Dual-Member Switch Activation to Prevent Accidental Tool Startup

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Solution Overview

Problem

Existing power tools and garden equipment with electric drives often have switches that can be accidentally activated, posing safety risks due to heavy or sharp moving components.

Innovation Solution

A two-stage activation mechanism using a first manually operable member and a second manually operable member, where the switch is activated only after a distinct second motion following a first motion, and can be easily deactivated with a single motion of the second member.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a single-motion switch activation mechanism is used, then the ease of operation is improved, but the reliability is worsened due to accidental activation

Engineering Contradiction:

Improveease of switch activationVSAvoidswitch activation reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The switch activation mechanism is segmented into two distinct manual operations: a first motion (e.g., pushing a trigger) and a second motion (e.g., squeezing a grip). This segmentation ensures that accidental activation is prevented because both specific motions must be performed in sequence, while still maintaining ease of operation through intuitive body movements.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a two-stage activation mechanism is used, then the reliability is improved by preventing accidental activation, but the device complexity increases

Engineering Contradiction:

Improveswitch activation reliabilityVSAvoidswitch mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The mechanism uses manually operable members (such as a trigger and grip) that serve dual purposes: they are natural, ergonomic components for operating the powered device and simultaneously function as the two-stage switch activation mechanism. This multi-functionality increases reliability without adding separate complex activation components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If the second manually operable member is added for switch activation, then the reliability is improved, but the ease of operation is worsened

Engineering Contradiction:

Improveswitch activation reliabilityVSAvoidease of switch deactivation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The mechanism is designed so that the second motion (e.g., squeezing the grip) both activates and deactivates the switch through the same operable member. This inversion approach ensures that deactivation is as easy as activation, since the user simply releases the grip squeeze, while still requiring the two-stage sequence for intentional activation.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP4513520A1Switch activation mechanism

Publication Date: 2025.02.26 BLACK & DECKER CORP

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AI summary

A mechanism for operating a switch for a powered device, the mechanism comprising a first manually operable member and a second manually operable member, the mechanism being configured to activate the switch in response to a first motion and a different second motion of the first manually operable member, wherein the second manually operable member is configured to move in response to the second motion of the first manually operable member.