Patent Publication Number: US-11655120-B2

Title: Elevator load bearing member including a unidirectional weave

Description:
BACKGROUND 
     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. 
     SUMMARY 
     An illustrative example embodiment of an elevator load bearing member includes a unidirectional weave of a plurality of load bearing fibers including at least a first material and a second material. A melting point of the first material is higher than a melting point of the second material. The plurality of load bearing fibers are bonded together by at least some of the second material that is at least partially melted. A coating covers the plurality of load bearing fibers. 
     In an example embodiment having one or more features of the elevator load bearing member of the previous paragraph, the first material comprises a first type of polymer, the second material comprises a second type of polymer, at least some of the load bearing fibers comprise the first type of polymer and at least some others of the load bearing fibers comprise the second type of polymer. 
     In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, at least some of the load bearing fibers comprise the first material and the second material. 
     In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the coating comprises a jacket that defines a traction surface of the elevator load bearing member. 
     In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the jacket comprises a thermoplastic material and the coating comprises an adhesive between the thermoplastic material and at least some of the load bearing fibers. 
     In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, a ratio of the first material to the second material is 1:1. 
     In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, a ratio of the first material to the second material is 2:1. 
     In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, a ratio of the first material to the second material is 3:2. 
     In an example embodiment having one or more features of the elevator load bearing member of any of the previous paragraphs, the first material comprises at least one of carbon, liquid crystal polymer, aramid, polyhydroquinone-diimidazopyridine, polybenzimidazole, polypyridobisimidazole and polybenzoxazole; and the second material comprises at least one of ultrahigh molecular weight polyethylene and ultrahigh molecular weight polypropylene. 
     An illustrative example embodiment of a method of making an elevator load bearing member includes unidirectional weaving a plurality of load bearing fibers including at least a first material and a second material. A melting point of the first material is higher than a melting point of the second material. The method includes bonding the load bearing fibers together by at least partially melting at least some of the second material and coating the plurality of load bearing fibers. 
     In an example embodiment having one or more features of the method of the previous paragraph, the first material comprises a first type of polymer, the second material comprises a second type of polymer, at least some of the load bearing fibers comprise the first type of polymer, and at least some others of the load bearing fibers comprise the second type of polymer. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, at least some of the load bearing fibers comprise the first material and the second material. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, the coating comprises applying a jacket onto the load bearing fibers and the jacket defines a traction surface of the elevator load bearing member. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, the jacket comprises a thermoplastic material and the coating comprises applying an adhesive onto the load bearing fibers between the thermoplastic material and at least some of the load bearing fibers. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, the bonding comprises heating and applying pressure to the load bearing fibers. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, the heating includes exposing the load bearing fibers to a temperature that is at least as high as the melting point of the second material and below the melting point of the first material. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, the bonding comprises pressing the load bearing fibers between first rollers that are heated and pressing the load bearing fibers between second rollers that are not heated. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, a ratio of the first material to the second material is between 1:1 and 4:1. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, the ratio is 2:1. 
     In an example embodiment having one or more features of the method of any of the previous paragraphs, the first material comprises at least one of carbon, liquid crystal polymer, aramid, polyhydroquinone-diimidazopyridine, polybenzimidazole, polypyridobisimidazole and polybenzoxazole; and the second material comprises at least one of ultrahigh molecular weight polyethylene and ultrahigh molecular weight polypropylene. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    schematically illustrates selected portions of an elevator system including a load bearing member designed according to an embodiment of this invention. 
         FIG.  2    schematically illustrates an example embodiment of an elevator load bearing member. 
         FIG.  3    is an end view of another example embodiment of an elevator load bearing member. 
         FIG.  4    schematically illustrates selected features of a process for making an elevator load bearing member like those shown in  FIGS.  2  and  3   . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    schematically shows selected portions of an elevator system  20  including an elevator car  22  and counterweight  24 . A traction sheave  26  associated with a machine (not specifically illustrated) selectively controls movement of a load bearing member  30 , which suspends the elevator car  22  and counterweight  24 , to control the movement or position of the elevator car  22 . For illustration purposes, a single load bearing member  30  is represented in  FIG.  1   . Multiple load bearing members would be included in many embodiments. 
       FIG.  2    schematically illustrates an example load bearing member  30 . A plurality of load bearing fibers  32  serve as the primary load bearing components of the load bearing member  30 . The load bearing fibers  32  are woven into a unidirectional weave. The load bearing fibers  32  are arranged as warp fibers extending in a length direction L of the load bearing member  30 . A unidirectional weave has fibers extending in a single direction and does not include weft fibers that would be parallel to a width direction W of the load bearing member. 
     In some embodiments the unidirectional weave may include some weft fibers transverse to the single direction of the warp fibers but such weft fibers are far fewer in number than the warp fibers and are not considered significant to the load bearing performance of the unidirectional weave. Any such weft fibers may serve a limited purpose during manufacturing, for example. 
     Weaving the load bearing fibers into a unidirectional weave avoids any braiding of the fibers and, therefore, provides improved strength characteristics compared to other types of weaves. A unidirectional weave of load bearing fibers  32  also provides improved flexibility characteristics. 
     In the embodiment shown in  FIG.  2   , the load bearing fibers  32  are arranged or grouped as cords  34  and the cords  34  are woven into the unidirectional weave. In the embodiment shown in  FIG.  3   , the load bearing fibers  32  are individually woven into the unidirectional weave, which effectively forms a layer or sheet  36 . 
     The load bearing fibers  32  include at least two different types of material. Some embodiments include at least one polymer and another type of material such as carbon or another organic material. One of the materials is selected to at least partially melt for bonding the load bearing fibers  32  together. The material that provides the bonding has properties including a melting point that allows for at least partially melting that material without compromising the mechanical properties of another material that at least some of the other load bearing fibers  32  are made. 
     For discussion purposes, the illustrated example embodiment includes a first type of polymer material and a second type of polymer material that have different melting points. The first type of polymer material has a higher melting point than the melting point of the second type of polymer material. Including different types of polymer with different melting points allows for bonding the load bearing fibers  32  of the unidirectional weave together in a way that preserves the mechanical properties of the fibers made of the first type of polymer and maintains the configuration of the unidirectional weave. For example, the plurality of load bearing fibers  32  are bonded together by at least some of the second type of polymer that is at least partially melted without melting any of the first type of polymer material. 
     In some embodiments each of the load bearing fibers  32  comprises only one type of polymer. For example, some of the fibers  32  are made of the first type of polymer while others are made of the second type of polymer. In other embodiments at least some of the fibers  32  include more than one material and may include multiple polymers or at least one type of polymer and another type of material. 
     The unidirectional weave of fibers  32  includes a ratio of the first type of polymer to the second type of polymer (e.g., higher melting point polymer to lower melting point polymer) in a range from 4:1 to 1:1. Some embodiments include a ratio of the first type of polymer to the second type of polymer of 3:2. An example embodiment includes a ratio of 2:1. In preparation of the multi-polymer composite, the ratio of high melt point fibers to low melting point fibers depends on the processing and linear density of the fibers. 
     The unidirectional woven fibers are consolidated under a selected pressure at the specific temperature that the second or low melting point polymer material melts and forms a hot fluid that adheres the higher melting point fibers together. On cooling from the consolidated high temperature, the low melting point polymer fibers recrystallize, which forms a resin matrix in composite. The original mechanical properties of the low melting point polymer fibers will change because they are at least partially melted. Including the higher melting point material allows for preserving the mechanical properties of the higher melting point fibers. The final property of the composite provides the necessary characteristics for elevator system operation when there are enough higher melting point fibers, such as having more higher melting point fibers than lower melting point polymer fibers. 
     Example higher melting point and high strength polymers include liquid crystal polymer, aramid, polyhydroquinone-diimidazopyridine, polybenzimidazole, polypyridobisimidazole and polybenzoxazole. Example lower melting point and high strength polymers include ultrahigh molecular weight polyethylene and ultrahigh molecular weight polypropylene. 
     A jacket  38  covers the load bearing fibers in each of the illustrated example embodiments. The jacket  38  comprises a material that is suitable for establishing the desired traction with the traction sheave  26  to achieve the desired traction for controlling movement of the elevator car  22 . Example materials that are useful include compressible materials, such as a thermoplastic material or an elastomer. In some embodiments the jacket  36  comprises a thermoplastic polyurethane material. 
       FIG.  4    schematically illustrates an example method of making the disclosed load bearing member embodiments. The plurality of polymer load bearing fibers  32  are introduced or fed into unidirectional weaving equipment  40  where the fibers  32  are woven into the unidirectional weave. Then the woven fibers  32  are heated and pressed together by bonding equipment  42 . For example, the bonding equipment  42  includes heating elements that subject the woven fibers  32  to a temperature that is at least as high as the melting point of the second type of polymer and less than the melting point of the first type of polymer. Such heating at least partially melts at least some of the second type of polymer without melting any of the first type of polymer. Any fibers composed of only the first type of polymer are not melted or altered during such heating. 
     In the illustrated example arrangement the unidirectionally woven fibers  32  are fed through and pressed between heated rollers  44 . At least the rollers  44  heat the woven fibers  32  to a temperature sufficient to at least partially melt at least some of the second type of polymer. That melted polymer bonds the woven fibers  32  together. 
     In  FIG.  4   , the bonding equipment  42  includes cooling rollers  46  to facilitate shaping or maintaining the shape of the unidirectional weave of fibers  32  while any melted polymer recrystallizes. 
     Once the unidirectional weave is at a suitable temperature it is coated by coating equipment  50 . In the illustrated example arrangement, the coating equipment  50  includes an adhesive applicator  52  that applies an adhesive coating onto the polymer load bearing fibers  32 . A jacket application device  54 , such as an extruder, applies the material of the jacket  38 . 
     A load bearing member including a multi-polymer unidirectional weave of load bearing fibers as disclosed above provides improved strength characteristics compared to traditional elevator roping or belts that rely on steel wires as the primary load bearing components. Additionally, load bearing members consistent with the example embodiments of this disclosure are lighter weight and provide cost savings compared to previous configurations. 
     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.