Abstract:
A compressed air braking system for a railcar and railcar moving vehicle combination. The railcar moving vehicle comprises a modified semi-tractor configured to ride on railroad track and couple to a railcar, having a conventional pneumatic braking system for braking itself, and a conventional pneumatic trailer brake system for providing compressed air for actuating the brakes of a semi trailer. In accordance with the invention, the brake line connecting the railcar brake system to the railcar brake cylinder is disconnected, and in its place the trailer brake line is connected directly to the brake cylinder of the railcar, whereby the railcar brakes may be actuated independently or in concert with the tractor brakes by an operator of the modified semi-tractor using either the standard brake pedal or a separate trailer brake lever.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to braking systems for railcars. More particularly, the present invention relates to an improved braking system for a lightweight railcar moving vehicle comprising a modified semi-tractor wherein the braking system of the connected railcar(s) is connected to and actuated by the compressed air braking system of the semi-tractor. 
     2. State of the Art 
     In the railroad industry, maintenance of way is a critical activity and a major expense. Frequently, when maintenance is needed at a particular location along the right-of-way and heavy equipment or materials are required, a work train and crew are sent to that location to perform the needed repairs. For example, a work train may carry a load of railroad ties and short sections of rail for repairing track, along with heavy equipment for unloading and installing these items. Often, a work train consists of a locomotive pulling a single work car, and the maintenance work can be performed by one or two workers. 
     However, this approach can be very cost inefficient. Because maintenance of way crews and locomotive crews are differently trained and unable to perform each other&#39;s duties, the work train will frequently employ a crew much larger than actually needed at any given time. Obviously, this is costly. Furthermore, the use of a typical locomotive—which may cost in excess of a million dollars—to transport a single car and a few workers is extremely cost inefficient. For these reasons, it would be desirable to have a railcar moving vehicle that can pull one or a few railcars along the railroad track at mainline speeds, but that is not a conventional locomotive, and thus is not as costly as a locomotive, nor requires a full locomotive crew. With such a vehicle, a work crew could transport themselves to the work site with their materials and equipment, and perform the work with far less expense. 
     Additionally, it would be desirable to have such a railcar moving vehicle that is operable both on rails and on roadways. Such a vehicle would be valuable for maintenance of way crews by allowing a work crew to transport themselves and their equipment by highway to a rail siding, where the crew simply transfers their materials and equipment to a waiting railcar, and uses the semi-tractor on the rails to pull the railcar to the work site. 
     This sort of vehicle would have additional uses, as well. For example, many railroad customers have a need to move railcars and highway trailers within a rail yard or industrial siding. However, except for the largest industries, the cost to purchase and maintain a conventional switching locomotive is prohibitive or economically unwarranted. Thus, lightweight, multipurpose railcar moving vehicles have been developed and used to perform many functions normally assigned to switching locomotives, but which may also be used off the track to move trailers and containers about a switching yard or industrial site. Such modified or hybrid vehicles are more economical for many industries because of their relatively low cost and high versatility. They allow smaller industries to take advantage of the efficiency and economy of rail transport for heavy freight where otherwise they would not be able to do so. 
     However, conventional railcar moving vehicles are still relatively highly specialized, limited production vehicles. The cost per horsepower of these vehicles is significantly higher than the cost of a conventional semi-tractor, for example, which enjoys the cost advantages of much greater mass production. Additionally, conventional railcar moving vehicles are not designed or configured to operate on public highways as long or short haul trucks, but are confined to the industrial site or switching yard. Many of them do not have the functional and safety equipment required to be street legal, and are designed for low speed operation only, being unable to travel at speeds beyond 15 to 20 miles per hour. Moreover, they cannot operate at top speed for extended periods of time without overheating their hydraulic systems. To address these problems, railcar moving vehicles which are constructed from mass produced vehicles such as semi-tractors have been devised to reduce the acquisition cost and versatility of these vehicles. 
     Normally, the brakes of railroad cars are linked through a common line to the locomotive, which provides pressurized air to operate the braking system of all attached railroad cars. However, when a lightweight railcar moving vehicle such as a modified semi-tractor is coupled to a standard railcar, braking is a major concern. Because a single loaded railcar may weigh many times more than the lightweight railcar moving vehicle, the lightweight vehicle will be able to provide only a small fraction of the braking force needed for stopping in a reasonable distance, especially in an emergency. Obviously, it is desirable to utilize the railroad car brakes in order to take advantage of the weight of the railcar in braking. Conventional railcar moving vehicles known in the art do this by providing a compressed air link to the brake pipe of the connected railcar, thus using the railcar&#39;s braking system to stop. 
     A schematic diagram of a conventional railroad car braking system is given in FIG. 1, which depicts a string of conventional railcars  10  having steel wheels  12  riding on steel rails  14 , and coupled together by couplers  16 . Each railroad car  10  has installed thereon a brake pipe  18 , piston valve  20 , reservoir  22 , and brake cylinder  24 . The brake pipe  18  is in fluid communication with the piston valve  20  through valve  26  which can be opened or closed to allow or prevent compressed air in the brake pipe  18  to pass. Under normal conditions, and as shown in FIG. 1, valve  26  is open. Two conduits  28  and  30  connect the piston valve  20  to the reservoir  22 , and one similar conduit  32  connects the piston valve  20  to the brake cylinder  24 . The brake cylinder  24  comprises an actuating rod  34  which extends from the cylinder and is axially reciprocally moveable depending on the pressure in the brake cylinder  24 . This actuating rod  34  is connected via a mechanical linkage  35  (not shown in its entirety) to the individual brake actuators  36  on each wheel  12  of the railcar in a manner well known in the art. 
     The brake pipe  18  is connected to the brake pipes  18  of both preceding and following railcars  10 , by flexible hoses  38 . It will be appreciated that any railcar  10  may be connected to a locomotive and the brake pipe of the locomotive, rather than another railcar, in the same manner. 
     The typical railcar braking system thus shown operates in the following manner. The locomotive provides compressed air to the brake pipe  18  which communicates along the entire length of the train. Railcar braking systems typically maintain a running pressure of 90 psi in the brake pipe and associated components. With valve  26  open, this operating pressure is maintained within piston valve  20 , conduit  28 , and reservoir  22 . In a non-braking condition, the pressure in conduit  32  is less than that in the brake pipe and other components mentioned, and is approximately equal to atmospheric pressure. 
     To actuate the brakes of the railcar, the locomotive engineer moves a brake actuating lever (not shown) which opens a valve to allow pressure to escape from the bake pipe  18 . Because the brake pipes of all connected railcars are in fluid communication, this action simultaneously releases the pressure in the brake pipes of all connected railcars. When pressure is released from the brake pipe  18 , the change in pressure actuates the piston valve  20  to close off its connection to the brake pipe, and simultaneously release compressed air from the cylinder  22 , through conduit  30 , thence into conduit  32  and the brake cylinder  24 . This actuation thus prevents compressed air from reservoir  22  from escaping through the brake pipe, but sends it instead to the brake cylinder  24 . Pressurization of brake cylinder  24  in turn causes actuating rod  34  to extend, thus mechanically actuating the brakes  36  of the railcar. 
     To release the brakes, the system must regain its operating pressure. This requires that the engineer move the brake lever back to the position which will close the release valve, so that the compressor on the locomotive may repressurize the system. Repressurization requires that pressure be built up in all components of all railcars—the brake pipe  18 , piston valve  20 , and reservoir  22 . As pressure in the brake pipe increases, the piston valve  20  changes position such that reservoir  22  is repressurized, and the pressure in the brake cylinder  24  is simultaneously released. 
     The design of this braking system provides a “failsafe” design because while the brake cylinders operate by means of pressurized air, the system which powers these cylinders is actuated by the release of pressure, not the maintenance of pressure. Thus, a leak anywhere in the system (except in an individual brake cylinder) will automatically cause the brakes to be applied on the entire train. For example, if two connected railcars become uncoupled, the connecting hoses  38  will pull apart, causing the pressure in the brake pipe  18  to be released. This rapid pressure drop will cause the full pressure of the reservoir  22  of each railcar to immediately actuate the brakes on each railcar. It will be apparent that the actuating pressure of the brake cylinder  24  will be something less than the operating pressure maintained in the cylinder  22  because of the need to pressurize a larger volume (both the reservoir  22  and the brake cylinder  24 ) using the compressed air in the reservoir  22 . 
     However, conventional railroad car braking systems suffer from several problems in their normal operating mode, which adversely affect operation when connected to a lightweight railcar moving vehicle, especially for maintenance work. First, due to the “failsafe” design, it is rather slow to react. Brake actuation is a two step process, requiring the release of pressure from the brake pipe common to all connected railcars before the brake cylinders begin to actuate. This can involve a substantial volume of air, which takes time to release through the single release valve in the locomotive. Additionally, because of this slow reaction time, a train that has just braked to a stop cannot quickly release its brakes and resume movement again. Obviously, this slow braking system reaction time will slow down the work of a maintenance crew. 
     Moreover, frequent stopping and starting is problematic with conventional railcar braking systems. Each time the brakes are applied, some portion of the compressed air in the system is released. If the brakes are applied several times in close succession, enough of the pressure in the brake reservoirs can be bled away that the brakes become inoperable until the system regains its operating pressure. This can take a substantial amount of time, potentially leaving a moving train without brakes, and possibly creating a “runaway” train. This is a particular nuisance when using a lightweight railcar moving vehicle for maintenance of way operations where very brief stops are required at locations very close together, such as to throw rail switches, or to set out or pick up railroad ties or other track material. 
     Semi-tractors normally include compressed air systems for powering the brakes of a standard highway trailer. However, these are actuated by means of providing high pressure air, not by releasing it. Accordingly, it is apparent that the respective braking systems of the train and semi-tractor operate in directly opposite manners. Nevertheless, it would be desirable to have a braking system for a lightweight railcar moving vehicle constructed from a conventional semi-tractor, wherein the compressed air system for providing braking power to a highway trailer is adapted to power the braking system of a railroad car, and the braking system for the railcar may be actuated by the same means that actuates the highway trailer brakes on conventional semi-tractor trailer combinations. It would also be desirable for a lightweight railcar moving vehicle to have a braking system that uses the brakes of the railcar, but does not rely on the slow reaction time of the railcar braking system. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a braking system for a railcar moving vehicle that has been constructed from a semi-tractor, wherein the braking system of the connected railcar is connected to and actuated by the compressed air system of the semi-tractor. 
     It is another object of this invention to provide a braking system for a railcar moving vehicle wherein the braking system of the connected railcar is actuated by the same means which actuates the trailer brake for a conventional highway trailer. 
     It is another object of this invention to provide a braking system for a railcar moving vehicle that uses the brakes of the railcar, but does not rely on the slow reaction time of the railcar braking system. 
     The above and other objects are realized in a preferred embodiment of a compressed air braking system for a railcar and railcar moving vehicle combination. The railcar moving vehicle comprises a modified semi-tractor configured to ride on railroad track and couple to a railcar, having a conventional pneumatic braking system for braking itself, and a conventional pneumatic trailer brake system for providing compressed air for actuating the brakes of a semi trailer. In accordance with the invention, the brake line connecting the railcar brake system to the railcar brake cylinder is disconnected, and in its place the trailer brake line is connected directly to the brake cylinder of the railcar, whereby the railcar brakes may be actuated independently or in concert with the tractor brakes by an operator of the modified semi-tractor using either the standard brake pedal or a separate trailer brake lever. 
     In an alternative embodiment, the modified semi-tractor is provided with a secondary brake system for use in concert with the above mentioned brake system when two or more railcars are coupled to said modified semi-tractor. The previously mentioned brake system is connected to the first railcar, while the secondary brake system provides compressed air to the brake pipes of the second and subsequent attached railcars through the brake pipe of the first railcar. A valve is closed in the system of the first railcar so that the brake pipe of the first railcar is isolated from the modified braking system thereof. A railcar brake controller is provided to allow selective release of air pressure in the brake pipe to actuate the brakes of the second and subsequent railcars in the manner of conventional railcars. 
     The above and other objects and features of the present invention will be apparent to those skilled in the art, based on the following description, taken in combination with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings: 
     FIG. 1 is a schematic diagram of a conventional railcar braking system; 
     FIG. 2 is a schematic diagram of the railcar braking system of the present invention for use with a modified semi-tractor railcar moving vehicle; 
     FIG. 3 is a side view of a semi-tractor configured for use as a railcar moving vehicle and coupled to a railcar and provided with a railcar braking system in accordance with the present invention; and 
     FIG. 4 is a schematic diagram of an alternative embodiment of the railcar braking system of the present invention configured for use with two or more railcars coupled to the railcar moving vehicle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings: 
     FIG. 2 provides a schematic diagram of a pneumatic railcar braking system according to the present invention. This braking system is configured for use with a modified semi-tractor railcar moving vehicle  50  coupled via coupler  16  to a modified railcar  110 . The modified railcar  100  has a braking system substantially similar to that of the standard railcar  10  shown in FIG. 1, which comprises a brake pipe  18 , piston valve  20 , reservoir  22 , and brake cylinder  24 . It will be apparent that additional railcars may be coupled to the opposite end of railcar  110  if desired, in the conventional manner. The railcar moving vehicle  50  is a modified semi-tractor having a cab  52 , and steel wheels  54  and  55  which are configured for riding on the rails  14 . The modified semi-tractor has a conventional pneumatic braking system comprising a compressor  56 , master reservoir  58 , and controller  60 . Typical master reservoirs have a capacity of approximately 100 gallons (˜13.4 ft 3 ), and typical semi-tractor compression systems are capable of attaining a peak pressure of approximately 120 psi. 
     The controller  60  receives compressed air from the master reservoir  58 , and receives control input via electrical, mechanical, or hydraulic linkages  62  and  64  from the semi-tractor brake pedal  66  and trailer brake lever  68 . In many semi-tractors the trailer brake lever  68  is conveniently mounted on the steering column  70  as shown in FIG.  2 . The controller  60  has a first pneumatic output  72  which communicates with the pneumatic braking actuator (not shown) of each wheel  54  of the semi-tractor for normal braking thereof. The controller  60  also has a second pneumatic output  74  which provides compressed air for actuation of a trailer brake. 
     The brake compressor  56 , master reservoir  58 , controller  60 , first pneumatic output  72 , and brake actuators associated with wheels  54  and  55  collectively comprise the tractor braking system. The compressor  56 , master reservoir  58 , controller  60 , and second pneumatic output  74  collectively comprise the trailer brake system. 
     When operating the semi-tractor in its conventional manner to pull a highway trailer, the second output  74  is connected to the highway trailer to power the brakes thereof. However, in an advantageous feature of the present invention, when the railcar moving vehicle is configured for pulling a railcar as in FIG. 2, conduit  32  which normally supplies compressed air from the railcar reservoir  22  to the railcar brake cylinder  24  is disconnected, and the second output  74  is connected directly to the railcar brake cylinder  24  by hose  76  for directly providing compressed air from the railcar moving vehicle  50  to the railcar brake cylinder. In this configuration, valve  26  is closed, such that the braking system of car  110  does not communicate with the brake pipe  18 . It will be apparent that the connecting hose  38  of the brake pipe  18  is not connected to any compressed air source. 
     It will be apparent to those skilled in the art that various additional components of conventional railroad braking systems such as pressure gages, pressure release valves, check valves, and so forth, will be employed in the system thus described to create a complete and workable system. Naturally, these additional components may be incorporated in a variety of configurations which will serve the purposes of the present invention. The present disclosure is intended to indicate the essential elements of the invention, without repeating all additional elements which could be included, and are well known in the art. 
     This system advantageously allows the driver of the railcar moving vehicle to directly apply the brakes of the railcar by depressing the brake pedal  66  of the semi-tractor. Alternatively, the driver may apply the brakes of the railcar alone by using the trailer brake lever  68 . Because the railcar may weigh much more than the railcar moving vehicle, sufficient braking force may be generated in this manner alone. Using either method, however, the railcar brakes may be actuated in the same manner that truck brakes are actuated, such that an individual with truck driving skills needs no additional training to operate the brakes of the railcar moving vehicle. Additionally, because the semi-tractor&#39;s braking system is directly connected to the railcar brake cylinder  24 , the reaction of the brakes is much faster, and the brakes may also be released much faster. 
     FIG. 3 provides a side pictorial view of the railcar moving vehicle of the present invention. The railcar moving vehicle  50  comprises a modified semi-tractor having an elongate frame  80 , a cab  52  housing the truck engine and controls, and standard fifth-wheel assembly  82  for pivotally connecting the tractor to a conventional highway trailer (not shown). However, to function as a railcar moving vehicle, the semi-tractor is provided with drive wheels  55  located toward the rear of the frame  80 , and typically smaller guide wheels  54  to support the front of the vehicle. It will be apparent that the drive wheels  55  must be affixed to the drive axles of the tractor so as to propel the vehicle. As shown in FIG. 3, the vehicle  50  is also provided with unpowered rubber tired auxiliary wheels  85  which are common on large trucks, and which may be selectively raised and lowered by hydraulic or pneumatic means for contact with a roadway so as to spread the weight when the truck is carrying a particularly heavy load. It will be apparent that when configured for use as a railcar moving vehicle, the rubber-tired wheels  84  used for highway operation are removed. 
     Attached to the rearward portion of the frame  80 , immediately behind the fifth wheel assembly  82 , is a coupler  16  and drawbar  86  for coupling to a typical railcar, such as a boxcar  110  as depicted in FIG.  3 . The coupler  16  and drawbar  86  are typically connected to the frame  80  by means of a hydraulic lifting mechanism, indicated generally at  88 , which allows an upward force to be applied by the railcar moving vehicle  50  to the front of the railcar  110 , so as to transfer a portion of the weight of the railcar  110  to the railcar moving vehicle  50  in order to give the railcar moving vehicle sufficient traction. 
     The components of the air compression brake system as shown in FIG. 2 are not entirely shown in FIG.  3 . However, the controller  60 , the brake pedal  66 , and trailer brake lever  68  are schematically shown in this view. On conventional semi-tractors, the second outlet  74  typically terminates in a coupler  90  located on the back of the cab  52 . This coupler is designed for the connection of a trailer brake line. In the present invention, hose  76  is connected to coupler  90 , and extends backward along the vehicle frame  80  to the railcar  110 . There, the hose  76  is connected directly to the brake cylinder  24  of the railcar (not shown in FIG.  3 ). As shown in FIG. 3, the hose  76  is preferably disposed along the inboard side of the frame  80 , but may be connected in any suitable manner. It will be apparent that hose  76  must have adequate flexibility to accommodate the motion and variable positions of the hydraulic lift mechanism  88 . 
     FIG. 4 is a schematic diagram of an alternative embodiment of the railcar braking system of the present invention. This embodiment is configured for use when two or more railcars are coupled to the railcar moving vehicle. In this embodiment, the railcar moving vehicle is provided with a secondary compressed air system for powering conventional railcar brakes. The system may be powered by the same compressor  56  as the truck brake system, assuming this system has adequate power and capacity. Alternatively, a secondary compressor may be provided for supplying pressurized air to the secondary railcar braking system. If one compressor is used, it is connected both to the main reservoir  58 , and a secondary reservoir  92 , preferably separated by a check valve  100  or other pressure regulating mechanism to allow different pressures to reside within main reservoir  58  and the secondary reservoir  92 . 
     The secondary reservoir is connected to a secondary controller  94 , which receives input from a railroad brake switch  96 , located in the cab  52  of the vehicle. The brake switch  96  may comprise a multi-position electrical switch, or may comprise a multiple valve assembly for selectively releasing pressure from the secondary reservoir  92 . In embodiment of FIG. 4, the first railcar is the modified railcar  110  having its brake cylinder  24  directly connected to the truck braking system. However, the second railcar  10  (and subsequent railcars, if any) have a conventional railcar brake system as in FIG. 1, which is powered by the secondary brake system. The secondary controller  94  provides compressed air to line  98 , which leads to a connecting hose  38 , which in turn connects to the brake pipe  18  of the first railcar  10 . However, with the valve  26  of the first railcar in the closed position, the pressure in the brake pipe has no effect on the first car  10 . However, the brake pipe  18  of the first car communicates with the brake pipe  18  of the subsequent cars, so as to power the pressurized brake system of those cars as described with regard to FIG.  1 . 
     The brake switch  96  will preferably have Run, Brake, and Emergency modes for controlling the railcar brake system for these subsequent cars, similar to the configuration of braking systems in conventional locomotives. In the Run mode, full pressure is maintained in the brake pipe  18 , which keeps the brakes of railcars  10  disengaged. When the operator moves the brake switch to the Brake mode, pressure is gradually released from the brake pipe  18 , to cause the brakes of the second and subsequent cars to engage any desired amount. In the Emergency mode, all pressure is rapidly released from the secondary brake system, causing immediate maximum braking of all connected cars. 
     The railcar moving vehicle described herein is very economical because it may be used both on and off of the rails. Also, because it is a modified semi-tractor, rather than a limited production specialty vehicle, the economics of mass production help to keep its cost relatively low. The greatest advantage, however, is the avoidance of the need to provide an additional compressor system to power the brakes of a railcar, and the use of the conventional truck braking control mechanisms located in the cab of the semi-tractor. These controls allow an operator familiar with large trucks to safely and easily apply the brakes of a railcar to provide more effective braking with a lightweight railcar moving vehicle. In addition, the hybrid embodiment utilizing a secondary pneumatic system allows the railcar brakes of a second and subsequent coupled railcars to be operated by the operator of the railcar moving vehicle. 
     It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements.