Patent Application
20070107993
This invention generally relates to guide rails for elevator systems. More particularly, this invention relates to elevator guide rails made from a lightweight material with a more wear-resistant material on at least a portion of the rail to provide a braking surface.
Elevator systems typically include guide rails that guide movement of a car within a hoistway. Conventional guide rails are made of steel. While steel guide rails provide a stable structure that is able to provide the necessary guiding function and provide a braking surface during braking operations, they are not without drawbacks. Steel guide rails are heavy and relatively expensive. A significant portion of the installation time associated with installing an elevator system is devoted to installing the guide rails. When steel guide rails are used, their heavy and awkward nature contributes to the additional labor cost. Additionally, the running surface along which guide rollers travel during elevator car movement must be machined into the steel using a separate machine process.
One attempt to avoid using steel guide rails has been to utilize aluminum guide rails. A significant shortcoming associated with aluminum guide rails is that the aluminum material is not hard enough to withstand the surface forces associated with an elevator braking operation. This is particularly true in safety braking situations where the elevator car is traveling at a high speed before being stopped. The heat associated with a braking operation can reach the melting point of aluminum, which significantly degrades the rail. Additionally, typical braking materials used in elevator systems are hard and scar the surface of an aluminum rail. Accordingly, while aluminum rails provide cost savings from a materials and installation standpoint, and an improved running surface, they do not typically provide adequate properties for required elevator system operation.
This invention provides the ability to use an aluminum guide rail structure that is adapted to withstand the conditions associated with braking applications in an elevator system.
In general terms, this invention is a two-material guide rail that is more economical and yet as durable as a conventional steel rail.
One example guide rail designed according to this invention includes a body made of a first material. The body includes a nose portion that provides a guiding surface along which guide rollers travel during elevator car movement. A second material covering extends over at least part of the nose portion and provides a braking surface against which elevator bralke components act during a braking application.
In one example, the guide rail body is made from aluminum and the cover is made from steel.
In one example, a bonding agent secures the steel covering to the appropriate portion of the aluminum guide rail. The bonding agent in one example is thermally conductive so that it assists in dissipating heat that tends to build up in a brake member during a braking application.
In one example, the covering is an elongated, bent clip made from a steel sheet that closely surrounds the brake area on the nose portion of an aluminum guide rail. The covering provides a durable steel surface for direct contact with brake pads. In one example, the formed steel sheet extends continuously along the entire length of the guide rail.
A guide rail designed according to this invention provides all of the advantages associated with using a lightweight material such as aluminum to form the guide rail body yet provides the durability such as that associated with steel guide rails for braking applications, for example.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiments. The drawings that accompany the detailed description can be briefly described as follows.
As best appreciated from
The nose portion 32 provides a guiding surface 34 on opposite sides of the nose portion 32. The guiding surface is configured to receive conventional guide rollers that travel along the guiding surface 34 for achieving a desired movement of the elevator car 22, for example.
A distal end 36 of the nose portion 32 provides a braking surface against which a braking device 38 can act to stop movement of the elevator car 22 in a conventional manner. As best appreciated from
In one example, the covering 40 comprises steel while the guide rail body comprises aluminum.
In this example a bonding agent 42 is located between the covering 40 and the nose portion 32 to secure the covering 40 in place. The bonding agent preferably is selected to provide sufficient shear strength to avoid any relative longitudinal movements between the distal end 36 of the nose portion 32 and the covering 40. In one example, a thermally conductive bonding agent is utilized to distribute heat associated with a braking application. Example bonding agents that are useful with guide rails designed according to this invention include polymer-based adhesives, concrete and concrete-like adhesives.
In one example, the high temperature bonding material is distributed evenly throughout the contact area between the steel covering 40 and the aluminum nose portion 32. The bonding material preferably has a high compressive strength to prevent any fracture that might otherwise occur responsive to the squeezing forces associated with brakes acting against the covering 40 on the rail 24. The covering 40 provides a durable surface for direct contact with conventional elevator system brake pads.
In one example, the covering 40 is essentially a clip formed from a continuously bent roll of sheet metal and provides a continuous braking surface along the entire longitudinal length of the rail 24. In one example, the clip of sheet steel is formed at the elevator system installation site from a roll of sheet metal using a conventional forming tool, for example.
During operation of the braking device 38 brake pads 44 engage the outer surface of the covering 40. The heat generated at the interface between the pads 44 and the covering 40 is distributed along a length of the rail where the braking occurs. Once the elevator car 22 has come to a stop, however, a highly concentrated amount of heat typically is stored within the brake pads 44. The so-called “soak-back” effect rapidly transfers heat to the portion of the rail 24 against which the brake pads 44 are resting. The covering 40 and the bonding material 42 in one example provide thermal resistance between the nose portion 32 of the aluminum rail and the brake pad surface. As the rail body has good thermal conductivity, the insulation thickness provided by the covering 40 and the bonding material 42 can be relatively small. As known, higher speed elevators will generate more heat during a braking application. Accordingly, the thickness of the covering 40 may be selected based upon the expected operating parameters of the elevator system. Those skilled in the art who have the benefit of this description will be able to decide what thickness of the covering 40 and the bonding material 42 will sufficiently curtail maximum heat transfer associated with the soak-back effect to prevent any softening of the aluminum while still allowing the rail to dissipate the heat energy at a required rate.
The bonding material 42 might soften upon soakback, but re-casts after such a heat cycle. This material could be mechanically captured inside the steel clip 40 upon installation onto the aluminum extrusion. In this example and as shown schematically in
As schematically shown in
In this example, the steel covering 40 is swaged or otherwise deformed at least partially into the recesses 50 to secure the covering 40 in place.
Another example includes using concrete as the bonding agent securing the covering 40 to the nose portion 32.
In one example designed according to the teachings of
In another example, the interior surface of the covering 40 and the exterior surface of the nose portion 32 are treated so that the surfaces are roughened. Such rough surfaces enhance the ability of a bonding agent like concrete to enhance compressive loading into the surface defects to provide a better bond between the covering and the rail nose portion.
A significant advantage of this invention is that it permits the use of aluminum for forming a guide rail body while still being able to withstand the forces associated with conventional braking applications in elevator systems. Extruding aluminum allows for making the rail into a final shape without requiring any machining for a guiding surface, for example. The ability to mount the rails within a hoistway is enhanced because of the lighter weight of aluminum and the additional ease of installation reduces the cost associated with labor for that portion of installing an elevator system. Further, lighter weight rails enable longer rails to be used, without increasing shipping cost, for example. Longer rail portions reduces the amount of joints along the rail within a building, which enhances system economies and improves the ride quality of the elevator car.
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.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US03/39076 | 12/9/2003 | WO | 5/30/2006 |
