Sewing Machine Presser Foot Dynamics for Loop Control
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Solution Overview
Problem
Sewing machines experience skipped stitches due to oversized needle thread loops that sag or topple, causing loop seizure failures, particularly when the needle bar is in certain swing positions, leading to inconsistent seam formation.
Innovation Solution
A sewing machine with a presser foot lifting/lowering mechanism controlled by a controller that adjusts the size of the needle thread loop by lifting the presser foot to a predetermined height in coordination with the needle bar's swing position and height, ensuring consistent loop formation and prevention of skipped stitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the needle bar is swung to certain positions, then the needle thread loop becomes oversized, but the loop sags or topples causing skipped stitches
Solution Approach 1:
The presser foot lifting/lowering mechanism dynamically adjusts the presser foot height based on the needle bar swing position. When the needle bar swings to positions that would create oversized loops, the presser foot is automatically lifted to allow controlled cloth elevation, resizing the loop to prevent sagging while maintaining swing adaptability
Solution Approach 2:
The system changes the presser foot height parameter in response to needle bar swing position changes. By varying the presser foot elevation, the loop size parameter is controlled to remain within optimal ranges regardless of swing position, ensuring reliable loop seizure
2Manufacturing precision
If the presser foot pressure is reduced to allow cloth elevation with rising needle, then the needle thread loop size can be adjusted, but the loop may become oversized and sag
Solution Approach 1:
The presser foot lifting/lowering mechanism provides dynamic, position-dependent pressure adjustment. Rather than uniform pressure reduction, the presser foot height is varied according to the needle bar swing position, allowing loop size control while preventing excessive loop enlargement that would cause sagging
Data Source
AI summary
A sewing machine is disclosed that includes a needle bar allowing attachment of a sewing needle including a needle eye to a lower end of thereof; a needle-bar lifting/lowering mechanism that moves the needle bar up and down; a presser foot; a presser foot lifting/lowering mechanism that moves the presser foot up and down; a hook that is provided with a beak for seizing a needle thread loop formed at the needle eye and that rotates in coordination with the up and down movement of the needle bar; and a controller that controls the presser foot lifting/lowering mechanism so as to resize a needle thread loop by lifting the presser foot to a predetermined height in coordination with a swing position of the needle bar and a predetermined height of the needle bar where the beak meets the needle thread loop.