Sewing Machine First-Stitch Control to Prevent Workpiece Lifting
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Solution Overview
Problem
Sewing machines using movement detectors can inadvertently perform unintended actions, such as starting sewing based on incorrect detection results, leading to issues like the workpiece lifting from the needle plate during free motion mode.
Innovation Solution
A sewing machine design that includes a controller to perform a first-stitch operation by moving the needle bar and presser bar in a specific sequence, ensuring the presser bar is at a lowered position before the needle bar moves upward, and a second-stitch operation based on movement detector feedback to adjust needle bar movement accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the movement detector is used to detect fabric movement and control sewing operations, then sewing automation and stitch length adjustment are improved, but unintended sewing operations may be triggered by false detection results
Solution Approach 1:
The system performs preliminary actions by lowering the presser bar before the needle bar rises during the first-stitch operation. This preliminary positioning of the presser bar prevents the fabric from lifting during needle insertion, thereby preventing false detection signals that would trigger unintended sewing operations.
2Reliability
If the presser bar is lowered before needle bar rises during first-stitch operation, then fabric lifting is prevented, but device complexity increases due to coordinated control requirements
Solution Approach 1:
The controller is programmed to execute the presser bar lowering action before the needle bar rising action during the first-stitch operation. This preliminary coordination ensures the fabric is securely pressed down before needle insertion, preventing lifting without requiring complex real-time coordination mechanisms.
Solution Approach 2:
The system uses feedback from the movement detector to control subsequent operations. After the first-stitch operation completes the preliminary presser bar lowering, the system waits for fabric movement detection before initiating the second-stitch operation, creating a feedback-based control loop that manages complexity through sequential decision-making.
3Ease of operation
If the presser bar remains at normal position during needle bar movement, then device operation is simple, but the sewing needle may pull the workpiece upward causing lifting
Solution Approach 1:
The system implements a preliminary action during the first-stitch operation where the presser bar is lowered before the needle bar rises. This preliminary presser bar positioning prevents the harmful effect of workpiece lifting during needle insertion, while the presser bar returns to its normal position afterward, maintaining operational simplicity.
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 design reduces the likelihood of unintended workpiece lifting and erroneous sewing by synchronizing needle and presser bar movements, improving control over the sewing process.
Implementation Method 1
a light receiving element for detecting light to detect the movement of the fabric
Data Source
AI summary
A sewing machine includes a needle bar, a needle plate formed with a needle hole, a presser bar, a sewing machine motor, a presser motor, and a controller. The controller is configured to perform a first-stitch operation of, at start or restart of sewing, driving the sewing machine motor to move the needle bar from a lower needle position to an upper needle position, and then driving the presser motor to move the presser bar from a lowered position to a normal position. The controller is configured to perform a second-stitch operation of, based on a detection result of movement of a sewing workpiece placed on the needle plate, driving the sewing machine motor to move the needle bar in the upper-lower direction in a state where the presser bar is located at the normal position.