Sewing System Clamping and Cutting for Thread Nest Prevention
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Solution Overview
Problem
Existing sewing systems face challenges in creating error-free seam starts with double lockstitch seams, often resulting in thread nests and long thread protrusions that require manual post-processing, increasing production costs.
Innovation Solution
A sewing system with a clamping device on the pressure bar and a cutting element that shortens the upper thread immediately after the seam start, ensuring a clean stitch pattern without manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relatively long free beginning of the thread protrudes from the needle to avoid thread nests, then thread nest formation is prevented, but the long thread beginning protrudes on the visible side of the finished seam requiring manual post-processing
Solution Approach 1:
The patent applies preliminary action by cutting the thread beginning to a specific length before the sewing process completes. The cutting element is positioned to trim the upper thread beginning shortly after seam production starts, ensuring the thread is neither too long (causing protrusion) nor too short (causing thread nests). This preliminary trimming action resolves the contradiction by establishing the optimal thread length in advance.
Solution Approach 2:
The patent changes the parameter of thread length dynamically during the sewing process. Instead of using a fixed long thread length, the system adjusts the effective thread length by cutting it to a precise length after a few stitches are formed. This parameter change allows the thread to be long enough to prevent nests during sewing but short enough to avoid protrusion on the finished seam.
2Manufacturing precision
If manual post-processing is performed to shorten protruding thread beginnings, then seam quality is improved, but production costs and time increase
Solution Approach 1:
The patent implements self-service by enabling the sewing machine to automatically trim its own thread beginnings during the sewing process. The cutting element, positioned in the feed path, automatically cuts the upper thread beginning to the appropriate length without requiring external manual intervention. This self-service mechanism eliminates the need for separate post-processing operations to remove protruding threads.
Solution Approach 2:
The patent maintains continuity of useful action by integrating the thread cutting function into the ongoing sewing process. The cutting element operates while the material continues to be fed through the machine, allowing thread trimming to occur without interrupting or pausing the sewing operation. This continuous operation eliminates idle time associated with manual thread shortening.
3Productivity
If the upper thread is cut very close to the needle to achieve a short thread start, then thread protrusion is minimized, but the risk of incorrect stitch formation and thread nests increases
Solution Approach 1:
The patent applies preliminary action by allowing the sewing process to establish a small initial segment of stitches before the cutting element activates. This preliminary sewing action ensures that the thread is properly positioned and tensioned near the needle area before cutting occurs. By performing this preliminary action, the system minimizes the risk of incorrect stitch formation while still achieving a short final thread start length.
Data Source
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AI summary
The invention relates to a sewing system and to a sewing method, having at least one double lockstitch sewing machine for producing at least one seam on sewing material, in particular for producing at least one dart on the sewing material. The sewing system is provided with a driven sewing material transport system for a defined or definable advancing direction of the sewing material relative to stitch-forming tools which are provided to produce the at least one seam on the sewing material in question. The sewing material transport system has a pressure bar (18) with which the sewing material can be pressed against a worktop and the sewing material can be moved to produce an advancing movement past the stitch-forming tools. According to the invention, to allow a seam to start without stitching faults but with a short thread starting end when using such a sewing system to produce darts, without manual post-processing being necessary, a clamping device (25) arranged on the pressure bar (18) can be moved together with the pressure bar (18) during the advancing movement thereof, wherein the clamping device (25) is provided to clamp a thread starting end of the top thread (30), and the sewing system has a cutting element (34) which is arranged, at least temporarily immediately after the start of seam production, in a region between the clamping device and the presser foot in order to cut the top thread between the clamping device and the presser foot.