Envelopes – wrappers – and paperboard boxes – Paperboard box – A sidewall includes a horizontally or downwardly extending...
Reexamination Certificate
1999-10-18
2001-01-30
Elkins, Gary E. (Department: 3727)
Envelopes, wrappers, and paperboard boxes
Paperboard box
A sidewall includes a horizontally or downwardly extending...
C493S070000, C493S080000, C493S162000
Reexamination Certificate
active
06179204
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a die cut lock tray, its method of manufacture, and its use in an automated food production line.
BACKGROUND OF THE INVENTION
Die cut trays are erected from cardboard or other corrugated sheet material and folded into the desired shape. They are often held in position by appropriately folding and interlocking various parts of the tray. Friction can be used to interlock the parts, but such friction-based locks can fail when the cardboard changes shape through use, wear or from environmental changes. Thus, interlocking parts typically require cutting holes or slots through the tray and inserting parts through the holes and completely through the parts in order to mechanically lock the parts together. But this mechanical interlocking that uses slots weakens the trays in the area where the slots are placed.
The slotted interlocks cause further problems when they are used in some applications. The low cost of these trays makes them suitable for use in mass produced products where the trays assembly can be automated and the trays used on assembly lines. For example, these trays provide an economical way to process and distribute food products, such as cakes and muffins.
A machine forms a die cut tray from a palette of die cut blanks and drops the formed tray onto a conveyor belt. A wax-paper liner is placed on the tray to prevent the food from being absorbed by and sticking to the paper. Batter is poured into the tray for baking, and the batter-filled tray passes through an oven where the cake is baked in the tray. If the shape of the tray changes, the shape of the cake is altered and may render the cake unsuitable for sale. Thus, it is important that the tray holds its shape during the filling and baking process. Further, because thousands of cakes are baked on these automated lines, even a small percentage of trays losing shape or leaking can cause a large loss of money as the baked cakes are much more expensive than the trays. Thus, the tray assembly and the ability to maintain the tray shape must be not only inexpensive, but very reliable.
While the slotted interlocking trays hold their shape, the interlocking slots are typically located on or near the bottom of the tray. The slots thus allow the batter to leak and contaminate the assembly line. Given that tens of thousands of cakes can be baked daily, even a small leakage from a small percentage of trays quickly causes numerous problems, ranging from health and contamination concerns, to equipment maintenance and breakage problems. There is thus a need for low-cost trays that can be inexpensively made, assembled by automated equipment, yet maintain their shape during use and not leak. These objectives must be achieved with a very high repeatability and reliability.
SUMMARY OF THE INVENTION
These objectives are achieved by providing a serrated edge on an end roll that engages a lip formed along a slit edge surrounding a crushed area into which the serrated edge is inserted. The lip engages the end roll and serrated edge to form a mechanical lock that maintains the shape of the tray. The slit does not go through the material, so there is no leakage, and a stronger tray is formed. The crushed area allows the serrated edge to enter a portion of the material sufficient to interlock with the lip formed by the slit, in order to form a strong interlock. The serrated edge allows a variable interconnection with the lip sufficient to increase the formation of a successful interlock to an acceptable level of reliability and repeatability.
The tray is made from a die cut blank of corrugated paper that is formed into a tray by an automated process. The tray has a bottom wall, two opposing end rolls each connected to an opposing side of the bottom wall by an end-fold line. At least one slit and crushed area is placed in the bottom wall adjacent to each of the fold lines. The crushed area is bounded by the slit, and the area is crushed sufficiently so a slight lip is formed along the slit. A serration is formed along a length of the distal edges of the end rolls, parallel to the fold line. When assembled, the serrated edge enters the crushed area and the lip formed along the slit restrains the serrated edge from leaving the crushed area in order to form a mechanical lock that holds the tray together.
The tray also has a pair of side walls, one connected to each side of the bottom wall along a side wall fold line that is substantially perpendicular to the fold lines connecting the end rolls to the bottom wall. At each of the four corners of the bottom is a tab that is connected to an end of the side wall by a tab fold line. The tab fold line is substantially perpendicular to the side wall fold line connection between said side wall and said bottom wall.
The tabs, sides and ends are folded perpendicular to the bottom, with the tabs being further folded along the ends, parallel to the end fold line on an interior side of the end rolls. Suitable tapers are formed on the tabs to allow this folding. The distal end of each end roll is then further folded over the tabs so the serrated edge enters the crushed area and the lip along the slit engages the end roll along the serrated edge to lock the ends in position. A pair of edge defining fold lines can be added to the end roll to define the top edge of the folded tray formed by the end roll and to assist in folding the end roll. The edge defining fold lines are located slightly more toward the end fold line than they are toward the serrated edge.
This assembly can be done using automated equipment that forms the assembled tray from a die cut sheet of material. The assembled tray is then placed on an assembly line. A liner or release material is placed on the bottom of the tray. Batter is placed on the bottom of the tray. The cake is baked, cooled and packaged in the tray.
REFERENCES:
patent: 1997523 (1935-04-01), Katz
patent: 2942768 (1960-06-01), McCall
patent: 3139228 (1964-06-01), Wilkins
patent: 3904106 (1975-09-01), Elder
patent: 4279374 (1981-07-01), Webinger
patent: 5211329 (1993-05-01), Patton
patent: 5328090 (1994-07-01), Hanlon
patent: 5718337 (1998-02-01), Carr et al.
patent: 458312 (1951-04-01), None
Andruss Frank D.
Blower James F.
Escutia Raul
Hansen Todd A.
Ramirez Galdino V.
Blower-Dempsey Corporation
Elkins Gary E.
Knobbe Martens Olson & Bear LLP
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