Sewing Machine Upper Thread Drawing Mechanism for Stitch Quality
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Solution Overview
Problem
Conventional buttonhole stitching machines face issues with thread consumption differences across various sections, leading to stitch skipping, irregular stitches, and sewing shrink, which deteriorate the quality of the sewn fabric.
Innovation Solution
A sewing machine with an upper thread drawing mechanism that includes an upper thread drawing motor and a data memory system to adjust the upper thread drawing amount for each stitch, synchronized with the cloth feed mechanism, allowing precise control of thread consumption based on sewing pattern data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the upper thread drawing member is switched among three fixed positions before and after sewing, then the upper thread path length can be adjusted, but thread consumption differences occur during actual sewing operations
Solution Approach 1:
The invention transforms the static three-position switching mechanism into a dynamic system where the upper thread drawing member can be positioned at arbitrary locations along the thread path. This is achieved by replacing the discrete position switching with a continuous positioning mechanism that allows real-time adjustment of the drawing member's position during sewing operations, thereby adapting to varying thread consumption requirements across different sewing sections.
Solution Approach 2:
The invention changes the parameter control approach from discrete position switching to continuous parameter adjustment. By enabling the upper thread drawing member to be positioned at any location along the thread path rather than being restricted to three fixed positions, the system can precisely control thread consumption parameters to match the specific requirements of different sewing sections, eliminating thread consumption variations.
2Manufacturing precision
If the upper thread drawing member is positioned to shorten the upper thread path, then thread supply control is improved, but the upper thread cannot be properly fed out from the thread supply source
Solution Approach 1:
The invention enables dynamic positioning of the upper thread drawing member along the thread path, allowing the system to optimize the thread path length based on real-time sewing requirements. When thread feeding from the supply source is needed, the drawing member can be positioned to provide sufficient path length; when precise thread supply control is required, the drawing member can be positioned to shorten the path, thus resolving the contradiction between these two opposing requirements.
3Productivity
If the upper thread drawing member is positioned to lengthen the upper thread path, then thread can be fed out from the thread supply source, but thread tension becomes difficult to control
Solution Approach 1:
The invention resolves this contradiction by enabling dynamic adjustment of the upper thread drawing member's position. The system can lengthen the thread path when thread feeding from the supply source is required, and subsequently position the drawing member to optimize thread tension control during the actual sewing operation, thus achieving both thread feeding capability and tension control precision.
4Device complexity
If conventional three-position switching is used, then device complexity is reduced, but stitch skipping and irregular stitches occur
Solution Approach 1:
The invention accepts increased device complexity as necessary to achieve reliable stitch quality. By implementing a dynamic positioning mechanism that allows continuous adjustment of the upper thread drawing member's position rather than relying on simple three-position switching, the system can precisely control thread consumption for each stitch, thereby eliminating stitch skipping and irregular stitches.
Solution Approach 2:
The invention incorporates feedback control mechanisms that monitor thread consumption and positioning information, allowing the system to automatically adjust the upper thread drawing member's position to achieve consistent thread tension and eliminate stitch defects. This feedback-based approach ensures high stitch quality by continuously optimizing thread supply based on actual sewing conditions.
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 solution effectively manages thread consumption variations, reducing stitch skipping and sewing shrink, thereby improving the overall sewing quality by ensuring consistent thread tension and supply.
Implementation Method 1
an upper thread drawing mechanism having an upper thread drawing member which is operable to engage with the upper thread positioned on an upper thread path between the thread tensioning device and the thread take-up bar and to move in a direction crossing the upper thread path
Implementation Method 2
a thread tensioning device which gives a tension to the upper thread from the thread supply source
Implementation Method 3
a thread take-up bar which reciprocates in synchronization with up and down movements of the needle bar to pulls up an upper thread from the needle or to feed out the upper thread from a thread supply source
Implementation Method 4
a needle up-down movement mechanism which moves a needle bar up and down, wherein the needle bar holds a needle
Implementation Method 5
a cloth feed mechanism which moves a workpiece by using a cloth moving motor, in synchronization with the up and down movements of the needle bar, and by an optional moving amount along a plane crossing the needle bar
Data Source
Figure 1
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AI summary
The invention relates to a sewing machine (1). The sewing machine (1) includes a needle up-down movement mechanism which moves a needle bar (12), a thread take-up bar (14) which reciprocates in synchronization with up and down movements of the needle bar (12), an upper thread drawing mechanism (40) which draws an upper thread using an upper thread drawing member (41), a cloth feed mechanism (50) which moves a workpiece in synchronization with the needle bar (12) and by an optional moving amount, an operation control means (70) which controls a cloth moving motor (52, 53) during a sewing operation such that the workpiece is moved by a preset moving amount, and a data memory (74) which stores sewing pattern data in which an upper thread drawing amount is set. The upper thread drawing mechanism (40) has an upper thread drawing motor (44) which moves the upper thread drawing member (41). The operation control means (70) controls the upper thread drawing motor (44) based on the sewing pattern data such that the upper thread drawing member (41) is moved by an optionally set amount for each stitch during the sewing operation.