US3534732A - Anesthetic vaporizer - Google Patents

Description

United States Patent 72] Inventor Allan M. Bickford Huntington Station, New York [21 Appl. No. 592,406 [22] Filed Nov. 7, 1966 [45] Patented Oct. 20, 1970 [73] Assignee The Foregger Company Inc.

Roslyn Heights, New York a corporation of New York [54] ANESTHETIC VAPORIZER 5 Claims, 18 Drawing Figs.

[52] US. Cl 128/188,

l37/625.29, 261/104 [51] Int. Cl ..A6lm 17/00 [50] Field ofSearch 128/186,

188,189,190, 196,197, 209-21 1; 261/99, 46, 39.79.104(Vap.Digest): 137/625.29 (up to date) [56] References Cited UNITED STATES PATENTS 2,085,155 6/1937 Heidbrink 128/186 2,206,688 7/1940 Bloomheart 128/186 2,915,061 12/1959 Edmondson ct a1.. 128/188 3,077,191 2/1963 Stanton 128/197X 3,107,689 10/1963 Schreiber et a1 128/188X 3,162,192 12/1964 Gardner et al 128/188 3,192,924 7/1965 Edmondson et a1.. 128/188 3,298,674 l/1967 Gilbertson 128/188X 3,353,535 11/1967 Gardner 128/188 FOREIGN PATENTS 144,260 10/1957 U.S.S.R. 128/188 206,898 3/1957 Australia... 128/188 648,191 1/1951 Great Britain. 128/188 701,206 12/1953 Great Britain 128/188 Primary Examiner-Richard A. Gaudet Assistant ExaminerKy1e l... Howell Att0rneyAlbert M. Parker ABSTRACT: An anesthetic vaporizer for use with anesthetics having relatively low vapor pressure permits selective adjustment of flow rate and gas mixture. A shut-off valve permits a stream of carrier gas to by-pass a container of liquid anesthetic or to mix with vapor carrying gas. Mixing is controlled by a composite gas flow control valve comprising a temperature responsive cone valve and a non-temperature responsive cone valve coupled for mutually opposed operation. A pressure re lief valve permits flushing of the system.

/47 #19 I38 I40 I46 Patented Oct. 20, 1-970 Sheet i of 7 VOL PENTHRANI; [I]

INVENTOR. A LA A N M 6/c/rF0R0 A TTORNY.

Patented 0a. 20, 1970 3,534,732

Sheet of '7 INVENYUR. ALLA N M B/CKFOAD ATTORNEY Pa tented Oct. 20, 1970 Sheet '5 of? "ON Pos/ r/o/v A TTORNEX Patented Oct. 20, 1970 Sheet 7 of '7 s 0 5 5 o 5 a s o s a 4 a 3 2 2 I 4 3 a Z 2 L 1 m2 v63 uk kQEm$ Q m2 105 QHQXQIKQQ N INVENTOR. ALLA/v MB/CKFORD ATTORNEX ANESTHETIC VAPORIZER This invention relates to anesthesia apparatus, and more particularly relates to an anesthetic vaporizer wherein liquid anesthetic is vaporized and entrained in a carrier gas for delivery to a patients breathing circuit.

The anesthetic vaporizer of the present invention is similar in some respects to that disclosed and claimed in applicants prior US. Pat. application Ser. No. 473,300, filed July 20, I965, now U.S. Pat. No. 3,420,232 bearing the same title. In the embodiment disclosed in such prior application, the anesthetic vaporizer was more particularly adapted for use with anesthetics such as halothane, sold under the trademark Fluothane, which have a relatively high vapor pressure. The apparatus of the present invention, on the other hand, is more particularly adapted for use with anesthetics having a relatively low vapor pressure. One such anesthetic is methoxyllurane or 2, 2-dichloro-l, l-dilluorocthyl methyl ether, which is sold under the trademark Pcnthrame. Such anesthetic is administered to the patient in the form of a vapor mixed with a gas such as oxygen or air. The anesthetic is provided in liquid form in the bottom of a closed chamber, a portion of the carrier gas being circulated in a first gas circuit across the top of the liquid anesthetic and over wicking saturated with the anesthetic so as to vaporize it and become mixed with it. The resulting mixture is then led through a temperature responsive control valve which meters it to hold it to the desired percent age in the final gas mixture, the thus metered gas being mixed with carrier gas flowing through a second gas circuit in the apparatus, the final mixture of carrier gas and vaporized anesthetic mixture being then discharged into the patients breathing circuit.

The concentration of vaporized anesthetic, that is, its percentage volume, that can be contained in a saturated mixture of carrier gas and vaporized anesthetic is dependent upon the vapor pressure of the liquid anesthetic. The vapor pressure of the liquid anesthetic varies with temperature. Accordingly, it is highly desirable to employ in the apparatus adjustable temperature responsive means for controlling the rate of flow of the vaporized anesthetic-gas mixture in at least that portion of the range of flow rates of such mixture wherein the patient is maintained under anesthesia after the preliminary induction" of the patient. Thus during by far the predominant por tion of the time that a patient is under anesthesia the percentage of anesthetic in the mixture delivered to the patient will remain substantially constant, in at least the lower, anesthesia maintaining, anesthcstic concentrations, at the value to which the adjustable temperature responsive means has been adjusted.

When employing liquid anesthetics having low vapor pressures, it has been found to be highly desirable to control the rate of flow of the carrier gas to the mixing chamber at the same time as the rate of flow of the anesthetic-carrier gas mixture is being adjusted, the adjustment of the rates of flow of the two gases being in opposite directions or inversely relative to each other. This permits effective control of the anesthetic concentration over the entire range from zero to the maximum anesthetic vapor by volume employed.

It is desirable to maintain the vaporizer unit connected at all times between the source of supply of carrier gas and the breathing circuit of the patient. With such system it is necessary to provide for the positive shutting off of the portion of the first gas circuit which includes the liquid anesthetic containing chamber, while still permitting carrier gas to flow through the vaporizer. It is also necessary, in such system, to provide for an occasional flow of carrier gas at a high rate through the vaporizer without having the resistance of the vaporizer cause an excessive build up of the pressure at the input line. Such latter condition might otherwise occur, for example, when the breathing circuit is being flushed with oxygen. The apparatus of the present invention provides all of the above features in novel manners, as will appear hereinafter. In addition, it provides for the improved venting of the liquid anesthetic containing chamber when the shutoff valve of the apparatus is in its off position, thus making the chamber easier to fill.

It is accordingly among the objects of the invention to provide a novel improved anesthesia apparatus which is particularly advantageous when employed with normally liquid anesthetics having a low vapor pressure.

A further object of the invention lies in the provision of an improved anesthetic vaporizer which is particularly characterized by its ease of control, the ease with which liquid anesthetic may be supplied to the anesthetic containing chamber of the apparatus, and its freedom from drip or carryover once the shutoff valve has been placed in its off position.

Yet another object of the invention lies in the provision of an improved anesthetic vaporizer which when employed with liquid anesthetics having a low vapor pressure maintains a substantially constant percentage of vaporized anesthetic in the finally delivered gas mixture in at least the lower, anesthesia maintaining range of gas flow, despite changes in ambient temperature and in the rate of llow of the carrier gasvaporized anesthetic mixture.

A still further object of the invention lies in the provision of a novel composite valve, adapted for use in an anesthetic vaporizer, such valve simultaneously adjusting in inverse manners the rate of flow of a carrier gas in one gas circuit of the apparatus and the rate of flow of a carrier gas, volatilized liquid anesthetic-gas mixture in another gas circuit of the apparatus.

The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not intended as a definition of the limits of the invention.

FIG. 1 is a view in side elevation of an illustrative embodiment of anesthetic vaporizer made in accordance with the invention;

FIG. 2 is a view in end elevation of such vaporizer, the view being taken from a position at the right of FIG. I and looking to the left;

FIG. 3 is a view in plan of the vaporizer of FIGS. 1 and 2, the common operating knob for the adjustable gas control valve and the shutoff valve being removed for clarity of illustration, the means interconnecting such valves being shown in the position which it occupies when both such valves are open;

FIG. 4 is a view similar to FIG, 3 but with the means connecting the flow control and the shutoff valves being shown in the position which it occupies when such valves are closed;

FIG. 5 is a view in vertical cross section through the vertical axis of the illustrative embodiment of the apparatus, the section being taken along the line 5-5 looking in the direction of the arrows in FIG. 3, certain of the parts being shown in elevation, the central composite valve, for (a) controlling the rate of flow of the carrier gas to the mixing chamber and (b) the rate of flow of the anesthetic-gas mixture to such chamber, being shown in an intermediate position, the shutoff valve being open;

FIG. 6 is an enlarged view in vertical axial section through the central composite valve of the apparatus, certain of the elements being shown in elevation, the valve being shown in the same intermediate position as that in FIG. 5;

FIG. 7 is a fragmentary view in horizontal section through an intermediate portion of the apparatus, the section being taken along the line 77 of FIG. 6 looking in the direction of the arrows;

FIG. 8 is a view in bottom plan of the valve head or valvecontaining body of the apparatus, a portion of such body at the opposite sidewalls of the right-hand cavity containing the pressure relief valve being broken away for clarity of illustration;

FIG. 8A is a fragmentary view in vertical section taken along the line SA-SA in FIG. 8 looking in the direction of the arrows;

FIG, 9 is a view in vertical longitudinal section through the valve'containing body, the section being taken in the same manner as the section of FIG. 5;

FIG. is a fragmentary view in vertical section through the left-hand end of the valve-containing body in FIG. 5, FIG. 10 showing the shutoff valve in its open or on position;

FIG. 11 is a fragmentary view in horizontal section through the shutoff valve in its open position, the section being taken along the line 11-11 in the direction of the arrows in FIG. 10;

FIG. 12 is a view similar to FIG. 11 but with the movable valve element of the shutoff valve being turned to its closed or off position;

FIG. 13 is an enlarged view in vertical axial section through the pressure relief valve of the apparatus, the section being taken similarly to that of FIG. 5 but with certain of the internal elements of the valve being shown in section;

FIG. 14 is a schematic view in perspective of the illustrative embodiment of the apparatus showing the paths of flow of the carrier gas, the vaporized anesthetic, and the mixture of vaporized anesthetic and gas, the figure also showing the valves for the control of such gas and gas-vapor mixture, the shutoff valve being shown in its open or on position;

FIG. 15 is a schematic view in perspective of the apparatus similar to FIG. 14 but with the shutoff valve positioned in its off position;

FIG. 16 is a graph in which the percentage of methoxyflurane in the gas mixture delivered to the patient's breathing circuit is plotted against the rate of flow per minute in liters; and

FIG. 17 is a graph in which the percentage of methoxyflurane in the gas mixture delivered to the patients breathing circuit is plotted against temperature in degrees centigrade in the range I 5-30 at a flow rate of 4 liters per minute.

The embodiment of anesthetic vaporizer shown, which is generally designated by the reference character 10, has a main outer container 11 which in use is sealed except for the various valves and conduits contained in the head or body 12 which is applied and sealed to the container as shown. The head 12 is provided with a gas inlet fitting 14 which, in the embodiment shown, is of the internally tapered sleeve type, and with a fitting 15 of the externally tapered sleeve type through which the mixture of volatilized anesthetic and carrier gas is delivered. Device 10 is provided with a funnel 16 adjacent the base thereof through which liquid anesthetic is supplied to the space within the lower end of the container 11. The funnel is closed by a stopper 17. The rate of flow of carrier gas through the first gas circuit of the apparatus, when the shutoff valve is open, and the rate of flow of the volatilized anesthetic-carrier gas mixture through the second gas circuit of the apparatus, when the shutoff valve is open, is controlled by a composite valve generally designated 13, to be described, which may be adjusted by a rotatable knob 19 disposed at the top of the apparatus. The container 11 is provided with a sight glass 20 through which the level of liquid anesthetic in the container may be observed, and with a drain valve having an operating knob 21 and a drain pipe 22 through which liquid anesthetic may be withdrawn from the apparatus when desired.

The apparatus 10 is provided with a base plate 24 having four projecting ears 26 to each of which a rubber covered foot is attached. A centrally disposed upwardly directed thumb screw 27 secures the base plate 24 to a fitting 29 which is secured to the bottom of the container 11 by a central pilot portion 23 which projects through a central hole in the bottom of the container and is sealed thereto. Fitting 29 has an upstanding threaded stem 28 which is threadedly connected to and secures the lower end of a standard 30 in the form of an upstanding rod which is disposed centrally within the container 11. The upper end of standard 30 is threaded (FIG. 5) and is screwed into a central threaded bore 101 in a depending hollow central boss 18 on the block 12, which constitutes the head of the apparatus, to secure such block to the container 11. The lower end of the block or head 12 is telescoped within the upper end of container 11, the head having an annular outwardly projecting flange 31 which rests upon the upper edge of the outer sidewall 33 of the container 11 (FIG. 5). The head 12 is sealed to such sidewall of the container by an O-ring 32 which is disposed within an annular groove at the upper inner edge of the outer sidewall 33.

The gas inlet sleeve 14 forms a part of an inlet fitting 35 which is secured to the right-hand end of the block 12, as it is shown in FIGS. 1 and 3-5, incl. Within the fitting 35 and across the inner larger portion of the flared passage therethrough there is secured a filter 36. Gas entering the sleeve 14 passes through the filter 36 and into an inlet port 41 on the end of the block 12 to which the fitting 35 is secured. Port 41 opens into an annular groove 38 in the sidewall of a first cavity 37 in the head 12, there being a pressure relief valve 42, to be described, disposed in cavity 37. The head 12 contains two other cavities, a central cavity 39 containing the above mentioned composite gas flow control valve 13, and a third cavity 40 containing an operating disc 43 for an inlet and outlet shutofi valve 73. Such cavities and the valves contained therein are disposed in alignment, as shown in FIGS. 5 and 9. As will appear hereinafter, the composite valve 13 includes a temperature responsive valve 105 for the anesthetic-carrier gas mixture, and a nontemperature responsive valve 98 for the carrier gas to be mixed with such mixture.

GENERAL OPERATION OF THE APPARATUS Briefly, as shown in FIG. 14, when the shutoff valve 73 and the composite gas flow control valve 13 are open, gas introduced into the apparatus through the sleeve 14 of the inlet fitting 35 in its normal flow passes into the cavity 37, and thence through the passage 52, 53 to the now open first, inlet portion of the shutoff valve 73. From such inlet portion of valve 73 the gas flows through a passage 77 to a pipe coil 87 which provides a chamber of substantial volume and length therefor. The pipe coil is disposed in a can 79 within the container 11. From the pipe coil the gas flows through a discharge port 91 through the bottom of the can 79 downwardly across the top of the liquid anesthetic 92 in the bottom of the chamber and thence upwardly in a spiral path defined between turns of a coiled wire 94, which is walled between outer and inner wicking members 95 and 96, respectively, disposed along the sidewall of container 11. The carrier gas thus progressively becomes saturated with anesthetic vapor to form a mixture. Such mixture is then led upwardly from the chamber and through a second, outlet portion of the valve 73 from which it flows through a passage 206, thence through the temperature responsive valve 105, which forms a part of the composite valve 13, to a mixing chamber 113 which is disposed within the central cavity 39 of the valve head and between the valves 98 and (FIGS. 5 and 6) of the composite valve 13. This much of the carrier gas and carrier gas anesthetic vapor mixture conducting portion of the apparatus is designated the first gas circuit of the apparatus.

A further portion of the carrier gas which is introduced into the apparatus is led from the cavity 37 through a passage 88 to the second, upper adjustable but nontemperature responsive valve 98 of the composite valve 13 and thence to the mixing chamber 113. This portion of the apparatus, which conducts the second stream of carrier gas is designated the second gas circuit of the apparatus. After the gaseous mixture flowing from the first gas circuit into the mixing chamber 113 and the carrier gas flowing through the second circuit of the apparatus into the mixing chamber have become intimately mixed in the proportions designated by the setting of the composite valve 13, such final mixture flows out of the apparatus to the outlet fitting 15 of the apparatus. Such final gaseous mixture, as shown in FIG. 14, flows to the outlet fitting through the passage 202, 69.

As will appear, the apparatus is shut off by turning the control knob 19 of the composite valve 13 to its ofF position, such turning of the composite valve likewise turning the movable valve element 72 of the shutoff valve 73, 90 clockwise as viewed from above into its off position, as shown in FIG. 15. As there shown, flow of the carrier gas in the second gas circuit continues, the carrier gas now also passing from the cavity 37 through the passage 52, 53 to the valve 73 which is now positioned so that it directs such gas upwardly through a conduit 123 which is connected to the passage 69. Such two streams of the carrier gas combine and then pass outwardly to the outlet fitting l5 and thence to the patients breathing circuit. In such closed position of the valve 73, it positively shuts off both the inlet passage 77 leading to the pipe coil 87 of the anesthetic vaporizer and the passage 206 leading from the vaporizer. At the same time, the interior of the vaporizer is connected to the atmosphere through a passage 163 through the movable element 72 of the valve 73 and thence to a venting conduit 166.

THE PRESSURE RELIEF VALVE The pressure relief valve 42, which is disposed in cavity 37 in the valve block 12, is shown more particularly in FIG. 13. Such valve has an outer body 44 which fits within the cavity 37, such cavity having an upper circular cylindrical portion 45' and a lower portion 45 having a downwardly converging frustoconical peripheral surface disposed coaxially of the cylindrical upper portion of the cavity. The wall of cavity 37 at the lower end of portion 45 thereof is provided with an axially long annular groove 38 communicating with the passage 41. As shown in FIG. 13, the frustoconical lower surface of body 44 is held tightly against the surface of the lower tapered end 45 of cavity 37 to form a seal therebetween.

The outer body 44 of the valve 42 is retained in the cavity 37 as follows: Body 44 at its lower end is provided with a central depending hollow boss 83 which telescopes within a correspondingly shaped central bore in body 12. Boss 83 is inwardly threaded and threadedly receives the upper stern portion 70 of a threaded stud which is permanently fixed to the body 12 and is held against travel upwardly with respect thereto by engagement between an enlarged lower end 71 of the stud and the lower surface of valve block 12. Thus the valve 42 may be initially installed or removed when required by rotating the entirevalve 42 within its cavity 37 as by engaging shallow holes 48 provided in the upper end of the valve body 44 with a suitable spanner wrench.

The upper end of the body 44 of the valve is sealed to the circular cylindrical upper sidewall of the cavity 37 by an O- ring 47 seated in an annular groove 46 near the upper end of body 44. Disposed below such sealing means 47 and generally symmetrically with respect to the inlet port 41, the body 44 has a relatively deep and axially long annular groove 49 confronting the groove 38 in the Wall of cavity 37, the two grooves forming a portion of the passage of normal flow of the carrier gas from the inlet fitting to the shutoff valve 73, as above described. The carrier gas upon entering through port 41 flows peripherally around the groove 38, 49. The upper portion of the body 44 radially inwardly of the groove 49 is provided with a central cavity into which gas flows from groove 49 through ports 50 and 51 in the upper portion of body 44. As shown in FIGS. 8, 9, and 13, the upper portion of the cavity 37 in the block 12 is provided with an outlet passage 88 diametrically aligned with passage 41, passage 88 communicating with the above described annular groove 38, 49 in the outer valve body 44, and ex- .tateiastbrsasmh .Wall etween the and 9s...v

Extending upwardly in the valve block 12 to terminate at its upper end adjacent the bottom of the upper larger diametered portion of the cavity 37 (FIGS. 8 and 9) is a vertical portion of a passage 52, 53 which forms a part of the above described second gas circuit of the apparatus. The passage 52, 53 is composed of a number of intersecting drilled passage portions, the parts of the passages which penetrate the surface of the block being appropriately plugged. For simplicity, the portions of the passages beyond their points of intersection, and the plugs at the outer ends of such passage portions, are omitted. This is also true with respect to various other passages in the block 12, presently to be described.

Telescoped within the lower end portion of the body 44 of the pressure relief valve, and sealed thereto, is a centrally disposed inner body 55 having a vertical passage, including an upper cavity and a lower valve seat, centrally therethrough.

The body 55 projects upwardly through the central cavity in body 44 and is centrally located by having its upper end telescoped within a central recess in the lower portion of a plug member 56 which is telescoped into the upper end of the central cavity of body 44. Plug member 56 is retained in the cavity by a spring ring 57 which fits within a groove in body 44 and overlies the plug member. The plug member 56 is sealed to the member 44 by an O-ring 58 which is disposed in an annular groove in the plug member. The inner body 55 is sealed to body 44 near the lower end of the former by an O-ring 59. Between the O- rings 47 and 59 the body 55 is provided with a vertically elongated annular groove 80.

The inner body 55 of valve 42 carries a vertically reciprocable poppet member 60 having a stem 62, such valve selectively sealingly cooperating with an upwardly converging frustoconical valve seat 61 disposed at the bottom end of the body 55. The poppet member 60 has a lower enlarged head on its stem 62, there being an annular groove in such head carrying an O- ring 63 which sealingly cooperates with the valve seat 61. The surface of the poppet member 60 above the Oring 63 is subjected at all times to the gas pressure existing within the upper part of the vertical passage in the body 55.

The poppet member 60 is resiliently urged toward its upper, sealing position by a coil compression spring 64 which acts between a spider 65, affixed to the upper end of the elongated central valve stem 62, the spider being slidable within the central bore of the body 55, and an annular spring seat 66 formed as the upper annular surface of an inwardly projecting flange on body 55. Generally horizontally aligned with the passages 50 and 51 in body 44 there are passages 67 through the upper sidewall portion of the inner body 55 of valve 42.

It will thus be seen that with a spring 64 having a predetermined desired compressive strength, the poppet member 60 will remain closed until the upper surface of its enlarged head is subjected to gas pressure which is sufficiently high to overcome the spring 64 and thus open the valve. The compressive strength of the spring 64 is such that in normal operation the poppet member 60 is in closed position. Under such condition the gas which enters the inlet fitting 35 passes directly through the aligned passages 41, 50, 67, 51, and the interposed annular grooves 38, 49, and to pass through the passage 88 into the central cavity 39 of the valve block 12. It is only when the poppet member 60 is opened by an excess pressure in such entering carrier gas that communication is afforded through the valve 42 with a pressure relief passage which is shown schematically at 69 in FIGS. 14 and 15 as being connected to a horizontally disposed outlet passage 69 in block 12.

As shown in FIG. 8, such passage 69 in block 12 communicates with the space 78 (FIG. 13) at the lower end of the cavity 37 beneath the body 44 of the valve 42. Passage 69 extends generally lengthwise of block 12 to join the outlet passage 69 which communicates directly with the outlet fitting 15 of the apparatus. Thus passage 69 (FIGS. 6 and 8) extends from beneath the central composite valve 13 horizontally forwardly toward the outlet fitting 15 to a vertical passage 82 in block 12 (FIG. 8). Passage 82, in turn, is connected to a cross passage 93 which extends to the outlet passage 123'. Thus gas which passes through the valve 42, under an excess pressure condition, flows through holes 68 in the lower end of valve body 44, into space 78, and then into passage 69 which forms a prolongation of the passage 69, finally to be discharged through passages 69, 82, 93, and 123' into the outlet fitting 15 of the apparatus. Such undue pressure rise in the carrier gas may occur, for example, when flushing the patients breathing circuit with oxygen at a high flow rate.

THE SHUTOF F VALVE The shutoff valve 73 to which the carrier gas flows in the normal operation of the apparatus through the above described port 52 and passage 53 is shown in FIGS. 10-42, inclusive. Such valve has a movable valve member in the form of a disc 72 which is disposed for rotation about an axis which lies normal to the broad extent of the valve block 12. Disc 72 includes a circular lower metal plate with a central upstanding hollow boss, and an annular resilient rubberlike sealing member 72' which is carried on such plate and is telescoped over the hollow boss. The upper and lower surfaces of the member 72' are flat, parallel, and disposed in planes parallel to the main extent of the valve block 12; the upper surface of member 72' sealingly cooperates with the flat lower surface 168 of the valve block 12 at the location of valve 73. The valve member 72 is pinned to a vertical shaft 74 which is accurately journalled in and sealed to a vertical bore extending through the valve block 12 centrally of the cavity 40. Shaft 74 is sealed to the valve block, as shown. Fixed to the upper end of the shaft 74 is a valve operating disc 43 which is also fixed to the shaft 74. Telescoped about the upper end of the shaft 74 is a coil compression spring 99, the lower end of which rests upon the surface at the bottom of cavity 40 and the upper end of which is received within an annular spring seat in the lower surface of the valve operating disc 43. The spring 99 constantly thrusts the shaft 74 and valve disc 72 upwardly, thereby insuring sealing contact at all times between the member 72' and the lower surface of the valve block 12 confronting such member.

As shown in FIGS. 8, 11, and 12, the portion of the valve block 12 confronting and cooperating with the resilient sealing member 72' of the disc 72, 72' of the shutoff valve 73 is provided with five angularly spaced ports 164, 167, 76, 54, and 128; the resilient annular member 72' is provided with an arcuate groove 75 subtending a 90 angle in its upper portion. The disc 72 is provided with a passage 163 therethrough. When the valve 73 is in its open position, as shown in FIGS. 11 and 14, the groove 75 in the resilient valve member 72' of the valve 73 connects ports 54 and 76, passage 163 registers with port 164, and ports 128 and 167 are closed by imperforate portions of member 72'. The port 54, which is connected to passage 53, communicates with the space above the chamber which contains the mixture of carrier gas and vaporized anesthetic through the groove 75, the port 76, the passage 76, 77, and the pipe coil 87, so that such mixture flows upwardly from the space 100 (FIG. at the top of the chamber through the passage 163 in disc 72, through the port 164 communicating therewith, and into the passage 206.

When the valve 73 is in its closed or off position, as shown in FIGS. 12 and 15, the groove 75 in the resilient annular member 72' connects ports 54 and 128, and passage 163 in such disc is aligned with port 167 of venting passage 166. The ports 164 and 76 are now closed by imperforate portions of the member 72 which confront them. Thus flow of the carrier gas to the vaporizing chamber is shut off, the carrier gas is discharged directly to the outlet 15 of the apparatus through passage 53, the groove 75 in valve member 72, and passage 123, 123'. The vaporizing chamber is now vented through passage 163 in the valve disc 72' to passage 166.

As shown in FIGS. 8, 8A, 11, and 12, the vent passage 166 is horizontally offset from venting port 167. Thus passage 166 lies to one side of passage 206, and port 167 lies below passage 206, the two being connected by an angular bore 161 in valve block 12. Also, as shown in FIGS. 8 and 9, the passage 77 is formed of a horizontal passage portion 77' in block 12 connected to port 76 by the vertical passage 76', and by a further vertical bore 77", shown in phantom lines in FIG. 9, which leads to the upper, inlet fitting 85 of the pipe coil 87.

The positioning of the valve 73 beneath the valve block 12 and above the vaporizing chamber provides for the ready drainage of any condensed liquid that may have become trapped in the valve and the passages in block 12 thereabove down into the liquid chamber. The valve 73 when in the ofF position also provides a bypass of the input gas to the outlet fitting with relatively low resistance. Finally, the valve 73 when in off position provides direct venting of the liquid chamber, through the passage 167 in the valve disc 72 and the venting passage 166, making the liquid chamber easier to fill.

8 THE VAPOR'IZWG CHAMBER The container or can 79 is provided with an axially extending sleeve member 81 which is joined and sealed as by soldering at its lower end to the bottom 90 of the can and is similarly joined and sealed to the top 84 of the can at a shoulder adjacent the upper end of member 81. The upper end of member 81 extends upwardly into sealing contact with the lower surface of a central boss 18 on block 12. The top 84 is joined and sealed to the upper edge of the body of the can, as by being soldered to it. The upper end of the standard 30 is threaded, and is received within a central passage, which is internally threaded at 101, in the boss 18 on block 12. The standard 30 has an annular shoulder 82 intermediate its length, the can 79 being supported on such shoulder, as shown. When the head or block 12 is screwed onto the upper end of standard 30 (FIG. 5), the sleeve member 81 is clamped between the shoulder 82, acting through the central portion of bottom 90 of can 79, and the central boss 18 on the block 12.

The above-described passage 77 from port 76 of valve 73 is connected at its lower end to an inlet fitting which is sealed to the disclike member 84 which closes the top of the can 79. The upper end of pipe coil 87 is connected to fitting 85 at 86, as shown in FIG. 5. The lower end of coil 87 is connected to an outlet fitting 89, which is sealed to the bottom 90 of the can 79, such outlet fitting having a discharge opening 91 through which gas issues from the coil 87 to flow into the space above the body of liquid anesthetic 92 in the bottom of the container 11.

Disposed along the inner sidewall of container 11 is an external layer of wicking 95. A coil of wire 94 with widely spaced turns is disposed within wicking 95; a further inner layer of wicking 96 is located between the side wall 80 of can 79 and the helical wire 94. The bottom ends of wicking layers 95 and 96 extend downwardly adjacent the bottom of the can and are thus immersed in the liquid anesthetic 92. The gas emerging from discharge port 91, in flowing across the liquid anesthetic 92, picks up volatilized liquid anesthetic to form an anesthetic-gas mixture. The only path of escape of such mixture from the container 1 1 is through the wicking layers 95, 96 and the spaces presented between successive turns of the helical wire 94. The carrier gas in travelling upwardly through such helical path between the layers of wicking soaked with liquid anesthetic becomes saturated with anesthetic vapor.

The apparatus presents an annular space between the upper surface of cover 84 of can 79 and the bottom surface of the valve-containing block 12, such space being generally designated 100. The above-described rotatable valve element 72 of the shutoff valve 73 lies within space 100, as shown. The anesthetic-gas mixture rises from the described vertical passage between the side walls of containers 11 and 79, respectively, and turns at the locations 97 (FIG. 5) to flow generally radially into the space 100 from which it is discharged into a central cavity 104 leading to the temperature responsive valve 105. Communication between the space 100 and the central cavity 104 is afforded by the passage 163 through the rotatable valve element 72' of the shutoff valve 73, such passage 163 then being aligned with port 164 of the passage 206, as shown in FIG. 11.

THE COMPOSITE GAS CONTROL VALVE The structure of the composite gas control valve 13 is particularly shown in FIGS. 5 and 6. As shown particularly in FIG. 6, the valve 13 has an outer generally circular cylindrical housing having a lower end portion 106 and an upper end portion 109. Housing 106, 109 is accurately received within the cavity 39 in the valve-containing block 12. Such cavity 39 has a bottom wall 107 which is centrally apertured to provide the above-described cavity or chamber 104. The upper end portion 109 of the housing of the valve 13 is sealed to the sidewall of the cavity 39 at the upper end thereof by an O-ring 110 received within a groove in such upper portion 109 of the housing. The lower end portion 106 of the housing is sealed to the sidewall of the cavity 39 adjacent the lower end thereof by an O-ring 11 1, as shown. The housing of the valve 13 includes a bottom member 106' which is screwed into the lower end 106 of the outer, main part of such housing at 108. The larger diametered lower portion of the top member 109 of the housing of valve 13 is disposed beneath a sheet metal cover member 112 which is retained upon the top of block 12 and which also covers the pressure relief valve 12 and the shutoff valve 73, as shown in FIG. 5.

The gas control valve 105 of the composite valve 13 has a first fixed downwardly converging frustoconical valve seat 1 1 1 which is formed in a central upstanding sleeve member 115 which is integral with the part 106' of the valve housing. Member 106', 115, in the illustrative embodiment, as well as housing 106, 109, are formed of brass, which has a coefficient of linear expansion on the order of 19 X l per degree C. The valve seat 114 has a relatively small conical angle on the order, for example, of l5". Telescoped within the fixed valve seat 114 is a member 117 which has a frustoconical outer surface 120 which is complementary to the valve seat 11 1 and thus forms the second seat of the valve 105. In the illustrative embodiment the member 117 is formed as a sleeve of plastic material having a relatively large positive linear coefiicient of thermal expansion, that is, the material expands upon an increase in temperature. Preferably, member 117 is made of a fluorocarbon plastic material of which polytetrafluoroethylene is one preferred example. Such material, which is also known as PTFE or TFE, has a linear coefficient of thermal expansion on the order of X l()' per degree C. Such material is highly resistant to attack by the anesthetics encountered in the use of the apparatus, including methoxyflurane. Member 117 may also be made of other materials having generally similar properties, with suitable changes in the diameters of member 117 and of seat 114 to accommodate for the different coefficient of thermal expansion of the different materials used. The surface of the valve seat 120 on member 117 coacts with the valve seat 114 so as to provide the valve 105 with temperature compensating characteristics whereby to maintain, with a nontemperature responsive valve 98 forming another portion of the composite valve 13, the percentage of volatile anesthetic in the anesthetic-gas mixture substantially within the relationships illustrated in the graphs of FIGS. 16 and 17.

The member 117 is secured to a vertically reciprocable adjustable valve stem 116 whereby the effective cross section of the passage between the valve seats 115 and 120 may be adjusted manually. Thus the valve has a central stem member 116 over which the member 117 is telescoped. Member 117 is retained upon the stem 116 by a cross pin 119 (FIG. 5) which penetrates both members at a location above the upper end of the main body of member 117.

The above-described lower member 106 of the valve housing has a depending central sleeve portion 122, the lower end of portion 122 being telescoped within the upper end of the cavity 104 in the valve block 12 and sealed thereto by an O- ring seated in an annular groove in the sleeve portion 122, as shown. The sleeve portion 122 is provided with a central vertical bore within which there is mounted a resilient bushing which guides and forms a seal with a smaller diametered pilot pin 116 on the lower end of the stem 116. The sleeve portion 122 is provided with a plurality (four shown) of vertical passages 124 which permit gas entering the valve 105 from chamber 104 to pass upwardly to the seats 114 and 120 of the valve 105, between the seats, and into the mixing chamber 1 13 between valves 98 and 105.

The nontemperature responsive valve 98, for controlling the rate of flow of carrier gas from the inlet fitting 35 to the mixing chamber 113, is disposed above valve 105 in the housing 106, 109. Valve 98 has a first, inner movable valve element 210 which is formed integral with the stern 116 of valve 105. The stem 116 and the element 210 are formed of a material, such as brass, having a low coefficient of expansion.

Element 210 in its lower, main portion is of upwardly converging frustoconical shape, the outer surface 211 of such portion, which is coaxial with stem 116, forming a first, inner seat of valve 911. Cooperating with the first seat 211 is a second, outer fixed seat 212 which surrounds the inner seat 21 1 and is coaxial of and complementary thereto. The fixed seat 212 forms the inner surface of a radially inwardly thickened part of the upper portion 109 of the valve housing. 1t will be apparent that, because of the opposite inclination of the valve seats 114 on the one hand and 211, 212 on the other, the valves 93 and 105 function in inverse manners, that is, as valve 105 opens, valve 911 closes, and vice versa.

The upper end of the valve stem 116, which continues upwardly from element 210, is of circular cylindrical shape and is accurately guidingly received within a vertical central bore 126 of an upstanding central sleeve portion 127 of the abovedescribed upper portion 109 of the housing for the valve 13. The valve stem 116 is thus accurately guided for vertical adjustment along the common axis of the two sets of valve seats 111i, 120, and 211,121.

The valve stem 116 is constantly urged in a downward direction, by a coil compression spring 134 which is telescoped about the upper part of stem 116 and is disposed between the annular lower surface 135 of the sleeve portion 127 of member 109 and the lower annular surface 132 in an elongated annular space cavity which extends downwardly a substantial distance within the inner valve element 210. The valve stem 116 is adjusted vertically by an adjusting screw 137 which is threadedly received within a central bore 136 in. the upper end of portion 125 of the valve stem 116. The screw 137 has an enlarged head portion 138 which has an annular groove therein receiving an O-ring 139 which seals the head of the screw to the wall of the bore 136 in member 127. Above such head 138 the screw 137 is provided with a flange 140 which rests upon the upper edge of the sleeve 127 and prevents downward travel of the screw. Thus turning of the screw 137 in one direction permits the spring 134 to advance the valve stem 116 toward its lower position, and the turning of the screw 137 in the opposite direction raises the valve stem against the opposition of spring 134.

The valve stem 116 and the valve elements 117 and 210 attached thereto are prevented from rotation in the following manner: A threaded pin 21 1 is mounted in a threaded radially directed bore 215 in housing part 109. The inner end 216 of pin 214, which is of reduced diameter, is slidably received in a vertical slot 217 through the radially thin upper edge portion of valve element 210. Thus portion 216 of pin 21 1 may slide freely with respect to member 210 as the valve stem 116 is raised and lowered. The pin 214, 216, however, prevents the valve stem 116 from rotating when the valve adjusting screw 137 is turned.

The apparatus shown incorporates means whereby the valve 13 may be adjusted without subjecting the valve stem 116 to sidewise forces which, without the turning of the valve stem, might alter the effective area of the passages between the valve seats 114, 120 and 211, 212. Thus, as shown in FIG. 5, the adjusting knob 19 of valve 13 is provided with a hub which is journalled upon the outer surface of the upwardly projecting sleevelike upper end portion 127 of member 109. Such hub 145 rests upon a shoulder 148 at the base of such sleevelike member 127 and is retained upon the member by a spring ring 146 which is snapped into a groove at the upper end of the sleevelike member and overlies the central portion of the hub. A crank member 149, which overlies the hub 145, is secured by a set screw to the upper end 141 of the valve adjusting screw 137. Mounted upon the crank member 149 as by being press fitted thereinto is a downwardly projecting pin 147, the lower end of which extends into a hole, which is somewhat larger than the pin, located in the hub 145. It will thus be seen that sidewise forces exerted upon the knob 19, as by the resting of the operators hand thereon, are isolated from the adjusting screw 137, the screw being subjected only to turning movement caused by the interaction of the pin 147 and the crank member 149.

The valve 98 controls the flow of carrier gas into the mixing chamber 113, in the manner shown in FIG. 6. Thus, such gas flows through passage 88 into an annular cavity 156 formed by an annular groove 157 in the outer surface of the housing part 109 and the side wall of the cavity 39. From cavity 156 the carrier gas flows inwardly through a plurality of radial passages 158, of which one is shown in FIG. 6, to a radially inner annular space above the seats 21 1, 212 of the adjustable, nontemperature responsive valve 98, and thence between such seats to the chamber 113 where it mixes with the anesthetic-carrier gas mixture. The final gas mixture flows out of chamber 113 through a plurality (two shown in FIG. 6) of vertical passages 159 in the sleevelike member 115 and into an annular chamber 160. From chamber 160 the final mixture flows through a short vertical passage 202 and into the abovementioned discharge passage 69.

The operating gaps between the cooperating seats of the upper, nontemperature responsive valve 98 and of the lower, temperature responsive valve 105 of composite valve 13 are selected so that they are small with respect to their lengths. The ratio of length/width of each of valves 98 and 105 may be on the order of 100 or more. This reduces turbulence in the gases flowing through such gaps, and promotes laminar flow thereof at the gaps.

THE SINGLE CONTROL MEANS FOR VALVES I05, 98. AND 73 In the embodiment of the apparatus shown, the valve 105 is opened and the valve 98 is closed upon the turning of the valve adjusting knob 19 clockwise. The apparatus incorporates valve controlling or operating means whereby the turning of the knob 19 not only adjusts the valves 105 and 98, but operates the shutoff valve 73.

The valve controlling means is such that upon the turning of the knob 19 clockwise toward its open position from the closed position of FIG. 4, the shutoff valve 73 is opened during the first fraction of a turn of the knob 19, as shown in FIG. 3, and upon turning of the knob 19 counterclockwise to close the valve 105 and open valve 98, the shutoff valve 73 is closed as the knob 19 reaches the position at which valve 105 is closed. The means linking the valves 105, 98 with the shutoff valve 73 is shown more particularly in FIGS. 3, 4, and v As there shown, the rotatable disc 43 connected to the rotatable valve element 72 of valve 73 is provided with an upstanding pin 154 which projects through an arcuate slot in the cover plate 112 for the apparatus. Pin 154, when the shutoff valve 73 is open, lies in the position shown in FIGS. 3, 5, and 10, and when the shutoff valve is closed lies in the position shown in FIG. 4. Attached to the hub 145 of the knob 19 at its lower end is a partcircular plate 155 having a generally radially projecting arm with a radius which somewhat exceeds the distance which the pin 154 lies from the axis of the hub 145 in either the open or closed positions of the shutoff valve. As shown, plate 155 is attached to the hub 145 by a plurality of machine screws, of which one is designated 169.

The plate 155 has on one edge of its arm adjacent its radially outer end a pocket 171 which, in the closed positions of both valves 105 and 73 shown in FIG. 4 receives pin 154 therewithin. The pocket 171 is in the form of more than half of a circle. The radially outer side of the entrance passage to such pocket 171 is in the form of a straight surface 172; the radially inner side of such entrance passage is smoothly convexly rounded, as shown at 173. The other edge of plate 155 has a shallow arcuate pocket 170 therein located to receive the pin 154 when both valves 105 and 73 are turned to their fully open positions, shown in FIG. 3.

To open valves 105 and 73 (and thus to adjust valve 98 toward its closed position), the knob 19 is, as noted above, turned clockwise from its closed position of FIG. 4. In the first part of such clockwise turning of knob 19, the pin 154 is contacted by the convex surface 173 on plate 155, and thus the pin 154, the disc 43, and the valve element 72 of valve 73 connected to the disc are turned counterclockwise sufficiently to open valve 73. Thereafter. the knob 19 may be turned further in a clockwise direction to adjust the valves and 98 to the desired rate of flow of the anesthetic-gas mixture therethrough, and the desired rate of flow of carrier gas into the mixing chamber 113. Such adjusted position of the knob 19 will ordinarily lie somewhat short of the fully open position of valve 105 shown in FIG. 3. At such fully open position, the pin 154 is received within the pocket 170, which with pin 154 serves as a mechanical stop for the valve 105 in its fully open position.

When it is desired to shut off the apparatus 10, the knob 19 is then turned counterclockwise, whereupon the valve 105 is not only closed and'the valve 98 opened further, but the pin 154 is then contacted by the outer end of the camlike surface 172, so that the pin 154 enters the pocket 171. The pin 154, together with the disc 43 and the movable valve element 72 of the shutoff valve 73, are thus turned clockwise into the position shown in FIG. 4, wherein the movable valve element 72 occupies the closed position shown in FIG. 13. Further turning of the knob 19 in a counterclockwise direction is prevented by engagement between the bottom of pocket 171 and the pin 154, as shown in FIG. 4. The bottom of such pocket and the pin thus function as a mechanical stop for valve 13 in the position thereof wherein the valve 105 is closed.

THE OPERATION OF COMPOSITE VALVE 13 The manner of response of the valve 105 to changes of temperature has been described in detail in my above-referred-to prior pending US. Pat. application Ser. No. 473,300, filed July 20, I965, now US. Pat. No. 3,420,232 and need not be described here. Such US. Pat. application Ser. No. 473,300 is incorporated herein in its entirety by reference.

As we have seen above, the flow of carrier gas through the gap of valve 98, and the flow of carrier gas-anesthetic mixture through the gap of valve 105 is laminar and without substantial turbulence. This causes each of such valves to have a relatively constant flow resistance for any one setting even though the rate of flow of the gases to the valves is varied widely. As a result, there is very little change in the concentration of anesthetic in the gas mixture presented to the outlet of the apparatus over a wide range of the rate of gas flow through the apparatus.

As can be seen from FIGS. 5 and 6, the combination of upper (98) and lower (105) cone valves controls the mixture of saturated (or nearly saturated) gas from the wick chamber with the diluting fresh gas depending upon the vertical shaft position. The nature of methoxyflurane is that it has a relatively low vapor pressure with respect to other agents such as Fluothane (Halothane) or ether. The desired concentrations in volume percentage for anesthetic purposes are perhaps 3 or 4 percent for induction of the patient and in the order of .5

to 1 percent for "maintenance of anesthesia. Such approxi- I mate, illustrative anesthetic concentrations ranges have been thus labelled in FIGS. 16 and 17.

Since at normal room temperatures, percentages of methoxyflurane in the vicinity of 3 or 4 percent are obtainable only if all of the fresh gas is passed through the wick chamber 11, then no temperature compensation by regulation of mixing is possible without heat control. In any case, the high percentage (3 or 4 percent, for example) is required for only a few minutes for induction and is not critical, since it is used in conjunction with barbiturates and other medication. Consequently, the vaporizer of the invention ignores temperature compensation at the high percentage range.

The temperature expandable cone valve 105 is designed to accurately temperature compensate the percentage range of .5 to l percent anesthetic concentration used for maintenance of anesthesia. This is the range used for long periods during an operation where temperature compensation is most desirable. At settings above this range, the temperature regulation decreases to the point where at the maximum setting, i.e. where all of the gas is directed through the wick chamber 11,

the actual percentage concentration is dependent upon the temperature of the liquid in the vaporizer.

In the illustrative embodiment, the dial on knob 19 is marked "OFF, .25, 0.5, 1.0, 1.5, 2.0, 2.5, and MAX. The OFF position is obtained when the disc valve 73 is turned to OF F by movement of the knob 19 below the .25 position to the mechanical stop. At the Maximum position of knob 19, all of the input or carrier gas is directed through the wick chamber 11, or in other words, the upper cone valve 98 is now closed.

Considering the graph of FIG. 16 in detail, it will be seen that in the methoxyflurance concentration range up to l percent and somewhat above, which is employed for anesthesia maintenance, the percentage of anesthetic remains substantially constant over the entire range of gas flow per minute into the apparatus from 1 to liters per minute. In the same, anesthesia maintenance concentration range, as shown by the graph of FIG. 17, the anesthetic concentration does not vary substantially over the temperature range l5-30C. (59-86 F.) which includes all temperatures which might conceivably be encountered in an operating room.

Although the anesthetic vaporizer of the invention has been described in connection with its use with anesthetics having relatively low vapor pressure, it is to be understood that such apparatus may be employed to advantage, with slight adjust ment, with anesthetics such as Fluothane having a relatively high vapor pressure. When the apparatus is employed with anesthetics having a high vapor pressure, it is preferred that the inner body 44 of valve 42 be raised, by appropriate adjustment of the retaining means, including stud 70, 71, therefor, so there is presented a gap of the desired radial width between the outer frustoconical lower surface of body 44 and the inner surface 45 of cavity 37 in the valve block 12. The carrier gas flowing through the thus provided gap passes to the space 78, and thence directly to the outlet fitting by way of passages 69', 69 to be mixed with the carrier gas and carrier gasanesthetic mixture which flows through valves 98 and 105, respectively.

Although only one embodiment of the invention has been illustrated in the accompanying drawings and described in the foregoing specification, it is to be especially understood that various changes, such as in the relative dimensions of the parts, materials used, and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention, as will now be apparent to those skilled in the art.

I claim:

1. Anesthetic apparatus comprising: a container for liquid volatilizable anesthetic gas; a valve block mounted on the container and including a gas mixing chamber, an inlet for receiving a carrier gas and an outlet for discharging a mixture of the carrier gas and volatized anesthetic; a conduit leading from the inlet into the container for conducting gas to the container so as to entrain vaporized anesthetic therein and thence leading from the container to the mixing chamber; a passage connecting the inlet to the mixing chamber without passing through the container; first and second valves in opposed, spaced relationships, the space therebetween constituting the mixing chamber, the first valve being positioned in said conduit for regulating the flow of gas having anesthetic entrained therein to the mixing chamber and the second valve being positioned in said passage for regulating the flow of carrier gas without anesthetic to the mixing chamber; a gas outlet passage interconnecting the mixing chamber and the outlet; a third valve in said conduit adapted selectively to shut off the flow of gas to the container by connecting said conduit to said gas outlet passage upstream of the container; said first valve including a first valve member and a second valve member, the positions of the first and second members being relatively adjustable, and the second member being of a polymeric material having a positive linear coefficient of thermal expansion which is considerably greater than the coefficient of thermal expansion of said first member, for automatically adjusting flow space between the valve members in response to temperature changes.

2. Anesthetic apparatus comprising: a container for liquid volatilizable anesthetic gas; a valve block mounted on the container and including a gas mixing chamber, an inlet for receiving a carrier gas and an outlet for discharging a mixture of the carrier gas and volatized anesthetic; a conduit leading from the inlet into the container for conducting gas to the container so as to entrain vaporized anesthetic therein and thence leading from the container to the mixing chamber, a passage connecting the inlet to the mixing chamber without passing through the container; first and second valves in opposed, spaced relationships, the space therebetween constituting the mixing chamber, the first valve being positioned in said conduit for regulating the flow of gas having anesthetic entrained therein to the mixing chamber and the second valve being positioned in said passage for regulating the flow of carrier gas without anesthetic to the mixing chamber; a gas outlet passage interconnecting the mixing chamber and the outlet; a third valve in said conduit adapted selectively to shut off the flow of gas to the container by connecting said conduit to said gas outlet passage upstream of the container; and a pressure relief valve in the valve block in communication with the inlet and with the passage and the conduit having at least one normally closed hole operable at inlet pressure in excess of those of normal operation to open and to pass inlet gases to the outlet through a pressure relief passage.

3. Apparatus according to claim 2 wherein each of the first and second valves has a first, fixed valve member and a second, movable valve member cooperating therewith, and means interconnecting the movable members of the first and second valves in fixed spaced relationship for simultaneously operating the first and second valves to open the first valve as the second closes and vice versa.

4. Apparatus according to claim 2 including a means for manually adjusting the first and second valves, and means coupling the third valve to the adjustment means for shutting off the flow of gas to the container whenever the first valve is closed.

5. Apparatus according to claim 2 including a vent passage from the container to the ambient and. a fourth valve positioned in the vent passage and coupled to the third valve to open whenever the flow of gas to the container is shut off. for venting the container.

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