Multiple-disc type filters - Patent Review 4966702

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The present invention relates to multiple-disc-filters, such as are now widely used in a number of different applications for removing solid particles from a fluid, such as dirt from water in a water irrigation system.

Briefly, the multiple-disc filter includes a housing having an inlet connectable to an upstream pipe and an outlet connectable to downstream pipe, and a stack of filter discs disposed within the housing and formed with grooved side faces for separating solid particles from the fluid flowing between the discs from the upstream side of the stack to the downstream side. Usually, the filter discs are of annular configuration, and the fluid flows in a radial direction through the stack, either radially inwardly if the outer surface of the stack faces the housing inlet, or radialy outwardly if the inner surface of the stack faces the housing inlet. Cleaning the filter can be done manually by opening the filter housing and rinsing the discs with a water spray, or automatically by including a backwash nozzle which is automatically made operative by a differential pressure device sensing the pressure drop across the stack of filter discs.

Theoretically, multiple-disc-filters have a larger capacity of removing and retaining solid particles, as compared to apertured-screen filters, before cleaning is required because of clogging. However, in practice most of the solid particles removed in multiple-disc-filters are removed and retained along the upstream edges of the discs, and even the little which penetrates into the spaces between the grooved side faces of the discs have a large tendency to clog the filter. A number of proposals have been made for increasing the capacity of multiple-disc-filters by increasing the length of the edge-filtering passageways between the filter discs. For example, British Patent No. 1,096,739 describes a multiple-disc-filter including grooved bands of zigzag shape between the discs, and U.S. Pat. No. 2,847,126 describes an arrangement including strips or fingers between discs, which fingers are of smaller thickness than the discs so as to provide a series of chambers interconnected by the clearance between the fingers for removing and retaining the dirt particles.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a multiple-disc filter having a capacity for removing and retaining large quantities of solid particles from the fluid before cleaning of the filter is required and which is operative even at relatively low pressures.

There is thus provided in accordance with a preferred embodiment of the invention a filter including a housing having an inlet connectable to an upstream pipe, and an outlet connectable to a downstream pipe; and a stack of discs disposed within the housing for separating solid particles from a fluid flowing between the discs from the upstream side of the stack to the downstream side thereof; characterized in that the stack includes:

a plurality of cooperating filter elements defining a plurality of paired co-operating filter surfaces, including a first surface having a large surface area and a second surface contacting only a portion of the large surface area of the first surface and leaving a portion of the large surface area on the upstream side of the stack not contacted thereby, at least one of said first and second surfaces being formed with grooves at the areas at which the first and second surfaces contact, thereby to form:

(a) compartments on the upstream side of the stack for accumulation of solid particles; and

(b) edge filtering passageways extending along the grooves in contact with the second surface, which passageways define the minimum size of particles separated by the filter and extend from the compartments to the downstream side of the stack.

In accordance with one embodiment of the present invention the first surface contains grooves in the areas of said compartments, which grooves communicate with the edge filtering passageways for permitting liquid flow therethrough even when the compartments become clogged.

Further in accordance with an embodiment of the present invention, the second surface contacts the first surface such that a portion of the large surface area of the first surface at the downstream side of the stack is not contacted by the second surface.

Additionally in accordance with an embodiment of the invention, both the first and second surfaces contain grooves at the areas at which the first and second surfaces contact.

In accordance with one embodiment of the invention, the plurality of filter elements includes a first plurality of filter discs interspersed with a second plurality of spacer discs.

In accordance with an alternative embodiment of the present invention the plurality of filter elements includes a plurality of filter discs having the first surface formed on one face thereof and the second surface formed on an opposite face thereof.

Additionally in accordance with an embodiment of the invention the second surface where it contacts said first surface is flat.

Further in accordance with an embodiment of the invention the area of the first surface which is not contacted by the second surface is greater than the area of the first surface which is contacted by the second surface.

Additionally in accordance with one embodiment of the present invention, the first surface has grooves extending in a generally radial direction and the second surface defines upstream edges which are mostly circumferential in orientation.

In accordance with an alternative embodiment of the invention the first surface has grooves extending in a generally circumferential direction and the second surface defines upstream edges which are mostly radial in orientation.

Further in accordance with an embodiment of the invention, the second surface defines edges in a sinuous configuration.

According to an alternative embodiment of the present invention, the second surface defines accumulator grooves which are substantially wider than the grooves of the first surface, the grooves of the first surface being contacted by the crests of the accumulator grooves and being spaced from the valleys of the accumulator grooves.

According to one embodiment of the invention, the accumulator grooves extend generally in the radial direction and the grooves in the first surface also extend generally in the radial direction but at a different angle than the accumulator grooves.

According to an alternative embodiment of the invention, the accumulator grooves extend generally in the radial direction and the grooves in the first surface extend in the circumferential direction.

Further in accordance with an embodiment of the present invention, the grooves in said first surface are tapered, thereby to define a fluid flow passageway in the narrowed region thereof even when the remainder thereof is filled with particles.

Additionally in accordance with an embodiment of the present invention, there is provided a filter including a housing having an inlet connectable to an upstream pipe, and an outlet connectable to a downstream pipe; and a stack of discs disposed within the housing for separating solid particles from a fluid flowing between the discs from the upstream side of the stack to the downstream side thereof; characterized in that the stack includes:

a plurality of cooperating filter elements defining a plurality of paired co-operating filter surfaces, including a first surface having a large surface area and a second surface contacting only a portion of the large surface area of the first surface and leaving a portion of the large surface area on the upstream side of the stack not contacted thereby, at least one of said first and second surfaces being formed with circumferentially extending grooves at the areas at which the first and second surfaces contact.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

FIG. 1 is a longitudinal sectional view illustrating one form of filter constructed in accordance with the present invention;

FIG. 2a is an enlarged fragmentary view illustrating the main elements of the filter stack in the filter of FIG. 1 according to one embodiment of the invention;

FIG. 2b is a sectional view along lines b--b of FIG. 2a;

FIG. 2c is an elnarged view along lines c--c of FIG. 2a;

FIGS. 3 and 4 illustrate two modifications in the filter of FIG. 1;

FIGS. 5a and 5b are views corresponding to FIGS. 2a and 2b but illustrating a further modification in the filter of FIG. 1;

FIGS. 6-10, 10a and 11 illustrate further variations in the structure of the filter of FIG. 1;

FIG. 12 illustrates a further construction which may be used in the filter of FIG. 1;

FIG. 12a is a section along lines a--a of FIG. 12;

FIGS. 12b and 12c illustrate the construction of each filter disc and each separator disc in the filter of FIG. 12;

FIGS. 13, 13a, 13b and 13c are views corresponding to FIGS. 12, 12a, 12b and 12c, of a further modification in the construction of the filter;

FIG. 14 is a sectional illustration of a non in-line filter which may employ filter elements in accordance with the present invention;

FIG. 15 is an illustration of a portion of a filter disc having a first surface defining grooves and a second surface which acts as a spacer;

FIG. 16 is an illustration of two stacked filter discs of the type illustrated in FIG. 15;

FIG. 17 is an illustration of two stacked filter discs of the general type illustrated in FIG. 15 but having grooved second surfaces;

FIG. 18 is an illustration of a filter disc having a first surface defining a slanted groove pattern and a second surface defining an accumulator groove pattern having an opposite slant;

FIG. 19 is an illustration of two stacked filter discs of the general type illustrated in FIG. 18;

FIGS. 20 and 21 are respective illustrations of a single filter disc and three stacked filter discs of the same configuration, each disc bearing first and second surfaces having the respective groove patterns which appear on separate discs in the embodiment illustrated in FIG. 12;

FIGS. 22, 23 and 24 are respective illustrations of a single filter disc and two stacked filter discs of the same configuration, each disc bearing first and second surfaces having the respective groove patterns which appear on separate discs in the embodiment illustrated in FIG. 13;

FIGS. 25, 26 and 27 are respective pictorial illustrations of both sides and a sectional illustration of two stacked filter discs of the same configuration, each disc bearing first and second surfaces having respective groove patterns;

FIGS. 28 and 29 are respectively a pictorial illustration of a filter disk having another configuration and a partially cut away pictorial illustration of a stack of such filter disks;

FIG. 30 is a sectional illustration of the filter disk of FIG. 28 taken along the lines A--A in FIG. 28;

FIGS. 31 and 32 are respectively a pictorial illustration of a filter disk having yet another configuration and a partially cut away pictorial illustration of a stack of such filter disks;

FIGS. 33 and 34 are respectively a pictorial illustration of a filter disk having still another configuration and a partially cut away pictorial illustration of a stack of such filter disks;

FIG. 35 is a pictorial illustration of a stack of filter disk having still another configuration; and

FIG. 36 is an illustration of a second surface of a filter disk having a plurality of upstream facing edges in generally circumferential orientation.

DETAILED DESCRIPTION OF THE DRAWINGS

The filter illustrated in FIG. 1 is of the in-line type including a housing 2 comprising an inlet 4 connectable to the upstream pipe and an outlet 6 connectable to the downstream pipe. Disposed within housing 2 is a filter body 8. The inlet includes a deflector 10 causing the inletted water to flow through inlet openings 12 to an annular chamber 14 around filter body 8, radially inwardly through the filter body 8, and then through outlet openings 16 to the housing outlet 6.

Filter body is of the multiple-disc-type, including a plurality of filter discs secured in a stack between end rings 18 and 19. Housing 2 is made of a plurality of sections which may be opened in order to provide access into the interior of the housing, and ring 19 is threadedly applied to one section to permit the filter discs of filter body 8 to be disassembled for purposes of cleaning or repair.

Such filters are well known and in extensive use today and therefore further details with respect to the construction, operation or cleaning of such filters are not necessary here.

As in the conventional multiple-disc-filter in use today, filter body 8 comprises a plurality of filter discs 20 (FIGS. 2a, 2b) of annular configuration and formed on both side faces with a plurality of grooves 22 extending generally in the radial direction; the term "generally radially" is intended to include grooves formed tangential to the opening through the filter disc, which grooved formation is also sometimes used.

In the filter illustrated in FIGS. 1, 2a and 2b, the filter body 8 further includes a plurality of spacer members 22, there being one such member interposed between each pair of adjacent filter discs 20. The spacer members are of annular configuration and are disposed to contact only the inner portion of the grooved faces of the filter discs, this being the portion of the grooved faces on the downstream side of the stack; thus, the annular spacer members 22 do not contact the outer portion of the grooved faces of the filter discs 20, which grooved faces are on the upstream side of the filter stack. The provision of spacer members 22 to cover only a portion of the grooved faces of the filter discs 20 on the downstream side of the discs produces the following effects:

(a) The spacer members form compartments 24, as shown in FIG. 2b, on the upstream side of the stack for the accumulation of solid particles removed from the fluid inletted into the housing; these solid particles tend to settle within the grooves 20a, 20b (FIG. 2c) of the filter discs 20, because there is a fluid flow through these grooves as will be described more particularly below.

(b) Spacer members 22 also form edge-filtering passageways along the upstream edges (outer edges) of the spacer members in contact with the grooved faces of the filter discs; these passageways actually define the size of th solid particles separated by the filter stack 8.

(c) The provision of spacer members 22 produce further filtering passageways in the compartments 24, these latter passageways including the spaces between the particles settling within the grooves 20a, 20b of the filter discs, and extending through these grooves to the downstream side of the stack.

It will thus be seen that there is fluid flow not only through the grooves 20a, 20b covered by the upstream (outer) edge of the spacer members 22, but also through the portion of the grooves not covered by the spacer members. Because of the latter fluid flow, the particles will tend to settle within the portions of the grooves 20a, 20b not covered by the spacer members 22. This arrangement thus provides a large surface area of the filter discs to receive and retain the separated particles, and thereby distributes the separated particles over a larger surface area than, for example, in the conventional arrangement wherein the separate particles accumulate primarily at edge-filtering passageways. Accordingly, the described arrangement enables very substantial quantities of solid particles to be separated and retained within the filter before cleaning is required.

FIG. 3d illustrates a variation wherein the spacer members 32 are also of annular configuration but each includes a plurality of radial extensions 34 extending in the upstream direction to overlie the filter discs 30. These radial extensions 34 are provided primarily for mechanical purposes, to mechanically support the outer edges of the filter discs 30.

FIG. 4b illustrates another variation, wherein the filter discs 40 are formed along their outer (upstream) edges, with a plurality of projections 44 for mechanically supporting the outer edges of the discs since their inner edges are spaced from each other by the annular spacer members 42 corresponding to members 22 in FIGS. 2a-2c.

FIGS. 5a and 5b illustrate another variation wherein the annular spacer members 52 are interposed between the grooved filter discs 50 along their outer edges. This arrangement would be used when the fluid flow is in the radial outward direction, rather than in the radial in