Linear Motor Switch Transition Force Control

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Solution Overview

Problem

Existing transport systems with linear motor drives face malfunctions due to manufacturing and operational tolerances, leading to imbalances in magnetic forces that affect the normal and switching forces, causing directional issues and system instability, particularly in transition areas where branch lines diverge from the main railway.

Innovation Solution

The solution involves optimizing the ratio of normal force to switching force in the transition area by adjusting the air gap and magnetic conductivity of linear motor strands, using independently controllable electromagnets, and modifying the linear motor base material to ensure reliable directionality and switching efficiency, allowing transport elements to be guided accurately along the main railway or branch lines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the normal force is increased to improve guidance stability, then the transport element is held more securely on the track, but the switching force ratio becomes unbalanced causing directional malfunctions in transition areas

Engineering Contradiction:
Improveguidance stabilityVSAvoidswitching reliability
Core Design Contradiction:
Stability of the object's compositionVSReliability

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the air gap distance between the linear motor strands and the transport element in transition areas. By increasing the air gap, the normal magnetic force is reduced, which balances the force ratio and prevents directional malfunctions during switching operations while maintaining adequate guidance stability in non-transition areas.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent implements local quality by applying different air gap settings to different spatial locations: a larger air gap is used specifically in transition areas where switching occurs, while a smaller air gap is used in straight track sections. This localized adjustment optimizes both switching reliability and guidance stability in their respective operational contexts.

Inventive Principle:
Principle #3Local quality

2Ease of manufacture

If manufacturing and operational tolerances are present in the system, then the system is easier to manufacture and operate, but imbalances in magnetic forces occur leading to system instability

Engineering Contradiction:
Improvemanufacturing toleranceVSAvoidsystem stability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by pre-configuring a larger air gap in transition areas before operational issues occur. This preventive measure compensates for potential force imbalances caused by manufacturing and operational tolerances, ensuring that even with component variations, the system maintains stability and avoids directional malfunctions.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the air gap is increased to reduce normal force interference, then switching reliability improves, but the magnetic coupling between stator and mover decreases

Engineering Contradiction:
Improveswitching reliabilityVSAvoidmagnetic coupling force
Core Design Contradiction:
ReliabilityVSForce

Solution Approach 1:

The patent applies local quality by implementing different air gap distances in different operational zones: a larger air gap in transition areas to reduce normal force and improve switching reliability, and a smaller air gap in straight track sections to maintain strong magnetic coupling for efficient propulsion. This spatially differentiated approach optimizes both switching and propulsion performance.

Inventive Principle:
Principle #3Local quality

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 approach enhances the reliability of the switching process by reducing normal force interference, ensuring accurate path selection and maintaining system stability by adjusting forces in the transition area, thereby preventing malfunctions and ensuring smooth operation.

Implementation Method 1

a defined propulsive force can be applied to each individual moving element along a transport path by the interaction of generated magnetic fields on one or more linear motor strings (also called stators) and a magnetic reaction element

Methodology Applied
Scientific EffectElectromagnetic interaction: Electromagnetic Induction

Implementation Method 2

it is also known to use a normal force (magnetic normal force) to guide the movable transport elements on the transport track, which exerts a holding force on the movable transport elements

Methodology Applied
Scientific EffectMagnetic normal force: Magnetic Field

Implementation Method 3

The magnetic reaction elements on the moving transport elements can consist of, or comprise, permanent magnets and/or non-switching electromagnets

Methodology Applied
Scientific EffectMagnetic attraction: Magnetism

Implementation Method 4

By selectively energizing the linear motor trains on both sides of the movable transport elements, the forces in the transition area can now be influenced. In particular, the resulting force on the desired side of the switch can be increased, thus switching the switch so that the movable transport element is guided in the desired direction

Methodology Applied
Scientific EffectSwitching force generation: Electromagnetic Propulsion

Data Source

PatentEP3625079B1Magnet switch for a transport system
Publication Date: 2023.02.15 KRONES AG
  • EP3625079B1 patent drawingFigure 1a~1b
  • EP3625079B1 patent drawingFigure 2a~2b
  • EP3625079B1 patent drawingFigure 3a~3b

AI summary

The invention relates to a switch (1) of a transport system for a movable transport element (T), wherein: the switch (1) comprises a main path (3) and a secondary path (4) which branches off; the movable transport element (T) can, proceeding from a transition region (2) in which the secondary path (4) branches off from the main path (3), either be guided along the main path (3) or transferred into the secondary path (4); one or more linear motor windings (5a, 5b, 5c, 5d) for moving the movable transport element (T) are provided both on the main path (3) and on the secondary path (4); and a normal force is present between the movable transport element (T) and the adjacent linear motor winding or the adjacent linear motor windings (5a, 5b, 5c, 5d); characterised in that means for altering the normal force are provided in the transition region. The invention also relates to a transport system comprising such a switch and a transport element for such a transport system.