Abstract:
An elevator system includes an elevator car, a motor, and traction sheave operably connected to the motor to drive rotation of the traction sheave. A belt is operably connected to the elevator car and in frictional contact with the traction sheave to urge movement of the elevator car. One or more deflector sheaves are located between the traction sheave and the elevator car over which the belt is routed to guide the belt to the elevator car. The one or more deflector sheaves include an outer sheave surface having a distance from a sheave axis that varies along a width of the traction sheave. The outer surface includes a first portion having a first coefficient of friction and a second portion having a second coefficient of friction less than the first coefficient of friction, the first portion guiding an elevator belt toward a lateral center of the outer surface.

Description:
BACKGROUND 
       [0001]    The subject matter disclosed herein relates to elevator systems driven by coated steel belts. More specifically, the subject disclosure relates to sheave configurations for elevator systems driven by coated steel belts. 
         [0002]    Elevator systems utilize coated steel belts operably connected to an elevator car, and driven by a motor to propel the elevator car along a hoistway. Coated steel belts in particular include a plurality of wires located at least partially within a jacket material. The plurality of wires is often arranged into one or more strands and the strands are then arranged into one or more cords. In an exemplary belt construction, a plurality of cords is typically arranged equally spaced within a jacket in a longitudinal direction. 
         [0003]    The motor drives a sheave, in this case a traction sheave, over which the coated steel belt is routed. The belt gains traction at the traction sheave, such that rotation of the traction sheave consequently drives movement of the elevator car. The coated steel belt is then routed over one or more idler or deflector sheaves to guide the belt between the traction sheave and the elevator car. It is desired for the belt to travel, or track, over a center portion of the deflector sheave to evenly distribute tension in the belt cords and to prevent cords, especially end cords, of the belt from going into compression and buckling. One method to center the belt on the deflector sheave is to incorporate a crown into the sheave surface geometry. A further requirement for the deflector sheave, however, is a low surface coefficient of friction in order reduce sticking or slipping of the belt over the deflector sheave and thereby reducing associated noise. If the deflector sheave coefficient of friction is too low, however, the belt will not have enough lateral traction to climb and remain at the crown. 
       BRIEF DESCRIPTION 
       [0004]    In one embodiment, a deflector sheave for an elevator system includes an outer sheave surface having a distance from a sheave axis that varies along a width of the traction sheave. The outer surface includes a first portion having a first coefficient of friction and one or more second portions having a second coefficient of friction less than the first coefficient of friction, the first portion guiding an elevator belt toward a lateral center of the outer surface. 
         [0005]    Additionally or alternatively in this or other embodiments, the first portion is positioned at a center area of the outer sheave surface relative to the width of the deflector sheave. 
         [0006]    Additionally or alternatively in this or other embodiments, the first portion comprises about 25% to 50% of the width of the traction deflector. 
         [0007]    Additionally or alternatively in this or other embodiments, the first coefficient of friction of the first portion is defined by an abrasive blast applied to the first portion. 
         [0008]    Additionally or alternatively in this or other embodiments, the second coefficient of friction of the one or more second portions is defined by masking the one or more second portions during the abrasive blast operation. 
         [0009]    Additionally or alternatively in this or other embodiments, the first coefficient of friction of the first portion is defined by a coating applied to the first portion. 
         [0010]    Additionally or alternatively in this or other embodiments, the one or more second portions are two second portions. 
         [0011]    Additionally or alternatively in this or other embodiments, each second portion comprises about 25% to 40% of the width of the deflector sheave. 
         [0012]    Additionally or alternatively in this or other embodiments, the second coefficient of friction of the one or more second portions is defined by a coating applied to the one or more second portions. 
         [0013]    Additionally or alternatively in this or other embodiments, the first coefficient of friction is defined by masking the first portion while applying the coating to the one or more second portions. 
         [0014]    Additionally or alternatively in this or other embodiments, the coating is a Teflon nickel coating. 
         [0015]    Additionally or alternatively in this or other embodiments, the first portion and the one or more second portions are formed by machined grooves in the outer surface of the deflector sheave. 
         [0016]    Additionally or alternatively in this or other embodiments, the outer sheave surface has a spherical crown. 
         [0017]    Additionally or alternatively in this or other embodiments, the spherical crown has a radius of between 250 mm and 1000 mm. 
         [0018]    Additionally or alternatively in this or other embodiments, the first coefficient of friction is greater than or equal to 0.1. 
         [0019]    n another embodiment, an elevator system includes an elevator car, a motor, and traction sheave operably connected to the motor to drive rotation of the traction sheave. A belt is operably connected to the elevator car and is in frictional contact with the traction sheave such that rotation of the traction sheave urges movement of the elevator car. One or more deflector sheaves are located between the traction sheave and the elevator car over which the belt is routed to guide the belt to the elevator car. The one or more deflector sheaves include an outer sheave surface having a distance from a sheave axis that varies along a width of the traction sheave. The outer surface includes a first portion having a first coefficient of friction and one or more second portions having a second coefficient of friction less than the first coefficient of friction, the first portion guiding an elevator belt toward a lateral center of the outer surface. 
         [0020]    Additionally or alternatively in this or other embodiments, the first portion is positioned at a center area of the outer sheave surface relative to the width of the deflector sheave. 
         [0021]    Additionally or alternatively in this or other embodiments, the first portion comprises about 25% to 50% of the width of the traction deflector. 
         [0022]    Additionally or alternatively in this or other embodiments, the first coefficient of friction of the first portion is defined by an abrasive blast applied to the first portion. 
         [0023]    Additionally or alternatively in this or other embodiments, the second coefficient of friction of the one or more second portions is defined by masking the one or more second portions during the abrasive blast operation. 
         [0024]    Additionally or alternatively in this or other embodiments, the first coefficient of friction of the first portion is defined by a coating applied to the first portion. 
         [0025]    Additionally or alternatively in this or other embodiments, the one or more second portions are two second portions. 
         [0026]    Additionally or alternatively in this or other embodiments, each second portion comprises about 25% to 40% of the width of the deflector sheave. 
         [0027]    Additionally or alternatively in this or other embodiments, the second coefficient of friction of the one or more second portions is defined by a coating applied to the one or more second portions. 
         [0028]    Additionally or alternatively in this or other embodiments, the first coefficient of friction is defined by masking the first portion while applying the coating to the one or more second portions. 
         [0029]    Additionally or alternatively in this or other embodiments, the coating is a Teflon nickel coating. 
         [0030]    Additionally or alternatively in this or other embodiments, the first portion and the one or more second portions are formed by machined grooves in the outer surface of the deflector sheave. 
         [0031]    Additionally or alternatively in this or other embodiments, the outer sheave surface has a spherical crown. 
         [0032]    Additionally or alternatively in this or other embodiments, the spherical crown has a radius of between 250 mm and 1000 mm. 
         [0033]    Additionally or alternatively in this or other embodiments, the first coefficient of friction is greater than or equal to 0.1. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1A  is a schematic of an exemplary elevator system having a 1:1 roping arrangement; 
           [0035]      FIG. 1B  is a schematic of another exemplary elevator system having a different roping arrangement; 
           [0036]      FIG. 1C  is a schematic of another exemplary elevator system having a cantilevered arrangement; 
           [0037]      FIG. 2  is a cross-sectional view of an elevator belt; 
           [0038]      FIG. 3  is a cross-sectional view of a cord or rope; 
           [0039]      FIG. 4  is a view of an embodiment of a deflector sheave for an elevator system; 
           [0040]      FIG. 5  is a view of another embodiment of a deflector sheave for an elevator system; and 
           [0041]      FIG. 6  is a view of yet another embodiment of a deflector sheave for an elevator system. 
       
    
    
       [0042]    The detailed description explains the invention, together with advantages and features, by way of examples with reference to the drawings. 
       DETAILED DESCRIPTION 
       [0043]    Shown in  FIGS. 1A, 1B and 1C  are schematics of exemplary traction elevator systems  10 . Features of the elevator system  10  that are not required for an understanding of the present invention (such as the guide rails, safeties, etc.) are not discussed herein. The elevator system  10  includes an elevator car  12  operatively suspended or supported in a hoistway  14  with one or more belts  16 . The one or more belts  16  interact with one or more deflector sheaves  18  to be routed around various components of the elevator system  10 . The one or more belts  16  could also be connected to a counterweight  22 , which is used to help balance the elevator system  10  and reduce the difference in belt tension on both sides of the traction sheave during operation. It is to be appreciated that while the embodiments herein are described as applied to coated steel belts, it is to be appreciated that the disclosure herein may similarly be applied to steel ropes, either coated or uncoated. 
         [0044]    The deflector sheaves  18  each have a diameter  20 , which may be the same or different than the diameters of the other deflector sheaves  18  in the elevator system  10 . At least one of the sheaves could be a traction sheave  24 . The traction sheave  24  is driven by a machine  26 . Movement of the traction sheave  24  by the machine  26  drives, moves and/or propels (through traction) the one or more belts  16  that are routed around the traction sheave  24 . 
         [0045]    In some embodiments, the elevator system  10  could use two or more belts  16  for suspending and/or driving the elevator car  12 . In addition, the elevator system  10  could have various configurations such that either both sides of the one or more belts  16  engage the one or more deflector sheaves  18  (such as shown in the exemplary elevator systems in  FIGS. 1A, 1B or 1C ) or only one side of the one or more belts  16  engages the one or more sheaves  18 . 
         [0046]      FIG. 1A  provides a 1:1 roping arrangement in which the one or more belts  16  terminate at the car  12  and counterweight  22 .  FIGS. 1B and 1C  provide different roping arrangements. Specifically,  FIGS. 1B and 1C  show that the car  12  and/or the counterweight  22  can have one or more deflector sheaves  18  thereon engaging the one or more belts  16  and the one or more belts  16  can terminate elsewhere, typically at a structure within the hoistway  14  (such as for a machineroomless elevator system) or within the machine room (for elevator systems utilizing a machine room). The number of deflector sheaves  18  used in the arrangement determines the specific roping ratio (e.g., the 2:1 roping ratio shown in  FIGS. 1B and 1C  or a different ratio).  FIG. 1C  also provides a cantilevered type elevator. The present invention could be used on elevator systems other than the exemplary types shown in  FIGS. 1A, 1B and 1C . 
         [0047]      FIG. 2  provides a schematic of a belt construction or design. Each belt  16  is constructed of a plurality of wires  28  (e.g. twisted into one or more strands  30  and/or cords  32  as shown in  FIG. 3 ) in a jacket  34 . As seen in  FIG. 2 , the belt  16  has an aspect ratio greater than one (i.e. belt width is greater than belt thickness). The belts  16  are constructed to have sufficient flexibility when passing over the one or more deflector sheaves  18  to provide low bending stresses, meet belt life requirements and have smooth operation, while being sufficiently strong to be capable of meeting strength requirements for suspending and/or driving the elevator car  12 . The jacket  34  could be any suitable material, including a single material, multiple materials, two or more layers using the same or dissimilar materials, and/or a film. In one arrangement, the jacket  34  could be a polymer, such as an elastomer, applied to the cords  32  using, for example, an extrusion or a mold wheel process. In another arrangement, the jacket  34  could be a woven fabric that engages and/or integrates the cords  32 . As an additional arrangement, the jacket  34  could be one or more of the previously mentioned alternatives in combination. 
         [0048]    The jacket  34  can substantially retain the cords  32  therein. The phrase substantially retain means that the jacket  34  has sufficient engagement with the cords  32  to transfer torque from the machine  26  through the jacket  34  to the cords  32  to drive movement of the elevator car  12 . The jacket  34  could completely envelop the cords  32  (such as shown in  FIG. 2 ), substantially envelop the cords  24 , or at least partially envelop the cords  32 . 
         [0049]    An exemplary deflector sheave  18  is shown in  FIG. 4 . A sheave outer surface  38  includes a crown, in some embodiments a spherical crown, such that a sheave radius  40  from a sheave axis  42  to the sheave outer surface  38  is greater at a sheave center  44  of the deflector sheave  18  than at either sheave end  46  of the deflector sheave  18 . The crown configuration aids the belt  16  in being substantially centered on the sheave outer surface  38  between sheave ends  46 . As stated above, however, the crown of the deflector sheave  18 , in some embodiments a crown radius between 250 mm and 1000 mm, and the desire for low coefficient of friction of the deflector sheave  18  makes it difficult for the belt  16  to climb the crown of the deflector sheave  18  and remain centered. 
         [0050]    The deflector sheave  18  is uniquely configured to address the problems noted with prior art deflector sheaves. The deflector sheave  18  includes a high friction zone  48  and one or more low friction zones  50 , with the high friction zone  48  characterized as having a higher coefficient of friction than the low friction zones  50 . The high friction zone  48  is located, for example, around the sheave center  44  of the deflector sheave  18 , and in some embodiments includes about a center 25% to 50% of the sheave outer surface  38 . The high friction zone  48  is treated by abrasive blasting or other surface treatment or coating to provide a high friction surface to effectively guide the deflector sheave  18  up the crown of the deflector sheave  18 . The low friction zones  50  are located, for example, outboard of the high friction zone  48  and extend to the sheave ends  46 , and in some embodiments include about the outer 25% to 40% of the sheave outer surface  38 . The low friction zones  50  are characterized by having a lower coefficient of friction than the high friction sheave  48 . The lower coefficient of friction in the low friction zones  50  is achieved by, in some embodiments, applying a reduced-friction coating to the low friction zones  50 , for example, a Teflon nickel coating, an electroless nickel coating, a thin dense chrome coating, or a low friction plasma coating. In other embodiments, the lower coefficient of friction in the low friction zones  50  is achieved by masking the low friction zones  50  during the abrasive blast operation on the high friction zone  48 . It is to be appreciated that lower coefficient of friction in the low friction zones  50  may further be achieved via other means, for example, by the use of different materials to form the low friction zones  50 , relative to the high friction zone  48 . In some embodiments, the high friction zones  48  are defined as having a coefficient of friction greater than or equal to 0.1, while low friction zones  50  are defined as those having a coefficient of friction of less than 0.1. 
         [0051]    Referring now to  FIG. 5 , in some embodiments, the deflector sheave  18  includes two or more high friction zones  48  arranged as bands in the deflector sheave  18  outer surface  38 . Further, in other embodiments, as shown in  FIG. 6 , grooves  52  are formed in the outer surface  38  by, for example, machining. In some embodiments, the grooves  52  are as wide as a cord  32  of the belt  16 , are may be as small in width as 0.1 mm. A depth of the grooves  52  is determined by a depth required to introduce friction at edges of the grooves  52  between the edges of the grooves  52  and the belt  16 . In some embodiments, the groove depth, measured as a radial difference between a groove peak and a groove valley is between 0.1 mm and 1.0 mm. In other embodiments, the depth is between 0.25 mm and 0.5 mm. The groove peak may be positioned either radially above, below or at the outer surface  38 . In embodiments where the peak of the groove  52  is above or below the outer surface  38 , a radial distance between the peak and the outer surface is about 0.1 mm maximum to maintain tension balance of the belt  16 . 
         [0052]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.