Electromagnetic Tool Brake Armature Pivot for Vibration Stability

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Solution Overview

Problem

Existing hand-operated tools with braking devices, such as angle grinders, experience unintended brake triggering due to vibrations causing relative movement between the electromagnet and actuating element, leading to reduced holding forces and increased wear.

Innovation Solution

The armature is mounted on the armature bolt via a pivot joint, allowing it to pivot about a pivot axis, maintaining its orientation relative to the electromagnet even during transverse displacement, and a guide system limits relative movements to prevent detachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the armature is rigidly fixed to the actuating element, then the structure is simple and stable, but vibrations cause relative movement between the electromagnet and actuating element, leading to reduced holding forces and unintended brake triggering

Engineering Contradiction:
Improvebrake triggering reliabilityVSAvoidarmature mounting complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The armature is mounted on the armature bolt via a pivot joint, allowing it to pivot about a pivot axis. This dynamic mounting allows the armature to adapt its position relative to the electromagnet during vibrations, maintaining optimal alignment and preventing unintended brake triggering while managing the complexity through a straightforward pivot connection.

Inventive Principle:
Principle #15Dynamics

2Reliability

If the armature is mounted via a damping element allowing slight movement, then tolerances are compensated, but relative movement causes the armature to become inclined relative to the electromagnet, significantly reducing holding forces

Engineering Contradiction:
Improveholding force stabilityVSAvoidarmature alignment
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The pivot joint enables the armature to dynamically adjust its orientation relative to the electromagnet during operation. When vibrations cause the armature bolt to move or tilt, the armature can pivot about its axis to maintain proper alignment with the electromagnet, ensuring stable holding forces throughout the operation cycle.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The pivot joint introduces an additional degree of freedom (rotational movement about the pivot axis) to the armature mounting system. This extra dimensional movement capability allows the armature to compensate for misalignments and maintain optimal positioning despite vibrations and tolerances in the actuating element and electromagnet.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Reliability

If the armature can pivot relative to the armature bolt, then inclination is compensated and holding forces are maintained, but the device complexity increases due to the pivot joint mechanism

Engineering Contradiction:
Improvecontinuous operation reliabilityVSAvoidpivot joint complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The pivot joint provides a simple yet effective dynamic connection between the armature and armature bolt, enabling the armature to pivot about a pivot axis. This single-degree-of-freedom mechanism is sufficiently simple in construction while effectively preventing unintended brake triggering by maintaining proper armature alignment with the electromagnet during vibrations.

Inventive Principle:
Principle #15Dynamics

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 configuration prevents unintended brake triggering and maintains holding forces, reducing wear and ensuring continuous operation without interruptions.

Implementation Method 1

the holding forces of the electromagnet acting on the armature

Methodology Applied
Scientific EffectMagnetic force: Magnetism

Implementation Method 2

The armature is mounted on the armature bolt via a pivot joint so that it can be pivoted about at least one pivot axis

Methodology Applied
Scientific EffectPivoting motion: Hinge

Implementation Method 3

a guide system limits relative movements to prevent detachment

Methodology Applied
Scientific EffectMechanical constraint: Physical Containment

Data Source

PatentEP3412392B1Hand-held work device with a tool and a braking device for the tool
Publication Date: 2021.09.01 ANDREAS STIHL AG & CO KG
  • EP3412392B1 patent drawingFigure 1~2
  • EP3412392B1 patent drawingFigure 3~4
  • EP3412392B1 patent drawingFigure 5~6

AI summary

A hand-held tool has a tool and a braking device (15) for the tool. The braking device (15) has an actuating element that acts on a braking element of the braking device (15). The actuating element is movable between a fixed position (41), in which the tool is not braked, and a released position (40), in which the braking element brakes the tool. To fix the actuating element in the fixed position (41), an electromagnet (33) with a yoke (34) and a coil (35) is provided, which interacts with an armature (36) on the actuating element. The armature (36) is pivotally mounted on the armature bolt (55) via a pivot joint (50) about at least one pivot axis (51, 52, 53).A guide (60) is provided which, in a fixed position (41) of the actuating element, guides the anchor (36) relative to the yoke (34) in a transverse direction (38) of a boom (7) of the working device, a guide part connected to the anchor (36) and a guide part connected to the yoke (34).