Patent GB-1293991-A (GB)
Title: Apparatus for use in anaesthetisation
IPC: A61M16/18
Filed: 1970-05-04
Abstract: 1293991 Anaesthetising apparatus DRAGERWERK AG 4 May 1970 [2 May 1969 12 May 1969] 21422/70 Heading A5T An aparatus for use in anaesthetisation comprises a container for containing an anaesthetic, a conduit into which said container is connected, a by pass conduit communicating at its ends with said conduit and by passing said container, first and second valves arranged to regulate carrier gas flow through said conduit and said by-pass conduit, respectively, said valves each comprising a valve port and a movable member which closes said valve port to an adjustable extent, a temperaturesensitive device which moves the moveable member of one valve relatively to the valve port of said one valve dependent on the temperature of anaesthetic in said container, and a control member by which the movable member of the other valve is displaceable relatively to the port of said other valve, the arrangement being such that when said movable member of said other valve is displaced by said control member while said temperature remains constant, said moveable member of said one valve and said valve port of said one valve move with said movable member of said other valve without change of the degree of closure of said valve port of said one valve. In the embodiment shown in Fig. 1, carrier gas enters through the aperture 1, the flow is divided at the point 2, a portion of the gas passes through the conduit 3, 4, 5, 6 and enters the evaporation chamber 12 at the point 10. The gas saturated with anaesthetic vapour then pases through a valve 15 into a chamber 16 where it mixes with a second portion of carrier gas which has passed into the chamber 16 directly from the division point 2 via the by-pass valve 17. The gas mixture issues from the apparatus at the gas outlet aperture 18. The by-pass valve 17 comprises a frusto-conical valve seat 19 which is secured to the housing, and a mobile valve member 20, the member 20 being mounted to be displaceable in the aperture 22 of the housing. For adjustment of the valve 17 the member 20 is provided with an adjusting wheel 27 and a compression spring 28. The mobile valve member 20 is also provided with a downwardly projecting closed supporting member 29 which carries a temperature sensor 31 immersed in the anaesthetic, the sensor containing a liquid 32 of high coefficient of thermal expansion sealed by bellows 33. Attached to the closure member 34 of the bellows is a spindle 35 which is adjustably secured to the valve member 37, said valve member being situated in a bore of the mobile valve member 20. The mobile valve member 37 comprises at its lower end a frusto-conical surface 39 which forms the regulating valve 15 with the frusto conical valve seat 40. A shut-off valve 46, for use when the apparatus is in the inoperative condition, comprises a piston 47, the upper face of which abuts on the lower face 48 of the adjusting wheel 27. When the apparatus is not required for operation the adjusting wheel is turned until the spring 54 presses the upper face of the piston 47 into a recess (not shown) in said wheel, and in this upper position the piston part 52 closes the gas inlet aperture 1 and simultaneously the narrowed part 49 unmasks the aperture (50), Fig. 2 (not shown), of a conduit (51) leading to the outlet 18. The displacement of the lower piston portion 52, also opens the venting bore 53 communicating the evaporation chamber 12 with the atmosphere. For use with anaesthetics having a non-linear temperature-vapour pressure gradient, an alternative embodiment for the temperature-sensitive device is provided, Fig. 3 (not shown).