Abstract:
An on site railroad rail welding repair apparatus wherein a railroad rail is an operating railroad track and a defect in the rail has been removed to provide a void and a rail-void interface while maintaining continuity of the rail having pair of cooling blocks which have an internal configuration to complement the rail, and an arc welder that fills the void with appropriate molten metal and causes the molten metal and the rail at the rail-void interface to bond. Also, a robotic welding apparatus and a weld containment apparatus engageable with the rail-void interface by movement having a pivotal and longitudinal component. Further, a mobile weld delivery unit delivering materials through an umbilical to a robotic welding apparatus having a welding device proximate the rail-void interface so that a weld can be made joining the rail-void interface.

Description:
CLAIM OF PRIORITY  
       [0001]     This application is a continuation-in-part of our PCT Application PCT/US2003/02470 filed Aug. 8, 2003 claiming priority from our provisional application Ser. No. 60/402,184 filed Aug. 9, 2002. 
     
    
     BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to a rail welding apparatus for repairing a railroad rail having a defect in the top portion of the rail wherein the defect is cut out to provide a rail void and rail-void interface and the apparatus welds the rail-void interface on site.  
         [0004]     2. Description of Related Art  
         [0005]     Railroads have to maintain their track to ensure safe operation of trains. Some of this maintenance is centered on the repair of rail defects. Railroad rails may be manufactured with internal defects or, as a result of wear-and-tear or fatigue, develop defects. These defects are found using non-destructive test methods. The Federal Railway Administration (FRA) mandates periodic ultrasonic testing of railroad rails to locate defects in the rail. When a defect is found, a temporary accommodation or a repair must be made to the track structure. Many of these defects are located in the top portion (i.e. the head and/or web) of the rail.  
         [0006]     There are two common welding processes used to facilitate the repair of defects in railroad rails. They are the thermite welding process and the flash-butt welding process. Rails repaired using a flash-butt weld is typically stronger and higher in quality than those repaired using a thermite weld. Repairs made using the thermite process are initially less costly due to the labor and additional equipment cost components required using the flash-butt process. Additionally, rail defects may be temporarily repaired through the use of Joint Bar splices (mechanical joints). The rail integrity is best maintained by having the lowest number of joints (mechanical or welded) in the track.  
         [0007]     When repairing a rail defect, a length of rail localized around the defect is removed from the existing rail. This creates a gap (typically 13 to 19 feet in length) in the rail. A rail plug is inserted in the resulting gap to make up for the bulk of the rail length removed. A weld is then made at each end of the rail plug, welding the rail plug to the existing rail, and creating a continuously welded rail.  
         [0008]     Regardless of the welding process used to install the rail plug, there is a need to maintain the Adjusted Rail Temperature (ART). The ART is the temperature at which the rail contains no longitudinal thermally induced rail stresses. The track is not designed to allow the rails to contract and expand in response to environmental temperature changes. It is designed to constrain the rail and to allow the rail to have tension and compression. The amount of tension or compression is determined by the ART and the Current Rail Temperature (CRT). The ART must be controlled because too low of an ART can cause the rail to buckle when the CRT of the rail is too high and too high of an ART can cause the rail to pull apart when the CRT of the rail is too low. Buckles and pull aparts cause unsafe conditions and can cause serious accidents.  
         [0009]     When a repair is accomplished by installing a rail plug, it is unlikely that the rail plug installed will be of the exact length necessary to maintain the ART of the rail. The ART of the rail is altered. As such, the installed segment will have a different ART than desired. The ART of the entire rail adjacent to the repair plug installation is changed. Management of the ART could be simplified if the rail was not severed during the repair of a defect.  
         [0010]     A thermite weld can be used to weld the existing rail to a rail plug. A rail plug is cut to a length approximately two inches shorter than the length of the rail, containing the defect, which is being cut out. The rail ends to be welded are aligned. A sand mold is attached to both the existing rail and the rail plug around an approximate one-inch gap between the end of the existing rail and the end of the rail plug. The thermite charge is contained in a crucible immediately above the sand mold. After the mold is pre-heated, the thermite charge is ignited. The thermite charge creates molten steel which pours into the sand mold. As the molten steel solidifies, it forms a casting which bonds to, and is contiguous with, both the existing rail and the rail plug. In this manner, the rail plug is welded to the existing rail to form a continuous section.  
         [0011]     The rail ends at the other end of the rail plug are aligned. A second thermite weld is made at an approximate one-inch gap at the opposite end of the rail plug, joining the rail plug to the existing rail. The area of the rail containing the thermite weld is not as strong as and is not of the same quality as a normal rail. Moreover, such welds are not clean as they can include numerous inclusions from the welding process. As such, the thermite welds typically require subsequent repairs in order to maintain the railroad rail in a safe condition. This method also requires the repair crew to transport a rail plug to the repair site and the section of the rail containing the defect away from the site.  
         [0012]     A flash-butt weld can be used to weld the existing rail to the rail plug. A rail plug is cut to a length approximately three inches longer than the length of the rail, containing the defect, which is being cut out. Rail anchors are removed from the existing rail until the gap created by the removal of the defect containing the plug is three inches longer than the defect containing the rail plug. This can only occur when the CRT is below the ART. When the CRT is below the ART, the rail is in a longitudinally tensile condition. The rail plug is put in to place in the track. The rail ends to be welded are aligned. A flash-butt welderhead is clamped across the abutment of the rail plug and the existing rail. The flash-butt welding cycle is carried out. The welderhead passes a high current across the interface between the existing rail and the rail plug. The current produces arcing between the mating surfaces. The arcing produces heat in both rails as well as a “flashing” away of the surfaces. As the cycle progresses and sufficient heat has been generated, the welderhead forges the two pieces of rail together to form an essentially single rail. The flashing away of the rail and the forging of the rail consume about one and one half inches of the rail from the rail plug. In this manner, the rail plug is welded to the existing rail to form a continuous section. A shear die is then pushed across the weld to remove the upset material and to return the profile to the rail contour.  
         [0013]     The rail ends at the other end of the rail plug are aligned. The flash-butt welderhead is moved to the other end of the rail plug and clamped across the abutment of the rail plug and existing rail. The rail consumed during the production of the first flash-butt weld of the rail plug has created a gap at the location for the second weld. The rails are stretched to close the gap and the flash-butt weld cycle is carried out. The flash-butt weld consumes about one and one half inches of the rail at the second weld location. The rail is now returned to the pre-existing tensile condition. Rail anchors are placed onto the existing rail. The flash-butt welding process is typically more costly than a thermite process but produces a cleaner and stronger weld. However, this method also requires the repair crew to transport a plug to the rail repair site and the section of the rail containing the defect away from the site.  
         [0014]     When rail plugs are installed using either the thermite or the flash-butt welding process, the rail is taken out of service. This prevents the railroad from running revenue producing trains. Thermite and flash-butt welding trucks need to occupy the track. The installation of a rail plug and resulting two welds uses valuable track time and needs to be kept at a minimum.  
         [0015]     Joint Bar splices are, essentially, a reinforcing clamp applied to the rail to affect a temporary repair. A Joint Bar splice is used when there is not enough time to perform a complete repair or when other repair materials are not available. A Joint Bar splice, by government regulation, is a temporary repair and must be replaced within about 90 days. The Joint Bar splice reduces the operational limit of the rail in the repair area.  
         [0016]     In the area of gas shielded arc welding of railroad rails, several approaches have been taught, although they have not necessarily met with functional success in the field. These include U.S. Pat. Nos. 6,407,364, 6,278,074, 6,207,920 and 6,201,216, all entitled “Method and system for welding railroad rails” and U.S. Pat. No. 5,605,283 entitled “Weld joint between two rails arranged behind each other along a rail track.” Fixtures for rail welding are taught in U.S. Pat. No. 6,396,020 entitled “Rail welding apparatus incorporating rail restraining device, weld containment device and weld delivery unit.” A key portion of computer robotic control for rail welding is taught in publication WO 0195132 entitled “Gap Welding Process.” U.S. Pat. Nos. 5,605,283, 6,396,020 and WO 0195132 are all assigned to the same company as this application. All of the above patents, U.S. Pat. Nos. 6,407,364, 6,278,074, 6,207,920, 6,201,216, 5,605,283, 6,396,020 and WP 0195132 are incorporated by reference as if fully set forth herein.  
         [0017]     In addition to the above, it has been found that the amount of heat introduced into the rail during welding or gap closure can produce an annealing effect at the rail interface. This can, in turn, result in the migration of carbon from the rail as well as a change in microstructure and material properties.  
         [0018]     Moreover, the welding process can introduce hydrogen (H 2 ) into the final weld which has the effect of embrittling the weld material and causing a weld failure.  
         [0019]     Thus, it is desirable to provide a rail defect repair system that addresses above-identified issues and is acceptable to railroads for their use.  
       SUMMARY  
       [0020]     The aforementioned issues can be addressed by solutions offered by the instant welding apparatus. As more fully described below, the welding apparatus repairs a railroad rail defect in a portion of the rail and more preferably in the rail head or in the rail web, or in the rail head and rail web.  
         [0021]     As more fully detailed hereinafter, our welding apparatus provides a clean weld, a weld as strong as the parent rail, has a small heat affected zone (HAZ), provides a good bond with the rail, does not exhibit hydrogen (H 2 ) embrittlement, deals with the issues of ART and CRT, and avoids transporting long sections of rail.  
         [0022]     Other and further features of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The description which follows, and the embodiments described therein, is provided by way of illustration of an example, or examples of particular embodiments of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. The drawings are not necessarily to scale and in some instances proportions may have been exaggerated in order more clearly to depict certain features of the invention.  
         [0024]      FIG. 1  is a side elevational view of a railroad rail with a defective portion removed.  
         [0025]      FIG. 2  is a sectional view taken along lines  2 - 2  of  FIG. 1 .  
         [0026]      FIG. 3A  is a front elevation of a rail clamp.  
         [0027]      FIG. 3B  is a side elevation of a rail welding alignment device.  
         [0028]      FIG. 3C  is a top plan view of  FIG. 3B .  
         [0029]      FIG. 4  is a front elevation of the rail weld containment device.  
         [0030]      FIG. 5  is a top plan view of the rail weld containment device.  
         [0031]      FIG. 6  is a sectional view of a weld delivery unit.  
         [0032]      FIG. 7  is a top plan view of an alternative embodiment of the weld delivery unit.  
         [0033]      FIG. 8  is a side elevation of a guide rod of the weld containment device.  
         [0034]      FIG. 9  is a front elevation of the guide rod of  FIG. 8 .  
         [0035]      FIG. 10  is a side elevation of the cam guide of the weld containment device.  
         [0036]      FIG. 11  is a front elevation of the cam guide of  FIG. 10 .  
         [0037]      FIG. 12  is a top plan view of the preferred rail welding alignment device.  
         [0038]      FIG. 13  is a front elevation view of the preferred rail clamp on the rail welding alignment device.  
         [0039]      FIG. 14  is a sectional view of the preferred rail clamp on the rail welding alignment device showing the clamping arms in open and closed positions.  
         [0040]      FIG. 15  is an enlarged section of the twist pin and cam adjustment of the weld containment device.  
         [0041]      FIG. 16  is a side elevation of the preferred twist pin of the weld containment device.  
         [0042]      FIG. 17  is a front elevation of the twist pin of  FIG. 16 .  
         [0043]      FIG. 18  is a side elevation of the preferred cam guide of the weld containment device.  
         [0044]      FIG. 19  is a front elevation of the cam guide of  FIG. 18 .  
         [0045]      FIG. 20  is a rear elevation of the alternate embodiment of the weld delivery unit.  
         [0046]      FIG. 21  is a side sectional view of the alternate embodiment of the weld delivery unit.  
         [0047]      FIG. 22  is a top plan view of the alternate embodiment of the weld delivery unit.  
         [0048]      FIG. 23  is a top plan view of the preferred rail alignment with robotic welding device.  
         [0049]      FIG. 24  is a side elevation of  FIG. 23 .  
         [0050]      FIG. 25  is a sectional view of an embodiment of the van supporting the weld delivery unit using a separate robot. 
     
    
     DETAILED DESCRIPTION  
       [0051]      FIG. 1  illustrates a railroad rail  10  having a base  12  with opposed flanges  14 ,  16 , an upstanding web  18  extending upward from the base  12  between the flanges  14 ,  16  and a head  20  at the top of the web. The use of our welding apparatus begins when a rail defect is identified and located, such as by using an ultrasonic rail-testing car and then removed to provide a slot or rail-void interface  28  that has opposing vertical walls  22  and  24  and a rounded base  26 . The ultrasonic rail-testing car can precisely locate and mark the area of the rail containing the defect. Additionally, manual testing of the defect may further delineate the areas of the rail which contain the defect. For illustrative purposes we show that the ultrasonic testing confirmed that the defect is totally contained in the rail head  20  and web  18 . The top portion of the rail is then removed, as more fully described below. Although this top portion is directed to the rail head and portion of the web, the top portion can include a selected portion of the rail head, or the entire rail head, and when necessary a selected portion of the rail web, the entire rail web, and when necessary a selected portion of the rail base. However, the rail is not completely severed and is still connected and continuous as only a portion of the rail has been removed. When the entire rail is severed the system as described in our U.S. Pat. No. 6,396,020 and U.S. application Ser. No. 10/118,481 are used.  
         [0052]     To repair the defective rail, the top portion of the rail containing the defect is removed. The removal is preferably accomplished by machining a slot in the head and the web of the rail, or by hole coring and cutting of the rail, by grinding the rail or by machining the rail, but other methods may be used. Hole coring or drilling in the web initially leaves a round aperture, with the cutting of side walls  22 ,  24  through the hole, leaving a weld-void interface semicircular bottom  26 . Machining, grinding or other methods leave a void or a slot with various geometry at the bottom. Some geometries are preferential to certain filler weld processes. The preferred geometries are a beveled bottom or a double J (i.e., opposed J shapes) shaped bottom.  
         [0053]     Because only the top portion of the rail  10  is removed, there is no change in the length of the rail and the ART remains unaffected. There is no need to accurately align the rail heads because the rail head is held in alignment by the lower portion of the rail which has not been removed for replacement.  
         [0054]     Referring to  FIGS. 3A-3C , the rail welding apparatus has rail repair alignment device  201  that has a pair of clamps  31 . Each of the clamps has a fixed clamp member  32  and a movable clamp member  33 . One of the clamps will engage the rail on one side of the rail-void interface to be welded and the other clamp will engage the rail on the other side of the rail-void interface.  
         [0055]     Each moveable clamp member  33  has an eccentric pivoting action and can be clamped in place by the action of hand wheel  34 . A horizontal plate supports the device on the crown of the rail.  
         [0056]     Each of the clamps is provided with a base twist assembly. The twist assembly bears at an angle through a shaft  35  on a pad  36  that engages the rail base  12 . In this manner, the welding apparatus can be aligned with the rail-void interface  28  to enable the next step of the operation utilizing the weld containment device.  
         [0057]     Referring to  FIGS. 4 and 5  a weld containment device  290  works with the rail repair alignment device  201 . The weld containment device connects to or can be part of the repair alignment device  30 . While preferably used together, and providing unique advantages in combination, weld containment device  290  may be suitable for other welding operations, merely providing its advantages in compactness and rapid deployment.  
         [0058]     The weld containment device  290  is generally loosely secured to the rail repair alignment device  201  using four clamps  287  ( FIG. 12 ) which allows the weld containment device  290  to automatically center itself when the cooling blocks  310  are deployed.  
         [0059]     The weld containment device  290  is set up on a rigid frame  291 . Two yokes  293  are actuated by a pair of cylinders  297  mounted exterior to frame  291  and the cylinder rods are connected to the yokes  293  causing them to move inwardly. Cylinders  297  are operated through pressure transmitted in hydraulic fittings  298  in the ordinary manner of hydraulic operation. The yokes are mounted on two linear bearings or bushings  300  secured to the yoke using shoulders  301 . Other fasteners, such as snap rings, might be suitable, but need to have adequate strength. The bearings  300  slide on two hardened steel shafts  302 . The shafts cause the motion of the yoke to be precisely linear and parallel with each other.  
         [0060]     A twist pin  259  is rigidly connected to the block holders  292  through the use of pins  299  preventing rotation of the twist pin  259 . Cooling blocks  310 , preferably constructed of copper, are connected to the block holders  292  by a plurality of fasteners  304  and  305 . The cooling block  310  and corresponding block holder  292  are the major components in the swinging components referred to generally as the quadrants  294 .  
         [0061]     A smaller non-moving cooling block  306  is held to the frame  291  by a plurality of fasteners  307 . As the cylinder extension causes the motion of the yokes inward from the open position to the closed position, the action of the twist pins  259  engaged by the cam guide  296  causes a rotation of the quadrants  294 . The scope of the swing may be as little as about 15 degrees to about 30 degrees with about twenty degrees currently preferred.  
         [0062]     In the preferred embodiment, in  FIGS. 4-5  and  FIGS. 15-19 , adjustment of the precise rotation of the cam guides  296  is provided through the use of an adjustable hub device  295 . This device  295 , which is commercially available and is sold under the trademark Trantorque, uses twin tapered shaft segments  308 ,  309  to impinge on the cam guide  296  while at the same time impinging on the hole in the frame  291 . This operates in a manner analogous to a collet, release of the load on the tapered shaft segments  308 ,  309 , by loosening adjusting nut  311 , and permitting movement of the cam guides  296 .  
         [0063]     Precise adjustment of the cam guides  296  provides for a tightening effect as the blocks  310  contact the rail on the extend stroke. A compliant fit of the blocks  310  against the cutout rail  10  is provided by a pair of springs  303  in each block.  
         [0064]     Cooling blocks  310  and  306 , when in place on the rail, provide for a welding head aperture  64  through which the welding head can fill the rail web and head as described below, even when the blocks are closed and the shoe quadrants touch on the extend stroke.  
         [0065]     During the return stroke, the yoke  293  pulls the quadrants  294  back by engaging a shoulder  317  on the twist pin shaft  318 . This shoulder  317  holds the quadrant in relative proximity while still allowing a rotation about shaft  318 . Since the twist pins  259  are fixedly fastened to the quadrants, parting of the containment shoes is accomplished by pulling the pins apart. The clearance is preferably somewhat less than about one and one half inches (1.5″) thereby providing access to the rail-void interface  28  of about 1 to 3 inches, yet providing a level of preload on the yoke and quadrant arrangement.  
         [0066]     An early prototype pin or rod  45  for right hand travel is shown in  FIGS. 8 and 9 . Cam portion  65  has twist to provide 30 degrees rotation in ¾ to 1-{fraction (3/4)} inches of travel. Shaft portion  66  is provided with groove  67  to receive ring  53 . Knurled or splined portion  68  abuts head  69 . Preferably about thirty two teeth will be formed in splined portion  68 . Head  69  fits in aperture  70  in holder  72 . A press fit into aperture  70  is anticipated. At the quadrant end, set screw  52  also serves to firmly fix the unit in position. In certain embodiments, a large number of small profile splines could be used with mating splines in the frame  291  to enable some level of adjustment by removal and replacement at a different alignment. This would enable mechanical adjustment but would be limited in the increments available by the size and number of splines. The preferred arrangement permits adjustment in infinite increments and is expected to be adjustable in the field.  
         [0067]     The early prototype cam guide  46  in  FIGS. 10-11  has a body portion  80  and aperture  82  with opposed lobes  84  receiving cam portion  65 . Lobes  84  could be formed with a profile enabling them to receive either the right or left hand cam portions  65 . For improved strength and precision, however a left and right cam guide could also be provided.  
         [0068]     The twist pin  259  ( FIG. 16 ) is designed to have about 15-30 degrees of rotation in about ¾ to  1{fraction (3/4)} inches of linear travel with  15-20 degrees being preferred. One set of twist pins  259  and cam guides  296  will have right hand travel and the other set  259  L and  296  L left-hand travel ( FIG. 5 ).  
         [0069]     The twist pin  259  and cam guide  296  for right hand travel is shown in  FIGS. 16-19 . Cam portion  315  is shown having a twist of 15 degrees rotation in three quarters inch (¾″) travel. However, 20 degrees may be preferred. Shaft portion  316  is provided with a shoulder  317 . Shaft end  318  provides for insertion into the block holders  292  and through bushing  297  and secured with pins  259 .  
         [0070]     Cam guide  296  has a body portion  330  aperture  332  with opposed lobes  334  receiving cam portion  315 . Preferably lobes  334  can be formed with a profile enabling them to receive either the right or left hand cam portions  315 . For improved strength and precision, however a left and right cam guide could also be provided. The degree of twist will conform to that of the corresponding pin  259 ,  259  L.  
         [0071]     Unlike the prior art, this geometry for operating quadrants  294  permits operation in very close clearance locations. The combination of longitudinal movement of yokes  293  into and out of engagement and the outward swinging of block holders  292  on horizontal, longitudinally aligned shafts  302  and pins  259  enables adequate clearance for the welding head to move reciprocally and vertically to weld the rail bases together, while closing the blocks to maintain the welding material in the web, and thence such clearance as is necessary to weld the head of the rail. This movement provides for both effective welding and compact size.  
         [0072]     The blocks  310  conform to the profile of the rail  10  for the purpose of containing molten material as the weld progresses. The welding operation will be accomplished by the following steps: placing a ceramic base mold below the rail base and then commencing the welding operation whereby approximately a 1 to 3 inch void between the rail walls  22  and  24  is filled by welding material.  
         [0073]     Using a continuous precisely controlled welding cycle will move the welding element back and forth across the void resulting in the filling of the void with metal material having mechanical properties commensurate with that of the metal in the rail itself. To control this weld, the transverse distance the welding element will travel at the head being a long distance, while only a short distance of travel is necessary in the web portion. As the welding operation progresses in a vertical manner through the web of the rail, the blocks will be closed on the web to maintain the molten material in place. The weld will progress up the web while the blocks provide the required containment yet also providing the necessary clearance for the welding element. This movement can be controlled and coordinated by processing data on positioning and the like received from a robotic controller.  
         [0074]     A specific welding procedure will be a function of the welding unit used, which is not a part of this invention. For example, arc welding could be used, while theoretically, gas welding, aluminothermic bonding, electroslag, portable foundry or thermite welding may be adapted to take advantage of certain aspects of the invention, such as weld containment. The preferred welding method would be arc welding. However, great flexibility is provided by the invention adaptable to the metallurgy of the rails, the equipment available, and the equipment in operation at any particular time.  
         [0075]     One possible weld delivery unit  100  alternative, shown in  FIG. 6-7 , will have a frame  102  mounted in truck  104 . A vertical support piece  106  fits sliding rack  108 . Vertical support piece  106  at its lower portion  108  supports horizontal cradle  110  adapted to have rail engaging bogie wheels  112 . Thus, the device can be raised for transportation, maintenance, or the like, and lowered for alignment on the railroad rail to reduce the load on the structure and steady the unit for operation and enable indexing to the rail, the welds along any given section of rail being staggered as between the left and right rail head.  
         [0076]     The weld delivery unit  100 , as shown in  FIG. 25 , has sufficient space to receive the welder  114  itself; control devices  116  generator  118 , induction heater  502 , boom not shown and shielding gas  516 ; as well as the welding robot  500  shown in  FIG. 24  stored on the unit  100  retracted in the body of the truck for protection and ease of transportation.  
         [0077]     As taught in  FIGS. 6-7  the alternative weld delivery unit is basically indexed to the rail  10  by virtue of cradle  110  and bogie wheels  112 . This provides an advantage in quick movement and lack of bracing or other connection to the roadbed. In certain conditions this type of alignment could have significant utility.  
         [0078]     The preferred weld delivery unit  100 , shown in  FIG. 25 , will essentially be a welding skid  506  mounted in a transport vehicle such as a truck  104 . Equipped with a boom not shown, the weld delivery unit  100  can deploy the rail repair alignment device  201 , the weld containment device  290  and the portable welding robot  500  which together are called the robotic welding head  508 . The robotic welding head  508  has a welding range from the weld delivery unit  100  that is only limited by the length of the umbilical  510  which supplies the robotic welding head  508  with commands, power and coolant.  
         [0079]     The preferred rail repair alignment device  201  ( FIGS. 12-14 ) which provides the structure on which the clamps  31  are mounted in pairs. One of the clamp pairs would engage the rail on one side of the rail-void interface  28  and the other clamp would engage the rail on the other side of the rail-void interface. Fixed clamp member  202  has downwardly depending arm  205  with a clamping member including a pad  223  that provides a base against which the rail  10  can be clamped, and provides the requisite electrical contact as may be required by the welding operation. These are paired for each clamp assembly.  
         [0080]     The movable clamp member  203  with downwardly depending arm  219  has an eccentric pivoting action around pin  207  which can be clamped in place by the action of a cylinder  211 . The rod  225  of cylinder  211  is fastened to a clevis  208  and pinned to a link  210  with a pin  209 . The rotation of link  210  is constrained by link adjustment assembly  213  which is composed of a rotating structural beam  212 , a screw  214  penetrating through the beam  212  with a rotary joint  215  connected to the clevis  208  and pin  209  using a block  217 . Block  217  rotates around pin  209 . The force applied by the cylinder acts through the clevis pin  209  with a variable reaction force taken by the shoulder bolts  220  directing a clamping force downward against moveable clamp. The structural beam  212  is held in the rail repair alignment device  201  using shoulder bolts  220 .  
         [0081]     It will be seen that said arm  203  has an inverted L shape with pin or pivot  207  being located proximate the end of the short leg of the L. Pin  221  provides the second pivot, this being located proximate the intersection of the short leg of the L and the long leg of the L. Clamping pad  225  is located at the end of the long leg of the L.  
         [0082]     The length of this link adjustment assembly  213  is controlled by rotation of a hand wheel  206  attached to the screw  214 . The length of the final adjustment length of the link adjustment assembly  213  is held in place using check nut  222  for locking.  
         [0083]     Link adjustment assembly  213  provides one arm in a scissors arrangement with link  210  providing a second arm and the top portion  218  of clamp  203  a third. The extension or retraction of cylinder  211  acting on pivot  209  results in the pivoting of link adjustment assembly at pin  209  and bolts  220 . Link  210  pivots at pins  209 ,  221  and portion  218  around pins  207 ,  221  results in exertion of a substantial clamping force owing to the fixed positions of pins  207  relative to bolts  220  in beam  212 .  
         [0084]     The force applied by the cylinder acts through the clevis pin  209  with a variable reaction force taken by the shoulder bolts  220  directing a clamping force downward against moveable clamp  203  and carried on ball unit  224  fastened by nut  226 . The cylinder is mounted in the beam  212  of repair alignment device  201  with cylinder mounting pins  204 .  
         [0085]     Stabilizing legs  274  are adjustable and provide additional stability of the rail restraint support. The legs  274  are allowed to slide in the bushing  275  and held in place with setscrews  276  which may alternatively be actuated with wing nuts ( FIG. 13 ) or handles ( FIG. 12 ) or other appropriate manual gripping end. The rail repair alignment device  201  is lowered into place by use of the boom located on the weld delivery unit  100 .  
         [0086]     By comparison to the alternative embodiment, the use of legs  274  provides a platform fixed relative to the ground or roadbed. This enables the use of various bars, clamps and jacks, familiar to one in the track art, which may be hooked or otherwise fixed to a rail and jacked against the ground or roadbed to directly control twist. In addition to the greater precision of alignment this also enables track workers to use familiar alignment and adjustment tools as may be necessary to specific jobs.  
         [0087]     Depending on the type of welding robot used, touch sensing plates  279  may need to be attached to blocks  278  which are attached to the frame  270  to allow the robotic controller to establish the location of the rail repair alignment device  201  and thence the weld void by touching the plates with an electrically live torch tip. Pluralities of these plate assemblies are mounted on the frame  270  for accurate location of the weld void. Around the perimeter of the frame  270  are located a plurality of windscreens or flaps  281  for prevention of ambient winds affecting the gas shield of the welding process.  
         [0088]     When the preferred portable welding robot  500  is used, as shown in  FIGS. 23-25 , and attached to the rail repair alignment device  201 , the touch sensing plates are unnecessary since they are a single unit and the robot welder no longer needs to orient itself to the rail repair alignment device  201 . Also when the portable welding robot  500  is attached to the rail repair alignment device  201 , the robotic welding head  508  can be enclosed in an environmental protection shield  512 .  
         [0089]     The rail repair alignment device  201  is supported on the rail using jacking screw assemblies  280  in which handle  282  rotates screw  283  mounted in a fixed horizontal plate  286  by threading, and having rotary shoes  284  attached to the end of screw  283 . Shoe  284  is positioned so as to be centered on and bear against the head of the rail  10 . In this manner, clockwise rotation of a right hand threaded screw  283  will raise rail repair alignment device  201 .  
         [0090]     The preferred embodiment includes the use of the hydraulic cylinder  210  and scissors mechanism; use of adjustable legs  274  and screw assembly  280  and addition of the portable welding robot  500  and environmental protection shield  512  for superior weld control.  
         [0091]     The preferred weld delivery unit  100  ( FIG. 25 ) will consist of a welding skid  506  that can be attached to a common truck chassis specially equipped to be operable on railroad rail by use of front and rear rail-engaging bogies. Mounted on the truck chassis is a van-style cargo box, which houses and protects all of the associated process equipment. The process equipment includes a welder  114 , a portable welding robot  500 , a robot controller  116 , and an induction heating system  502 . Alternatively, the welding skid  506  can be used as a stand alone unit or can be mounted in a transport container or other device that can be moved to the welding site.  
         [0092]     Auxiliary equipment includes an electric power generator  118 , driven from the truck engine through a power take-off transmission  416 , as shown in  FIG. 21 , and drive shaft  418  through a right angle gear box  420  and a belt drive  422 . Alternatively the generator  118  can be powered by a separate gas engine. Gas bottles  516  for welding shielding gas are also provided. A hydraulic system  428  which can be belt-driven from the truck engine provides hydraulic power to operate the rail repair alignment device  201  and weld containment device  290 . Various tools and devices to assist in alignment of the rail are also stored on board in tool case  432  and storage rack  434 . A drop-down tool shelf  436  allows for temporary storage of frequently used tools and supplies.  
         [0093]     The cargo box can be stabilized, as shown in  FIG. 20 , by use of external stabilizer legs  438  which are hydraulically operated to keep the cargo box from swaying.  
         [0094]     The portable welding robot  500 , best shown in  FIGS. 23 and 24 , is mounted to the rail repair alignment device  201  which increases the accuracy of the robot  500  during weld orientation and operation. It will be seen that the robot, as is known to one in the robotics art, has a base  430  mounted to rotational bearing  432  which enables the robot to rotate around a rotational axis  434 . As is typical of robot devices, robot  500  has articulated arm  436  which is articulated to bearing  432  and base  430  having a series of joints  438  and, for this application, terminates in welder head  440 . While the robot  408  is typical in that it operates in three dimensions using controller  410 , the ability to remotely place the robot at a specific weld location provides a major departure from known art. This portability provides considerable advantages when used in the field as a robotic welding head  508 . Instead of a work piece being brought to and located proximate a fixed robot, this apparatus brings the welder to the work piece—in this case railroad rail  10 —and uses interfacing with rail  10  to automatically weld the slot  28  in rail  10 . The use of touch sensing enables controller  116  to precisely align and operate the welder head  440  to form a precisely controlled and metallurgically sound weld in very tight spaces.  
         [0095]     The robotic welding head  508  may be loaded onto the welding skid  506  for transportation, and storage. It may also be unloaded and extended for maintenance or for welding of the rail. The robot  500  welding range from the weld delivery unit is only limited by the length of the umbilical  510 . Thus the robot  500  can be readily and quickly stored or deployed for use. The portable welding robot  500  could function as a stand-alone device or be temporarily clamped to the rail repair alignment device  201  for welding. The joined rail repair alignment device  201 , portable welding robot  500 , weld containment device  290  and the protection shield  512  function together as the robotic welding head  508 . As a combined unit, the robotic welding head  508  can center the rail-void interface, contain and produce the weld. The robotic welding head  508  functions with the aid of an umbilical  510  that extends from the robotic welding head  508  to the weld delivery unit  100 . The umbilical  510  is a flexible group of cables that enable the robotic welding head  508  to make the weld. The welding skid contains the robot controller  514 , shielding gas  516 , hydraulics  518 , compressed air  520 , welder power leads  522 , grounding cable  524 , induction heater  526 , boom  504  and coolant hoses  528 . The materials located on the skid supply the robotic welding head  508  through the use of the umbilical  510 . The welding robot  500  and rail repair alignment device  201  can be separated for easier handling by employees or can be moved as a one piece unit by using the boom. If the weld location is such that the robotic welding head  508  cannot be placed by use of the boom  504  then the welding robot  500  and the rail repair alignment device  201  can separated and carried to the weld site. Alternatively, the welding skid  506  can be outfitted with multiple robotic welding heads  508  so several weld voids can be welded simultaneously. The ability to weld several voids at the same time is desirable in high rail traffic areas such as on commuter lines where trains travel on strict schedules.  
         [0096]     The protection shield  512  is attached to the rail repair alignment device  201  and can be made out of plexiglass or other weather shielding material. During welding, the protection shield is moved to the closed position, which encloses the weld area, protecting the welding robot  500  and the weld from wind and other elements which may affect the accuracy of the welding procedure.  
         [0097]     The robotic welding head  508  is positioned at the weld slot by first removing it from the weld delivery unit  100  by using the boom  504 . The robotic welding head  508  is positioned over the weld-void interface and the rail repair alignment device  201  is fastened to the rail  10  by use of the clamping members. Once the rail repair alignment device  201  is fastened to the rail  10  the robot controller  116  located on the weld delivery unit  100  instructs the robot  500  to determine the rail-void interface configuration and then maneuvers the robot  500  to create the weld. By being able to place the robotic welding head  508  within a close proximity to the weld-void interface, set-up is simplified and the time required is greatly reduced. By attaching the portable welding robot  500  to the rail repair alignment device  201 , welding accuracy is greatly improved because a smaller, lighter robot can be used which decreases undesired movements during welding. Also, since the portable welding robot  500  is directly clamped to the rail  10 , steadying devices and proximity adjustments are eliminated.  
         [0098]     As many and varied modifications of the subject matter of this invention will become apparent to those skilled in the art from the detailed description given hereinabove, it will be understood that the present invention is limited only as provided in the claims appended hereto.