Handheld Torque Tool Housing Angular Displacement Compensation
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Solution Overview
Problem
Existing methods for achieving high clamp force accuracy in threaded joint mounting processes using hand held power tools are hindered by the influence of friction forces and variations in friction coefficients, leading to inconsistencies in measured tightening torque and inaccurate determination of clamp force, as they fail to account for true rotational movements relative to an immobile point.
Innovation Solution
A method that registers and compensates for both tightening and loosening torques, along with angular displacements of the power tool housing relative to an immobile point, using gyro or accelerometer units to calculate the true rotational movements and determine the clamp force coefficient, allowing for precise application of a target clamp force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If friction compensation is performed by subtracting loosening torque from tightening torque, then clamp force accuracy is improved, but measurement precision deteriorates due to inability to determine true rotational movements
Solution Approach 1:
The patent introduces an intermediary reference system (immobile point or reference housing) to measure angular displacements. By measuring housing displacements relative to this reference and compensating for them, the system obtains true rotational movements of the output shaft, thereby resolving the measurement precision issue while maintaining clamp force accuracy through friction compensation
Solution Approach 2:
The patent replaces the simple relative measurement system with a more sophisticated measurement system that uses gyro units or accelerometers to detect angular displacements. This substitution enables accurate determination of true rotational movements by compensating for housing movements, thus resolving the contradiction between friction compensation and measurement precision
2Productivity
If hand held power tools are used for tightening threaded joints, then productivity is improved, but manufacturing precision deteriorates due to manual support-induced angular displacements
Solution Approach 1:
The patent implements a feedback mechanism where angular displacements of the housing are continuously measured during the tightening process and used to compensate for the true rotational movements. This feedback loop allows hand held tools to maintain manufacturing precision despite manual support-induced displacements, thereby resolving the contradiction between productivity and manufacturing precision
3Measurement precision
If angular displacement compensation is implemented, then true rotational movements are determined accurately, but device complexity increases due to additional sensors and measurement systems
Solution Approach 1:
The patent makes the housing serve multiple functions: it acts as both the support structure for the motor and output shaft, and as a reference body for measuring angular displacements using gyro units or accelerometers. By making the housing multi-functional, the patent reduces overall device complexity while maintaining high measurement precision for true rotational movements
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 enhances clamp force accuracy and extends the use of hand held power tools for critical threaded joints, improving productivity by ensuring accurate torque application and counteracting manual support-induced inaccuracies.
Implementation Method 1
occurring angular displacements of the housing in relation to an immobile point are registered via signals delivered by one or more gyro units attached to the housing
Implementation Method 2
occurring angular displacements of the housing in relation to an immobile point are registered via signals delivered by one or more accelerometer units attached to the housing
Implementation Method 3
the influence of the friction forces on the measured applied tightening torque, not only the friction forces per se but the variations in the friction coefficient
Data Source
Figure 1~2
Figure 3~4
AI summary
A method for obtaining a high clamp force accuracy at a threaded joint mounting process performed by means of a hand held torque delivering power tool which includes a housing (10), and a motor driven output shaft (13) rotatably supported in the housing (10) about a rotation axis (A), comprising the steps of tightening the joint to a certain level, loosening the joint over a certain angular interval (φ2 - φ1), and retightening the joint up to a target torque level (TT), whereby occurring angular displacements of the tool housing (10) during the process are determined and compensated for when determining the true angular movement of the output shaft (13) and the threaded joint. An angle sensing unit (15) is carried on the housing (10) for registering occurring angular displacements of the housing (10) in relation to an immobile point, and the true angular movement of the output shaft (13) of the tool is calculated and used for determining the target clamp force (FT) corresponding torque level (TT).