D E S C R I P T I O N

1. Technical Field.

The present invention relates to apparatuses for filtering particulate matter from hydraulic fluids and other dielectric fluids and more particularly to such a fluid fil¬ tering apparatus which is adapted to remove fine, particulate matter from hydraulic and other dielectric fluids by the elec¬ trostatic floculation of the particles thereof and the cap- turing of the floe so formed by filter media within the filter.

2. Background Art.

A number of methods, apparatuses and devices have been previously proposed to remove contaminants, such as par- ticulate matter, from hydraulic fluids, and other dielectric fluids. It has long been known, for instance, to remove par¬ ticulate contamination by mechanical filtration. However, . such mechanical filtration of particles having a dimension of less than about 5 to 10 microns, known as "fines" in the art, has either been ineffectual due to the relative ease with which such fines travel through the filter medium employed or because the relatively small size of the particles requires filters of considerable bulk and volume to avoid an excessive pressure drop within the fluid system due to the necessarily small filter openings required. It has long been known that some such mechanical filtration also incidentally removes many desirable additives in the fluid.

As an alternative to purely mechanical filtration, a number of different devices have been proposed to remove the fines from the fluids electrostatically by passing contaminated fluid over or through a plurality of electrodes, alternately charged positively and negatively or alternately energized and grounded. In some of the electrostatic filters known in the art, porous filter media are disposed intermediate adjacent electrodes for trapping particulate matter. Filtration is accomplished in one of two or more ways. One manner is the creation of an electric field between two adjacent electrodes whereby the filter medium itself is caused to be charged and to attract the particulate matter to itself. Alternatively,

filters known in the art cause, particulate matter to be var¬ iously charged negatively or positively so that oppositely charged particles will attract to each other to form a floe of larger particulate clumps which may be satisfactorily re- moved by mechanical filtration.

While many of the prior art electrostatic filters heretofore known and available have been more or less effec¬ tive for their intended purposes, many of the devices and ap¬ paratuses are expensive to construct, bulky or of complicated structure. Further, many of the prior art electrostatic fil¬ ters are best suited for use in central fluid purifying in¬ stallations in a substantially stable environment.

Therefore, it has long been known that it would be desirable to have an improved electrostatic filter for remov- ing particulate contaminants from hydraulic fluid and other dielectric fluids and which is adapted for use, for instance, on individual vehicles or the like having fluid systems sus¬ ceptible of particulate contamination and resultant damage due to wear and blockage of passages caused by such contamin- ation. Moreover, it has long been known that it would be desirable to have such a device which is adapted to be con¬ structed inexpensively and of minimal dimensions; which can be constructed as a disposable, rapidly and easily replaced component in a fluid system; and whose construction permits the deployment thereof within a conventional fluid system without substantial structural modification to the fluid sys¬ tem whereby replacement of the filter requires a minimum a- mount of labor and time.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present inven¬ tion to provide an improved electrostatic filter adapted for use in removing particulate contaminants from dielectric flu¬ ids, such as hydraulic fluids and the like. Another object is to provide such a filter which is operable effectively to remove even fine particulate matter having a diameter at least as small as about 5 microns and smaller.

Another ob ect is to provide such a filter which can be constructed in a variety of forms for use in numerous differing fluid systems, such as hydraulic and other dielec¬ tric fluid systems, lubrication systems, and the like in ve- hides or machinery.

Another object is to provide such a filter which is adapted to be constructed compactly and which can be de¬ ployed within a conventional fluid system without substantial modification thereof. Another object is to provide such a filter which is of substantially simple structure and function and which can be constructed inexpensively, whereby the.filter can eco¬ nomically be disposed of at the end of its effective life. Another object is to provide such a filter which is adapted for quick and simple attachment to the components of an existing fluid system to facilitate the replacement of a used filter by a new one.

Another object is to provide such a filter which can be safely handled during the operation thereof. Further objects and advantages are to provide im¬ proved elements, and arrangements thereof in an apparatus for the purposes described which is dependable, economical, dura¬ ble and fully effective in accomplishing its intended purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front elevation of a first form of the fluid filter of the best contemplated modes of the present invention.

Fig. 2 is a top plan view of the filter of Fig. 1. Fig. 3 is a transverse section taken on line 3-3 in Fig. 1.

Fig. 4 is a longitudinal section taken on line 4-4 in Fig. 2, shown in perspective.

Fig. 5 is a side elevation of a second form of the filter of the best contemplated modes of the present invention. Fig. 6 is a top plan view of the filter of Fig. 5. Fig. 7 is a transverse section taken on line 7-7 in Fig. 5.

Fig. 8 is a fragmentary, transverse section taken on line 8-8 in Fig. 7.

Fig. 9 is a longitudinal section taken on line 9-9 in Fig. 6, shown in perspective.

BEST MODES FOR CARRYING OUT THE INVENTION

First Form . Referring more particularly ^" to the drawings, the filter of the first form of the present invention is gener- ally indicated by the numeral 10 in Figs. 1, 2, 3 and 4.

As shown therein, tha. filter generally provides a housing or case 11 of substantially cylindrical construction substantially symmetrical about a longitudinal axis, as can best be seen in Figs. 2, 3 and 4. The case has a first or inlet end portion 14 and an opposite, second or outlet end portion 15 spaced longitudinally therefrom. The case is of predetermined dimensions and provides an interior - volume generally related to the anticipated rate of flow of fluids through the particular fluid system in connection with which it is adapted to be used.

As can best be seen in Figs. 1 and 4, the inlet end portion 14 provides a substantially circular end cap member - 20 secured in substantially fluid-tight relation on the inlet end portion 14 and having a substantially cylindrical inlet tube 22 disposed substantially centrally thereof. The inlet tube 22 provides a longitudinal axis disposed substantially coextensively with the longitudinal axis of the case 11. The inlet tube protrudes from the end cap 20 to provide an exter¬ nal portion 24 mounting an annular O-ring 25 circumferentially thereabout, whereby the external portion 24 can be connected to an. appropriate fluid supply conduit (not shown) in snap- fitting or other connective fluid-tight relation for the de¬ livery of fluid from the conduit into the external portion 24 and through the inlet tube 22 into the case. An end cap 30 of substantially circular configu¬ ration is secured on the outlet end portion 15 in substantially close-fitting, fluid-tight relation to the outlet end portion. An outlet tube 32 is deployed substantially centrally thereof

and has a longitudinal axis disposed substantially coaxially with that of the inlet tube 22. The outlet tube provides an external portion 35 extending axially from the end cap 30 and mounts an 0-ring or annular member 37 in close-fitting, cir- cumscribing relation thereabout. Similarly to the inlet tube 22, the outlet tube 32 is adapted to be connected in fluid- flow relation with a fluid conduit of conventional design in a fluid system to permit the flow of fluid from the case 11 to the conduit (also not shown). The case provides a substantially tubular wall 40 having an exterior surface 42 and an interior surface 44. A pair of elongated, electrically conductive strips or buss bars 50 are adhered diametrically spaced from each other on the exterior surface 42, and each extends longitudinally from the inlet end portion 14 incompletely toward the outlet end por¬ tion 15. An electrically-conductive connector portion 52 is secured in electrically-conductive relation on a predeter¬ mined end of each buss bar 50. Preferably, although not nec¬ essarily, the connector portions 52 are secured on the ends of the buss bars 50 nearest the outlet end portion 15. The connector portions 52 can be configured and dimensioned as needed for connection to a preexisting electrical system of a vehicle or the like or to another conventional source of electrical energy and, as can be seen in Fig. 4, are config- ured and dimensioned substantially similarly to conventional spark plug connectors. Each buss bar 50 is enclosed along substantially its entire length by a substantially semi- cylindrical guard or shield 54 constructed of non-conductive material to protect the buss bar against damage and to pre- vent harm to persons which might otherwise occur in the event of accidental contact of the buss bar by a person during the operation of the filter while the buss bar is energized by an electrical source.

An annular support member 60 is disposed in sub- stantially concentric relation to the interior surface 44 of the wall 40 of the inlet end portion 14 of the case 11. A porous, substantially planar, electrically- conductive metal electrode 62 having a substantially circular

configuration is disposed atop the annular member 60 and is supported thereby. The electrode is spaced from the end cap 20 a predetermined distance to provide a pooling chamber or space 63 of predetermined volume therebetween. The electrode 62 provides a multiplicity of perforations or bores 64 there¬ through. The electrode 62 provides a substantially circular, peripheral edge portion 66 having an electrically-conductive retaining tab member 68 projecting slightly obliquely from the plane of the electrode 62 and disposed in proximity to that portion of the interior surface 44 of the wall 40 near¬ est the buss bar 50.

An electrically-conductive pin member 70 providing a head portion 72 and a distal portion 74 extends through the wall 40 to dispose the distal portion 74 thereof in electrically-conductive engagement with the tab portion 68. Preferably, the tab member 68 is dimensioned and configured to permit biasing of the distal portion 74 of the pin member 70 between the tab member and the peripheral edge portion 66 whereby the electrode is prevented against accidental dis- placement or dislodging and electrical conduction between the buss bar and the electrode is insured.

A filter pad member 80 of substantially circular configuration and predetermined thickness is supported on the electrode 62. Preferably, the filter pad 80 is of a dia- meter whereby it is disposed in contact with the interior surface 44 of the wall 40 about its periphery. Preferably, the filter pad 80 is constructed of reticulated foam material or like material having communicating pores, although other suitable porous filter media may be used. A second electrode 62, constructed in the manner of the first filter pad, is supported on the filter pad 80 and the tab 68 thereof is engaged by the distal portion 74 of a pin 70 extended through the buss bar 50 diametrically opposite that through which the first pin 70 is extended, whereby the application of opposite electrical potentials to the buss bars will oppositely charge the adjacent elec¬ trodes. A plurality of similar filter pads 80 and elec¬ trodes 62 are similarly alternately disposed in close- fitting, over-laying relation to each other to provide a

stack of electrodes and filter pads, as can best be seen in Fig. 4, whereby adjacent electrodes are capable of being charged oppositely of each other by the application of oppo¬ site electric charges to the buss bars. The electrodes are preferably spaced axially of each other a distance sufficient to prevent arcing across adjacent electrodes upon the appli¬ cation of an electrical charge thereto.

The electrodes 62 are each attached to the buss bars 50 in parallel electrical relation, whereby each can be charged substantially equally to the others attached to the same buss bar. Further, accidental dislodging of an electrode from a pin will not prevent the remaining connected electrodes from functioning normally.

A second annular member 85 is disposed within the outlet end portion 15 of the case 11 preferably in contact with the peripheral edge portion 66 of the electrode 62 near¬ est the outlet end portion to retain the stack of electrodes and filter pad members against axial movement within the case in the event of accidental movement thereof or disposition of the filter 10 in an inverted attitude wherein the outlet end portion 15 is disposed lower than the inlet end portion 14 to permit the flow of fluid through the case 11 toward the outlet end portion 15 by gravity. The second annular member 85 serves the further purpose of maintaining the final electrode 62 nearest the outlet end portion 15 in spaced re¬ lation from the end cap 30 to define a space 88 of predeter¬ mined volume between such electrode and the end cap.

Second Form The second form of the filter embodying the prin¬ ciples of the present invention is generally indicated by the numeral 100 in Figs. 5, 6, 7, 8 and 9.

As shown therein, the filter of the second form generally provides a housing or-.case 110 of substantially cylindrical construction having a first or inlet end portion 114 and an opposite second, or outlet end portion 115 spaced longitudinally therefrom. As can best be seen in Figs. 6 and 7, the case 110 is substantially circular in transverse

cross section. A substantially circular end wall 117 is se¬ cured on the inlet end portion in fluid-tight relation there¬ to. A substantially circular end wall 118 is secured on the outlet end portion in fluid-tight relation thereto. An elongated, substantially cylindrical tube member

120 providing an inlet end portion 122 and an opposite, out¬ let end portion 124 is extended through the inlet end wall 117 and outlet end wall 118 to dispose the tube 120 in co¬ axial relation to the case 110 with the inlet end portion 122 and outlet end portion 124 external thereof. The tube 120 provides an internal portion 127 disposed completely within and axially coextensive of the case 110. Preferably, although not necessarily, the case 110, end walls 117 and 118, and tube 120 are constructed of polyvipyl chloride or other suitable non-conductive material.

An elongated, first conductive strip or buss bar member 130 is secured on the inner aspect 132 of the tube 120 and has a first end portion 134 disposed within the in¬ let end portion 122 of the tube and a. second, opposite end portion 136 disposed in proximity to the outlet end portion 115 of the case 110 within the tube 120.

A second electrically-conductive strip or buss bar member 140 is secured on the interior aspect 132 of the tube 120 and is of a construction similar to that of the first buss bar member 130. The second buss bar member 140 pro¬ vides a first end portion 142 within the outlet end portion 124 of the tube 120 and an opposite, second end portion 144 disposed in proximity to the inlet end portion 114 of the case 110 within thetube 120. The second buss bar member 140 is spaced substantially diametrically oppositely of the first buss bar member 130 on the interior aspect 132 of the tube 120.

The tube 120 provides a first deflector or baffle member 150 disposed in sealing relation within the internal portion 127 thereof in proximity to the inlet end portion 114 of the case 110 and spaced slightly internally axially there¬ from. A radial bore 154 communicates through the internal end portion 127 of the tube 120 intermediate the baffle member

150 and the inlet end wall 117. A second deflector or baffle member 156 is similarly provided in the internal portion 127 of the tube 120 in proximity to and spaced slightly longi¬ tudinally internally from the outlet end portion 115 of the case 110. A second radial bore 158 is provided in the inter¬ nal portion 127 intermediate the second baffle member 156 and the outlet end wall 118.

A plurality of electrically-conductive rods or pin members 160 extend from the first buss bar member 130 through the tube 120 radially within the case 110. A plurality of electrically-conductive rods or pin members 162 are disposed in electrically-conductive relation to the second buss bar member 140 and extend therefrom radially through the tube 120 within the case 110. As can best be seen by reference to Fig. 9, the pin members 160 and 162 are spaced longitu¬ dinally a predetermined distance from each other and are al¬ ternately disposed longitudinally along the internal portion 127 of the tube 120.

A plurality of electrically-conductive plates or electrode members 170 are provided. As can best be seen in Fig. 7, each electrode is of substantially circular configu¬ ration of a diameter slightly less than that of the case 110. Each electrode has an inner edge portion 172 defining a sub¬ stantially circular hole therethrough, the inner edge portion having a pair of substantially diametrically spaced, cut-out portions 175 extending radially from the inner edge 172 to¬ wards the outer edge 177 of the electrode. The electrode members 170 are substantially planar and provide a tab por¬ tion 180 projecting obliquely from the electrode member 170 adjacent the inner edge portion 172, as can best be seen by reference to Fig. 8. Preferably, although not necessarily, the tab portion 180 of each electrode is disposed inter¬ mediate the cut-out portions 175 about the circumference of the inner edge 172. The tab portion 180 of each electrode member 170 is disposed to define a notch or recess 182 be¬ tween the tab portion 180 and the electrode member 170. As can best be seen by reference to Figs. 8 and 9, each elec¬ trode 170 is disposed within the case to deploy the electrode

member 170 substantially transversely to the longitudinal axis of the case and is positioned to dispose the notch 182 in capturing relation about a pin member 160 or 162, whereby the tab 180 and electrode member 170 are in substantially 5 electrically-conductive relation to such a pin. As can best be seen by reference to Fig. 9, the electrode members 170 are disposed in spaced relation longitudinally of each other within the case whereby adjacent electrode members engage diametrically opposed pin members and are in electrically- conductive relation to opposite buss bar members 130 and 140. Each electrode member 170 is constructed of a material similar to that of the electrode members 62 of the first form of the preferred embodiment and provides a multiplicity of bores or perforations 185 completely therethrough. As are the electrodes 62 of the first form, the elec¬ trode members 170 are connected in parallel electrical rela¬ tion and are spaced to prevent arcing across adjacent electrodes.

The electrode member 170 nearest the end wall 117 of the inlet end portion 114 is preferably spaced from the end wall a predetermined distance to define and bound a pool¬ ing chamber or space 187 of predetermined volume communica¬ ting with the radial bore 154. Thus, fluid passing through ^• the radial bore 154 from the inlet end portion 122 of the tube 120 is caused to pool or accumulate within the space 187 to permit substantially even distribution of such fluid prior to engagement of the electrode member 170 thereby, when the case 110 is disposed in a substantially axially erect attitude.

Similarly, the electrode member nearest the outlet end portion 115 of the case 110 is preferably spaced from the end wall 118 thereof and defines a pooling chamber or space 188 bounded by the electrode member and the end wall. Fluid pooled within the space 188 is thus permitted to be discharged through the radial bore 158 substantially without obstruction to the flow thereof and to prevent stagnation of the fluid which might otherwise occur if the electrode abutted the end wall.

As does the first form of the best modes, the second form provides a plurality of filter pad members 190 constructed

of reticulated foam or other suitable material having com¬ municating pores therethroughout. Each pad member 190 is of predetermined thickness and has an outer edge portion 193 of substantially circular configuration. Preferably, each filter pad member 190 has a diameter substantially equal to that of the interior of the case 110 whereby the outer edge portion 193 of each filter pad is- disposed in close-fitting relation with the case.

Each filter pad member 190 further provides an inner edge portion 195 of substantially circular configura¬ tion dimensioned closely to be received about the tube 120.

A pair of substantially identical, tubular coupling members 200 are provided for connection of the filter 100 in fluid-flow relation to a flow line or conduit (not shown) of a hydraulic or other fluid system. Each coupling member provides a substantially tubular body 202 having a substan¬ tially cylindrical inner wall 204 mounting an annular, electrically-conductive ring portion 206. An electrically- conductive conductor member 208 extends in electrically- conductive relation from the ring radially out of the coup¬ ling member 200 and is adapted to be connected in electrically conductive relation to one terminal of a source of DC electrica potential. While the conductor member 208 is illustrated as having a substantially rodlike configuration, it is to be understood that it can also be constructed in the manner of the connector portion 52 of the filter 10 of the first form, or in any suitable form adapted for connection to a pre¬ existing electrical conductor of a conventional source of electrical energy. The coupling member 200 is dimensioned for slidable, close-fitting deployment thereof in fluid- tight relation about either the inlet end portion 122 or outlet end portion 124 of the tube 120, as appropriate. The ring member 206 is positioned to be brought into electrically- conductive relation with a buss bar member 130 or 140 when the couplingmember 200 is received upon such end portion of the tube. One or more O-ring members 210 can be provided to insure a fluid-tight seal between the coupling member 200 and the end portion of the tube on which it is received.

INDUSTRIAL APPLICABILITY First Form For use as a fluid filter in a conventional di¬ electric fluid system, and more particularly for use in a 5 hydraulic fluid or lubricating fluid system, the filter 10 of the first form of the best modes of the present invention is connected in fluid-flow relation to a fluid supply flow line of such system. A fluid delivery line, not shown, is connected in fluid-flow delivering relation on the external 0 portion 24 of the inlet tube 22 of the inlet end portion 14 of the filter 10, employing an appropriate conventional con¬ nector. Similarly, a second fluid flow line, also not shown, is connected in fluid-flow receiving relation on the external portion 35 of the outlet tube 32 on the outlet end portion 15 5 of the case 11. Preferably, although not necessarily, the case 11 is disposed in a substantially axially erect attitude with the outlet end portion elevated above the inlet end por¬ tion to afford maximal distribution of the fluid throughout the case and maximal contact of the"electrode members and 0 filter pads by the fluid.

A source of DC electrical potential, preferably capable of generating voltage in the range of from about ^• 5,000 to 50,000 volts, is then connected to the connector portions 52. An electrical conductor, not shown, adapted to conduct a positive charge from one terminal of the DC source is connected to either one of the connector portions 52, as desired or appropriate, by conventional means. A second electrical conductor, not shown, adapted to deliver a negative charge is connected by appropriate conventional means 0 to the remaining connector portion 52. Thus, one buss bar 50 will be charged positively by the application thereto of a positive electric charge from the source of DC potential through a connector portion 52, and the remaining buss bar 50 will similarly be charged negatively. in operation, fluid is caused or permitted to flow through the inlet tube 22 of the inlet end portion 14 from the fluid delivery line, not shown. In most conventional fluid systems, the rate of flow of the fluid will be sufficiently

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a filter constructed according to the first form of the pre¬ ferred embodiment of the present invention having a total of 17 electrodes sandwiched about reticulated foam filter pads of a thickness of 5/8 of an inch (1.58 cm) and having approxi- mately 80 pores per square inch of surface area is effective in substantially eliminating particles of a diameter in the range of from about 0.5 microns to about 10 microns from fluid passing therethrough. . Further, it has been experimen¬ tally found effective to provide electrodes having apertures or bores having diameters in the range of from about 1/16 of an inch (.158 cm) to about 1/8 of an inch (.317 cm.). How¬ ever, it will be appreciated that the diameter of the aper¬ tures can be less than or greater than those stated without significant loss of efficiency in the operation of the filter. Further modifications in the construction of the filter of the first form of the preferred embodiment are pos¬ sible as well. For example, the electrodes can be in the form of screens having substantially rectangular or square openings rather than circular bores as illustrated. Also, for some filtering purposes, it may be desirable to substitute filter pads of differing degrees of porosity for some of the filter pads within the case 11. Filter media of various sorts can be employed within a single filter having a porosity in a range of from about 20 pores per square inch or lower to about 10Q pores per square inch or. higher, depending upon the type of contamination anticipated to be encountered, the pres¬ sure demands of the system, and the relative diameters of the particulate matter desired to be filtered. For instance, the filter pads disposed nearer to the inlet end portion can be of greater porosity than those more remote from the inlet end portion, with progressive decreases in porosity of the filter pads therebetween. In that manner, the mechanical filtration afforded by the filter pads may be maximized with a minimal resultant drop in pressure in the fluid system. Still further, a plurality of filters constructed according to the principles of the present invention can be employed in a single system, either deployed throughout the system remotely from each other or disposed in series or parallel flow relation to each other.

Second Form The operation of the second form of the preferred embodiment of the present invention is substantially identical to that of the first form. That is, for use as a filter in 5 a fluid system, the filter 100 of the second form of the pre¬ ferred embodiment of the present invention is first connected in a fluid-flow relation to such fluid system. A coupling member 200 is slid longitudinally over the inlet end portion 122 of the tube 120 and is connected using conventional means 10 in fluid-flow receiving relation to a fluid supply flow line of the fluid system. A coupling member 200 is slid longitu¬ dinally over the outlet end portion 124 of the tube 120 and is connected to a fluid flow line of the fluid system in fluid delivering relation thereto. 15 The conductor 208 of the coupling member 200 on the inlet end portion 122 is connected to one terminal of a source of DC electrical potential by appropriate electrically- conductive means whereby a charge either positive or negative can be applied thereto. Similarly, the conductor 208 of the 20coupling member 200 on the outlet end portion 124 is connected to the oppositely-charged terminal of the source of DC elec¬ tric potential (not shown) in electrically-conductive relation thereto.

Fluid is caused to flow through the coupling member 25200 and the inlet end portion 122. The- fluid will engage the baffle member 150 and be directed through the radial bore 154 into the space 187 between the end wall 117 of the inlet end portion 114 of the case 110 and the first electrode 170. The fluid then will well-up or accumulate and subsequently flow 30axially of the case 110 toward the outlet end portion 115.

As is the case with the first form of the preferred embodiment, the fluid flows axially through the case 110, and particulate matter carried by the fluid is alternately charged positively and negatively and caused to floculate whereby it 35can be filtered from the fluid by the filter pads 190.

Filtered fluid collects in the space 188 between the last electrode 170 and the outlet end wall 118 exiting through the second bore 158 whereby it is conducted out of the case

through the outlet end portion 124 of the tube 120 and the coupling member 200 mounted thereby.

Thus, it will be seen that the first and second forms of the best modes of the present invention each pro- vide an improved filter adapted for use in removing even the finest particulate contaminants from hydraulic fluid and other dielectric fluids and, further, provide such a filter which is adapted to be constructed compactly and which can be de¬ ployed singly or in multiples in fluid-flow relation within a variety of conventional fluid systems without substantial modification thereof. Moreover, thefilter of the present invention can be constructed inexpensively whereby the filter may be disposed of at the end of its effective life. The first and second forms also each provide a filter inherently resistant to malfunction or inadvertent dislocation of its component parts.

Although the invention has been herein shown and described in what are conceived to be the most practical and preferred modes, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the illustrative details disclosed.