Abstract:
The invention relates to an elevator installation with a number of cars in a shaft, with a second car disposed underneath a first car. Associated with each car is a drive with a traction sheave and at least one cable strand, which is led over the traction sheave and by means of which the car is connected to a counterweight. The second car is kept in a suspension ratio of 1:1 and is connected to its counterweight by means of two cable strands associated with different sides of the second car and led over the traction sheave of the second car. A cable guiding device is provided which subjects the two cable strands of the second car to equal loading.

Description:
This application is a continuation of international application number PCT/EP2005/011545 filed on Oct. 28, 2005. 
    
    
     The present disclosure relates to the subject matter disclosed in international application number PCT/EP2005/011545 of Oct. 28, 2005 and European application number 05 005 444.4 of Mar. 12, 2005, which are incorporated herein by reference in their entirety and for all purposes. 
     BACKGROUND OF THE INVENTION 
     The invention relates to an elevator installation with a number of cars in a shaft, a second car being disposed underneath a first car and there being associated with each car a drive with a traction sheave and also at least one cable strand, which is led over the traction sheave and by means of which the car is connected to a counterweight, the second car being kept in a suspension ratio of 1:1 and being connected to its counterweight by means of two cable strands associated with different sides of the second car and led over the traction sheave of the second car. 
     The use of a number of cars which can be made to travel up and down separately from each other in a common shaft allows the handling capacity of an elevator installation to be increased. The cars may be driven by means of traction sheaves, over which the cable strands which connect the cars to their counterweight are led. Only a single cable strand is required for the first car. Usually two cable strands are used for the second car, which is disposed underneath the first car, these cable strands being disposed on two different sides of the car and running laterally outside the first car. In U.S. Pat. No. 5,419,414, it is proposed for this purpose to lead the two cable strands of the second car respectively over a separate traction sheave, so that the drive of the second car takes place by means of two traction sheaves which are separated from each other by the width of the car and are coupled to a common drive motor by means of a drive shaft. However, this requires a separate drive motor with a long drive shaft for the second car and also requires a large shaft space, with the effect of increasing the production and operating costs of the elevator installation. 
     In EP-A-1 329 412, it is proposed to lead the two cable strands of the second car over a common traction sheave. This allows shaft space to be saved and a standard motor to be used for driving the second car. However, the two cable strands of the second car are worn in different ways during its operation, so that they reach their maximum permissible degree of wear at different points in time. To exchange the cable strands, the elevator installation has to be taken out of operation, and, in order to keep these inoperative times as short as possible, the two cable strands are usually exchanged at the same time, although strictly speaking only the more severely worn cable strand needs to be exchanged in this way, while the maximum permissible degree of wear has not yet been reached for the less worn cable strand. 
     It is an object of the present invention to develop an elevator installation of the type mentioned at the beginning in such a way that, as far as possible, the two cable strands of the second car reach their maximum permissible degree of wear at the same point in time, in order in this way to lower the operating costs. 
     SUMMARY OF THE INVENTION 
     This object is achieved according to the invention in the case of an elevator installation of the generic type by the traction sheave associated with the second car having two traction sheave parts, over each of which one of the two cable strands of the second car is led, the distance between the traction sheave parts being less than the distance between the two cable strands in the region of the second car, and by the elevator installation having a cable guiding device which subjects the two cable strands of the second car to equal loading. The loading of the cable lines is brought about not only by the tensile force to which the cable lines are subjected but also by the deflection of the cable lines at deflecting rollers and at the associated traction sheave. According to the invention, it is provided that the two cable strands of the second car are disposed and guided by means of the cable guiding device in such a way that they are exposed to virtually the same cable loading. They are therefore worn out equally and reach their maximum permissible degree of wear at approximately the same point in time. At this point in time, both cable strands can be exchanged, both exhibiting the same degree of wear. It is consequently not necessary for one of the cable strands to be exchanged before it has reached the end of its service life. The elevator installation according to the invention is therefore distinguished by lower operating costs. 
     A single traction sheave is used for driving the second car, over which sheave the two cable strands of the second car are led. The traction sheave has two traction sheave parts, over each of which one of the two cable strands is led. The distance between the traction sheave parts is less than the distance between the two cable strands in the region of the second car. 
     It may be provided in particular that the two traction sheave parts lie against each other. A configuration of the elevator installation of this type is distinguished by a particularly compact form of construction, which takes up relatively little shaft space. 
     The term car is used here to refer both to an elevator cabin without a car frame and to an elevator cabin including a car frame on which the elevator cabin is held. The cable strands may be fixed directly to the elevator cabin or else to the car frame that is possibly used. 
     The second car is kept in a suspension ratio of 1:1, that is to say the cable strands of the second car are fixed to it, so that the cable speed of the two cable strands is identical to the speed of the car. This allows running noises and vibrations in the second car to be kept down. The first car may also be kept in a suspension ratio of 1:1, so that the elevator installation according to the invention is distinguished overall by a low noise level. In the case of a suspension ratio of 1:1, a change in height of the car is identical to the advancement of the respective cable strands by means of which the car is connected to its counterweight. 
     In the case of the elevator installation according to the invention, standard drive motors may be used both for the first car and for the second car. This likewise allows the production and operating costs of the elevator installation to be lowered. 
     It is of advantage if the cable guiding device comprises deflecting rollers, the two cable strands of the second car being led over the same number of deflecting rollers and over the traction sheave of the second car. Since each cable strand undergoes wear both at deflecting rollers and at the traction sheave, the use of an equal number of deflecting rollers for the two cable strands has the effect that they are worn more equally. 
     It is advantageous if the cable guiding device comprises deflecting rollers, the distances between two adjacent deflecting rollers and between the traction sheave of the second car and deflecting rollers adjacent to this traction sheave being the same for both cable strands of the second car. The wear of the cable strands led over deflecting rollers and the traction sheave is also dependent on the distances between the respective deflecting rollers and between them and the traction sheave. If the distances coincide for the two cable strands, more equal wear of the cable strands of the second car can be achieved. 
     In the case of a particularly preferred embodiment of the invention, it is provided that the cable guiding device comprises deflecting rollers, the sequence of the changes in direction that take place at the respective deflecting rollers and the traction sheave of the second car being the same for the two cable strands of the second car. The bending direction experienced by the cable strands on account of the deflecting rollers and the traction sheave consequently coincides for the two cable strands. In particular, it is ensured as a result that a change in the bending direction takes place in the same way for both cable strands. Such a change in direction entails great loading of the respective cable strand. Ensuring that changes in direction coincide for both cable strands allows their loading, and consequently also their wear, to be made approximately the same. 
     It is of particular advantage if the cable guiding device comprises deflecting rollers, the two cable strands of the second car being deflected respectively by the same angle at mutually corresponding deflecting rollers and at the traction sheave of the second car. For instance, it may be provided that a deflecting roller at which the respective cable strand is in each case deflected by the same angle is disposed at the same height for each of the two cable strands, so that the cable strands are respectively subjected to the same loading and wear at the deflecting rollers and at the traction sheave. 
     In the case of a preferred embodiment, the two cable strands of the second car run mirror-symmetrically in relation to each other with respect to a plane of symmetry. Symmetrical running of the two cable strands allows particularly equal wear of the two cable strands to be achieved. 
     It is advantageous if the two cable strands of the second car have in each case a first cable strand portion, starting from the second car and extending as far as a first deflecting roller, and a second cable strand portion, joined to the first, the second cable strand portions being aligned perpendicularly in relation to the first cable strand portions. This makes it possible to bring the two cable strands which are led past different sides of the first car together in the second cable strand portion, in order in this way to save shaft space. 
     It is of advantage if the second cable strand portions are horizontally aligned. The cable strands of the second car consequently undergo a deflection of 90° as they extend from the second car at a first deflecting roller. The first cable strand portion that extends from the second car runs in a vertical direction past the first car and, after a deflection by 90°, the first cable strand portion is joined to the horizontally aligned second cable strand portion. 
     The second cable strand portion may extend as far as a second deflecting roller, at which it is joined to a third cable strand portion. Here it is advantageous if the third cable strand portions of the two cable strands of the second car are aligned parallel to each other, in particular the third cable strand portions may be vertically aligned. The two cable strands of the second car can consequently be led vertically upward or downward in each case in their third cable strand portion. 
     In the case of a preferred embodiment of the invention, the third cable strand portions extend as far as a third deflecting roller or as far as the traction sheave of the second car, at which they are joined to a fourth cable strand portion, the fourth cable strand portions of the two cable strands of the second car being aligned parallel to each other. 
     The fourth cable strand portions may extend from the traction sheave directly to the counterweight of the second car. In this case, the fourth cable strand portions run in a vertical direction. 
     Alternatively, it may be provided that the fourth cable strand portions are, for example, horizontally aligned. 
     The fourth cable strand portions may extend from the traction sheave of the second car as far as a third deflecting roller, at which they are joined to a fifth cable strand portion, the fifth cable strand portions of the two cable strands of the second car being aligned parallel to each other. It may be provided in particular that the fifth cable strand portions are vertically aligned. 
     In the case of a preferred embodiment of the invention, the fifth cable strand portions extend as far as the counterweight of the second car, that is to say the two cable strands of the second car have in each case a total of four deflections, three deflecting rollers and additionally the common traction sheave of the second car being used for each cable strand. 
     The invention is not restricted to a specific number of deflections for the two cable strands of the second car. However, as far as possible, both cable strands should undergo the same number of deflections. It is of particular advantage if the cable strands are deflected by the same angle at the deflecting locations and if the distances between the deflecting locations are the same for both cable strands. It is also advantageous if the sequence of the deflections is the same for the two cable strands and if the bending changes also take place at the same locations. 
     It is of particular advantage if the axis of rotation of the traction sheave associated with the second car is aligned parallel to a horizontal joining line, which joins the points of intersection of the first cable strand portions, joined onto the second car, of the two cable strands with a horizontal plane. It has been found that this makes it possible for the cables to be guided with particularly equal wear of the two cable strands. 
     The counterweights of the first and second cars can be made to travel within the shaft, preferably next to each other. This allows the cable strands of the two cars to be held directly on the respective counterweight, without it being necessary for the counterweight of the second car to have a through-opening through which the cable strand of the first car is led. The two counterweights can therefore have an identical construction, whereby the production costs of the elevator installation can be lowered. 
     In order to achieve the most equal possible wear of the two cable strands of the second car, it is of advantage if the cable tensions of the two cable strands are equal. The two cable strands are consequently also distinguished by virtually identical extension and slippage behavior. 
     The elevator installation may have more than two cars. A third car may be disposed underneath the second car, and there may also be further cars disposed in the shaft, likewise kept in the suspension ratio of 1:1 on separate cable strands, and it is possible to achieve the same advantages for guiding their cables if a cable guiding device according to the present invention is used. 
     The following description of two preferred embodiments of the invention serves for more detailed explanation in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a simplified graphic representation of an elevator installation, with two cars disposed one above the other, and a first embodiment of a cable guiding device; 
         FIG. 2  shows a schematic plan view of the elevator installation from  FIG. 1  and 
         FIG. 3  shows a schematic plan view corresponding to  FIG. 2  of an elevator installation with a second embodiment of a cable guiding device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawing, an elevator installation  10  is schematically represented, with a first car  12  and a second car  14  disposed under it, which cars can be made to travel up and down separately from each other in a shaft  16 . The first car  12  is connected to a counterweight  20  by means of a single cable strand  18 , the cable strand  18  being led over a traction sheave  22  and a deflecting roller  24 , which are held in a shaft region or machine space  26  disposed at the upper end of the shaft  16 . The traction sheave  22  is driven by a drive motor  28 , so that the first car can be made to travel up and down within the shaft  16 . The cable strand  18  may comprise a number of individual cables. 
     The second car  14  is connected by means of two cable strands  30 ,  31  to a separate counterweight  33 , which is disposed laterally next to the counterweight  20  of the first car  12 . The two cable strands  30 ,  31  of the second car  14  may in each case comprise a number of individual cables. They are fixed to the car  14  on sides lying opposite each other, and therefore run laterally outside the first car  12 , so that the latter is not hindered by the cable strands  30 ,  31 . Starting from the second car  14 , there extends in each case a first cable strand portion  30   a  and  31   a , respectively, in a vertical direction upward as far as a first deflecting roller  35  and  36 , respectively, which is disposed within the upper shaft region or machine space  26  and is joined to a second cable strand portion  30   b  and  31   b , respectively. The second cable strand portions  30   b ,  31   b  run in a horizontal direction as far as a second deflecting roller  38  and  39 , respectively, at which they are in each case joined in a vertical direction to a third cable strand portion  30   c  and  31   c , respectively. The cable strands  30  and  31  are deflected by 90° in each case both at the first deflecting roller  35  and  36 , respectively, and at the second deflecting roller  38  and  39 , respectively. 
     The third cable strand portions  30   c  and  31   c  extend in a vertical direction as far as a common traction sheave  41 , which is driven by a drive motor  44  and has a first traction sheave part  42  and a second traction sheave part  43 , lying directly against the latter. The traction sheave parts  42  and  43  may be connected rigidly, in particular integrally, to each other. The cable strand  30  is led around the first traction sheave part  42  and the cable strand  31  is led around the second traction sheave part  43 . At the respective traction sheave part  42 ,  43 , in the case of the embodiment represented in  FIGS. 1 and 2 , the cable strands  30  and  31 , respectively, undergo a renewed deflection by 90°, so that the respective third cable strand portion  30   c  and  31   c , respectively, is joined to a fourth cable strand portion  30   d  and  31   d , respectively, which is horizontally aligned. The fourth cable strand portion  30   d  and  31   d , respectively, is joined, after a third deflecting roller  45  and  46 , respectively, to a fifth cable strand portion  30   e  and  31   e , respectively, which is directed vertically downward and ends at the counterweight  33  of the second car  14 . The third deflecting rollers  45  and  46  lie directly against each other. They may also be configured as a common, freely rotatable deflecting roller in the form of a single component. 
     As is clear in particular from  FIG. 2 , the two cable strands  30 ,  31  of the second car  14  run mirror-symmetrically in relation to each other with respect to a plane of symmetry  48 , the first cable strand portions  30   a ,  31   a  as well as the third, fourth and fifth cable strand portions  30   c ,  31   c ;  30   d ,  31   d  and  30   e ,  31   e  running parallel to the plane of symmetry and the second cable strand portions  30   b ,  31   b  being inclined in each case at the same angle in relation to the plane of symmetry. 
     It is also clear from  FIG. 2  that the axis of rotation  50  of the traction sheave  41  of the second car  14  runs parallel to a joining line  52 , which joins to each other the imaginary points of intersection  54 ,  55  of the first cable strand portions  30   a ,  31   a  with the horizontal plane  57  defined by the two cable strand portions  30   b ,  31   b . The joining line  52  runs perpendicularly in relation to the fourth cable strand portion  30   d ,  31   d.    
     The two cable strands  30  and  31  each have the same cable tension and the sequence of the changes in direction taking place at the deflecting rollers  35 ,  36 ,  38 ,  39 ,  45 ,  46  and the traction sheave  41  is identical for the two cable strands  30 ,  31 . The cable strands  30  and  31  in each case undergo a single bending change in the region between the second car  14  and the counterweight  33 , since the running-around direction which the cable strands  30 ,  31  have at their respective first deflecting roller  35  and  36  is opposite to the running-around direction at the respectively second deflection roller  38  and  39 , while the running-around direction is in each case identical in the region of the second deflecting rollers  38 ,  39  as well as in the region of the traction sheave  41  and the third deflecting rollers  45 ,  46 . The distance between the first deflecting roller  35  and the second deflecting roller  38  of the cable strand  30  is identical to the distance between the first deflecting roller  36  and the second deflecting roller  39  of the cable strand  31 . The same applies correspondingly to the distances between the second deflecting rollers  38  and  39 , respectively, and the traction sheave  41  and also to the distances between the traction sheave  41  and the third deflecting rollers  45  and  46 , respectively. The distances between the respective cable fastening points  59  and  60  of the two cable strands  30 ,  31  to the second car  14  and the respective first deflecting roller  35  and  36  as well as the distances between the third deflecting rollers  45  and  46 , respectively, and the common cable fastening points  62  of the two cable strands  30 ,  31  to the counterweight  33  are also identical. 
     In  FIG. 3 , a plan view of an elevator installation according to the invention with a second embodiment of a cable guiding device is schematically represented. The elevator installation is largely identical to the elevator installation  10  represented in  FIGS. 1 and 2  and explained above. Therefore, the same reference numerals as in  FIGS. 1 and 2  are used for identical components in  FIG. 3 . To avoid repetition, reference is made in this respect to the explanations given above. 
     In the case of the embodiment represented in  FIG. 3 , starting from the first car  12 , the cable strand  18  first runs over the deflecting roller  24  and then, after a deflection by 90° and a horizontal cable strand portion, meets the traction sheave  22 . From the latter, the cable strand  18  extends in a vertical direction directly to the counterweight  20 . 
     In a way corresponding to the embodiment represented in  FIGS. 1 and 2 , in the case of the embodiment according to  FIG. 3 , too, the second car  14  is connected by means of two cable strands  30 ,  31  to a counterweight  33 , which is disposed laterally next to the counterweight  20  of the first car  12 . The two cable strands  30 ,  31  are fixed to the car  14  on sides lying opposite each other, and run laterally outside the first car  12  past the latter. A first cable strand portion  30   a  and  31   a , respectively, extends from the second car  14  upward in a vertical direction as far as a first deflecting roller  35  and  36 , respectively, which is disposed within the upper shaft region or machine space  26  and at which it is joined to a second cable strand portion  30   b  and  31   b , respectively. As a difference from the first embodiment represented in  FIGS. 1 and 2 , the second cable strand portions  30   b ,  31   b  run in the direction of the side of the car  14  that is facing the counterweight  33  of the second car  14 . They run in a horizontal direction as far as a second deflecting roller  38  and  39 , respectively, at which it is in each case joined upwardly in a vertical direction to a third cable strand portion  30   c  and  31   c , respectively. The cable strands  30  and  31  are deflected by 90° in each case both at the first deflecting roller  35  and  36 , respectively, and at the second deflecting roller  38  and  39 , respectively. 
     The third cable strand portions  30   c  and  31   c  extend in a vertical direction as far as the common traction sheave  41 , which has the two traction sheave parts  42  and  43 , which lie directly against each other and over each of which a cable strand  30  and  31 , respectively, of the second car  14  is led. The cable strands  30  and  31  undergo a deflection by 180° at the respective traction sheave part  42  and  43 . This has the consequence that, in the case of the embodiment represented in  FIG. 3 , the respective third cable strand portion  30   c  and  31   c  is joined to a vertically aligned fourth cable strand portion  30   f  and  31   f , respectively, which extends from the traction sheave  41  directly to the counterweight  33 . 
     Both in the case of the first embodiment, represented in  FIGS. 1 and 2 , and in the case of the second embodiment, represented in  FIG. 3 , the two cable strands  30 ,  31  of the second car  14  are subjected to virtually the same cable loading during the operation of the elevator installation  10 , and for this reason also have virtually the same wear. This has the result that the two cable strands  30 ,  31  reach their maximum permissible degree of wear at approximately the same point in time, when they must be exchanged. The extension and slippage behavior of the cable strands  30  and  31  is also virtually identical. The exchange of the cable strands  30  and  31  can be carried out at the same time and the cable strands  30 ,  31  can both be used out optimally. As a result, the operating costs of the elevator installation  10  can be kept relatively low.