Abstract:
A brake cylinder maintaining may include spool valves or poppet valves. When the pressure in the brake cylinder drops below its original set pressure, such a maintaining valve may feed brake pipe (BP) pressure through a choke to replenish and maintain brake cylinder (BC) pressure up to a certain point. If the leak is too great (i.e., to the extent it exceeds the capacity of the choke), the brake cylinder will not be maintained. Such a maintaining valve may be either integrated into the control valve, or it may be mounted remotely to the brake system. If mounted remotely, it may be connected by multiple ways, including through a conventional 4-port access plate.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of and claims the priority benefit of copending U.S. patent application Ser. No. 13/652,896, filed on Oct. 16, 2012, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND AND SUMMARY 
       [0002]    The present disclosure relates generally to control valves for use in freight car brake equipment, and more particularly to a valve that maintains the brake cylinder pressure in such control valves. 
         [0003]    Control valves used in freight car brake equipment (e.g., the DB-60 control valve manufactured by New York Air Brake Corporation, Watertown, N.Y. USA or the ABDX control valve manufactured by Wabtec Corporation, Wilmerding, Pa. USA) are well known. If such control valves supply air pressure to the brake cylinder of a freight car, and the plumbing between the control valve and the freight car has a leak, then the brake cylinder will not maintain the original set pressure. This could be due to, for example, a leaking packing cup in the brake cylinder, a leaking hose, or any other reason that would lead to the leaking of pressure between the connection of the control valve and the brake cylinder. 
         [0004]    One means of avoiding such problems may be to have a valve that maintains the brake cylinder pressure. When the pressure in the brake cylinder drops below its original set pressure, such a maintaining valve may feed brake pipe (BP) pressure through a choke to replenish and maintain brake cylinder (BC) pressure up to a certain point. If the leak is too great (i.e., to the extent it exceeds the capacity of the choke), the brake cylinder will not be maintained. Such a maintaining valve may be either integrated into the control valve, or it may be mounted remotely to the brake system. If mounted remotely, it may be connected by multiple ways, including through a conventional 4-port access plate. 
         [0005]    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 
         [0006]      FIG. 1  is a schematic of freight car brake equipment according to the prior art; 
           [0007]      FIG. 2  is a diagrammatic view of a service portion of a brake control valve used in the freight car brake equipment shown in  FIG. 1 ; 
           [0008]      FIG. 3  is a diagrammatic view of a brake cylinder maintaining valve according to one embodiment of the present invention; 
           [0009]      FIG. 4  is a diagrammatic view of a brake cylinder maintaining valve according to another embodiment of the present invention; 
           [0010]      FIG. 5  is a diagrammatic view of a brake cylinder maintaining valve in its charging lap position utilizing a sandwich plate between the service portion of the brake control valve and its release valve; 
           [0011]      FIG. 6  is a diagrammatic view of a brake cylinder maintaining valve in its service lap position utilizing a sandwich plate between the service portion of the brake control valve and its release valve; 
           [0012]      FIG. 7  is a diagrammatic view of an ABDX-type brake cylinder maintaining valve in its charging lap position; and 
           [0013]      FIG. 8  is a diagrammatic view of an ABDX-type brake cylinder maintaining valve in its service lap position. 
           [0014]      FIG. 9  is a diagrammatic view of a brake cylinder maintaining valve integrated into the control valve in its charging lap position; 
           [0015]      FIG. 10  is a diagrammatic view of a brake cylinder maintaining valve integrated into the control valve in its service lap position; 
           [0016]      FIG. 11  is a diagrammatic view of a brake cylinder maintaining valve shown as a sandwich plate between the service portion and release valve and in its service lap position; and 
           [0017]      FIG. 12  is a brake cylinder maintaining valve according to still another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Exemplary embodiments are discussed in detail below. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. In describing and illustrating the exemplary embodiments, specific terminology is employed for the sake of clarity. However, the embodiments are not intended to be limited to the specific terminology so selected. Persons of ordinary skill in the relevant art will recognize that other components and configurations may be used without departing from the true spirit and scope of the embodiments. It is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. The examples and embodiments described herein are non-limiting examples. 
         [0019]    Referring now to the drawings, wherein like reference numerals and characters represent like or corresponding parts and steps throughout each of the views, there is shown in  FIG. 1  a schematic representation of a brake system associated with a prior art freight or rail car  100 . The system may be used to operate air brakes (not shown) in accordance with known embodiments of the prior art. As illustrated, the freight car brake equipment includes a brake control valve  102  having a service portion  104  and an emergency portion  106  connected to a pipe bracket  108 . A cut-off cock  110  connects, through a branch pipe tee  112 , brake pipe  114  to the pipe bracket  108  at port BP. A retaining valve  116  connected to exhaust is connected to pipe bracket  108  at retainer port RET. A combined reservoir  118 , having an auxiliary AUX RES and an emergency reservoir EMER RES is connected to respective ports AR and ER of pipe bracket  108 . A brake cylinder  120  may be connected through an empty/load device (not shown) to brake cylinder port BC. The elements described so far are part of normal freight car brake equipment. The service portion  104 , emergency portion  106 , and pipe bracket  108  are standard parts, for example, a DB-60 from New York Air Brake Corporation or Knorr Bremse AG. Similarly, they may be an ABDX or other AAR approved brake valves. 
         [0020]    Air used to operate the brakes on rail cars may be transmitted through brake pipe  114  to brake control valve  102 , and may accumulate in combined reservoir  118 . Brake pipe  114  may be coupled with corresponding brake pipes in attached rail cars (not shown) through AAR standard air brake hoses  122  to form a train line operable to communicate air from an associated locomotive (not shown) to each rail car  100  attached to the locomotive as part of a train. Brake pipe  114  may serve at least two purposes. First, air may travel through brake pipe  114  to accumulate in combined reservoir  118  for each individual rail car  100 . Second, brake pipe  114  may facilitate transmission of a pressure drop that activates respective brakes associated with each rail car  100 . 
         [0021]    Although the improvement herein will be shown in  FIGS. 3-10  to have been incorporated into the service portion of the DB- 60 , the present improvement may be provided to any brake control valve portion which includes a piston responsive to brake pipe pressure on one side and a reservoir as the source of brake cylinder pressure on the other side of the diaphragm. Thus, the invention may be used in other AAR-styled brake control valves or non-AAR brake control valves, including ABDX-type control valves as shown in  FIGS. 7-8 . Only those portions of the service portion of the DB-60 and ADBX which explain the operation of the present invention have been included in the schematics and others have been intentionally deleted for sake of clarity. 
         [0022]    Pipe bracket  108  supports and aligns both service  104  and emergency  106  portions and supplies air to the valvular components. The precontrolled flow of air to and from the brake pipe  114 , brake cylinder  120 , combined auxiliary/emergency reservoir  118  and retaining valve  116  is also directed through the pipe bracket  108  to which all connections are made, with butt or socket welded flange fittings. 
         [0023]    The specific functions of the service portion  104  are to supply air to the combined reservoir  116  during initial charging of the system and recharging following release of an application; to direct auxiliary reservoir AR air into the brake cylinder  118  depending on a predetermined rate and amount of brake pipe pressure reduction; to exhaust brake cylinder BC air during release after an application; to guarantee stability of the brake system in release condition against undesired application of the brakes which may result from permissible brake system leakage; and to guarantee stability of the brake system in service lap condition against undesired release of the brakes which may result from permissible auxiliary reservoir leakage. The service portion  104  also functions to support recharge of the brake system during the release of a service application by feeding emergency reservoir ER air into the brake pipe  112  independent from the main piston system; to guarantee minimum reduction during initial brake pipe reduction and maintain minimum brake cylinder BC pressure by connecting quick service chamber QS-Ch. and brake cylinder BC pressures; to support initial brake pipe reduction by venting brake pipe BP air to the atmosphere ATM during the preliminary quick service stage; to support recharge of the brake system after manual release subsequent to an emergency application by connecting the pressure of the auxiliary reservoir to the brake pipe  112 , to permit exhaust of retainer held brake cylinder pressure in the retainer pipe and volumes during manual release subsequent to a service reduction; to directly release brake cylinder pressure independent of the main piston system after any application by manual activation of the release handle; to provide manual drain means for auxiliary reservoir and emergency reservoir pressures; and to release the main piston system after a service application by manual activation of release handle. 
         [0024]    In order to perform these functions, the service portion  104  is equipped with the following subcomponents. 
         [0025]    As shown in  FIG. 2 , the service main piston  202  compares brake pipe BP and auxiliary reservoir AR pressures acting on equal areas. Auxiliary reservoir charging  204 , emergency reservoir charging  206 , and balancing valves  208  are spaced uniformly at  120 ° intervals around the same diameter and are mechanically operated by the bottom side of the piston. The coaxially arranged balancing piston  210  is pressurized with auxiliary reservoir AR air by the balancing valve  208  and acts on the balancing spring  212  which stabilizes the main piston system  202  in service lap position. 
         [0026]    The main piston  202  operates the quick service inlet valve  214 , which allows brake pipe 
         [0027]    BP air to flow to the quick service chamber (QS-Ch.). The auxiliary reservoir/brake cylinder inlet  216  and brake cylinder/retainer outlet valves  218  are also mechanically operated by the main piston  202 . Stability of the main piston system  202  in the release position is provided by means of the sensitivity  220  and stability chokes  222 ; stability in the service lap positions is provided by means of the stability choke  222 . A separate emergency reservoir charging check valve/choke  224  arrangement prevents uncontrolled return flow of emergency reservoir ER air into the auxiliary reservoir when releasing the brakes from a service application. Thus, no undesired reapplication of the brakes will occur during release. 
         [0028]    A metal reinforced rubber diaphragm  225  of the service accelerated release valve  226  also compares brake pipe BP and auxiliary reservoir AR pressures acting on equal areas; this component operates independently of the service main piston system  202 . When the service accelerated release valve  226  is triggered, emergency reservoir ER air passes by the high sensitivity back flow check valve  228  into the brake pipe BP. 
         [0029]    A metal reinforced rubber diaphragm  229  of the quick service limiting valve  230  is pressurized by brake cylinder BC air and allows restricted flow of brake pipe/quick service air to the brake cylinder  118  to a predetermined value. The quick service limiting check valve  232  prevents return flow of brake cylinder BC air to atmosphere ATM during emergency applications and in the event of a retainer is being set in “high pressure retaining” position with the service main piston system  202  in the release position. 
         [0030]    A metal reinforced rubber diaphragm  233  of the emergency release auxiliary reservoir reduction valve  234  is pressurized by brake pipe and brake cylinder air in opposite sides. After manual release of brake cylinder pressure subsequent to an emergency application, increasing brake pipe pressure during recharging operates the valve and allows auxiliary reservoir air to flow via the emergency release auxiliary reservoir reduction check valve  234  into the brake pipe and assists during brake pipe recharging. The retaining check valve  236 , by means of a choke, allows reduction of retainer held brake cylinder air to a pressure level which allows the brake cylinder piston to move to release position. 
         [0031]    The quick service valve  238  piston is pressurized by auxiliary reservoir AR air on one side and controls the flow of quick service QS air to atmosphere ATM. As soon as the service main piston system  202  allows the balancing valve  208  to pressurize the larger opposite area of the quick service valve piston with auxiliary reservoir air, the venting of quick service/brake pipe air will be interrupted. The piston of release valve  240  is pressurized on both sides with brake cylinder BC air and seals the connection from brake cylinder  120  to atmosphere ATM. 
         [0032]    Upon activation of the release valve handle  242 , the upper side of the piston is vented through the release exhaust valve  244  which allows the piston to open the passage from brake cylinder  120  to atmosphere ATM. The piston remains in this position until brake cylinder lockup pressure below the piston is released by the service main piston system  202  upon its release. Auxiliary reservoir exhaust  246  and emergency reservoir exhaust  248  valves are mechanically operated by the release valve lifter  250  and allow high capacity flow of auxiliary reservoir/emergency reservoir air to the atmosphere in order to drain the brake system. 
         [0033]    Charging Lap Position 
         [0034]    Compressed air from the brake pipe  114  flows into the pipe bracket  108  via the combined dirt collector and cut-out cock. One flow path leads through the pipe bracket strainer into the service  104  and emergency  106  portions to supply those with filtered air. The other flow path bypasses the pipe bracket strainer and leads to the vent valve (not shown) in the emergency portion  106  to allow unrestricted venting of brake pipe BP air during an emergency application. During charging, brake pipe air pressurizes the following valve components: 
         [0035]    Brake pipe BP air pressurizes the main piston, the valve seat area  214 , and flows to the service accelerated release valve  226  and the emergency release auxiliary reservoir reduction valve  234 . The auxiliary reservoir is charged directly by the service main piston system  202 . From the brake pipe  118 , the air flows via choke  220  and an open valve seat  204  to the volume below the main piston, pressurizing the upper side of balancing piston  210 . Auxiliary reservoir air further flows to the AR/BC inlet valve  216 , to the release valve  240 , to the valve seat in the balancing valve  208 , to the quick service valve  238  and the auxiliary reservoir via the pipe bracket  108 . Additional auxiliary reservoir charging is accomplished by air flow via stability choke  222 . 
         [0036]    If, during charging, the pressure differential created by chokes  220  and  222  across the main piston exceeds a predetermined value, the main piston moves into retarded recharge position and returns to charging lap position when brake pipe BP and auxiliary reservoir AR pressures approach equalization. 
         [0037]    The emergency reservoir is charged from auxiliary reservoir air via open valve seat  206 . 
         [0038]    The auxiliary reservoir AR air in the volume below the main piston  202  flows via an open valve seat in the emergency reservoir charging check valve  224  to the service accelerated release valve  226 , to the release valve  240 , to the emergency portion (not shown) and via the pipe bracket  118  into the emergency reservoir. 
         [0039]    The left side of diaphragm  225  is pressurized with brake pipe BP air, the right side with auxiliary reservoir AR air. Emergency reservoir ER air flows to the closed valve seat via back flow check valve  228 . The left side of diaphragm  233  is pressurized with brake pipe BP air. The diaphragm  233  is thereby forced on its right-hand stop against the force of a spring. Simultaneously, the emergency release auxiliary reservoir reduction check valve  239  is forced on its valve seat by the combined forces of a spring and brake pipe BP pressure. 
         [0040]    Auxiliary reservoir AR air in the volume below the main piston also pressurizes the upper area of piston  241 . The piston  241  is thereby forced downward and opens the valve seat against the force of the spring. Auxiliary reservoir AR air pressurizes auxiliary reservoir exhaust valve  246 . Emergency reservoir ER air pressurizes emergency reservoir exhaust valve  248 . 
         [0041]    Service Lap Position 
         [0042]    During a service brake application, the brake cylinder is charged from the auxiliary reservoir by the service main piston system  202 . As soon as the auxiliary reservoir pressure is reduced to approximately the value of the brake pipe pressure, the service main piston system  202  moves from the service position to the service lap position. Herewith, valve seat  216  is closed and the flow path between auxiliary reservoir and brake cylinder is interrupted. The balancing piston  210  acts on the balancing spring  212  through its spring guide. This introduces a defined force in the service main piston system  202 , which holds it in the service lap position. 
         [0043]    Brake pipe BP and auxiliary reservoir AR are connected through the very small stability choke  222  which determines the release stability. During a further brake pipe reduction, the service main piston system  202  will again move the service position, and the flow path from auxiliary reservoir to brake cylinder will be opened. Subsequently, the same procedure as described above will take place and move the service main piston system  202  back again to service lap position. The reduction of brake pipe pressure and hence the increase in brake cylinder pressure can be continued until the auxiliary reservoir pressure is equal to the brake cylinder pressure. A further reduction of brake pipe pressure does not affect the level of the brake cylinder pressure during a service application, but moves the main piston system  202  to the service position. The quick service limiting valve  230  assures a predetermined minimum brake cylinder pressure. Should the brake cylinder pressure drop below this value—for example, due to brake cylinder leakage—the quick service limiting valve  230  will open and feed brake pipe pressure via the quick service chamber to brake cylinder. 
         [0044]    In the service lap position, the control valve has moved from charging lap and undertaken the following steps. The first step is quick service, where BP is reduced lower than AR to the point that the quick service check valve  214  is opened and the valve moves up into the service zone. Once the valve is in the service zone, the valve fills AR pressure into BC through check  216 . The valve continues to fill BC until BP and AR are roughly equal. The limiting valve  230  will run until BC pressure under diaphragm  231  reaches about 8 to 12 pounds per square inch. At this point, the quick service limiting valve  230  will shut off Once the AR and BP are roughly equalized and the filling of BC has been completed, the valve is in service lap. 
         [0045]    Referring now to  FIG. 3 , there is shown a brake cylinder (BC) maintaining valve  300  according to a first embodiment of the present invention. This poppet valve embodiment is shown in the service lap position. Accordingly, the valve  300  has made a brake application where the valve has charged BC up to its set point. At this point, BC 1  is roughly 15 psi lower than BC 2 . If BC starts to leak, then BC 2  pressure will become lower than BC 1  and the diaphragm  302  will move down opening check valve  304 , allowing BP air to flow into BC which will do so until BC pressure is maintained to roughly the original set pressure. During the release of the valves, there will be a rise in BP pressure, and when BP becomes greater than AR diaphragm  306  will open check valve  308  and exhaust the trapped air putting the valve back into charging lap position. 
         [0046]    The spool design shown in  FIG. 4  has the same function as the poppet design shown in  FIG. 3 , but it has been designed using spool valve technology. This valve  400  is in the state where the control valve has gone into the service lap position where BC 2  is roughly 15 psi lower than BC 1 . If BC starts to leak, then BC 1  pressure will become lower than BC 2 , and the spool valve  402  will move down connecting BP to BC. This will stay connected until BC has been maintained to roughly the original set pressure. During the release of the valve, there will be a rise in BP, and when BP becomes greater than AR, spool valve  404  will move up connecting the trapped BC to atmosphere. This will put the BC maintaining valve  400  back to its initial charging state. 
         [0047]    Referring now to  FIGS. 5 and 6 , the operation of the brake cylinder maintaining valve utilizing a sandwich plate between the service portion of the brake control valve and its release valve will now be described. During charging or release, valve  505  will be open to atmosphere which will exhaust the reference BC pressure on top of diaphragm  502 . In the charging lap position (i.e., where BP is about equal to AR) as shown in  FIG. 5 , exhaust check valve  505  will be open. Once in a service application, BC pressure under diaphragm  502  is substantially equal to the actual brake cylinder (BC) pressure. On top of diaphragm  502 , BC is roughly 15 psi lower than the pressure in the brake cylinder (BC). This  15  psi difference is created by the cracking pressure of check valve  503 . 
         [0048]    If a leakage occurs, the BC pressure under diaphragm  502  will become lower than the pressure on top of the diaphragm  502  causing the diaphragm  502  to open check valve  504  and maintain BC against the leakage in the brake cylinder by supplying BP air through valve  504 . It should also be noted that check valve  503  could be removed and check valve  505  could be ported to BC and used as the feed check valve for the reference BC air. In such a manner, when the reference air is exhausted it will be exhausted to the retainer line RET. The brake cylinder maintaining valve may be integrated (see, e.g.,  FIGS. 9 and 10 ) into the control valves of either a DB-60 or an ABDX and on either side, either in the emergency portion or in the service portion. It may be preferable if it is on the service portion side, where it can be upstream of the release valve so the lock out feature of the release valve will work. 
         [0049]    For example,  FIGS. 7 and 8  illustrate its incorporation into an ABDX-type control valve  700 . In charging lap, port  701  vents BC air from the top of diaphragm  703 . Also, port  708  will not be connected to supply the quick service limiting valve  705 . So when the valve  700  is in this position there will be no BC maintaining. In service lap (as shown in  FIG. 8 ), the control valve  700  has moved from charging lap and gone through the following steps. 
         [0050]    The first step is quick service where BP is reduced lower than AR to the point that the quick service is opened and the valve moves up into the service zone. Once the valve is in the service zone, the valve fills AR pressure into BC. The valve continues to fill BC until BP and AR are roughly equal. The limiting valve will run until BC pressure under diaphragm  703  reaches 8 to 12 psi. 
         [0051]    At this point, the quick service limiting valve  705  will shut off. During this time, BC pressure will open the back flow check valve  706  which has a high enough cracking pressure to not to interfere with the function of the limiting valve. Once the AR and BP are roughly equalized and the filling of BC has been completed the valve is in service lap. 
         [0052]    Once in service lap, if the BC leaks off then the BC pressure under the diaphragm  703  will become lower than the original reference pressure which is bottled on top of the diaphragm due to port  701  being closed when the valve is in the service zone. Once the pressure differential is high enough, the diaphragm will push the spool down opening port  704  allowing BP to flow into BC until diaphragm  703  is balanced again. Once the valve moves back to its charging lap position, port  701  opens and the bottled air is released putting the modified limiting valve  705  back into charging lap position. And, the BC pressure is exhausted to atmosphere. 
         [0053]      FIGS. 9 and 10  are diagrammatic views of a brake cylinder maintaining valve integrated into the control valve in its charging lap and service lap positions, respectively. In the charging lap position as shown in  FIG. 9 , check  901  will be venting BC air from the top of diaphragm  905 . Also, there will be no air in the quick service chamber QS Ch. to supply the modified limiting valve  230 ′. So when the valve is in this position there will be no BC maintaining. 
         [0054]    In its service lap position as shown in  FIG. 10 , the control valve has moved from charging lap and gone through the following steps. The first step is quick service, where BP is reduced lower than AR to the point that the quick service check  909  is opened and the valve moves up into the service zone. Once the valve is in the service zone, the valve fills AR pressure into BC through check  910 , and the valve continues to fill BC until BP and AR are roughly equal. The quick service limiting valve  230 ′ will run until BC pressure under diaphragm  905  reaches 8 to 12 psi. At this point, the quick service limiting valve  230 ′ will shut off. During this time, BC pressure will open the back flow check  904 , which has a high enough cracking pressure to not interfere with the function of the quick service limiting valve  230 ′. Once the AR and BP are roughly equalized and the filling of BC has been completed, the valve is in service lap. Once in service lap, if the BC leaks off, then the BC pressure under the diaphragm  905  will become lower than the original reference pressure, which is bottled on top of the diaphragm  905  due to check  901  being closed when the valve is in the service zone. Once the pressure differential is high enough, the diaphragm will push the check  906  open allowing BP to flow into BC until diaphragm  905  is balanced again. 
         [0055]    Once the valve moves back to its charging lap position, check  901  is opened and the bottled air is released putting the modified quick service limiting valve  230 ′ back into charging lap position. And the BC pressure is exhausted to atmosphere. 
         [0056]      FIG. 11  shows yet another embodiment of a brake cylinder maintaining valve  1100 . According to this embodiment (which is shown in its service lap position), the valve  1100  is in its home position. During a service application, BC pressure will enter volume  1103  through check  1102  which will have a cracking pressure of roughly 15 psi. Once in service lap, if BC leaks, the pressure on top of diaphragm  1104  will be greater than the pressure under the diaphragm causing the diaphragm to open check  1105 . This, in turn, will supply BP pressure to the brake cylinder to compensate for the leak therein. Check  1106  will then keep BC from flowing back into BP in the event that BP is lower than BC this could be during an over reduction or during an emergency application. During the release of the valve  1100 , BP will be greater than AR, which will cause diaphragm  1101  to move down and open check  1102 . This, in turn, will allow the bottled BC air to exhaust out through the retainer line. 
         [0057]      FIG. 12  shows still another embodiment of a brake cylinder maintaining valve  1200 . In contrast to the embodiment shown in  FIGS. 9 and 10  (where the reference pressure is charged through back flow check  904  from BC 1 ), the embodiment shown in  FIG. 12  charges from the same back flow check  904  but from BC 2 . In regards to exhausting in the embodiment shown in  FIGS. 9 and 10 , such exhausting takes place through check  901 . The exhausting takes place in the embodiment shown in  FIG. 12  through an exhaust valve  1202  into BC  1 . 
         [0058]    Although the present brake cylinder maintaining 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 scope of the present invention is to be limited only by the terms of the appended claims.