Abstract:
A pneumatic control system for a freight car having a brake pipe, auxiliary and emergency reservoirs normally charged with pressurized fluid from the brake pipe, a fluid pressure activated brake cylinder device and an exhaust including an electronic controller, at least one pressure sensor, an electrically operated supply valve controlled by the electronic controller selectively communicating the brake cylinder with one of the reservoirs to perform a brake application, an exhaust valve selectively communicating the brake cylinder with the atmosphere thereby performing a brake release function, and an electronically operated exhaust latching valve controlled by the electronic controller to selectively signal the exhaust valve to connect the brake cylinder to the exhaust.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates generally to train brakes and, more particular, to a pneumatic control system for use with electronically controlled and non-electronically controlled train brakes. 
     Traditional train brakes utilize compressed air entering a brake cylinder to actuate each cars brakes. A normally pressurized brake pipe extends the entire length of the train and is used as a control signal such that a reduction in air pressure in the brake pipe causes the brakes to actuate. Each car has a reservoir of compressed air to power the brake cylinders. While the system has satisfactorily functioned in the past, certain deficiencies exist. 
     Due to the substantial length of many freight trains, the use of pressure drop as an actuation signal sometimes cause undesirable results. Specifically, a substantial amount of time is required for the pressure drop to propagate from car to car. The pressure drop propagation lag causes a corresponding delay in the application of brakes on each subsequent car. Unfortunately, the brake actuation delay increases the train stopping distance. 
     To avoid the time lag between first signaling for a brake application and when the last brakes apply, each of the car brakes would optimally apply simultaneously to achieve the shortest possible stopping distance. As such, electronically controlled brakes are highly desirable. Unfortunately, the cost of equipping each existing railway car with an electronic brake system is very high. Additionally, implementation of such a change would take years to achieve. It would also be difficult to assure that each and every car was equipped with the proper electronics. 
     Therefore, it is desirable to produce a pneumatic control system capable of using electronic or brake pipe pressure signals to actuate the brakes of a train car. Such a system is able to take advantage of electronically braked cars while also utilizing a brake pipe pressure drop to actuate the brakes in non-electronically controlled cars. 
     Accordingly, the pneumatic control system of the present invention operates in at least three separately definable modes. Firstly, the brake control system is operable without the use of electrical power. In this pneumatic mode, the brakes are actuated once a pressure drop in the brake pipe causes motion of certain pneumatic valves. Secondly, the brake control system of the present invention is operable in an electronically controlled pneumatics mode where each brake is operated via an electronic signal. Lastly, the system may operate in an emulation mode. Cars equipped with the pneumatic control system of the present invention operating in emulation mode electronically sense brake pipe pressure. Based on the rate of pressure drop, the brakes are actuated accordingly as will be described in greater detail hereinafter. The pneumatic control system also electronically signals a valve to exhaust the brake pipe on each car so equipped. The further exhaustion of brake pipe assists in sending the brake pipe signal down the train in an expedited manner. Cars in the train that are not equipped with the present invention will be signaled with a brake pipe pressure drop. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a schematic of a pneumatic control system constructed in accordance with the teachings of the present invention; 
     FIG. 2 is a schematic depicting the pneumatic control system in the present invention in a pressurized condition; 
     FIG. 3 is a schematic depicting a service brake application; 
     FIG. 4 is a schematic depicting service brake release; 
     FIG. 5 is a schematic depicting a first-time segment of an emergency train stop in accordance with the teachings of the present invention; 
     FIG. 6 is a schematic of a second-time segment of the emergency train stop of FIG. 5; 
     FIG. 7 is a third-time segment of the aforementioned emergency train stop; 
     FIG. 8 is a fourth-time segment of the emergency train stop; 
     FIG. 9 is a fifth and final segment of the emergency train stop condition; 
     FIG. 10 is a schematic of the pneumatic control system of the present invention depicting the valve positions and flow paths corresponding to a manual vent valve in a second position; 
     FIG. 11 is a schematic showing the manual vent valve after it has been released from the second position as in FIG. 10, but at a later time; 
     FIG. 12 is yet another schematic depicting the manual vent valve after it has been released from the second position at a time after FIGS. 10 and 11; 
     FIG. 13 is a schematic depicting the manual vent valve in a third position; 
     FIG. 14 is a schematic showing the exhausting of the reservoir while the manual vent valve is in the third position; and 
     FIG. 15 is a schematic depicting the pneumatic control system of the present invention in a fully exhausted condition. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, a pneumatic control system constructed in accordance with the teachings of the present invention is generally identified at reference numeral  10 . Pneumatic control system  10  is depicted in schematic form using standardized pneumatic and fluid system symbols. It should be appreciated that each car of a freight train is preferably equipped with similar pneumatic control systems  10 . Accordingly, only one pneumatic control system  10  will be described in detail. 
     Pneumatic control system  10  includes a block manifold  12  having a service side  14  and an emergency side  16 . Pressurized air is supplied from a brake pipe  18  which extends substantially along the entire length of the train. Brake pipe  18  is plumbed to a brake pipe port  20  on service side  14  and a port  22  on the emergency side. Brake pipe  18  is also coupled to ports  24  and  26  via a filter  28 . 
     Pneumatic control system  10  functions to provide service brake applications and emergency brake applications via electronic input or pneumatic input as previously described. Accordingly, pneumatic system  10  may function in a purely electronic mode, a purely pneumatic mode, or an emulation mode. In the mixed or emulation mode, some cars are equipped with fully electronic braking control systems while others are not. 
     Block manifold  12  also includes reservoir ports  30 ,  32  and  34  in fluid communication with an emergency reservoir  36  and an auxiliary reservoir  37 . An exhaust port  38  is also provided on the service side. Ports  40 ,  42 ,  44  and  46  are also plumbed in communication with exhaust port  38 . A quick action chamber port  48  is in communication with a quick action chamber  50 . Quick action chamber  50  is preferably sized to store 150 to 175 cubic inches of air. A brake chamber port  52  is in communication with a brake chamber  54 . Brake chamber  54  converts the pressure supplied therein to a linear force acting upon a push rod  56 . Push rod  56  in turn actuates the car brakes. 
     A manual vent valve  58  is plumbed in communication with an exhaust port  60  and reservoir port  30 . The opposite side of manual vent valve  58  communicates with a plurality of valves via a line  62  as will be described in greater detail hereinafter. Manual vent valve  58  is a three position directional control valve which is spring biased in the up position as shown in FIG.  1 . Manual vent valve  58  includes a lever  64  selectively operable to reposition the valve to one of the two other positions shown. 
     A variety of sensors and valves comprise the remaining portion of pneumatic control system  10 . For clarity, each component will be initially introduced and subsequently described. A check and orifice valve  66  is plumbed between the brake pipe and the reservoirs to control the rate at which each car reservoir fills. Check and orifice valve  66  assures that the cars along the entire length of the train pressurize at approximately the same time. Under certain conditions, this also assures that the brakes are released at approximately the same time. 
     Pneumatic control system  10  also includes a quick release valve  68 . Quick release valve  68  is a two position directional control valve that includes a spring biasing the valve to the position shown in FIG.  1 . Quick release valve  68  also includes an electrical solenoid  70  that is selectively energized to bypass check and orifice valve  66 . Therefore, quick release valve  68  provides a method of quickly filling the brake pipe of the car. 
     A supply valve  72 , an exhaust valve  74  and an exhaust latching valve  76  comprise the requisite valves for conducting a service brake application. Supply valve  72  is a two-way, two position directional control valve spring biased in the up position as shown in FIG.  1 . Supply valve  72  also includes an electrical solenoid  78  which may be selectively energized to move supply valve  72  to the down position. Exhaust valve  74  is also a two-way, two position directional control valve having a spring bias. Exhaust valve  74  includes a pneumatic pilot  80 . Upon receipt of a pressure signal to pilot  80 , exhaust valve  74  shifts to the blocked, down position. Exhaust latching valve  76  is a three-way, two position directional control valve having an upper solenoid  82  and a lower solenoid  84 . Each of the solenoids may be selectively energized to displace the valve. In addition, exhaust latching valve  76  includes an upper pilot  86  and a lower pilot  88 . It should be appreciated that lower pilot  88  acts upon a larger piston diameter than upper pilot  86 . Accordingly, if both upper and lower pilots receive equal pressure signals, pilot  88  will cause exhaust latching valve  76  to move to the up position as shown in FIG.  1 . 
     Pneumatic control system  10  also includes a quick service valve  90  in communication with the filtered brake pipe. Quick service valve  90  is a two position directional control valve that is spring biased to the position shown in FIG.  1 . Quick service valve  90  includes an electrical solenoid  92  which is selectively energizable to move it to the down position. 
     An emergency valve assembly  94  is represented by four separate valves schematically. One skilled in the art will appreciate that a variety of physical valve constructions may exist to achieve the functions schematically depicted. Therefore, valve variants which include different combinations of the valves schematically depicted in one or more housings are contemplated as being within the scope of the present invention. For example, emergency valve assembly  94  includes an emergency backup pilot valve  96 , a pressure sensing valve  98 , a first emergency backup valve  100  and a second emergency backup valve  102  physically mounted within a single housing. Valve  96  is a three-way, two position directional control valve which is spring biased in the up position. Valve  96  also includes an electrical solenoid  104  which is selectively energizable to move valve  96  to the down position. Valve  98  is also a three-way, two position directional control valve which is spring biased in the up position. Valve  98  includes a pair of upper pilots  106  and  108  as well as a lower pilot  110 . Lower pilot  110  acts upon a piston diameter equal to pilot  106 . Accordingly, if a greater pressure signal is present at pilot  106 , sufficient to overcome the combined force of lower pilot  110  and the lower spring, valve  98  will move to the down position as shown in FIG.  7 . 
     Valve  100  is a two-way, two position directional control valve which is spring biased to the up position as shown in the figure. Valve  100  includes a pair of upper pilots  112  and  114  along with a lower pilot  116 . Pilots  112  and  114  act upon a diameter greater than pilot  116 . As such, valve  100  shifts to the down position if a signal is placed upon pilot  112  and  114  regardless of the presence of a signal upon pilot  116 . Valve  100  also includes a mechanical push rod  118 . Valve  100  includes a push rod  118  mechanically engagable with valve  102  such that when valve  100  is in the down position valve  102  is in the down position as well. If valve  100  were subsequently switched to the up position, valve  102  would not necessarily follow because push rod  118  is not coupled to valve  102 . 
     Valve  102  is a three-way, two position directional control valve that is spring biased in the up position. Valve  102  includes an upper pilot  119  and two lower pilots. The pilot valves are sized such that a signal upon either lower pilot causes valve  102  to be in the up position regardless of the presence of a signal upon pilot  119 . 
     A brake cylinder dump valve  120  is plumbed in communication with manual vent valve  58  and brake cylinder  54 . Brake cylinder dump valve  120  is required because a number of trains are equipped with a retainer valve  122  in line with the exhaust of the brake cylinder. Retainer valve  122  supplies a restriction to the exhaust of brake cylinder  54 . The restriction is used to maintain a brake application for a desired length of time. However, retainer valve  122  maintains the pressure in the range of 10 to 22 P.S.I. within the system. In order to completely evacuate brake cylinder  54 , brake cylinder dump valve  120  is plumbed as shown. Brake cylinder dump valve  120  is a two-way directional control valve having a pair of upper pilots  128  and  130  along with a pair of lower pilots  132  and  134 . 
     With reference to FIG. 2, pneumatic control system  10  has been pressurized by providing a supply of pressurized air at the inlet or brake pipe  18 . It should be appreciated that at this time emergency reservoir  36 , auxiliary reservoir  37  and quick action chamber  50  are pressurized as well. High pressure within a given line is indicated by a bold line. Low pressure is indicated by a dashed line. An evacuated line is depicted by a solid line of standard weight. Typically, pneumatic control system  10  is pressurized to approximately 90 P.S.I. when fully charged. 
     An electronic controller  135  is coupled in electrical communication with each of the solenoids and pressure sensors described. An electronic controller  135  is mounted to each car equipped with the present invention. With reference to FIGS. 3 and 4, a service brake application and a service brake release are depicted. During a service brake application, pressure from reservoirs  36  and  37  is supplied to brake cylinder  54 . Entry of pressurized fluid within brake cylinder  54  causes push rod  56  to axially displace and actuate the car brakes. To initiate a service brake application, a brake pipe pressure drop is generated by the engineer at the locomotive. The brake pipe pressure is sensed by a pressure sensor  136 . Electronic controller  135  then electrically energizes solenoid  82  of exhaust latching valve  76  thereby causing the valve to move to the down position as shown in FIG.  3 . By switching exhaust latching valve  76  to the down position, pilot  80  of exhaust valve  74  is signaled. Upon receipt of the pilot signal, exhaust valve  74  shifts to the closed position. Once exhaust latching valve  76  shifts down, a signal is sent to pilot  86 . Therefore, exhaust latching valve  76  “latches” in the down position without the need for electrical energy to solenoid  82 . Another electrical signal is sent to solenoid  78  of supply valve  72 . Supply valve  72  shifts to the down position thereby providing a pathway for pressurized fluid to enter a line  137  and fill brake cylinder  54 . A pressure sensor  138  is coupled to line  137  to provide brake cylinder pressure data to electronic controller  135  if the train is so equipped. 
     With reference to FIG. 4, the service brakes are released by de-energizing solenoid  78  of supply valve  72 . Because supply valve  72  has a spring bias, the valve shifts to the closed, up position once solenoid  78  is no longer actuated. Also, an electrical signal is sent to lower solenoid  84  of exhaust latching valve  76  to shift the valve to the up position. Because of the exhaust latching valve shift, a line  141  coupled to pilot  80  is exhausted. Once the signal to pilot  80  has been removed, exhaust valve  74  returns to its spring biased up position. At this time, pressurized air from brake cylinder  54  travels through exhaust valve  74  and a shuttle valve  142  up through ports  46 ,  44 ,  42  and  40  to finally arrive at exhaust port  38 . Pressurized fluid vents to atmosphere at retainer valve  122 . 
     FIGS. 5-9 depict valve states and line pressure conditions corresponding to an emergency train stop. The figures correspond to an emergency train stop in emulation mode where an electronic controller senses a rapid decrease in brake pipe pressure. Specifically, cars connected to an electrical supply are signaled to energize a predetermined set of valve solenoids to begin an emergency stop. Pneumatic control system  10  also functions to propagate the pneumatic signal to cars not equipped with the present invention by rapidly dropping the brake pipe pressure in each car equipped with the present invention. 
     To initiate the emergency train stop, solenoid  82  of exhaust latching valve  76  is electrically energized. Exhaust latching valve  76  shifts to the down position to provide pilot  80  of exhaust valve  74  with a signal. Exhaust valve  74  shifts to the down position to close the pathway to exhaust. Pressure is supplied to pilot  86  on the top of exhaust latching valve  76  to “latch” valve  76  in the down position without the presence of an electrical signal to solenoid  82 . To conserve energy, the signal to solenoid  82  is applied only momentarily. Additionally, solenoid  78  of supply valve  72  is electrically energized. Upon energization, supply valve  72  shifts to the down position to pressurize line  137  and brake cylinder  54 . One skilled in the art will appreciate that the time required to actuate the brakes in the aforementioned emergency situation is minimal due to the use of solenoids  78  and  82 . At this time, it is desirable to exhaust the brake pipe on each car equipped with electricity to signal cars which are currently operating in pneumatic mode only. 
     FIG. 6 represents the next state of pneumatic control system  10  to further continue the emergency train stop and exhaust brake pipe  18 . Electrical solenoids  78  and  82  are de-energized. Due to the spring bias within supply valve  72 , the valve resets to the up position once solenoid  78  is de-energized. To reset exhaust latching valve  76 , an electrical signal is sent to energize solenoid  104  of valve  96 . Valve  96  shifts to the down position allowing pressurized fluid to pass through valve  98  and pressurize a line  144 . Pressurized fluid from line  144  passes through a shuttle valve  146  and provides a signal to pilot  88  on the lower side of exhaust latching valve  76 . As such, exhaust latching valve  76  is reset in the up position. Once exhaust latching valve  76  is reset, pressure in line  141  that was previously acting upon pilot  80  is exhausted. As a result, exhaust valve  74  shifts to the spring biased up position shown in FIG.  6 . 
     Additionally, because line  144  has been pressurized, a signal is sent to pilot  112 . As discussed earlier, valve  100  is constructed such that the valve shifts to the down position if both pilots  112  and  114  are energized regardless of the presence of a signal on pilot  116 . Thus, brake pipe  18  is exhausted to atmosphere at vent  148 . As valve  100  is shifted to the down position, push rod  118  mechanically shifts valve  102  to the down position. When valve  102  is in the down position, pressurized air from reservoir  36  passes through valve  102 , shuttle valve  142  and exhaust valve  74  to further pressurize brake cylinder  54 . Further pressurization of brake cylinder  54  is required because train brake cylinders typically leak. Even though the brake should theoretically maintain actuation once the pressurized air is trapped within the brake cylinder, the actual brake force decreases unless pressure is continuously supplied. 
     FIG. 7 depicts the further decay of brake pipe pressure through valve  100 . A water expulsion valve  150  is plumbed in communication with filtered brake pipe port  26  and located at an elevational low point to provide a purge point for any water trapped in the line. During the filtered brake pipe exhaust, the signal on pilot  110  is depleted. An accumulator  152  is plumbed in combination with an orifice  154  to maintain a signal on pilot  106  during venting of the brake pipe. Based on these signal conditions, valve  98  shifts to the down position and orifice  156  limits the depletion of quick action chamber  50  to maintain the signal at pilot  108  for a desired period of time. Accordingly, the quick acting chamber acts as a timing mechanism that holds valve  98  off it&#39;s seat until quick action chamber  50  is depleted. Similarly, pilot  112  of valve  100  is signaled with pressurized air until brake pipe  18  and quick action chamber are fully exhausted. 
     With reference to FIG. 8, solenoid  104  is deactivated. It is important to note that reservoir pressure continues to supply brake cylinder  54  and brake pipe pressure continues to be exhausted after solenoid  104  is de-energized. Valve  96  provides an excellent example of how power is conserved during operation of pneumatic control system  10 . Specifically, an electrical signal of very short duration is all that is required for solenoid  104  to shift valve  96  and begin exhausting the brake pipe. Once valve  100  has been shifted, pilot  112  maintains the proper position of valve  100 . As such, solenoid  104  may be deactivated to conserve energy. 
     FIG. 9 represents the last state diagram corresponding to an emergency train stop. At this time, the brake pipe, filtered brake pipe and quick action chamber have been completely exhausted. Valve  98  returns to the spring biased up position. Valve  100  also returns to the spring biased up position. Once valve  100  resets, the exhaust path of brake pipe  18  is closed. Valve  102  does not automatically reset upon movement of valve  100  but stays in the down position based on the signal to pilot  119 . As described earlier, valve  102  remains in this position to maintain the supply of pressurized fluid to brake cylinder  54 . Therefore, the brakes will remain actuated until the reservoirs are completely depleted due to cylinder leakage or intervention of another signal from the train operator. 
     For example, if the operator wishes to manually release the brakes after an emergency stop, manual vent valve  58  may be actuated. With reference to FIG. 10, manual vent valve  58  is deployed in its second or middle position by pulling and holding lever  64 . Once in the second position, manual vent valve  58  supplies pressure to line  62  to reset valves  76  and  102  and to open valve  120 . To shift valve  120  to its reset or down position, pilot  128  is signaled. Similarly, the lower pilot of valve  102  and pilot  88  of valve  76  are also signaled. It should be appreciated that valve  120  is incorporated within pneumatic control system  10  because some trains are equipped with retainer valves while others are not. If the train is equipped with a retainer valve, a residual amount of pressure is maintained within brake cylinder  54  and the brakes are not fully released. Valve  120  is plumbed directly to an exhaust port  158  thereby allowing the pressure to completely dissipate. 
     FIG. 11 depicts the state of pneumatic control system  10  after lever  64  of manual vent valve  58  has been released to allow the valve to return to its spring biased first position. The pilot signal which was previously introduced to line  62  is now exhausted to atmosphere. 
     FIG. 12 depicts pneumatic control system  10  in a state where the brake cylinder  54  has been completely evacuated. The only remaining pressure within the system is stored in emergency reservoir  36 , auxiliary reservoir  37  and the associated lines. The condition depicted is known as the brakes off mode of the train. 
     In FIG. 13, manual vent valve  58  is shifted to the third position shown. The third position couples emergency reservoir  36  and auxiliary reservoir  37  to exhaust through the manual vent valve. For maintenance purposes, it is at times desirable to service a “dead car”. A dead car contains no pressures within any lines, storage tanks or accumulators on the car. It should be appreciated that manual vent valve  58  may be shifted to the third position shown in FIG. 14 immediately following an emergency stop. It is not a requisite step to first enter the second position of manual vent valve  58  prior to entering the third position. Accordingly, if it is desirable to produce a dead car and completely evacuate the reservoirs after an emergency stop, an operator preferably actuates lever  64  to index manual vent valve  58  to the third position thereby venting the brake cylinder and the reservoirs to atmosphere through the manual vent valve. FIG. 15 depicts a completely exhausted car which is the result of holding manual vent valve  58  in the third position shown in FIGS. 13 and 14. 
     While the invention has been described in the specification and illustrated in the drawings with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalence may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. For example, those skilled in the art will understand that emergency valve assembly  94  may alternatively be constructed as two or more separate valve assemblies to accomplish the function previously described. Similarly, electrical solenoids may be substituted for fluid pilots and fluid pilots may be substituted for electrical solenoids where feasible. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings described in the specification as a best mode presently contemplated for caring out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.