Electric Pulse Tool Torque Phasing for Accurate Clamp Force
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Solution Overview
Problem
Existing pulse tools struggle to accurately measure angular displacement of screw joints during tightening operations due to high torque pulses causing significant angular displacement, making it difficult to estimate the clamp force accurately.
Innovation Solution
An electric pulse tool that delivers low torque pulses of less than 15% of its maximum torque value until a low threshold torque value is reached, allowing for angular displacement measurement, and then transitions to higher torque pulses until a target parameter is met, enabling precise angular displacement tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high torque pulses are used to tighten screw joints quickly, then productivity is improved, but angular displacement measurement accuracy deteriorates
Solution Approach 1:
The tightening process is divided into two distinct phases: a first phase using low torque pulses (less than 15% of maximum torque) for angular displacement measurement, and a second phase using high torque pulses for rapid tightening. This segmentation allows each phase to be optimized for its specific function, resolving the contradiction between measurement accuracy and productivity.
Solution Approach 2:
The pulse tool dynamically adjusts torque pulse magnitude based on the tightening phase. The control system switches between low torque pulses during the measurement phase and high torque pulses during the tightening phase, making the system adaptive to different operational requirements and eliminating the need to choose between measurement accuracy and productivity.
2Measurement precision
If low torque pulses are used to measure angular displacement, then measurement accuracy is improved, but productivity deteriorates
Solution Approach 1:
The tightening operation is segmented into a measurement phase using low torque pulses and a tightening phase using high torque pulses. This segmentation ensures that measurement accuracy is achieved during the first phase while productivity is maximized during the second phase, resolving the contradiction between the two objectives.
Solution Approach 2:
The pulse tool employs periodic low torque pulses during the measurement phase to accumulate angular displacement data without causing substantial screw joint movement. This periodic action allows accurate measurement while maintaining the ability to transition to high torque pulses for rapid tightening, thus resolving the productivity concern.
3Manufacturing precision
If torque pulses are reduced towards the end of tightening to improve accuracy, then clamp force accuracy is improved, but reaction force on operator increases
Solution Approach 1:
The tightening process is segmented into phases with distinct torque levels. Low torque pulses are used during the measurement phase to ensure accurate angular displacement measurement and clamp force estimation, while high torque pulses are used during the tightening phase to minimize reaction force on the operator. This segmentation resolves the contradiction between accuracy and operator comfort.
Data Source
AI summary
An electric pulse tool performs a tightening operation in which torque is delivered in pulses to tighten a screw joint. The electric pulse tool includes an output shaft, a torque sensor to determine a torque value associated with tightening of the screw joint, and an angle sensor to determine an angular displacement of the screw joint. The tool provides low torque pulses of a torque value of less than 15 percent of an electric pulse tool max torque value on the output shaft until a low threshold torque value is reached. Next the tool starts measuring an angular displacement of an element of the screw joint and provides tightening torque pulses of a torque value of more than 15 percent of the electric pulse tool max torque value on the output shaft. The tool stops providing torque pulses on the output shaft when a target parameter is reached.