This invention generally relates to load bearing members for use in elevator systems. More particularly, this invention relates to an elevator load bearing member having a specialized jacket surface.
Elevator systems typically include a cab and counterweight that move within a hoistway to transport passengers or cargo to different landings within a building, for example. A load bearing member, such as roping or a belt typically moves over a set of sheaves and supports the load of the cab and counterweight. There are a variety of types of load bearing members used in elevator systems.
One type of load bearing member is a coated steel belt. Typical arrangements include a plurality of steel cords extending along the length of the assembly. A jacket is applied over the cords and forms an exterior of the assembly. Some jacket application processes result in grooves being formed in the jacket surface on at least one side of the assembly. Some processes also tend to cause distortions or irregularities in the position of the steel cords relative to the exterior of the jacket along the length of the assembly.
In the case of some coated steel load bearing members, an extrusion process for applying a jacket over the cords requires selecting a urethane material having chemical properties that are beneficial for the process of applying the jacket. The resulting jacket, however, may present difficulties in having the desired level of traction when installed in an elevator system. With some urethane materials that are beneficial from a processing standpoint, the resulting coefficient of friction between the jacket and an elevator sheave surface may be higher or lower than desirable for meeting the traction requirements within the hoistway.
Typical processes result in a smooth or glossy exterior of the jacket on the sheave contacting surfaces. In some instances, this smoothness can introduce undesirable adhesion between the jacket and a traction sheave. In most cases, the resulting coefficient of friction between the smooth surface and a traction sheave is not consistent with desired traction performance.
An alternative arrangement is required to minimize or eliminate the undesirable friction characteristics of a urethane jacket. This invention addresses that need.