Middle-Drive Elevator Tractor Load Distribution

Solution Overview

Problem

The existing structural design of elevators causes the traction wheel to bear the majority of the weight of the lift car and counterweight device, leading to a significant reduction in the service life of the tractor.

Innovation Solution

A middle-drive type elevator design where the tractor is installed between the lift car and the guide pulley, with the tractor located below the guide pulley, and the wire rope connecting the counterweight and lift car passing through the guide pulley and traction wheel, utilizing a combination of full-wound and semi-wound winding to distribute the load effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If the tractor is located above the guide pulley (traditional design), then the structural design is simple, but the tractor bears the majority of the weight of the lift car and counterweight device, reducing service life

Engineering Contradiction:

Improveservice life of tractorVSAvoidload borne by tractor

Core Design Contradiction:

Duration of action of stationary objectVSForce

Solution Approach 1:

The patent inverts the traditional arrangement by placing the tractor below the guide pulley instead of above it. This inversion changes the load distribution mechanism: the guide pulley now bears the majority of the weight through the wire rope arrangement, while the tractor only bears a minority of the load, thereby extending the tractor's service life without complicating the overall structure

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The guide pulley acts as an intermediary element that redistributes the load. By positioning the tractor below the guide pulley and arranging the wire rope to pass over the guide pulley, the system uses the guide pulley as a mediator to transfer the majority of the weight burden from the tractor to the guide pulley structure, which is better positioned to handle this load

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the tractor bears the majority of the weight, then the lifting function is maintained, but the service life of the tractor is greatly reduced

Engineering Contradiction:

Improveservice life of tractorVSAvoidweight borne by tractor

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent inverts the traditional arrangement by placing the tractor below the guide pulley instead of above it. This inversion changes the load distribution mechanism: the guide pulley now bears the majority of the weight through the wire rope arrangement, while the tractor only bears a minority of the load, thereby extending the tractor's service life without complicating the overall structure

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the positional parameter of the tractor from above to below the guide pulley. This parameter change fundamentally alters the force distribution in the system, transforming the tractor's role from the primary load-bearing component to a secondary component that experiences reduced stress, thereby improving reliability

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10450167B2Middle-drive type elevator

Publication Date: 2019.10.22 SHANGHAI YANGTZE 3 MAP ELEVATOR

AI summary

A middle-drive type elevator has a lift car, tractor, wire rope, guide pulley and counterweight device. The tractor is installed between the lift car and guide pulley. Both the tractor and guide pulley are disposed above the lift car. The tractor is located below the guide pulley. One end of the wire rope connects to the top of the counterweight device, and the other end connects to the top of the lift car after passing through the guide pulley and a traction wheel on the tractor successively. To make the tractor arranged in the middle, the guide pulley bears the majority of the weight of the lift car and counterweight device, while the tractor only bears the minority of the weight of the lift car and counterweight device. It can effectively reduce the load borne by the tractor and greatly improve the service life of the tractor.