Chemical apparatus and process disinfecting – deodorizing – preser – Physical type apparatus – Heat treating vessel with heating means
Patent
1991-07-23
1993-10-26
Warden, Robert J.
Chemical apparatus and process disinfecting, deodorizing, preser
Physical type apparatus
Heat treating vessel with heating means
422 28, 422 37, 422292, 422298, 422305, 219401, 392394, 392400, 392402, 392403, A61L 204, A61L 220
Patent
active
052563820
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a heating appliance which provides a vapour-heated chamber. It has particular, but not exclusive, reference to an ambient pressure steriliser capable of rapidly sterilising a small charge (e.g. up to 2 kg) of artifacts (e.g. dentist's or surgeon's tools), but can also be used for general heating applications (e.g. curing of plastics articles or vapour-phase soldering).
It is known to sterilise small artifacts in a chamber filled with the vapour of a liquid having a boiling point above 100.degree. C. (e.g. above 150.degree. C.), brought to boiling point in an electrically-heated reservoir forming a lower region of the chamber during a heating phase and, following a sufficient dwell time in the vapour to achieve sterilisation, to cause the vapour to condense down back into the reservoir during a condensation or cooling phase, leaving the chamber free of vapour. One example of an appliance which operates in this way is described in GB-A-2160772.
For the fastest recycling up to sterilising temperature and back to a safe handling temperature, both the heating and condensation phases need to be as short as possible. It is known to cool the chamber externally with air during the condensation phase to reduce the duration of this phase, but it is important to control the cooling process so that liquid condensate is not left on the artifacts or the trays or other platforms used to support them. It is known to locate an immersion heater directly in the liquid to reduce the duration of the heating phase, despite the risk this brings of hot spots occurring on the heater that may take the heating liquid above a recommended safe operating temperature.
It is known (see for example GB-A-353832) to use a reservoir for the heating liquid in a steriliser which has spaced-apart inner and outer walls defining therebetween a volume for the heating liquid.
SUMMARY OF THE INVENTION
According to this invention a heating appliance (and in particular a steriliser) including a vapour-heated chamber, a reservoir adapted to contain a vaporisable heating liquid and heating means for the liquid to vaporise the latter and to supply the vapour to the chamber, the reservoir having spaced-apart inner and outer walls defining therebetween a volume for the heating liquid, is characterised in that one of the inner and outer walls is used to heat the liquid during the heating phase and the other of the walls is used for cooling the liquid during the condensation phase.
Conveniently both walls are cylindrical walls (e.g. of circular cylindrical form) and are concentrically mounted with their common axis extending vertically. Suitably the inner wall is formed as an extension of a domed lower wall of the chamber, the domed lower wall being convex towards the chamber. The inner wall has a smaller surface area than the outer wall and it may be thermally more efficient to use the inner wall for transfer of heat into the reservoir and the outer wall for transfer of heat out of the reservoir. Practically however, wrapping a band heater around the outer wall is a very easy way of heating the liquid leaving the inner wall free for cooling. Air cooling is preferred, but liquid cooling (e.g. via water flows) is not excluded. Where air cooling is employed it may be desirable to improve the heat exchange coefficient of the appropriate wall of the reservoir, e.g. by the use of fins, a surface coating or a surface treatment on the reservoir wall/walls.
Where air cooling is employed, a simple fan can be located outside the chamber adjacent to the chamber walls, the air flows from the fan being used partly to cool the chamber walls and partly to cool one or both walls of the reservoir. The proportion of air used for these two purposes can remain unchanged during the condensation phase or varied (e.g. on a preset pattern) depending on the stage of cooling reached in the condensation phase.
To further reduce the time needed for the condensation phase, means can be provided to move vapour within the chamber so that enhanc
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patent: 4909999 (1990-03-01), Cummings
Bailey Christopher R.
Ford Michael A. J.
Autocar Equipment Limited
Smith Stephanie
Warden Robert J.
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