WO2009109955A2

WO2009109955A2 - High viscosity fluid filter and filtering device

Info

Publication number: WO2009109955A2
Application number: PCT/IL2008/000305
Authority: WO
Inventors: Raanan Ben Horin; Itai Pomerantz
Original assignee: Arkal Filtration Systems C.S. Ltd.
Priority date: 2008-03-06
Filing date: 2008-03-06
Publication date: 2009-09-11
Also published as: WO2009109955A3; TW200946203A

Abstract

A device for viscous fluid filtration comprising a first chamber adapted to receive viscous fluid, a second chamber adapted to receive filtered viscous fluid, and a filter between the outer and inner chambers, wherein the filter comprises a set of tightly stacked filtering elements.

Description

HIGH VISCOSITY FLUID FILTER AND FILTERING DEVICE

FIELD

The invention relates to filtration systems for removing particulate material from fluids, such as oils and emulsions.

BACKGROUND

Oils and emulsions are typically used in systems where equipment and other system components require lubrication and/or cooling of parts comprised in the components. In machining operations, for example, they are frequently also used for lubricating and cooling a workpiece being machined. Lubrication generally protects the surfaces of the parts from deterioration as a result of friction, wear, and/or corrosion. Cooling generally protects the parts and the workpiece from deterioration due to thermal stress. An important function of the oils and/or emulsions used in machining processes is to collect and remove particulate (particles) that are formed during the processing. The removal of the particulates from the contact point(s) between a cutting tool and the workpiece prevents the particulates from interrupting (for example by blocking passes between the tools and the workpiece) during the cutting process. By properly selecting the oil or the emulsion which will be used as a lubricant, particulate removing media and/or coolant, hereinafter referred to as "fluid", it is possible to reduce damage in the equipment and other system components, and/or in the workpiece. Consequently, the probability of failure of the system components is reduced, and the system benefits from an increased reliability.

Particle contamination in fluids is a common problem, and may be a major contributor to failure in equipment and/or other system components. Although particle contamination generally exists in new oils and emulsions, usually, the level of contamination is substantially greater in a fluid which is reused in a system. Reusing of fluids is a relatively common practice as it may afford substantial cost savings in a production process. The fluid is generally collected in a collection tank, or a plurality of tanks, Which may be located at the end of the system, and/or optionally in different points throughout the system. The collected fluid, prior to being reused back into the system, is typically filtered to remove particles, which may have accumulated in the fluid while flowing through different portions of the system. An example of how particle contamination occurs may be seen in machining operations, where relatively large chips, micro chips and other sized and/or shaped particles may separate from a cutting tool and/or a grinding tool, and from a workpiece, and find their way into the fluid used to lubricate and/or cool the workpiece. The fluid used to lubricate and/or cool the workpiece, including the particles, is generally collected into a tank after use for reusing.

The rate at which failure may occur in equipment and/or system components is generally dependent on the quantity and the size of the particles, on the pressure at which the fluid flows through the equipment and/or system components, and on the internal clearances of the parts comprised in the components. Particles of approximately the same size as a clearance may cause damage to the part through friction. Particles of a smaller size than the clearance may cause damage to the part through abrasion at relatively high pressure flow rates. Friction and abrasion generally contribute to accelerated wear in the parts and to eventual component breakdown. System components which may require relatively frequent replacement due to wear may include, for example, pumps, spindles, and axes. Particles of a larger size than the clearance may create blockages, wholly or partially, in the path of flow of the fluid through a component. Interrupting the flow of the fluid through the component may result in damage to the component, and may affect other components following the blocked components. System components which require relatively frequent replacement due to blockage may include, for examples, pipes, pumps, valves, tools, and nozzles.

As previously discussed, filters are typically used in the system to control buildup in the quantity of particles under filtration rating. Some types of filters commonly used include hydrocyclone (cyclone), paper gravity, centrifuge, drum filter, candle filter and precoated filter, and cartridge filter.

The hydrocyclone filter uses centrifugal force to separate particles from the contaminated fluid. The separated particles drop into a reservoir where they accumulate and are later removed. Some advantages of the hydrocyclone include high removal rates for relatively heavy weight particles. Additionally, the hydrocyclone is generally of a relatively simple construction and compactly sized. A major disadvantage in the use of the hydrocyclone is a relatively large volume of fluid flow into filter drain components, possibly comprising up to 15% of the volume of the contaminated fluid. Reusing this relatively large volume of fluid in the drain components may result in a costly operation. Additionally, there is a risk in emulsions breaking down into oil and water due to their different densities. The paper gravity filter generally comprises a paper band adapted to retain particles in contaminated fluids as the contaminated fluid flows through the paper band. For convenience hereinafter, a filtered fluid may be referred to as "clean fluid". Advantages in using the paper gravity filter include a relatively simple and inexpensive construction; relatively low costs involved in replacing the paper band; and disposing of the paper band generally has little, if any, impact on the environment (environmentally friendly material). A disadvantage in using the paper gravity filter is its relatively low reliability.

The centrifuge generally comprises a cylinder which is substantially rapidly rotated, such that clean fluid is driven out of the cylinder through a periphery by a centrifugal action. Contaminating particles in the fluid remain trapped inside the cylinder and may be automatically, or optionally, manually, discharged. Some advantages of the centrifuge include a relatively compact size, an ability to separate heavy particles from the fluid, and internal storing of sludge (the contaminating particles removed from the fluid). Some disadvantages include a small flow rate, high maintenance costs, and lack of suitability for use with emulsions.

The drum filter is generally adapted to remove relatively large particles in contaminated fluid, usually in operations involving rough machining. Some advantages of the drum filter include automatic backwash, generally integrated in conveyor belts used in machining operations, saving production floor space. Backwash is a process generally used in some filtering methods typically comprising flushing a fluid in the opposite direction to that of the flow of a fluid being filtered, in order to remove accumulated particles in the filtering elements. Some disadvantages include production shutdowns due to filter failure, high wear in sealing device; unsuitability for relative small particle filtering, and backwash nozzle blockage, which may cause production floor flooding. Additionally, tears in the drum filter screen are generally difficult to spot, allowing the contaminated fluid to flow through the tear into clean tanks contaminating the clean fluid inside the tanks. The contaminated fluid may cause blockages in pipes and other system components, interfering with the production process.

The candle filter and the precoated filter are generally used as a fine filter for finishing operations. Some relative advantages are fine filtration capabilities, relatively low equipment cost, and that filter disposal generally has little, if any, impact on the environment

(environmentally friendly material). Disadvantages include variations in stability while filtering. The paper and/or polymeric cartridge filter is generally adapted to filter contaminated fluids in applications as a polisher filter, and as a safety filter to protect a component. Some relative advantages include relatively low equipment cost; and filter disposal generally has little, if any, impact on the environment (environmentally friendly material).

The use of contaminated fluids and/or inadequate filtering may result in production downtime and tool wear. In machining operations, contaminated fluids and/or inadequate filtering may have a negative effect on cutting edges of tools so that the edges may require resharpening or replacement, which may contribute to an increase in setup downtime. Furthermore, quality of the workpiece may be affected.

The terms "contamination", "contaminated" or "contaminating" as referred to herein may include any element present in a fluid, which is not dissolved in the fluid. Such elements may include, for example but are not limited to, solid elements, residues, liquid containing elements, suspended solids and the like.

SUMMARY

An aspect of some embodiments of the invention relates to providing a filter and a filtering device adapted to remove particulate contamination (particles) from fluids having properties different from water, for example, fluids having higher viscosity than that of water (for convenience hereinafter, these liquids may be referred to as "viscous" fluids).

Other examples may include fluids having different density, polarity, surface tension characteristics, electrical characteristics, optical characteristics (such as transparency, refractivity, reflectivity or the like), capillary action, pH, hardness, load and shape, contamination material, tramp oil content, chemical compatibility with polymers, or any other characteristic which is different from that of water.

An aspect of some embodiments of the invention relates to providing a filter and a filtering device adapted to remove particulate contamination of essentially all sizes from fluids, wherein the particles have essentially a needle shape or essentially a cork-screw shape, for example, metal particles (such as, stainless steel, iron, copper, aluminum, tempered steel, alloys, glass, diamonds, polycarbonate, and the like). An aspect of some embodiments of the invention relates to providing a filter and a filtering device adapted to remove particulate contamination from fluids, wherein the particles are produced in CNC (computer numerical control) machining process, for example, of metals (such as, stainless steel, cast iron, copper, aluminum, tempered steel, and the like), polymers (such as PP - polypropylene, PA - polyacetylene, PE - polyethylene, PTFE - polytetrafluoroethylene, PA66 - polyamide, POM - polyoxymethylene, polycarbonate, and the like), ceramics, carbon, glass, diamonds, sapphire, and the like, extra-soft materials (such as, Styrofoam, soft plastic, sponges, and the like).

According to an aspect of some embodiments of the invention, the filtering device includes a filter which comprises a plurality of relatively tightly stacked, relatively flat filtering elements, the stack of filtering elements adapted to trap particles contaminating the viscous fluid. The filtering elements may comprise a circular shape, or optionally, an elliptical shape, a rectangular shape, or any regular polygonal shape, or irregular shape including irregular polygonal shape. The filtering elements comprise channels on both sides, substantially flat surfaces separating between the channels. Optionally, the filtering elements may comprise channels only on one side. The channels slantedly extend from an outer perimeter towards an inner perimeter, generally conforming to a direction of flow of the viscous fluid. The inner perimeter forms a border of an opening located inside the filter element. Optionally, the channels may slantedly extend a portion of a distance to the inner perimeter. Optionally, the filtering elements may comprise a plurality of support points. Additionally, the channels on one side of a filtering element are slanted in a same direction as on a second side of the filtering element.

According to an aspect of some embodiments of the invention, the filtering elements are adapted to stack such that the channels on one side of a first filtering element may partially, or fully, align with the channels or flat surfaces on an adjoining side of a second filtering element. Partial or full alignment of a channel on one side of the first filtering element with a channel on the adjoining side of the second filtering element forms a conduit through which the viscous fluid may flow from the outer perimeter of the filtering elements into the opening in the filtering elements. A conduit may also be formed by the alignment of a channel on one side of the first filtering element with a flat surface on the adjoining side of the second filtering element. Optionally, the viscous fluid may flow from the opening in the filtering elements in a direction from the inner perimeter to the outer perimeter. The cross-sectional characteristics, such as size and shape of the conduits, may vary from conduit to conduit according to how the channels and/or flat surfaces align. Additionally, the cross-sectional characteristics of the conduit may vary along the length of the conduit, generally as the conduit nears the opening. The conduits are adapted to trap particles of different sizes in the viscous fluid as the fluid flows through the conduit into the opening, the size and shape of the trapped particles generally determined, among others, by the cross-sectional characteristics of the conduit. A single conduit may trap one or more particles of different sizes; the size of the particles may decrease as the conduit nears the opening. Optionally, the size of the particles may increase as the conduit nears the opening. The conduit may further be adapted to substantially prevent particles larger than a conduit aperture from entering into the conduit.

According to an aspect of some embodiments of the invention, the filtering device may be adapted to filter particles of different size ranges in viscous fluids. The filtering device is fitted with a filter which includes a stack of filtering elements comprising channels of a width and a depth, which may also be referred to as "channel dimensions", such that the conduits formed by the alignment of the channels trap particles of a first size range. Replacing the filter comprising a stack of filtering elements with a second filter comprising a stack of filtering elements of different channel dimensions may facilitate filtering particles of a second size range. Optionally, replacing and/or adding to a stack of filtering elements with a second stack of filtering elements of different channel dimensions may facilitate the process of filtering particles of a second size range. The addition and/or replacement of filter stacks may be repeated any number of times.

In some embodiments of the invention, the filtering elements may be formed from a polymeric material, such as PP, PA, PTFE, rubber, silicon and the like, and/or from other materials such as, for examples, metals and/or glass.

In some embodiments of the invention, the filtering elements may include an antibacterial material, such as, but not limited to, antibiotics, in order to prevent or reduce bacterial growth on the filtering elements, in the fluid and/or in any component of the system.

The filtering elements may be coated with an antibacterial material. The filtering elements may also include an antibacterial material incorporated in the filter material itself.

Antibacterial material may include quarternary ammonium compounds, triclosan, tolyl diiodomethyl sulfone, zinc pyrithione, sodium pyrithione, ortho phenylphenol, sodium ortho phenylphenol, iodo-2-proρynyl butylcarbamate, poly[oxyethylene(dimethyliminio) ethylene(dimethyliminio)ethylene chloride], propiconazole, tebuconazole, bethoxazin, thiabendazole, polyhexamethylene biguanide, and l,3,5-triazine-l,3,5-(2H,4H,6H)-triethanol, isothiazalinones, or any combination thereof.

Antibacterial material may include, metal salts, such as, salts of silver, copper, zinc, mercury, tin, lead, bismuth, barium, cadmium, chromium, or any combination thereof. The silver salts may include silver acetate, silver benzoate, silver carbonate, silver iodate, silver iodide, silver lactate, silver laurate, silver nitrate, silver oxide, silver palmitate, silver sulfadiazine, ceramics containing silver, zeolites containing silver, or any combination of any of the materials disclosed herein or any other appropriate antibacterial material. Similarly, other materials, such as antifungal materials, may also be utilized.

In some embodiments of the invention, the filtering device comprises an outer chamber adapted to receive a flow of a viscous fluid through an inlet, a filter, and an inner chamber adapted to receive the viscous fluid after filtering. The filter comprises a stack of filtering elements adapted to trap particles of a predetermined size range in the viscous fluid. The filtering device additionally comprises an outlet through which the filtered viscous fluid, which may be referred to hereinafter as "clean fluid", exits from the device. The filtering device further comprises a dirty liquid outlet through which a flushing liquid, adapted to flush out particles trapped in the conduits, may flow out of the filtering device during backwash. Optionally, the dirty liquid outlet may be the inlet. Optionally, the filtering device may comprise a flushing liquid inlet through which the liquid may flow into the device at a relatively high pressure during backwash.

In some embodiments of the invention, the viscous fluid may flow into the filtering device through the outlet and into the inner chamber. The viscous fluid may then flow through a filter, which comprises a stack of filtering elements adapted to trap particles in the viscous fluid, into the outer chamber which receives the viscous fluid after filtering. The clean fluid exits the device through the inlet. During backwash, the flushing liquid may flow into the filtering device through the inlet, or optionally, the dirty liquid outlet, and be flushed out through the outlet, or optionally, the flushing liquid inlet.

In an embodiment of the invention, the filtering device is adapted to automatically switch to backwash operation, responsive to detection of a predefined pressure difference in the flow of the clean fluid. A pressure difference equal to or above a predefined level, for example in a range of 0.5 - 1.0 bar in the clean fluid, is indicative of a blockage in the filter. Responsive to the blockage, the tightly stacked elements are automatically released so that they may be free to rotate. A liquid, which may be, for example, a relatively small amount of the clean fluid, may then be flushed into the filtering device in order to remove particles stuck between the disks. Optionally, a gas, for example nitrogen, and/or a gaseous mixture such as air, may be flushed into the filtering device. Optionally, the gas may be adapted to disinfect the filtering device, for example, chlorine gas. Additionally or alternatively, the gas or gaseous mixture may be combined with the liquid and then flushed into the filtering device. Optionally, the gas may be an inert gas at a high temperature. Optionally, upon termination of backwash, the tightening of the stacked elements may be performed automatically.

There are numerous advantages to using the filtering device to produce substantially clean oils and emulsions for lubricating and/or cooling applications. An advantage is that equipment and/or system components require less cleaning, and as a result, there are less work interruptions. Other advantages include reduction in the frequency of blockages, and/or wear, in system components. In machining operations, observations have shown that surface damage in the workpiece is substantially reduced and greater quality stability achieved as a result of tool wear minimization. Additional advantages include extending the life of the fluids, substantial reduction in corrosion in collection tanks, and substantial reduction in fungal and bacterial contamination in the fluids, which reduces the development of unpleasant odors in the fluids.

Measurements were performed by the inventors on a filtering device comprising a filter with filtering elements shaped as annular (ring) disks (the opening in the center of the disks) in order to evaluate the flow rates of oil and emulsions through the filter. The viscosity of the viscous fluids ranged from 1 - 30 cst (centistokes). The results obtained are the following:

Filter Grade (μm Flow Rate (liters per

Disk Color - microns) minute)

Clean

Emulsions Clean Oil yellow 200 200 100 red 130 150 100 black 100 100 75 brown 70 75 50 green 55 55 40 purple 40 50 30 gray 20 40 25 setpoint pressure difference before backwash (bar) 0.5 -0.8 0.5 - 1.5 setpoint pressure difference with clean filter (bar) 0.2 0.7

Filtering devices are known in the art for use in water filtration applications. Generally, water filtration requirements are substantially different from filtration requirements for oils and emulsions, and more particularly oils and emulsions used in machining operations. The extent of particulate contamination in water is generally less demanding since natural water is relatively clean and any particle contamination is usually limited to substantially small particles. In machining operations, however, oils and/or emulsions are used as lubricants, particulate removing media and/or coolants. The oil and/or emulsion are intended to collect and remove particles. As a result, these fluids carry a large amount of particulates, which generally include large chips, microchips, other size and/or shaped particles which separate from a cutting tool, grinding tool, and/or a workpiece. Filtering oils and emulsions, particularly in machining operations, are therefore very challenging.

In addition, filtering demands for devices adapted to filter oils and/or emulsions are much more stringent than for water filtering devices. One of the reasons for the strict filtering demands is the undesired effect of particulates in the lubricants and/or coolants on the machining tools and on the resulted workpiece. Furthermore, particle buildup over time in the fluid will affect its stability, requiring that the fluid be replaced.

There are other significant differences in the use of water filtering devices and the filtering device adapted for use with oils and/or emulsions. Forces acting on the surfaces of the filtering elements due to, for example, surface tension, capillary effect, density, and other fluid properties, are substantially different in oils and/or emulsions, compared to water. In machining operations, the filters filtering the oils and/or emulsions, may additionally have to deal with contaminant interaction particles, tramp oil, bacteria, and calcium-soap coming with water make-up to compensate evaporation. Additionally, biological activity is substantially different in oils and/or emulsions compared with water. Water filtering devices typically filter water from treatment plants, which has been pre-treated in order to substantially reduce biological activity in the water. Emulsions, on the other hand, may serve as a nutrient base for organism growth. These factors need to be taken into consideration in filtration processes. There are many additional applications for a filtering device adapted to remove particles from liquids with a relatively high viscosity. Such may be the case in the food industry where, for example, in the production of nectars and thick fruit juices, particles from pulps and seeds may require removal. Another example may be in the production of consumable oils, such as olive oil, corn oil, and the like, where here also particles may be required to be filtered out of the liquids. Some other applications which may require filtering devices for the removal of particles from liquids with a relatively high viscosity may include, for example, cosmetics manufacturing, hygienic products manufacturing (soaps, shampoos and the like), and pharmaceutical products manufacturing, among many others.

There is provided, in accordance with an embodiment of the invention, a device for viscous fluid filtration, comprising a first chamber adapted to receive viscous fluid; a second chamber adapted to receive filtered viscose fluid; and a filter between the outer and inner chambers, wherein the filter comprises a set of tightly stacked filtering elements. Optionally, the first chamber is an outer chamber and the second chamber is an inner chamber. Optionally, the first chamber is an inner chamber and the second chamber is an outer chamber.

In accordance with some embodiments of the invention, the filter is adapted to filter particles of a size range 5 to 3000 microns in viscous fluids of a viscosity range 1 to 30 cts. Optionally, the filter is replaceable. Optionally, the filter is disposable.

In some embodiments of the invention, the filtering elements are stacked concentrically. Optionally, the filtering elements are stacked eccentrically.

In some embodiments of the invention, the device is further adapted to backwash the filter. Optionally, backwash comprises the use of the filtered viscose fluid. Additionally or alternatively, backwash comprises flushing a liquid into the device. Optionally, backwash comprises flushing a gas into the device. Optionally, the gas comprises a disinfectant substance.

In accordance with some embodiments of the invention, the device is further adapted to automatically initiate a backwash of the filter upon detection of a predetermined pressure difference in the flow of filtered viscose fluid. Optionally, the predetermined pressure difference is in the range of 0.05 - 10.0 bar, for example, during filtering. Optionally, the predetermined pressure difference is in the range of 0.5 — 1.0 bar, for example, when backwash is initiated, and 3 - 10 bar during backwash. There is provided, in accordance with an embodiment of the invention, a filtering element for viscous fluid filtration, comprising non-radial channels at least on a portion of at least one surface of the filtering element, and the filtering element is adapted to form conduits when used in conjugation with other filtering elements. Optionally, the filtering element comprises an annular disk shape. Optionally, the filtering element comprises an elliptical shape.

In some embodiments of the invention, the non-radial channels are v-shaped channels. Optionally, the non-radial channels are flat bottom channels. Optionally, the non-radial channels are round bottom channels. Additionally or alternatively, the non-radial channels are comprised at least on a portion of one surface of the filtering element. Optionally, the non- radial channels are comprised at least on a portion of two surfaces of the filtering element.

There is provided, in accordance with an embodiment of the invention, a filtering element for viscous fluid filtration, comprising rough texture at least on a portion of at least one surface of the filtering element, and the filtering element is adapted to form conduits when used in conjugation with other filtering elements.

There is provided, in accordance with an embodiment of the invention, a viscous fluid filter comprising a stack of viscous fluid filtering elements, the filter adapted to tightly stack the filtering elements during filtering, and further adapted to loosely stack the filtering elements during backwash. Optionally, the fluid filtering elements are concentrically stacked. Optionally, the fluid filtering elements are eccentrically stacked.

There is provided, in accordance with an embodiment of the invention, a method of filtering viscous fluid, comprising passing a viscous fluid from a first chamber into a second chamber through a filter, wherein the filter comprises a plurality of stacked filtering elements.

BRIEF DESCRIPTION OF FIGURES

Examples illustrative of embodiments of the invention are described below with reference to figures attached hereto. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. Figure IA schematically shows an exemplary filtering device for viscous liquids, in accordance with an embodiment of the invention;

Figure IB schematically shows an exemplary filtering device for viscous liquids, in accordance with some embodiments of the invention;

Figure 2A schematically shows a top view of an exemplary filter disk, in accordance with an embodiment of the invention;

Figure 2B schematically shows a cross-sectional view A-A of the exemplary disk of Figure 2A, in accordance with an embodiment of the invention;

Figure 2C schematically shows a top view of an exemplary filter disk, in accordance with some embodiments of the invention;

Figure 2D schematically shows a top view of an exemplary filter disk, in accordance with some embodiments of the invention;

Figure 2E schematically shows exemplary filtering elements comprising different cross-sections, A through E, in accordance with some embodiments of the invention;

Figure 2F schematically shows exemplary filtering elements comprising different shapes, A through I, and further comprising different shaped openings, in accordance with some embodiments of the invention;

Figure 2G schematically shows a face view of an exemplary filter disk comprised in a filter, in accordance with some embodiments of the invention;

Figures 3A_> 3B, 3C, and 3D schematically show cross-sectional views of exemplary channels formed between two adjoining disk surfaces, in accordance with an embodiment of the invention;

Figures 4A and 4B show SEM (scanning electron microscope) images of particle contamination in oils used for cooling a lathing machine before and after use of the filtering device comprising filtering disks, respectively, in accordance with an embodiment of the invention; and Figures 5 A and 5B show SEM images of particle contamination in oils used for cooling a CNC milling machine before and after use of the filtering device comprising filtering disks, respectively, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

Reference is made to Figure IA, which schematically shows a longitudinal sectional view of an exemplary filtering device for viscous liquids 100, in accordance with an embodiment of the invention. Filtering device 100 includes a housing 101 adapted to receive in an outer chamber 109, viscous fluid 120, shown by hatched arrows, arriving at a relatively high pressure through an inlet 106. Inlet 106 is shown at one end of housing 101 although inlet 106 may optionally have other locations in housing 101. Housing 101 is further adapted to facilitate flow of viscous fluid 120 as the fluid spreads throughout outer chamber 109. For example, housing 101 may comprise a cylindrical shape and a dome at one end, as shown, or optionally, housing 101 may conceivably comprise other shapes, for example, cylindrical with a dome at each end, or spherical, or ellipsoidal, or quadrilateral, or any other polyhedral shape, or any combination of polyhedral shapes..

Filtering device 100 additionally includes a filter 102, which comprises a plurality of filtering elements 103, tightly stacked together. Filtering device 100 further comprises an inner chamber 110 running longitudinally through the center of filtering elements 103. Filtering elements 103 are concentrically disposed about an axis A extending longitudinally through a center of both housing 101 and inner chamber 110. Optionally, filtering elements 103 may be eccentrically disposed about axis A. Additionally or alternatively, axis A is not centered in housing 101.

In accordance with an embodiment of the invention, filter 102 is adapted to filter particles contaminating viscous fluid 120 as the fluid flows between filtering elements 103 in the filter into inner chamber 110. Particles which are filtered are those substantially prevented from entering between filtering elements 103, or are trapped between the filtering elements, the size of the particles determined by a predetermined filtering size range of the filtering elements. For convenience hereinafter, viscous fluid 120 flowing through filter 102, may be referred to as filter fluid 121, shown in the figure by a thin arrow. Filter fluid 121 flowing into inner chamber 110 is relatively free of contaminating particles, and may be hereinafter referred to as clean fluid 122, shown by thick arrows. Inner chamber 110 connects at one end to an outlet 107 comprised in housing 101, outlet 107 adapted to conduct the flow of clean fluid 122, out of filtering device 100.

Stacked filtering elements 103 are held tightly in place by a first clamp 104 and a second clamp 105, one at each end of filter 102. Clamps 104 and 105 are adapted to tightly clamp stacked filtering elements 103 for filtering viscous fluid 120, and to loosely clamp stacked filtering elements 103 for backwash operations associated with blockages in filter 102.

First clamp 104 and second clamp 105 may be electrically initiated by an electrical signal received responsive to a pressure change in the flow of clean fluid 122 due to blockage, and optionally, by an electrical signal received responsive to removal of the blockage.

During backwash operations, stacked filtering elements 103 are released such that they are loosely stacked. A liquid used for backwash, which may be for example, a relatively small quantity of clean fluid 122, or optionally a gas or a gaseous mixture, or any combination thereof, is introduced at a relatively high pressure from outside filtering device 100 through outlet 107 into inner chamber 110. Alternatively, the liquid may be introduced into inner chamber 110 through a flushing liquid inlet (not shown). The pressurized liquid then flows from inner chamber 110 between loosely stacked filtering elements 103 into outer chamber 109. This "reverse" flow of liquid, that is, from the inner chamber into the outer chamber, substantially displaces particles trapped between elements 103 which flow into outer chamber 109. The liquid in outer chamber 109, which may include both displaced trapped particles and particles which did not enter between the elements during filtering, flows out of filtering device 100 through a flushing liquid outlet 108 comprised by housing 101. In some embodiments of the invention, the liquid flows out of filtering device 100 through inlet 106.

Reference is made to Figure IB, which schematically shows a longitudinal sectional view of an exemplary filtering device for viscous liquids 10OA, in accordance with some embodiments of the invention. Filtering device IOOA comprises a housing 101A, a filter 102A comprising filtering elements 103A, a first clamp 104A, a second clamp 105A₅ an outlet 106A, an inlet 107A, a flushing liquid inlet 108A, an outer chamber 109A, and an inner chamber

HOA. Housing 101A, first clamp 104A, second clamp 105A, outer chamber 109A, and inner chamber HOA, are the same or substantially similar to that shown in Figure 1 at 101, 104, 105,

109, and 110, respectively. In filter device 10OA, viscous fluid 12OA comprising contaminating particles, shown by thick solid arrows, flows through inlet 107A at a relatively high pressure into inner chamber HOA. Viscous fluid 120A flows from inner chamber HOA through filtering elements 103A comprised in filter 102 A. Filter 102A₅ when filtering elements 103 are tightly stacked by the clamping action of clamps 104A and 105A, is adapted to filter viscous fluid 120A. For convenience hereinafter, viscous fluid 120A flowing through filter 102A may be hereinafter referred to as filter fluid 121A, shown by a thin solid arrow. Filter fluid 121A flows into outer chamber 109A relatively free of contaminating particles, and may be hereinafter referred to as clean fluid 122A, shown by hatched arrows. Clean fluid 122A flows out of filter device through outlet 106A. During backwash, the flushing liquid may flow into filtering device IOOA through outlet 106 A, or optionally, flushing liquid inlet 108 A, and flushed out through inlet 107 A, or optionally, through a flushing liquid outlet (not shown).

Reference is made to Figures 2A and 2B which schematically show a face view of filter element 103 shown in Figure 1 and a cross-sectional view A-A of filter element 103, in accordance with an embodiment of the invention. Reference is also made to Figure 1. Filter element 103 is shown as an annular shaped disk with an opening 111 in the center. For convenience hereinafter, filter element 103 may also be referred to as filter disk or disk. Disk 103 comprises v-shaped channels 152 on both sides of the disk, and is adapted to be tightly stacked, one disk on top of another. An outer perimeter 150 forms an outer boundary of disk 103 and an inner perimeter forms a boundary with an opening 111 centrally located in the disk. Optionally, opening 111 may be eccentrically located. When tightly stacked in filter 102, openings 111 comprise inner chamber 110.

In accordance with an embodiment of the invention, channels 152 slantedly (non- radially) extend from outer perimeter 150 towards inner perimeter 151. Channels 152 are oriented in a general direction such that flow of filter fluid 121 through the channels maintains a same general direction as flow of viscous fluid 120, for example counterclockwise as shown. Alternatively, channels 152 may be oriented such that flow of filter fluid 121 is in a general clockwise direction for flow of viscous fluid 120 in a clockwise direction.

In accordance with an embodiment of the invention channel dimensions are of a uniform depth h, measured from a flat surface 153 between channels 152, and a bottom 154 of the channel; and of a variable width w which is at a maximum at outer perimeter 150, and decreases as channel 152 approaches inner perimeter 151. Optionally, channel 152 may increase in width w from outer perimeter 150 to a predetermined point along a length of the channel, and then w decreases from the point onwards towards inner perimeter 151. Optionally, width w may be uniform along the length of channel 152. In some embodiments of the invention, the channel dimension may vary from channel to channel, or from some channels to other channels, or any combination thereof, either on one side of disk 103, or optionally, on both sides. In Figure 2B, the two sides of disk 103 are shown as mirror images of one another, that is, flat surfaces 153 and channels 152 on one side of the disk are aligned with those on the other side of the disk. Optionally, fiat surfaces 153 and channels 152 on one side of disk 103 may not be aligned with those on the other side of the disk.

Reference is made to Figure 2C which schematically shows a face view of a filter disk

203, comprised in a filter 202 in accordance with some embodiments of the invention. Filter 202 may be the same or substantially similar to filter 102 shown in Figure 1. Disk 203 comprises channels 252, an outer perimeter 250, an inner perimeter 251, and an opening 211, the same or substantially similar to that shown in Figure 1 at 152, 150, 151 and 111. Additionally, disk 203 comprises one or more support points 255 on one side, and optionally on a second side. The support points may be round as shown, although they may optionally have other shapes, and may be uniformly, or optionally non-uniformly, distributed throughout either one or both sides of disk 203. Support points 255 may optionally be associated with a manufacturing process of disk 203.

Reference is made to Figure 2D, which schematically shows a face view of a filter disk

303 comprised in a filter 302, in accordance with some embodiments of the invention. Filter 302 may be the same or substantially similar to filter 102 shown in Figure 1. Disk 303 comprises channels 352, an outer perimeter 350, an inner perimeter 351, and an opening 311, the same or substantially similar to that shown in Figure 1 at 152, 150, 151 and 111. A variation from disk 103 is that channels 352 do not extend to inner perimeter 351. Instead, channels 352 extend to a flat surface area 355 peripherally located between inner perimeter 351 and channels 352. In some embodiments of the invention, disk 303 may comprise one or more support points, the same or substantially similar to that shown in Figure 2C at 255. The support points may be located among channels 352, similar to support points 255 in Figure 2C, and/or located in flat surface area 355.

In some embodiments of the invention, disk 103 may comprise channels 152 only on one side, or optionally other types of channel shapes on one side or both sides of the disk. Additionally or alternatively, the surface on one side, or optionally, both sides, may have a rough texture. Non-limiting, exemplary filtering elements comprising different cross-sections, A through E, are schematically shown in Figure 2E. For example, A comprises a disk with v- shaped channels only on one side; B comprises rounded channels on both sides; C comprises rough surfaces on both sides; D comprises rounded channels on one side; E comprises flat- bottom channels on both sides.

In some embodiments of the invention, disk 103 may comprise other shapes, such as elliptical, rectangular shapes, square, regular polygonal shapes, or irregular shapes including irregular polygonal shapes. Furthermore, opening 111 may have other shapes, for example, elliptical, rectangular shapes, square, regular polygonal shapes, or irregular shapes including irregular polygonal shapes. Non-limiting, exemplary filtering elements comprising different shapes, A through I, and further comprising different shaped openings, are schematically shown in Figure 2F. For example, A comprises a square shaped filter element with a square shaped opening; B comprises a triangular shaped filter element with a triangular shaped opening, C comprises an octagonal shaped filter element with an octagonal shaped opening; D comprises an elliptical shaped filter with an elliptical shaped opening; E comprises an irregular shaped filter with an irregular shaped opening; F comprises a square shaped filter with a circular shaped opening; G comprises a triangular shaped filter with a circular shaped opening; H comprises an octagonal shaped filter with a circular opening; I comprises an elliptical shaped filter with a rectangular shaped opening.

Reference is made to Figure 2 G, which schematically shows a face view of an exemplary filter disk 303' comprised in a filter 302', in accordance with some embodiments of the invention. Filter 302' may be the same or substantially similar to filter 102 shown in Figure 1. Disk 303' may comprise channels which are shaped in different patterns, and/or surfaces with different textures, or any combination thereof. For example, disk 303' comprises channels shaped in a zigzag pattern with curved corners, as shown at 310'; or channels shaped in a zigzag pattern with sharp corners, as shown at 314'; or channels shaped in a curved pattern, as shown at 313'; or a flat surface with prism-shaped protrusions randomly, or optionally non- randomly, distributed throughout the disk surface, as shown at 312'; or a textured surface as shown at 312' with recessed flat surfaces on the disk side, or optionally protruding flat surfaces, the flat surfaces distributed so as to form a labyrinth-like configuration, as shown at 311'; or any combination thereof. Optionally, the channels shown in 310' and 314' may be radially oriented, or optionally, non-radially oriented. Additionally or alternatively, the channels may be oriented in essentially any direction. Optionally, the flat surfaces shown in 311' may be oriented in essentially any direction.

In some embodiments of the invention, disk 303' may comprise channels only on one side, or optionally other types of channel shapes and patterns on one side or both sides of the disk. Additionally or alternatively, the surface on one side, or optionally, both sides, may have a rough texture. Additionally or alternatively, disk 303' may comprise other shapes, such as elliptical, rectangular shapes, square, regular polygonal shapes, or irregular shapes including irregular polygonal shapes. Optionally, disk 303' may comprise an opening which may have other shapes, for example, elliptical, rectangular shapes, square, regular polygonal shapes, or irregular shapes including irregular polygonal shapes.

Reference is made to Figures 3A, 3B, 3C, and 3D which schematically show sectional views of exemplary channels 170, formed between two adjacent disks 103 shown in Figure 1, in accordance with an embodiment of the invention. Reference is also made to Figures 1, 2 A and 2B. For explanatory purposes two adjacent disks 103 may be designated as disk 103A and disk lO3B.

Disks 103 are tightly stacked in filter 102 such that channels 152, comprised in a side of first disk 103A, may partially, or fully, align with channels 162 and/or flat surfaces 163 in an adjoining side of second disk 103B. Alternatively, channels 162, comprised in a side of second disk 103B, may partially, or fully, align with channels 152 and/or flat surfaces 153 in an adjoining side of first disk 103A. In accordance with an embodiment of the invention, partial, or full, alignment of channels 152 and/or flat surfaces 153 with channels 162 and/or flat surfaces 163 respectively, result in the formation of conduits 170 between disks 103A and 103B. Conduits 170 are adapted to allow through the flow of filter fluid 121 from outer perimeter 150 to opening 111, and are further adapted to trap particles 199 contaminating filter fluid 121, as the filter fluid flows through the conduit. Conduits 170 are additionally adapted to restrict the entry of relatively large particles contaminating viscous fluid 120 into the conduit.

The range of sizes of particles 199 trapped by conduits 170 is dependent, among others, on the cross-sectional characteristics of the conduits, the cross-sectional characteristics varying according to the channel dimensions and the type of alignment between channels 152 and 162.

For example, Figure 3 A illustrates a condition of full alignment between channels 152 and 162, and between flat surfaces 153 and 163, respectively. Figures 3B and 3C illustrate conditions of partial alignment between channels 152 and 162, flat surfaces 153 and 163 partially aligning with channels 162 and 152, respectively. In Figure 3D for example, there is full alignment between channels 152 and flat surfaces 163, and between channels 162 and flat surfaces 153, respectively. Between any two disks 103, there may be a plurality of conduits 170 with different cross-sectional characteristics as shown, or other variations thereof, the conduits adapted to trap particles 199 of different sizes and shapes. Furthermore, a single conduit 170 may be adapted to trap particles 199 of different sizes, this due to a decreasing cross-sectional size in conduit 170 as the conduit nears opening 111. Smaller particles are first trapped in conduit sections closer to opening 111 and larger particles are later trapped in conduit sections closer to outer perimeter 150.

In accordance with an embodiment of the invention filter 102 is adapted to filter particles 199 of different size ranges in viscous fluid 120. Filter 102 comprises a stack of disks 103 of channel dimensions such that conduits 170, formed by the alignment of channels and/or flat surfaces, trap particles of a first size range. Replacing filter 102 with a second filter comprising a stack of filtering disks 103 of different channel dimensions provides for filtering particles 199 of a second size range. Optionally, replacing a stack of filtering disks 103 in filter 102 with a second stack of filtering disks of different channel dimensions provides for filtering particles of a second size range using filter 102

Reference is made to Figures 4A and 4B which show SEM (scanning electron microscope) images of particle contamination in oils used for cooling a lathing machine before and after use of the filtering device comprising filtering disks, respectively, in accordance with an embodiment of the invention. The lathing machine, adapted to produce precision components, was cooled by oil 22 cSt, at a temperature range 30 - 45 degrees Celsius, a coolant flow rate of 30 liters/minute and a pressure of 20 bar.

Figures 5A and 5B show SEM images of particle contamination in a semi-synthetic emulsion used for cooling a CNC milling^' machine before and after use of the filtering device comprising filtering disks, respectively, in accordance with an embodiment of the invention. The CNC milling machine, adapted to produce components for automobiles, was cooled by a semi-synthetic emulsion 7 - 10 %, at a temperature range 20 - 40 degrees Celsius, a coolant flow rate of 30 liters/minute and a pressure of 20 bars. In the description and claims of embodiments of the present invention, each of the words, "comprise" "include" and "have", and forms thereof, are not necessarily limited to members in a list with which the words may be associated.

The invention has been described using various detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments may comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the invention that are described and embodiments of the invention comprising different combinations of features noted in the described embodiments will occur to persons with skill in the art.

Claims

1. A device for viscous fluid filtration, comprising:

a first chamber adapted to receive viscous fluid;

a second chamber adapted to receive filtered viscose fluid; and

a filter between said outer and inner chambers, wherein said filter comprises a set of tightly stacked filtering elements.

2. The device of claim 1 wherein said first chamber is an outer chamber and wherein said second chamber is an inner chamber.

3. The device of claim 1 wherein said first chamber is an inner chamber and wherein said second chamber is an outer chamber.

4. The device of claim 1 wherein said filter is adapted to filter particles of a size range 5 to 3000 microns in viscous fluids of a viscosity range of 1 to 30 cts.

5. The device of claim 4 wherein said filter is replaceable.

6. The device of claim 4 wherein said filter is disposable.

7. The device of claim 1 wherein said filtering elements are stacked concentrically.

8. The device of claim 1 wherein said filtering elements are stacked eccentrically.

9. The device of claim 1 further adapted to backwash said filter.

10. The device of claim 9 wherein said backwash comprises the use of the filtered viscose fluid.

11. The device of claim 9 wherein said backwash comprises flushing a liquid into the device.

12. The device of claim 9 wherein the backwash comprises flushing a gas into the device.

13. The device of claim 12 wherein said gas comprises a disinfectant substance.

14. The device of claim 1 further adapted to automatically initiate a backwash of said filter upon detection of a predetermined pressure difference in the flow of filtered viscose fluid.

15. The device of claim 12 wherein said predetermined pressure difference is in the range of 0.05 - 10.0 bar.

16. The device of claim 12 wherein said predetermined pressure difference is in the range of 0.5 - 1.0 bar.

17. A filtering element for viscous fluid filtration, comprising non-radial channels at least on a portion of at least one surface of said filtering element, said filtering element is adapted to form conduits when used in conjugation with other filtering elements.

18. The filtering element of claim 17 comprising an annular disk shape.

19. The filtering element of claim 17 comprising an elliptical shape.

20. The filtering element of claim 17 wherein said non-radial channels are v-shaped channels.

21. The filtering element of claim 17 wherein said non-radial channels are fiat bottom channels.

22. The filtering element of claim 17 wherein said non-radial channels are round bottom channels.

23. The filtering element of claim 17 comprising non-radial channels at least on a portion of one surface of said filtering element.

24. The filtering element of claim 17 comprising non-radial channels at least on a portion of two surfaces of said filtering element.

25. A filtering element for viscous fluid filtration, comprising rough texture at least on a portion of at least one surface of said filtering element, said filtering element is adapted to form conduits when used in conjugation with other filtering elements.

26. A viscous fluid filter comprising a stack of viscous fluid filtering elements, said filter adapted to tightly stack said filtering elements during filtering, and further adapted to loosely stack said filtering elements during backwash.

27. The fluid filter of claim 26 wherein said fluid filtering elements are concentrically stacked.

28. The fluid filter of claim 26 wherein said fluid filtering elements are eccentrically stacked.

29. A method of filtering viscous fluid, comprising:

passing a viscous fluid from a first chamber into a second chamber though a filter wherein the filter comprises a plurality of stacked filtering elements.