Magnetic Bobbin Tension Control for Sewing Machines
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Solution Overview
Problem
The existing techniques for adjusting the tension of the lower thread in sewing machines face difficulties in precision and reproducibility, making it challenging to accurately control the thread tension.
Innovation Solution
A lower thread supply device with a bobbin and bobbin case system that utilizes a magnetic force member to attract and control the tension of the lower thread, allowing for adjustable tension through a magnetic force change mechanism, eliminating the need for cumbersome screw adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tension adjustment screw is used to adjust lower thread tension, then the tension can be changed, but quantitative adjustment is difficult and reproducibility is poor
Solution Approach 1:
The patent replaces the traditional mechanical screw adjustment system with a magnetic field-based control system. An electromagnet generates adjustable magnetic force to attract the bobbin, providing precise and reproducible tension control without requiring manual screw adjustments. The magnetic force can be quantitatively controlled through electrical parameters, solving the imprecision of mechanical adjustment.
Solution Approach 2:
The patent changes the control parameter from mechanical screw position to electrical current/magnetic field strength. By adjusting the electrical parameters (current, voltage, or pulse width) supplied to the electromagnet, the magnetic force and thus the thread tension can be precisely and reproducibly controlled, enabling quantitative adjustment that was not possible with mechanical screws.
2Measurement precision
If a magnetic force member is introduced to control bobbin position, then tension control precision is improved, but device complexity increases
Solution Approach 1:
The electromagnet serves multiple functions: it acts as both the tension control mechanism and the bobbin positioning mechanism. The same magnetic force member that attracts the bobbin to control thread tension also maintains the bobbin in its proper position within the bobbin case, eliminating the need for separate positioning components and reducing overall device complexity.
Solution Approach 2:
The magnetic force member automatically maintains bobbin position and tension control through its inherent magnetic attraction, without requiring additional mechanical stops, springs, or adjustment mechanisms. The system self-regulates the bobbin position based on the magnetic force applied, reducing the number of components needed.
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
Facilitates precise and reproducible adjustment of lower thread tension, enhancing sewing performance by providing a reliable and easy-to-use method for controlling thread tension without the limitations of traditional adjustment methods.
Implementation Method 1
a magnetic force member (46) which is arranged at the front surface side of the bobbin case (41-1) and attracts the front surface side flange portion (39) of the bobbin (36-1) by the magnetic force via the bobbin case (41-1)
Data Source
AI summary
A lower thread supply device of a sewing machine includes a bobbin, a bobbin case, a magnetic force member, and a magnetic force change portion. The bobbin has a cylindrical portion for inserting into a spindle of a shuttle, a shuttle side flange portion, and a front surface side flange portion which is magnetic, and a lower thread is wound around an outer circumference of the cylindrical portion between the shuttle side flange portion and the front surface side flange portion. The bobbin case has a non-magnetic cover portion having a front surface side part and a side wall part, housing the bobbin and transmitting a magnetic force. The magnetic force member is arranged at the front surface side of the bobbin case and attracts the front surface side flange portion of the bobbin by a magnetic force via the bobbin case.