Abstract:
A direct drive apparatus for an elevator wherein a movable part of the direct drive, particularly a linear motor, is connected with an elevator car or counterweight for transmission of compression and tension in the travel direction by a tension/compression strut with settable damping properties. The tension/compression strut includes first and second rods which lie on a longitudinal axis of the strut and extend into opposite ends of a sleeve. First and second nuts are threadably received in the ends of the sleeve. First and second spring elements are positioned in the sleeve abutting the first and second nuts respectively. A central spring element is positioned between first and second spring plates which abut the first and second spring elements respectively. Each rod extends through the respective nut, spring element and spring plate into the central spring element and is attached the respective spring plate to optimize the oscillation and body sound insulation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to elevator drives and, in particular, to a direct drive apparatus for an elevator car.  
           [0002]    A linear motor arrangement for an elevator is shown in the European patent document EP 0 846 646, in which a movable part of a linear motor is arranged near a counterweight and is connected with the counterweight by way of a horizontal, non-conductive connection. The movable part of the linear motor is thereby horizontally movable with the counterweight, so that horizontal forces are not transmitted between the motor and the counterweight. The counterweight is guided at a guide rail and the movable part is guided on an adjacent plane. A resilient connecting element between the counterweight and the movable part serves the purpose of avoiding excess allowances which can arise due to the different guidances of the movable part and the counterweight.  
           [0003]    In this known solution the oscillations and vibrations arising in the direction of travel are not damped by the described construction of the connecting element.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention concerns a direct drive arrangement that has the advantage, compared with the state of the art drives, that the oscillations and vibrations arising in the direction of travel are significantly reduced and damped. Advantageously, no disturbing vibrations in the car body are caused by the drive.  
           [0005]    A further advantage of the present invention is that the damping properties of the tension/compression strut can be set coarsely and finely. The tension/compression strut is advantageously provided with material transitions in order to undertake not only an oscillation damping function, but also a body sound insulating function.  
           [0006]    Of further advantage is the spring behavior of the tension/compression strut independent of direction. This is the same in both directions of loading.  
           [0007]    An advantage is further to be seen in that not only the car, but also the counterweight can be used as the driven body of the elevator.  
           [0008]    All explained features are usable not only in the respectively indicated combination, but also in other combinations or in isolation with departing from the scope of the present invention.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]    The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:  
         [0010]    [0010]FIG. 1 is a schematic view of the direct drive apparatus according to the present invention; and  
         [0011]    [0011]FIG. 2 is an axial sectional view of a tension/compression strut according to the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]    In FIG. 1 there is illustrated, as a driven body of an elevator, an elevator car  1  that is guided by means of a direct drive, for example a linear motor  2 , on a guide  4 , for example a guide rail, which is fastened in an elevator shaft  3 , by means of, for example, guide shoes (not shown). A guidance by guide rollers is also possible. The car  1  can be connected in the usual manner by way of cables and cable rollers, which are not shown, with a counterweight, which is similarly not shown. A movable part  2 . 1  of the linear motor  2  is in turn guided on a guide structure  5 , which is arranged in the elevator shaft  3  and on which a stationary part, which is not shown, of the linear motor is disposed. The guidance can be effected, for example, with the assistance of guide shoes or guide rollers. The thrust forces arising between the stationary part and the movable part  2 . 1  of the linear motor  2  set the car  1  in motion. The stationary part  2 . 1  of the linear motor  2  and the guide structure  5  extend in the elevator shaft  3  over the entire travel path of the linear motor. The arrangement of the guides of the car  1  and the guide structure  5  of the motor  2  in the elevator shaft  3  can be freely selected according to purpose and installation. There is shown in FIG. 1 only one of many possible arrangements, in which the guide  4  of the car  1  lies opposite the guide structure  5  of the motor  2 .  
         [0013]    The side of the movable part  2 . 1  of the linear motor  2  that faces the elevator car  1  is connected with one side of the car by means of a resilient, damping tension/compression strut  6 , which serves for transmission of compression and tension forces in the direction of travel of the elevator. In the shown variant, the tension/compression strut  6  is fastened by way of ball joints  7  to a first projection  8  of the movable part  2 . 1  and to a second projection  9  of the car  1 . Other modes of fastening the strut  6  to the car  1  and to the motor  2  are also possible.  
         [0014]    The details of the tension/compression strut  6  are shown in the FIG. 2. The tension/compression strut  6  preferably comprises a first rod  10 . 1  and a second rod  10 . 2 , which lie in a longitudinal axis  11  of the tension/compression strut  6 , a sleeve  12  which is, for example, tubular, a first fixing element  13 . 1  and a second fixing element  13 . 2 , a first spring element  14 . 1 , a second spring element  14 . 2  and a central spring element  15 , as well as a first spring plate  16 . 1  and a second spring plate  16 . 2 .  
         [0015]    In a preferred variant, the first and second fixing elements  13 . 1  and  13 . 2  are constructed as nuts and are designated as a first nut  13 . 1  and a second nut  13 . 2 .  
         [0016]    The first and the second nuts  13 . 1  and  13 . 2  are each screwed in at a respective one of the ends of the sleeve  12 , i.e. at the ends of the sleeve  12  facing the driven body  1  and the movable part  2 . 1  of the linear motor  2 . The sleeve  12  is provided with internal threads which mate with corresponding external threads of the first and second nuts  13 . 1  and  13 . 2 , respectively. The first and second nuts  13 . 1  and  13 . 2  are provided with continuous bores, into which the first and second rods  10 . 1  and  10 . 2 , respectively, extend. Arranged between the two nuts  13 . 1  and  13 . 2  are the first, second and central spring elements  14 . 1 ,  14 . 2  and  15 , which in turn are separated by the first and second spring plates  16 . 1  and  16 . 2 . The first, second and central spring elements  14 . 1 ,  14 . 2  and  15  as well as the first and second spring plates  16 . 1  and  16 . 2  are similarly provided with continuous bores, which are traversed by extremities of the first rod  10 . 1  and the second rod  10 . 2 .  
         [0017]    The first nut  13 . 1 , the first spring element  14 . 1 , the first spring plate  16 . 1  and part of the central spring element  15  lie on the first rod  10 . 1  within the sleeve  12 . The first spring element  14 . 1  lies between the first nut  13 . 1  and the first spring plate  16 . 1 , wherein one side of the first spring element  14 . 1  co-operates with one side of the first nut  13 . 1  and the other side of the first spring element  14 . 1  co-operates with one side of the first spring plate  16 . 1 . The same construction also applies to the second rod  10 . 2 . The structure of the tension/compression strut  6  is symmetrical with respect to the center transverse axis of the central spring element  15 .  
         [0018]    Supports  17 , which serve as abutments for the first and second spring elements  14 . 1  and  14 . 2 , are present on the sides, which face the first and second spring elements  14 . 1  and  14 . 2 , of the first and second nuts  13 . 1  and  13 . 2 .  
         [0019]    The central spring element  15  is arranged between the first and second spring plates  16 . 1  and  16 . 2  and surrounds the extremities of the first and second rods  10 . 1  and  10 . 2 . The first and second spring plates  16 . 1  and  16 . 2  are fixedly connected with the first and second rods  10 . 1  and  10 . 2 , respectively, for example with the aid of threads. The first and second spring plates  16 . 1  and  16 . 2  lie directly against corresponding abutments  18 , which are present on the outer surface of the first and second rods  10 . 1  and  10 . 2  and which can arise, for example, by an abrupt reduction in the rod diameter. The first and second rods  10 . 1  and  10 . 2  are freely movable in the bores of the first and second nuts  13 . 1  and  13 . 2 , respectively, as well as in the bores of the first, second and central spring elements  14 . 1 ,  14 . 2  and  15 .  
         [0020]    In order to improve the rigidity of the tension/compression strut  6 , slide guides, which are not shown and on which the rods  10 . 1  and  10 . 2  can be guided to be stable and secured against high buckling loads, are provided on the inner surfaces of the nuts  13 . 1  and  13 . 2  in one possible variant. The extremities of the first and second rods  10 . 1  and  10 . 2  extend by a predetermined length into the central spring element  15 . A centering of the rods  10 . 1  and  10 . 2  is thus guaranteed, even when the rods are withdrawn from the central spring element  15  beyond a predetermined critical point.  
         [0021]    In a preferred embodiment, the first, second and central spring elements  14 . 1 ,  14 . 2  and  15  consist of polymer or elastomer and are denoted in the following as first, second and central polymer springs. The first, second and central polymer springs  14 . 1 ,  14 . 2  and  15  have the same properties, wherein the central polymer spring  15  is twice the length compared to the first and second polymer springs  14 . 1  and  14 . 2 , respectively. This ensures the same spring behavior of the rod in both directions of loading, i.e. in the compression state and the tension state. The spring plates  16 . 1  and  16 . 2  consist of a material different from the polymer springs  14 . 1 ,  14 . 2  and  15  and, in fact, the spring plate  16 . 2  and  16 . 2  preferably consist of steel. In this manner, the combination of steel spring and polymer spring produces a material transition in the axial direction of the tension/compression strut  6 , i.e. parallel to the longitudinal axis  11 . A material transition is to be understood as a change in material.  
         [0022]    Rings, preferably neoprene rings  19 , are present between the first rod  10 . 1  and the first nut  13 . 1  and in the same manner between the second rod  10 . 2  and the second nut  13 . 2  as well as also around each of the spring plates  16 . 1  and  16 . 2  in order to produce, by the combination of neoprene rings and steel, a material transition also in the radial direction of the tension/compression strut  6 , i.e. transverse to the longitudinal axis  11 .  
         [0023]    The mentioned material transition in the tension/compression strut  6  has the effect of obtaining an adequate and effective body sound insulation with high-frequency oscillations in axial and radial directions.  
         [0024]    The low-frequency oscillations are damped by the three polymer springs  14 . 1 ,  14 . 2  and  15  biased against one another. Due to the respective use of polymer spring elements with different spring characteristics the oscillation damping can be coarsely preset. As the polymer springs  14 . 1 ,  14 . 2  and  15  preferably exhibit non-linear spring characteristics, the oscillation damping can be finely set by adjustment of the bias of these polymer springs.  
         [0025]    The principle of the function of the tension/compression strut  6  is described in the following:  
         [0026]    In the unloaded state of the rods  10 . 1  and  10 . 2 , the polymer springs  14 . 1 ,  14 . 2  and  15  are biased by a predetermined force by way of the spring plates  16 . 1  and  16 . 2  via the nuts  13 . 1  and  13 . 2  in the sleeve  12 . The spring rate can be set by the non-linear characteristics of the polymer springs  14 . 1 ,  14 . 2  and  15 .  
         [0027]    In the compression state, the rods  10 . 1  and  10 . 2  respectively act on the plate springs  16 . 1  and  16 . 2  and further, by way of shape locking, on the central polymer spring  15 . The central or inner polymer spring  15  is thus compressed and the two other, outer polymer springs  14 . 1  and  14 . 2  relieved.  
         [0028]    In the tension state, the rods  10 . 1  and  10 . 2  respectively act on the spring plate  16 . 1  and  16 . 2  and further, by way of shape locking, on the outer polymer springs  14 . 1  and  14 . 2 . The inner polymer spring  15  is relieved and the outer polymer springs generate a compressive force on the nuts  13 . 1  and  13 . 2 , respectively. Finally, a tension force on the sleeve  12  arises. The spring rate is the same as in the compression state.  
         [0029]    With such construction of the tension/compression strut  6  the oscillation and body sound insulation is optimized in the case of a direct drive of an elevator car.  
         [0030]    The rods  10 . 1  and  10 . 2  as well as the sleeve  12  preferably have a cylindrical cross section, but other shapes, for example rectangular, etc., are equally conceivable. The same consideration also applies to the polymer springs  14 . 1 ,  14 . 2  and  15 , the spring plates  16 . 1  and  16 . 2  and the nuts  13 . 1  and  13 . 2 .  
         [0031]    The spring elements  14 . 1 ,  14 . 2  and  15  can consist not only of polymer or elastomer, but also of any kind of resilient material.  
         [0032]    The rods  10 . 1  and  10 . 2 , the sleeve  12 , the nuts  13 . 1  and  13 . 2  and the spring plates  16 . 1  and  16 . 2  preferably consist of steel. Other metals or materials which are appropriate and suitable for the function provided in this invention can equally be used.  
         [0033]    With this construction of the tension/compression strut  6  high buckling loads can be absorbed for smallest constructional space. This means that a compact mode of construction is thus obtained with high static and dynamic loads. The tension/compression strut  6  needs only a small constructional space, particularly in relation to its diameter.  
         [0034]    In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.