Multi-Part Drive Shaft for Transit Doors

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Solution Overview

Problem

Conventional transit door systems with universal joints and spline connections suffer from backlash and require periodic lubrication, complicating design and maintenance, especially in curved door applications where precise alignment and smooth operation are critical.

Innovation Solution

A multi-part drive shaft system comprising an upper and lower drive shaft connected by a flexible core shaft, eliminating the need for intermediate universal joints and reducing backlash, with the flexible shaft transferring torque without the need for lubrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If universal joints and spline connections are used to connect offset drive shafts, then the door system can accommodate curved door configurations, but backlash and vibration increase, requiring periodic lubrication and complicating maintenance

Engineering Contradiction:

Improvecurved door configuration accommodationVSAvoidbacklash and vibration

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent removes the intermediate shaft with universal joints and spline connections from the drive system. By extracting these problematic components, the invention eliminates the sources of backlash and vibration while maintaining the ability to connect offset drive shafts through a direct rigid connection, thus resolving the technical contradiction between adaptability and reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The drive shaft is divided into multiple segments (first drive shaft portion, second drive shaft portion, and intermediate drive shaft portion) that can be independently positioned and connected. This segmentation allows the system to accommodate curved door configurations through precise positioning of each segment without requiring universal joints, thereby maintaining adaptability while eliminating backlash

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If universal joints and spline connections are used in the drive shaft system, then offset drive shafts can be connected, but the device complexity increases due to multiple connection elements requiring assembly and maintenance

Engineering Contradiction:

Improveoffset drive shaft connectionVSAvoidnumber of connection elements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the intermediate shaft, universal joints, and spline connections from the system. This removal of unnecessary components directly reduces device complexity while maintaining the functional capability to connect offset drive shafts through a simplified rigid connection structure

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the functions of the intermediate shaft, universal joints, and spline connections into a single rigid intermediate drive shaft portion. This consolidation eliminates multiple separate components and their associated connections, thereby reducing device complexity while achieving the same offset connection function

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If intermediate shafts with universal joints are used to connect drive shafts, then production tolerances in the bus frame can be accommodated, but the need for periodic lubrication and maintenance increases

Engineering Contradiction:

Improveproduction tolerance accommodationVSAvoidlubrication and maintenance requirements

Core Design Contradiction:

Adaptability or versatilityVSEase of repair

Solution Approach 1:

The patent removes the lubrication-dependent components (universal joints and spline connections) from the system. By extracting these elements, the invention eliminates the need for periodic lubrication and maintenance while maintaining the ability to accommodate production tolerances through precise positioning of the rigid drive shaft segments

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The rigid intermediate drive shaft portion is designed to self-accommodate production tolerances through its precise positioning and rigid connection, eliminating the need for maintenance services such as lubrication. The system becomes self-sufficient, requiring no periodic intervention to maintain its tolerance-accommodating capability

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

Simplifies installation, reduces backlash and vibration, and eliminates maintenance needs, ensuring smooth and efficient operation of curved transit vehicle doors by maintaining linear speed and torque transmission.

Implementation Method 1

A flexible drive shaft is secured at one end to the upper drive shaft for rotation with the drive shaft and at the other end similarly secured to an output fitting arranged to be clamped and keyed onto the lower drive shaft

Methodology Applied

Scientific EffectFlexibility: Elasticity

Data Source

PatentUS8371638B2Drive for transit door

Publication Date: 2013.02.12 WABTEC HLDG CORP

AI summary

A multi-part drive shaft for a transit vehicle door comprises an upper drive shaft connected to a door operating mechanism and having a door panel operating arm extending therefrom, a lower drive shaft journaled for rotation, a door panel operating arm extending therefrom and a flexible drive shaft secured at one end to the upper drive shaft and at the other end to the lower drive shaft. Rotation of the upper drive shaft will transfer torque to the lower drive shaft at the same angular speed.