WATER SEPARATOR

Abstract: A water separator is disclosed for removing water from a minute flow of gas/water sampled from a patients exhalation and prior to the gas being introduced into an analyzer. The separator comprises a housing with an inlet (l8), an outlet (38), and a pair of chambers (24, 30) in series through which the sample is drawn. The first chamber (24) has a pair of substantially closely aligned wall surfaces of predetermined narrow distance from each other such that the surface tension causes the liquid in the sample to adhere to the wall surfaces. As the sample progresses to the second chamber (30), the wall surfaces are further apart and thus the tension effect is broken and only the gas continues through the second chamber (30) to the separator outlet (38). A drain (40, 42) is located in the lower part of the first chamber (24) for withdrawal of the accumulated liquid from that chamber.

Description: The invention relates to a water separator according to the preamble of claim 1. Water separators are conventionally utilized in connection with monitors for analyzing one or more of the constituents of a patient's exhaled breath. Typically, such separators are used with carbon dioxide analyzers that withdraw a sample of the patients exhalation and which detect and display that carbon dioxide component by use of an infrared analyzer. Such IR analyzers are readily available commercially, however it is paramount that the moisture in the breath sample be removed prior to the sample entering the IR analyzer. US-PS 4 579 568 shows a separator comprising a barrier which serves to prevent liquid from moving directly from the input port to an upper output port. Liquid tends to fall off the barrier downwardly, toward a lower output port. Since the fluid flow velocity in the first chamber is relatively high, the liquid is pushed in the direction of the lower output port and prevented from entering the upper output port. However, when using this known water separator, the quality of water separation depends very much on the velocity of the gas in the first chamber and on gravity conditions. If these conditions are not optimized the results of water separation are not satisfactory. The underlying problem is therefore to provide a water separator according to the preamble of claim 1 which works effectively and reliably under all conditions, and is in particular independent of the velocity of the incoming fluid and gravity conditions. According to new claim 1, this problem is solved by a water separator which is characterized in that said aligned surfaces of said first chamber are sufficiently close to remove liquid from said gas/liquid stream passing from said inlet to said outlet by surface tension with said liquid adapted to adhere to said aligned surfaces, that said wall surfaces of said second chamber are spaced apart wide enough to break the surface tension effect and that said liquid drain outlet communicates with said first chamber at a point remote from said second chamber and is oppositely disposed from said second chamber with respect to said inlet. According to claim 8, an inventive method of removing moisture from a sample of a patient's exhaled breath comprises the steps of: a. removing a sample of the patient's exhaled breath; b. separating moisture from the sample by introducing the sample to an inlet of a first chamber and then through said first chamber having closely spaced wall surfaces of predetermined narrow distance apart to adhere the moisture by surface tension to the wall surfaces; c. passing the dry sample from the first chamber into a second chamber having spaced wall surfaces of a further distance apart to break the surface tension effect; d. draining the moisture from said first chamber at a point further remote from said second chamber than the inlet to said first chamber; and e. drawing the sample from the second chamber. The water separator defined above may be easily manufactured in two basic components making up a housing and fitted with inlet, outlet and water drain fittings. Actual water separation takes place by means of surface tension where the gas containing the water is passed to a first chamber constructed by a pair of substantially flat, planar parallel surfaces that are spaced apart a narrow predetermined distance. As the gas liquid passes through the first chamber, the narrow passageway causes the liquid to adhere to the flat planar surfaces and the gas continues through relatively unimpeded. Thus the gas passes into a second chamber that has its side surfaces spaced further apart than the surfaces of the first chamber causing a break in the surface tension phenomenon and the gas continues on via an outlet to the gas analyzer. A drain in the lower most portion of the first chamber is provided to remove accumulated liquid that flows downward to the bottom of the first chamber by gravity or slight vacuum. By use of slight vacuum, the water separator can function in a variety of positions independent of gravity. Thus, the water separator is relatively easy to manufacture, being constructed of very few parts and yet which effectively removes the water from the gas/water stream withdrawn from the patient circuit for analysis. An embodiment of the invention will now be described by way of example, reference being made to the Figures of the accompanying diagrammatic drawings in which: FIG. 1 is an isometric view of the water separator of the present invention showing the chambers and passageways therethrough; FIG. 2 is a front view of one of the two main stream of the housing of the water separator; FIG. 3 is a cross-section view of the section of FIG. 2 taken along the lines 3-3 of FIG. 2; FIG. 4 is a front view of the second of the two main sections of the housing of the water separator; and FIG. 5 is a broken, cross-sectional view of a portion of the section of FIG. 5 taken along the lines 5-5 of FIG. 4. Referring now to FIG. 1 there is shown an isometric view of a water separator 10 and which comprises a housing made up of two sections, namely (as shown) a front section 12 and a rear section 14. The front and rear sections 12 and 14 are joined together to construct water separator 10 and that joining can, of course, be by a variety of methods. In the described embodiment, holes 16 are drilled through both the front and rear sections 12 and 14 for suitable bolts and nuts, not shown, to firmly secure the sections together. The housing itself is preferably of a transparent plastics material such as a polycarbonate so that a visible inspection can be made of the interior passageways when desired. An inlet 18 is formed in the front section 12 and may be threaded to secure a fitting. The inlet 18 receives the sample of withdrawn gas from the patient's breath and which may contain water. Flow of this withdrawn stream is generally a very low flow and typically is in the range of 25 to 500 ml./min. Turning briefly to FIGS. 2 and 3, the inlet 18 can be seen in more detail and narrows down to a bore 20 of approximately 1,02 mm (.040 inches) in diameter at its innermost point. The inner surface 22 of the front section 12 is a flat, planar surface, the purpose of which will be later described. The bore 20 of inlet 18 opens into a first chamber 24 at or near the lower portion of first chamber 24. The first chamber 24 is thus a narrow passageway formed between the front and rear section 12 and 14 when they are affixed together. Turning briefly to FIGS. 4 and 5, the first chamber 24 is formed by the recess 26 on the inner surface 28 of the rear section 14 and is typically about 0,76 mm (.030 inches) deep. When front section 12 is then joined together with the rear section 14 as in FIG. 1, the flat planar surface 22 of front section 12 is parallel to the recess 26 in the inner surface 28 of rear section 14, thus creating an extremely narrow passageway of predetermined area and having a cross sectional depth of about 0,76 mm (.030 inches). Returning to FIG. 1, it can be seen that the moisture laden sample that is drawn in through inlet 18 to the first chamber 24 continues upwardly through the first chamber 24 and is thus drawn between two flat planar surfaces that have an extremely narrow gap or distance there between. Thus, the surface tension effect causes water to cling to the sides of the first chamber 24 and the gas continues to pass through the first chamber 24. At the top of the first chamber 24, there is a second chamber 30 that is provided to break the surface tension of first chamber 24. That break in surface tension is accomplished through the side walls of the second chamber being spaced sufficiently further apart than the side walls of the first chamber. Again referring to FIGS. 2-5, the second chamber 30 may be of various configurations, however, in the preferred embodiment, the second chamber 30 comprises a pair of triangular shaped passages and is formed by a pair of triangular shaped recesses 32, joined together at their bottoms, on the inner surface 22 of the front section 12. The depth of the recesses 32 may be about 0,76 mm (.030 inches). The use of dual passages is preferred in that if one of the passages is occluded by the water, its resistance increases and thus the other passage will selectively increase its flow. Corresponding mating recesses 34 are formed in the inner surface 28 of rear section 14 and the depth of such recesses 34 are about 1,52 mm (.060 inches) into inner surface 28 or about 0,76 mm (.030 inches) deeper than the recess 26 formed in the first chamber 24 (see FIG. 5). At the top apex of each of the triangular shaped passages of the second chamber 30 are passageways 36 that join together into outlet passageway 38 formed in the inner surface 28 of the rear section 14 and which communicates with outlet 38 drilled through the rear section 14 from passageway 38 out through the outer surface. Again, a suitable fitting such as a male stub (not shown) may be fitted to the outlet 38 for connection to flexible tubing to withdraw the gas from outlet 38 of the water separator 10. A further passageway 40, formed in the inner surface 28 of rear section 14 communicates with the bottom of first chamber 24 for the withdrawal of accumulated water as it moves downwardly along the walls of the first chamber 24 by gravity or slight vacuum. Passageway 40 ends at water outlet 42 which, again, is a bore drilled through the rear section 14 so that water may be continuously withdrawn from water outlet 42 by a slight vacuum.

Claims: A water separator for use with a breath gas analyzer, for analyzing the breath of a patient, said separator comprising a housing having an inlet (18) for receiving gas/liquid removed as a sample from the patient's breath and an outlet (38) for discharging gas from said water separator to the analyser, first and second chambers (24, 30) formed in said housing intermediate said inlet (18) and said outlet (38), said first chamber (24) adapted to receive said gas/liquid from said inlet (18) and having a pair of substantially closely aligned wall surfaces of predetermined narrow distance from each other, said second chamber (30) adapted to receive said gas stream from said first chamber (24), said second chamber (30) having wall surfaces spaced apart a wider distance than said wall surfaces of said first chamber (24), said outlet (38) communicating with said second chamber (30) for removal of the gas, a liquid drain outlet (40, 42) communicating with said first chamber (24) to remove accumulated liquid, characterised in that said aligned surfaces of said first chamber (24) are sufficiently close to remove liquid from said gas/liquid stream passing from said inlet (18) to said outlet (38) by surface tension with said liquid adapted to adhere to said aligned surfaces, that said wall surfaces of said second chamber (30) are spaced apart wide enough to break the surface tension effect and that said liquid drain outlet (40, 42) communicates with said first chamber (24) at a point remote from said second chamber (30) and is oppositely disposed from said second chamber with respect to said inlet (18). A water separator as claimed in claim 1 characterised in that said second chamber (30) comprises at least two passages (32, 34) joined at their bottoms and each having independent discharge passageways (36). A water separator as claimed in claim 2 characterised in that said at least two passages (32, 34) comprise triangular passages having said discharged passageways (36) at their top apexes. A water separator as claimed in Claim 1, 2 or 3 characterised in that said closely aligned wall surfaces of said first chamber (24) are approximately 0,76 mm (.030 inches) apart. A water separator as claimed in any one of Claims 1 to 4 characterised in that said closely aligned wall surfaces comprise two parallel, planar surfaces. A water separator as claimed in Claim 5 characterised in that said parallel planar surfaces are approximately 0,76 mm (.030 inches) apart. A water separator as claimed in Claim 6 characterised in that said wall surfaces of said second chamber (30) are approximately 1,52 mm (.060 inches) apart. A method of removing moisture from a sample of a patients exhaled breath comprising the steps of: a. removing a sample of the patients exhaled breath; b. separating moisture from the sample by introducing the sample to an inlet (18) of a first chamber (24) and then through said first chamber (24) having closely spaced wall surfaces of predetermined narrow distance apart to adhere the moisture by surface tension to the wall surfaces; c. passing the dry sample from the first chamber (24) into a second chamber (30) having spaced wall surfaces of a further distance apart to break the surface tension effect; d. draining the moisture from said first chamber (24) at a point further remote from said second chamber than the inlet (18) to said first chamber (24); and e. drawing the sample from the second chamber (30).

Inventors: NELSON, PETER ELWOOD
Applicants: BOC HEALTH CARE, INC.
Application year: 1987
Main classification: A61B5
IPC codes: G01N33, B01D53, B01D45, A61B5, B01D46, G01N1