Abstract:
A method for determining the alignment of a rotational body. The method includes the steps of locating a sensor on an outer surface of a rotational body, targeting a reference laser beam at the sensor such that the reference laser beam intersects the sensor at a reference coordinate, and recording the reference coordinate. The method further includes rotating the rotational body about the axis of rotation of the rotational body, targeting a measurement laser beam at the sensor such that the measurement laser beam intersects the sensor at a measurement coordinate, and comparing the reference coordinate and the measurement coordinate.

Description:
This application claims priority to U.S. Provisional Application Serial No. 60/124,588, filed Mar. 16, 1999. 
    
    
     The present invention is directed to methods and apparatuses for measuring the alignment of rotational bodies, and more particularly, to methods and apparatuses for measuring the alignment of rotational bodies using a laser and a sensor mounted onto the rotational body. 
     BACKGROUND OF THE INVENTION 
     In manufacturing and other industries, machines utilizing a variety of rollers, gears, shafts, axles and other rotational bodies are commonly used. The axes of the various rotating bodies must be aligned to ensure proper functioning of the machines. Of particular interest for alignment purposes are out-of-square measurements (the deviation of the rotational axis of the rotational body with respect to a vertical plane passing through the rotational axis) and out-of-level measurements (the deviation of the rotational axis of the rotational body with respect to a horizontal plane passing through the rotational axis). In order to measure out-of-square of a particular rotational body, typically a reference plane is established, and a measurement device is passed across the face of the rotational body (i.e., along the length of the rotational body). The reference plane may be defined by a laser, a wire, a rope, or the like. The measurement device cooperates with mechanical or electronic distance-measuring apparatuses as the measurement device is passed along the face of the rotational body to detect the out-of-square or out-of-level measurements relative the reference plane. Alternately, the distance between the reference plane (e.g., a taut string) and various points on a rotational body may be manually measured to calculate out-of-level. 
     However, these measurement methods require access to the face of the rotational body, and are therefore ineffective when the rotational body is surrounded by other components or is otherwise inaccessible. In this case, the alignment of the rotational body cannot be measured, or the machine must be partially or fully disassembled to gain access to the rotational body. However, the disassembly of the machine is inconvenient and time consuming. Furthermore, disassembly of the machine alters the machine&#39;s operating characteristics, and the resulting measurements may not present a true picture of the alignment of the rotational body during operation. Furthermore, taking manual measurements is time consuming and often imprecise. 
     Accordingly, there is a need for a method and an apparatus for detecting the alignment of a rotational body that can quickly and accurately measure the out-of-square and out-of-level of the rotational body without requiring access to the face of the body. 
     SUMMARY OF THE INVENTION 
     The present invention is a method and apparatus for measuring the alignment of rotational bodies that is quick and accurate. The invention uses real-time laser measurements to measure out-of-square and out-of-level quickly and accurately, and can carry out such measurements without access to the front surface of the body. Furthermore, because the measurements are displayed in real time, the rotational body may be manually adjusted, and the system provides immediate feedback such that the rotational body can be located in the desired position. The present invention may also be used to measure both out-of-square and out-of-level without changing the location or setup of measuring equipment. 
     In a preferred embodiment, the invention is a method for determining the alignment of a rotational body. The method includes the steps of locating a sensor on an outer surface of a rotational body, targeting a reference laser beam at the sensor such that the reference laser beam intersects the sensor at a reference coordinate, and recording the reference coordinate. The method further includes rotating the rotational body about the axis of rotation of the rotational body, targeting a measurement laser beam at the sensor such that the measurement laser beam intersects the sensor at a measurement coordinate, and comparing the reference coordinate and the measurement coordinate. 
     Accordingly, it is an object of the present invention to provide a method and apparatus for measuring the alignment of rotational bodies that is quick and accurate. Other objects and advantages of the present invention will be apparent from the following description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a preferred embodiment of the alignment system of the present invention, shown in association with a machine having a rotational body; 
     FIG. 2 is a detail perspective view of a rotational body to be measured with the present invention; 
     FIG. 3 is a front schematic representation of the alignment system and rotational body of FIG. 1; 
     FIG. 4 is a top schematic representation of the alignment system and rotational body of FIG. 1; 
     FIG. 5 is a front perspective view of one embodiment of a sensor used with the alignment system of the present invention; 
     FIG. 6 is a side view of the alignment system and rotational body of FIG. 1, shown with a sensor mounting system, the rotational body and sensor mounting system being shown in a variety of positions; 
     FIG. 7 is a top schematic illustration of an alternate embodiment of the alignment system of the present invention, shown with a pair of rotational bodies; 
     FIG. 8 is a front view of the sensor carrier of the sensor mounting system of FIG. 6, shown with a sensor mounted thereon; and 
     FIG. 9 is an end view of the sensor carrier and sensor of FIG.  8 . 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1, a machine, generally designated  10 , treats workpieces (not shown) that are passed downstream through the machine  10  in the direction indicated by arrow  12 . The machine  10  includes one or more rollers or rotational bodies  14 ′,  14  that may act upon and/or treat the workpieces, transmit forces to other rotational bodies  14 , or perform other functions. The rotational bodies  14  may be nearly any type of rotating members, including gears, rollers, shafts, pulleys, axles, rolls, belt drives and the like. Each rotational body  14  rotates about an axis  16 , and each rotational body  14  is preferably aligned with the axes of the machine  10  and with the rotational axes  16  of the other rotational bodies  14 . With reference to FIG. 2, a rotational body  14  is preferably aligned with plane A and plane B. Plane A represents the vertical plane of the machine  10  and plane B represents the horizontal plane of the machine  10 . In order to ensure proper functioning of the machine  10 , it is desired to align the axis  16  of the rotational body  14  with plane A and plane B. Out-of-square of the body  14  is measured by the deviation of the axis  16  from the vertical plane A and out-of-level of the body  14  is determined by the deviation of the axis  16  from the horizontal plane B. 
     Plane C represents a plane that is swept when a point, for example point  13  on the body  14  is swept 360° during a rotation of the body  14 . The plane C is necessarily perpendicular to the rotational axis  16 . A reference plane E, termed the baseline plane (not shown in FIG. 2) is perpendicular to the plane A and the plane B. The present invention measures the alignment of the rotational body  14  by measuring the deviation of plane C relative plane E. By comparing the horizontal and vertical alignment of plane C relative the baseline plane E, the out-of-square and out-of-level of the rotational body  14  can be determined. 
     FIG. 1 schematically illustrates the various components of one embodiment of the alignment system of the present invention. A laser emitter  20  is aligned with plane A and plane B (not shown in FIG. 1) of the machine  10 , and is plumb to the ground. The laser emitter  20  may be any acceptable emitter, such as a model FL 11 laser transmitter manufactured by Fixtur-Laser of Molndal, Sweden. In a preferred embodiment, the laser emitter  20  is supported on a tripod  22 , and the tripod  22  is centered above one or more marks on the machine floor (not shown) so that repeatable measurements may be taken. In this case, plugs may be mounted in the floor and punch marks are formed in the plugs that define a reference line for aligning the emitter  20 . The laser emitter  20  includes a pivotal guide  22  that is movable in a vertical plane. Because the laser emitter  20  is aligned with plane A and plane B of the machine, the laser  24  emitted by the laser emitter  20  is movable in plane E that is perpendicular to plane A and plane B. FIG. 1 illustrates two possible positions for the laser, shown as  24  and  24 ′, and plane E is illustrated as the plane between the lasers  24  and  24 ′. Thus, the laser  24  may be swept generally vertically within the plane E. The rotatable body  14  intersects plane E at a locus of points shown as a circle  26 . 
     FIG. 3 is a top schematic view of a rotational body  14  and laser emitter  20  of FIG.  1 . The body  14  is shown having a out-of-square deviation; that is, the axis  16  of the body  14  deviates from the vertical plane A of the machine by a distance  28  at the distal end surface  30  of the body  14 . In order to measure the out-of-square deviation, a sensor  32  is mounted onto the body  14 . The sensor  32  is shown in greater detail in FIG. 5, and includes a face  34  having a grid  36  thereon. The sensor  32  includes its own xy coordinates system, as shown in FIG.  5 . When a laser  24  hits the sensor face  34 , the sensor  32  can sense the xy location of the laser  24  relative to a reference position on the face  34 . The sensor  32  can transmit the xy location data to a computer  38  or other processing device (FIG.  3 ), that can process the raw data and supply an output signal to an output device  40 . The output device  40  displays the output, for example, as xy coordinates. The xy coordinates represents the position on the sensor  32  that the laser  24  hits relative the reference point on the sensor face  34 . The sensor  32  is mounted to the rotational body  14  such that it always faces the laser emitter  20 . One such mechanism for mounting the sensor  32  is shown in FIGS.  6  and  8 - 9 , and is described in greater detail below. 
     The sensor  20  is mounted on the body  14  such that it can receive the laser  24  from the laser emitter  20 . For example, in FIG. 1, although the sensor is not shown, it may be mounted at any point on the body such that the sensor face  34  intersects with the circle  26 . Returning to FIG. 3, the sequence for determining the out-of-square deviation for the body  14  will now be described. As noted above, the out-of-square deviation is the distance that the axis  16  of the body  14  deviates from the vertical plane A of the machine at the distal end surface  30  of the body  14 , indicated by distance  28  of FIG.  3 . The out-of-square deviation shown in FIG. 3 is greatly exaggerated, for ease of illustration, beyond the normally expected deviation. In order to measure the out-of-square of the body  14 , the body is rotated about its rotational axis  16  until the sensor  32  is located at a 9 o&#39;clock position. The sensor is shown as sensor  32   a  having sensor face  34   a  in this position in FIG. 3, and is also shown in the 9 o&#39;clock position as sensor  32   a  in FIG.  6 . Next, the laser guide  22  is vertically adjusted such that the laser emitter  20  emits a laser  24  that is received on the sensor face  34   a.  The laser  24  hits the sensor face  34   a  at point  42  (FIG.  3 ). The sensor  34   a  registers the location that the laser  24  hits the sensor face  34   a,  and sends the signal to the computer  38 . The x location of where the laser  24  hits the sensor face  34   a  is of particular interest, and the y location may be disregarded. Next, the x location of where the laser  24  hits the sensor  32   a  is preferably “zeroed out” by the computer  38  or user such that this x value becomes a reference point for any subsequent measurements. 
     Next, the body  14  is rotated 180° about its axis  16  such that the sensor  32  is in the 3 o&#39;clock position. The sensor is shown in this location in FIG. 3 as sensor  32   b.  The laser guide  22  is then adjusted within the plane E until the laser hits the sensor face  34   b  at point  44 . The x coordinate where the laser  24  hits the sensor face  34   b  is then sent to the computer  38  and displayed as an output. In FIG. 3, the point where the laser  24  hit the sensor face  34  when the rotational body  14  was in the 9 o&#39;clock position is shown as  42  on the sensor face  34   b.  The display device  40  then displays the numerical value of the distance  46 , which represents the distance between point  42 ′ and point  44 . The distance  46  represents the deviation of the rotational body  14  with respect to the baseline plane E. Using the value of the distance  46 , the value of the distance  28 , which represents the distance between the plane A and the axis  16  of the body  14  at the distal end surface  30  of the body  14 , may be calculated. 
     The value for the distance  28  may be calculated as follows. From analyzing the geometric relations of FIG. 3, it is seen that the triangle defined by points  42 ,  42 ′ and  44  is substantially equal to the triangle abc in terms of angles and relative side lengths. For ease of calculations, the triangle defined by points  42 ,  42 ′, and  44  has sides labeled d, e, and f, as shown in FIG.  3 . Side e represents the distance  46 . The triangle having points a, b, and c has sides ab, bc, and ca. Accordingly, a ratio of the lengths of the sides of the triangles may be set up wherein:                e   d     =     bc   ca             (     Eq   .              1     )                                
     Rearranging Equation 1, it seen that:              bc   =       e   *   ca     d             (     Eq   .              2     )                                
     As shown in FIG. 3, the distance of the side ca is the lateral distance (x- distance) between the point  42  and the distal end surface  30  of the body  14 . However, this distance can be accurately approximated by measuring the distance between the midpoint of the sensor face  34  and the distal end surface  30  of the body  14 . Furthermore, although not shown in FIG. 3, the sensor  32  is preferably located over the end surface  50  of the body  14  such that the distance of side ca is substantially equal to the length  52  of the body  14 . Although the sensor  32  is not shown located adjacent the end surface  50  of the body in FIG. 3, the sensor  32  is moved away from the end surface  50  for illustrative purposes. In a preferred embodiment, the sensor face  34  is centered over the end surface  50 . 
     The distance represented by the side d is the distance between the point  42  and the point  42 ′. This distance may also be measured, but in the illustrated embodiment the distance of the side d is substantially equal to the diameter  58  of the body  14 . Again, this is a preferable arrangement wherein the sensor  32  is located near the outer sides  54 ,  56  of the body  14  when the measurements are taken. 
     Thus, substituting into Equation 2, it is seen that the distance  28  (side bc) can be calculated by multiplying the measured x deviation  46  (side e) by the of the length  52  of the rotational body  14  (side ca), and dividing the result by the diameter  58  of the body  14  (side d). Because the diameter  58  of the body and the length  52  of the body  14  may be measured directly, the value of the out-of-square (distance  28 ) of the rotational body  14  can be calculated. The computer  38  may also be programmed to calculate this value and display it on the display device  40 . 
     Once the value for the out-of-square distance  28  is determined, the body  14  may be adjusted the desired amount in the desired direction such that the out-of square deviation is zero. For example, in the illustrated embodiment, the body  14  may be rotated around point a until the axis  16  is aligned with plane A. Alternately, because the display device  40  displays a real time value of the distance  28 , the body  14  may be manually adjusted until the displayed value for the distance  28  is zero. At this point, the rotational axis  16  of the body is aligned with the plane A, and the out-of-square deviation is zero. 
     The measurements and dimensions to measure the out-of-level for the body  14  are shown in FIG. 4, which is a front elevational view of the body  14  and laser emitter  20  of FIG.  1 . Again the deviation  60  of the body from the plane B is exaggerated for ease of illustration. To measure the out-of-level of the body  14 , the body  14  is moved about its rotational axis  16  until the sensor  32  is located at the 12 o&#39;clock position, shown as sensor  32   c  at this point in FIG.  4 . The sensor is shown in this position as sensor  32   c  in FIG. 6 as well. The laser guide  22  is then adjusted within plane E until the laser  24  hits the sensor face  34   c  of the sensor  32   c  at location  61 . The laser  24  may be termed the reference laser at this point. The x position where the laser hits the sensor face is provided to the computer  38  and displayed on the output device  40 . Again, this value for the x location is preferably zeroed out such that it is a reference point for any subsequent measurements. 
     The body  14  is then rotated about its rotational axis  16  such that the sensor is located at the 6 o&#39;clock position, shown as sensor  32   d  in FIG.  4 . The laser emitter  20  is then adjusted such that the laser  24  hits the sensor face  34   d.  The laser  24  may be termed the measurement laser at this point. The sensor  32  then provides an output as to the x location where the laser  24  hits the sensor face  34   d.  The distance in the x direction  62  between where the laser  24  hits the sensor at the 12 o&#39;clock location ( 61 ) and at the 6 o&#39;clock position ( 63 ) is displayed on the output device  40 . As above, the distance  60  between the axis of rotation  16  of the body  14  and the plane B may be calculated by dividing the measured distance  62  by the distance between point  61 ′ and point  61 , and by multiplying the result by the lateral distance along the Y axis between the point  61  and the distal end surface  30  of the body  14 . As before, the alignment system is preferably calibrated such that the distance between the point  61 ′ and point  61  is the diameter of the rotational body  14 , and the lateral distance between the point  61  and the distal end surface  30  of the body  14  is the length of the body  14 . Also, as was the case above, the body  14  may be manually adjusted while viewing the output device  40  until the displayed value for the distance  62  is zero, at which time the out-of-level deviation  60  of the body  14  is zero. 
     In this manner, both the out-of-square and out-of-level measurements of a rotational body may be measured simply by taking measurements at 12 o&#39;clock, 6 o&#39;clock and 3 o&#39;clock and 9 o&#39;clock. The system need not be disassembled or moved in order to take the different sets of measurements. Measurements may be taken at other rotational positions and the rotational body may thereby be aligned, or its deviations calculated. Mathematical transformations may have to be conducted upon the data if out-of-square and out-of-level values are required based upon measurements taken at positions other than at 3, 6, 9, and 12 o&#39;clock. 
     Another advantage of the present invention is that any portion of the rotational body  14  that is exposed may be used to take the requisite measurements, such as the exposed portion  66  of the member  14  in FIG.  1 . The exposed portion  66  may have the sensor  32  attached thereto such that the required measurements may be taken. Furthermore, even if there is no exposed portion, an extension may be located on the rotational body  14 , and the sensor  32  mounted on the extension to carry out the calibration. The baseline plane E may also be defined by diverting the laser  24 . For example, it may be inconvenient to align the emitter  20  so that the laser  24  is in the same plane as the end surfaces  30 ,  50  of the body  14 . In this case, the emitter may aligned and/or located in a variety of positions, and the laser  24  deflected to form the plane E. For example, the emitter may be aligned such that the resultant laser  24  is parallel to the axis  16  of the body  14 , and the laser  24  may be diverted 90 degrees to thereby form the baseline plane E. A variety of positions and configurations of the system in this manner are possible. 
     It should be understood that although a preferred method of calibrating the rotational body is described, the specifics of the method may be varied without departing from the scope of the invention. For example, the order of taking measurements may vary, and the equipment, including the sensor  34  and laser emitter  20  may be replaced with other equipment that achieves the same or equivalent results. The system may also be used to calibrate rotational bodies having non-circular cross sections, such as bodies having square hexagonal, or gear-shaped cross sections. 
     As shown in FIG. 7, the present invention may be used to calibrate two non-overlapping rotating elements  70 ,  72  to ensure that they are parallel. For example, the shaft  70  may be a driving shaft  70  that is connected to driven shaft  72  by a transmission shaft and a pair of universal joints, or other driving or connecting means shown generally as  74 . A laser emitter  20  emits a laser  76  that is movable in a vertical plane. The laser  76  defines a plane E and the driven shaft  72  is calibrated to plane E in a manner described above. After the driven shaft  72  is calibrated, a prism (not shown) in the laser emitter  20  is moved into the path of the laser  76  and diverts the laser  76  such that a bridging laser  78  comes out of the side of the laser emitter  20  perfectly perpendicular to the laser  76 . Reflector  80  receives the bridging laser  78  therein, and has a prism therein (not shown) that deflects the bridging laser  78  perpendicular to the path of the bridging laser  78 . The resultant laser  82  is parallel to the laser  76  and to plane E. Laser  82  defines a second baseline reference plane F. The driving shaft  70  may then be aligned to the plane F in the same manner described above. After the driving shaft  70  is aligned, the driving shaft  70  is parallel to the driven shaft  72 . 
     As noted above, the sensor  32  is mounted to the rotational body  14  such that it may face the laser emitter  20  at all times. A preferred mounting system  86  for mounting the sensor  32  to the rotational body  14  is shown in FIGS.  6  and  8 - 9 . The mounting system  86  (FIG. 6) includes a sensor carrier  88  and a mounting portion  90 . The mounting portion  90  includes a magnet  92  shaped to abut against the rotational body  14  to mount the mounting system  90  to the rotational body  14 . Various other methods, such as fasteners, brackets, clamps, wires, rope, and the like may be used to attach the mounting system  90  to the body  14 . A support  94  is coupled to the magnet  92 , and the support  94  includes a pair of posts  96  extending generally outwardly therefrom. The posts are received in a pair of holes  98  a frame  100  of the sensor carrier  88  (FIG.  8 ). 
     A support  102  is pivotably coupled to the frame  100  by means of a shoulder bolt  104 . The support  102  receives the sensor  32  thereon, and is free to rotate relative the frame  100  and mounting portion  90 . This free rotation helps to ensure the sensor face  34  faces the laser emitter  20 . As shown in FIG. 6, the sensor carrier  102  is shown in the 12 o&#39;clock, 9 o&#39;clock, and 1:30 positions, and the support  102  is mounted such that the sensor  32  carried thereon can face a laser  24  from a stationary, adjustable laser emitter  20 . The sensor  32  may be mounted on any available surface on the support  102 , and in a preferred embodiment is mounted on the outer mounting surface  106  (FIG.  8 ). Nearly any mechanism that can receive the sensor  32  thereon, and that can pivot relative the body  14  to allow the sensor  32  to receive the laser  24  on its sensor face  34  may be used without departing from the scope of the invention. 
     Having described the invention is detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention.