GB2329006A

GB2329006A - Venting valve for a rapid pressure drop

Info

Publication number: GB2329006A
Application number: GB9819162A
Authority: GB
Inventors: Ruediger Meckes
Original assignee: Draeger Aerospace GmbH
Current assignee: BE Aerospace Systems GmbH
Priority date: 1997-09-06
Filing date: 1998-09-02
Publication date: 1999-03-10
Anticipated expiration: 2018-09-02
Also published as: GB9819162D0; GB2329006B; DE19739161C1

Abstract

A ventilation valve which is mounted on a pipe line 1 for conveying breathing gas in an aeroplane comprises a closure member 13 which is mounted on a diaphragm 6 provided between chamber 8 which directly communicates with the surroundings and chamber 9 which only communicates with the surroundings via a delay mechanism 4,5. The closure is biassed closed 7 and the delay mechanism is preferably a nozzle 5 and filter 4. In operation sudden pressure loss in chamber 8 causes the valve 13 to open and vent the contents of the pipe line 1. Venting can occur through an adjustable pressure relief valve 30.

Description

2329006 Ventilation valve for rapid pressure drop is The invention relates

to a ventilation valve, particularly for installation in air-conditioned aircraft cabins.

The invention is particularly suitable for ventilating pipe lines conveying breathing gas, and containers, to a specific settable pressure during a sudden drop in pressure in an aircraft cabin.

This is to ensure that the aircraft crew immediately gets pure oxygen for breathing from the moment that the sudden drop in pressure occurs.

Normally, modern jet aircraft are equipped with molecular sieves for the continuous generation of oxygen during the flight, which frequently is at high.

altitudes. As soon as there is a sudden drop in pressure in the aircraft cabin it is absolutely essential to provide pure oxygen from a corresponding oxygen container as breathing gas to the aircrew. This is necessary in order to avoid symptoms of altitude sickness which may occur as a result of the fact that the breathing gas supplied from the molecular sieves has less than 100t oxygen.

According to the invention there is provided a valve comprising: an aperture-closing member movable between a first position in which it can close an aperture in a gas pipe to prevent venting of gas in the gas pipe to the surroundings and a second position in which it can permit such venting; a first chamber directly open to the surroundings; a second chamber connected to the surroundings in a manner such that the gas in the second chamber slowly equilibrates with the surroundings; a movable member between the first and second chambers and operably connected to the aperture closing member; a resilient bias means urging the first movable member in the direction from the first towards the second chamber so as to urge the aperture-closing member into its aperture closing first position, wherein the movable member moves towards the first chamber against the action of the resilient bias means, when the rate of depressurisation of the surroundings in such that the pressure difference between the first and second chambers exceeds a predetermined value, so that the aperture-closing member can move to its second position and allow gas to vent to the surroundings.

The invention provides a simply constructed, but very effective, ventilation valve which makes possible the controlled emission to the surroundings of a gas at over-pressure. The invention allows for molecular sieve gas, still present in a gas pipe line conveying breathing gas after switching, to be vented into the surroundings quickly and in a controlled manner, so that the remaining amount of residual gas is minimal.

A significant advantage of the invention is that the valve of the invention can be installed or retrofitted, even into existing breathing gas supply lines, due to its compact construction, with minimum expense.

Specific embodiments of the invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:- Figure 1 shows a ventilation valve according to a first embodiment of the invention in section, and Figure 2 shows a ventilation valve according to a second embodiment of the invention in section.

The ventilation valve of the first embodiment of the invention shown schematically in Figure 1 is provided for installation in the airconditioned aircraft cabin area and is used to depressurise a gas pipe line 1 conveying breathing gas, when oxygen is supplied to an aircraft crew, in order to make possible the controlled venting of a breathing gas mixture which is still present in a pipe line 1 but which contains too little oxygen. In the case of a rapid drop in pressure in the aircraft cabin, a correspondingly large pressure change also occurs in the first chamber 8 which is open to the cabin but more slowly in the second chamber 9 because the pressure in the second chamber is only slowly reduced via a leakage flow via a nozzle 5 and a filter 4. This results in a large pressure difference across the movable member 6 in the form of a diaphragm 6 between first and second chambers 8, 9. The pressure difference generates a force tending to lift the diaphragm 6 and its finger (or valve tappet) 10 against the action of a resilient bias means constituted by a spring 7 and away from member 13 closing an aperture in the gas pipe line. The spring 7 is characterised so that when there are maximum supply pressures in the pipe line the aperture closing member 13 remains in a first position, in normal operation, in which the aperture is closed. The volume of the second chamber 9, the nozzle 5 and the filter 4 are designed so that the time constant achieved ensures the reliable ventilation of the installation in the required time. In addition, with maximum rate of climb of the aircraft, i.e. maximum drop in pressure per time unit, in interference-free operation, i.e. without a sudden drop in pressure in the aircraft cabin, the ventilation valve should remain closed. The diaphragm area of the diaphragm 6 is selected so that when the pressure difference across the diaphragm 6-exceeds the predetermined value the finger 10 moves counter to the spring force of the spring 7 and lifts off the aperture closing member 13. 35 The seal 3 is provided so that the gas pressure from the second chamber 9 cannot escape into the area is of a third chamber 11 which is open to the atmosphere in the cabin. The cabin pressure spreads through the aperture 2 into the third chamber 11.

After the finger 10 has been lifted, the aperture closing member 13 is no longer held shut by the f inger 10 and moved to an open second position if the force exerted on the aperture closing member 13 by the pressure difference across the main valve 13 is greater than the force exerted by the valve spring 12 (a further resilient bias means).

Through the selection of the spring, in particular as regards material, dimension and shape, minimal supply pressures can be set up in the pipe line 1, whereby reliable venting is possible when there is a predetermined rapid drop in pressure in the cabin.

The gas content from the pipe line 1 can escape, as long as the finger 10 is lifted, until a specific desired pressure is achieved in the pipe line 1. After this occurs, the aperture closing member 13 is moved back to its first positions by the action of the valve spring 12. Later, the finger 10 moves downwards at a rate that depends on its time constants and retains the aperture closing member 13 in its closed first position.

Figure 2 shows a second embodiment of the ventilation valve of the invention. In this embodiment, the supply pressure in the pipe line 1 actively helps the closure of the aperture closing member 13. This means that there is no loss of pressure if the spring 7 breaks.

with a sudden drop in pressure in the aircraft cabin, and hence also in the first chamber 8, a large pressure difference occurs across the diaphragm 6 because in the second chamber 9 on the other side of the diaphragm the pressure before the sudden drop in pressure is only slowly reduced by a leakage flow through a nozzle 5 and filter 4.

The volume of the second chamber 9, the nozzle 5 and the filter 4 are designed so that the time constant thus achieved ensures the reliable ventilation of the pipe line 1 and/or the installation connected with it. Furthermore, with a maximum aircraft climb rate, i.e. maximum pressure drop per time unit, in interferencefree operation without sudden pressure drop, the ventilation valve should remain closed.

In this embodiment the finger 10 is integrally formed with the aperture closing member 13. The pressure difference across the diaphragm 6 generates a force, against the spring 7, which causes the aperture closing member 13 to move from its closed first position to an open second position. The spring 7 is selected so that during pressure equalisation between the third chamber 11 and the pipe line 1 the aperture closing member 13 securely closes the aperture in the pipe line against aerodynamic and mechanical resistances. When the aperture-closing member 13 is in its open second position the gas flows out of the pipe line 1 into the third chamber 11 and, when the pressure is greater than the minimum pressure set by the pressure relief valve 30, can flow away via the pressure relief valve 30 into the surroundings (e.g. the cabin).

The advantage of this second embodiment of the invention is that adjustment of the pressure relief valve 30 after installation is very easy, preferably using an adjustment screw 50 with a pressure relief valve spring 40 (a further resilient bias means).

The spring 7 and the size and shape of the pressure relief valve 30 are selected so that on the one hand the required pressures, and on the other hand the mass throughputs necessary for a desired ventilation are achieved.

The gas content from the pipe line 1 can escape when the aperture closing member 13 is open until a specific gas pressure is achieved in the pipe line 1. The pressure relief valve 30 then closes the path into the surroundings. Depending on its time constants, the aperture closing member 13 then moves upwards, helped by the spring 7, and closes the pipe line 1.

Claims

1. A valve comprising: an aperture-closing member movable between a first position in which it can close an aperture in a gas pipe to prevent venting of gas in the gas pipe to the surroundings and a second position in which it can permit such venting; a first chamber directly open to the surroundings; a second chamber connected to the surroundings in a manner such that the gas in the second chamber slowly equilibrates with the surroundings; a movable member between the first and second chambers and operably connected to the aperture-closing member; a resilient bias means urging the first movable member in the direction from the first towards the second chamber so as to urge the aperture-closing member into its aperture closing first position, wherein the movable member moves towards the first chamber against the action of the resilient bias means, when the rate of depressurisation of the surroundings in such that the pressure difference between the first and second chambers exceeds a predetermined value, so that the aperture-closing member can move to its second position and allow gas to vent to the surroundings.

2. A valve apparatus according to claim 1 further comprising a further resilient bias means acting against a pressure relief valve in the gas path from the aperture-closing member to the surroundings, the pressure relief valve closing the gas path unless the movable member is moved towards the second position and the pressure difference exceeds another predetermined value.

is

3. A valve apparatus according to claim 2, wherein the pressure relief valve is constituted by the aperture-closing member, and a finger is provided on the movable member to transmit the force of the resilient bias means to urge the aperture-closing member shut so as to operably connect the movable member to the aperture-closing member.

4. A valve apparatus according to claim 2, wherein the aperture closing member is integrally formed with the movable member.

5. A valve apparatus according to claim 4, wherein the pressure relief member and the further resilient bias means constitute an adjustable pressure relief means, which is separated from the aperture closing member by a third chamber.

6. A valve apparatus according to claim 5, wherein the further resilient bias means comprises an adjustment screw acting on a bias spring.

7. A valve apparatus according to any preceding claim in which a filter is provided in the path from the second chamber to the surroundings.

8. A valve apparatus according to any preceding claim, wherein the movable member comprises a diaphragm.

9. A valve apparatus substantially as hereinbefore described with reference to and as shown in Fig. 1 or 2 of the accompanying drawings.

10. Use of a valve apparatus according to any preceding claim for rapidly venting a breathing gas pipe line when the pressure in the surroundings rapidly decreases.