Abstract:
An elevator system includes an elevator car located in a hoistway. One or more belts are operably connected to the elevator car to drive and/or support the elevator car along the hoistway. The one or more belts are routed over one or more sheaves. The one or more sheaves include an outer surface rotatable about a central axis and a flange located at at least one lateral end of the sheave. The sheave further includes a tracking compensator to limit lateral motion of the belt along the outer surface to prevent the belt from contacting the flange.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This continuation application claims priority to International Patent Application No. PCT/US2013/032155 filed on Mar. 15, 2013 and is a continuation of U.S. Non-Provisional Application 14/777,058 filed on Sep. 15, 2015. The content of this application is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The subject matter disclosed herein relates to elevator systems driven by belts. More specifically, the subject disclosure relates sheave configurations from elevator systems driven by belts. 
         [0003]    Elevator systems utilize one or more belts, such as 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. 
         [0004]    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 system may further include other sheaves around which the coated steel belts are routed to change direction of the coated steel belt. In some systems, the roping arrangement of belts is such that sheaves are used to rotate or twist the belts as required. For example, as shown in  FIG. 9 , is a single belt  100  system the sheaves  102  may be arranged as shown such that a pure twist of the belt  100  is achieved, with no draw of the belt  100  between sheaves  102 . Referring now to  FIG. 10 , in systems with multiple, parallel belts  100 , for example, two belts  100 , the sheave  102  arrangement imparts draw, as well as twist between the sheaves  102 . The arrangement produces pure twist in one belt  100 , while also producing twist and draw in the other belt  100 . The draw results in tracking problems for the belt  100 , causing the belt to move laterally on a sheave crown  104  and hit flanges  106  of the sheave. This causes excessive wear on the belt  100 , especially at edges thereof, and also causes belt-sheave noise and uneven stress on the belt  100  which leads to premature belt  100  failure. 
         [0005]    Further, in some systems, one sheave pair  108  is at a fixed location in the hoistway, while the other sheave pair  110  is located at an elevator car. As the elevator car moves in the hoistway, the distance between sheave pairs  108  and  110  changes, so that the draw angle also changes. For example, as the sheave pairs  108  and  110  move closer together, the draw angle increases, Tracking deviation is therefore not constant, and becomes more severe as the sheave pairs  108  and  110  move closer together. 
       BRIEF DESCRIPTION 
       [0006]    In one embodiment, an elevator system includes an elevator car located in a hoistway. One or more belts are operably connected to the elevator car to drive and/or support the elevator car along the hoistway. The one or more belts are routed over one or more sheaves. The one or more sheaves include an outer surface rotatable about a central axis and a flange located at at least one lateral end of the sheave. The sheave further includes a tracking compensator to limit lateral motion of the belt along the outer surface to prevent the belt from contacting the flange. 
         [0007]    In this or other embodiments, the tracking compensator comprises an asymmetrical crown on the outer surface of the sheave. 
         [0008]    In this or other embodiments, a first sheave radius at a first lateral end of the sheave is greater than a second sheave radius at a second lateral end of the sheave. 
         [0009]    In this or other embodiments, the belt travels at substantially a lateral center of the sheave. 
         [0010]    In this or other embodiments, the one or more belts are two or more belts. 
         [0011]    In this or other embodiments, the plurality of sheaves are arranged in sheave groups each sheave of a sheave group guiding a separate belt of the two or more belts. 
         [0012]    In this or other embodiments, wherein each sheave of a sheave group includes an asymmetrical crown on the outer surface of the sheave such that a first sheave radius at a first lateral end of the sheave is greater than a second sheave radius at a second lateral end of the sheave. 
         [0013]    In this or other embodiments, wherein a direction of crown of a first sheave of the sheave group is substantially the same as a direction of crown of a second sheave of the sheave group. 
         [0014]    In this or other embodiments, a first central axis of a first sheave of the sheave group intersects a second central axis of a second sheave of the sheave group at a sheave angle. 
         [0015]    In this or other embodiments, wherein the sheave angle is configured to normalize a stress distribution on the belts. 
         [0016]    In this or other embodiments, wherein the first sheave and the second sheave are connected by a steered shaft to have a same rotational speed. 
         [0017]    In another embodiment, an elevator system includes an elevator car located in a hoistway and two or more belts operably connected to the elevator car to drive and/or support the elevator car along the hoistway. The system further includes a plurality of sheave groups over which the two or more belts are routed. Each sheave of a sheave group includes an outer surface rotatable about a central axis and a flange located at at least one lateral end of the sheave. The sheave further includes a tracking compensator to limit lateral motion of the belt along the outer surface to prevent the belt from contacting the flange. 
         [0018]    In this or other embodiments, the two or more belts twist and draw between a first sheave group and a second sheave group. 
         [0019]    In this or other embodiments, a draw angle of a first belt of the two or more belts is equal to a draw angle of a second belt of the two or more belts. 
         [0020]    In this or other embodiments, the elevator system has a 4:1 roping arrangement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a schematic of an embodiment of an elevator system having a 4:1 roping arrangement; 
           [0022]      FIG. 2  is a cross-sectional view of an elevator belt; 
           [0023]      FIG. 3  is a cross-sectional view of a cord or rope; 
           [0024]      FIG. 4  is a perspective view of an embodiment of a sheave arrangement for an elevator system; 
           [0025]      FIG. 5  is an illustration of a prior art sheave; 
           [0026]      FIG. 6  is an illustration of an embodiment of an asymmetrically crowned sheave for an elevator system; 
           [0027]      FIG. 7  is an illustration of an embodiment of an asymmetrically crowned sheave pair for an elevator system; 
           [0028]      FIG. 8  is an illustration of another embodiment of a sheave pair for an elevator system; 
           [0029]      FIG. 9  is an illustration of a prior art sheave arrangement for a single belt elevator system; and 
           [0030]      FIG. 10  is an illustration of a prior art sheave arrangement for a two-belt elevator system. 
       
    
    
       [0031]    The detailed description explains the invention, together with advantages and features, by way of examples with reference to the drawings. 
       DETAILED DESCRIPTION 
       [0032]    Shown in  FIG. 1  is a schematic of an embodiment of a traction elevator system  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 two or more belts  16 . The arrangement shown is referred to a 4:1 roping arrangement, though the structure disclosed herein may be utilized in elevator systems  10  having other roping arrangements. In the system of  FIG. 1 , a first belt  16   a  and a second belt  16   b  extend from a traction sheave  18  which is driven by a machine  20 . The first belt  16   a  and the second belt  16   b  support the elevator car  12  via support sheave pairs  22  secured to the elevator car  12 , for example, at a car bottom  24 . The support sheave pairs  22  comprise support shaves  22   a  and  22   b , which are coaxial in their rotation. The system of  FIG. 1  includes two sheave pairs  22  to transfer the first belt  16   a  and the second belt  16   b  under and across the elevator car  12  from a drive side  26  of the hoistway  14  (the side closest to the machine  20 ) to a non-drive side  28  of the hoistway  14  (the side furthest from the machine  20 ). 
         [0033]    The first belt  16   a  and second belt  16   b  are extended from the support sheave pairs  22  up and around a transfer sheave pair  30  comprising a first transfer sheave  30   a  and a second transfer sheave  30   b.  The transfer sheave pair  30  is secured at a fixed position in the hoistway  14 , for example at or near a top  32  of the hoistway  14 . Due to the orientation of the transfer sheave pair  30 , it is necessary for the first belt  16   a  and second belt  16   b  to twist, in some embodiments about 90 degrees, between the support sheave pair  22  and the transfer sheave pair  30 . More detail regarding the twist of belts  16   a ,  16   b , and the configuration of transfer sheaves  30   a  and  30   b  will be provided below. The first belt  16   a  and second belt  16   b  are routed over a second transfer sheave pair  30  and down the hoistway  14  to another support sheave pair  22  at the car bottom  24 , between which the first belt  16   a  and second belt  16   b  twist again to match the orientation of the support sheave pair  22 . The belts  16   a  and  16   b  pass under the elevator car  12  from the non-drive side  28  to the drive side  26  then up the hoistway  14  to a termination point. 
         [0034]    In some embodiments, as shown in  FIG. 2 , the belts  16   a  and  16   b  are coated steel belts. Each belt  16  is constructed of a plurality of wires  36  (e.g. twisted into one or more strands  38  and/or cords  40  as shown in  FIG. 3 ) in a jacket  42 . 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 sheave 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  42  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  42  could be a polymer, such as an elastomer, applied to the cords  40  using, for example, an extrusion or a mold wheel process. In another arrangement, the jacket  42  could be a woven fabric that engages and/or integrates the cords  40 . As an additional arrangement, the jacket  42  could be one or more of the previously mentioned alternatives in combination. 
         [0035]    The jacket  42  can substantially retain the cords  40  therein. The phrase substantially retain means that the jacket  42  has sufficient engagement with the cords  40  to transfer torque from the machine  20  through the jacket  42  to the cords  40  to drive movement of the elevator car  12 . The jacket  42  could completely envelop the cords  40  (such as shown in  FIG. 2 ), substantially envelop the cords  40 , or at least partially envelop the cords  40 . 
         [0036]    Referring to  FIG. 4 , a view looking down the hoistway  14  at transfer sheave pair  30  and support sheave pair  22  is shown. In this embodiment, the transfer sheave pair  30  and the support sheave pair  22  are positioned such that a first draw angle  44   a  of belt  16   a  between support sheave  22   a  and transfer sheave  30   a  is equal and opposite to a second draw angle  44   b  of belt  16   b  between support sheave  22   b  and transfer sheave  30   b.    
         [0037]    Referring now to  FIG. 5 , in a typical prior art system, sheaves  102  are crowned symmetrically between flanges  106  is an effort to guide belts  100  toward a center of the sheave  102 . When twist and/or draw is introduced to the system, however, such as in multi-belt systems, the belts  100  tend to reside and travel on one side of the symmetrically crowned sheave  102 . 
         [0038]    Referring now to the embodiment of  FIG. 6 , shown is an embodiment of first transfer sheave  30   a  and belt  16   a.  It is to be appreciated, however, that the following disclosure may be applied to any of the sheaves and belts in the elevator system  10  to realize the benefit thereof. Since draw in the system  10  causes the belt  16   a  to ride to one side of a peak  46  (where the sheave  30   a  has the largest radius), the sheave  30   a  includes a tracking compensator, in this embodiment an asymmetrical crown  48 , so that peak  46  is not equidistant between flanges  50 , but such that a position where belt  16   a  tends to ride is equidistant between the flanges  50 . This increases a minimum distance between the belt  16   a  and flanges  50  and reduces the likelihood that the belt  16   a  will rub flange  50 , thus preventing excessive wear on the belt  16   a.  The crown shown in  FIG. 6  is a circular crown  48  having a substantially continuous radius, but in other embodiments other crown shapes may be utilized, such as those with multiple radii or polynomial shapes. 
         [0039]    As shown in  FIG. 7 , pairs of asymmetrically crowned sheaves can be utilized to form transfer sheave pairs  30 , and/or support sheave pairs  22 . In embodiments such as those of  FIG. 4 , where transfer sheave pairs  30  and support sheave pairs  30  are arranged such that belts  16   a  and  16   b  have equal and opposite draw angles  44   a  and  44   b , the transfer sheaves  30   a  and  30   b  may be configured to have equal and opposite crown such that belts  16   a  and  16   b  remain substantially centered on transfer sheaves  30   a  and  30   b.  Although not shown, one skilled in the art will readily appreciate that support sheaves  22   a  and  22   b  may similarly have equal and opposite 
         [0040]    In another embodiment, shown in  FIG. 8 , rather than residing on the same linear axis of rotation as in other embodiments, the tracking compensator includes a common jointed or steered shaft  52  about which the first transfer sheave  30   a  and second transfer sheave  30   b  rotate. The steered shaft  52  offsets the transfer sheaves  30   a  and  30   b  such that a sheave angle  54  exists between the first transfer sheave  30   a  and the second transfer sheave  30   b.  In some embodiments, the sheave angle  54  is up to about 10 degrees. The sheave angle  54  normalizes a stress distribution on the belts  16   a  and  16   b  over the first transfer sheave  30   a  and second transfer sheave  30   b.  Normalizing the stress distribution reduces lateral motion of the belts  16   a  and  16   b  at the first transfer sheave  30   a  and the second transfer sheave  30   b  and reduces the likelihood of belts  16   a  and  16   b  impacting and rubbing on flanges  50 . It is to be appreciated that first support sheave  22   a  and second support sheave  22   b  may be similarly configured to normalize stress distribution in the belts  16   a  and  16   b.    
         [0041]    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.