GB1312558A - Anaesthetic vaporizers - Google Patents

Abstract

1312558 Anaesthetic vaporizers LONGWORTH SCIENTIFIC INSTRUMENT CO Ltd 10 Feb 1972 [25 Feb 1971] 5476/71 Heading A5T [Also in Division F2] An anaesthetic vaporizer has an inlet 1 connectible to a supply of carrier gas and an outlet 24 to supply a mixture of carrier gas and entrained anaesthetic to the patient and incorporates a proportioning valve 7 which is settable to control the proportion of carrier gas which passes over the anaesthetic 20 and a valve assembly 18 comprising two cooperating valve members 30, 34 which define a fluid flow passage 36 whose size is variable by the relative movement of the valve members, one 30 of which is settable to provide a means of setting an upper limit on the above mentioned proportion and the other of which 34 is movable under the control of a temperature sensitive means 43. The one valve member 30 is a tapered needle which is screw-threadedly mounted in a housing 25 for axial adjustment relative to a valve seat provided by the other valve member 34. The needle may be conically or parabolically tapered or may be formed as a series of steps, the edges of which define a parabola. The other valve member can move in a bore 29 in the housing 25 and is urged downward by a spring 40 and engaged with a lever 40 which is moved by a temperaturesensitive capsule 43. The valve seat provided by member 34 may have an annular knife edge (50) (Fig. 3 not shown). In use the carrier gas passes into a chamber 3 from where some gas passes into a chamber 16 bypassing the anaesthetic chamber 19 whilst the remainder passes through valve assembly 18 into the chamber 19 containing anaesthetic and a wick 21. The vapourised anaesthetic is mixed with the by-passing carrier gas in chamber 16 and to the patient (e.g. via a mask) through outlet 24. The proportioning valve 7 is adjusted using the screw thread 9 on the shaft 8.