Abstract: An internal ink filter (12) located within an ink jet print head (10) is formed by overlapping filter portions (100 and 102) of two laminated plates (22 and 24) that comprise the print head. Each plate includes an array of holes (120) in the filter portion. The individual holes have an opening dimension (122) such that the plates can be easily manufactured using conventional techniques, although the opening dimension may be too large for effective filtering. The plates are juxtaposed with the holes of each plate partly overlapping the holes of the other plate. The areas of overlap define a filter pore smaller than the individual holes in each plate.

Abstract: The disclosure describes an apparatus for treating fountain solution which comprises a recirculation assembly and a microporous filter assembly. The recirculation assembly disconnected between the outlet and inlet of a fountain solution tray of a printing system. The recirculation assembly includes a fountain solution sump and a return line which extends from the outlet of the fountain solution tray to the sump. The microporous filter assembly is positioned in the sump or in the return line and includes a filter position across a fountain solution flow path and having a removal rating of at least about 99.98% at about 20 microns or finer.

Abstract: A filtration membrane module submerged with processed liquid in the processing tank. Plural plate-like, rigid membrane cartridges are vertically placed in parallel to each other as properly spaced from the adjoining membrane cartridges. The cleaning stream generating means for supplying a flow parallel to the membrane surfaces of the membrane cartridges opposes the gaps between the membrane cartridges opposite to each other. The sucking means for sucking the permeated liquid in each membrane cartridge is communicated with each passage of permeated liquid in each membrane cartridge. The membrane supporting plate for retaining the filtration membrane of the membrane cartridge is made hollow using a rigid structure member.

Abstract: A gradient density filter made from sheets of blown polypropylene microfibers where the microfibers of at least one of the sheets have an effective fiber diameter less than that of the other sheets is described. This filter is especially useful in solid phase extraction processes, particularly those where biological fluids are being analyzed.

Abstract: There is provided a composite ceramic foam filter having an outer edge which is surrounded by a protective sleeve, with the outer edge of the filter being bonded to the inner surface of the sleeve. The composite is preferably made by forming a ceramic sleeve having an opening therein, and forming a ceramic foam filter of a size and shape to fit the opening in the sleeve; placing the filter into the sleeve opening thereby forming a composite; and drying and firing the composite thereby bonding the filter to the sleeve, resulting in a single piece. Alternatively, a dried foam filter could be placed into the opening of an unfired sleeve and the two pieces are then fired together.

Abstract: An inlet plate is normally connected to an extruder and formed with an inlet port for supplying a molten synthetic resin under pressure to the port and an outlet plate is normally connected to or part of a mold and is formed with an outlet port in line with and confronting the inlet port for receiving the molten synthetic resin. A movable filter support engageable snugly between the plates at the ports thereof is formed with at least two laterally offset cavities each having an inlet side against the inlet plate and an outlet side against the outlet plate. This support element can be displaced between at least two respective positions in each of which one of the cavities is aligned between the ports for flow through the one cavity therebetween. A respective filter unit in each of the cavities has a plurality of separate cells each having an outside exposed to flow from one of the ports and an inside exposed to the other of the ports.

Abstract: A liquid purification system is provided which is capable of separating a first liquid, that is wholly or partly immiscible in and forms a discontinuous phase with a second, continuous phase-forming liquid, from the second liquid, which includes at least one coalescing element or assembly for coalescing the first liquid having at least one fluid inlet at the top thereof; and at least one separating element or assembly for separating droplets of the first liquid from the second liquid, the at least one coalescing element or assembly being arranged in superposed and fluid communicable relationship above the at least one separating element or assembly

Abstract: In a method of producing spacer elements between pairs of mutually facing membrane surfaces for a fluid purifier, to minimize the number of separate parts required in the assembly of a membrane module for the fluid purifier, the sides of mutually parallel strings of spacer material are joined with the surfaces obliquely to a longitudinal extension of the surfaces. The surfaces are turned to face one another with respective parallel strings intersecting and abutting one another.

Abstract: The invention relates to an apparatus for removing dirt particles (with and without oil deposition) from water or from waste water without free oil, in particular waste water which occurs in commercial laundries after the washing of garments, work clothes and the like. It includes a closeable tank (10) which has an inflow opening (11) and at the bottom a sieve drain (12, 13), and in the interior above the drain a layer of textiles is provided which contains in particular used garments as filter.

Abstract: Devices are provided for producing plasma or serum from blood samples, where the plasma or serum is substantially free of red blood cells, hemoglobin, and metabolites and degradation products thereof. The sample can be used in various assays without interference from the interfering components of red blood cells.

Abstract: A grid structure and screen device including the grid structure are provided for a vibrating shaker for filtering solids out of a moving fluid stream passing across this screen device. The grid structure has openings defined by intersecting lines of substantially continuous solid grid lines forming an angle. The angle formed at the intersection being from between less than 90.degree. and more than 0.degree., such that the grid structure fatigued resistance is enhanced while providing maximum open area therethrough.

Abstract: Embodiments of this invention include pressure differential barrier members for separating selected substances from fluid, gaseous and/or liquid, and methods of making same. They include separation material which, with respect to the fluid to be treated, is pervious and exhibits desired separation capabilities. They may also, at least in part, include material which is substantially impervious to the fluid. They include bridges spanning flow paths to form lateral flow paths, and they may also include flow paths that are unbridged. All flow paths through such embodiments are either through structural elements which themselves have desired separation capabilities or are occupied by separation material that is pervious to the fluid being treated and is of such desired characteristics.

Abstract: The invention is directed to a filter device for the removal of coarse components from a liquid component used in the manufacture of plastic materials. The filter device has a hollow housing in which a rotor is mounted. The rotor is provided with agitator blades which comb out any dead-flow zones.

Abstract: A filter element comprising at least one coiled filter strip defining first and second butt ends, one of the butt ends being arranged to define an upstream surface during normal filtering operation, receiving fluid to be filtered, and the other of the butt ends being arranged to define a downstream surface during normal filtering operation, through which filtered fluid leaves the coiled strip.

Abstract: A two-layered filter medium for liquid filtration comprises a support composed of organic fibers of 7 .mu.m or more in diameter and basis weight of 30-150 g/m.sup.2, and a filtering layer composed of three kinds of organic fibers different in diameter, a part or all of the kind of organic fibers having the largest diameter being a fibrous organic binder.

Abstract: An orifice shield for preventing blockage of an orifice restriction by large particulate matter relative to the size of an orifice restriction in a fluid power control circuit. The orifice sheild incorporates a unitary body provided with a wire coil wound about an external threaded portion of the body. The body includes an internal blind bore and longitudinal slots which cooperate to communicate with the opening between coils of the wire. One end of the body is provided with a rotational driver receiving recess to permit external thread on the body to be threaded into a mating bore. A conventional set screw or round head bolt may be readily modified to form the one piece body portion.

Abstract: A filter assembly includes a housing having an inlet and an outlet, at least two filter elements stacked inside the housing, and a spacer positioned between the filter elements. The spacer includes a body having an opening which is larger than the inner diameter of at least one of the filter elements and is no smaller than about one-third of the outer diameter of a filter element. The spacer is free of any structure which extends into the opening.

Abstract: An apparatus and method for removing particles from refinery fluid hydrocarbon and organic streams comprising an elongated housing containing multiple layers of non-woven fabric arranged in said housing as discrete stratified layer array of filter fabric of increasing particle retentive power thus arranged in the housing in the direction of fluid flow. The fabric layer comprise thermally stable materials of different permeability which are mineral coated to provide structural, fluid compression resistance, and to which flint or talc particles are added to impact surface roughness to the fibers. A final layer of uncoated needled felt fine fabrics end caps the array. In operation the refinery fluid is passed through the filter array such that the direction of fluid flow is in the direction of increasing retentive power of the filter fabric array.

Abstract: A device for separating plasma from blood is provided comprising a synthetic polymeric fibrous structure having a CWST in excess of 65 dynes/cm, the structure having a first region for receiving a blood sample and a second region for accumulating plasma.

Abstract: An edge type filter for liquids comprises an elongated member which has spaced cylindrical portions which are a close fit within a bore in a filter body. The part of the member intermediate the cylindrical portions the member is of square section to define with the wall of the bore, controlled clearances which provide the filtering action. Grooves place alternate ones of the flow channels defined between the wall of the bore and the sides of the part with either the inlet or the outlet. The member is retained in the bore by providing on the cylindrical portion adjacent the inlet, a projecting edge which is defined at the junction of a radial end surface of the cylindrical portion and a side surface which inclines inwardly towards the surface of the cylindrical portion. At the outlet end the member is located against the end of the bore.

Abstract: A well strainer is provided which includes a plurality of stacked, annular, filter segments with each segment including a plurality of elongate, arcuate, threaded rod receiving slots, ramped bearing surfaces near each slot, and position indicators in the vicinity of the ramped bearing surfaces and slots. The gap between adjacent annular filter segments is selected by rotating one segment relative to another to a desired position whereat indicator points are received within respective indicator sockets. Guide members adjacent the ramped bearing surfaces help to keep adjacent filter segments in true superimposed relation.

Abstract: A charge containing dewaxed oil/dewaxing solvent may be treated to effect separation of components by a thermally cross-linked hydrocarbon-derived elastomer membrane, typified by polybutadiene.

Abstract: A disk-type filter comprising a housing having an inlet connectable to an upstream pipe and an outlet connectable to a downstream pipe, and a stack of filter units disposed within said housing for separating solid particles from a fluid flowing between filter units in said stack of filter units from an upstream side of said stack of filter units to a downstream side thereof, characterized in that said stack of filter units includes a plurality of co-operating filter units defining a plurality of paired co-operating filter surfaces, including first and second surfaces each defining a plurality of fingers, said fingers defined by said first surface being arranged in registration with said fingers defined by said second surface, the exteriors of said fingers defined by said first and second surfaces communicating with either one of an upstream side and a downstream side and the interiors of said fingers defined by said first and second surfaces communicating with the other one of said upstream side or downstream

Abstract: Each separator frame constitutes a single part. It is made by assembling two thermoplastic films having the shape of the seal plane and sandwiched over two different types of thermoplastic expanded structure, e.g. polyethylene grids, a first one of these structures being designed to occupy the central opening of the frame and the second type of structure being designed to occupy the diffusers. According to the invention, and prior to assembly, the first expanded structure is crushed by hot compression over its entire area apart from the central opening. This crushing reduces the thickness of the expanded structure, preferably by more than 50%. Cut-outs are formed in the first structure after it has been compressed in this way and cut-out pieces of the second expanded structure are placed therein, which pieces are themselves crushed in side strips for the purpose of retaining them in the assembly.

Abstract: A disk-type filter comprising a housing having an inlet connectable to an upstream pipe and an outlet connectable to a downstream pipe and a stack of filter units disposed within the housing for separating solid particles from a fluid flowing between filter units in the stack of filter units from an upstream side of the stack of filter units to a downstream side thereof, characterized in that the stack of filter units includes a plurality of co-operating filter units defining a plurality of paired co-operating filter surfaces, including first and second surfaces each defining a plurality of fingers, the fingers defined by the first surface being arranged in registration with the fingers defined by the second surface, the exteriors of the fingers defined by the first and second surfaces communicating with either one of an upstream side and a downstream side and the interiors of the fingers communicating with the other one of the upstream side or downstream side, spaces being defined in association with the fin

Abstract: A filter element comprising at least one coiled filter strip defining first and second butt ends, one of the butt ends being arranged to define an upstream surface during normal filtering operation, receiving fluid to be filtered, and the other of the butt ends being arranged to define a downstream surface during normal filtering operation, through which filtered fluid leaves the coiled strip.

Abstract: A coreless filter cartridge, and apparatus for adapting a filter housing to support such coreless filter cartridges. A coreless filter cartridge has an elongate array of filtering material which defines an interior cavity. The array is surrounded by a sheath of perforated paper. The ends of the array and sheath are embedded into polyurethane end-caps. The filter housing is adapted to accept coreless filter cartridges by adding a rigid, perforated standpipe that uses a bushing to fit over a housing fluid egress spud. The coreless filter cartridge is placed over the standpipe and secured in place by a retaining spider or by the housing cover, which exerts bias via a compression spring and compression cup. Gaskets on each end-cap prevent fluid by-pass and a stand-off cup is located near the base of the standpipe to provide a surface against which the end-cap gasket can seat.

Abstract: Filtering apparatus for the separation of microparticles such as bacteria has two planar sheets each with an array of laser drilled or etched pores. One or both of the sheets can be displaced relative to the other under feedback control to bring the pores into greater or lesser register. The effective pore size is thus varied to provide controlled selectivity.

Abstract: The self-cleaning filter particularly for high-viscosity pasty fluids has a fixed body having a substantially cylindrical elongated chamber in which a filtration drum is supported and defines a central region, at one end of which there is an inlet for the fluid to be filtered, and an outer annular region, at the other end of which there is a duct for the removal of the filtered fluid; a shaft is axially supported and rotationally actuated in the chamber and has a helical crest the profile whereof is suitable for grazing the inner surface of the drum to remove therefrom the impurities which are present and is suitable for pushing the fluid toward an impurity discharge duct arranged at the other end of the chamber, the constant cleaning of the drum being suitable for keeping constant the pressure drop on the filter.

Abstract: Filters, catalytic converters and the like, for separating particulate matter and/or other constituents from a stream of gas or liquid so arranged that substantially all of the fluid passing through the filter must pass through separation material which permits the passage of the fluid therethrough while separating out and retaining the selected substances. Continuums of material are arranged parallel to each other in planar arrays, with periodic spacings between the continuums in each array. Such arrays are superimposed to form a "laminated" grouping, with each continuum in each array angularly oriented with respect to and in contact with the continuums in each next adjacent array which that continuum crosses. Internal distribution paths for the fluid thereby formed by the spacings between the continuums include passageways which extend laterally within each layer and cross-array or translaminar distribution channels produced by aggregations of intersecting paths of the lateral array channels.

Abstract: The invention relates to a device for the fractionation of pulp, having a chamber (1) which has a circular cross section and has in its upper section an inlet (2) for the pulp to be fractionated and in its lower section an outlet (3) for the first fraction. In addition, the chamber (1) has a screen which is rotatable about its vertical axis (7), has a circular horizontal cross section and is closed at its ends in relation to the chamber, the screen having on its circumference a plurality of apertures and inside it an outlet (4) for the second fraction. In order to prevent clogging, the circumferential wall of the screen (5) is made up of substantially parallel laminae (8, 9), secured one above the other at a distance from one another, the outer edges of the laminae (8) being oriented obliquely downward.

Abstract: A filter for cylindrical of flat filter equipment for the mechanical purification of liquids as described which is assembled of several filter elements (4) arranged one above the other which disclose always gap-shaped filter openings between them and which are fastened by rods led through them and locking flanges. The passage openings for the rods are formed as sleeves (7) to which distance holders (8) belong. The filter elements have trapezoidal cross-section, the outer longer base side (16a) of which, together with the height of a filter opening, make out the height of the sleeve (7).

Abstract: A rotary screening device for separating unwanted solid matter such as sewage, weeds, tar globules and fish from water which is to be used for special purposes such as water cooling or other plant processes. The device comprises a rotating hollow stack of closely spaced coaxially mounted annular discs, each of which is provided with peripheral teeth upon which unwanted solid matter may be caught and carried away to a collection zone and by scraper elements engaging annular tracking surfaces between the teeth on adjacent discs. The tracking surfaces have apertures or slits to permit passage of cleaned water to the interior of the hollow stack to which may be connected stationary ducting means for conveying the cleaned water therefrom.

Abstract: A modular filter assembly is described comprising a filter stack having a plurality of filter sheets and a plurality of filter support plates each having a perimeter and an internal filter flow passageway portion. The filter sheets are sandwiched between surrounding filter support plates forming the stack and the filter flow passageway portions of the plates and filter sheets are aligned to form a filter flow passageway extending from the top to the bottom of the stack. The filter stack has engaging means capable of keeping the filter support plates together while minimized top to bottom dimension because it is not necessary to use external clamps for keeping the support plates together. Also described are support plates for modular filters and a method for forming a modular filter assembly.

Abstract: A blood oxygenator having a defoaming device for separating foam and bubbles from a liquid, such as blood, is disclosed. The defoaming device of the oxygenator is designed for separating air from blood while minimizing blood contact with the antifoam agent used in the device. In a first embodiment, the device includes a reservoir and a filtering material that does not contain any antifoaming agent. This filtering material is positioned in a lower portion of the reservoir to separate foam and bubbles from the liquid. An element containing an antifoaming agent is positioned in the reservoir above the maximum surface fluid level therein and receives the foam and bubbles that rise from the filtering material. Contact of the liquid with the antifoaming agent is substantially avoided. In a second embodiment, an element containing an antifoaming agent is positioned in the reservoir within the fluid therein.

Abstract: In a filter device with a filter stack (32) which is held in sealing position by two end plates (9, 2). At least one of which comprises fluid connections (3, 4, 5), and consists of round flat-filter elements (41) and alternatingly arranged, congruent, draining support elements (38), the end plate (2) comprising the fluid connections (3, 4, 5) is part of a housing (1, 2) surrounding the filter stack (32) and the peripheral approach flow of the filter stack (32) takes place via an annular housing space (11). The filter stack (32) is penetrated approximately in the direction of its diameter by a slot-like shaft (30, 30') for the fluid guidance of the retentate which shaft empties in the end plate (2) comprising the fluid connections (3, 4, 5). At least one permeate shaft (31) for removing the permeate from the plane of the filter elements (41) is arranged in the diametric end area of the stack surface. The permeate shafts (31) empty in the end plate (2) with connections (3, 4, 5).

Abstract: A filter nozzle equipped with annular filter discs which establish flow paths (26, 28), serving to conduct the filter liquid and which paths are radial (28) and also penetrate through (26) the filter discs (18). These passages (26) through the filter discs (18) are in themselves formed as passages (26) that become narrow in the flow direction of the filtered water, and are distributed uniformly over the disc (18). The discs (18) have projections which ensure that the passages (26) of two adjacent discs are not in alignment. With such a filter nozzle, the danger of blockage is much less than with known nozzles, assuring a steady operation and requiring less frequent cleaning.

Abstract: A disk-type filter comprising a housing having an inlet connectable to an upstream pipe and an outlet connectable to a downstream pipe, and a stack of filter units disposed within said housing for separating solid particles from a fluid flowing between filter units in said stack of filter units from an upstream side of said stack of filter units to a downstream side thereof, characterized in that said stack of filter units includes a plurality of co-operating filter units defining a plurality of paired co-operating filter surfaces, including first and second surfaces each defining a plurality of fingers, said fingers defined by said first surface being arranged in registration with said fingers defined by said second surface, the exteriors of said fingers defined by said first and second surfaces communicating with either one of an upstream side and a downstream side and the interiors of said fingers defined by said first and second surfaces communicating with the other one of said upstream side or downstream

Abstract: A pool filter with a housing having at least one opening for an inlet and at least one additional opening for an outlet, in which housing at least one filter pad in contact with its margins is arranged with both its sides freely accessible such that one side of the pad is connected to an inlet chamber and the other side of the pad to an outlet chamber, is configured for the purpose of easy adaptability to various filter capacity and fineness requirements and for easy handling and maintenance such that the housing includes a plurality of flatly stackable housing elements each with at least one filter pad which form terminal units and intermediate units of a pool filter set, the intermediate units being configured identical to one another and having next to the filter pad a bottom for separating the inlet chamber and outlet chamber of adjacent filter pads.

Abstract: A disc-type 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; andb) edge filtering passageways extending along the grooves in co

Abstract: A well structure suitable for use as a shallow well having a large diameter includes a well curb, and one or more water intake segments mounted in a part of the well curb. Each water intake segments includes a frame made of a vertically arranged pair of flanges extending in the circumferential direction and a laterally arranged pair of flanges extending in the axial direction, the frame having a form which constitute a part of a cylinder, a screen element such as wires and wire supporting rods secured to the frame, and one or more reinforcing members secured at ends thereof to either of the vertically arranged pair of flanges or the laterally arranged pair of flanges for reinforcing the frame.

Abstract: A spacer element for guiding flowing medium, especially for apparatus for separating the medium by reverse osmosis and ultrafiltration, with a respective filter element being accommodated between each two essentially plate-like spacer elements, about which the medium flows. The spacer element includes a plate member having a rim region in which is provided at least one passage for the flowing medium. The plate member has two oppositely disposed plate-like surfaces, on at least one of which are disposed a plurality of raised bosses that project from the surface, with the filter element resting on the bosses. The filter element is in the form of a diaphragm pad, with the medium flowing on both sides thereof.

Abstract: A filter cartridge comprising a framework and a surrounding envelope of filter material. The framework is reusable and provided with a rough, granular surface texture to provide increase surface area available for the propagation of aerobic bacteria. The envelope is disposable. Thus, biological filtration of the water provided by the aerobic bacteria is not interrupted upon replacement of the filter material. A second filter medium may be disposed within the envelope. The envelope is held in place by a pair of flaps which sandwich an edge of the filter material.

Abstract: This invention relates to a filtering apparatus for filtering liquids, in particular beverages. To attain an effective seal between two superimposed filter supports and the associated filter bodies in such a filtering apparatus, the upper side of an underlying filter support has formed therein a groove which opens upwards and has a substantially trapezoidal cross section and whose interior groove wall is substantially parallel to the inner wall of the apron of the filter support respectively lying thereabove, and the profiled seal has, on the whole, a substantially rectangular cross section, with the profiled seal portion supported on the respectively lower filter support being adapted to the cross section of the groove.

Abstract: A double filtering filter for lubricating oil of internal combustion engines of motor vehicles comprises a cylindrical housing containing a rough filtering cartridge and a superimposed fine filtering cartridge, both in form of cylindrical sleeves and fitted over a tube extending within the rough filtering cartridge from a cover of said housing. A cover is provided with a plurality of peripheral inlet holes for the oil to be filtered, an axial hole for the outlet of the roughly filtered lubricant, and an intermediate radial hole for the outlet of the finely filtered lubricant. The filter further comprises an annular seal gasket on the tube between said two cartridges, and a pair of annular seal gaskets on the cover, one gasket being positioned outside said plurality of peripheral holes for the inlet of the lubricating oil, and the other gasket being positioned between said eccentric outlet hole and said axial outlet hole.

Abstract: A multiple-disc filter body for separating solid particles from a fluid flowing through the filter body from its inlet side to its outlet side, comprises a stack of filter discs in which the side faces of each pair of adjacent discs are formed with ribs of at least two different heights such as to define filtering passageways of a larger size on the inlet side of the filter stack and filtering passageways of a smaller size on the outlet side of the filter stack in series with the larger-size filtering passageways, whereby coarse particles are first separated by the fluid in the larger size filtering passageways, and then finer particles are separated from the fluid in the smaller size filtering passageways.

Abstract: A filter plate which is longitudinally partitioned between its inlet and outlet ends, and features liquid feed and collection troughs at the respective ends. Such plates may be associated in opposed, relatively inverted pairs to form enclosed flow channels characterized by fluid flow rates which are substantially uniform across the full transverse extent of the flow path and which facilitate the utilization of the full areal extent of the filter media employed therewith. Also described is a unitary filter element which may be usefully employed in the filter. The filter of the invention may be highly efficiently employed for dewatering of aqueous biomass suspensions, desalting of proteins, removal of secreted metabolites from cellular suspensions, and the like.

Abstract: A filter element comprising at least one coiled filter strip defining first and second butt ends, one of the butt ends being arranged to define an upstream surface during normal filtering operation, receiving fluid to be filtered, and the other of the butt ends being arranged to define a downstream surface during normal filtering operation, through which filtered fluid leaves the coiled strip.

Abstract: A high efficiency filter and method for its production. An array of tube-type sleeves, each sleeve composed of a filtering medium and joined longitudinally along its exterior surface to the adjacent sleeve, is expandably fixed into a framework and all margins of the array are sealed to the framework in order that a fluid passing orthogonally through the plane of the array and its frame must pass through at least two filtering surfaces. The process and machine used to make the aforementioned product start with a relatively narrow roll of filtration media and, through a series of steps, form, cut and glue the media so as to form the requisite sleeve structure and then by means of controlled curing, affix a predetermined number of the sleeves in to the desired array.

Abstract: A filter including a plurality of filter discs each formed with a central opening and disposed in a stack within a filter housing with the side faces of adjacent discs contacting each other for filtering the fluid flowing through the housing from its inlet to its outlet, the filter discs being maintained in a stack by a plurality of axially-extending rods arranged in a circular array around the outer faces of the discs and circumferentially spaced from each other to permit the filter disc stack to be cleaned by passing a cleaning nozzle through the central openings of the filter discs in the stack.