Sewing Machine Thread Cutting Activation Device
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Solution Overview
Problem
Household sewing machines face challenges in synchronizing path and time-dependent motion for thread cutting and stitching, particularly in ending and starting seams, where precise actuator elements are required to ensure optimal thread cutting and knot formation.
Innovation Solution
An activation device driven by the sewing machine's primary shaft, utilizing a single stroke magnet to trigger motions via cams synchronously with stitch-forming organs, ensuring correct and predetermined starting points for cutting and lead-in stitching, with independent mechanical coupling for precise timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single stroke magnet is used to trigger motions via cams, then device complexity is reduced and manufacturing cost decreases, but precise path and time-dependent motion control becomes more challenging
Solution Approach 1:
The motion control system is segmented into multiple independent cams, each responsible for a specific motion function (thread cutting, lead-in stitching, thread brake). Each cam is equipped with its own follower that converts the rotational motion from the primary shaft into the required linear or oscillating motion. This segmentation allows complex synchronized motions to be achieved through simpler individual components.
Solution Approach 2:
The stroke magnet acts as an intermediary triggering mechanism that initiates the motion sequence. The magnet activates a trigger mechanism that releases the cams at the correct moment in the stitching cycle. This intermediary approach decouples the timing trigger from the continuous motion control, allowing precise activation without requiring complex continuous control systems.
2Manufacturing precision
If multiple actuator elements are used for thread cutting and stitching functions, then motion precision and timing control are improved, but device complexity and production cost increase
Solution Approach 1:
The primary shaft serves as a universal driving element for all actuator components. Through this single rotational shaft, multiple cams are activated in sequence to control thread cutting, lead-in stitching, thread brake, and tension control functions. This multi-functionality approach reduces the need for multiple independent actuators while maintaining precise timing control through the synchronized rotation of the primary shaft.
Solution Approach 2:
The system utilizes periodic action through the cyclic rotation of the primary shaft, which periodically activates each cam at the appropriate phase of the stitching cycle. The stroke magnet provides periodic triggering signals that synchronize with the shaft rotation. This periodic activation pattern ensures precise timing for all functions without requiring continuous control of multiple actuators.
3Ease of manufacture
If mechanical coupling is made independent from activation timing, then ease of manufacture is improved, but reliability of synchronous operation may be compromised
Solution Approach 1:
The cams are pre-positioned and pre-adjusted during manufacturing to establish the correct timing relationships with the primary shaft rotation. The stroke magnet is pre-calibrated to trigger at the precise moment required for each function. This preliminary action ensures that when the device is assembled, the synchronous operation is automatically established without requiring complex timing adjustments, thereby maintaining reliability while simplifying assembly.
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
Enables cost-effective, synchronous operation of all functions with the primary shaft, ensuring precise path and time-dependent progression for thread cutting and lead-in stitching, improving seam quality and efficiency.
Implementation Method 1
The trigger of the various motions with regards to point of time and path occurs by a single stroke magnet
Data Source
AI summary
The activation for a path and time related motion of a thread cutting and lead-in stitching unit (7) and the thread brake (25) occurs by a cam drive driven by the primary shaft (9) and a cam drum (75) arranged on the upper shaft (17). This way, an absolute synchronization of the elements of the thread cutting and lead-in stitching unit (7), the thread brake (25), and the hook as well as the needle is ensured.