Straight Hinge Pin Retention via Polyolefin Creep
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Solution Overview
Problem
Existing hinge pin assembly designs for container and lid assemblies are inefficient in automation due to the need for complex and costly orientation of protrusions or bends, which complicate the assembly process.
Innovation Solution
A substantially straight hinge pin is used with a polyolefin material that undergoes elastomeric and creep properties to securely retain the pin by closing the hinge line with a plastic wall, allowing the pin to be inserted and then retained through residual stresses as the hole contracts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protrusion or bend is added to the hinge pin for retention, then the pin can be retained in the lid, but the assembly process becomes complex and expensive due to orientation requirements
Solution Approach 1:
The invention extracts the retention function from the hinge pin itself and transfers it to the plastic wall material. Instead of modifying the pin with protrusions or bends, the plastic wall's elastomeric properties provide the retention mechanism, allowing a simple straight pin to be used.
Solution Approach 2:
The invention changes the physical state and properties of the plastic wall material. By selecting polyolefin materials with specific elastomeric and creep properties, the material temporarily yields during pin insertion then recovers to create retention, transforming the retention mechanism from a geometric feature to a material property.
2Reliability
If a protrusion is interference fitted into a slot for pin retention, then the pin is retained, but significant plastic removal is required which increases manufacturing complexity
Solution Approach 1:
The invention removes the need for pre-formed retention features (protrusions and slots) from the design. The retention function is extracted and provided by the plastic wall's material properties alone, eliminating the need for complex molding features and reducing manufacturing steps.
Solution Approach 2:
The invention uses a homogeneous plastic wall structure without embedded retention features or separate components. The entire plastic wall is made of polyolefin material that provides both structural support and retention function, simplifying the manufacturing process to a single molding operation.
3Reliability
If automated feeding mechanisms are designed to properly orient pins with protrusions, then pin retention is achieved, but the equipment becomes prohibitively complex and expensive
Solution Approach 1:
The invention makes the assembly process self-aligning and self-retaining. The straight pin and plastic wall design allow the pin to be inserted without precise orientation, and the plastic wall's elastomeric properties automatically provide retention. This eliminates the need for complex automated orientation and positioning mechanisms.
4Extent of automation
If a straight hinge pin is used to simplify automation, then assembly automation is simplified, but pin retention becomes problematic
Solution Approach 1:
The invention changes the physical parameters of the plastic wall material to enable retention of a straight pin. By using polyolefin materials with specific elastomeric and creep properties, the material temporarily yields during pin insertion then recovers to create friction and geometric interference that retains the pin without requiring any features on the pin itself.
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
This solution simplifies the automation of the assembly process by securely retaining the hinge pin without significant plastic removal, reducing labor and costs, while maintaining structural integrity and weight-bearing capability.
Implementation Method 1
the polyolefin material has elastomeric and creep properties such that a predetermined period of time after a 0.100 inch diameter pin is passed through the plastic wall, an entry hole therein is about 0.06 inch diameter
Implementation Method 2
the polyolefin material has elastomeric and creep properties such that a predetermined period of time after a 0.100 inch diameter pin is passed through the plastic wall, an entry hole therein is about 0.06 inch diameter
Data Source
AI summary
A hinge assembly incorporates a substantially straight hinge pin for securing a lid to a container. At least one end of a hinge line is initially closed via a plastic wall. The substantially straight hinge pin is secured in the hinge line via passing the hinge pin through the plastic wall. Subsequently, residual axial and radial stresses caused by passing the hinge pin through the wall cause the opening to contract, thereby retaining the pin. By providing a hinge assembly including a substantially straight hinge pin, the assembly process can be more easily automated.