Interlock Mechanism for Angle Grinder Handle Positioning

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Solution Overview

Problem

Hand-held power tools, such as angle grinders, face challenges in providing secure handle positioning without increasing manufacturing costs, as existing solutions like clamping devices are costly to produce and may not adequately prevent accidental tool actuation during use.

Innovation Solution

A hand-held power tool design featuring a rotatable handle with a manually actuated latch and interlock mechanism, where the interlock mechanism cooperates with the trigger to lock the handle in multiple positions, using a pivoted interlock lever and torsion spring to ensure secure positioning and prevent accidental actuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a clamping device is used to improve handle security, then the reliability of handle positioning is improved, but the manufacturing cost increases

Engineering Contradiction:
Improvehandle positioning securityVSAvoidmanufacturing cost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The locking mechanism is divided into two independent parts: a latch mechanism for basic positioning and an interlock mechanism for security. This segmentation allows each mechanism to be simpler and cheaper while collectively providing high reliability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The interlock mechanism is combined with the trigger mechanism, so that the same trigger operation simultaneously activates the motor and engages the interlock. This merging eliminates the need for separate actuation mechanisms, reducing cost while maintaining reliability.

Inventive Principle:
Principle #5Merging (Combining)

2Adaptability or versatility

If a rotatable handle with multiple positions is provided to accommodate different operating orientations, then the adaptability of the tool is improved, but the device complexity increases

Engineering Contradiction:
Improveoperating orientation flexibilityVSAvoidhandle positioning mechanism complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Instead of using a complex mechanism to lock the handle in multiple positions, the invention uses a simple latch that works in reverse: the handle naturally wants to rotate, and the latch simply prevents it from rotating when locked. The spring-loaded latch uses the handle's own movement to engage and disengage locking positions.

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

Solution Approach 2:

The latch mechanism is spring-loaded and automatically engages with the locking positions on the motor housing when the handle is rotated into place. The system uses its own movement and the spring force to automatically lock, without requiring additional actuators or complex control mechanisms.

Inventive Principle:
Principle #25Self-service

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 design enhances security and operational efficiency by preventing accidental handle rotation during tool use, while maintaining a simple and cost-effective construction, ensuring the handle is securely fixed in multiple positions without additional costly components.

Implementation Method 1

an interlock mechanism having a locking and an unlocking position, the interlock mechanism cooperating with the trigger such that with the trigger in the extended position the interlock mechanism is in the unlocking position and moving the trigger to the retracted position engages the trigger with the interlock mechanism and moves the interlock mechanism to the locking position for fixing the handle in the at least two different rotational positions

Methodology Applied
Scientific EffectTorsion spring: Torsion Spring

Data Source

PatentEP2688715B1Hand held power tool with locking rotatable handle
Publication Date: 2019.05.15 TECHTRONIC POWER TOOLS TECHNOLOGY LTD(GB)
  • EP2688715B1 patent drawingFigure 1
  • EP2688715B1 patent drawingFigure 2~3
  • EP2688715B1 patent drawingFigure 4

AI summary

In an angle-grinder with a rotating handle and a latch for fixing the handle in two different rotational positions, an interlock mechanism is provided for greater security against unwanted rotation of the handle when the tool is being used. The interlock mechanism is moved to a locking position by depressing the trigger to start the motor, and thus provides a safety lock backing up the latch, in case the latch is accidentally released during use. In its unlocking position the interlock mechanism may prevent actuation of the trigger when the handle is not properly aligned in one of its operating positions.