Post-Bed Sewing Machine Thread Trimmer Near Needle Hole
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Solution Overview
Problem
Conventional thread trimmers for post-bed sewing machines leave a relatively long loose thread end on workpieces, requiring additional manual trimming, which increases operational time and reduces productivity.
Innovation Solution
A thread trimmer assembly with a fixed cutter and movable cutter, driven by a transmission device, is positioned closer to the needle hole, allowing the movable cutter to swing between a thread-hooking and thread-trimming position, with adjustable swing distance and time, ensuring only a short loose thread end remains after cutting, eliminating the need for secondary trimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thread trimmer is positioned with cutters mounted on the shuttle holding base, then the cutting mechanism is simple and easy to manufacture, but a relatively long loose thread end is left on the workpiece requiring additional manual trimming
Solution Approach 1:
The patent repositions the cutting mechanism from the horizontal plane (shuttle holding base) to the vertical dimension by mounting the fixed cutter on the needle plate and the movable cutter on the presser foot, which moves vertically during the sewing cycle. This dimensional change allows the cutters to be positioned closer to the needle hole, cutting the thread near the workpiece surface and leaving only a short loose thread end.
2Loss of time
If the cutters are positioned closer to the needle hole, then a shorter loose thread end is left on the workpiece, but the device structure becomes more complex
Solution Approach 1:
The patent integrates the cutting mechanism into existing multi-functional components of the sewing machine. The needle plate serves both as a support structure and as the mounting base for the fixed cutter. The presser foot, which already applies pressure to the fabric during sewing, is adapted to carry the movable cutter. This multi-functionality approach allows the cutting mechanism to be positioned close to the needle hole without significantly increasing device complexity.
3Productivity
If the movable cutter is positioned to cut near the needle hole, then productivity increases by eliminating secondary trimming, but the adjustment mechanism for swing distance becomes more complex
Solution Approach 1:
The patent employs a dynamic adjustment mechanism that allows the swing distance of the movable cutter to be modified during operation. The link connecting the presser foot to the movable cutter includes an adjustable connection point, enabling the swing arc and cutting position to be dynamically adjusted according to different thread types and workpiece requirements. This dynamic capability allows optimization of cutting performance for different materials while maintaining a relatively simple overall structure.
Data Source
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AI summary
A thread trimmer (2) of post-bed sewing machine is assembled to a feed wheel support post (231) of the sewing machine and includes a cutter set (30), a transmission device (40) and a lower shaft (24). The cutter set (30) includes a fixed cutter (31) located behind a needle hole (271) formed on a top of the feed wheel support post (231) for a sewing thread to extend therethrough, and a movable cutter (32) movably assembled to the feed wheel support post (231) and driven by the transmission device (40) to swing about a swing axis (231e) in parallel with the lower shaft (24), such that the movable cutter (32) can swing from a thread-hooking position adjacent to the needle hole (271) to a thread-trimming position for cutting the sewing thread. With these arrangements, only a relatively short loose thread end will be left on the workpiece being sewed when the sewing thread is cut by the fixed and the movable cutter.