Gas and liquid contact apparatus – Contact devices – Porous sheet
Patent
1986-12-17
1988-09-27
Miles, Tim
Gas and liquid contact apparatus
Contact devices
Porous sheet
261DIG65, 12820413, 29445, 228155, 228182, B01F 304
Patent
active
047740329
DESCRIPTION:
BRIEF SUMMARY
This invention relates to vaporizers, in particular anaesthetic vaporizers, and to wick assemblies therefor.
Various types of wick assembly are known for use in anaesthetic vaporizers. One type of known vaporizer includes a vaporizing chamber partly filled with liquid anaesthetic in which a lower portion of the wick assembly is immersed. A carrier gas stream flows over the vaporizing surface of the wick to entrain anaesthetic vapour and the mixture is then delivered to the patient. In order that the gas should become sufficiently saturated with anaesthetic vapour it must remain in contact with the vaporising surface of the wick for a long period, and this has been achieved by guiding the gas downwards via a helical path formed in an annular chamber defined by the space between two concentric cylinders of wick material.
In another known vaporizer the wick assembly comprises a number of vertical, spaced apart sheets of wick material which are partly immersed in liquid anaesthetic, in which the gas flows past each such sheet via a multiplicity of horizontal passages.
However both these known wick assemblies are relatively complex in structure and fitting thereof to a vaporizer and removal for servicing can require specialist attention.
One particularly effective type of wick material, known for example from British patent No. 1043110, is metallic wire cloth. The capillary action of such cloth can be greatly enhanced by securing it in contact with a smooth unperforated metal surface, due to the formation of additional small upwardly directed passages between the wires of the mesh and the surface of the metal plate.
Viewed from one aspect the invention provides a wick assembly for a vaporizer, such assembly comprising an absorbent wick material provided with a substantially impermeable backing layer, the wick material and the backing layer being rolled into a substantially spiral configuration so as to define a substantially spiral flow passage extending through the assembly, fastening means being provided to hold said wick material and backing layer in such spiral configuration whereby the assembly forms a self-contained unit adapted to be detachably mounted in a vapouriser.
With a wick assembly in accordance with the invention a flow passage of sufficient length to provide a desired degree of vapour saturation may be achieved with a relatively simple wick structure.
Generally, the wick assembly will be rolled into the spiral configuration in such a manner that its outside shape is generally cylindrical i.e. having a circular outer cross-section which exhibits internally the spiral configuration. However it is possible for the precise configuration of the spiral to vary such that the cross-section of the cylinder can be any convenient shape. For example it may be oval or elliptical, or possibly square or rectangular.
In use in a vaporizer, one longitudinal end of the wick assembly is immersed in a liquid which is drawn up through the wick material by capillary action, such action being assisted by the presence of the backing layer since this provides additional upward passages defined between the absorbent material and the impermeable layer. The drawing up may take place along substantially the whole length of the spiral. A stream of carrier gas is then passed from one end of the spiral to the other, either from the outside thereof to the centre or vice versa, via the spiral flow passage and the carrier becomes saturated with vapour due to its prolonged contact with the wick material carrying the liquid. The wick assembly is particularly suitable for use in an anaesthetic vapouriser, in which case the liquid is a suitable anaesthetic agent.
Since the assembly is a self-contained unit it may be mounted in a vapouriser in an interchangeable manner, and the wick assembly may thus be readily replaced and/or removed for servicing as necessary and this represents a significant practical advantage.
The wick material is preferably in sheet form and may comprise a plurality of sheets spaced at intervals or adjacent eac
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Coates John R.
East Ralph J.
Sugg Basil R.
Miles Tim
Penlon Limted
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