Impact Wrench Anvil Position Sensing for Controlled Impacts

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Solution Overview

Problem

Existing power tools with impact mechanisms lack precise control over the anvil position and motion, leading to inefficiencies and potential damage due to uncontrolled impacts.

Innovation Solution

Incorporating a brushless DC motor with a rotor and stator, an impact mechanism featuring a hammer and anvil with a varying relief feature, and a sensor to generate signals indicative of the anvil's position and motion, allowing for precise control of the anvil's rotational and translational movements through a controller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a sensor and controller are added to detect anvil position and control impact, then control precision and safety are improved, but device complexity increases

Engineering Contradiction:

Improveanvil position detection precisionVSAvoidsystem structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical position sensing mechanisms with a magnetic field-based sensor system. The relief feature on the anvil shaft modulates the magnetic field detected by the sensor, providing precise position information without requiring direct mechanical contact or complex linkages between the rotating anvil and the sensor.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The magnetic field acts as an intermediary between the anvil's mechanical motion and the sensor's electrical detection. The relief feature modulates this magnetic field to encode position information, allowing non-contact transmission of mechanical position data to the control system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If impact forces are increased to improve productivity, then output increases, but harmful factors and potential damage increase

Engineering Contradiction:

Improveimpact outputVSAvoidimpact damage risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The sensor continuously monitors the anvil's position and motion, providing real-time feedback to the controller. This feedback loop enables the system to detect when the anvil is in the optimal position for impact and when to inhibit impacting, allowing high-force impacts only when safe and productive.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the impact mechanism's operation based on real-time anvil position and motion conditions. The controller can enable or disable impacting capability depending on whether the anvil is properly positioned, allowing the system to optimize between productivity and safety on a cycle-by-cycle basis.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4171883B1Systems and methods for detecting anvil position using a relief feature

Publication Date: 2025.11.19 MILWAUKEE ELECTRIC TOOL CORP

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AI summary

A power tool including a housing, a brushless direct current (DC) motor, an impact mechanism including a hammer and an anvil, an output drive device, a position sensor, and a controller. The position sensor is adjacent to a relief feature, which may be a recessed relief feature or a raised relief feature, and is configured to generate an output signal indicative of a position of the anvil. The controller is configured to calculate a drive angle based on the determined position of the anvil, and control the brushless DC motor based on the drive angle of the anvil.