Hollow Cylindrical Screw Thread Recesses Radial Injection Shrinkage
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Solution Overview
Problem
Existing screw parts with annular cross-sections face dimensional instability and uneven mechanical stress distribution during assembly due to locally non-uniform shrinkage behavior of the polymer mass during injection molding, leading to deformations and impaired thread functionality.
Innovation Solution
Incorporating recesses in the thread area opposite the injection points, created by inserting suitable cores into the mold, to prevent raised areas and ensure uniform shrinkage, thus maintaining dimensional stability and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If radial injection of plasticized polymeric mass containing fibers is performed through at least one injection opening in the inner channel, then the base body can be produced with integrated thread structure, but locally non-uniform shrinkage behavior occurs during solidification causing dimensional instability and uneven stress distribution
Solution Approach 1:
The patent applies local quality by creating recesses at specific locations in the thread structure - specifically at least in one thread flank and optionally in both thread roots - to locally compensate for the non-uniform shrinkage caused by radial injection. These recesses are strategically positioned to counteract the deformation tendencies in high-stress areas, allowing the overall integrated structure to maintain dimensional stability while benefiting from the manufacturing efficiency of radial injection molding.
2Strength
If radial injection is performed through inner channel, then fiber alignment can be optimized for axial tension and torsion, but raised areas form in the thread structure impairing thread functionality
Solution Approach 1:
The patent addresses this contradiction by introducing recesses at specific locations in the thread structure - particularly in thread flanks and thread roots - to locally remove the raised areas that form during radial injection. These recesses are positioned to eliminate deformation in critical thread regions while preserving the overall fiber alignment achieved through radial injection, thus maintaining both strength and thread functionality.
Solution Approach 2:
The patent converts the harmful effect of raised areas formed during radial injection into a benefit by using these raised areas as indicators to strategically position recesses. The recesses are deliberately placed at locations where raised areas most commonly occur (thread flanks and roots), transforming the deformation problem into a guided solution that improves thread functionality while maintaining the advantages of radial injection molding.
3Manufacturing precision
If recesses are added to compensate for shrinkage deformation, then dimensional stability is improved, but device complexity increases due to additional mold components
Solution Approach 1:
The patent applies segmentation by dividing the mold cavity into multiple sections, with at least one section containing the recesses for the thread structure. This allows the recesses to be integrated into the mold design without requiring completely separate molding operations or complex additional components. The segmented approach enables precise control over recess geometry and positioning while maintaining manufacturing efficiency.
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 prevents deformations and ensures a uniform progression of mechanical stresses, enhancing the screw part's stability and holding pressure effectiveness, reducing the need for complex rework and ensuring high-quality production with minimal effort.
Implementation Method 1
the base body is produced by radially injecting a plasticized polymeric mass containing fibers into a cavity of a mold through at least one injection opening of the mold
Implementation Method 2
the polymeric mass flowing annularly around an inner core of the tool and flowing together between the injection openings
Implementation Method 3
by subsequent demoulding from the mold after the polymeric mass has solidified
Implementation Method 4
locally non-uniform shrinkage behavior of the polymer mass during injection molding
Data Source
Figure 1~2
Figure 2a
Figure 3~4
AI summary
The invention relates to a screw piece (1) with annular cross-section, such as a screw, a nut, a sleeve part, a pipe connector, a pipe coupling or the like, said screw piece comprising a hollow cylindrical main body (2) with a lumen (4), said lumen being surrounded by a wall (5) of the main body (2), and a screw thread (3) being formed on said wall, wherein the main body (2) is produced by radial injection of a fibre-containing plasticized polymer compound into a cavity of a mould through at least one injection opening in the mould and by subsequent demoulding from the mould after solidification of the polymer mass, wherein a sprue is removed so that the main body (2) has at least one injection point (A), preferably in the lumen (4). In order to create such a screw piece (1) which remains dimensionally stable during installation and has a uniform distribution of internal mechanical stresses after installation in the main body (2), it is proposed that a recess (6) be provided in a region of the screw thread (3), in particular an external screw thread (3), which is opposite the region of the injection point (A) and separated therefrom by the wall (5) of the main body (2).