GB2145336A

GB2145336A - Expiratory valve

Info

Publication number: GB2145336A
Application number: GB08421120A
Authority: GB
Inventors: Dr J A Gil-Rodriquez
Original assignee: Automated Process & Control
Current assignee: Automated Process & Control
Priority date: 1983-08-18
Filing date: 1984-08-20
Publication date: 1985-03-27
Also published as: GB2145336B; GB8421120D0; GB8322263D0

Abstract

An expiratory valve has a body 12 which defines an inlet port 13 and an annular valve seat 14. A valve body 15, incorporating a hollow control knob 16, screws into the body and carries a valve 17 and valve stem 18. The valve is biassed by spring 19 and the biassing force is adjustable by turning knob 16. Exhaust gases at pressures above the predetermined pressure flow through inlet 13 into a chamber 20 and out of an outlet port 21. A positive pressure relief valve is provided in the hollow knob 16 and comprises a mica disc 23 resiliently biassed by spring 25 against another valve seat 24. The hollow interior of the knob is in communication with chamber 20 by way of four holes 27 spaced at equiangular differences about the periphery of the valve body 15. The spring characteristics are such that at a predetermined pressure the disc lifts to allow gas to escape through an outlet port 28 in the knob 16. <IMAGE>

Description

SPECIFICATION Anaesthetic gas scavenging exhaust valve This invention relates to an exhaust valve for use in an anaesthetic gas scavenging system.

According to this invention there is provided an expiratory valve comprising a body defining an inlet port and a valve seat located at the inlet port, a valve body engaged in the body and carrying a valve, which valve is movable with respect to said valve body and which is resiliently biassed against the valve seat, an outlet port which communicates with a volume, which volume in turn communicates with the inlet port only when the pressure of gases at the inlet port is sufficient to overcome the biassing pressure urging the valve onto the valve seat, said valve body also carrying a positive relief valve which is in communication with said volume.

It is a preferred feature of the invention that said valve body comprises a knob projecting beyond the body and is screw-threadedly engaged in the body and the valve is biassed against the valve seat by means of a coiled spring compressed between the valve and the valve body in such a way that turning of the knob varies the biassing pressure imparted on the valve and thus varies the pressure at which exhaust gases pass through the valve, into the volume and then out of the outlet port.

It is another preferred feature of the invention that said relief valve is incorporated in the knob, said knob being hollow and having a cover on its end projecting beyond the body, said relief valve comprising an inlet orifice to the interior of the knob disposed at the end of the knob opposite the cover, which inlet orifice defines a further valve seat, upon which valve seat a valve member is resiliently biassed, said cover incorporating an outlet orifice and the interior of the knob communicating with said valve in such a way that gases in the volume communicate with the inlet orifice of the relief valve but are able to communicate with the interior of the knob, and thus with the outlet orifice of the knob, only when the pressure of the gases in the volume is sufficient to overcome the biassing of the valve member and displace the valve member from its position on the further valve seat.

According to another preferred feature of the invention said valve member comprises a mica disc which disc is resiliently biassed against said further valve seat by a coiled phosphor-bronze spring, which spring is compressed between the disc and the cover of the knob.

Preferably, communication between the inlet orifice of the hollow knob and the volume is by way of four holes spaced at equiangular distances about the periphery of the valve body.

Reference will now be made to Figure 1 of the accompany drawings, which is a diagram of a known kind of anaesthetic gas scavenging system. In Figure 1, anaesthetic gases exhaled by the patient are collected in a collecting system 1 which comprises a ducted expiratory valve 2. A conical connector 3 couples the valve to a transfer tube 4 through which the gases are passed to a receiving system 5. In the receiving system there is a safety block comprising a positive pressure relief valve 6, a negative pressure relief valve 7 and a reservoir bag 8. From the receiving system the gases are drawn to a disposal system 9 which comprises a fixed pipe 10, an air mover 11 and an external termination E, which is outside the operating theatre.

Patient safety during anaesthetic gas scavenging depends upon the correct position and functioning of the positive and negative pressure relief valves.

As shown, these valves are usually incorporated in safety blocks located between the transfer and disposal systems of the scavenging system. Such arrangement, however, does not protect the patient in the event of an obstruction taking place in the transfer tube before the safety block. Patient protection will only be complete if the positive pressure safety valve is situated as near to the patient as possible.

The present invention provides an improvement whereby the positive pressure relief valve is situated nearer the patient.

According to the invention the expiratory valve of the scavenging system incorporates the positive pressure relief valve.

The invention is realised in a preferred form by incorporating the positive pressure relief valve in the hollow manual adjustment knob of an expiratory valve.

The invention will further be described with reference to Figure 2 of the accompanying drawing, which is a cross-sectional view of a valve in accordance with the invention.

Referring to Figure 2 the valve is a modification of that known as the MIE Superlite exhaust valve. This comprises a body portion 12 which defines an inlet port 13 and an annular valve seat 14. Avalve body 15 comprises a control knob 16 and screws into the body portion 12. The valve body carries a valve 17 with a valve stem 18. A valve spring 19 urges the valve against the valve seat and the effective pressure of the spring can be adjusted by turning the knob 16. Exhaust gases escape through the valve at a pressure determined by the setting of the knob 16 and pass from the inlet port to chamber 20 and thence through vent apertures to an outlet port 21 which is defined by a swivelling gas-tight hood 22, the outlet being coupled in use to the transfer tube 4 (Figure 1).

The modification consists in providing a positive pressure relief valve in the hollow control knob 16.

The relief valve comprises a mica disc 23 which is kept firmly pressed against the flat bottom 24 of the hollow knob 16 by a phosphor-broze spring 25 compressed between the cover 26 of the knob and the disc. The spring characteristics are such that it allows the disc to lift at a pressure of approximately 1000Pa(10cmH2O).

Inlet to the the interior of the knob is by four equidistante holes 27 of 3 mm diameter. The outlet is by a hole 28 of 5 mm diameter in the cover 26.

With a relief valve of this kind the through-flow rate at the relief pressure of approximately 1000 Pa is 30 litres per minute.

Claims

1. An expiratory valve comprising a body defining an inlet port and a valve seat located at the inlet port, a valve body engaged in the body and carrying a valve, which valve is movable with respect to said valve body and which is resiliently biassed against the valve seat, an outlet port which communicates with a volume, which volume in turn communicates with the inlet port only when the pressure of gases at the inlet port is sufficient to overcome the biassing pressure urging the valve onto the valve seat, said valve body also carrying a positive relief valve which is in communication with said volume.

2. An expiratoryvalve as claimed in claim 1 wherein said valve body comprises a knob projecting beyond the body and is screw-threadedly engaged in the body and the valve is biassed against the valve seat by means of a coiled spring compressed between the valve and the valve body in such a way that turning of the knob varies the biassing pressure imparted on the valve and thus varies the pressure at which exhaust gases pass through the valve, into the volume and then out of the outlet port.

3. An expiratoryvalve as claimed in claim 2 wherein said relief valve is incorporated in the knob, said knob being hollow and having a cover on its end projecting beyond the body, said relief valve comprising an inlet orifice to the interior of the knob disposed at the end of the knob opposite the cover, which inlet orifice defines a further valve seat, upon which valve seat a valve member is resiliently biassed, said cover incorporating an outlet orifice and the interior of the knob communicating with said volume in such a way that gases in the volume communicate with the inlet orifice of the relief valve but are able to communicate with the interior of the knob, and thus with the outlet orifice of the knob, only when the pressure of the gases in the volume is sufficient to overcome the biassing of the valve member and displace the valve member from its position on the further valve seat.

4. An expiratoryvalve as claimed in claim 3 wherein said valve member comprises a mica disc which disc is resiliently biassed against said further valve seat by a coiled phosphor-broze spring, which spring is compressed between the disc and the cover ofthe knob.

5. An expiratory valve as claimed in claim 4 wherein communication between the inlet orifice of the hollow knob and the volume is by way of four holes spaced at equiangular distances about the periphery of the valve body.

6. An expiratory valve substantially as hereinbefore described with reference to the accompanying drawings.