Abstract:
The invention concerns a device for the precise positioning of a measurement probe along a probe axis A and which can rotate around this axis. By the coaxial arrangement of adjustment units for rotating and longitudinal displacement of the probe as well as by an rpm step-down gear arranged therebetween, a compact construction of the device is made possible and a coaxially situated passage is kept free, through which the probe shaft can be inserted and removed.

Description:
FIELD OF THE INVENTION 
     The invention concerns a device for positioning a measurement probe relative to a probe axis. 
     BACKGROUND 
     Positioning devices serve for the most varied positioning tasks, in which probes, sensors, grippers, tools, and the like must be introduced at a specific place determined in advance and in a defined position. In flow measurement segments, for example, the most varied flow measurement probes, such as pressure, temperature, anemometer, directional and special measurement probes must be positioned at measurement sites precisely indicated in advance. The positioning, which must be conducted very exactly depending on the measurement task, is frequently made difficult by special environmental conditions, such as, for example, high temperatures. In the case of probes with probe heads turned away from the probe axis, a movement along the probe axis and rotationally around the probe axis is at least necessary, in order to align the probe head as desired on the object to be measured. Thus, frequently, displacement paths of several dozen cm and rotations of +/−180 angular degrees are necessary. Such positioning devices are controlled for the most part with the help of a computer programmed according to the positioning task. In order to be able to conduct measurements or positionings in spatially limited installation conditions, devices with compact dimensions are desired. 
     SUMMARY OF THE INVENTION 
     Proceeding from this, it is an object of the invention to provide a device of this type for the positioning of a measurement probe, which makes possible a very precise positioning of the measurement probe along a probe axis A and in rotation relative to this axis, whereby the device should occupy as little installation space as possible. 
     The invention has the advantage that due to a coaxial arrangement of the adjusting units for rotation and for longitudinal displacement of the probe as well as a step-down gear lying therebetween, on the one hand, a very compact construction of the device is made possible, and on the other hand, a coaxially arranged passage can be left free, through which the probe shaft can be inserted and moved. The adjustment units and their motors thus surround the probe shaft concentrically, which in turn brings about a useful reversal of the rotary motion of the motors by means of the gear. The rotational motion of the motors can be reversed with small mechanical expenditure into a rotating or longitudinal motion of the measurement probe with very small play. Due to the fact that the linear adjustment unit is flange-mounted at the gear output, and the rotational movement of the probe is designed accordingly, the linear movement of the probe can be designed independently of the rotational movement. Again, a simplified construction results relative to positioning units introduced outside the probe axis, which in turn leads to an increased precision due to the small play. On the other hand, a module-type construction of the adjustment units and the gear makes possible a simple exchange of modules, if, for example, different transmission ratios are desired, or to replace defective parts. 
     Further advantageous forms of embodiment of the invention will result from claims  2  to  15 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Preferred forms of embodiment of the invention are described hereafter with reference to the attached drawing. Herein: 
     FIG. 1 is a diagrammatic illustration of a fluid conduit equipped with a moveable measurement probe, which is moved by a positioning device; 
     FIG. 2 a  is a longitudinal section of a positioning device with spindle nut guided in a displaceable manner; and 
     FIG. 2 b  is a longitudinal section of a positioning device with a stationary spindle nut. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a tube  1  through which flows a fluid F. A measurement probe  2 , whose axis extends transversely to the longitudinal axis L of the tube projects in the flow path, in order to measure the flow-mechanical quantities of fluid flow F. The measurement probe is comprised of a rod-shaped shaft  3  and a probe head  4  extending at right angles at the end of shaft  3 . Measurement probe  2  is guided in a cylindrically shaped positioning device  5  at the end of shaft  3  projecting from tube  1 . Positioning device  5  is disposed at the periphery of the tube  1  concentrically surrounds probe shaft  3  and makes it possible to shift measurement probe  2  in a translating manner along its probe axis A, and to rotate the probe shaft about axis A so that probe head  4  is displaced approximately radially and can be rotated relative to fluid flow F. 
     The first form of embodiment of positioning device  5  shown in FIG. 2 a  is comprised of a linear adjustment unit  6  for adjusting probe head  4  along probe axis A and a rotation adjustment unit  7  for rotation of probe head  4  around probe axis A. Both adjustment units  6  and  7  are arranged for axial displacement relative to one another, coaxial to device axis G, which coincides with probe axis A, within a hollow cylindrical housing  8 . The adjustment units  6  and  7  use d.c. hollow shaft motors  9   b  and  9   a  as a drive, such that a hollow shaft  11  surrounded by rotors  10   a  and  10   b  of motors  9   a  and  9   b  to rotate and displace adjustment unit  7 . This acts in turn on a step-down gear  12 , known under the name “harmonic drive”, which is also coupled to hollow-shaft motors  9   a  and  9   b  concentric to axis G in a first housing part  13 . A second hollow cylindrically shaped housing part  14  is flange-mounted at the drive output, in which linear adjustment unit  6  is affixed in rotation and also coaxial with axis G, so that the latter rotates with second housing part  14 . The d.c. hollow-shaft motor  9   b  serves as a drive for linear adjustment unit  6 , and this moves measurement probe  2  along probe axis A by means of a spindle arrangement  15 ,  16 . A coaxial threaded spindle  15  is directly secured to rotor  10   b  of hollow shaft motor  9   b  in second housing part  14  and is rotationally driven thereby. A spindle nut  16  surrounded by a guide cage  17  in turn engages threaded spindle  15 , and travels longitudinally along axis G upon rotary motion of threaded spindle  15 . A lifting tube  18  has one end secured to spindle nut  16  so that lifting tube  18 , which concentrically surrounds threaded spindle  15 , travels in or out of second housing part  14  with longitudinal motion of spindle nut  16 . A clamping device  19  is connected to the opposite end of lifting tube  18  to secure probe shaft  3  in positioning device  5  for longitudinal and rotational displacement of measurement probe  2  by the motion of lifting tube  18 . Therefore, a telescopic type of movement of measurement probe  2  is produced by means of lifting tube  18  secured directly on spindle nut  16 . In order to be able to precisely guide spindle nut  16  in its longitudinal motion, it is surrounded by guide cage  17 , which in turn is guided in the longitudinal direction by guide rails  20  arranged inside second housing part  14  parallel to axis G. These guide rails  20  formed as bars are arranged concentrically around spindle arrangement  15 ,  16  and extend in guide slots  21  of guide cage  17 , so that the latter slides in longitudinal motion on guide rails  20 . 
     Another measure for increasing the precision results due to the embodiment of spindle drive  15 ,  16  as a ball-and-nut drive. 
     For a precise angular control of drive motors  10   a ,  10   b , an incremental encoder is connected to each of its rotors  10   a ,  10   b  so that the rotary motion of the rotors or the adjusting motion of measurement probe  2  can be produced by computer control. 
     Based on the aligned hollow cylindrical design of threaded spindle  15 , drive motors  9   a, b  and gear  13 , probe shaft  3  may be inserted through positioning device  5 , whereby a very compact, space-saving arrangement is obtained with high adjustment accuracy. 
     An alternative embodiment of positioning device  5  is shown in FIG. 2 b . This embodiment is distinguished from the embodiment according to FIG. 2 a  by the design of linear adjustment unit  6 , according to which, hollow shaft motor  9   b  drives spindle nut  16  instead of threaded spindle  15 . Here also, hollow shaft motor  9   b  of linear adjustment unit  6  is arranged in second housing part  14 , such that rotor  10   b  drives spindle nut  16  without the intermediate connection of a gear. For this purpose, spindle nut  16  is mounted on roller bearings in second housing part  14 . Threaded spindle  15  also designed as a hollow cylinder is kept secured in rotation with respect to second housing part  14  by means of a catch element  22 , so that when spindle nut  16  is rotated, threaded spindle  15  moves along axis G or probe axis A with measurement probe  2 . Since it is not lifting tube  18 , but rather threaded spindle  15  which travels out of the housing during adjustment, in contrast to the design according to FIG. 2 a , threaded spindle  15  is joined at its outer end with a lift housing  23 , which concentrically surrounds second housing part  14  in the driven-in state. Now, if threaded spindle  15  travels out, it is protected from contamination and damage by the surrounding lift housing  23 . 
     Based on the fact that spindle nut  16  does not move inside housing  8  in the longitudinal direction, positioning device  5  may be constructed shorter overall. In comparison to the design according to FIG. 2 a , rotation adjusting unit  7  with associated step-down gear  12  is held in an identical manner, so that the number of different components can be kept small. 
     One of the essential features of both forms of embodiment is the axially displaced arrangement of linear and rotation adjusting units  6 ,  7  with step-down gear  12  disposed therebetweem, whereby linear adjusting unit  6  with measurement probe  2  uniformly executes the rotational motion. Together with the concentric arrangement of adjusting units  6 ,  7  to probe shaft  3 , this permits a very direct driving of measurement probe  2 .