Abstract:
A cargo locking device for locking of freight in a vehicle such as the stowage of containers or pallets in aircraft in which track connectors, namely the tensile studs are arranged in such a manner that tensile load is distributed between the floor beams. The cargo lock has a lock length about equal to or exceeding the transverse beam pitch, the tensile studs being placed in groups at both ends of the lock and the pawls in the middle of the lock such that pawl loads are split between the forward and the aft stud.

Description:
RELATED APPLICATION 
     This application is a divisional of application Ser. No. 09/120,552 filed Jul. 22, 1998, now U.S. Pat. No. 6,193,453, which claims priority to provisional application Serial No. 60/053,643 filed Jul. 24, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The field of the present invention relates to a cargo lock device that holds cargo pallets in place within vehicles such as aircraft. The aircraft includes seat or cargo tracks located in the cargo floor. The seat tracks are located in the cargo floor and run lengthwise through the aircraft. The seat tracks are supported at regular intervals typically by transverse floor beams. Typically, the cargo lock device includes hooks referred to as pawls and a number of support rollers. The device is connected to a seat track by means of tensile studs and shear ties. The studs restrain the lock against vertical motion and the shear ties restrain the lock against horizontal motion. 
     The present inventor has recognized that these cargo locks are structurally inefficient for the aircraft floor because of their geometry and the locations of their studs, shear ties and rollers relative to the pawls. With the lock in an unfavorable position in the seat track relative to the transverse floor beams, most of the load applied by the cargo pallet will transfer through just one floor beam. This situation occurs when the stud that is closest to the pawls is located directly over top of a floor beam. For example, U.S. Pat. No. 5,433,564 discloses a device which employs a resiliently deformable section in its floor hooks, but does not disclose relative distribution of tensile forces relative to floor support points. 
     The existing lock designs may minimize cost and weight of the locks themselves, but these cost and weight savings are disadvantageously offset by the additional structure required in the transverse floor beams and the seat tracks. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved cargo locking device for locking of freight in a vehicle such as the stowage of containers, or pallets in aircraft. The improved cargo locking device avoids the aforementioned disadvantages by arranging track connectors, e.g. the tensile studs, in such a manner that tensile load is distributed between the floor beams. 
     In its preferred embodiment, the cargo lock has a lock length about equal to or exceeding the transverse beam pitch. The tensile studs will be placed in groups at both ends of the lock. The pawls will be placed in the middle of the lock. This arrangement will split the pawl loads (from the cargo pallet) between the forward and the aft stud. The separation of the studs is such that the combined loading from the two groups of studs into a single transverse floor beam never exceeds about 50% of the pawl load. The invention will now be described further as illustrated on the attached drawings of examples of its preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a cargo lock according to a preferred embodiment of the present invention. 
     FIG. 2 is a top plan view of the cargo lock of FIG.  1 . 
     FIG. 3 is a side view of the cargo lock of FIG.  1 . 
     FIG. 4 is a side view of a cargo lock similar to the cargo lock in FIG.  1  and further including a cross section of the transverse floor beams and supporting seat track. 
     FIG. 5 is a front view of the cargo lock in the seat track of FIG.  4 . 
     FIG. 6 is a top view of a tensile stud and a shear tie in a seat track. 
     FIG. 7 is a side view of an alternate embodiment of the cargo lock also of similar configuration to the cargo lock of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will now be described with reference to the drawings. To facilitate description, any identifying numeral representing an element in one figure will represent the same element in any other figure. 
     FIGS. 1-3 illustrate a cargo lock  70  having a configuration which is generally applicable to the details in the cargo lock  70   a  embodiment of FIGS. 4-6 or the cargo lock  70   b  embodiment of FIG.  7 . 
     Referring to FIGS. 1-6, the cargo lock  70 / 70   a  is connected to the seat track  40  arranged in the floor of the aircraft, the floor  50  being supported by beams  51 ,  52 . The cargo lock  70 / 70   a  comprises a frame or baseplate  10 , a pair of pawls  31  and  32 , shear ties  21  and  22 , and track connectors, shown as tensile studs  11  and  12 . The pawls  31  and  32  are located in the center of the cargo lock  70 / 70   a . The pawls  31 ,  32  have a curved or hook portion which secure cargo pallets  33  and  34  to the cargo lock  70 / 70   a . For the purposes of this description, a pawl may comprise any suitable connector which secures the cargo pallet to the cargo lock. The shear ties  21  and  22  fit in scalloped holes  41  in the seat track  40  to prevent horizontal movement of the cargo lock  70 / 70   a . 
     Details of the tensile studs  11 ,  12  are best shown in FIG.  5 . The stud  11  is in the shape of an inverted “T” formed with a flange portion  11   a  and a leg portion  11   b . Typically, the leg portion  11   b  may have threads  11   c  at the end for attachment to the baseplate  10  either directly or via a nut or other suitable connection mechanism. 
     The tensile studs  11  and  12  are inserted into the seat tracks  40  through the scalloped holes  41  and subsequently moved to a position in-between the holes  41  by sliding a short distance p along the length of the seat track  40  (before the shear ties  21  and  22  are inserted). In this position, the circular flange  11   a  of each stud  11  is locked below the seat track inner flange  42 . The lock  70 / 70   a  is secured in this position by inserting shear ties  21  and  22 . Thus secured in seat track  40 , the lock  70 / 70   a  is held in position both vertically and horizontally. 
     The tensile stud  11  is located at one side of the pawls  31  and  32  on baseplate  10  and tensile stud  12  at the other side of the pawls  31  and  32  on baseplate  10 . The distance between the two tensile studs is d. The pawls  31  and  32  are centrally located near the middle of the distance d. The transverse floor beams  51  and  52  support the seat track  40  at an interval b. The cargo lock is designed with a distance d preferably selected to be as close to b as possible, with the maximum benefit realized as d is equal to b or as d exceeds b. 
     The cargo lock  70 / 70   a  includes a plurality of rollers  35 ,  36 ,  37  and  38  secured to the baseplate  10 . The rollers  35 - 38  extend outward from the bottom of the frame  10  and serve to allow the cargo pallets to roll along the cargo locks thereby facilitating movement of pallets  33  and  34  during loading and unloading. Outer rollers  35 ,  38  are located at the extremities of baseplate  10 . The purpose of these outer rollers  35 ,  38  is to ensure that the pallets edge does not become blocked against the edge of the baseplate  10 . Inner rollers  36 ,  37  are located close to pawls  31  and  32  within a distance e. The purpose of locating inner rollers  36 ,  37  close to the pawls  31 ,  32  is to distribute a load from a single container in the downward direction over as much as possible the full length of the baseplate  10 . Without these inner rollers, this down load would be concentrated at an extremity of baseplate  10  on either roller  35  or roller  38 . 
     FIG. 7 illustrates an alternative embodiment for a cargo lock in which the same reference numerals have been used as in FIGS. 1 through 6 to indicate corresponding parts. In the embodiment of FIG. 7, the number of tensile studs has been increased to two per side resulting in studs  11  and  13 , the first track connector, on one side and studs  12  and  14 , the second track connector, on the other side, which is the same number of studs as illustrated in FIGS. 1-3. The centroid  71  of the group of tensile studs  11  and  13  is the location of the effective working axis of force when both tensile studs are equally loaded with a vertical force (for groups comprising of two tensile studs the centroid is located half way between tensile studs). Similarly, the centroid  72  of the group of tensile studs  12  and  14  is located in between these studs. The distance between the centroids  71  and  72  of the two groups of tensile studs now defines d′. The pawls  31  and  32  continue to be located near the middle of the distance d′. One advantage of the alternative embodiment is that the load per tensile stud is reduced. In addition, the baseplate  10  and the seat track  40  are fixed together at the stud groups more securely. This arrangement may have several additional beneficial effects, including but not limited to: 1) preventing the potential rolling over of the top flanges  53  and  54  of the transverse floor beams  51  and  52  when the stud groups are located offset from the beams as shown; and 2) reducing maximum bending moment in baseplate  10  which occurs near the pawls  31  and  32 . 
     In use, the tensile studs secure the cargo locks to the tracks in the event of a downward acceleration of the vehicle resulting in large tensile forces being applied to the lock. The tensile force is transmitted from the pawls  31 ,  32 , through the baseplate  10 , and to the studs  11 ,  12 . The studs then transmit the upward force to the track  40  which in turn transmit the forces to the floor and support beams  51 ,  52 . The distance d is defined as the length of the effective separation of the tensile attachment points of the cargo lock  70   a  to the tracks. In the cargo lock  70   a  of FIG. 4, the tensile attachment points are located at the center of the tensile studs  11  and the center of tensile stud  12 . The tensile studs  11 ,  12  are intentionally positioned at the outer ends of the cargo lock  70   a  so as to provide desired separation between the attachment points. Where additional tensile studs are provided such as in cargo lock  70   b  of FIG. 7, the attachment points (i.e. the centroid of attachment) are between the stud pairs, namely centroid  71  between stud pair  11 ,  13  and centroid  72  between stud pair  12 ,  14 . The stud pairs of cargo lock  70   b  are still separated by a distance d′ providing the desired effective separation between the attachment points. 
     If additional studs are included along the length of the cargo lock (for example studs  16 ,  17 ,  18 ,  19  shown in FIG. 4 in phantom) such studs are preferably designed in conjunction with the flexibility of the tracks and aircraft floor so as not to negate the force separation quality of the primary attachment points at the outer ends of the cargo lock. Such flexibility may be accomplished by including additional vertical spacing or elastomeric connection in the center studs  16 - 19  such that even though the upward tensile force is applied at the center of the cargo lock by the pawls  31 ,  32 , the majority of the upward tensile force is transferred to the primary end studs  11 ,  12  and thereby distributed between the support beams  51 ,  52 . 
     In a preferred construction, the cargo lock is elongated a having a relatively low aspect ratio r defined as the ratio of the height h (i.e. a maximum height of the lock as measured with the pawls  31 ,  32  retracted) to the length d (the effective distance between the end attachment points): 
     
       
         r=h / d. 
       
     
     Preferably, the aspect ratio of an elongated cargo lock is less than about ⅛th (0.125) or even smaller, namely about 0.10, with certain implementations being about 0.06. The aspect ratio h/d of the cargo lock  70   a  of FIG.  4  and the aspect ratio h/d′ of the cargo lock  70   b  of FIG. 7 are about 0.05. In a Boeing  727  aircraft, the distance b between the support columns is about 20 inches. In actual construction, the dimensions of a cargo lock  70   b  for this Boeing  727  aircraft may be 
      h=1.15 in 
     
       
         d=20 in 
       
     
     
       
         r=0.06 
       
     
     In smaller aircraft, the distance between support beams will be smaller, but the size of the cargo locks will also be smaller but would be designed such that d≧b and having an aspect ratio r less than 0.125 to provided the desired spacing of attachment points. 
     In a preferred configuration, the cargo lock comprises 
     a baseplate with a lengthwise orientation over a seat track; 
     one or more pawls to secure cargo pallets to the lock mounted on the baseplate; 
     a tensile stud set (of one or more tensile studs) mounted on the baseplate on each side of the pawl(s), the stud set being spaced from the pawl(s) at a distance that is about half the spacing of the seat track support points; 
     shear ties mounted on the baseplate; 
     rollers mounted to the baseplate on opposite sides of the pawl(s). 
     Preferably, the distance between the pawl(s) and the tensile studs is larger than half the spacing of the seat track support points. The distance may be somewhat smaller, but if the distance is too small, the preferred weight distribution advantages may be lost. 
     The rollers are preferably located a distance e (see FIG. 3) away from the pawl(s) where e is about less than one-fifth the spacing of the seat track support points. 
     In another preferred configuration, a single stud is used on each side of the pawls. 
     In another preferred configuration, a pair of tensile studs are disposed on each side of the pawls, the studs of the pair being separated by about one seat track hole distance ( 2   p ). 
     In another preferred embodiment, a shear tie is located in-between the two tensile studs in a group. 
     In another preferred embodiment, a single stud is replaced with a group of two or more tensile studs in any arrangement for which the distance between the pawl(s) and the closest tensile stud is about equal to half the distance between the seat track support points. 
     In another preferred embodiment, a cargo lock may include additional rollers to further distribute the compressive load across the floor. The cargo locks  70   a / 70   b  of FIGS. 4 and 7 have four rollers  35 - 38 . A cargo lock may include for example six rollers as the lock  70  in FIGS. 1-3, which has a roller  39   a  mounted to the baseplate  10  between rollers  35  and  36  and another roller  39   b  mounted between rollers  37  and  38  at the other end of the baseplate  10 . The cargo lock may be provided with any number of additional rollers. The rollers are preferable separated as much as possible to distribute the loads. In the embodiment of FIGS. 1-3, the center rollers  36 ,  37  are located adjacent the pawls  31 ,  32 . The rollers  36 ,  37  are shown so close to the pawls  31 ,  32  that the pawls  31 ,  32  or the rollers  36 ,  37  may require movable connections (not shown) to the baseplate  10  in order to accommodate retraction of the pawls  31 ,  32 . 
     Though the present invention has been set forth in the form of its preferred embodiments, it is nevertheless intended that modifications to the disclosed embodiments may be made without departing from inventive concepts set forth herein. The invention, therefore, is not to be restricted except in the spirit of the claims that follow.