Patent Application
20210024328
A variety of elevator systems are known. Some elevator systems use a hydraulic arrangement for moving the elevator car. Others are traction-based and include roping that suspends the elevator car and a counterweight. A machine causes movement of a traction sheave that, in turn, causes movement of the roping for moving the elevator car as desired.
For many years, roping in elevator systems included round steel ropes. More recently, flat belt technologies were developed that provided advantages over traditional, round steel rope arrangements. Even with the advancement, those skilled in the art have been striving to improve elevator load bearing member technology.
An illustrative example embodiment of an elevator load bearing member includes a plurality of load bearing cords and a jacket at least partially surrounding the cords. The jacket includes an inner portion received on the cords and a fluoropolymer outer portion that establishes a fire-resistant exterior of the jacket.
In an example embodiment having one or more features of the elevator load bearing member of the previous paragraph, the fluoropolymer portion completely encases the inner portion.
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the fluoropolymer portion comprises a functional fluoropolymer.
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the fluoropolymer portion comprises tetrafluoroethylene-ethylene copolymer
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the fluoropolymer portion comprises a perfluoroalkoxy alkane.
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the fluoropolymer portion comprises a copolymer of tetrafluoroethylene and a perfluorinated vinyl ether.
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the functional fluoropolymer comprises a functional group comprising at least one of anhydride, silane, glycidyl, and isocyanate.
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, a ratio of an amount of a material of the inner portion to an amount of fluoropolymer is in a range from 1:2 to 1:40.
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the ratio is in a range from 1:5 to 1:20.
In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the ratio is 1:8 or 1:15.
An illustrative example embodiment of a method of making an elevator load bearing member includes forming an inner portion of a jacket on a plurality of load bearing cords and establishing a fire-resistant fluoropolymer portion on the inner portion to define an exterior of the jacket.
In an example embodiment having one or more features of the method of the previous paragraph, the forming and the establishing are performed by coextruding a material of the inner portion and the fluoropolymer of the fluoropolymer portion.
An example embodiment having one or more features of the method of any of the previous paragraphs includes separately forming the inner portion and at least one layer of fluoropolymer material and laminating the at least one layer and the formed inner portion
The various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
The jacket 32 includes An inner portion or layer 34 that is received against the cords 30. The inner portion 34 comprises a compressible material that provides good adhesion with the cords 30 to provide adequate pullout strength to maintain the desired configuration of the load bearing member 26 over its useful life. Example embodiments include inner portions 34 that comprise at least one of polyurethane, polyamide, polyester, or ethylene propylene diene monomer rubber (EPDM).
The jacket 32 also includes a fluoropolymer portion or layer 36 that establishes a fire-resistant exterior of the jacket 32. In the illustrated embodiment, the fluoropolymer portion 36 surrounds the first portion 34 and establishes the entire exterior of the jacket 32. The fluoropolymer portion 36 is self-extinguishing and resistant to igniting, melting or dripping when exposed to fire or other high-temperature conditions. Including the fluoropolymer portion 36 gives fire-resistant properties to the load bearing member 26 while establishing an exterior surface on the jacket 32 that provides the necessary traction for controlling the movement and position of the elevator car 22.
The fluoropolymer portion 36 in at least some embodiments also improves the wear characteristics of the jacket 32, which can extend the useful life of the load bearing member 26. For example, a fluoropolymer has superior hardness, breaking stress and tensile elongation at break properties compared to a polyurethane so a jacket including an exterior fluoropolymer portion 36 has superior wear characteristics compared to previously used jacket materials. Moreover, the fluoropolymer portion 36 provides better mechanical performance properties for such a jacket compared to blends of polyurethanes with fire-retardant agents.
The fluoropolymer in an example embodiment comprises tetrafluoroethylene-ethylene copolymer. Another example embodiment includes a perfluoroalkoxy alkane, such as copolymer of tetrafluoroethylene and a perfluorinated vinyl ether that has been functionalized to include an adhesive group within the polymer backbone. Such materials do not melt or drip when exposed to flame and give the jacket 32 excellent fire resistant properties including the ability to maintain the geometry of the load bearing member 26.
The fluoropolymer material in some embodiments comprises a functional fluoropolymer including a functional group such as anhydride, silane, glycidyl, isocyanate, carboxylic acid, amine, and amide.
Another example method is illustrated in
The jacket 32 may include various amounts of the respective materials of the inner portion 34 and the fluoropolymer portion 36. A ratio of the amount of inner portion 34 material to the amount of fluoropolymer portion 36 material in the jacket 32 is in a range from 1:2 to 1:40. An example embodiment includes a ratio of those materials in the range from 1:5 to 1:20. One example embodiment has a preferred ratio of 1:8 or 1:15.
A load bearing member designed according to an embodiment of this invention may have a different configuration than the flat belt style of load bearing member in the illustrations and described above. For example, the load bearing member may have a round cross-section.
Including a fluoropolymer portion as the exterior of the jacket provides smoke-suppressant and fire-resistant properties including avoiding dripping or melting of the jacket 32. The fluoropolymer provides such protection along with superior mechanical performance compared to elevator load bearing member jacket compositions that attempted to incorporate fire resistant materials in to a blend with a polyurethane or other jacket material.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
