Sewing Machine Needle Thread Tension Control via Motor Torque
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Solution Overview
Problem
Existing sewing machines face challenges in controlling needle thread tension, particularly in multi-needle head embroidery machines, due to unstable frictional resistance, leading to difficulties in maintaining uniform tension, detecting thread breaks, and managing thread accumulation.
Innovation Solution
A sewing machine configuration with a thread take-up lever, upstream and downstream grip sections, and a turning section, controlled by a motor and actuation system, which applies torque and position control to manage needle thread tension and detect breaks, ensuring consistent tension and accurate thread management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If frictional resistance components (tension disc and rotary tension component) are used to control needle thread tension, then thread tension can be regulated, but the frictional resistance becomes unstable and variable making it difficult to control tension uniformly across multiple needle threads
Solution Approach 1:
The patent removes the traditional friction-based tension control components (tension disc and rotary tension component) from the needle thread path. Instead of using frictional resistance to control tension, the invention extracts these components entirely and replaces them with a direct motor-driven turning section that pulls the needle thread through the fabric, eliminating the unstable frictional resistance while maintaining tension control capability.
Solution Approach 2:
The patent replaces the mechanical friction-based tension control system with an electromechanical system. A motor directly drives the turning section to pull the needle thread, substituting the passive friction-based mechanical system with an active electromechanical system that provides stable and controllable tension through motor torque control.
2Force
If friction-based tension components are used, then thread tension can be applied, but thread breaks are difficult to detect accurately due to slippage between components and thread
Solution Approach 1:
The patent removes the intermediate friction-based components (tension disc and rotary tension component) that caused slippage and detection errors. By extracting these components, the motor connects directly to the turning section, eliminating the slippage problem and enabling accurate thread break detection through direct monitoring of motor current and turning section position.
Solution Approach 2:
The patent implements feedback control by monitoring motor current, turning section position, and needle thread tension in real-time. This feedback system detects thread breaks accurately by identifying abnormal changes in motor load or position, replacing the unreliable friction-based detection method with a precise electromechanical sensing system.
3Quantity of substance
If traditional tension control components are used, then thread can be guided through the system, but excess or deficiency in thread accumulation occurs due to inability to precisely control thread drawing
Solution Approach 1:
The patent replaces the passive mechanical thread guidance system with an active electromechanical thread feeding system. The motor-driven turning section precisely controls thread drawing length and timing, eliminating the accumulation problems caused by the inability to precisely measure and control thread feed in the traditional friction-based system.
Solution Approach 2:
The patent performs preliminary positioning and tension adjustment before the actual sewing operation. The motor pre-tensions the needle thread and positions the turning section correctly, ensuring precise thread accumulation from the start of each stitch, preventing both excess and deficiency in thread feeding.
Data Source
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AI summary
[Problem] There is provided a needle thread tension controller that can control a magnitude of tension on a needle thread for each stitch, that can draw the needle thread with a slim chance of occurrence of a thread break, that easily, accurately detects occurrence of the thread break when the thread break has occurred, and that does not cause any excess or deficiency of a quantity of accumulated thread, which would otherwise be caused by drawing a needle thread. [Means for Resolution] There are provided an upstream grip section 40 and a downstream grip section 60 for gripping a needle thread and a turning section 80 for turning the needle thread. In a torque control zone, rotating force is imparted to a turning arm in accordance with a torque value while an upstream grip section main body 41 is closed and while a downstream grip section main body 61 is opened in such a way that tension is exerted on a needle thread against a direction in which a thread take-up lever 12a draws the needle thread. In the meantime, inaposition control zone, rotating force is imparted to the turning arm 81 in accordance with angle position data pertaining to a needle thread motor 86 while the upstream grip section main body 41 is opened and while the downstream grip section main body 61 is closed in such a way that an angle of the needle thread motor returns to an initial angle position of the needle thread motor 86.