Patent Description:
Typical traction-based elevator systems include a roping arrangement that has a plurality of tension members such as steel ropes, for example. The roping arrangement follows a path defined by sheaves placed strategically within the elevator system. At least one of the sheaves operates as a traction sheave causing the roping arrangement to move responsive to operation of a machine that causes the traction sheave to rotate. Other sheaves are considered idler sheaves that move responsive to movement of the roping arrangement. Controlling the direction and speed of movement of the traction sheave provides the ability to move the elevator car in a desired direction at a desired speed.

It is necessary to have sufficient traction between the traction sheave and the tension members to achieve desired elevator car movement and to control car position, for example. In high rise buildings, the elevator system typically requires higher levels of traction. One approach to having a sufficient traction surface on a traction sheave involves controlling the surface roughness. A roughened surface provides more traction than a smoother surface, for example.

One drawback to that approach is that the sheave is subject to wear and increased traction can increase the rate of sheave wear. Sheave liners have been used so the liner can be replaced instead of the sheave. While sheave liners can provide cost savings by avoiding the need to replace or recondition the entire sheave, the liners may not provide the desired level of traction, especially at the level desired in a high rise elevator system.

<CIT> discloses a traction sheave for an elevator which has a composite coating applied directly to its surface. <CIT> discloses a traction sheave with a urethane resin coating, optionally filled with micron-sized particles (<NUM>-<NUM>).

An illustrative example embodiment of an elevator sheave liner (e.g. an elevator sheave liner made by the method as disclosed herein) includes a liner body having an inner surface configured to be received against a sheave and an outer surface configured to engage an elevator tension member. The liner body comprises a composite material and a plurality of wear resistance particles in the composite material. The wear resistance particles are nanoparticles or microparticles. At least some of the wear resistance particles establish a traction characteristic of the outer surface (of the sheave liner). The composite comprises thermoplastic polyurethane and at least some of the wear resistance particles are nanoparticles having a size in a range from about <NUM> to about <NUM>.

In an example embodiment including the features of the elevator sheave liner of the previous paragraph, at least some of the wear resistance particles are microparticles and the size of the microparticles is between about <NUM> and about <NUM>.

In an example embodiment including at least one of the features of the elevator sheave liner of any of the previous paragraphs, the wear resistance particles are uniformly dispersed throughout the composite material of the liner body.

In an example embodiment including at least one of the features of the elevator sheave liner of any of the previous paragraphs, the liner body comprises between <NUM>% and <NUM>% by weight wear resistance particles.

In an example embodiment including at least one of the features of the elevator sheave liner of any of the previous paragraphs, the wear resistance particles have a hardness of at least <NUM> on the Moh's hardness scale.

In an example embodiment including at least one of the features of the elevator sheave liner of any of the previous paragraphs, the wear resistance particles comprise silicon carbide (SiC), Silicon Nitride (Si<NUM>N<NUM>) or diamond.

In an example embodiment including at least one of the features of the elevator sheave liner of any of the previous paragraphs, the at least some of the wear resistance particles that establish the traction characteristic are exposed on the outer surface.

An illustrative example embodiment of an elevator sheave includes a sheave body and the elevator sheave liner of any of the previous paragraphs.

An illustrative example embodiment of a method of making an elevator sheave liner (e.g. an elevator sheave liner as disclosed herein) includes preparing a composite material; mixing a plurality of wear resistance particles into the composite material, wherein the wear resistance particles are nanoparticles or microparticles; and forming a sheave liner body of the mixed composite material and wear resistance particles. The composite material comprises thermoplastic polyurethane and at least some of the wear resistance particles are nanoparticles having a size in a range from about <NUM> to about <NUM>.

In an example embodiment including the features of the method of the previous paragraph, the wear resistance particles have a hardness at least <NUM> on the Moh's hardness scale.

In an example embodiment including at least one of the features of the method of any of the previous paragraphs, the particles comprise silicon carbide (SiC), Silicon Nitride (Si<NUM>N<NUM>) or diamond.

In an example embodiment including at least one of the features of the method of any of the previous paragraphs, at least some of the wear resistance particles are microparticles having a size in a range from about <NUM> to about <NUM>.

In an example embodiment including at least one of the features of the method of any of the previous paragraphs, mixing the wear resistance particles into the composite material includes uniformly dispersing the wear resistance particles throughout the composite material.

In an example embodiment including at least one of the features of the method of any of the previous paragraphs, mixing the wear resistance particles into the composite material includes adding an amount of the wear resistance particles to establish between <NUM> wt% and <NUM> wt% wear resistance particles.

In an example embodiment including at least one of the features of the method of any of the previous paragraphs, the wear resistance particles have a hardness of at least <NUM> on the Moh's hardness scale.

In an example embodiment including at least one of the features of the method of any of the previous paragraphs, the wear resistance particles comprise silicon carbide (SiC), Silicon Nitride (Si<NUM>N<NUM>) or diamond.

In an example embodiment including at least one of the features of the method of any of the previous paragraphs, forming the sheave liner body includes leaving at least some of the wear resistance particles exposed on an outer surface of the formed sheave liner body and the exposed wear resistance particles establish a traction characteristic of the sheave liner.

<FIG> shows selected portions of an elevator system <NUM>. An elevator car <NUM> and counterweight <NUM> are suspended by a roping arrangement of tension members <NUM>. In the disclosed example embodiment, the tension members <NUM> include a plurality of round ropes.

A traction sheave <NUM> and an idler sheave <NUM> establish a path along which the tension members <NUM> travel for purposes of moving the elevator car <NUM> as desired. An elevator machine <NUM> causes the necessary movement of the traction sheave <NUM> to achieve the desired elevator car movement. In some example embodiments, the traction sheave <NUM> could be a surface of the machine shaft rather than a separate component.

<FIG> shows one example traction sheave <NUM> including a metallic body <NUM>. One example comprises low carbon steel as the material used for forming the metal body <NUM> of the traction sheave <NUM>. Sheave liners <NUM> are situated in grooves of the sheave <NUM> where the tension members <NUM> engage the traction sheave <NUM>. The sheave liners <NUM> have a sheave liner body with an inner surface <NUM> that is received against the sheave <NUM> and an outer surface <NUM> that engages a tension member.

The sheave liners <NUM> comprise a material that provides a desired level of traction for engagement with the tension members <NUM> and resists wear of the sheave liner <NUM>. A portion of the material of the sheave liners <NUM> is shown in <FIG>. In the example embodiment, the material includes a composite material <NUM> and wear resistance particles <NUM> in the composite material <NUM>. In this example, the wear resistance particles <NUM> are embedded and evenly distributed in the composite material <NUM> throughout the sheave liner body.

The wear resistance particles <NUM> include some that are situated along the outer surface <NUM>. In some embodiments the wear resistance particles <NUM> along the outer surface <NUM> are at least partially exposed instead of being coated or covered with the composite material <NUM>. The wear resistance particles <NUM> along the outer surface <NUM> establish a traction characteristic of the sheave liner <NUM>. The wear resistance particles <NUM> introduce a surface structure, texture or roughness along the outer surface <NUM> that differs from an entirely flat or smooth surface that would be typical of a molded sheave liner. Even if a sheave liner made of composite material without wear resistance particles were made with a surface texture or roughness, that surface would become worn and smoother over time during operation of the elevator system.

Including the wear resistance particles <NUM> throughout the sheave liner body provides the traction characteristic established by the wear resistance particles <NUM> even if the sheave liner <NUM> wears over time and the thickness between the inner surface <NUM> and the outer surface <NUM> decreases. The wear resistance particles <NUM> provide the desired traction characteristic of the outer surface <NUM> throughout the expected useful life of the sheave liner <NUM>.

The material properties of any partially exposed wear resistance particles <NUM> also contribute to the traction characteristic. The coefficient of friction between the tension member <NUM> and the composite material <NUM> is different than the coefficient of friction between the tension member <NUM> and the wear resistance particles <NUM>. Including wear resistance particles <NUM> along the outer surface <NUM> provides a desired coefficient of friction between the outer surface <NUM> and the tension member <NUM> to establish a desired amount of traction.

The hardness of the wear resistance particles <NUM> contributes to the wear resistance of the sheave liner <NUM>. In some embodiments, the metallic particles have a hardness of at least <NUM> on the Moh's hardness scale. Some embodiments include Silicon Carbide (SiC) wear resistance particles <NUM>. Other embodiments include Silicon Nitride (Si<NUM>N<NUM>) or diamond wear resistance particles <NUM>.

The wear resistance particles wear resistance particles of the example embodiment are nanoparticles or microparticles. In some embodiments, at least some of the wear resistance particles <NUM> are microparticles that have a size in a range from about <NUM> micron to about <NUM> microns. In other embodiments, at least some of the wear resistance particles <NUM> are nanoparticles that have a size in a range from about <NUM> to about <NUM>. The size of each particle corresponds to a cross-sectional dimension such as a width or diameter of the particle.

The composite material <NUM> is a thermoplastic polyurethane composite. Including the wear resistance particles <NUM> provides longer life as the wear resistance particles <NUM> tend to resist wear better than a thermoplastic polyurethane composite could on its own. At the same time, the disclosed sheave liners <NUM> provide the advantages of a thermoplastic sheave liner, such as easy installation.

<FIG> is a flowchart diagram <NUM> that summarizes an example approach to make a sheave liner <NUM>. At <NUM>, a composite material, i.e. polyurethane-based, is prepared. At <NUM>, the wear resistance particles <NUM> are mixed into the composite material. The mixing in this example embodiment includes uniformly distributing the wear resistance particles <NUM> throughout the composite material.

The amount of wear resistance particles <NUM> may be varied to achieve different traction characteristics or wear characteristics. The example embodiment includes selecting a combination of the wear resistance material, the size of the particles <NUM> and the amount of particles. Using different amounts of different materials or particle sizes may provide the same traction characteristic. The material of the sheave liner body in this example includes between one-tenth of one percent by weight (<NUM> wt%) and twenty percent by weight (<NUM> wt%) wear resistance particles <NUM>. Those skilled in the art who have the benefit of this description will be able to determine what amount is useful for their particular implementation.

Sheave liners consistent with this description include wear resistance particles <NUM> in a composite material <NUM>. The wear resistance particles <NUM> enhance the wear resistance and a traction characteristic of the sheave liner compared to one that is made of a composite material without wear resistance particles. A traction surface of the sheave liner <NUM> has a surface structure, texture or roughness that establishes a desired traction characteristic throughout the expected useful life of the sheave liner <NUM>.

Claim 1:
An elevator sheave liner (<NUM>), comprising a liner body including an inner surface (<NUM>) configured to be received against a sheave (<NUM>) and an outer surface (<NUM>) configured to engage an elevator tension member (<NUM>), whereby
the liner body comprising a composite material (<NUM>) and a plurality of wear resistance particles (<NUM>) in the composite material (<NUM>), wherein the composite comprises thermoplastic polyurethane and the wear resistance particles (<NUM>) are nanoparticles or microparticles, at least some of the wear resistance particles (<NUM>) establishing a traction characteristic of the outer surface (<NUM>), and further wherein at least some of the wear resistance particles are nanoparticles having a size in a range from <NUM> to <NUM>.