Abstract:
An apparatus and method for inspecting a rail joint bar transported along a railway rail by an inspection vehicle is provided. The apparatus and method includes a pair of ultrasonic transducers housed in liquid-filled wheels. The wheels are positionable for a stored position to a measurement position in rolling contact with the vehicle surfaces of the rail joint bars on each side of the rail. The ultrasonic transducer transmits a signal into the rail joint bar and the reflected signal is detected by the transducer and analyzed to identify flaws in the rail joint bar.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of co-pending application Ser. No. 61/238,484, filed on Aug. 31, 2009, entitled APPARATUS FOR METHOD OF DETECTING DEFECTS IN A RAIL JOINT BAR. 
     
    
     FIELD 
       [0002]    The present invention relates generally to an apparatus for and method of detecting defects in a rail joint bar and, more particularly, to a mobile apparatus for and method of performing nondestructive-type testing using ultrasonic transducers to detect flaws and defects in a rail joint bar. 
       BACKGROUND 
       [0003]    The United States Federal Railroad Administration has published statistics which indicate that train accidents caused by track failures including rail, joint bars and anchoring resulted in approximately 2700 derailments from 1992 to 2002. The primary cause of these track failures is a transverse defect and fissure running perpendicular to the rail running direction in the rail and rail bar joint. 
         [0004]    A pair of rail joint bars holds the two ends of a rail in place and act as a bridge between the rail ends. The rail joint bars prevent lateral and vertical movement of the rail ends and permit longitudinal movement of the rails to accommodate expanding and contracting. Bolts extending through holes in the joint bars and the rail ends secure the rail ends together. Rail joint bars are typically 24 or 36 inches long with four or six bolt holes, respectively. 
         [0005]    Various methods of rail inspection include magnetic, contact, ultrasonic and video. One such video system is the Automated Optical Joint Bar Inspection System developed by ENSCO, Inc. in cooperation with the Federal Railroad Administration. One such ultrasonic system is disclosed in U.S. Pat. No. 6,055,862 entitled “Method of and Apparatus for Detecting, Identifying and Recording the Location of Defects in a Railway Rail,” which is incorporated herein by reference. 
         [0006]    One problem with video inspection systems is the inability to see into the rail joint bar and the area of the rail joint bar hidden under the head of the rail. Further, the most common failure of rail joint bars begins in an area centrally located within the bar. Video systems are also susceptible to false readings because of debris, rust and discoloration or streaks on the joint bar. 
         [0007]    Ultrasonic testing of rails is performed with ultrasonic transducers housed in a liquid-filled wheel. The wheel rides along the top of the rail head while the transducers transmit ultrasonic waves into the rail head and receive reflected waves from the rail head. The orientation of the transducers and the wave path are used to identify defects in the rail head and web. However, the wave cannot pass from the rail head into the rail joint bar. 
       SUMMARY 
       [0008]    The present invention provides an apparatus for and method of detecting defects in a rail joint bar. The apparatus includes a pair of opposed liquid-filled transducer wheels which are repositionable laterally and vertically. Each wheel is protected by a pair of idler rollers one on opposite sides of the wheel to ensure that the wheel is in contact with the head of the rail joint bar for measurement. 
         [0009]    Pneumatic or hydraulic cylinders or electromechanical devices may be used to reposition the wheels laterally and vertically to align the wheels with the joint bar head and to move the wheel assembly away from rail obstructions. The apparatus is mounted to a carriage assembly which is secured to a rail inspection vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective side view of the rail joint bar inspection device of the present invention. 
           [0011]      FIG. 2  is a front view of the cradle assembly of the rail joint bar inspection device. 
           [0012]      FIG. 3  is a perspective front view of the rail joint bar inspection device. 
           [0013]      FIG. 4  is a bottom plan view of the idler arm of the rail joint bar inspection device. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The drawings are not necessarily to scale, some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0015]    Moreover, except where otherwise expressly indicated, all numerical quantities in this description and in the claims are to be understood as modified by the word “about” in describing the broader scope of this invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary, the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures or combinations of any two or more members of the group or class may be equally suitable or preferred. 
         [0016]    Referring to the drawings, a rail joint bar inspection device is generally indicated by reference numeral  10 . Rail joint bar inspection device  10  includes a cradle  12  secured to a carriage  14 . The cradle  12  is movable vertically in relationship to the carriage  14 . The carriage  14  provides a platform for mounting the cradle  12  and related equipment. 
         [0017]    The cradle  12  is generally an inverted U-shaped structure with a top plate  16  and a pair of legs  18  extending downwardly from the top plate  16 . A pair of cradle to carriage interface plates  20  slidably secure the cradle  12  to the carriage  14 . The cradle to interface plates  20  are secured to the carriage  14  and thus fixed to allow the cradle  12  to move in a vertical plane relative to the carriage  14 . A motor  22  is mounted to a motor support  24 , which is secured to the interface plates  20 . The motor  22  drives a screw or threaded rod  26  which passes through a nut  28  which is welded to the top plate  16 . As the motor  22  turns the screw  26 , the cradle  12  moves up or down. It should be understood that other mechanisms for moving the cradle  12  may be used such as a pneumatic cylinder, solenoid or hydraulic cylinder, for example. 
         [0018]    Extending outwardly from each cradle leg  18  is an actuator  30 , which is mounted to the lower end of the respective cradle leg  18  with a bracket  32 . In the preferred embodiment the actuator  30  may be a rod-less pneumatic cylinder with a one-inch bore and a two-inch stroke, however, other actuators such as motors, solenoids and hydraulic cylinders, for example, may be used. Slidably attached to each actuator  30  is an idler arm  34  which supports a pair of idler rollers  36  and a sensor assembly  38 . The sensor assembly  38  is a liquid-filled wheel known in the art, which houses an ultrasonic transducer mounted at an angle between approximately 35 degrees to 55 degrees, and more particularly 37.5 degrees to 52.5 degrees to the outside vertical surface  40  of the head  42  of the rail joint bar  44 . The ultrasonic transducer produces an ultrasonic beam that is transmitted in a horizontal plane. The width of the sensor assembly  38  may be minimized to avoid contact with bolt heads and nuts holding the rail joint bars  44  to the rails  47 . In  FIG. 2 , the idler roller  36  on the left idler arm  34  is shown in broken lines to more clearly show the orientation of the sensor assembly  38  relative to the rail joint bar head  42  and vertical surface  40 . 
         [0019]    The idler rollers  36  limit the inward movement of the idler arm  30 . When the idler rollers  36  are in contact with the vertical surface  40  of the rail joint bar head  42 , the spacing between the ultrasonic transducer mounted within the sensor assembly  38  is maintained at an optimal and constant distance from the vertical surface  40 . 
         [0020]    The pair of carriages  14  is coupled to a rail inspection vehicle (not shown) which pushes or pulls the carriages  14  along a railway. Each carriage  14  includes a pair of rail wheels  46 , which ride on the rails  47  and provide a stable reference plane for the cradle  12  and sensor assembly  38 . At least one of the carriages  14  may also include a camera mount  48  to support a camera  50 . The camera  50  may be used to help an operator identify a rail joint bar  44  and to position the cradle  12  and idler arms  34  relative to the rail joint bar head  42 . 
         [0021]    In a manual operation, the carriage  14  is pulled along a railway by an inspection vehicle. An operator riding in the inspection vehicle monitors a display (not shown) coupled to the camera  50 . As the inspection vehicle approaches a rail joint bar  44 , the operator energizes the motor  22  to turn the screw  26  in a direction to lower the cradle  12  to a height where the surface of the sensor assembly  38  is aligned in a horizontal plane perpendicular to the vertical surface  40  of the rail joint bar head  42 . The operator also activates the actuators  30  to slide the idler arms  34  inwardly until the idler rollers  36  and sensor assemblies  38  are in contact with the rail joint bar head  42 . As the sensor assemblies  38  roll along the vertical surface  40  the rail joint bar head  42 , the ultrasonic transducers mounted within the sensor assembly  38  transmits an ultrasonic wave into the rail joint bar head  42 . The return signal is received and analyzed to identify defects in the rail joint bar head  42  at an angle of approximately 35 degrees to 55 degrees, and preferably 37.5 degrees to 52.5 degrees relative to the vertical surfaces  40  of the rail joint bar head  42 . When the sensor assembly  38  passes the end of the joint bar  44 , the pressure may be released from the actuators  30  allowing the idler arms  34  to return to their initial or stored position translating the idler rollers  36  and sensor assemblies  38  away from the vertical surface  40  of the rail joint bar head  42 . The motor  22  may also be reversed to turn the screw  26  to raise the cradle  12 . This procedure may be repeated for each joint bar  44  encountered along the rails. 
         [0022]    It should be understood that the cradle  12  need not be raised after reaching the end of a rail joint bar  44 . It may be advantageous to leave the cradle  12  in the lowered position to minimize the time necessary for the sensor assembly  38  to initially contact a rail joint bar head  42  vertical surface  40 . However, because the idler arms  30 , idler rollers  36  and sensor assemblies  38  extend below the horizontal plane of the top surface of the rail head  47 , it may be desirable to raise the cradle  12  to avoid damage to the inspection device  10  when approaching a crossing or switch, for example. 
         [0023]    In an automatic operation, the leading end  15  and/or trailing end  17  of the carriage  14  may be equipped with limit, whisker, or optical switches/sensors  19  and  21 , respectively, to detect the leading and/or trailing edges and thereby the presence of the rail joint bars  44 . When the leading limit switch  19  encounters the leading edge of the rail joint bar head  42 , the cradle  12  may be automatically lowered to a height where the surface of the sensor assembly  38  is aligned in a horizontal plane perpendicular to the vertical surface  40  of the rail joint bar head  42 . The actuators may then be  30  actuated to slide the idler arms  30  inwardly until the idler rollers  36  and the sensor assemblies  38  engage the vertical surface  40  of the joint bar head  42 . As the sensor assemblies  38  roll along the vertical surface  40  the rail joint bar head  42 , the ultrasonic transducers mounted within the sensor assembly  38  transmits an ultrasonic wave into the rail joint bar head  42  at an angle of approximately 37.5° to 52.5° relative to the vertical surface  40  of the rail joint bar head  42 . The return signal is received and analyzed to identify defects in the rail joint bar head  42 . When the trailing limit switch  21  is disengaged from the rail joint bar head  42 , the sensor assembly is automatically disengaged from the rail joint bar head  42  and the cradle  12  may be raised. Various combinations of video and electromechanical activation of the rail joint bar inspection device  10  may be used to control the movement of the sensor assembly  38  to inspect the rail joint bar head  42 . 
         [0024]    Because the majority of hairline fractures and other defects are found at the rail joint  49  between two rails  47 , and the standard length of a rail joint bar  44  is 24 or 36 inches, the maximum time from the engagement of the leading limit switch  19  and contact of the sensor assembly  38  with the vertical surface  40  of the rail joint bar head  42  may be approximately X/2 divided by Y, where X is the length of the rail joint bar  44  and Y is the speed of the rail inspection vehicle. Preferably, the maximum time is X/4 divided by Y to ensure that the sensor assembly  38  is in contact well before passing the rail joint  49 . 
         [0025]    By way of example, suppose a rail inspection vehicle is traveling along a railway at ten miles per hour, or 177 inches per second. For the sensor assembly  38  to make contact within six inches of the front edge of the rail joint bar  44  it needs to move from a disengaged position to an engaged position within 0.034 seconds. Solenoids, air cylinders or hydraulic cylinders, for example, may be used to rapidly move the idler arm  30  and attached idler rollers  36  and sensor assembly  38  from a disengaged position to an engaged position. 
         [0026]    It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto, except in so far as such limitations are included in the following claims and allowable equivalents thereof.