GB2233237A - Valve for breathing apparatus - Google Patents

Abstract

A manual override (37) is provided in a valve arrangement for supplying air to the facial cavity in a safety breathing apparatus and comprising a casing with a diaphragm (33) defining separated 1st and 2nd volumes (B and C) therein the two volumes (B and C) being in continuous open communication with respectively the facial cavity and the surrounding atmosphere. The valve includes an air supply valve (31, 32) with an actuating member (28) in the first volume (B) and which engaged by the diaphragm (33) to open the air supply valve (31, 32), and allow air flow to the facial cavity, when the diaphragm (33) is deflected either by the pressure in the first volume (B) falling below a predetermined pressure or by the manually actuable device (37) which, when actuated, causes the diaphragm (33) to act on the said actuating member (28) to open said air flow valve (31, 32) irrespective of the pressure in said first volume (B). <IMAGE>

Description

"IMPROVEMENTS IN OR RELATING TO VALVES" This invention relates to valves and, more specifically, to valves for controlling the air supply to a facial cavity defining the breathable volume in a safety breathing apparatus.

Valves for controlling the air supply from an air reservoir to the facial cavity of a breathing mask or helmet are well known in the art.

One popular form for such valves comprises a casing with a diaphragm defining two separated volumes within the casing, an air supply inlet to the valve from the air reservoir an air outlet from the valve arrangement, opening directly to, or connectable with, the facial cavity and an air control valve for controlling the air supply from said supply inlet to said air outlet.

One of said two volumes is open to the surrounding atmosphere through an opening in the casing and is, therefore, maintained at a relatively stable pressure.

The other of said volumes, is in continuous open communication with the facial cavity and is thereby subject to the variable pressures in the facial cavity generated by the breathing cycles of the wearer.

The said volume in open communication with the facial cavity includes an actuating element for the air control valve and the actuating element is displaceable by the diaphragm, to open communication between the air supply inlet and the said air outlet for the valve arrangement, when the pressure in the volume communicating with the facial cavity falls below a !predetermined value. The air supply valve closes the air flow passage through the valve when the diaphragm is displaced to a position out of pressure contact with said actuating member when the pressure in said volume communicating with said facial cavity is above said predetermined value.

With the above arrangement, and with the facial cavity at a pressure greater than atmosphere indicative of the wearer exhaling, the pressure in the volume to the facial cavity is above atmospheric pressure, the diaphragm is displaced away from the said actuating element and the air control valve closes the air flow passage through the valve arrangement. On the wearer inhaling there is a pressure drop in the facial cavity, the pressure drop is communicated to the said volume in communication with the facial cavity, and as the pressure in said volume falls below the predetermind pressure the diaphragm is displaced, thereby to engage the actuating element and open the flow passage through the air supply valve, thus permitting air flow to the facial cavity.

A serious problem, with such valve arrangements arises because the air supply valve is only supplying breathable air to the facial cavity when the pressure in the volume communicating with the facial cavity falls below said predetermined pressure and, apart from controlling his or her breathing cycle, the wearer has no control over the quantity of air being delivered to the facial cavity over each breathing cycle. With such an arrangement, and with the wearer engaged in physical effort such as in heavy rescue work, there is always a danger that the wearer may suffer oxygen depravation. Further, and more seriously, in the event that the wearer should be rendered unconscious and suffer shallow breathing cycles, the safety of the wearer can be seriously endangered, particularly as personnel attending upon the wearer cannot affect the air supply to the wearer through the valve.

The present invention seeks to provide a valve arrangement of the type defined and wherein the air passage through the valve arrangement may be opened on demand.

According to the present invention there is provided a valve arrangement, for controlling the air supply to the facial cavity of a safety breathing apparatus, comprising a casing, a diaphragm in said casing defining separated first and second volumes within said casing, said first volume being in continuous open communication with the facial cavity and said second volume being in continuous open communication with the surrounding atmosphere, and an air control valve arranged to open to allow air to flow to the facial cavity whilst the pressure in said first volume is below a predetermined value, characterised by a manually actuable device arranged, when actuated, to open the said air control valve irrespective of the pressure in the said first volume.

Preferably the said air control valve includes an actuating member located in said first volume and arranged to be actuated, to open the said air control valve, by the said diaphragm deflecting to reduce the first volume whilst the pressure in said first volume is below said predetermined pressure.

In one embodiment according to the invention said manually actuable device, when actuated, is arranged to deflect the said diaphragm and cause the said diaphragm to actuate the air control valve actuating member.

Preferably said manually actuable device is loaded by spring means towards its inoperative position.

In one embodiment said manually actuable device extends through a rigid wall of the casing defining said second volume.

Preferably said manually actuable device comprises a body of revolution, supported by said casing for axial displacement along an axis at right angles to the plane of the diaphragm.

In one preferred embodiment said manually actuable device comprises a cylindrical mid-region with an enlarged head on each of its ends.

In such a preferred embodiment the cylindrical midregion is slidably located in an opening in the rigid wall of the casing whereupon one of said enlarged heads is supported in said second volume, to be engageable with the diaphragm when the device is actuated, and the other of said enlarged heads is externally of the casing and manually actuable.

Preferably the valve arrangement includes a resilient cover and the manually actuable device is beneath said cover and manually actuabls by deflecting said resilient cover.

The invention will now be described further by way of example with reference to the accompanying drawings in which; Fig. 1. shows a cross section through one form of valve for a safety breathing apparatus, and Fig. 2 sh ms, on a slightly enlarged scale, a cross section through a manually-actuable valve opening arrangement according to the invention applied to the valve arrangement illustrated in Fig.l Throughout this description terms such as "lower", "upper", "left" and "right" shall refer to said directions as apply to the assembly illustrated in Fig. 1.

In the valve arrangement illustrated in Fig. 1 a generally cylindrical body 11 has a generally cylindrical recess 12 in its upper radial face.

An air supply bore 13 open to the lower radial face of the body 11 extends to the recess 12 axially parallel with the axis of the body 11 and has a filter 14 in its lower end and a sintered restrictor arrangement 15 in its upper regions.

An air outlet duct 16 extends from the lower radial face of body 11 to one side of an annular recess 17 in the lower regions of the recess 12 and a reduced diameter part 18, in the lower regions of recess 17, is in open communication with the air supply bore 13 via a transverse bore 19. That end of bore 19 adjacent the outer cylindrical surface of the body 11 is closed by a plug, conveniently illustrated as a ball bearing 20.

The outlet duct 16 is closed at its upper end, by a diaphragm 21, hereinafter to as the "second" diaphragm, located in the lower regions of recess 17 and a diaphragm retainer plate 22 is located in the recess 17 above said second diaphragm 21 and has its outer periphery engaged with the outer periphery of the diaphragm 21. A conical extension 22a centrally of the diaphragm retainer plate 22 engages the central regions of the diaphragm 21.

A gasket 23 is located in the lower regions of the recess 12 and has an aperture 23a therethrough. An annular plate 24 is seated on the gasket 25, and is retained by a screw 25, and a valve closure assembly support plate 26 is seated on the plate 24 and secured therewith by a screw 27.

The air supply control valve arrangement is supported by the plate 26 and comprises an actuating element, in the form of a lever 28 pivotally connected to the supporting plate 26 by a pivot pin 29 such that the lever 28 lies substantially parallel with, but spaced from, the plate 26, a coil compression spring 30, seated in a recess 26a in the support plate 26, acting on the undersurface of the lever 28 to the left of the pivot pin 29, to continuously urge the lever 28 clockwise, and a valve closure seal 31 on the right hand undersurface end regions of the lever 28. The e seal 31 is engageable with the upper open end of a tubular member 32 which extends through the plate 25 and has its bore open to the aperture 23a in gasket 23. Seal 31, when engaged with the member 32, closes the upper end of said open bore.

The aperture 23a in the gasket 23 is also open to the upper regions of the recess 17 and, with the upper end of bore in tubular element 32, closed by the seal 31, the aperture 23a defines a volute A open to air flows through the restrictor 15.

An annular diaphragm 33 above the lever 28, and vertically spaced therefrom when in a neutral position closes the lower regions of the recess 12 and defines therebeneath a volume B and the upper regions of the recess 12 are closed by a rigid cover 34, retained with the body 11 by annular ring gila, The cover 34 includes a central opening 34a, connecting the volume C between diaphragm 33 and the cover plate 34 with atmosphere.

When it intended that the facial cavity of a face or helmet is normally intended to be above atmospheric pressure to prevent leakage of a dangerous atmosphere thereinto, the valve arrangement will include a coil compression spring 35 acting between the cover plate 34 and the diaphragm 33, and selected to have a compression loading determined by the relationship between atmospheric pressure and the preferred pressure within the facial cavity of the breathing mask or helmet.

The valve arrangement described above operates as follows.

When the facial cavity is at the desired normal pressure, or above the desired pressure as during an exhalation cycle, the volume B beneath the diaphragm 33 is, via a duct 36, at the same pressure and as this pressure exceeds the forces acting downwardly on the diaphragm 33, (the atmospheric pressure in the volume C and the force of the spring 35), the diaphragm 33 is upwardly deflected away from the actuating lever 28. With the diaphragm 33 upwardly deflected clear of the lever 28 the compression spring 30 urges lever 28 clockwise about the axis of pivot 29, whereupon the seal 31 closes the upper end of the bore in tubular member 31, thus isolating the volume A from the volume B.

Air from the air supply duct 13, leaking through the restrictor 15, charges the volume A to the air delivery pressure and, acting through the diaphragm retainer plate 22, the air pressure in volume A forces diaphragm 21 into its low position within the recess 17 where said diaphragm 21 closes the upper end of the air outlet duct 16, thus blocking the air supply to the facial cavity of the mask or helmet.

When an inhalation cycle is initiated there is a fall pressure in the facial cavity and this fall in pressure is extended to the volume B via duct 36, whereupon there is a loading difference across the diaphragm 33 and, under said loading difference, the diaphragm 33 is displaced downwardly, reducing the volume B, until said diaphragm 33 engages the free end of lever 28 and causes said lever to rotate anticlockwise about pivot 29.

On such anti-clockwise rotation of lever 28 the seal 30 is elevated out of contact with the tubular element 31, allowing air flow from the volume A to the volume B at a faster rate than the flow through restrictor 15, whereupon the pressure in the volume A falls and the reduced pressure acting on the upper surface of the diaphragm 21 is overcome by the air supply pressure, extended from the duct 13, through the duct 19 to recess 18, and the diaphragm 21 is thereby upwardly displaced, opening the upper regions of the duct 16 and whereupon air can flow from the air supply duct 13 via duct 19 and recess 18 through the duct 16 to the breathable volume in the facial cavity.

As stated hereinbefore the valve arrangement described above suffers from the disadvantage that air is supplied to the facial cavity only as and whilst the combined forces acting downwardly on the diaphragm 33, defined by the pressure in the volume B and the action of the coil spring 34, overcome the pressure in the volume B sufficient to angularly displace the lever 28. Thus, there is no facility by which the wearer can adjust the air supply and, in the event that the wearer should be overcome and/or fall into a shallow breathing phase, the valve can fail, to the detriment of the wearer.

Further, in the event that the wearer should be overcome, there is no way in which other personnel can effect the air supply to the breathing mask or helmet other than to remove the mask or helmet, which could be extremely dangerous in a harmful atmospheric environment.

In accordance with the present invention the valve includes a manually actuable valve opening device comprising, in the embodiment illustrated in Fig. 2, a body of revolution 37 defined by a cylindrical mid-region 37a, which is a sliding fit through the aperture 34a in the cover plate 34, an enlarged cylindrical head 37b below the cover 34 and a mushroom head 37a on its end remote from the head 3Tb. For convenience in assembly the mushroom head 37c may be screwed onto the cylindrical body 37a part.

The cylindrical head 37a has four bores 38, arranged on a comnon pitch circle, drilled parallel to the axis of the cylindrical body 37a and the pitch circle of the bores 38 is less than the diameter of the cylindrical body 37a plus the diameter of the bores 38 whereupon, in the drilling of said bores 38, the drilling tool cuts annular groove 39 in the cylindrical body 37a. By this means, the volume C is always open to atmosphere.

A coiled compression spring 40 surrounds the cylindrical body 37 and acts between the cover plate 34 and the underside of the mushroom head 37a and thus continuously urges the enlarged cylindrical head 37a towards the undersurface of the cover plate 34.

A flexible resilient dust cover 41 surrounds the body 37 and has a cylindrical side wall 43 which frictionally engages the cylindrical outer surface of the body 11. Said cylindrical wall 42 conveniently has apertures 43 therethrough, each covered by a filter 44, so that the interior of the dust cover 41 is continuously in communication with the surrounding atmosphere.

In normal usage the manually actuable device is in a position shown in Fig. 2, with the spring 40 retaining the enlarged cylindrical end 37b against the undersurface of the cover plate 34'and, with the body 37 so located, the valve operates in identical manner to the valve described above with reference to Fig. 1.

However, in the event that the wearer requires more breathing air or personnel attending upon the wearer wish to increase the air supply to the facial cavity, is only necessary to depress the central radial regions of the resilient dust cover 41. The dust cover 41, when depressed, engages with the mushroom head 37c of the body 37 and forces said body 37 downwardly against the action of said spring 40 and, as the depression of the body 37 continues, the lower radial face of the enlarged cylindrical end 37a engages the diaphragm 33 and causes said diaphragm 33 to engage with and angularly displace the lever 28, whereupon the bore of tubular element 31 is open to volume B, the pressure in volume A falls and the diaphragm 21 is displaced to connect the duct 16 with the air supply. Air then flows continuously into the air space until the body 37 is released and returns to its inoperative position, as shown in Fig. 2.

In alternative arrangements in accordance with the invention the manually actuable device may cooperate with the cover plate 34 via cooperating screwthreads or cam means, whereupon the device is manually actuable between its operative and inoperative modes by rotation of the device and, in other embodiments, the axis of the device may extend generally parallel with the plane of the diaphragm and be rotatable to affect the diaphragm 33, via cam means.

However, in practise, the form for the manually actuable device shown in Fig. 2 has been found most advantageous for use with the valve arranged of the type shown in Fig. 1 and whereby the wearer can over-ride the normal working of the valve arrangement for short periods, or when the wearer has been overcome, the attending personnel may manipulate the manually actuable device in accordance with a desired breathing rate over a longer period of time.

Whilst the present invention has been described by example with reference to a specific embodiment the invention is not restricted thereto and many modifications and variations will become apparent to persons skilled in the art.

Claims (10)

1. A valve arrangement, for controlling the air supply to the facial cavity for a safety breathing apparatus, comprising a casing, a diaphragm in said casing defining separated first and second volumes within said casing, said first volume being in continuous open communication with the facial cavity and said second volume being in continuous open communication with the surrounding atmosphere, and an air control valve arranged to open to allow air to flow to the facial cavity whilst the pressure in said first volume is below a predetermined value, characterised by a manually actuable device arranged, when actuated, to open the said air control valve irrespective of the pressure in the said first volume.

2. A valve arrangement according to claim 1, characterised in that the said air control valve includes an actuating member located in said first volume and arranged to be actuated, to open the said air control valve, by the said diaphragm deflecting to reduce the first volume.

3. A valve arrangement according to claim 2, characterised in that said manually actuable device, when actuated, is arranged to deflect the said diaphragm and cause the said diaphragm to actuate the air control valve actuating member.

4. A valve arrangement according to claim 1, 2 or 3, characterised in that said manually actuable device is loaded by spring means towards its inoperative position.

5. A valve arrangement according to claims 1, 2, 3 or 4, characterised in that said manually actuable device extends through a rigid wall of the casing defining said second volume.

6. A valve arrangement according to any preceding claim, characterised in that said manually actuable device comprises a body of revolution, supported by said casing for axial displacement along an axis at right angles to the plane of the diaphragm.

7. A valve arrangement according to any preceding claim, characterised in that said manually actuable device comprises a cylindrical mid-region with an enlarged head on each of its ends.

8. A valve arrangement according to claim 7, when dependant upon claim 5, characterised in that the said cylindrical mid-region is slidably located in an opening in the said rigid wall of the casing whereupon one of said enlarged heads is supported in said second volume, to be engageable with the diaphragm when the device is actuated, and the other of said enlarged heads is externally of the casing and manually actuable.

9. A valve arrangement according to any of the preceding claims, characterised by a resilient cover for the valve arrangement, the manually actuable device being beneath said cover and manually actuable by deflecting said resilient cover.

10. A valve arrangement, substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2 of the accompanying drawings.