Abstract:
A rail section weld inspection device [ 1000 ] is described for inspecting a rail [ 10 ] for internal defects [ 19,21 ]. A central ultrasonic (US) probe [ 1330 ] transmits at least one US beam [B] through the rail [ 10 ] and receiving a reflected signal. At least one angled US probe [ 1310 ] transmits at least one US beam [A 1 -A 5 ] through the rail [ 10 ] at an oblique angle at least partially covering the same region as the central probe [ 1330 ]. An encoder identifies the location of the US probes [ 1330 ] and [ 1310 ] along the rail [ 10 ] and pairs the locations of the probes with the signals received. The Calculation device [ 1500 ] receives the signals from the US probes and uses their different views to create an image of the flaws within the rail [ 10].

Description:
TECHNICAL FIELD 
     The present disclosure relates to a system for accurately inspecting a rail weld for weld defects, and more specifically a system for employing ultrasound to accurately inspect a rail weld for weld defects. 
     BACKGROUND 
     As sections of railroad are constructed it is necessary to weld one rail to the adjacent rail. The rails are welded end-to-end by a process called thermetic welding. In this process, the rails are placed in the desired positions. A material designed to burn at high temperature is wrapped around the rail joint and ignited. It burns at a high temperature and welds the rails together their entire cross-section. 
     This process sometimes creates bubbles or other flaws that lead to a weakening of the joint. It is necessary to identify these flaws so that the joint be replaced with a stronger joint without weld flaws. 
     Rails and weld also deteriorate with time and use. Therefore there is also a need to inspect rails and welds for flaws created by extended service &amp; fatigue. 
     Since there is a large amount of weight carried by the rails, flaws may cause weakened sections and result in a derailment. 
     There are ultrasonic inspection devices to inspect welds in specific geometries such as sheets and plates, such as U.S. Pat. No. 3,552,191 Jan. 5, 1971 by Heseding. This uses multiple ultrasound (US) transmitters that are also US receivers on one side of a weld on a sheet or plate. They also have embodiments that transmit across the weld to be received by a receiver on the other side of the weld. This apparatus is designed to inspect welds in flat plates and does not function well to inspect objects with substantially different geometry such as railroad rails. 
     U.S. Pat. No. 3,028,751 issued Apr. 10, 1962 to I. L. Joy describes a device designed to quickly detect locations that may possibly have flaws. It does not perform a thorough scan through the rail, but a more cursory scan to detect a general region have a large flaw. 
     Currently, there is a need for an inspection device that more accurately identifies flaws in railroad rail thermite welds. 
     SUMMARY 
     The present invention may be embodied as a rail weld inspection device 
     for inspecting internal volumes of an elongated object [ 10 ] for defects, the elongated object  10  extending in a horizontal “z” direction with a vertical direction being a “y” direction and a direction perpendicular to both the “y” and “z” directions, being the “x” direction and for providing the information to a calculation device [ 1500 ], comprising: 
     a central ultrasonic (US) probe [ 1330 ] for transmitting at least one US beam [B] through said elongated object [ 10 ], for receiving a reflected signal, and for providing the signal to said imaging device; 
     at least one angled US probe [ 1310 ] for transmitting at least one US beam [A 1 -A 5 ] through the elongated object [ 10 ] at an oblique angle within an y, z, plane which intersects with the beam B from the central US probe [ 1330 ], and adapted to receive reflected signals from the same oblique angle, and for providing the signal to said imaging device; 
     an encoder [ 1380 ] adapted to identify a location of the US probes [ 1330 ] and 
     along the elongated object [ 10 ] as the reflected signals are received and for pairing the locations of the probes corresponding to the received signals and for providing this information to the imaging device to create a map of flaws within the elongated object [ 10 ]. 
     The central US probe  1330  may transmit a plurality of parallel US beams [B 1 -B 5 ] generally in the “y” direction. 
     The central US probe [ 1330 ] may also transmit a plurality of US beams [D 1 -D 10 ] obliquely in an “x, y” plane. 
     Also, the angled US probes [ 1310 , 1350 ] may transmit beams [A 1 -A 5 ], [C 1 -C 5 ] at a plurality of angles and receive each reflected signal independently from the same angle as each had been transmitted. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide an accurate weld inspection system for railroad rails. 
     It is another object of the present invention to provide an accurate weld inspection system that accurately inspects rail welds without having to remove the rails. 
     It is another object of the present invention to provide an accurate weld inspection system that is portable. 
     It is another object of the present invention to provide a thorough inspection through a rail weld and identify flaws within the weld. 
     It is another object of the present invention to scan through a volume of a welded rail at various angles to identify flaws within the weld. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, wherein like items are numbered alike in the various Figures: 
         FIG. 1  is a schematic illustration of the ultrasound beams scanning through a railroad rail weld according to one embodiment of the present invention. 
         FIG. 2  is a schematic illustration of the ultrasound beams of the embodiment of  FIG. 1  wherein the beams have been moved relative to the weld. 
         FIG. 3  is an illustration of the US beam geometry of the central probe of one embodiment of the present invention. 
         FIG. 4  is a perspective view of the weld inspection system according to one embodiment of the present invention. 
         FIG. 5  is an enlarged perspective view of the runner of the weld inspection system according to one embodiment of the present invention. 
         FIG. 6  is a side elevational view of the runner of the weld inspection system shown in  FIGS. 4 and 5 . 
         FIG. 7  is a top plan view of the runner of the weld inspection system shown in  FIGS. 4 ,  5  and  6 . 
     
    
    
     DETAILED DESCRIPTION 
     Theory 
     When inspecting at a flaw from a given viewing angle, it is sometimes hard to detect the flaw. This may be due to the fact that the flaw has a very small cross section when viewed from a given viewing angle. The same flaw viewed from another angle has a much larger cross section and is easier to detect and view. 
     Therefore, proper inspection through a volume is not only dependent upon the portions of an object scanned, but also on the angle from which the inspection is performed. 
     Commonly inspection is performed using ultrasound. Typically, an ultrasound (US) transceiver is used having both an US transmitter and an US receiver. In the present invention, the ultrasound is transmitted as a beam at various angles. The US beam reflects off of metal air interfaces and is received by the transceiver. Therefore, one may locate a flaw by knowing the angle of the transmitted beam, the shape and geometry of the material through which it is transmitted (to determine reflective interfaces) and the time at which a reflected US beam (an “echo”) is received from the transmitted direction. 
     Some transmitters, transmit in a given direction, and move to a new direction and transmit in that direction. Echoes (if any) are detected from each of the transmitted directions, and the times of reception stored. Therefore, a volume may be sequentially scanned over a time period. If the transducer is moved during the scanning process, a number of echoes are received at various locations and angles. This may result in locations being missed. 
     The transducers may also transmit several beams at different angles simultaneously, and receive the reflected echoes at different various receive angles. The time delays indicate the location along the beam path of where a reflecting object (flaw) is located. 
     Also, due to the shape of the transmitted beams and the geometry of the object being inspected, it may not be possible to reach certain volumes of the object being inspected. 
     Therefore, for thorough inspection of an object by ultrasound, one must take into account the shape of the beam used, the placement of the transducer or transducers, the location of the transducers relative to the object, and the geometry of the object being scanned and other factors. 
     The present invention addresses all of these issues. It employs several transmitter/detectors modules. Each transducer module has a plurality of transducers each transmitting and receiving at different angles. Therefore, a full set of data is received at each instant allowing the device as it is moved relative to the object. 
     The multiple transducer modules are angled to converge on a central location. Therefore, multiple views from the multiple modules are simultaneously provided for the central location. 
     Therefore, a flaw may be inspected by several transducers from different angles at the same time. These signals may be used to provide a composite view. Since there is some redundancy in the data, the redundancy may be used to eliminate imaging artifacts. The redundancy may also be used to corroborate the existence of a flaw and more accurately delineate the bounds of the flaw. 
     One intended use of the present invention is for inspecting welds in railroad rails for flaws. A railroad rail has the base, vertical wall and the runner sections. The left-right dimension is the “x” axis, with the up-down direction being the “y” axis. The “z” axis is taken along the length of the rail. 
     Therefore, the weld is generally a thin volume between the rails in the x-y plane with a small thickness in the z direction. 
     There is only access to the top and sides of the rail. Therefore, any inspection must take place from these locations. The thermetic weld extends outward from the rail to both side and the top. The top section is ground down to make it smooth with the top of the rail. This allows the train wheels to smoothly roll over the top surface of the rail. This also allows the present invention to slide easily over the top surface of the rail. The sides are typically not ground down and provide obstructions to sliding along the sides. Therefore, the present invention should slide along the top surface of the rail, images from the top of the rail, have multiple transducers which provide multiple simultaneous views of volume, encode its location with the signals, and cover the volumes of interest within the rail. 
       FIG. 1  shows a schematic diagram illustrating the inspection geometry of a railroad rail  10  being inspected. This rail  10  has been welded leaving a weld section  17 . There are two flaws  19 ,  21  inside of weld section  17 . These may have been created during the welding process or have been created over time as deterioration of the rail  10  or weld section  17 . 
     In this embodiment, there are three probes, a front probe  1150 , a center probe  1130  and a rear probe  1150 . The front probe  1110  transmits a plurality of US beams at different angles into rail  10 . For the sake of clarity, only five beams are represented here labeled A 1 , A 2 , A 3 , A 4 , A 5 . Beam A 5  impinges upon and is reflected back by flaw  21 . This is detected as an echo by front probe  1110 . Flaw  21  has a small cross-section as viewed from front probe  1110 . It is small enough so that the other beams A 1 -A 4  do not impinge upon it, and the image is difficult to discern with the information from a single reflected beam. 
     Similarly, the rear probe  1150  transmits a plurality of US beams at different angles into rail  10 . For the sake of clarity, only five are represented here labeled C 1 , C 2 , C 3 , C 4 , C 5 . These US beams do not intersect either flaw  19  or  21  and are not reflected. 
     The center probe  1130  rests upon a top surface  23  of rail  10  and transmits a plurality of parallel US beams into rail  10 . In this view they are stacked behind each other. Therefore they may all be represented by B 1 . These pass through the rail top section  15 , the vertical wall  13  and the rail base  11 . These US beams also do not intersect either flaw  19  or  21  and are not reflected. 
     The probes are attached to a runner  1300  that is allowed to move probes  1110 ,  1130 ,  1150  in the direction of the arrows relative to the rail  10 . Runner  1300  includes a position encoder and wheels. Therefore, the position of the runner is known as it moves. 
       FIG. 2  shows a schematic diagram illustrating the probes of  FIG. 1  inspecting the railroad rail  10  at near the weld section. In this figure, center probe  1130  is now positioned above weld section  17 . Now beams B of center probe  1130  are reflected by flaw  19 . 
     Beams C 1 , C 2  of rear probe  1150  are reflected by flaw  19 . Similarly beams A 2  and A 3  of front probe  1110  are reflected by flaw  19 . None of the beams from front or rear probes  1110 ,  1150  impinge upon flaw  21  in this position. 
     Each transducer in the probes is capable of determining when a beam was transmitted and when a corresponding signal (echo) is received. 
     The reflected signals from the probes are sent to a processing unit along with an identification of the angle in which the beam was transmitted and where the probe was located during the transmission in relation to the rail being inspected. The elapsed time between transmission and reception of each echo is determined and this, along with the other transmitted information is used to reconstruct an image of the rail  10  and flaws  19 ,  21 . Since multiple signals may be used to indicate a singe flaw, the redundancy may be used to eliminate artifacts and further specify the bounds of the flaw. As is shown in  FIG. 2 , flaw  19  is better seen from the front and rear probes  1110 ,  1150  as compared with center probe  1130 . Center probe  1130  only sees a small cross section, whereas probes  1150  and  1110  see a larger side of the flaw  19 . 
     Similarly, flaw  21  has a very small cross section when viewed by front probe  1110  since it lines up with the beams and allows only its small cross section to be visible. 
       FIG. 3  is an illustration of the US beam geometry of the central probe of one embodiment of the present invention. From this view, only flaw  19  can be seen. This shows cross-sectional shape that is viewed from  90  degrees away from the view of  FIGS. 1 ,  2 . The cross section of a railroad rail  10  can be seen. 
     Here a cross section of rail  10  through the weld  17  can be seen. The base  11  that is fixed to a structure to hold the rail  10 . The vertical wall  13  has a flaw  19  inside of it. 
     Central probe  1130  is designed to function to scan through the rail  10 . As stated above, it functions to provide parallel US beams through the vertical wall  13  a base  11 . This would detect flaw  19 . 
     It may also produce a set of beams D 1 , D 2 , D 3 , D 4 , D 5  angled through one side of the top portion  15 . It may also produce a set of beams D 6 , D 7 , D 8 , D 9 , D 10  angled through the other side of top portion  15 . This creates a thorough inspection of the entire top section  15 , vertical wall and a critical portion of the base  11 . 
       FIG. 4  is a perspective view of the weld inspection system according to one embodiment of the present invention. Here two rails  10  are shown welded together with a thermetic weld at weld section  17 . Rail  10  and weld section  17  are intended to be inspected for flaws by rail inspection device  1000 . 
     End structures  1100 ,  1700  are removeably attached to rails  10 . This may be through the use of magnets as front attachment unit  1110  and rear attachment unit  1710 . Other attachment means may also be implemented. 
     A plurality of rod supports  1130 ,  1730  hold rods  1600  substantially parallel to rails  10 . 
     A runner  1300  is slidingly attached to rods  1600  and is allowed to move along the length of rails  10  by sliding on rods  1600 . 
     An encoder (not shown) is used to identify where the runner is with respect to rails  10 . 
     In this embodiment, runner  1300  includes three ultrasound (“US”) transmitter/receivers, a front probe  1310 , a central probe  1330  and a rear probe  1350 . 
     Both the front probe  1310  and the rear probe  1350  transmit US beams at an angle to a location within the rails  10  below central probe  1350 . They also receive reflected US signals from the same direction. This is more clearly seen in  FIGS. 1 and 2  where beams “A 1 -A 5 ” of the front probe  1110  and beams C 1 -C 5  of the rear probe  1150  intersect beam “B” of the central probe  1130 . This provides simultaneous imaging of a location by more than one beam and from more than one direction. 
     The signals acquired by the front probe  1310 , central probe  1330  and rear probe  1350  are send to a calculation device  1500 . Calculation device  1500  identifies the location of the flaws from the signals provided to it. It may also reconstruct an image of the flaws and perform other characterizations of the flaws. 
     Calculation device  1500  also has the ability to store information for later comparison. Therefore, prior stored signals may be compared with newer signals to determine changes of the flaw over time. This may be important for identifying crack growth. 
     Calculation device  1500  may employ known reconstruction, or new algorithms to perform these functions. 
       FIG. 5  is an enlarged perspective view of the runner  1300  of the weld inspection system  1000  according to one embodiment of the present invention. 
       FIG. 6  is a side elevational view of the runner of the weld inspection system shown in  FIGS. 4 and 5 . 
       FIG. 7  is a top plan view of the runner of the weld inspection system shown in  FIGS. 4 ,  5  and  6 . 
     The embodiment of the present invention will now be described with reference to  FIGS. 5-7 . 
     The runner  1300  has sliders  1301  that slide along rods  1600 . Rods  1600  are held by rod supports  1130 ,  1730 . A user positions the runner  1300  by moving one or more handles  1303  attached to runner  1300 . 
     A front probe support  1333  secures the front probe  1310  to abase  1370 . The base  1370  may be an elongated plate, or other anchoring structure attached to runner  1300 . A rear probe support  1353  secures the rear probe  1310  to the base  1370 . 
     Central probe  1330  is held in place at its lower end by central probe base support  1331 . It is also held in place by central probe side supports  1333 . 
     The present invention functions by moving the runner  1300  with the probes  1110 ,  1130 ,  1150  are relative to the rail  10  keeping the same convergent view of a central location such that the central location corresponds to a different volume within rail  10  as the probes are moved to a new location. This allows the probes to scan through rail  10  as they are moved relative to the rail  10 . The signals from the front probe  1310 , the central probe  1330  and the rear probe  1350  are passed through cables  1315 ,  1335 ,  1355  to calculation device ( 1500  of  FIG. 4 ). 
     The encoder ( 1380  of  FIGS. 1 ,  2 ) also provides to the calculation unit an encoded location along rail  10  where each probe was located when a signal was received along with the corresponding signals. Therefore, for each instant of a received signal is paired with a location at which the signal was received. This allows the calculation device  1500  to create use conventional methods to create a map of the flaws. 
     Redundant data from other probes is used to eliminate noise and rule out false positives. They may also be used to create multi dimensional models of the flaws. 
     The present invention has been described in connection with the embodiment shown in the figures for illustration purposes. It is understood the present invention also covers devices having more or fewer transducers, and which may be positioned at different angles relative to each other. 
     In an alternative embodiment, the runner  1300  may also have a motor that moves it and the probes along the rail  10 . 
     Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention. Accordingly, other embodiments are within the scope of the following claims.