Abstract:
A locking element is described for securing containers, pallets or similar freight items in the cargo bay of an aircraft, wherein a first and a second locking claw are mounted on a frame swivellable from a lowered loading position into a raised working position for securing containers. A remotely controllable adjustment device is provided to change and adjust the state of the locking claws between the loading state in which the locking claws are in the loading position, a holding state in which the locking claws are in the working position and fixed, and a trigger state in which the locking claws are in the working position but can be swivelled from the working position into the loading position if a force acting on the locking claws exceeds a predetermined amount.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to, and is a National Phase application of, pending PCT/EP2009/004485 entitled, Locking Element, filed Jun. 22, 2009, the disclosure of which is hereby incorporated by reference in its entirety. 
     FIELD OF THE INVENTION 
     The invention concerns a locking element for securing containers or similar freight in a cargo bay of an aircraft. 
     BACKGROUND OF THE INVENTION 
     To transport air freight, the items of freight to be transported, in particular containers or pallets produced to particular standards, are attached inside the cargo bay by means of locking elements on the floor of the cargo bay. 
     In the military freight sector there is a particular standard, according to which containers or pallets have recesses on the edges at regular intervals in which hook-shaped locking elements can engage to hold the containers in the x direction i.e. the longitudinal direction of the aircraft. These hooks are formed swivellable in the plane of the cargo bay i.e. the x-y plane. 
     Such locking elements are particularly critical if during a flight, freight must be unloaded via parachute. In this case, when the rear loading hatch is opened and the freight is to be extracted via a parachute previously ejected from the cargo bay, the locking elements must open reliably otherwise there is a danger of crashing, in particular from low altitude. Some embodiments in accordance with the invention create a locking element of the type cited initially such that the locks are reliably releasable. 
     A locking element for securing containers or similar freight in the cargo bay of an aircraft in the longitudinal direction may be provided. The locking element may include: a frame, a first and a second locking claw which are mounted on the frame swivellable about a first or a second swivel axis from a lowered loading position to a raised working position in order to secure the container, wherein a remotely controllable adjustment device is provided to change and adjust the state of the locking claws between a loading state in which the locking claws are in the loading position (retracted/released), a holding state (locked) in which the locking claws are in the working position and fixed, and a trigger state (armed) in which the locking claws are in the working position but can be swivelled out of the working position into the loading position when a force acting on the locking claws in the longitudinal direction exceeds a predetermined amount. 
     In some embodiments as the conventional positions (“loading position” and “working position”) in which the locking claws are retracted such that containers can be moved over the locks (loading position) or the locks engage in the recesses of the containers (working position), a third lock position is provided. In this third lock position the containers are still secured, but on application of a sufficiently large force by the container itself they can be lowered to the loading position so that the containers are now free. 
     This ensures that when the parachute opens, the freight can be safely extracted from the cargo bay. 
     Furthermore it is possible to move the locking claws from the holding state (locked) directly into the loading position (retracted/released). This function is used in particular when the load must simply roll out (i.e. without any parachute) on command at low altitude by raising the aircraft nose by around 4°. This is known as the gravity drop method. 
     Preferably this predetermined amount of force differs depending on whether it is acting in one or the opposite direction. Such a locking element can be mounted in the cargo bay such that forces which act on the flight direction, such as occur during deceleration of the aircraft, practically do not lower the locking claws while forces which act in the unloading direction cause the locking claws to lower. 
     The locking elements can be formed such that the locking claws are mobile in the plane of the cargo bay floor in the normal manner. Preferably the locking element is formed such that it can be mounted in a plane perpendicular to this. The locking claws are therefore swivelled in an x-z plane i.e. a plane running perpendicular to the cargo bay floor. 
     Preferably the two locking claws each have a stop surface which can be brought to rest on stop edges of recesses of the containers when the containers are locked. The locking claws here are formed mobile such that the two stop surfaces move away from the stop edges when moving out of the working position into the loading position. This ensures that the lock can be opened even if a container has moved during flight and is lying closely against one (or both) stop surfaces with its stop edges. 
     The stop surfaces are preferably attached to the swivellable locking claws such that in the working position they are arranged parallel and aligned to each other. This guarantees optimum holding of the containers and at the same time easy release from the locking position. 
     For definition of the predetermined amount of force which when exceeded swivels the locking claws from the working position to the loading position, preferably a spring device is provided. This is a reliable means which is easy to produce. Preferably in this arrangement, a tensioning device is provided which can be adjusted in particular by electric motor and which allows setting of the pretension of a retaining spring. As a result it is possible to adjust each lock in the cargo bay to the freight it must retain and release when the predetermined force is exceeded. As a result freight weighing half a tonne can be released with a low force acting on the locking claws in the same way as freight weighing ten tonnes. 
     The locking claws preferably have a movement spring element which pretensions the locking claws from the working position into the loading position. This achieves a reliable release of the load. 
     The two locking claws are preferably connected together rotating in opposing directions such that movement of the one locking claw carries with it the other locking claw. This leads to a simpler overall design of the arrangement. 
     Preferably the adjustment device comprises a securing lever which can be swivelled from an upper securing position for securing the claws into a lower release position in which the securing lever releases the claws. Such a lever mechanism is simple to construct. 
     The adjustment device furthermore comprises preferably a cam plate which is rotatable such that it can be moved into the following three positions: 1) a holding position for fixing the locking claws in the working position (locked), 2) a trigger position for releasing the locking claws in the working position (armed), and 3) a loading position for swivelling the locking claws into the loading position (released). 
     This trigger position is the third position mentioned initially in which the locking claws are indeed in the working position but can be lowered when a predetermined force is applied. The setting of the positions by means of the cam plate constitutes a reliable and tested method. 
     A cargo bay floor is also claimed to which locking elements of the types described are mounted. Such a cargo bay floor is particularly suitable for unloading freight e.g. military goods or accessories during flight via a rear hatch. 
     Furthermore some embodiments of the invention may concern a method for unloading containers or similar freight from the cargo bay of an aircraft, wherein the containers or similar freight are secured with locking elements of the type cited initially, the may include: setting the trigger state of the locking claws to secure the container, loading the locking claws in the unloading direction with a force exceeding the predetermined amount in order to release the containers, and moving the containers out of the cargo bay. 
     This movement of the containers takes place preferably via a parachute device previously ejected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment example of the invention is described in more detail below with reference to drawings. These show: 
         FIG. 1  a perspective view of a locking element according to one embodiment of the invention; 
         FIG. 2  the locking element according to  FIG. 1  from the other side; 
         FIG. 3  a part longitudinal section of the locking element according to  FIGS. 1 and 2 ; and 
         FIGS. 4A-4D  a principle depiction of the locking element in its various positions. 
     
    
    
     DETAILED DESCRIPTION 
     In the description below the same reference numerals are used for the same parts and those with similar effect. 
       FIGS. 1 and 2  show an embodiment of the locking element according to the invention in perspective view from two sides. These depictions show that the locking element has a frame  30  comprising two half-shells connected together. Fixing tabs  32  are provided to attach the frame  30  and hence the entire locking element to a cargo bay floor. 
     Locking claws  20 ,  21  are mounted swivellably in the frame  30 , as will be described in more detail below. These locking claws  20 ,  21  each have stop surfaces  22 ,  22 ′ which come to rest on stop edges  3 ,  3 ′ (see  FIGS. 4A-4D ) of a recess  2  of a container  1  when the container is locked. 
     For mechanical (supporting) activation of the arrangement i.e. for lowering the locking claws  20 ,  21 , a control element  73  is provided which in the embodiment shown here is formed as a socket head. 
     As shown in  FIG. 3 , the locking claws  20 ,  21  are mounted swivellably on swivel axes  50 ,  51  in frame  30 . A spring  25  is provided as a movement spring element which acts counter-clockwise on the locking claws  21  in  FIG. 3 . A corresponding spring (not shown) is provided for lowering the locking claws  20 . 
     The two locking claws  20 ,  21  are connected together via a connecting pin  80  (on locking claw  21 ) and a recess as a connecting slide  81  (on the other locking claw  20 ) in order to transfer a rotary movement of locking claw  21  to locking claw  20 . 
     Furthermore a cam plate  70  is mounted rotatably in the frame  30  which on its outer periphery has a crown gear  72  connected rotationally stationary with electric motor  100  via a gear  101 . The cam plate  70  can be turned via said control element  73  wherein the rotor of the electric motor  100  is also turned. 
     The cam plate  70  has an adjustment cam  71 , the precise function of which will be explained below with reference to  FIG. 4 . 
     A securing lever  60  is also mounted swivellably on a lever bearing peg  63  in the frame  30 . The securing lever  60  has a holding lug  64  and a release lug  65 , the functions of which are described below. 
     Furthermore on the securing lever  60  is provided a limiting lug  62  which engages in a limiting recess  31  of frame  30  such that the swivel movement of the securing lever  60  is limited. 
     Furthermore a trigger spring element  90  is provided which has a retaining spring  91  with a thrust point  92  at the end that presses on a press stud  61  of the securing lever  60 . The trigger spring element  90  furthermore comprises a spring adjustment device  110  containing an electric motor  111  which via a gear  112  is connected rotationally stationary with a spindle sleeve  113  that is mounted rotatably but linearly stationary in the frame  30 . The spindle sleeve  113  sits on a spindle  114  which forms the bearing of the retaining spring  91  opposite the thrust point  92  of this retaining spring  91 . When current is applied to the tensioning electric motor  111 , the spindle sleeve  113  is turned so that the spindle  114  moves and the retaining spring  91  is tensioned (or released). Thus overall an electric adjustment device  40  is formed which comprises firstly the cam plate  70  rotatable by electric motor  100  with associated control elements and secondly the spring adjustment device  110 . 
     The function of the embodiment of the locking element shown here is explained with reference to  FIGS. 4A-4D  in which the elements necessary to achieve the various states of the locking claws are shown. 
       FIG. 4A  shows a holding state in which the locking claws  20 ,  21  are in the raised position and engage in the recess  2  of a container  1  such that the stop surfaces  22 ,  22 ′ can come into contact with stop edges  3 ,  3 ′ of recess  2 . In this position the adjustment cam  71  supports the lower sections of locking claws  20 ,  21  so that these cannot rotate about their swivel axes  50 ,  51 . In this holding state, the locking claws  20 ,  21  are fixed in the working position. 
     After activating electric motor  100  (and twisting the cam plate  70  clockwise) up to the position shown in  FIG. 4B , there is no longer a direct support of locking claws  20 ,  21  by the adjustment cam  71 . In this position which corresponds to the trigger state described initially, a retaining peg  23  connected with the right locking claw  21  ( FIG. 4 ) is connected with the holding lug  64  of the securing lever  60 . As a result the locking claw  21  is held in the raised working position. If now a force F acts on the locking claw  21  and attempts to twist this counter-clockwise, the retaining peg  23  exerts a torque on the securing lever  60  which also attempts to turn this counter-clockwise. This twist of the securing lever  60  is counteracted by the trigger spring element  90  since the thrust point  92  of the retaining spring  91  presses on the press stud  61  of the securing lever  60 . If the force F is now sufficiently large, the pretensioned spring  91  is compressed and the securing lever  60  twisted counter-clockwise. If the twist is sufficiently large, the retaining peg  23  snaps over the holding lug  64  and locking claw  21  is swivelled down by the spring  25  (shown in  FIG. 3 ). On this swivel movement, the connecting pin  80  also moves down (in a circular movement about swivel axis  51 ) and carries with it the other locking claw  20  by its stop in the connecting slide  81 . This position is shown in  FIG. 4D  wherein the position of the adjustment cam  71  is shown as a dotted line. Force F at which the locking claws  20 ,  21  “drop down” can thus be adjusted by the trigger spring element  90 . 
     If motor  100  is moved further so that the cam plate  70  turns further clockwise, the securing lever  60  is swivelled counter-clockwise against the force of the trigger release element  90  whereby the retaining peg  23  moves out of engagement with holding lug  64  ( FIG. 4C ). Spring  25  then swivels both locking claws  20 ,  21  together so that the position shown in  FIG. 4D  is reached in which the stop surfaces  22 ,  22 ′ are out of engagement with stop edges  3 ,  3 ′. 
     The difference between the transition from  FIG. 4B  to  FIG. 4D  and that from  FIG. 4C  to  FIG. 4D  is that in the trigger state shown in  FIG. 4B , a force F must act to swivel the securing lever  60  and release the retaining peg  23  from the holding lug  64 , whereas the swivelling of the securing lever  60  on transition from  FIG. 4C  to  FIG. 4D  takes place by the electric motor  100  and no force need act on the locking claws  20 ,  21 . 
     When the freight is to be unloaded using the “gravity drop” method in which the nose of the aircraft is raised by approximately 4° and the freight is moved with only low force, locking claws  20 ,  21  are brought (mechanically or electrically) by twisting the cam plate  70  out of the position shown in  FIG. 4A  to that in  FIG. 4D  (and beyond) i.e. from the working position (locked) into the loading position (retracted/released). 
     Furthermore by the construction of the locking element shown here and its description, it is clear that not only the force F shown in  FIG. 4B  acting on the right locking claw  21  can swivel the securing lever  60  and thus release the claws, but also a force (−F) acting in the opposite direction which acts on the locking claw  20 . The different geometric conditions and the transfer of forces via the connecting pin  80  and connecting slide  81  however ensure that this force (−F) must be very much larger than the force (F) acting on the locking claw  20  to achieve the trigger state in which locking claws  20 ,  21  are lowered. 
     According to a further embodiment of the invention not shown here, the geometric conditions (lever arm, form of connecting slide) are selected such that the locking claws  20  cannot be lowered at all by a force −F acting on this. This is important to absorb the extreme loads occurring on a crash. 
     It is furthermore evident from  FIG. 4  that the stop surfaces  22 ,  22 ′ of the locking claws  20 ,  21  move closer together on lowering so that seizing in the recess  2  of the container  1  is practically impossible. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Container 
           2  Recess 
           3 ,  3 ′ Stop edge 
           20  Locking claw 
           21  Locking claw 
           22 ,  22 ′ Stop surface 
           23  Retaining peg 
           25  Movement spring element 
           30  Frame 
           31  Limiting recess 
           32  Fixing tab 
           40  Electric adjustment device 
           50  Swivel axis 
           51  Swivel axis 
           60  Securing lever 
           61  Press stud 
           62  Limiting lug 
           63  Lever bearing peg 
           64  Holding lug 
           65  Release lug 
           70  Cam plate 
           71  Adjustment cam 
           72  Crown gear 
           73  Control element 
           80  Connecting pin 
           81  Connecting slide 
           90  Trigger spring element 
           91  Retaining spring 
           92  Thrust point 
           100  Motor 
           101  Gear 
           102  Plug contact 
           110  Spring adjustment device 
           111  Tensioning electric motor 
           112  Gear 
           113  Spindle sleeve 
           114  Spindle