Lower Thread Tension Control Device Electromagnetic Actuation
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Solution Overview
Problem
Conventional lower thread tension control devices for sewing machines cannot individually adjust the initial tension of the lower thread and fail to adapt to changes in thread thickness or stitch type during operation, leading to inadequate tension control and reduced sewing quality.
Innovation Solution
A lower thread tension control device featuring a cylindrical bobbin case with a thread tensioning spring and an electromagnet, where the support member is L-shaped and made of magnetic material, allowing for adjustable tension control through both the electromagnet's current supply and an adjust screw, enabling precise initial and operational tension adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional thread tensioning spring with adjust screw is used, then the initial tension can be adjusted, but the tension cannot be adjusted during sewing operation
Solution Approach 1:
The patent applies the dynamics principle by making the thread tensioning spring movable through electromagnetic actuation. The spring can dynamically change its position between an initial state (pressing the lower thread) and an adjusted state (separated from the bobbin case), enabling real-time tension adjustment during sewing operation without requiring manual intervention.
Solution Approach 2:
The patent replaces the purely mechanical adjust screw system with an electromagnetic actuation system. The electromagnet converts electrical energy to mechanical motion, automatically moving the thread tensioning spring to adjust tension during operation, thereby substituting manual mechanical adjustment with automated electromagnetic control.
2Force
If the electromagnet is positioned far from the thread tensioning spring, then the structure is simple, but the magnetic force is insufficient for effective tension control
Solution Approach 1:
The patent applies the dimensionality change principle by repositioning the electromagnet from a lateral position to a position directly above the thread tensioning spring, utilizing the vertical dimension. This perpendicular arrangement maximizes the magnetic force efficiency while maintaining a compact overall structure, as the magnetic field acts directly along the movement path of the spring.
3Extent of automation
If the thread tensioning spring is made of magnetic material, then electromagnetic control is enabled, but the spring itself is attracted by the electromagnet causing unwanted movement
Solution Approach 1:
The patent applies the segmentation principle by dividing the magnetic system into two separate components: the thread tensioning spring (non-magnetic) and the magnetic attractor plate (magnetic material). This segmentation ensures that only the plate is attracted by the electromagnet, which in turn moves the spring through mechanical coupling, thereby preventing direct magnetic attraction of the spring itself and maintaining positional stability.
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
Enables easy and reliable adjustment of lower thread tension during sewing, improving tension control range and sewing quality by optimizing magnetic force generation and reducing operational complexity.
Implementation Method 1
an electromagnet disposed outside the bobbin case to face the thread tensioning spring means. A magnetic force of the electromagnet rotates the support member around the support shaft to press the thread pressing portion of the thread tensioning spring toward the outer circumferential surface of the bobbin case
Data Source
Figure 1
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Figure 4
AI summary
A lower thread tension control device (1) includes a thread tensioning spring means (20) and an electromagnet (26). The thread tensioning spring means (20) includes a support member (17) having an L-shaped section and is made of a magnetic material, an adjust screw (19) which is screwed to the support member (17) through an intermediate portion (14c) of the thread tensioning spring (14), and a support shaft (18) which having both ends attached to the bobbin case (11) to rotatably support the support member (17). A pressing force of the thread pressing portion (14a) of the thread tensioning spring (14) against the lower thread is controlled in accordance with a change in a current to be supplied to the electromagnet (26), and by adjusting an initial tension of the lower thread in accordance with a screwing amount of the adjust screw (19).