Angular Interlock Swivel for Breathing Conduit Shrinkage
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Solution Overview
Problem
Existing swivel features for breathing therapy conduits face interference issues due to shrinkage during injection molding, leading to poor sealing and rotational limitations, as rectangular interlocks cause binding and leakage.
Innovation Solution
The implementation of an angular interlock protrusion and receiving portion in the swivel feature, allowing for controlled shrinkage and clearance creation during injection molding, enabling proper rotation and minimizing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rectangular interlock protrusion is used in injection molding, then manufacturing precision is improved, but the swivel feature experiences binding and interference due to shrinkage
Solution Approach 1:
The patent applies asymmetry by changing the interlock protrusion from a rectangular shape to an angular shape with non-perpendicular sides. The first side is angled at a first angle relative to the mold surface, and the second side is angled at a second angle, creating an asymmetric geometry that accommodates material shrinkage during injection molding while maintaining precise interlocking.
2Ease of manufacture
If two separate plastic pieces are snapped together, then ease of manufacture is improved, but sealing performance deteriorates due to unwanted spacing
Solution Approach 1:
The patent merges two separate components into a single injection-molded piece. The outer swivel component and inner swivel component are formed as one integrated part with the angular interlock protrusion and receiving portion created in a single molding operation, eliminating gaps and ensuring reliable sealing while maintaining manufacturing efficiency.
3Manufacturing precision
If uniform material with constant thickness is used, then manufacturing precision is improved, but shrinkage causes interference with rectangular interlocks
Solution Approach 1:
The patent changes the geometric parameters of the interlock protrusion from rectangular to angular with specific angles. The first side is angled at a first angle and the second side at a second angle, creating clearance on both sides of the protrusion that accommodates material shrinkage during cooling, thereby eliminating interference while maintaining dimensional consistency.
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 angular interlock design ensures effective rotation and sealing of the swivel feature, reducing manufacturing complexity and costs by integrating the components in a single step, while maintaining the conduit's rotational capability and minimizing leakage.
Implementation Method 1
the shrink rates of the materials used for molding allow the spacing to be controlled and minimized. Plastics, such as polypropylene, have high shrinkage rates.
Implementation Method 2
the injected material would shrink away from the inner surface of the outer mold, as well as also shrinking inwards along the longitudinal axis of the swivel component
Data Source
AI summary
An angular interlock for a swivel feature formed using injection molding techniques is described herein. In one exemplary embodiment, the swivel feature is used for a conduit for delivering breathing therapy to a patient, and includes an outer swivel component and an inner swivel component formed using a two-shot molding technique. The outer swivel component is formed first out of a material, such as polycarbonate, having a low shrink rate, whereas the inner swivel component is formed of a material, such as polypropylene, having a high shrink rate. The material for the inner swivel component is injected into the formed outer swivel component and allowed to cool, creating a clearance. The outer swivel component includes an angular interlock protrusion that allows the inner swivel component to be formed without creating an interface about the angular interlock protrusion, which typically occurs with standard rectangular interlocks.