Abstract:
A ball transfer unit for use in association with installed trays in vehicle cargo bays. Ball transfer unit is a modular unit that includes a larger main roller ball, a semi-spherical housing for holding the larger main roller ball, a plurality of smaller roller balls interposed between the housing and the main roller ball and a unitary cover affixed to the housing for securing the various ball elements in relation to the housing and cover. The large roller ball protrudes partially through the cover, and the cover is designed to discourage the ingress of water and contaminants from entering the housing.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Application No. 61/807,532 filed on Apr. 2, 2013, which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a ball transfer unit configured to be mounted on a floor of a cargo hold. 
       BACKGROUND OF THE INVENTION 
       [0003]    Various systems for movably supporting cargo on the floor of cargo holds, such as those found in aircraft, sea-going cargo ships and other cargo-carrying vehicles, have been previously proposed. Typically, such systems include a plurality of roller ball elements mounted on the floor of the cargo hold, thereby providing a low friction support surface over which cargo may be moved. In a typical cargo hold, the floor, and sometimes the walls, are provided with a plurality of elongated trays that are permanently or semi-permanently attached to the floor or other interior surface of the cargo hold. Each tray accommodates one or more ball transfer units, which are removably secured to the trays, thereby permitting the ball transfer units to be replaced when worn or damaged. 
         [0004]    While prior systems may have certain functional and useful features, many of the prior system suffer from common shortcomings For example, it is not uncommon for cargo holds in vehicles to be subject to the periodic ingress of water, dirt or other contaminants. As a result, many prior designs are prone to contamination and may act as receptacles for unwanted water. As dirt, dust and other debris find their way into cargo holds, prior designs have a tendency to allow, or even facilitate, the entry of such contaminants into the ball transfer units. At some point, oxidation of the internal components of ball transfer units may occur, and the collection and concentration of debris in the interior of the units may significantly increase the internal friction occurring within the units, which may render them inefficient and make it difficult for cargo to be easily moved over the ball transfer assemblies. In addition, many prior devices have seams on their upper surfaces that may provide opportunities for cargo to get caught and immobilized during the loading and unloading processes of the cargo bay. 
         [0005]    Additionally, currently known products are typically manufactured from metal castings. The loads imposed on ball transfer units by movement of cargo over such units are substantial, sometimes concentrating hundreds of pounds per square inch of load to an individual ball transfer unit. It is not uncommon for cast units to fracture under these loads, rendering the damaged ball transfer unit useless. 
         [0006]    There is a need, therefore, for an improved ball transfer unit which restricts the ingress of water, contaminating fluids, dirt, dust and other debris, which present a smooth and unobstructed surface to minimize unintentional interference between the ball transfer unit and cargo being moved there over, and for a ball transfer unit design being constructed from machined versus cast materials to enhance the overall strength of the unit, thereby increasing its durability and useful life. 
       SUMMARY OF THE INVENTION 
       [0007]    According to the present invention, there is provided a ball transfer unit for use in association with installed trays in vehicle cargo bays. The ball transfer units are modular units that comprise a large or main roller ball element, a semi-spherical housing for holding that element, a plurality of smaller ball elements interposed between the housing and the main ball element and a unitary cover affixed to the housing for securing the various ball elements in relation to the housing and cover, whereby the large ball element protrudes partially through said cover and where the cover is designed to discourage the ingress of water and contaminants into the housing. 
         [0008]    The cover is manufactured without seams, and includes a transitional elevated portion of sufficient height to prevent most ingress of water or contaminants. The housing and cover may be machined, rather than cast, from high strength steel stock, such as, for example, stainless steel, which imparts substantial strength to the unit, reduces deterioration resulting from elemental exposure and provides the necessary strength to support a significant distributed and undistributed loads. 
         [0009]    The preferred embodiments of the invention will be described by way of example with reference to the accompanying drawings herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The various features, advantages and other uses of the present apparatus will become more apparent by referring to the following detailed description and drawings in which: 
           [0011]      FIG. 1  is a schematic illustration of a typical cargo hold employing an exemplary roller unit; 
           [0012]      FIG. 2  is a perspective view of the roller unit of  FIG. 1  including an exemplary ball transfer unit attached to a roller tray and a second ball transfer unit shown removed from the roller tray; 
           [0013]      FIG. 3  is top plan view of the roller tray with the ball transfer unit removed; 
           [0014]      FIG. 4  is cross-sectional view of the roller tray taken along section line  4 - 4  of  FIG. 2 ; 
           [0015]      FIG. 5  is partial cross-sectional view of the roller unit taken along section line  5 - 5  of  FIG. 2 ; 
           [0016]      FIG. 6  is a top a plan view of the roller unit; 
           [0017]      FIG. 7  is partial cross-sectional view of the roller unit taken along section line  7 - 7  of  FIG. 6 ; 
           [0018]      FIG. 8  is partial cross-sectional view of the roller unit taken along section line  8 - 8  of  FIG. 6 ; 
           [0019]      FIG. 9  is a bottom view of the ball transfer unit mounted to the roller tray; 
           [0020]      FIG. 10  is a top plan view of the ball transfer unit; and 
           [0021]      FIG. 11  is a top plan view of a bearing housing of the ball transfer unit. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0022]    A typical cargo hold  20 , such as may be found, for example, in an aircraft, is illustrated in  FIG. 1 . The cargo hold  20  may include a cargo hold floor  22 , opposing cargo hold walls  24  and a cargo hold ceiling  26 , which serve to define a generally confined compartment  28  in which a wide range of cargo  30  may be positioned, secured and transported. Attached to the cargo hold floor  22  are multiple elongated roller unit  31  that include a roller tray  32  configured to support a ball transfer unit  33 . The roller unit  31  may also be mounted to the cargo hold walls  24 . The number of roller units  31  disposed within the cargo hold  20  may depend, at least in part, upon the size of the cargo hold  20  and the configuration and weight of the cargo  30  to be distributed along the roller unit  31 . The roller unit  31  may be permanently or semi-permanently mounted to the cargo hold floor  22 . 
         [0023]    With reference to  FIGS. 2-5 , the roller tray  32  may be generally configured in the shape of a rectangular tube. In one exemplary configuration, the roller tray  32  may have an overall height “H” of approximately two to three inches. Each roller tray  32  may include a top wall  34 , a bottom wall  36  and opposing side walls  38 , surrounding an approximately rectangular roller tray cavity  40 . The top wall  34  of each roller tray  32  is provided with a plurality of tray openings  42  configured to receive the ball transfer unit  33 . Each tray opening  42  has a diameter  44  which generally corresponds to an outer diameter  46  of a retainer cover  48  of the ball transfer unit  33 . The outer diameter  46  of the retainer cover  48  may be sized slightly smaller than the diameter  44  of the tray opening  42  to enable the ball transfer unit  33  to be positioned within the tray opening  42 . 
         [0024]    Each tray opening  42  may include a lip  50  for supporting the ball transfer unit  33  within the tray opening  42 . The lip  50  extends generally inward from a circumferential edge  52  of the tray opening  42 . The retainer cover  48  of the ball transfer unit  33  engages a top surface  51  of the lip  50  when the ball transfer unit  33  is positioned within the tray opening  42 . The outer diameter  46  of the retainer cover  48  may be sized larger than an inner diameter  62  as measured between diametrically opposed points on lip  50  (see for example  FIG. 3 ). This enables the retainer cover  48  of the ball transfer unit  33  to rest on the lip  50 . 
         [0025]    To provide a generally smooth transition between an outside surface  56  of the retainer cover  48  of the ball transfer unit  33  and an outside surface  58  of the roller tray  32 , the lip  50  may be displaced downward from the top wall  34  of the roller tray  32  by an offset  54  (see for example  FIG. 5 ). The offset  54  may generally correspond to a thickness “T” (see for example  FIG. 5 ) of the retainer cover  48  to enable the outside surface  56  of the ball transfer unit  33  align approximately flush with the outside surface  58  of the roller tray  32 . 
         [0026]    The lip  50  may include one or more lip cutouts  64  to provide clearance for locking features on the ball transfer unit  33  used for connecting the ball transfer unit  33  to the roller tray  32 . The locking features are discussed in more detail subsequently. 
         [0027]    With reference to  FIGS. 7-11 , each ball transfer unit  33  includes a bearing housing  66  having an upper lip or housing annulus  68 . The housing annulus  68  may be sized to have an outer circumferential diameter  71  less than the inner diameter  62  of the lip  50  of roller tray  32 . The bearing housing  68  is preferably seamlessly machined of stainless steel, rather than cast, inasmuch as the machining process may impart substantially higher strength and resiliency to the housing, in comparison to cast housings. The bearing housing  66  may include a bearing cup  70  having a semi-spherical interior  72 . The bearing cup  70  includes a wall  74  having an outer surface  76  and an opposing inner surface  78  defining the interior region  72  of the bearing cup  70 . The housing annulus  68  extends generally radially outward from the wall  74  of the bearing cup  70 . 
         [0028]    The housing annulus  70  is provided with a pair of retaining tabs  80  spaced approximately 80° apart around the housing annulus  70 . The retaining tabs  80  engage the cutouts  64  in the lip  50  of the roller tray  32  when the ball transfer unit  33  is attached to the roller tray  32 . Diametrically opposed from a midpoint of the housing annulus  68  between the two retaining tabs  80  is a cutout  82  that is dimensioned and configured to accommodate passage of a clamp  84  (see  FIGS. 6 ,  7 ,  9  and  10 ) used to secure the ball transfer unit  33  to the roller tray  32 . A drain hole  86  may be provided at a bottom  88  of the bearing cup  70  to facilitate drainage of fluids. 
         [0029]    With particular reference to  FIGS. 5 ,  7  and  8 , the bearing housing  66  is provided with a plurality of small roller balls  90  and a single large roller ball  92 . The small roller balls  90  are arranged within the bearing cup interior  72  along the inner surface  78  of the bearing cup  70 . The large roller ball  92  is also positioned within the bearing cup interior  72  and is supported by the small roller balls  90 . The large roller ball  92  disperses the small roller balls  90  along the bottom and side walls of the bearing cup  70 . The small roller balls  90  form a movable generally low friction layer between the inner surface  78  of the bearing cup  70  and an exterior  94  of the large roller ball  92 . This configuration helps to evenly transmit forces associated with the weight of the cargo  30  (see  FIG. 1 ) positioned on the large roller ball  92  to the small roller balls  90  and to the bearing housing  66 . 
         [0030]    With reference to  FIGS. 5-8 , the retainer cover  48  may be formed as a one-piece unitary annular machined component that attaches to the housing annulus  68  of the bearing housing  66 . The diameter  46  of retainer cover  48  is larger than a diameter  71  of housing annulus  68  and inner diameter  62  of lip  50 . The retainer cover  48  includes a center opening  96  through which the large roller ball  92  extends. A tapered lip  98  extends generally upward and inward from the center opening  96  to form a generally cone-shaped configuration. The tapered lip  98  surrounds and guides the large roller ball  92  into a generally centralized relationship with a central axis of the bearing housing  66 . The tapered lip  98  terminates at a distal circumferential edge defining a circular opening  100  having a diameter  102  smaller than a diameter  104  of the large roller ball  92 . The tapered lip  98  may extend above a surface  106  of the retainer cover  48  a distance of at least one-half of the segment  108  of the large roller ball extending above the surface  106 . The height and generally cone-shaped configuration of the tapered lip  98  of the retainer cover  48  helps prevent ingress of water and contaminants from entering the interior  72  of the bearing housing  66 . 
         [0031]    With particular reference to  FIGS. 10-11 , the retainer cover  48  may be secured to the bearing housing annulus  68  using threaded fasteners  110 . The housing annulus  68  may be provided with a plurality of tapped and threaded holes  112  for engagement the fasteners  110 . A plurality of corresponding counter-sunk fastener holes  114  may be provided in the retainer cover  48  that align with the tapped holes  112  in the housing annulus  68  of the bearing housing  66 . In this fashion, when the retainer cover  48  is secured to the bearing housing  66 , the large roller ball  92  is generally centered in the bearing housing  66 , and a portion of the larger roller ball  92  protrudes through the circular opening  100  in the tapered lip  98 . 
         [0032]    Referring to  FIGS. 7 and 10 , retainer cover  48  may be provided with the pivoting clamp  84  for releasably attaching the ball transfer unit  33  to the roller tray  32 . The clamp  84  may be pivotally secured to an outer rim  116  of the retainer cover  48  using a threaded fastener  118 . The clamp  84  may be selectively moved between an unlatched position and a latched position. For example, the clamp unlatched position is illustrated in phantom in the  FIGS. 9-10 , and the latched position is illustrated in solid line. 
         [0033]    With reference to  FIGS. 6-9 , the ball transfer unit  33  may be attached to the roller tray  32  by inserting the retaining tabs  80  of the housing annulus  68  through the lip cutout  64  in the roller tray  32  and sliding the retaining tabs  80  under the top wall  34  of the roller tray  32 . With the clamp  84  rotated to an unlatched position (illustrated in phantom in  FIG. 9 ) generally tangential to an outer circumference of the retainer cover  48 , the retainer cover  48  may be positioned within the tray opening  42 , thereby permitting the entire ball transfer unit  33  to come to rest on the tray opening lip  50 . With the ball transfer unit  33  positioned within the tray opening  42  the retaining tabs  80  on the bearing housing  66  engage an underside  120  of the top wall  34  of the roller tray  32 , and the retainer cover  48  rests on the lip  50  of the tray opening  42 . 
         [0034]    The clamp  84  may be pivotally secured to the retainer cover  48  using the threaded fastener  118 . The clamp  84  may be positioned in the unlatched position so as to clear the tray opening  42 , and engages the underside surface  120  of the top wall  34  when rotated 90° from the unlatched position to the latched position and secured with the threaded fastener  118 . The ball transfer unit  33  may be secured to the roller tray  32  by rotating the clamp  84  approximately 90° from unlatched position to bring the clamp  84  into engagement with the underside surface  120  of the roller tray top wall  34 , thereby preventing removal of the ball transfer unit  33  from the roller tray cavity  40 . By this operation, the ball transfer unit  33  will be removably secured within the tray opening  42 . 
         [0035]    While recited characteristics and conditions of the invention have been described in connection with certain embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.