Expansion Anchor Setting via Dynamic Impact Speed Control
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Solution Overview
Problem
Conventional methods using impact screwdrivers for setting expansion anchors result in high loss of pre-stress force due to rapid setting speed, leading to reduced load values and limited application fields, as there is no time to reduce tension peaks between setting intervals.
Innovation Solution
A method and power tool, specifically an impact screwdriver, that exerts rotary impacts at a first rotational speed until a predetermined tightening torque is reached, followed by a predetermined number of impacts at that speed, then transitions to a reduced rotational speed for a period to balance setting effects without increasing pre-stress force further.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If setting is performed using an impact screwdriver with high rotational speed, then productivity is improved, but loss of pre-stress force increases
Solution Approach 1:
The impact screwdriver dynamically adjusts the rotational speed during the setting process. It operates at a first rotational speed to reach the tightening torque threshold, then transitions to a second reduced rotational speed for a predetermined time period. This dynamic speed adjustment optimizes both productivity and pre-stress force retention by matching the setting speed to the material's relaxation behavior at different stages of the process.
Solution Approach 2:
The setting process is divided into distinct periodic phases: an initial phase with higher rotational speed to achieve the tightening torque threshold, followed by a phase with reduced rotational speed to allow tension peak reduction. This periodic action pattern mirrors the manual setting process with its intervals, enabling the material to relax between loading phases while maintaining overall productivity.
2Loss of energy
If setting is performed manually with torque key in multiple intervals, then loss of pre-stress force is reduced, but productivity deteriorates
Solution Approach 1:
The patent replaces the manual torque key system with an automated impact screwdriver that incorporates sensors and control mechanisms. The device automatically detects when the tightening torque threshold is reached and automatically transitions between different rotational speed phases, eliminating the need for manual intervention while replicating the beneficial intermittent setting pattern of manual operation.
Solution Approach 2:
The impact screwdriver performs self-regulation during the setting process. The control device automatically monitors the tightening torque, detects when the threshold is reached, and autonomously adjusts the rotational speed from the first to the second value. This self-service capability maintains the optimized setting pattern without requiring operator intervention, thereby preserving both productivity and pre-stress force retention.
3Productivity
If tightening torque is applied continuously without intervals, then productivity is improved, but tension peaks in material are not reduced
Solution Approach 1:
The setting process incorporates periodic intervals where the rotational speed is reduced after reaching the tightening torque threshold. These periodic reductions in speed create intervals that allow tension peaks in the material to subside, preventing excessive stress concentration while maintaining overall high productivity through the initial high-speed phase.
Solution Approach 2:
The control device applies a preliminary anti-action by reducing the rotational speed before the material can accumulate excessive tension peaks. This preventive measure counteracts the harmful effect of continuous high-speed tightening by proactively introducing intervals that allow stress relaxation, thereby protecting the material from damage while maintaining productivity.
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
Optimizes the setting process to achieve the highest possible tensile loading of expansion anchors by balancing setting effects without increasing pre-stress force, thereby enhancing the anchoring resilience and application field.
Implementation Method 1
a percussion mechanism (21) for generating rotary impacts which can be transferred from and to the expansion anchor (1)
Implementation Method 2
Relaxation here describes the gradual loss of pre-stress force of the expansion anchor set in a material due to setting effects
Data Source
AI summary
A method for setting an expansion anchor by a power tool, and a power tool that performs the method, is disclosed. In an embodiment, the method includes exerting rotary impacts on the expansion anchor in order to expand an expansion sleeve in dependence on a first rotational speed until a tightening torque corresponds to a threshold value, exerting a predetermined number of rotary impacts on the expansion anchor in dependence on the first rotational speed, and exerting rotary impacts on the expansion anchor by the power tool in dependence on a generated second rotational speed for a predetermined period of time.