Patent Publication Number: US-2013232998-A1

Title: Vertical storage rack for cold storage units

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to storage racks and, more particularly, to storage racks configured for use in cold storage units such as cryogenic dewars for storing samples at about −180° C., or lower. 
     BACKGROUND OF THE INVENTION 
     Cold storage units such as freezers and dewars are used for various purposes, including the storage of biological samples over short and long periods of time. For example, biological materials for transplantation such as blood, tissue, or plasma may require storage for short periods of time before use. In another example, biological cells such as DNA samples may be stored for longer periods of time. Conventional cold storage units may be cooled by mechanical cooling circuits or by liquid nitrogen (“LN2”). 
     In a known cold storage unit referred to as a LN2 cryogenic dewar, the dewar includes a tank having a vacuum-insulated shell enclosing a pool of liquid nitrogen and a storage space located above the pool of liquid nitrogen (which boils at −196° C.). The storage space is usually configured to receive a plurality of storage racks for containing boxes of vials or other containers holding biological samples. The tank includes an insulated lid or plug at an opening in the top to provide selective access into the storage space for retrieval and replacement of the storage racks. In order to limit the exposure of the liquid nitrogen and storage space to the external environment, the opening in the tank is sized smaller than the storage space and each storage rack is rotatable or moveable into alignment with the opening for removal. As a result, storage racks for LN2 cryogenic dewars are generally oriented as a vertical storage rack that can be lifted or lowered through the opening at the top of the tank. 
     The vertical storage racks used with LN2 cryogenic dewars generally include multiple shelves for holding vertically-stacked storage boxes. The storage racks are manufactured from stainless steel and the shelves are spot welded into position with a plurality of side walls and/or runners to ensure sufficient structural strength and rigidity of the storage rack during use in the cryogenic dewar and during movement into and out of the cryogenic dewar. The manufacturing process for these conventional storage racks is highly time-consuming and requires skill-intensive labor. Additionally, when fully loaded with storage boxes filled with vials, each storage rack defines a relatively heavy weight that may be difficult to lift into and out of the opening at the top of the tank. 
     There is a need, therefore, for a storage rack for use with LN2 cryogenic dewars and other cold storage units that improves the manufacturing process while providing improved performance compared to conventional storage racks. 
     SUMMARY OF THE INVENTION 
     In one embodiment according to the present invention, a storage rack for holding storage boxes within a cold storage unit includes a rack body including a rear wall and first and second opposed sidewalls extending from the rear wall. A plurality of shelves is defined by a series of first lips punched from the first sidewall and a series of second lips punched from the second sidewall. The first and second lips are bent towards each other and spaced from each other. The storage rack also includes a handle supported by the rack body and configured to support the storage rack during movement into and out of the cold storage unit. Forming the plurality of shelves by punching and bending lips from the first and second sidewalls saves material and weight of the storage rack while simplifying manufacturing of the storage rack. 
     In one aspect, the storage rack also includes a top wall coupled to the first and second sidewalls and a bottom wall coupled to the first and second sidewalls. The plurality of shelves is located between the top wall and the bottom wall. A rack reinforcement plate is engaged with the first and second lips of one of the shelves. In some embodiments, the rack reinforcement plate extends from the first sidewall to the second sidewall. The rack reinforcement plate is spot welded to the first and second lips of the corresponding shelf. 
     In another aspect, the rack body includes a plurality of apertures cut from each of the rear wall and the first and second sidewalls. In yet another aspect, the handle includes an upper end configured to be positioned adjacent an opening of the cold storage unit when the storage rack is located within a storage space of the vessel. The handle also includes a lower end coupled to the rack body and an elongate intermediate portion extending between the upper and lower ends. The upper end and the intermediate portion define a circular cross section, while the lower end defines a flattened rectangular cross section so that the lower end may be spot welded to the rack body. As a result, the storage rack is manufactured by a plurality of punching and bending steps that may be automated with a minimized number of spot welds performed by a skilled worker. A plurality of the storage racks may be used with a cold storage unit such that a pool of liquid nitrogen within the vessel maintains the temperature of any biological samples within the storage boxes at a low temperature such as about −180° C. 
     According to another embodiment, a method of manufacturing a storage rack for holding storage boxes within a cold storage unit includes providing a flat sheet sized to define a rack body having a rear wall and first and second sidewalls. The method also includes punching a plurality of first lips from the flat sheet at the first sidewall and bending the first lips generally perpendicular to the flat sheet. A plurality of second lips is punched from the flat sheet at the second sidewall and bent generally perpendicular to the flat sheet. The method also includes bending the flat sheet to form a rack body with the first and second sidewalls extending from the rear wall such that the plurality of first lips and the plurality of second lips extend towards one another and are spaced from each other. The method further includes coupling a handle to the top wall. The first and second lips on the rack body collectively define a plurality of shelves. 
     In one aspect, the method also includes stamping a plurality of apertures from the flat sheet at the rear wall and at the first and second sidewalls to reduce material in the storage rack. A rack reinforcement plate extending from the first sidewall to the second sidewall may also be engaged with the first and second lips of one of the shelves. The flat sheet and rack body may further include a top wall and a bottom wall, and the method in these circumstances also includes bending the top and bottom walls and coupling the top and bottom walls to each of the first and second sidewalls. The rack reinforcement plate, the handle, and the top and bottom walls are each spot welded into final positions in the storage rack. 
     These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a perspective view of a LN2 cryogenic dewar including a vertical storage rack according to an exemplary embodiment of the present invention, with the storage rack being inserted into the dewar. 
         FIG. 2  is a perspective view of the vertical storage rack of  FIG. 1  located outside the LN2 cryogenic dewar. 
         FIG. 3  is a front view of the vertical storage rack of  FIG. 2 . 
         FIG. 4  is a side view of the vertical storage rack of  FIG. 2 . 
         FIG. 5  is a top view of a flat sheet blank used to manufacture the vertical storage rack of  FIG. 2 . 
         FIG. 6  is a perspective view of a vertical storage rack according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the figures, and more specifically to  FIGS. 1 through 4 , a liquid nitrogen cryogenic dewar  10  including an exemplary vertical storage rack  12  according to one embodiment of the present invention is illustrated. Although the term “cryogenic dewar” is used throughout the specification when referring to this embodiment of the invention, it will be understood that this and other embodiments of the vertical storage rack  12  disclosed herein may be used with any type of refrigerator, freezer and cryogenic vessel (collectively referred to hereafter as “cold storage units”), such as, in one example, a chest freezer. In addition, it will be understood that the cryogenic dewar  10  may be cooled by liquid nitrogen, by a mechanical cooling circuit, or by any other known cooling methods. The vertical storage rack  12  is shaped and sized to receive a column or stack of cryogenic storage boxes  14  (alternatively a column or stack of “micro plates”) as shown in  FIG. 1 . The storage boxes  14  typically contain a grid (not shown) or other internal structure for receiving and orienting a plurality of vials or tubes (not shown) filled with biological samples in an array. However, the storage boxes  14  may be sized to receive other types of containers for biological samples. In the exemplary embodiment, each of the storage boxes  14  is supported on one of a plurality of shelves  16  located on the storage rack  12 . The storage rack  12  also includes an elongate handle  18  for supporting the storage rack  12  during movement into and out of the cryogenic dewar  10 , as shown in  FIG. 1 . 
     With continued reference to  FIG. 1 , the cryogenic dewar  10  includes a tank  20  configured to contain a pool of liquid nitrogen  22  and a plurality of the vertical storage racks  12 . The tank  20  includes double-walled insulation that defines a vacuum space  24  between an outer tank wall  26  and an inner tank wall  28 . The vacuum space  24  limits the transfer of environmental heat into a storage space  30  located within the inner tank wall  28 . The storage space  30  extends from a bottom end  32  (shown as grating  32 ) adjacent the pool of liquid nitrogen  22  to a top end  34  including an opening  36  in outer and inner tank walls  26 ,  28 . The opening  36  is sized smaller than the storage space  30  such that the tank  20  defines a narrowing neck portion  38  adjacent the opening  36 . The opening  36  is also sized to be just large enough to receive the storage rack  12  as the storage rack  12  is moved into and out of the cryogenic dewar  10 , as shown in  FIG. 1 . To this end, the exposure of the storage space  30  and the pool of liquid nitrogen  22  to the external environment is limited during removal or insertion of a storage rack  12 . 
     In use, after the storage rack  12  is fully inserted into the center of the storage space  30 , the handle  18  may be used to push the storage rack  12  towards the periphery of the storage space  30 . In the illustrated embodiment, an upper end  40  of the handle  18  engages with one of a plurality of handle slots  42  located around the opening  36  when the storage rack  12  is moved to the periphery of the storage space  30 . These handle slots  42  enable each handle  18  to be accessed from the opening  36 . Thus, the storage space  30  receives a plurality of storage racks  12  (for example, four, six, eight, or some other number) in the periphery of the storage space  30 , each of which may be independently accessed by moving the storage rack  12  to the center of the storage space  30  and then pulling the storage rack  12  out through the opening  36 . The tank  20  also includes tank handles  44  adjacent the neck portion  38  for moving the cryogenic dewar  10  when necessary and a lid (not shown) configured to close the opening  36  and seal the storage space  30  from the external environment when the storage racks  12  do not need to be moved into or out of the cryogenic dewar  10 . 
     During operation, the liquid nitrogen  22  boils off over time at a temperature of about −196° C. to maintain the temperature within the storage space  30  at a low cryogenic temperature, thereby keeping the biological samples on the storage racks  12  at a desired storage temperature. For example, the biological samples may be maintained at a desired storage temperature of about −180° C. It will be understood that the dewar  10  may include additional monitoring sensors and alarms that indicate when the level of liquid nitrogen is low and needs to be replenished to maintain the desired storage temperature within the storage space  30 . 
     Details of the vertical storage rack  12  according to this embodiment are more clearly shown in  FIGS. 2 through 4 . According to one embodiment, the vertical storage rack  12  includes a generally rectangular or C-shaped rack body  50  with a top wall  52  and a bottom wall  54 . The various walls of the rack body  50  may be collectively formed from a flat sheet blank  90  of type  201  stainless steel shown in  FIG. 5  and described in further detail below with reference to a method of manufacturing the storage rack  12 . Returning to  FIGS. 2 through 4 , the C-shaped rack body  50  also includes a rear wall  56  and first and second opposed sidewalls  58 ,  60  extending in generally parallel relation from the rear wall  56 . More particularly, the first and second sidewalls  58 ,  60  each extend from a rear edge  58   a,    60   a  connected to the rear wall  56  to a front edge  58   b,    60   b  positioned away from the rear wall  56 . 
     Accordingly, the rack body  50  partially encloses a rectangular space  62  configured to receive storage boxes through an open front  64  of the rack body  50 . The top wall  52  and the bottom wall  54  are coupled to the first and second sidewalls  58 ,  60  to bound the rectangular space  62  at ends of the rack body  50 . For example, the top wall  52  and the bottom wall  54  each include connection tabs  66  that are bent from the top and bottom walls  52 ,  54  so that the connection tabs  66  may be spot welded to the first and second sidewalls  58 ,  60 . The top wall  52  and the bottom wall  54  each extend from respective rear edges  52   a,    54   a  connected to the rear wall  56  to front edges  52   b,    54   b  located between the front edges  58   b,    60   b  of the first and second sidewalls  58 ,  60 . In this regard, the set of front edges  52   b,    54   b,    58   b,    60   b  of the top wall  52 , bottom wall  54 , and first and second sidewalls  58 ,  60  collectively defines the open front  64  of the rack body  50 . It will be understood that the top wall  52  and the bottom wall  54 , if present, may be connected to the rear wall  56  and the first and second sidewalls  58 ,  60  in other known manners in alternative embodiments within the scope of the present invention. 
     The vertical storage rack  12  also includes a plurality of apertures  68  cut from the rear wall  56  and from the first and second sidewalls  58 ,  60 . These apertures  68  reduce the total amount of stainless steel material used to form the vertical storage rack  12 . The apertures  68  located along the first and second sidewalls  58 ,  60  are shaped to produce respective first and second lips  70 ,  72  that may be bent inwardly towards the rectangular space  62  from the first and second sidewalls  58 ,  60 . To this end, the first and second sidewalls  58 ,  60  include a plurality of first and second lips  70 ,  72  that are punched from the remainder of the first and second sidewalls  58 ,  60  and bent or folded generally perpendicular to the first and second sidewalls  58 ,  60 . In the assembled state shown in  FIGS. 2 through 4 , these first and second lips  70 ,  72  produce a plurality of shelves  16  within the vertical storage rack  12  and located between the top wall  52  and the bottom wall  54 . 
     The plurality of apertures  68  and the plurality of shelves  16  are shown in further detail in  FIGS. 3 and 4 . Although each of the apertures  68  defines a generally rectangular shape in the illustrated embodiment, it will be appreciated that any shape may be cut or punched from the rear wall  56  and first and second sidewalls  58 ,  60  in other embodiments of the present invention. Each of the shelves  16  is defined by a pair of first and second lips  70 ,  72  extending inwardly from the corresponding first and second sidewalls  58 ,  60 . As clearly shown in  FIG. 3 , the first and second lips  70 ,  72  are spaced from one another in the final assembled state of the vertical storage rack  12 . Consequently, each of the shelves  16  consists of only first and second lips  70 ,  72  that collectively require significantly less stainless steel material than conventional shelves that extend entirely across the space  62  between first and second sidewalls  58 ,  60 . However, the first and second lips  70 ,  72  are sized large enough to reliably support storage boxes  14  filled with vials or containers of biological samples or other materials without buckling. In addition to using less stainless steel material, the plurality of shelves  16  is advantageously manufactured by a machine press or similar mechanism that punches and bends the first and second lips  70 ,  72  from the first and second sidewalls  58 ,  60  rather than requiring skilled laborers to spot weld separate shelves into position within the rack body  50 . 
     In the embodiment shown in  FIGS. 2 through 4 , the storage rack  12  includes five shelves  16 . However, it will be understood that the relative size, spacing, and number of shelves  16  may be modified in other embodiments to accommodate storage boxes  14  having different sizes. In embodiments of the storage rack  12  with four or more shelves  16  such as the exemplary embodiment illustrated, a structural reinforcement located at an intermediate area between the top and bottom walls  52 ,  54  may be desirable to maintain the rigidity of the rack body  50  along the length thereof. To this end, the storage rack  12  also includes a rack reinforcement plate  76  engaged with or coupled to the first and second lips  70 ,  72  of one of the shelves  16 . The rack reinforcement plate  76  is spot welded to the first and second lips  70 ,  72  in one example, although an alternative method of connection between these elements may be used without departing from the scope of the present invention. In one embodiment, the rack reinforcement plate  76  extends from the first sidewall  58  to the second sidewall  60  to add structural support and rigidity to an intermediate portion of the rack body  50 . The rack reinforcement plate  76  is also formed from a thin sheet of stainless steel such that the reinforcement plate  76  does not add significant material weight to the storage rack  12  and also does not significantly impact the storage capacity within the rectangular space  62 . 
     Once the rack body  50  of the storage rack  12  has been folded and assembled as discussed above, the handle  18  is connected to the top wall  52  of the storage rack  12 . In this regard, the handle  18  of this embodiment is shown in further detail in  FIGS. 2 through 4  and includes a lower end  80  configured to be coupled to the rack body  50  at the top wall  52 , the upper end  40 , and an elongate intermediate portion  82  extending between the upper end  40  and the lower end  80 . The upper end  40  is defined by a rod-shaped or circular cross section member of stainless steel bent into a hook shape for engagement with the handle slots  42  at the opening  36  of the tank  20 . The intermediate portion  82  is also defined by a circular cross section member, although the intermediate portion  82  may be formed from a fiberglass material or similar material having lighter weight than stainless steel. The lower end  80  is formed from stainless steel and defines a flattened generally rectangular cross section as most clearly shown in  FIG. 3 . The flattened cross section of the lower end  80  advantageously provides a relatively large surface for connection to the top wall  52  by spot welding rather than by tack welding or other methods. With particular reference to  FIG. 3 , the plurality of spot welds  84  used to couple the handle  18  to the top wall  52  and used to couple the elements of the rack body  50  and rack reinforcement plate  76  together are schematically shown. The number of spot welds  84  has been minimized to reduce the time and skill-intensive labor necessary to manufacture the storage rack  12 . 
     Thus, the vertical storage rack  12  of the exemplary embodiment is produced by the following manufacturing method. A flat sheet blank  90  (hereinafter “flat sheet”  90 ) sized to define the rear wall  56 , the first and second sidewalls  58 ,  60 , the top wall  52 , and the bottom wall  54  is provided as shown in  FIG. 5 . The flat sheet  90  is machined such as by punching or stamping to cut the plurality of apertures  68  into the rear wall  56  and the first and second sidewalls  58 ,  60 . From the state shown in  FIG. 5 , the first and second lips  70 ,  72  are punched and bent from the flat sheet  90  to be generally perpendicular to the flat sheet  90 . The first and second lips  70 ,  72  are bent along the bend lines  92  shown in phantom line form in  FIG. 5 . It will be understood that the bend lines  92  may be scored on the flat sheet  90  prior to bending, although such scoring is not necessary in all embodiments of the present invention. The flat sheet  90  is then further bent along the remaining bend lines  92  (including the rear edges  52   a,    54   a,    58   a,    60   a  of the top wall  52 , bottom wall  54 , and first and second sidewalls  58 ,  60 ) to form the generally rectangular shape of the vertical storage rack  12 . 
     After these portions of the flat sheet  90  are bent into position, the connection tabs  66  of the top and bottom walls  52 ,  54  are spot welded to the first and second sidewalls  58 ,  60 . In embodiments including a rack reinforcement plate  76 , the rack reinforcement plate  76  is then inserted into position and spot welded to the corresponding first and second lips  70 ,  72  of the shelf  16 . The handle  18 , which has been separately manufactured, is then coupled to the top wall  52  by spot welding the flattened lower end  80  of the handle  18  onto the top wall  52  of the vertical storage rack  12 . As a result, the vertical storage rack  12  is manufactured with a minimal number of required spot welds and a minimized amount of stainless steel material. Accordingly, the overall manufacturing time is reduced and the weight of the storage rack  12  is also reduced. 
     An alternative embodiment of the vertical storage rack  112  is shown in  FIG. 6 . In this embodiment, the vertical storage rack  112  includes substantially all of the elements previously described with reference to  FIGS. 1 through 4  with the exception of the handle  18 , and these elements (rack body  50 , top wall  52 , bottom wall  54 , shelves  16 , etc.) have been labeled with the same reference numbers without further description below. Instead of the elongate handle  18  used with the previous embodiment, the vertical storage rack  112  of  FIG. 6  includes a foldable wire handle  118  coupled to the top wall  52  at a pair of pivot joints  120 . The wire handle  118  is freely pivotable between the folded position shown in  FIG. 6  and an unfolded position (not shown) in which the wire handle  118  may be gripped for moving the storage rack  112  into and out of a corresponding cold storage unit. For example, in embodiments of a cryogenic dewar with an opening along the periphery of the tank, the wire handle  118  may be used to enable rotatable movement of the plurality of storage racks  112  into and out of alignment with the opening in the tank so that each storage rack  112  is independently removable. However, the vertical storage rack  112  of this embodiment is most advantageously used with chest freezers and similar types of cold storage units. To this end, it will be understood that this embodiment of the vertical storage rack  112  may also be used with the cryogenic dewar  10  of the previously-described embodiment and other cold storage units without departing from the scope of the present invention. 
     While the present invention has been illustrated by a description of exemplary embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.