Most modern Diving Helmets seal at the diver's neck with some sort of stretch material such as latex or foam neoprene. Care is taken to prevent this material from ballooning, as this interferes with the diver's trim and buoyancy and also tries to lift the helmet off the head. Emergency breathing systems, in case of hose rupture or other loss of gas, basically revert to open- circuit scuba, with a small bottle on the back feeding a demand regulator on the helmet. However, the deeper you go, the quicker you use up this supply. A single breath by a diver at 40 Atmospheres pressure contains as many molecules as 40 similar breaths at sea- level. With a heavy breathing rate at the depths now being considered, a normal 'bail-out bottle' (as they are called) is exhausted in less than a minute.

Because of this, there has recently been a drive to adopt more efficient bail-out systems, such as closed or semi-closed circuit scuba equipment. Both of these contain the common elements of a gas supply, a breathing bag (i.e. an expandable volume), a C0_ scrubbing canister, and a way of metering gas into the system to maintain a high enough oxygen level.

Using a semi-closed system, the ^* less-than-one- minute ¹ bai l-out cylinder described above can be made to last for a half hour or more.

To date, however, attempts to adopt semi-closed or closed-circuit scuba to conventional diving helmets have all resulted in the strapping on of a separate breathing bag and canister to the diver, with at least one large diameter breathing hose connection now necessary between the helmet and this new equipment. It takes longer to dress the diver; he is encumbered by the extra equipment; and the extra hose(s) restrict his movement and, being certainly much more easily damaged than his fibreglass or metal helmet, lessen his level of protection. It is

the common story of safety equipment actually mak ng things less safe.

An object of this invention is to pro ide an improved breathing apparatus. According to the present invention there is provided breathing apparatus including headgear and means for supplying breathable gas thereto which further comprises a stowable bag connected directly to the headgear and bag deployment means whereby the bag may be deployed for use with the headgear as a means of containing a breath¬ able volume of gas. The direct connection may be made by mounting the bag directly on a helmet or face mask forming part of the headgear thereby avoiding the use of additional connecting hoses. Preferably, the breathing apparatus comprises a helmet, a breathable gas supply connected to the helmet, means for pro iding a neck seal for the ^" helmet, a flexible bag stowable in the neck region of the helmet and releasable retaining means for securing the bag in a stowed position in said neck region of the helmet, the said retaining means being operable to release the bag from the stowed position to a deployed position where breathable gas supplied to the helmet inflates the bag to form a gas-containing breathing bag. Preferably, the headgear has directly connected thereto a canister containing CO -absorbent material which under normal use of the headgear s protected against exposure to C0 _? and water, and has. means for exposing said absorbent material to gas breathed by a user of the headgear whenever the bag is deployed. The canister s preferably directly connected to the head¬ gear by mounting the canister directly on a helmet or face mask forming part of the headgear thereby avoiding the use of additional hoses. It is particularly preferred that the C0 _? scrubber canister is mounted directly at the

oral-nasal mask in- order to reduce C0--retaining dead space to a minimum and thus allow pendulum breathing (i .e. bi-directional flow), thereby getting a double pass through the CO^'absorbent material and minimising the required volume and weight of C0-,-absorbent material. Preferably, the cannister is provided with sealing means whereby rotation of the canister with respect to the sealing means, or vice versa, exposes the C0 _? - absorbent material to gas breathed by a user of the headgear. Preferably also, the canister is sealed by means including low pressure relief valves communicating ith the helmet interior and operative in opposite di rections.

The bag may be formed as part of the neck dam material normally provided in diving headgear. Altern¬ atively, it may be a separate item which is directly connected to the helmet or face mask.

In its simplest form the improved breathing apparatus of this invention provides a flexible helmet- neck dam material restricted from ballooning in normal use by releasable fasten ng means, but capable upon release of expanding n response to helmet pressure to form a breathing bag.

There are many ways of restrain ng the bag, and making it serve as a neckdam. One could simply put a strap around the neck with a Velcro (Registered Trade Mark) fastener, but there would be little bits of the bag above the strap still expanding and contracting, so this, although usable, would be an aggravation to the diver.

Another way is to have a band of flexible but reasonably stiff material extending up from the neck ring or yoke into the helmet, forcing the breathing bag up with it and into a fold around it. The bag material cannot balloon, as it is trapped between either

the helmet and the strip, or the strip and the diver.

However, the most advantageous method of pro iding a stowable breathing bag for a helmet, which incidentally allows a larger volume than that just described above, is to form a bag of a flexible material, fasten it in the neck region of the helmet, and stow it within the helmet by turning the bag inside out and pushing it into the interior of the neckdam to fill the space under the chin and beneath the jaw on either side of the neck of a user of the headgear. The release of the bag for use is preferably achieved by using bag deployment means comprising a flexible rod attached at both ends thereof to said bag at opposing side portions of the bag which are intended to be stowed on either side of the neck of a user of the apparatus, and a pull handle attached to said rod in a central position.

An advantage of t is arrangement is that with the bag within the helmet and inside-out, it is flattened into the stowed position by helmet pressure so that there is no possibility of 'ballooning' with resultant trim and buoyancy changes in then normal mode.

The invention will now be described by way of example with reference to the accompanying drawings in which:- Fig. 1 shows a cross sect on through a diving helmet forming part of breathing apparatus of this invention in wh ch the neckdam/breathing bag is in the normal stowed position;

Fig. 2 shows an enlarged iew of part of the helmet showing one possible form of the releasable fastening means for retaining the neckdam/bag in the stowed position as illustrated in Fig.1;

Fig. 3 shows a breathing bag in the stowed position beneath the chin and on either side of the neck of a user of the breathing apparatus (helmet removed); and

Fig. 4 shows a breathing bag in the deployed position beneath a helmet forming part of the apparatus of this i nvent i on. Examp le 1 In a first embodiment of the invention as i ll¬ ustrated in Figs. 1 and 2 of the drawings, a diver's helmet (1) is prov ded with a flexible material (2) capable of being stowed (Fig. 1) within the confines of the helmet (1) to act as a πeckdam or of being deployed ⁽ not shown) as an emergency breathing bag which expands by virtue of breathable gas pressure within the helmet ⁽ 1 ⁾ from the stowed position to a deployed position out¬ side the he Imet (1 ) .

The flexible material (2) has an upper edge fixed to the neck ring (10) of the helmet (1) and is stowed within the neck region (3) of the helmet (1) by use of releasable restraining means comprising a strip- (4) of flexible but reasonably stiff material extending up from the neck ring or yoke (5) into the helmet (1), forcing the material (2) up with it and into a fold around it. The flexible material cannot balloon, as it is trapped between either the helmet (1) and the strip (4); or the strip (4) and the neck of a diver wearing the apparatus and in this position serves as a neckdam.. A flexible rod (6) (more preferably two rods, one on either side of the helmet (1)) is threaded through a series of loops (7) which are linked by a cord (8) passing through the yoke (5) to a retainer (9) on the far side of the strip (4). The end(s) _. of the rod(s) (6) stick(s) out at the front of the helmet (1) and a hand grip (not shown) is provided at the end(s) . By grasping the hand grip and giving a good yank forward, the diver pulls the rod (6 ⁾ through the series of loops (7 ⁾ thus freeing the flexible strip (4). Since the far end of the cord (8) is fixed to the far side of the strip (4) by

retainer (9), the strip (4) will also be pulled out, thus releasing the membrane (2) and making it possible for it to billow outside the helmet (1) by means of gas pressure from within the helmet (1) to thereby form a breathable gas chamber to provide a re-breathable volume of gas available to the d ver and prolong his survi al time. Example 2

A second and preferred embodiment as shown in Figs. 3 and 4 comprises a diver's helmet (11) which is located in the yoke ⁽ 15) of a diver's suit and sealed with a neckdam material ⁽ 12). Besi ^' de this neckdam material (12), in the neck region (13) to the front of the yoke (15), there is located a breathing bag (14) which s stowed (Fig. 3) inside-out so as to lie flat under the diver's chin and beneath the jaw to either side of his neck. In this embodiment the bag (14) i.s secured to the neckdam material, but it could easily be secured else¬ where as long as the method of secural did not interfere with deployment of the bag (14) from the helmet (11).

In order to deploy the bag (14) from the stowed position within the helmet (11), a flexible rod (16) is attached at both ends thereof to the bag (14) at opposing side portions (141, 14r) of the bag (14) which are intended to be stowed in the helmet (11) to either side of the neck of a diver. A pull handle (17) is attached by cord (18) to the flexible rod (16) at a central position.

As can be best seen from Fig. 4 the bag (14) when inflated is of substantially cylindrical shape, but tapering towards the middle where an opening (20) provides a connecting passage between the helmet interior andthe bag interior.

The helmet (11) is also provided with a CO -removing canister (21) which contains CO^-absorbing material.

This canister (21 ⁾ is mounted close to and directly connected to the helmet oral-nasal mask (22) to reduce CO -retai ni ng dead space to a minimum and thus allow pendulum breathing (bi-directional flow). Thus, in breathing, the diver inhales and exhales via the oral- nasal mask (22) through the bag opening (20) and in and out of the breathing bag (14).

An oxygen make-up tank is pro ided on the diver's back (not illustrated) and this completes the three elements required to turn the diving headgear into a semi-closed system.

It wi ll be appreciated that in normal diving with¬ out the emergency 'bail-out' system being used, none of the three basic elements (Op make-up, COp scrubber and breathing volume bag) are necessary. Indeed, they should not be employed, since they are intended to fulfil the erne rgency. ' bai l-out ^* function only. If the Op- in ection system was used other than in 'bail-out' conditions, the breathable gas reaching ^' the diver's lungs would not be acceptable to sustain him. Similarly, unnecessary use of the C0p scrubber would quickly use up the C0p absorbent. Deployment of the breathing bag in the normal mode results in variable excess buoyancy which is obviously undesirable. Therefore, the system is controllable so that the C0p canister (21) and 0 _? make-up can be deployed when required for use with the bag (14).

In this embodiment, rotation of the C0 _? removal canister (21) opens a) the in-and-out from the oral- nasal mask (22); b) the in-and-out from the canister (21) to the helmet interior; and c) the metabolic oxygen make-up flow, supplied from a cylinder of oxygen- rich, helium/oxygen mixture on the diver's back.

Prior to deployment, the canister is essentially sealed off, but protected by low pressure relief valves

communi cat i ng with the helmet interior facing both in and out. Thus, there will be some gas flowing in and out as the diver goes up and down in the water, but it will be slight. Likewise, the 0 _? make-up flow is shut off.

Deployment of the neckdam bag (14) requires no more than a sharp tug on the handle (17) which instantly deploys the bag (14).

When in the stowed position, the bag (14) gives no discomfort to the diver since, being inside the helmet and inside-out, it is trapped in the space under the diver's chin and under the helmet liner and so held in place. Additionally, since it is in the outside position and helmet pressure tends to flatten it into t is position there is absolutely no 'ballooning' of the bag (14) and so no trim and buoyancy changes in the normal mode of use .

With a helmet-mounted COp absorbent canister (21) and oxygen replenishment system, what results is a conventional helmet (with a small protrusion for the C0 _? canister, roughly 4" diameter x 4"; 10.1 cm diameter x 10.1 cm), which contains the entire semi-closed 'bail¬ out' system, aside from the 'bail-out' 0- make-up bottle itself. The diver would have to wear a 'jockstrap' (an adjustable strap going from the back of the helmet, through his crotch, and up to the front of the helmet) to hold his helmet down when the breathing bag is in use, but this is non-restricting conventional equipment worn, in any case, by many divers. The excess buoyancy and disturbance ^" of trim are penalties paid by the inflation of any breathing bag. They are merely a slight nuisance and of no real handicap to a diver (a 3 litre volume going back and forth between the lungs and the bag adds on average about 1.5 kg to what existed before.) The significant feature of this 'bail-out' system

is that additional hoses are wholly unnecessary and totally avoided, so that a compact diver-acceptable headgear incorporating the bail-out system is provided