Abstract:
A drive machine ( 10 ) for elevators has a rotatable drive sheave ( 18 ) that has an inner surface and an outer surface with at least one groove ( 34 ) for receiving a hoist rope. A rotor ( 36 ) is attached to the inner surface of the sheave ( 18 ). A stator ( 38 ) is connected to a fixed hollow shaft ( 22 ), wherein the stator ( 38 ), rotor ( 36 ), and drive sheave ( 18 ) are concentrically positioned about a centerline of the fixed hollow shaft ( 22 ). A plurality of bearings ( 42 ) are placed between the shaft ( 22 ) and rotor ( 36 ).

Description:
BACKGROUND 
       [0001]    The present disclosure relates to elevator drive machines. More specifically, the disclosure relates to elevator drive machines with a rotor attached to a sheave of the drive machine. 
         [0002]    A typical traction elevator system includes a car and a counterweight disposed in a hoistway, a plurality of ropes that interconnect the car and counterweight, and a machine having a traction sheave engaged with the ropes. The drive machine of the traction elevator has a traction sheave with grooves for the hoisting ropes of the elevator and an electric motor driving the traction sheave either directly or through a transmission. The ropes are driven by rotation of the traction sheave that results in repositioning of the car and counterweight within the hoistway. The traction machine, and its associated electronic equipment, along with peripheral elevator components, such as a governor and safety features, are housed in a machine room located adjacent the hoistway. Conventional traction machines make use of alternating current (AC) permanent magnet hoist motors, which have permanent magnets in the rotor in order to improve the efficiency of the machine. The conventional machines, however, are limited to relatively low duty cycles and low speeds. 
         [0003]    The physical dimensions of an elevator drive machine affect the size of the elevator shaft and/or the building itself, depending on where the machine is located. When the machine is placed in or beside the elevator shaft or in a machine room, the size of the machine has an importance with respect to the space required. One of the problems encountered in gearless elevator machines of conventional construction has been their large size and weight. Such motors take up considerable space and are difficult to transport to the site and to install. In large elevator machines, transmitting the torque from the drive motor to the traction sheave can be a problem. These types of machines are large in size, and asymmetrical. This imposes special requirements on the electric drive of the motor to allow full-scale utilization of the motor, and the size of the motor becomes unwieldy. Specialized equipment and large cranes are required for getting such motors in place during construction of structures. Further, the size of the motors and machines and area required might be greater than that of the cross-sectional area of the hoistway of the elevator, again requiring specialized mounting arrangements. Special requirements generally result in a complicated system or a high price, or both. 
         [0004]    Thus there is a need in the art to develop elevator systems that efficiently utilize the available space and meet the duty load and speed requirements over a broad range of elevator applications. Further, there exists a need to have a machine which operates reliably and which is compact, in particular in order to make it easier to install in an elevator shaft. There also exists a need for a machine that is relatively easy to manufacture and versatile in design. 
       SUMMARY 
       [0005]    In one aspect, a drive machine for elevators has a rotatable drive sheave that has an inner surface and an outer surface for receiving a hoist rope. A rotor is attached to the inner surface of the sheave. A stator is connected to a fixed hollow shaft, wherein the sheave and rotor are positioned to rotate about a centerline of the fixed hollow shaft. A plurality of bearings are placed between the shaft and rotor. 
         [0006]    In another aspect, a drive machine for an elevator has a machine frame and a cylinder having a first side, a second side, an inner diameter and an outer diameter with the outer diameter forming a sheave. The machine also has a rotor attached to the inner diameter of the cylinder, a first support structure and second support structure that are attached to the machine frame, and a hollow shaft attached at a first end to the first support structure and at a second end to the second support structure. A stator is attached to the hollow shaft. The cylinder is connected to the shaft through first and second bearings at each respective side of the cylinder, resulting in a motor contained within the cylinder. 
         [0007]    In another aspect, a drive machine for an elevator has a cylinder having a first side, a second side, an inner diameter and an outer diameter with the outer diameter forming a sheave. The machine also has a rotor attached to the inner diameter of the cylinder. A first support structure and second support structure are attached to a hollow shaft. A stator is also attached to the hollow shaft, and a first bearing and a second bearing are connected to each respective side of the cylinder to mount the cylinder to the shaft. Each bearing has a stationary inner race attached to the hollow shaft and a rotating outer race secured to each respective side of the cylinder. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a drive machine for an elevator. 
           [0009]      FIG. 2  is a sectional perspective view of a drive machine for an elevator. 
           [0010]      FIG. 3  is a cross-sectional elevation view of a drive machine for an elevator. 
           [0011]      FIG. 4  is a cross-sectional view of a drive machine for an elevator illustrating cooling air flow through the motor. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]      FIG. 1  is a perspective view of drive machine  10  on frame  12  for an elevator. Drive machine  10  includes cooling system  14 , cylinder  16  with sheave  18 , electrical box  20 , shaft  22 , supports  24   a  and  24   b,  and brake system  26 . Supports  24   a  and  24   b  provide a structure for mounting shaft  22 . Cylinder  16  and sheave  18  are designed to rotate about a central axis of shaft  22 . Cylinder  16  is attached to sheave  18 . Alternatively, cylinder  16  and sheave  18  are a singular structure. Sheave  18  contains grooves for ropes or cables that attach to the elevator car and/or counterweight. Cylinder  16  and sheave  18  are constructed from metals, alloys, and similar materials. 
         [0013]    Supports  24   a  and  24   b  also provide structure for mounting of cooling system  14  and electrical box  20 . Brake system  26  is attached to outer cylinder  16 , and may also be attached to supports  24   a  and  24   b.  Electrical box  20  may be a NEMA or galvanized steel box, and contains the electrical connections, terminals, and controls for drive machine  10 . Electrical wires (not shown) will run from electrical box  20  and connect to a power source to provide the electrical power to run drive machine  10 . Cooling system  14  includes a fluid moving device attached to fluid directing structures, and acts to lower the temperature of the drive machine  10 . 
         [0014]    Braking system  26  is mounted adjacent to cylinder  16 , and may also have components attached to supports  24   a  and  24   b.  Braking system  26  engages cylinder  16  to slow or stop the rotation of cylinder  16  about shaft  22 . 
         [0015]    Frame  12  is fabricated from structural supports  28  and  30 . As illustrated, two structural supports  28  are generally parallel to one another, and are attached to the bottom surfaces of supports  24   a  and  24   b.  Structural support  30  is a cross piece to provide additional structural integrity to frame  12 . Frame  12  elevates drive machine  10  from a surface (for example, the floor of a machine room in a building), and assures that cylinder  16  can freely rotate about shaft  22 . 
         [0016]      FIG. 2  is a sectional perspective view of drive machine  10  on frame  12 . Drive machine  10  includes cooling system  14 , outer cylinder  16  with sheave  18 , electrical box  20 , supports  24   a  and  24   b,  and brake system  26 , which have been previously described. In this view, cylinder  16  has centrally located side portions  32  and outer disc  17  extending therefrom. Side portions and outer disc  17  may be fabricated a single part, or may be separate parts joined together. Outer disc  17  may be steel, cast iron, or similar materials. Brake system  26  receives outer disc  17 . When a friction force is applied to outer disc  17 , cylinder  16  will slow or stop turning, and thus outer disc  17  acts as a brake disc. Side portions  32  are at each end of cylinder  16 , and act as a motor endbell. 
         [0017]    Side portions  32  also provide support for sheave  18 . Sheave  18  contains a series of grooves  34  that receive the ropes of the elevator system. Sheave  18  may be constructed from cast iron. Rotor  36  is attached to the radially inner side of sheave  18  opposite grooves  34 . Rotor  36  and sheave  18  are secured together so that the pieces may rotate about the central axis of shaft  22 . Rotor  36  is a disc with permanent magnets attached to the disc by any suitable method. The permanent magnets may be of different shapes and may be divided into component magnets situated radially side by side, or one after another in an axial direction. Rotor  36  may also include a field iron core between the magnets and sheave  18 . 
         [0018]    Directly adjacent and coaxially located within rotor  36  is stator  38 . Rotor  36  and stator  38  form a motor that causes sheave  18  to rotate. Stator  38  is a winding of metallic wire, and may be a slot winding that creates the armature for the motor of drive machine  10 . Stator is affixed to shaft  22 . Shaft  22  is a hollow tube with a central axis, is fabricated from a metal. The hollow tube of shaft  22  allows shaft  22  to act as a fluid flow path for cooling system  14 , as well as a housing for wiring harness  44 . Wiring harness  44  is the electrical lead wires from the stator to electrical box  20 . A first end of shaft  22  terminates adjacent electrical box  20 , while a second end of shaft  22  terminates adjacent a blower housing of cooling system  14 . 
         [0019]    Shaft  22  is supported at both ends by supports  24   a  and  24   b.  As illustrated in  FIGS. 1 and 2 , supports  24   a  and  24   b  may be mirror replications of each other. Supports  24   a  and  24   b  are illustrated as containing a central “A” with side braces extending from the horizontal line that extend down to the lower surface adjacent the angled legs, although in other embodiments the supports  24   a  and  24   b  can be of varying geometries. 
         [0020]    Cylinder  16  creates a motor housing for rotor  36  and stator  38 , which in turn create a motor for drive machine  10 . Cylinder  16 , sheave  18 , and rotor  36  comprise the rotating part of drive machine  10 . This rotating assembly is rotatably mounted on stationary shaft  22  through bearings  42 . Supports  24   a  and  24   b  position shaft  22  so that the rotating assembly can turn freely without interference from the mounting surface. Alternately, frame  12  can be positioned below supports  24   a  and  24   b  and add additional distance between shaft  22  and the mounting surface on which drive machine  10  is secured. 
         [0021]      FIG. 3  is a cross-sectional elevation view of another aspect for drive machine  10  for an elevator. Again, drive machine  10  includes cooling system  14 , outer cylinder  16  with sheave  18 , electrical box  20 , supports  24   a  and  24   b,  and brake system  26 . In this embodiment, cylinder  16  contains side portions  32 , provide support for sheave  18 . Side portions  32  act as a casing for the motor components, including rotor  36  and stator  38 . Brake system  26  has been moved due to the absence of a brake disc extending radially outward from side portions  32 , but still will provide friction to slow or stop cylinder  16  from rotating when applied. Side portion  32  of cylinder  16  is attached to bearing holder  48 , which assures that the rotating assembly of the motor is maintained in the required location with respect to shaft  22 . 
         [0022]    Stator  38  includes an iron core fixed to shaft  22  and has several discrete windings represented by winding areas  38   a  and  38   c.  The windings contain a hollow central area represented by area  38   b.  This arrangement of coil windings reduces the mass of the motor, and thus drive machine  10 . Alternatively, area  38   b  contains a filler material, or is an iron core. Lead wires  40  extend from electrical box  20 , through the hollow shaft  22 , and exit at aperture  52  where they are connected to the windings of stator  38 . 
         [0023]      FIG. 4  is a cross-sectional view illustrating the cooling of drive machine  10 . Cylinder  16  with sheave  18 , cooling system  14 , electrical box  20 , and braking system  26  are shown in  FIG. 4 . Cooling system  14  includes blower  14   a  connected to duct  14   b , which is connected to the hollow shaft  22 . Air flow represent by arrow A is created by blower  14   a  of cooling system  14 . As illustrated, air flow A enters shaft  22  at inlet aperture  60 . Shaft  22  contains a plurality of circumferentially and axially spaced outlet apertures (over vent holes)  62 , through which the air flow A continues on a radial outward path through stator  38 . In this embodiment, stator  38  has a series of laminations separated by gaps  64 . A stator with a stack of magnetic laminations limits loss due to induction currents. Apertures  62  align with gaps  64  in the coil windings of stator  38 . The air flow continues through gap  50  between stator  38  and rotor  36 , and exits through apertures  66  and  68  within side portions  32  of cylinder  16 . Heat produced during operation of drive machine  10  must be removed. Air flow A cools the components of drive machine  10  to prevent high operating temperature, which can affect performance or damage the motor and other components of drive machine  10 . 
         [0024]    Cylinder  16  of drive machine  10  contains outer disc  17 . In this embodiment, outer disc  17  is a brake disc, and is connected to sheave  18 . Braking system  26  contains brake calipers  46  that engage outer disc  17 , which are common in the art. These are connected to the elevator control system (not illustrated) to slow or hold in place drive machine  10 . Outer disc  17  may be fabricated as a single part with sheave  18 . Alternatively, outer disc  17  and side support  32  are constructed as single part, or outer disc  17 , side support  32 , and sheave  18  may all be separately fabricated and later attached joined together. Rotor  36  is mounted to shaft  22  through bearing  42 . Bearing  42  contains a stationary inner race secured to shaft  22 , and rotating outer race attached to side support  32 . 
         [0025]    Drive machine  10  may also contain locating system  70 . Locating system  70  will measure or detect the speed and relative position of the magnetic fields of stator and rotor  36 , and acts a position feedback device. This information is then passed along to the elevator control system and is used to control hoist motor operation, which is in turn used to locate elevator cars within a hoistway that are attached to drive machine  10 . In one aspect, locating system  70  may include a ring that acts an absolute value encoder. The encoder ring surrounds a projected flange on cylinder  16 , and is joined to the flange through a bearing, which is common in the art. Another portion of the encoder is secured to shaft  22 . The encoder detects the position of the permanent field magnet of rotor  36 , and the phases of currents supplied to the armature windings of stator  38  are controlled by the elevator control system based on the detected position. Locating system  70  can detect the speed and rotating distance of sheave  18  traveling in either clockwise or counterclockwise directions. Alternatively, locating system may include an optical sensor or mechanical sensor, such as a pulley that contacts rotor  36 . 
         [0026]    Cylinder  16  with sheave  18  and side supports  32 , as well as rotor  36  and stator  38  may be symmetrical about a centerline CL. Cylinder  16  with sheave  18  and rotor  38  is coaxially aligned and concentric with respect to shaft  22  and stator  36 . The location of the rotor  36  on the inner diameter of sheave  18  permits symmetry of the motor and sheave  18  of drive machine  10 . The symmetry of the motor of drive machine  10  allows for smoother operation and reduces vibration in the elevator system, as well as reduces the length and size of drive machine  10 . 
         [0027]    Shaft  22  is a hollow structure. Stator  38  is attached to shaft  22 , and the assembly is stationary. Thus, shaft  22  does not experience the stress associated with a moving shaft. This allows shaft  22  to be a lighter structure as shaft  22  experiences negligible fatigue loading. Conventional rotating shafts are typically constructed from steel that has a known fatigue and stress rating. Hollow shaft  22  can be constructed from a wider variety of materials. Shaft  22  may be cast, and contain vent holes  62  illustrated in FIG.  4 . In addition, a cast shaft  22  can contain numerous features that benefit motor and drive machine  10  operation. Shaft  22  can also be machined to include critical features. For example, shaft  22  in  FIGS. 1 and 2  contains the greatest wall thickness adjacent stator  36 , has machined areas for bearing lands to position bearings  42 , and contains a thinner wall thickness that may taper for mounting shaft  22  to supports  24 . Further, with stationary shaft  22  and bearing  42  having a stationary inner race, lead wires could be run along a slot fabricated in shaft  22  directly beneath the inner race of one bearing  42 . 
         [0028]    Also, with an external rotor motor design, the motor has a lower mass compared to conventional internal rotor motors. The smaller motor design results in external rotor  36  having a larger air gap diameter, which leads to a shorter motor length for the same torque output of the motor. The motor is inside and concentric with sheave  18 , rather than adjacent the sheave with conventional machines. The smaller size and symmetry of the motor means machine room layout is easier and more versatile. Further, with a symmetrical machine, bearing loads are evenly distributed between bearings  42 , which benefits the design of drive machine  10 . The reduced size and mass of the motor results in lower cost of drive machine  10 . 
         [0029]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.