Abstract:
A arrangement for determining the alignment of marked axes ( 22, 28, 36, 38, 48, 50 ) of a first ( 20, 30, 40 ) and a second body ( 26, 32, 42 ) relative to one another, which is provided with a first and a second measurement device ( 10, 12 ) which can be attached to the first body or to the second body in a fixed spatial relation to the respective marked axis, the first measurement device ( 10 ) having a first source (L 2 ) for delivering a light beam and a second (D 1 ) and a third optoelectronic sensor (D 3 ), and the second measurement device ( 12 ) having a second (L 1 ) and a third source (L 3 ) for a light beam and a first optoelectronic sensor (D 2 ), the optoelectronic sensors being made such that they can determine the impact point of a light beam on the sensor, and the first light source being assigned to the first sensor and the second and the third light source being assigned to the second and third sensor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an arrangement and a process for determining the alignment of marked axes of a first and a second body, for example two rollers, shafts or pulleys. 
     2. Description of Related Art 
     WO 01/50082A1 and corresponding published U.S. patent application Ser. No. 2000/005134A1 disclose a device and a process for determining the alignment of two pulleys relative to one another. To do so, there are two measurement means which correspond to one another and which each can be attached to the running surface of one of the two pulleys. Each measurement means comprises a laser light source which delivers a fan-shaped laser beam, which lies in a plane which is parallel to the end face of the respective pulley. On either side of each laser light source, there is a respective light sensor, the laser light source and the two light sensors each lying on one line. When the axes of rotation of the pulleys are parallel to one another and the pulleys do not have any parallel offset, the laser light fan delivered by the opposing measurement means runs through the two light sensors. Correct alignment of the two pulleys relative to one another will be recognized using the corresponding signals of two sensors of the two measurement means at a time. Furthermore, the use of the system for determining the alignment of two rollers relative to one another is also described. 
     The disadvantage, in this system is the poor accuracy with respect to determining twisting of the shaft axes or pulley axles relative to one another, i.e., skewing of the two axles relative to one another can only be ascertained with relatively poor accuracy. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to devise an arrangement and a process for determining the alignment of the marked axes of two bodies relative to one another, and determination of the skew of the marked axes will be enabled with relative accuracy. 
     This object is achieved in accordance with the invention by an arrangement for determining the alignment of marked axes of a first and a second body relative to one another, with a first and a second measurement means which can be attached to the first body or to the second body in a fixed spatial relation to the respective marked axis, the first measurement means having a first light source for delivering a light beam and a second and a third optoelectronic sensor, and the second measurement means having a second and a third light source for a light beam and a first optoelectronic sensor, the optoelectronic sensors being made such that they can determine the impact point of a light beam on the sensor, and the first light source being assigned to the first sensor and the second and the third light source being assigned to the second and third sensor. 
     This object is also achieved in accordance with the invention by a process for determining the alignment of the alignment of marked axes of a first and a second body relative to one another, in which a first and a second measurement means are attached to the first body and to the second body in a fixed relation to the respective marked axis, a first light beam is delivered by the first measurement means by means of a first light source to a first optoelectronic sensor provided on the second measurement means, and a second and a third light beam are delivered by the second measurement means, by means of a second and third light source, to a second and third optoelectronic sensor provided on the first measurement means, the impact point of the assigned light beam on the sensor surface being determined by the optoelectronic sensors, and the relative alignment of the two measurement means being computed from the determined impact points of the first, second and third light beam. 
     In the approach in accordance with the invention, it is advantageous that skewing of the marked axes of the two bodies relative to one another can be determined with relative accuracy. 
     The invention is explained in detail below by way of example using the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically shows a perspective view of an arrangement for determining the alignment of two bodies relative to one another, including the emitted light beams; 
     FIG. 2 schematically shows the use of the arrangement from FIG. 1 for determining the alignment of two rollers, 
     FIG. 3 schematically shows the use of the arrangement from FIG. 1 for determining the alignment of two coupled shafts to one another, and 
     FIG. 4 shows the use of the arrangement from FIG. 1 for determining the alignment of two pulleys. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 schematically shows one example for an arrangement in accordance with the invention for determining the alignment of two bodies relative to one another, which comprises a first measurement means  10  and a corresponding second measurement  12  which interacts with it. The first measurement means  10  comprises a laser light source L 2  and two optoelectronic sensors D 1  and D 3 , the laser light source L 2  being located in the middle between the two sensors D 1  and D 3 . The sensors D 1  and D 3  and the laser light source L 2  are located on the front  14  of the measurement means  10  roughly on a straight line. The sensors D 1  and D 3  on the front  14  of the measurement means  10  have a planar sensor surface and are made such that they can detect the impact point of the light beam or light spot on the sensor surface, for example, the x and y coordinates of the impact point are determined and are output as the sensor signal (the y axis and the x axis of the sensor surface of the sensor D 1  are shown schematically in FIG. 1, the x axis running in the horizontal direction and the y axis in the vertical direction), i.e. the sensors D 1 , D 2  and D 3  being duo-lateral detectors. The sensor surfaces of the sensors D 1  and D 3  lie in the same plane. 
     The laser light source L 2  is made such that it emits an essentially collimated, i.e., nondivergent, laser beam which is perpendicular to the plane of the sensor surfaces of the sensors D 1  and D 3 . 
     The back  16  of the measurement means  10  is provided with a device (not shown), by means of which the measurement means  10  can be securely attached in a suitable manner to the body which is to be measured, as is explained in detail below. 
     The second measurement means  12  is made as a corresponding counterpart to the measurement means  10  and has two laser light sources L 1  and L 3  and a light sensor D 2  which is located in the middle between the two laser light sources on a straight line with them. The laser light sources L 1  and L 3  and the sensor D 2  are made analogously to the laser light source L 2  and the sensors D 1  and D 3 . The laser beams emitted by the light sources L 1  and L 3  are parallel to one another and are perpendicular to the sensor surface of the sensor D 2 . 
     The arrangement of the light sources L 1 , L 2 , and L 3  and the sensors D 1 , D 2 , D 3  is chosen such that, if the two measurement means  10  and  12  are arranged exactly opposite one another and parallel to one another, the laser beam which is delivered by the light source L 1  strikes the surface of the sensor D 1  exactly in the middle, the laser beam of the light source L 2  strikes the sensor D 2  in the middle and the laser beam of the light source L 3  strikes the sensor D 3  in the middle. In this case the laser beams of the light sources L 1 , L 2  and L 3  are parallel to one another and lie in the same plane which is horizontal according to FIG.  1 . 
     The relative alignment of the two measurement means  10  and  12  is computed using the impact points of the laser beams of the light sources L 1 , L 2 , and L 3 , which points are determined by the detectors D 1 , D 2 , and D 3 , by means of suitable electronics (not shown). 
     FIG. 2 shows by way of example one application for the measurement arrangement shown in FIG. 1, the measurement means  10  with its back  16  being mounted by form-fit on the outside peripheral surface  18  of the roller  20 . Here, the plane of the sensor surfaces of the sensors D 1  and D 3  runs tangentially to the peripheral surface  18  of the roller  20 . The line on which the sensors D 1  and D 3  and the light source L 2  lie runs parallel to the lengthwise axes  22  of the rollers. 
     The second measurement means  12  is mounted analogously on the outside peripheral surface  24  of a second roller  26  which is located essentially parallel to the first roller  20 , i.e. the roller axes  22  and  28  run essentially parallel. In this example, the measurement means  10  and  12  are used to ascertain whether, and optionally which, deviation from an exactly parallel alignment of the roller axes  22  and  28  is present. 
     Before the start of the actual measurement, the two measurement means  10  and  12  are shifted on the peripheral surface  18  and  24  such that the laser beam of the light source L 2 , as much as possible, strikes the center of the sensor surface of the sensor D 2 , i.e., the deviation of the impact point from the coordinate origin of the sensor surface of the sensor D 2  should be as small as possible. Then, the actual measurement is taken, i.e., the determination of the impact points of the laser beams of the light sources L 1  and L 3  on the sensor surface of the sensors D 1  and D 3 . In the evaluation, the measurement results of all three sensors D 1 , D 2  and D 3  are considered. An exactly parallel alignment of the roller axes  22  and  28  is present when either all three laser beams hit the center of the respective detector surface or if, in general, the determined y-coordinate of the sensors D 1  and D 3  is the same, and furthermore, the x-cordinate of the sensors D 1 , D 2  and D 3  is the same (rotation around the axes  22 ,  28  or a displacement along the axes  22 ,  28  has no effect on the parallelism; a corresponding deviation in the calibration of the two measurement means  10  and  12  relative to one another is thus automatically corrected; thus, it is not necessary for the laser beam of the light source L 2  to hit exactly the center of the detector surface of the detector D 2 ). 
     Deviations from the exact parallelism of the axes  22  and  28 , specifically a skewed and/or divergent arrangement of the axes  22  and  28  relative to one another, lead to a corresponding torsion or tilting of the measurement means  10  and  12  relative to one another so that the lines on which the sensors D 1 , D 3  and the light source L 2  as well as the sensor D 2  and the light sources L 1 , L 2  lie are no longer parallel to one another; this leads to corresponding “asymmetrical” impact coordinates of the laser beams, from which the position deviations can be quantitatively determined. 
     FIG. 3 shows one application in which the measurement means  10  and  12  are used for checking the flush alignment of the axes of rotation  36  and  38  of the two coupled shafts  30  and  32 . Here, the measurement means  10  and  12  are mounted by means of the corresponding schematically shown fasteners  34  by form-fit on the outside periphery of the corresponding shaft  30  and  32 ; in contrast to the example from FIG. 2, the planes of the sensor surfaces of the sensors D 1 , D 2 , and D 3  are not tangential, but perpendicular to the outside peripheral surfaces of the shafts  30  and  32 . 
     Based on the different geometrical arrangement, compared to the embodiment as shown in FIG. 2, here, other criteria apply to the evaluation of the measurement results. Thus, for example, in the embodiment as shown in FIG. 3, displacement in the y direction between the two measurement means  10  and  12  is an indication of parallel offset of the two shaft axes, conversely relative skewing between the two measurement means  10  and  12  around the axis of the light beams of the light source L 2  or the axis parallel to it is acceptable, since this is only an indication of inexact initial calibration of the measurement means  10  and  12 . 
     FIG. 4 shows another application of the measurement arrangement, it being used to check the alignment of two pulleys  40  and  42  relative to one another. Here, the measurement means  10  and  12  are each mounted on the outside periphery or the running surface  44  and  46  of the pulley  40  and  42 , the type of attachment corresponding geometrically to that from FIG. 2, i.e., the sensor surfaces are tangential to the peripheral surface  44  and  46 . For detecting the parallelism of the axes  48  and  50  of rotation of the pulleys  40 ,  42 , thus, the same criteria apply as in the embodiment as shown in FIG.  2 . However, in the embodiment as shown in FIG. 4, in addition, the determination of the parallel offset between the pulleys  40  and  42  is of interest, since the pulleys should lie in the same plane for optimum transfer of force and to minimize the wear. Accordingly, the type of attachment of the measurement means  10  and  12  to the pulleys  40 ,  42  is selected such that displacement along the axes  48  and  50  of rotation is not possible (for example, by fixing in the belt groove). 
     According to the described embodiments, the measurement arrangement from FIG. 1 can be used as a roller alignment device, a shaft alignment device and a belt alignment device by providing the corresponding mounting possibilities. Six degrees of freedom can be measured with the described arrangement. 
     In one modification of the described embodiments, the laser beams of the light sources L 1  and L 3  in the x direction have a slight divergence, by which distance measurement between the two measurement means  10  and  12  is enabled, since then the impact point depends on the distance. In this embodiment, the calibration procedure and the evaluation process must be adapted accordingly to be able to separate the distance effects from the misalignment effects. The divergence angle is chosen such that, for the intended distance measurement task, between the minimum distance A min  and the maximum distance A max , the detector size DX, i.e., the corresponding transverse dimension of the detector, is scanned, so that the divergence angle Div follows from the relationship: 
     
       
           Div=DX /( A   max   −A   min ). 
       
     
     In this invention, in addition to the good accuracy in determination of a skewed position, it is advantageous that a slight rotational misalignment of the measurement means  10  and  12  relative to one another around the axes  22 ,  28  and  48 ,  50  which are to be measured is not a barrier to exact measurement, since this can be corrected by the evaluation of all three sensors accordingly.