GB2470130A - Spool valve for air supply which automatically switches when second air supply is connected - Google Patents

Abstract

An air supply valve 300 for connection between a compressed air cylinder and a respirator of a breathing apparatus. The air supply valve 300 comprises a valve body having a first inlet for connection to an air supply cylinder, a second inlet 310 including a coupling for connection to an auxiliary air supply, an outlet for the supply of air to a respirator and, a switching means 330 to selectively communicate the first inlet or the second inlet 310 with the outlet for the supply of air thereto. The switching means comprises a spool valve 330 in the first inlet to open and close an airflow passage therefrom and, an actuator 331 associated with the second inlet 310 operable to close the spool valve 330 when an auxiliary air supply 322 is connected to the second inlet 310.

Description

Air Supply Valve

Description

The present invention relates to an air supply valve suitable for use with an emergency breathing apparatus.

Emergency breathing apparatuses are known in the art for use in situations where there has been a sudden hazardous leak of gas or toxic airborne particles that would injure a person if inhaled. Such breathing apparatuses are known as escape sets', and generally comprise a bag or other container containing a mask and/or hood (generally called a respirator' hereafter) connected via a hose and a valve means to a source of breathable air in a high-.pressute compressed air cylinder. In an emergency situation, a user dons the respirator, which, in the case of a mask, makes a seal with his face or, in the case of a hood, seals around his neck enclosing his head, and allows him to breath from the air supply, isolated from the harmful atmosphere.

The valve means is provided between the cylinder and the respirator to reduce the high pressure from the cylinder to a pressure suitable for the wearer to breathe.

These escape sets are provided in environments where there is a possibility of such a hazardous leak occurring, such as chemical plants or oil platforms, in convenient locations so that if a hazardous leak occurs, the people in the vicinity of the leak can quickly get to an escape set and don the respirator to allow them to leave the hazardous area and get to safety.

The valve means provided in such escape sets generally comprises a reducer' which reduces the pressure in the hose from the high pressure in the cylinder (typically around 200 bar) to a much lower pressure, (around 8 bar), and a demand valve' which supplies air from the reducer and the hose, to the respirator at a pressure

suitable to breathe.

Breathing apparatuses generally include a supply of breathable air provided with the escape set' which would generally be in the form of a pressurised air cylinder.

However, to make the escape sets' of a convenient size, the air cylinder must be small enough to fit into a bag, and light enough for a user to easily carry around with them as they make their evacuation from the hazardous environment, This means that a compromise must be made between size and weight of the air cylinder, and the amount of pressurised breathable air available with each escape set cylinder.

Generally, a cylinder which provides between 20 -30 minutes of breathing time is suitable. Therefore, it is important to be able to conserve the air in the cylinder as much as possible to maximise the available breathing, and therefore escape, time.

However, if the escape sets are to be used in large premises, such as big industrial plants or chemical factories, an evacuation procedure may well involve hundreds of people, and would very often be organised in a regimented and well-practiced operation. In such procedures, groups of people are often trained to congregate at designated areas or muster stations' and once it is ascertained that everyone on a register has been accounted for, the group then evacuates together. This can result in people waiting around the muster station for 5 -10 minutes, maybe even longer, and so if they have been wearing their respirator all of that time, the valuable supply of pressurised breathable air would be severely depleted, possibly meaning that not enough air would be left for the time taken to complete the evacuation from the large building/plant. Therefore, it is possible that the designated muster stations could be provided with a plurality of air hoses connected to a pressurised breathable air supply system. Such a system could comprise a network of pipes running throughout the building/plant and could be fed by an external air pump and filter device so that pressurised breathable air is always available though any air hose at any of the designated muster stations.

Accordingly, it is an object of the present invention to provide a supply valve to enable breathing apparatuses to be used with such an air supply system.

Accordingly, the present invention provides an air supply valve for connection between a compressed air cylinder and a respirator of a breathing apparatus, comprising a valve body having a first inlet for connection to an air supply cylinder, a second inlet including a coupling for connection to an auxiliary air supply, an outlet for the supply of air to a respirator and, a switching means to selectively communicate the first inlet or the second inlet with the outlet for the supply of air thereto, wherein the switching means comprises a spooi valve in the first inlet to open and close an airflow passage therefrom and, an actuator associated with the second inlet operable to close the spooi valve when an auxiliary air supply is connected to the second inlet.

In a preferred embodiment, the spool valve is axially slidable between the open and closed positions and includes a spooi spring which biases the spool valve into the open position.

The actuator is preferably positioned adjacent to the second inlet such that it is engaged by a connector of an auxiliary air supply when an auxiliary air supply is connected to the second inlet, which operates the actuator to close the spool valve.

The actuator preferably comprises a lever pivotally mounted to the supply valve body.

Preferably, the lever is moveable from a first position, to a second position in which the lever is configured to move the spool valve to the closed position.

Conveniently, the lever includes a cam member positioned adjacent one end of the spool valve and configured to push the spool valve from the open position to the closed position when the lever is moved from its first position to its second position. Advantageously, the lever includes a lever spring to bias the lever into the first position.

In a preferred embodiment, the coupling comprises a male connector protruding from the supply valve and the lever extends at least partially around the coupling such that when a corresponding female connector of an auxiliary air supply is connected thereto, the lever is forced to move from the first position to the second position.

The male connector preferably includes a one-way valve to allow the flow of air from an auxiliary supply into the supply valve but prevent the flow of air from the supply valve out of the male connector.

The spooi valve of the air supply valve preferably includes an enlarged head protruding out of a side of the supply valve body, and a clip attachable to a portion of the spool valve between the head and the valve body to hold the spool valve in the closed position when the lever is in the first position A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a breathing apparatus usable with the air supply valve of the present invention; Figure 2 is a schematic cross-sectional view of a control valve of the breathing apparatus of Figure 1, in a first position; Figure 3 is a view of the control valve of Figure 2 in a second position; Figure 4 is a detailed cross-sectional view of a control valve of the invention schematically shown in Figures 2 and 3; Figure 5 is a cross-sectional view of a positive pressure demand valve used in the breathing apparatus of Figure 1; Figure 6 is a cross-sectional view of a respirator mask of the breathing apparatus in place on a wearer's face; Figure 7 is a cross-sectional view of a combined control valve and demand valve of the breathing apparatus of the invention; Figurc 8A is a sectional view of a portion of the inflatable harness of the breathing apparatus in a deflated state; Figure 8B is a sectional view of a portion of the inflatable harness of Figure 8A in an inflated state; Figure 9 is a partial cut away perspective view of a supply valve of the invention, in a closed position; Figure 10 is a partial cut away perspective view of the supply valve of Figure 9 in an open position; Figure 11 is a cross sectional view of the supply valve of Figures 9 and 10; Figure 12 is a partial cut away perspective view of the supply valve of Figures 9 -11 in a third position; and Figure 13 is a side view of the supply valve of Figures 9 -12 in the third position.

Referring now to Figures 1 -8B, an emergency breathing apparatus 10 which can be used with the air supply valve of the present invention is shown, for information purposes. The breathing apparatus comprises a respirator mask 12 and an inflatable harness 14 to secure the respirator 12 to a wearer's head. The respirator 12 has a seal 13 around its peripheral edge that, in use, makes a substantially air-tight seal around the wearer's face. The respirator 12 and harness 14 are fluidly connected to a source of compressed air (not shown) by a supply hose 19 via a control valve 20 on the front of the respirator 12. The respirator 12 also includes a positive pressure exhalation valve (not shown) to allow air exhaled by a wearer to be expelled from the respirator 12, and an inhalation valve 50 (described in detail hereafter) to allow air into the respirator 12. The whole breathing apparatus 10, including the compressed air supply, is contained within a bag 17 made of suitably tough material, such as PVC coated weatherproof material, or an anti-static material if the apparatus is to be used in potentially explosive environments.

The control valve 20 is shown in detail in Figures 2 -4, and comprises a housing 21 having a first chamber 22 and a second chamber 23, fluidly connected by a connecting passage 24. The housing 21 has an inlet port 25 leading to the first chamber 22 for the supply of compressed air thereto, and a first outlet 26 extends from the first chamber 22 through the valve housing 21 for the supply of compressed air to the inside of the respirator mask 12. A second outlet 27 extends from the first chamber 22 through the wall of the housing 21 and is open to atmosphere providing a first vent 27 for reasons which will be explained hereafter.

A third outlet 28 extends from the second chamber 23 through the housing 21 to supply pressurised air to the inflatable harness 14, and a fourth outlet 29 extends from the second chamber 23 through the housing 21 and is open to atmosphere to provide a second vent 29 to enable air in the second chamber 23 to vent to atmosphere.

A piston 31 is slidably disposed in the first chamber 22, and comprises a head 32 and an elongate shaft 33. A rubber seal 34 extends around the head 32 and makes an air-tight seal against the inside wall of the first chamber 22. The shaft 33 extends from the centre of the head 32 perpendicularly therefrom, away from the inlet port 25, and extends through the connecting passage 24. A passage seal 35 is provided to make an air-tight seal between the shaft 33 and the inside wall of the connecting passage 24 to ensure that air is not able to pass therebetween. The piston 31 is thereby able to slide axially within the first chamber 22 and the connecting passage 24 from a first position shown in Figure 2, to a second position shown in Figure 3.

The first vent 27 allows air trapped in the first chamber between the piston head 32 and a wall 21a adjoining the second chamber 23, to escape to atmosphere, to prevent the pressure of air trapped therein increasing through compression, which would increasingly restrict the movement of the piston 31. The piston 31 has a hollow bore 36 extending axially through the head 32 and though the shaft 33 which allows the flow of air though the piston 31 from the inlet port 25 into the second chamber 23.

A first valve seat 37 is located where the inlet port 25 opens into the first chamber 22 and is positioned such that the head 32 of the piston 31 abuts the first valve seat 37 when in the first position, shown in Figure 2, and makes a seal therewith. In this position, the hollow bore 36 is in fluid communication with the inlet port 25. A piston spring 38 is provided around the piston shaft 33 between the piston head 32 and the adjoining wall 2la of the first and second chambers 22, 23 to bias the piston 31 into the first position.

A small bypass orifice 39 extends from the inlet port 25 though to the first outlet 26 and is dimensioned so as to only allow a restricted flow of air therethrough when the piston 31 is in the first position sealingly engaged with the first valve seat 37.

A poppet 41 is slidably disposed in the second chamber 23 and comprises a head 42 and a shaft 43 extending perpendicularly therefrom. The poppet 41 is similar in configuration to a small piston, except that the head 42 of the poppet does not make a seal against the inside surface of the second chamber 23, as a piston' would, but instead is spaced therefrom. The second chamber 23 has a narrow section 23a and a wide section 23b and a second valve seat 47 is disposed at the transition between the narrow 23a and wide 23b sections. The third outlet 28 extends from the narrow section 23a and the fourth outlet (or second vent') 29 extends from the wide section 23b. The poppet 41 is slidable from a first position (shown in Figure 2) to a second position (shown in Figure 3). In the first position, the head 42 of the poppet 41 abuts the second valve seat 47 and sealingly engages therewith so that the third and fourth outlet outlets 28, 29 are sealed from each other. A poppet spring 48 is provided in the wide section 23b of the second chamber 23, between the poppet head 42 and an adjacent wall 21b of the valve housing 21, to bias the poppet 41 into the first position. When the poppet 41 is in the second position, the head 42 is spaced from the second valve seat 47 and so the narrow and wide sections 23a, 23b of the second chamber 23 are in fluid communication, and so the third and fourth outlets 27, 28 are also in communication with each other.

The inflatable harness 14 comprises a plurality of expandable resilient tubes 15 in fluid communication with each other, each contained within a fabric sleeve 16 (see Figures 8A and 8B). The sleeves 16 are made from an inextensible, flexible corrugated material and loosely cover the tubes 15 when the tubes 15 are in their relaxed deflated state (see Figure 8A). However, when compressed air is supplied to the tubes 15, the tubes 15 inflate and expand within the sleeves 16, enlarging the overall dimensions of the harness 14, and also forming a more rigid frame shape (as shown in Figure 1). The degree to which the tubes 15 are able to expand is limited by the sleeves 16 surrounding the tubes. As the tubes 15 expand, the corrugations of the sleeves 16 are straightened out until the material of the sleeves 16 is pulled taut. At this point, the sleeves 16 are unable to extend any further and they thereby limit the maximum size which the harness 14 can expand to.

The breathing apparatus 10 comprises a reducer valve (not shown) disposed between the compressed air supply and the control valve 20. This serves to reduce the pressure from the compressed air supply (typically around 200 bar) to a less elevated pressure above atmosphere (around 8 bar). As mentioned above, the reducer may include an automatic activation switch which is shut to isolate the compressed air supply from the respirator 12 when the breathing apparatus 10 is not in use, but is automatically activated upon removal of the breathing apparatus from the bag 17 when it is to be used. This can be any suitable mechanism, such as a release cord secured to the bag and to the reducer valve, which, for example, pulls a switch or releases a pin to open the reducer valve when the breathing apparatus 10 is removed from the bag 17 and the cord is thereby pulled.

The first outlet 26 from the valve housing 21 communicates with an inlet valve of the respirator 12 which comprises a positive pressure demand valve 50. This demand valve 50 is shown in more detail in Figure 5, and is designed to allow a flow of breathable air from the compressed air supply and the control valve 20 to the interior of the respirator 12. Before the respirator 12 is sealed against a wearer's face, it is open to atmosphere, and so the demand valve 50 allows a constant flow of air through it. However, once the respirator 12 is sealed against a wearer's face and a sealed respirator cavity is created, the demand valve 50 is configured to allow a supply of air into the respirator 12 until the pressure within the respirator cavity reaches a predetermined value, after which the demand valve 50 stops the supply of air to the respirator 12, and thereafter maintains the pressure within the respirator cavity at the predetermined pressure. The way the demand valve 50 is configured to achieve this function will be explained in detail hereafter with reference to Figure 5.

The positive pressure demand valve 50 (hereafter referred to simply as demand valve') comprises a housing 51 including an inlet jet 52 in communication with the first outlet 26 of the control valve 20, and an outlet 53 in communication with the inlet jet 52 and with the interior of the respirator 12. A seal 54 is mounted on a sliding seal carrier 55 and is positioned adjacent to the inlet jet 52. A diaphragm 56 is pivotally mounted to the housing 51 at a pivot point 57 and comprises a solid rigid disc 56a with a flexible outer skirt 56b which connects the periphery of the rigid disc 56a to the housing 51 and closes the housing such that the only inlet and outlet to the housing are the inlet jet 52 and the outlet 53. The pivot point 57 is positioned proximate an edge of the rigid disc 56a off-centre thereof. A portion of the rigid disc 56a between the pivot point 57 and the closest edge thereto, is disposed adjacent the end of the seal carrier 55 remote from the seal 54, such that pivoting the diaphragm 56 about the pivot point 57 causes the rigid disc 56a to contact the seal carrier 55 and push the seal carrier 55 so that the seal 54 seals against the open end of the inlet jet 52 to prevent air from flowing therethrough. A protective covet 58 encloses the front of the demand valve 50 to hide the diaphragm 56, and includes an aperture 59 therethrough to ensure the space between the diaphragm 56 and the cover 58 is maintained at ambient atmospheric pressure.

The operation of the positive pressure demand valve 50 will now be described with reference to Figure 5. Air above atmospheric pressure is supplied from the control valve 20 (as will be explained later) to the inlet jet 52. The pressurised jet of air impinges on the seal 54 which pushes the seal carrier 55 away from the inlet jet 52 and so tilts the diaphragm 56 about the pivot 57, and allows air to flow through the demand valve 50 and out of the outlet 53 into the respirator.

If the respirator 12 is not in place on a wearer's face with the edge seal 13 sealing thereagainst, no sealed respirator cavity is formed between the respirator 12 and the wearer's face, and so no air pressure is able to build up inside the respirator 12. In this case, the air simply continues to flow through the respirator 12 to atmosphere providing a flushing flow of air into the respirator so that when a user dons the respirator, fresh breathable air fills the respirator cavity to displace a large proportion of the harmful atmosphere to avoid it being trapped in the resulting respirator cavity. However, once the wearer dons the respirator 12 and creates a sealed respirator cavity, the air flowing into the respirator 12 though the demand valve 50 collects inside the respirator and so the air pressure in the respirator increases. The pressure F inside the respirator 12 acts over the main area 56c of the diaphragm 56 on the side of the pivot 57 remote from the sliding seal carrier 55.

This moment is counteracted by the force F1 of the air flow from the inlet jet 52 impinging on the seal 54 and being exerted, via the seal carrier 55, on the other side 56d of the diaphragm 56, on the other side of the pivot 57 from the main area 56c.

So long as the moment about the pivot 57 caused by the inlet airflow force F1 acting on said other side 56d of the diaphragm 56 is greater than the moment caused by the respirator cavity pressure F acting over the main area 56c of the diaphragm, the seal 54 is held away from the inlet jet 52 and so air continues to flow into the respirator cavity. Other additional forces also affect this balance of the diaphragm 56 about its pivot 57, although these forces are small compared to those major moments of force desctibed above. Such additional forces include the pressure F also acting over said other side 56d of the diaphragm 56 against the pivoting moment of force created by the pressure F acting over the main area 56c of the diaphragm 56. Also, the flexible outer skirt 56b connected between the demand valve housing 51 and the rigid disc 56a of the diaphragm 56 will exert a small resistance to pivotal movement of the diaphragm 56 about its pivot 57.

So long as the seal 54 on the seal carrier 55 is held away from the inlet jet 52, the respirator cavity pressure F increases until it reaches the pre-determined value, at which point, the demand valve 50 is configured such that the moment about the pivot 57 caused by the respirator cavity pressure F acting over the main area 56c of the diaphragm 56 is greater than the inlet airflow force F1 acting on said other side 56d of the diaphragm 56, taking into consideration the additional moments of force mentioned above, and so the diaphragm 56 tilts about the pivot 57, pushing the seal carrier 55 towards the inlet jet 52 and engaging and holding the seal 54 against the inlet jet 52, preventing further airflow into the respirator cavity, and thereby maintaining the pressure F therein at the pre-determined value. In practice, the pressure F maintained in the respirator cavity is around 3OmmH2O, although the geometry of the demand valve 50 (e.g. position of pivot 57, surface area of diaphragm 56) can be adjusted to maintain other pressures as required.

It will be appreciated that as a user inhales air from the respirator 12, the pressure F will drop, and so the diaphragm 56 will pivot to allow more air into the respirator cavity, until the pre-determined pressure is reached again, when the diaphragm 56 will pivot back to seal the inlet jet 52 once more. As mentioned above, the outlet -11 -valve (not shown) provided in the respirator 12 is a positive pressure valve which means that it is biased to remain closed up until the predetermined pressure is reached within the respirator 12, so that such pressure may build up in the respirator cavity and so that the pressurised air supplied to the respirator does not simply flood straight out of the outlet valve.

For the breathing apparatus 10 to function correctly, it is important that the demand valve 50 is in its open position prior to, and at the moment of, the supply of air being activated. This is because any momentary build up of pressure caused by the demand valve 50 being closed when the air supply is activated, may cause the control valve 20 to operate prematurely, as will be better understood from the description hereafter. To avoid this, the diaphragm 56 may be configured to normally rest in the open position, or separate biasing means may be provided to ensure that the diaphragm 56 is biased away from the inlet jet 52. Such biasing means could include a spring located adjacent the seal carrier 55 to push the other side 56d of the diaphragm 56 away from the inlet jet 52. Alternatively, a spring could be provided between the rigid plastic disc 56a part of the diaphragm 56 on the main side 56c thereof, and the outer protective cover 58 to push the main side 56c away from the protective cover 58 and thereby bias the other side 56d of the diaphragm 56 away from the inlet jet 52.

The particular arrangement of the diaphragm 56 contacting a sliding seal carrier 55 to push the seal 54 into engagement with the inlet jet 52, is particularly advantageous over, for example, a portion of the tilting diaphragm 56 directly contacting the inlet jet 52 to seal it, because in the illustrated embodiment, the seal 54 approaches and engages the inlet jet 52 completely square-on -that is to say, the whole of the seal 54 comes into contact with the inlet jet 52 at one instance. If the tilting diaphragm 56 directly sealed the inlet jet 52, the pivoting configuration of the diaphragm means it would approach the inlet jet 52 at an angle from one side, which would adversely affect the ability to effectively seal the inlet jet 52.

The general operation of the breathing apparatus 10 of the invention will now be described. When a user wishes to use the breathing apparatus 10 of the invention, -12 -he opens the bag 17 and pulls out the respirator 12 and compressed air supply, and the automatic activation system opens the reducer valve to allow compressed air at around 8 bar to flow into the control valve 20. The air enters the inlet port 25 and flows through the hollow bore 36 of the piston 31, into the narrow section 23a of the second chamber 23, and out of the third outlet 28 into the harness 14. This inflates the harness 14 and the resilient flexible tubes 15 expand within the corrugated fabric sleeves 16 until they reach their maximum permitted expansion.

The harness 14 is thereby in its expanded, semi-rigid state, to facilitate donning of the breathing apparatus 10 over the wearer's head. Simultaneously, the air flows from the inlet port 25, through the bypass orifice 39 and out of the first outlet 26 to the demand valve 50. As described above, because the user has not put the respirator 12 against his face to create a sealed respirator cavity, no pressure can build up within the respirator and so the demand valve 50 remains in its open state and allows a flushing flow of air though the respirator 12 to atmosphere. In this condition, the piston 31 is biased into the first position against the first valve seat 37. Any air pressure exerted on the area A1 of the head 32 of the piston 31 though the inlet port 25 is not sufficient to overcome the biasing force of the piston spring 38, and so the piston 31 remains in the first position. Because any air around the first outlet 26 can flow freely through the demand valve 50 and out through the respirator 12, no air pressure above atmospheric pressure acts over the larger surface area A2 of the head 32 of the piston 31.

When the wearer dons the respirator 12 and the edge seal 13 seals against his face, a sealed respirator cavity is formed and so the air flowing into the respirator 12 builds up pressure within the cavity. Once the pressure reaches the pre-determined value, the demand valve 50 automatically pushes the seal 54 against the inlet jet 52 to prevent any further inflow of air. into the cavity. This back-pressure that has then built up in the inlet port 25, in the first outlet 26 and in the first chamber 22 on the inlet port 25 side of the piston 31, is able to act over the larger surface area A2 of the head 32 of the piston 31. The resulting force is sufficient to overcome the biasing force of the piston spring 38, and so the piston 31 moves to the second position. In doing so, the end of the shaft portion 33 of the piston 31 abuts the end of the shaft 43 of the poppet 41. Firstly, this blocks the hollow bore 36 through the -13 -piston 31 and so prevents any more air from flowing into the second chamber 23.

Secondly, the force exerted by the air pressure acting over the larger surface area A2 of the piston 31 is sufficient to overcome the biasing force of the poppet spring 48 as well as that of the piston spring 38, and so the piston 31 pushes the poppet 41 into the second position, as shown in Figure 3. As the piston 31 moves to the second position, air between the piston head 32 and the wall 21a adjoining the second chamber 23 is expelled though the first vent 27, preventing the build up of pressure which would further restrict movement of the piston 31. Therefore, the only force resisting movement of the piston 31 is that of the piston spring 38.

Thirdly, the head 32 of the piston 31 moves away from the first valve seat 37 and so allows a full, unrestricted flow of air from the inlet port 25 through the first chamber 22 and out of the first outlet 26 to the demand valve 50 and respirator 12.

This full flow is then sufficient to provide the wearer with enough air to breath comfortably and maintain the elevated pressure within the respirator cavity.

When the poppet 41 is in the second position, the head 42 is spaced from the second valve seat 47, which allows air to flow between the narrow and wide portions 23a, 23b of the second chamber 23, and thereby allows the inflatable harness 14 to deflate via the third outlet 28 to outside of the valve housing 21 though fourth outlet, or second vent, 29. As the resilient tubes 15 of the harness 14 deflate, they contract around the wearer's head, and hold the respirator 12 into sealing engagement with his face.

During normal operational use, the piston 31 and poppet 41 of the control valve 20 remain in their respective second positions so that a full flow of air is provided to the demand valve 50 for the wearer to breathe, and the inflatable harness 14 remains deflated and contracted around the wearers head. The wearer can thereby safely breathe from the compressed air supply despite being surrounded by a harmful atmosphere, and get to safety. The compressed air supply is typically designed to provide 10 -15 minutes breathing time, although more or less breathing time could be provided by altering the size of a compressed air supply cylinder provided with the breathing apparatus 10.

-14 -When the supply of compressed air runs out, the breathing apparatus is designed to automatically release the harness 14 from the wearer's head to prevent him from suffocating. As the pressure from the air supply drops, the force exerted over the area A2 of the piston 31 reduces, until it is less than the combined biasing force of the piston and poppet springs 38, 48, and then less than the biasing force of the piston spring 38. This results in the piston 31 and poppet 41 moving back to their respective first positions, and so the head 42 of the poppet 41 seals against the second valve seat 47 sealing the inflatable harness 14 from the fourth outlet 29. As the piston 31 moves away from the poppet 41, the hollow bore 36 of the piston 31 is open again, and so the remaining air pressure from the supply is able to flow though the piston 31 to the second chamber 23 and into the inflatable harness 14.

The resilience of the tubes 15 of the harness 14 is designed such the tubes are able to inflate even with the reduced air pressure available as the air supply runs low.

Therefore, the inflatable harness 14 expands, loosening from around the wearer's head, allowing the wearer to easily remove the respirator 12 from his face.

The breathing apparatus 10, described above, includes a supply of breathable air provided with the escape set' which would generally be in the form of a pressurised air cylinder (not shown). However, to make the escape sets' of a convenient size, the air cylinder must be small enough to fit into the bag 17, and light enough for a user to easily carry around with them as they make their evacuation from the hazardous environment. This means that a compromise must be made between size and weight of the air cylinder, and the amount of pressurised breathable air available with each escape set cylinder. Generally, a cylinder which provides between 20 -30 minutes of breathing time is suitable. Therefore, it is important to be able to conserve the air in the cylinder as much as possible to maximise the available breathing, and therefore escape, time. However, if the escape sets are to be used in large premises, such as big industrial plants or chemical factories, an evacuation procedure may well involve hundreds of people, and would very often be organised in a regimented and well_practiced operation. In such procedures, groups of people are often trained to congregate at designated areas or muster stations' and once it is ascertained that everyone on a register has been accounted for, the group then evacuates together. This can result in people waiting around the muster station for 5 -15 -10 minutes, maybe even longer, and so if they have been wearing their respirator all of that time, the valuable supply of pressurised breathable air would be severely depleted, possibly meaning that not enough air would be left for the time taken to complete the evacuation from the large building/plant. Therefore, it is possible that the designated muster stations could be provided with a plurality of air hoses connected to a pressurised breathable air supply system. Such a system could comprise a network of pipes running throughout the building/plant and could be fed by an external air pump and filter device so that pressurised breathable air is always available though any air hose at any of the designated muster stations.

In order to enable such breathing apparatuses to be used with such an external air supply system, a special external air supply valve according to the present invention, may be disposed either on the cylinder itself, or between the cylinder and the reducer valve.

Such an external air supply valve 300 according to the present invention is shown in Figures 9 -13 and comprises a male coupling 310 for connecting to a corresponding female coupling 320 provided on the end of an air hose 322. A spool valve 330 communicates the cylinder to an outlet from the supply valve 300 (not shown) which is connected to the respirator supply hose 19. The spool valve 330 comprises a rod 331 having a section of reduced diameter 332, and scalloped recesses 333 cut into the reduced diameter section 332. The rod 331 is located in a cylindrical aperture within the body of the external supply valve 300 between three 0-rings 334, 335, 336. The rod 331 is slidable about its axis A-A between a closed position in which the cylinder is sealed from the respirator supply hose 19, as shown in Figures 13, 15 and 16, to an open position in which the cylinder is in communication with the respirator supply hose 19, as shown in Figure 14. A rod spring 337 is provided (see Figures 15 and 16) which biases the rod 331 into the open position.

The external supply valve 300 includes a spring-loaded lever 312 which is movable from a first position shown in Figures 13 and 14 in which the lever 312 stands upright adjacent the male coupling 310, to a second position (see Figures 16 and -16 - 17), in which it lies flat pivoted away from the male coupling 310. The lever 312 includes an arm 314 extending therefrom with a cam face 316 at the end thereof.

The cam face 316 is located adjacent one end of the rod 311. The lever 312 is biased into the first position by a lever spring 313.

In use, when a wearer first removes the respirator incorporating a supply valve 300 as described above, from its storage bag, the lever 312 is biased into the first position by the lever spring 313 and the rod 331 is held in the closed position against the force of the rod spring 337 by a clip 338 (see Figures 13 and 17). The clip 338 is placed between a head of the rod 331 and the body of the supply valve 300 housing and prevents the rod 331 from moving into the open position.

As the wearer removes the respirator from the bag, an automatic activation device such as a lanyard attached between the bag and the clip 338 causes the clip to be pulled off the rod 331 and so the rod 331 is allowed to slide under the force of the rod spring 337 to the open position. In this position, the section of reduced diameter 332 and the scalloped recesses 333 communicate an air flow path between the two adjacent 0-rings 335, 336 through the spooi valve 330 for the high pressure air from the cylinder to flow to an outlet to the respirator 19, to allow the respirator to function as described above to provide a breathable supply of air to the respirator mask and for the inflatable harness to hold the respirator in place. The purpose of the scalloped recesses 333 is to equalise pressure in the gap between the two adjacent 0-rings 335, 336 and the section of reduced diameter 332 as the rod 331 moves across to the open position, to avoid damage to said 0-rings 335, 336.

When the wearer reaches a designated muster station, they connect a female coupling 320 of an available air supply hose 322 to the male coupling 310 on the external supply valve 300. A known type of sprung one-way valve in the male coupling 210 prevents air from escaping from the supply valve 300 out through the male coupling 210. However, the male coupling 210 is configured such that when the female coupling 320 is connected to the male coupling 310, the sprung one-way valve is opened to allow air to flow from the supply hose 322 into the external supply valve 300 and to the respirator supply tube 19. Simultaneously, as the female -17 -coupling 322 is connected to the male coupling 310, it pushes the lever 312 into the second position as shown in Figures 16 and 17. As the lever 312 moves to the second position, the arm 314 rotates correspondingly, and the cam face 316 of the arm acts against the end of the spool valve rod 331 and pushes it from the open position to the closed position, thereby sealing the cylinder from the respirator so that the wearer breathes air from the supply hose 322 oniy, and so conserves the limited amount of pressurised breathable air within the cylinder.

Once everyone has assembled at the muster station and evacuation can commence, the wearer dis-connects the female coupling 320 from the male coupling 312. This allows the lever 310 to return to the first position, and the arm 314 and associated cam surface 316 correspondingly rotates, allowing the spool valve rod 331 to move into the open position under the force of the spooi spring 337 to allow the pressurised air in the cylinder to be supplied to the respirator supply hose 19 once again. The wearer can therefore continue to breathe safely though the respirator, and is then free to evacuate the plant/building.

Although specific embodiments of the invention have been described in detail above, it will be apparent to those skilled in the art that modifications may be made to the above embodiments within the scope of the invention, which is defined in the claims hereafter.

Claims (11)

1. -18 -Claims 1. An air supply valve for connection between a compressed air cylinder and a respirator of a breathing apparatus, comprising a valve body having a first inlet for connection to an air supply cylinder, a second inlet including a coupling for connection to an auxiliary air supply, an outlet for the supply of air to a respirator and, a switching means to selectively communicate the first inlet or the second inlet with the outlet for the supply of air thereto, wherein the switching means comprises a spool valve in the first inlet to open and close an airflow passage therefrom and, an actuator associated with the second inlet operable to close the spooi valve when an auxiliary air supply is connected to the second inlet.
2. 2. An air supply valve according to claim I wherein the spool valve is axially slidable between the open and closed positions and includes a spool spring which biases the spool valve into the open position.
3. 3. An air supply valve according to claim 1 or 2 wherein the actuator is positioned adjacent to the second inlet such that it is engaged by a connector of an auxiliary air supply when an auxiliary air supply is connected to the second inlet, which operates the actuator to close the spool valve.
4. 4. An air supply valve according to claim 3 wherein the actuator comprises a lever pivotally mounted to the supply valve body
5. 5. An air supply valve according to claim 4 wherein the lever is moveable from a first position, to a second position in which the lever moves the spool valve to the closed position.
6. 6. An air supply valve according to claim 5 wherein the lever includes a cam member positioned adjacent one end of the spool valve and configured to push the spool valve from the open position to the closed position when the lever is moved from its first position to its second position.-19 -
7. 7. An air supply valve according to any of claims 4 -6 wherein the lever includes a lever spring which biases the lever into the first position.
8. 8. An air supply valve according to claim 7 wherein the coupling comprises a male connector protruding from the supply valve and the lever extends at least partially around the coupling such that when a corresponding female connector of an auxiliary air supply is connected thereto, the lever is forced to move from the first position to the second position.
9. 9. An air supply valve according to claim 8 wherein the male connector includes a one way valve to allow the flow of air from an auxiliary supply into the supply valve but prevent the flow of air from the supply valve out of the male connector.
10. 10. An air supply valve according to any of claims 3 -9 wherein the spool valve includes an enlarged head protruding out of a side of the supply valve body, and a clip attachable to a portion of the spooi valve between the head and the valve body to hold the spool valve in the closed position when the lever is in the first position.
11. 11. An air supply valve substantially as hereinbe fore described with reference to the accompany drawings.