Patent Number: 
Section: description

Referring now to the drawings, particularly to FIG. 1, there is illustrated a shipping container constructed in accordance with a preferred embodiment of the present invention and generally designated 10. Shipping container 10 includes an outer container 12, an inner containment vessel 14 and a pair of product pails 16 stacked one on top of the other and disposed within the inner containment vessel 14. Shipping container 10 also includes upper and lower dunnages 18 and 20, respectively, and a top 22 for the outer container 12. Outer container 12 is generally cylindrical and preferably fabricated from stainless steel. Reinforcing ribs 17 are formed at axially spaced locations along the container 10 and preferably two such ribs are closely spaced to one another and to the top of the container to reinforce the container, particularly adjacent the top 22. Also, between the outer container 12 and the inner containment vessel 14 is provided a heat-retardant-foam, preferably a polyurethane foam 19. Referring now to FIGS. 3, 4 and 5, the inner containment vessel 14 is preferably cylindrical, having a bottom 24 and an open top closed by a lid 26. A plurality of spiders or rods 28 project outwardly, preferably radially, from the cylindrical containment vessel 14 and into the region between the vessel 14 and outer container. 12 to ensure that the vessel remains centered. Preferably, four rods 28 are equally spaced about the periphery of the vessel 14 adjacent its upper end and a similar number and spacing of the rods are provided adjacent the lower end of the vessel 14. The rods 28 extend into the foam which is adhered to the outer container. Consequently, the vessel 14 remains centered within the outer container and is prevented from rotation relative to the outer container. Additionally, neutron-absorbing material such as cadmium may be provided about the external surface of the inner vessel 14 in the form of poison panels 29. The panels 29 preferably extend between the top and bottom of the inner vessel and may be provided in an arcuate length of 90xc2x0. The panels overlie the external peripheral surface of the inner vessel 14 and are provided with openings to receive the spiders 28, as well as the gussets described below. The panels 29 as illustrated in FIG. 1 are overlaid by the foam 19. An annular flange 30 extends about the periphery of the vessel 14 adjacent its open upper end and projects radially outwardly therefrom. A plurality of gussets 32 are disposed between the upper end of the vessel 14 and the underside of the flange 30 to reinforce the lid sealing region about the open end of the vessel 14. Lid 26 comprises a circular disk overlying the flange 30 and a gasket 21 formed of a fire retardant material is disposed between the lid and flange. The lid has a plurality of predrilled holes for registration with tapped holes in the flange 30 whereby bolts 36 passing through the holes and threaded into the tapped openings secure the lid and gasket to the vessel 14, closing its upper end. As illustrated in FIG. 5, the flange 30 may also mount two or more dowel pins 38 to assist in orienting the lid 26 onto the vessel 14 during installation. Referring back to FIG. 1, the product pails 16 are preferably formed of 18-20-gauge stainless steel. The product pails are closed containers having a lid with a retaining ring and bolt about the lid securing the lid to the pail. The radioactive material is, of course, located in the product pails. Referring now to FIGS. 6 and 7, the upper dunnage 18 is illustrated. The upper dunnage comprises a foam core and ceramic fiberboard panels 40 and 41, respectively, sandwiched between a pair of plates 42 and 44, preferably formed of 24-guage stainless steel. The plates, as well as the foam and ceramic fiberboard panels, have cutouts 48 along their margins for receiving portions of the bolt lugs used to secure the top 22 to the outer container 12 during assembly as described below. Additionally, a circular ceramic fiberboard panel 46 having an underlayer 47 of stainless steel is secured to the bottom of the upper dunnage 18 to bear against the lid 26 of the inner containment vessel 14 in assembly. The lower dunnage 20 illustrated in FIG. 1 is constructed of a similar upper layer of foam 50 underlaid by a ceramic fiberboard panel 52. The bottom of container 12 is closed by steel plate 54. Referring now to FIGS. 11, 12 and 16, the top 22 for the outer container 12 is circular and formed from stainless steel. From a review of FIGS. 11, 12 and 16, it will be appreciated that top 22 includes a plurality of bolt holes extending through lugs 60 for threaded engagement with inserts 62 threaded into bolt brackets 63 secured to the inside surface of the outer container 12. The bolts 64 are threaded into the inserts 62 to secure the top 22 with a watertight O-ring seal 61 to the container 12. As seen in FIGS. 11 and 12, three of the bolts 64 and associated lugs, plugs and brackets are spaced 90xc2x0 from one another about the margin of the top 22. The remaining two bolts are placed approximately 30xc2x0 from one another and centered on opposite sides of a weld seam 68 extending down the side of the outer container 12. Thus, the bolted connections between the top and the container in the region of the seam 68 provide added reinforcement for the lid. To supplement the securement of the top 22 to the outer container 12 and as illustrated in FIGS. 2 and 17, a heavy-duty retaining ring 70 is applied about the arcuate rolled edge 72 of the top 22 and a beaded rim 74 formed along the upper edge of the outer container 12. The ring 70 terminates at opposite ends in lugs 76 formed to lie close along the outer drum wall rather than projecting radially so that the extent of the projection of the lugs is minimized to avoid shearing of the lugs. As illustrated in FIG. 17, the wall of the outer container immediate the area about the lugs is further supported by a stainless steel plate 81 welded to the outside of the outer drum 12. The steel plate prevents the bolt lugs from cracking the outer drum weld seam 68 due to accidental impact. Additionally, a bolt 83 threadedly secures the lugs 76 to one another. Lock nut 87 keeps the threaded bolt 83 from coming loose while securing the retaining ring 70 about the margin of top 22 and outer container 12 to reinforce the securement of the top and outer container one to the other. A plurality of vent holes 80 (FIG. 1) are provided at vertically and circumferentially spaced positions about the outer container 12. For example, three vent holes are provided through the container 12 in vertically spaced relation to one another at 90xc2x0 intervals about the container 12. Each vent hole is sealed by a plastic plug 82. Upon reaching a predetermined temperature, the plastic of the plug 82 melts, opening the vent hole, enabling the escape of expanding gases from within the container. Additionally, and referring to FIG. 11, the top 22 has a vent hole 84 filled with a plastic plug 86. Likewise, the bottom 54 of the container 12 has a central vent hole and a plastic plug. The top and bottom vent holes operate similarly as the side vent holes 80 in FIG. 1 to preclude a buildup of pressurized gases within the container which otherwise might rupture the container. The size and geometry of the invention is such that a standard sea van can accommodate up to 72 containers. Older-style containers had sizes and geometries that would only allow a maximum 54 containers per sea van. Referring now to FIG. 18, which illustrates initial fabricating steps for the shipping container hereof, the bottom 54 of container 12 is provided with a central hole 90. Next, the ceramic fiberboard panel 52 and the layer of foam 50 of the lower dunnage 20 are placed in the bottom of the outer container 12. A fixture assembly is then provided. The fixture assembly includes a pair of channel members 92 and 94 connected at their centers to one another by welding and/or by a bolt 96 and extending at right angles to one another. Each of the channels has a slot at its distal end for receiving the lower end of a threaded rod 98. It will be appreciated that four threaded rods 98 are disposed about the outer container 12 and secured at their lower ends by nuts 100 to the channel members 92 and 94. The outer container 12 is then centered within and on the fixture. Referring to FIG. 19, a closure member or disk assembly comprised of a series of disks is disposed on top of the flange 30 of the inner container 14. In the order placed on the flange 30 of inner vessel 14, the disk assembly includes a first disk 104 having a plurality of circumferentially spaced bolt holes 106, vent holes 108 and apertures 110 for receiving the dowel pins 38 formed on the flange 30. Disk 104 is preferably formed of xe2x85x9cxe2x80x3 thick stainless steel and has an outer diameter corresponding to the outer diameter of flange 30. The next disk 112 is preferably formed of 22-gauge stainless steel having bolt holes 114 and vent holes 116. The third disk 118 is preferably formed of xc2xdxe2x80x3 thick aluminum and has bolt holes 120 and vent holes 122. From a review of FIG. 19, it will be appreciated that disks 104, 112 and 118 have like diameters. A final disk 124, preferably formed of xc2xdxe2x80x3 thick aluminum, includes bolt holes 126, vent holes 128 and a pair of openings 130 at diametrically opposite locations about the disk 124. The diameter of disk 124 is slightly smaller than the inner diameter of the outer container 12. Additionally, a hook 140 is provided in the center of the top disk 124 for purposes of lifting the inner container 14. In assembling these disks, the vent holes 108, 116, 122 and 128 are aligned with one another and bolts 132 (FIG. 20) extend through the four disks and thread into correspondingly located threaded bolt openings 136 (FIG. 19) in flange 30. It will be appreciated that the dowel pins 38 in this assembly are received in the apertures 110 and 111 of the lower disk 104 and disk 112. Additionally, a quick-release material is provided along the underside of the margin about the disk 124 which projects beyond the outer diameters of the disks 104, 112 and 118 to facilitate release of the disk assembly from the foam, i.e., prevents the foam from sticking to the fixture during the foaming operation. The inner container 14 with the four disks attached is then lifted, using hook 140, and located and centered in the outer container 12. In placing the inner vessel 14 within the outer container 12, it is aligned with the seam weld 68 along the outer container 12. Levelers, not shown, are placed on top of the disk 124 to ensure that the inner container is set within the outer container as level as possible. A similar fixturing assembly like 92, 94, 95 and 100 in FIG. 18 is then applied to the top of the inner and outer containers as illustrated in FIG. 20. Particularly, a pair of channel-shaped elements 150 and 152 are located at right angles to one another and secured to one another, extending across the open top of the outer container. The ends of the members 150 and 152 have slots for receiving the upper ends of the threaded rods 98. The rods are secured in place by nuts 154. Elongated bolts 156 extend through the members 150 and 152 and their lower ends engage the upper surface of the upper disk 124, ensuring that the inner container remains level within the outer container 12. The container is now ready for the foaming operation. Foam is injected through the two openings 130 in the upper disk 124 to fill the annular space between the inner vessel 14 and outer container 12. The foam is injected simultaneously through holes 130 and fills the annular space to a level corresponding to an elevation above flange 30 to the bottom side of disk 124, at which time the foaming operation ceases. After curing, the fixtures, both top and bottom, are removed. Additionally, the disk assembly is removed from the flange 30 of the inner vessel 14. From a review of FIG. 20, it will be appreciated that the spiders 28 extend into the foam 19 securing the inner vessel 14 within outer container 12. Next, the bolt brackets 63 (FIG. 16) are drilled and tapped and the inserts 62 are threaded into the brackets. The brackets 63 are then welded to the inside surface of the outer container 12, with two of the brackets closely straddling the seam 68. A master template gauge, not shown, may be used to locate the brackets about the inner circumference of the outer container 12. The backing plate 80 (FIG. 17) can also be welded to the outer container at this time. Next, a template, also not shown, may be used to locate the lugs 60 (FIG. 12) and holes for drilling through the top 22 for the outer container 12. Additionally, the template may be used to locate the center vent hole 84 in top 22. The lugs 60 are then welded to the top 22. The ceramic fiberboard panel 52 is pre-drilled with a central opening through the openings 84 and 90 in the top and bottom of the outer container 12. A plug 86 is installed in these openings, the bottom one of which is inserted prior to foaming. The upper dunnage 18 is then located overlying the top of the inner vessel 14 and the foam 19, the slots 48 being provided to enable the dunnage 18 to pass by the lugs 63 (FIG. 16). Next, the container""s top 22 and outer ring 70 is bolted into place. An opening is drilled through part of the upper dunnage disks 41 and 42 in FIG. 7 for venting purposes. Also, a translucent silicone is used to seal around the lugs 60 on the top of the top 22. An O-ring washer 61 seals bolt 64 to the top 22, making the top 22 completely watertight. It will be appreciated from the foregoing that there has been provided a shipping container having substantial structural integrity and resistance to fire and water intrusion as well as a quick and inexpensive method of fabricating the container. Importantly, the container provides safety from radiation and criticality while material parts of the shipping container are formed of materials resistant to rust and corrosion, such as stainless steel, whereby the integrity of the container can be maintained over long periods of time and in hundreds of shipments. The structural integrity of the container is enhanced by the retaining ring, the spiders or rods which maintain the inner vessel centered within the outer container and the engagement of the upper and lower dunnages against the top and bottom of the inner vessel, respectively, the dunnages being sandwiched between the vessel and the top and bottom of the container. The arrangement of the reinforcing ribs on the outer container, particularly adjacent the top of the container, reinforce the top of the container, enhancing its resistance to impact. Fire resistance is provided by the combination of foam and ceramic fiberboard panels. Resistance to the destructive effects of high temperatures is also provided by the provision of vent holes disposed and arranged to vent any gases generated within the container upon the container reaching a predetermined temperature. That is, the plastic plugs melt at high temperature and enable the container to be vented. Further, the use of bolt brackets with removably threaded inserts improves the life cycle of the container by permitting the inserts to be removed and replaced by fresh threaded inserts. Consequently, any damage to the bolts or female threads may be readily repaired. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.