WO2012119055A1

WO2012119055A1 - Emergency portion of a pneumatic brake control valve

Info

Publication number: WO2012119055A1
Application number: PCT/US2012/027438
Authority: WO
Inventors: Derick Call; Marc S. Thomas; Michael J. SPANDACCINI; Robert L. NEULIEB; Christopher J. FERGUSON
Original assignee: New York Air Brake Corporation
Priority date: 2011-03-02
Filing date: 2012-03-02
Publication date: 2012-09-07

Abstract

An emergency portion of a brake control valve has a piston with brake pipe pressure on a first side of the piston and a reference volume pressure on a second side of the piston. A plurality of actuators interconnect the piston to and operate the high pressure valve, the vent valve, the reference volume discharge valve, the brake pipe discharge valve, and the emergency accelerated release valve as a function of positions of the piston. Some of the valves have a common valve element or actuator.

Description

EMERGENCY PORTION OF A PNEUMATIC BRAKE CONTROL VALVE

Background and Summary

[0001 ] The present invention relates to rail vehicle brake control valves and more specifically to an emergency portion of the brake control valve.

[0002] A brake control valve offered by New York Air Brake Corporation is the DB-60 valve. It is a pneumatic valve having a service portion and an emergency portion mounted to a pipe brake portion. The elements and the operation of the emergency portion are described in U.S. Patent Nos. 4,552,441 and 4,586,756 to Hintner. As presently constructed, the DB-60 valve's emergency portion, shown in Figure 1 , has 125 parts, including four diaphragms, and weights 23 pounds. The present redesign reduces the number of parts to about 60 with one diaphragm and a weight of approximately 19 pounds.

[0003] Other examples of emergency portions using poppet valves include U.S. Patent No. 4,025,125 to Wickham and U.S. Patent No. 4,043,605 to Hart.

[0004] The present emergency portion of a brake control valve includes: a piston with brake pipe pressure on a first side of the piston and a reference volume pressure on a second side of the piston; a first choke connecting the two sides of the piston; a high pressure valve for connecting a reservoir port to a brake cylinder port for an emergency pressure in the brake pipe; a vent valve for connecting a brake pipe port to atmosphere for an emergency pressure in the brake pipe; a reference volume discharge valve for initially connecting the reference volume to atmosphere for a decrease in brake pipe pressure; and a brake pipe discharge valve for connecting brake pipe to atmosphere for a decrease in brake pipe pressure.

[0005] One improvement is a plurality of actuators interconnect the piston to and operate the high pressure valve, the vent valve, the reference volume discharge valve, and the brake pipe discharge valve as a function of positions of the piston. The vent valve, the reference volume discharge valve and the brake pipe discharge valve may be coaxial in a stack. A common valve element may be used for the reference volume discharge valve and the brake pipe discharge valve. [0006] An emergency accelerated release valve is interconnected to and operated as a function of positions of the piston for connecting the brake cylinder port to the brake pipe first side of the piston for an increase in the brake pipe pressure after an emergency application. The high pressure valve and the emergency accelerated release valve may be parallel to and displaced from the stack or the emergency accelerated release valve is in the stack and the high pressure valve is parallel to and displaced from the stack.

[0007] The emergency accelerated release valve may connect a check valve between the brake cylinder port and the brake pipe first side of the piston for an increase in the brake pipe pressure after an emergency application. The check valve is opened when the pressure in brake cylinder port is greater than the pressure on the brake pipe first side of the piston by a fixed amount.

[0008] A second choke may be provided in parallel to a bypass valve. The second choke and the bypass valve are connected between the reference volume and exhaust, and the bypass valve is responsive to the position of the piston via an actuator to initially open for a decrease of brake pipe pressure to bypass the second choke and subsequently close for a large drop in brake pipe pressure. The reference volume discharge valve and the bypass valve each include a valve element, and the reference volume discharge valve's valve element may include an actuator for the bypass valve. The bypass valve may have a separate actuator.

[0009] The vent valve includes a valve element having a first side for engaging a valve seat, and a second side of the valve element opposite the first side has a peripheral area exposed to brake pipe pressure of less than 20% of its total area. 0010] In another emergency portion of a brake control valve having a piston with brake pipe pressure on a first side and a reference volume pressure on a second side, a first choke connecting the two sides of the piston, one or more valves actuated by the position of the piston to effect emergency braking only for emergency brake pipe pressure, a second choke is provided connecting the first and second sides of the piston. The second choke has a smaller restriction than the restriction of the first choke. A check valve in series with the second choke connects the first and second sides of the piston through the second choke when the pressure in the brake pipe first side is greater than the reference volume second side. The first and second chokes and the check valve may be mounted on the piston.

[0001 1 ] Another emergency portion of a brake control valve has: a piston with brake pipe pressure on a first side of a head of the piston and a reference volume pressure on a second side of the piston head; a vent valve responsive to the position of the piston for connecting a brake pipe port to atmosphere for an emergency pressure in the brake pipe; and a reference volume discharge valve responsive to the position of the piston for initially connecting the reference volume to atmosphere for a decrease in brake pipe pressure. Further provided is a piston rod connected to the piston head having a passage with a first end connected with the reference volume second side of the piston head and a second end connected to atmosphere. A valve element of the reference volume discharge valve includes a closure area for the first end of the passage and a valve element of the vent valve includes a closure area for the second end of the passage.

[00012] The first end of the passage is closed and the second end is open for a balanced position of the piston. The piston moves and the first end opens and the second ends remains open for an initial decrease in brake pipe pressure. The piston subsequently moves and the first end remains open and the second end is closed for a further decrease in brake pipe pressure and further piston movement opens the vent valve, and the first end remains open and the second end opens for further opening of the vent valve.

[00013] An actuator extends between the valve elements of the reference volume discharge vale and the vent valve for opening the reference volume discharge valve. The piston head engages a stop after opening the vent valve such that further opening of the vent valve opens the second end of the passage while maintaining the first end open.

[00014] A brake pipe discharge valve connects a port connected to the first brake pipe side of the piston head to the first end of the passage for a decrease in brake pipe pressure. The valve element of the reference volume discharge valve includes a closure area for the port connected to the first brake pipe side of the piston head. A shroud surrounds the closure area for the second end of the passage on the vent valve.

[00015] In another emergency portion of a brake control valve having a piston with brake pipe pressure on a first side of a head of the piston and a reference volume pressure on a second side of the piston head and a reference volume discharge valve responsive to the position of the piston for initially connecting the reference volume to atmosphere for a decrease in brake pipe pressure; a chamber is provided having a first port connected to the brake pipe first side of the piston, a second port connected to the reference volume second side of the piston and a third port connected to atmosphere. The reference volume discharge valve includes a common valve element for controlling the connection of both the first and ports to the third port in response to the position of the piston. The valve element engages and covers the first and third ports.

[00016] A vent protection element is mounted across the atmosphere port for brake pipe vent by a bayonet connection.

[00017] These and other objects, features, and advantages of the present disclosure may be better understood and appreciated from the following detailed description of the embodiments thereof, selected for purposes of illustration and shown in the accompanying drawings.

Brief Description of the Drawings

[00018] Fig. 1 is a schematic diagram of an emergency portion of a brake control valve of the prior art.

[00019] Fig. 2 is a schematic diagram of an emergency portion of a brake control valve according to the present disclosure in the charged lap condition.

[00020] Fig. 3 is a schematic diagram of an emergency portion of Figure 2 in the quick service condition.

[00021 ] Fig. 4 is a schematic diagram of an emergency portion of Figure 2 in the start of emergency application condition. [00022] Fig. 5 is a schematic diagram of an emergency portion of Figure 2 in the emergency application condition.

[00023] Fig. 6 is a schematic diagram of an emergency portion of Figure 2 in the start of the emergency accelerated release condition.

[00024] Fig. 7 is a schematic diagram of an emergency portion of Figure 2 in the emergency accelerated release condition.

[00025] Fig. 8 is a schematic diagram of an emergency portion of Figure 2 with a modification of the emergency accelerated release valve and the reference volume charging chokes/check valve.

[00026] Fig. 9 is a schematic diagram of an emergency portion of Figure 2 with a modification of the reference volume charging chokes/check valve.

[00027] Fig. 10 is an exploded view an implementation of an emergency portion of Figure 2.

[00028] Fig. 1 1 is a schematic diagram of a portion of the emergency portion of Figure 2 with a modification of the reference volume bypass valve and the vent protector.

[00029] Fig. 12 is a schematic diagram of a portion of the emergency portion of Figure 2 with a blow back preventer of reference volume to brake pipe.

[00030] Fig. 13 is a schematic diagram of an emergency portion of Figure 2 with the emergency accelerated release valve of Fig. 1.

Detailed Description of the Drawings

[00031 ] Figure 1 shows a pipe bracket 30 with a complete emergency portion 20 mounted to the emergency interface 32. 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", and the control valve or brake signal passage from the emergency portion for the brake cylinder by a "V". [00032] The emergency portion 20 is shown as the emergency portion of a DB60, known as DB20 available from New York Air Brake Corporation. 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 sensor valve 212.

[00033] The cover 220 includes cavities and passages for an emergency accelerated release valve 222, an emergency accelerated release check valve 224, a pulsating valve 226 and a brake pipe discharge valve 228. The pulsating valve 226 and the brake pipe discharge valve 228 form an accelerated application valve.

[00034] The cover 230 includes passages and cavities for a high pressure valve 232 and the spring portion 234 of an inshot piston 236. Valve portion 238 of the inshot piston 236 defines the two stage build up of the brake cylinder. A restriction or choke 235 connects the seat 233 of the high pressure valve 232 to one side of the inshot piston 236. A restriction or choke 237 connects the other side of the inshot piston 236 to the brake cylinder interface ports C32 and C34 and to the high pressure valve 232.

[00035] The casting 240 includes a cavity 242 in face 241 for an emergency piston 244 with a diaphragm 244'. The emergency piston 244 is connected by lost motion arrangement 246 and spring 270 to discharge valve element 248 in cavity 250. The discharge valve element cooperated with two valve seats 247 and 249. The cover 210 including the accelerated application sensor valve 212 covers the cavity 242.

[00036] 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 piston 236 and cavity 254 for the vent valve 256. A vent cover protector 253 is shown as a flexible filter element over the outlet of the cavity 254 and may be opened by excessive pressure in cavity 254.

[00037] The casting 240 includes cavities 262, 264, 266 and 268 in face 243 for the emergency accelerated release valve 222, the emergency accelerated release check valve 224, pulsating valve 226 having spring 267 and the discharge valve 228 having spring 269 of the accelerated application valve. These cavities are covered by cover 220 and are bored into the face 243 of casting 240 to connect with the internal passages which are part of the casting 240. The other cavities described are part of the casting and are not bored.

[00038] As is well known, the emergency piston 244 has brake pipe pressure on its top surface via brake pipe interface port B32. The bottom of the emergency piston is connected at control volume interface port CV32 to a control or reference volume 34 in the pipe bracket 30, known in the industry as a "quick action chamber". The control volume 34 is charged by the brake pipe from brake pipe interface port B32 via choke or restriction 239. The change of the brake pipe pressure changes the position of the emergency piston 244. The emergency piston 244 operates the accelerated application sensor 212 via actuator 21 1. It also operates the discharge valve 248 through the lost motion apparatus 246.

[00039] The vent valve 256 selectively connects the brake pipe and brake pipe interface port B34 to exhaust. The left side of the piston portion of the vent valve 256 is connected via CV22 to the control volume interface port CV32. The right side of the vent valve is selectively connected by the discharge valve 248 to either the vent or exhaust in chamber 254 or the control volume port CV32 as determined by discharge valve element 248. In response to an emergency pressure drop in the brake pipe, the emergency piston 244 operates discharge valve 248 to move off seat 249 and onto seat 247 thereby allowing the vent valve 256 to open and connect the brake pipe port B34 to exhaust.

[00040] The inshot valve 236 is shown in the position for a service application thereby allowing the brake cylinder port C32 to have unrestricted flow. In an emergency application, the vent valve 256 opens against spring 259 and releases the high pressure valve 232 by removing actuator 257 biased extended by spring 255. Under emergency reservoir pressure from emergency reservoir interface port E32 and spring 261 , the high pressure valve 232 moves from resting on seat 231 and comes to rest on seat 233. This connects the emergency reservoir interface port E32 to the inshot piston 236 via restriction 237, which moves the inshot valve 236 to the left causing the end valve portion 238 to be restricted and thereby slow down the build up of the brake cylinder pressure at port C32 during the first stage of an emergency application. After given a period of time, the inshot piston 236 is move 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.

[00041 ] The pulsating valve 226 and the discharge valve 228 of the accelerated application valve are responsive to the acceleration application sensor valve 212 to initially connect the brake pipe interface port B32 via restriction or choke 261 and brake pipe discharge valve 228 and the control volume side of the piston 244 to the exhaust chamber 254 via restrictions or chokes 263 and 265 of the pulsating valve 226. Subsequently, the pulsating valve 226, in parallel to the coke 263, opens connecting the brake pipe port B32 and the control volume side of the piston 244 to exhaust at chamber 254 via choke 265. This accelerates the drop in pressure or emergency signal of the brake pipe as well as the operation of the emergency piston 244.

[00042] The preferred embodiment of the improved emergency portion 20 is shown in Figures 2-7. It is a redesign which reduces the number of parts including diaphragms, the weight and easy of manufacture. All of the required functions are performed. Those elements of the redesign having the same function will have the same three digit number with the addition of a thousand or 1200s. The new elements will have a reference number in 1300s.

[00043] The improved emergency portion 20 is shown in Figs. 2-10 and includes a body 1200 having covers 1210 and 1230 mounted on faces 1241 and 1245 of a casting 1240. The body 1240 and covers 1210 and 1230 may have the same foot print or profile as shown in an exemplary implementation in Fig. 10.

[00044] The body 1240 has a main cavity 1242 for the emergency piston 1244 having a piston head 1244A, B, diaphragm 1244' and a piston rod 1244C. The piston head 1244A,B divides the cavity 1242 in a portion 1242A connected to the brake pipe through the filter by passage B32 and a portion 1242B connected to the Quick Action (QA) or control chamber or reference volume 34 by passage CV32. The change of the brake pipe pressure changes the position of the emergency piston 1244. [00045] The reference volume 34 is charged by the brake pipe BP from brake pipe interface port B32 via choke or restriction 1239. An additional choke or restriction 1339 with a series check valve 1340 also connects and charges the reference volume 34 by the brake pipe BP from brake pipe interface port B32 when the pressure in the brake pipe BP is greater than the pressure in the reference volume 34. The restriction of choke 1239 is smaller than the restriction of choke 1339.

[00046] The choke 1239 is a stabilization choke by continuously connecting the brake pipe to the reference volume 34. The choke 1339 with check valve 1340 is only active to charge the reference volume 34 quickly after, for example, an emergency brake application when the brake pipe is being recharged and the reference volume 34 is generally depleted.

[00047] The check valve 1340 is shown as a duck bill check, but other check valves may be used. The use of duck bill check eliminates a valve seat and allows ease of incorporation into the piston head 1244A, B. The chokes 1239 and 1339 are shown with an integrated screen.

[00048] Wherein the chokes 1239 and 1339 are shown mounted in the piston head 1244 A, B in Figs. 1-7, they may also be mounted in the cover 1210 as shown in Figs. 8 and 9. While the chokes 1239 and 1339 are shown in parallel in Figs. 1-8, they may also in series as shown in Fig. 9. When the check valve 1340 against spring 1341 opens in Fig. 9, the choke 1239 has little if any affect on the air flow. In all the illustrated versions, the chokes 1239 and 1339 interconnect the two sides of piston head 1244A, B or chambers 1242A, B.

[00049] The piston rod 1244C has a passage 1244D with a first end 1249 connected with the reference volume second side 1242B of the piston head via chamber 1266 and chokes or restrictions 1265 and 1263 A second end 1248 connected to atmosphere or exhaust via cavity 1254. A valve element 1228 of the reference volume discharge valve includes a closure area 1328 for the first end 1249 of the passage and a valve element 1256 of the vent valve includes a closure area 1247 for the second end 1248 of the passage.

[00050] In the charged lap condition of Fig. 2, the first end 1249 of the passage is closed by engagement with closure area 1328C of valve element 1228 and the second end 1248 is open for a balanced position of the piston 1244. An actuator portion 1328 A of the valve element 1228 engages the vent valve element 1256. The closure area 1328C is double beaded since it not only engages and closes the first end 1249 of the passage from the cavity or chamber 1266 and the reference volume side 1242B of the piston, but also closes the port into chamber 1266 from the brake pipe side 1242A of the piston via choke 1261. In Fig. 8, the double beading is on the body part in chamber 1266. The valve element 1228 is a common valve element for venting both sides of the emergency piston 1244 and thus is a common valve element for the reference volume discharge valve and the brake pipe discharge valve.

[00051 ] For an initial decrease in brake pipe pressure as shown in Fig. 3, the piston 1244 moves down in the figures moving valve element 1228 off of the first end 1249 of passage 1244D by actuator portion 1328A and compressing spring 1269. This connects chamber 1266, the reference volume side 1242B of the piston via chokes 1263 and 1265 and the brake pipe side 1242 A of the piston via choke 1261 to the passage 1244D. The second end 1248 of passage 1244D is opened to exhaust. This is generally a service application drop in brake pipe pressure. Both sides of the piston head 1244A, B are vented to prevent the emergency piston from going into an emergency condition.

[00052] An actuator portion 1328B of the valve element 1228 also engages a valve element 1226 of the bypass valve. At higher brake pipe pressure drops, the piston 1244 moves further down in the figures opening bypass valve element 1226 and bypassing the restriction or choke 1265. This allows the reference volume side 1245B of the piston to exhaust at a higher rate and initially prevent the valve from initiating an emergency.

[00053] For a further decrease in brake pipe pressure as shown in Fig. 4, the piston 1244 moves further down in the figures as an initial stage or starting of an emergency braking. This results since the stability choke 1239 and the venting of the brake pipe BP and the reference volume QA through passage 1244D cannot keep up with the drop in pressure in the brake pipe. This further movement of the emergency piston 1244 causes the second end 1248 of passage 1244D to engage the closure area 1247 of valve element 1256 of the vent valve. This stops the venting of the brake pipe BP and the reference volume QA 34. The differential pressure between the reference volume QA and the dropping brake pipe BP over comes spring 1259 and subsequent piston movement opens the vent valve 1256 to connect the brake pipe via B34 directly to exhaust EX as shown in Fig. 5. Also, the bottom 1244A of the emergency piston engages actuator 1332 to open high pressure valve element 1232 off of valve seat 1231 connects the emergency reservoir at E32 to the end valve portion 1238 via C34 and onto the brake cylinder BC via C32.

[00054] The high pressure valve element 1232 subsequently engages valve seat 1231 disconnecting the top of the inshot piston 1236 from the brake cylinder BC via C32, C34 through seat 1257 and restriction or choke 1235. As pressure in the brake cylinder builds under the inshot piston 1236 via C32 and restriction or choke 1237, the inshot piston 1236 moves end valve portion 1238 to restrict the connection of the emergency reservoir ER to the brake cylinder BC and thereby slow down the build up of the brake cylinder pressure at port C32 during the first stage of an emergency application. After given a period of time, the inshot piston 1236 is move back to the unrestricted flow.

[00055] Once the bottom 1244A of the emergency piston engages a stop 1242C after opening the vent valve 1256, further opening of the vent valve slightly opens the second end 1248 of the passage 1244D while maintaining the first end 1249 open. Also, bypass valve element 1226 is closed. Thus, the reference volume QA is bled to exhaust until it is depleted.

[00056] Since the valve seat area 1247 for the second end 1248 of the passage 1244D is on the vent valve an in chamber 1254, it is exposed to atmosphere and the brake pipe when the vent valve is open. To protect this area, a shroud 1347 surrounds the valve seat area 1247. The shroud 1347 may be formed as a portion of the vent valve element 1256 as shown in Figs. 2-7 or mounted thereto as shown in Fig. 1 1. The end of the shroud is received and rides in recess 1348 of the body 1240 as shown in Figs. 2-7 or about the body 1240 as shown in Fig. 1 1.

[00057] A sleeve 1356 extends from the bottom of vent valve element 1256 and moves along seal 1358 separating the brake pipe port B34 and atmosphere. The sleeve 1356 divides a surface opposite the valve seating surface into a peripheral area 1256A exposed to the brake pipe and an area 1256B exposed to atmosphere. By minimizing the peripheral area exposed to brake pipe pressure, the spring 1259 is the major determinative of the force needed to open the vent valve 1256. The peripheral area 1256A exposed to brake pipe pressure may be less than 20% of the total area, for example.

[00058] To release an emergency brake application, the brake pipe is re-pressurized.

Since the reference volume QA is depleted, the initial rise in brake pipe pressure moves the emergency piston 1244 up as shown in Fig. 6. The reference volume QA is charged by the brake pipe BP via B32, through chokes 1239 and 1339 and open check valve 1340. At a low rate of brake pipe build up, the chokes 1239 and 1339 and spring 1270 raises the piston 1244, but keeps it from moving actuator 1322 to open valve element 1222 of the emergency accelerated release valve.

[00059] At a high enough rate of brake pipe build up, the chokes 1239 and 1339 cannot keep up and the differential pressure rises as shown in Fig. 7. The piston 1244 moves to open valve element 1222 of the emergency accelerated release valve by actuator 1322 against springs 1223, 5. Once valve element 1222 is open, the brake pipe pressure at B32 is provided to one side of check valve 1224. The other side of check valve 1224 is exposed to the brake cylinder pressure at C32.

[00060] Initially the brake cylinder pressure is great than the brake pipe pressure and check valve 1224 opens connecting the brake cylinder to brake pipe. Thus, the brake cylinder pressure is used to charge the brake pipe. Once the brake pipe pressure plus the force of spring 1223, 5 exceeds the brake cylinder pressure, the check valve 1224 closes.

[00061 ] An exploded view of the improved emergency portion 20 is shown in Fig.

10. The diaphragm 1244' has been left out for clarity. The vent protector 1253 is shown in more detail in Fig. 1 1.

[00062] As can be seen from Figs. 2-8, a plurality of actuators 1332, 1244C, 1328B respectively interconnect the piston 1244 to and operate the high pressure valve 1232, the vent valve 1256, the reference volume discharge valve 1228, and the brake pipe discharge valve 1228 as a function of positions of the piston 1244. The vent valve 1256, the reference volume discharge valve 1228 and the brake pipe discharge valve 1228 may be coaxial in a stack. A common valve element 1228 may be used for the reference volume discharge valve and the brake pipe discharge valve and even the reference volume choke bypass valve 1226.

[00063] The high pressure valve 1232 and the emergency accelerated release valve 1222, 1224 may be parallel to and displaced from the stack as shown in Figs. 2-7. Alternatively the emergency accelerated release valves 1222, 1224 is in the stack and the high pressure valve 1232 is parallel to and displaced from the stack as shown in Fig. 8. The actuator 1322 for the valve element 1222 is an extension of the piston head portion 1244B. As shown in Fig. 13, the emergency accelerated release valves 1222, 1224 of the prior art of Fig. 1 may be used.

[00064] The reference volume choke bypass valve 1226 may be displaced from the center stack and have a separate actuator responsive to the piston 1244 as illustrated in Fig. 1 1. An accelerated application sensor valve 1212 is shown as a spool valve with holes 1312 which move up and down with respect to o-ring 131 1. The actuator 121 1 of the accelerated application sensor valve 1212 is an extension of the piston head portion 1244B. When the piston 1244 moves down for drops in brake pipe pressure, the holes 1312 connect the reference volume side 1242 B to the bypass valve element 1226 initially open against spring 1267 by actuator 1328B moved by the piston 1244. The reference volume exhaust fast bypassing the restriction or choke 1265 with a direct connection to exhaust chamber 1254. For an emergency drop in brake pipe pressure, the downward movement of the piston will allow the bypass valve element 1226 so seat. The combination of accelerated application sensor valve 1212 and bypass valve element 1226 form a bypass valve which s closed for small drops of brake pipe pressure, opened to exhaust for greater drops of brake pipe pressure and finally closed for large drops of brake pipe pressure as determined by an actuator responsive to the emergency piston's position.

[00065] As shown in Fig. l 1 , the vent protector 1253 includes a filter element 1380 held between two body portions 1382 and 1384. A lock or wing 1386 extends from the body portion 1384. The body portions 1240 and 1230 include an exterior bore 1390 connected to the vent chamber 1254 by a counter bore 1392. A bayonet type recess 1394 is provided in counter bore 1394 to receive and lock the wing 1386 of the vent protector 1253. The wing 1386 enters the recess 1394 axially into the bores 1390 and 1392. The wing is rotated and then moves axially outwardly. The filter element 1380 flexes against the transition between bore 1390 and counter bore 1392.

[00066] Fig. 12 shows a portion of the emergency portion of Figure 2 with a blow back preventer of reference volume to brake pipe. A check valve 1370 in a chamber of the piston 1244 is in series between the brake pipe chamber 1242A and the choke 1261 via a pair of channels 1372. The check valve 1370 is open when valve element 1228 opens 1249 to connect the brake pipe chamber or side 1242A to chamber 1266 and the reference volume chamber or side 1242B and onto to atmosphere or exhaust. If the reference volume pressure attempts to flow through restriction or choke 1261 , the check valve 1370 closes.

[00067] Accordingly, it will be understood that the preferred embodiment has been disclosed by way of example and that other modifications and alterations may occur to those skilled in the art.

Claims

What is claimed:

1. An emergency portion of a brake control valve having: a piston with brake pipe pressure on a first side of the piston and a reference volume pressure on a second side of the piston; a first choke connecting the two sides of the piston; a high pressure valve for connecting a reservoir port to a brake cylinder port for an emergency pressure in the brake pipe; a vent valve for connecting a brake pipe port to atmosphere for an emergency pressure in the brake pipe; a reference volume discharge valve for initially connecting the reference volume to atmosphere for a decrease in brake pipe pressure; and a brake pipe discharge valve for connecting brake pipe to atmosphere for a decrease in brake pipe pressure; and wherein:

a plurality of actuators interconnect the piston to and operate the high pressure valve, the vent valve, the reference volume discharge valve, and the brake pipe discharge valve as a function of positions of the piston.

2. The emergency portion of Claim 1 , wherein the vent valve, the reference volume discharge valve and the brake pipe discharge valve are coaxial in a stack.

3. The emergency portion of Claim 2, including an emergency accelerated release valve interconnected to and operated as a function of positions of the piston for connecting the brake cylinder port to the brake pipe first side of the piston for an increase in the brake pipe pressure after an emergency application; and wherein the high pressure valve and the emergency accelerated release valve are parallel to and displaced from the stack.

4. The emergency portion of Claim 2, including an emergency accelerated release valve interconnected to and operated as a function of positions of the piston for connecting the brake cylinder port to the brake pipe first side of the piston for an increase in the brake pipe pressure after an emergency application; and wherein the emergency accelerated release valve is in the stack and the high pressure valve is parallel to and displaced from the stack.

5. The emergency portion of Claim 1 , including a common valve element for the reference volume discharge valve and the brake pipe discharge valve.

6. The emergency portion of Claim 1 , including a second choke in parallel to a bypass valve; and wherein the second choke and the bypass valve are connected between the reference volume and exhaust, and the bypass valve is responsive to the position of the piston via an actuator to initially open for a decrease of brake pipe pressure to bypass the second choke and subsequently close for a large drop in brake pipe pressure.

7. The emergency portion of Claim 1 , including an emergency accelerated release valve interconnected to and operated as a function of the position of the piston for connecting a check valve between the brake cylinder port and the brake pipe first side of the piston for an increase in the brake pipe pressure after an emergency application; the check valve is opened when the pressure in brake cylinder port is greater than the pressure on the brake pipe first side of the piston by a fixed amount.

8. The emergency portion of Claim 1 , including a third choke connecting the first and second sides of the piston, the third choke having a smaller restriction than the restriction of the first choke, and a check valve in series with the third choke for connecting the first and second sides of the piston through the third choke when the pressure in the brake pipe first side is greater than the reference chamber second side.

9. The emergency portion of Claim 1 , wherein the vent valve includes a valve element having a first side for engaging a valve seat, and a second side of the valve element opposite the first side having a peripheral area exposed to brake pipe pressure of less than 20% of its total area.

10. The emergency portion of Claim 1 , wherein the reference volume discharge valve includes a valve element which engages a valve seat on a valve element of the vent valve and is the actuator of the vent valve, and including a shroud surrounding the valve seat when the vent valve is open.

1 1. An emergency portion of a brake control valve having a piston with brake pipe pressure on a first side and a reference volume pressure on a second side, a first choke connecting the two sides of the piston, one or more valves actuated by the position of the piston to effect emergency braking only for emergency brake pipe pressure, and including:

a second choke connecting the first and second sides of the piston;

the second choke having a smaller restriction than the restriction of the first choke; and

a check valve in series with the second choke for connecting the first and second sides of the piston through the second choke when the pressure in the brake pipe first side is greater than the reference volume second side.

12. An emergency portion of a brake control valve having: a piston with brake pipe pressure on a first side of a head of the piston and a reference volume pressure on a second side of the piston head; a vent valve for connecting a brake pipe port to atmosphere for an emergency pressure in the brake pipe; and a reference volume discharge valve responsive to the position of the piston for initially connecting the reference volume to atmosphere for a decrease in brake pipe pressure; and including:

a piston rod connected to the piston head having a passage with a first end connected with the reference volume second side of the piston head and a second end connected to atmosphere;

a valve element of the reference volume discharge valve includes a closure area for the first end of the passage;

a valve element of the vent valve includes a closure area for the second end of the passage; and

wherein the first end of the passage is closed and the second end is open for a balanced position of the piston, the piston moves and the first end opens and the second end remains open for an initial decrease in brake pipe pressure, the piston subsequently moves and the first end remains open and the second end is closed for a further decrease in brake pipe pressure and further piston movement opens the vent valve, and the first end remains open and second end opens for further opening of the vent valve.

13. The emergency portion of Claim 12, including an actuator extending between the valve elements of the reference volume discharge valve and the vent valve for opening the reference volume discharge valve.

14. The emergency portion of Claim 13, including a stop and the piston head engages the stop after opening the vent valve such that further opening of the vent valve opens the second end of the passage while maintaining the first end open.

15. The emergency portion of Claim 12, including a brake pipe discharge valve for connecting a port connected to the first brake pipe side of the piston head to the first end of the passage for a decrease in brake pipe pressure.

16. The emergency portion of Claim 15, wherein the valve element of the reference volume discharge valve includes a closure area for the port connected to the first brake pipe side of the piston head.

17. The emergency portion of Claim 12, including a shroud surrounding the closure area for the second end of the passage on the vent valve.

18. An emergency portion of a brake control valve having: a piston with brake pipe pressure on a first side of a head of the piston and a reference volume pressure on a second side of the piston head; and a reference volume discharge valve responsive to the position of the piston for initially connecting the reference volume to atmosphere for a decrease in brake pipe pressure; and including:

a chamber having a first port connected to the brake pipe first side of the piston, a second port connected to the reference volume second side of the piston and a third port connected to atmosphere;

the reference volume discharge valve includes a common valve element for controlling the connection of both the first and ports to the third port in response to the position of the piston.

19. The emergency portion of Claim 18, wherein valve element engages and covers the first and third ports.

20. The emergency portion of Claim 18, including a check valve in series with the first port to prevent flow from the chamber into the brake pipe first side of the piston.

21. An emergency portion of a brake control valve having: a piston with brake pipe pressure on a first side of a head of the piston and a reference volume pressure on a second side of the piston head; a vent valve for connecting a brake pipe port to an atmosphere port for an emergency pressure in the brake pipe; and a vent protection element extending across the atmosphere port; wherein the atmosphere port has a bore including a bayonet recess and the vent protection element includes:

a body;

a filter mounted to the body and sized to cover the atmosphere port when the vent protection element is mounted to the emergency portion; and

a lock extending from the body to be received into the bayonet recess to mount the vent protection element to the emergency portion.