CA1054073A

CA1054073A - Gas purging fluid filter

Info

Publication number: CA1054073A
Application number: CA064,819A
Authority: CA
Inventors: Nat Shaye; David Bellamy (Jr.)
Original assignee: Baxter Travenol Laboratories Inc
Current assignee: Baxter International Inc
Priority date: 1968-12-26
Filing date: 1969-10-14
Publication date: 1979-05-08
Also published as: DE1959679C3; GB1221625A; DE1959679B2; IL33294A0; FR2027609A1; IL33294A; BE741069A; DE1959679A1

Abstract

GAS PURGING FLUID FILTER

ABSTRACT OF THE DISCLOSURE

Gas blocking of fluid through a filter, when disposed at any aspect, is prevented by a non-wettable porous membrane which is spaced from the filter a distance such that a volume of air which would be sufficient to cover upstream surface of the filter simultaneously will engage the porous membrane and be vented.

Description

)'73 GAS PIJRGI~G FLUID FILTER ;:

The invention relates to a gas purging device in a liquid flow systern. ParticularLy the invention relates to a filtering device for liquids with means for venting gases tending to inter-fere with liquid flow.
In many types of medical treatment it is necessary to introduce liquids into a patient in large volumes. A problem incldent to the administration of such liquids has been in the elimination of air bubbles to prevent potential fatality because of 10 air embolism. According to heretofore known techniques air is cleared from an administration line prior to liquid injection into a patient by permitting its escape from the downstream end of the administration equipment. If a sufficiently large volume of liquid is required so that more than one supply container is needed, the injecting needle may require removal from the patient as each new supply source is provided to clear air which would enter the line following administration of the contents of each container. To obviate the requirement for needle removal, various time consuming and difficult techniques, including the use 20 of a bleeder valve, have been proposed and are used.
Advances in the art, however, have resulted in routine use of a microporous filter in a fluid administering line with a view to barring entry into the body of particulate and even bacteria. To ;
facilitate flow, these filters are of a class defined as wettable or ;~
hydrophilic; and in administration sets of usual construction they block the flow of gases. In consequence, danger OI embolism is ; ; -'73 ;: ' ` .
minimized inasmuch as air will pass the ïilter only under pressures which exceed the bubble point of the filter, such conditions not being conventionally present. As a result a plurality of supply reservoirs ~ ~
may be connected in sequence to a patient wlthout removal of the ;
administering needle from a patient's body.
Another problem of using a filter is that liquid flow through the filter will be irl~paired, even blocked, by a volume of air sufficient to cover the surface of the filter, unless the air is dis-placed therefrom, One prior means employed for that purpose is a flexible filter housing which permits blocking air to be squeezed up-10 stream for the purpose of be?ng exchanged with blocked fluid inorder to reestablish flow in an administering line. This procedure is time consuming and there is always a risk that sufficient pressure may be generated during squeezing to pass the bubble point of a filter. Then, rather than displace the air upstream of the blocked fluid, the air may be displaced through the filter downstream with potential dangerous consequences of embolism.
Venting means also have been suggested for removal of air ~ ~
from the chamber immediately above the filter. However, then - ;
there is a risk of losing administered liquid through the venting ;-20 means. To overcome that likelihood a hydrophobic vent can be arranged adjacent the filter chamber to the end that air will be purged through the vent while flow of fluid will be prevented from flow through such vent. However, the- mere provision of a vent repellent to the liquid is not an entire solution because of the problem of position sensitivity.
That is to say. the air in an administration set ordinarily ; . . ....... - , . :

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1()54~73 will tend to rise in the fil~er chamber if the filter housing i5 at an aspect which positions the vent in the path o~ the rising air, the latter will escape ~he system through the vent.
~lowever, the filter housing of a medical administration set may assume an aspect duxing use in which -the vent will not be disposed in the path of rising gas in the line; and this condition may arise even though the filter housing is designed with a view to having the vent il~ an uppermost position. Then, the air, upon rising, would become trapped within the filter housing, there, to exercise its detrimental flow blocking effec-t.
It is an object of the present invention to provide an improved filter construction for a liquid, adapted for purging gases mixed therewith, and of such construction as to be position insensitive. That is to say, it is an object of the invention that gas upstream of a filter in fiow apparatus for a liquid be purged from the system regardless of the angular aspect of the filter or the housing in which the filter is disposed.
To effect the foregoing object a filter construction comprises a housing. ~n inlet is adapted for admission of a mixture of gas and liquid into the housing. First and second outlets are provided for removing the liquid and the gas, respectively, from said housing. A li~uid-wettable filter member is arranged for intersecting fluid moving from the inlet toward the first outlet; and a liquid-repellent porous member is spaced from and overlying the wettable filter member at such a small distance that a minimum volume of gas of a magnitude sufficient to cover the wettable filter member wnen the housing is oriented in space so that the filter member above the porous member will -~
simultaneously engage the liquid-repellent porous member and a portion of such gas will be vented from the housing through the second outlet. The housing comprises a pair of casing sections, ~ -one of said casing sections having ports defining said second out-let, and means associated with said casing sections for supporting said filter member and , '.
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1~541s~73 said liquid-repell~nt member in a pair of opposed, convex, curved planes, with central portions of said filter member and said liquid-repellent member in close approximation.
How to further effect the foregoing ~,nd o-ther ob jects, features and advantages of the invention will become more apparent upon consideration of the following description and appended claims, when considered in conjunction with the accompanying drawings wherein the same reference character or numeral refers to like or corresponding parts throughout the several views of which:
Figure 1 is a vertical sectional view of a filter co~struction embodying one form of the invention;
~ igure 2 is a view of a modified embodiment of the invention according to the section line 2--2 of Figure 4;
Figure 3 is a view of said modified embodiment according to the section line 3--3 of Figure ~; and Figure 4 is a top plan view of the modified e~bodiment.
Referring now more particularly to Figure 1, the filter construction shown comprises a housing generally designated 10 and is formed from first and second preferably flexible and like proportioned casing members 11 and 12 which are disposed in opposed relationship. Preferably said casing members are trans~
parent and may be fabricated from a plastic, such as ~inyl of suitable guage. The casing members may be rectangular sections prior to assembly and in the construction are secured together about their perimeters in any suitable fashion such as with an adhesive which may be of a solvent type. Preferred, however, is heat-sealing because of the ease of manufacture.
The seal is continuous except at the position of entry of an inlet 14 and outlet 16 to which proximate portions ~;

of said casing ' . ,~ .

~5~ 3 mem~ers are secured, such as by heat, in a fluid tight seal. The inlet and outlet may be a pair of plastic flexible tube sections of suitable fabrication such as vinyl but with walls having thickness such that desired rigidity is imparted. In the exemplary embodi-ment in Figure 1, the tubes comprising said inlet and outlet are coaxially spaced apart and project from opposite ends of housing 10 in communication with a liquid chamber 17 defined within said housing .
A separator 18, which may be a section of vinyl sheeting ;
proportioned with substantially the same dimensions as casing members 11 and 12, is perimetrically secured in an airtight seal to the casing members at one side of inlet 14 and outlet 16 when viewed in section (as in Figure 1); and, is disposed ~between said ~ ;
casing members to delineate said liquid chamber 17 and an adjacent air chamber 20. The separator has foramina or pores 30 for passing gas from one side to the other thereof. As will be apparent from the ensuing description, separator 18 is not critical to the invention. In the exemplary embodiment now being described it is provided to insure an appropriate marginal seal for a gas vent 22 when the parts are secured together by application of heat and ~-pressure.
The gas vent 22, is a porous membrane or suitably treated mesh or the like which is disposed adjacent separator 18, said vent being proportioned to extend over the entire of that surface of the separator which faces chamber 20. The vent is marginally or perimetrically secured in a gastight seal between the separator and casing member 12. In Figure 1 it is seen that the foregoing con-,.. , , ., ., ~ , .. ... . . ............................................... .
. ' ~ ' :, : ~ - : ~ .' ' 11~5~373 struction results in securance of medial portions of opposite ends of separator 18 and vent 22 to a common side of inlet 14 and outlet ;;
16 when considered in vertical section.
Vent 22 is characterized in that it is highly repellent to a liquid being handled in the filter construction. To that end, the fabric or material of the vent itself may be liquid repellent or may be treated in any suitable manner known in the art for producing the highest liquid repellency. Herein, vent 2 is a nylon mesh as a base and a thin coat of polyvinyl chloride acrylic polymer over said base for producing a hydrophobic member.
~ filter member or porous body 24, wettable by the liquid to ;;
be handled, is shown in the form of a membrane. The filter member has medial marginal or perimetric portions of opposite faces of its opposed ends secured to opposite sides of the inlet 14 and outlet 16 when considered in vertical section. The remainder of the perimeter of filter member 24 is secured between casing members 11 and 12 in a manner such that said membrane is arranged in somewhat of a diagonal aspect in chamber 17, dividing said chamber into an up- ~ ~
stream compartment 26 and a downstream compartment 28. Com- ~ -partment 26 is in direct fluid communication with inlet 14 and down-stream compartment 2B is in direct fluid communication with outlet ,-16 for removal of liquids passed by said filter member.
Herein filter member 24 is hydrophilic, being a nylon based mesh with a cover of polyvinylchloride-acrylic with its surface coated with a wetting agent such as sodium lauryl sulfate, polyvinyl alcohol, or the like. The pore size of member 24 is small enough to filter out particulate which may be normally encountered or expected to be encountered in the liquid undergoing filtration. If ,:

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, :~15~73 the filter construction is for a medical fluid administration set and it i,s desired to filter microorganisms, the pore size should be less than three-tenths of a micron.
The manner in which the ~ilter construction operates is as follows: a mixture of gas and fluid (influent~ enters the filter housing through inlet 14 from which the mixture flows into compartment 26, Once filter member 24 is wet, the liquid portion of the influent will flow through it and be removed from housing 10 through said outlet.
The character of a wettable membrane is such that once wetted 10 it is repellent to gas. Accordingly, the filter membrane will not pass gas unless gas pressure in chamber 26 is at or above its bubble point. Normally, any gas which enters chamber 26 mixed with `
liquid will tend to rise and if it can escape through vent 22 no problem is encountered.
In a heretofore known filter construction of the type with which the present invention is concerned, if its housing becomes disoriented so that its vent is not in an uppermost aspect, gas entering the filter ~ -housing may be trapped therein. The volume of trapped gas in such event may be large enough to cover a part or all of the wettable 20 filter membrane. In such event liquid flow through the latter member will be curtailed or cut off completely. ~ ` -In accordance with the present invention, vent 22 is arranged or spaced from filter member 24 a distance such that a gas bubble sufficient to cover the upstream surface of said filter member will simultaneously engage the vent. Thereby, at least a portion of the gas will be relieved through chamber 20 to the exterior via ports or openings 32 in casing member 12. Accordingly, regardless of the ~5~73 aspect of housing 10 or filter member 24, sufficient gas will be purged from compartment 26 to at least partially uncover the filter member, thereby preventing blockage of liquid flow therethrough.
The modified filter construction (Figures 2 - 4) may also be characterized as having position insensitivity. It comprises a housing 110 defined by casing sections 111 and 112 which may be fabricated of rigid transparent plastic or other suitable material.
The housing has a medial section 113 on opposite sides of which sections 111 and 112 are rigidly secured. A plurality of straight 10 ties of plastic fabrication serve as the connecting agency, being ~ ~
sealed by deforming in aligned holes in sections 111, 112 and 113. `
Medial $ection 113 spaces sections 111 and 112 one from the other to define therebetween a chamber 117. An inlet 114 to chamber 117 is a tube which may be integrally fashioned with medial section 113.
Section 112 has a central elevated portion defined by a plurality of arcuate ridges or ribs llS ~only some of which are numbered) and which project from said last section in concentric association.
Ridges 115 are integrally fashioned with section 112 and are of 20 varying heights to provide a curved support for a convex cylindrical shape, ~ ;
~ plurality of arcuate channel sections 119 (only some of which are numbered) are generated between ridges 115 and outermost of the ridges and the outer wall of section 112. By means of a straight channel 121 which is formed by aligned ends of some of ridges 115, the arcuate channel sections 119 are communicatively connected one with another and with an outlet passage 116. The latter is formed in ~os'~
section 112 and communicates with the exterior through a tubular casing exten.sion 129.
Channels 119 open toward chamber 117 from which they are physically separated by a wettable porous body or filter member -;
124, the latter having the same characteristics as filter member `
24 herein described in connection with Figure 1. Filter member `
124 is supported on ridges 115 to form a cylindrical section with ~ ~
j ,, ;~.
a rim or perimeter portion 123 sealed in its entirety between medial section 113 and casing section 112 in a manner such that chamber 117 communicates with outlet 116 only through said filter member.
A plurality of integral arcuate ridges or ribs 125 (only some `
of which are numbered) extend outwardly from casing section 111 in concentric assoclation with one another. E~idges I25 are of varying height and are proportioned as a support for a convex cylindrical section.
Fsidges 125 generate in casing section 111 a plurality of communicating channel sections 127 (only some of which are ~-numbered). Said channel sections also communicate with the exterior of the housing 110 throu~h a plurality of venting pores 132 fashioned in said last casing section.
A non~wettable liquid repellent porous member comprises a vent 122 and has the characteristics of vent 22 heretofore defined in connection with Figure 1, Vent 12Z is supported on the ridges ~ ;
125 and has a perimetric portion which is disposed in an airtight `
.:
seal between the casing section 111 and the medial section 113.
Thereby only gas may pass from chamber 117 into channels 127 .~
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.... .. ..... ... ..... .... . . . . . . . . .. .. .. .. . . .
.. .. : ,. ", .. -07~

and then only through vent 122, the passage of liquid being pre-vented by the liquid repellent characteristics of said vent.
Ridges llS and 125 comprise means, respectively, for supporting mernbers 124 and 1~2 in planes which are curved convexly toward each other. They are proportioned in a manner such that they come exceedingly close to contact one with the other, that is to say, they are fashioned so that chamber 117 enlarges by tapering outwardly from its narrowest dimension which is disposed medially of housing 110. Moreover, the height of said ridges is such that any volume of gas sufficient to cover the liquid wettable filter member 124 will simultaneously engage vent 122. Thereby at least a portion of such gas will be immediately vented through gas vent pores 132 to prevent complete blocking of liquid flow through housing 110.
As many substitutions and changes could be made in the ~ . :
above described construction, and as many apparently widely different embodiments could be constructed without departing ~ ~
from the scope and spirit of the invention, it is intended that all .
matter contained in the accompanying specification shall be interpreted as being illustrative ~d n~t in a limiting e:enee.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

Claim 1. A filter construction comprising: a housing; an inlet for admission of a mixture of a gas and a liquid into said housing; first and second outlets for removal from said housing of a liquid and a gas, respectively; a liquid-wettable filter member arranged for intersecting fluid in said housing moving toward said first outlet; a liquid-repellent porous member spaced from and overlying the liquid-wettable member at such a small distance that the minimum volume of gas of a magnitude sufficient to cover the liquid-wettable filter member when the housing is oriented in space so that the filter member is above the porous member will simultaneously engage the liquid-repellent porous member for venting at least a portion of such gas from said housing through the second outlet, said housing comprising a pair of casing sections, one of said casing sections having ports defining said second outlet, and means associate with said casing sections for supporting said filter member and said liquid-repellent member in a pair of opposed, convex, curved planes, with central portions of said filter member and said liquid-repellent member in close approximation.
Claim 2. A filter construction according to claim 1 in which said liquid-wettable filter member being disposed between said casing members and defining upstream and downstream compartments, said downstream compartment communicating with said first outlet and said upstream compartment communicating with said inlet and said second outlet, said liquid-repellent porous member being positioned in said upstream compartment to separate said inlet and second outlet.
Claim 3. A filter construction according to claim 2 in which said casing members, said liquid-wettable filter member, and said liquid-repellent porous member are flexible, flat members perimetrically sealed together.
Claim 4. A filter construction according to claim 3 character-ized by a foraminous partition disposed in said housing in overlaid association with said liquid-repellent porous member, said partition having an outer portion heat sealed to said casing members about said inlet and first outlet.
Claim 5. A filter construction of Claim 2 in which said second outlet comprises a plurality of openings in a casing section adjucent said upstream compartment.
Claim 6. A filter construction according to Claim 2 in which said casing members are of plastic fabrication and having perimetric portions fusedly sealed about said inlet and first outlet, one of said casing members being sealed to one side of said inlet and said first outlet and the other of said casing members being sealed to the other side of said inlet and said first outlet.
Claim 7. A filter construction according to Claim 6 in which the filter member has opposite sides secured, respectively, between one of said casing members and said one side of said first outlet and said other of said casing members and said other side of said inlet.
Claim 8. A filter construction according to Claim 1 characterized in that said housing comprises first and second casing sections having opposed end portions, said first casing section having ports defining said second outlet, said filter member and said porous member having opposite end sections, a first end portion of each said first casing section, said filter member, and said porous member secured together at a first side of one of said inlet and said first outlet, the other end portion of said filter member and a corresponding end portion of said second casing section secured to opposite side of said inlet.
Claim 9. A filter construction according to Claim 8 in which the other end portion of said first casing section and said porous member are secured to the same side of the other of said inlet and first outlet.
Claim 10. A filter construction according to claim 1 in which the supporting means comprises a convexly curved structure on each of said casing sections for supporting said filter and porous member.
Claim 11. A filter construction according to claim 10 in which the easing sections are of rigid plastic fabrication, the first outlet being defined by one of said casing sections, and the second outlet being defined in the other of said easing sections.
Claim 12. A filter construction according to claim 10 in which said supporting means defined curved ridges.
Claim 13. A filter construction according to claim 12 in which said housing has a chamber for receiving said mixture, said chamber having a medial part at which said liquid-repellent and filter members are proximate, and a tapered part extending radially about said medial part.