Horizontal Rotary Hook Magnet Fixation via Rotation Stopper
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Solution Overview
Problem
The existing configurations for stabilizing the inner rotary hook in sewing machines, which use a magnet to prevent random movement, face issues with adhesives detaching and needle threads getting caught in protrusions, leading to operational noise and sewing performance hampering, especially when the outer rotary hook is made of synthetic resin.
Innovation Solution
A horizontal rotary hook design featuring a magnet plate with a rotation stopper positioned inward of the permanent magnet, which is securely fixed to the outer rotary hook without protrusions, using a shaft hole and engaging portions to prevent rotation and ensure stability without obstructing the needle thread.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive or adhesive tape is used to fix the magnet to the bottom surface of the outer rotary hook, then the magnet can be attached, but the adhesiveness is low and the magnet is likely to detach during operation
Solution Approach 1:
The patent replaces the chemical bonding method (adhesive) with a mechanical fixation system consisting of a magnet fixing holder and rotation stopper. The holder is fitted into a recess in the outer rotary hook, and the rotation stopper prevents rotational movement, providing reliable mechanical fixation without relying on adhesive strength.
2Reliability
If cleaning and degreasing treatments are performed on the bottom surface of the outer rotary hook, then adhesive bonding improves, but the assembling operation becomes cumbersome and complicated
Solution Approach 1:
The patent eliminates the need for cleaning and degreasing operations by replacing adhesive bonding with a mechanical fixation system. The magnet fixing holder and rotation stopper provide secure attachment without requiring surface preparation, thereby simplifying the assembling operation.
3Stability of the object's composition
If protrusions are formed on the yoke member to prevent rotation, then the yoke member is fixed stably, but needle threads are likely to be caught by the protrusions and engaging portions
Solution Approach 1:
The patent extracts the rotation prevention function from the yoke member by implementing it in the magnet fixing holder instead. The holder includes a rotation stopper that prevents rotation of the magnet plate, while the yoke member maintains a smooth surface without protrusions, eliminating the thread catching problem.
4Stability of the object's composition
If a yoke member with circumferential wall notches is used to fix the magnet, then rotation is prevented, but the configuration becomes complex and manufacturing steps increase
Solution Approach 1:
The patent extracts the rotation prevention function from the yoke member's circumferential wall and relocates it to the magnet fixing holder. This separation allows the yoke member to remain simple and easy to manufacture, while the holder provides the necessary rotation stopping capability through its rotation stopper.
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
The solution provides stable fixation of the magnet without additional manufacturing steps or protrusions, preventing thread catch and enhancing mechanical strength, thus improving sewing performance and reducing operational noise.
Implementation Method 1
The inner rotary hook might make random movement such as oscillation during a sewing operation. Such random movement of the inner rotary hook causes noise and affects sewing performance. Japanese Patent Application Laid-open No. 2006-94905 discloses a specific configuration for addressing this problem. Specifically, the configuration is one of various configurations in which a magnet is used to prevent the inner rotary hook accommodated in the outer rotary hook from floating during the sewing operation.
Data Source
AI summary
Provided is a horizontal rotary hook for a sewing machine including: an inner rotary hook including an attracted member made of metal in an outer lower surface portion; a permanent magnet that attracts the inner rotary hook; a magnet plate that accommodates the permanent magnet and is provided with a shaft hole for mounting at a center of a diameter thereof; a non-metallic outer rotary hook that accommodates the magnet plate and has a shaft hole at a center of a diameter of an inner bottom portion thereof; and a hook supporting shaft that is inserted through the shaft hole of the magnet plate and the shaft hole of the outer rotary hook, and that includes, at an upper end thereof, a flange for rotatably supporting the outer rotary hook and the magnet plate. A rotation stopper for the magnet plate is disposed to be positioned more inward than an outer circumference edge of the permanent magnet placed in the magnet plate.