In-Mold 4-Bar Link Assembly via Differential Shrinkage
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Solution Overview
Problem
The assembly of 4-bar kinematic links is labor-intensive and requires multiple separate injection molding tools, leading to increased costs, labor, and equipment needs, as well as potential assembly errors due to the need for post-mold assembly of multiple parts.
Innovation Solution
A 4-bar kinematic link design that allows for in-mold assembly, featuring a base member with multiple apertures and integrally formed upper and lower arms with hinge pins, using different shots of molten materials with varying shrinkage rates to create clearance for rotational movement, eliminating the need for manual assembly and reducing assembly time and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate injection molding tools are used for each part, then each part can be manufactured with high precision, but the number of tools increases and assembly complexity increases
Solution Approach 1:
The patent combines multiple separate injection molding operations into a single integrated mold assembly that can produce the base member, upper arm, lower arm, and hinge pins simultaneously or in sequence within the same molding cycle, eliminating the need for multiple separate molding tools and subsequent assembly operations
2Ease of manufacture
If parts are assembled after molding, then each part can be optimized independently, but labor intensity and assembly time increase
Solution Approach 1:
The hinge pins are pre-formed as integral parts of the base member during the injection molding process itself, rather than being added separately afterward. This preliminary formation of connecting elements enables the arms to be directly attached to the base member in the same molding cycle, eliminating post-mold assembly operations while maintaining the ability to independently design and optimize each component's geometry
3Adaptability or versatility
If multiple separate parts are used, then design flexibility is improved, but assembly errors and tracking complexity increase
Solution Approach 1:
The patent integrates multiple components into a single molded assembly where the base member, upper arm, lower arm, and hinge pins are all formed together in one operation. This merging eliminates the need for tracking and assembling separate parts, reducing assembly errors while maintaining design flexibility through the ability to create complex integrated geometries that would be difficult to achieve with separate components
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 approach reduces production costs and time by enabling the 4-bar kinematic link to be formed in a single mold without manual assembly, improving efficiency and reducing errors through integrated hinge pin formation and rotational clearance, thus streamlining the manufacturing process.
Implementation Method 1
The body, hinge pin in two tabs of the upper arm are all integrally formed together as one piece and the hinge pin is formed through the one of the at least two sets of plurality of apertures of the base member to allow the upper arm to pivot about the hinge pin relative to the base member
Data Source
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AI summary
The present invention is directed to a 4-bar kinematic link component and method for forming the 4-bar kinematic link using a single rotary molding tool. The invention eliminates the need to form individual components of the bracket from several different tools, which will then requires additional assembly steps. The 4-bar kinematic link is formed from two different materials each having a different in mold shrinkage value. This allows for hinge pins to be formed through a base component in a way that will prevent sticking of the components together thereby allowing the parts to have it relative to one another using the hinge pin. The final component is a 4-bar kinematic link that can be used as a 4 bar link mechanism for providing motion.