Patent Publication Number: US-2009229932-A1

Title: Brake pipe vent valve for locomotive brake system

Description:
BACKGROUND AND SUMMARY 
     The present disclosure relates to locomotive brake systems and more specifically to a brake pipe vent valve for locomotive brake systems. 
     A locomotive brake system generally includes a brake valve with brake handles, e.g., an automatic brake handle and an independent brake handle to provide control signals to a brake control valve. The brake control valve controls the brake cylinder and the brake pipe. 
     The brake control valve provides service brake, emergency brake, and release brake signals on the brake pipe. Connected at each end of the locomotive are vent valves which are responsive to an emergency condition in the brake pipe to exhaust the brake pipe and accelerate the transmission of the emergency signal. The brake valve includes an emergency valve which is responsive to the emergency position of the automatic brake handle to also vent the brake pipe. In some systems this is connected directly to the brake pipe or it is connected to the brake control valve to vent the brake pipe. The brake control valves may include a brake pipe vent valve which is responsive to electric signals from the brake valve or other safety valves, e.g., dead man&#39;s switch or various penalties to also vent the brake pipe in response to unsafe conditions. The vent valve is only responsive to an emergency condition in the brake pipe. The discussion of the prior art systems will be described with respect to  FIGS. 1 through 5 . 
     The present locomotive brake system includes a brake controller operable by an operator, a brake valve and a brake pipe vent valve. The brake controller includes an emergency output port which provides an operator emergency pneumatic signal on the emergency output port when the brake controller is in an emergency position. The brake valve is responsive to brake signals from the brake controller for generating brake signals on a brake pipe. 
     The brake pipe vent valve includes a housing having brake pipe, emergency input and exhaust ports, and a first valve. The emergency output port is fluidly connected to the emergency input port and the brake pipe port is connected to the brake pipe. The first valve selectively connects the brake pipe port to the exhaust port when opened in response to an emergency signal on the brake pipe port and in response to the operator emergency signal on the emergency input port. 
     The first valve opens in responsive to a greater pressure in a first volume, which is connected to a second volume by a choke, than pressure in the second volume, which is connected to the brake pipe port. The first valve opens in also responsive to a smaller pressure in a third volume, which is connected to the emergency input port, than pressure in the first volume. 
     The first and second volumes are separated by a diaphragm and an stem connected to the diaphragm engages a valve element of the first valve to move the valve element off a valve seat to open the first valve. The first and third volumes are separated by the valve element. A spring biasing the valve element onto the valve seat. 
     These and other aspects of the present disclosure will become apparent from the following detailed description of the disclosure, when considered in conjunction with accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic of a locomotive brake system of the prior art as provided by U.S. Pat. No. 5,172,316. 
         FIG. 2  is a schematic of the emergency valve EMRV of  FIG. 1 . 
         FIG. 3  is a schematic of the vent valve of  FIG. 1 . 
         FIG. 4  is a schematic of a locomotive brake system of the prior art as exemplified by U.S. Pat. No. 6,036,284. 
         FIG. 5  is a schematic of the brake pipe valve of  FIG. 4 . 
         FIG. 6  is a schematic of a locomotive brake system according to the present disclosure. 
         FIG. 7  is a schematic of a vent valve according to the present disclosure. 
         FIG. 8  is a cross-sectional view of an embodiment of a vent valve of  FIG. 7 . 
         FIG. 9  is a schematic of another vent valve according to the present disclosure. 
         FIG. 10  is a cross-sectional view of an embodiment of a vent valve of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One of the brake control systems of the prior art is illustrated in  FIGS. 1 through 3 . 
     The brake valve BV includes an automatic brake handle AB and an independent brake handle IB. It also includes an emergency valve EMRV which is responsive to the emergency position of the automatic brake handle AB to connect the brake pipe BP to exhaust. This propagates an emergency brake signal or emergency rate of depletion of the brake pipe throughout the train. The brake valve BV provides control signals through the brake control valve BCV which controls the brake cylinder BC on the locomotive as well as providing service brake signals, emergency brake signals and release brake signals onto the brake pipe BP. At each end of the train is a vent valve VV which is responsive to emergency brake pipe pressure in the brake pipe to connect the brake to exhaust to more quickly deplete the brake pipe and therefore accelerate the brake pipe signal. A complete description is found in U.S. Pat. No. 5,172,316. 
     The emergency vent valve EMRV of  FIG. 1  is illustrated in  FIG. 2  as including a valve  10  having a chamber  12  connected to a brake pipe BP directly. An opposed chamber  14  is connected to the brake pipe BP via choke  16 . A spring  18  in combination with the pressure in chamber  14  keeps the valve  10  in the block position against the pressure in chamber  12 . Once the brake pipe is stabilized and chamber  14  is fully charged, fluctuation of the brake pipe does not affect the position of the EMRV. A valve  20 , which is also connected to chamber  14 , includes a spring  22  biasing it in its closed position. The automatic brake handle AB, when moved into the emergency position, moves the valve  20  down to connect the chamber  14  to exhaust. This causes the valve  10  to move to its second position connecting the brake pipe BP to exhaust EXH. This propagates a brake signal directly from the brake valve BV down the brake pipe. The automatic brake handle AB may be connected through cams to the valve  20  or it may be an electropneumatic valve controlled from an electrical sensor to sense the emergency position of the automatic brake valve AB. 
     A vent valve VV of the prior art is illustrated in  FIG. 3 . The valve  30  includes a chamber  32  connected directly to the brake pipe BP and an opposing chamber  34  connected to the brake pipe BP via choke  36 . A spring  38  in combination with the pressure in chamber  32  biases the valve  30  to the closed position shown. Once the system is stable and the brake pipe charges the chamber  34 , the valve  30  is stable. Upon a drop in pressure in the brake pipe at an emergency rate, chamber  32  is depleted while chamber  34  maintains substantially as charged. This moves the valve  30  to the second or open position, which connects the brake pipe BP to exhaust EXH. This accelerates the exhausting of the brake pipe which accelerates the emergency signal down the brake pipe. 
     A later version of the locomotive brake system is illustrated in  FIGS. 4 and 5 . The brake control valve BCV includes a brake pipe vent valve  40 . The emergency valve EMRV of the brake valve EBV is connected via a line known as # 21  to the brake pipe vent valve  40  in the brake control valve BCV. The brake pipe vent valve  40  vents the brake pipe in response to the emergency position of the automatic brake handle AB as well as to other safety systems. A complete description is found in U.S. Pat. No. 6,036,284. The modification of the brake pipe vent valve BPV is illustrated in  FIG. 5 . Valve  40  has a first chamber  42  connected directly to brake pipe BP and a second opposed chamber  44  connected to brake pipe by choke  46 . A spring  48  biases the valve  40  to the shown position cutting off the brake pipe. Once the system is stabilized and the brake pipe has charged chamber  44 , the valve is maintained in the position shown. Fluctuations in the pressure of the brake pipe does not cause the valve  40  to change its position. 
     Valve  40  is also known as the PVEM in the described patent. Chamber  44  is also connected to a magnetic valve MVEM  52  and a magnetic emergency valve EMV  54  via emergency input pilot port  58 . These are under control of the electronic brake valve EBV or other systems within the locomotive. When the electropneumatic valves  52 , 54  are actuated, they move from the position shown to their second position which connects chamber  44  to exhaust EXH. This causes the PVEM valve  40  to move from the position shown to a second position connecting brake pipe BP to exhaust EXH. Chamber  44  is also connected at port  58  by  56  to the # 21  pipe which is connected to the EMRV valve in the EBV as well as to other safety valves within the locomotive. This will also connect chamber  44  to exhaust causing the PVEM valve  40  to move to the position where the brake pipe BP is connected to exhaust EXH. As previously discussed, the PVEM valve  40  is responsive to the signal on port  58  and is not responsive to brake pipe which is only used to charge the chambers  42  and  44 . 
     The vent valve of the present disclosure in a brake system is illustrated in  FIG. 6 . 
     The system including an electric brake valve EBV connected to the brake control valve BCV directly and via emergency valve EMRV with pipe # 21  is connected to the brake pipe vent valve BPV. The brake control valve BCV is connected to brake pipe BP as well a brake cylinder BC. The elements just discussed is the same as that of the prior art of  FIG. 4 . The major difference is that the present system includes a dual vent valve DVV which is also connected to the # 21  pipe and emergency pilot port  58 . The DVV is responsive to an emergency reduction of brake pipe pressure in the brake pipe BP as well as the emergency signal on port  58 . The dual vent valve DVV has a housing which has a brake pipe, emergency input and an exhaust port input ports. 
     As will be shown with respect to  FIG. 7 , the valve DVV may have a first valve which selectively connects the brake pipe port to the exhaust port when open in response to emergency signal on the brake pipe. It may also include a second valve which selectively connects the brake pipe port to the exhaust port when opened in response to an operator emergency signal on the emergency input pilot port  58 . As will be shown with respect to  FIG. 9 , the valve DVV may have a first or single valve which selectively connects the brake pipe port to the exhaust port when open in response to emergency signal on the brake pipe and in response to an operator emergency signal on the emergency input pilot port  58 . 
     A detailed structure of a first embodiment is illustrated in  FIG. 7 . The vent valve  30  is the same vent valve structure as that in  FIG. 3  of the prior art. The brake pipe port BP is connected to the first chamber  32  directly and to the second opposing chamber  34  through choke  36 . The spring  38  biases the valve  30  to its closed position as illustrated. In addition, there is a second valve  60  also connected to the brake pipe port BP and having a first chamber  62  connected directly to the brake pipe port BP and an opposing second chamber  64  connected to the emergency signal # 21  from the electronic brake valve EBV and the emergency input pilot port  58 . A spring  68  biases the valve  60  to the closed position shown. 
     As previously discussed, the # 21  pipe is pressurized during normal conditions and during an emergency position of the automatic brake valve AB the pressure in the # 21  pipe goes to zero. Thus when the automatic brake handle AB is in the emergency position, port  58  and chamber  64  is exhausted and the brake pipe pressure in chamber  62  forces the valve to its second position connecting the brake pipe BP to exhaust EXH. Activation of valves MVEM  52  and EMV  54  will also connect port  58  and chamber  64  to exhaust EXH. When the brake pipe is connected to exhaust, it also reduces the pressure in chamber  32  causing the vent valve  30  to assume its open position also connecting brake pipe BP to exhaust EXH. This parallel connection of the brake pipe to exhaust through the two open valves increase the capacity and therefore further accelerates the depletion of the pressure in the brake pipe accelerating the emergency signal down the brake pipe. The capacity of valve  60  may be equal to the capacity of valve  30  or may be small. 
     The valve  60  is not responsive to the pressure in the brake pipe and is maintained in the closed position as long as there is pressure in chamber  64  indicating that the automatic brake valve AB is not in the emergency position and neither of emergency valves MVEM  52  and EMV  54  are activated. Thus the valve  30  is responsive to both an emergency signal on the brake pipe as well as the opening of the valve  60  to exhaust whereas the valve  60  is only responsive to the emergency signal on port  58  from the electronic brake valve EBV and brake pipe valve BPV. 
     An embodiment or implementation of the dual vent valve DVV of  FIG. 7  is illustrated in  FIG. 8 . The housing  100  includes a main body portion  102  having a canister  104  attached thereto. The canister secures a diaphragm piston  106 , spring  38 , valve element  116 . Valve seat  108  is provided in a bore of the main housing portion  102 . The diaphragm piston  106  is secured between housing portions  102  and  104 . A first end of a stem  110  of the diaphragm piston  106  is received in sleeve  112  which acts as a stop for the diaphragm piston  106 . The choke  36  is an internal passage in the stem  110 . Diaphragm piston  106  divides volumes or chambers  32  and  34  of valve  30 . A second end of the stem  110  engages and moves valve element  116  off the valve seat  108  when the pressure in chamber  34  is greater than the pressure in chamber  32 . 
     The brake pipe port BP is connected through filter  114  to chamber  32  of valve  30 . It is also connected to chamber  62  of the valve  60 . The emergency input pilot port EP  58  is connected to chamber  64  of valve  60 . Body portion  120  maintains spring  68 , diaphragm piston  122 , spring  130  and valve element  124  in the main housing portion  102 . The diaphragm piston  122  is secured between the housing portions  102  and  120 . The valve element  124  rests on valve seat  126 . Spring  130  provides a loss motion between stem  128  of the piston and the valve element  124 . 
     As can be seen, chamber  32  is responsive to a drop of pressure in the brake pipe port BP or from opening of valve  60 . Valve  60  is only responsive to a drop in pressure at the emergency pilot port  58 .  FIG. 8  is only one example of a combined dual vent valve of the present disclosure. 
     A detailed structure of a second embodiment is illustrated in  FIG. 9 . The vent valve  30  is the same vent valve structure as that in  FIG. 3  of the prior art. The brake pipe port BP is connected to the first chamber  32  directly and to the second opposing chamber  34  through choke  36 . The stem  110  of piston  106  separating the chambers  32  and  34  opens the valve  30  when the pressure in the second chamber  34  is greater than the pressure in chamber  32 . The spring  38  biases the valve  30  to its closed position as illustrated. In addition, a third chamber  64  connected to the emergency signal # 21  from the electronic brake valve EBV and the emergency input pilot port  58 . The third chamber  64  opposes the first chamber  32  and the valve  30  is opened when the pressure in chamber  32  is greater than the pressure in chamber  64 . 
     As previously discussed, the # 21  pipe is pressurized during normal conditions and during an emergency position of the automatic brake valve AB the pressure in the # 21  pipe goes to zero. Thus when the automatic brake handle AB is in the emergency position, port  58  and chamber  64  is exhausted and the brake pipe pressure in chamber  32  forces the valve  30  to its second position connecting the brake pipe BP to exhaust EXH. Activation of valves MVEM  52  and EMV  54  will also connect port  58  and chamber  64  to exhaust EXH. 
     When the brake pipe has a drop in pressure for an emergency condition, the pressure in chamber  32  decreases. This causes the diaphragm  106  to move up and stem  110  engages the valve  30  and moves it to the second position connecting the brake pipe BP to exhaust EXH. Thus the valve  30  is responsive to both an emergency signal on the brake pipe as well as to the emergency signal on port  58  from the electronic brake valve EBV and brake pipe valve BPV. 
     An embodiment or implementation of the dual vent valve DVV of  FIG. 9  is illustrated in  FIG. 10 . The housing  100  includes a main body portion  102  having a canister  104  attached thereto. The canister secures a diaphragm piston  106 , spring  38 , valve element  116 . Valve seat  108  is provided in a bore of the main housing portion  102 . The diaphragm piston  106  is secured between housing portions  102  and  104 . A first end of a stem  110  of the diaphragm piston  106  is received in sleeve  112  which acts as a stop for the diaphragm piston  106 . The choke  36  is an internal passage in the stem  110 . Diaphragm piston  106  divides volumes or chambers  32  and  34  of valve  30 . A second end of the stem  110  engages and moves valve element  116  off the valve seat  108  when the pressure in chamber  34  is greater than the pressure in chamber  32 . 
     The brake pipe port BP is connected through filter  114  to chamber  32  of valve  30 . The emergency input pilot port EP  58  is connected to chamber  64  which house the spring  38 . The valve element  116  separates chambers  32  and  64 . 
       FIG. 10  is only one example of a combined dual vent valve of the present disclosure. 
     Although the present disclosure had been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present disclosure is to be limited only by the terms of the appended claims.