Abstract:
A method, apparatus and system for non-contact measurement of a railway wheel profile are disclosed herein. To measure the wheel profile, a laser having a distance displacement sensor and angular displacement sensor projects a beam of light onto the surface of a railway wheel to measure the wheel profile. In an alternate embodiment, a rail thickness measurement gauge is provided. In another alternate embodiment, a witness groove measurement gauge is provided.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates generally to wheel profile measurement, and more specifically, to a method, apparatus, and system for non-contact profile measurement of a train wheel. 
   2. Description of Related Art 
   Manual wheel measurement is a well established practice in the railway industry. Over a period of use, a train wheel will experience wear and possibly damage. The metallic structure of train wheels is designed to allow for slow deformation caused by wear or damage over a period of time, thereby reducing the possibility of complete structural failure. To monitor this deformation, the profile of the train wheel is constantly monitored. 
   Although in certain circumstances a railway wheel profile can be measured while a train is in motion, wheel profiles are also measured in the field or in a repair shop while the train has stopped or while the railway wheel is uninstalled. Proper maintenance, cost savings and derailment prevention are major goals of wheel profile measurement. There are two ways in which the above goals can be accomplished while the train is stopped or while the wheel is uninstalled, contact measurement and non-contact measurement. 
   Contact measurement means include measuring devices that, when taking measurements, the measuring device must physically touch the railway wheel at the point of measurement. These means include, among others, caliper-based, gauge-based and roller-based measurement devices. Contact means has certain disadvantages and limitations, though. Contact measurement devices are typically inaccurate and difficult to use because of the various points of measurement required to obtain a wheel profile. 
   Non-contact wheel profile measurement devices include magnetic, eddy current, and laser (or light) measurement methods. Current art magnetic and eddy current measurement methods are limited in that structure differences from wheel to wheel, either through latent defects or defects caused while the railway wheel is in operation, may cause erroneous or inaccurate readings. 
   Current art non-contact measurement means that use light carry certain limitations as well. For instance, in order to measure multiple wheel data points to construct a profile, current art methods typically require multiple sensors and/or multiple light emitters to measure reflected light. Because of the number of sensors used, these apparatuses are typically bulky, difficult to align, difficult to use, and have power requirements that reduce the usefulness as a hand-held device, if embodied in that manner. 
   Additionally, current art methods cannot measure certain measurement points that are beyond the visible and measurable viewing area of the lasers and their sensors. As an example, a witness groove of a railway wheel, which is typically located on the outside surface of the railway wheel, is measured to determine the wear on the railway wheel. 
   Because of its location, on a side of the wheel, the witness groove is not visible or measurable from current art non-contact measurement devices. Further, because the calculation of the wheel diameter uses the witness groove measurement, current art methods are limited in their ability to provide a wheel diameter measurement as well. 
   Furthermore, because of the multiple lasers and sensors used by current art non-contact measurement devices, a number of points of contact are required to properly locate the device to take accurate measurements. Some devices, in order to obviate the difficulty in placement of the device in a calibrated location, require additional sensors and placement detectors that assist the user in determining when the device is in a calibrated position. This limitation not only increases the complexity of the device, but causes time delays in measuring railway wheels as the user must intricately position the device prior to measurement. 
   Additionally, because current art non-contact measurement devices are typically a static size that fits over the railway wheel, current are devices do not provide for variability of wheel size. Deviations, whether slight or significant, from a standard railway wheel size may cause measurement errors because of the static size of the measurement device. Significant deviations may cause the device not to be able to fit onto a railway wheel. As such, current art non-contact measurement devices are limited in the size and shape of a railway wheel that the devices may be used on. 
   Finally, witness groove diameters may vary from manufacturer to manufacturer. Because of the limited variability of current art non-contact measurement devices, the inability to measure the witness groove to determine wheel diameter, and thus wear, further limits the capabilities of the current art. 
   What is needed is a system, method and apparatus that overcomes the limitations of the prior art, namely, accuracy, portability, ease of use, and provides the user with an ability to measure the witness groove and wheel diameter as well as other measurement points. 
   BRIEF SUMMARY OF THE INVENTION 
   Briefly described, in a preferred embodiment, the present invention overcomes the above-mentioned limitations and meets the recognized need by providing a system, method and apparatus for non-contact wheel profile measurement having a hand-held measurement device mounted on a railway train wheel capable of measuring the witness groove and calculating the wheel diameter based upon the witness groove measurement. Further, the present invention is capable of measuring various wheel sizes. 
   In a preferred embodiment, the measurement device of the present invention comprises a laser rotatably attached to a rotary encoder, preferably an absolute rotary encoder, having a witness groove measurement device removably attached to the railway wheel witness groove. By rotating the laser along a measurement path substantially perpendicular to the wheel circumference, the present invention measures points along the pathway of the laser to generate a wheel profile. 
   As the user rotates the laser to illuminate the railway wheel, the present invention measures the distance displacement for the laser beam and the angle at which the laser beam is emitted, or the angular displacement. After the laser is rotated to illuminate a planar pathway substantially perpendicular to the wheel circumference, the data is converted from a polar coordinate system to a Cartesian coordinate system to output a wheel profile. 
   Because the laser beam does not emanate at a point located on the axis of rotation, and rather emanates from the end of a laser unit, to compensate for both the difference in rotation and an inherent change in height caused by the laser rotation, a calibration procedure is used. 
   For attaching the device to a train wheel, the measurement device includes a series of magnets that allow it to be readily attached and removed along any accessible location along the train wheel. Additionally, to increase the accuracy of the measurements, the device further comes with a series of holder pins that, when placed in communication with the train wheel or some other fixed structure, the placement of either being calibrated, provide for accurate measurements. 
   A first aspect of an embodiment of the present invention provides a method of measuring a railway wheel with the steps of: placing a laser having angular displacement and distance displacement sensing units in a calibrated location proximate to a railway wheel; energizing said laser to emanate a laser beam; rotating said laser said to cause said laser beam to reflect off a plurality of points substantially perpendicular to the wheel circumference on at least a portion of said railway wheel; capturing angular displacement and distance displacement data of said plurality of points; and calculating a set of wheel parameters based upon said captured distance displacement data and angular displacement data of said plurality of points. 
   A second aspect of an embodiment of the present invention provides an apparatus for measuring a railway wheel, the apparatus comprising: a means for placing a laser having angular displacement and distance displacement sensing units in a calibrated location proximate to a railway wheel; a means for energizing said laser to emanate a laser beam; a means for rotating said laser said to cause said laser beam to reflect off a plurality of points substantially perpendicular to the wheel circumference on at least a portion of said railway wheel; a means for capturing angular displacement and distance displacement data of said reflected beam from said plurality of points; and a means for calculating a set of wheel parameters based upon said captured distance displacement data and angular displacement data of said plurality of points. 
   A third aspect of an embodiment of the present invention provides an apparatus for measuring a railway wheel, the apparatus comprising: a laser rotatably attached to a measurement unit, said measurement unit comprising a laser displacement sensor to measure distance displacement data of a beam of said laser and a rotary encoder to measure the angular displacement data of said laser when emitting said beam; and a bracket for mounting said measurement unit on a railway wheel wherein said laser housing is attached to said bracket. 
   A fourth aspect of an embodiment of the present invention provides an apparatus for measuring a railway wheel witness groove, the apparatus comprising: a laser rotatably attached to a measurement unit, said measurement unit comprising a laser displacement sensor to measure distance data of a beam of said laser and a rotary encoder to measure the angular displacement data of said laser when emitting said beam; a bracket for mounting said measurement unit on a railway wheel wherein said laser housing is attached to said bracket; and a witness groove measurement device, wherein said witness groove measurement device comprises a magnet for removably attaching said witness groove measurement device onto a train wheel, wherein said witness groove measurement device further comprises a surface extending distally from said magnet, wherein said surface is removably engaged with the witness groove, said witness groove measurement device further comprising a shaft of known length extending in a direction substantially parallel to the radius of the railway wheel, wherein said shaft has sufficient length such that a portion of the length of said shaft may be measured by said laser. 
   A fifth aspect of an embodiment of the present invention provides a method for measuring a railway wheel diameter, with the steps of: placing a laser having angular displacement and distance displacement sensing units in a calibrated location proximate to a railway wheel; energizing said laser to emanate a laser beam; rotating said laser to cause said laser beam to reflect off a plurality of points on a witness groove measurement device and along outer surface of said railway wheel substantially perpendicular to the wheel circumference; capturing angular displacement and distance displacement data of said plurality of points; and calculating the wheel diameter based upon said captured distance displacement data and angular displacement data of said plurality of points. 
   These and other objects, features, and advantages of the invention will become more apparent to those ordinarily skilled in the art after reading the following Detailed Description of the Invention and Claims in light of the accompanying Figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Accordingly, the present invention will be understood best through consideration of, and reference to, the following Figures, viewed in conjunction with the Detailed Description of the Invention referring thereto, in which like reference numbers throughout the various Figures designate like structure and in which: 
       FIG. 1  is a front-side diagram of the apparatus of a preferred embodiment of the present invention; 
       FIG. 2  is a back-side diagram of the apparatus of  FIG. 1 ; 
       FIG. 3  shows an illustrative set of measurements for a railway wheel; 
       FIG. 4  shows the apparatus of  FIG. 1  mounted on a railway wheel; 
       FIG. 5  shows measured data using the apparatus of  FIG. 1 ; 
       FIG. 6  shows the measured data of  FIG. 5  converted to a Cartesian coordinate apparatus; 
       FIG. 7  is a rim index measurement device used in an alternate embodiment of the apparatus of  FIG. 1 ; 
       FIG. 8  is the witness groove index measurement device of the apparatus of  FIG. 1 ; 
       FIG. 9  shows both the rim index and the witness groove index measurement devices installed on the apparatus of  FIG. 1 ; and 
       FIG. 10  shows the calibration apparatus for the apparatus of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In describing preferred embodiments of the present invention illustrated in the Figures, specific terminology is employed for the sake of clarity. The invention, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
   In that form of the preferred embodiment of the present invention chosen for purposes of illustration,  FIG. 1  shows apparatus  100  used to measure points along a wheel surface to determine the wheel profile. In a preferred embodiment of the present invention, apparatus  100  is removably mounted to a railway wheel (as shown in  FIG. 4 ) by placing mounting bracket  104  against the outer rim of the outside of the wheel (as shown in  FIG. 4 ). The user then manipulates apparatus  100  until pins  102   a,b  are in communication with the top edge of the wheel&#39;s flange (as shown in  FIG. 4 ). Magnets  80   a - c  magnetically hold apparatus  100  onto the railway wheel. 
   Although the preferred embodiment of the present invention is described in a manner such that the present invention is mounted directly on the railway wheel, it is anticipated and considered to be within the scope of the present invention to use other mounting methods. For illustrative purposes only, a stand may be placed in proximity to the railway wheel and calibrated so that the present invention may be operated according to embodiments described herein. 
   To measure the wheel profile, once apparatus  100  is magnetically mounted to the wheel, the user will energize laser unit  106 , the unit having laser housing  92 . Housing  92  has aperture  90   b  through which the beam of laser  106  will emanate. Further, aperture  90   a  allows the beams of laser  106  which are reflected off the surface of the wheel to be received by a sensing unit inside laser unit  106  to measure the distance displacement of the laser beam. Electronic housing unit  108  is in communication with the distance displace sensing unit through communication wire  110 . Distance displacement data is send via wire  110  to a data receiving computer unit disposed in electronic housing unit  108 . 
   Laser unit  106  is rotatably mounted to electronic housing unit  108  through shaft  122 . As laser unit  106  is rotated, thus rotating shaft  122 , a rotary encoder located inside electronic housing unit  108  detects and measures the angular displacement of laser unit  106 , shown in more detail in  FIG. 4 . Angular displacement data and distance displacement data are stored in the computer unit in electronic housing unit  108  and are communicated to an external computational unit (not shown) to convert the collected data, which is in a polar coordinate system format, to a Cartesian coordinate system format. 
   In an alternate embodiment of the present invention, apparatus  100  may also have a rim index measurement device  160  having rim index pin  112  and measurement surface  114 , shown in greater detail in  FIGS. 7 and 9 , and described more fully below with reference thereto. 
     FIG. 2  shows the back-side of apparatus  100 . As shown, laser unit  106  has apertures  90   a  and  90   b , laser unit  106  being rotatably mounted to electronic housing unit  108  through shaft  122 . The collected angular displacement and distance displacement data is communicated to an external computation unit (not shown) via communication port  120 . The external computational unit may include, but are not limited to, personal data assistants and personal computers. Laser unit  106  emits a laser beam through aperture  90   b . Distance displacement sensors (not shown) sense the reflected laser beams of laser unit  106  through aperture  90   a . Additionally, rim index measurement device  160  is shown in more detail. 
   The user manipulates rim index measurement device  160  up or down until pin  112  is engaged with the rim corner of the railway wheel, as shown in  FIG. 9 . Once engaged, tightening screw  124  prevents further movement of rim index measurement device  160 , allowing the user to commence measurement of the wheel. It should be understood and appreciated by those of ordinary skill in the art that tightening screw  124  is used for illustrative purposes, and that any means of securing rim index measurement device  160  has been contemplated and is considered to be within the scope of the present invention. 
     FIG. 3  shows an illustrative set of measurements that may be desired for a railway wheel. More specifically, profile  210  is determined by measuring the wheel using apparatus  100 . The measurements include: rim tape line C and point A which is the end of the rim corner; flange height Sh, which comprises a vertical distance between tape line C and flange top point F; flange thickness Sd, which comprises a horizontal distance between point D, which is typically 10 mm above tape line C, and flange wall line AB; flange slope qR, which comprises a horizontal distance between points E and D; tread hollow Hd, which comprises the depth of the valley of the railway wheel tread area, if it exists; witness groove reading DWG, which comprises the vertical distance between tapeline T and the top of witness groove  202 ; and wheel diameter Dm, which preferably comprises witness groove reading DWG and the known diameter of witness groove  202 . 
     FIG. 4  shows a side view of apparatus  100  mounted on railway wheel  200 . As shown, laser unit  106  is rotatably mounted on electronic housing unit  108 . Rotary encoder  210  measures the angular displacement of laser unit  106  as it is rotated. Pin  102   b  and  102   a  (not shown) facilitate the mounting of apparatus  100  onto railway wheel  200  into a calibrated position. The calibration of apparatus  100  is described in more detail in  FIG. 10  below. 
     FIG. 4  also shows rim index measurement device  160 . As described above in  FIG. 3 , according to an alternate embodiment of the present invention, to measure the rim thickness of wheel  200 , the user manipulates rim index measurement device  160  until pin  112  is engaged with wheel  200  at point A. The user rotates laser unit  106  past the surface of wheel  200  and measures measurement surface  114  of rim index measurement device  160 . Because surface  114  is of a known length, as shown in further detail in  FIG. 7 , the rim thickness can be calculated based upon the height of rim index measurement device  160  measurement surface  114 . 
   Apparatus  100  measures the distance displace of the laser beam emanating from laser unit  106  after being reflected by wheel surface  200  and the angular displacement of laser unit  106 . Illustrative measurements are shown more fully in  FIG. 5 . The illustrative measurements in  FIG. 5  reflect the distance displacement of the laser beam along the horizontal axis, the angular displacement of laser unit  106  at the measured distance along the vertical axis, a radial offset, R o , which is the apparent change in height caused by the laser beam location off the axis of rotation, and an angular offset, Θ o , the offsets determined by the calibration process, as more fully described with reference to  FIG. 10  below. 
   Upon completion of a scan, the illustrative measurements of  FIG. 5  are converted from a polar coordinate system to a Cartesian coordinate system, compensated by calibration parameters R o  and Θ o  as shown in  FIG. 6 . As shown, measured points are represented both in vertical displacement by the Y-axis and horizontal displacement by the X-axis. The illustrative measurements show a wheel profile. Shown further are certain points used in an alternative embodiment of the present invention, namely point SA, which is the rim reference point used to determine the rim thickness. 
   Because the present invention is rotated around a single axis, some wheel profile measurement points may not be visible to laser unit  106 . For instance, the rim thickness is measured using two points that are blocked, or are not open to scanning, by the wheel flange, as shown and described more fully with reference to  FIG. 9  below. To measure the rim thickness, in an alternate embodiment of the present invention, a rim index measurement device is used to present a detectable and measurable surface to laser unit  106 , the surface proportional to the rim thickness. 
     FIG. 7  more fully illustrates the rim index measurement device  168  that provides a detectable and measurable surface to calculate a railway wheel&#39;s rim thickness. A user manipulates rim index measurement device  160  until pin  112  engages with the railway wheel rim corner (best seen with reference to  FIG. 9 ). When laser unit  106  detects and captures the visible and measurable length of rim index measurement device  160 , the length of rim index measurement device  160  measured to angle θ provides a means to measure the rim thickness, as shown more fully in  FIG. 9  below. 
     FIG. 8  shows witness groove measurement device  180  as used in a preferred embodiment of the present invention. More fully, witness groove measurement device  180  has shaft  162  of known length, pin  168  which sits in the witness groove of the railway wheel, angle α, a known angle, and upper angular surface  164 . To hold witness groove measurement device  180  onto the railway wheel, affixed magnet  166  is provided. As laser unit  106  is rotated and measures the measurable length of shaft  162  to angle α, based upon the difference between the known length of shaft  162  to angle α, the witness groove profile can be measured. Both angle α and upper angular surface  168  are used to calculate witness groove measurement DWG, as depending upon the size and diameter of the railway wheel, all or part of angle α may not be visible and measurable by laser unit  106 , as well as a portion of upper angular surface  164  in railway wheels having a witness groove diameter significantly smaller than the railway wheel diameter. 
   The placement of rim index measurement device  160  and witness groove measurement device  180  are shown more fully in  FIG. 9 . Rim index measurement device  160  pin  112  is manipulated until pin  112  rests on the outer circumference of rim corner A of railway wheel  200 . Further, witness groove measurement device  180  pin  168  is disposed within witness groove  220  of wheel  200 . As laser unit  106  is rotated, the lengths of rim index measurement device  160  and witness groove measurement device  180  visible to laser unit  106  are measured and converted, using the calibration parameters R o  and Θ o  to measure the rim thickness and witness groove reading DWG. 
   To determine and compensate for calibration parameters R o  and Θ o  apparatus  100  is calibrated using calibration stand  300 , as shown in  FIG. 10 . Described more fully in reference to  FIG. 10 , calibration stand  300  has flat surface  302  upon which apparatus  100  is placed, the positioning of which is set at a calibrated position using pins  102   a,b . To calibrate apparatus  100 , the user scans surface  302  and a calibration unit determines calibration parameters R o  and Θ o . Once calibration parameters R o  and Θ o  have been determined for the placement of apparatus  100  upon a railway wheel with pins  102   a,b  touching the railway wheel, when apparatus  100  is subsequently placed upon a railway wheel to measure the wheel profile, if pins  102   a,b  are touching the railway wheel, apparatus  100  is in a calibrated position. 
   Having, thus, described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the within disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope and spirit of the present invention. Accordingly, the present invention is not limited to the specific embodiments as illustrated herein, but is only limited by the following claims.