Knitting Needle Jack Asymmetric Boring Design
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Solution Overview
Problem
The existing construction of flatbed knitting needles is prone to stress concentration and breakage at the coupled portion of the needle jack, leading to reduced productivity due to edge remnants from polishing and increased inertia weight when attempting to speed up knitting operations.
Innovation Solution
The design features a needle jack with a convex portion having a larger tail end side boring, an extension part with a curved shape, and a width enlarging part, which disperses stress and avoids concentration, allowing for increased curvature radius and reduced edge remnants, thus enhancing the strength and durability of the coupled portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the convex portion of the needle jack is made with smaller boring curvature radius to secure strength, then the strength is improved, but edge remnants remain after polishing and stress concentration occurs
Solution Approach 1:
The patent applies asymmetry by making the tail end side boring larger than the front end side boring. The tail end side boring has a curvature radius of 0.5mm while the front end side has 0.3mm, creating an asymmetric configuration that optimizes both strength and manufacturability. This asymmetric design allows the larger tail end boring to be more easily polished without edge remnants while maintaining overall structural strength.
Solution Approach 2:
The patent applies local quality by providing different boring specifications at different locations of the convex portion. The tail end side boring (0.5mm radius) differs from the front end side boring (0.3mm radius), with each location optimized for its specific functional requirements. This local differentiation resolves the contradiction by allowing the tail end to have better polishing quality while the front end maintains sufficient strength.
2Productivity
If the needle jack is made lighter to reduce inertia weight for faster knitting, then the productivity is improved, but the strength and durability may be compromised
Solution Approach 1:
The patent applies local quality by concentrating the boring features specifically at the foot of the convex portion where stress concentration occurs during operation. By optimizing only the critical areas (the borings at the foot) rather than redesigning the entire needle jack, the invention reduces material usage and inertia weight while maintaining strength where it is most needed.
Solution Approach 2:
The patent applies curvature by specifying that the borings at the foot of the convex portion have a curvature radius of 0.3mm to 0.5mm. This curved geometry eliminates sharp corners that would cause stress concentration, thereby maintaining strength and durability while allowing for a lighter overall design that improves knitting speed.
3Reliability
If the coupled portion is designed with symmetric borings to prevent dropping off, then the reliability is improved, but stress concentration occurs and breakage is prone
Solution Approach 1:
The patent applies asymmetry by deliberately making the tail end side boring larger than the front end side boring. This asymmetric configuration prevents the needle jack from dropping off while simultaneously reducing stress concentration. The larger tail end boring provides better retention, while the size difference distributes stress more evenly, preventing breakage.
Solution Approach 2:
The patent applies curvature by specifying that both borings have rounded edges with curvature radii of 0.3mm to 0.5mm. This curved geometry eliminates sharp corners that would cause stress concentration, thereby maintaining reliability for preventing dropout while significantly improving resistance to breakage.
Data Source
Figure 1~2
Figure 3
Figure 4~5(b)
AI summary
Provided is a knitting needle having a construction of a coupled portion suited for speeding up. A compound needle 11 has a front end side boring 16d and a tail end side boring 16e, at the foot of a convex portion 16b protruding from the front end side of a needle jack 16. Between the front side end portion 2d and the tail side end portion 2e of the concave portion 2b of the needle body 2, a clearance is formed. The tail end side boring 16e is larger than the front end side boring 16d. However, even when the tail end side boring 16e increases in size, the boring is formed on the tail end side from the center line 2c of the concave portion 2b. This kind of large tail end side boring 16e relaxes stress concentration, and is able to make the convex portion 16b difficult to break even when an impact load is applied through driving of the needle jack 16.