Abstract:
A method and device for testing the tensile stress in tension elements of a tension element cord utilizes a measuring gage which is clamped between two tension elements of the tension element cord. The gage establishes a reference point relative to a fixed point stationary with respect to the tension element cord. The gage extends horizontally between two vertically extending length portions of the two tension elements. Then it is determined whether the reference point of the measuring gage is shifted with respect to the fixed point in the horizontal direction, wherein such a shift is dependent on a difference in the tension stresses in the two tension elements.

Description:
FIELD 
     The invention relates to a method and a device for testing the tension stress in tension elements of a tension element cord. 
     BACKGROUND 
     There are various elevator and load transport systems which have a number of tension elements, for example flat or V-ribbed belts, for carrying and driving the elevator car or a platform. The tension elements are typically fixed in the region of a counterweight, carry a counterweight, are deflected at an upper (driving) pulley and then, for example in the form of an underloop, run through under the elevator car and are fixed on the other side of the elevator car. This fixing is also designated as a car-side tension element fixed point, whereas fixing in the region of the counterweight is designated as a counterweight-side tension element fixed point. 
     There are various possibilities for implementing these tension element fixed points in concrete terms. 
     In the elevator and load transport systems, during assembly, but also during maintenance, it is determined whether the tension elements of a suspension cord are uniformly loaded, for example in order to test whether uniform load distribution is ensured. The outlay hitherto involved in this respect is relatively high, and the equipment which is sometimes used is costly and sensitive. 
     A corresponding measuring instrument is known from the published patent application EP 573831 A1. This measuring instrument comprises a torsionally and flexurally resistant force sensor, so that as accurate evidence as possible as to the instantaneous tensile forces of a rope can be obtained. A tension element is retained at two points, and the tension element is deflected in the middle between these two points and is measured. When a load limit is overshot, for example, a signal may be triggered. 
     Another solution for tension element monitoring is known from the published patent application EP 1847501 A1. The means for tension element monitoring are fastened firmly to a guide track of an elevator system. The belt-like tension element to be monitored is led past a sensing surface. A sensing arrangement is integrated into this sensing surface, for example so that variations in the structure of the monitored tension element can be detected. 
     A type of measuring gage or alignment aid is known from the published patent application EP 0 498 051 A2. However, this measuring gage or alignment aid is not designed as a measuring gage for clamping between two tension elements, but serves instead for the alignment of guide rails. 
     SUMMARY 
     An object, then, is to provide another method and a corresponding device so that differences in the tension stresses in tension elements of a tension element cord can be detected simply and quickly. 
     One advantage of the invention is that there is no need for additional tools or equipment for the field test of tension stress. Moreover, it is considered an advantage of the invention that the measuring gage is cost-effective and simple to handle. Relative determination of the tension stress of the tension elements of the tension element cord is possible by means of the measuring gage. Also, by means of the measuring gage according to the invention, the tension stress of the tension elements can be set simply and quickly and different tension stresses between the tension elements can be compensated. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention is described in detail below by means of exemplary embodiments illustrated in the drawings in which: 
         FIG. 1  shows a diagrammatic view of a first previously known elevator system in which a measuring gage according to the invention can be used; 
         FIG. 2  shows details of a tension element fastening according to the prior art; 
         FIG. 3  shows a sectional illustration of the tension element fastening according to  FIG. 2 ; 
         FIG. 4  shows a diagrammatic view of a first measuring gage according to the invention; 
         FIG. 5A  shows details of a tension element cord with two tension elements which run along a guide rail and which both have a uniform tension load, a first method step of the invention being shown; 
         FIG. 5B  shows details of the tension element cord according to  FIG. 5A , a second method step of the invention being shown; 
         FIG. 5C  shows a diagrammatic illustration of a parallelogram of forces; 
         FIG. 6A  shows details of a tension element cord with two tension elements which run along a guide rail and which both have a nonuniform tension load, a first method step of the invention being shown; 
         FIG. 6B  shows details of the tension element cord according to  FIG. 6A , a second method step of the invention being shown; 
         FIG. 6C  shows a diagrammatic illustration of a parallelogram of forces; 
         FIG. 7  shows a diagrammatic view of a second measuring gage according to the invention; 
         FIG. 8  shows a diagrammatic view of a third measuring gage according to the invention; 
         FIG. 9A  shows details of a tension element cord with four tension elements which run along a guide rail, a first method step of the invention being shown; 
         FIG. 9B  shows details of the tension element cord according to  FIG. 9A , a further method step of the invention being shown; 
         FIG. 9C  shows details of the tension element cord according to  FIG. 9A , yet a further method step of the invention being shown; and 
         FIG. 10  shows a diagrammatic view of a fourth measuring gage according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary elevator system  20 , in which a measuring gage according to the invention can be used, is shown in  FIG. 1  in a diagrammatic perspective view. This figure shows an elevator system  20  which has no machine space and which comprises an elevator shaft or may be of the shaftless type. 
     The elevator system  20  comprises an elevator car  13  and at least one first guide rail  25  for the vertical guidance of the elevator car  13 . The guide rail  25  is illustrated in  FIG. 1  merely by a dashed line. Two tension elements which run essentially parallel to one another are provided here. In the following description and in the figures, the front tension element is designated by  22 . 1  and the rear tension element by  22 . 2 , where this is necessary to distinguish between them more clearly. At the car-side end of the tension elements, these are fixed in the region of first tension element fixed points  29  to the guide rail  25  or to a shaft wall (not shown). Each of the tension elements  22 . 1  and  22 . 2  loops under the elevator car  13 , loops around a driving pulley  12 , which is arranged upstream of a drive (not visible in  FIG. 1 ) and carries a counterweight  18 . In the example shown, the tension elements carry the counterweight  18  in that the tension elements revolve around counterweight rollers  21  and are fixed at the counterweight-side end in the region of second tension element fixed points  28 . In the embodiment shown, the underlooping of the elevator car  13  takes place by means of car carrying rollers  17 . 1  and guide rollers  17 . 2  which are in this case designed in pairs. The second tension element fixed points  28  may be provided, for example, on a shaft wall or on the console of the drive unit (not shown). 
     The two tension elements  22 . 1  and  22 . 2  run essentially parallel to one another. As seen from the counterweight-side tension element fixed points  28 , the tension elements run downward, loop partially around the counterweight carrying rollers  21  and are led further up in the elevator shaft  11  around the driving pulley or driving pulleys  12 . The tension elements run from there downward along the left sidewall of the elevator car  13  and are then led at least partially around the car carrying rollers  17 . 1 . This type of suspension is designated as underlooping. On the right side of the elevator car  13 , the tension elements are led upward, where each of the tension elements is fastened in the region of car-side tension element fixed points  29  to the guide rail  25  or to a shaft wall. 
     The term “tension element” is to be understood here as a synonym for any type of rope and means which are suitable for carrying and moving the elevator car  13  and the counterweight  18 . The tension elements are preferably flat or V-ribbed belts. In the context of the invention, however, steel or plastic ropes of round cross section may also be used as suspension means. 
       FIG. 2  shows exemplary details of the car-side tension element fixed points  29 . Fastening may take place, for example, by means of a crossbar  30  which is fastened in the upper region of the guide rail  25 . 
     The two fastening points  29 . 1  and  29 . 2  are arranged symmetrically with respect to the vertical axis VA of the guide rail  25 . In the example shown, the fastening of the tension elements  22 . 1  and  22 . 2  takes place by means of round rods  23 . 1 ,  23 . 2  (also called tension rods) which are mounted in the upper region in lugs  24 . 1 ,  24 . 2 . The lugs  24 . 1 ,  24 . 2  are seated on axles, screws or the like and are thus fastened to the crossbar  30 . Clamping or screwing devices  19 . 1 ,  19 . 2  (also designated as a belt fastener) are provided, which receive and fix the ends of flat or V-ribbed belts  22 . 1 ,  22 . 2 . The round rods  23 . 1 ,  23 . 2  may be designed as threaded spindles, so that the position of the tension element end or the tension stress F 1  or F 2  of the respective tension element  22 . 1 ,  22 . 2  may be set by rotating the round rods  23 . 1 ,  23 . 2 . 
       FIG. 3  shows a section through the fastening region of the device of  FIG. 2 .  FIG. 3  serves for explaining the geometric arrangement of the individual elements. 
       FIG. 4  shows a first embodiment of a measuring gage  100  for testing the tension stress in tension elements  22 . 1 ,  22 . 2  of a tension element cord. This measuring gage  100  is distinguished in that it is designed especially for horizontal clamping between two vertically running tension elements  22 . 1 ,  22 . 2 , as is described below. For this purpose, the measuring gage  100  has at least two side faces  101 . 1 ,  101 . 2  which lie symmetrically to a reference point M 1  or to a center line L 1  of the measuring gage  100  and which extend parallel to the center line L 1  running through the reference point M 1  of the measuring gage  100 . The measuring gage  100  is depicted in  FIG. 4  on the same scale as the elements of  FIG. 3 . In order to implement the method according to the invention, the measuring gage  100  is clamped between the two tension elements  22 . 1 ,  22 . 2  of  FIG. 3 , the inwardly pointing side faces  31 . 1 ,  31 . 2  of the tension elements  22 . 1 ,  22 . 2  bearing against the outwardly pointing side faces  101 . 1 ,  101 . 2  of the measuring gage  100 . 
     The reference point M 1  lies on the center line L 1  because the tension elements  22 . 1 ,  22 . 2  are arranged symmetrically to the guide rail  25  and the guide rail  25  serves as a fixed point. If an off-center fixed point is referred to, the center point M 1  serving as a reference point no longer lies on the center line L 1 . The reference point M 1  is then aligned with the fixed point. 
     The measuring gage  100 , as seen in a top view, preferably has a U-shape or a C-shape, for example so as to be capable of engaging around the guide rail  25  located in the middle. If the measuring gage  100  is to be used at some other point of the elevator system (for example, on the counterweight side), it may also have a different shape, but one in which at least the side faces  101 . 1 ,  101 . 2  are designed symmetrically to the center line L 1 . 
     In further embodiments, the measuring gage  100  may have, in addition to the two side faces  101 . 1 ,  101 . 2 , for example two further side faces  102 . 1 ,  102 . 2  which also lie symmetrically to the center line L 1  of the measuring gage  100 . In the embodiment shown in  FIG. 4 , these further side faces  102 . 1 ,  102 . 2  point inward. 
     The method according to the invention for testing the tension stress in tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4  of a tension element cord is explained, then, by means of the exemplary  FIGS. 5A-5C . The method preferably comprises the following steps:
     a. Provision of a measuring gage  100  which is designed to be clamped between at least two tension elements  22 . 1 ,  22 . 2  of the tension element cord. The measuring gage  100  may, for example, be the embodiment of  FIG. 4 ,  7 ,  8  or  10 .   b. Definition of a fixed point M at a stationary point (for example, on the guide rail  25 ). This takes place, for example, in that the measuring gage  100  is held essentially horizontally to the tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4  or at right angles to the tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4  such that the two inwardly pointing faces  102 . 1 ,  102 . 2  coincide with the outwardly pointing side faces of the tension elements  22 . 1 ,  22 . 2 . Preferably, in this step b., care is taken to ensure that the tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4  are not displaced or pressed to the side. In step b., the reference point M 1 , which may be marked, for example, on the measuring gage  100 , is transferred to the guide rail  25 , for example, by means of a pencil, sticker or other marking. The corresponding stationary point or fixed point is identified here by M.   c. This is then followed by the essentially horizontal clamping of the measuring gage  100  between the essentially vertically running length sections of the two tension elements  22 . 1 ,  22 . 2  of the tension element cord, as shown in  FIG. 5B . For this purpose, the measuring gage  100  may be tilted, for example, through 90°. Preferably, the measuring gage  100  is clamped such that the inwardly pointing side faces  31 . 1 ,  31 . 2  of the tension elements  22 . 1 ,  22 . 2  bear against the outwardly pointing side faces  101 . 1 ,  101 . 2  of the measuring gage  100 .   d. It is then determined whether the reference point M 1  of the measuring gage  100  deviates in an essentially horizontal direction with respect to the fixed point M. In the example shown in  FIG. 5B , the measuring gage  100  is seated exactly in the middle between the tension elements  22 . 1 ,  22 . 2 , and the reference point M 1  of the measuring gage  100  is ideally congruent with the defined fixed point M on the guide rail  25 . It can be concluded from this that the tension stresses F 1  and F 2  in both tension elements  22 . 1 ,  22 . 2  are identical, that is to say F 1 =F 2 .  FIG. 5C  shows by means of a diagrammatic parallelogram of forces that, in a fully symmetrical tension stress situation, the two horizontal force vectors V 1  and V 2  which act laterally upon the measuring gage  100  cancel (compensate) one another.   

     If, in step d, a displacement of the reference point M 1  with respect to the fixed point M in the horizontal direction occurs, the following proposition applies. The displacement is in each case proportional to the absolute amount of the difference of the tension stresses |F 1 −F 2 | in the two tension elements  22 . 1 ,  22 . 2 . 
     The exemplary  FIGS. 6A-6C  show a situation with asymmetric tension stresses F 1 &gt;F 2 , F 1  being the tension stress in the tension element  22 . 1  and F 2  being the tension stress in the tension element  22 . 2 . Since a higher tension stress F 1  is present in the tension element  22 . 1  than in the tension element  22 . 2 , the measuring gage  100 , after being clamped (step c. of the method), is pressed slightly to the left. This displacement can be seen if the position of the reference point M 1  of the measuring gage  100  is considered in relation to the stationary fixed point M. M 1  here lies somewhat to the left of M. By means of the parallelogram of forces in  FIG. 6C , it can be shown that the force vector V 1  is greater than the force vector V 2 . The center line L 1  of the measuring gage  100  is thereby displaced with respect to the vertical axis VA of the guide rail  25 . 
       FIG. 7  shows a further embodiment of a measuring gage  100  for testing the tension stress in tension elements  22 . 1 ,  22 . 2  of a tension element cord. This measuring gage  100  is distinguished in that it is designed specially to be clamped horizontally between two essentially vertically running tension elements  22 . 1 ,  22 . 2 , as is described below. For this purpose, it has at least two side faces  101 . 1 ,  101 . 2  which lie symmetrically to a reference point M 1  or to a center line L 1  of the measuring gage  100  and which extend essentially parallel to the center line L 1  running through the reference point M 1  of the measuring gage  100 . The measuring gage  100  in  FIG. 7  has embedded (stability) bodies  103  in order to prevent distortion or flexion. That is to say, the (stability) bodies  103  serve for increasing the inherent rigidity of the measuring gage  100 . The measuring gage  100  according to  FIG. 7  may also be clamped between the two tension elements  22 . 1 ,  22 . 2  of, for example,  FIG. 3 , the inwardly pointing side faces  31 . 1 ,  31 . 2  of the tension elements  22 . 1 ,  22 . 2  bearing against the outwardly pointing side faces  101 . 1 ,  101 . 2  of the measuring gage  100 . 
     The measuring gages  100  are preferably provided with a defined reference spacing RA. The reference spacing RA may amount, for example, to 175 mm in the embodiment according to  FIG. 7 . This applies to all the embodiments shown. 
       FIG. 8  shows a further embodiment of a measuring gage  100  for testing the tension stress in a plurality of tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4  of a tension element cord. This measuring gage  100  is distinguished in that it is designed specially to be clamped essentially horizontally between a plurality of the essentially vertically running tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4 , as is described below. For this purpose, it has a plurality of side faces  101 . 1  and  101 . 2  and also  101 . 3  and  101 . 4  which lie in pairs symmetrically to a reference point M 1  or to a center line L 1  of the measuring gage  100  and which extend parallel to the center line L 1  running through the reference point M 1  of the measuring gage  100 . The measuring gage  100  in  FIG. 8  may again have embedded (stability) bodies  103  which, however, are not shown here. 
     It is shown by means of  FIGS. 9A ,  9 B and  9 C how the measuring gage  100  of  FIG. 8  can be used on tension element cords having a plurality of tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4 . 
     The measuring gage  100  according to  FIG. 8  can be used to define a fixed point M (called step b.) at a stationary point of, for example, an elevator system  20 . This takes place, for example, in that the measuring gage  100  is held, for example, on the two middle tension elements  22 . 1 ,  22 . 2  such that the two inwardly pointing faces  102 . 3 ,  102 . 4  coincide with outwardly pointing side faces of the tension elements  22 . 1 ,  22 . 2 . Preferably, in this step b., care is taken to ensure that the tension elements  22 . 1 ,  22 . 2  are not displaced or pressed to the side. In step b, the reference point M 1 , which may be marked, for example, on the measuring gage  100 , is transferred, for example, by means of a pencil or by other means to the guide rail  25 . The corresponding stationary point is identified here by M and is designated as a fixed point. 
     This is followed by the essentially horizontal clamping (called step c.) of the measuring gage  100  between the vertically running length sections of the two tension elements  22 . 1 ,  22 . 2  of the tension element cord, as shown in  FIG. 9B . For this purpose, the measuring gage  100  may be tilted, for example, through 90°. The measuring gage  100  is preferably clamped such that the inwardly pointing side faces  31 . 1 ,  31 . 2  of the suspension means  22 . 1 ,  22 . 2  bear against the outwardly pointing side faces  101 . 3 ,  101 . 4  of the measuring gage  100 . It can thus be determined whether an essentially horizontal displacement of the point M 1  with respect to the fixed point M occurs due to asymmetric tension bad distribution in the two inner tension elements  22 . 1 ,  22 . 2 . 
     In a purely symmetrical procedure which still refers to the previously defined fixed point M, the measuring gage  100  can then be clamped, for example, with the outwardly pointing side faces  101 . 1 ,  101 . 2  between the two outer tension elements  22 . 3 ,  22 . 4  (this not being shown in the figures), in order, here too, to determine whether horizontal displacement of the reference point M 1  with respect to the fixed point M occurs due to asymmetric tension load distribution in the two outer tension elements  22 . 3 ,  22 . 4 . 
     However, other relative considerations may also be implemented, in that, for example, the measuring gage  100  is clamped with the outermost side face  101 . 2  between the outermost tension element  22 . 4  and with the side face  101 . 3  against the tension element  22 . 1 . This situation is indicated in  FIG. 9C . If, then, in this situation the instantaneous position X 1  of the reference point M 1  is transferred to a stationary fixed point, for example, on the guide rail  25 , in a further step the measuring gage  100  can be used in a reversed situation (in a position mirrored with respect to the vertical axis VA). In this reversed situation, the measuring gage  100  would then be seated in a similar way between the tension elements  22 . 3  and  22 . 2 . Here, too, once again, the instantaneous position X 2  (not shown) of the reference point M 1  is transferred to a stationary fixed point, for example, on the guide rail  25 . Since the measuring gage  100  is used here asymmetrically with respect to the absolute middle position (defined, for example, by the vertical axis VA), the horizontal spacing between the points X 1  and X 2  must then be related, for example, to the position of the vertical axis VA. If the spacing between the vertical axis VA and the point X 1  and the spacing between the vertical axis VA and the point X 2  are identical, then the tension loads in all four tension elements are identical (called a case of symmetry). 
     The measuring gage may also be used for measuring the tension stress in the tension elements  22 . 1 ,  22 . 2  running underneath the elevator car  13 . In this case, a stationary fixed point M is defined, and this is transferred as a reference point to the measuring gage before clamping essentially at right angles to the tension stresses between two tension elements. The distance between the fixed point and reference point and the displacement direction of the reference point are the measure for different tension stresses in the tension elements. 
     However, the invention may also be used on other elevator systems with different tension element configurations (for example, with an asymmetric tension element cord having, for example, three tension elements on one side of the guide rail). The method is employed here in a similar way so that relative evidence is possible. 
     In order to make it possible to clamp the measuring gage  100  horizontally between two or more vertically running tension elements  22 . 1 ,  22 . 2 ,  22 . 3 ,  22 . 4 , in a preferred embodiment the measuring gage  100  may comprise a spirit level. Preferably, a spirit level attachment is provided on the measuring gage  100  or, as indicated in  FIG. 10 , a spirit level bubble  104  is integrated into the measuring gage  100 . 
     The measuring gage  100  is preferably manufactured from a plastic (for example, acrylic or nylon). However, for example, a measuring gage  100  manufactured from metal may also be used. 
     The present invention may advantageously be used in an elevator system according to FIG. 6 of the initially mentioned patent application EP 1847501 A1. There, the respective tension elements are supported on a console by means of a tension rod, belt fastener and compression spring. The compression spring is intended to compensate different tension stresses in the individual tension elements. In practice, however, the compression springs have high tolerances in terms of length and rigidity, thus leading, in turn, to different tension stresses and different loads in the individual tension elements. If the measuring gage  100  is used in such an elevator system, then different tension stresses can be revealed quickly and simply. Differences can be compensated by adjusting the tension rods. 
     However, the principle according to the invention can also be applied to elevator systems which have no compression springs, as shown, for example, in  FIG. 2 . Here, too, any differences can be compensated by adjusting the round rods  23 . 1 ,  23 . 2 . 
     It is obvious that there are other similar possibilities for using a measuring gage  100  according to the invention. Arrangements having at least one tension element cord composed of belts, ropes or bands (belt drives, ropeways or conveyor bands) may be envisaged for the use of the measuring gage according to the invention. 
     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.