Backwashing-type filtering apparatus

A filtering apparatus suitable for being cleaned by backwashing includes an outer housing (11) and an inner filter (13) disposed in the outer housing defining an outer annular flow passage (16) and an inner flow passage (17). The outer housing is tapered in relation to the external shape of the filter to provide a substantially uniform liquid velocity through the filter in both forward flow and backflow directions. The filter is made up of a plurality of ring-like segments (38) stacked end to end on which a filter medium (37) is mounted.

What is claimed is:

1. In a filtering apparatus for removing solid particles and the like from a liquid adapted to be cleaned by backwashing, the combination comprising:

an outer housing and an inner filter disposed within the outer housing defining therebetween an annular outer flow passage,

said filter having an inner flow passage and having an outer face and an inner face with liquid flow openings extending between said outer and inner faces through which the liquid flows to pass between said inner and outer flow passages whereby a forward flow liquid with solid particles is passed through an inlet into said outer flow passage, the solid particles being deposited on said filter and the liquid passing through the filter openings into and along said inner flow passage and out an outlet in said inner flow passage in the forward flow direction, and whereby a backwash liquid is passed into and along said inner flow passage, through said filter openings, and into said outer flow passage to remove solid particles collected on said filter in a backflow direction,

said outer housing having an internal dimension related to the external dimension of said inner filter so that said outer flow passage changes in dimension along the filter surface that has said liquid flow openings in such a way as to provide substantially a uniform liquid velocity through said filter at all points along said filter in both said forward flow direction and said backflow direction,

said outer housing being tapered along its length to converge in a direction away from said inlet toward said outlet in the forward liquid flow direction and wherein said inner filter has a substantially uniform external dimension substantially throughout its lengthwise extent.

2. In a filtering apparatus as set forth in claim 1 wherein said outer housing has a tapered shell, an outlet pipe reducer of lesser internal dimension on the outlet end of said shell, and an outlet pipe and on the end of said pipe reducer with a peripheral groove for releasably coupling said shell to an adjacent flow control valve housing.

3. In a filtering apparatus as set forth in claim 2 including an O-ring between said filter and said outlet pipe reducer to close the annular outer passage at the outlet end to flow in the axial direction.

4. In a filtering apparatus as set forth in claim 2 wherein said outer housing has an inlet pipe end connected at the inlet end, said inlet pipe end having a peripheral groove for releasably coupling said tapered shell to an adjacent flow control valve housing.

5. In a filtering apparatus as set forth in claim 1 wherein said filter has a front end plate, said front end plate having an end support that carries a dome-shaped deflector plate to direct an incoming liquid at the inlet moving in the forward flow direction into said outer flow passage.

6. In a filtering apparatus as set forth in claim 5 wherein the inlet end of said filter is supported by relatively thin, flat plates extending radially out from the deflector plate to a retaining ring disposed within an inner slot in said inlet pipe end.

7. In a filtering apparatus as set forth in claim 1 wherein said filter includes an inner support grid having a plurality of liquid flow openings extending between the outer and inner faces to pass a liquid therethrough and a filter medium mounted on said support grid between said inner and outer flow passages.

8. In a filtering apparatus adapted for being cleaned by backwashing, the combination comprising:

a hollow filter with an inner flow passage closed at an inlet end to flow in an axial direction and open at an outlet end to flow in the axial direction, said hollow filter having an outer face and an inner face with a plurality of liquid flow openings extending between said outer and inner faces; and

a filter medium forming said outer face, and an inner support grid defining said inner face and supporting said filter medium,

said hollow filter being disposed in an outer housing to define an outer annular flow passage between said outer housing and said filter and having an inlet,

whereby a liquid with solid particles to be filtered therefrom is passed through said inlet into said outer annular flow passage and between said outer and inner faces through said openings, the solid particles collecting on the outer surface of said filter medium and said liquid passing through said inner flow passage and out said outlet in a forward flow direction, and

whereby a backwashing liquid is passed back through said outlet, into said inner passage, between said inner and outer faces through said openings, through said outer passage, and out said inlet in a blackflow direction to remove particles collected on said medium in a backwashing operation,

said outer housing being tapered along its length in relation to the external dimension of said hollow filter along the filter face that has said liquid flow openings so that said outer flow passage between said outer housing and said inner filter along the filter face that has said liquid flow openings converges in the direction away from said inlet to provide a decrease in liquid velocity and an increase in liquid pressure in the direction away from said inlet during a forward flow of liquid and, conversely, an increase in liquid velocity and a decrease in liquid pressure in the direction toward said inlet in said outer flow passage during the backflow,

said taper providing substantially the same pressure drop between said outer face and said inner face of said filter along substantially the lengthwise extent of said filter face that has said liquid flow openings during both said forward flow operation and said backflow operation,

said outer housing being tapered along its length to converge in a direction away from said inlet toward said outlet in the forward liquid flow direction and wherein said inner filter has a substantially uniform external dimension substantially throughout its lengthwise extent.

9. In a filtering apparatus for removing solid particles and the like from a liquid adapted to be cleaned by backwashing, the combination comprising:

an outer housing and an inner filter disposed within the outer housing defining therebetween an annular outer flow passage,

said filter having an inner flow passage whereby a forward flow liquid with solid particles is passed through an inlet into said outer flow passage, the solid particles being deposited on said filter and the liquid passing through the filter into and along and out an outlet in said inner flow passage in the forward flow direction, and whereby a backwash liquid is passed into said inner flow passage, through said filter, and into said outer flow passage to remove solid particles collected on said filter in a backflow direction,

said outer housing having an internal dimension related to the external dimension of said inner filter so that said outer flow passage changes in dimension along the filter in such a way as to provide substantially a uniform liquid velocity through said filter at all points along said filter in both said forward flow direction and said backflow direction,

said outer housing being tapered along its length to converge in a direction away from said inlet toward said outlet in the forward liquid flow direction and wherein said inner filter has a substantially uniform external dimension substantially throughout its lengthwise extent.

10. In a filtering apparatus as set forth in claim 9 wherein said outer housing and said inner filter have a circular transverse cross section.