Patent Publication Number: US-2007107993-A1

Title: Guide rail for an elevator system

Description:
FIELD OF THE INVENTION  
      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.  
     DESCRIPTION OF THE RELATED ART  
      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.  
     SUMMARY OF THE INVENTION  
      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.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  schematically and diagrammatically illustrates selected components of an elevator system designed according to an embodiment of this invention.  
       FIG. 2  is a cross-sectional illustration of an example guide rail embodiment as seen along the lines  2 - 2  in  FIG. 1 .  
       FIG. 3  illustrates a selected portion of the embodiment of  FIG. 2 .  
       FIG. 4  is a cross-sectional illustration similar to that in  FIG. 2  but of an alternative embodiment of a guide rail designed according to this invention.  
       FIG. 5  is a cross-sectional illustration similar to that in  FIG. 2  but of an alternative embodiment.  
       FIG. 6  schematically illustrates, in perspective view, another example cover useful with an embodiment of a guide rail designed according to this invention.  
       FIG. 7  is a cross-sectional illustration similar to that in  FIG. 2 , but showing an embodiment incorporating the cover illustrated in  FIG. 6 .  
       FIG. 8  schematically shows a portion of an example installation process. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 1  schematically shows an elevator system  20  where a car  22  is supported for vertical movement and guided by guide rails  24 . A plurality of mounting brackets  26  secure the guide rails  24  in a desired position within a hoistway (not illustrated) in a known manner.  
      As best appreciated from  FIGS. 2 and 4 , the guide rails  24  are made of two different materials. The body of the guide rail includes a base portion  30  that is adapted to be secured relative to a stationary surface  28  in the hoistway, for example, using the conventional mounting brackets. A nose portion  32  extends away from the base portion  30 . In the example of  FIG. 2 , the guide rail has a T-shaped cross section.  
      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  FIG. 3 , a covering  40  made from a different material than the guide rail body covers over at least a portion of the distal end  36  of the nose portion  32 . In this example, the covering  40  comprises a steel sheet that is formed as a clip that fits over the distal end  36  of the nose portion  32 .  
      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  FIG. 8 , after everything is in place (i.e., the rail body is installed in the hoistway), a robotic tool  100  progresses along the rail, heating the interface and casting the bond between the steel and aluminum while forming to exacting tolerances.  
      As schematically shown in  FIG. 3 , the example rail nose portion  32  includes a plurality of recesses  50  longitudinally spaced along the rail. The covering  40  includes projections  52  that extend at least partially into the recesses to stabilize the covering  40  relative to the end  36  of the nose portion  32 . The projections  52  may be formed by crimping or deforming an appropriate portion of the covering to establish the desired connection.  
       FIG. 4  illustrates another example embodiment where the nose portion  32  extends away from the base portion  30  at an oblique angle. Utilizing aluminum as the material for forming the body of the rail allows for customizing the final shape of the rail without requiring any machining operations, which increases design flexibility and enhances system economies. Possible configurations include a single rail extrusion having car and counterweight guiding portions integrated into a single extrusion. The arrangement of  FIG. 4  provides a guiding surface  34  along which guide rollers  46  travel and a braking surface provided by the covering  40  over the distal end  36  of the nose portion  32 .  
       FIG. 5  illustrates another example arrangement where the nose portion  32  includes a plurality of recesses  50  longitudinally spaced along the rail similar to those shown in  FIG. 3 . In this example, there is no adhesive between the steel cover  40  and the distal end  36  of the nose portion  32 . Instead, in this example, there is a mesh fabric that is made of glass fibers in one example. The fabric layer  60  provides high temperature insulation at the inner face between the covering  40  and the nose portion  32 . The insulating fabric  60  avoids excessive temperature transferred to the aluminum material of the example nose portion  32 .  
      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 .  FIG. 6  shows one example covering  40  that is made of a bent steel sheet. In this example, a plurality of openings  62  are formed in the covering  40 . As can be appreciated from  FIG. 7 , when the bonding agent  42  extends into and effectively fills the openings  62 . In this example, the bonding agent  42  is concrete. Allowing the concrete  42  to extend into the openings  62  provides compressive characteristics for loading to provide a secure bond that withstands breaking forces.  
      In one example designed according to the teachings of  FIGS. 6 and 7 , after the concrete  42  is supplied between the nose portion  32  and the inside of the covering  40 ′, any excess concrete extending out of the holes  62  is wiped off to ensure an appropriately continuous outer surface along the corresponding portion of the guide rail assembly.  
      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.