Abstract:
A box for housing breathing masks in a passenger aircraft has a housing closed by a door and a pipe in the housing for delivering respiratory gas under a first pressure to the masks via a flexible line. In rest condition a catch holds the door in closed position. It may be disabled for providing access to the masks. A command, electrical or in the form of a second pneumatic pressure in the pipe, limits the opening of the box to a partially-open position preventing the masks from falling out upon release of the latch.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to boxes for housing breathing masks used on board aircraft in order to accommodate such masks and comprising a door which is opened in such a way that each mask drops down at the disposal of a passenger and is supplied with a breathable gas, generally oxygen, in the event of depressurization.  
           [0002]    For that, the boxes, each of which contains one or more masks, are normally kept closed by a catch. The catches of-all the boxes are simultaneously disarmed in an emergency by supplying the mask supply pipes at a pressure higher than a determined threshold or by sending an electrical command to them.  
           [0003]    The boxes have to be checked systematically on a regular basis. To do that, the box is opened manually by an operator who checks that a mask is stored and connected to the gas supply. During this operation, it often happens that a mask drops down and has to be put back, this being a tricky operation which takes time even though time is limited, especially when the operation is performed immediately before boarding.  
         SUMMARY OF THE INVENTION  
         [0004]    It is an object of he present invention to provide boxes that make checking easier. To this end there is provided a box, the catch of which is associated with means which are rendered active by command, for example in response to a second pneumatic pressure (lower than a first pressure which disarms the catches when the catches are disarmed by applying a pneumatic pressure to the mask supply pipe), or via an electrical route, the said means then limiting the opening of the box to a partially opened position which prevents the mask or masks from dropping out when the catch is subsequently disarmed.  
           [0005]    In an embodiment, said means consist of a plunger carried by the door, urged by return means into a position in which it is inactive and moved pneumatically into a position in which it cooperates with means carried by a housing of the box so as to limit the opening of the door when this plunger is moved by applying the second pressure. The door catch may be a simple magnet-ferromagnetic component assembly, the force of attraction of which is overcome by a push-rod when the latter is subjected to a breathable-gas pressure higher than a determined threshold.  
           [0006]    The invention also has a second aspect, which can advantageously be used with the first, but which may be used independently thereof, takes account of the fact that the oxygen supply available on board an aircraft is limited. Following depressurization at high altitude, the masks drop down, the passengers are permanently supplied as soon as they open the individual supply tap to the mask by pulling on a cord to which the mask is attached, and the crew begins a descent then generally cuts off the oxygen supply once the aircraft has returned to about 10,000 feet or 3000 meters.  
           [0007]    However, there is then the problem of maintaining an oxygen supply to those of the passengers who have not coped well with the depressurization or whose state of health so demands. The use of portable oxygen cylinders, which are bulky and heavy, provides only a rather unsatisfactory solution. Maintaining the supply by asking the cabin crew to shut off all the oxygen inlet taps of the masks other than those to which a supply needs to be maintained takes a great deal of time.  
           [0008]    The invention also sets out to provide a masks box and an emergency oxygen supply device to address the above difficulties. To this end there is provided a box comprising, in addition to the tubes supplying the masks receiving the oxygen through a valve that opens automatically in the event that a supply pressure at least equal to a first value pi is provided via an inlet pipe, an oxygen tapping equipped with a valve that opens automatically for as long as the pressure in the pipe exceeds a second value p 3 , less than p 1  and possibly less than p 2 . The pressures p 1  and p 3  may, for example, lie respectively between 3 and 4 bar and between 2 and 2.5 bar with respect to the pressure in the cabin. When the box is fitted with a catch allowing its opening to be limited, the pressure p 3  will be chosen to be lower than p 2 . The following levels are, for example, possible:  
           [0009]    p 1 : 350 kPa  
           [0010]    p 2 : 240 kPa  
           [0011]    p 3 : 200 kPa 
       
    
    
       [0012]    The above characteristics, together with others, will become better apparent from reading the description which follows of some particular embodiments which are given by way of non-limiting examples. The description refers to the accompanying drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a diagram intended to show how to implement the invention, in a particular case;  
         [0014]    [0014]FIG. 2 is an exploded view showing the essential components of a device for implementing a particular embodiment of the invention;  
         [0015]    [0015]FIG. 3 is an exploded overall view of the oxygen circuit in the box according to a variant of FIG. 2;  
         [0016]    [0016]FIG. 4 is a diagram showing one method of supplying an emergency tapping;  
         [0017]    [0017]FIG. 5 is a view in part section showing one possible construction of the emergency tapping and mask supply;  
         [0018]    [0018]FIG. 6 is a simplified sectional view showing yet another embodiment;  
         [0019]    [0019]FIG. 7, similar to FIG. 6, shows the same box in the partially open state;  
         [0020]    [0020]FIG. 8 is a depiction of yet another embodiment;and  
         [0021]    [0021]FIG. 9 is a simplified representation of an airplane oxygen distributing system according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0022]    The box, the catch system of which is shown diagrammatically in FIG. 1, comprises a housing or casing  10  which is closed, outside of periods of use or of inspection of the mask, by a lower door  12 . This door is articulated to the housing by means which have not been depicted. It may have a conventional overall construction or a construction in accordance with patent application FR 00/10676 to which reference can be made.  
         [0023]    A catch that keeps the door in the closed position consists of a magnet  14  mounted in the housing and of a component  16  made of ferromagnetic material, generally in the form of a washer, fixed to the door. The magnet  14  has a clearance in which it can move in the housing so that the door of an individual box can be opened manually using a tool such as a rod  18  introduced through a passage made in the door. This rod, projecting out of the door, allows the operator to push the magnet  14  back from its position shown in FIG. 1 and therefore to separate the magnet from the washer and open the door. In an alternative, the rod allows the door to be pulled. The magnet may then be fixed to the housing.  
         [0024]    To allow the invention to be implemented, the housing comprises means for limiting the opening. The means depicted comprise an opening-limiting tab  20  having an opening  22  which is oblong or ovalized in the direction of opening, the length of which sets the extent to which the door can be partially opened for checking purposes.  
         [0025]    Formed in the door is a chamber  24  in which the piston  28  of a plunger  26  slides. A spring  30  tends to hold the plunger in a position in which it is away from the tab  20 . The dimensions of the chamber are such that the plunger can advance as far as a position in which it enters the opening  22 .  
         [0026]    Also formed in the door is a chamber  31  that houses the piston of a push-rod  32  for pneumatically opening the door. This push-rod projects upwards from the door. A spring  33  urges it into a retracted position in which it is depicted in FIG. 1. In that state, the push-rod exerts no force on the housing.  
         [0027]    The bottom of the chamber  31  and the piston define a compartment connected to an oxygen supply pipe  34  intended also to supply the breathing masks. A control unit  36  allows the pipe  34  and therefore the chambers  31  of all the boxes to be connected either to the atmosphere or to a pressure p 2  that arms the plungers  26 , or to a pressure p 1 , higher than p 2 , for opening the boxes and supplying taps connected to the individual flexible tubes coupled to the masks.  
         [0028]    The chamber  31  is connected to the chamber  24  by a calibrated hole  38  intended to slow the rise in the pressure in the chamber  24  by comparison with the rise in the chamber  31  and therefore to produce a time delay when the chamber  31  is supplied. A vent  40  plugged by a bleed screw  42  allows the chamber  24  to be connected to the atmosphere and the plunger to be retracted.  
         [0029]    Normal operation of the box is conventional. When all the boxes have to be opened, in an emergency, the supply unit is commanded so that it provides all the chambers with a pressure at least equal to p 1  and greater than p 2  which is generally between 2 and 2.5 bar. The pressure in the chambers  31  rises far more quickly than the pressure in the chambers  24 , as a result of the time delay, and reaches a value such that the push-rods  32  exert on the housing, a force which causes the doors to open before the plungers  26  have entered the ovalized openings of the tabs. The doors open completely and the masks, generally supported by the doors, drop down.  
         [0030]    When, on the other hand, the doors have to be partially opened to inspect the masks, the opening operation is performed in three stages.  
         [0031]    In a first stage, the chambers are supplied at a pressure at least equal to p 2  but less than p 1 . In general, p 2  will be between 2 and 2.5 bar when p 1  is between 3 and 4 bar. This pressure p 2  and the characteristics of the return spring  33  are chosen such that the push-rod  32  exerts no force for opening the door.  
         [0032]    The calibrated hole is provided so that the pressure in the chamber  24  needed to engage the push-rod  26  in the opening  22  is reached after a time t 1 , generally about ten seconds. For example, it will be possible to adopt a supply at 2 bar for a duration of 15 seconds for p 1 =3 bar.  
         [0033]    At the end of the time t 1 , the supply pressure is increased to the value p 1 . The push-rod  32  rises and causes the door to open. The time of a few seconds, for example 4 seconds, is generally enough to open the door partially to the extent allowed by the size of the opening  22 .  
         [0034]    During the third stage, which is the one during which the checking takes place, the supply can be brought back down to the value p 2  for maintaining the plunger  26 ; the push-rod  32  retracts and the box remains partially open.  
         [0035]    It remains possible for each box to be fully opened at any time. When the door is simply partially opened, all that is required is for the screw  42  to be unscrewed. Only the box whose screw has been unscrewed will open completely, because the corresponding plunger  26  retracts. It is also possible to bring about full opening of a particular box by unscrewing the bleed screw before beginning the opening sequence.  
         [0036]    The embodiment shown in FIG. 1 constitutes just one example. The various constituents of the catch, of the pushing mechanism and of the opening-limiting mechanism may be arranged differently from those described. In particular, the arrangement may be reversed, it being possible for some of the elements indicated in FIG. 1 as belonging to the door to be transferred to the housing, and vice versa.  
         [0037]    In the embodiment shown in FIG. 2, the door consists of a flat panel to which is fixed a body  44  in which the chambers  31  and  24  are formed. The return spring  33  that returns the push-rod  32  is kept in compression by a washer  46  fixed to the body by means which have not been depicted. The return spring  30  of the plunger  26  is itself kept in compression by a clip  48 .  
         [0038]    [0038]FIG. 3 shows part of a pneumatic circuit implementing a variant of FIG. 2. The corresponding elements in the two figures are denoted by the same reference numeral. The body  44  is fixed to a distributor unit  52  allowing five masks to be supplied via a valve which is calibrated to open at the pressure p 1  and each individually via a tap which is opened by pulling out a pin  50  when the passenger pulls on the cord of his mask. The means for limiting the opening have not been depicted.  
         [0039]    According to another aspect of the invention, shown schematically in FIG. 4, the box comprises, in addition to the mask supply tappings, an oxygen tapping equipped with a mechanically opening valve which opens when a therapeutic mask is connected. In the case illustrated, the master oxygen supply pipe  34  is still connected in each box to the pneumatic command that disarms the catch and holds the door of the box and to a directional-control value  52 . Unlocking is commanded by applying a pressure exceeding p 1 , from the unit  36  that operates the oxygen supply. The flexible tubes  56  supplying the masks  57 , each fitted with a restrictor  58  that limits the flow, are supplied via a valve  60  which is calibrated to remain open only when the supply pressure reaches at least the threshold value of p 1 .  
         [0040]    The assistance tapping  62  (which may be provided so that it is accessible without opening the box) is supplied by the pipe  34  through a valve  64  which remains open as long as the mask remains connected. Thus, the arrival of oxygen at the emergency breathing masks can be shut off as soon as the aircraft has dropped back down to a safe altitude, maintaining the supply to the first aid tappings. All that is required for that is for the relative pressure with respect to the cabin to be reduced to a value at least equal to p 3  but less than p 1  (and then p 2  if a command for partially opening is provided, as indicated in dashed line in FIG. 4). When p 2  is between 2 and 2.5 bar, a value of between 1.5 and 2 bar, depending on the value of p 2 , can be used.  
         [0041]    The supply to the master pipe  34  is then cut off when it is no longer needed. The construction of the valve  64  may be the one depicted schematically in FIG. 5 which also shows a directional control valve making it possible to supply five masks and comprises a tapping with mechanical opening of the outlet valve when a first-aid mask is connected.  
         [0042]    The box, the catch system of which is shown schematically in FIG. 6, in which the components corresponding to those of the previous figures are denoted by the same reference numerals, also comprises a housing  10  and a door  12 . The housing is in actual fact made of several assembled parts. A catch for holding the door consists of one or more beads  66  trapped in radial passages  68  of a sheath  70 . When the door is closed, the beads are held in the position in which they hold the door  12  by a push-rod  72  that is kept in a lowered position by its weight (FIG. 6).  
         [0043]    To open the door, a coil  73  carried by the housing is powered from a source, not depicted. It then attracts the push-rod from the position shown in FIG. 6 to the position of FIG. 7. This upwards movement of the push-rod brings a bulge  74  of the push-rod over the location of the beads. These then return inwards under the pressure of a flared wall  76  of an opening in the door. The door is released and can drop down. At the same time, a dish  78  sliding in a bore of the housing is brought by a spring  80  into a position in which it keeps the beads in an internal position. Because the beads  66  are thus being held by the dish, it is possible to close the door again simply by pushing it upwards.  
         [0044]    The means for limiting the opening of the box which are shown in FIGS. 6 and 7 comprise a plunger  82  fixed to the door and an electromagnet  84  mounted to float in a cavity of the housing. When the box is closed, the door  12  keeps the plunger  82  in the position shown in FIG. 6.  
         [0045]    When the desire is simply to open the door partially, the electromagnet  84  and the coil  73  are both powered. The electromagnet  84  therefore holds the plunger  82  which cannot move beyond the position shown in FIG. 7 because it remains stuck to the electromagnet  84 , itself retained by a rim  86  of the cavity. Unlocking of the door then causes the latter to move into the position shown in FIG. 7.  
         [0046]    When, on the other hand, the desire is to open the box completely in order to release the masks, just the coil  73  is powered. The door  12  and the plunger  82  can then move beyond the position of FIG. 7.  
         [0047]    As shown by FIG. 6, the push-rod projects under the door when the box is closed which means that it is possible to unlock the box and to open it simply by pressing on the projecting portion using a tool.  
         [0048]    In the embodiment variant shown in FIG. 8, the door retaining catch has the same construction as in FIG. 6. The means for limiting opening consist of a plunger  87  which is active when it occupies the position shown in solid line in the figure, in which it enters an opening  22  formed in an angle bracket tab of the door  12 . This plunger is urged by a spring  88  into a retracted position (in dashed line) in which it releases the door. A coil  90  brings the plunger  87 , when this coil is powered, into the position in which it limits the opening of the door to the position shown in FIG. 8.  
         [0049]    By powering both coils at once when the door is closed, it can be made to open partially. Powering the coil  73  alone makes it possible to bring about complete opening.  
         [0050]    In yet another modified embodiment, the two coils are powered by the same wires, but bringing the plunger  74  into the retracted position merely demands a supply current lower than a determined threshold below which the plunger  87  remains retracted.  
         [0051]    The embodiments shown in FIGS.  6  to  8  are of particular benefit when the masks are supplied not by an on-board oxygen network that can be supplied at adjustable pressure, but by chemical generators.  
         [0052]    Referring to FIG. 9, the control unit of an oxygen system comprises a command panel  92  and a distribution unit  94 . The command panel carries a rotating knob having four positions controlling the following functions:  
         [0053]    OFF: boxes closed  
         [0054]    AUTO: boxes are automatically fully opened upon occurrence of depressurisation  
         [0055]    DEPLOY; boxes are fully opened when the knob is put into that position  
         [0056]    LATCH: boxes are partially opened when the knob is turned into that position starting from OFF.  
         [0057]    The command panel delivers electrical signals to the distribution unit for achieving different sequences of operation.  
         [0058]    Responsive to the knob being moved to AUTO by a pilot or maintainance people, the distribution unit applies oxygen pressures p 2  and p 1  to the pipe  98  feeding the mask boxes, in proper time succession.  
         [0059]    When the knob is on AUTO, depressurisation sensed by a sensor (not shown) causes delivery of oxygen originating from the pressure reducer  100  of an oxygen bottle to the mask boxes and also to the oxygen masks  102  for the crew members, stored in the cockpit. The pressure p 1  may be adjusted depending on the actual pressure prevailing in the cabin after the boxes have opened. It is typically reduced by distribution unit  96  when the altitude of the aircraft has decreased upon action by the pilot.  
         [0060]    When the knob is moved to DEPLOY, the same steps as above occur whatever the cabin pressure.  
         [0061]    In the embodiment of FIG. 9, the first aid connectors are fed via a separate line  106  upon actuation of a push button  108  rather than via the common line  98 . However a modification of the system for delivery of oxygen to the common pipe at pressure p 3  is possible as well.