Abstract:
A lock for a pallet to be discharged from aircraft in flight by deploying a parachute connected to the pallet behind the aircraft. The loaded pallet or container is locked in place by one or more abutments until the tension applied by the opened parachute reaches a predetermined value. Each abutment is maintained in locked position by pressure responsive lock mechanism. This lock mechanism may be in the form of a punch and penetrable fuse plate, or a compressible or deformable fuse adapted upon predetermined loading to yield a predetermined amount. The lock mechanism is carried by a rail extended longitudinally of the aircraft which is adapted to move between an upright operating position in which it overlies an edge of a pallet, and a lowered position in which it is beneath the pallet supporting surface.

Description:
BRIEF SUMMARY OF THE INVENTION 
     Aerial delivery systems are known in which loaded pallets or containers are supported on a floor of the aircraft normally provided with anti-friction means such as rollers. The pallet or cargo container, which will hereafter be referred to simply as a pallet, has connected thereto one or more packed parachutes. When the cargo is to be delivered in flight, a rear door of the aircraft is opened and the parachute means is deployed and opened. The air resistance acting on the opened parachute applies a tension tending to pull the pallet rearwardly through the open door, after which it will be lowered to the ground under the restraint imposed by the parachute. 
     In general the pallet is retained in the aircraft by longitudinally extending guide rails having inwardly directed overhanging flanges. The flanged rails prevent lateral movement of the pallet as well as preventing upward displacement from the supporting surface as a result of aircraft movement. 
     In order to retain the loaded pallet in position until the parachute has opened and has established a predetermined minimum tension on the pallet, abutment means are applied comprising a movable abutment engageable with the pallet in position to prevent rearward movement thereof. The abutment is constructed and arranged so that pressure applied to the abutment by the pallet establishes forces tending to move the abutment to unlocked position, to permit the parachute to withdraw the loaded pallet from the aircraft. 
     A construction of this general type is disclosed in a prior patent to Mollon, et al, U.S. Pat. No. 3,335,983 which is assigned to the assignee of the invention disclosed herein. 
     In accordance with the present invention, lock retaining means is provided opposing movement of the abutment to unlocked position until pressure on the abutment reaches a predetermined value. In the preferred embodiment, the lock retaining means includes a cartridge comprising a punch and metal or plastic fuse plate arranged so that pressure applied to the punch is variable in accordance with a pressure applied to an abutment. When this pressure reaches a predetermined value, the punch abruptly penetrates the fuse plate and releases the abutment, which thereupon is moved by pressure of the pallet from its previously locked position to a position which permits withdrawal of the pallet. Alternatively, the fuse may be in the form of a compressible or penetrable material which yields to permit continued movement of a punch or similar pressure applying element when the load applied to the abutment reaches a predetermined value. 
     In accordance with the present invention, longitudinally extending pairs of rails are provided in the side of the aircraft which serve as guides and lateral retainers for the pallet. The locking means including the abutment and lock retainer is mounted within one of the rails, the abutment being movable from an unlocked position within the rail, through an opening in the inner wall of the rail, into locked position where it is engageable with the pallet. Conveniently, an abutment in locked position extends into a lateral recess provided at a side of the pallet. 
     When the locked mechanism is in its inoperative position within a rail, the rail may be pivoted downwardly about a longitudinally extending axis into a recess in the floor of the aircraft. 
     The tension responsive release device is in the form of an elongated cartridge in which the punch or driver is longitudinally slideable. Removable and replaceable fuse plates or compressible cells are provided which may be inserted through a slot in the side of a housing in position to be engaged by the operating end of the punch. The housing at its interior includes means for supporting the fuse plate in position to be penetrated by the punch and means for guiding the operating end of the punch as it penetrates the fuse plate. 
     Of course a single tension release device may be responsive to the total pull of the parachute means, and when activated, may operate a plurality of pallet locking devices. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary elevational view of a rail in elevated position and locking abutment means in locked position. 
     FIG. 1A is an end view of the rail structure shown in FIG. 1. 
     FIG. 2 is a fragmentary sectional view on the line 2--2, FIG. 1. 
     FIG. 3 is a view similar to FIG. 2 showing the pallet locking device in loading position. 
     FIG. 4 is a view similar to FIG. 2 showing the pallet locking device in emergency release airdrop position. 
     FIG. 5 is a view similar to FIG. 2 showing the locking device in normal airdrop unlocked position. 
     FIGS. 6 through 9 are sectional views on the line 6--6, 7--7, 8--8 and 9--9, FIG. 1. 
     FIG. 10 is a view similar to FIG. 8 with the rail swung to inoperative position. 
     FIG. 11 is an enlarged longitudinal sectional view of the pressure release cartridge. 
     FIG. 12 is a side elevational view of a fuse plate of a collapsible honeycomb material. 
     FIG. 13 is an end view of the structure shown in FIG. 12. 
     FIG. 14 is a fragmentary end elevation of a pressure applying member for use with the device of FIG. 12. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIGS. 1, 1A and 2, there is shown a section of a rail 10 which has been swung about the axis of a pivot pin 12 to upright operating position in which the rail extends above deck 14 of the load carrying compartment of an aircraft in position to overlie the edge of a pallet P supported on rollers (not shown). The rail is located in its upright operating position by having its lower portion 16 engage a fixed abutment 18 on the bottom of an elongated chamber 20 which receives the rail in its inoperative position. Suitably carried by the rail as will subsequently be described in detail is a locking abutment 22 which is adapted to be received in a recess 24 formed in the edge of the pallet P. The rail 10 is provided with a flange 26 which overlies the edge of the pallet and prevents upward movement thereof. The inner surface 28 of the rail constitutes a guiding and lateral retaining surface which may be engaged by the pallet as it is rolled forwardly in the aircraft to the position in which it is to occupy in flight. The surface 28 also prevents lateral movement of the pallet P which might otherwise result from motion of the aircraft in flight. 
     Mounted for longitudinal movement in the chamber 20 which houses the rail 10 in its inoperative position, is an elongated control bar 30, the function of which will subsequently be described in detail. Pallet locking mechanism is for the most part housed within a compartment 32 located in the rail 10, as best seen in FIG. 2. This compartment includes the inner wall 28 of the rail which is provided with an opening 34 through which locking abutment means are movable. As illustrated in FIG. 2 an abutment means indicated generally at 22 is provided which is adapted to be projected into the illustrated position through the opening 34. The abutment means includes the movable abutment 38 engageable with the forward wall 40 of the recess 24 provided in the edge of the pallet. 
     The abutment means indicated generally at 22 in FIG. 2 is provided by a pair of L-shaped levers 42 and 44 as best illustrated in FIGS. 3 through 5. The lever 42 is pivoted on a pin 46 and includes a laterally extending arm 48 provided along its free edge with a relatively thin connector portion 50 and the full width rounded abutment 38. The lever 44 is provided with the laterally extending arm 52 which is bifurcated as indicated at 54 to receive the portion 50, the bifurcated portion 54 and the relatively thin portion 50 being pivotally interconnected by pivot pin 56. Lever 44 is provided with a guide pin 58 slidably movable in elongated longitudinally extending slots or recesses 60. Pin 58 carries a roller 61 for a purpose which will later be described. Lever 42 is mounted on a fixed pivot pin 46 so that as the locking device is moved from the locking position shown in FIG. 2 to the unlocked position indicated in FIGS. 3-5, in which position pivot pins 46, 56 and 58 come into alignment, the pin 58 is shifted to the left in the guide slot 60. 
     Also pivoted within the compartment 32 is a latch lever 64 having a dog 66 received in a notch 68 in lever 42. In the position illustrated in FIGS. 3-5 the latch lever prevents movement of the locking levers 42, 44 into the locking position illustrated in FIG. 2. 
     Also pivotally mounted within the compartment 32 is a pressure responsive cartridge 70 which will subsequently be described in detail. For the present it is sufficient to note that when locking levers 42, 44 are in the locked position illustrated in FIG. 2, the cartridge 70 may be pivoted into the illustrated position about the axis of a shaft 72 which extends downwardly to the lower edge of the rail and is there provided with an actuating arm 74 carrying a roller 76 for a purpose which will presently be described. 
     Referring now to FIG. 2, a spring 80 is provided urging the locking levers 42, 44 upwardly as seen in this Figure to an unlocked position as indicated by arrow 81. A spring 82 is provided urging the latch lever 64 upwardly in this Figure as indicated by arrow 83. A spring 84 is connected to the cartridge 70 or shaft 72 urging it clockwise as indicated by arrow 85 as seen in FIG. 2 into its operating position. 
     From the foregoing description it will be apparent that forces applied by a deployed parachute to the pallet are transmitted to the abutment 38 as illustrated in FIG. 2 and will tend to rock lever 42 clockwise about the pivot pin 46. This motion when permitted is transmitted to the lever 44 through the connecting pin 56 and will move the pin 58 to the left in FIG. 2. The roller 61 is engageable by the lock retainer cartridge 70 and will be described later. 
     Reference is now made to FIGS. 6 through 10 which illustrate details of the rail 10 and the lock mechanism including levers 42 and 44. 
     As best seen in FIG. 6, rail 10 is in an elevated position and this figure illustrates the shaft 72 which is adapted to control the position of the cartridge 70 as previously described. The lever arm 74 at the bottom of the shaft 72 carries the roller 76 which is engageable with the longitudinally movable control rod 30 which is retained in guided relationship in brackets 90 bolted or otherwise secured to the bottom wall of the chamber 20 as indicated at 94. Comparing FIG. 6 with FIG. 2 it will be observed that the cartridge 70 is in an operating position in which it prevents retraction of locking levers 42, 44 and that in this condition the roller 76 is received within a notch 96 in the control rod 30. It will be apparent that movement of the control rod 30 to the right as seen in FIG. 2 will swing cartridge 70 counterclockwise out of its lock retaining position as seen in FIG. 4. 
     Referring now to FIG. 7 which is a sectional view through the rail structure at the position occupied by the pin 58 carrying roller 61. At this point it will be observed that the control rod 30 is of a full circular cross-section. 
     Referring now to FIG. 8 it will be observed that this section view is taken through the portion of the lock containing the pivot pin 56 which interconnects the interleaved portions of the levers 44, 42. 
     Referring now to FIG. 9 it will be observed that this section view is taken through the pivot pin 46 which provides a fixed pivot mounting for the lever 42. In this figure as in FIG. 1A it will be observed that the rail has its lower portion 16 in solid abutment with the stop 18 which prevents the rail from being swung counterclockwise as a result of upward forces applied to its retaining flange 26. 
     Referring now to FIG. 10 it will be observed that the rail 10 has been pivoted clockwise from the position illustrated in FIG. 8 about the pivot pin 12 so that it and the locking mechanism is completely received within the chamber 20. The rail 10 is provided with a shallow recess 100 which engages the control rod 30. A pivoted cover plate 102 is provided which may be moved to the closed position indicated in full lines and retained in such position by a suitable fastening means such as a quick-turn screw or the like. 
     Referring now to FIG. 11 the pressure responsive cartridge 70 is illustrated in detail. As seen in this figure the cartridge comprises an elongated generally tubular housing 104 provided intermediate its ends with a transversely extending web or wall 106 having an aperture 107 to receive the inner punch portion 108 of a punch 110. The punch includes the larger portion 112 which is slidably received in the bore 114 of the housing 104. Portion 112 is grooved as indicated in 116 and receives the inner end of a stop screw 118 which prevents the punch from separating from the housing 104. 
     At its opposite end the housing 104 is provided with an internal thread as indicated at 120 and this portion receives an externally threaded tubular anvil member 122, the inner end of which is provided with a reduced opening 124, dimensioned to receive the inner end of the punch 108. Outwardly from the reduced opening 124, anvil 122 is provided with an enlarged through opening 126 which freely receives a plug cut from a fuse plate for ready disposal. At its outer end the anvil 122 is provided with ears 128 apertured to receive the noncircular upper end of the shaft 72. 
     Extending laterally into the interior of the housing 104 is a slot 130 dimensioned to receive a flat fuse plate or disc portion 132 having a laterally extending ear 134 to facilitate removal of the punched fuse plate after operation of the lock release mechanism. 
     The flat plate portion 132 of the fuse is inserted into the opening to the position illustrated after which the anvil 122 is tightened down to mount the fuse plate 132 against the side of the anvil in position to have a slug punched out of it by inward movement of the punch portion 108. 
     The outer end of the enlarged portion 112 of the punch is provided with a cylindrically formed recess 136 to be engaged by the roller 61 mounted on the pin 58. 
     When sufficient force is applied to the punch portion 104 as a result of pressure applied to the abutment 38 by the locked pallet P, the punch abruptly penetrates the plate 132 permitting substantially free movement of the roller 61 to the left as the pivot pin 56 assumes a position in line with the pins 46 and 58, thus permitting the abutment 38 to be freely retracted through the opening 34 and thereby freeing the pallet for unloading movement by the parachute. 
     While the punch 110 is movable relatively freely after the fuse plate has been punched, nevertheless it will be apparent that substantial force may be required to move it again to the initial position illustrated in FIG. 11, in order to withdraw the punch portion 108 from the hole punched into the fuse plate. When the punch has been withdrawn from the hole punched into the fuse plate, the used fuse plate may be withdrawn by the ear 134 and discarded. A new fuse plate may be inserted into the slot 130 and the threaded anvil 122 tightened to place the parts in the condition illustrated in FIG. 11. 
     It has been found that the pressure responsive punch provides for release of the lock under accurately predetermined tension applied by the connection between the parachute and the loaded pallet. It will, of course, be understood that variable factors may be controlled to provide this release at predetermined different tensions. Conveniently the fuse plate may be formed of metal, either a soft metal such as copper or aluminum, or a harder iron or steel alloy. Also the fuse plates may conveniently be formed of suitable relatively hard plastic materials or otherwise suitably formed metals such as, for example, laminated or honeycombed construction of suitable material such as metals, plastics, fibrous metals, etc. It will, of course, also be apparent that the force required to cause the punching actuation may be varied by varying the thickness of the fuse plate and/or the diameter of the punch. When a particular size and material of punch is selected it is found that tension release occurs with highly satisfactory uniformity. 
     In the preferred embodiment of the invention, actuation of the tension release mechanism is accompanied by complete penetration of the fuse plate, so that a slug is punched out of it. However, the operation may involve, instead of complete penetration through the fuse plate, a predetermined penetration or distortion thereof by the punch or pressure applying member. In this case the fuse plate may be a laminated or honeycomb construction, in which a predetermined force applied by the punch or pressure-applying member causes compression or displacement of the material together with a corresponding movement of the punch or pressure applying member sufficient to actuate the release mechanism. 
     While the operation of the tension load release mechanism is believed apparent from the foregoing, certain various operating conditions will be described. 
     It will be noted in FIG. 2 that the draw bar 30 is in neutral position and that the spring 84 has moved cartridge 70 into position within the compartment 32 such that the punch 110 is engaged by the roller 61 thus preventing movement of the abutment 38 out of the locked position. It will also be apparent that at this time the roller 61 is engaged in the recess 136 thus retaining the cartridge 70 in the illustrated position. The spring 80, biasing the lever 42 clockwise as seen in this figure applies a bias to this roller 61 sufficient to retain the parts in the illustrated position, even in the absence of any force applied by the pallet to the abutment 38. 
     It will be noted at this time that the latch lever 64 has been moved inwardly so that its detent 66 is out of engagement with the notch 68 thus permitting movement of levers 42, 44 from the position illustrated for example in FIG. 3 to the position of FIG. 2. It will be understood that with lever 64 in the position illustrated in FIG. 3, it prevents movement of levers 42, 44 to the blocking position of FIG. 2. 
     With the part in position as illustrated in FIG. 2, when no pallet is in position, to load a pallet, the draw bar 30 is moved to the right to the position illustrated in FIG. 3 to release cartridge 70 for movement by spring 84 into alignment with the pivot pins 46, 58. It will be noted at this time that the latch 64 is in the position in which its detent 66 is engaged in the notch 68 thus preventing manual displacement of the locked lever 42, 44 to the locked or pallet-blocking position. At this time the pallet is moved into position so that its locking recess 24 is adjacent the opening 34 in the rail 10. The portion of the latch lever 64 which projects outwardly from the rail 10 is kicked inwardly to the position illustrated in FIG. 2, releasing lever 42, 44, at which time the outwardly projecting portions of these levers may be pressed inwardly to the position shown in FIG. 2. This moves the abutment means 22, including the abutment 38 into the recess into the pallet. At the same time this results in the movement of the pin 58 and roller 71 to the right as seen in FIG. 2, permitting the cartridge 70 to move into the operating position illustrated in this figure. 
     Referring now to FIG. 4, the parts are illustrated in the position occupied when in emergency release or airdrop position. This condition is brought about by movement of the control rod 30 forwardly or to the right as seen in FIG. 4 so that roller 76 is operated by cam surface at 139 to swing the cartridge 70 out of operating position. When this is done, spring 80 swings lever 42 and cooperating lever 44 outwardly to the retracted or unlocked position, thus releasing the pallet for emergency airdrop. It will be observed that when the levers 42, 44 are swung outwardly that the spring 82 will swing latch lever 64 to the position illustrated in FIG. 4 thus positively retaining levers 42, 44 in unlocked position. 
     Referring now to FIG. 5, the parts are illustrated in the position which they occupy as the pallet is moved toward release position by the parachute. At this time the control rod 30 is in the position in which the notch 96 has permitted the cartridge 70 to move into its operating position. In this figure it is assumed that sufficient force has been applied to the abutment 38 by the abutment surface 40 to cause sufficient force to be applied to the punch 110 to cause the punch to penetrate the fuse plate 132. As soon as the punching operation occurs, the punch 110 is relatively freely movable inwardly of the cartridge housing so that pin 58 and roller 61 move to the left as seen in FIG. 5 as the abutment 38 is withdrawn from the pallet recess 24. Again at this time latch lever 64 moves to the latching position illustrated in FIG. 5 and must be moved inwardly by the operator before again engaging the locking mechanism with another plate. 
     In the foregoing a single pressure releasable pallet locking device has been described in considerable detail. The device as so far described has as an operating characteristic the ability to oppose a very substantial predetermined resistance without appreciably yielding and then to yield abruptly to effect substantially instantaneous release of the loaded pallet for aerial delivery. 
     It is usually desirable to provide two or more and in some cases a substantial number of pressure release devices so that each can provide a predetermined fraction of the pressure required to release the pallet. Where a device as described in the foregoing is employed in multiple installations it is, of course, necessary that the devices be capable of absorbing its own fraction of the entire load. Of course, when the total load reaches the predetermined amount, one particular locking device will yield and the entire load is absorbed by the remaining devices with the result that the release of all devices is substantially simultaneous. 
     The invention is also capable of being carried out by using the pressure release device to trigger release of a plurality of load locking devices. Thus for example in prior U.S. Pat. No. 3,335,983 also assigned to assignee herein, there is illustrated a manual system for simultaneously releasing a plurality of pallet locking devices. 
     The pressure responsive devices may be connected to operate control rod or rods, similar to rods 30 disclosed herein, so that upon puncture of the fuse plate 132, the rod will be shifted to effect simultaneous release of all locking devices to release the pallet or other load for withdrawal by the parachute means. 
     Where the term &#34;fuse plate&#34; is used herein, unless otherwise specified, it is to be understood to include a solid plate from which a slug may be punched, or a plate of compressible penetrable, or collapsible material. Alternatively, the fuse may be in the form of a collapsible honeycomb. Such a fuse plate is shown in FIGS. 12 and 13 at 140, where the portion of the fuse plate 142 to which pressure is applied by an element similar to punch 108 of FIG. 11, is shown as of honeycomb form, with cells 144 extending parallel to the direction of pressure application. Each individual cell is of course equivalent to a tube, and the tubes of the honeycomb give mutual support to each other. The punch may have the form shown in FIG. 14, having a flat nose 146 so that as it penetrates the fuse, its effective cross-section area remains the same, providing a constant or only slightly increasing resistance to movement of the punch. By this means the desired pressure may be correlated to amount of punch movement so that release occurs at a predetermined pressure. This permits the loading to be distributed substantially equally between a plurality of release devices. 
     As best seen in FIG. 13, the honeycomb element 142 is preferably provided with cover sheets 143, a portion of the sheet being shown as removed to expose the interior honeycomb structure. 
     A comparison of FIGS. 2 and 3, 4 or 5 illustrates an important feature of the invention which is referred to herein as a &#34;self-seeking&#34; function. It will be observed that locking levers 42 and 44 have a similarly shaped rearwardly facing abutment constituted by a rounded portion on the laterally extending arm 52. In FIG. 2 it will be observed that these two abutments are locked substantially in alignment with the pivot pin 56, thus causing the abutment surfaces to define a detent structure of maximum width. Referring to FIG. 3 for example, it will be noted that the abutment 38 and the corresponding abutment on the arm 52 are moved closer together by virtue of the fact that the pivot pin 56 has moved out of its position in alignment therebetween. 
     For simplicity the present disclosure has referred to pallet locking structure and has identified the recess 24 as provided in a pallet. It will of course be understood that this pallet need not be a separate support structure but may in fact constitute the floor of an open-top container or a completely enclosed load housing structure.