Patent Grant
10864388
This application is a National Stage of International Application No. PCT/GB2016/051422, filed May 17, 2016, the subject matter of which is herein incorporated by reference in its entirety.
The present invention relates to the field of high-altitude parachuting and, specifically, to a system to supply oxygen to a parachutist that is adaptable for use both before and during descent.
High-altitude parachuting carries risks additional to those that are immediately apparent when jumping out of a plane at lower altitudes. It is not uncommon for parachutists to exit an aircraft at altitudes above 15,000 and often up to 35,000 feet. The timing at which a parachutist chooses to deploy the parachute depends on circumstances: it can be relatively soon after exiting the aircraft or it can be far later during the descent, perhaps at an altitude of around 5,000 feet. In both cases however, the parachutist is required to be sufficiently alert to act.
As is well-known, atmospheric pressure reduces with altitude and so less oxygen is available for consumption. At altitudes above 22,000 feet (6,700 m), the partial pressure of oxygen in the Earth's atmosphere is, in most cases, too low to support consciousness. Even below this level, the reduction in oxygen can lead to hypoxia as insufficient oxygen reaches the body tissues.
The symptoms of hypoxia are varied, for example: fatigue, light-headedness, nausea, disorientation, confusion, euphoria and potentially loss of consciousness. A jumper losing consciousness will clearly be unable to deploy a parachute but, even with lesser symptoms, life-threatening situations can be brought about by the effect hypoxia has on the parachutist's ability to make properly rational decisions. In addition, vision may be affected, which reduces the ability to spot potential hazards.
For this reason alone high-altitude parachutists carry their own source of oxygen. This is usually a cylinder with a regulator and valve arrangement to supply pressure to a demand valve, connected to a mask sealed to the users face. In certain situations, for example, a military exercise, the parachutist is required to carry a significant amount of equipment for use on landing. It is accordingly desirable to keep the oxygen cylinder that they must also carry as small as possible. This leads to a requirement for efficient oxygen delivery.
Another significant risk to the high-altitude parachutist is decompression sickness. This occurs as a result of a large drop in environmental pressure. This is a danger for deep-sea divers coming to the surface, as is well known, but also for parachutists following, for example, a rapid ascent in the jump aircraft or depressurisation of the aircraft cabin in preparation for a jump. As a result of such sudden decompression, nitrogen within the body can come out of solution and form bubbles in the tissues and blood stream. Symptoms include joint pain from bubbles forming near joints, but also more severe complications such as paralysis, breathing problems and unconsciousness. Untreated decompression sickness can lead to permanent disability and even death.
In order to prevent decompression sickness, nitrogen should be flushed from the bloodstream prior to the reduction in atmospheric pressure. This is typically achieved by “pre-breathing” 100% oxygen for a period of 30-45 minutes before cabin depressurisation and the jump.
This second risk provides an additional need for a parachutist to have access to a supplementary supply of oxygen.
Typically, the parachutist will make use of a bailout system. This includes the oxygen cylinder, mask and valve arrangement noted previously. Whilst the aircraft cabin is still pressurised, the bailout system is donned by the parachutist and connected to the aircraft oxygen supply for the pre-breathing phase. As there is no requirement for the parachutist to be mobile at this point, and it is advantageous to minimise the size, and therefore oxygen content, of the cylinder, pre-breathing is carried out using, so far as possible, the aircraft oxygen supply and not that of the bailout cylinder. Pre-breathing can continue while the aircraft cabin is depressurised and the cabin door opened in preparation for jumping.
When the user is about to jump, the aircraft supply is disconnected and breathing continues from the bailout cylinder oxygen supply.
During the descent, ambient pressure and air oxygen content increase. Whilst the parachutist will therefore need to be provided with a 100% oxygen breathing gas at altitudes above around 20,000 feet, the requirement for supplemental oxygen diminishes during the course of the jump. With the desire to lighten the load carried by the parachutist therefore, it is desirable to avoid over-consumption of cylinder oxygen by reducing the percentage supplied to the parachutist. This is achieved in the prior art by use of a diluter demand valve.
An example of a diluter demand valve is described in, for example, Intertechnique U.S. Pat. No. 6,994,086 (B1). Oxygen is supplied to a user but the demand valve also includes an air intake, which is opened and closed by an aneroid. An aneroid is an evacuated metal bellows arrangement that therefore expands as the pressure around it decreases. The shortening of an aneroid during a descent can be used to adjust the degree of opening of the air intake, thus increasing the amount of oxygen drawn from the environment and reducing that drawn from the cylinder. The intake is closed above a threshold altitude.
The arrangement means that the user is supplied with a gas mixture that gradually increases the air percentage that dilutes the oxygen as the parachutist falls. Overall therefore, less oxygen is consumed.
Known diluter demand valves that are used to give oxygen below the threshold at which 100% oxygen is needed do not provide an efficient mechanism for oxygen delivery. Broadly speaking, the timing of oxygen delivery is a long way from being optimised with respect to the respiration cycle. Oxygen is delivered throughout the inhalation phase, whereas only about the first ⅓ finds its way to the alveoli for absorption. The oxygen delivered during the later part of the inhalation phase ends up in the mask dead-space and airways from which it is exhaled, without being absorbed. To compound this, at the very initial stage of inhalation, gas is first drawn from the mask and this is the gas that has just been exhaled. That is, at the onset of inhalation, oxygen-depleted gas is drawn from the mask before it is replaced with oxygen from the demand valve, which is then inhaled for the remainder of the inhalation phase.
Aneroids with a consistent movement characteristic are difficult and expensive to make. It is relatively straightforward to make an aneroid that will open or close a valve at a given pressure. It is however difficult to do so when a repeatable variation of length with altitude is needed. For repeatable operation, the diluter demand valve requires an aneroid with a consistent expansion and contraction rate, in order to ensure that the oxygen input varies properly with altitude. This can be difficult to achieve, as there are a number of factors during bellows manufacture in which the dimensions, e.g. material thickness, bellows convolution width, have a cubed effect on the rate, making manufacture on the limits of what is possible.
Moreover, aneroids are delicate devices and, at a size that is feasible for incorporation in a diluter demand valve, offer little force. If one is relied on to close the air intake, there is a risk of it not closing properly. Consequently, if the mask is used during the pre-breathing phase, there is a possibility of air being drawn in through the intake. This introduces nitrogen to the inhaled gas, which then risks decompression sickness.
In addition to mask leakage through the inhalation valve, prior art systems are also susceptible to admit nitrogen during the changeover from the pre-breathing phase to reliance on the oxygen cylinder, particularly if problems are encountered attaching the cylinder. Even a single breath of air at a higher pressure (lower altitude) may elevate the jumper's arterial nitrogen to a level that can cause decompression sickness at a lower pressure.
Automation is desirable as this removes the responsibility of decision regarding the oxygen system from the parachutist. This leaves him free to concentrate on the job in hand and reduces the likelihood of mistakes. Prior art bailout systems have variable amounts of user input required. For example, when pre-breathing in a pressurised cabin, it is necessary to switch to a 100% mode, in which the diluted air path is closed. If there are actions to remember, there is the chance of forgetting, which can give rise to subsequent problems.
It is known that a pulsed oxygen delivery system is much more efficient at getting oxygen to the alveoli than a diluter demand valve. A pulsed delivery system detects the onset of inhalation and immediately delivers a pulse of oxygen, which ensures that it is included with the first gas inhaled. Oxygen inhaled early in the respiration cycle is far more likely to end up in the alveoli. Furthermore, as the pulse is short, there is no oxygen delivered with the gas that ends up in the airways and mask dead-space. Typically about three to five times as much oxygen is required in a continuous delivery system to achieve the same oxygen delivery into the lungs.
Despite the drawbacks of the prior art, the diluter valve bailout system is commonly used. There is a perceived need for an alternative design of oxygen delivery system that is capable of delivering oxygen to the lungs with increased efficiency than known in the prior art.
The present invention provides a supplementary oxygen system or bailout system that can be used in activities such as parachuting. The bailout system of this invention delivers 100% oxygen from a demand valve at altitudes above a set threshold, and pulsed oxygen at altitudes below the threshold.
More specifically, the present invention provides a supplementary oxygen system for variable-altitude use, the system comprising:
a valve manifold that is connectable via a regulator to a pressure vessel containing compressed oxygen, the valve manifold having first and second outputs and an output selection valve;
a pulse gas delivery system in fluid communication with the second output and that is activatable to deliver a pulse of gas of predetermined duration; wherein
the output selection valve is switchable between a first position in which gas flowing through the manifold is directed to the first output and a second position in which gas flowing through the manifold is directed to the second output and to the pulse gas delivery system.
On the face of it, it would appear that a pulsed delivery system and demand valve have requirements that render them mutually exclusive. The demand valve requires operation with a closed mask to ensure only the 100% oxygen that flows through it is delivered to the lungs. On the other hand, a conserving device based on a pulsed delivery system requires an intake in the mask that is able to pass air from the environment to a user, this air being only supplemented by the pulse of oxygen delivered at the start of inhalation. It is accordingly not readily apparent how a demand valve and pulse system could be integrated.
In another aspect therefore, this invention provides a mask for use with a bailout system. The mask includes a demand valve that is connectable to the first output of the valve manifold of the bailout system; an inhalation valve; a connection manifold that is connectable with an output of the pulse gas delivery system; an exhalation valve; and a sensing line that provides fluid communication between the inhalation valve and an input to the demand valve. The inhalation valve is configured such that it is closed if a gas pressure above ambient is present in the sensing line i.e. if the demand valve is needed to supply 100% oxygen. Otherwise, it is openable to allow ambient air to be drawn into the mask. The pulse gas delivery system is configured to be responsive to a drop in pressure inside the mask to deliver a pulse of oxygen.
The bailout system can donned when the aircraft cabin is still pressurised and connected to the aircraft oxygen supply. This automatically selects ‘100% Oxygen’ mode, regardless of cabin pressure. This allows pre-breathing on 100% oxygen from the console supply without draining the bailout system oxygen supply. Pre-breathing can therefore continue while the aircraft cabin is de-pressurised.
If the aircraft supply pressure is running out and the pressure drops too low for operation, the system will switch to using oxygen from the bailout cylinder, so breathing is uninterrupted.
The system allows the user to disconnect from the aircraft supply.
If the ambient pressure is below the mode switching threshold (around 20,000 ft, but can be set to any altitude, in accordance with medical advice), the system would keep the supply to the ‘100% Oxygen’ demand valve, so the user will keep breathing 100% oxygen, both when in the aircraft and after jumping.
As the parachutist descends and the pressure rises above the threshold for which 100% oxygen is required, a system in accordance with this invention will switch automatically to ‘Pulse Dose’ mode, and will continue in this mode until the parachutist lands.
The system is capable of significantly improved oxygen delivery in comparison with the prior art. This means that the same size cylinder can provide oxygen for longer, which may be particularly useful if the parachute is deployed early in the descent. Alternatively, a smaller cylinder may be used, reducing the burden on the parachutist. Moreover, this system, with no reliance on aneroid control of the degree of valve opening, is easier to manufacture. It is also capable of providing fully automatic operation, so that there are as few decisions to be made in the operation of the system as is possible.
The invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:
With reference to
A cylinder (or other pressure vessel) (1) containing oxygen at high pressure (2) is connected to a bailout manifold valve (3). The detail of the manifold valve is shown in
The manifold valve has two outlets. The first is a supply (4) to a demand valve (6). The demand valve uses known technology to deliver 100% oxygen in response to a user's demand. The second supply (5) is to a connection (5a) on a mask (9). This outlet is used to deliver pulsed oxygen in response to a user's inhalation. A flow indicator (8) may be incorporated in the second supply line (5) to give a visual indication of pulsed flow.
The supply to the demand valve is also fed to an inhalation valve (7) via a tube (4a). The inhalation valve is closed when pressure to the demand valve (6) is present, thus ensuring that all inhalation is from the demand valve. When there is no pressure to the demand valve (6), the inhalation valve is open, allowing the user to inhale though a valve with a small opening pressure. The pressure required to open the inhalation valve is relatively small, but still set to be higher than that needed to activate a pulsed delivery system in the bailout manifold valve (3). This timing of oxygen delivery ensures that oxygen is included at the start of the inhalation gas intake. That is, the user will first inhale the pulsed oxygen and then the remainder of their inhalation breath will be formed from ambient air drawn through the inhalation valve.
An oxygen supply hose (10) includes a connector (11), which is used to connect to the aircraft oxygen supply, typically at 5 bar, two lengths (12, 14) of hose and a pressure shut-off valve and regulator (13). The hose (12) extends between the connector (11) and the input of the minimum pressure shut-off valve and regulator (13). This device (13) reduces the input pressure in the supply hose (14) to the working pressure of the bailout manifold valve (3), which is lower than the normal output pressure of the aircraft oxygen supply. If the pressure of the aircraft oxygen supply falls below a threshold, typically just below the level of the working pressure of the bailout manifold, the minimum pressure shut-off (13) activates and shuts.
The output of the minimum pressure shut-off valve and regulator (13) feeds through a hose (14) to a connector (15), which connects into a port in the bailout manifold valve (3). Fitting the connector (15) to the bailout manifold valve mechanically switches the output to be 100% oxygen through the demand valve and supplies the system with oxygen from the aircraft supply.
If the aircraft oxygen supply fails, but connector (15) is still connected to the bailout manifold valve (3), a valve in the bailout manifold valve switches, so that the user inhales from the bailout cylinder (1), without interruption to their breathing.
When the connector (15) is disconnected from the bailout manifold valve (3), the valve becomes responsive to ambient air pressure. A valve within the bailout manifold valve determines either 100% oxygen delivery or pulsed oxygen delivery, each delivered from the bailout cylinder. The valve switches automatically between these two states, as dictated by ambient pressure.
These
The high pressure valve and regulator (201) delivers low pressure (typically 4 bar) oxygen to the parts downstream. It consists of a threaded connection (202) to the cylinder (1), with an on-off valve (203) a fill connection (204), a pressure indicator (205), burst disc, (206) and a regulator (207). These elements are well known to one skilled in the art, so will not be described in detail. The on-off valve may be omitted or replaced with a valve on the low pressure side, after the regulator.
This is described in more detail with reference to
The manifold (211) includes an arrangement of valves and passages. The configuration of the valves determines which particular passages are brought in to form a fluid connection between one of two inputs: one from the regulator (201) via interface (208) and a second being an oxygen input (209) from the aircraft oxygen supply; and one of two outputs: a first being an input (213) of the oxygen pulse delivery system via interface (210) and the second being the outlet (4) to the demand valve.
The oxygen input (209) receives the connector (15) from the aircraft oxygen supply. The connector mechanically activates a valve (shown in
The detail of the input and output mode selection manifold can be more clearly understood with reference to
Examples of pulse delivery units are known in the prior art. In this embodiment, the unit (212) receives oxygen from the input and output selection manifold, as determined by various components within the manifold (211). The unit delivers a pre-determined pulse of oxygen to a user immediately in response to a drop in pressure, at the onset of the user's inhalation. Such devices are, for example, described in EP1863555, “Conserving device for breathable gas”.
The function of the input and output selection manifold in all operating states, is shown in the progression of
With reference first to
The Aircraft oxygen supply connection (15) is connected to a port (315) in the housing (300). A seal (316) on a connector (317) seals against the side of the port (315). The connector (317) is held in the port by a hand-wheel (318) retained by a thread (319). The connector (15) and its parts can be seen more clearly in
When the aircraft oxygen supply connection is disconnected from the connection (315), as shown in
The input selection valve directs oxygen to a passage (304). The oxygen enters the input selection valve (301) either from a port (303) in connection with the regulator (207) (hence from the bailout cylinder) or from a connector (15) of the aircraft oxygen supply hose (14) The passage (304) connects to the input of the output selection valve (302).
If the aircraft oxygen supply is connected and pressure is present, the aircraft oxygen supply is selected. If the aircraft oxygen supply fails, or is not connected, the passage (304) is connected via port (303) to the regulator output (207).
A pressure supply spool piston (305) runs in spool seals (306), (307), (308). The piston includes an end (309) located at the aircraft oxygen supply connection port (315) and a sliding piston head seal (350) running in a bore (351) that defines a chamber (310) in the housing (300). If aircraft oxygen supply pressure is present, it acts on the end (309) of the piston and also builds up in the chamber (310). Pressure in this chamber (310) acts on the sliding piston head seal (350), in a direction that reinforces the effect of pressure at the end (309). The bias supplied by the spring (314) counters this effect of aircraft supply pressure. The net result of the forces on the piston (305) is that it can be biased into either of two positions. The aircraft oxygen supply pressure is communicated to the chamber (310), via a passage (311). A vent to atmosphere (348) ensures that there is no trapped pressure on the spring side (314) of the supply spool piston and so is free to move.
The spring and piston sizes are arranged such that when the aircraft oxygen supply is at a normal level, pressure biases the piston to be in the position shown in
When the aircraft oxygen supply level fails and drops to zero, or the connector (15) is disconnected, the spring biases the spool piston (305) to be in the second position seen in
The output selection valve supplies oxygen from the passage (304) to:
In
When the connector 15 is removed and the ambient pressure is lower than the threshold for 100% oxygen, and so supply to the demand valve needs to be maintained, it is necessary that the piston is kept in this position, even though the hand-wheel (318) is not there to push it.
This alternative mechanism to maintain position (A) is achieved by a pressure building up in the chamber (335), which acts on a seal (349) on the head (347) of the piston, sliding in a bore (337). When pressure at the output pressure of the regulator (207) is present in chamber (335), the piston (347) is held in the position shown in
Position (B) is achieved as follows: When pressure is not present in the chamber (335), the spring (352) moves the piston to the second position, as shown in
A vent to atmosphere (346) ensures that there is no trapped pressure on the spring side (347) of the output selection spool piston (326) and so the spool piston is free to move.
The pressure in chamber (335) is controlled as follows:
Gas from a connection from the regulator (207, not shown) communicates with a port (336). The pressure acts to push gas through a bleed restrictor (353) into a passage (338). The restrictor is set to give a low flow, arranged to be small in the context of the cylinder and expected duration e.g. in the region 10 ml/min.
Passage (338) communicates with a seat (339), which can be sealed or open according to the position of a seal (340) under the action of an aneroid (342).
In
The situation shown in
As the parachutist falls and the pressure around him increases, the aneroid (342) compresses in response to the ambient pressure increase. As the pressure increases above the threshold for 100% oxygen, the seal (340) moves away from the seat (339), and breaks the seal. The pressure in the chamber (335) and the passage (338) escapes, and exits through the vent (339), and the spring (334) urges the piston to position (A), as seen in
In
The aneroid (342) can be adjusted by the thread (343) of an adjusting screw (344), which is advantageously connected to the aneroid. The screw can be set such that the aneroid opens at a given pressure by holding it at the threshold pressure, monitoring the pressure in chamber (335), and adjusting the thread using a screwdriver in the slot (345). The setting can be checked by changing the pressure around the parts, and noting the pressure around the aneroid at which the pressure in chamber (335) collapses. The thread (343) can be locked by use of a suitable sealant.
This figure shows an embodiment of a mask assembly according to an aspect of the present invention, with its parts. Most are known so will not be described in detail, and, where necessary, additional detail is shown in subsequent figures.
A face-seal (401) made of a resilient material such as rubber is shaped to seal against the face of a user. A hard shell or exoskeleton (402) may be used on the outside of the rubber with a number of fastening features (403), which are used to attach a harness or similar to hold the mask to the face.
The mask and harness may be available in a number of sizes to seal to the faces of a variety of users.
The supply (4) to the demand valve (6) supplies oxygen according to the input and output selection manifold (211). The demand valve may be any of a number of types, able to provide oxygen to the user to meet their demand, for example that described in EP14168160.1 “Medical breathing apparatus”. It may be advantageous for the demand valve to provide a slightly positive pressure—i.e. slightly above atmospheric pressure so that if there are any leaks, they are out, and not in. Achieving positive pressure with a demand valve is known.
A connector (406) at the feed to the demand valve allows the same pressure that is feeding the demand valve to be fed via a tube (4a) to a combined inhalation and anti-suffocation valve (7) which is shown in more detail in
A tube (5) to the connection manifold (5a) joins the mask to the pulse delivery unit (212), such that the pressure in the mask at the onset of inhalation is communicated to the pulse delivery unit and flow from the pulse delivery unit is delivered into the mask. The connection manifold inside the mask directs the oxygen to the region of the mouth and nose of the user, so that as much of the pulse of oxygen as possible is inhaled with the initial inhalation. A conformable tube, i.e. one that is able to be bent to a shape, which is then maintained, may be provided inside the mask, connected to the inside of the connection manifold (5a) to help achieve this for difference face shapes and sizes.
An exhalation valve (404) allows exhalation. If the demand valve delivers negative pressure (i.e. when breathing from the demand valve, there is never a pressure higher than ambient inside the mask during inhalation), the exhalation valve would have to have an opening threshold above the range of positive pressure encountered, so that the demand valve did not leak gas out of the exhalation valve. This is known, and normally achieved by a sprung valve, or a resilient flap valve, arranged to be deflected at the point it is closed. Typically a housing around the exhalation valve directs the exhaled gas downwards through a “snood”, (405), which also helps to prevent icing of the exhalation valve in cold conditions, by shielding it from ambient air and protecting the heat transferred from the exhaled air. The direction downwards also helps to prevent misting of any goggles or visor the user may be wearing.
A housing (501), which is on the atmosphere side of the mask (9), receives the pressure connection (4a) communicating pressure to a piston (502) with a seal (503) operating in a bore (504) that urges the piston against a closing spring (505) to a closed position, where a resilient sealing member (506), mounted on the outside of the piston (507), is held closed against a seat (508) of a second housing (509).
A gap in the second housing (509) seals to the mask.
An inhalation valve (511), consisting of a disc (512) of resilient material, fixed in the middle with a fastener (513), and arranged to be deformed against an inhalation valve seat (514) in the closed position, such that the pressure in the mask has to be a little lower or negative compared to the ambient pressure. The level of the negative pressure for opening the inhalation valve (511) is arranged to be at a level such that the pulse delivery unit (212 in
This allows the user to inhale the remainder of their inhalation from ambient atmosphere, thus providing a pulsed oxygen supplement.
An inlet (601) in a housing (600) receives pressure from the hose (12 in
The regulator is a standard piston regulator which is well known, arranged to deliver a substantially constant pressure, typically 4 bar, which is about 1 bar, lower than that normally supplied by the aircraft oxygen supply.
When the pressure from the aircraft oxygen supply is in its normal range, the piston is held in an open position, and the regulator delivers normal 4 bar pressure to the hose (14 in
As the supply pressure from the aircraft oxygen supply falls, the pressure becomes insufficient to hold the piston (603) open against the closing spring (606), and the closing piston moves to a closed position, in which the seal (608) closes the inlet to the regulator (609).
The aim of this arrangement is to ensure that as soon as the aircraft oxygen supply pressure drops below a level suitable for operation, the supply to the cylinder valve manifold is cut off. At this point the pistons in the valve manifold as described in
It will be apparent to one skilled in the art that this embodiment of the invention provides an integration of 100% oxygen delivery via a demand valve and a pulsed oxygen delivery system in which a predetermined pulse of oxygen is delivered at the start of the inhalation cycle to supplement the oxygen in the ambient air. This alone leads to a remarkable improvement in the efficiency of oxygen delivery during a parachuting trip. In an alternative embodiment, the pulsed delivery system can be adapted to deliver a pulse of variable volume. The volume of oxygen in the pulse can be reduced as the parachutist descends, the pressure increases and the amount of oxygen drawn from the environment increases. This refinement represents, with increased conservation of oxygen, a still further improvement over the prior art.
It will be clear to one skilled in the art that the present invention provides a means to provide supplementary oxygen to a parachutist in a way that uses the oxygen more efficiently than prior art, allowing for a smaller cylinder or longer duration or a combination of both.
It will also be clear that all the parts of the system lend themselves to be designed to give very clear “digital” function, in which there are no functions that rely on very precise characteristics.
The present invention provides a system that may be fully automatic in its operation, so that the user has merely to turn on the cylinder valve (203) and connect and disconnect the aircraft oxygen supply. All other changes happen automatically, so the user can concentrate on their other tasks, increasing safety and effectiveness.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1508529.3 | May 2015 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2016/051422 | 5/17/2016 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2016/185201 | 11/24/2016 | WO | A |
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| 20180133523 A1 | May 2018 | US |
