Elevator Jacket Dual Polymer Composition
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Solution Overview
Problem
Traditional load bearing assemblies for elevator systems face challenges in balancing the need for sufficient pull-out strength between the polymer jacket and tension member with avoiding adhesion between the jacket and sheave, as some polymer materials provide good performance in one aspect but undesirable adhesion in another.
Innovation Solution
A load bearing assembly is designed using a first polymer composition for the interior portion to ensure strong adhesion with the tension member and a second, different polymer composition for the exterior portion to minimize friction and adhesion with sheaves, utilizing various polymers such as polyurethanes, nylons, and fluorinated polymers, with additives to enhance specific characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single polymer composition is used for the jacket, then the manufacturing process is simple, but it cannot simultaneously provide sufficient pull-out strength and avoid adhesion with the sheave
Solution Approach 1:
The jacket is segmented into two distinct polymer composition zones: an inner polymer composition that provides strong adhesion to the tension member for sufficient pull-out strength, and an outer polymer composition that minimizes friction and adhesion with the sheave. This segmentation allows each zone to independently optimize its function without compromising the other.
Solution Approach 2:
Different regions of the jacket are assigned different material properties tailored to their specific functional requirements. The inner region near the tension member has high adhesion characteristics, while the outer region contacting the sheave has low friction characteristics. This local differentiation resolves the contradiction by providing appropriate material quality at each location rather than using a uniform composition throughout.
2Strength
If a polymer material provides sufficient pull-out strength, then it bonds well with the tension member, but it may cause undesirable adhesion with the sheave
Solution Approach 1:
The jacket material is segmented into an inner polymer composition optimized for strong bonding to the tension member (providing pull-out strength) and an outer polymer composition optimized for minimal adhesion to the sheave. This segmentation enables the inner layer to deliver sufficient bond strength while the outer layer prevents harmful adhesion during sheave contact.
Solution Approach 2:
The inner region of the jacket employs a polymer composition with high adhesion properties for strong tension member bonding, while the outer region uses a polymer composition with low adhesion properties for reduced sheave friction. This local quality differentiation allows the jacket to simultaneously achieve sufficient pull-out strength and minimize harmful adhesion with the sheave.
3Reliability
If friction between the jacket and sheave is reduced, then wear and damage are minimized, but pull-out strength may be compromised
Solution Approach 1:
The jacket is segmented into an inner polymer composition that ensures strong adhesion to the tension member for adequate pull-out strength, and an outer polymer composition that reduces friction with the sheave to minimize wear and damage. This segmentation allows the outer layer to provide wear resistance through reduced friction while the inner layer maintains necessary pull-out strength.
Solution Approach 2:
The outer region of the jacket uses a polymer composition with low friction characteristics to minimize wear and damage during sheave contact, while the inner region uses a polymer composition with high adhesion characteristics to ensure sufficient pull-out strength. This local quality assignment allows the jacket to simultaneously achieve wear resistance and maintain pull-out strength.
Data Source
AI summary
An elevator load bearing assembly (30) includes a jacket (34) having different portions comprising different polymer compositions. In a disclosed example, a plurality of tension members (32) are at least partially surrounded by a first portion (36) comprising a first polymer composition. A second portion (38) establishes at least one exterior surface (40) of the jacket (34) and comprises a second polymer composition. In one example, a surface-modifying agent is added to alter the composition of at least a portion of the jacket (34). In another example, co-extrusion techniques using different polymer compositions establish different portions of the jacket (34).