Rail Vehicle Foldable Step Mechanism for Access and Clearance

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Solution Overview

Problem

Rail vehicle drivers face challenges in safely and easily accessing the driver's cab due to the predetermined height of the lowest step, which requires a long vertical step and poses safety concerns during operational conditions, while maintaining the required clearance profile to avoid collisions with track installations.

Innovation Solution

A foldable step mechanism connected to side bars via hinges and cylinder drives, allowing the step to extend when needed for access and retract to maintain the clearance profile, with a locking mechanism to ensure safety and stability, and an integrated actuation mechanism in the handrail for controlled operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a fixed step is provided at the required clearance height, then the clearance profile is maintained during operational conditions, but the driver must overcome a long vertical step which reduces ease of access

Engineering Contradiction:
Improveease of accessVSAvoidvertical step height
Core Design Contradiction:
Ease of operationVSLength of moving object

Solution Approach 1:

The step is designed as a movable component that can change its position between a first position (extended for access) and a second position (retracted for clearance). The step is connected to the vehicle body via a folding mechanism with hinges and can be actuated by a cylinder drive, allowing it to dynamically adapt to different operational requirements - providing assistance during boarding/disembarking while maintaining clearance during operation.

Inventive Principle:
Principle #15Dynamics

2Ease of operation

If a movable step is provided to reduce vertical step height, then ease of access is improved, but the device complexity increases

Engineering Contradiction:
Improveease of accessVSAvoidstep mechanism complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The step mechanism is divided into separate functional components: the step itself, the folding mechanism with hinges connecting the step to side bars, the cylinder drive for actuation, and the locking mechanism. This segmentation allows each component to perform its specific function independently while working together to achieve the overall goal of movable step positioning.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The step mechanism incorporates a locking mechanism that automatically engages when the step reaches its first position, providing self-contained functionality. The cylinder drive and folding mechanism work together to automatically extend and lock the step when actuated, reducing the need for external control systems and simplifying the overall device.

Inventive Principle:
Principle #25Self-service

3Ease of operation

If the step is extended for access, then ease of boarding is improved, but the clearance profile may be compromised during operational conditions

Engineering Contradiction:
Improveease of boardingVSAvoidcollision risk with track installations
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The step is designed as a movable component that can change its position between a first position (extended for access) and a second position (retracted for clearance). The step is connected to the vehicle body via a folding mechanism with hinges and can be actuated by a cylinder drive, allowing it to dynamically adapt to different operational requirements - providing assistance during boarding/disembarking while maintaining clearance during operation.

Inventive Principle:
Principle #15Dynamics

4Reliability

If a locking mechanism is added to secure the step position, then safety and stability are improved, but the device complexity increases

Engineering Contradiction:
Improvestep position stabilityVSAvoidlocking mechanism complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The step mechanism incorporates a locking mechanism that automatically engages when the step reaches its first position, providing self-contained functionality. The cylinder drive and folding mechanism work together to automatically extend and lock the step when actuated, reducing the need for external control systems and simplifying the overall device.

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 solution provides a secure, easily accessible step for rail vehicle drivers while maintaining the necessary clearance profile, ensuring safety and comfort during both ascent and descent, and is cost-effective with fail-safe functionality in case of pressure loss.

Implementation Method 1

a cylinder drive (ZYL1, ZYL2) which actuates the folding mechanism

Methodology Applied
Scientific EffectPneumatics and hydraulics: Hydraulic Press

Implementation Method 2

The step (TS) is connected to the vehicle body (FZK) via a folding mechanism with hinges (SC11, SC12, SC13, SC14)

Methodology Applied
Scientific EffectHinge: Hinge

Data Source

PatentEP3793878B1Rail vehicle with an ascent aid
Publication Date: 2024.05.08 SIEMENS MOBILITY GMBH
  • EP3793878B1 patent drawingFigure 1
  • EP3793878B1 patent drawingFigure 2
  • EP3793878B1 patent drawingFigure 3

AI summary

The invention relates to an ascent aid on a rail vehicle (SFZ) which has a vehicle body (FZK), comprising a step (TS) and comprising at least one folding mechanism (KMER, KMAR). The folding mechanism (KMER, KMAR), as seen in the longitudinal direction of the step (TS), is fastened to the step (TS) at one end thereof. The folding mechanism (KMER, KMAR) has two lateral rods (SS11, SS12, SS21, SS22) which connect the step (TS) to the vehicle body (FZK) via hinges (SC11, SC12, SC21, SC22, SC13, SC14, SC23, SC24). The folding mechanism (KMER, KMAR) has a connecting rod (VS1, VS2) which additionally connects one of the lateral rods (SS12, SS21) to the vehicle body (FZK) via hinges (SC15, SC16, SC25, SC26). The connecting rod (VS1, VS2) is split into two parts by a folding hinge (KS1, KS2). The folding hinge (KS1, KS2) is coupled to an action of force in such a way that the action of force on the folding hinge (KS1, KS2) causes the step (TS) to be folded via the hinges (SCxy) between a first position (POS1) and a second position (POS2) with respect to the rail vehicle (SFZ). In the first position (POS1) of the step (TS), an ascent to a driver's cab (FS1, FS2) of the rail vehicle (SFZ) is assisted. In the second position (POS2), the step (TS) is folded in such a way that a predetermined clearance gauge of the rail vehicle (SFZ) is maintained.