Focal Plane Shutter Drive Arm Restriction to Prevent Dust
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Solution Overview
Problem
Focal plane shutters generate dust due to engagement between the drive pin and drive arm, which can affect image quality.
Innovation Solution
A focal plane shutter design featuring a restriction portion on the drive arm that is thicker than the drive arm, with an engagement hole allowing abutment only at the terminal edge of the drive pin's movement, preventing contact with the first edge and thus reducing the likelihood of chipping and dust generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive pin engages with the drive arm through the engagement hole, then the blade can be driven effectively, but chipping occurs at the edges of the engagement hole causing dust generation
Solution Approach 1:
The engagement hole is divided into two distinct edges: a first edge and a second edge. The restriction portion selectively allows engagement only at the second edge while preventing contact at the first edge, thereby segmenting the engagement function to eliminate harmful chipping while preserving necessary drive transmission.
Solution Approach 2:
Different regions of the engagement interface are given different functional properties. The second edge is designed to be engaged (allowing drive transmission), while the first edge is protected from engagement (preventing chipping). This local differentiation of engagement quality resolves the contradiction between effective driving and dust prevention.
2Device complexity
If the drive pin moves freely within the engagement hole, then the drive mechanism has simple structure, but the drive pin may contact both edges causing chipping and dust
Solution Approach 1:
The restriction portion acts as an intermediary element between the drive pin and the first edge of the engagement hole. It physically blocks the drive pin from contacting the first edge, preventing chipping without adding complex control mechanisms or increasing overall device complexity.
Data Source
AI summary
A focal plane shutter includes: a board including an opening; a blade movable between a position where the blade recedes from the opening and a position where the blade covers at least part of the opening; a drive arm connected to the blade, the drive arm including an engagement hole; a drive lever including a drive pin engaging the engagement hole; and a restriction portion provided in the drive arm, the restriction portion abutting the drive pin and being thicker than the drive arm.