Abstract:
A vent valve made from a standard emergency brake valve portion. It includes an emergency portion body with an interface to be mated with the emergency portion interface of the pipe bracket. The body includes a casting with at least one cover and the casting including all the cast cavities and passages for an emergency portion. A vent valve selectively connects a first brake pipe port to a vent port on the body, A vent piston controls the vent valve and a discharge valve pneumatically controls the vent piston. An emergency piston is responsive to brake pipe pressure for controlling the discharge valve. The body does not include at least one of an inshot valve and an accelerated application valve.

Description:
BACKGROUND AND SUMMARY 
     The present invention relates generally to emergency vent valves and more specifically to emergency vent valve and accelerated application sensor valve of a brake control valve. 
     A pneumatic brake control valve generally includes a service portion and an emergency portion mounted to a pipe bracket as shown in  FIG. 1 . The emergency portion  20  is shown as the emergency portion of a DB60, known as DB20 available from New York Air Brake Corporation and is described in U.S. Pat. No. 4,586,756. 
     The DB -  20  and DB - 20 L emergency portions currently use an accetrated application sensor valve which is either open or closed, but is otherwise independent to the emergency piston position and pilot pressure (i.e. Brake pipe reduction). This type of feature is an open-loop control system since it is either fully operating or closed. The drawback to this type of system is that in some reductions, the sensor valve may become self propagating. This occurs when relatively short lengths of brake pipe are attached to the emergency portion  20 . 
     The function of the accelerated application is to propagate a brake pipe (BP) reduction signal throughout the train for improved braking application time. This is currently accomplished by the emergency piston moving upward in response to a drop in brake pipe pressure a pre-established distance to open the accelerated application sensor valve. This sensor valve allows quick action volume (QA) pressure to mix with brake pipe in a mixing chamber, and then is exhausted to the atmosphere by way of the accelerated application or pulsating valve. When sufficient brake pipe and quick action volume have been exhausted, the emergency piston stabilizes, closing the sensor valve, and hence arrest accelerated application activity. 
     However, as the brake pipe to quick action volume ratios decrease for the respective valve designs, the ability of the brake pipe pressure to stabilize the emergency piston becomes more difficult. As mentioned before, the sensor valve is both opened and feeding QA pressure to the mixing chamber, or it is closed stopping the accelerated application activity. As the sensor valve remains open, a constant volume of air is fed to the mixing chamber via a fixed orifice of the sensor valve. 
     This constant volume of air will continue the accelerated application activity until one of two events occur: 1) the QA pressure reduces to the point were when equalized in the mixing chamber, the pressure is unable to overcome the spring force of the pulsating valve; or 2) the sensor valve closes due to piston stability, stopping the flow of QA pressure to the mixing chamber. If this does not transpire, a further reduction in brake pipe pressure occurs, causing more piston instability, and continuing the cycle. 
     To eliminate the problem of a self propagating accelerated application, the introduction of a closed-loop control system is necessary. The present design of the emergency vent valve and the accelerated action sensor valve provides a closed-loop control of the accelerated application and stabilization of the emergency piston. 
     A brake control valve includes a volume and an emergency vent valve connected to an interface of a pipe bracket. The emergency vent valve includes a vent valve for selectively connecting a first brake pipe port to a vent port and a vent piston for controlling the vent valve. An emergency piston includes a first side connected to the volume port and a second side connected to a second brake pipe port A discharge valve is connect to the emergency piston and selectively interconnects the second side of the vent piston, the vent port and the volume port as a function of the displacement of the emergency piston. An accelerated application valve selectively connects the volume port and the second brake pipe port to the vent port in response to pressure from the volume port. An accelerated application sensor valve connected to the emergency piston and selectively connecting the volume port to the accelerated application valve as a function of the displacement of the emergency piston. 
     In a first embodiment, the discharge valve operates as and replaces the accelerated application sensor valve so as to also selectively connect the volume to the accelerated application valve. In which case, the discharge valve&#39;s connection of the vent port and the accelerated application valve to the second side of the vent piston and the volume port is a variable orifice whose opening varies as a function of the displacement of the emergency piston. In a second embodiment, the accelerated application sensor valve has a variable orifice. This may be the separate sensor valve or the combined valve of the first embodiment In a third embodiment, the discharge valve&#39;s connection of the vent port to the second side of the vent piston and the volume port is a variable orifice whose opening varies as a function of the displacement of the emergency piston. This discharge valve may be used alone or with the separate sensor valve of the second embodiment. 
     The variable orifice of the valves may include a valve seat and a tapered valve member connected to the emergency piston. 
     The discharge valve disconnects the volume port and the second side of the vent piston from the vent port for a brake release position of the emergency piston; connects the volume port and the second side of the vent piston to the vent port for a brake apply position of the emergency piston; and disconnects the volume port from the second side of the vent piston and the vent port and connects the second side of the vent piston to the vent port for an emergency position of the emergency piston. 
     In the first embodiment, the discharge valve disconnects the volume port from the accelerated application valve for the brake release position of the emergency piston, and connects the volume port to the accelerated application valve for the brake apply position of the emergency piston. 
     In the second embodiment, the accelerated application sensor valve disconnects the volume port from the accelerated application valve for the brake release position of the emergency piston, and connects the volume port to the accelerated application valve for the brake apply position of the emergency piston. 
     The discharge valve and the accelerated application sensor valve may be poppet valves in-line with the emergency piston. In the second and third embodiments, the discharge valve may be connected to the emergency piston by a lost motion mechanism such that the accelerated application sensor valve opens before the discharge valve opens. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of a brake control valve having a service portion and emergency portion mounted to a pipe bracket according to the prior art. 
         FIG. 2  is a schematic representation of a first embodiment of a modified portion of an discharge valve and accelerated application sensor valve according to the present disclosure. 
         FIG. 3  is an enlarged detail of the modified discharge valve and the accelerated application sensor valve of the first embodiment. 
         FIG. 4  is a schematic representation of a second embodiment of a modified portion of an accelerated application sensor valve according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The intent of this design is to provide such a system for both the DB-20 and DB-20L emergency portions, for example. As mentioned previously, the accelerated application operation relies on the equalization of BP and QA pressure in the mixing chamber. The mixing chamber contains system BP pressure at all times during normal service operation. This pressure remains in the chamber via a diaphragm seal. As sufficient QA air pressure enters the chamber, the diaphragm opens, and equalized air is admitted to the accelerated application or pulsating valve, and then on to atmosphere. 
     The present design takes advantage of the piston position to control the flow of QA from the volume  34  to the mixing chamber MX. This is accomplished by creating a variable orifice for QA air flow to the mixing chamber MX (See  FIGS. 1 and 2 ). As the emergency piston  244  moves toward the service stability position; QA air flow to the mixing chamber is reduced to a sufficient level to assist in arresting accelerated application activity (i.e. reduction in equalization pressure). This feature will prevent reductions in BP as the emergency piston  244  is stabilizing. The geometry of the needle valve  270  used for this control may be optimized to allow the necessary air flow in all service positions of the piston  244 . 
     Because this design directly relates emergency piston position to QA air flow, accelerated application activity is more precisely controlled during service applications (i.e. Brake pipe reductions). As larger reductions are required, more QA air will be admitted to the mixing chamber MX, thus assisting in proper accelerated application activity, and signal propagation. Normal emergency functions will not be impacted due to the modification of the accelerated application sensor valve or the discharge valve. 
     The basic idea for the closed loop control mechanism for the accelerated application is illustrated in  FIG. 2  for example. During the service lap position, the needle valve  270  is seated on the lower bushing seat  247 , sealing pressure to both the atmosphere and the mixing chamber MX. A service lap position is created by equal BP (top side of piston  244 ) and QA (bottom side of piston  244 ) pressure. As BP reduces, a pressure differential between BP and QA forces the piston  244  upward, thus unseating the needle valve  270  off seat  247 . This allows QA air into the lower bushing and out to: 1) atmosphere; and 2) the mixing chamber MX. The piston travel and hence the QA air flow are a function of the initial BP reduction. The more aggressive the reduction (i.e. higher BP drop) the greater the upward movement of the piston  244 , and the greater the air flow to the mixing chamber MX. This allows for precise control of accelerated application activity, and incorporates feedback control mechanism into the accelerated application function. 
     The emergency application feature of the emergency portion  20  are accomplished by the upward movement of the emergency piston  244  such that the needle valve  270  seals on the upper bushing seat  249 . This will allow for the normal sequence of events to occur which are necessary to produce an emergency application. This includes opening the vent valve  256  to connect the brake pipe port B 34  to atmosphere. 
     An example of the prior art brake control valve is illustrated in  FIG. 1  and the modifications are illustrated in  FIGS. 2-4 . A description of the operation of the prior art will proceed the description of the modifications. 
       FIG. 1  shows a brake control valve according to the prior art. The brake control valve includes a standard service portion  10  is mounted to a pipe bracket  30  at interface  31  and a standard emergency portion  20  is connected to the adaptor plate  40  at interface  32 . The brake control valve will operate in a pneumatic mode using service portion  10  and an emergency portion  20 . If an electrical controlled pneumatic (ECP) portion is used in an overlay with the standard brake control valve, the car control device of the ECP will control the braking of the brake cylinder. See U.S. Pat. No. 5,967,620 to Truglio et al. as an example. 
     To aid in understanding the various passages within the control valve, the brake pipe passage is represented by a “B”, the brake cylinder passages by a “C”, the emergency reservoir passages by an “E”, the retainer passage by an “R”, the auxiliary reservoir passage by a “A”, the quick action or control volume by “QA”, exhaust or atmosphere by “EX” and the control valve or brake signal passage from the emergency portion for the brake cylinder by a “V”. 
     The emergency portion  20  is shown as the emergency portion of a DB60, known as DB20 available from New York Air Brake Corporation and is described in U.S. Pat. No. 4,586,756. 
     The emergency portion  20  includes a body  200  having covers  210 ,  220  and  230  mounted on faces  241 ,  243  and  245  of a casting  240 . The cover  210  includes passages and a cavity for an accelerated application in the sensor valve  212 . 
     The cover  220  includes cavities and passages for an emergency acceleration release valve  222 , an emergency acceleration release check valve  224 , mixing chamber MX, a pulsating valve  226  and a brake pipe (BP) discharge valve  228 . The pulsating valve  226  and the BP discharge valve  228  form an accelerated application valve. 
     The cover  230  includes passages and cavities for a high pressure valve  232  and the spring portion  234  of an inshot valve  236 . Valve portion  238  of the inshot valve  236  defines the two stage build up of the brake cylinder. 
     The casting  240  includes a cavity  242  in face  241  for an emergency piston  244 . The emergency piston  244  is connected by lost motion arrangement  246  to discharge valve  248  in cavity  250 . The inshot valve  236  is in cavity  252  in face  245  of the casting  240 . Cavity  254  also in face  245  is provided for a vent valve  256 . The cover  230  covers the cavities  252  for the inshot valve  236  and cavity  254  for the vent valve  256 . The casting  240  includes cavities  262 ,  264 ,  266  and  268  in face  243  for the emergency acceleration release valve  262 , the emergency acceleration release check valve  264 , pulsating valve  266  and the BP discharge valve  228  of the accelerated application valve. These cavities are covered by cover  220  and are bored into the face  243  of casting to connect with the internal passages which are part of the casting  240 . The other cavity described are part of the casting and are not bored. 
     As is well known, the emergency piston  244  has brake pipe pressure on its top surface via passage B 36  to the brake pipe interface port B 32 . The bottom of the emergency piston is connected by passage QA 34  to control volume interface port QA 32  for a control volume  34  in the pipe bracket  30 , known in the industry as a “quick action chamber”. The change of the brake pipe BP pressure changes the position of the emergency piston  244 . The emergency piston  244  operates the accelerated application sensor  212 . It also operates the discharge valve  248  through the lost motion apparatus  246 . 
     The vent valve  256  selectively connects the brake pipe and brake pipe interface port B 34  to exhaust via passage EX 32 . The left side  256 ′ of the piston portion of the vent valve  256  is connected via passage QA 36  to the control volume port QA 32 . The right side  256 ″ of the piston portion of the vent valve is selectively connected via passage  255  by the QA discharge valve  248  to the either the vent port or the control volume port CV 32 . In response to an emergency pressure drop in the brake pipe, the emergency piston  244  operates QA discharge valve  248  to move the vent valve  256  to open and connect the brake pipe port B 34  to exhaust. 
     The inshot valve  236  is shown in the position for a service application thereby allowing the brake cylinder port C 32  to have unrestricted flow. In an emergency application, the high pressure valve  232  changes position from that shown, which allows the inshot valve  236  to move to the left causing the end  238  to be restricted and thereby slow down the build up of the brake cylinder pressure at port C 32  during its first stage. After given a period of time, the inshot valve  236  is moved back to the right for unrestricted flow. This two stage build up is standard to prevent different cars of the train coming on to full emergency brake before others start braking. This restriction of flow prevents the use of the emergency portion  20  from being used to drive more than one car set form the brake cylinder port BC. 
     The pulsating valve  226  and the BP discharge valve  228  of the accelerated application valve are responsive to the pressure provided to the mixing chamber MX by the opening of the acceleration application sensor valve  212  via passage QA 38  to connect the brake pipe port B 32  to exhaust at chamber  254 . This accelerates the signal of the brake pipe as well as the operation of the emergency piston  244 . 
       FIGS. 2 and 3  show the first embodiment wherein the quick action sensor valve  212  has been incorporated into the quick action discharge valve  248  as in a single valve  270 . Since they are combined, the connection  246 ′ of the combined quick action QA discharge and sensor valve  270  to the piston  244  is a direct connection instead of a lost motion as in  FIG. 1 . The combined QA valve  270  still rests against the lower valve seat  247  for release condition, is released from valve seat  247  but does not reach valve seat  249  for a service application and comes to rest on the valve seat  249  in emergency conditions. The QA valve  70  is tapered and forms a variable orifice with valve seat  247 , which opening varies as a function of the displacement of the emergency piston  244 . 
     With the elimination of the QA sensor valve  212  at the top of the housing, the passage QA  38  from the QA sensor valve to the mixing chamber MX is removed from the cover  210  and is connected internal the body  200  to the mixing chamber MX. 
     Cavity  250  includes a first bushing  272  secured in the cavity  250  by o-rings  274 . The connection  246 ′ of the QA valve  270  to the piston  244  is spaced from the interior bushing  272 , so as to create a passage QA  40  between the QA air under the diaphragm  244  and the cavity  250 . Valve seat  249  is on the face of the bushing  272 . A lower bushing  276 , which includes the valve seat  247 , is also secured in the cavity  250  by o-rings  278 . A restriction or choke  280  connects the bore of the bushing  276  to exhaust passage EX  32 . The cavity  250  between the two valve seats  247  and  249  is connected to the vent valve  256  by passage  255 . A choke  282  connects the interior bushing  276  to the mixing chamber MX by the passage QA  38 . This is the passage which is removed from the cover  210 . 
     As discussed previously, the tapered valve  270  forms a variable orifice and the closed loop control mechanism for the accelerated application. During the service lap position, the needle valve  270  is seated on the lower bushing seat  247 , sealing pressure to both the atmosphere and the mixing chamber MX. A service lap position is created by equal BP (top side of piston  244 ) and QA (bottom side of piston  244 ) pressure. As BP reduces, a pressure differential between BP and QA forces the piston  244  upward, thus unseating the needle valve  270  off seat  247 . This allows QA air into the lower bushing and out to: 1) atmosphere via EX 32 ; and 2) the mixing chamber MX via QA 38 . The piston  244  travel and hence the QA air flow are a function of the initial BP reduction. The more aggressive the reduction (i.e. higher BP drop) the greater the upward movement of the piston  244 , and the greater the air flow to the mixing chamber MX. This allows for precise control of accelerated application activity, and incorporates feedback control mechanism into the accelerated application function. 
     Another feedback mechanism for the accelerator application operation is illustrated in  FIG. 4 .  FIG. 4  differs from the prior art of  FIG. 1  by basically creating a variable orifice at the quick action sensor valve  212 ′. The new valve  212 ′ has a tapered body similar to the tapered body  270  of  FIG. 3 . Thus it functions the same way to provide a variable orifice which is a function of the position of the emergency piston  244 . The QA discharge valve  240  is not modified from that of  FIG. 1 . As a variation of  FIG. 4 , the QA discharge valve  248  may be replaced by the tapered valve  270 . In which case, the connection  246  of the valve  270  may be a direct connection to the emergency piston  244  since lost motion would not be necessary. The tapered valve  270  would provide a variable orifice, which is a function of the displacement of the emergency piston  244 . 
     As even a further option, only the QA discharge valve  248  may be the tapered valve  270 . It could be connected to piston  244  by a direct connection  246 ′, instead of a lost motion connection. The regular QA sensor valve  212  would be used. This would provide feedback of stabilization of the emergency piston  244  since the variable orifice would be a function of the position of the piston  244 . This may require some modification to the brake valve. 
     Although the present brake valve has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The vent valve of the present invention may be also used at the emergency portion interface of a single sided pipe bracket. The scope of the present invention are to be limited only by the terms of the appended claims.