Abstract:
An elevator car assembly includes a car frame, a car connected to the car frame and having a first guide axis between a first side and a second side of the car frame, a plurality of traction members, a first plurality of sheaves rotatably connected to the car frame between the first side and the second side for respectively receiving the plurality of traction members, and a first guide attached to either the car frame or the car below the first plurality of sheaves for movably engaging a first rail. The first guide is aligned with the first guide axis and is configured to be aligned with the first rail. One of the plurality of traction members and the first guide are vertically aligned at the first guide axis.

Description:
BACKGROUND 
     The present invention relates to an elevator system. More particularly, the invention relates to a traction elevator system including a guide axis aligned with a traction member. 
     Traction elevator systems commonly include one or more guide rails running vertically on opposite sides of a hoistway. The guide rails commonly have a T-shaped horizontal cross-section with the top of the T attached to the side of the hoistway and the leg of the T extending into the hoistway toward the elevator car. The guide rails are arranged to guide the elevator car up and down the hoistway. Some traction systems may include a car frame attached to the elevator car. In systems including a car frame, the frame is attached to the car and connected to the guide rails such that the car frame, which rides vertically on the rails, carries the car up and down the hoistway. The connection at the guide rails, either between the car and the guide rails or between the car frame and the guide rails, commonly includes one or more guides, such as rollers or slides, which provide a sliding connection to the guide rails and often include damping devices to improve the ride quality of the elevator car. Some traction elevator systems also include sheaves provided above the car in, for example, a front to back arrangement along the sides of the car adjacent to the guide rails. Traction members, such as belts or ropes, loop around the sheaves and transmit force provided by a drive system, commonly called a hoist machine, to move the elevator car, and in some systems the car frame, up and down the hoistway along the guide rails. 
     Two important design considerations for elevator systems are the weight capacity, sometimes referred to as the duty, of the car and the ride quality of the car. The duty of the elevator car in traction systems depends upon the roping ratio (e.g., 2:1 or 3:1) as well as the number of traction members, for example belts, used to drive the car, and in some cases the car and the car frame. For example, for a given roping ratio, the duty of an elevator car driven by five traction belts is greater than the duty of an elevator car driven by four similar traction belts. Additionally, the ride quality of the elevator car may be related, in part, to the relative position of the traction belts with respect to the car and the path along which the car travels, i.e. the path along the guide rails. 
     In some traction elevator systems in which the sheaves are provided in a front-to-back arrangement along the sides of the top of the car frame, the traction members that engage the sheaves are arranged such that they do not interfere with the guides&#39; interactions with the guide rails. Unfortunately, as a result of the guides&#39; position relative to various traction members, the possibility of providing an additional traction member(s) in the location occupied by the guides is precluded, thereby reducing the duty that the car may otherwise be capable of lifting. Additionally, the position of the guides may prevent aligning one of the traction members with the guide and guide rails, thereby reducing the ride quality of the car. 
     In light of the foregoing, the present invention aims to resolve one or more of the aforementioned issues that afflict such traction elevator systems. 
     SUMMARY 
     The present invention includes an elevator car assembly comprising a car frame, a car connected to the car frame and having a first guide axis between a first side and a second side of the car frame, a plurality of traction members, a first plurality of sheaves rotatably connected to the car frame between the first side and the second side for respectively receiving the plurality of traction members, and a first guide attached to either the car frame or the car below the first plurality of sheaves for movably engaging a first rail. The first guide is aligned with the first guide axis and is configured to be aligned with the first rail. One of the plurality of traction members and the first guide are vertically aligned at the first guide axis. 
     Embodiments of the present invention also include an elevator system comprising a hoistway, one or more rails vertically disposed in the hoistway and respectively defining one or more guide axes, and an elevator car assembly. The elevator car assembly includes a car frame connected to a car and arranged with the one or more guide axes between a first side and a second side of the car frame, a plurality of traction members, a plurality of sheaves rotatably connected to the car frame between the first side and the second side for respectively receiving the plurality of traction members, and one or more guides attached to either the car or the car frame below the plurality of sheaves for respectively movably engaging the one or more rails. The one or more guides are respectively aligned with the one or more guide axes. One of the plurality of traction members is vertically aligned with the one or more guides at the one or more guide axes. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are hereafter briefly described. 
         FIG. 1  is a perspective view of a prior art elevator system. 
         FIG. 2  is a schematic partial side view of a prior art elevator system including an alternative guide and traction member arrangement. 
         FIG. 3  is a schematic partial side view of an embodiment of an elevator system according to the present invention. 
         FIG. 4  is a schematic partial front view of the elevator system of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Efforts have been made throughout the drawings to use the same or similar reference numerals for the same or like components. 
       FIG. 1  is a perspective view of a prior art elevator system  10 , which includes a car  12 , a frame  14 , guide axes  16 , roller guides  18 , sheaves  20 , belts  22 , and guide rails  24 . In  FIG. 1 , the car  12  is connected to the frame  14 . The roller guides  18 , the sheaves  20 , and the belts  22  are connected to the top  13  of the frame  14 . The roller guides  18  are connected to the top  13  of the frame  14  above the sheaves  20 . The sheaves  20 , which are positioned between a front, first side  15  and a second, rear side  17  of the car frame  14 , are rotatably connected to the top  13  of the frame  14  below the roller guides  18 . The belts  22 , which are looped under the sheaves  20  on top  13  of the frame  14 , travel below the top  13  of the frame  14  from a right, third side  19  to a left, fourth side  21  of the car frame  14  on opposite sides of the roller guides  18 . The third and fourth sides  19 ,  21  of the car frame  14  are respectively provided adjacent opposite sides of a hoistway to which hoistway sides are attached the guide rails  24 . The guide rails  24  run the length of the hoistway and are centered along the respective guide axes  16 . The roller guides  18  are movably connected to the guide rails  24  to guide the car  12  and the frame  14  up and down the hoistway. The sheaves  20  and the belts  22  are arranged on opposite sides of the roller guides  18 , which are adjacent the sides of the hoistway to which are attached the guide rails  24 . The belts  22  transmit force provided by a drive system (not shown), for example a hoist machine, to move the car  12  and the frame  14  up and down the hoistway along the guide rails  24 . 
     In  FIG. 1 , none of the four sheaves  20  or four belts  22  is aligned with the guide axes  16 , and thereby none of the sheaves  20  or belts  22  is aligned with the roller guides  18 . Rather, the sheaves  20  and the belts  22  are arranged on opposite sides of the guide axes  16  toward the front  15  and back  17  of the car frame  14 . 
       FIG. 2  is a schematic side view of one side of an alternate prior art elevator system  26 , which includes an alternative guide and traction member arrangement. In  FIG. 2 , a sliding guide  28 , the sheaves  20 , and the belts  22  are arranged in a line between the front  15  and the back  17  of the car frame  14  and connected to the top  13  of the frame  14 . A traction axis  30  is centrally aligned with one of the three sheaves  20  and one of the three belts  22 . The guide rail  24  runs the length of the hoistway and is centered along a guide axis  32 . The sliding guide  28  is centrally aligned with and movably connected to the guide rail  24 . The guide axis  32  is offset from the traction axis  30 . As a result of the placement of the sliding guide  28 , the number of sheaves  20  and belts  22  which may be used to drive the car  12  in system  26  is limited. Additionally, offsetting the guide axis  32  from the traction axis  30  may act to degrade the ride quality of the car  12  by creating a discontinuity between the path along which the car  12  travels, i.e. the guide axis  32 , and the direction of the force moving the car  12  along this path, i.e. the traction axis  30 . 
       FIG. 3  is a schematic partial side view of one side  19  of an embodiment of an elevator system  34  according to the present invention, which view shows the car  12 , the car frame  14 , a guide axis  16 , a roller guide  18 , sheaves  20 , and belts  22 . In  FIG. 3 , the roller guide  18 , the sheaves  20 , and the belts  22  are connected to the top  13  of the frame  14 . The roller guide  18  is connected to the top  13  of the frame  14  below the sheaves  20 . The sheaves  20  are rotatably connected to the top  13  of the frame  14  above the roller guide  18 . The belts  22  are looped under the sheaves  20  on top  13  of the frame  14  and above the roller guide  18 . 
     In  FIG. 3 , the guide axis  16  may define a vertical center of the car  12 , which is located halfway between, for example, the front  15  and the back  17  of the car frame  14 . The guide axis  16 , and thereby the vertical center of the car  12 , is aligned with the roller guide  18 , which is aligned with and movably engages the guide rail  24  (see  FIG. 4 ). One of the five sheaves  20  and one of the five belts  22  may also be aligned with the guide axis  16 , and thereby with the vertical center of the car  12 . The remaining four of the five sheaves  20  and the remaining four of the five belts  22  may be, as is shown in  FIG. 3 , arranged on opposite sides of the guide axis  16 , and the vertical center of the car  12 , toward the front  15  and back  17  of the car frame  14 . 
       FIG. 4  is a schematic partial front view of the elevator system  34  of  FIG. 3  showing the relative arrangement of the system  34  with respect to the guide rails  24 . As shown in  FIG. 4 , the sides  19 ,  21  of the car frame  14  are adjacent opposite sides  23 ,  25  of a hoistway  27  to which the guide rails  24  are attached. The guide rails  24  run the length of the hoistway  27  and are centered along the guide axes  16 , one of which axes is shown in  FIG. 3 . The roller guides  18  are movably engaged with the guide rails  24  to guide the car  12  and the frame  14  up and down the hoistway  27 . Arranging the roller guides  18  below the sheaves  20  and the belts  22 , as shown in the embodiment of  FIGS. 3 and 4 , creates openings at the top  13  of the car frame  14  and the car  12  for at least one additional set of sheaves  20  and a corresponding belt  22  and enables the alignment of one of the belts  22  (and the sheaves  20  that engage the belt  22 ) with the guide axes  16 . 
     Although  FIG. 3  shows a set of five sheaves  20  and a corresponding set of five belts  22 , the number and placement of the sheaves and corresponding belts may vary across different embodiments of the present invention. For example, embodiments of the invention may involve two, three, four, or six or more belts. By way of specific example, one embodiment may include a set of three sheaves on each side  19 ,  21  of the car frame and three belts, with one of the three sheaves in each set and one of the three belts aligned with the guide axes of the car. The two remaining sheaves in each set and the two remaining belts may be arranged on opposite sides of the guide axes of the car, for example, one of the remaining sheaves in each set could be positioned toward the front  15  of the car frame and the other remaining sheaves in each set could be positioned toward the back  17  of the car frame respectively. Embodiments of the present invention also include a car frame and a car guided along guide rails by sliding guides, instead of roller guides. Additionally, the car frame and the car may be pulled up and let down the hoistway by ropes, instead of belts, looped around sheaves connected to the top of the car frame in a position vertically above the guides, e.g., roller guides or sliding guides. 
     Elevator systems according to the present invention provide significant advantages over prior systems by simultaneously increasing the duty and the ride quality of the elevator car. Arranging the guides, such as roller guides or sliding guides, below the sheaves and traction members, for example belts or ropes, at the top of the car allows for placement of a traction member in alignment with the guide axes of the car. Moreover, the additional traction member in alignment with the guide axes facilitates increasing the duty of the elevator car. 
     The aforementioned discussion is intended to be merely illustrative of the present invention and should not be construed as limiting the appended claims to any particular embodiment or group of embodiments. Thus, while the present invention has been described in particular detail with reference to specific exemplary embodiments thereof, it should also be appreciated that numerous modifications and changes may be made thereto without departing from the broader and intended scope of the invention as set forth in the claims that follow. 
     The specification and drawings are accordingly to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims. In light of the foregoing disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope of the present invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.