Stackable Egg Tray Locking Mechanism and Spacing Design
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Solution Overview
Problem
Existing stackable trays made by vacuum molding of plastic sheets for egg-boxes face issues with interlocking between trays, leading to friction and air lock problems, which cause jamming in automated packaging systems and inadequate protection of fragile contents due to lack of rigidity.
Innovation Solution
The trays feature a hinge portion dividing them into a cover and base portion with two-part locking means and spacing stoppers with negative angles to prevent interlocking, providing structural rigidity and preventing accidental opening, while the base portion includes inwardly projecting ribs for better egg support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If trays are stacked one into the other, then storage space is optimized, but friction and air lock are created between neighboring trays causing interlocking
Solution Approach 1:
A sheet of paper or thin flexible material is placed between neighboring trays in the stack. This intermediary layer prevents direct contact between the trays, eliminating friction and air lock effects that cause interlocking. The paper sheet acts as a mediator that allows trays to be stacked closely for space optimization while preventing harmful interlocking forces.
2Productivity
If trays are stacked closely to save space, then storage efficiency improves, but tray removal becomes difficult due to interlocking
Solution Approach 1:
The paper sheet placed between trays serves as a release agent that prevents adhesion and interlocking. When trays need to be removed from the stack, the paper sheet allows smooth separation without the friction and vacuum effects that would otherwise make removal difficult, thus maintaining both storage efficiency and ease of operation.
3Device complexity
If the box is made from folding a cover portion over the base portion, then the structure is simple and lightweight, but rigidity is insufficient to protect fragile content
Solution Approach 1:
Locking means are pre-formed as integral parts of the cover and base portions during the thermoforming process. These locking features (such as protrusions and recesses) are created in advance before assembly, enabling simple folding construction while providing pre-engineered rigidity and strength to protect fragile contents like eggs.
4Strength
If locking means are added to increase box rigidity, then content protection improves, but manufacturing complexity and cost increase
Solution Approach 1:
The locking means are merged with the cover and base portions as single integrated components formed in one thermoforming process. Rather than adding separate locking mechanisms, the design combines the structural elements into unified pieces with built-in locking features (protrusions and recesses), maintaining manufacturing simplicity while achieving the required rigidity for content protection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for easy denesting of trays, prevents jamming in automated systems, ensures the integrity of contents during transport, and provides substantial rigidity to prevent deformation and damage, while being lightweight and inexpensive to manufacture.
Implementation Method 1
stackable tray obtained by thermoforming, especially vacuum molding, of a sheet of plastic material
Data Source
AI summary
A stackable tray obtained by vacuum molding of a sheet of plastic material, the tray comprising, in open position: a) a top and a bottom; b) at least one receiving cavity opened upwardly; c) a hinge portion dividing the tray into a cover portion and a base portion; the receiving cavity being at least provided in the base portion; d) spacing members to keep, in a stack of trays, the top portion and the bottom portion of neighboring trays at distance from each other to thereby prevent interlocking therebetween; and e) at least one two-part locking members, each part being provided in the top of the sheet and positioned to engage one into the other when the cover portion is folded over the base portion along the hinge portion to bring the tray into a closed position defining a box. A stack of the trays and a method using the trays are also provided.