Machine Tool Protective Cover Rotation Limiting Mechanism

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Solution Overview

Problem

Existing machine tools, such as angle grinders, face safety issues due to the risk of the protective hood being twisted beyond a permissible angular range when a tool breaks, caused by inertial forces, especially with the one-piece design of the clamp and hood, which lacks effective rotation limiting mechanisms.

Innovation Solution

A design where the protective hood and clamping device are separate components, with a stop element on the hood that directly contacts a counterpart on the machine flange, providing a radial clamping force and limiting rotation to a safe range, and optionally incorporating a damping element to absorb energy upon impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the protective hood and clamping device are designed as a one-piece structure, then the structure is simpler, but the rotation can be limited less reliably and the hood may twist beyond the permissible angular range due to inertial forces

Engineering Contradiction:
Improvestructure complexityVSAvoidrotation limiting reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The protective hood is divided into separate components: the hood body and the clamping device are no longer a one-piece structure but are connected through a clamping collar that can be independently adjusted. This segmentation allows the clamping device to be optimized for securing the hood while the hood body can be designed for optimal protection, and the connection point can be precisely controlled to limit rotation reliably.

Inventive Principle:
Principle #1Segmentation

2Ease of manufacture

If the clamping device is integrated with the protective hood, then manufacturing is easier, but the stop device cannot effectively limit rotation when tool breakage occurs due to inertial forces

Engineering Contradiction:
Improvemanufacturing easeVSAvoidexcessive rotation during tool breakage
Core Design Contradiction:
Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

A clamping collar is introduced as an intermediary component between the protective hood and the clamping device. This collar serves as a mediator that transmits the limiting rotation force from the stop device to the hood body. The clamping collar can be positioned at a precise angular location where it interacts with the stop device, ensuring that when tool breakage occurs, the rotation is effectively limited before inertial forces can cause excessive twisting.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Strength

If the protective hood has large mass to provide adequate protection, then protection is improved, but the risk of twisting beyond permissible angular range increases due to inertial forces

Engineering Contradiction:
Improveprotective strengthVSAvoidinertial force effect during rotation
Core Design Contradiction:
StrengthVSObject-affected harmful factors

Solution Approach 1:

The stop device is positioned to engage with the clamping collar at a precise angular location before the hood can twist beyond the permissible range. This preliminary anti-action counteracts the inertial forces that would otherwise cause excessive rotation. The stop device creates a mechanical constraint that opposes the rotational motion generated by inertial forces during tool breakage, preventing the hood from twisting beyond the safe angular range.

Inventive Principle:
Principle #9Preliminary anti-action

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

This design enhances safety by reducing the risk of excessive rotation and energy transmission during tool breakage, ensuring the protective hood can only rotate until the stop is reached, even if the tensioning device fails, and dissipates energy through friction, thereby reducing the impulse at the stop.

Implementation Method 1

Via the clamping device, the clamping collar is subjected to a radial clamping force against the contact surface on the machine-side flange

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

the stop device comprises a stop element on the protective hood which, in the stop position, bears against an associated counterpart on the flange or a component connected to the housing of the machine tool

Methodology Applied
Scientific EffectMechanical Force: Mechanical Force

Implementation Method 3

a damping element which absorbs the rotational energy of the protective hood and thus leads to a reduction in the impulse at the moment when the stop element strikes the counterpart

Methodology Applied
Scientific EffectDamping: Damping

Data Source

PatentEP2464494B1Machine tool having a protective cover
Publication Date: 2016.03.30 ROBERT BOSCH GMBH
  • EP2464494B1 patent drawingFigure 1
  • EP2464494B1 patent drawingFigure 2
  • EP2464494B1 patent drawingFigure 3

AI summary

The invention relates to a machine tool comprising a protective cover having a clamping joint that can be attached in a flange on the machine by means of a clamping device. A stop device is provided for limiting the relative rotary motion between the protective cover and the flange.