Sewing Machine Needle Bar Positioning and Feed Dog Control
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Solution Overview
Problem
Existing sewing machines require manual and cumbersome adjustments to position the workpiece cloth relative to the sewing needle, and the elevated position of the needle bar and feed dog interfere with precise positioning, leading to displacement issues with the workpiece cloth.
Innovation Solution
A sewing machine with a controller that automatically adjusts the needle bar, presser foot pressure, and feed dog position, allowing for precise and easy workpiece cloth positioning by detecting cloth thickness and needle bar position, and switching the feed dog to an inoperative state during positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the needle bar is kept at an elevated position during standby, then the sewing machine is ready for operation, but the workpiece cloth positioning becomes difficult and troublesome
Solution Approach 1:
The needle bar is automatically lowered to a predetermined position immediately before the needle tip contacts the workpiece cloth surface, based on detected cloth thickness. This preliminary positioning action eliminates the need for manual pulley operation and prepares the optimal positioning state in advance, making workpiece cloth positioning easy and reliable.
2Ease of operation
If the feed dog protrudes above the needle plate during needle bar elevation, then the feed mechanism is ready for sewing, but the workpiece cloth movement becomes restricted and prone to displacement
Solution Approach 1:
The feed dog position is dynamically switched between protruding and retracted states based on the sewing operation phase. During workpiece positioning, the feed dog is retracted below the needle plate to allow free cloth movement. During active sewing, the feed dog protrudes to feed the cloth. This dynamic adaptation resolves the contradiction between movement freedom and positioning stability.
3Reliability
If the presser foot exerts high pressure on the workpiece cloth, then the cloth is held firmly for sewing, but the cloth displacement prevention during positioning becomes excessive and troublesome
Solution Approach 1:
The presser foot pressure is dynamically adjusted based on the operational phase. During workpiece positioning, the presser foot pressure is reduced to allow easy cloth movement and adjustment. During active sewing, the pressure is increased to firmly hold the cloth for precise stitching. This dynamic pressure adjustment resolves the contradiction between holding reliability and adjustment ease.
Data Source
AI summary
A controller of a sewing machine configured to execute a pre-positioning operation including controlling a needle bar driving mechanism, based on a thickness of a workpiece cloth detected by a thickness detection mechanism and a vertical position of a needle bar detected by a needle bar position detection mechanism, to stop a needle bar at a preset position immediately before a tip of a sewing needle pierces the workpiece cloth, controlling a pressure adjustment mechanism to adjust a pressure of a presser foot at a predetermined pressure that allows movement of the workpiece cloth, and controlling a feed dog switching mechanism to switch a feed dog to an inoperative state.