Patent Abstract:
The present invention is directed to an elevator system. The elevator system comprises a car, a counterweight, at least one belt connecting the car and counterweight, and at least one sheave having a surface that engages with the belt. At least part of the surface of the sheave that interfaces with the belt has a plurality of features for reducing unwanted noise created due to the interaction between the belt and the sheave surface.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention generally relates to systems in which a belt interacts with a pulley (some technologies refer to pulleys as sheaves). More particularly, this invention relates to systems, such as lifting devices or power transmission devices (e.g. drive belts) in which the interaction between the belt and the pulley may produce undesired noise. 
         [0002]    Elevator systems are one example of the aforementioned lifting devices. Some elevator systems are traction elevator systems that use one or more belts to support and/or provide a lifting force to the elevator car and/or the counterweight. The belts can comprise a plurality of tension members, such as cords formed from steel wire, within a jacket, such as a polymer. The belts route around one or more sheaves of the elevator system, typically made of metal, to perform these functions. 
         [0003]    These elevator systems rely upon sufficient traction between a sheave driven by the elevator machine (referred to as a drive sheave and/or traction sheave) and the belt for several reasons. First, sufficient traction ensures that the belt moves along with the drive sheave during rotation of the drive sheave by the elevator machine in order to achieve the desired movement of the car and/or counterweight. Second, sufficient traction ensures that the belt does not move relative to the drive sheave when the drive sheave is not rotating in order to keep the elevator car at a desired position (e.g. when the elevator car is at a landing). 
         [0004]    These elevator systems may also include one or more other sheaves that help guide the belt around various components of the elevator system in a desired arrangement (referred to as deflector sheaves, idler sheaves and/or diverter sheaves). 
         [0005]    Under certain conditions, the belt could slip relative to the sheave. This slip condition could produce an undesired noise. The undesired noise could be airborne (e.g. travelling through the air in the hoistway) or structure borne (e.g. travelling along the belt to other components of the elevator system). 
         [0006]    A variety of approaches have been proposed for reducing or eliminating such noise. Most of those efforts have focused on the belt. Exemplary approaches include using a different jacket material, adjusting the wax content in the jacket material, or periodically conditioning the installed belt (e.g. applying a wax to the jacket). 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is directed to an elevator system. According to one aspect of the invention, the elevator system comprises a car, a counterweight, at least one belt connecting the car and counterweight, and at least one sheave having a surface that engages with the belt. At least part of the surface of the sheave has a plurality of features that reducing unwanted noise created by the interacted between the surface and the belt. 
         [0008]    Alternatively or in addition to this or other aspects of the invention, the plurality of features on the surface of the sheave is made up of either indentations, projections or a combination thereof. 
         [0009]    Alternatively or in addition to this or other aspects of the invention, wherein the coverage ratio of the plurality of features is in the range of 20 to 80 percent. 
         [0010]    Alternatively or in addition to this or other aspects of the invention, the angular spacing between each of the plurality of features ranges between 3 and 5 degrees of the central angle of the sheave. 
         [0011]    Alternatively or in addition to this or other aspects of the invention, the plurality of features, specifically indentations and/or projections, on the surface of the sheave are identical. 
         [0012]    Alternatively or in addition to this or other aspects of the invention, the plurality of features are arranged randomly. 
         [0013]    Alternatively or in addition to this or other aspects of the invention, the plurality of features are arranged in a pattern. 
         [0014]    Alternatively or in addition to this or other aspects of the invention, the sheave is a deflector sheave in an elevator system. 
         [0015]    Alternatively or in addition to this or other aspects of the invention, the plurality of features produces a pressure distribution at the interface between the surface of the sheave and the belt. The pressure distribution has regions with a first pressure and regions with a second pressure. The second pressure is lower than the first pressure. 
         [0016]    Alternatively or in addition to this or other aspects of the invention, the region of second pressure is in the ranges from 0 to about 50% of the first pressure. 
         [0017]    According to another aspect of the invention, a pulley comprises a surface for engaging with a belt and a means for reducing unwanted noise caused by the interaction between the surface and said belt. 
         [0018]    According to another aspect of the invention, a pulley comprises a surface for engaging with a belt and a plurality of features on said surface for reducing unwanted noise created from the interaction between the surface and the belt. 
         [0019]    Alternatively or in addition to this or other aspects of the invention, the pulley is a deflector sheave, also referred to as an idler sheave, in an elevator system. 
         [0020]    According to another aspect of the invention, a method for reducing unwanted noise at the interface of a pulley and a belt comprising providing a pulley with at least one surface that engages with a belt, and providing a plurality of features of said surface. 
         [0021]    Alternatively or in addition to this or other aspects of the invention, the plurality of features comprises indentations, projections, or a combination thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  schematically shows an exemplary elevator system including a sheave designed according to this invention. 
           [0023]      FIG. 2  is a perspective, diagrammatic illustration of an example of a sheave designed according to this invention. 
           [0024]      FIG. 3A  is a magnified illustration of the section of the sheave indicated in  FIG. 2  showing one possible embodiment of the sheave surface. 
           [0025]      FIG. 3B  is a magnified illustration of the section of the sheave indicated in  FIG. 2  showing another possible embodiment of the sheave surface. 
           [0026]      FIG. 3C  is a magnified illustration of the section of the sheave indicated in  FIG. 2  showing another possible embodiment of the sheave surface. 
           [0027]      FIG. 3D  is a magnified illustration of a portion of the cross-section of the sheave taken along line  3 - 3  of  FIG. 2  showing another possible alternate embodiment of the sheave surface. 
           [0028]      FIG. 3E  is a magnified illustration of the section of the sheave indicated in  FIG. 2  showing another possible alternate embodiment of the sheave surface. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  is a schematic illustration of an exemplary fraction elevator system  20 . Components of the elevator system  20  not relevant to the present invention (e.g. guide rails, controller, safeties etc.) will not be discussed. The elevator system  20  includes an elevator car  11  operatively suspended or supported in a hoistway with at least one belt  13 . The number of belts  13  used in the elevator system  20  is determined by factors not related to the present invention. The one or more belts  13  could also be connected to a counterweight  12  that helps balance the elevator system  20  and maintain belt tension on both sides of a traction sheave  15  (also referred to as a drive sheave) during operation. 
         [0030]    A machine  14  rotates the traction sheave  15 . Since the belts  13  engage the traction sheave  15 , rotation of the traction sheave  15  moves the belts  13  thus moving the elevator car  11  and counterweight  12 . 
         [0031]    The schematic illustration of the elevator system  20  in  FIG. 1  includes multiple deflector sheaves  16 ,  17 ,  18  (also referred to as idler sheaves or diverter sheaves). The deflector sheaves could be associated with the car  11  (i.e. deflector sheaves  16 ,  17 ), with the counterweight  12  (i.e. deflector sheaves  18 ), or with the machine  14  or mounting structure of the machine  14  (not shown). Deflector sheaves  16 ,  17 ,  18  guide or direct the belts  13  during movement of the elevator system  20 . Although  FIG. 1  shows an overslung arrangement with the deflector sheaves  16 ,  17  located above the car  11 , the present invention could be used with other arrangements, such as an underslung arrangement with the deflector sheaves  16 ,  17  located below the car  11 . Similarly, although  FIG. 1  shows a 2:1 roping arrangement, the present invention could be used with other roping arrangements. The deflector sheaves  16 ,  17 ,  18  generally act to guide the belts  13  without requiring traction between those sheaves and the belts  13 . 
         [0032]      FIG. 2  shows an exemplary sheave  19  representative of any one or more of the sheaves in contact with one or more of the belts  13  in an elevator system. In other words, the sheave  19  could be a deflector sheave  16 ,  17 ,  18  and/or a traction sheave  15 . The sheave  19  includes one or more surfaces  21  for engagement with the one or more belts  13 . The sheave  19  could have an equal or greater number of surfaces  21  than the number of belts in the elevator system, or could have one or more surfaces  21  that engage multiple belts  13 . Sheave  19  could have a diameter in the range of between about 50 mm and about 250 mm. 
         [0033]      FIG. 2  shows the sheave  19  having a crowned sheave surface  21  for engaging a generally flat belt  13 . However, the present invention could also be used with other types of sheaves  19  that could engage other types of flat belts. For example, the sheave  19  could have a flat cross section if another means of guidance was utilized. Alternately, the sheave  19  could have circumferential grooves in the sheave surface  21  to accommodate the ribs of a so-called “poly-V” belt  13 . 
         [0034]    Sheave  19  includes an arrangement of geometric features on the sheave surface  21 . In one alternative, the features populate the entire circumference of the sheave surface  21  (the circumferential direction also being the rotation direction of the sheave  19 ) which enable or allow localized relaxation of strain energy in the jacket material as the jacket passes over the sheave. In the axial direction (i.e. along the length of the sheave  19 ), the features can populate the entire sheave surface  21  or just a portion of sheave surface  21 . In one alternative, the features can reside on the portion of the sheave surface  21  that the belt  13  may contact during operation of the elevator system  20 . In other words, the features need not be applied to portions of the sheave surface  21  that will not contact the belt  13  during operation of the elevator system  20 . 
         [0035]    Generally speaking, the features on the sheave  19  are designed and/or arranged to affect the interaction between the belt  13  and the sheave  19 . The features on the sheave  19  help mitigate the effects of strain energy buildup by enabling local surface slip between the belt  13  and the sheave  19 . Without these features on the sheave  19 , the build-up of strain energy caused by shear between the belt  13  and the sheave  19  results in a stick-slip behavior which could produce structure-borne noise, by generation of an impulse that travels longitudinally along the length of the belt  13  and propagates through the elevator system  20 , and/or airborne noise. 
         [0036]    The features on the sheave  19  could be indentations and/or projections  22 . In other words, the sheave  19  could have all indentations, all projections or a combination of indentations and projections. The indentations/projection  22  may have any suitable shape, including but not limited to any of the following individually or in combination: circles, ovals, triangles, rectangles, hexagons, and trapezoids, straight lines, and wavy lines. An indentation/projection  22  may be identical to one or more of the other indentations/projections  22  on the sheave  19 , have the same shape (but a different size) as one or more of the other indentations/projections  22  on the sheave  19 , or have a different shape than the other indentations/projections  22  on the sheave  19 . 
         [0037]    The features on the sheave  19  could be arranged in a regular pattern, such as the exemplary rectilinear possibility shown in  FIG. 3A  or a curvilinear arrangement (e.g. a helicoid). Alternatively, the features could be arranged in an irregular pattern, namely a pattern that is non-uniform and/or non-symmetric, such as the one exemplary possibility shown in  FIG. 3B . Even further alternatively, the irregular pattern could be a random pattern, such as the one exemplary possibility shown in  FIG. 3C . 
         [0038]    The features on the sheave  19  could be discrete, such as the exemplary arrangements of  FIGS. 3A ,  3 B and  3 C. In other words, the features could be spaced apart so as to be discontinuous in the circumferential and axial direction of the sheave  19 . Alternatively, the features on the sheave  19  could be continuous in the circumferential and/or axial direction of the sheave  19 .  FIGS. 3D and 3E  show two possible arrangements of this alternative. In  FIG. 3D , the sheave  19  includes indentations  22   i  immediately adjacent to projections  22   p  so as to produce a continuously wavy sheave surface  21 . In  FIG. 3E , an indentation/projection  22  is continuous in the circumferential direction of the sheave  19  (i.e. the indention/projection is now a groove/rib  22 ). The groove/rib  22  could alternatively be continuous in the axial direction of the sheave  19 . In either event, the groove/rib  22  need not be rectilinear—the groove/rib  22  could be curvilinear (e.g. wavy). As will become more clear below, grooves such as those described with reference to  FIG. 3E  are not intended to receive the belt (or a feature of the belt, such as a rib of a poly-V type belt) for guidance and/or for providing traction. 
         [0039]    Various techniques could be used (individually or in combination) to provide the indentations/projections  22  to the sheave  19 . For example, mechanical techniques (e.g. machining, peening) and/or chemical techniques (e.g. etching) could be used to form the indentations into and/or projections from the sheave surface  21 . 
         [0040]    Another alternative or additional technique to provide the indentations/projections  22  to the sheave  19  to enable local relaxation of strain energy involves placing over all or part of the sheave surface  21  a secondary material, such as an adhesive tape or ring. In one possibility, discrete pieces of tape or rings, for example made from a low friction material such as polytetrafluroethylene, are applied to the sheave surface  21  (i.e. forming the projections). In another possibility (similar to a stencil template), tape having apertures therein is applied to the sheave surface  21 . In yet another possibility, tape including both the indentations and projections is applied to the sheave surface  21 . In another possibility, paint is applied to the sheave surface  21  with a mask to create a pattern of projections  22 . 
         [0041]    The features on the sheave  19  can have various attributes (e.g. depth/height, length, width, spacing, etc.). These attributes may depend on other attributes either directly (e.g. the width of a circular indentation equals the length) or indirectly (e.g. the depth of an indentation may be limited by the length/width of the indentation), and may depend on other aspects of the elevator system (e.g. wrap angle, belt jacket material, roping arrangement, elevator loading, belt speed, etc.). In light of these other elevator system aspects, the various attributes of the features are selected to achieve the desired effect on the interaction between the belt  13  and the sheave  19 . In other words, these various attributes of the features are chosen to reduce unwanted noise at the interaction between the belt  13  and the sheave  19 . 
         [0042]    In one implementation, the depth of the indentation  22  should be sufficient so that the belt  13 , during operation of the elevator system, does not contact the surface of the indentation  22 . In other words, a gap should exist between the belt  13  and the indentation. As an example, a 150 mm diameter sheave that engages a 30 mm wide belt with a thermoplastic polyurethane jacket could have an indentation  22  with a depth of greater than about 30 μm (microns). Alternatively, contact with the surface of the indentation can occur if the local pressure is insufficient to prevent local slip and therefore allow relaxation. 
         [0043]    The height of the projection  22  should be sufficient to lift adjacent sections of the belt  13  from the sheave surface, during operation of the elevator system, to enable relaxation of the strain energy. Alternatively, the contact pressure in these sections adjacent to projections  22  should be low enough to allow local slip and relaxation to dissipate strain energy to inhibit impulse generation. As an example, a 100 mm diameter sheave that engages a 30 mm wide belt with a thermoplastic polyurethane jacket could have a projection  22  with a height of 20-100 microns. In one embodiment, the height may range from approximately 20 to 30 microns. 
         [0044]    The width w (see  FIG. 3A ) of the indentation/projection  22  should have a minimum value such that the indentation/projection  22  alters the interaction between the belt  13  and the sheave  19 . The width w of the indentation/projection  22  should also have maximum value, for example at a point where further incremental changes to width w no longer impact the interaction between the belt  13  and the sheave  19  or where the indentation/projection  22  begins to affect negatively the elevator system (e.g. increased belt wear, additional acoustic noise, etc.). As an example, a 100 mm diameter sheave that engages a 30 mm wide belt with a thermoplastic polyurethane jacket could have an indentation  22  with a minimum width w in the range of between about 1 mm and about 2 mm and a maximum width w in the range of between about 5 mm and about 6 mm. 
         [0045]    Similarly, the length l (see  FIG. 3A ) of the indentation/projection  22  should have a minimum value such that the indentation/projection  22  alters the interaction between the belt  13  and the sheave  19 . The length l of the indentation/projection  22  should also have maximum value, for example at a point where further incremental changes to length l no longer impact the interaction between the belt  13  and the sheave  19  or where the indentation/projection  22  begins to affect negatively the elevator system (e.g. increased belt wear, additional acoustic noise, etc.). As an example, a 100 mm diameter sheave that engages a 30 mm wide belt with a thermoplastic polyurethane jacket could have an indentation  22  with a minimum length l in the range of between about 1 mm and about 2 mm and a maximum length l in the range of between about 5 mm and 6 mm. 
         [0046]    The spacing between indentations/projections  22  could be described in several ways. A first possibility of describing spacing is using the distance between adjacent indentations/projections  22 . As an example, a 100 mm diameter sheave that engages a 30 mm wide belt with a thermoplastic polyurethane jacket and having 2.5 mm circular indentations/projections  22  could have a spacing in the axial direction Sa (see  FIG. 3A ) in the range of between about 2.5 mm and about 7.5 mm between centers of adjacent indentations/projections  22 , and a spacing in the circumferential direction Sc (see  FIG. 3A ) in the range of between about 2.5 mm and about 7.5 mm between centers of adjacent indentations/projections  22 . The axial spacing of the indentations/projections  22  can be different than, or the same as, the circumferential spacing of the indentations/projections  22 . This first possibility of describing spacing can be suitable for example with a regular pattern of features such as the exemplary arrangement shown in  FIG. 3A . 
         [0047]    A second possibility of describing spacing is using angular distance. As an example, a 100 mm diameter deflector sheave that engages a 30 mm wide belt with a thermoplastic polyurethane jacket could have an angular spacing between the indentations/projections  22  along the circumference of the sheave  19  in the range of between about 3° and about 5° of the central angle of the sheave  19 . That means, for example with sheaves having a wrap angle of about 90° (e.g. deflector sheaves  16 ,  17  in  FIG. 1 ) the belt  13  could contact between about 18 to about 30 features along the circumference of the sheave  19  at any given time. With sheaves having a wrap angle of about 180° (e.g. deflector sheave  18  or traction sheave  15  in  FIG. 1 ) the belt  13  could contact between about 36 to about 60 features along the circumference of the sheave  19  at any given time. 
         [0048]    A third possibility of describing spacing is using the coverage ratio of the indentations/projections  22 . The phrase “coverage ratio” means the ratio of the projected area of the indentations/projections  22  to the total area of the sheave surface  21  receiving such indentations/projections  22  (which, depending on the specific alternative used, could be the entire sheave surface  21 , the one or more contact areas, or just a portion of the one of more contact areas). As an example, a 100 mm diameter sheave that engages a 30 mm wide belt with a thermoplastic polyurethane jacket could have a coverage ratio in the range of between about 20% and about 80%. In one alternative of this example, the coverage ratio could be about 50%. This third possibility of describing spacing can be suitable for example with irregular patterns (e.g. non-uniform, non-symmetric and/or random) such as the exemplary arrangements shown in  FIGS. 3B ,  3 C and  3 D. 
         [0049]    As discussed above, the features on the sheave  19  affect the interaction between the belt  13  and the sheave  19 . At the interface between the belt  13  and sheave  19 , the features create regions of lower pressure and regions of higher pressure. The difference between “lower” pressure and “higher” pressure should be significant enough to produce a desired and/or noticeable effect on the interaction between the belt  13  and the sheave  19 . As an example, a “lower” pressure could be in the range of between about 0% and about 50% of the “higher” pressure. 
         [0050]    This pressure distribution dissipates the strain energy caused by slip between the belt  13  and the sheave  19  at multiple locations (i.e. at the boundaries of the lower and higher pressure regions). With the dissipation of strain energy now occurring at multiple locations, there is less build-up of strain energy. This produces less structure-borne noise, since smaller (if any) impulses travel longitudinally along the length of the belt  13  to propagate through the elevator system  20 , and/or airborne noise. As an example, a 100 mm diameter sheave having 2.5 mm circular indentations/projections  22  engaging a 30 mm wide belt with a thermoplastic polyurethane jacket can reduce the amplitude of the impulse by approximately 80% and reduce noise by approximately 12 dB. 
         [0051]    Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited but by the specific disclosure herein, but only by the appended claims.

Technology Classification (CPC): 3