Movable Feed Dog Cover for Free-Motion Sewing Control
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Solution Overview
Problem
Maneuverable sewing machines face challenges in accurately following intricate patterns on fabric due to difficulties in maintaining precise control over the feed dog mechanism, making it difficult to switch between fixed and free motion modes.
Innovation Solution
A sewing machine assembly with a feed dog assembly and a control unit that allows the feed dog cover to change positions, transitioning between disengaged and engaged states, thereby enabling conversion between fixed and free motion modes, and includes a sensor and controller to adjust the feed dog's speed and position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the feed dog is exposed to pull fabric through the machine, then fabric feeding capability is improved, but maneuverability for creating intricate patterns deteriorates
Solution Approach 1:
The feed dog cover is made movable between two positions: engaged (covering the feed dog) and disengaged (exposing the feed dog). This dynamic configuration allows the machine to switch between free motion mode (cover engaged, feed dog hidden) for intricate patterns and fixed motion mode (cover disengaged, feed dog exposed) for automatic fabric feeding, thus resolving the contradiction between fabric feeding capability and maneuverability
2Adaptability or versatility
If the feed dog cover is added to enable mode switching, then adaptability is improved, but device complexity increases
Solution Approach 1:
The feed dog cover incorporates a sensor tab with a sensor that automatically detects its own position (engaged or disengaged) and sends signals to the controller. This self-service mechanism eliminates the need for separate position detection systems, reducing overall device complexity while maintaining adaptability for mode switching
3Productivity
If the feed dog reciprocates at high speed for productivity, then fabric processing speed is improved, but residual vibration increases making precise pattern following difficult
Solution Approach 1:
The controller receives feedback from the sensor about the feed dog cover position and automatically adjusts the feed dog reciprocation speed. When the cover is engaged (free motion mode), the controller reduces speed to minimize vibration and enable precise pattern following. When disengaged (fixed motion mode), the controller increases speed for higher productivity, thus resolving the contradiction between processing speed and vibration control
Data Source
AI summary
A sewing machine assembly includes a sewing machine frame, a presser bar mounted to a frame head of the sewing machine frame, and a feed dog assembly. The feed dog assembly includes a feed dog mounted to the frame base to reciprocate vertically and horizontally relative to the frame base to pull fabric between the pressure bar and the frame base through the sewing machine frame, a feed dog drive system coupled to the feed dog to drive reciprocation of the feed dog relative to the frame base, and a feed dog cover selectively coupled to a frame base of the sewing machine frame to extend over the feed dog to shield the fabric from the feed dog.