Patent Publication Number: US-8522927-B2

Title: Drive motor for an elevator installation and method of mounting a drive motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 10/655,790, filed on Sep. 5, 2003 which claims priority to European Patent Application No. 02405768.9, which was filed Sep. 5, 2002 and European Patent Application No. 03405297.7, which was filed Apr. 29, 2003, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a drive motor for an elevator installation and a method of mounting the drive motor in a drive unit. 
     The PCT specification WO99/43593 shows a drive motor with two drive pulleys engaging belts connecting an elevator car to a counterweight. The drive pulleys are arranged in the outer regions of the car plan profile, at least in the respective outer third of the car dimension corresponding with the orientation of the drive axis, or outside the car profile. The drive pulleys are arranged at both ends of the drive motor. The illustrated embodiment has various disadvantages: 
     Space requirement: The drive motor occupies a large amount of space. 
     Force introduction: The support forces have to be conducted by way of solid sub-constructions into the support structure of the elevator. 
     Assembly handling: The assembly and, in particular, the alignment of the drive pulley axis with respect to the running direction of the support means and drive means is costly. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a drive unit for an elevator installation with car and counterweight movable in a shaft. Support and drive devices connect the car with the counterweight. The support and drive devices are termed drive means in the following. The drive means are guided by way of the drive unit. The drive means are driven by a drive shaft of the drive motor. The areas of the drive shaft that transmit the force to the drive means are termed drive zones in the following. The car and the counterweight are guided by means of car guide rails and counterweight guide rails, respectively. 
     The drive shaft has two mutually spaced-apart drive zones. The drive zones are matched to the form of the drive means. The number of drive means is distributed symmetrically to the two drive zones, wherein each drive zone offers space for at least one drive means. 
     The present invention concerns a drive unit for an elevator installation having a car and a counterweight movable in a shaft comprising: a drive motor and a brake coupled to a drive shaft; at least two drive means connected to said drive shaft and driven by said drive motor, and adapted to be connected to the car and the counterweight; and at least two mutually spaced-apart drive zones through which said drive shaft extends, each one of said at least two drive means being arranged in an associated one of said at least two drive zones and wherein at least one of said drive motor and said brake is arranged to one side of said at least two drive zones. The spacing between the at least two drive zones is at least a width of a foot of a car guide rail or a counterweight guide rail, is no more than three times a width of a foot of a car guide rail or a counterweight guide rail, and is in a range of 100 millimeters to 250 millimeters. 
     An object of the present invention is the provision of a drive unit and a method of mounting the same which optimize the force flow and thus keep down the demands on the adjoining construction as well as minimize the space requirement for the drive unit. The drive unit, in addition, allows a flexible arrangement in the shaft. The drive unit has two drive zones that divide support and drive means into two force transmitting paths. 
     According to the present invention at least one component of the drive unit, such as, for example, the motor or the brake, is arranged to the left or the right of the two drive zones. The utility of this arrangement resides in the fact that the dimensions of the drive unit are reduced. The spacing of the two drive zones can thereby be reduced in correspondence with a purpose by, for example, arranging the drive means at the smallest possible distance to the left and the right of the guide rails. The space requirement of the drive unit and of the entire drive arrangement is thereby minimized. The small dimensions of the drive unit allow a compact constructional form. The compact constructional fowl moreover allows an optimal introduction of the support forces into the support structure, which in turn enables simpler shapes of the sub-constructions. The assembly handling and the alignment of the drive unit are significantly improved by the compact constructional shape and the consequently possible pre-assembly of the individual sub-assemblies in an assembly-friendly environment. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1   a  is a schematic elevation view of a drive unit according to a first embodiment of the present invention with bearings and brackets arranged to the left and right of drive zones; 
         FIG. 1   b  is a schematic elevation view of a drive unit according to a second embodiment of the present invention with a central bracket, a level setting means and with bearings arranged to the left and right of drive zones; 
         FIG. 1   c  is a schematic elevation view of a drive unit according to a third embodiment of the present invention with a central bearing and with brackets arranged to the left and right of drive zones; 
         FIG. 1   d  is a schematic elevation view of a drive unit according to a fourth embodiment of the present invention with a central bearing, a central bracket and a level setting means with a variant; 
         FIG. 1   e  is a schematic elevation view of a drive unit according to a fifth embodiment of the present invention with a central bearing, a central bracket and a variant of a level setting means; 
         FIG. 2  is a perspective view of the drive unit shown in  FIG. 1   d  having a gearless drive motor in a 2:1 ratio suspension and in vertical projection above a counterweight; 
         FIG. 3  is an enlarged cross section of the drive unit shown in  FIG. 2 ; 
         FIG. 4  is a schematic plan view of an elevator installation with the drive unit shown in  FIG. 1   a  arranged in an elevator shaft; 
         FIG. 5  is a schematic elevation view of the elevator installation shown in  FIG. 4  with the drive unit in a 2:1 suspension ratio; 
         FIG. 6  is a view similar to  FIG. 5  with the drive unit above a ceiling of the shaft; 
         FIG. 7  is a view similar to  FIG. 5  with the drive unit above the car in a 2:1 suspension ratio; and 
         FIG. 8  is a view similar to  FIG. 5  with the drive motor above the car in a 1:1 suspension ratio. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A drive unit  20  comprises, as illustrated in  FIGS. 1   a  to  1   e  and  FIG. 2  to  FIG. 4 , a drive shaft  4  that is provided with two drive zones  3 ,  3 ′ spaced from one another. A motor  1  (M) and a brake  2  (B) are coupled to the drive shaft  4 . The drive zones  3 ,  3 ′ operate drive means  19 ,  19 ′, which, as illustrated by way of example in  FIGS. 5 to 8 , drive a car  11  and a counterweight  12 . A spacing D between the drive zones  3 ,  3 ′ is advantageously selected to be as small as possible and it results from, for example, the envisaged arrangement of the drive zones  3 ,  3 ′ or the drive means  19 ,  19 ′ at both sides of a car guide rail  5 . The motor  1  and/or the brake  2  and/or other components, such as rotational speed sensors, evacuation aids or optical indicators, are arranged, according to the invention, to the left and/or right of the two drive zones  3 ,  3 ′. The best combination can be ascertained with utilization of the arrangement possibilities of the components of the drive unit  20 . The use of this arrangement results from the fact that the space requirement for the drive unit  20  can be minimized in correspondence with the requirement of the installation arrangement. The drive unit  20  is executed with a small overall length. This enables a significant degree of pre-assembly of the drive unit in a suitable working environment. The assembly is thereby simplified and sources of error are excluded. 
       FIG. 1   a  shows a first embodiment of the drive unit  20  having the arrangement of the motor  1  (M) and a first bearing  28  on one side of the drive zones  3 ,  3 ′ and the brake  2  (B) and a second bearing  28 ′ on the other side of the drive zones  3 ,  3 ′. Brackets  29 ,  29 ′ are fastened to the support structure of the elevator installation in correspondence with the arrangement of the bearings  28 ,  28 ′. This variant is advantageously used when the spacing D between the drive zones  3 ,  3 ′ is selected to be small, which by way of example is rational in the case of very small guide rail dimensions. 
     In departure from  FIG. 1   a ,  FIG. 1   b  shows a second embodiment drive unit  20   a  that uses a central bracket  22  which guides the support forces of the drive unit  20   a  centrally substantially to a position in the support structure of the elevator installation. The central bracket  22  is arranged at right angles to the axis of the drive unit  20   a  to act in a plane S of symmetry of the two drive zones  3 ,  3 ′. This enables a particularly economic embodiment of the connecting construction. In addition, this arrangement enables the use of a level setting means  27  shown engaged at the end of the motor  1  adjacent to the brake  2 . The level setting means  27  in that case has only small force differences to overcome, which result substantially from the weight forces of the drive itself and from inaccuracies in the drive means arrangement. The level setting means  27  enables, without special cost, alignment of the axis of the drive shaft  4  to the direction of running of the drive means  19 ,  19 ′. This alignment is advantageous particularly in the case of use of belts as drive means, since the wear behavior and noise behavior are thereby decisively influenced. In the case of inaccurate alignment of the drive motor the wear of the drive means strongly increases, which leads to early replacement of the drive means and to correspondingly high costs. For example, in this  FIG. 1   b  the brake  2  and the motor  1  are arranged on one side of the drive zones  3 ,  3 ′. This arrangement is advantageous if the space on the opposite side of the drive zones is otherwise occupied. 
       FIG. 1   c  shows a third embodiment drive unit  20   b  having the arrangement of a central bearing  21  which absorbs the radial force, which is produced by the tension forces present in the drive means  19 ,  19 ′ applied to the drive shaft  4  at a central position. The central bearing  21  is arranged at right angles to the axis of the drive motor to act in the plane S of symmetry of the two drive zones  3 ,  3 ′. A support bearing  24  is arranged at the motor end of the drive shaft  4 . It takes over the difference forces arising in the drive system. The different forces substantially result from the weight forces of the drive itself and from inaccuracies of the drive means arrangements. The support bearing  24  additionally guarantees an exact maintenance of the air gap between the stator and the rotor of the motor  1 . The drive unit  20   b  is fastened by means of two brackets  29 ,  29 ′ to the support structure of the elevator installation. This arrangement is particularly advantageous when the spacing D between the drive zones  3 ,  3 ′ allows sufficient space for the arrangement of the central bearing  21  and the demands on alignment accuracy of the drive shaft are low. 
       FIG. 1   d  shows a fourth embodiment drive unit  20   c  having the arrangement of the central bearing  21  and the central bracket  22 , which conducts the support forces of the drive unit  20   c  centrally substantially to a position in the support structure of the elevator installation. The central bracket  22  and the central bearing  21  are arranged at right angles to the axis of the drive unit  20   c  to act in the plane S of symmetry of the two drive zones  3 ,  3 ′. The level setting means  27  is preferably arranged at the outer end of the motor  1 . The support bearing  24  is arranged as shown in  FIG. 1   c . The arrangement of the drive unit  20   c  in correspondence with  FIG. 1   d  is particularly advantageous, since small dimensions of the drive unit  20   c  result, the forces are conducted in an optimum manner to the support structure of the elevator installation, use of only two bearing positions in the drive unit  20   c  enables a secure design of the drive shaft  4  and the alignment of the axis of the drive shaft  4  to the direction of running of the drive means  19 ,  19 ′ can be carried out in simple manner. 
       FIG. 1   e  shows a fifth embodiment drive unit  20   d  having another possibility of arrangement of the level setting means  27 . The level setting means  27  is arranged to directly engage at the bearing housing in this embodiment. It is identical in its effect to the embodiments shown in  FIGS. 1   b  and  1   d . Other forms best suited for a specific case of use can be devised from the teachings herein. 
     The drive unit arrangements shown in  FIGS. 1   a  to  1   e  can be combined to result in other component configurations. Foe example, the brake  2  can be arranged between the drive zones  3 ,  3 ′. 
       FIGS. 2 and 3  show in detail, by way of example, of the fourth embodiment arrangement illustrated in  FIG. 1   d . The illustrated drive unit  20   c  comprises the drive shaft  4  with the two spaced-apart drive zones  3 ,  3 ′. In this example the spacing D of the two drive zones is 100 to 250 mm. This allows the arrangement of guide rail profiles which are currently used in elevator installations and which have a rail foot width of 50 to 140 mm. The preferred spacing D is in a range of one to three times the width of the foot of the guide rails being used. The drive shaft  4  is mounted in a bearing housing  7 . The central bracket  22  in this case is integrated in the bearing housing  7 . The central bracket  22  is arranged in the plane S of symmetry, which is at right angles to the drive axis and defined by the two drive zones, between the two drive zones  3 ,  3 ′. The drive shaft  4  is mounted in the bearing housing  7  by means of the central bearing  21  arranged between the drive zones  3 ,  3 ′. The central bearing  21  is similarly arranged to act in the plane S of symmetry. The central bearing  21  accepts the support forces due to the drive means  19 ,  19 ′ and conducts them by way of the bearing housing  7 , the central bracket  22  and by way of an intermediate member to the support structure of the elevator installation. The drive zones  3 ,  3 ′ are machined directly into the drive shaft  4 . The drive zones  3 ,  3 ′ can alternatively also be mounted by means of separate elements, such as, for example, in the form of discs, on the drive shaft  4 . The drive shaft  4 —or the drive zones  3 ,  3 ′—is connected with the motor  1  and the brake  2  in a force-effective manner, preferably integrally and gearlessly, and thus enables drive of the drive means  19 ,  19 ′ by means of the drive zones  3 ,  3 ′. The drive zones  3 ,  3 ′ are, in the illustrated embodiment, similarly integrally integrated in the drive shaft  4 . This is advantageous in the case of use of belts as drive means, since these drive means enable small deflecting or drive radii. Through the arrangement of the central bearing  21  between the drive zones  3 ,  3 ′ the constructional space available there is utilized efficiently and the external dimensions are reduced. Due to the reduction in the number of varying positions, costs are reduced. The quality of the drive unit  20   c  is significantly increased by this arrangement, since due to the reduction in the bearing positions an over-determination of the shaft mounting is redundant. 
     Advantageously the brake  2  and the motor  1  are arranged, as shown in the examples, at the left and the right of the two drive zones  3 ,  3 ′. The motor  1  and the brake  2  are force-effectively connected by way of the bearing housing  7 . The drive moments produced by the motor  1  and/or the braking moments produced by the brake  2  are conducted into the bearing housing  7  and by way of the central bracket  22  into the support structure of the elevator installation. The illustrated arrangement of the drive zones  3 ,  3 ′ between the brake  2  and the motor  1  enables, together with the force-effective connection of brake  2 , the motor  1  and the bearing housing  7 , a particularly space-saving embodiment. In addition, accessibility with respect to the brake  2  and the motor  1  is ensured in ideal manner. 
     The support bearing  24  is arranged at the motor end of the drive shaft  4 . The support bearing  24  accepts the difference forces arising in the drive system. The difference forces substantially result from the weight forces of the drive itself and from inaccuracies in the drive means arrangements. The support bearing  24  additionally ensures an exact maintenance of the air gap between the stator and the rotor of the motor  1 . The support bearing  24  conducts the difference forces into the housing of the motor and the bearing housing  7 . The resulting support forces are accepted by the level setting means  27  and conducted into the support structure of the elevator installation. The level setting means  27  serves at the same time for accurate and simple leveling of the longitudinal axis of the drive shaft  4  relative to the drive means  19 ,  19 ′. This alignment is advantageous particularly in the case of use of belts as drive means, since the wear behavior and noise behavior are thereby decisively influenced. 
     Alternatively, the level setting means  27  can be arranged, for example, horizontally as shown in  FIG. 1   e.    
     The bearing housing  7  illustrated in  FIGS. 2 and 3  partly encloses the drive shaft  4  together with the drive zones  3 ,  3 ′. This fauns a direct protection of the drive zones  3 ,  3 ′ against unintended contact and risk of assembly or service personnel being caught, but also prevents damage of the drive zone or the drive means by objects dropping down. At the same time the bearing housing  7  thereby gains the requisite strength in order to accept the forces and moments from the motor  1  and the brake  2 . 
     The drive unit  20   c  is fastened by means of vibration insulation means  23 ,  26 . This enables a significant degree of vibration decoupling of the drive unit  20   c  from the support structure of the elevator installation. Noises in the elevator installation and/or in the building are thereby reduced. 
     For simple design of the central bearing  21 , the internal diameter of the central bearing is selected to be greater than the diameter of the drive zones  3 ,  3 ′ in the illustrated embodiment. 
     A drive unit form optimal in terms of cost and space is offered by the illustrated form of construction. In particular, the assembly and alignment of the drive unit can take place simply and quickly. The layout of the drive components is simplified, since the loading of the drive shaft  4  and the bearing housing  7  is defined in ideal manner by the achieved two-point mounting. 
       FIG. 2  shows a perspective view of the fourth embodiment of an arrangement of a gearless drive motor in the drive unit  20   c . The drive unit  20   c  is mounted on a crossbeam  8  arranged substantially horizontally in an elevator shaft  10 . The crossbeam  8  is, for example, an elongate square member formed, of proven materials such as steel. In this example, the crossbeam  8  is fastened to counterweight guides  9 ,  9 ′ and to the car guide  5  at a first wall of the shaft. Advantageously the crossbeam  8  is fastened by way of two end regions to the counterweight guides  9 ,  9 ′ and by way of a center region to the car guide  5 . The fastening of the crossbeam  8  to these three guides is carried out in the three fastening regions by way of, for example, screw connections. A bracket  122  connected at one end to the crossbeam  8  may be used to support the drive unit  20   c . An intermediate member  125 , also referred to as a support platform, for supporting the drive unit includes a generally horizontal support member  120 , a pair of opposing, generally parallel, sidewalls  124  extending downward from the support member  120  toward the crossbeam  8 , and a rear wall  126  extending downward from the support member  120  and located in between the two opposed sidewalls  124 . Each of the sidewalls  124  is tapered, with a greater width at an upper end of the sidewall in relation to a width at a lower end of the sidewall  124 . The tapering of the sidewalls  124  is linear in nature in  FIG. 2 . The support member  120 , the two opposing sidewalls  124 , and the rear wall  126  form a three dimensional support structure for the drive unit  20   c , and with a portion of the crossbeam  8  forms a generally three dimensional open box structure. The illustrated form of embodiment results in an optimum utilization of the constructional space and enables a significant degree of preparation of the assembly in a cost-optimal manner in construction works or in a corresponding environment. 
     A control and/or a transformer  6  of the elevator installation is, as shown in  FIG. 2 , fastened in the vicinity of the drive unit, advantageously similarly on the crossbeam  8 . This fastening is, if necessary, insulated against vibration. The drive unit can thus be delivered and assembled together with the associated converter with prefinished cabling. Possible changes in position, which can result due to construction contraction, cannot have any effect and the entire unit can be produced particularly economically. If appropriate, the control and/or transformer  6  can additionally be supported relative to the wall. 
     As shown in  FIG. 3 , a leveling balance  25  is advantageously arranged at the drive unit  20   c . The leveling balance  25  is, for example, a water balance that indicates the horizontal position of the drive unit  20   c . The leveling balance  25  allows a simple check of correct leveling and accordingly enables a quick correction of the alignment of the drive unit  20   c.    
     The use of the drive unit  20   c  shown by way of example is universally possible for many types of installation. The arrangement shown in  FIG. 2  refers to an elevator without a separate motor room. However, the use is not limited to elevator installations without a motor room. If a motor room is present the drive unit can, for example, be mounted on the shaft roof as shown in  FIG. 6 . 
     With the illustrated possibilities the arrangement of the drive unit can be flexibly adapted, for example in the case of modernizations, to predetermined shaft conditions, which flexibility thus enables use of standard parts and avoids costly special solutions. 
     Different possibilities of arrangement of the drive unit are illustrated, by way of example, in the following. 
       FIGS. 4 and 5  show a preferred use of the drive unit according to the present invention as is used, for example, in the case of new installations.  FIG. 4  shows a triangular arrangement of the guides  5 ,  5 ′,  9 ,  9 ′ in the substantially vertical shaft  10  of an elevator installation. The shaft  10  has, for example, a rectangular cross-section with four walls. Substantially vertically arranged car guides  5 ,  5 ′ and counterweight guides  9 ,  9 ′ are arranged in the shaft. The two car guides guide the car  11  and the two counterweight guides guide the counterweight  12 . The guides are fastened to adjacent walls. The two counterweight guides  9 ,  9 ′ and the car guide  5  are fastened to a first wall. The car guide  5 ′ is fastened to a second wall. The second wall is disposed opposite the first wall. The first car guide  5  is arranged substantially centrally between the two counterweight guides  9 ,  9 ′. The guides are formed of proven materials, such as steel. The fastening of the guides to the walls takes place by way of, for example, screw connections. However, other shaft shapes with square, oval or round cross-section can be realized. 
     The two counterweight guides  9 ,  9 ′ and the first car guide  5  define apices of a substantially horizontal triangle T in the shaft  10 . An imaginary line horizontal connector between the two counterweight guides forms a first side or base of the triangle T. Imaginary line horizontal connectors between each counterweight guide and the first car guide form second and third sides of the triangle T. Advantageously the horizontal connector of the car guides intersects an imaginary line horizontal connector H of the counterweight guides substantially centrally so that the triangle T is substantially equilateral. 
     Advantageously the two drive zones  3 ,  3 ′ of the drive unit  20  are arranged symmetrically to the left and right of the horizontal connector H of the car guides  5 ,  5 ′. 
     The drive unit  20  arranged substantially horizontally in the shaft  10  moves the car  11  and the counterweight  12 , which are connected together by means of the at least two drive means  19 ,  19 ′, in the shaft  10 . Each of the drive means has two ends  18 ,  18 ′. The drive means is a cable and/or a belt of any nature. The load-bearing regions of the drive means usually consist of metal, such as steel, and/or plastic material, such as aramide. 
     The cable can be a single cable or multiple cable and the cable can also have an external protective casing of plastic material. The belt can be flat and externally unstructured to be smooth or, for example, structured in wedge ribs or as a cogged belt. The force transmission takes place, in correspondence with the form of embodiment of the drive means, by way of friction couple or mechanically positive connection. The drive zones  3 ,  3 ′ of the drive shaft  4  are executed in correspondence with the drive means. According to the present invention at least two drive means are used and several drive means can be provided. 
     Each of the ends  18 ,  18 ′ of the drive means  19 ,  19 ′ is fixed to a shaft wall, a shaft roof, a car guide, a counterweight guide, the crossbeam  8 , the car  11  and/or the counterweight  12 . Advantageously the ends of the drive means are fixed by way of resilient intermediate elements for the damping of solid-borne sound. The intermediate elements are, for example, spring elements which prevent transmission of oscillations, which are perceived as unpleasant, from the drive unit to the shaft wall the shaft roof, the car guides, the counterweight guides, the crossbeam, the car and/or the counterweight. Several forms of fixings of the ends of the drive means are possible, for example: 
     In the installations according to  FIGS. 5 ,  6  and  7 , one or both of the ends  18 ,  18 ′ of the drive means is or are fastened to the shaft wall, the shaft ceiling, the car guides, and/or the crossbeam. 
     In the installation according to  FIG. 8 , a first end  18  of the drive means is fastened to the car  11  and a second end  18 ′ of the drive means is fastened to the counterweight  12 . 
       FIG. 5  is a schematic elevation view of the elevator installation shown in  FIG. 4  with the drive unit  20  in a 2:1 suspension ratio. The drive means  19 ,  19 ′ extends about deflecting rollers  13 ,  13 ′ and  14 ,  14 ′ mounted on the bottom of the car  11  and deflecting rollers  17 ,  17 ′ mounted on the top of the counterweight  12 . 
       FIG. 6  is a view similar to  FIG. 5  with the drive unit  20  above a ceiling  10   a  of the shaft  10 . 
       FIG. 7  is a view similar to  FIG. 5  with the drive unit  20  above the car  11  in a 2:1 suspension ratio. Deflecting rollers  15 ,  15 ′ are provided between the drive unit  20  and the deflecting rollers  13 ,  13 ′ and deflecting rollers  16 ,  16 ′ are provided between the drive unit  20  and the deflecting rollers  17 ,  17 ′. 
       FIG. 8  is a view similar to  FIG. 5  with the drive unit  20  above the car  11  in a 1:1 suspension ratio and the deflecting rollers  16 ,  16 ′ provided between the drive unit  20  and the counterweight  12 . 
     While the drive unit  20  has been shown in the  FIGS. 4 through 8 , any of the drive units  20   a  through  20   d  could be substituted therefor. 
     According to the examples shown herein, two drive zones move at least two drive means by way of static friction. With knowledge of the present invention, one of experience in elevator construction can also use drive methods different from those illustrated in the examples. Thus, a drive unit with more than two drive zones can be used. Also, a drive pinion, which drive pinion is disposed in mechanically positive engagement with a cogged belt, can be used as the drive means. 
     The method of mounting a drive unit is significantly simplified by the illustrated drive units and, in particular, by the arrangement of the central bracket  22  between the drive zones, in the axis of symmetry of the resultant force traction of the drive means  19 ,  19 ′, and the arrangement of a level setting means  27  at the motor end of the drive motor  1  in the drive unit  20   a  and the drive unit  20   c . The orientation of the drive axis relative to the traction axis of the drive means can be carried out in simple, rapid and precise manner by means of the provided level setting means  27 . Otherwise-usual, costly methods such as placement underneath of underlying members, wedges, etc., can be eliminated. 
     With knowledge of the present invention the expert in the field of elevators can vary the set fauns and arrangements as desired. For example, he or she can construct the central bracket  22  separately from the bearing housing  7 . 
     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.