is carried out, the compression on the mass may be released entirely and even beyond so that if balls constitute the mass, they will be loose within the enclosure. The turbulence created by backwashing can then knockthe balls around, their mutual inpingement helping to dislodge any deposits.

1. Afiltercomprising an enclosure of adjustable size with an inlet and outlet and containing a resilient porous mass providing interstices through which fluid flowing from inletto outlet must pass and whose porosity is variable by adjustment of size ofthe enclosure.

2. A filter as claimed in Claim 1,wherein the mass is a plurality of discrete bodies whose closest packing leaves said interstices.

3. Afilteras claimed in Claim 2, wherein the bodies are balls of rubber or resilient plastics material.

4. Afilter as claimed in Claim 2 or 3, wherein the bodies are of uniform size.

5. Afilter as claimed in Claim 2 or3, wherein the bodies are of non-uniform size, the larger ones being disposed adjacentthe inlet and the small ones adjacent the outlet.

6. Afilter as claimed in any preceding claim, wherein the bodies are of uniform resilience.

7. Afilter as claimed in any one of Claims 2 to 5, wherein the bodies are of non-uniform resilience the harder ones being disposed adjacent the inlet and the softer ones adjacent the outlet.

8. Afilterasclaimed in Claim 5 or 7, wherein the bodies of different character are sepa rated by coarse mesh screens.

9. Afilteras claimed in Claim 1 ,wherein the mass isformed by at least one block of open cell foam.

10. Afilteras claimed in Claim 9, wherein there are two or more such blocks with different cell structures arrangedforfluidtoflowthroughthem in sequence.

11. A filter as claimed in any preceding claim, wherein the adjustable size is provided by a movable wall of the enclosure.

12. Afilter as claimed in Claim 1 1,whereinthe movable wall contains the inlet or outlet and the opposite wall contains the outlet or inlet, respectively.

13. A filtersubstantially as hereinbefore described.

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

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements relating to filters This invention relates to filters. Most filters have a set mesh size which cannot be altered, or at least not unless the assembly is partially dismantled and one element exchanged for another. Another problem is cleaning. Most filters can be cleaned to a certain extent by backwashing, but this does not guarantee complete removal of all deposits. The alternative is again to take the filter apart and laboriously clean a fine pore screen or equivalent element. It is the aim ofthis invention to provide a filter where the effective mesh size can be readily altered without any dismantling, and one which is also simple and straightforward to clean. According to the present invention there is provided a filter comprising an enclosure of adjustable size with an inlet and outlet and containing a resilient porous mass providing interstices through which fluid can pass when flowing from inlet to outlet and whose porosity is variable by adjustment of size of the enclosure. In one preferred form the mass is a plurality of discrete bodies whose closest packing leaves said interstices. The i nte rstice sizeis a Itera ble by adjusting the volume of the enclosure. In particular, as that is reduced, so the bodies are squeezed and deformed to increase the packing density and reduce the size of the fluid passages. Conveniently, the bodies are balls of rubber or resilient plastics material. They may be of uniform size, orthey may be non-uniform. In the latter case, the larger ones may be disposed adjacent the inlet while the smaller ones are adjacent the outlet, with perhaps graduated sizes in between. Thus, the filterwill first stop large particles and then progressively smaller ones as a suspension advances through the filter. There may also be differences in resilience. In particular, the harder balls may be disposed adjacent the inlet while the softer ones are adjacent the outlet, again perhaps with graduated ones in between. If they are all ofthe same size, then with no pressure applied thefilterwill be uniform throughout. But asthey are squeezed, so the interstices nearthe outletwill be restricted more than those near the inlet and the effect will be to trap coarse particlesfirstand then progres sivelysmallerones. As the pressure on the balls increases so the differential between the interstices adjacent the inlet and outletwill also increase. These balls of different character may be separated by coarse mesh screens so that when the enclosure is opened forcleaning the balls can be keptseparate and replaced correctly. In anotherform the mass may be formed by at least one block of open cell foam. When there are two or more such blocks, they may have different cell structure and be arrangedforfluidtoflowthrough them in sequence. The shape ofthe enclosure may take many different forms, but the simplestwill probably be a cylinder with one of the circular end walls movable axially into the cylinder to compress the resilient balls. It will be preferred to have either the inlet orthe outlet in this movable end wall,with the outletorthe inlet respectively in the opposite end wall. There is a tendency for a body or mass, when squeezed by such a movable wall, to compress more in the region ofthatwall than elsewhere. Thus, even with a uniform mass of balls or block offoam, a suitably graduated filter may be obtained by having theoutletwall asthemeansbywhichthevolume Is varied. For cleaning the filter otherthan by backwashing, the movable wall is conveniently made entirely removable and the resilient mass maythen be taken outandwashed. Fortheballs,atumbling action should help remove all traces of deposits. If cleaning by backwashing is carried out, the compression on the mass may be released entirely and even beyond so that if balls constitute the mass, they will be loose within the enclosure. The turbulence created by backwashing can then knockthe balls around, their mutual inpingement helping to dislodge any deposits. CLAIMS

1. Afiltercomprising an enclosure of adjustable size with an inlet and outlet and containing a resilient porous mass providing interstices through which fluid flowing from inletto outlet must pass and whose porosity is variable by adjustment of size ofthe enclosure.

2. A filter as claimed in Claim 1,wherein the mass is a plurality of discrete bodies whose closest packing leaves said interstices.

3. Afilteras claimed in Claim 2, wherein the bodies are balls of rubber or resilient plastics material.

4. Afilter as claimed in Claim 2 or 3, wherein the bodies are of uniform size.

5. Afilter as claimed in Claim 2 or3, wherein the bodies are of non-uniform size, the larger ones being disposed adjacentthe inlet and the small ones adjacent the outlet.

6. Afilter as claimed in any preceding claim, wherein the bodies are of uniform resilience.

7. Afilter as claimed in any one of Claims 2 to 5, wherein the bodies are of non-uniform resilience the harder ones being disposed adjacent the inlet and the softer ones adjacent the outlet.

8. Afilterasclaimed in Claim 5 or 7, wherein the bodies of different character are sepa rated by coarse mesh screens.

9. Afilteras claimed in Claim 1 ,wherein the mass isformed by at least one block of open cell foam.

10. Afilteras claimed in Claim 9, wherein there are two or more such blocks with different cell structures arrangedforfluidtoflowthroughthem in sequence.

11. A filter as claimed in any preceding claim, wherein the adjustable size is provided by a movable wall of the enclosure.

12. Afilter as claimed in Claim 1 1,whereinthe movable wall contains the inlet or outlet and the opposite wall contains the outlet or inlet, respectively.

13. A filtersubstantially as hereinbefore described.