Patent Publication Number: US-2010107925-A1

Title: Method and apparatus for applying railway ballast

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims priority to co-pending U.S. patent application Ser. No. 11/566,484, filed on Dec. 4, 2006, which is a divisional of patent application Ser. No. 10/870, 843, filed on Jun. 17, 2004, now U.S. Pat. No. 7,152,347, which prior applications are hereby incorporated by reference to the extent permitted by applicable law. 
    
    
     BACKGROUND OF THE INVENTION 
     Conventional railroads in the United States and elsewhere are typically formed by a compacted sub-grade, a bed of gravel ballast, wooden cross-ties positioned upon and within the ballast, and parallel steel rails secured to the ties. Variations of construction occur at road and bridge crossings and in other circumstances. The ballast beneath and between the ties stabilizes the positions of the ties, keeps the rails level, and provides some cushioning of the composite structure for loads imposed by rail traffic. Vibrations from the movement of tracked vehicles over the rails and weathering from wind, rain, ice, and freeze and thaw cycles can all contribute to dislodging of some of the ballast over time. Thus, in addition to other maintenance activities, it is necessary to replace ballast periodically to maintain the integrity and safety of railroads. 
     Ballast has been spread in the past using specially designed ballast hopper cars which include a hopper structure holding a quantity of ballast, a ballast chute communicating with the hopper, and a power operated ballast discharge door in the chute. The door can be controlled to selectively open or close to control the discharge of ballast. In some designs, the discharge door can be controlled to open outboard toward the outside of the rails, to close, or to open inboard toward the inside between the rails. Typical ballast hopper cars have a front hopper and a rear hopper, and each hopper has two transversely spaced doors, one to the left and one to the right. Thus, each hopper door can be controlled to discharge ballast outside the rails on the left and/or the right or between the rails. A typical configuration of a ballast hopper car is described in more detail in U.S. Pat. No. 5,657,700, which is incorporated herein by reference. 
     Ballast spreading has most often been controlled manually in cooperation with human spotters who walk alongside the moving ballast cars to open or close the ballast doors as necessary. A more recent ballast spreading control technique is by the use of a radio linked controller carried by an operator who walks alongside the moving ballast cars. Both conventional control methods are slow and thus disruptive to normal traffic on the railroad section being maintained, thereby causing delays in deliveries and loss of income. 
     U.S. Pat. No. 6,526,339 to Herzog, et al. generally discloses methods for spreading railroad ballast with location control based on data received from the global positioning system or GPS. The GPS system, is a “constellation” of satellites traveling in orbits which distribute them around the earth, transmitting location and time signals. As process the signals and triangulate position coordinates accurate to about ten to twenty meters. Current generations of commercially available GPS receivers, using differential GPS techniques, are able to achieve accuracies in the range of one to five meters. Such accuracy is adequate for depositing ballast where desired and inhibiting the deposit of ballast where it is not desired. Additional information regarding the development of GPS technologies can be obtained from U.S. Pat. No. 4,445,118 and U.S. Pat. No. 5,323,322. Development of the GPS system referred to herein was sponsored by the United States government. However, satellite based positioning systems developed or operated by other nations are also known. 
     Because railroad companies typically maintain hundreds or thousands of miles of track on a recurring schedule, the ballast replacement component of track maintenance alone can be a major undertaking in terms of equipment, materials, traffic control, labor, and management. Implementation of a GPS based system of the type disclosed in U.S. Pat. No. 6,526,339 can increase the accuracy and efficiency of ballast application on railways, however, the use of other techniques for controlling the application of ballast can be as good as GPS techniques and, in some applications, even better in some respects. 
     SUMMARY OF THE INVENTION 
     The present invention provides methods and apparatus for controlled spreading of ballast on a railroad on a large scale basis using multiple ballast hopper cars spreading simultaneously, at times. The system of the present invention uses various different techniques for determining where ballast needs to be applied and for controlling the opening of ballast doors to spread controlled quantities of ballast on sections where ballast is desired and to inhibit spreading ballast where not desired or not needed. The system allows the ballast train to spread ballast mostly at a high enough speed that normal traffic on the railroad on which it is operating is only minimally affected by its presence. 
     In practice of the present invention, a ballast train may include one or more locomotives, a control car (not required), and one or more ballast hopper cars, such as fifty hopper cars. Each hopper car may have two hoppers, left and right ballast chutes for each hopper, a ballast door for each chute, and a hydraulic actuator for each door. The actuator can be controlled to open its associated door to an inboard direction, between the rails, or to an outboard direction, outside of the rails. Each hopper can hold a known load of a particular type of ballast, and the average flow rate of a given type of ballast through a ballast door is also known. Each hopper car has car logic circuitry, referred to as a car control unit or CCU and also as a microprocessor control system, which controls operation of the hydraulic actuators and which monitors certain functions on the car. 
     The CCU&#39;s communicate with a network control unit or head end controller (HEC) through a network including a bus referred to at places herein as a “wireline”. The bus extends from the HEC through the CCU of each car. The HEC may be a general purpose type of computer, such as a laptop, and it can have a differential GPS receiver interfaced thereto to provide geographic coordinates. The relative location of each ballast door on each hopper car of the train will be determined in relation to a known reference location. Ordinarily, the ballast train will use a plurality of virtually identical hopper cars with known distances between the ballast doors on a given car and between the ballast door of one car and the next adjacent car. 
     In order to control the spreading of ballast on a length of track, it is necessary to obtain the geographic location of the track. This is most conveniently accomplished by a rails, such as a Hy-Rail vehicle (trademark of Harsco Technologies Corporation). The track survey vehicle may be equipped with a suitable instrument for determining the location and with a computer, which may be the HEC computer, and track survey software. As the survey vehicle travels along the track, the survey crew, which may be or include a “roadmaster”, marks spread zones where ballast is to be spread and non-spread zones, such as bridges, road crossings, and the like, where ballast is not to be spread. The location of the spread and no-spread zones are recorded by the instrument, which can take a variety of different forms. 
     Alternatively, other procedures for determining the spread and non-spread coordinates are foreseen. For example, if a previously obtained track coordinate data file is available, it is foreseen that it could be processed to designate spread and non-spread zones. Further, under some circumstances, track surveying may even be conducted on a ballast train, forward of concurrent ballast spreading activity. Under normal circumstances of pre-spread surveying, a track survey data file is created which is transferred to the HEC computer for processing during a ballast spreading run. 
     In addition to surveying the track for its coordinates to thereby locate zones requiring ballast and those on which ballast is not desirable, it is necessary to survey the ballast train for car identities car order, and car orientation. Each car control unit or CCU includes a designated front Discrete Auto-Manifest (DAM) relay and a designated rear DAM relay, both of which are normally inactive. These discrete lines are independent control lines residing within the interconnecting wireline cable that connects each car to the network. The hopper cars can be assembled into the ballast train in any random order and with some cars oriented front to rear while the rest are oriented rear to front. It is not economically feasible to assemble the ballast train in any particular order or to charge the orientation of any particular car. However, the HEC must determine the order and orientation of the cars to enable communication of ballast door commands to the proper car during ballast spreading. 
     In the process of surveying the CCU&#39;s of the hopper cars, the HEC may query the CCU&#39;s to report their identities or neuron identification numbers. Then, through an iterative procedure of commanding the cars to open their front and then rear DAM relays and report their identities, the HEC can determine the order of the cars and their orientations. In particular, after the identities are determined, the HEC may broadcast a command for a selected car to activate its front DAM relay. Then the HEC may call for any cars that see a DAM line active to identify itself. The same car is then instructed to activate its rear DAM relay and the interrogation is repeated. This process is repeated using the cars that responded to the previous interrogations until all cars are linked together. The data file of identified, ordered, and oriented hopper cars is stored as the manifest data file. 
     The spreading of ballast may be controlled in terms of the amount or weight of ballast spread per unit of track length. From historic experience and for accounting purposes, the required quantity of ballast may be determined in tons per mile. While such a scale is more convenient for determining the cost of the operation, it is too coarse for dynamic control of ballast spreading at a relatively high traveling speed. The track length may be divided into “buckets” which are “filled” to achieve an overall desired tons of ballast per mile. The length of the buckets may be any convenient length and may be set at one foot lengths of track, for example. Each ballast door can spread either to the inboard side or the outboard side, and both can be effected at the same time. Each bucket has designated coordinates which may include the GPS coordinates of a set of buckets along with a sequential member of such a set. The bucket coordinates are derived by processing a previously generated track survey file. 
     The spreading process tracks the current location of the ballast train reference point in terms of its “bucket” location, the current load of ballast in each car, the fill percentage of each bucket, the state of each door as closed or opened and in which direction, and the speed of the train. Because of the lag in response of the ballast door actuators and the movement of the ballast and because of the movement of the train, the spreading process may “look ahead” in order to effectively correlate a door state to a given bucket. The spreading process can be timer driven and begins executing a series of actions at each timer interval or “tick”. The timer interval may be at 100 milliseconds or one tenth of a second. Spreading actions are affected by the speed and location of the train and, thus, all calculations factor in the speed and location. In contrast, the flow rate of ballast through a ballast door can generally be considered to be a constant. Preferably, the ballast doors are operated in such a manner as to be considered fully closed or fully open; however, the present invention foresees the capability of operating with the ballast doors in partially open states and the use of flow sensors. 
     At each clock tick, the state of each ballast door in succession can be checked along with a “lookahead” set of buckets and, if the door is currently open, the fill percentage of a current bucket or set of buckets which will receive ballast from the door in the current time interval. If the door is closed, the state of the lookahead bucket set is checked to determined if opening the current door will exceed the target fill of those buckets. If not, the current door is opened. If the current door is already open, the fill percentages of the current bucket set are updated, and the lookahead bucket set is checked to determine if the current fill exceeds the target fill. If not, the door stays open. 
     In general, the threshold to keep a door open is not as strict as the threshold to open a closed door. In zones where spreading is desired, it is preferable to spread somewhat more than the target fill than less. Subsequent maintenance activity involves crews who will properly position the ballast and tamp it into place. Thus, a small excess of ballast is preferable to an inadequate amount. However, in the case of a no-spread zone, any ballast which is deposited may constitute a hazard, such as on a road crossing, and may require a clean-up. For processing purposes, buckets in no-spread zones are initialized as full so that lookahead routines which encounter them always require the current door to close if open or to remain closed. 
     The spreading process may continue until all buckets of a spreading run are filled, all ballast from the hopper cars is exhausted, until the process is interrupted by a detected malfunction in the system, or until the operator shuts the process down for any reason. Ballast may be supplied from the forward most hopper cars initially, moving rearwardly as the ballast is exhausted from the forward cars. If functions on a hopper car are inoperative, the car is simply bypassed in processing, although it may be necessary to bridge the computer network across such a “dead” car. It is possible that some buckets, particularly near the end of a spreading run, will not be completely filled. Thus, it is desirable to save data representing the final state of any unfilled buckets for a future spreading run. It may also be desirable to save the final state of all buckets and hopper cars for record keeping and accounting purposes. 
     The present invention contemplates a variety of methods and apparatus for determining the location where ballast is to be spread along a railway bed and applying using a gyroscope for stabilization and one or more accelerometers for determining forward and angular momentums. This inertial system can be augmented using various position reference techniques to improve the overall accuracy and reliability. 
     Due to drift, a position reference must be re-established from time-to-time. Various methods and techniques can be used. 
     One example involves using fixed mile-markers that are typically installed along railways at one mile intervals or less. One way to use the markers is for a human operator to depress a button or otherwise record when each marker is reached. A controller can then recalibrate the distance and compute the speed of the railway vehicle. The controller can open ballast hopper doors when spread zone locations are reached and leave them open long enough to cover the entirety of each spread zone before the doors are closed. Alternatively, a visual recognition device such as a camera can use stored imagery of the railway to determine when known locations are reached by comparing current images with stored images of known locations. 
     Laser techniques can also be used. Laser beams reflected from known wayside reference locations can be received and used to calculate the distance to the reference locations and thus the current location of the train. The velocity can be computed based on the delay of the reflected signal and the frequency shift. These data can be used by the controller to open and close ballast doors properly to apply ballast to spread zones. 
     Law enforcement radar equipment can be employed and may have advantages in many applications. A radar signal directed at a wayside reference point can be received after detection and used to determine the distance from the reference location and the train speed, all using known techniques that are commonly used in law enforcement applications. 
     Radio frequency technology using either active or passive devices is another option. A radio transponder on the train can transmit rf signals to wayside devices which send response signals back to the onboard transponder. Location and speed data are thus acquired and used by the controller to apply ballast to the spread zones. Active devices at the wayside locations require external or battery power allowing them to function effectively at distances up to one mile or more. Passive wayside devices can use the energy from the signals they receive and are inexpensive, but their range is much more limited. 
     Magnetic sensing devices on board the train can sense either the presence of magnets placed along the railway bed at known locations or natural variations in the magnetic field of the earth at known locations. In either case, by magnetically detecting when the train reaches known locations, the location of the train relative to spread zones can be determined. By measuring the time between consecutive locations that are sensed magnetically, the current train speed is known so that control of the ballast hopper doors can be effected. 
     The present invention further contemplates thermal sensing to detect the current location and speed of the train. A thermal sensor on board the train can sense the current thermal characteristics of the earth along the rail bed and compare them with a known thermal profile to determine the current train position. Objects along the railway at known locations that can be detected thermally can also be used. Fixed objects such as engines, street lights, crossing signals and other wayside devices can be sensed as the train passes them. 
     The ballast condition along the railway bed can be profiled using a laser, radar or other instrument to create a profile map as a survey vehicle travels on the track. The current profile can be compared with a reference profile to detect when a zone is deficient in ballast and the location and amount of the deficiency. The controller can use this information to control the ballast doors in a manner to correct the deficiency. 
     The present invention additionally contemplates combining the steps of obtaining a survey and then applying ballast where needed in a separate operation. In this regard, a human operator on the ballast train can record when a spread zone is encountered and signal its location as well as the ballast requirements there. The controller then quickly adjusts the ballast door operation dynamically to apply the proper amount of ballast at each zone that is deficient. 
     Aerial photogrammetry techniques may also be employed in accordance with the invention, using satellite imagery or photogrammetry from manned or unmanned aircraft. 
     Other objects and advantages of this invention will become apparent from the following description taken in relation to the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. 
     The drawings constitute a part of this specification, include exemplary embodiments of the present invention, and illustrate various objects and features thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The present invention is described in detail below with reference to the attached drawing figures, wherein: 
         FIG. 1  is a diagrammatic view of a railway ballast spreading system embodying the present invention, shown implemented on a railcar. 
         FIG. 2  is a diagrammatic view of a hydraulic actuator subsystem for operating ballast hopper doors of the ballast spreading system. 
         FIG. 3  is a perspective view of a ballast hopper car adapted for use in the present invention. 
         FIG. 4  is an enlarged fragmentary perspective view of a ballast discharge control mechanism including a ballast door and hydraulic actuator therefore thereof. 
         FIG. 5  is a fragmentary diagrammatic view illustrating principal components of an alternative embodiment of a position control subsystem for use in present invention. 
         FIG. 6  is a block diagram illustrating principal components of a car control logic unit (CCU) which is installed on each hopper car of the present invention. 
         FIGS. 7 ,  8 , and  9  are interrelated flow diagrams which illustrate respective portions of the principal control functions of the car control unit (CCU) present on each hopper car of the present invention. 
         FIG. 10  is a flow diagram illustrating principal functions of a track survey routine of the present invention. 
         FIG. 11  is a flow diagram illustrating principal functions of a ballast train manifest routine of the present invention. 
         FIG. 12  is a flow diagram illustrating the principal functions of a ballast spreading control process of the present invention. 
         FIG. 13  is a flow diagram illustrating in more detail than  FIG. 12  the principal functions monitored and actions taken in the ballast spreading control process of the present invention. 
         FIG. 14  is a diagrammatic representation illustrating a ballast train for use in practice of the ballast spreading system of the present invention. 
         FIG. 15  is a diagrammatic representation illustrating a railroad track and spread sections intended to receive ballast spread by the present invention and no-spread sections which are not to receive such ballast. 
         FIG. 16  is a diagrammatic view of an implementation of the present invention using wayside markers and manual detecting of them to obtain location and speed data; 
         FIG. 17  is a diagrammatic view of an implementation of the invention using stored visual images and a visual recognition device to obtain location and speed data; 
         FIG. 18  is a diagrammatic view of an implementation of the invention using wayside reference points and laser techniques to obtain location and speed data; 
         FIG. 19  is a diagrammatic view of an implementation of the invention using radar techniques to obtain location and speed data; 
         FIG. 20  is a diagrammatic view of an implementation of the invention using onboard and wayside radio frequency transponders to obtain location and speed data; 
         FIG. 21  is a diagrammatic view of an implementation of the invention using magnetic referencing techniques to obtain location and speed data; 
         FIG. 22  is a diagrammatic view of an implementation of the invention using thermal sensing techniques to obtain location and speed data; 
         FIG. 23  is a diagrammatic view of an implementation of the invention wherein a profile device is used to obtain a current ballast profile along the railway bed for comparison with a reference ballast profile to detect areas of ballast deficiency; 
         FIG. 24  is a diagrammatic view of an implementation of the invention making use of aerial photogrammetry utilizing satellite imagery to survey railway bed conditions; 
         FIG. 25  is a diagrammatic view of an implementation of the invention making use of manned aircraft for aerial photogrammetry; 
         FIG. 26  is a diagrammatic view of an implementation of the invention making use of an unmanned aerial vehicle for aerial photogrammetry; and 
         FIG. 27  is a diagrammatic depiction of an inertial system and components thereof which may be used in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     Referring to the drawings in more detail, the reference numeral  2  generally designates a railway ballast application system embodying the present invention. The system  2  is also referred to herein as a ballast spreading system. Without limitation on the generality of useful applications of the system  2 , it is shown installed on a ballast train  3  ( FIG. 14 ) including a plurality of ballast hopper cars  4  for ballast spreading operations. 
     The system  2  may generally make use of an on-board position control subsystem  8 , a hydraulic actuator subsystem  10 , a ballast discharge mechanism  12  ( FIG. 4 ), an inertial system  14 , a GPS receiver  16  and a transponder/sensor system  18 . 
     The on-board position control subsystem  8  ( FIG. 2 ) is mounted on the railcar and operates with the transponder/sensor  18 , which obtains location and speed data. The system  18  can include a variety of different types of devices, as will be described in more detail. 
     The system  18  is connected to a control computer  20  which receives positioning data signals from the system  18 , processes same and interfaces with the actuator subsystem  10 . The control computer  20 , also referred to herein as a head end controller (HEC) can, for example, be a fairly conventional desktop or laptop type of personal computer, preferably with typical capabilities in currently available computers of this type. 
     The controller  20  includes decoder circuitry  21  which receives command signals addressed to specific hydraulic actuators or piston/cylinder units  32  in the actuator subsystem  10 . The output of the decoder  21  is input to a relay bank  26  with multiple relays corresponding to and connected to respective components of the hydraulic actuator subsystem  10 . The position control subsystem  8  is connected to a suitable, on-board electrical power source  22 , which can utilize a solar photovoltaic collector panel  24  for charging or supplementing same. Alternatively, the power source  22  may be a conventional DC charging bus, as is found on conventional trains for powering electrical subsystems on railroad cars. 
     The hydraulic actuator subsystem  10  ( FIG. 2 ) includes multiple solenoids  28  each connected to and actuated by a respective relay of the relay bank  26 . Each solenoid  28  operates a respective hydraulic valve  30 . The valves  30  are shifted between extend and retract positions by the solenoids  28  whereby pressurized hydraulic fluid is directed to the piston/cylinder units  32  for respectively extending and retracting same. The piston/cylinder units  32  can comprise two-way hydraulic units, pneumatic units, or any other suitable actuators. A hydraulic fluid reservoir  34  is connected to the valves  30  through a suitable motorized pump  36  and a pressure control  38 . 
     The ballast discharge mechanism  12  ( FIG. 4 ) includes four hopper door assemblies  40  (up to eight can be employed) installed on the underside of the hopper car  4  and arranged two (or four) to each side. The ballast hopper car  4  includes front and rear hoppers  41  ( FIG. 3 ), each with left and right discharge chutes  42  with in and out doors. A hopper door assembly  40  is installed at each discharge chute  42  and controls the flow of ballast  44  ( FIG. 15 ) therefrom. The hopper door assemblies  40  discharge the ballast  44  laterally and are adapted to direct the discharge inboard (toward the center of a rail track  5  between the rails) or outboard (toward the outer edges of the rail track  5 ). A more detailed description of the construction and function of the hopper door assemblies  40  can be found in U.S. Pat. No. 5,657,700, which is incorporated herein by reference. As shown in  FIG. 4 , each hopper door assembly  40  is operated by a respective hydraulic actuator  32  for selectively directing the flow of ballast  44  therefrom. 
     As will be described in more detail below, the position control subsystem  8  is preprogrammed with various data corresponding to the operation of the logistic system  2 . For example, discharge operations of the ballast discharge mechanism  12  can be programmed to occur at particular locations. Thus, ballast  44  can be applied to a particular section of rail track  5  by inputting the corresponding track coordinates and programming the position control subsystem  8  to open the hopper door assemblies  40  in the desired directions and for predetermined durations. The data obtained by the system  18  and used by the on-board position control subsystem  8  can provide relatively precise information concerning the position of the hopper car  4 . 
     The reference numeral  102  ( FIG. 5 ) generally designates a ballast spreading control system using a position control subsystem  104 . The position control subsystem  104  can comprise any suitable means for measuring the travel of a vehicle, such as the railcar  4 , and/or detecting its position along the rail track  5  or some other travel path. 
     The position control system  104  include a computer  106  which may interface with a transponder or sensor  108  for detecting position markers  110 . For example, the position markers  110  can be fixed wayside reference points located alongside the rail track  5  whereby the device  108  provides a signal to the computer  106  when the railcar  4  is positioned in proximity to a respective position marker  110 . The position control subsystem  104  can alternatively include an image sensor such as a camera  116  which optically or visually senses wayside images  112 . The computer  106  can interface with an hydraulic actuator subsystem  10 , such as that described above, to control the discharge of ballast  44  therefrom in relation to the detected position. 
     The material applying or ballast spreading system described above is principally directed to controlling the material spreading activities of a single rail car under position coordinate control by a computer. Ballast spread by a single car, or several such cars, can provide some utility in relatively small operations, such as small scale maintenance operations. However, rail maintenance is often a very large undertaking, involving hundreds or thousands of miles of tracks on a recurring basis. The present invention is adaptable to such larger scale rail maintenance operations. 
       FIGS. 6-15  illustrate an embodiment of the ballast spreading system  201  of the present invention. Referring to  FIGS. 14 and 15 , the system  201  includes a ballast train  3  including a locomotive  203 , a control car  204  (optional), and a plurality of ballast hopper cars  4 , as described above, positioned on a railroad track  5 . A typical ballast train  3  may include up to 100 hopper cars  4 . The system  201  includes a main computer or head end controller (HEC)  205 , a plurality of car control units (CCU)  207 , a location-detector  209 , and a network  211  interconnecting the HEC  205  with the CCU&#39;s  207 . The detector  209  is interfaced to the HEC  205  and provides a spatial reference of the ballast train  3 . Referring to  FIG. 15 , the system  201  is adapted for controlled and coordinated spreading ballast  44  (represented by cross-hatching in  FIG. 15 ) in spread zones  217  and inhibiting the spreading of ballast  44  in no-spread zones  219 , according to positions detected by the detector  209 . 
     The detector  209  outputs position data, such as latitude and longitude coordinates, in a format which can be further processed by the HEC  205 . 
     The HEC  205  may be a desktop or laptop type of personal computer. Currently available personal computers based on Pentium III (Intel) or AMD Athlon (American Micro Devices) class of microprocessors, or better, are adequate for use as the HEC  205 , although not specifically required. 
     The network  211  may be any suitable type of computer network to allow communication between the HEC  205  and the CCU&#39;s  207 , and possibly the GPS receiver  215 . In the system  201 , the network  211  is preferably based on the Lontalk and Neuron components and protocols of Echelon Corporation of Palo Alto, Calif. The network  211  may be a relatively low bandwidth network since only low data density control commands, status reports, and the like are required to be carried. Alternatively, other types of networks and communication protocols may be suitable for use in the system  201 . 
       FIG. 6  illustrates further details of a typical car control unit or CCU  207 . The CCU  207  includes a CCU controller  222  which may include a microprocessor or microcontroller in addition to other logic components and circuitry. The CCU controller  222  is connected by a parallel interface to the network bus  211 . The CCU  222  is interfaced through the DAM Tx relays which activate sensor inputs in adjacent cars. The CCU controller  222  is also interfaced through relay input/output logic  228  to hydraulic valves  230  which control operation of the front and rear sets of right and left hydraulic actuators  32 , which operate the ballast hopper doors  40 . The relay I/O logic  228  may also receive inputs from sensors  232  on the car  4 , such as DAM discrete inputs, door status switches, hydraulic pressure switches, and the like (not shown). As shown, the CCU controller  222  is interfaced through the relay I/O logic  228  to the car relays  224  and  226 , also referred to as DAM relays, and is able to selectively close the relays  224  and  226  for a purpose which will be detailed further below. 
     The CCU controller  222  is programmed for certain automatic functions, such as “dead man” type functions wherein the CCU controller  222  causes the associated ballast doors  40  to close after a communication timeout in which no data communications are received by the CCU controller  222  from the HEC  205 . This is a safety feature which causes the cessation of ballast spreading or prevents the initiation of ballast spreading in the event of loss of control communication. 
       FIGS. 7 ,  8 , and  9  illustrate the principal software functions  233  of the CCU controller  222 . Referring to  FIG. 7 , a hopper car “dead man” loop  234  is shown in which the CCU  222  waits for any command from the HEC  205  at  236  for a two second communication timeout at  238 . If no command is received, all ballast doors  40  are closed at  240 , manual control of the doors  40  is enabled at  242 , and control is returned to the wait function at  236  can process a door command at  244 , a DAM or car relay open command at  245 , a DAM relay close command at  246 , a set car ID (identification) command at  247 , a set car index command at  249 , a set NID (Neuron ID) response command at  250 , an HEC beacon command at  251 , a request NID command at  252 , a request car status command at  253 , or a request car data command at  254 . Although the commands  244  through  254  are shown in a sequence, the CCU controller  222  merely waits for one of the commands and processes it. Additionally, the connection or entry points X, Y, and Z are for graphic convenience. 
     Referring to  FIG. 7 , whenever the DAM relays  224  or  226  are closed, DAM input sensors on adjacent cars are activated. The car index command  249  is used set the sequential position of a car  4  on the ballast train  3 . The HEC beacon command  251  is normally broadcast periodically to all cars CCU&#39;s  207  at an interval of less than the two second dead man timeout interval to maintain the status quo of all functions. Thus, if a CCU  207  receives no other commands, it will periodically receive the HEC beacon  251 . The remaining CCU functions  233  are either self-explanatory or will be referred to in more detail below. 
       FIG. 10  illustrates a track survey process  260  for obtaining position coordinates for the spread zones  217  and no-spread zones  219  by surveying the track  5 . The process  260  may be carried out, for example, using a small vehicle such as a Hy-Rail vehicle which is driven along the track  5  with a location detector and a computer, such as the detector  209  and HEC  205 , on board. The process  260  receives position data at  262  from the detector  209  and updates the track definition data at  264  at 100 millisecond intervals determined by loop timer at  266 . At any time, the roadmaster or other operator conducting the survey may toggle a switch to indicate a change from a spread condition to a no-spread condition at  268 . The process  260  continues until it detects a command from the operator at  270  to end the survey process  260 . At that time, the geographic coordinate data gathered is stored in a track survey data file at  272 . 
     For the most part, the survey process  260  can gather all the required location data to conduct a ballast spreading run. In some circumstances, it may be necessary to conduct parts of the survey on foot to mark starting and ending locations of spread zones or no-spread zones. Additionally it may be necessary to mark some zones which are not appropriate for ballast spreading using the system  201 . For example, if multiple transitions from spreading to non-spreading status would be required, there may not be enough time to cycle the hydraulic actuators  32  because of lags in hydraulic fluid supply. In such circumstances, it may be necessary to spread ballast on such a zone by more conventional techniques. 
     In order to control the individual ballast doors  40  of the cars  4 , it is necessary for the HEC  205  to “know” the position of each door  40  relative to the reference point  215  and to be able to “talk” to or communicate with each individual hydraulic actuator  32 . The system  201  includes a train manifest process  280  ( FIG. 11 ) for querying the CCU&#39;s  207  to determine the order of the cars  4  and their forward or reversed orientation. The process  280  initially captures all the Neuron ID numbers (NID&#39;s) at  282  by broadcasting the request NID command  252  ( FIG. 9 ). The first CCU  207  to respond is placed in a non-responsive mode by the set NID response command  250  ( FIG. 9 ). The capturing routine  282  is repeated until no more responses are received. By the routine  282 , the HEC  205  is able to identify all the cars  4  with functioning CCU&#39;s  207 . 
     Next, a car sequence/orientation survey loop  284  is executed. In the loop  284 , the front DAM relay  224  and rear DAM relay  226  are sequentially opened, checks made for any responding CCU&#39;s  207 , and setting any responding CCU to a no response state. At  286 , the command is broadcast to a selected CCU&#39;s to open their front DAM relay  224 . A command for any CCU to respond at  288  is made. Any CCU which responds with its front DAM relay  224  closed is determined to be reversed. At step  290 , the car  4  with the responding CCU  207  is designated as a starting point for manifest and as reversed in orientation and is set to the no-response mode. A test is made at  294  for any responding CCU. If so, the car  4  with the responding CCU  207  is determined at  296  to be forwardly oriented, its Neuron ID is stored as the first car  4 , and the CCU responding is set to no-response mode. At test  298 , if all CCU&#39;s  207  have not been identified and the orientation of their cars  4  determined, the loop  284  returns control to step  286 . The loop  284  is repeated until all CCU&#39;s  207  which were identified in step  282  have been processed as to their sequential order and orientation. When that happens at  298 , the manifest data is stored as a manifest data file at  302 . 
       FIG. 12  illustrates the principal control functions of the system  201  in controlling the spreading of ballast  44  along the track  5 . In the system  201 , the length of surveyed track is divided into track unit lengths or “buckets”. The size of the buckets is arbitrary; however, in an exemplary embodiment of the system  201 , the buckets are equal to one foot lengths of the track  5 . It should be noted that the type of ballast doors  40  employed in the present invention can be opened inboard or outboard or both ways simultaneously. Thus, if it is desired to spread ballast both between the rails and outside the rails, it is then necessary to track the activities in relation to two parallel sets of buckets, inboard buckets and outboard buckets. However, in some maintenance practices, particularly those in which subsequent activities involve lifting the rails and ties to position the deposited ballast, it is only necessary to spread outside the rails. For illustrative purposes, the system  201  will be described in terms of a single set of buckets. 
     In the ballast spreading control process  310  shown in  FIG. 12 , a bucket preparation and initialization set  315  receives the track survey data file  317  and the ballast train manifest data file  319 . The manifest file  319  has been initialized with the average flow rate of ballast through the opened ballast doors at  321  and with the initial hopper ballast loads at  323 . The bucket initialization step  315  also receives a user input target bucket quantity  325  which may actually be derived from a tons per mile entry. The target bucket quantity  325  is the amount of ballast per foot of a track to be applied in the spread zones  217 . The bucket in no-spread zones  219  are initialized as full while the buckets in spread zones  217  are initialized at zero, or at another appropriate value if data has been inherited from a previous ballast spreading run. The process receives current geographic coordinate data  327  from the detector. Distances to each ballast door  40  are determined in relation to the train reference point coincident with the antenna detector  209 . 
     The illustrated ballast spread control process  310  initiates a ballast spread control loop  330  at 100 millisecond or tenth of a second intervals, as shown by the wait step  332 . During each loop  330 , the HEC  205  determines a reference track position at  334 , based on the location data, checks the state of all ballast doors  40  at  336 , checks the state of buckets at  338  which can be affected by a door  40  currently being checked, updates all the door states at  340  by either maintaining the status quo or changing the state as required by conditions detected or calculated, updates all bucket states at  342  which have changed by addition of ballast  44 . The control loop  330  continues until a test at  346  detects that the last bucket has been passed by the ballast train  3 , at which point control exists at  348  from the ballast spread control process  310 . 
       FIG. 13  shows additional details of the ballast spread control loop  330 . As part of determining the current track position  334  at a clock tick  322 , the current bucket number that the train reference  215  coincides with is determined at step  350  and a determination of the number of buckets moved since the last tick is made at  352 . The steps  350  and  352  enable a determination of train speed and shifts the sets of buckets referenced at each door state check  336  ( FIG. 12 ). The process  310  focuses on sets of buckets whose state of fill will be affected by the current state or potential change of state of a current ballast door  40  being checked. 
     The actual door state test at  354  determines if each ballast door  40  is currently open or closed. Depending on the detected state of the current door  40 , the process  330  will enter a closed door loop  356  or an open door loop  358 . 
     If the current door is closed, the closed door loop  356  checks a lookahead set of buckets at  360 . The lookahead set of buckets are buckets positioned at such a distance ahead of the current door that, at the currently detected train speed and with the known response lag of the actuator  32 , a change in door state “now” will begin to affect such lookahead buckets. The loop  356  considers a set of lookahead buckets since a given processing interval and train speed may so require. The set may also comprise a single bucket. The loop  356  calculates at  362  whether the current or actual fill of the test bucket plus a project fill from opening the current door would be less than the target fill for the bucket. If so, the current door  40  is opened  364 ; if not it stays closed at  366 . All buckets in the current lookahead set are processed until a test at  368  determines that the last bucket has been processed. Afterwards, the loop  356  advances to the next door at  370 . 
     If a door is detected as open at  354 , the states of fill of a set of buckets which will receive ballast from the currently open door in the current clock tick interval are updated at  372 . Afterward, the door open loop  358  is somewhat similar to the door closed loop  356  and includes a fill test  376  which determines if the actual fill of the lookahead buckets is less than the target fill. If not, that is the target is currently exceeded, the current door  40  is closed at  378 . If the test  376  is true, the door stays open at  380 . The lookahead loop exits at  382  when the last lookahead bucket for the current door  40  has been processed. Then the loop  358  proceeds to the next door at  384 . When the last door has been checked, as indicated by the test  386 , the process  330  waits for the next clock tick at  388 . 
     The door open loop  358  allows some overfill of the buckets. As a practical track maintenance matter, this is preferable to not enough ballast available. However, it is highly undesirable to spread ballast in a no-spread zone  219 , which may be a road crossing. Such an occurrence may constitute a road traffic hazard. For this reason, buckets in the no-spread zones always causes the current door  40  to be closed at  378 . 
     The logic of the closed loop fill test  356  is designed to cause multiple ballast doors  40  to open if appropriate to quickly fill the desired buckets. It is desirable to maximize the number of filled buckets in the system  201  rather than partially fill a larger number of buckets. 
     As the ballast is depleted from hoppers  41 , they are bypassed in processing and more rearward hoppers  41  are activated. Thus, ballast spreading proceeds from the forward hoppers  41  to the more rearward hoppers. 
     It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown. 
       FIG. 16  depicts an implementation constituting one technique for obtaining current train location and speed. A plurality of fixed wayside markers  400  are located at known positions along the railway. The markers  400  may be mile-markers that are commonly located along railroads at one mile intervals (or less in some cases). An input button  402  or another type of input device is located onboard the train and can be depressed or otherwise activated by an operator when he visually determines that the train has reached one of the markers  400 . Each time one of the markers  400  is reached by the train, the button  402  is depressed, and it provides a signal to the HEC  205  each time it is depressed. Because the locations of the fixed markers  400  are known, the HEC is thus provided with information as to the location of the train along the railway. Additionally, the HEC clocks the time between successive depressions of the button  402  and uses this information to calculate the train speed. The HEC then activates the ballast application system to open and close the ballast doors  40  in a manner to discharge ballast to the railway bed where necessary, as previous described. 
     In this manner, the mile markers  400  are visually detected, and a manual signal is provided by way of the button  402  to the HEC  205  so that the HEC can activate the control system in a manner to open the ballast doors when a spread zone is encountered and close the doors at the end of the spread zone. 
     In accordance with the system shown in  FIG. 17 , a number of stored visual images  404  are recorded and stored at known locations along the railway. The stored images are provided to a camera  406  or another visual sensor device on board the train. As the train travels along the railway, the camera obtains current visual images and compares them with the stored images  404 . When there is a match between a current image and a stored image, as indicated by blocks  406 ,  408  and  410 , the HEC  205  is signaled and thus becomes aware of the current location of the train. Also, the HEC  205  can calculate the train speed by clocking the time between successive matches with the stored images. The HEC then controls the application of ballast by opening the ballast doors in spread zones and closing the ballast doors when the spread zones have been traversed. 
       FIG. 18  depicts a modified system that makes use of an onboard laser  412  to obtain distance and speed information of the train. A series of reflectors  414  are spaced apart at known locations along the railway. The laser generates laser beams  416 . When these beams are intercepted by one of the reflectors  414 , a return beam  418  is reflected back to the laser  412 . The return signals  418  are decoded by suitable decode circuitry  420  using the time delay between the transmitted and return signals and the frequency shift to determine the current distance to each reflector  414  and the train velocity. This location and speed information is provided by the circuitry  420  to the HEC  205 . The HEC  205  then operates the ballast doors in a manner to apply the required amount of ballast to the ballast spread zones and discontinue the spreading when the end of each spread zone has been reached. 
       FIG. 19  depicts diagrammatically an alternative system that makes use of an onboard radar device  422  which may be of the type commonly used on roadways and the like by law enforcement organizations. A plurality of reference points  424  are established along the roadway at fixed and known locations. The radar device  422  transmits radar signals  426 . These signals are reflected as return signals  428  by the reference points  424  and received by the radar device  422 . A suitable interface  430  can be provided to the HEC  205 . The radar deice  422  uses the return signals  428  to determine the current location and speed of the train, and this information is provided to the HEC  205  through the interface  430 . The HEC then controls the hopper doors in order to apply ballast to the spread zones in the manner described previously. 
     With reference to  FIG. 20 , the train can be provided with an onboard radio frequency transponder  432 . Wayside radio frequency transponders  434  can be provided at known locations along the railway. The onboard transponder  432  transmits RF interrogation signals  436 . When one of the signals  436  is picked up by a wayside transponder  434 , that transponder sends an RF response signal  438  to the onboard transponder  432 . The response signals  438  can be used by the transponder  432  to determine the current location of the train as well as its velocity. The onboard radio transponder provides the location and velocity information to the HEC  205  so that the HEC can control the ballast doors in a manner to apply ballast sufficient to make up the deficiency in each spread zone. 
     The wayside transponders  434  can be either active or passive devices. If the transponders  434  are active devices, they require battery power or external power for operation. Such devices can be effective at distances in excess of one mile. Using passive transponders  434  has the advantage of being inexpensive and requiring no external power. The radiated power received by the interrogation signals  436  can be used by passive transponders for transmission of the response signals  438 . However, the range of such a passive device is typically between 15 and 50 feet for reliable operation. 
       FIG. 21  depicts a system that makes use of magnetic techniques to obtain the train location and speed. A suitable sensor  440  is carried on the train and is sensitive to variations in the ambient magnetic field. Magnets  442  can be placed along the railway or rail bed at known locations such that the sensor provides a signal to the HEC  205  each time one of the magnets  442  is encountered by the train. The HEC thus keeps track of the location of the train through signaling from the sensor  440  and can calculate the train speed by taking into account the time between successive signals. The HEC then controls the ballast doors in the manner previously described to apply ballast to spread zones in the proper amounts. 
     The sensor  440  can instead make use of variations in the earth&#39;s magnetic field at known locations along the rail bed. This type of sensor requires high sensitivity in order to interpret variations in the magnetic field of the earth reliably enough to provide dependable location information. Further, the effects of the rotation of the earth and gravitational disturbances from the moon need to be taken into account, along with other minute disturbances that can occur. However, such a system has the advantage that there is no need to place magnetic devices or other wayside devices along the railway. 
     Thermal sensing techniques can also be used.  FIG. 22  illustrates a system in which a thermal sensor  444  is mounted on the train. The sensor  444  may be provided with a reference thermal profile along the railway. As the train moves along the railway, the sensor  444  senses the current terminal profile along the railway, as indicated at  446 . By comparing the current thermal profile with the reference profile, the sensor  444  can detect the current location of the train and provide the location information to the HEC  205 . The HEC can compute the train velocity by taking into account the time required to move between different known locations along the railway. 
     Alternatively, the sensor  444  can make use of man made thermal devices that are located along the railway. For example, a heat generating engine  448  may be located at a known position along the railway. Street lights  450 , crossing signals  452 , traffic signals  454  and other miscellaneous wayside instrumentation, power units or buildings at known locations may also be sensed by sensor  444  and used to determine the train location. A particularly strong heat absorbing surface  458  along the railway may also be sensed to determine the train location. 
     The ballast spread zones are marked by an integrated GPS system as described, and the inertial system  14  serves as a backup system to the GPS system. As shown in  FIG. 27 , the inertial system  14  includes a fiber optic gyroscope  600 , a series of accelerometers  602 , tilt sensors  604 , and a Doppler sensor  606 . The inertial system  14  serves as a backup system to the GPS system and produces latitude and longitude coordinates in situations when a GPS signal is not received, such as when the train is in a tunnel. 
     The fiber optic gyroscope  600  detects changes in heading using known gyroscopic techniques and instrumentation. The accelerometers  602  act to detect changes in acceleration and deceleration. The tilt sensors  604  detect changes in vertical position perpendicular to the rails along which the train travels. The Doppler sensor  606  provides a wireless means for detecting the ground speed of the train. 
     These sensors and/or systems may be used together in various combinations or separately and independently to accurately and repeatedly mark spread zones along the railway and control the application of ballast to spread zones. 
     The present invention also contemplates a unique method and apparatus for surveying a railway bed. With reference to  FIG. 23 , this survey technique makes use of a reference profile of the terrain along the railway bed. A profiling device such as a laser or radar can be used to obtain the reference terrain profile  460 . The reference profile  460  represents an ideal ballast condition. A survey vehicle travels along the track carrying a profile device  462  which may be a device such as a laser or radar. The profile device  462  obtains a profile of the current ballast condition  464  and provides that information to the HEC  205 . The current ballast condition can be compared by suitable software with the reference profile to determine the location of each spread zone in which there is ballast deficiency, and the extent of the deficiency at each spread zone. In this manner, the location of each spread zone can be determined by the survey and stored so that the ballast spreading train can then travel along the railway and apply ballast in the necessary amount to make up the deficiency in each spread zone. 
     The present invention further contemplates a manual ballast application system in which the survey and application are done “on the fly”. In a system of this type, the group of interconnected rail cars are transported along the railway. A trained operator on board the train visually detects when a zone along the railway bed that is being approached by the train is deficient in ballast, along with the location of the zone and the extent of the ballast deficiency. The operator then signals the HEC  205  that a spread zone is being approached and provides information as to its location and the extent of the ballast deficiency. The controller then operates in the manner described previously to open or partially open at least one of the ballast doors when the no spread zone location is reached in order to discharge ballast at a rate sufficient to make up the deficiency of ballast at the spread zone. When the end of the spread zone is reached, the door is closed in order to discontinue the application of ballast to the railway pad. 
     Because the survey and application are combined using this technique, considerable time and expense are saved. However, relatively high level personnel are normally required to assure accuracy in the calling out of the spread/no spread zones along with the application rate requirements. Such a system finds its greatest utility in low risk spreading areas such as areas where there is an absence of no spread zones. 
       FIGS. 24-26  depict implementations of the invention that make use of aerial photogrammetry. In accordance with these embodiments of the invention, indications of areas along the railway bed that are deficient in ballast are determined by obtaining high resolution images of the railway from airborne locations. 
     Referring first to  FIG. 24 , a satellite  500  makes use of high technology photogrammetry having sufficient resolution to allow recognition of railway bed characteristics. By way of example, the satellite  500  may use known imaging technology to determine the location of a known landmark  502 . A DGPS grid  504  may be overlaid on a known location either at or a known distance from the landmark  502 . In this manner, the location of spread and no spread zones can be accurately identified, as can other railway conditions such as the location of track equipment, bridges, crossings and the like. Image updates can be determined by orbital satellite speed or by camera rotation speed for geostationary satellites. Restrictions can occur due to cloud cover or other atmospheric conditions, but even then, satellite imaging can be used as an effective backup for other surveying, including ground based surveying. 
     The ballast train  506  carrying one or more railcars that are operable to spread ballast in the manner previously described travels along a railway bed  508 . The train  506  obtains GPS information from a constellation of GPS satellites  510  and differential GPS correction information as an option. 
     Images that are captured at an airborne location by the satellite  500  with information indicating the location of the images can be directly transmitted to the ballast train  506 , and the onboard computer in the train  506  can automatically recognize track and roadbed requirements using image recognition. 
     Alternatively, the image information can be transmitted to a base station (not shown) where a more thorough analysis of the information can be performed. The base station can then transmit the analyzed information to the train that is used for spreading of ballast. 
     In this manner, the ballast train  506  is provided with accurate and reliable information as to locations of ballast spread zones that are deficient in ballast. Train  506  can then discharge ballast at the no spread zones as the railcars that carry the ballast are transported over the no spread zones. The image information captured by the satellite  500  can be used to determine the amount of ballast that needs to be applied in order to make up the deficiency in each zone that has a ballast deficiency. Consequently, the correct amount of ballast is discharged at the proper locations to make up for any deficiencies that are present along the railway bed  508 . 
     With reference to  FIG. 25 , aerial photogrammetry can also be implemented using manned aircraft such as the rotary winged aircraft  520  (or a fixed wing aircraft if desired). The manned aircraft  520  receives GPS information and makes use of a DGPS generated position grid  522  that may be located at or a known distance from a fixed landmark  524 . The aircraft  520  captures real time photogrammetric data using photographic images in the DGPS grid  522 . Analysis of the image and position data may be done onboard the aircraft using image recognition along with operator modifications or other techniques if necessary. In this fashion, the manned aircraft  520  determines the locations of ballast spread zones that are deficient in ballast. This information can be transmitted as indicated at  526  to a ballast spreading train  528  traveling along a railway bed  530 . Alternatively, the information can be transmitted from the aircraft  520  to an earth based station which then transmits the information to the ballast train  528 . 
     Using this technique, ballast train  520  can apply ballast from the railcars to each of the no spread zones that are deficient in ballast, and the correct amount of ballast can be applied in each instance. 
     Other photogrammetric methods can be used for survey data collection, including a remotely piloted vehicle (RPV) or an unmanned aerial vehicle (UAV) such as the vehicle  540  shown in  FIG. 26 . Use of a UAV (or RPV) provides close up observations of the railway conditions without the heavy payload requirement demanded by manned aerial vehicles. UAV  540  (or RPV) can receive GPS and differential GPS correction information. The use of alignment and orientation techniques allow the UAV  540  to compare this information to the graphic imagery collected from cameras that are onboard the vehicle  540 . Previously collected data can be used to establish reference points, and a DGPS grid  542  can also be used. The UAV  540  uses multiple data collection means to achieve its goal of data collection in either sunny or inclement weather. Among the techniques that can be used are laser or lidar, infrared, radar, and photogrammetry. The use of these techniques allows operation at all times of the day and in all but extreme conditions. 
     The UAV  540  (or RPV) may be sent out to survey the railway bed from a launching facility which may be the bed of truck  544  or a railcar formed as part of the ballast train  546 . The flight of the vehicle  540  is directed by the onboard computer in the ballast train or another land based vehicle such as the truck  540  or another land base. The vehicle  540  has geographical information stored onboard as well as automated flight control equipment that insures complete autonomy in data collection. It can also be monitored by a ground based system for flight course modifications or emergency situations. 
     The vehicle  540  obtains resolution images that provide information as to the locations of ballast spread zones along the railway bed  548  so that the ballast train  546  can apply the needed ballast to each ballast spread zone in the manner described previously. It is contemplated that information as to the locations of the ballast spread zones and the images captured by the vehicle  540  will be transmitted directly to the train as indicated at  550 . The information can be analyzed and used by the train  546  for the accurate application of ballast. 
     Unmanned vehicle  540  can be recovered by directing it to a landing facility using a predetermined landing sequence. Direct recovery from the launching vehicle  544  or other launching facility can also be implemented. 
     From the foregoing it will be seen that this invention is one well adapted to attain all ends and objects hereinabove set forth together with the other advantages which are obvious and which are inherent to the structure. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
     Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.