GB2191270A - Fluid pressure relief valve - Google Patents

Abstract

A fluid pressure relief valve (11), for use in an oxygen partial pressure monitor (12), includes a valve head (14) axially movable between closed and open (as shown) positions, a rolling diaphragm (30) adapted to close a fluid passageway, including holes (28) in head (14), through the valve when the valve head is in the closed position, and spring means (26) operative to retain the valve head in either of the open or closed positions. An outer end (17) of the valve head protrudes from a housing when in the open position to provide an indication of valve operation. The valve is reset by pressure on end (17). The spring means comprises a compression spring (26) located around a pin (23) and is snap-acting <IMAGE>

Description

SPECIFICATION Fluid pressure relief valves THIS INVENTION relates to fluid pressure relief valves.

An object of this invention is to provide a simple and inexpensive fluid pressure relief valve which operates automatically to relieve pressure from within a device or apparatus on which it is fitted when the pressure increases beyond a predetermined maximum pressure, which provides a visual indication that overpressure has occurred and which is easily resettable.

Accordingly, the invention provides a pressure relief valve having a generally cylindrical valve head axially movable in a valve housing between closed and open positions, a rolling diaphragm having a radially outer portion fixed to the housing, a radially inner portion fixed to said valve head and a rolling wall located in an annulus between the valve head and the valve housing so as to close a fluid passageway through the valve when the valve head is in the closed position, and spring means to retain the valve head in either of the said open or closed positions.

Movement limiting means may be provided to limit axial movement of the valve head and may comprise a valve closed stop in which an outer end of said valve head is generally flush with an outer surface of the housing, and a valve open stop in which said outer end of the valve head protrudes from the housing.

preferably said open and closed stops comprise radially outwardly extending flanges axially spaced-apart on the valve head for abutment with a radially inwardly extending flange on the housing.

The fluid passageway may include a first axial bore extending partially through the valve head from its outer end, an aperture through the wall of the valve head communicating with the annulus, a second axial bore extending partially through the valve head from its inner end, and a plurality of radially extending holes communicating with said second bore and terminating at the outer surface of said valve head for closure by the diaphragm rolling wall when the valve is in the closed position.

The spring means may comprise a snap action overcentre mechanism and preferably includes a pin extending across the first bore and having a pointed head portion protruding through an aperture in the wall of the valve head for engagement by spring adjusting means, the other end of the pin being located in a further aperture through the wall of the valve head diametrically opposite the first aperture, and a compression spring retained around the pin and between the head portion and the inner surface of the wall of the valve head around the aperture.

Conveniently said spring adjusting means includes a threaded screw having a recessed surface for engagement by said pointed head portion and threadably mounted in the valve housing.

The invention will now be described by way of example only and with reference to the accompanying drawings in which, Figure 1 is a fragmentary sectioned side elevation of a fluid pressure relief valve according to the invention in a closed position to prevent release of a pressurised fluid from a unit in which it is fitted, and Figure 2 is a fragmentary sectioned side elevation similar to Figure 1 showing the valve in an open position.

Fluid pressure relief valve 11 is shown installed in the wall of apparatus for containing fluid under pressure, in the form of an oxygen partial pressure monitor 12 to automatically release fluid pressure from the interior 13 of the monitor 12 in the event that the fluid pressure increases during operation beyond a predetermined limit.

The pressure relief valve 11 includes a generally cylindrical valve head 14 axially movable within a valve housing 15 that is secured in a hollow boss of monitor 12. Movement limiting means comprise a radially inwardly extending flange 16 spaced inwardly from an outer end of the housing 15 and axially spaced-apart radially outwardly extending flanges 17 and 18 axially spaced-apart on the outer surface of the valve head 14. Flange 17 comprises a valve closed stop located at an outer end of valve head 14 and it will be noted from Figure 1 that with the flange 17 abutting the flange 16 an external surface of the valve head 14 is generally flush with the external surface of the valve housing 15.

A first axial bore 19 extends partially through the valve head 14 from its outer end and an axially extending slot 20 and an aperture 21 are located in diametrically opposed positions through the wall of the valve head 14 within the length of the bore 19 to communicate during certain phases of operation with an annulus 29 between the outer surface of the valve head 14 and the inner surface of the valve housing 15. The slot 20 and aperture 21 are aligned with an aperture 22 through the wall of the valve housing 15.

A second axial bore 27 extends partially through the valve head 14 from its inner end and communicates with four radially extending holes 28 which terminate at the outer circumferential surface of valve head 14 to also communicate during certain phases of operation with annulus 29.

A rolling diaphragm 30 has a radially outer portion 31 fixed to the valve housing 15 and a radially inner portion 32 fixed to the transverse surface of the inner end of valve head 14. An intermediate rolling wall portion 33 of diaphragm 30 is located in annulus 29 and is adapted when the valve head 14 in the closed position of Figure 1 to obturate the ends of the four holes 28 and effectively close a fluid passageway through the valve.

A central aperture 34 in rolling diaphragm 30 is aligned with the bore 27 in the inner end of valve head 14.

A pin 23 with a pointed head portion 24 extends across the bore 19 with one end located in aperture 21 and the pointed head portion protruding through the slot 20 and aperture 22 to locate in the recessed end of a threaded screw 25 screwed into a boss 33 on monitor unit 12. The head portion 24 seats one end of a compression spring 26 located around the pin 23 the other end of which seats against the surface of bore 19 around aperture 21.

In operation of the relief valve 11 of this invention the spring loaded pin 23 acts as a snap action over-centre mechanism to retain the valve head 14 in either its closed position (Figure 1) or its open position (Figure 2). During normal operation of a unit on which the relief valve 11 is fitted, such as the aforementioned oxygen partial pressure monitor, in which the fluid pressure in internal area 13 remains below a predetermined value, the valve head 14 is retained in its closed position shown in Figure 1 in which the rolling wall 33 of rolling diaphragm 30 obturates the ends of the holes 28 to prevent fluid leakage from the unit.

Should the fluid pressure in internal area 13 rise due perhaps to a malfunction in the unit 12 or in another part of the system, the increased pressure acts on the surface area of the inner end of the valve head 14 to move the valve head 14 away from the fully closed position of Figure 1 in which flange 1 7 abuts flange 16. As the fluid pressure in internal area 13 reaches a predetermined maximum the spring loaded pin 23 passes through a central position and the spring 26 snaps the valve head 14 to the fully open position of Figure 2 in which flange 18 abuts flange 16 to provide a valve open stop.In this position it will be noted that the rolling wall 33 of rolling diaphragm 30 uncovers the ends of holes 28 so that fluid pressure in the internal area 13 escapes through a fluid passageway comprising bore 27, holes 28, annulus 29, slot 20 and bore 19 to release fluid pressure from internal area 13.

Operation of the relief valve 11 is clearly visible due to the outer end of the valve head 14 fitted with flange 17 protruding from the housing 15 in which it is fitted, and visual awareness of operation can be enhanced by painting the flange 1 7 in an appropriate colour. Additionally, of course, the protruding portion of valve head 14 provides for tactile indication which is useful in poor light conditions or visually inaccessible locations.

The actual cracking pressure of relief valve 11 is adjustable by adjustment of the threaded screw 25 which in turn changes the compression loading applied by spring 26.

Once the fault is remedied the relief valve 11 of the invention is easily reset by pressure on the protruding end of valve head 14 to overcome the force of spring 26 which in turn snaps the valve head 14 to the closed position once the pin 23 moves past its central position.

Whilst one embodiment has been described and illustrated it will be apparent that many modifications can be made without departing from the scope of the invention as defined in the appended claims. For example, screw 25 could be threaded into a boss formed integral with valve housing 15 to make the relief valve 11 a completely self contained unit suited for ready installation in any pressurised device or apparatus that it is desired to protect from over pressure.

Claims (11)

1. A fluid pressure relief valve having a generally cylindrical valve head axially movable in a valve housing between closed and open positions, a rolling diaphragm having a radially outer portion fixed to the housing, a radially inner portion fixed to the valve head and an intermediate rolling wall portion located in an annulus between the valve head and the valve housing so as to close a fluid passageway through the valve when the valve head is in the closed position, and spring means to retain the valve head in either of said open or closed positions.

2. A valve as claimed in Claim 1, including movement limiting means to limit axial movement of the valve head.

3. A valve as claimed in Claim 2, wherein said movement limiting means includes a valve closed stop in which an outer end of said valve head is generally flush with an outer surface of the housing and a valve open stop in which said outer end of the valve head protrudes from the housing.

4. A valve as claimed in Claim 3, wherein said open and closed stops comprise radially outwardly extending flanges axially spacedapart on the valve head for abutment with a radially inwardly extending flange on the housing.

5. A valve as claimed in any preceding Claim, wherein said fluid passageway includes a first axial bore extending partially through the valve head from its outer end, an aperture through the wall of said valve head communicating with said annulus, a second axial bore extending partially through the valve head from its inner end and a plurality of radially extending holes communicating with said second bore and terminating at the outer surface of said valve head for closure by the diaphragm rolling wall when the valve is in the closed position.

6. A valve as claimed in any preceding Claim, wherein said spring means comprise a snap action over-centre mechanism.

7. A valve as claimed in Claim 6 when dependent from Claim 5, wherein said mechanism includes a pin extending across the first bore and having a pointed head portion protruding through the aperture for engagement by spring adjusting means, the other end of said pin being located in a further aperture through the wall of the valve head diametrically opposite the first aperture, and a compression spring retained around the pin and between said head portion and the inner surface of the wall of the valve head around said second aperture.

8. A valve as claimed in Claim 7, wherein said spring adjusting means includes a screw threadably retained in the valve housing.

9. A fluid pressure relief valve substantially as hereinbefore described with reference to the accompanying drawings.

10. Apparatus for containing fluid under pressure, provided with a fluid pressure relief valve as claimed in any one of Claims 1 to 9.

11. Every novel feature and every novel combination of features disclosed herein.