Polygonal Mirror Gate Mark Placement for Weld Line Control
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Solution Overview
Problem
Conventional polygonal mirrors used in optical scanning apparatuses face issues with profile irregularity due to non-uniform injection pressure and weld lines generated during resin molding, affecting the accuracy of reflecting surfaces.
Innovation Solution
A polygonal mirror design featuring gate marks and contact portions positioned non-overlapping with respect to the rotation center, ensuring even resin flow and minimizing weld line influence on reflecting surfaces, with the same number of gate marks as reflecting surfaces, and perpendicular bisectors aligning with vertexes to prevent profile irregularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gate marks are disposed on rectilinear lines passing through the center and vertexes of the polygonal mirror, then the resin material can be injected efficiently, but weld lines generate on the reflecting surfaces causing profile irregularity
Solution Approach 1:
The patent positions gate marks asymmetrically relative to the polygonal mirror's geometry, specifically avoiding alignment with vertexes. The gate marks are disposed such that the perpendicular bisector of the line segment connecting adjacent gate marks does not pass through the vertexes, creating an asymmetric configuration that prevents weld line formation on reflecting surfaces while maintaining manufacturing efficiency
Solution Approach 2:
The patent converts the potentially harmful effect of weld lines into a beneficial design constraint by strategically positioning gate marks so that their perpendicular bisectors avoid the vertexes. This transforms the welding process, which typically creates defects, into a controlled process where the weld lines are deliberately positioned away from critical reflecting surfaces, turning a manufacturing challenge into a design feature that ensures surface quality
2Device complexity
If the number of gate marks is less than the number of reflecting surfaces, then the molding process is simplified, but injection pressure becomes non-uniform affecting profile irregularity
Solution Approach 1:
The patent applies local quality by positioning each gate mark at a specific location where the perpendicular bisector of the line segment connecting adjacent gate marks passes through the corresponding vertex. This localized positioning strategy ensures that each reflecting surface receives uniform injection pressure from its associated gate mark, maintaining surface uniformity without requiring an equal number of gate marks for each reflecting surface
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 design enhances the stability and accuracy of the polygonal mirror's reflecting surfaces, reducing profile irregularity and ensuring high-definition imaging by preventing weld line formation on reflecting surfaces and maintaining precise contact with the rotatable member.
Implementation Method 1
a plurality of reflecting surfaces capable of reflecting laser light emitted from a light source
Data Source
AI summary
A polygonal mirror includes reflecting surfaces, a molded member including a first surface and a second surface, a contact portion, and gate marks. Each of said first surface and said second surface has a polygonal shape. The contact portion and the gate marks are formed at non-overlapping positions with a line segment connecting a vertex of the polygonal shape with a rotation center. The gate marks and the reflecting surfaces are the same in number. A perpendicular bisector of a line segment connecting centers of the gate marks adjacent to each other with respect to a rotational direction of the polygonal mirror is formed at a position passing through an associated vertex of the polygonal shape and the rotation center.