Power Tool Lock-Off Mechanism Preventing Inadvertent Trigger Activation

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Solution Overview

Problem

Hand-operated power tools often experience inadvertent activation, leading to potential accidents, waste, and safety concerns due to the risk of triggering the tool while handling or applying weight on the handle.

Innovation Solution

A trigger lock-off mechanism is introduced, featuring a locking pin that blocks trigger movement until a release button is pressed, allowing the pin to pivot out of the trigger's path, enabling controlled activation and preventing accidental start-ups. This mechanism is designed to be ergonomic and ambidextrous, ensuring safe operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a trigger lock-off mechanism is added to prevent inadvertent activation, then safety is improved, but device complexity increases

Engineering Contradiction:
ImprovesafetyVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The lock-off mechanism is integrated into the existing trigger assembly, merging the safety function with the trigger structure. The locking pin and release button are incorporated as part of the trigger mechanism rather than as a separate system, reducing overall device complexity while maintaining safety functionality.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The lock-off mechanism is designed to be self-actuating through the biasing member that automatically engages the locking pin to block trigger movement. The system serves itself by using spring pressure to maintain the locked state without requiring additional actuators or complex control systems.

Inventive Principle:
Principle #25Self-service

2Reliability

If a locking pin blocks trigger movement to prevent accidental start-ups, then safety is improved, but ease of operation deteriorates

Engineering Contradiction:
ImprovesafetyVSAvoidease of operation
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The release button extracts the unlocking function from the trigger itself, providing a separate, dedicated control element. This allows the trigger to remain simple for operation while the release button handles the lock-off function, maintaining ease of operation for both triggering and releasing.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of requiring the user to actively engage the lock-off mechanism before use, the system is inverted so that the lock-off is automatically engaged by default (through the biasing member), and the user simply needs to press the release button to enable operation. This reversal simplifies the user's interaction while maintaining safety.

Inventive Principle:
Principle #13The other way round (Inversion)

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

The lock-off mechanism effectively prevents accidental activation of power tools, enhancing user safety and control by requiring deliberate action to initiate tool operation, thus reducing the risk of accidents and wasteful operation.

Implementation Method 1

a biasing member that directs the locking pin into the first position blocking movement of the trigger

Methodology Applied
Scientific EffectElastic force: Elasticity

Implementation Method 2

pressing the release button in a direction into the housing causes the locking pin to rotate into the second position that does not block movement of the trigger

Methodology Applied
Scientific EffectRotational movement:

Data Source

PatentEP2794193B1Method and mechanism for power tool lock-off
Publication Date: 2022.03.16 ROBERT BOSCH TOOL
  • EP2794193B1 patent drawingFigure 1
  • EP2794193B1 patent drawingFigure 2
  • EP2794193B1 patent drawingFigure 3~5

AI summary

Embodiments of the present invention disclosed herein present forms of a method and mechanism for a power tool lock-off, wherein accidental activation of the power tool (10) may be inhibited. Pressing a lock-off release button (30) on the tool housing (12) induces a locking member (32) to move from a first position to a second position, allowing a trigger (20) to access a power switch (50)within the housing. Various forms and methods of lock-off mechanisms are enabled.