Patent Publication Number: US-2017356132-A1

Title: Braided Polyester Fiber Core in Steel Wire Rope

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/348,432, filed Jun. 10, 2016, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates, in general, to a wire rope and, in particular, a steel wire rope with a braided polyester fiber core for use in elevator systems. 
     Description of Related Art 
     Wire ropes or elevator ropes are used to hoist, compensate, and govern elevator cars within an elevator system and require a high tensile strength for hoisting and holding the individual elevator cars. Wire ropes are typically made by twisting together metallic wires or strands and typically have a substantially round cross-sectional shape. Current elevator wire ropes include a rope construction utilizing a textile core (e.g., sisal) with outer steel strands wound thereon. These wire ropes are designed to have a predetermined weight per unit length for each rope size. The elevator operation and functioning, such as required motor power, friction characteristics, and payload that can be lifted, are based on such specific weight that usually can vary by ±5%, but not more unless the design of the elevator operation is modified. 
     The geometry or configuration of a wire rope cross-section and method and material of its manufacture are precisely designed to perform in a predetermined manner and to a predetermined end. The core of the wire rope is the foundation of the wire rope and the core material may be natural or synthetic. Consistency of the diameter and even wear of the wire rope is important in an elevator system due to the wire ropes being used in a parallel configuration of between 2-14 wire ropes. If all of the rope diameters are not consistent and the wear of the individual wire ropes is uneven, the safety of the passengers in the elevator cars may be compromised. Ropes with diameters that vary can vibrate and cause noise, which creates an unpleasant ride for passengers in the elevator car and the elevator cars may bounce more at the start-up and stopping points in the elevator system. The inconsistent and uneven wire ropes can damage sheaves or pulleys in the elevator system costing the customer additional costs in repair or replacement. 
     Consistency of the diameter of the wire rope throughout all environmental conditions is an important feature. Wire rope diameters should always remain consistent to ensure a safe and smooth ride and to save wear and tear on other, more expensive parts of the elevator system. The ability to maintain a diameter in humid and/or wet conditions is a benefit to wire ropes that helps to lengthen the service life of the wire rope. Wire ropes with twisted sisal cores absorb large amounts of water and condensation and often increase in diameter due to swelling in humid and/or wet conditions. Water softens the natural sisal fiber and reduces the support provided by the core to the outer steel strands, which causes a short service life for the wire rope. Typically, even upon drying, a wire rope with a twisted sisal core will remain slightly swelled from its original diameter. 
     Currently, all sisal core wire ropes are lubricated with a light oil. Depending on the origin of the oil, the oil can be 7-13% of the core weight. It is often difficult to obtain a consistent lubrication content throughout a continuous length of twisted sisal material. Inconsistent and high lubrication contents from a sisal rope manufacturer can cause problems during the manufacturing of wire ropes and for end users of the wire ropes. High lubrication content can be squeezed out of the core of the wire rope during a closing process of the wire rope or during the use of the wire rope in an elevator system. In the event the lubrication squeezes out while in the elevator system, the lubrication can mix with the lubrication put on the outer steel strands of the wire rope and can displace from the wire rope. This typically creates a mess in the machine room, elevator shafts, basements, and elevator cars. Many elevator systems are provided in high priced, high profile buildings, and building owners do not want their buildings messy with grease from wire ropes. 
     Sisal is a naturally grown fiber making the fiber diameters and densities uncontrollable and often inconsistent. When these fibers of different diameters and densities are twisted together to make a sisal core, a rather inconsistent wire rope is formed. Subsequently, lubrication is added to the sisal core, which also adds weight and can cause lubrication issues as discussed above. Therefore, using a sisal core can often create an inconsistent wire rope along its length, with different diameters and densities. It is often difficult to provide a consistently round and safe wire rope throughout the length of a production run and between production runs. 
     Therefore, a problem to be solved is the need to provide the elevator industry with a more consistent product. A more consistent product can lessen or eliminate issues such as vibration, premature rope wear, lubrication issues, and diameter reduction in the wire rope. Lessening or eliminating these issues, in turn, provides a better, longer service life for both the wire rope and any peripheral equipment. These issues are currently addressed by closely monitoring the wire ropes to check for premature rope wear and diameter reduction, checking tensions for equalization to reduce vibration, and lubricating, or wiping ropes if lubrication is needed or in excess while wire ropes are operating in the elevator systems. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, a need exists for a wire rope with a rounder, more consistent core that will produce a rounder, more consistent wire rope. A further need exists for a wire rope that includes a core that prevents or reduces moisture absorption in the wire rope. An even further need exists for a wire rope that removes the need for lubrication in the core of the wire rope. Lastly, there is a need for a wire rope that includes a core that provides a consistent diameter and density along its length. 
     In one aspect of the disclosure, an elevator wire rope may include a braided polyester core and at least six outer strands provided around the braided polyester core. 
     In another aspect, the polyester core may have a plurality of single-braided outer strands. The polyester core may have a plurality of double-braided outer strands. Underlying layers of the braided polyester core may have a parallel configuration, a twisted configuration, a single-braided configuration, or a double-braided configuration. Six to ten outer strands may be provided around the braided polyester core. The outer strands may be made of steel. The outer strands may include a central wire, at least four intermediate wires surrounding the central wire, and at least four exterior wires surrounding the intermediate wires. The braided polyester core may include an inner core with a plurality of braided strands and an outer core with a plurality of braided strands. The braided strands of the inner core may be either single-braided or double-braided. The braided strands of the outer core may be either single-braided or double-braided. The braided polyester core may include an inner core with a plurality of twisted strands and an outer core with a plurality of braided strands. The braided strands of the outer core may be either single-braided or double-braided. The braided polyester core may include an inner core with a plurality of strands extending parallel to a longitudinal length of the elevator wire rope and an outer core with a plurality of braided strands. The braided strands of the outer core are either single-braided or double-braided. 
     In another aspect, an elevator wire rope may include a braided polyester core comprising an inner core and an outer core, and at least six outer strands provided around the braided polyester core, each outer strand may include a central wire, at least four intermediate wires surrounding the central wire, and at least four exterior wires surrounding the intermediate wires. 
     In another aspect, the braided polyester core may include an inner core with a plurality of braided strands and an outer core with a plurality of braided strands. The braided strands of the inner core may be either single-braided or double-braided. The braided strands of the outer core may be either single-braided or double-braided. The braided polyester core may include an inner core with a plurality of twisted strands and an outer core with a plurality of braided strands. The braided strands of the outer core may be either single-braided or double-braided. The braided polyester core may include an inner core with a plurality of strands extending parallel to a longitudinal length of the elevator wire rope and an outer core with a plurality of braided strands. The braided strands of the outer core are either single-braided or double-braided. 
     These and other features and characteristics of the wire rope will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various drawings. It is to be expressly understood, however, that the drawings are for the purposes of illustration and description only and are not intended as a definition of the limits of the invention. As used in the specification and the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a wire rope according to the present invention; 
         FIG. 2  is a side view of a braided polyester core of the wire rope of  FIG. 1  next to a twisted sisal fiber core according to the prior art; 
         FIG. 3A  shows a side view of a single- or double-braided polyester core construction; 
         FIG. 3B  shows a side view of a twisted polyester core construction; 
         FIG. 3C  shows a side view of a parallel polyester core construction; 
         FIG. 4  is a chart illustrating results of a water soak test performed on a polyester rope according to the present disclosure and a sisal rope; 
         FIG. 5A  is a chart illustrating comparisons of tested sisal rope diameters and densities to manufacturer&#39;s certification requirements for a sisal rope diameter and density; and 
         FIG. 5B  is a chart illustrating comparisons of tested polyester rope diameters and densities to manufacturer&#39;s certification requirements for a polyester rope diameter and density. 
     
    
    
     DESCRIPTION OF THE DISCLOSURE 
     For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal”, and derivatives thereof shall relate to the invention as it is oriented in the drawings. However, it is to be understood that the invention may assume alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific aspects and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary aspects of the invention. Hence, specific dimensions and other physical characteristics related to the invention disclosed herein are not to be considered as limiting. 
     The present disclosure is directed to, in general, a wire rope used to hoist elevator cars in an elevator system and, in particular, to a wire rope having a braided polyester core. 
     With reference to  FIG. 1 , a wire rope  2  according to the present disclosure is described. The wire rope  2  may include a plurality of outer strands  4  that surround a core  6 . In one embodiment, eight (8) outer strands  4  may surround the core  6 . It is contemplated, however, that alternative numbers of outer strands  4  may surround the core  6 . For example, the number of outer strands  4  provided around the core  6  may range from 6-10 outer strands  4 . The wire rope  2  may have a substantially circular cross-sectional shape. In one aspect, the outer strands  4  may be made of steel. It is contemplated, however, that alternative materials may be used for the outer strands  4 . Each outer strand  4  may include a central wire  8  surrounded by a plurality of intermediate wires  10 . The plurality of intermediate wires  10  may be surrounded by a plurality of exterior wires  12 . In one aspect, the outer strands  4  may have a specific color to correspond to a certain type of wire rope  2  for identification purposes by a vendor or manufacturer. 
     With reference to  FIG. 2 , the core  6  may be made of polyester. It is also contemplated that alternative materials, such as polypropylene, may be used to form the core  6 . In one aspect, the core  6  may be braided. The core  6  may be made of single-braided or double-braided strands. In one aspect, a single-braided strand includes a plurality of strands braided within one another. In one aspect, a double-braided strand includes a central member and a plurality of strands braided around the central member. In one aspect of the disclosure, a wire rope  2  for hoisting an elevator car may include a braided polyester core  6  and between 6 and 10 outer steel strands  4 . There may be an intermediate layer of between 6 and 10 steel strands between the braided polyester core  6  and the outer steel strands  4 . The braided polyester core  6  may have a minimum of 8 and a maximum of 24 single- or double-braided outer strands. The braided core  6  polyester construction beneath the braided outer strands may be parallel, twisted, single-braided, or double-braided or a combination of parallel, twisted, single-braided, or double-braided. These types of construction are illustrated in  FIGS. 3A-3C . 
     As shown in  FIGS. 3A-3C , the core  6  of the wire rope  2  may include an inner core  18  and an outer core  16 . Both of the inner core  18  and the outer core  16  may be made of polyester strands. In one aspect shown in  FIG. 3A , the core  6  may be a braided polyester core. The core  6  may include a single- or double-braided inner core  18  and a single- or double-braided outer core  16 . The inner core  18  and/or the outer core  16  may include a plurality of single-braid strands or double-braid strands. In another aspect shown in  FIG. 3B , the core  6  may have a twisted inner core  18  and a single- or double-braided outer core  16 . The outer core  16  may be made of single-braid strands or double-braid strands. The twisted inner core  18  may twist or wrap around a central axis running longitudinally through the core  6 . In another aspect shown in  FIG. 3C , the core  6  may have an inner core  18  with a parallel configuration that does not include a braid and an outer core  16  that includes a single- or double-braid. The outer core  16  may be made of single-braid strands or double-braid strands. The parallel configuration of the inner core  18  may include polyester fibers that run parallel to a longitudinal length of the wire rope  2 . By utilizing a polyester core in the wire rope  2 , a rounder, more consistent core is provided for the wire rope  2 , which in turn provides a rounder, more consistent wire rope  2 . A rounder and more consistent wire rope  2  will wear more evenly in the elevator system. Consistency of diameter and even wear of the wire rope  2  is important in an elevator system due to the wire ropes  2  being used in a parallel configuration of between 2-14 ropes. By using a braided polyester core  6  including 8-24 outer strands  4  with specified diameters and densities as opposed to a core of 3 or 4 strands of twisted sisal, polyester, or polypropylene, the steel outer strands  4  can rest on a rounder core  6  and the outer strand-to-core pressures can be equalized allowing for a rounder wire rope  2  that will wear more evenly. The benefits of a more consistent diameter and even wire rope wear are an enhanced ride quality, enhanced ride safety, the wire rope  2  is easier to produce, customers can save money on installation costs of the wire rope  2 , customers can save money by not damaging other parts of the elevator system, and customers can save money by increasing the service life of the wire rope  2 . A wire rope utilizing a sisal fiber core does not provide these advantages that are provided by a wire rope  2  with a braided polyester core  6 . The braided polyester core  6  may have specific dimensions and density to ensure that the wire rope  2  is sufficient for hoisting, compensating, and governing an elevator car. Each size of polyester rope maintains a consistent diameter and density along its length. Unlike the polyester rope, the sisal fiber rope used in current wire ropes typically has an inconsistent diameter and density along its length that produces an inconsistent diameter and density for the entire wire rope. Further, the braided polyester core  6  requires no oil or lubrication, thereby eliminating any lubrication problems that are typically experienced when using a twisted sisal fiber core  14 . 
     With reference to the chart in  FIG. 4 , a wire rope  2  including a braided polyester core  6  maintains a more consistent diameter during water/humidity absorption than a wire rope including a sisal fiber core  14  (shown in  FIG. 2 ). Testing on water absorption into a braided polyester core  6  and a twisted sisal fiber core  14  was conducted to compare each core&#39;s ability to maintain diameter during the water absorption. Samples of each core were weighed and the diameter of each sample was measured. For example, an average pre-soak diameter for the length of single-braid polyester core  6  was 0.3095 inches and an average pre-soak diameter for the length of double-braid polyester core  6  was 0.3185 inches. The average pre-soak diameter for the length of twisted sisal fiber core  14  was 0.337 inches. The samples were then submerged in water for 24 hours and re-weighed and measured for diameter. The braided polyester core  6  gained approximately 20% of its weight in water, but the water was not absorbed in the braided polyester core  6 . The water was caught in between very small synthetic fibers in the core  6 . The diameter of the braided polyester core  6  did not increase. The average post-soak diameter for the length of single-braid polyester core  6  was 0.3100 inches and the average post-soak diameter for the length of double-braid polyester core  6  was 0.3195 inches. The water trapped in-between the fibers of the braided polyester core  6  had no ill effects on the strength or integrity of the braided polyester core  6 . The twisted sisal fiber core  14  absorbed approximately 61% of its weight in water and swelled 23% in diameter. The average post-soak diameter for the length of twisted sisal fiber core  14  was 0.414 inches. The water softened the natural sisal fibers and caused the twisted sisal fiber core  14  to provide less support for the outer steel strands and created a shorter service life for the wire rope. 
     Both of the samples were then allowed to air dry for 24 hours. The braided polyester core  6  dried completely with no change in diameter. The average dried diameter for the length of single-braid polyester core  6  was 0.3100 inches and the average dried diameter for the length of double-braid polyester core  6  was 0.3195 inches. The twisted sisal fiber core  14  almost dried completely, but the diameter remained swelled to +20% of the original diameter. The average dried diameter of the length of twisted sisal fiber core  14  was 0.403 inches. Therefore, the braided polyester core  6  provides a more consistent wire rope  2  throughout all environmental conditions to ensure a safe and smooth ride and to reduce wear on other, more expensive parts of the elevator system. The ability to maintain a diameter in humid and/or wet conditions is an advantage that a wire rope  2  with a braided polyester core  6  can provide to increase the service life of the wire rope  2 . A wire rope with a twisted sisal fiber core  14  will have an inconsistent diameter along its length in humid/wet conditions due to the swelling of the twisted sisal fiber core  14 . The inconsistent diameter will increase the wear on the wire rope and shorten the service life of the wire rope. A wire rope  2  with a braided polyester core  6  improves over this type of wire rope to provide a more consistent wire rope diameter. 
     The chart shown in  FIG. 5A  illustrates certificate diameters and densities for sisal fiber ropes that are typically requested from vendors. Manufacturers of wire rope typically request sisal fiber ropes having these certified diameters and densities to use in wire rope for elevator systems. As illustrated in the chart of  FIG. 5A , the certificate diameters and densities typically fall within predetermined specification tolerances. However, upon delivery to the manufacturers, the sisal fiber rope does not typically have the requested certificate diameters and densities. A number of samples of sisal fiber rope of varying sizes were measured upon receipt from a vendor. As shown in the chart of  FIG. 5A , the tested diameters and densities of the samples upon receipt from the vendor did not correspond to the requested certificate diameters and densities. On average, the difference between the tested diameters and the certificate diameters was +2.59%. On average, the difference between the tested densities and the certificate densities was +5.03%. The positive percentages show that the tested diameters and densities are below the values stated on the vendor&#39;s certificates. Although the tested diameters were still within the specification tolerances, the tested diameters were not close to the requested certificate diameters. It was also determined that the tested densities did not pass incoming inspection and did not fall within the specification tolerances. Therefore, the chart of  FIG. 5A  illustrates the inconsistency in the diameter and density of sisal fiber rope that is provided from vendors. Sisal is a naturally grown fiber making the fiber diameters and densities uncontrollable. When the fibers of different diameters and densities are twisted together to make a twisted sisal fiber core  14 , the core  14  makes an inconsistent rope. Further, lubrication is added to the sisal rope, which also adds weight to the rope. 
     The chart shown in  FIG. 5B  illustrates certificate diameters and densities for polyester ropes that are typically requested from vendors. As illustrated in the chart of  FIG. 5B , the certificate diameters and densities typically fall within predetermined specification tolerances. Unlike the sisal fiber rope, upon delivery to the manufacturers, the polyester rope has the requested certificate diameters and densities. A number of samples of polyester rope of varying sizes were measured upon receipt from a vendor. As shown in the chart of  FIG. 5B , the tested diameters and densities of the samples upon receipt from the vendor corresponded to the requested certificate diameters and densities. On average, the difference between the tested diameters and the certificate diameters was −1.17%. On average, the difference between the tested densities and the certificate densities was −1.02%. The negative percentages show that the tested diameters and densities are above that which was stated on the vendor&#39;s certifications. All of the polyester rope samples passed incoming inspection and the tested diameters and densities were very consistent and close to the vendor certificate diameters and densities. Synthetic fibers, such as the polyester core  6 , are extruded to the same density and diameter every time, which makes the process and outcome highly repeatable and consistent. Therefore, the specifications for the wire rope  2  can remain consistent, which is important in order to produce a consistently round and safe wire rope  2  throughout the length of a production run and between production runs. 
     While various aspects of the wire rope  2  were provided in the foregoing description, those skilled in the art may make modifications and alterations to these aspects without departing from the scope and spirit of the invention. For example, it is to be understood that this disclosure contemplates that, to the extent possible, one or more features of any aspect can be combined with one or more features of any other aspect. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The invention described hereinabove is defined by the appended claims and all changes to the invention that fall within the meaning and the range of equivalency of the claims are to be embraced within their scope.