Cleaning assembly for use in fluid filtration systems
Cleaning assemblies and particulate tolerant fluid bearings that are particularly well suited for use in centrifugal separation enhanced filtration devices are described. In one aspect of the invention, at least one bearing is arranged to carry a circulating cleaning assembly such that the cleaning assembly can rotate around a filter membrane during filtering operation of the filtration device. The bearing is preferably arranged to maintain the circulating cleaning assembly in a substantially coaxial alignment with the filter membrane and in a substantially stable longitudinal position relative to the filter membrane as the circulating cleaning assembly is rotated around the filter membrane. In another aspect of the invention a variety of particulate tolerant bearings are described.
1. A centrifugal separation enhanced filtration device comprising:
a tank having a fluid inlet, a filtered fluid outlet, an effluent outlet and an internal chamber having an internal chamber wall;
a filter membrane positioned within the internal chamber, there being a fluid circulating region in a space between the internal chamber wall and the filter membrane;
a circulating cleaning assembly positioned in the fluid circulating region between the chamber wall and the filter membrane, wherein the circulating cleaning assembly includes at least one cleaning element arranged to clean the filter membrane when rotated about the filter;
at least one bearing that carries the circulating cleaning assembly and is arranged to enable the circulating cleaning assembly to rotate around the filter membrane during filtering operation of the filtration device, wherein the at least one bearing is arranged to maintain the circulating cleaning assembly in a substantially coaxial alignment with the filter membrane and in a substantially stable longitudinal position relative to the filter membrane as the circulating cleaning assembly is rotated around the filter membrane; and
wherein the at least one bearing includes a bearing plate arranged to rotate together with the circulating cleaning assembly, wherein the bearing plate is journaled about a race.
2. A filtration device as recited in claim 1 wherein the bearing plate includes a central opening that is faces the race and a plurality of throughholes in a main body portion of the plate that permit particulates to pass between opposite sides of the bearing plate.
3. A filtration device as recited in claim 1 wherein:
the bearing plate is sandwiched between a pair of adapter plates that constrain axial movement of the bearing plate; and
the race is integrally formed with one of the adapter plates.
4. A filtration device as recited in claim 1 wherein:
each bearing of the at least one bearing has a plurality of circumferentially spaced apart cleaning structure support arms; and
the cleaning assembly includes a plurality of distinct cleaning structures that are carried by the bearing, each cleaning structure including an associated cleaning element arranged to swipe over or against the filter membrane to clean the filter membrane as the cleaning assembly rotates relative to the filter.
5. A filtration device as recited in claim 4 wherein each cleaning structure includes a clip arranged to snap into the bearing and the cleaning element is selected from the group consisting of:
a brush that contacts the filter membrane;
a squeegee that contacts the filter membrane; and
a structure that does not physically contact the filter membrane but causes sufficient agitation of fluid located between the cleaning structure and the filter to effectively clean the surface of the filter.
6. A filtration device as recited in claim 1 wherein the cleaning assembly includes a plurality of paddles positioned such that at least one of a fluid inlet stream and circulatory motion of a fluid within the fluid circulating region drives the rotation of the cleaning assembly.
7. A filtration device as recited in claim 1 wherein the at least one bearing includes a first bearing and a second bearing that is spaced apart from the first bearing, the first and second bearings being arranged to carry the circulating cleaning assembly and cooperate to maintain the circulating cleaning assembly in a substantially coaxial alignment with the filter assembly and in a substantially stable longitudinal alignment with the filter assembly as the circulating cleaning assembly is rotated around the filter assembly.
8. A filtration device as recited in claim 7 wherein each bearing of the first and second bearings includes including a support ring and a multiplicity of flexible resilient members extending inward from the support ring.
9. A filtration device as recited in claim 1 wherein the at least one bearing is formed from a lubricious material selected from the group consisting of: (a) an oil impregnated polyethylene; and (b) polyoxymethylene.
10. A filtration device as recited in claim 1 configured as a hydroclone filtration device, wherein:
the tank has a substantially frusto-conical section;
during operation, a vortex is formed about the filter membrane; and
the filter membrane is part of a filter assembly that has a filtered fluid chamber located in a central region of the vortex.
11. A filtration device as recited in claim 1 configured as a cylindrical centrifugal separation enhanced filtration device, wherein:
the tank has a substantially cylindrical section;
the filter membrane is part of a filter assembly positioned within the substantially cylindrical section; and
during operation, a feed liquid to be filtered circulates around the filter membrane.
12. A filtration device as recited in claim 1 wherein the filter membrane is a surface filter membrane.
13. A filtration device as recited in claim 1 wherein the filter membrane is positioned within the tank such that the filter membrane acts as a cross-flow filter during filtering operation of the filtration device.
14. A filtration device as recited in claim 1 wherein:
the filter membrane is a surface filter that is part of a filter assembly positioned within the tank and the flow of a liquid fluid being filtered rotationally circulates around the filter membrane such that the filter membrane acts as a cross-flow filter; and
during filtering operation of the filtration device the cleaning assembly is driven rotationally about the filter membrane by the flow of the liquid fluid about the filter assembly and the cleaning elements sweep over or against the surface of the surface filter to help dislodge particulates that are trapped by pores in the filter membrane.