Thread Pulling Blade With Segmented Gripping Grooves
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Solution Overview
Problem
Existing thread-pulling knives for sewing machines often fail to reliably cut thick threads, which are common when sewing resistant materials like leather or plastic, as they can interfere with each other during cutting.
Innovation Solution
A thread-pulling knife with separate thread gripping grooves for the upper and looper threads, allowing for controlled cutting and reducing the maximum cutting force, is designed with a pivot axis parallel to the hook axis and offset cutting edges to prevent interference and ensure reliable cutting of thick threads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single thread-pulling knife is used to cut both upper and looper threads, then the device structure is simple, but the threads may interfere with each other during cutting especially when thick threads are used
Solution Approach 1:
The single thread-pulling knife is divided into two separate thread-pulling knives, each equipped with its own thread gripping groove. This segmentation allows independent control and cutting of the upper thread and looper thread, preventing interference between thick threads during the cutting process while maintaining reliable operation
2Productivity
If both threads are cut simultaneously, then the cutting process is fast, but the maximum cutting force increases which may cause problems with thick threads
Solution Approach 1:
The cutting process is divided into two sequential phases: first the upper thread is cut, then the looper thread is cut. This periodic action reduces the instantaneous cutting force required at any given moment compared to simultaneous cutting, while still achieving rapid thread trimming by maintaining the knives close to the stitch formation point
3Manufacturing precision
If the thread-pulling knife is positioned close to the stitch formation point, then short thread ends remain on the material, but the risk of disrupting the thread course increases
Solution Approach 1:
Thread gripping grooves are introduced as intermediary structures that securely hold the threads before cutting. These grooves act as mediators that guide the threads into the correct position for cutting close to the stitch formation point while preventing disruption of the thread course through the curved design that follows the natural thread path
Data Source
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AI summary
The thread drawing blade is pivoted between a basic position and a thread spinning position centering on a pivot axis. A blade main portion is provided with the thread spinning channels and a cutting blade. The blade main portion is provided for supporting the supply housing for receiving untwisted yarn supply. The thread spinning channels are positioned separately. A hook shaft is extended in a horizontal direction of the blade main portion. The thread spinning channels are arranged on both sides of a blade base.