Rail Passenger Table Pantograph Mechanism Reduces Guide Forces
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Solution Overview
Problem
Passenger tables in rail vehicles face challenges with limited space for gear mechanisms, leading to high internal forces and the risk of self-locking when extending the table surface, due to the required load-bearing structure and limited space for accommodating the gear mechanism.
Innovation Solution
A planar cam mechanism with a pantograph mechanism is used to scale the movement of the table extension panel, providing a wider support base and reducing internal forces by allowing the first coupling point to travel a longer trajectory, which includes a first cam roller mounted on a guideway and a second cam roller for rotary positioning, ensuring a broad base of support and optimized path curves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the table extension is moved directly without a scaling mechanism, then the gear mechanism space is minimized, but the internal forces and bending moments become excessively high causing guide overload and self-locking
Solution Approach 1:
The patent introduces a pantograph mechanism as an intermediary between the cam mechanism and the table extension. This pantograph acts as a motion scaling intermediary that transforms the small linear movement of the cam follower into a larger, more distributed movement trajectory, thereby reducing the forces transmitted through the guide mechanism while still achieving the desired table extension movement.
Solution Approach 2:
The patent changes the movement parameters by using a pantograph mechanism that scales the motion trajectory. The cam follower travels a shorter distance while the table extension travels a longer distance, effectively changing the motion parameters to reduce internal forces. The pantograph mechanism allows the coupling point to follow an optimized path that minimizes force requirements.
2Device complexity
If a linear guide is used for table extension, then the structure is simple, but the guide components become overloaded and sliding guides threaten self-locking under high bending moments
Solution Approach 1:
The pantograph mechanism serves as an intermediary that protects the linear guide from excessive loads. By scaling the motion and distributing the forces through the pantograph's linkage system, the guide components operate within safe force limits, preventing overload and self-locking while maintaining the simplicity of the linear guide structure.
3Force
If the cam follower travels a long trajectory, then the support base is wide reducing internal forces, but the gear mechanism requires excessive space within the table top
Solution Approach 1:
The pantograph mechanism acts as a motion scaling intermediary that allows the cam follower to travel a short distance while the table extension coupling point travels a longer, more beneficial trajectory. This intermediary mechanism decouples the cam follower's travel distance from the table extension's effective movement, enabling wide support base without excessive gear space requirements.
Solution Approach 2:
The patent changes the motion parameters by using the pantograph to scale the trajectory. The cam follower follows a compact path within the table top, while the table extension achieves a longer effective movement with optimized force distribution, effectively changing the motion parameters to resolve the space-force contradiction.
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 reduces internal forces to practical values, allowing the table extension to be supported effectively and enabling easy operation without significant force requirements, even in collision scenarios, while maintaining a compact design.
Implementation Method 1
a first cam roller (7) which is mounted on a first guideway (8) rolls
Implementation Method 2
a movement of the linear cam mechanism via a flat pantograph mechanism, which has a first coupling point rotatably connected to the table extension board and a second coupling point that is stationary relative to the table top, is scaled
Data Source
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AI summary
The invention relates to a passenger table with a stationary tabletop (1) and a table extension panel (2), which can be moved by means of a gear mechanism from a retracted position below the tabletop (1) into a working position in which the table extension panel (2) abuts an associated outer edge of the tabletop (1), wherein the gear mechanism is designed as a linear cam gear arranged below the tabletop (1), in which a first cam roller (7) rolls on a first guide track (8) that is stationary relative to the tabletop (1), and a movement of the linear cam gear via a planar pantograph mechanism, which has a first coupling point (4.1) that is stationary relative to the tabletop (1) and a second coupling point (5.2) that is rotatably connected to the table extension panel (2), is scaled such that the second coupling point (5.2) on the table extension panel (2) when moving the table extension panel (2) from the retracted position to the operating position or vice versa, travels a longer path in space than the first curve roller (7).