TECHNICAL FIELD 
       [0001]    This disclosure generally relates to train braking systems, and more particularly, relates to an automatic train braking system. 
       BACKGROUND 
       [0002]    Rail transportation is commonly used to move people and cargo. Trains of wheeled vehicles often provide a more efficient and timely means of travel than other forms of transportation. Material can be moved solely via rail, or can use rail transportation as a segment within an inter-modal system. Trains generally travel on one or more rails, but can also use other stabilization and directional devices, including electromagnetics. 
         [0003]    Trains are powered by one or more locomotives or powered cars, and are usually controlled by an operator. The operator is generally present on board the train, although other arrangements are possible. Propulsion can be provided by a variety of on-board motors, including reciprocating engines, turbines, electric motors, diesel-electric systems or electromagnetic systems. The energy source can be carried on board the train in the form of fuel or battery power. Alternatively, the train can draw power from an external system, such as overhead power lines or an additional electrified rail near ground level. 
         [0004]    The operator may control the train by manipulating manual controls or issuing vocal or electronic signals in a cab or a remote location. Trains may have a manual control mode where the train can directly respond to operator inputs regarding commands for applied throttle or other systems. Such a manual control mode may receive operator commands through a hand throttle, or other manual control. The operator may be located within the locomotive, or remotely relative to the locomotive. 
         [0005]    Alternatively, the train may be operated by an automatic drive system (ADS). An operator may elect to engage the ADS over operating the train using manual commands. The ADS may determine train settings for applied throttle or other systems, and it may select these settings using pre-set algorithms that optimize train performance variables in light of various factors or functional preferences. 
         [0006]    A train braking system, used to slow or stop the train, may also be controlled either manually or through an ADS. The braking system may use a pressurized brake pipe to control train braking. Alterations in the pressure within the brake pipe may allow a braking operation to occur. Such alterations may be triggered manually or by automatic systems. 
         [0007]    Kane (U.S. Pat. No. 7,772,2134) discloses a “Failsafe Electronic Braking System for Trains.” Kane describes a system for activating a pressure valve on a brake pipe in response to an overspeed signal, a loss of power to the train control system or a braking signal from the cab or an alerter. However, Kane does not describe a braking system that activates braking in response to a sensed brake pipe pressure. Further, Kane does not describe a redundant brake pipe sensor that may also activate a braking operation. 
         [0008]    Accordingly, there is a need for an improved braking system to ensure operability. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    In one aspect, a locomotive braking system is disclosed. The locomotive braking system may include a plurality of interconnected cars, a brake pipe extending through each of the plurality of interconnected cars and communicating a pressurized fluid, a pressure valve operatively associated with the brake pipe, a pressure sensor operatively associated with the brake pipe, the pressure valve being directed to reduce a pressure in the brake pipe in response to data from the pressure sensor, and a secondary pressure sensor operatively associated with the brake pipe, a pressure in the brake pipe being reduced in response to data from the secondary pressure sensor. 
         [0010]    In another aspect, a brake pipe is disclosed. The brake pipe may include a pressure valve operatively associated with the brake pipe, a pressure sensor operatively associated with the brake pipe, the pressure valve being directed to reduce a pressure in the brake pipe in response to data from the pressure sensor, and a secondary pressure sensor operatively associated with the brake pipe, a pressure in the brake pipe being reduced in response to data from the secondary pressure sensor. 
         [0011]    In another aspect, a method for altering a pressure of a brake pipe is disclosed. The method may include sensing the pressure in a brake pipe using a pressure sensor, directing a pressure valve to reduce a pressure in the brake pipe in response to data from the pressure sensor, sensing the pressure in the brake pipe using a secondary pressure sensor, and directing a secondary pressure valve to reduce a pressure in the brake pipe in response to data from the secondary pressure sensor. 
         [0012]    These, and other aspects and features of the present disclosure, will be better understood upon reading the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic side view of a train including a number of cars constructed in accordance with the present disclosure. 
           [0014]      FIG. 2  is a schematic diagram of elements which may be included in an embodiment of the present disclosure. 
           [0015]      FIG. 3  is a flowchart depicting a sample sequence of actions which may be practiced in an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring now to the drawings, and with specific reference to  FIG. 1 , a locomotive constructed in accordance with the present disclosure is generally referred to by reference numeral  10 . The locomotive  10  may include a cab  11 , a plurality of wheels  12  and an engine  13 , and may pull a train  14  consisting of a variety of cars  15  along one or more rails  17 . The engine  13  may consist of one or more reciprocating engines, turbines, electric motors or electromagnetic systems. A fuel or energy source can be carried on board the train  14  in the form of fuel or battery power, or can be positioned along the rails  17 . 
         [0017]    The locomotive  10 , or a powered car  15 , may power one or more of the wheels  12  in contact with the one or more rails  17 , propelling the train  14  along the rail  17 . An operator may be located within the cab  11 , train  14  or remotely relative to the train  14  in a remote operator station. The operator may issue commands to influence the performance of the train  14 . 
         [0018]    The locomotive  10  may include a manual mode of operation. In this mode, the operator may manually command settings which directly affect various train  14  actions and systems. The locomotive control interface  18  may include a manual control  20  and an electronic control  22 . Using the manual control  20  and electronic control  22 , an operator in the cab  11  may control the locomotive  10  and the train  14  settings. For example, the manual control  20  position may command a braking operation. Further, the electronic control  22  may be activated by an operator, entity or algorithm located at a remote location. 
         [0019]    For reducing train  14  speed, a braking system  26  may be provided on the train  14 . The braking system  26  may include a brake pipe  30 , which may pass through one or more cars  15 . The brake pipe  30  may contain pressurized air, or another fluid, which may be pressurized by a compressor  34 . Brakes  38  may be used to slow the rotation of one or more wheels  12 , thus slowing the speed of the train  14 . In one embodiment, the brakes  38  may be activated by a reduction in brake pipe  30  pressure. 
         [0020]    A braking control system  40  constructed in accordance with the present disclosure is shown in  FIG. 2 . The braking control system  40  may sense, analyze and command braking operations in response to a variety of inputs. A braking operation, or braking process, may be a reduction in brake pipe  30  pressure. Pressure in the brake pipe  30  may be reduced through a pressure valve  42  or a secondary pressure valve  46 . The pressure valve  42  and secondary pressure valve  46  may be solenoid valves. Further, pressure in the brake pipe  30  may be sensed by a pressure sensor  50  or a secondary pressure sensor  54 . The pressure sensor  50  and secondary pressure sensors  54  may be transducers. 
         [0021]    The braking control system  40  may also include a controller  58 . The controller  58  may be in electrical communication with the pressure valve  42 , secondary pressure valve  46 , pressure sensor  50 , secondary pressure sensor  54 , electronic control  22  and manual control  20 . In turn, the controller  58  may include a processor  62  and a memory  66 . The memory  66  may further include a primary algorithm  68  and a secondary algorithm  72 . Although shown in the memory  66 , the secondary algorithm  72  may be located in a different location or device. 
         [0022]    In operation, the train  14  may be traveling at a certain speed through various conditions. Braking ability may be a function of available brake pipe  30  pressure. Accordingly, to ensure adequate slowing and stopping ability, certain brake pipe  30  pressures may be treated as thresholds. Below such a threshold, the controller  58  may command a braking operation to ensure the train  14  is an appropriate speed. Further, the controller  58  may include more than one threshold. The thresholds may be determined based on a number of variables, including train  14  speed or composition, rail  17  condition, rail  17  layout, weather condition or other parameters, and they may further be determined based on the ability to perform different types of braking operations. Additionally, a first and a second threshold may be stored in the memory  66 , and each may vary according to the above-listed parameters. In one embodiment, the first threshold may correspond to a penalty braking threshold and the second threshold may correspond to an emergency braking threshold, although other thresholds and parameters are possible. A penalty brake may be a braking operation that cannot be reversed until the train  14  is not moving. An emergency brake may be a braking operation demanding the maximum stopping power provided by the braking system  26 . 
         [0023]    The memory  66  may also include a primary algorithm  68  and a secondary algorithm  72 . As the train  14  is operating, the first threshold regarding brake pipe  30  pressure may be continuously calculated by the controller  58 . Simultaneously, the brake pipe  30  pressure may be sensed by the pressure sensor  50 . Prior braking operations, or damage to the brake pipe or other components, may cause a drop in brake pipe  30  pressure. Accordingly, when the brake pipe  30  pressure drops below the first threshold, the pressure sensor  50  may signal the controller  58 . Upon receiving this data, the primary algorithm  68  may command the pressure valve  42  to decrease the pressure in the brake pipe  30 , thus slowing the train  14 . Alternatively, the pressure sensor  50  may send the data to an operator or other entity, who can then command a braking operation. 
         [0024]    Finally, upon an indication that the train  14  speed and brake pipe  30  pressure are now within acceptable bounds, the controller  58  may generate a confirmation signal that no further braking action is needed. Such an indication may come from the pressure sensor  50 , a time period elapsing, the pressure valve  42 , train  14  speed or another train  14  variable. 
         [0025]    As the train  14  is operating, the second threshold regarding brake pipe  30  pressure may also be continuously calculated by the controller  58 . Simultaneously, the brake pipe  30  pressure may be sensed by the secondary pressure sensor  54 . Prior braking operations, or damage to the brake pipe or other components, may cause a drop in brake pipe  30  pressure. Accordingly, when the brake pipe  30  pressure drops below the second threshold, the secondary pressure sensor  54  may signal the controller  58 . Upon receiving this data, the secondary algorithm  72  may command the pressure valve  42 , and/or the secondary pressure valve  46  to decrease the pressure in the brake pipe  30 , thus slowing the train  14 . Alternatively, the secondary pressure sensor  54  may send the data to an operator or other entity, who can then command a braking operation. 
         [0026]    In another embodiment, when the brake pipe  30  pressure drops below the second threshold, and no confirmation signal is generated by the controller  58 , the secondary pressure sensor  54  may signal the controller  58 . Upon receiving this data, the secondary algorithm  72  may command the pressure valve  42 , and/or the secondary pressure valve  46  to decrease the pressure in the brake pipe  30 , thus slowing the train  14 . Alternatively, the secondary pressure sensor  54  may send the data to an operator or other entity, who can then command a braking operation. 
         [0027]    In a further embodiment, when the brake pipe  30  pressure drops below the second threshold, and a time period has passed since the pressure sensor  50  signaled the controller  58  that the brake pipe  30  pressure fell below the first threshold, the secondary pressure sensor  54  may signal the controller  58 . Upon receiving this data, the secondary algorithm  72  may command the pressure valve  42 , and/or the secondary pressure valve  46  to decrease the pressure in the brake pipe  30 , thus slowing the train  14 . Alternatively, the secondary pressure sensor  54  may send the data to an operator or other entity, who can then command a braking operation. 
         [0028]    The system provides redundancy and automation to critical areas of train  14  operation, advantageously improving train efficiency and safety. By ensuring the train  14  slows upon a brake pipe  30  pressure drop past certain thresholds, operators are assured that a damaged brake pipe  30 , other damaged equipment or repetitive cyclic braking will not cause adverse situations. 
         [0029]    A method for altering a pressure of a brake pipe can best be understood by referencing the flowchart in  FIG. 3 . The method may comprise sensing the pressure in a brake pipe using a pressure sensor, as shown in step  300 . The method may also include directing a pressure valve to reduce a pressure in the brake pipe in response to data from the pressure sensor, as shown in step  304 , and sensing the pressure in the brake pipe using a secondary pressure sensor, as shown in step  308 . Further, the method may include directing a secondary pressure valve to reduce a pressure in the brake pipe in response to data from the secondary pressure sensor, as shown in step  312 . 
       INDUSTRIAL APPLICABILITY 
       [0030]    In operation, the present disclosure sets forth a braking system which can find industrial applicability in a variety of settings. For example, the disclosure may be advantageously employed in the automatic control of locomotives, or other vehicles. More specifically, a pressure sensor may sense a brake pipe pressure, and determine when said pressure falls below a first threshold. The determination may be sent to a controller, which may issue a braking command. Upon receiving an indication that the train speed and brake pipe pressure are now within acceptable bounds, the controller may generate a confirmation signal that no further braking action is needed. 
         [0031]    As a train is operating, a second threshold regarding brake pipe pressure may also be continuously calculated by the controller. Simultaneously, the brake pipe pressure may be sensed by the secondary pressure sensor. Prior braking operations, or damage to the brake pipe or other components, may cause a drop in brake pipe pressure. Accordingly, when the brake pipe pressure drops below the second threshold, the secondary pressure sensor may signal the controller. Upon receiving this data, the secondary algorithm may command the pressure valve, and/or the secondary pressure valve to decrease the pressure in the brake pipe, thus slowing the train. Alternatively, the secondary pressure sensor may send the data to an operator or other entity, who can then command a braking operation. 
         [0032]    The system provides redundancy and automation to critical areas of train operation, advantageously improving train efficiency and safety. By ensuring the train slows upon a pressure drop beyond certain thresholds, operators are assured that a damaged brake pipe, other damaged equipment or repetitive cyclic braking will not cause adverse situations. 
         [0033]    The disclosed system braking system may be original equipment on new machines or locomotives, or added as a retrofit to existing machines or locomotives.
A braking system includes a brake pipe, a pressure sensor and a pressure valve, each operatively associated with the brake pipe. The pressure valve is directed to reduce a pressure in the brake pipe in response to data from the pressure sensor, and a secondary pressure sensor is operatively associated with the brake pipe, wherein a pressure in the brake pipe is reduced in response to data from the secondary pressure sensor.