Patent Publication Number: US-6339630-B1

Title: Sealed drive screw operator

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sealed screw operator for operating wedge drive screws or the like without breaching a hazardous material control border. 
     2. Related Art 
     Although the invention is not limited to such an application, the invention is particularly useful as applied to dual cask arrangements wherein an inner container or cask is installed inside of an outer shipping cask. In such arrangements, the inner container or cask is adapted to be removed from the shipping cask in instances where the exterior of the cask is contaminated with a hazardous material or materials. Loading and/or unloading operations may take place in a dry, non-hazardous environment and, under these circumstances, the inner container is not removed from the shipping cask. The inner cask includes a closure head which is secured by a series of wedge blocks operated by drive screws in the inner container walls. Because the inner container is not removed from the shipping cask, access to the drive screws during security of the closure head must be obtained through the wall of the shipping cask. It will be appreciated that, during operations, the goal is to avoid breaching boundaries contaminated with hazardous materials. 
     Patents of interest in this field include: U.S. Pat. No. 4,893,022 (Hall, et al.) which discloses an improved closure for covering and sealing a single cask radioactive waste system using sealing bolts. The sealing bolts are inserted through a bore having a shoulder to prevent the sealing bolts from inadvertently falling through the bore and breaking the seal. U.S. Pat. No. 4,456,827 (Botzem, et al.) discloses a transportation and storage container for radioactive wastes which are socketed screws in tapped sockets to seal the container from the admission of water. U.S. Pat. No. 4,636,645 (Kessinger) discloses a closure system for a storage cask for spent nuclear fuel which can be temporarily closed with a shear key and permanently closed via welding. U.S. Pat. No. 4,983,352 (Efferding) discloses a closure system for storing spent nuclear fuel. Studs are coated with sealant before screwing the studs into bores. U.S. Pat. No. 4,576,779 (McWilliams) discloses a wedge shaped member which is used to close the end of a transport flask and which advances a seal plate to close an opening in the base of the flask. U.S. Statutory Invention Registration No. HII (Basnar et al.) and U.S. Statutory Invention Registration No. HIO (Frank, et al.) both disclose a can-out hatch assembly. In both, an actuating shaft is inserted through a bore in a container for the purpose of positioning a hex head coupling against a pressure plate. The actuating shaft and the bore are provided with complimentary threads. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is provided a sealed operator for operating (e.g., engaging and locking) a controllable element (e.g., a wedge screw drive such as disclosed above) in a dual container hazardous waste storage system. 
     In accordance with one aspect of the invention, there is provided, for use in a dual container hazardous waste containment system comprising an inner container, an outer container and an internal locking control element disposed inwardly of the outer container (such as the wedge screw drive element described above), a sealed operator device for operating the locking control element and adapted to be mounted in an aperture in the outer container, said operator comprising: a housing adapted to be sealingly mounted in said aperture, a bushing sealingly mounted within said housing for longitudinal movement with respect to said housing; a bearing assembly sealingly mounted within said bushing and comprising an outer bearing secured within said bushing and an inner bearing pivotably movable with respect to said outer bearing; and an operator element sealingly mounted within said inner bearing for movement therewith, said operator element including a stem portion secured within said inner bearing and a driving head adapted to engage the locking control element. 
     Preferably, the inner and outer bearings form a spherical bearing assembly. The bearings advantageously include respective polymer coated bearing surfaces. 
     In a preferred implementation, the outer bearing is a press fit within the bushing and the stem portion of the operator element is a press fit within the inner bearing. Advantageously, the outer surface of the housing is threaded for mounting in the aperture in the outer container. 
     In accordance with a further feature of importance, the bushing has an outer cylindrical surface including longitudinally extending guide track therein and the housing includes an inwardly extending guide pin received in the guide track for limiting angular movement of the bushing. 
     Preferably, at least one o-ring seal is provided between said bushing and said housing. More preferably, at least first and second o-rings are mounted in annular grooves in an outer cylindrical surface of the bushing. 
     In accordance with a further aspect of the invention a dual container hazardous waste containment system is provided which comprises an inner container, an outer container, a controllable element (e.g., the aforementioned wedge drive element) associated with the inner container and disposed inwardly of the outer container and a sealed operator device mounted in an aperture in the outer container for operating the controllable element, the sealed operator comprising: a housing sealingly mounted in the aperture; a bushing sealingly mounted within the housing for longitudinal movement with respect to the housing; a bearing assembly mounted within the bushing and comprising an outer bearing press fit within the bushing and an inner bearing pivotably movable with respect to the outer bearing; and an operator element mounted within the inner bearing for movement therewith, said operator element including a stem portion press fit within the inner bearing and a driving head adapted to engage the controllable element. 
     Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a side view of a sealed operator in accordance with a preferred embodiment of the invention; and 
     FIG. 2 shows a side view of a dual container system incorporating the sealed operator of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown a sealed operator, generally denoted  10 , constructed in accordance with a preferred embodiment of the invention. The sealed operator  10  includes, inter alia, the following elements or components described in more detail below: a cylindrical or tubular housing  12 , a tubular bushing  20  mounted in housing  12 , a bearing assembly  30  press fit to and supported by bushing  20 , an operator element  40  press fit to and supported by bearing assembly  30 , a pair of o-rings  50  providing a seal between the bushing  20  and the housing  12 , and a guide pin  52  affixed to housing  12  for controlling the rotational movement of bushing  20  during rotation of operator element  40 . 
     The sealed operator  10  is, in use, incorporated in a dual container hazardous waste system such as that shown in FIG.  2  and denoted  100  in that figure. The container system  100  includes an outer container or shipping cask  102  having an aperture or recess  104  therein in which the sealed operator  10  is housed, and an inner container  106 . The inner container  106  includes a wedge drive screw support element  108  which supports a wedge drive screw  110  for a wedge block (not shown) corresponding to that described above. A sleeve  112  is provided to guide the movement of the associated wedge. As indicated above, the wedge block is one of a plurality of wedge blocks used to secure in place a closure head (not shown) for the inner cask  106 . It will be understood that the wedge and wedge drive assembly are conventional and thus will not be further described. 
     Referring again to FIG. 1, and considering the specific components of the sealed operator  10  in more detail, the housing  12  includes an outer surface  14 , an inner surface  16 , and a hole or opening  18  in which guide pin  52  is affixed. As shown in FIG. 2, the tubular housing  12  is inserted into the aperture  104 , so that the outer surface  14  frictionally engages the wall defining aperture  104 . In a preferred embodiment, the outer surface  14  of the tubular housing  12  is threaded and the aperture  104  has an opposing abutment surface for receiving the threads of the tubular housing  12 . Thread sealant is preferably applied to the opposing abutment surface or to the outer surface  14  of the housing  12  or to both. All components of the dual-container, operator assembly-system shown in FIGS. 1 and 2 are manufactured from materials selected for corrosion resistance and compatibility with the other materials. In the preferred embodiment, the housing  12  is manufactured from aluminum bronze. 
     The cylindrical or tubular bushing  20  includes an outer surface  22 , an inner surface  24 , and a plurality of annular grooves  26  in outer surface  22  in which o-rings  50  are received. The outer diameter of bushing  20  is smaller than the inner diameter of housing  12  so that bushing  20  can be inserted into and translate within the tubular housing  12 . In the preferred embodiment, the tubular bushing  20  is manufactured from stainless steel, e.g., NITRONIC 60, a trademark of Armco Steel. Stainless steel has good compatibility with the aluminum bronze and does not cause galling during the sliding contact associated with the engagement/disengagement of the operator described below. 
     As indicated above, bushing  20  has a plurality of annular grooves  26  (two are shown) which receive a like plurality of o-rings  50  so as to enhance sealing between the outer surface  22  of the bushing  20  and the inner surface  16  of the housing  12 . 
     Bushing  20  also includes a longitudinally extending guide track  21  located in an upper portion of outer surface  22 . The aforementioned guide pin  52 , which is affixed in the opening  18  in the housing  12 , engages in track  21  so as to prevent rotation of the bushing  20 , i.e., to limit the movement of bushing  20  to a translating movement. This feature prevents potential damage to the o-rings  50  due to “wrapping up” during operation. 
     The bearing assembly  30  includes an outer bearing  32  including an outer cylindrical surface  32   a  and an inner concave, part spherical bearing race  32   b , and inner bearing  34  including an outer convex, part spherical bearing surface  34   b  and an inner cylindrical surface  34   a . The overall bearing assembly  30  is press fit into a cylindrical recessed portion of bushing  20  with the outer surface  32   a  of the bearing  32  engaging the associated mating surface of bushing  20 . The mating part spherical surfaces  32   b  and  34   b  of bearings  32  and  34  permit a limited pivoting movement so that operator element  40  can still engage the wedge drive screw  110  where there is misalignment between the wedge drive screw  110  and the operator element  40 . In a preferred embodiment, the pivoting movement provided will accommodate an angle of approximately seven to eight degrees between drive screw  110  and the operator element  40  which is equivalent to an offset between the inner container  106  and the outer container or shipping case  102  of approximately 0.2 inches. 
     The bearings  32  and  34  fit together sufficiently closely to provide sealing of the bearing assembly  30  under typical operating conditions. In addition, bearing assembly  30  preferably includes a polymer coating which increases its effectiveness as a seal. If there is a likelihood of a flood of hazardous material, a sealed bearing assembly can be used as bearing assembly  30 . The press fit between bearing assembly  30  and bushing  20  and operator element  40  provides effective sealing between the corresponding interfaces. 
     The operator element  40  has a stem  42  interconnecting a driven end  44  and a driving head  46 . The operator element  40  is a press fit in bearing  34  with the outer surface of stem  42  engages the cylindrical inner surface  34   a  of bearing  34 . The driving head  46  is adapted to engage the wedge drive screw  110  discussed above in connection with FIG.  2 . In a preferred embodiment, a hex-head driving head  46  is employed, but, in general, any shape is appropriate as long as the head  46  properly couples with the driven end of the wedge drive screw  110 . In the preferred embodiment, the flats of the hex-head driving head  46  are radiused to avoid binding where, for example, the inner container  106  is misaligned with respect to the outer container  102  during shipping. The driven end  44  of the operator element  40  includes an opening  48  adapted to receive an appropriate tool for driving the operator element  40 . The driven end  44  of the operator element  40  also includes a threaded opening  54  adapted to receive a tool (not shown) for translating the bushing  20  outwardly within the housing  12 . 
     In operation, the aforementioned driving tool (not shown) is coupled to opening  48  of the driven end  44  of the operator element  40  and pushed in so as to provide translation of the operator element  40  forwardly, i.e., to the left, as viewed in FIG.  1 . The operator element  40  is translated and manipulated until the driving head  46  operator couples with wedge drive screw  110 . The wedge drive screw  110  is rotated to drive the wedge in a leftward, horizontal direction, as viewed in FIG.  1 . As indicated above, the wedge drive screw  110  drives a corresponding wedge block (not shown) to secure the closure head (not shown) of the inner cask or container  106 . It is, of course, understood that the bearing assembly  30  and bushing  20  also translate with operator element  40  relative to housing  12 . 
     During shipment, a plug  114  (see FIG. 2) is screwed Into the housing  12  and jammed against the operator element  40  to lock the assembly in place. 
     When removal of the inner container  106  from the shipping cask  102  is desired, a tool (not shown) is threaded into opening  54  permitting translation of bushing  20  in the outward direction (to the right in FIG. 1) to disengage the driving head  46  of operator  40  from the wedge drive screw  110 . 
     Although the invention has been described above in relation to preferred embodiments thereof, it will be understood by those skilled in the art that variations and modifications can be effected in these preferred embodiments without departing from the scope and spirit of the invention.