Sewing Machine Thread Tension Dial with Cam Adjustment
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Solution Overview
Problem
Conventional thread tension devices in sewing machines require cumbersome operations to adjust needle thread tension, involving the detachment of exterior covers and manual turning of adjusting members, which is time-consuming and troublesome.
Innovation Solution
A thread tension device with a thread tension dial, spring force adjusting cam, transfer plate, and adjusting members that allow for quick tension adjustment using an external tool, simplifying the process by enabling easy engagement and rotation of the adjusting members through a through hole and gear mechanism, reducing the need for extensive cover detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the exterior cover is detached and the thread tension adjusting member is manually turned using an adjustment tool, then the needle thread tension can be adjusted, but the operation becomes troublesome and time-consuming
Solution Approach 1:
The patent extracts the essential adjustment function from the complex cover-detachment process. The adjusting member is designed to be accessible through a through-hole in the thread guide assembly, allowing the adjustment tool to interact with the cam mechanism without requiring removal of the exterior cover. This isolates the adjustment function from the protective cover structure.
Solution Approach 2:
The patent introduces an intermediary mechanism - the through-hole in the thread guide assembly - that mediates between the external adjustment tool and the internal cam mechanism. This intermediary structure allows the adjustment tool to transmit rotational motion to the cam without direct exposure of the cam, maintaining protection while enabling adjustment.
2Ease of operation
If the thread tension adjusting member is manually turned, then the spring force can be adjusted, but the adjusting operation becomes cumbersome
Solution Approach 1:
The patent replaces direct manual turning of a threaded adjusting member with a cam-based mechanical substitution. The cam mechanism converts simple rotational motion of the adjusting member into linear displacement that directly adjusts the spring force, eliminating the need for complex threading operations while maintaining precise control.
Solution Approach 2:
The patent employs a dynamic cam mechanism that allows continuous adjustment of spring force through rotational motion. The cam profile is designed to provide smooth, progressive adjustment of the adjusting member's position relative to the spring, enabling dynamic control of thread tension without discrete steps or complex mechanisms.
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 rapid and easy adjustment of needle thread tension by allowing the operator to adjust the spring force without fully detaching the outer cover, significantly reducing the time and effort required for tension adjustments.
Implementation Method 1
a spring force adjusting cam which is formed in the thread tension dial and is capable of adjusting the spring force of the thread tension spring
Implementation Method 2
a thread tension spring biasing one of the thread tension discs toward the other and having two ends
Implementation Method 3
a first adjusting member which is threadingly engaged with the transfer plate to receive one end of the thread tension spring
Data Source
AI summary
A thread tension device includes paired thread tension discs holding a needle thread, a thread tension spring biasing one of the discs toward the other, a thread tension dial adjusting a tension exerted on the needle thread, a spring force adjusting cam formed in the thread tension dial, a transfer plate following the cam so as to be capable of adjusting the spring force, and a first adjusting member threadingly engaged with the transfer plate to receive one end of the thread tension spring, a thread guide assembly having a through hole formed so that the adjusting tool is insertable into the through hole, and a second adjusting member rotatably mounted on the transfer plate and engageable with the distal end of the adjusting tool inserted into the through hole so as to be rotatable with the tool, thereby rotating the first adjusting member by rotation of the tool.