Stationary Drum Yarn Feeder with Optical Speed Control
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Solution Overview
Problem
Existing yarn-feeding apparatuses for textile machines, particularly knitting machines, face inaccuracies in controlling yarn speed and tension due to yarn slipping and inertia, leading to frequent mechanism wear and delayed response in tension control.
Innovation Solution
A yarn-feeding apparatus using a stationary drum with braking means and a consumption-measuring sensor to maintain constant yarn tension, independent of yarn-feeding speed, allowing for precise control of yarn tension and stitch adjustment without direct influence on feeding speed, thereby reducing mechanism wear and enhancing response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotating yarn-winding drum is used to feed yarn, then the yarn can be drawn from the reel and delivered to the machine, but the yarn-feeding speed calculated from drum rotation and diameter considerably differs from the actual speed due to yarn slipping and inertia
Solution Approach 1:
The patent replaces the mechanical speed measurement method (based on drum rotation and diameter calculations) with a direct optical measurement system. A non-contact optical sensor measures the actual yarn-feeding speed by detecting the position of the yarn over time, eliminating errors caused by yarn slipping on the drum and drum inertia. This substitution of mechanical measurement with optical measurement directly resolves the accuracy problem.
2Reliability
If tension control directly influences yarn-feeding speed, then yarn tension can be maintained constant, but the loop compensating for speed variations activates very frequently causing high wear of stitch adjustment mechanisms
Solution Approach 1:
The patent separates the tension control function from the speed control function. Tension is controlled by adjusting the braking torque on the drum independently, while speed is controlled by adjusting the drum rotation speed independently. This segmentation allows tension to be stabilized without causing frequent speed variations that would trigger the compensation loop and wear the stitch adjustment mechanisms.
Solution Approach 2:
The patent introduces a braking mechanism as an intermediary between the motor and the yarn feeding system. The brake applies friction torque to the drum to control yarn tension without directly affecting the motor speed control. This intermediary allows independent control of tension and speed, preventing the harmful coupling that causes frequent compensation activations and mechanism wear.
3Speed
If a rotating yarn-winding drum is used, then yarn feeding can be achieved, but variations of speed are subjected to delay due to the inertia of the yarn-winding drum affecting the quickness of response
Solution Approach 1:
The patent extracts the yarn from the rotating drum system and measures its speed directly as it travels through the air from the drum to the machine. By measuring the yarn speed in flight rather than inferring it from drum rotation, the system eliminates the delay caused by drum inertia. The optical sensor detects yarn position changes directly, providing immediate feedback without the lag introduced by the drum's rotational mass.
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
The apparatus achieves more accurate and rapid control of yarn speed and tension, reducing mechanism wear and improving system responsiveness by using a stationary drum with braking and consumption-measuring technology.
Implementation Method 1
braking means comprising a frustoconical, hollow braking member 28 which is coaxially arranged with its larger base in front of stationary drum 20 and is biased with its inner surface against the delivery edge of the drum by actuator means 30. The yarn delivered by feeder 18 is pressed between the delivery edge of drum 20 and braking member 28, whereby it is subjected to a braking action by friction.
Implementation Method 2
Yarn feeder 18 is also provided with a sensor 34 for continuously measuring the yarn consumption, preferably a piezoelectric sensor connected as described in EP 1 335 054 of Applicant. Alternatively, an optical sensor as described in EP 0 327 973 could be used.
Data Source
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Figure 2
AI summary
Yarn loops are unwound from a yarn feeder (18) provided with a stationary yarn-winding drum (20) upon request from a textile machine (16). Braking means (28, 128) apply a braking action by friction on the unwinding yarn in such a way as to maintain the yarn tension substantially constant. A yarn consumption sensor (34) continuously measures the actual yarn consumption and generates a corresponding signal (PS) indicative of the consumption. Processing means (32, 36) calculate a consumption signal (YC) on the basis of the corresponding signal (PS), compare it with a predetermined consumption range, and adjust the stitches as a function of the difference between the two values.