Electric resistance heating devices – Heating devices – Vaporizer
Patent
1998-04-02
1999-11-02
Walberg, Teresa
Electric resistance heating devices
Heating devices
Vaporizer
12820312, 12820326, 12820327, F22B 2906, A61M 1500, A61M 1600
Patent
active
059785489
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device of the general type specified in the first part of claim 1.
Such a device is intended for gasifying liquid, especially liquid anaesthetic, and for metering the gas thereby obtained to a stream of fresh gas, especially in an anaesthesia apparatus.
STATE OF THE ART
For a gasification chamber of the abovementioned type, the general or principle is that the chamber constitutes a cavity or closed space where the liquid in question, which is accordingly a liquid anaesthetic when metering gas to a fresh gas stream in an anaesthesia apparatus, is gasified and is then conveyed onwards to, and metered into, the stream of fresh gas. The basic principle of gasification is that the liquid in question is vaporized by being made to boil, as a result of which a 100% saturated vapour is obtained. Since the liquid which is made to boil (vaporized) and the vapour are under pressure, it can be metered in gaseous form into the stream of fresh gas by means of opening a valve in the line via which the metering gas is introduced into the stream of fresh gas. It is important in this respect that the vapour (gas) thus generated is cooled only after it has been metered into the stream of fresh gas. Otherwise, it would be condensed, i.e. liquid would then be metered into the stream of fresh gas as would the vapour, and this would lead to the vapour pressure in the fresh gas becoming unpredictable and too high.
For an example of a known device of the type mentioned in the introduction, reference may be made to the metering and gasifying device which is described in European Patent Specification 0 231 513. This known device is intended especially for supplying anaesthetic gas to a stream of fresh gas in an anaesthesia apparatus. This device comprises a source of gas at constant pressure, a second source containing a liquid which is to be gasified, a gasification chamber and a metering line through which the gas is conveyed from the chamber to a mixing point where it is mixed with another gas (which is the fresh gas where the application involves an anaesthetic gas apparatus), and a valve device which is arranged to deliver a defined dose of gas for each metering stroke of a control valve in the valve device. The distinguishing feature of this known metering and gasifying device is that the gasification chamber is intended to be kept at a constant pressure and, by means of a controllable heating device, to be maintained at a temperature which is such that the liquid fed from the liquid source into the gasification chamber is in the main gasified directly, so that when equilibrium has been reached, no more liquid is supplied from the liquid source to the gasification chamber than is dosed/metered by means of the valve device in the metering line.
Another example of a known metering device intended for the same medical engineering application is found in U.S. Pat. No. 5,243,973.
OBJECTS OF THE INVENTION
The primary object of the present invention is to make available a device in which the free liquid surface inside the gasification chamber--which is located somewhere between the lower part of the chamber (containing the liquid phase) and the upper part of the chamber (containing the gas phase)--can be maintained at a virtually constant level in the gasification chamber.
The underlying idea of the solution which is provided by the invention to this problem will be that the gasification chamber is designed in such a way that a well-defined heating zone, which can be controlled/monitored by simple means, is obtained in an intermediate area in the gasification housing in which the gasifi-cation chamber is accommodated.
A secondary object of the invention will be that the gasification housing can be designed in a way which is simple and reliable in terms of construction and so that any variations in the level of the liquid surface inside the gasification chamber can be easily detected, which is made easier by the fact that the gasification housing (and with it the gasification chamber) can have a
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Holmstrand Niklas
Nyman Rune
Datex Engstrom AB
Paik Sam
Walberg Teresa
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