Sewing Machine Feed Dog Control via Thread Cut Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional sewing machines experience unpleasant rattling noise and frequent switching of the feed dog to a lowered position, leading to potential machine failure perception and cloth entanglement issues due to the synchronization of the feed dog lowering mechanism with the presser foot lifting lever.
Innovation Solution
A sewing machine configuration that includes an input unit for thread cut instructions, a thread cutting mechanism to cut the needle and bobbin threads, a feed dog vertically moving mechanism, a feed dog activating switch unit, and a control unit to manage the thread cutting and feed dog positioning, ensuring the feed dog is only switched to a lowered position after thread cutting, thereby preventing unnecessary noise and cloth entanglement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the feed dog lowering mechanism operates in synchronism with the presser foot lifting lever, then the feed dog is lowered when the presser foot is lifted, but this causes frequent switching of the feed dog position leading to rattling noise and potential machine failure perception
Solution Approach 1:
The feed dog lowering condition is determined in advance by detecting thread cut state before the actual lowering action occurs. The control unit stores thread cut state information and uses it to control feed dog lowering, preventing frequent unnecessary switching that causes noise and reliability issues.
2Ease of operation
If the feed dog is lowered every time the presser foot lifting lever is operated, then the workpiece cloth can be removed, but this causes the feed dog to switch position frequently causing rattling noise and cloth entanglement
Solution Approach 1:
The control unit detects the thread cut state through a switch unit and uses this feedback information to determine when to lower the feed dog. By basing the lowering decision on actual thread cut feedback rather than mere presser foot lifting, the system avoids frequent unnecessary feed dog switching and the associated rattling noise.
3Device complexity
If the feed dog switching is synchronized with presser foot lifting, then the mechanism is simple, but this causes the feed dog to be in the lowered position unnecessarily during ongoing sewing operations
Solution Approach 1:
The system performs preliminary detection of thread cut state and stores this information before executing feed dog lowering. This preliminary action ensures that feed dog position changes occur only when actually needed (after thread cutting), maintaining sewing operation continuity while keeping the control mechanism relatively simple.
Data Source
AI summary
A sewing machine including an input unit that inputs a thread cut instruction; a thread cutting mechanism that cuts a needle thread and a bobbin thread based on the thread cut instruction; a feed dog vertically moving mechanism that vertically drives a feed dog for feeding a workpiece cloth; a feed dog activating switch unit that switches the feed dog between an active state in which the feed dog is vertically driven by the feed dog vertically moving mechanism and an inactive state in which an upper surface of the feed dog is positioned in a lowered position below an upper surface of a needle plate provided in a sewing machine bed; and a control unit that drives the thread cutting mechanism based on the thread cut instruction inputted from the input unit and that controls the feed dog activating switch unit to switch the feed dog to the inactive state in which the feed dog is positioned in the lowered position.