Sewing Machine Motor Speed Control via Thread Consumption

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing sewing machines face challenges in maintaining consistent stitch-pitch during quilting due to inaccuracies in detecting movement distance caused by factors like cloth color, material, and external light, which affects the workability and quality of the quilts.

Innovation Solution

An electronic sewing machine with a sewing machine motor that includes a stitch-pitch setting unit, consumed thread amount detection, and speed control units to adjust the rotational speed of the motor based on calculated thread consumption, ensuring consistent manual cloth feed regardless of cloth properties or light conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an image sensor is placed in the head of the sewing machine arm to detect cloth movement distance, then the detection system can be implemented, but the detection accuracy is affected by cloth color, material, external light, and distance variations

Engineering Contradiction:

Improvemovement distance detection accuracyVSAvoiddetection consistency under varying conditions

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the optical image sensor-based detection system with a thread consumption detection system. Instead of using light and images to measure cloth movement, the invention uses a detection unit to measure the amount of thread consumed during sewing, which directly correlates to the stitch pitch. This substitution eliminates the problems of optical detection affected by cloth color, material, and lighting conditions, providing more reliable and consistent measurements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces thread consumption as an intermediary measurement parameter. Rather than directly measuring cloth movement distance (which is affected by various external factors), the system measures thread consumption as an intermediate quantity that can be more reliably detected and then uses this information to calculate and control stitch pitch. This intermediary approach provides a more stable basis for control.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the image sensor is placed in close proximity of the workpiece cloth to improve detection accuracy, then measurement precision improves, but workability deteriorates due to impeding the user during sewing

Engineering Contradiction:

Improvemovement distance detection accuracyVSAvoidworkability during sewing

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent replaces the image sensor placement near the cloth with a thread consumption detection mechanism. The detection unit is positioned to measure thread usage rather than to visually track cloth movement near the needle area. This substitution allows accurate measurement without placing any physical obstacle in the user's path or near the needle drop position, thus maintaining both precision and workability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Extent of automation

If image processing is used to calculate movement distance from static images, then the system can function, but the complexity increases due to processing multiple images and calculating distances

Engineering Contradiction:

Improveautomatic stitch pitch controlVSAvoidimage processing complexity

Core Design Contradiction:

Extent of automationVSDevice complexity

Solution Approach 1:

The patent replaces the complex image processing system with a simpler thread consumption detection and measurement system. Instead of capturing multiple static images, processing them through computer vision algorithms, and calculating movement distances, the invention directly measures thread consumption during sewing. This mechanical/electrical measurement approach is inherently simpler than optical processing while achieving the same automatic control objective.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the essential measurement function from the complex image processing system. Rather than using the entire image processing pipeline (capturing images, processing pixel data, calculating distances), the invention extracts only the necessary information (movement distance) by measuring it directly through thread consumption, eliminating the unnecessary complexity of intermediate image processing steps.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS7806063B2Electronic sewing machine and sewing machine motor control program

Publication Date: 2010.10.05 BROTHER KOGYO KK

AI summary

An electronic sewing machine includes a sewing machine motor that vertically drives a sewing needle via a rotation of a main shaft; a stitch-pitch setting unit that sets a stitch-pitch in sewing manually fed workpiece cloth; a consumed thread amount detection unit that detects consumed thread amount of at least either of a needle thread or a bobbin thread consumed in each ongoing sewing cycle; a consumed thread amount calculation unit that calculates consumed thread amount based on an output from the consumed thread amount detection unit; and a speed control unit that controls rotational speed of the sewing machine motor based on calculated result of the consumed thread amount calculation unit so that an amount of manual cloth feed equals the stitch-pitch set by the stitch-pitch setting unit.