Adjustable Counter Knife Assembly for Sewing Machine Thread Cutting
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Solution Overview
Problem
Existing sewing machines with thread knives and counter knives face challenges in cutting reliability and counter knife service life due to fixed positions leading to excessive wear and inefficient cutting processes.
Innovation Solution
A sewing machine design featuring a counter knife assembly with continuous adjustability between extreme stop positions, enabled by a pivotable bearing and stop bolts, allowing precise positioning and reduced wear, and a multi-part holder with a thread clamping spring for defined thread management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the counter knife is fixed in a stationary position, then the structure is simple, but cutting reliability decreases and service life is reduced due to excessive wear
Solution Approach 1:
The counter knife is transformed from a fixed stationary component to a dynamically adjustable component. The adjustment mechanism allows the counter knife position to be continuously modified along the cutting path, enabling optimization of the cutting angle and contact point with the thread knife. This dynamic positioning improves cutting reliability by allowing precise alignment while maintaining a manageable structural complexity through the use of a threaded adjustment rod and locking nut system.
2Duration of action of stationary object
If the counter knife position is fixed, then the device complexity is low, but the service life of the counter knife decreases due to unnecessary wear
Solution Approach 1:
The counter knife assembly incorporates an adjustment mechanism with a threaded rod and locking nut that enables continuous position modification. This allows the operator to optimize the cutting geometry to minimize wear on the counter knife edges, thereby extending service life. The mechanism maintains relatively low complexity by using standard mechanical components (threaded rod, nut, and slot guides) rather than complex actuation systems.
3Productivity
If the counter knife is mounted in a fixed holder, then the mounting is simple, but cutting efficiency is reduced due to inability to optimize cutting position
Solution Approach 1:
The counter knife holder is designed with a slot-shaped opening that guides the adjustment rod, allowing the counter knife to be positioned at multiple locations along the cutting path. This dynamic positioning capability enables optimization of the cutting interaction between the thread knife and counter knife, improving cutting efficiency. The holder structure remains relatively simple by using a slot guide rather than complex mechanical linkages, maintaining ease of construction while enabling positional optimization.
Data Source
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AI summary
A sewing machine (1) with a housing (6), a driven movable thread cutter (16) for cutting at least one sewing thread and a counter-knife (19) fixed to the housing which cooperates with the thread cutter (16), wherein the counter-knife (19) is arranged to be continuously displaceable in a housing-fixed counter-knife receptacle (23) in a position range between a first stop-counter-knife position (191) and a second stop-counter-knife position (192) shifted relative to this in a cutting-counter-knife position.