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BACKGROUND 
       [0001]    Railroads tracks generally include two parallel rails, which are supported by a series of ties perpendicular to the rails. The rails are attached to the ties via plates and spikes. The plates are located on the tops of the ties and provide a secure housing for the rails. The rails are attached to the ties by driving spikes through the plates into the ties so that the heads of the spikes clamp the rails to plates. As the tracks age, the tracks, portions of the tracks and/or components of the tracks may need to be repaired or replaced. In order to perform repairs and replacements, a variety of railroad equipment has been developed, such as, mechanized gangs with automatic spiking machines, spike removal machines and tie replacement equipment. 
         [0002]    When making repairs, the railroad equipment may be supported by and ride along one or both of the rails. For example, during a rail change-out process, one of the rails may be removed at some time. The rail change-out process includes removing the fasteners (such as spikes), rail and tie plates from the railroad ties, installing new rail and fastening the new rail to the ties using tie plates and fasteners, such as spikes. The railroad equipment used for a rail change out process may ride on both rails to reach the location at which the repair is to be made (the “job site”). However, at the job site, the railroad equipment rides along one rail where the other rail is missing. Thus, the railroad equipment used for such repairs must include some mechanism for supporting the equipment on the side of the missing rail and which enables the equipment to move along the track. For example, the equipment may include a crawler system. Thus, the equipment can ride on the existing rail on one side and on the ties on the side of the missing rail. An example of such railroad equipment, a ride-on tie plugger, is described in U.S. Pat. No. 6,832,558, which is herein incorporated by reference in its entirety. However, if such railroad equipment is used to repair a track with one rail removed over a bridge, additional equipment, steps and/or safety precautions need to be used. 
         [0003]      FIG. 2  (prior art) shows a cross-sectional view of an exemplary track supported by a bridge  200 . The bridge  200  generally includes a support  204 , a cap  206 , a pair of stringers  208  and a track  224 . The track  224  includes ties  210  (only one is visible), first and second rails  216 ,  218  and first and second guard timbers  212 ,  214 . The first end of the bridge support  201  is secured to the ground  202  and the second end of the bridge support  201  supports a cap  206 . Secured to the cap  206  are the stringers  208  that support the track  224 . The rails  216 ,  218  are secured to the ties  210 , which maintain a consistent distance between rails  216 ,  218 , via spikes (not shown). The guard timbers  212 ,  214  run perpendicular to the ties  210  and maintain a consistent distance between each tie  210 . 
         [0004]    When railroad equipment travels across a bridge  200  that is missing one rail (for example, the first rail  216  is missing), it is possible for the equipment to derail if the equipment comes in contact with the guard timber  212 . Therefore, tie plates or timbers need to be placed in front of the equipment in order to raise the equipment high enough to clear the guard timber. This procedure requires workers to be located on the bridge  200 , which creates a dangerous situation. Therefore, the relevant Occupational Safety and Health Administration (OSHA) standards require that any workers working outside the rails of a railroad bridge must use fall protection if the bridge does not have a walkway or side restraints. 
       SUMMARY 
       [0005]    A movable crawler system that moves a crawler of railroad equipment from a first position to a second position is disclosed. The crawler system includes a crawler and a positioning system that moves the crawler. The positioning system includes a horizontal positioner that moves the crawler in a direction parallel or approximately parallel to the ground (horizontally) and may include a vertical positioner that moves the crawler in a direction perpendicular or approximately perpendicular to the ground (vertically). 
         [0006]    In general, the horizontal positioner includes a horizontal hydraulic member, an inner horizontal member and an outer horizontal member. The inner and outer horizontal members are hollow and coaxial with each other and the inner horizontal member is positioned within the outer horizontal member. The horizontal hydraulic member may be positioned along the outside of and parallel to the inner and outer horizontal members. 
         [0007]    The horizontal positioner is secured to the crawler and the railroad equipment. More specifically, the second end of the outer horizontal member is secured to the railroad equipment, and the second end of the inner horizontal positioner is secured to the crawler. The first end of the horizontal hydraulic member is secured to the first end of the inner horizontal member via a first connector. The second end of the horizontal hydraulic member is secured to the outer horizontal member via a second connector. To move the crawler in an approximately horizontal direction, the pressure is increased or decreased in the horizontal hydraulic member depending on the direction desired. 
         [0008]    In general, the vertical positioner includes a vertical hydraulic member, an inner vertical member and an outer vertical member. These vertical members are coaxial with each other. The inner and outer vertical members are hollow, and the vertical hydraulic member is positioned within the inner vertical member and the inner vertical member is positioned within the outer vertical member. 
         [0009]    The vertical positioner is connected with the crawler and the railroad equipment. More specifically, the first end of the outer vertical member is secured to the railroad equipment and the second end of the vertical hydraulic member, and the second end of the inner vertical member are secured to the crawler. The first end of the vertical hydraulic member is secured to the first end of the outer vertical member via a first connector. The second end of the vertical hydraulic member is secured to the crawler frame via a second connector. To move the crawler in an approximately vertical direction, the pressure in the vertical hydraulic member is increased or decreased depending on the direction desired. 
         [0010]    The crawler systems may be used in a variety of railroad equipment, such as equipment used in rail change-out processes. An example of such equipment is an RTP. In general, at least two crawler systems are attached to the frame on one side of the RTP or other railroad equipment. In this implementation, the crawler systems enable, for example, the crawlers (and thus one side of the RTP or other railroad equipment) to be moved between a position on or above the railroad ties and a position on the guard timber. Because the crawlers can be moved so that they are positioned on the guard timber, when the equipment is operated on a track suspended by a bridge, which has one rail missing, there is no need to place tie plates or timbers in front of the equipment in order to raise the equipment high enough to clear the guard timber. This eliminates the need for workers to work outside the rails and thus, the need for fall protection. 
     
    
     
       BRIEF DESCRIPTION THE DRAWINGS 
         [0011]    The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings: 
           [0012]      FIG. 1 . An isometric view of a ride-on tie plugger. 
           [0013]      FIG. 2 . A front cross-sectional view of a timber bridge (prior art). 
           [0014]      FIG. 3 . A simplified left side view of the ride-on tie plugger of  FIG. 1 . 
           [0015]      FIG. 4 . A top view of a frame of the ride-on tie plugger of  FIG. 1 . 
           [0016]      FIG. 5 . An isometric view of an adjustable crawler of  FIG. 1  shown positioned on the railroad ties. 
           [0017]      FIG. 6 . An isometric view of the adjustable crawler of  FIG. 1  positioned on a guard timber of a timber bridge. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows an example of first and second crawler systems  114 ,  116  as implemented in a ride-on tie plugger (RTP)  100 . However, crawler systems may be used with and/or implemented in a variety of railroad equipment, such as equipment used in a rail change-out process. The RTP  100  is used in railroad repair to enable workers  160 ,  162  to plug holes in the railroad ties  210  that are too large to securely hold the spikes that are used to attach the rails  216 ,  218  ( FIG. 1 ) to the ties  210 . The RTP  100  includes a frame  108  to which vertical supports  112 ,  113 ,  140  are attached. The vertical supports  112 ,  113 ,  140  support a top  110 . 
         [0019]    The frame  108 , vertical supports  112 ,  113 ,  140  and top  110  define a worker area  106  in which the workers  160 ,  162  operate the RTP  100  via control panels  132 ,  144  and perform the tie plugging operation. The worker area  106  may also include two seats  150 ,  152  on which the worker  160 ,  162  may sit. The workers  160 ,  162  plug the holes in the ties  210  by injecting one or more chemicals into the holes with a hand-held device (not shown). 
         [0020]    The RTP  100  also includes a motor  142 , first, second, third and fourth rail wheels  134 ,  136 ,  138 ,  140 , respectively (see  FIG. 4 ) and first and second crawler systems  114 ,  116 , respectively. If both rails are present (such as rails  216 ,  218  in  FIG. 2 ), the first and second rail wheels  134 ,  136 , respectively, are positioned on top of one rail (such as rail  218  in  FIG. 2 ) and the third and fourth rail wheels  138 ,  140 , respectively, are positioned on top of the other rail (such as rail  216  in  FIG. 2 ). The crawler systems  114 ,  116  are positioned on the same side of the RTP  100  as the third and fourth rail wheels  138 ,  140 , respectively and on or above the ties  210 . The rail wheels  134 ,  136 ,  138 ,  140 , along with the motor  142 , propel the RTP  100  along the rails  216 ,  218 . Alternately, if one of the rails is missing (such as rail  216  in  FIG. 2 ), the crawler systems  114 ,  116  are moved so that they are positioned on top of the railroad ties  210  or a guard timber (such as guard timber  212  in  FIG. 2 ) located on the same side of the track  224  as the missing rail. Together with the motor  142 , the crawler systems  114 ,  116  propel the RTP  100  along the guard timber (such as guard timber  214  in  FIG. 2 ). 
         [0021]    The crawler systems  114 ,  116  each include a positioning system  170 ,  172 , respectively, and a crawler  122 ,  124 , respectively. The positioning systems  170 ,  172  move the crawlers  122 ,  124 , respectively, from a first position (such as, on or above the ties  104  shown in  FIG. 5 ) to a second position (such as, on the guard timber  218  shown in  FIG. 6 ). Each positioning system  170 ,  172  includes a vertical positioner  370 ,  372 , respectively, (shown in  FIG. 3 ) and a horizontal positioner  420 ,  422 , respectively, (shown in  FIG. 4 ). As the crawler systems  114  and  116  are virtually identical, the following will describe crawler system  116 . However, the description also applies to crawler system  114 . 
         [0022]      FIG. 3  is a simplified side view of the RTP  100  in which the vertical positioners  370 ,  372  are shown more clearly. The vertical positioners  370 ,  372  move the crawlers  188 ,  120 , respectively, vertically in a line parallel to the vertical support  113  of the RTP  100 . As the vertical positioners  370 ,  372  are virtually identical, the following will describe vertical positioner  372 . However, the description of vertical positioner  372  also applies to vertical positioner  370 . 
         [0023]    In general, the vertical positioner  372  includes a vertical hydraulic member  306 , an inner vertical member  326  and an outer vertical member  324 . These vertical members  306 ,  326  and  324  are coaxial with each other. The inner and outer vertical members  326 ,  325 , respectively, are hollow and the vertical hydraulic member  306  is positioned within the inner vertical member  326  and the inner vertical member  326  is positioned within the outer vertical member  324 . 
         [0024]    The vertical positioner  372  is connected with the crawler  120  and the RTP  100 . More specifically, the first end of the outer vertical member  314  is secured to the second vertical support  113  of the RTP  100 , and the second end of the vertical hydraulic member  310  and the second end of the inner vertical member  316  are secured to the crawler frame  124 . The first end of the vertical hydraulic member  308  is secured to the first end of the outer vertical member  314  via a first connector  325 . For example, the first connector  325  may include a pin and bushing made from a material such as, steel. The second end of the vertical hydraulic member  310  is secured to the crawler frame  124  via a connector, such as a pivot connector  340 . The pivot connector  340  enables the crawler  120  to adjust to height variations in the guard timber  502  (shown in  FIG. 5 ). 
         [0025]    To move the crawler  120  upward, the pressure in the vertical hydraulic member  306  is decreased. This pulls the second end of the inner vertical member  336  further into the outer vertical member  324  and thus, raises the crawler  120 . To move the crawler  120  downward, the pressure in the vertical hydraulic member  306  is increased. This extends the second end of the inner vertical member  336  from the outer vertical member  324  and thus, lowers the crawler  120 . 
         [0026]    In order to prevent wear between the inner and outer vertical members  326 ,  324 , respectively, the vertical positioner  372  may include a buffer  382  located between the inner and outer vertical members  326 ,  324 , respectively. The buffer  328  may include a metal plate, such as a brass plate. The vertical positioner  372  may also include one or more slack adjusting mechanisms  330 . These adjusting mechanisms  330  protrude through the outer vertical member  324  to contact the buffer  328  and hold it in place between the inner and outer vertical members  326 ,  324 , respectively. As the buffer is worn down by movement between the inner and outer vertical members  326 ,  324 , respectively, the adjusting mechanism  330  may be tightened so that the buffer  328  remains in place. 
         [0027]      FIG. 4  is a top view of the frame  108  of the RTP  100  in which the horizontal positioner  422  is more clearly shown. The frame  108  includes first, second, third and fourth frame members  402 ,  404 ,  406  and  408 , respectively, which are secured together to form a generally rectangular structure. The frame  108  also includes first, second, third and fourth rail wheels  134 ,  136 ,  138 ,  140 , respectively. The first and third rail wheel  134 ,  138 , respectively, are connected with each other and with the first and second frame members  402 ,  404 , respectively, via a first axel  410 . The second and third rail wheels  136 ,  140 , respectively, are connected with each other and with the first and second frame members  402 ,  404 , respectively, via a second axel  410 . 
         [0028]    The frame  108  also includes first and second horizontal positioners  420 ,  422 , respectively, and crawlers  118 ,  120 . The first and second horizontal positioners  420 ,  422 , respectively, move the crawlers  118 ,  120 , respectively, horizontally in a line perpendicular to the horizontal support  113  of the RTP  100 . As the horizontal positioners  420 ,  422  are virtually identical, the following will describe horizontal positioner  422 . However, the description of horizontal positioner  422  also applies to horizontal positioner  420 . 
         [0029]    In general, the horizontal positioner  422  includes a horizontal hydraulic member  424 , an inner horizontal member  446  and an outer horizontal member  436 . The inner and outer horizontal members  446 ,  436 , respectively, are coaxial with each other. The inner and outer horizontal members  446 ,  436 , respectively, are hollow and the inner horizontal member  446  is positioned within the outer horizontal member  436 . The horizontal hydraulic member  424  may be positioned to be along the outside of and parallel to the inner and outer horizontal members  446 ,  436 , respectively. 
         [0030]    The horizontal positioner  422  is secured to the crawler  120  and the RTP  100  via a series of pins, such as steel pins, and weldments on the crawler frame  124 . More specifically, the second end of the outer horizontal member  440  is secured to the first frame member  402 , and the first end of the inner horizontal positioner  444  is secured to the crawler frame  124 . The first end of the horizontal hydraulic member  426  is secured to the first end of the inner horizontal member  444  via a first connector  460 , such as a pivot connector. The second end of the horizontal hydraulic member  426  is secured to the outer horizontal member  436  via a second connector  462 , such as a pivot connector. The pivot connectors  460 ,  462  enable the crawler  120  to adjust to variations in the horizontal movement of the RTP  100 . 
         [0031]    To move the crawler  120  outward, away from the second rail wheel  136 , the pressure in the hydraulic member  306  is increased. This pushes the first end of the inner horizontal member  444 , and thus the crawler  120  away from the second rail wheel  136 . To move the crawler  120  inward, towards the second rail wheel  136 , the pressure in the hydraulic member  306  is decreased. This pulls the inner horizontal member  446  into the outer horizontal member  436 , thus moving the crawler  120  inward, towards the second rail wheel  136 . The crawler  120  may be moved horizontally to any number of distances. For example, the crawler  120  may be moved horizontally outward by a distance of twelve (12) inches so that it is horizontally aligned with a guard timber  212  of a bridge  200  ( FIG. 2 ). 
         [0032]    The horizontal positioner  422  may also include a mechanism that prevents the horizontal positioner  422  from moving horizontally. One example of such a mechanism is lock bar  452  and a lock bar guide  454 . The lock bar  452  includes a plurality of holes and is attached to the inner horizontal member  446 . The lock bar guide  454  includes a hole and is attached to the outer horizontal member  436 . The lock bar  452  and lock bar guide  454  may be engaged with each other by aligning one of the holes of the lock bar  452  with the hole of the lock bar guide  454  and inserting a pin (not shown) through the aligned holes. In this manner, horizontal movement of crawler  120  is prevented. 
         [0033]    In order to prevent wear between the inner and outer horizontal members  446 ,  436 , respectively, the horizontal positioner  422  may include a buffer  456  located between the inner and outer horizontal members  446 ,  436 , respectively. The buffer  456  may include a metal plate, such as a brass plate. The horizontal positioner  422  may also include one or more slack adjusting mechanisms  454 . These adjusting mechanisms  454  protrude through the outer horizontal member  436  to contact the buffer  456  and hold it in place between the inner and outer horizontal members  446 ,  436 , respectively. As the buffer  456  is worn down by movement between the inner and outer horizontal members  446 ,  436 , respectively, the adjusting mechanisms  454  may be tightened so that the buffer  456  remains in place. 
         [0034]    In one example, the crawler  120  of the RTP  100  may be moved from a first position to a second position via the positioning system  172 , which moves the crawler  120  vertically upward so that it is above the first position, horizontally so that it is over the second position and vertically downward into the second position. 
         [0035]    An example of the crawler  124  in a first position is shown in  FIG. 5  and an example of the crawler in a second position is shown in  FIG. 6 . In these examples, the first position is on (or alternately, above) the ties  104  of a railroad track  218  and the second position is on the guard timber  218 . However, the crawler  124  may be moved from and to a variety of other positions. 
         [0036]    As shown in  FIG. 5 , the crawler  120  is in a position in which the crawler wheels  126  are postponed on (or alternately, above) the ties  104 . In this position, the vertical hydraulic member  30  is in an expanded state causing the inner vertical member  326  of the vertical positioner  372  (see  FIG. 3 ) to protrude from the outer vertical member  324 . Because the inner vertical member  306  is connected with the crawler frame  124 , the crawler  120  is in a position below the top of the guard timber  218 . In addition, the horizontal hydraulic member  424  is in a retracted state causing the inner horizontal member  446  to retract into the outer horizontal member  436  further than it was in  FIG. 5 . Because the inner horizontal member  446  is connected with the other vertical member  324 , the crawler  120  is located in a position away from the guard timber  218 . 
         [0037]    As shown in  FIG. 6 , the crawler  120  is in a position in which the crawler wheels  126  are located on the guard timber  218 . In this position, the vertical hydraulic member  306  is in a retracted position causing the inner vertical member  326  to withdraw into the outer vertical member  324 , but not to the extent shown in  FIG. 5 . This positions the crawler wheels  126  at the level of the top of the guard timber  218 . In addition, the horizontal hydraulic member  424  is in an expanded state causing the inner horizontal member  446  to protrude further from the outer horizontal member  436  than it did in  FIG. 5 . This positions the crawler  120  away from the RTP  100 . 
         [0038]    To move the crawler  120  from its position in  FIG. 5  to its position in  FIG. 6 , two vertical and one horizontal moves are made. Starting in its position in  FIG. 5  (on or above the ties  104 ), the crawler  120  is moved upward to a position higher than the top of the guard timber  218  by the vertical positioner  372 . The crawler  120  is then moved horizontally to a position vertically aligned with the guard timber  218  by the horizontal positioner  422 . Then, the crawler  120  is moved vertically downward until it comes into contact with the top of guard timber  218  by the vertical positioner  372 . To move the crawler  120  from its position in  FIG. 6  to its position in  FIG. 5 , the previously-described steps may be taken in reverse. 
         [0039]    While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.

Summary:
A movable crawler system that moves a crawler of railroad equipment from a first position to a second position is disclosed. The crawler system includes a crawler and a positioning system that moves the crawler. The positioning system includes a horizontal positioner and may include a vertical positioner, which move the crawler horizontally and vertically, respectively. The crawler system may be used in railroad equipment for rail change-out processes. When used in this manner, the crawler system enables the crawler to be moved between a position on a guard timber and a position on or above the railroad ties. Because the crawler can be moved to a position on the guard timber, when the equipment is operated on a track suspended by a bridge, which has one rail missing, the need for workers to work outside the rails to raise the equipment above the guard timber is eliminated.