Railroad track rails are subject to wear due to the passage of trains over the rails. Burrs, corrugations, and uneven wear of the rail head are common deformities created in railroad track rails by the passage of heavy rolling stock over the rails. Unchecked, such wear can lead to rail - failure and derailment of trains using the rails.

The replacement of track rails is labor intensive and extremely expensive. Accordingly, specialized rail grinding machines have been developed to restore worn and deformed rails to their original profile. An example of such a rail grinding machine is disclosed in U.S. Patent No. 4,622,781. A grinding stone for use in such grinding machines is disclosed in U.S. Patent No. 4,693,039.

Successful restoration of a rail depends on

accurate determination of the defects in the rail profile prior to grinding, proper placement of the grinding stones during the grinding process, and accurate measurement of the rail profile subsequent to grinding. Measurement of rail profiles has traditional¬ ly been accomplished with the use of so called star gauges, that have a plurality of different radiused edges. An edge of the star gauge that has a radius similar to the desired radius of the measured rail is manually placed on the head of the rail and is visually checked to determine whether any space exists between the star gauge and the rail head. If there is a space (indicating a deformity in the rail profile) , grinding stones of a rail grinding machine are set in one of several predetermined, standard grinding patterns, based on the judgment of the machine operator.

It will be appreciated that the traditional, manual method of determining the profile of a railroad track rail is highly subject to measurement inaccuracies and operator skill. Moreover, while use of a star gauge provides at least a qualitative measure of the rail running surface radius, the presence of burrs, gauge wear, and off ^" center ^" alignment of the railhead are subject to only a visual check. Modern rail grinding machines can control grinding to within several thou¬ sandths of an inch tolerance. The ability to maintain such tight tolerance can be in large part wasted when rail measurement and grinding stone orientation are done by an unskilled or inexperienced operator. An automated apparatus and method that would accurately measure the profile of a railroad track rail prior to grinding, and that could be used in a grinding system to set the grinding stones in an optimal orientation for grinding based on the measurement, would provide a decided advantage.

Summary of the Invention The problems outlined above are in large

measure solved by the apparatus and method for measuring and maintaining the profile of a railroad track rail in accordance with the present invention. The method and apparatus hereof provides an accurate measurement of the profile of a rail that is largely independent of operator judgment or skill. A unique method for placing the stones of a grinding machine is disclosed that restores a worn rail to an acceptable profile with a minimum of grinding of the rail . The apparatus for measuring a rail profile in accordance with the present invention includes a light strobe for projecting a beam of light onto the rail to be measured. A pair of optical cameras view the light beam projected onto the rail, and provide an electronic signal indicative of the light beam shape. The light lines reflected from the foot of the rail are viewed by one of the cameras to provide a reference point for measuring the profile of the railhead. The second camera receives the light reflected from the crown surface of the railhead.

The information received through the optical cameras is digitized and compared to the profile of an ideal rail. The difference between the actual profile and ideal profile is then calculated, and the comparison information is manipulated in a unique way to ensure optimal positioning of the grinding machine's grinding stones .

Brief Description of the Drawings Fig. 1 is a perspective view of a section of a typical railroad track rail;

Fig. 2 is an elevational view of the rail depicted in Fig. 1;

Fig. 3 is a plan view of the rail depicted in Fig. 1; Fig. 4. is an elevational view of an ideal

railroad track rail with the profile of a worn track rail indicated in phantom line;

Fig. 5 is an enlarged, elevational view of the railhead of an ideal railroad track rail, with profiles of various worn railheads superimposed thereon in phantom lines;

Fig. 6 is a schematic view of a typical railroad track rail;

Fig. 7 is an enlarged, elevational view of an ideal rail, with a representative worn rail profile and the wheel of a railroad car depicted in phantom lines;

Fig. 8 is a block diagram of the apparatus for measuring and maintaining the profile of a track in accordance with the present invention; Fig. 9 depicts the light line projected onto the railhead of a railroad track rail by the vision system of the apparatus in accordance with the inven¬ tion;

Fig. 10 depicts the light lines projected onto the foot of the rail;

Fig. 11 is a schematic view of a typical railroad track rail indicating the placement of the light beam on the track rail;

Fig. 12 is a front elevational view of a grinding machine having an apparatus for measuring and maintaining the profile of a track rail in accordance with the present invention mounted thereon;

Fig. 13 is a side elevational view of the grinding machine shown in Fig. 12; Fig. 14 is a sectional view taken along line

14-14 of Fig. 13 depicting the optical front ends of the vision system in accordance with the present invention mounted within an environmental protective container;

Fig. 15 depicts the structure depicted in Fig. 14, but from a top plan view;

Fig. 16 is an enlarged top plan view of an

optical front end of the vision system;

Fig. 17 is a sectional, elevational view of the structure depicted in Fig. 16;

Fig„ 18 is a flow chart depicting the method for measuring and maintaining the profile of a railroad track rail in accordance with the present invention;

Fig. 19 is a flow chart depicting in greater detail the View Rail Profile step of Fig. 18;

Fig. 20 is a flow chart depicting in greater detail the Place Stones step of Fig. 18; and

Fig. 21 is a schematic diagram of a worn rail profile with an ideal rail profile superimposed thereon, depicting the placing of tangent lines at grinding points along the worn rail profile and the results of grinding at one of the grinding points .

Detailed Description of the Drawings The method and apparatus for measuring and maintaining the profile of a railroad track rail in accordance with the present invention is best understood in conjunction with a detailed explanation of the structure of a typical railroad track rail 20. Referring to Figs. 1, 2, and 3, a typical rail 20 includes railhead 22, web 24, and foot 26. The railhead 22 includes upper, arcuate, crown surface 28, and opposed head sidewalls 30, 32. Web 24 defines vertical rail centerline & in a vertical, center line plane. Crown surface 28 presents a surface radius of about six inches to about fourteen inches, depending upon user specifications. Foot 26 includes opposed, inclined, field side and gauge side upper surfaces 34, 36. The railhead 22, web 24 and foot 26 are preferably symmetrically formed about centerline fc.

Fig. 4 depicts an ideal railroad track rail I with the profile of a worn rail W superimposed thereon in phantom lines. Headloss L is the vertical difference between the ideal profile I and the worn profile W at

the centerline h of the rail. Alternatively, head loss can be measured as the percentage loss of area in a transverse cross section of the head. Gauge wear G is the horizontal difference between the worn rail W and ideal rail I at the gauge side head sidewall 30 of the rail, as measured 5/8th of an inch below the top T of the ideal rail profile I. The portion RS of the crown surface 28 which comes into actual contact with the wheels of a railroad car is commonly referred to as the rail running surface (see Fig. 7). Fig. 5 shows the profile of various worn rail configurations in phantom lines, superimposed on the profile of an ideal rail. Note, in particular, the occurrence of burrs B on the field side of the rail. Referring in particular to Fig. 6, the inclined field side and gauge side foot upper surfaces 34, 36 define planes that intersect along a line 38 in the center line plane. The angle of inclination of the foot upper surfaces is held to an industry standard 14°. Variance of the intersection line 38 from the vertical plane of the centerline Es is accordingly less than +/- 1/32", and the vertical distance of line 38 above the bottom surface of the rail 20 remains constant to within +/- 1/32". Referring to Fig. 6, the overall height (h) of the rail can therefore accurately be determined if the distance (d) between the crown surface 28 and the line 38 can be accurately determined. Moreover, the line 38 provides an origin for locating points in x and y coordinates on the crown surface 28 of a cross section of the rail 20.

The apparatus 40 for measuring and maintaining the profile of a railroad track rail in accordance with the present invention is specifically designed to take advantage of the above described structure of a track rail. Referring to Fig. 8, the apparatus 40 broadly includes a vision system 42 and a grinding system 44.

The vision system 42 includes an optical front end 46 and control section 48. The optical front end 46 includes a strobe light 50, railhead camera 52, and rail foot camera 54. Control section 48 includes vision computer 56, terminal 58, and display 60. A second optical front end 46 having additional cameras 52', 54' and strobe light 50' can be connected to the vision computer 56 for viewing a second rail, or for viewing the same rail in a different position (i.e., behind the grinding modules for immediate evaluation of the grinding process). Grinding system 44 includes grinding control computer 62 and grinding modules 64.

The strobe light 50 is oriented at an angle θ relative to the horizontal, and projects a generally planar beam of light 66 on to rail 20. Referring to Figs. 9, 10, and 11, the reflection of the angled light beam 66 from the rail 20 presents an illuminated, arcuate light line 68 on the railhead 22, and linear light lines 70, 72 on the foot upper surfaces 34, 36. It will be appreciated that the precise configurations of the light lines 68, 70, 72 are a function of the profile of the surfaces of the rail 20.

Fig. 11 is a schematic, top plan view of the illuminated lines 68, 70, 72 reflected by the 'rail 20, as seen by the railhead camera 52 and foot camera 54. The field of view of cameras 52, 54 are indicated by phantom lines 74, 76. Referring to Fig. 11, it will be understood that the extension of linear light lines 70, 72, as depicted by dashed lines 70', 72 ' ₇ intersect at rail centerline £. Moreover, when the strobe light 50 is oriented at a preferred angle of θ = 45°, the horizontal length d (as depicted in Fig. 11) is equal to the vertical height d (as depicted in Fig. 6), since tan 45° = 1. Using the intersection point of extended light lines 70', 72' as a reference, sample points along arcuate light line 68 can be represented in two

dimensional, x-y coordinates. The x-y coordinates, as will be discussed in detail below, can be used to compare the actual rail profile to an ideal rail profile, and the comparison data can be used for optimum placement of grinding modules 64.

The apparatus 40 for measuring and maintaining the profile of ^* a rail is depicted as mounted on a grinding machine 100 in Figs. 12 and 13. The rail grinding machine 100 is a self-propelled vehicle having a main frame 102 supported on railroad track rails 20 by rail engaging wheels 104. An undercarriage 106 depends from the main frame 102, and is supported along the railroad track rails 20 by undercarriage rail engaging wheels 108. The plurality of grinding modules 64 are carried by the undercarriage 106. The grinding machine includes an engine compartment 112 and operator's cab 114.

The optical front end 46 of the vision system 42, comprising strobe light 50, and cameras 52, 54, is mounted within an environmental enclosure 116. Refer¬ ring to Figs. 14-17, a separate optical front end 46 with its own strobe light 50, and separate pair of rail head and rail foot cameras 52, 54 is dedicated to each of the two track rails 20. Moreover, referring to Fig. 13, front and rear environmental enclosures 116a, 116b, each having its own optical front ends 46 can be mounted in front of (116a), and following (116b) the grinding modules 64.

The environmental enclosure 116 provides a temperature controlled, clean environment for the optical front ends 46 of the vision system 42. Enclosure 116 is mounted by brackets 118 to a carriage mounted to the frame 102 of grinding machine 100. The cameras 52, 54 and associated strobe light 50 of each optical front end 46 are contained within an individual optical equipment box 120. Each box 102 is mounted on

shock absorbing pads 122 within the enviromental enclosure 116. Ventilation duct 124 provides a path for forced air to travel across the field of view of the cameras 52, 54 and outwardly onto the rails 20, thereby clearing the field of view from dust, dirt, snow, and debris.

The process for measuring a railroad track rail and restoring the profile of the rail through grinding in accordance with the present invention is depicted in flow chart form in Figs. 18-20.

Referring to Fig. 18, the process is begun at program block 202 by using vision system 42 to view a rail 20 to determine the rail profile. The view rail profile step is discussed in detail below, and is depicted in greater particularity in Fig. 19.

Program flow is directed from the view rail profile step 202 to decision block 204 for determination of whether enough profiles over a given interval of railroad track rail have been acquired to compute a representative rail profile for the interval. The determination of whether enough profiles have been taken to comprise a complete interval can be done in one of two ways. In the first method, a predetermined number of rail profiles can be chosen to comprise a complete interval. Once the appropriate number of profiles have been accepted, program flow would be directed to block 206 for determination of a representative rail profile over the interval. In this regard, it will be appreciated that the profile of a rail will change along the length of the rail. A "representative rail profile" could be an average of each of the profiles taken along the interval, a median of the profiles, a least square's fit, or any other numerical analysis of the profiles within the given interval. The second method for computing an acceptable representative profile is to compute the representative

profile on the fly from each of the rail profiles as they are acquired. An "interval" would be considered as complete once the trend of the representative profile becomes constant. With either method, a new rail profile will be viewed at generally evenly spaced lengths (such as every 36 inches) along the railroad track rail, and the viewed rail profiles will be manipulated to present a represen¬ tative profile at least every 39 feet (39 feet being the length of a typical railroad track rail in a jointed railroad track system) .

Moreover, viewing of the rail profile is a

• continuous process. The optical front end 46 in the enclosure 116b at the rear of the grinding machine 100 can be used to prepare a representative rail profile for r& -second grinding pass as the rail is ground during a first forward grinding pass of the machine 100 over the rail.

Once a representative rail profile for an interval of railroad track is determined, program flow is directed to block 208 where the representative rail profile is compared to the profile of an ideal rail. The comparison is made in order to determine what metal should be removed to restore the viewed rail's profile to an ideal shape. The definition of an "ideal" profile can depend on the kind of terrain over which the railroad track is laid, the type of loads carried by trains using the railroad track, or on whether the rails of the track are on a straightaway, a curve, or a switch. Moreover, individual railroad companies may have differing criteria for the shape of an "ideal" rail. The differing descriptions of what an "ideal" rail profile comprises can each be stored in the memory of grinding control computer 62 and can be retrieved from memory as needed.

The step of comparing the representative rail

profile to an ideal profile is best understood with reference to Fig. 7. In Fig. 7, a representative rail profile R as measured by the vision system 42 and determined by the grinding control computer 62 is depicted in phantom lines. Also depicted in phantom lines is the wheel of a railroad car shown resting on the representative rail profile. An ideal rail I is superimposed on the representative rail profile R by first aligning the gauge points of the representative and ideal profiles . The ideal rail profile is then shifted downwardly relative to the representative rail profile R so that all points of the running surface RS on the ideal profile I lie on or below the representa¬ tive rail profile R. The reasons for so aligning the ideal and representative profiles is that metal must be ground away from the representative rail profile in order for the representative rail profile to approximate the ideal profile; it is not possible to add metal to build up the worn rail. Moreover, it is only along the actual running surface RS, and the gauge sidewall 30, that the ideal and representative rail profile must be aligned as described above, since those are the only places where the wheel of a railroad car actually makes contact with the rail. Program flow is next directed to decision block 210 where it is determined whether the railroad track rail, as described by the representative profile of the rail, requires grinding. If the rail profile is satisfactory, and no grinding needs to be done, the process ends. If grinding is required, program flow is directed from block 210 to decision block 211 where it is determined whether the representative rail profile can be corrected through grinding. If the rail is so deformed that grinding would not materially improve the rail profile, the process is complete, and the rail must be replaced. If it is determined in decision block 211

that the rail profile can be improved through .grinding, program flow is directed to block 212 for placement of the grinding modules 64 of the rail grinding machine 100 ₌ Program flow is next directed to block 214 where the rails are ground along the measured interval. Once grinding is complete, program flow is redirected to block 202 to again view the rail along the interval for determination of whether more grinding is required.

The view rail profile step of block 202 is depicted with greater particularity in Fig. 19.

The railroad rail 20 is first illuminated by the strobe 50 of vision system 42 in block 215. Program flow is next directed to block 216 where the intersec¬ tion of the rail footlight lines 70, 72 is used to establish a reference origin. Program flow is then directed to block 217 where a number of sample points

•across the crown surface 28 of railroad track rail 20 are represented in Cartesian coordinates relative to the reference origin established in block 216. Alternative- ly, one of the sample points can be selected as a reference point for establishing the relative portion o the other points. While the number of points selected is somewhat arbitrary, fifty data points across the crown surface 28 of the rail 20 provides an adequate description of the surface of the rail 20 without unduly complicating the calculation of the representative rail profile in block 206. The fifty points across the crown surface 28 are not necessarily evenly spaced, but are more advantageously concentrated around the edges of the rail where the curvature of the rail changes the most.

Program flow is next directed from block 217 to decision block 218 where it is determined whether enough valid sample points across the crown surface 28 of the rail were obtained in an individual illumination (or vision frame) of the rail. In this regard, an obstruction, such as a rock or other foreign object, may

be lying across the rail at the point of illumination, preventing a full set of valid sample points from being obtained from a particular vision frame. If enough sample points are not obtained, the vision frame is discarded and another illumination of the rail 20 immediately takes place. If a satisfactory number of sample points are obtained from a vision frame, program flow is returned from block- 218 to decision block 204 of Fig. 18 for a determination of whether enough valid vision frames have been acquired to make up a valid interval .

The place stone step of block 212 is set forth in greater particularity in Fig. 20.

The process of placing grinding stones is begun at block 220 by assigning a predetermined number of potential grinding contact points along the represen¬ tative rail profile surface. The grinding contact points are analogous to the sample points described above in conjunction with the view rail profile step of block 202. The sample points, however, relate to the actual, viewed profile of a vision frame. The grinding contact points relate to the representative rail profile, which is the result of the numerical analysis of all of the vision frames in a given interval. Program flow is next directed to block 222 where the tangent of each grinding point is determined. The grinding depth between the representative rail profile and the ideal rail profile along the perpendicu¬ lar to the tangent line of each grinding point is then determined in block 224.

The steps of program blocks 222 and 224 are best understood with reference to Fig. 21. Three grinding points GP along a representative rail profile R are depicted in Fig. 21. The tangent lines, Tl, T2, T3, for each of the grinding points GPl, GP2, GP3 are also depicted. While there are a variety of angles that a

stone can be placed into contact with a particular grinding point, placing the stone of a grinding module along the tangent to the grinding point is considered as the most efficient orientation of the grinding module. The tangent for each grinding point is determined by taking a point to the left and to the right of each grinding point, calculating the slopes of the three lines defined by the three points, and then averaging the three slopes. The perpendicular line PL1, PL2, PL3 is then calculated for each tangent line SPl, SP2, SP3. The length of each perpendicular line PL between the representative profile and the ideal profile is then calculated as the grinding depth.

Program flow is directed from block 224 to decision block 226 where it is determined whether there =aτe grinding modules 64 available. If all grinding modules 64 have been assigned, the program flow is directed to block 228, described in detail below. If there are grinding modules 64 remaining for assignment, program flow is directed to block 232 for the assignment of a grinding module. Once a grinding module 64 is assigned, program flow is directed to block 234 to begin the determination of the appropriate grinding point and grinding angle for the assigned grinding module. The grinding point having the largest grinding depth, as measured along the perpendicular line PL to its tangent T, is selected as the grinding point for the assigned grinding module. If only a limited number of passes over the rail 20 by the grinding machine 100 can be made, choosing the grinding points in descending order of grinding depth ensures that at least the worst portions of the rail profile will be ground. Alterna¬ tively, it may be decided in advance that, for instance, burrs along portions of the field side of the rail need not be ground. In that case, grinding points at the predetermined positions will not be considered for

grinding, regardless of their grinding depth relative to the other grinding points . Program flow is next directed to block 236 where the tangent line to the grinding point selected in block 234 is determined as the preferred grinding angle for the assigned grinding module.

Program flow is next directed to block 238 where the grinding control computer 62 predicts how much surface area of the rail 20 will be removed by grinding at the selected point and angle in one pass of the grinding machine 100 along the rail being ground. Moreover, the new position and tangent lines of the grinding points affected by one pass of the selected grinding module are predicted in block 238. The prediction step of block 238 can be understood with refer nce to Fig. 21, where the predicted positions of grinding points GPl, GP2, GP3 ^* are depicted as GPl',. GP2', and GP3 ' . Referring to Fig. 13, it will be appreciated that the grinding modules 64 are lined up one behind the other. The prediction step of block 238 is carried out so that the orientation of trailing grinding modules will be based on what the profile of the rail 20 is likely to be after grinding is accomplished by a leading grinding module. Program flow is next directed to block 240, where it is determined whether the results of grinding, as predicted in block 238, will cause interference with known obstructions (such as at a switch or crossing in the railroad track), or whether grinding at the proposed angle will remove more material than desired at any of the grinding points due to gross irregularities in the rail profile or the like. Program flow is next directed to decision block 242 where the results of the analysis in block 240 are queried to determine whether the angle selected is satisfactory. If the grinding angle is not satisfactory, program flow is directed to block 244

where the grinding angle is adjusted to avoid the obstruction or to avoid the interference determined to exist at block 240. Program flow is then directed to decision block 245 to determine whether the adjusted angle can be attained by the assigned grinding module. If the adjusted angle is attainable, .program flow is redirected to block 240 to analyze whether the new, adjusted angle avoids interference and obstructions.

Once an acceptable grinding angle for the assigned grinding module is selected, program flow is directed from decision block 242 to decision block 246. Block 246 determines whether too much metal will be removed from the railhead by grinding the rail with the grinding module operating at standard horsepower and at the selected angle. If too much metal will be removed (i.e., the rail. 20 will be ground below the ideal profile) program flow is directed to the block 248 where the horsepower to the assigned grinding module is reduced, it being understood that operation of a module at reduced horsepower will remove less metal from the railhead. Program flow is then directed to decision block 250 where it is determined whether the reduced horsepower falls below the minimum required horsepower to operate the grinding module. Program flow is directed from decision block

246 to block 252 if it is determined that grinding at standard horsepower will not remove too much metal from the railhead. Program flow will also be directed to block 252 from block 250 if it is determined that reducing the horsepower to the selected grinding module does not bring the horsepower level below the minimum required to operate the grinding module. At block 252, the calculated grinding angle and grinding horsepower for the selected module are stored in computer memory. Program flow is then directed to block 253 where any of the grinding points removed from consideration in block

247 (to be described below) are replaced, and program flow is directed to block 226 for the assignment of further grinding modules .

Program flow is directed to block 247 from either decision block 245 or 250 if it is determined that either the selected grinding angle (block 245) or the horsepower requirements for the grinding module (block 250) are not within acceptable limits. The grinding point for which the angle or horsepower requirements is unacceptable is removed from considera¬ tion at block 247. Once the grinding point has been removed from consideration, program flow is directed to decision block 251 to determine whether there are further grinding points for consideration. If there are grinding points remaining, program flow is redirected to block 234 for selection of another grinding point. It will be appreciated that the grinding module previously selected in block 232 is still available for assignment to a selected grinding point. Since the previously considered grinding point was removed from consideration in block 247, the grinding point with the next largest grinding depth will now be selected at block 234.

Program flow will be directed from block 226 to block 228 once it is determined that all the grinding modules of grinding machine 100 have been assigned for grinding. At decision block 228, the grinding horse¬ power requirements of the individual grinding modules are summed to determine whether the sum of the grinding module horsepower requirements is less than or equal to the optimum grinding machine horsepower. In other words, decision block 228 determines whether the programmed grinding operation will make use of all of the available grinding machine horsepower. If the power requirement is determined to be at the optimum horse- power, program flow is directed to block 214 (Fig. 18) for grinding of the rail. If horsepower requirements

fall below the optimum, program flow is directed from block 228 to decision block 253, where it is determined whether the speed of the grinding machine 100 over the rails is less than the maximum desired speed for grinding operations. If machine speed is not less than the maximum desired speed, program flow is returned to block 214 for commencement of the grinding operation.

Assuming that the horsepower demands of the grinding modules will be less than the optimum available machine horsepower, and further assuming that machine speed can be increased, program flow will be directed from decision block 253 to block 230 where all grinding module settings are reinitialized, and the grinding machine speed is increased. In this regard, it will be appreciated that the amount of metal removed from a rail is a function of Taoth the horsepower of the individual grinding module, and the speed with which the grinding module is carried across the rail. As the speed of the grinding module over the rail increases, grinding module horsepower must be increased to effect the same amount of metal removal. Increasing machine speed will therefore increase grinding module horsepower require¬ ments. In the situation where the programmed grinding operation does .not use all of the available machine horsepower, the same amount of grinding can be accom¬ plished in a shorter time by increasing grinding machine speed and proportionately increasing the operating power of the grinding modules.