Abstract:
A sterilization tray has a smooth exterior, ruggedness, light weight, high thermal conductivity, comfortable gripping surfaces, stackability, and low cost construction. The tray is constructed of stamped and folded sheet metal, but in such a way as to provide rounded corners. A molded handle insert is attached to the ends of the tray to provide the multiple utility of reducing the number of handles required, maximizing space utilization, providing a comfortable gripping surface on the outside and inside of the tray, and providing stackability.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a sterilization tray. 
     Surgical instruments are typically stored, transported and prepared for use in sterilization trays. The trays include rigid enclosing walls to provide protection. The walls are typically perforated with multiple holes to allow ingress and egress of a sterilant, e.g. steam, when the tray is placed in a sterilizer. Typically, the trays are wrapped in paper or cloth to maintain the sterility of the contents in storage. It is desirable for the trays to have smooth exteriors, e.g. rounded corners, ruggedness, light weight, high thermal conductivity, and low cost construction. U.S. Pat. No. 5,882,612 teaches a sterilization tray having plastic end panels or comer pieces to simplify the construction of the tray. The patent points out that trays are typically constructed of stamped and folded sheet metal and that it is extremely difficult, if not impossible, to produce a tray with rounded corners using such a construction. 
     It is further desirable for the trays to have comfortable gripping surfaces and stackability. Increasingly, such trays are used in conjunction with European DIN standard storage containers. A typical DIN container will contain one or more trays stacked within it. Typical prior art trays include one set of handles for lifting the tray from the DIN container and a second set of handles for carrying the tray. 
     SUMMARY OF THE INVENTION 
     The present invention provides a sterilization tray having a smooth exterior, ruggedness, light weight, high thermal conductivity, comfortable gripping surfaces, stackability, and low cost construction. The tray is constructed of stamped and folded sheet metal, but in such a way as to provide rounded corners. This construction makes a rugged, lightweight, and low cost tray. A molded handle insert is attached to the ends of the tray to provide multiple utility of reducing the number of handles required, maximizing space utilization, providing a comfortable gripping surface on the outside and inside of the tray, and providing stackability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a sterilization tray according to the present invention. 
     FIG. 2 is a perspective view of the inside of the tray of FIG.  1 . 
     FIG. 3 is a side plan view of the tray of FIG.  1 . 
     FIG. 4 is a top plan view of a sheet metal stamping prior to folding to form the tray of FIG.  1 . 
     FIG. 5 is a perspective view of a handle insert component used in the tray of FIG.  1 . 
     FIG. 6 is a top plan view of the handle insert component of FIG.  5 . 
     FIG. 7 is a side sectional view of the handle insert component taken along line  7 — 7  of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-3 depict an exemplary embodiment of a sterilization tray  2  according to the present invention. The tray  2  includes a bottom wall  4 , upstanding side walls  6 , and upstanding end walls  8 . The walls are joined together to form an open box having rounded corners  9 . The walls include perforations  10  for allowing sterilant, e.g. steam, in and out of the tray. The interior of the tray may include various racks and fixtures for holding instruments as is known in the art. A lid  10  is removably secured to the tray to cover the open top. Preferably the tray is made of a lightweight, thermally conductive, and strong material such as sheet metal, e.g. aluminum. The lid  10  can also be made of sheet metal. However, it is preferably made of a transparent material such as plastic. Each end wall  8  includes elongate handle aperture  12  forming a handle in the sheet metal. A handle insert  14  is attached adjacent the aperture  12 . Preferably the handle insert is attached on the inside of the tray so as to maintain a smooth exterior surface on the tray. Attachment ears  11  formed on the handle insert  14  extend into slots  13  formed in the end wall  8  to secure the handle insert  14  to the end wall  8 . An upper portion  15  of the end wall extends over a portion of the handle insert  14  to reinforce the attachment of the handle insert  14  to the end wall  8 . The upper portion  15  of the end wall adds lifting strength to the handle insert  14 . 
     The handle insert  14  includes a grip aperture  16  bounded on the top by a gripping surface  18 . The gripping surface has a thickness greater than the thickness of the end wall  8  such that the gripping surface distributes the weight of the tray over a greater area of the users fingers and thus providing a more comfortable handle than the aperture  12  alone. Scalloped fingergrips  20  are advantageously formed in the grip surface  18 . Preferably the aperture  16  extends through the handle insert so that it can be gripped from the inside or outside of the tray. Preferably the handle insert is a low cost, light weight, molded plastic part. An example of a suitable plastic for use in this application is Radel® R polyphenylsulfone manufactured by BP Amoco Chemicals. This material has high strength and can be repeatedly autoclaved. 
     The extra grip thickness and double sidedness of the handle insert  14  is further advantageous where the tray is to be inserted into another container, e.g. a DIN container. When the tray is inserted into such a container with the end wall  8  closely adjacent the end wall of the container, there is insufficient room to position fingers on the outside of the tray  2  and extend the fingers through the aperture  12  to lift the tray. Likewise, because of the close proximity of the container wall to end wall  8 , without handle insert  14  there would be insufficient space to extend the fingers through the aperture  12  and lift the tray. However, handle insert  14  provides a grip surface  18  that permits a secure grip on the tray from the inside without the fingers needing to extend past aperture  12 . 
     The handle insert  14  also includes stacking lugs  22  extending upwardly above the top edge of the walls. Corresponding stacking lug receiving holes  24  are formed in the bottom wall  4  of the tray. Thus, when one tray is stacked on another, stacking lug  22  is received in hole  24  to keep the trays from sliding relative to one another. 
     Tray feet  26  are provided on the outside corners of the bottom wall  4  to space the bottom wall  4  away from a support surface to facilitate circulation of sterilant through the perforations  10 . Preferably the feet are made of a molded plastic material such as Radel® R. 
     FIGS. 4-7 depict the sheet metal blank  30  and handle insert  14  from which the tray is assembled. As can be seen in FIG. 4, the tray bottom wall  4 , side walls  6 , and end walls  8  are formed from a single piece of stamped sheet metal. The sheet metal blank  30  includes bottom portion  34 , side tabs  36  and end tabs  38 . Bottom portion  34  includes rounded corners  40 . Side tabs  36  extend beyond the bottom portion  34  at each end. End tabs  38  include elongate handle aperture  12  and upper tab  42 . 
     The tray  2  is formed by first bending a slot  13  in each end of each side tab. The side tabs  36  are then bent upwardly to form a right angle with the bottom portion  34 . The side tabs  36  are bent at each end to form the smooth rounded corners  9  and part of the end walls  8 . In the exemplary embodiment of FIGS. 2 and 3, the sheet metal blank is shaped to produce a gap  35  separating the side tab  36  and the bottom portion  34 . This gap facilitates bending the side tab  36  to match the rounded corners  40  of the bottom portion  34 . The upper tabs  42  are each bent to form a right angle with the end tabs  38  thus forming the upper portions  15 . The end tabs  38  are bent upwardly to form a right angle with the bottom portion  34  and to overlap the side tabs  36 . Preferably the side walls are each bent at each of their ends to form lap joints with the end walls such that the exterior of the side and end walls are flush. Handle insert  14  is placed with attachment ears  11  engaging slots  13  and being trapped within the slots by end tab  38 . Aperture  16  is aligned with aperture  12  and upper portion  15  contacts the top of handle insert  14 . Preferably a recessed shelf  17  is formed in the top of the handle insert  14  to receive the upper portion  15  so that the top of upper portion  15  is flush with the remaining top of the handle insert. End tab  38  and side tab  36  are riveted  44  together above and below slot  13  to hold the tray in rigid alignment. Alternatives to rivets include screws and weld beads and other attachments known in the art. Preferably no rivets are inserted through the handle insert  14  and the handle insert is allowed some freedom of movement within the slots  13 . Thus, when the tray  2  is heated in an autoclave, and the handle inserts  14  and end walls  8  expand different amounts, no breakage occurs. 
     It will be understood by those skilled in the art that the foregoing has described a preferred embodiment of the present invention and that variations in design and construction may be made to the preferred embodiment without departing from the spirit and scope of the invention defined by the appended claims.