Патент USA US2407190код для вставки
Sept. 3,' 1946. w. o. TAIT 2,407,190 FILTER FOR FLUID FLOW SYSTEMS Filed „nine 50, 1944 20 fa 2 /fv aff/WOR M4 0. 7A? / T . j 5y Patented Sept. _3, '1946 2,407,190 UNITED _STATES PATENT OFFICE l »_ _ FIIAQT‘Éi-t roaFLUm FLOW SYSTEMS i >`Williamp.Tait,"Garden City, N. Y., assignor to Sperry Gyròscopé Company, Inc., a corpora "tion of New York ` ’ [1f Y „Applicationìniiièsd1944,seria1N0.54as55 _'A ’i (Banner> (Cl. 21a-'7164) 2 'Iì‘his invention relates to the artV of filtering and is particularly concerned with a novel method of and apparatus for filtering fluids in reverse flow circulating systems, While theY invention hasa special _utility inrconnection with high pressure hydraulic servo systems _it _has awide range of application in filtering fluids lin. fluid circulating . channel. -In other words, the pressure difference above mentioned is in the -nature of a drop in static pressure between any section in the uncon stricted region of the l fluid channel and the 5 throat of the _channel Whether that section be upstream or downstream of the throat. Hence, by operatively connecting a filter ,between any systemsof all types. 'A A, u . Y A point subject `to relatively high pressure and a For several reasons filtration of the working point of reduced pressure in the fiow channel, a fluid in reversible ñow high pressure systems has 10 filtering system is produced in which the pressure not heretofore appeared feasible.- With the fil drop always occurs in the same direction irre tration methods previously tried, reversal of fluid flow in thesystem _has meant a reversal of pres spective of the direction of fluid flow in the other parts of the system, whereby a portion of the sure within the filtering unit accompanied by the circulating fluid .passes undirectionally through return of foreign particles, and other previously 15 the filter even when a reversing fluid flow exists removed substances to the main circulation chanin the main flow channels _of the system. nels of the system, a result highly undesirable. A similar» result is produced in unifiow systems stricted and constrictedregions of the fluid stream when excessive loading causes a temporary Vre is independent of the >actual working pressure Since the pressure drop between the uncon~ versalof flow, of the working fluid. Furthermore 20 ofthe system it is possible to control this pres in high pressure systems a filtering element strong sure drop by judicious selection of the cross sec enough to resist system pressure frequently allows tional area of the constricted region relative to small but destructive foreign lparticles to 'pass the cross sectionalgarea of the unconstricted'sec through the filterV and lcontinueV in circulation. tion and thus keep the pressure drop across the There has also been the further diiiicult problem 25 filter small enough to prevent rupturing of the of__ obtaining a filtering rate high enough to effece delicate filtering elements often used to remove tively cleanse the fluid Without unduly obstruct small particles from the fluid in the system', even ing the flow of fluid through thevsysterm.4 In hy in installations where the working pressure is relatively high. t v draulic _systems used for control purposes, par ticularly if high pressures are used, any com 30 Moreover since the filtering element is located pressibility of the working medium introduces out of _the main channel of flow and may be con error into the operation of the controls. Obvi nected therewith-by short, low resistance con ously adding a filter to the system usually entails duits, filtering of the system working-medium is increasing thefiuid content of the system, thus 'obtained With only a slight obstruction ofthe increasing the compressibility error above men tioned. - ` ' main` channel of flow. ' f The novel apparatus and methods of the present invention overcome the- ‘above ‘cited difficulties in the following ingenious manner. By introduc ing a constriction into the path of the main fluid stream, an'increase in velocity and a reduction in the static pressure of the stream is created in the region of the constriction, the velocity of flow and the static pressure of the stream in regions removed from the constricted region being rela 45 ’ ‘ The compactness ‘of the filtering system of th invention makes possible the filtering of the fluidA without materially increasing the vvolumetric capacity of the system, hence the effecten the compressibility error of the system is kept at a minimum. ~ > - v - ~ The objects of this invention may therefore be briefly enumerated -as‘followsz the provision of a filter and associated circulatory system suitable tively little affected by, this change inthe shape' for use in a reversible flow fluid system; the pro vision of a filter which may be used withhigh of the channel through which the fluid passes;V There is thus created a pressure difference be pressure fluid systems without danger of rupture of relatively delicate filtering materials or fine tween points located in the reduced diameter mesh screens; the provision of a filter having an `region and `points located in the full diameter 50 associated circulatory or auxiliary filtering circuit regions of the flow channel which is a function arranged for minimum obstruction of the work of the rate of stream flow and which operates-to ing passages of the fluid flow system in which it maintain the reduced diameter region at reduced is-used; the provision of filtering apparatus hav static pressure -irrespective of the *Y direction of ing the smallest fluid content consistent with fluid flow inthe constricted region ofthe »flow 55 effective filtering ofthe fluid in the system with 2,407,190 3 in by boss 22 on cap I1 and boss 23 on channel which the i’ilter is employed; the provision of a member 5, filtering element 2l being designed filtering method suitable for use in relatively to provide a large filtering surface in a unit of high pressure iluid flow systems; the provision compact dimensions. of a ñltering system which will induce constant Channel member 5 contains at least two, and if recirculation of the fluid through the ñlter, thus Cil desired may contain more than two, lateral open producing high filtering rate and effective cleans ings or conduits into ñltering chamber I9, these ing of the ñuid circulating through it; and the openings being as short as possible and being provision of filtering apparatus having no mov shaped to provide free and unobstructed passage ing parts to wear rapidly or break loose and interfor the iluid between the main flow channel 6 and fere with the operation of the system in which the ñltering chamber I9. One of these lateral the ñlter is installed. openings 24 which connects filtering chamber I9 Other objects and uses of the invention- willr be apparent from the following description and the to throat I4 serves as an exit conduit or outlet accompanying drawing wherein, from the filtering chamber .to the main channel of flow 6. One or more of these lateral openings 26 connects ñlteri'ngchamber I9 to a point of low ve Fig. 1 is a longitudinal section through one form of filter incorporating the principles of this invention. Fig. 2 is a sectional view on the line 2-2 of Fig. 1 taken at right angles to the main path of iiuid ñow through the ydevice of the invention, the filtering element being shown partly in ele vation and partly in section. Fig. 3' is a long‘fi'tudinalV section of'- a slightly modiñed version of the filter of'Fi'g. 1, the filter ing element being shown partly in section and partly in elevation. The apparatus of' the invention, in general, , lo‘city and high static pressure such as sections I2 or any relatively high pressure point located else where in `the main channels of flow; such connec tion or connections serve as inlets to lead fluid from channel 6, to filtering chamber I9, where the iiuid ls cleansed by passing through ñltering element 2|, thereafter flowing' back to channel 6 by way of lateral opening 24. This invention provides apparatus- characterizedV by> marked sim plicity and highlyv eiïective filtering performance which is obtained with a negligible increase in the resistance .to the ñow of thev working substance comprises a unit adapted to be' inserted at a con~ through the passageways of thel system. vement point in the main' path offl'ow of a closed In operation, iiui'd under high staticA pressure circulatory system whose working substance or 30 fluid may require- filtering, this unit containing a passageway which permits the iiuid to pass through with minimum obstruction ofthe fluid stream. In addition, means are provided for di verting a portion ofthe fluid from the main channel of flow into an auxiliary or local path of flow wherein the ilui'd is forced through a suitable ñl tering element and after cleansing is> returned to the main channel of’ flow at a point where the cross' section of this channel has been reduced for the purpose of creating a low pressure point in the main fluid stream. Thus, after filtering, the fluid in the auxiliary or filtering channel is returned to and intermingled withv the- fluid mov ing through the main passageways of the control or operating system. As illustrated in Fig; 1, one form of appara tus in which the principles of the invention may be embodied comprises a main channel> or' body member 5 having a channel 6 for passing' ñuid enters channel 6 or'member 5~ from' supply pipe 1, and ñows, for example as shown by arrow F in Fig. l, from the' unconstricted section I2 at the right hand end of channel 6, through the ' tapered approach passageway I5 into throat I4, out of throat I4 through they tapered exit pas sageway I5 into the unconstricted section I2', at the left hand end of channel 6, from which re gion it then flows into~` return pipe 8. As the 40 fluid passes from the upstream, unconstricted section I2 into the throat' I4, it experiences an increase in its velocity of flow' and a decrease in its static pressure; as it continuesV ori its way flowing back into the downstream, unconstricted 45 section I2, the reverse phenomenon occurs, the velocity of stream flow decreases and the static pressure of the fluid increases until it is' again atf the original value, except for slight- frictiona'l losses.- It will be noted that the pressure differ 50 ential thus created between the unconstricted regionsl of the channel of'flow and the constricted completely through body member 5y from supply region I4 is alwaysv in the nature of a fall in pipe 1 to return pipe 8 of the system with which static pressure; and this is true whetherv the un the' apparatus of the invention is employed, which constricted region I2 be upstream or downstream pipes are secured for ñuidti’ght" connection to member 5 as by bolts 9 and flange- Iß’using pack" 55 of throat I4'. The. laterall openings 26, being connected to regions of relatively high pressure ing‘ glands or sealing rings || to prevent the es I2, will always be inlet` passageways to filtering cape of iiuid from the interior of the' system. chamber I9, and lateral opening 24v being con Channel 6 is formed with .a full diameter section nected to the region of- relatively low static pres I2 'at' each end thereof and with a throated or constricted section I4 intermediate theA full> di 60 sure, i. e'., throat I4, will alwaysA be the outlet passageway for flltering'chamber I9, irrespective ameter sections I2, typically with symmetrically of whether the fluid is flowingY from right to left tapered funnel-shaped passageways I5, on’ both or vice versa in channel 6. A unidirectional now sides thereof for connecting throat I4 to- the full of ñuid through inlets' 26, iiltering' element 2|., diameter or unconstricted sections I2, in the and outlet 24 is thus providedA that is- not affected manner of a Venturi tube. by' a reversal of ilow through channel 6; Hence Channel member 5 also includes a hollow lat any foreign particles removed- from thef fluid erally projecting, externally threaded collar I6stream by' ñlter 2| will not be'A discharged back upon which an internally threaded cap or cover into the working iiuid ofthe system by a reversal' plate I1 is adapted to be> screwed’so ,as to form, ofV the direction of flow in the system. More~ with the aid of sealing ring I8, a fluid tightv con over, since the magnitudel of` the pressure differ nection. 'I‘he chamber formed by collar I6 and> ential created between throat |-4 andthe full' di' cap ÁI‘I is appropriately shaped and properly sized ameter regions Í'2 at the mouths of the' Venturi to form a filtering chamber I9. Filtering cham section in' channel 6, is a function of the velocity ber I9 may' contain a replaceable cartridge type of flow at these points, i‘,he~ap`paratusî of the in_ filtering element 2| held centrally secured there 2,407,190 5 6 vention provides a convenient means for creat ing a safe pressure diiîerential across a selected an internally threaded cap adapted for iiuidtîght attachment to said collar, a ñltering chamber filtering element irrespective of whether the sys tem operating pressure is above or below the rup turing pressure of the particular filtering ele ment. Filtering of minute particles from the formed by said collar and said cap, a re i placeable working fluids in relatively high pressure systems thus becomes practicable through the use of this invention. filtering element rigidly positioned between centrally located bosses in said filtering chamber, a small bore centrally located lateral fluid passageway between the throat of said Ven turi section aid said filtering chamber, and a pair of small bore lateral fluid passageways between said filtering chamber and points on said main flow channel adjacent the tapered portions and equispaced from the throat of said Venturi sec ' It will be readily discerned that locating the ñltering chamber and filtering elementl below the Venturi section of the main flow channel re sults in two additional advantages. Firstly, any foreign particles which do not adhere to the fil tering element will fall to the -bottom of the ñl tering chamber rather than pass back into the main fluid stream as they would do if the ñlter tion, thus providing a simple, rugged filter par- . ticularly suitable for use in relatively high pres sure iluid flow systems. 2. A filtering device for filtering fluid compris ing a conduit section adapted to form a Dart of were above rather than below the main flow chan a closed fluid-circulating system and shaped to nel. Secondly, since air is lighter than the work provide a venturi responsive to flow in either di ing medium ordinarily. used in such systems, any 20 rection to produce a reduced static pressure and bubbles of air which may accumulate on the ex yincreased velocity of the fluid at one point in terior of the filtering element are free to rise back said conduit, an auxiliary passage leading from into the main flow channel during periods when another point in the same conduit as the first point but in a region of higher static pressure the fluid in this channel is motionless, thus pro viding a self-Venting filter. i and discharging into the conduit at said one Tests of the above described ñltering device point, and a ñltering element in said passage have shown that a pressure difference as low as whereby a portion of the fluid flowing in the sys 20 lb. per square inch may be obtained across the tem is directed through the filtering element al filter in a system where the load pressure reaches ways in the same direction while flow in the sys ticles with dimensions as small as 10 microns may tem takes place in either direction. 3. A filtering device for filtering fluid com be ñltered out of the working duid by the appa prising a conduit section adapted to form a part ratus of invention. of a closed fluid-circulating system and shaped to as high as 2000 lbs. per square inch, and that par- - ` The version of the invention illustrated in Fig. 3 is `but slightly different from the device of Fig. 1. In the Fig. 3 version the taper of the approach and recession passageways of the Venturi section provide a reduced-diameter throat and two op positely directed and symmetrical tapered sec tions forming a venturi responsive to ilow in either direction to produce a reduced static pressure and is more gradual and a cover plate 21 secured to increased velocity of the fluid at said throat, an channel member 5 by holding bolts 28, 29 is used ' auxiliary passage leading from a point in said in place of screw threaded cap l1 of Fig. l. Oth 40 conduit adjacent the outer end of one tapered sec erwise a slight difference in physical dimensions is the feature primarily distinguishing the Fig. 3 filter from the Fig. 1 filter. In use, these two versions of the invention exemplify the same op erating principle. `Since the above described inventive concept could be readily embodied in many apparently different physical forms without departing from the scope of this invention, it is intended that all matter contained in the speciñcation or shown . in the accompanying drawing be interpreted in an illustrative and not in a limiting sense. Having thus illustrated the manner in which the principles of this invention may be applied, what is claimed is: 1. A filter for closed fluid flow systems com prising a body member arranged for fluidtight at tachment to spaced conduit terminals of said system, a main flow channel passing through said body member, a symmetrically tapered Venturi section having equal angles of approach and re cession centrally located in said flow channel, a hollow externally threaded collar integral with and projecting laterally from said body member, l'x 2.1 tion and discharging into the conduit at said throat, and a filtering element in said passage whereby a portion ofthe fluid flowing in the sys tem is directed through the filtering element al ways in the same direction while ilow in the sys tem takes place in either direction. 4. A filtering device for filtering fluid compris ing a conduit section adapted to form a part of a closed fluid-circulating system and shaped to provide a Venturi responsive to flow in either di rection to produce a reduced static pressure and increased velocity of the fluid at one point in said conduit, means forming a ñlter chamber at one side of the conduit section, an outlet from the chamber comprising a short direct passage to said one point, an inlet to the chamber com prising a passage leading from another point of higher static pressure in the conduit section, and a ñltering element removably positioned in the chamber whereby a portion of the fluid flowing in the system is directed through the ñlterirng ele ment always in the same direction while flow in the system takes place in either direction. WILLIAM O. TAIT.