Screw Length Detection During Tightening for Accurate Fastening
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Solution Overview
Problem
Existing screw length determination methods are inaccurate due to variations in the distance between the bolt and the fastening target, leading to potential screw tightening failures.
Innovation Solution
A screw length determination system that calculates the screw length based on the axial position and rotation of the driver during specific tightening phases, including descent completion, provisional seating, primary tightening, and holding periods, using predetermined torque values to define these phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the time required for bolt seating is used to determine screw length, then the determination process is simple, but the accuracy deteriorates due to variations in distance from the bolt to the fastening target
Solution Approach 1:
The patent replaces the time-based measurement method with an ultrasonic wave-based measurement method. Ultrasonic pulses are transmitted through the screw, and the propagation time is measured to determine the screw length. This substitution of the measurement principle eliminates the influence of distance variations and seating time variations, achieving accurate screw length determination independent of operational variations.
Solution Approach 2:
The patent introduces ultrasonic waves as an intermediary medium to measure screw length. Instead of directly measuring time-related parameters that are influenced by operational variations, the ultrasonic wave propagation through the screw provides an indirect but accurate measurement of the screw's physical length, serving as a reliable intermediary that is not affected by distance variations or seating characteristics.
2Measurement precision
If ultrasonic pulse propagation time is measured to determine screw length, then accuracy is improved, but device complexity increases due to additional measurement equipment
Solution Approach 1:
The ultrasonic measurement system is integrated into the existing screw tightening system, allowing the same apparatus to perform both tightening operations and length measurements. The ultrasonic measurement function is combined with the tightening control function, enabling multi-functionality without requiring completely separate measurement equipment, thus reducing overall system complexity.
Solution Approach 2:
The patent merges the ultrasonic measurement function with the screw tightening control system. The measurement of ultrasonic pulse propagation time is integrated into the tightening process control, allowing simultaneous acquisition of tightening parameters and screw length data from a single integrated system rather than requiring separate independent measurement devices.
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
This method allows for precise determination of screw length, reducing the likelihood of screw tightening failures and ensuring adequate fastening force is applied.
Implementation Method 1
ultrasonic pulses are repeatedly coupled into the screw starting from the head of the screw using a pulse-echo method before and during the tightening process and the time it takes the ultrasonic pulses to traverse the length of the screw (propagation time) is measured
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(b)
AI summary
Provided is a screw length determination system capable of determining the length of a screw with a high degree of accuracy. A PLC (10) determines the length of a screw on the basis of the amount of rotation or the position in the axial direction of a driver during a period lasting from the time when the screw completes its descent until any time from among the time when provisional seating occurs, the time when the primary tightening period ends and the time when the period of holding for primary tightening ends.