US4935126A — Filtering apparatus

Claim 1

Independent Claim 136 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, said fluid filter also comprising a filter aid material located within said housing and in engagement with the upstream surface of said filter element.

Claim 2

Dependent Claim 136 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, said fluid filter also comprising a filter aid material located within said housing and in engagement with the upstream surface of said filter element.

Claim 3

Dependent Claim 56 words

Apparatus according to claim 1 and wherein said filter aid is a material selected from the group consisting of diatomaceous earth, plastic-coated diatomaceous earth, diatomaceous silica, bentonites, carbon, asbestos, cellulose, perlite, pumice, pumicite, obsidian, pitchstone, volcanic ash, volcanic glass, attapulgite clay, wood pulp, fly ash, kieselguhr, a combination of perlite and diatomaceous earth, or calcium hypochlorite.

Claim 4

Dependent Claim 84 words

Apparatus according to claim 1 and also comprising a manually operable multi-flow valve having a normal position wherein fluid to be filtered is coupled to the upstream side of the filter element and a backflush position wherein fluid to be filtered is prevented from reaching the upstream side of the filter element and is directed to the means for providing a pressurized flow and wherein a backflush drain communicating with the upstream side of the filter element is coupled for draining to the atmosphere.

Claim 5

Dependent Claim 27 words

Apparatus according to claim 1 and also comprising one way valve means permitting high pressure flow to bypass the filter element from the inlet to the outlet.

Claim 6

Dependent Claim 40 words

Apparatus according to claim 4 and wherein said one way valve means comprises a first one way valve arranged between the inlet and the downstream side and a second one way valve arranged between the upstream side and the outlet.

Claim 7

Dependent Claim 38 words

Apparatus according to claim 1 and wherein said filter element defines a multiplicity of generally outwardly extending chambers which are arranged such that the jet, when impinging thereon, is at least partially directed therethrough for enhanced backflushing operation.

Claim 8

Dependent Claim 138 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said rotating head comprises at least one fluid outlet arranged to provide an eccentrically directed stream for driving the rotating head in said rotational motion.

Claim 9

Dependent Claim 138 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said rotating head comprises at least one fluid outlet arranged to provide an eccentrically directed stream for driving the rotating head in said rotational motion.

Claim 10

Dependent Claim 64 words

Apparatus according to claim 7 and wherein said backflusing means comprises inlet pressure responsive valve means operative to open in response to a selected inlet pressure so as to permit fluid flow into engagement with the upstream surface and to close in the absence of the selected inlet pressure, preventing backflow or fluid from the interior of the housing to the inlet during backflushing.

Claim 11

Dependent Claim 48 words

Apparatus according to claim 8 and wherein said inlet pressure responsive valve means includes means for providing fluid coupling between the interior of the housing adjacent the upstream surface and a backflushing outlet when the valve means closes off the fluid inlet from the interior of the housing.

Claim 12

Dependent Claim 35 words

Apparatus according to claim 8 and wherein said pressure responsive valve means comprises means for deflecting fluid entering the housing via the inlet from direct impingement with the facing upstream surface of the filter element.

Claim 13

Dependent Claim 107 words

Apparatus according to claim 7 and wherein said filter element is characterized in that the stack comprises a plurality of co-operating filter disks defining a plurality of paired co-operating filter surfaces, comprising: a first surface defining a plurality of spaced, generally circumferentially extending raised line portions separated by generally circumferentially extending grooves; and a second surface defining a plurality of generally radially extending fingers each outlined by a raised line portion, the exterior of the fingers communicating with either one of the upstream side or the downstream side and the interiors of the fingers communicating with the other one of the upstream side or the downstream side.

Claim 14

Dependent Claim 40 words

Apparatus according to claim 7 and wherein said stack of filter disks comprises a multiplicity of disk-like elements of a porous material separated by a multiplicity of grooved spacer disk elements, each spacer disk element defining generally radially extending grooves.

Claim 15

Dependent Claim 65 words

Apparatus according to claim 12 and wherein said grooves defined by each of said multiplicity of spacer disk elements comprise, on a first side of said spacer disk element, generally radially extending grooves opening to the downstream side, and on a second side of said spacer disk element, generally radially extending grooves opening to the upstream side, each of said grooves thereby defining an opening.

Claim 16

Dependent Claim 24 words

Apparatus according to claim 13 and wherein the grooves on the first side are skewed with respect to the grooves on the second side.

Claim 17

Dependent Claim 55 words

Apparatus according to claim 13 and wherein the grooves facing opposite sides of each element of porous material are arranged in mutually skewed orientation such that each groove facing a given side of the element of porous material overlaps at least two of the grooves facing the opposite side of the element of porous material.

Claim 18

Dependent Claim 48 words

Apparatus according to claim 13 and wherein the grooves define upstanding members interposing therebetween and disposed generally parallel thereto and wherein the height of each individual upstanding member tapers downwardly from a maximum, said maximum occurring adjacent the opening of the groove disposed adjacent the individual upstanding member.

Claim 19

Dependent Claim 31 words

Apparatus according to claim 13 and wherein each of the grooves is terminated at the end opposite its opening, thus requiring all fluid to pass through the element of porous material.

Claim 20

Dependent Claim 291 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stck of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, and wherein said filter element is characterized in that the stack of filter disks comprises a plurality of co-operating filter disk defining a plurality of paired co-operating filter surfaces, comprising: a first surface defining a plurality of spaced, generally circumferentially extending raised line portions separated by generally circumferentially extending grooves; and a second surface defining a plurality of generally radially extending fingers each outlined by a raised line portion, the exterior of the fingers communicating with either one of the upstream side or the downstream side and the interiors of the fingers communicating with the other one of the upstream side or the downstream side, said fluid filter also comprising a filter aid located within said housing and in engagement with the upstream surface of said filter element, and wherein said filter aid is a material selected from the group consisting of diatomaceous earth, plastic-coated diatomaceous earth, diatomaceous silica, bentonites, carbon, asbestos, cellulose, perlite, pumice, pumicite, obsidian, pitchstone, volcanic ash, volcanic glass, attapulgite clay, wood pulp, fly ash, kieselguhr, a combination of perlite and diatomaceous earth, or calcium hypochlorite.

Claim 21

Dependent Claim 291 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stck of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, and wherein said filter element is characterized in that the stack of filter disks comprises a plurality of co-operating filter disk defining a plurality of paired co-operating filter surfaces, comprising: a first surface defining a plurality of spaced, generally circumferentially extending raised line portions separated by generally circumferentially extending grooves; and a second surface defining a plurality of generally radially extending fingers each outlined by a raised line portion, the exterior of the fingers communicating with either one of the upstream side or the downstream side and the interiors of the fingers communicating with the other one of the upstream side or the downstream side, said fluid filter also comprising a filter aid located within said housing and in engagement with the upstream surface of said filter element, and wherein said filter aid is a material selected from the group consisting of diatomaceous earth, plastic-coated diatomaceous earth, diatomaceous silica, bentonites, carbon, asbestos, cellulose, perlite, pumice, pumicite, obsidian, pitchstone, volcanic ash, volcanic glass, attapulgite clay, wood pulp, fly ash, kieselguhr, a combination of perlite and diatomaceous earth, or calcium hypochlorite.

Claim 22

Dependent Claim 27 words

Apparatus according to claim 18 and wherein said raised line portion on the second surface defines a filtering barrier between the upstream side and the downstream side.

Claim 23

Dependent Claim 24 words

Apparatus according to claim 18 and wherein said raised line portion is formed with a notched configuration to define an enhanced length filtering barrier.

Claim 24

Dependent Claim 27 words

Apparatus according to claim 18 and wherein the thickness of the raised line portion on the second surface is less than the separation between adjacent line portions.

Claim 25

Dependent Claim 27 words

Apparatus according to claim 18 and wherein said raised line portion on the second surface is continuous along the entire second surface and defines a closed loop.

Claim 26

Dependent Claim 58 words

Apparatus according to claim 18 and wherein said plurality of disks comprises a plurality of first disks and a plurality of second disks, each planar surface of each of said plurality of first disks comprising a said first filter surface and each planar surface of each of said plurality of second disks comprising a said second filter surface.

Claim 27

Dependent Claim 28 words

Apparatus according to claim 23 and wherein the radially extending parts of the raised line portions on the opposite second surfaces are displaced in out of phase relationship.

Claim 28

Dependent Claim 169 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stck of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said filter element comprises a multiplicity of disk-like elements of a porous material separated by a multiplicity of grooved spacer disk elements, each spacer disk element defining axially tapered generally radially extending grooves, said fluid filter also comprising a filter aid located within said housing and in engagement with the upstream surface of said filter element.

Claim 29

Dependent Claim 169 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stck of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said filter element comprises a multiplicity of disk-like elements of a porous material separated by a multiplicity of grooved spacer disk elements, each spacer disk element defining axially tapered generally radially extending grooves, said fluid filter also comprising a filter aid located within said housing and in engagement with the upstream surface of said filter element.

Claim 30

Dependent Claim 329 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said filter element comprises a multiplicity of disk-like elements of a porous material separated by a multiplicity of grooved spacer disk elements, each spacer disk element defining axially tapered generally radially extending grooves, wherein said grooves defined by each of said multiplicity of spacer disk elements comprise, on a first side of the spacer disk element, axially tapered generally radially extending grooves opening to a downstream side, and on a second side of the spacer disk element, axially tapered generally radially extending grooves opening to an upstream side, and wherein for each spacer disk element there are defined first and second peripheral sealing rims on the first side of the spacer disk element and third and fourth peripheral sealing rims on the second side of the spacer disk element for providing sealing engagement with said porous material interposed between adjacent stacked disks, whereby fluid entering an individual one of said grooves from the upstream side of the filter element during normal filtering may only exit the groove via the porous material to the downstream side of the filter element and whereby fluid entering an individual one of said grooves from the downstream side of the filter element during backflushing can only exit the groove via the porous material to the upstream side of the filter element.

Claim 31

Dependent Claim 329 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said filter element comprises a multiplicity of disk-like elements of a porous material separated by a multiplicity of grooved spacer disk elements, each spacer disk element defining axially tapered generally radially extending grooves, wherein said grooves defined by each of said multiplicity of spacer disk elements comprise, on a first side of the spacer disk element, axially tapered generally radially extending grooves opening to a downstream side, and on a second side of the spacer disk element, axially tapered generally radially extending grooves opening to an upstream side, and wherein for each spacer disk element there are defined first and second peripheral sealing rims on the first side of the spacer disk element and third and fourth peripheral sealing rims on the second side of the spacer disk element for providing sealing engagement with said porous material interposed between adjacent stacked disks, whereby fluid entering an individual one of said grooves from the upstream side of the filter element during normal filtering may only exit the groove via the porous material to the downstream side of the filter element and whereby fluid entering an individual one of said grooves from the downstream side of the filter element during backflushing can only exit the groove via the porous material to the upstream side of the filter element.

Claim 32

Dependent Claim 111 words

Apparatus according to claim 26 and wherein said first and second rims are located at respective upstream and downstream radial locations on the first side of the spacer disk element and said third and fourth rims are located at respective upstream and downstream radial locations on the second side of the spacer disk element, said third and fourth rims each being radially offset outwardly with respect to the respective corresponding first and second rims, such that the first and third rims lie in adjacent relationship on opposite sides of the spacer disk element and the second and fourth rims lie in adjacent relationship on opposite sides of the spacer disk element.

Claim 33

Dependent Claim 19 words

Apparatus according to claim 26 and wherein said sealing rims are generally coplanar with groove-defining upstanding portions adjacent thereto.

Claim 34

Dependent Claim 21 words

Apparatus according to claim 26 and wherein each of said first, second and third rims lies opposite upstanding members defining grooves.

Claim 35

Dependent Claim 70 words

Apparatus according to claim 26 and wherein said jet comprises a concentrated, relatively high pressure flow of backflushing fluid directed to the filter element from the downstream side thereof to the upstream side thereof an wherein said nozzle assembly is arranged to be movable axially, generally parallel to the longitudinal axis such that the relatively high pressure flow sequentially engages different regions of the filter element for sequential backflushing thereof.

Claim 36

Dependent Claim 44 words

Apparatus according to claim 30 wherein said backflushing means comprises means for providing said concentrated, relatively high pressure flow and wherein said means for providing comprises a fluid discharge device arranged for axial movement along the hollow volume in communication with the downstream side.

Claim 37

Dependent Claim 29 words

Apparatus according to claim 31 and wherein said discharge device is provided with valve means which seal the discharge device when it is fully seated within the hollow volume.

Claim 38

Dependent Claim 245 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said jet comprises a concentrated, relatively high pressure flow of backflushing liquid directed to the filter element from the downstream side thereof to the upstream side thereof and wherein said nozzle assembly is arranged to be movable axially, generally parallel to the longitudinal axis, such that the relatively high pressure flow sequentially engages different regions of the filter element for sequential backflushing thereof, said filter also comprising a filter aid located within said housing and in engagement with the upstream surface of said filter element, said filter aid being selected from the group consisting of diatomaceous earth, plastic-coated diatomaceous earth, diatomaceous silica, bentonites, carbon, asbestos, cellulose, perlite, pumice, pumicite, obsidian, pitchstone, volcanic ash, volcanic glass, attapulgite clay, wood pulp, fly ash, kieselguhr, a combination of perlite and diatomaceous earth, and calcium hypochlorite.

Claim 39

Dependent Claim 245 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said jet comprises a concentrated, relatively high pressure flow of backflushing liquid directed to the filter element from the downstream side thereof to the upstream side thereof and wherein said nozzle assembly is arranged to be movable axially, generally parallel to the longitudinal axis, such that the relatively high pressure flow sequentially engages different regions of the filter element for sequential backflushing thereof, said filter also comprising a filter aid located within said housing and in engagement with the upstream surface of said filter element, said filter aid being selected from the group consisting of diatomaceous earth, plastic-coated diatomaceous earth, diatomaceous silica, bentonites, carbon, asbestos, cellulose, perlite, pumice, pumicite, obsidian, pitchstone, volcanic ash, volcanic glass, attapulgite clay, wood pulp, fly ash, kieselguhr, a combination of perlite and diatomaceous earth, and calcium hypochlorite.

Claim 40

Dependent Claim 220 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said backflushing means comprises means for providing a concentrated, relatively high pressure flow of backflushing liquid to the filter element directed from the downstream side to the upstream side and arranged to be movable axially, generally parallel to the longitudinal axis, such that the relatively high pressure flow sequentially engages different regions of the filter element for sequential backflushing thereof, wherein said means for providing comprises a fluid discharge device arranged for axial movement along the hollow volume in communication with the downstream side, and wherein said fluid discharge device comprises fluid driven means for providing rotation of the relatively high pressure flow about the longitudinal axis.

Claim 41

Dependent Claim 220 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said backflushing means comprises means for providing a concentrated, relatively high pressure flow of backflushing liquid to the filter element directed from the downstream side to the upstream side and arranged to be movable axially, generally parallel to the longitudinal axis, such that the relatively high pressure flow sequentially engages different regions of the filter element for sequential backflushing thereof, wherein said means for providing comprises a fluid discharge device arranged for axial movement along the hollow volume in communication with the downstream side, and wherein said fluid discharge device comprises fluid driven means for providing rotation of the relatively high pressure flow about the longitudinal axis.

Claim 42

Dependent Claim 22 words

Apparatus according to claim 34 wherein said fluid discharge device is manually manipulatable for providing the axial movement along the hollow volume.

Claim 43

Dependent Claim 242 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said stack of filter disks is disposed with in the housing for separating solid particles from a fluid flowing between the filter disks from the upstream side of the filter element to the downstream side thereof and characterized in that the stack comprises a plurality of co-operating filter disks defining a plurality of paired co-operating filter surfaces, comprising a first surface defining a first array of grooves, extending in a first orientation, and a second surface defining an undulating strip defining a second array of grooves facing the first array of grooves and extending in a second orientation, skewed with respect to the first orientation, one side of the undulating strip communicating with the upstream side and the other side of the undulating strip communicating with the downstream side.

Claim 44

Dependent Claim 242 words

A fluid filter comprising: a housing defining a fluid inlet and a fluid outlet; a filter element defining an upstream surface communicating with the fluid inlet and a downstream cylindrical surface communicating with the fluid outlet, the filter element comprising a stack of filter disks defining a hollow volume interiorly thereof and a longitudinal axis; and backflushing means for removing filtered out sediment from the filter element, said backflushing means comprising an axially displaceable backflushing nozzle assembly disposed within the hollow volume comprising a rotating head coupled to the fluid inlet and having fluid outlet means, arranged to provide a generally radially directed pressurized jet and rotational motion of the rotating head, wherein said stack of filter disks is disposed with in the housing for separating solid particles from a fluid flowing between the filter disks from the upstream side of the filter element to the downstream side thereof and characterized in that the stack comprises a plurality of co-operating filter disks defining a plurality of paired co-operating filter surfaces, comprising a first surface defining a first array of grooves, extending in a first orientation, and a second surface defining an undulating strip defining a second array of grooves facing the first array of grooves and extending in a second orientation, skewed with respect to the first orientation, one side of the undulating strip communicating with the upstream side and the other side of the undulating strip communicating with the downstream side.

Claim 45

Dependent Claim 73 words

Apparatus according to claim 36 and also comprising a fitler aid located within said housing and in engagement with the upstream surface of said filter element, said filter aid being selected from the group consisting of diatomaceous earth, plastic-coated diatomaceous earth, diatomaceous silica, bentonites, carbon, asbestos, cellulose, perlite, pumice, pumicite, obsidian, pitchstone, volcanic ash, volcanic glass, attapulgite clay, wood pulp, fly ash, kieselguhr, a combination of perlite and diatomaceous earth, or calcium hypochlorite.

Claim 46

Dependent Claim 85 words

Apparatus according to claim 36 and wherein said undulating strip is configured to define a plurality of generally radially extending fingers each having formed thereon a pair of spaced, generally raised line portions separated by an interior area, said second array of grooves being disposed upon the raised line portions, the exterior of the fingers communicating with either one of the upstream side or the downstream side and interiors of the fingers communicating with the other one of the upstream side or the downstream side.

Claim 47

Dependent Claim 70 words

Apparatus according to claim 38 and wherein said first surface defines a plurality of generally radially extending fingers each having formed thereon a pair of spaced, generally raised line portions separated by an interior area, the fingers of the first surface being arranged in registration with the fingers of the second surface, whereby the raised line portions and grooves of the first and second surfaces extend in overlapping mutually-skewed orientations.

Claim 48

Dependent Claim 35 words

Apparatus according to claim 39 and wherein said raised line portions and grooves of the first and second surfaces define multiple branched paths for traversal of fluid from the upstream side to the downstream side.

Claim 49

Dependent Claim 27 words

Apparatus according to claim 40 and wherein said upstream facing edge of the second surface defines a filtering barrier between the upstream side and the downstream side.

Claim 50

Dependent Claim 25 words

Apparatus according to claim 41 and wherein said engaging mutually skewed groove arrays of the first and second surfaces define an enhanced length filtering pathway.

Claim 51

Dependent Claim 25 words

Apparatus according to claim 39 and wherein the raised line portions are of generally uniform thickness, thus providing a filtering barrier of generally uniform characteristics.

Claim 52

Dependent Claim 27 words

Apparatus according to claim 39 and wherein the raised line portion on the second surface is continuous along the entire second surface and defines a closed loop.

Claim 53

Dependent Claim 23 words

Apparatus according to claim 36 and wherein said first surface defines a continuous surface and said first orientation is a circumferentially extending orientation.

Claim 54

Dependent Claim 32 words

Apparatus according to claim 36 and wherein the undulating strip is configured in the form of curved fingers, thus producing an overall strip of enhanced length to filter element surface area ratio.

Claim 55

Dependent Claim 59 words

Apparatus according to claim 36 and wherein the plurality of filter disks comprises a plurality of first disks and a plurality of second disks, each planar surface of each of said plurality of first disks comprising a said first filter surface and each planar surface of each of said plurality of second disks comprising a said second filter surface.

Claim 56

Dependent Claim 73 words

Apparatus according to claim 47 and wherein said undulating strip is configured to define a plurality of generally radially extending fingers each having formed thereon a pair of spaced, generally radially extending generally raised line portions separated by an interior area, said pairs of spaced, generally radially extending generally raised line portions on the two second surfaces of each of said plurality of second disks being displaced in mutual out of phase relationship.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-06-18	1993-12-18	1994-06-19	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-06-18	1997-12-18	1998-06-19	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-06-18	2001-12-18	2002-06-19	$7700.00	Window Closed / Lapsed

Filtering apparatus

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