Abstract:
A device for quantitative assessment of the orientation of two machines relative to one another has auxiliary devices in the form of extenders or holding devices ( 40, 50 ) on which displacement and/or mounting of light transmitting or receiving devices ( 44, 52 ) are mountable in a manner that makes the use of a precision pivot bearing unnecessary.

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The invention relates to a device and the corresponding process for quantitative assessment of the orientation of two machines or machine parts relative to one another which are connected by a cardan shaft with two universal joints. 
   A device of this type is known and is shown in  FIG. 1 . Such a device requires a precise and relatively costly rotary joint  22  in order to keep a means  24  for sending and receiving a measurement light beam  28  from a source at distance from the machine shaft  10  which is to be measured. For this purpose, for example, an extender rail  20  and clamp devices  16  are used in addition. 
   SUMMARY OF THE INVENTION 
   A primary object of this invention is to devise a device that is comparable comparable to the known device but which is clearly more economical and does not adversely affect the ease of operation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is perspective view of a known device. 
       FIG. 2  is a perspective view showing alignment being performed with a device in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention is based on the finding that it is often necessary, in practice, to determine the parallel axial offset of machines which are structurally connected by a cardan shaft with two universal joints. Generally, a cardan shaft is used when there is, in principle, a parallel axial offset and knowing the absolute magnitude of the offset is not critical. However, for reasons of rotational kinematics, it is especially important that the axes of the shafts of the machines which have been coupled to one another in this way are, for the most part, parallel in order to avoid even the smallest variations of angular accelerations on the rotating machine elements. Accordingly, in accordance with the invention, it is not necessary to provide a measurement system which, at the same time, can detect the parallel and angular offset of shafts. Rather, it is sufficient to provide a measurement system which can detect simply the angular offset of these shafts in a precise manner. With consideration of certain geometrical boundary conditions and relationships, it is thus possible to devise a measurement device and a process in which a conventional measurement rotary joint can be completely eliminated. Conclusions regarding the angular misalignment of these shafts and the corresponding machines can be drawn from the detectable amounts of offset which are detected in different rotary positions of the shafts which are to be measured by means of conventional sensors using simple formulas. 
   Details of the invention are shown in  FIG. 2 . There, a cardan shaft  62  and universal joints  60 ,  64  are assumed to have been already removed for the measurement and therefore are schematically shown only by a broken line. As is apparent from the figure, the machines  30 ,  31  may stand on bases  32 ,  33  of different heights and thus have a parallel offset of their shafts. The extender  40  can be attached conventionally or by means of screws to the coupling support  36  and can carry an extra extender  42 ; but this is optional. In any case, either a light transmitter and/or receiver is mounted either directly on the extender directly or indirectly by means of the extra extender  42 . In this example, a receiving module  44  as is known in the prior art. 
   In the illustrated measurement position, which is also called the “3 o&#39;clock position,” the receiving module can determine the incidence site of the incident light beam  53  which is emitted by a light transmitter  52 . The light transmitter  52  is mounted on a second extender or a holding device  50  which is likewise mounted on the corresponding coupling support of the machine  31 . The measurement is taken such that the receiving module is operated in the conventional manner in one mode and that it allows determination of the incidence direction of an incident light beam by means of two photosensitive plates. 
   In accordance with the invention, it is simplest to turn the extender by 180° to determine the measurement quantities of interest (therefore, to set, for example. the “9 o&#39;clock position”), to move the corresponding module  44  such that it can also be hit by the light beam  53  in this position, and to take an additional measurement using the light transmitter and the receiving module in this position. (If the functions of the light transmitter and of the receiving module are combined in a single housing, it is also possible, in accordance with the invention, to provide this combination in interplay with a plane mirror, especially a large-area planar mirror). In this position, the two photosensitive plates of the receiving module thus see one direction of incidence of the light beam which, when the machines  30 ,  31  are not aligned parallel, is distinguished from the direction of incidence in the “3 o&#39;clock” position according to two detectable angle coordinates. Therefore, only the respective directions of incidence are measured and the position of the incident light beam is of subordinate importance in accordance with the invention. For this reason, it is therefore also possible and uncritical to move the light receiving or transmitting module ( 44 , optionally  52 , or both at the same time) relative to one another on the extender or extenders, and then, to fix it briefly thereon for an individual measurement. 
   In principle, the invention makes do without the extra extender  42  if measurement positions can be set which lie rotated roughly 180° apart. If this is not the case, the extra extender  42  should be used, and instead of simply structured determination equations for determining the relative position of the machines, then ones should be used which take into account the corresponding projections (therefore the sine and cosine portions) of the angle of rotation of the extenders which differs from 180°. 
   It is advantageous to take three or more measurements in additional measurement positions, i.e., rotational positions of the extenders and to combine them using statistical considerations or compensation computations into a more accurate measurement result than is possible with only two measurements. 
   In another advantageous embodiment of the invention, it is provided that the extenders  40  and/or  50  be equipped with compensation weights (not shown) such that the torques applied to the shafts or mountings can be kept as small as possible. In this way, detection of the measurement values is facilitated, especially for smoothly running shafts.