Jacketed Tension Members for Elevator Traction Sheave
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Solution Overview
Problem
Existing traction systems for elevators face challenges in efficiently transmitting high pulling forces without material fatigue, particularly with belts that are prone to shear stress and require wide sheaves and multiple components, whereas rope systems are cumbersome and require lubrication.
Innovation Solution
A composite traction device featuring jacketed tension members with a thin elastomer layer and a back layer, arranged in a plane with a clear space, allowing direct engagement with the traction sheave and minimizing shear stress, thus combining the advantages of both belt and rope technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a belt with thick elastomer material is used as a traction device, then the belt can transmit traction forces, but the elastomer material is exposed to high shear and shearing stresses causing fatigue
Solution Approach 1:
The invention extracts the tension members from the thick elastomer matrix and positions them directly at the contact surface with the traction sheave. This removes the harmful shear stress zone from the elastomer material by eliminating the need for a thick elastomer layer between the tension members and the contact surface, thereby preventing fatigue while maintaining traction force transmission capability.
Solution Approach 2:
The invention applies local quality by having tension members with different characteristics at different locations: the outer surface of the tension members has a specific friction coefficient optimized for traction contact, while the inner core contains the reinforcement elements. This localized differentiation allows optimal performance at the contact surface without subjecting the entire structure to high shear stresses.
2Reliability
If multiple belts are used in parallel for safety, then safety requirements are met, but wide traction sheaves and direction-changing sheaves are required
Solution Approach 1:
The invention merges multiple tension members into a single integrated belt structure with a unified back layer connecting them. This combination allows the belt to function as a single unit that can be guided over standard-sized sheaves while maintaining the safety redundancy of multiple load-bearing elements, eliminating the need for wide sheaves required when using multiple separate belts.
3Strength
If ropes are used as a traction device, then force can be transmitted directly from the traction sheave to the ropes, but handling is cumbersome and lubrication is required
Solution Approach 1:
The invention uses composite materials by combining reinforcement elements (for strength and direct force transmission like ropes) with an elastomer outer surface (for ease of handling and maintenance like belts). The elastomer coating eliminates the need for lubrication and simplifies handling, while the internal reinforcement structure maintains efficient direct force transmission from the traction sheave.
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 enables efficient high-force transmission with reduced material fatigue, simpler handling, and narrower sheave diameters, making the system virtually maintenance-free and lightweight, while maintaining high reliability and adaptability.
Implementation Method 1
the elastomer material transmits the traction forces. The belt as a traction device, especially the elastomer region between the tension members and the contact surface, is thus exposed to high shear and shearing stresses during operation
Implementation Method 2
the force that can be transmitted is dependent not only on the friction between the traction sheave and the elastomer
Data Source
AI summary
A traction device includes tension members (2) coated with an elastomer material to form jacketed tension members (3). The jacketed tension members (3) are arranged next to each other in a plane in the cross section of the traction device, at such a distance from each other that there is a clear space (6) between each two mutually adjacent ones of the jacketed tension members (3). The jacketed tension members (3) are connected at the back thereof by a back layer. The clear space (6) begins on the side facing away from the back layer (4) and extends at least beyond the center point (5) of the tension member, and the ratio of the second diameter (d2) of the jacketed tension member (3) in relation to the first diameter (d1) of the tension member (2) is between 1.05 and 2.25. The invention is also directed to a traction system which includes the traction device which can be driven by at least one traction sheave (9), and each jacketed tension member (3) engages in a corresponding groove (10) of the traction sheave (9). The back layer (4) is arranged on the side of the jacketed tension members (3) that faces away from the side engaging in the grooves (10) of the traction sheave (9). At least one tension member (2) engages in the corresponding groove (10) of the traction sheave (9) by between 5% and 25% of its diameter (d1).