Sewing Machine Stitch Length Adjuster Stability
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Solution Overview
Problem
Existing stitch length adjusting devices for sewing machines lack stability and precision in specifying stitch lengths, leading to undesirable relative movements between components and increased wear.
Innovation Solution
A stitch length adjusting device with a non-rotatable connection between the setting frame and lever body, utilizing an adjusting shaft for stability, and a changeover drive for automatic stitch direction changes, along with a calibration device for precise stitch length calibration, ensures precise and stable stitch length specification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotatable connection or separate components are used between the setting frame and lever body, then the device complexity is reduced or assembly is easier, but the stability and precision of stitch length specification deteriorates due to undesirable relative movements
Solution Approach 1:
The setting frame and lever body are merged into a single non-rotatable connection structure, eliminating relative movements between these components. This integration ensures that the stitch length specification remains stable and precise without requiring complex separate connection mechanisms.
Solution Approach 2:
The lever body serves multiple functions: it acts as both the setting element for stitch length and as a structural component that maintains fixed positional relationships with the setting frame. This multi-functionality reduces the need for additional stabilizing components.
2Ease of operation
If manual adjustment mechanisms are used for stitch length, then the device complexity is low, but the ease of operation deteriorates due to manual intervention requirements
Solution Approach 1:
The changeover drive mechanism dynamically switches the lever body between forward stitch and reverse stitch positions automatically based on the stitching direction, eliminating manual intervention while maintaining operational ease.
Solution Approach 2:
The system performs automatic changeover between forward and reverse stitches using the changeover drive, making the device self-adjusting without requiring operator intervention for each stitch direction change.
3Reliability
If direct stop of the short-stitch lever body on the short-stitch stop body is used, then the device complexity is reduced, but the reliability deteriorates due to increased wear
Solution Approach 1:
An intermediary stop position specification mechanism is introduced between the short-stitch lever body and the short-stitch stop body. This intermediary component prevents direct contact and wear between the lever body and stop body while still achieving the desired stop position.
Solution Approach 2:
The stop position specification mechanism is designed to prevent direct impact and wear between moving and stationary components by using an intermediary element that absorbs or distributes the stopping force, thereby protecting the lever body from wear.
4Manufacturing precision
If separate adjustment mechanisms are used for forward and reverse stitch lengths, then the adaptability is improved, but the manufacturing precision deteriorates due to calibration difficulties
Solution Approach 1:
The adjustment mechanism uses asymmetric design where the lever body has different stop positions for forward and reverse stitches, allowing independent adjustment while maintaining consistent needle penetration through calibrated geometric relationships.
Solution Approach 2:
The system adjusts stitch lengths by changing the angular position of the lever body to different predetermined stop positions, allowing independent control of forward and reverse stitch lengths while maintaining manufacturing precision through calibrated parameters.
Data Source
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AI summary
A stitch length adjusting device (25) for a sewing machine has a stop unit (26) for setting stops for a lever body (27). This lever body can be switched between a forward stitch stop position and a reverse stitch stop position by rotating it around an adjusting axis (28). The adjusting device (25) also has a stitch adjuster mechanism (49), which is connected on one side to the lever body (27) and on the other side to a feed dog drive shaft. An adjusting frame (52) of the stitch adjuster mechanism (49) is rotationally fixed to the lever body (27). This results in a stitch length adjusting device with improved stability of the stitch length setting.