Plastic Food Tongs Molded to Eliminate Fulcrum Weld-Lines
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Solution Overview
Problem
Disposable plastic tongs often fail at the fulcrum region due to compressive and tensile stresses, and existing designs suffer from stress concentration and breakage issues, particularly at weld-lines formed during mold-filling, leading to structural failures and increased failure rates.
Innovation Solution
Incorporating a longitudinal reinforcing member that connects the bridge to the gate area, altering the molding process to minimize central weld-lines and enhance structural stiffness, along with features like a reinforcing wall and anti-sliding tabs to prevent sliding into food containers, and metallization for appearance and functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a cross-member or bridge is provided between the arms proximate to the fulcrum end to reduce stresses in the gate region, then stress distribution is improved, but stress concentration occurs at the mid-point of the bridge causing breakage
Solution Approach 1:
The patent removes the problematic cross-member bridge structure that caused stress concentration and weld-line formation. Instead, it uses a longitudinal reinforcing member that extends along the arms without creating central weld-lines, thereby eliminating the source of breakage while maintaining stress distribution benefits
Solution Approach 2:
The patent transitions from a transverse cross-member bridge (perpendicular to arm length) to a longitudinal reinforcing member (parallel to arm length). This dimensional change allows the reinforcement to follow the stress flow direction without creating vulnerable junctions, solving both stress distribution and strength issues
2Ease of manufacture
If the arms are connected at the fulcrum end with central gate area for mold filling, then manufacturing is simplified, but weld-lines form at the center causing susceptibility to breakage
Solution Approach 1:
The patent reorients the reinforcing member from a transverse to a longitudinal configuration, changing the dimension of mold filling flow. This allows the gate to remain central for ease of manufacture while the longitudinal member guides melt flow along the arms, preventing weld-line formation at the vulnerable bridge mid-point
Solution Approach 2:
The longitudinal reinforcing member acts as an intermediary structure that mediates between the central gate area and the arm structures. It provides a continuous flow path for molten material from the central gate, eliminating the need for weld-lines to form at critical stress points while maintaining manufacturing simplicity
3Ease of manufacture
If the tongs are made from plastic material with inherent flexibility and resilience, then ease of manufacture is improved, but structural strength and breakage resistance are reduced
Solution Approach 1:
The patent creates a composite structure by incorporating a longitudinal reinforcing member within the plastic tong arms. This composite design combines the flexibility and resilience of molded plastic with the structural strength of the reinforcing member, achieving both ease of manufacture and improved breakage resistance
Solution Approach 2:
The patent applies local reinforcement by placing the longitudinal member specifically in regions requiring enhanced strength (along the arm length and connecting to the fulcrum), while maintaining the plastic material's flexibility in other areas. This localized quality enhancement solves the strength issue without compromising overall manufacturability
Data Source
AI summary
Food service tongs and a mold and method for making them, the tongs having first and second arms connected to a fulcrum end, and first and second grasping ends on the arms disposed in a mutually opposing and spaced-apart relationship and moveable in a common plane to a closed position for grasping food there between, and a transverse bridge disposed proximate to the fulcrum end and extending from the first arm to the second arm, with a longitudinal rib extending from the transverse bridge to the fulcrum end, the flow path through the longitudinal rib section of the mold resulting in reduction or displacement of fault lines caused by abutting flow fronts during mold filling. Articles of the invention can be coated with a thin metallic layer to impart a metal-like appearance to these articles.