EP0038643A2 — Filter with backwashing device

Claim 1

Independent Claim 292 words

A self-cleaning filter assembly, for removing solids from liquid, comprising a housing; a cylindrical filter element within the housing; an inlet for introducing liquid to be filtered under pressure into the housing on the inlet side of the filter element; a filtrate outlet communicating with the outlet side of the filter element for withdrawing filtered liquid from said housing; and a solids outlet for withdrawing solids from the housing, characterised by a shower assembly disposed coaxially of the filter element, the shower assembly including an eccentric portion having close-spaced jets distributed therealong in a substantially linear array extending substantially the effective length of said filter element, said jets being aimed toward and lying close to the surface of the filtrate outlet side of said filter element for orbiting with respect thereto, in that the filter element comprises a filtering surface backed by a rigid backing shell perforated by axially close-spaced circumferential rows of holes, in that each said jet faces toward its own said circumferential row of holes to orbit into substantially coaxial alignment with successive holes of its corresponding circumferential row, the spray pattern of each jet being of vertical extent to occupy substantially the full vertical diameter of successively presented holes of its corresponding circumferential row so as to maximize the amount of backwash spray from each jet which passes through each hole to said filtering surface; by means for causing relative rotation between the shower assembly and the filter element; and by means for supplying a backwash liquid simultaneously to said jets along substantially the effective length of said filter element, under a pressure exceeding said pressure of said liquid to be filtered for continuously pushing solids off the inlet surface of said filter element in circumferentially advancing fashion.

Claim 2

Dependent Claim 292 words

A self-cleaning filter assembly, for removing solids from liquid, comprising a housing; a cylindrical filter element within the housing; an inlet for introducing liquid to be filtered under pressure into the housing on the inlet side of the filter element; a filtrate outlet communicating with the outlet side of the filter element for withdrawing filtered liquid from said housing; and a solids outlet for withdrawing solids from the housing, characterised by a shower assembly disposed coaxially of the filter element, the shower assembly including an eccentric portion having close-spaced jets distributed therealong in a substantially linear array extending substantially the effective length of said filter element, said jets being aimed toward and lying close to the surface of the filtrate outlet side of said filter element for orbiting with respect thereto, in that the filter element comprises a filtering surface backed by a rigid backing shell perforated by axially close-spaced circumferential rows of holes, in that each said jet faces toward its own said circumferential row of holes to orbit into substantially coaxial alignment with successive holes of its corresponding circumferential row, the spray pattern of each jet being of vertical extent to occupy substantially the full vertical diameter of successively presented holes of its corresponding circumferential row so as to maximize the amount of backwash spray from each jet which passes through each hole to said filtering surface; by means for causing relative rotation between the shower assembly and the filter element; and by means for supplying a backwash liquid simultaneously to said jets along substantially the effective length of said filter element, under a pressure exceeding said pressure of said liquid to be filtered for continuously pushing solids off the inlet surface of said filter element in circumferentially advancing fashion.

Claim 3

Dependent Claim 82 words

An apparatus according to claim 1, wherein the solids outlet means includes a solids outlet valve adjustable between a normal operating condition and an open condition, and control means responsive to a preselected drop in liquid pressure at the filtrate outlet with respect to the liquid pressure at the inlet for changing the solids outlet valve from its normal operating condition to its open condition to vent solids from the said housing through said solids outlet valve at a high flow rate.

Claim 4

Dependent Claim 41 words

Apparatus according to claim 2, wherein the normal position of the solids outlet valve is a partly open position preselectable for providing a flow rate therethrough in the range of from 1/10 to 1/20 of the flow rate into the inlet.

Claim 5

Dependent Claim 82 words

Apparatus according to claim 2; wherein the normal position of the solids outlet valve is closed, and including timing means for periodically opening the solids outlet valve to discharge solids from a solids collection space in the housing on an intermittent basis, the arrangement being such that the solids outlet valve is openable both by the timing means in a normal timed manner and by the control means in response to an excessive increase in solids concentration in the solids collection space.

Claim 6

Dependent Claim 77 words

' 5. Apparatus according to any of claims 2 to 4 wherein the filtrate outlet includes a filtrate outlet valve having a normally open position and a closed position, and the control means is also responsive to the drop in liquid pressure for also shifting the filtrate outlet valve to its closed position in concert with opening of the solids outlet valve to ensure that liquid leaving said housing must do so through said solids outlet means.

Claim 7

Dependent Claim 129 words

Apparatus according to any of claims 2 to 5 wherein the control means includes a time delay means in series with a pressure differential switch such that switching to one state by the pressure differential switch actuates said time delay means, the time delay means including a portion responsive to actuation of said time delay means for opening said soilds outlet valve and thereby venting solids ; through said solids outlet valve at a high flow rate such that the differential pressure switch eventually opens, the time delay means being responsive to switching to the other state by the differential pressure switch for timing a delay interval of preselected duration, after which the time delay means causes the solids outlet valve to return to its normal operating position. !

Claim 8

Dependent Claim 165 words

Apparatus according to any of the preceding claims wherein the filter element is fixed in said housing and said shower assembly is rotatably disposed therewithin, said inlet means being an inlet pipe extending substantially . tangentially of said housing to near the top end of said housing and then curving in a decreasing radius spiral to communicate with a solids collection space between said housing and filter element, over a substantial fraction of the circumference of said housing so as to direct liquid ' spiralling inward toward said filter element in one circumferential direction, said solids outlet means comprising a solids outlet pipe extending tangentially from said soilds collection space in the same circumferential direction as said liquid inlet flow, said.elongate inward spiralling inlet pipe and outlet pipe direction contributing to a centrifugal movement of solids away from the face of the filter element, said rotation of said shower assembly contributing to said centrifugal movement of solids away from the face of the filter element.

Claim 9

Dependent Claim 258 words

Apparatus according to any of the preceding claims in which said housing comprises a removable top plate closing the upper end thereof and pendently supporting said filter element within said housing, said top plate defining one said housing end wall, one end of said shower assembly extending coaxially upward through a central opening in said top plate and having an annular flange releasably fixed thereon, said top plate fixedly carrying an inner sleeve engaging said shower assembly end with liquid seal and radial thrust bearing means and supporting said annular flange of said shower assembly on axial thrust bearing means, a cup member loosely surrounding said inner sleeve and annular flange and the adjacent end of said shower assembly, said cup member being removably affixed to the upper face of said top plate, said upper shower assembly end including a backwash liquid passage communicating between the interior of said cup member and said jet means in said eccentric portion, said cup member including means connectible to a supply of backwash liquid under pressure, said housing including a bottom plate closing the bottom end thereof and defining the other said housing end wall, said bottom plate carrying seal means and radial thrust bearing means through which the drive end of said shower assembly protrudes from said housing for connection to said means for rotating said shower assembly, said top plate, filter element-and shower assembly being removable as a unit from said housing upon release of said top plate from the upper end of the peripheral wall of said housing.

Claim 10

Dependent Claim 88 words

Apparatus according to any of the preceding claims, in which the shower assembly extends substantially the full axial length of said filter element and has means delivering backwash liquid substantially in a sheet extending the full axial height of the filter element and against the interior wall of the filter element to peel solids from the exterior of the filter element in an axially extending and circumferentially advancing line, said line advancing in the same circumferential direction as the flow directions of the inlet and solids outlet flow.

Claim 11

Dependent Claim 221 words

A self-cleaning filter assembly for removing solids from an incoming liquid to be filtered, including a housing; a cylindrical filter element within said housing; an inlet for introducing liquid to be filtered under pressure into the housing on one side of said filter element; a filtrate outlet communicating with the other side of the filter element for withdrawing filtered liquid from the housing, and a solids outlet for withdrawing solids from the housing, characterised in that the filter element is mounted within said housing adjacent the inlet and with a solids collection space between the inlet and the filtering surface of the filter element and connected with the solids outlet; the filter includes backwash means for backwashing the filter and thereby for moving solids from the filtering surface of said filter element into the solids collection space; the solids outlet includes a solids outlet valve adjustable between a normal operating position and an open position; and control : means responsive to a preselected drop in liquid pressure at the filtrate outlet with respect to the liquid pressure at the inlet indicative of an excessive increase in solids concentration in the solids collection space are arranged to shift the solids outlet valve to its open position to vent the solids collection space through the solids outlet valve at a high flow rate.

Claim 12

Dependent Claim 221 words

A self-cleaning filter assembly for removing solids from an incoming liquid to be filtered, including a housing; a cylindrical filter element within said housing; an inlet for introducing liquid to be filtered under pressure into the housing on one side of said filter element; a filtrate outlet communicating with the other side of the filter element for withdrawing filtered liquid from the housing, and a solids outlet for withdrawing solids from the housing, characterised in that the filter element is mounted within said housing adjacent the inlet and with a solids collection space between the inlet and the filtering surface of the filter element and connected with the solids outlet; the filter includes backwash means for backwashing the filter and thereby for moving solids from the filtering surface of said filter element into the solids collection space; the solids outlet includes a solids outlet valve adjustable between a normal operating position and an open position; and control : means responsive to a preselected drop in liquid pressure at the filtrate outlet with respect to the liquid pressure at the inlet indicative of an excessive increase in solids concentration in the solids collection space are arranged to shift the solids outlet valve to its open position to vent the solids collection space through the solids outlet valve at a high flow rate.

Filter with backwashing device

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