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CROSS REFERENCE TO A RELATED APPLICATION 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 61/889,096, filed Oct. 10, 2013 and entitled “Tie Plate Plugging Machine,” the subject matter of which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates in general to the field of railroad maintenance. More particularly, the present invention relates to a vehicle that dispenses a chemical solution into spike holes of railroad ties during track maintenance. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Rail anchors, used to secure a rail to railroad ties, typically are held in place by spikes driven into the ties. These spikes are removed during a variety of maintenance operations such as a rail re-lay or rail changeover operation, which results in the removal of the rail, the spikes that hold the tie plates to the ties, and tie plates associated therewith and also with the replacement of the rails. As a result of the pulling of the spikes that hold the rails to their plates, several holes remain in the tie at the location vacated by the plate. It is usually desirable to plug these “spike holes” to prevent rot and water freezing in the open spike holes from causing damage to the tie. In addition, should a spike be inserted into an existing spike hole, something of a substance should be in the location to retain the hold-down force of the spike within the tie. 
         [0006]    The classic approach to plugging spike holes was simply to manually insert cedar plugs into the holes as part of the rail re-lay operation. These plugs initially were inserted by laborers walking along the railway. Later, machines were developed that permitted riding operators to insert plugs using hand-held tools. 
         [0007]    More recently, several different chemical solutions have been developed that are injected into the holes and then react either with a component of the injected material, chemical, or water to form a relatively hard substance that approximates the physical characteristics of wood. Examples of such solutions include a polyurethane-based chemical, an epoxy-based chemical, and a water-based chemical. The first way of injecting these materials was to manually inject the solution into the spike holes using a caulk gun type device or “gun” that simultaneously mixes the constituent chemicals of the solution and injects the solution into the spike holes. This technique is still in use but generally is limited to relatively small-scale applications such as replacing a short section of railway. 
         [0008]    Vehicles have been developed permitting riding operators to manually inject solution into spike holes using guns of the type historically used by walking operators but supplied with chemicals via one or more on-board tanks rather than a self-contained cartridge on the gun. The machine may be either self-propelled and move along the rails or mounted on the back of a pickup truck or the like. They typically include a single gun that is manually directed and activated by an operator. Other than being transported by a vehicle and having tanks, these types of devices are, in essence, the same as the traditional caulk gun style operation. 
         [0009]    In all of these machines, the guns are controlled, manipulated and triggered by operator rather than being mounted on a work head and operated automatically. In addition, each of these prior machines or techniques required a dedicated operator to each gun rather than permitting a single operator to operate multiple guns. 
       SUMMARY AND OBJECTS OF THE INVENTION 
       [0010]    In accordance with an aspect of the invention, a railroad tie maintenance vehicle for sealing spike holes in a railroad tie includes a chassis with an integrated operator work station. The vehicle may move along railroad tracks with a plurality of wheels that support the chassis and that are configured to engage at least one railroad track. An optional motive power source, supported on the chassis, may be controlled by an operator within the operator work station to propel the vehicle along the railroad tracks. At least one storage vessel on the chassis contains a chemical solution used to fill holes in the ties formed by the removal of railroad spikes. To dispense the chemical solution, at least two injection devices, supported on the chassis, dispense the chemical solution directly into the spike holes. The at least two injection devices are remotely controlled by the single operator, possibly at least in part by the operation of a single controller such as a joystick, to move into alignment with respective spike holes and to fill the spike holes. In one configuration, a powered actuator assembly, is operable to move the at least two injection devices relative to the chassis to align the injection devices with the spike holes. The single operator manipulates the controller(s) to control the powered actuator assembly to move the at least two injection devices relative to the chassis into alignment with the spike holes, and also to dispense the chemical solution into the spike holes. 
         [0011]    The actuator assembly may be configured to move the injection devices vertically and laterally relative to the chassis with at least one swing arm. One or both of the injection devices may also be movable on the swing arm(s) longitudinally of the chassis. 
         [0012]    An automated locating function may be configured to move a work head on which the powered actuator assembly is mounted forward relative to the chassis based on a measured speed of the vehicle and a known distance between adjacent railroad ties, hence reducing the stroke required under operator control. 
         [0013]    In the event one of the rails is removed from the railroad tracks prior to the spike hole filling operation, a crawler assembly may be included that supports the vehicle. The crawler assembly may be in direct contact with the railbed including the upper surface of the railroad ties. 
         [0014]    A debris removal device may also be included in order to remove a debris on the railroad ties that obstruct the spike hole. 
         [0015]    A method of operating a railroad tie maintenance vehicle is also disclosed. The method includes, via action of a single operator, manually operating a controller supported on an operator chassis of a workstation on the vehicle. The controller may include one or more joysticks. The operator can simultaneously control at least two injection devices. The injection devices may move in tandem with one another and may be placed in alignment with the spike holes under manipulation of a single controller. The dispensing of a chemical solution into the spike holes may also be controlled with the single controller. 
         [0016]    The injection devices may be mounted on a work head that can be autonomously controlled at least in part without operator input to position the injection devices at least an approximate location above the spike holes. The approximate location may be calculated based on a measured speed of the vehicle and a known distance between successive railroad ties. The final location of the injection devices directly in alignment with the spike holes may then be precisely controlled by the single operator. 
         [0017]    These and other aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    A clear conception of the advantages and features constituting the present invention, and of the construction and operation of typical mechanisms provided with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which: 
           [0019]      FIG. 1  is a perspective view of a tie plugging machine constructed in accordance with an embodiment of the invention, viewed from a working side of the machine; 
           [0020]      FIG. 2  is a side elevation view of a tie plugging machine constructed in accordance with an embodiment of the invention, viewed from the working side of the machine; 
           [0021]      FIG. 3  is a side elevation view of a tie plugging machine of  FIG. 1 , viewed from the side of the machine opposite the working side; 
           [0022]      FIG. 4  is front end elevation view of a tie plugging machine of  FIGS. 1-3 ; 
           [0023]      FIG. 5  is top plan view of a tie plugging machine of  FIGS. 1-4 ; 
           [0024]      FIG. 6  is a detail view of the tie plugging machine of  FIGS. 1-5 , viewed from the working side of the machine and showing the work head in a first position along a guide rail; 
           [0025]      FIG. 7  is a detail view of the tie plugging machine corresponding to  FIG. 5 , viewed from the working side of the machine and showing the work head in a second position along the guide rail; 
           [0026]      FIG. 8   a  is a side view of the work head of the tie plugging machine of  FIGS. 1-7 , showing a swing arm support frame in a retracted position thereof; 
           [0027]      FIG. 8   b  is a side view of the work head of the tie plugging machine of  FIGS. 1-7 , showing the swing arm support frame in an extended position thereof; 
           [0028]      FIG. 9  is a front end elevation view of the work head of the tie plugging machine of  FIGS. 1-7 , showing the swing arms that support the injection devices in extended positions thereof; 
           [0029]      FIG. 10  is a front end sectional elevation view, taken through the center of the work head of the tie plugging machine of  FIGS. 1-7 ; 
           [0030]      FIG. 11  is a representation of a rail tie and rail section incorporating a hole pattern pluggable using the tic plugging machine of  FIGS. 1-7 ; 
           [0031]      FIG. 12  is a schematic top plan view of a pair of control panels for the work head; 
           [0032]      FIG. 13  is an isometric view of a joystick of the control panel shown in  FIG. 12 ; and 
           [0033]      FIG. 14  is a perspective view of an alternative control panel for the work head. 
       
    
    
       [0034]    In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the words “connected”, “attached”, “supported”, or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art. 
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0035]    The present invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments described in detail in the following description. 
         [0036]    Referring to the drawings and initially to  FIGS. 1-5 , a tie plugging machine  20  or vehicle for plugging spike holes  22  in railroad ties  24  is illustrated. The machine  20  typically will be used as part of a track re-laying operation in which a rail  26  is removed and replaced with a new rail. As part of this process, the spikes (not shown) holding the rail  26  to the tie  24  and holding the tie plate  28  to the rail  26  are removed by one or more machines (not shown) working ahead of the tie plugging machine  20 , leaving holes  22  in the ties  24 . Those holes  2 . 2  should be plugged to preserve the integrity of the tie  24  and to provide solid surfaces into which new spikes (not shown) may be driven. Plugging typically involves the injection of a two-part chemical solution  94  into the holes  22 , the solution  94  being formed from a two-part epoxy, polyurethane, or a water-based system. 
         [0037]    The tie plugging machine  20  illustrated in the drawings includes a self-propelled vehicle  30  bearing injection devices  32  supported on a work head  34  that is movably mounted on a platform or chassis  36  of a the vehicle  30 . Referring now to  FIG. 2 , the machine  20  has a “working side” on which the work head  34  is mounted. The vehicle  30  is supported on a rail  26  of the railway on at least one set of wheels  38  positioned along the side of the machine  20  opposite the working side of the machine  20 . The machine  20  may also include a second set of wheels  38  on the working side of the machine  20  for rolling along an opposite rail (not shown), if that rail is present. Crawlers  40 , positioned outboard of the second set of wheels  38 , also are provided for supporting the machine  20  on the railbed  42 , permitting propulsion along railway sections in which one rail  26  has been removed. Each crawler  40  is mounted on a mast  44  so as to be movable vertically into and out of engagement with the railbed  42  via operation of an associated hydraulic cylinder  46 . The tie plugging machine  20  may also be configured with crawlers  40  on both sides of the chassis  36 , allowing operation with both rails  26  removed from the track. The vehicle  30  is propelled by a motive power source  48  located, in this case, near the rear end of the machine  20 . The motive power source  48  may be, for example, a gasoline or diesel engine. Alternatively, the machine  20  could be towed by another machine. 
         [0038]    Two injection devices  32 A,  32 B, shown in greater detail in  FIGS. 6-10 , are provided on the work head  34 . Referring briefly to  FIG. 11 , the injection devices  32  are movable vertically, as shown by arrow  60 ; laterally, as shown by arrow  62 ; and longitudinally, as shown by  64 ; of the chassis  36  to permit them to be positioned over the desired spike holes  22  as the machine  20  travels along the railway. One of the injection devices  32 A (the “gauge side injection device”  32 A) is positioned over the inboard, or gauge side, of a set of spike holes  22  and the other (the “field side injection device”  32 B) is positioned over the outboard, or field set, of spike holes  22 . When the machine  20  is configured for filling holes  22  of the traditional four hole pattern shown in  FIG. 11 , the injection devices  32 A,  32 B preferably are offset diagonally from one another so that, when the gauge side injection device  32 A is positioned over the inboard front hole  22 , the field side injection device  32 B is positioned over the outboard, rear hole  22 .  FIG. 11  also shows a rail  26  section removed from the track. 
         [0039]    In a preferred mode of operation, injection devices on a second work head (not shown) positioned in front of or behind the work head  34  are of the opposite configuration so as to operate in tandem with the work head  34  to fill the remaining two diagonally opposed spike holes  22 . It is also possible to have a work head (not shown) on the opposite side of the chassis  36  from the working side, and have the same or another operator (not shown) control the injection devices  32  on that work head  34 . Purely automated operation is also possible with sufficiently sophisticated sensors and controls. 
         [0040]    Referring again to  FIGS. 1-5 , the injection devices  32 A,  32 B receive chemical solution from one or more storage tanks. A preferred solution is a two-part resin solution, the two components of which are stored in relative large storage tanks  70 ,  71  mounted on the chassis  36  in front of and behind the work head  34 , respectively. Alternatively, both tanks  70  and  71  could be located at a common end of the chassis  36 . Each tank  70 ,  71  preferably has a sufficient capacity to permit continuous operation of the vehicle  30  for an extended period of time. A minimum per-tank capacity of 50 gallons, and preferably of at least 100 gallons, is presently preferred. The chemicals are transferred from the tanks  70 ,  71  to the injection devices  32 A,  32 B through hoses  72  under control of the operator and are mixed to form the solution while they are flowing through hollow mixing nozzles  74  at the bottoms of the injection devices  32 A,  32 B. 
         [0041]    Still referring to  FIGS. 1-5 , the machine  20  is controlled by an operator located in an operator work station  80  located generally centrally of the chassis  36  adjacent the working side of the machine  20  next to the work head  34 . The operator work station  80  preferably takes the form of an environmentally controlled enclosed cab that shields a seated operator within from the elements as well as the chemicals dispensed by the injection devices  32 A,  32 B. Windows  82  may be provided on various sides of the operator work station  80  to allow the operator to direct the tie plugging machine&#39;s  20  movement. An additional window  84  may be provided towards the floor of the operator work station  80  that is angled towards the injection devices  32 . This window  84  provides a clear, unobstructed view of the spike holes  22  and the injection devices  32 . 
         [0042]    Referring specifically to  FIGS. 2 and 4 , brushes  90  are located at the front and rear ends of the tie plugging machine  20  and may be extended to contact the ties  24 , and retracted away from the ties  24 , in order to sweep aside any debris  92  on the surface of the ties  24 . This allows for unobstructed access to the spike holes  22  for injection of the chemical compound. Referring to  FIG. 4 , the brush  90  is shown in this view in the retracted position  90   a  in solid lines and in the deployed position  90   b  in phantom lines. Each brush  90  is driven by an electric or hydraulic motor (not shown) as the tie plugging machine  20  moves along the rail  26 . The brush rotation sweeps debris  92  away from the spike holes  22 , which could otherwise prevent injection of the chemical solution  94  into the spike holes  22 . Each brush  90  may also include an abrasive filament (not shown) designed to strip away damaged wood from the tie  24 . 
         [0043]    Referring again to  FIG. 6-10 , the work head  34  is mounted on the chassis  36  so as to be movable longitudinally, as shown by arrow  64 , relative to the chassis  36 , hence permitting coarse positioning of the injection devices  32  relative to the chassis  36  as the machine  20  travels along the railway as discussed in greater detail below. The movement is effected by a powered actuator assembly formed from several cylinders and motors. The field  32 B and gauge side  32 A injection devices are mounted on the work head  34 , and the work head  34  is mounted on the chassis  36 , so as to permit the injection devices  32 A and  32 B to be movable at least longitudinally and laterally relative to the chassis  36  and preferably vertically as well. The injection devices  32 A and  32 B preferably are movable about the work head  34  vertically, as shown by arrow  60 ; laterally, as shown by arrow  62 ; and longitudinally, as shown by arrow  64 ; relative to the chassis  36  so as to permit precise alignment of the injection devices  32  relative to the spike holes  22  as seen in  FIG. 11 . This alignment, in combination with controlled injection on demand, dramatically reduces the amount of wasted hole filling solution  94 , reducing both costs and environmental impact. In addition, in order to reduce operator effort, the mixing tips  96  of the injection devices  32  preferably may be positioned and locked in place to have a specific offset with respect to one another in order to accommodate a specific standard spike hole  22  pattern such as the one illustrated in  FIG. 11 . Locking the offset of the mixing tips  96  in position allows the operator to move both injection devices  32 A,  32 B in tandem with one another at all times. Hence, once one mixing tip  96  of the injection device  32 A is positioned directly above a spike hole  22 , the mixing tip  96  of the other injecting device  32 B will likewise be in proper position over a diagonally opposed spike hole  22 . 
         [0044]    The degrees of freedom desired to move the injection devices  32 A,  32 B could be accommodated using any of a variety of techniques, one of which will now be detailed. Specifically, the work head  34  of this embodiment includes a carriage  100 , front and rear vertical support rods  102  extending downwardly from the carriage  100 , and a swing arm support frame  104  that is movable vertically along the vertical support rods  102 . First and second (gauge and field) laterally spaced swing arms  106  are each mounted on the swing arm support frame  104  so as to be swingable about a respective longitudinally extending horizontal axis  136 . An injection device  32 A,  32 B is mounted on the lower end of each swing arm  106  so as to be moveable relative to the swing arm  106  longitudinally of the machine  20 . 
         [0045]    As best seen in  FIGS. 6 and 7 , the carriage  100  is mounted on an upper frame  137  of the chassis  36  by first and second laterally spaced, longitudinally extending guide rail  110 , each of which supports an associated sleeve  112  of the carriage  100 . The carriage  100  can be driven to move longitudinally along the guide rail  110  by an electric motor  114  of the powered actuator assembly coupled to a rack and pinion assembly  116  from a rearmost position illustrated in  FIG. 6  to a forward-most position illustrated in  FIG. 7 . This work head movement allows the tie plugging machine  20  to maintain a steady speed of travel along the rail  26  while maintaining the work head  34  over a given set of spike holes  22  for a period of time that permits the operator to finely position the pre-positioned injection devices  32 A,  32 B into alignment with the spike holes  22  and to inject the solution into the spike holes  22 . It also permits the work head  34  to “catch up” or shuttle into the vicinity of the next down-track tie  24  upon completion of a spike hole plugging operation on a given tie  24 . This movement may be partially or even wholly automated under control of an on-board computer (not shown) to reduce the need for operator input. Movement of hydraulic and electric controls that move with the carriage  100  is accommodated by a cable tray  118  located above the carriage  100 . 
         [0046]    Referring to  FIGS. 6-9 , the vertical support rods  102  are mounted on the carriage  100  by being suspended from front and rear horizontal support rods  120 . Specifically, the upper end of each vertical support rod  102  is mounted on an associated end of a cross-beam  122  ( FIG. 7 ). The cross beam  122  has front and rear ends coupled to respective sleeves  124  (the front of which is best seen in  FIGS. 8A-9 ), each of which rides along a respective horizontal support rod  120 . The cross beam  122  can be driven to move laterally by a hydraulic cylinder of the powered actuator assembly (not shown), permitting lateral centering of the swing arm support frame  104  over the spike hole pattern. This movement accommodates, amongst other things, changes in rail gauge. 
         [0047]    Referring now to  FIGS. 7-10 , the swing arm support frame  104  on which the field and gauge side swing arms  106  are mounted includes a central support  130  extending between and fixed to front and rear vertical sleeve assemblies  132 . Each vertical sleeve assembly  132  is slideably supported on a respective vertical support rod  102 . The upper end of each swing arm  106  has front and rear ends pivotally attached to a respective ear mount  134  supported on the corresponding sleeve assembly  132 . This pivotal mounting permits swinging of the swing arm  106  about the above-described horizontal axis  136  and permits lateral alignment of the injection devices  32 A,  32 B over the spike holes  22 . As best seen in  FIG. 9 , each swing arm  106  is driven to pivot about its respective axis  136  by a side actuator  138  in the form of a hydraulic cylinder of the powered actuator assembly. Each hydraulic cylinder has a first, barrel end  140  coupled to the respective swing arm and a second, rod end  142  coupled to a respective side of the swing arm support frame  104 . As best seen in  FIG. 7 , the swing arm support frame  104  can be driven to move vertically along the vertical support rods  102  via operation of an operator-controlled central actuator  144  of the powered actuator assembly located between the vertical support rods  102 . The range of movement can be appreciated by comparing  FIGS. 8A and 8B . In this embodiment, the actuator  144  comprises a vertically extending hydraulic cylinder having a lower, barrel end  148  attached to an upper surface of the swing arm support frame  104  and an upper, rod end  150  attached to the horizontal cross beam  122 . This movement not only can be used for fine positioning of the injection devices  32 A,  32 B during a spike hole plugging operation, but can also be used for coarse positioning to move the injection devices between stowed and deployed positions and/or to accommodate mixing nozzles  74  of different lengths. The range of injection device positions can be additionally extended by introducing the capability of bolting the injection devices  32 A,  32 B at different heights on the upper supports  152 . 
         [0048]    Referring to  FIGS. 6-11 , each injection device  32 A,  32 B comprises a lower mixing tip  96  (as described above) extending downwardly from an upper support  152 . The upper support of at least one of the injection devices is mounted on the associated swing arm  106  so as to be moveable along the swing arm  106  longitudinally of the machine  20  to permit fine positioning of the injection devices  32 A and  32 B relative to the work head  34  when the work head  34  has been positioned in the vicinity of the spike holes  22  by movement of the machine  20  along the railway and movement of the work head  34  along the machine  20 . In the illustrated embodiment, this movement is accommodated by upper and lower guide longitudinally extending rods,  153  and  154  respectively, that support corresponding guide sleeves,  155  and  156  respectively, which form an integral unit with the upper support  152  as best seen in  FIG. 10 . The upper support  152  can be driven to move along the guide rods  153  and  154  by a hydraulic cylinder (not shown) controlled by the operator to position the hollow mixing nozzles  74  in the general vicinity of the spike holes  22 . In the illustrated embodiment, only one of the injection devices, such as the field side injection device  32 B, may be imbued with the capability of longitudinal movement relative to the rails and thus need be fitted with rods  153  and  154  and the associated cylinder and related controls. Alternatively, and as illustrated, both of the field and gauge sides&#39; injection devices  32 B and  32 A may be capable of being driven to move longitudinally of the rail. 
         [0049]    The positions of the various moving components of the machine  20  may be monitored by any combination of various electrical sensors, optical sensors, limit switches, etc. (not shown). In a particularly simple embodiment each of the cylinders takes the form of a so-called “smart cylinder” having an internal sensor that monitors the stroke of the cylinder and, thus, the position of the driven component. 
         [0050]    The position of the side actuators  138 , as well as the extension or retraction of the work head  34 , may be set prior to operation to the known spacing of the spike holes  22 . Alternatively, the machine&#39;s  20  on-board computer may dynamically control the side actuators  138 , as well as the entire actuator assembly  160 , to control the positioning of the injection devices  32 A and  32 B in both the vertical and horizontal planes during operation to locate the mixing nozzles  74  in the proper position above each spike hole  22 . This operation may also be performed while the tie plugging machine  20  is moving along the railbed  42 . The operator within the operator work station  80  may manually control movement of the work head  34  during operation. Transitioning to  FIG. 10 , the work head  34  is shown in the retracted position and supported by the guide rail  110 . 
         [0051]    As mentioned above, all of the above-described aspects of the machine  20  can be controlled by a single operator stationed in the workstation  80 . Preferably, the injection devices  32  are positioned and operated by a single controller located within control panel  174  positioned adjacent one side, such as the left side, of the operator&#39;s seat. One such controller is shown in  FIG. 12  notably including a dual-axis joystick  172  shown in more detail in  FIG. 13 . In addition to supporting the joystick  172 , the control panel  174  may have various controls such as a switch  176  for “purging” the injection devices with a cleaning solution, field and gauge side switches  178  and  180  for moving the field and gauge side dispensing devices  32 B and  32 A to their stowed positions, etc. and/or for setting the limits the lateral movement of the field and gauge side swing arms. Another limit switch  182  can be used to adjust the limit of movement of the field side injection device  32 B longitudinally of the rail or left/right relative to the workhead. The control panel  174  thus allows the operator to not only manipulate the work head&#39;s motion and dispensing of chemical solution  94 , but also allows the operator to set the operating parameters of the work head  34 . The operating parameters thus include the inner and outer limits of the work head&#39;s  34  vertical motion, described above with respect to  FIGS. 8   a,    8   b,  and  9 , and the left and right limits of the work head&#39;s  34  lateral motion, described above with respect to  FIGS. 6 and 7 . 
         [0052]    The joystick  172  is best seen in  FIG. 13 . Movement of the joystick  172  along a first axis, such as side-to-side, actuates the side actuators  138  to pivot the swing arms  106  laterally of the rails about the axis  136 . Actuation of the joystick  172  along the second axis, such as fore-and-aft, actuates at least one cylinder to move the corresponding injection device fore and aft on the guide rods  153  and  154  relative to the swing arms  106 . As discussed above, in the illustrated embodiment, it is possible that only one such injection device, such as the field side injection device  32 B may have the capability to move longitudinally of the rail under the control of joystick  172 . 
         [0053]    Field and gauge side dispensing buttons  186  may also be provided on the joystick  172 , allowing the operator to control injection of chemical solution dispensed from the associated field and gauge side injection devices  32 B,  32 A as well as the duration of each injection event. For example, the operator may hold a dispensing button  186  down for a sufficient period of time for the injection devices  32 A and  32 B to continuously dispense enough chemical solution  94  to fill the allocated spike holes  22 . Alternatively, simply toggling a switch could dispense a designated volume of solution. 
         [0054]    Referring again to  FIG. 12 , a second joystick  192  may be provided on a control panel  194  positioned beside of the operator&#39;s seat opposite workstation opposite the control panel  174 . Joystick  192  also can be a dual axis joystick and can be used to control movement of carriage  100  relative to the chassis  36 . For example, lateral or side-to-side movement of the joystick  192  may be used to drive the cross beam  122  and thus the carriage  100  to move laterally of the rail to center the swing arm support the frame  104  over the spike hole pattern to accommodate, e.g., changes in rail gauge. Fore-and-aft movement of the joystick  192  can actuate the electric motor  114  to drive the workhead  34  and thus the carriage  100  to move longitudinally relative to the rail. 
         [0055]    In operation, the tie plugging machine  20  is driven along the railway continuously at a speed of, for example, approximately 2-5 mph. When the injection operation is complete in a given tie  24 , the carriage  100  automatically shuttles forward along the guide rods  110  to the next tie  24  under control of the machine&#39;s computer. The speed and extent of this movement is determined based on the prevailing speed of the machine  20  and the spacing between adjacent ties  24 , which may be measured using appropriate detectors (not shown) or simply pre-set for a given standard railway configuration. This “auto-advance” feature locates the injection devices  32  approximately above the spike holes  22 . The operator thereafter only needs to manipulate the joystick  172  to finely position the injection devices  32  so that mixing nozzles  74  are directly above or otherwise aligned with the spike holes  22 . See  FIG. 11 . Specifically, when the work head  34  is positioned generally over the spike holes  22  under operation of the computer, the operator moves the second joystick  192  to generally center the carriage  100  over the spike hole pattern. He then moves the first joystick  172  fore and aft to drive at least one of the injection devices  32 A,  32 B longitudinally along the guide rods  153  and  154  on the swing arms  106  to align the two opposed mixing nozzles  74  of the injection devices  32  longitudinally with a given set of spike holes  22 , such as the gauge and field side spike holes  22 . The operator may also move the joystick  172  left or right to control the cylinders  146  to pivot the swing arms  106  to position the injection devices  32  laterally over the associated spike holes  22 . The operator may then push the dispensing buttons  176  on the joystick  172  to dispense the chemical solution  94  into the spike holes  22  in a preset amount and/or in an amount controlled by the period of button actuation. 
         [0056]    In the process described above, the use left or right limits allows the operator to adjust the workhead position to account for staggered hole patterns in the tie. So, during normal operation, the operator uses the inner and outer limits with the left and right limits selected via the first joystick  172  in conjunction with moving the workhead left and right using the second joystick  192  to effectively fill all the spike holes  22  in the tie  24 . 
         [0057]    Alternatively, both injection devices  32 A and  32 B may be provided with the capability of being driven longitudinally of the rail. This extra degree of freedom allows the workhead  34  to do more of the operator&#39;s work. A first or left hand control system having this capability is shown in  FIG. 14 . The system includes a single controller located within control panel  274  that notably includes a dual-axis joystick  272 . Control panel  272  additionally includes start and stop buttons  276  and  278  for enabling and disabling operation of the spike hole plugger and a toggle switch  280  that enables or disables operation of components on the workhead  34 . The above-described chemical purge of the injection devices can be controlled by a switch  282 , which may take the form of a toggle switch permitting toggling between the gauge and field side injection devices  32 A and  32 B. In addition, switches  284  and  286  can be provided that allow the operator to set the field and gauge side spike hole pattern. Movement of the joystick  272  along a first axis, such as side-to-side, actuates the side actuators  138  to pivot the swing arms  106  laterally of the rails about the axis  136 . Movement of the joystick  172  along the second axis, such as fore-and-aft, actuates the cylinders to move the injection devices fore and aft on the guide rods  153  and  154  relative to the swing arms  106 . 
         [0058]    During set-up, the operator can use the joystick  272  to independently control movement of each dispensing mechanisms  32 A and  32 B longitudinally and laterally of the railway. The operator selects either the field side or gauge side to adjust via the respective pushbutton  284  or  286  on the panel  274 . Once pattern programming is complete, the joystick  272  can be to select one of up to four preset patterns. For example, Up=pattern  1 ; Down=pattern  2 , Left=pattern  3  and right=pattern  4 . 
         [0059]    In this embodiment, the operator will use the second joystick  192  ( FIG. 12 ) to position the workhead  34  laterally over the spike hole operation. After manipulating the joystick  172  to locate the first spike hole in the pattern, the operator can select between 4 or more different patterns on the fly by selecting them using the joystick  272  as described above. The machine is now capable of filling all of the holes in the selected without requiring the operator to reposition the workhead after the first hole is located. The operator thus only need up one hole in the pattern and pull a trigger (not shown) on the joystick  272  to fill the first spike hole in the pattern. The machine will then automatically move onto the next hole in the pattern, and then the next, until all holes in the pattern are filled. This procedure happens simultaneously on both sides of the vacated rail using both injection devices  32 A and  32 B. Once all the holes in the pattern are filled, the operator uses the joystick  192  ( FIG. 12 ) to move the workhead over the next tie, lines up with the first spike hole using the joystick  272 , then repeats the fill process by simply pulling the trigger on the joystick  272 . The workhead then completes the hole filling by remembering the programmed hole positions. 
         [0060]    Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications and rearrangements of the features of the present invention may be made without deviating from the spirit and scope of the underlying inventive concept. 
         [0061]    Moreover, the individual components need not be formed in the disclosed shapes, or assembled in the disclosed configuration, but could be provided in virtually any shape, and assembled in virtually any configuration. Furthermore, all the disclosed features of each disclosed embodiment can be combined with, or substituted for, the disclosed features of every other disclosed embodiment except where such features are mutually exclusive. 
         [0062]    It is intended that the appended claims cover all such additions, modifications and rearrangements. Expedient embodiments of the present invention are differentiated by the appended claims.

Summary:
A railroad tie maintenance vehicle is configured to seal spike holes in a railroad tie formed by the removal of railroad spikes. The vehicle includes a chassis with an integrated operator work station. The vehicle may move along railroad tracks with a plurality of wheels that support the chassis and that are configured to engage at least one railroad track. A motive power source, supported on the chassis, may be controlled by an operator within the operator work station to propel the vehicle along the railroad tracks. At least one storage vessel on the chassis contains a chemical solution used to fill the spike holes. At least two injection devices on the chassis are remotely controlled by the single operator, possibly by the operation of a single controller such as a joystick, to move into alignment with respective spike holes and to fill the spike holes with the chemical solution.