GB2057095A - Fluid pressure operated valves - Google Patents

Abstract

A valve suitable for the air duct of a routine pulmonary function analyser comprising a spring pressed valve disc 11 engaging two concentric sealing rings 16, 17 between which reduced pressure can be applied to assist the spring 12 in holding the valve closed against the rings. <IMAGE>

Description

SPECIFICATION Fluid pressure operated valves This invention relates to fluid pressure operated valves and its object is to provide a simple form of valve which can have a non-return function and when required can be held closed in both directions.

According to the invention the valve comprises a movable valve member arranged to close a duct, means to urge the valve member resiliently to its closed position two sealing rings concentric with each other engaged by the movable member to effect its closed function, and means to reduce the fluid pressure between the rings to hold the valve member in its closed position.

The means for urging the valve member to its closed position may be a helical spring and the valve member may be a flat disc.

The fluid may be air.

One application of the valve is for control of inspiratory gases in a four port valve box used in a "Routine Pulmonary Function Analyser".

A constructional form of the invention suitable for such analyser will now be described by way of example with reference to the accompanying diagrammatic drawing which is a cross-sectional view of a valve made in accordance with the invention.

A valve body 10 is shown as a single piece but in practice may be made in two or more parts secured together by any suitable means.

The valve body contains a movable valve member 1 1 in the form of a flat light weight mica disc which is urged towards its closed position by a helical spring 12 which is seated on a shoulder 13 on the body. The member 11 and spring are located in a cavity 14 in the valve body across the air duct 15 of a "Routine Pulmonary Function Analyser". The disc 11 in its closed position seats against two sealing O-rings 1 6, 17 one of which is larger than the other. The rings are located concentrically with each other in grooves in the body 10.

The body 10 has a conduit 18 connected by channels 20, 21 to the cavity 14 at positions between the rings 16, 17.

The valve may be connected at A to one of the ports of the Analyser so as to act as a one-way valve with no vacuum line being attached at 18.

The valve can be attached at B to each of the other three ports with vacuum applied as required at 18 on each valve to control the passage of particular gas mixtures through each valve in turn to the patient.

In the first mode of operation, gas entering the valve in the direction A acts on the light weight mica disc 11 and develops a small pressure on the face of the disc, causing it to lift off the O-rings.

The gas can flow around the side of the disc and hence out of the other end of the valve. When the flow stops the spring returns the mica disc to the O-rings.

When a flow is applied in the direction of arrow B pressure develops on the reversed face of the mica disc, so increasing the pressure against the O-rings so that the valve then prevents flow in the direction indicated by the arrow B.

In the second mode of operation the valve prevents flow in both directions. With the spring pressing the mica disc against the two concentric O-rings, the air pressure between the two O-rings is reduced by pumping with a suitable vacuum pump through the conduit 18. Normal atmospheric pressure now holds the mica disc in position against the O-rings. This is sufficient to prevent the disc from moving even if pressure is applied in the direction A.

The valve will return to normal one-way operation when the vacuum formed between the O-rings is allowed to return to atmospheric pressure.

The vacuum pressure required between the 0rings needs only to be in the 1-10 Torr region as this will allow the full atmospheric pressure of 14 PSI to hold the mica disc in place.

An important consideration in the design of a respiratory valve is that it must have a low resistance to gases under full flow condition.

Practical experience with the valve has proved that it meets this condition.

When this design of valve is used as part of the four port valve box for the Routine Pulmonary Function Analyser (R.P.F.A.), it must be capable of sterilization by autoclave or gas methods. This valve can be made of suitable materials for these processes, and can be easily demountable.

Although this valve was primarily designed for the Analyser it can be used in many other systems:- for example control of inspired gases through mixing boxes or in a closed circuit patient ventilator.

Claims (6)

1. A fluid pressure operated valve comprising a movable valve member arranged to close a duct, means to urge the valve member resiliently to its closed position, two sealing rings concentric with each other engaged by the movable member to effect its closed function, and means to reduce the fluid pressure between the rings to hold the valve member in its closed position.

2. A valve as claimed in claim 1 wherein the rings are in a common plane and the valve member is a flat disc urged by a spring against the rings.

3. A valve as claimed in claim 1 or 2 comprising a valve body having a cavity which contains the valve member and said rings and duct wherein the means for reducing the fluid pressure comprises a port in the body for connection to a vacuum device and a plurality of ducts connecting the port to positions between the rings and opening into said cavity.

4. A valve as claimed in any of the preceding claims wherein the valve member is a mica disc.

5. A valve substantially as described with reference to the accompanying drawing.

6. A pulmonary function analyser comprising a valve as claimed in any of claims 1 to 4 the said duct being the air duct of the analyser.