Abstract:
A compact, lightweight latch ( 38 ) especially adapted for use with an emergency deployment oxygen mask container ( 20 ) is provided which is made up of a minimum of parts and which can be delatched in multiple ways. The latch ( 38 ) includes a latch assembly ( 40 ) designed to be mounted in the oxygen mask container box ( 22 ) and a cooperating latch pin ( 44 ) secured to a cover ( 24 ). The assembly ( 40 ) has a primary latch body ( 46 ) supporting a diaphragm ( 48 ), latch member ( 50 ) and shiftable piston ( 52 ); the latch member ( 50 ) includes a plurality of laterally displaceable, hook-shaped locking legs ( 86 ) configured to interfit with latch pin ( 44 ). The piston ( 52 ) is shiftable in opposite axial directions within latch member ( 52 ), and cooperating surfaces on the member ( 50 ) and piston ( 52 ) serve to positively displace the latching legs ( 86 ) in response to piston movement. During pneumatic operation, the piston ( 52 ) is shifted within latch member ( 50 ) under the influence of diaphragm ( 48 ). The latching member ( 50 ), piston ( 52 ) and latch pin ( 44 ) are preferably in substantial axial alignment, and a passageway ( 116 ) in the latch pin ( 44 ) allows use of push or pull rods ( 126, 128 ) for manual delatching.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with an improved latch mechanism of simple, compact, lightweight construction using only a minimum of parts, and which is especially designed for use with emergency deployment oxygen mask containers used in passenger aircraft. More particularly, the invention pertains to such a latch mechanism which includes cooperating, substantially axially aligned components including displaceable latch elements and an operating piston shiftable in opposite directions relative to the latch elements; the piston includes structure for positively displacing the latching elements upon piston movement in either axial direction. 
     2. Description of the Prior Art 
     A number of latch mechanism designs have been proposed for use in emergency deployment oxygen mask containers situated above or adjacent passenger seats and in other locations such as lavatories in aircraft. Such mechanisms must meet a number of rather stringent requirements. First and foremost, the latch mechanisms must operate essentially flawlessly in the event of a cabin depressurization or other incident where supplemental passenger oxygen is required. At the same time, size and weight are sometimes controlling considerations in aircraft design, and therefore the container latch mechanisms must be compact and lightweight. 
     A common type of latch mechanism used in this context is a pneumatic latch having a clip and an actuator, where a latch pin is squeezed into the clip and is released when enough upward force is applied to the latch pin. This mechanism relies upon the balance of force between the clip tension and the upward force on the pin. One disadvantage of this design is that the force of the door on the pin affects the force required to open the latch, and since that force is dependent on how tightly the container is packed, the opening force is inconsistent. Further, the metal clip is likely to fatigue over time, causing it to be less able to restrain the pin. Therefore, the tolerance of opening force for the latch needs to be large to account for this variability. This latch design also requires a rather large number of parts, making it heavier and more costly to produce and repair. Finally, only two operating methods can be used with this mechanism, and thus simplified deployment testing is not possible. 
     Another common latch mechanism employs a complicated assembly in which a short hollow column attached to the container cover door is pushed over the top of a locking mechanism where friction against two protruding balls holds the column in place. When this mechanism is actuated, a plunger core with variable thickness moves to allow the restraining balls to retract and thus no longer make contact with the locking column. The complexity of this design, with five moving parts, makes it costly to manufacture and repair. This mechanism is also relatively heavy and tall, and would not be usable in new short-height container designs. Again, there are only two opening methods with this design, pressurization and thin rod insertion. In the latter case, the design is deficient in that if the rod is inserted at an angle, it can miss the plunger altogether and/or damage the assembly. 
     Electrically actuated latch mechanisms have also been proposed. In one design, three jaws are locked around a latch pin. In operation, a plunger releases the jaws, with the plunger being activated by a lever controlled by a solenoid. However, this unit is relatively heavy and has only two opening methods. Another electrical design exists in which a locking ball mechanism/latch pin is employed to keep the container cover closed. This unit includes over thirty parts (including five springs), and is thus large and heavy. Latch release is indirect: a solenoid drives a spring loaded cam and shaft which pushes another spring-loaded piston back to release the three balls locking the latch pin. A manual release button associated with this unit requires a separate mechanism which also works indirectly. Another mechanism of this general type uses the same dual shaft principle to indirectly move a piston. In this design, a hook end of a lever grabs the cover and keeps it closed; if the lever is rotated, the hook releases the door. While this design does have certain advantages, it is still a parts intensive mechanism of relatively large size. 
     There is accordingly a real and unsatisfied need in the art for a latch mechanism usable in emergency deployment oxygen containers which is compact, lightweight, and easy to assemble using only a minimum of parts, and wherein the latch mechanism can be opened by a variety of methods. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems outlined above and provides a latch mechanism for releasably latching two components together. The mechanism includes a latch assembly adapted for mounting on one of the components and has a latch member with at least one latch element displaceable between a latching position and a release position, together with a piston shiftable in opposite directions relative to the latch member. The overall mechanism also has a latch pin adapted for mounting on the other of the components and normally interfitted with the displaceable latch element for releasably latching the two components together. In preferred forms, the latch member, piston and latch pin are substantially coaxially aligned, and the piston includes structure oriented to positively displace the latch element from its latching to its release position during shifting of the piston in either of its movement directions. 
     Preferably, the latch member is of elongated, tubular design and includes a plurality of latch elements in the form of elongated, laterally displaceable latching legs each equipped with a hook-shaped end engageable with the latch pin. Similarly, the piston has a plurality of elongated slots with each of the legs received within a corresponding slot. The piston and displaceable legs have cooperating surfaces so that, upon movement of the piston in either axial direction, the latching legs are displaced laterally so as to effect delatching. 
     The latch mechanism is normally operated pneumatically, although in alternative designs, various operating mechanisms can be adopted. These would include electrical, mechanical, electromagnetic or chemical means for shifting of the mechanism piston. Hence, the preferred pneumatic/diaphragm operating mechanism could readily be replaced by a number of other operationally equivalent systems such as a solenoid mechanism. Further, the design permits a number of other opening methods, such as by pushing or pulling the piston by appropriate rod manipulations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of an oxygen mask container assembly in accordance with the invention, illustrated with the container door opened and prior to deployment of the oxygen masks; 
     FIG. 2 is an exploded view of the door latch mechanism, depicting the parts thereof, 
     FIG. 3 is a bottom view of the latch mechanism, without the latch pin; 
     FIG. 4 is a side elevational view of the latch mechanism without the latch pin; 
     FIG. 5 is secctional view taken along line  5 — 5  of FIG. 3; 
     FIG. 6 is a sectional view taken along line  6 — 6  of FIG. 3; 
     FIG. 7 is a fragmentary vertical sectional view depicting the oxygen mask container assembly and the associated latch mechanism, with the latter illustrated in its latched position; 
     FIG. 8 is a fragmentary vertical sectional view similar to that of FIG. 7, but illustrating the latch mechanism during pneumatic opening of the latch mechanism; 
     FIG. 9 is a fragmentary vertical sectional view similar to that of FIG. 7, but depicting manual opening of the latch mechanism through use of a rod; and 
     FIG. 10 is a fragmentary vertical sectional view similar to that of FIG. 7, but showing operation of the latch mechanism by a threaded rod screwed into the piston insert. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, and particularly FIG. 1, an emergency deployment oxygen mask container  20  is illustrated. The container  20  is in the form of a rectangular box  22  having a cover  24  secured to the box  22  by means of a pair of flexible lanyards  26 . The box  22  contains a plurality (here two) of deployable oxygen masks  28  normally retained therein but which can be readily removed when cover  24  is opened; for example, when the container  20  is mounted in overhead position above passenger seats, the masks  28  will fall under the influence of gravity to a convenient use position. As is well known to those skilled in the art, the masks  28  are designed for emergency use by aircraft passengers and are coupled to a source of oxygen through nipple  32  and appropriate pneumatic lines  34 . Oxygen may be delivered to the masks  28  from a central source or from chemical oxygen generators situated adjacent the container  20 . The containers  20  can be connected to each other in parallel or in series depending upon the aircraft configuration and design, using larger hoses that connect to each container via nipple  32 . 
     The cover  24  is normally retained in covering relationship to the box  22  by means of pivots  36  and a pneumatically operated latch mechanism  38 . In an emergency situation such as a cabin depressurization, the latch  38  is pneumatically actuated and the cover  24  drops downwardly as shown in FIG. 1, although retained by the lanyards  26 . This permits passenger access to the masks  28 , which may be through a gravity drop or by pulling on an access cord (not shown). 
     The present invention is particularly concerned with the latch  38 , which broadly comprises a latch assembly  40  adapted for mounting within the box  22  and specifically to the top wall  42  thereof (see FIG.  7 ), as well as a latch pin  44  designed for mounting on cover  24 . As indicated above, the latch  38  is preferably pneumatically operated, although other modes of operation, e.g., by a solenoid, could also be used. 
     The latch assembly  40  is made up of a latch body  46 , diaphragm  48 , latch member  50 , piston  52  and retaining ring  54 . These parts are shown in exploded relation in FIG. 2, and in assembled relation in FIGS. 3-10. 
     Latch body  46  is in the form of a synthetic resin body presenting a central diaphragm chamber  56  including a top wall  57  and a depending sidewall  57   a , a pair of tubular, pressurized oxygen passageways  58 ,  60  and a series of mounting lugs  62  each having a threaded, screw-receiving opening  64  therein. As best seen in FIG. 8, the passageways  58 - 60  communicate with chamber  56  via openings  66 ,  68  provided in the sidewall  57   a  of chamber  56 . The lower end of sidewall  57   a  as viewed in FIGS. 2 and 5, is provided with a circular diaphragm-receiving groove  70 . Pneumatic connection fittings  72 ,  74  are slidably received within the passageways  58 ,  60 , so as to permit connection of the latch  38  to a source of activating oxygen, and to a serially connected downstream latch provided in another container  20 . 
     The diaphragm  48  is a circular, integral resilient member having an outermost flange  76  and a central section  78 . Referring to FIG. 5, it will be observed that the flange  76  includes an upstanding annular securement rib  80  which is received within groove  70 ; also, the diaphragm  48  is sufficiently large to permit flexure thereof within the chamber  56 . 
     The latch member  50  is a generally tubular, synthetic resin integral member having an uppermost ring  82  supporting a total of four circumferentially spaced, depending ribs  84  along with four depending locking legs  86  located between each pair of ribs  84 . In more detail, each of the ribs  84  (see FIG. 6) extends downwardly from ring  82  and terminates with an inwardly extending projection  88  presenting an inboard, arcuate face. The legs  86  are somewhat longer than the adjacent ribs  84 , and terminate at their lower ends with hook-shaped, inwardly extending locking sections  90  having lowermost oblique surfaces  90   a  (see FIG.  5 ). Each of the legs  86  also presents an oblique, upwardly facing surface  91 . The legs  86  are laterally displaceable for purposes to be made clear. 
     The piston  52  is slidable within latch member  50  and includes an uppermost, circular in cross-section block  92 , a depending annular wall  94  and an annular lowermost foot  96 . Block  92  presents a central, circular opening  93 , and is equipped with a metallic, internally threaded insert  93   a . In addition, the block  92  presents a lower, oblique, inwardly extending operating wall  92   a  which is positioned adjacent the surfaces  91  of the locking legs  86 . As best seen in FIG. 2, the wall  94  has a total of four axially extending, circumferentially spaced slots  98  therein which are adapted to receive the respective locking legs  86  of latch member  50 . Additionally, the piston is provided with a total of four outwardly extending slide blocks  100  forming a part of the wall  94  and adjacent block  92 ; it will be observed that the slide blocks  100  are oriented between the spaced slots  98 . The foot  96  presents a flattened lower surface  102  as well as an opposed, annular oblique upper operating surface  104 . 
     The retaining ring  54  is likewise formed of aluminum and presents a stepped configuration in cross-section. This includes a main body  106  as well as an upstanding locking projection  108 . 
     The latch assembly  40  is assembled as best illustrated in FIG.  5 . That is, the diaphragm  48  is situated within chamber  56  with the securement rib  80  located within groove  70 , and with the remainder of the flange  76  loosely positioned so as to permit up and down movement of the central section  78  of the diaphragm. The latch member  50  is in abutment with the lower surface of the diaphragm flange, with the ring  82  serving to maintain the flange and securement rib in place. The piston  52  is located within the confines of latch member  50 , with the rib projections  88  engaging the outer surface of piston wall  94  between the slots  98 , and with the locking legs  86  situated within the slots  98 . Note that in this position the surface  92   a  of piston block  92  is in face to face proximity with the surfaces  91  of the locking legs. Note also that the locking leg surfaces  90   a  are in close adjacency with the upper operating surface  104  of the foot  92  of piston  52 . Finally, the retaining ring  54  is employed to secure all of the latch assembly components together, i.e., the upper projection  108  thereof is press fitted into the annular space between piston wall  94  and the depending wall  57   a  of chamber  56 . 
     The latch pin  44  comprises an upright, annular aluminum body  110  presenting a lowermost securement flange  112  and an uppermost locking flange  114 . A central passageway  116  is provided through the body  110  as shown. 
     In use, the latch assembly  40  is secured to wall  42  of box  22  by means of screws  118  extending into the threaded openings  64  of the lugs  62 . Typically, annular resilient spacers  120  are provided about the shank of each screw  118  to engage the underside of wall  42  and the upper surface of chamber  56 . The latch pin  44  is mounted on cover  24  within an appropriately sized opening  122  sized to accommodate the flange  112 . The latch assembly  40  and latch pin  44  are strategically located so that when cover  24  is in its closed position covering box  22 , the latch pin  44  interfits with the latch assembly  40 . In this orientation (see FIG.  7 ), the latch member  50 , piston  52  and latch pin  44  are in substantial axial alignment. Moreover, the hook sections  90  of the locking legs  86  engage the underside of locking flange  114  so as to securely hold the cover  24  in place. 
     As indicated, FIG. 7 illustrates the overall latch  38  in its normal position closing the box  22  with cover  24 . There are a number of ways in which the latch  38  may be operated so as to cause cover  24  to open the box  22  and assume the position of FIG.  1 . Turning first to FIG. 8, an operational sequence is depicted wherein a source of pressurized oxygen is delivered via passageway  58  for delatching purposes. When this occurs, air pressure is generated within chamber  58  above diaphragm  48 , so as to push the diaphragm downwardly, as illustrated by arrow  124 ; this also shifts piston  52  downwardly. As this occurs, the piston surface  92   a  comes into contact with the adjacent locking leg surfaces  91  thereby laterally deflecting the legs  86  outwardly so that the hook-shaped sections  90  move out of interengagement with flange  114  of latch pin  44 . At the same time, because of the downward movement of the piston  52 , the lower surface  102  of foot  96  comes into engagement with the inner surface of cover  24 . This creates a positive displacement force serving to positively move the cover  24  out of its closed position. Hence, the cover  24  is free to drop downwardly to its FIG. 1 position. 
     Another method of actuating latch  38  is shown in FIG.  9 . In this instance, a pin  126  is inserted through passageway  116  of latch pin  44  and into the piston block insert  93   a . Application of such an upwardly directed force serves to move the piston upwardly. When this happens, the upper foot operating surface  104  comes into engagement with the oblique lowermost surfaces  90   a  of the locking legs  86 . As a consequence, the legs  86  are deflected laterally outwardly, to again delatch the latching pin  44 . The cover  24  is then free to move downwardly to its open position. 
     FIG. 10 depicts a still further method of operating the latch  38 . In this instance, a threaded rod  128  is extended upwardly through the passageway  116  and is threaded into piston block insert  93   a . When it is desired to open the latch  38 , the user need only pull downwardly on the rod  128  (which may be conveniently equipped with a grasping hook or the like) to thereby move the piston  52  downwardly. As will be readily appreciated, such downward movement of the piston  52  accomplishes opening of the latch  38  in a manner essentially identical with that described in connection with FIG.  8 . 
     Another feature of this operating method is that the rod  128  may be equipped with an external stop or flag (such as a crosspin  128   a ) spaced somewhat downwardly from the latch pin  44  which will allow the door to open slightly but not enough for the masks  28  to drop. This feature allows testing of the latches while avoiding the labor of repacking the masks into the containers, which is cumbersome and time-consuming. It will also be appreciated that while threading is shown as a way of inserting a pin and stopping device, other ways of non-permanently inserting such a pin and stopping device into the latch could be used, such as complementary hooks, slots, or Velcro. 
     Finally, in an emergency situation, a user need only grasp cover  24  and pull it downwardly. Such a downwardly directed force, if of sufficient magnitude, will deflect the locking flange  114  of pin  44  sufficiently to clear the hook-shaped sections  90  of the locking legs  86 , thereby permitting the cover  24  to fall to its FIG. 1 position. It will be appreciated, however, that this last method of delatching is undertaken only in emergency situations. 
     It will thus be appreciated that the latch  38  of the invention uses a minimum of parts and is thus lightweight and easy to assemble. At the same time, the latch assembly can be operated using a variety of techniques as explained previously.