Sewing Machine Control Device for Cloth Feeding Error Correction
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Solution Overview
Problem
Existing buttonholing sewing machines face instability in pitch and feeding jam issues due to disturbances in cloth feeding, such as step portions, and incorrect error correction in previous stitches affecting subsequent stitches, leading to unstable sewing operations.
Innovation Solution
A control device for sewing machines that includes a pressing member with a movable pressing frame, feed detecting means, a feed dog, and a feeding motor, which accumulatively stores errors in cloth feeding position and amount, calculates correction values from multiple stitches, and adjusts the feeding motor to correct the cloth feeding amount in real-time, distinguishing between forward and reverse feeding directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a potentiometer is used to detect the pressing frame position and monitor reaching target position, then the sewing operation can be controlled, but pitch instability and feeding jam occur when cloth feeding is disturbed by step portions
Solution Approach 1:
The patent implements feedback control by detecting the actual pressing frame position with a potentiometer, comparing it with the target position to calculate feeding error, and correcting the cloth feeding amount in subsequent stitches based on this error. This closed-loop feedback mechanism resolves the contradiction by maintaining both accurate position detection and reliable sewing operation even when disturbances occur.
Solution Approach 2:
The patent performs preliminary detection of the pressing frame position at the end of each stitch before the next stitching operation. By detecting the position in advance and calculating the feeding error beforehand, the system can pre-adjust the cloth feeding amount for the next stitch, preventing pitch instability and feeding jam before they occur.
2Manufacturing precision
If error correction is applied in every stitch based on previous stitch error, then feeding error can be corrected, but accidental errors or noise in one stitch cause great errors in subsequent stitches
Solution Approach 1:
The patent applies partial correction by using a correction coefficient (e.g., 1/2 or 1/3) to multiply the detected feeding error before applying it to the next stitch. This partial correction approach resolves the contradiction by correcting feeding errors progressively without allowing accidental errors or noise to cause great deviations in subsequent stitches, thereby maintaining both precision and stability.
3Device complexity
If the pressing frame position is monitored only for reaching target position, then the control device is simple, but reduction in pitch from set pitch cannot be recognized when smooth cloth feeding is disturbed
Solution Approach 1:
The patent enhances the simple position monitoring by implementing feedback control that not only detects whether the target position is reached but also calculates the actual feeding error by comparing the detected position with the target position. This feedback mechanism resolves the contradiction by maintaining relatively simple device structure while enabling accurate pitch measurement and error detection even when cloth feeding is disturbed.
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
This solution stabilizes the sewing process by accurately correcting cloth feeding errors in real-time, reducing the influence of accidental disturbances and noise, and enhancing sewing quality by maintaining consistent pitch and preventing feeding jams.
Implementation Method 1
The potentiometer 105 includes a variable resistor. As shown in FIG. 16, when the pressing frame 102 is moved, a position in which the detecting portion 106 and the potentiometer 105 come in contact with each other is changed so that a resistance value changes.
Implementation Method 2
A starting position of the sewing is set such that the pressing member 101 abuts against the stopper 102a due to an elastic force of the spiral spring 103 which is constantly being applied thereto.
Implementation Method 3
Based on a voltage value applied to the resistance thus changing, it is possible to know a displacement amount of the pressing frame 102 (i.e., a sewing length).
Data Source
AI summary
A control device of a sewing machine includes a pressing member, a pressing frame supported by the pressing member, feed detecting means for detecting a position or a feeding amount of the pressing frame, a feed dog which feeds the workpiece in the cloth feeding direction every stitch in association with the pressing frame, a feeding motor which sets a cloth feeding amount of the feed dog, a storing portion which stores, in every stitch, an error between a target position or a target feeding amount of the pressing frame and a detected position or a detected feeding amount obtained by the feed detecting means, and control means operable, in every stitch, to determine a correction value from the errors in a plurality of stitches which are stored immediately before, and to control the feeding motor to drive with the cloth feeding amount corrected by the correction value.