Volatile anaesthetic vaporising apparatus

Claim 1

Vaporizing apparatus for a volatile anesthetic including; a body forming a container for liquid anesthetic and wherein such liquid can be vaporized by the inflow of gas; a bypass chamber for gas located above said container; a main inlet to, and a main outlet from, said bypass chamber for the through flow of gas; a bypass valve controlling the flow of gas into the bypass chamber; a temperature-responsive element connected to move said bypass valve to increase the pressure drop over the bypass valve as the temperature falls; a gas inlet to, and a gas-anesthetic outlet from, said container; gas inlet passage means for connecting said main inlet to said container gas inlet; gas-anesthetic outlet passage means for connecting said container gas-anesthetic outlet to said main outlet to mix with gas passing from said container; a rotary plate valve normally closing said gas inlet and gasanesthetic outlet passages; means on said plate valve for opening said gas inlet passage throughout a set range of angular movement of said plate valve; part-annular groove means on said plate valve for opening said gas-anesthetic outlet passage over a further range of angular movement of said plate valve, said groove means having its depth less than its width; presenting a gas-anesthetic flow path along an arch of at least 180* and being of inconstant cross-sectional area to vary the flow of gas-anesthetic into the main outlet and thus vary the anesthetic concentration delivered from the vaporizer; and manual operating means for causing rotation of said valve to initially allow gas flow into the vaporizer and then to control the anesthetic concentration delivered from the vaporizer.