WO2012073024A2

WO2012073024A2 - Case for breathing apparatus and cooling unit for breathing apparatus

Info

Publication number: WO2012073024A2
Application number: PCT/GB2011/052364
Authority: WO
Inventors: Christiane Goebel; Julian Stemp; Joerg Polzien; Gordon Wrigley
Original assignee: Draeger Safety Uk Limited
Priority date: 2010-12-02
Filing date: 2011-11-30
Publication date: 2012-06-07
Also published as: WO2012073024A3

Abstract

A case 20 for breathing apparatus 1 comprises front and rear casing portions 22, 24 arranged to be detachably attached to one another. The casing portions 22, 24 are arranged to house therebetween a variable volume breathing chamber 8 that can vary in volume between at least a first configuration and a second configuration. The volume of the breathing chamber 8 is larger in the second configuration than in the first configuration. A spring support is provided that is detachably attached to one of the casing portions. At least one spring 80 is supported by the spring support which is arranged to act on the variable volume breathing chamber 8 so as to resiliently bias it towards the first configuration. The front and rear casing portions 22, 24 may be injection moulded components. There is also disclosed a cooling unit 9 for cooling a flow of breathable gas in a breathing apparatus comprises a cooling chamber 102 having a gas inlet 104 and a gas outlet 106 and a cooling tank 108 disposed within the chamber 102 and arranged to contain a cooling medium such as ice. The cooling tank 08 is an injection moulded component. The cooling unit 9 further comprises a cooling tank opening 114 provided in an outer wall 112 of the chamber which leads to the interior of the cooling tank 102. In use, breathable gas flows through the cooling chamber 102 from the gas inlet 104 to the gas outlet 106 and is cooled by the cooling medium contained within the cooling tank 108.

Description

CASE FOR BREATHING APPARATUS AND COOLING UNIT FOR BREATHING APPARATUS

FIELD OF THE INVENTION

The invention relates to a case for breathing apparatus, in particular, although not exclusively, to a case for a closed circuit breathing apparatus. The invention also relates to a cooling unit for cooling a flow of breathable gas in a breathing apparatus, in particular, although not exclusively, for cooling a flow of breathable gas in a closed circuit breathing apparatus.

BACKGROUND OF THE INVENTION

Portable closed circuit breathing apparatus (CCBA) units which can be carried by a user are known. They typically comprise a closed breathing circuit comprising a carbon dioxide removal unit that removes carbon dioxide from the exhaled air, a cylinder of oxygen which enriches the exhaled air with oxygen, and a cooling unit that cools the air before it is inhaled by the user. The breathing circuit also typically comprises a counterlung which is a variable volume breathing chamber. The counterlung is arranged to change in volume by the same amount as the user's lungs when breathing. It allows the volume of the breathing circuit to expand when the user exhales and contract when the user inhales. This allows the total volume of gas in the breathing circuit and in the user's lungs to remain substantially constant. The carbon dioxide removal unit, the cylinder of oxygen, the cooling unit and the counterlung are usually housed within a case which can be worn on the back of the user.

One type of case that is currently known comprises front and rear parts that are made from a composite material comprising glass fibres and resin. The front and rear parts are manufactured by pressing a glass fibre matrix sheet coated in resin between a male and a female mould. Various mechanical fixing are then attached to the casing parts. These fixings may include fixings for attaching the two casing parts together, fixings for attaching the breathing apparatus components to the interior of the case, and fixings for attaching support straps to the case. Other features, such as holes or openings, may also be machined into the parts. Whilst such a case is satisfactory for some applications, they are time-consuming and therefore expensive to manufacture due to the large number of manufacturing steps involved. It is therefore desirable to provide an improved case for breathing apparatus which is less expensive to produce.

In order to aid breathing, it is known to resiliency bias the counterlung towards a configuration in which it has the minimum volume possible. The resilient bias adds pressure to the breathing circuit and therefore it is easier for the user to breathe. It is known to use springs to resiliency bias the counterlung towards the minimum configuration. In such a configuration, one end of the spring acts on the counterlung whilst the other end of the spring is supported by a support. Whilst this arrangement is satisfactory for some applications, the support may obstruct other breathing components and may make it difficult to maintain and clean the breathing apparatus.

It is therefore desirable to provide an improved arrangement which facilitates easy cleaning and maintenance of the breathing apparatus.

A previously considered cooling unit comprises a metal cooling tank, arranged to contain ice, disposed within a cooling chamber made from a plastics material through which the gas to be cooled flows. A metal cooling tank is used because of the relatively high-thermal conductivity. However, this component can be expensive to manufacture and attach to the plastic cooling chamber.

It is therefore desirable to provide an improved cooling unit which is less expensive to manufacture and easier to assemble.

STATEMENT OF THE INVENTION

The invention is defined in the attached independent claims to which reference should now be made. Further optional features may be found in the sub-claims appended thereto. According to a first aspect of the invention there is provided a case for breathing apparatus, comprising: front and rear casing portions arranged to be detachably attached to one another and arranged to house therebetween a variable volume breathing chamber that can vary in volume between a first configuration and a second configuration, wherein the volume of the breathing chamber is larger in the second configuration than the first configuration; a spring support detachably attached to one of the casing portions; and at least one spring supported by the spring support and arranged to act on the variable volume breathing chamber so as to bias it towards the first configuration. There may be a latching arrangement for latching or locking the spring support when it is attached to the casing portion. The spring support may be detachably attached to the rear casing portion. The spring support may be detachably attached to the casing portion which is arranged to retain breathing components.

The spring support may extend substantially across the casing portion to which it is detachably attached from one side to the opposing side. The spring support may extend substantially across the width of the casing portion to which it is detachably attached.

The spring support may comprise a bridge portion that extends across the casing portion to which it is detachably attached. The spring support may comprise first and second leg portions that are oblique to and disposed towards opposing ends of the bridge portion. The first and second leg portions may be substantially perpendicular to the bridge portion. The first and second leg portions may extend from the same side of the bridge portion.

The spring support may be detachably attached to the casing portion by an attachment projection provided on the spring support or the casing portion which is located within a corresponding attachment opening provided in the other of the spring support and the casing portion. There may be a plurality of attachment projections and a plurality of corresponding attachment openings. A first end of the spring support may be detachably attached to the casing portion by a corresponding attachment projection and attachment opening, and a second end of the spring support may be detachably attached to the casing portion by a corresponding attachment projection and attachment opening. At least a portion of the spring support may be resiliently deformable such that at least one attachment projection can be disengaged within at least one attachment opening to detach the spring support from the casing portion. There may be a plurality of springs supported by the spring support, each arranged to act on the variable volume breathing chamber so as to bias it towards the first configuration. The at least one spring may be a coil spring having a first end coupled to the spring support and a second end arranged to act on the variable volume breathing chamber.

The spring support may comprise a pressure relief valve mounting portion for mounting a pressure relief valve to the spring support.

The spring support may be an injection moulded component.

The spring support may be of a plastics material, or of a composition comprising a plastics material, or of a composition comprising a polymeric matrix and fibrous or particulate reinforcement. The spring support may be integrally formed.

According to a further aspect of the invention there is provided a breathing apparatus comprising a case in accordance with any statement herein; and a breathing circuit including an inhalation conduit, an exhalation conduit and a variable volume breathing chamber, wherein the variable volume breathing chamber is disposed within the case; and wherein the at least one spring acts between the spring support and the variable volume breathing chamber so as to bias it towards the first configuration.

The variable volume breathing chamber may be a bag.

The at least one spring may act on an intermediate plate which transfers the biasing force to the variable volume breathing chamber.

The breathing circuit may be a substantially closed breathing circuit. The breathing circuit may further comprise a carbon dioxide removal unit that is disposed within the case.

According to a second aspect of the invention there is provided a case for breathing apparatus, comprising: front and rear casing portions arranged to be detachably attached to one another and arranged to house at least a carbon dioxide removal unit and a cylinder of breathable gas therebetween; wherein the front and rear casing portions are injection moulded components. The front and/or rear casing portion may comprise a base and a side wall. When the front and rear casing portions are detachably attached a portion of the side wall of one of the casing portions may be located within the side wall of the other casing portion.

The front and/or rear casing portions may be injection moulded components of a plastics material or of a composition comprising a plastics material. The front and/or rear casing portions may be injection moulded components of a composition comprising a polymeric matrix and fibrous or particulate reinforcement.

The rear casing portion may comprise a substantially longitudinally extending spine recess on an outer surface that is arranged to accommodate at least a portion of a wearer's spine.

The front and rear casing portions may comprise corresponding casing attachment portions for detachably attaching the front and rear casing portions to one another. The corresponding casing attachment portions may comprise at least one opening and at least one projection. There may be a plurality of openings and a plurality of corresponding projections.

One of the casing portions may comprise a cylinder cradle for supporting the cylinder of breathable gas.

One of the casing portions may comprise at least one wall for supporting the carbon dioxide removal unit. The other casing portion may also comprise at least one wall for supporting the carbon dioxide removal unit. One of the casing portions may comprise an attachment portion for detachably attaching the carbon dioxide removal unit to the casing portion. The front and rear casing portions may be arranged to house a cooling unit

therebetween. One of the casing portions may comprise at least one wall for supporting the cooling unit. The other casing portion may comprise at least one wall for supporting the cooling unit. One of the casing portions may comprise an attachment portion for detachably attaching the cooling unit to the casing portion.

The front and/or rear casing portion may comprise a reducer valve mounting portion and/or an electronic module mounting portion and/or a minimum valve mounting portion.

The front and/or the rear casing portions may comprise strengthening ribs.

The front and rear casing portions may be arranged to house a variable volume breathing chamber therebetween. The case may further comprise a spring support that is attached to one of the casing portions and is arranged to support a spring acting on the variable volume breathing chamber. The spring support may be detachably attached to the casing portion.

The front and/or rear casing portion may comprise an inhalation conduit opening and/or an exhalation conduit opening and/or a cylinder valve opening and/or a drain valve opening. The front and/or rear casing portion may comprise at least one breathing conduit guide.

The rear casing portion may comprise shoulder strap attachment portions and/or waist belt attachment portions. At least one of the casing portions may comprise a handle.

The front and/or rear casing portions may be integrally formed.

According to a further aspect of the invention there is provided a breathing apparatus comprising: a case in accordance with any statement herein; and a breathing circuit including an inhalation conduit, an exhalation conduit and a carbon dioxide removal unit; and wherein the carbon dioxide removal unit is disposed within the case.

The breathing circuit may be a substantially closed breathing circuit. The breathing circuit may further comprise a variable volume breathing chamber and/or a cooling unit that is disposed within the case.

According to a further aspect of the invention there is provided a case for breathing apparatus, comprising: front and rear casing portions arranged to be detachably attached to one another and arranged to house at least a carbon dioxide removal unit and a cylinder of breathable gas therebetween; wherein the rear casing portion may comprise a substantially longitudinally extending spine recess on an outer surface that is arranged to accommodate at least a portion of a wearer's spine.

According to a third aspect of the invention there is provided a cooling unit for cooling a flow of breathable gas in a breathing apparatus, comprising: a cooling chamber having a gas inlet and a gas outlet; a cooling tank disposed within the chamber and arranged to contain a cooling medium, wherein the cooling tank is an injection moulded component; and a cooling tank opening provided in an outer wall of the chamber and leading to the interior of the cooling tank; wherein in use, breathable gas flows through the cooling chamber from the gas inlet to the gas outlet and is cooled by the cooling medium contained within the cooling tank. The cooling tank may be integrally formed with a supporting wall which forms part the cooling chamber and within which the cooling tank opening is provided, and wherein the cooling tank and supporting wall is an injection moulded component.

The cooling chamber may comprise an integrally formed base portion having an open face which is attached to the supporting wall such that the open face is covered, thereby forming the cooling chamber. The base portion may be attached to the supporting wall by electromagnetic resistance welding. The base portion may comprise the gas inlet and/or the gas outlet. The cooling unit may further comprise a removable cover that covers the cooling tank opening and which can be removed to provide access to the interior of the cooling tank.

The cooling tank may be substantially cylindrical. The gas inlet and gas outlet may be provided on opposite sides of the cooling chamber. The cooling tank may be disposed in a substantially central region within the cooling chamber. In use, breathable gas may flow around the cooling tank. The cooling tank may be arranged to contain ice. The cooling tank may be of a plastics material, or of a composition comprising a plastics material, or of a composition comprising a polymeric matrix and fibrous or particulate reinforcement.

According to a further aspect of the invention there is provided a breathing apparatus, comprising: a case comprising front and rear casing portions arranged to be detachably attached to one another and arranged to house therebetween breathing apparatus components; and a breathing circuit including an inhalation conduit, an exhalation conduit and a cooling unit in accordance with any statement herein, wherein the cooling unit is disposed within the case.

The breathing circuit may be a substantially closed breathing circuit. The breathing circuit may further comprise a variable volume breathing chamber and/or a carbon dioxide removal unit.

According to yet a further aspect of the invention there is provided a method of manufacturing a cooling unit in accordance with any preceding claim, the method comprising: (i) producing at least a portion of the cooling chamber by injection moulding; (ii) producing a cooling tank by injection moulding; and (iii) attaching the cooling tank to the at least a portion of the cooling chamber.

Step (i) may comprise producing an integrally formed base portion having an open face Step (ii) may comprise producing a cooling tank integrally formed with a supporting wall within which the cooling tank opening is provided. Step (iii) may comprise attaching the supporting wall to the base portion such that it covers the open face, thereby forming the cooling chamber. Step (iii) may comprise attaching by electromagnetic resistance welding. The method may further comprise (iv) radiating with radiation comprising gamma and/or beta radiation.

The invention may comprise any combination of the features and/or limitations referred to herein, except combinations of such features as are mutually exclusive. DETAILED DESCRIPTION

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 schematically shows a perspective view of a breathing apparatus unit;

Figure 2 schematically shows the breathing circuit of the breathing apparatus of Figure 1 ;

Figure 3 schematically shows a perspective view of the case for the breathing apparatus of Figure 1 ; Figure 4 schematically shows a perspective view of the inside of the rear casing portion of the case of Figure 3;

Figure 5 schematically shows a perspective view of the exterior of the rear casing portion of the case of Figure 3; and

Figure 6 schematically shows a perspective view of the inside of the front casing portion of the case of Figure 3;

Figure 7 schematically shows a perspective view of the rear casing portion housing breathing apparatus components;

Figure 8 schematically shows a cross-sectional view through the rear casing portion, the variable volume breathing chamber and the spring support; Figure 9 schematically shows a perspective view of the spring support;

Figure 10 schematically shows an enlarged view of the attachment features provided on the spring support and the rear casing portion; Figure 1 1 schematically shows an enlarged view of the spring support attached to the rear casing portion; Figure 12 schematically shows a perspective view of the cooling unit;

Figure 13 schematically shows a cross-section view through the cooling unit; Figure 14 schematically shows a perspective view of the cooling tank with an integrally formed supporting wall; and

Figure 15 schematically shows an exploded view of the cooling unit. With reference to Figure 1 , a breathing apparatus unit 1 comprises a breathing circuit having an inhalation tube or conduit 2, an exhalation tube or conduit 3, and a common mouthpiece connector 4. A case 20 is provided which contains part of the breathing circuit and other breathing apparatus components. A pair of shoulder straps 5 and a waist belt 6 is attached to the case 20 such that the breathing apparatus 1 can be worn and carried by a user.

Figure 2 shows the breathing circuit which in this embodiment is a substantially closed- circuit breathing circuit. In addition to the inhalation and exhalation tubes 2, 3 it comprises a carbon dioxide removal unit or scrubber 7, a variable volume breathing chamber or bag 8 and a cooling unit 9 which are connected together in series. The exhalation tube 3 leads to the carbon dioxide removal unit 7 which is connected to the breathing bag 8 which in turn is connected to the cooling unit 9 which the inhalation tube 2 is connected to. The breathing apparatus also comprises a cylinder of oxygen 10 which can supply oxygen to the breathing circuit. Exhalation and inhalation non- return valves 1 1 , 12 are disposed in the exhalation and inhalation tubes respectively 3, 2 in order to ensure that there is flow in only one direction. The breathing circuit is provided with a relief valve 13 that allows gas to be discharged from the breathing circuit if the volume exceeds a threshold. In use, a user exhales gas through a mouthpiece connected to the connector 4. This gas passes through the carbon dioxide removal unit 7 which removes carbon dioxide from the exhaled gas. The gas then passes into and expands the breathing bag 8. When the user inhales through the mouthpiece, the gas passes from the breathing bag 8 through the cooling unit 9 which reduces the temperature of the gas. Oxygen from the cylinder 10 is constantly added to the breathing circuit through the cooling unit and the gas enriched with oxygen is breathed by the user. This cycle continues as the user breathes in and out. If the user breathes particularly heavily extra oxygen may be added to the breathing circuit through a minimum valve 14. If the volume of gas within the system is too high then excess gas can be discharged through the relief valve 13. The volume of the breathing bag 8 contracts and expands as the user breathes in and out so that the total volume of gas in the breathing circuit and the user's lungs remains substantially constant. The volume of the breathing bag 8 can vary in volume between at least a first inhaled configuration, in which the breathing bag 8 is at or close to minimum volume, and a second exhaled configuration, in which the breathing bag 8 is at or close to maximum volume. In order to aid breathing, the breathing bag 8 is resiliency biased towards the first configuration. The breathing bag 8 is resiliency biased towards the first inhaled configuration by two coil springs 80 that act between a spring support 78 and the breathing bag 8. This is shown in Figures 7 and 8. With reference to Figure 3, the case 20 comprises front and rear (or first and second) 22, 24 casing portions that are detachably attached to one another and which house and retain therebetween breathing apparatus components. In this embodiment, the case 20 is arranged to contain the carbon dioxide removal unit 7, the breathing bag 8, the cooling unit 9, the oxygen cylinder 10 and other components.

The front and rear casing portions 22, 24 are integrally formed components that are injection moulded. This allows various features to be integrally formed with the front and rear casing portions. In this embodiment the casing portions 22, 24 are made from a composition comprising Nylon® 6 and glass fibres. However, the front and rear casing portions 22, 24 may be made from any other plastics material, such as polyphenylene (PPE), or from a composition comprising a plastics material or from a composition comprising a polymeric matrix and fibrous (such as glass fibres) or particulate reinforcement. As shown in Figure 4, the rear casing portion 24 comprises a substantially rectangular base 26 and a side wall 28 that extends around the base 26. A number of features are integrally formed in the interior of the rear casing portion 24. In particular, the interior of the rear casing portion 24 comprises an arrangement 30 for receiving, supporting and retaining the carbon dioxide removal unit 7. The arrangement 30 comprises a plurality of integrally formed supporting walls 32 for supporting the lower surface of the carbon dioxide removal unit 7 and an attachment portion 34, in the form of a resiliency deformable clip, for retaining the carbon dioxide removal unit 7 in position. Similarly, the interior of the rear casing portion 24 comprises an arrangement 36 for receiving, supporting and retaining the cooling unit 9. The arrangement 36 comprises a plurality of integrally formed supporting walls 38 for supporting the lower surface and the sides of the cooling unit 9 and an attachment portion 40, in the form of a resiliency

deformable clip, for retaining the cooling unit 9 in position. A space 41 is also provided, within which the breathing bag 8 can be disposed.

The interior of the rear casing portion 24 also comprises an integrally formed cylinder cradle 42 that is curved so as to support a cylinder of oxygen 10. A reducer valve mounting portion 44 is also provided on the interior of the rear casing portion 24 which allows a reducer valve for the oxygen cylinder to be mounted. A minimum valve mounting portion and an electronic module mounting portion (not shown) are also integrally formed on the interior of the rear casing portion 24 such that a minimum valve and an electronic module can be mounted. Various hose guides may also be integrally formed for guiding the hoses or conduits that fluidly connect the various breathing equipment components together. Two attachment openings 46 are formed on opposite side walls of the rear casing portion 24 and these allow the spring support (not shown in Figure 4) to be detachably attached to the rear casing portion 24.

The rear casing portion 24 also comprises three attachment openings 48 that allow the front and rear casing portions 22, 24 to be detachably attached together. Attachment projections on the front casing portion 22 locate within the attachment openings 48 on the rear casing portion (which will be described below) to attach the front and rear casing portions 22, 24 together.

As shown in Figure 5, a number of features are also integrally formed on the exterior of the rear casing portion 24. A longitudinally extending spine recess 49 is formed in the rear surface (or base) of the rear casing portion 24. In use, a portion of the wearer's spine is located within this recess 49 which improves the comfort for the wearer. A waist belt attachment portion 50 is also provided in the exterior surface which allows a waist belt 6 to be pivotally connected to the rear casing portion 24. Shoulder strap attachment portions 52 are also provided which allow a pair of shoulder straps 5 to be attached to the rear casing portion 24. A carrying handle 54 is integrally formed in the rear casing portion 24 such that a user can easily pick-up the case 20 by hand. A number of openings are integrally formed in the rear casing portion 24. In particular, a cylinder valve opening 56 is provided, through which a cylinder valve extends, and a drain valve opening 58 is provided, which allows any water in the breathing circuit to exit via a drain valve through the opening. An inhalation conduit opening 60 and an exhalation conduit opening 62 are provided in opposite upper corners of the rear casing portion 24. These allow the inhalation conduit 2 and the exhalation conduit 3 to pass through the case so as to connect to the cooling unit 9 and the carbon dioxide removal unit 7 respectively. In some embodiments, conduits that are integral with the cooling unit 9 and the carbon dioxide removal unit 7 may pass through these openings in which case the openings 60, 62 may also support these units 7. 9.

Referring now to Figure 6, the front casing portion 22 also comprises a substantially rectangular base 64 and a side wall 66 that extends around the base 64. The interior of the front casing portion 22 comprises a plurality of supporting walls 68 that are arranged to support the carbon dioxide removal unit 7 when the front and rear casing portions 22, 24 are attached. The interior of the front casing portion 22 also comprises a plurality of supporting walls 70 that are arranged to support the cooling unit 9 when the front and rear casing portions 22, 24 are attached. A number of longitudinally extending stiffening ribs 72 are integrally formed in the front casing portion 22 which improves the rigidity of the casing portion. Two locating projections 74 are also integrally formed in the interior of the front casing portion 22. As will be described later, these locate within locating openings to ensure proper attachment of the front and rear casing portions 22, 24. The front casing portion 22 is provided with three integrally formed catches, each comprising an attachment projection 76 on the distal end of a resiliency deformable lever. These attachment projections 76 locate within the attachment openings 48 to detachably attach the front and rear casing portions 22, 24 together. Referring now to Figures 7 and 8, the breathing apparatus 1 is assembled by locating the carbon dioxide removal unit 7, the breathing bag 8, the cooling unit 9 and the cylinder of oxygen 10 in their respective positions in the rear casing portion 24. The various components 7, 8, 9, 10 are supported and retained by the integrally formed features in the rear casing portion 24. A spring support 78 is detachably attached to the rear casing portion 24 and extends substantially across the width of the rear casing portion 24 from a first side to a second opposed side. The spring support 78 is located over the breathing bag 8 and two coil springs 80 are attached to, or are supported by, the underside of the spring support 78. The two coil springs 80 are spaced from one another and are located towards the first and second sides respectively. Each of the coil springs 80 has a first end attached, or coupled, to the spring support 78 and a second end that acts on an intermediate plate 86. The second end of the springs 80 may be attached to or coupled to the plate 86. The intermediate plate 86 acts on the breathing bag 8 and transmits a substantially uniform biasing force to the breathing bag 8. The springs 80 are arranged so as to resiliency bias (via the plate 86) the breathing bag 8 towards a first inhaled

configuration in which it is at, or close to, minimum volume. In other words, it biases the breathing bag 8 to a collapsed configuration. When a user exhales through the exhalation conduit 3 the user must overcome the resilient force of the springs 80 in order to expand the breathing bag 8. However, when a user inhales through the inhalation conduit 2 the resilient force of the springs 80 makes inhalation easier since they bias the breathing bag 8 towards a collapsed first configuration.

Although it has been described that the springs are coil springs 80, any other type of resilient device could be used as the spring. Examples include, but are not limited to, leaf springs and torsion springs, for example. Furthermore, there may be greater or less than two springs supported by the spring support 78. In one embodiment the or each spring may be integrally formed with the spring support 78. With reference to Figure 9, the spring support 78 comprises a bridge portion 88 and first and second leg portions 90, 92 that extend from either end of the bridge portion 88. In this embodiment the length of the bridge portion 88 is substantially the same as the width of the rear casing portion 24 and hence the bridge portion 88 extends across the rear casing portion 24. The first and second leg portions 90, 92 are approximately perpendicular to the bridge portion 88 and extend from the same side. The distal end of each leg portion 90, 92 is provided with an attachment feature 94 that allows each leg portion 90, 92 to be attached to a side of the rear casing portion 24. The

attachment feature 94 will be described in detail below. The bridge portion 88 also comprises a relief valve mounting portion 82 to which a pressure valve 13 can be mounted, and two locating openings 84 that correspond to locating projections (shown in Figure 6) formed on the inside of the front casing portion 22. When the front and rear casing portions 22, 24 are detachably attached the locating projections of the front casing portion 22 locate within the locating openings 84 to ensure correct alignment of the casing portions 22, 24. Referring now to Figure 10, first and second opposite side walls of the rear casing portion 24 are provided with a spring support attachment feature in the form of two attachment openings 46. The two attachment openings 46 are spaced from one another and each comprise a first portion 46a that is larger than a second portion 46b. Each attachment feature 94 of the spring support comprises two attachment projections 96 that correspond to the attachment openings 46. Each attachment projection 96 comprises a head portion 96a and a neck portion 96b that connects the head portion 96a to the distal end of the leg portion 90 of the spring support 78. The head portion 96a has a dimension that corresponds to the first portion 46a of the attachment opening 46 and the neck portion 96b has a dimension that corresponds to the second portion 46b of the attachment opening 46. The attachment feature 94 of the spring support 78 also comprises a resiliently deformable latch 98 comprising a lever arm 98a and a detent 98b. The detent 98b projects from the lever arm 98a and is configured to be located within the first portion 46a of one of the attachment openings 46.

In order to detachably attach the spring support 78 to the rear casing portion 24, the head portion 96a of each attachment projection 96 is located within the first portion 46a of a respective attachment opening 46a. The spring support 78 is then slid in a direction such that the neck portion 96b of each attachment projection 96 is located within the second portion 46a of the respective attachment opening 46a. At the same time, the detent 98b of the latch 98 locks into place within the first portion 46a of one of the attachment openings 46. This prevents accidental detachment of the spring support 78. The spring support 78 is shown in the locked, attached position in Figure 11.

If it is desired to remove the spring support 78 so that the breathing components may be removed and the case cleaned, for example, each detent 98b can be depressed and the spring support 78 can be slid such that it can be detached from the casing portion 24. This is a relatively simple and quick operation which allows the breathing apparatus to be cleaned and maintained with ease. In the above described embodiment the spring support 78 comprises attachment projections 96 which engage with attachment openings 46 in the rear casing portion 24. However, some or all of the projections may be located on the casing with

corresponding openings provided on the spring support.

The cooling unit is illustrated in Figures 12 and 13, and comprises a cooling chamber 102 having a gas inlet 104 and a gas outlet 106 that are disposed on opposite sides of the chamber 102. The cooling chamber 102 defines a chamber interior that the inlet 104 and outlet 106 open into. In this embodiment the cooling chamber 102 is approximately cube-shaped and has a top wall, a bottom wall and four side walls. The gas inlet 104 and gas outlet 106 are provided in opposite side walls and each comprises a connector 105, 107 for attaching breathing tubing thereto. In use, the inhalation conduit 2 is attached to the gas outlet 106 and a conduit leading from the breathing bag 8 is attached to the gas inlet 104. The cooling chamber 102 is further provided with an oxygen inlet 103 through which the cylinder of oxygen continuously adds oxygen to the breathing circuit.

An injection moulded cooling tank 108 is disposed within the interior of the cooling chamber 102 and is located approximately in a central region thereof. The cooling tank 108 in this embodiment is substantially cylindrical and has a height comparable to that of the cooling chamber 102. However, the diameter of the cooling tank 108 is somewhat less than the width of the cooling chamber 102 and there is therefore a fluid passageway 1 10 between the gas inlet and the gas outlet 104, 106. As best seen in Figure 14, the cooling tank 108 is integrally formed with a supporting wall 1 12 which forms the top wall of the cooling chamber 102. A cooling tank opening 1 14 is provided in the supporting wall 1 12 which leads to the interior of the cooling tank 108. The cooling chamber 102 includes a base portion 1 16 which comprises the bottom wall and the four side walls and has an open top face. The supporting wall 1 12 integrally formed with the cooling tank 108 is attached to the base portion 1 16 such that the cooling tank 108 is disposed within the cooling chamber 102 and the supporting wall 1 12 covers and closes the open top face of the base portion 1 16. The cooling chamber 102 is therefore sealed with the exception of the gas inlet 104 and outlet 106. The cooling unit 9 further comprises a two-part removable cover 1 18 having a O-ring seal 120 that can be used to seal the cooling tank 108. Before the cooling unit 9 is used, the cover 1 18 is removed and a cooling medium (or coolant), such as ice, is located within the interior of the cooling tank 108. The cover 1 18 is then replaced over the cooling tank opening 1 14 to seal the interior of the cooling tank 108. In this embodiment the cooling unit 9 comprises four integrally formed injection moulded components, namely, the base portion 1 16, the cooling tank/supporting wall 108, 1 12 and the cover 1 18 which is in two parts. These components can all be formed inexpensively by injection moulding. The injection moulded components may be formed from a composition comprising polyethylene and glass fibres, or from a composition comprising Nylon® 6 and glass fibres, for example. However, any other suitable material may be used such as a plastics material, a composition comprising a plastics material or a composition comprising a plastics material and fibrous or particulate reinforcement. The fibrous reinforcement may be glass fibres, for example. In this embodiment the supporting wall 1 12 (integrally formed with the cooling tank 108) is attached to the base portion 1 16 of the cooling chamber 102 by electromagnetic resistance welding. With reference to Figure 15, a metallic welding wire 122 is disposed between the upper edge 1 17 of the base portion 1 16 and the outer edge 1 13 of the supporting wall 1 12. The wire 122 is then heated in a contactless manner using electromagnetic radiation. As the wire is heated the supporting wall 1 12 and the base portion 1 16 are pressed together which causes the two parts to fuse together. The welding wire 122 remains between the components after assembly and therefore if it is desired to separate the two components again the wire 122 can be heated using electromagnetic radiation and the components can be pulled apart. It may be desirable for the supporting wall 1 12 (and hence the cooling tank 108) and the base portion 1 16 to be injection moulded from the same material.

After the two components have been welded together by electromagnetic resistance welding, they undergo a radiation cross-linking process. In this process the

components are irradiated with a predetermined dosage of energy-rich beta or gamma rays. The energy from the radiation is absorbed by the polymeric material and at least some of the chemical bonds break. This releases free radicals which react with one another and form a link between the molecular chains of the polymer. This crosslinking connects the molecules to one other and fundamentally limits their movement. The cross-linking process increases the thermal stability and mechanical strength of the components. In use, the interior of the cooling tank 108 is filled with a cooling substance such as ice. Gas to be inhaled by the user flows from the gas inlet 104, around the cooling tank 108, between its exterior wall and the interior wall of the cooling chamber 102, and out through the gas outlet 106. The gas flowing though the chamber 102 is cooled by the ice (or other cooling substance) within the cooling tank 108 due to the difference in temperature between the gas and the ice.

Once the components have been positioned within the rear casing portion 24 the front casing portion 22 is detachably attached to the rear casing portion 24 using the corresponding attachment openings 48 and projections 76 on the rear and front casing portions 22, 24. The projections 76 releasably locate within the openings 48 so as to secure the front casing portion 22 to the rear 24. The locating projections 74 of the front casing portion 22 locate within the locating openings 48 in the spring support to ensure that the front casing portion 22 is in the correct location. If it is desired to remove the front casing portion 22 to gain access to the interior of the case 20, the attachment projections 76 can be disengaged from the attachment openings 48.

Although it has been described that the attachment projections are on the front casing portion 22, some or all of them could be on the rear casing portion 24. Further, the front and rear casing portions 22, 24 may be attached together by discrete attachment clips. After the case 20 has been assembled, the shoulder straps 5, waist belt 6, inhalation tube 2 and exhalation tube 3 can be attached to the rear casing part 24.

When assembled the various integrally moulded support walls 32, 38, 68, 70 support the carbon dioxide removal unit 7 and cooling unit 9 and the attachment portions 34, 40 retain them in place. The front and rear casing portions 22, 24 co-operate so as to retain the aforementioned components.

Since the front and rear casing portions 22, 24 are injection moulded components they are relatively cheap to produce and further features can be easily integrally formed. This reduces the manufacturing costs and the assembly time.

Although it has been described that the breathing apparatus components are first located within the rear casing portion, it should be noted that they could equally be located within the front casing portion.

Claims

CLAIMS:

1 . A case for breathing apparatus, comprising:

front and rear casing portions arranged to be detachably attached to one another and arranged to house therebetween a variable volume breathing chamber that can vary in volume between at least a first configuration and a second configuration, wherein the volume of the breathing chamber is larger in the second configuration than the first configuration;

a spring support detachably attached to one of the casing portions; and at least one spring supported by the spring support and arranged to act on the variable volume breathing chamber so as to resiliency bias it towards the first configuration.

2. A case for breathing apparatus according to claim 1 , wherein the spring support extends substantially across the casing portion to which it is detachably attached from one side to the opposing side.

3. A case for breathing apparatus according to claim 1 or 2, wherein the spring support extends substantially across the width of the casing portion to which it is detachably attached.

4. A case for breathing apparatus according to any preceding claim, wherein the spring support comprises a bridge portion that extends across the casing portion to which it is detachably attached.

5. A case for breathing apparatus according to claim 4, wherein the spring support comprises first and second leg portions that are oblique to and disposed towards opposing ends of the bridge portion.

6. A case for breathing apparatus according to claim 5, wherein the first and second leg portions are substantially perpendicular to the bridge portion.

7. A case for breathing apparatus according to claim 5 or 6, wherein the first and second leg portions extend from the same side of the bridge portion.

8. A case for breathing apparatus according to any preceding claim, wherein the spring support is detachably attached to the casing portion by an attachment projection provided on the spring support or the casing portion which is located within a corresponding attachment opening provided in the other of the spring support and the casing portion.

9. A case for breathing apparatus according to claim 8, wherein there are a plurality of attachment projections and a plurality of corresponding attachment openings.

10. A case for breathing apparatus according to claim 9, wherein a first end of the spring support is detachably attached to the casing portion by a corresponding attachment projection and attachment opening, and a second end of the spring support is detachably attached to the casing portion by a corresponding attachment projection and attachment opening.

1 1 . A case for breathing apparatus according to any of claims 8-10, wherein at least a portion of the spring support is resiliency deformable such that at least one attachment projection can be disengaged within at least one attachment opening to detach the spring support from the casing portion.

12. A case for breathing apparatus according to any preceding claim, wherein there are a plurality of springs supported by the spring support, each arranged to act on the variable volume breathing chamber so as to bias it towards the first configuration.

13. A case for breathing apparatus according to any preceding claim, wherein the at least one spring is a coil spring having a first end coupled to the spring support and a second end arranged to act on the variable volume breathing chamber.

14. A case for breathing apparatus according to any preceding claim, wherein the spring support comprises a pressure relief valve mounting portion for mounting a pressure relief valve to the spring support.

15. A case for breathing apparatus according to any preceding claim, wherein the spring support is an injection moulded component.

16. A case according to any preceding claim, wherein the spring support is of a plastics material, or of a composition comprising a plastics material, or of a composition comprising a polymeric matrix and fibrous or particulate reinforcement.

17. A case for breathing apparatus according to any preceding claim, wherein the spring support is integrally formed.

18. A breathing apparatus, comprising:

a case in accordance with any preceding claim; and

a breathing circuit including an inhalation conduit, an exhalation conduit and a variable volume breathing chamber, wherein the variable volume breathing chamber is disposed within the case; and

wherein the at least one spring acts between the spring support and the variable volume breathing chamber so as to bias it towards the first configuration.

19. A breathing apparatus according to claim 18, wherein the variable volume breathing chamber is a bag.

20. A breathing apparatus according claim 18 or 19, wherein the at least one spring acts on an intermediate plate which transfers the biasing force to the variable volume breathing chamber.

21 . A breathing apparatus according to any of claims 18-20, wherein the breathing circuit is a substantially closed breathing circuit.

22. A breathing apparatus according to any of claims 18-21 , wherein the breathing circuit further comprises a carbon dioxide removal unit that is disposed within the case.

23. A case for breathing apparatus or breathing apparatus substantially as described herein with reference to the accompanying drawings.

24. A case for breathing apparatus, comprising:

front and rear casing portions arranged to be detachably attached to one another and arranged to house at least a carbon dioxide removal unit and a cylinder of breathable gas therebetween;

wherein the front and rear casing portions are injection moulded components.

25. A case according to claim 24, wherein the front and/or rear casing portions are injection moulded components of a plastics material or of a composition comprising a plastics material.

26. A case according to claim 24 or 25, wherein the front and/or rear casing portions are injection moulded components of a composition comprising a polymeric matrix and fibrous or particulate reinforcement.

27. A case according to any of claims 24-26, wherein the rear casing portion comprises a substantially longitudinally extending spine recess on an outer surface that is arranged to accommodate at least a portion of a wearer's spine.

28. A case according to any of claims 24-27, wherein the front and rear casing portions comprise corresponding casing attachment portions for detachably attaching the front and rear casing portions to one another.

29. A case according to claim 28, wherein the corresponding casing attachment portions comprise at least one opening and at least one projection.

30. A case according to claim 29, wherein there are a plurality of openings and a plurality of corresponding projections.

31 . A case according to any of claims 24-30, wherein one of the casing portions comprises a cylinder cradle for supporting the cylinder of breathable gas.

32. A case according to any of claims 24-31 , wherein one of the casing portions comprises at least one wall for supporting the carbon dioxide removal unit.

33. A case according to claim 32, wherein the other casing portion comprises at least one wall for supporting the carbon dioxide removal unit.

34. A case according to any of claims 24-33, wherein one of the casing portions comprises an attachment portion for detachably attaching the carbon dioxide removal unit to the casing portion.

35. A case according to any of claims 24-34, wherein the front and rear casing portions are arranged to house a cooling unit therebetween.

36. A case according to claim 35, wherein one of the casing portions comprises at least one wall for supporting the cooling unit.

37. A case according to claim 36, wherein the other casing portion comprises at least one wall for supporting the cooling unit.

38. A case according to any of claims 35-37, wherein one of the casing portions comprises an attachment portion for detachably attaching the cooling unit to the casing portion.

39. A case according to any of claims 24-38, wherein the front and/or rear casing portion comprises a reducer valve mounting portion and/or an electronic module mounting portion and/or a minimum valve mounting portion.

40. A case according to any of claims 24-39, wherein the front and/or the rear casing portion comprises strengthening ribs.

41 . A case according to any of claims 24-40, wherein the front and rear casing portions are arranged to house a variable volume breathing chamber therebetween.

42. A case according to claim 41 , wherein the case further comprises a spring support that is attached to one of the casing portions and is arranged to support a spring acting on the variable volume breathing chamber.

43. A case according to claim 42, wherein the spring support is detachably attached to the casing portion.

44. A case according to any of claims 24-43, wherein the front and/or rear casing portion comprises an inhalation conduit opening and/or an exhalation conduit opening and/or a cylinder valve opening and/or a drain valve opening and/or at least one breathing conduit guide.

45. A case according to any of claims 24-44, wherein the rear casing portion comprises shoulder strap attachment portions and/or waist belt attachment portions.

46. A case according to any of claims 24-45, wherein at least one of the casing portions comprises a handle.

47. A case according to any of claims 24-46, wherein the front and/or rear casing portions are integrally formed.

48. A breathing apparatus, comprising:

a case in accordance with any of claims 24-47;

a breathing circuit including an inhalation conduit, an exhalation conduit and a carbon dioxide removal unit; and

wherein the carbon dioxide removal unit is disposed within the case.

49. A breathing apparatus according to claim 48, wherein the breathing circuit is a substantially closed breathing circuit.

50. A breathing apparatus according to claim 48 or 49, wherein the breathing circuit further comprises a variable volume breathing chamber and/or a cooling unit that is disposed within the case.

51 . A cooling unit for cooling a flow of breathable gas in a breathing apparatus, comprising:

a cooling chamber having a gas inlet and a gas outlet;

a cooling tank disposed within the chamber and arranged to contain a cooling medium, wherein the cooling tank is an injection moulded component; and

a cooling tank opening provided in an outer wall of the chamber and leading to the interior of the cooling tank;

wherein in use, breathable gas flows through the cooling chamber from the gas inlet to the gas outlet and is cooled by the cooling medium contained within the cooling tank.

52. A cooling unit according to claim 51 , wherein the cooling tank is integrally formed with a supporting wall which forms part the cooling chamber and within which the cooling tank opening is provided, and wherein the cooling tank and supporting wall is an injection moulded component.

53. A cooling unit according to claim 52, wherein the cooling chamber comprises an integrally formed base portion having an open face which is attached to the supporting wall such that the open face is covered, thereby forming the cooling chamber.

54. A cooling unit according to claim 53, wherein the base portion is attached to the supporting wall by electromagnetic resistance welding.

55. A cooling unit according to claim 53 or 54, wherein the base portion comprises the gas inlet and/or the gas outlet.

56. A cooling unit according to any of claims 51 -55, further comprising a removable cover that covers the cooling tank opening and which can be removed to provide access to the interior of the cooling tank.

57. A cooling unit according to any of claims 51 -56, wherein the cooling tank is substantially cylindrical.

58. A cooling unit according to any of claims 51 -57, wherein the gas inlet and gas outlet are provided on opposite sides of the cooling chamber.

59. A cooling unit according to any of claims 51 -58, wherein the cooling tank is disposed in a substantially central region within the cooling chamber.

60. A cooling unit according to any of claims 51 -59, wherein in use breathable gas flows around the cooling tank.

61 . A cooling unit according to any of claims 51 -60, wherein the cooling tank is arranged to contain ice.

62. A cooling unit according to any of claims 51 -61 , wherein the cooling tank is of a plastics material, or of a composition comprising a plastics material, or of a composition comprising a polymeric matrix and fibrous or particulate reinforcement.

63. A breathing apparatus, comprising:

a case comprising front and rear casing portions arranged to be detachably attached to one another and arranged to house therebetween breathing apparatus components; and

a breathing circuit including an inhalation conduit, an exhalation conduit and a cooling unit in accordance with any of claims 51 -62, wherein the cooling unit is disposed within the case.

64. A breathing apparatus according to claim 63, wherein the breathing circuit is a substantially closed breathing circuit.

65. A breathing apparatus according to claim 63 or 64, wherein the breathing circuit further comprises a variable volume breathing chamber and/or a carbon dioxide removal unit.

66. A method of manufacturing a cooling unit in accordance with any of claims 51 -62, the method comprising:

(i) producing at least a portion of the cooling chamber by injection moulding;

(ii) producing a cooling tank by injection moulding; and

(iii) attaching the cooling tank to the at least a portion of the cooling chamber.

67. A method according to claim 66,

wherein (i) comprises producing an integrally formed base portion having an open face;

wherein (ii) comprises producing a cooling tank integrally formed with a supporting wall within which the cooling tank opening is provided; and

wherein (iii) comprises attaching the supporting wall to the base portion such that it covers the open face, thereby forming the cooling chamber.

68. A method according to claim 66 or 67, wherein (iii) comprises attaching by electromagnetic resistance welding.

69. A method according to any of claims 66-68, further comprising:

(iv) radiating with radiation comprising gamma and/or beta radiation.

70. A cooling unit or breathing apparatus substantially as described herein with reference to the accompanying drawings.