Dual Presser Foot Structure for Stable Free-Motion Sewing
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Solution Overview
Problem
Conventional sewing machine presser feet experience unstable thread tension due to fabric lifting and fluttering caused by the upper thread being pulled up by the sewing needle or thread take-up lever, especially during embroidery or free-motion sewing.
Innovation Solution
A dual presser foot system with a first presser foot that moves up and down in conjunction with the needle bar and a second presser foot that is adjustable to maintain a fixed position relative to the throat plate, using spring members for elastic support and adjustment, ensuring stable thread tension by preventing fabric lifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single presser foot moves up and down in conjunction with the needle bar, then the presser foot responds to needle bar movement, but the fabric is not held down during the entire sewing cycle causing lifting and flutter
Solution Approach 1:
The presser foot is divided into two independent presser foot portions (first and second) that can move independently. The first presser foot portion is connected to the needle bar via a contact arm, while the second presser foot portion is supported by a support member with adjustable height. This segmentation allows each portion to perform its specific function: the first responds to needle bar movement and the second maintains stable fabric holding throughout the sewing cycle.
Solution Approach 2:
The presser foot system transitions from a static single-point contact to a dynamic two-point contact system. The first presser foot portion dynamically follows the needle bar movement, while the second presser foot portion can be adjusted to maintain optimal contact with the fabric throughout the sewing cycle, providing continuous stable holding.
2Speed
If the presser foot portion moves up and down with the needle bar, then it follows needle bar motion, but there is a time gap where the presser foot does not hold down the fabric causing thread tension instability
Solution Approach 1:
The presser foot is segmented into two portions with different functional roles. The first presser foot portion is connected to the needle bar via a contact arm that transmits upward movement, while the second presser foot portion is supported by a support member with adjustable height. This segmentation ensures continuous fabric holding throughout the sewing cycle, eliminating time gaps and maintaining stable thread tension.
Solution Approach 2:
The second presser foot portion is pre-adjusted to a height position that ensures it is always in contact with the fabric during the sewing cycle. This preliminary positioning ensures that fabric holding is maintained continuously from the start to the end of the needle bar movement cycle, preventing fabric lifting and thread tension instability.
3Reliability
If a second presser foot portion is added with adjustable height, then fabric holding stability is improved, but the device complexity increases
Solution Approach 1:
The presser foot is divided into two portions supported by a support member. The first presser foot portion is connected to the needle bar via a contact arm, while the second presser foot portion has an adjustable height mechanism. This segmentation provides stable fabric holding while maintaining a relatively simple overall structure that can be easily integrated into existing sewing machines.
Solution Approach 2:
The second presser foot portion incorporates an adjustable height parameter that can be modified to optimize fabric contact. This adjustability allows the presser foot system to adapt to different fabric types and sewing conditions without requiring a completely complex redesign, maintaining structural simplicity while improving reliability.
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 dual presser foot system stabilizes thread tension by preventing fabric lifting during sewing operations, allowing for smooth and stable free-motion sewing.
Implementation Method 1
the first presser foot includes a spring member that biases the first presser foot portion toward the throat plate
Implementation Method 2
the second presser foot includes a spring member that biases the second presser foot portion toward the throat plate
Data Source
Figure 1
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AI summary
A sewing machine presser foot being attached to a presser foot bar provided near a needle bar via a presser foot support member in a sewing machine, the sewing machine including a throat plate and a needle bar up-down movement mechanism configured to cause an up-down movement of the needle bar holding a sewing needle. The sewing machine presser foot includes: a first presser foot and a second presser foot supported by the presser foot support member; a first presser foot portion supported to be movable up and down in conjunction with the up-down movement of the needle bar; a second presser foot portion supported to be movable up and down; and an adjustment portion configured to adjust a height position of the second presser foot portion with respect to the throat plate.