Importance

Loading Importance Indicators...

Abstract

A method and apparatus are described for controlling the rate of supply of a liquid cryogen, for example, for cryosurgical use. The flow rate of the liquid cryogen is controlled by controlling variably the pressure propellant gas acting directly or indirectly on the liquid cryogen. A means for controlling the propellant gas pressure may comprise a source of pressurised propellant gas, and control valve means coupled between the source and the liquid cryogen reservoir chamber for controlling the pressure supplied to the reservoir chamber. A plurality of reservoir chambers may be driven by a common pressure source. When the pressure source is a pressure raising system, the cryogen reservoir chambers may be contained within the vessel of the pressure raising system. A feedback control arrangement is also described for controlling the cryogen flow rate in response to a measured characteristic associated with, or affected by, the cryogen flow rate. For example, in cryosurgery, the measured characteristic may be temperature as measured by a temperature probe.

Loading the Abstract Image...

First Claim