Sewing Machine Cloth Edge Detection Using Collimated Light
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Solution Overview
Problem
Conventional sewing machines face challenges in accurately detecting the position of side edge portions of workpieces due to diffusion light causing displacement issues and structural limitations that hinder downsizing of cloth detecting units, leading to inaccurate seam allowance control and increased machine size.
Innovation Solution
The sewing machine employs a cloth edge detection system with a reflector plate, a light source emitting collimated light, and a detector with light receiving devices, where the light is directed orthogonally and inclined to the seam allowance direction, allowing for accurate detection of side edge positions and enabling downsizing of the detection unit by eliminating structural constraints, thus improving seam allowance control and machine compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If diffusion light is used to illuminate the workpiece, then the light source structure is simple, but the detection precision of side edge position deteriorates due to displacement caused by cloth floating or thickness
Solution Approach 1:
The patent changes the fundamental parameter of light propagation from diffusion to collimation. By using a collimated light source, the light rays travel in parallel, eliminating the displacement errors that occur with diffusion light when the cloth surface is uneven. This parameter change directly resolves the contradiction by improving detection precision while maintaining structural simplicity.
Solution Approach 2:
The patent substitutes the optical mechanism from a simple diffusion light source to a collimated light source with specific optical properties. This substitution changes how light interacts with the workpiece surface, ensuring that light rays remain parallel and accurately reflect off the side edge position regardless of cloth floating or thickness variations.
2Illumination intensity
If the light source is oriented in the vertical direction to illuminate the workpiece, then the illumination is effective, but the vertical size of the detection unit increases, preventing downsizing
Solution Approach 1:
The patent changes the orientation of the light source from the vertical direction to a horizontal direction. By illuminating the workpiece from the side rather than from above, the light rays travel horizontally and reflect off the side edge position. This dimensional change allows the detection unit to be downsized vertically while maintaining effective illumination and detection capabilities.
3Volume of moving object
If the detection unit is made compact by reducing vertical size, then the machine can be downsized, but the lateral-feeding mechanism cannot be placed close enough to achieve accurate seam allowance control
Solution Approach 1:
The patent repositions the light source and detection system from a vertical arrangement to a horizontal arrangement. By placing the light source horizontally and detecting light reflected from the side edge position, the system allows the lateral-feeding mechanism to be positioned closer to the detection unit. This spatial reconfiguration enables both compactness and high precision seam allowance control.
4Length of moving object
If the light source emits light in a direction inclined to the vertical direction, then the vertical size is reduced, but the light may not effectively illuminate the side edge portion of the workpiece
Solution Approach 1:
The patent completely changes the illumination direction from an inclined vertical direction to a horizontal direction. By positioning the light source to emit light horizontally toward the side edge position of the workpiece, the system achieves effective illumination while maintaining a compact vertical profile. The light rays travel horizontally, reflect off the side edge, and are detected by the sensor, ensuring both compactness and illumination effectiveness.
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 enables precise detection and control of side edge positions, enhancing sewing quality and allowing for a more compact sewing machine design by accurately aligning seam allowances and reducing the vertical size of the detection unit, facilitating closer placement of lateral-feeding mechanisms for improved accuracy.
Implementation Method 1
a light source configured to emit light to irradiate the reflector plate and the side edge portion of the workpiece
Implementation Method 2
optical means for collimating the light emitted by the light source and for directing the collimated light in a direction orthogonal to the seam allowance direction and inclined with respect to the cloth feeding direction
Implementation Method 3
a reflector plate disposed to overlap, in the vertical direction orthogonal to the horizontal plane, with the side edge portion of the workpiece that is being fed in the cloth feeding direction
Implementation Method 4
a detector including a plurality of light receiving devices arranged along the seam allowance direction to receive the light reflected by the reflector plate
Data Source
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AI summary
A sewing machine (100) includes a cloth feeding mechanism (20) configured to feed a workpiece (CU, CD) in a cloth feeding direction, a lateral-feeding mechanism (30, 36) configured to move the workpiece (CU, CD) in a seam allowance direction (X), cloth edge detection means (40, 60) for detecting a side edge portion of the workpiece (CU, CD) along the cloth feeding direction (Y), a controller (13) configured to control the lateral-feeding mechanism (30, 36) to control a seam allowance of the workpiece (CU, CD). The cloth edge detection means (40, 60) includes a light source (431, 631) for irradiating a reflector plate (12), a detector (45, 65) having a plurality of light receiving devices arranged along the seam allowance direction (X) to receive the light reflected by the reflector plate (12) and optical means (44, 64, 632) for collimating the light emitted by the light source (431, 631) and for directing the collimated light in a direction orthogonal to the seam allowance direction (X) and inclined with respect to the cloth feeding direction (Y) toward the reflector plate (12) to irradiate the reflector plate (12) over a range along the seam allowance direction (X).