CA2392197C - Unitized railcar brake equipment - Google Patents

Abstract

A unitized railcar brake equipment can have a relatively small integrated air supply and can be controlled electronically. The equipment can have a brake cylinder portion and a control valve portion. The brake cylinder portion can have a brake cylinder housing a piston head with a rod end of the piston connected to a railcar brake member. A pair of air chambers communicate on opposite sides of the piston head and an air reservoir can be integral with the brake cylinder housing.
Selective coupling of the air chambers and the air reservoir to each other, a source of pressure, or to the atmosphere can be controlled by appropriate valves to control the pressure in the brake cylinder.

Description

TITLE
UNITIZED RAILCAR BRAKE EQUIPMENT
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon copending United States Provisional Patent Application Serial No. 60/302,319, filed June 29, 2001.
BACKGROUND OF THE INVENTION
The present invention relates generally to controlling brakes on a train of xailcars, and more particularly to highly efficient, unitized railcar brake equipment that is based on electronic control of a pneumatically operated, stand-alone brake cylinder that can have a small, integrated air supply volume.
Historically, braking on railcars can has been implemented using pneumatic brake equipment provided on each railcar. Such prior art equipment typically can include a control valve which is connected to a brake pipe that interconnects the locomotive and each railcar in the train. The brake equipment on each car further can include a two compartment reservoir of pressurized air which the control valve can utilize to pressurize the brake cylinder on the car.
U.S. Pat. No. Re. 30;408, reissued Sept. 30, 1981, to the assignee of the present application; discloses railway brake apparatus including a brake cylinder device and a control valve device. The usual air reservoirs associated with conventional pneumatic brake equipment can be minimized or eliminated in the disclosed apparatus in favor of storing the compressed air within, the brake cylinder device itself. The brake cylinder device disclosed embodies a pair of tandem-connected pistons of unequal diameter, the larger piston cooperating with the brake cylinder body to form on the respective opposite sides of this piston two chambers that are charged with compressed air via the train brake pipe, and in which chambers the air required for use by the brake apparatus, including the brake cylinder device, is stored. The aforementioned control valve device operates in response to variations in the train brake pipe pressure to control the transfer of air stored in the brake cylinder device, so as to develop differential forces across the respective pistons thereof, and thereby effect a brake.application and brake release. In addition to the typical packing cup type pressure seals associated with the respective pistons of this brake cylinderdevice, there are several additional areas in which dynamic sealing is required, all of which are critical in the sense that leakage thereat affects the desired operation of the brake cylinder device. Further, passageways are required in the body of the brake cylinder device to conduct pressure between the control valve device and brake cylinder operating components. It is well known that the expense in the manufacture of a casting increases with the complexity in the configuration of these passages, as well as in the shape of the casting itself.
U.S. Patent No. 4,418,799; issued December 6, 1983 to the assignee of the present application, discloses a pneumatic brake cylinder device which improves upon the brake cylinder device disclosed in Re 30,408: This brake cylinder device employs a pair of different sized fluid motors the pressure chambers of which serve as air storage reservoirs. The cylinder of the larger fluid motor is forrded by the main casting anti contains a larger piston, while the cylinder of the smaller fluid motor is mounted to 2.

the main casting in coaxial relationship with the larger cylinder and contains a smaller piston having an elongated hollow body that is connected at its open end to one side of the larger piston to form a pressure chamber therebetween. The smaller, positioning piston fits within the smaller cylinder in spaced-apart relationship therewith to form a pressure chamber delimited by a seal fixed on the main casting for engagement with the piston periphery at any point along its longitudinal axis. The larger, power piston cooperates with the larger cylinder to form pressure chambers on opposite sides thereof. As compared to the device disclosed in Re 30;408, the arrangement in 4,418,799 provides for a design employing fewer seals and a simplified main casting in which all the passages to the respective pressure chambers are contained. A
similarity between the two devices is that a pair of pistons are employed, wherein the smaller piston displaces the larger piston in order to provide a brake application. As the smaller, positioning piston drives the larger, power piston air is transferred from an air chamber behind the power piston into a chamber on top of the positioning piston.
In an emergency application, air in the chamber behind the power piston can be vented while air from a third chamber is coupled to the chamber on top of the positioning piston. To release the brakes, the chamber on top of the positioning piston is vented and the chamber behind the power piston is recharged.
Railcar brake equipment, including the two brake equipment devices described above, historically initiate brake application and release operations on the railcar based upon pneumatic brake commands from a brake control valve on a locomotive. These pneumatic commands are typically communicated to each railcar by pausing pressure changes in a brake pipe connecting each railcar to the locomotive 3:

brake control valve. In the past, and particularly on freight ears operating in North America, the railcar brake equipment, including the specific brake equipment described above, can only implement a "direct" release of brakes on the railcar. Direct release means that the pressure in the brake cylinder on the railcar can only be fully released, as opposed to gradually releasing the pressure to gradually reduce the braking force.
However, some pneumatically operated brake equipment has been disclosed which can provided graduated release capability. Additionally;:graduated release of railcar brakes has recently been the target of brake system development in the American railway system and can be implemented using what is commonly referred to today as electrically controlled pneumatic (ECP) braking systems. ECP braking systems use specialized equipment on locomotives and railcars whereby brake command signals are generally instantaneously communicated, via a hardwired tramline or RF
communications, between the locomotive and each railcar. The ECP brake equipment on each railcar typically utilizes solenoid type valves to control the air pressure in the brake cylinders; and are thus easily controllable to gradually increase or decrease the level of braking on each railcar. However; use of ECP braking systems can require a trainline wire or RF communication equipment and electronic control valves on each railcar, as well as electronic control ystems on the locomotive.
SUMMARY
An efficient, unitized' railcar brake equipment can be provided wherein a pneumatically operated, stand-alone brake cylinder can have a relatively small, integrated air supply volume which can be selectively coupled to opposite sides of a 4.

singlepiston for gradually applying or releasing the brakes on the railcar.
The unitized brake equipment can be operated without; or independently of, a conventional pneumatic control valve, and can be controlled from a locomotive in an ECP
manner using, for example, a trainIine or an RF communication system. Furthermore, the unitized brake equipment could automatically initiate a full pneumatic brake application responsive to a loss of brake pipe pressure, without electronic intervention or control. The unitized brake equipment can include a brake cylinder and a piston member housed therein with a first air chamber in communication with the face of the piston and a second air chamber in communication with the opposite side of the piston.
An air reservoir can also be provided, and can be formed as an integral part of the brake cylinder. The first and second air chambers and the air reservoir can be interconnected by air passages and controlled by valves, so that they may be selectively coupled and uncoupled to control pressure in the brake cylinder. Some of the valves can be electrically operated remotely, for example, by a train engineer, to control air pressure in the brake cylinder to operate the brakes on the railcar.
Additionally; same valves can be co~gured to operate:automatically in response to fluid pressure conditions prevailing in the air passages in the unitized brake equipment, or pressure conditions in the brake pipe, to which the unitized brake equipment can be connected:
The unitized brake equipment can be supplied with pressurized air from, for example, the brake pipe for charging the reservoir andlor the first and second air chambers.
Additionally, the unitized brake equipment can be selectively vented to the atmosphere, for example, by appropriate valves, for reducing the pressure in the brake cylinder.
The valves for controlling the air pressure in the various chambers and reservoir can be 5.

provided as components of an electronic control valve portion, which can be mounted on the front or rear of the brake cylinder, via a pipe-bracket type of interface. The interface can be a separate component or can be formed as an integral part of the brake cylinder.
The unitized brake equipment can employ a "self: actuating" brake cylinder, wherein air pressure is admissible to both sides of the piston, but acts on unequal effective areas provided on the opposing sides. For example, the face of the piston can be provided with a larger effective area such that it has an effective advantage over the opposite side of the piston: The unitized brake equipment can be designed such that, in release position, the internal volume of the first chamber, acting on the face of the piston, is relatively small, whereas the largest portion of the internal volume of the brake cylinder can be provided as the second chamber, which acts on the opposite side of the piston. The second chamber can thus also be utilized as an integrated air reservoir. To apply the brakes, the piston is forced to the applied position simply by connecting the air chambers on either side of the piston, and allowing the pressure on the face of the piston to approach the pressure on the opposite side, due to the area advantage. To thereafter reduce pressure in the brake cylinder, the smaller first air chamber acting on the face of the piston can be controllably exhausted to the atmosphere: Because much of the volume of air stored on the opposite side of the piston is simply transferred to the face of the piston in moving the piston to apply the brakes, only a relatively small volume of air is left on the opposite side of the piston when piston travel is completed and the brakes are fully applied. Thereafter, the pressure of this small volume can easily be incrementally increased or reduced, to 6.

gradually apply or release braking force by any degree desired, while using relatively little compressed air.
Other advantages of the unitized brake equipment over conventional ECP (all electric)' controlled brake equipment can; in some instances, result in reduced cost, size and weight. Further advantages can include simplif ed piping and installation, higher braking force capability from a given initial pressure, reduced consumption of pressurized air, and faster train charging and recharging. With the unitized brake equipment, the separate air storage or supply reservoirs and associated piping used with conventional railcar brake equipment can be eliminated, as can be the separate pipe bracket.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
A more complete understanding of the invention can be obtained by considering the following detailed description in conjunction with the accompanying drawings, in which:
Figure l a is a diagrammatic drawing of prior art type pneumatic railcar braking equipment.
Figure I b is a diagrammatic drawing of prior art type ECP railcar braking equipment.
Figure 2 is a diagram bowing a presently preferred embodiment:
Figure 3 is a diagrammatic drawing of the unitized brake equipment with the piston shown in a release position.

7.

Figure 4 is a diagrammatic drawing of the unitized brake equipment of Figure 3, except shown with the piston in an applied position.
Figure 5 is a largerdiagrammatic drawing of the electronic control valve portion of the unitized brake equipment shown in Figure 3.
Figures 6a and 6b illustrate the concept of "offset area."
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
An example of a prior art type all-pneumatic railcar braking system is illustrated in Figure la, whereas an example of a prior art type ECP railcar braking system is illustrated in Figure 1 b: These two drawing figures are provided for purposes of a general comparison of the prior art type braking equipment with the unitized railcar brake equipment according to he present invention. Such a comparison will likely enable greater understanding and appreciation of the invention, certain preferred embodiments of which are described in more detail hereinafter in connection with Figures 2 through 6.
As shown in Figure Ia, the prior art type fully pneumatic railcar brake equipment 6 typically can include a standard pneumatic control valve 8, such as an ABD, ABDX or ABDW, manufactured by Westinghouse Airbrake Technologies Corporation ("WABTECTM"). The brake pipe ("BP") 10 connects to the central portion 13, i.e. the "pipe bracket," of the pneumatic control valve 8: Service 14 and emergency 17 portions of the pneumatic control valve 8 are mounted on either side of the pipe-bracket 12. The pipe-bracket 13 also communicates with auxiliary 20 and emergency 23 reservoir compartments of a dual compartment reservoir 24, the brake 8.

cylinder 26 and the atmosphere 29, usually through a retainer device 32. The total volume of the conventional dual compartment reservoir is typically about 6000 cubic inches.. Each reservoir compartment 20, 23 is pressurized from the brake pipe 10 via internal passages in the pipe-bracket 13. Similarly, pressurized air is selectively communicated by the pneumatic control valve 8 via internal passages in the pipe-bracket 13, between the reservoir compartments 20, 23 , the service 14 and emergency 17 portions, the brake cylinder 26, and the atmosphere 29, in order to control the air pressure in the brake cylinder 26 and thus the braking and release functions on the railcar.
Referring now to Figure 1 b, a prior art type ECP railcar brake equipment is illustrated typically including a local brake control device, such as an electronic car control device ("GCD") 38, which can control a pair of application valves 40, 42 to supply pressurized air from the dual compartment reservoir 24 to the brake cylinder 26. The CCD 38 also normally controls a release valve 45 to reduce pressure in the brake cylinder 26. As with the fully pneumatic brake control equipment shown in Figure la, the brake pipe 1;0 is utilized to supply pressurized air to each compartment 20, 23 of the dual compartment reservoir 24. In this case however, each compartment 20, 23, of the reservoir 24 can be individually connected to the brake pipe 10 for maintaining pressurization thereof. Back-flow check valves 35, 36 are also typically provided between each compartment 20, 23 so that pressure cannot escape back into the BP 10 if the pressure therein reduces below the prevailing pressure in either reservoir compartment 20, 23: . As shown; the separate application valves 40, 42 can be connected between each reservoir compartment 20, 23, respectively, and the 9.

brake cylinder 26, with the auxiliary reservoir 20 connected to the auxiliary application valve 40 and the emergency reservoir 23 connected to the emergency application valve 42. As mentioned above, the service and emergency brake application valves 40, 42 can be controlled by the CCD 38 to selectively communicate one or both of the reservoir compartments 20, 23 with the brake cylinder 2b to increase braking force on the railcar. Although not Shown; the brake cylinder 26 is conventionally connected to a linkage, commonly referred to as brake "rigging," for actuating the rigging to apply brake shoes to the wheels of the railcar. The CCD 38 can control the release valve 45 for venting the brake cylinder 26 to reduce the pressure therein and reduce braking force on the railcar: The CCD 38 can be controlled by a remote brake controller. In particular, the CCD 38 can receive command signals 48 from a train engineer using a brake controller 49, which can be remotely located on a locomotive and can control the CCD 38 via a wireline 11 or wireless communications, such as an RF communication system 12. The CCD 38 can also receive feedback 50 from a pressure sensor 52 which monitors the pressure in the brake cylinder 26.
Additional pressure sensors, although not shown, could be provided at other locations, such as the reservoir compartments 20, 23 and along the brake pipe 10, to monitor the pressure at those locations for added feedback.
A train brake system employing an embodiment of a unitized railcar brake equipment 60 according fo the invention is illustrated diagrammatically in Figure 2. As shown, the unitized brake equipment 60 can generally comprise a brake cylinder portion 63 and an electronic control valve portion 66, and can be controlled by a local brake control. device, such as the CCD 38, to regulate braking on the railcar.

10.

However, in contrast to the brake system in Figure 1a, a brake system having the unitized brake equipment 60 need not have a reservoir 24, or application 40, 42 and release 45 valves,, since these functions can all be combined into the unitized brake equipment 60. This can result in a simpler, lighter braking system which can still have the advantages of an ECP type system; for example one such as shown in Figure 1 a.
The unitized brake equipment can supplied with pressurized air via a pneumatic connection with the BP 10 and cambe electrically connected to the CCD 38 for control thereby. More specific details of the brake cylinder portion 63 and the electronic control valve portion 66 are provided below. As with the ECP type system illustrated in Figure la, the CCD 38 can receive commands from a remote brake control device, such as controller 49, by signals transmitted via wireline l l or wirelessly, such as by an RF communications system 12.
Referring to more detailed views in Figures 3 and 4, the electronic control valve portion 66 can be mounted directly to the pneumatic brake cylinder portion 63. The brake cylinder 63 portion can be comprised of several members, namely-- a brake cylinder 69; a piston 72 operably disposed in the brake cylinder 69, and an air reservoir'75 generally circumscribing the brake cylinder 69. The piston 72 can include a piston head 78 and a push rod 81 connected to the back side 80 of the piston head 78. Although not shown; it should be understood that the opposite end of the push rod 8 l can be connected to rigging for applying brake shoes to the wheels of the railcar.
In addition to the air reservoir 75, the volume within the brake cylinder 63 itselfcar! serve as an additional reservoit of pressurized air.
Moreover, the 1 T.

brake cylinder 6f can have a pipe bracket interface member 84; to which the electronic control valve 66 can be mounted, as shown in the drawing figures. A first bi-directional seal 87, as opposed to a single direction packing cup which may typically be used, can be provided between the piston head 78 and the brake cylinder 69.
Also, a mechanical return spring 90 can be provided acting on the back side 80 of the piston head 78. The push rod 81 can be hollow, and the end opposite the end connected to the piston head 78:can extend through an opening provided in a front cover member 64 of the pneumatic brake cylinder portion 63 for connection to brake rigging for applying brake shoes to the .wheels of the railcar. A second; sliding air seal 96 can be provided between the push rod 81 and the front cover 64. The brake cylinder portion 69 can comprise two chambers: an application chamber 97, or "chamber A,"
communicating on the face 79 of the piston head 78;; and a release chamber 98, or "chamber R,"
communicating on.the back side 80 of the piston head 78. The reservoir 75 can be an annular volume provided encircling, the brake cylinder 69. In one embodiment, the combined stored air volume of chambers A 97, chamber R 98, and the reservoir 75 can be about 2000 cubic inches, wherein the reservoir 75 can be about 11 SO cubic inches, and chamber R 98 can be about 850 cubic inches in release position. In the release position, the volume of chamber A 97 is generally negligible. In comparison, conventional freight railcar brake equipment typically can have a total air reservoir volume of 6000 cubic inches. The overall: size of the unitized brake equipment 60 can be very compact; for example-- only about 18 inches in diameter,and about 14 inches in length. Moreover, with the unitizEd brake equipment 60, the separate air storage or 12.

supply reservoirs and associated piiping used with conventional brake equipment can be eliminated, as can the separate pipe bracket.
The electronic control valve portion 66 can preferably be mounted to the front of the brake cylinder 63, as depicted in the drawing figures.
Alternatively; the electronic control valve 66 could be mounted to the back of the brake cylinder portion 63, which,would provide similar direct access to the internal brake cylinder 69 chambers A 97, R 98 and the reservoir 75, but would not need to avoid the piston push rod 81. However, such a rear mounting may not be as readily accessible on bulk commodity freight cars as a front mounted embodiment. The requisite internal passages can be provided in the pipe bracket interface member 84 , for example passages 99 and 102. These internal passages can mate with corresponding internal passages provided in the electronic control valve portion 66, for example passages 105, 108. The mating internal passages can provide for controlled access by employing appropriate valves; for example valves V 1-V4, in the electronic control valve portion 66 between the reservoir 75, chambers A 97 and R 98, brake pipe 10, and the atmosphere, via passage I09. The various internal passages and associated valves far controlling pressures in the different air volumes will be described in more detail below, primarily in connection with the enlarged view of the control valve portion 66 shown in Figure 5.
Figure 3 portrays the unitized brake equipment 60 with the piston 72 in a release position, whereas Figure 4 shows the piston-72 in the applied position: As displayed in both figures, chamber A 97 communicates with the face; e.g., the application side, of the piston head 78 and chamber R 98 communicates on the 13.

opposite side, e.g., the release side, of the piston head 78. The reservoir 75 can be formed integral with the brake cylinder 63, and in one presently preferred embodiment, can be provided in the form of an annular volume which encircles the brake cylinder b3.
The unitized brake equipment 60 can be "self actuating;" such that air pressure can be applied to both sides of the piston head 78, but acts on unequal surface areas provided on the opposing sides. For example, the face of the piston head 78 can be provided with a larger surface area such that it can have an effective advantage over the opposite side of the piston head 78. The unitized brake equipment 60 can be designed such that, in release position, the application chamber A 97 is relatively small, whereas the largest portion of the internal volume, i.e., the release chamber R 98, can be provided on the opposite side of the piston head 78: The release chamber R
98 can be charged to the brake pipe pressure, for example, from the brake pipe 10, and can be used as an additional air supply along with the air reservoir 75. The piston 72 can be forced to the applied position merely by coupling the application chamber A 97 with the release chamber R 98, thereby permitting the pressure in each chamber to approach equalization. In one embodiment, a return spring 90 can be provided on the release side of the piston head 78; in opposition to pressure acting on the face of the piston head 78. The force required to overcome the return spring 90 and move the piston 72 can be derived from providing an effective surface area advantage provided on the application side of the piston head 7$, with respect to the surface area provided on the opposite, release side of the piston head 78. Advantageously, as the piston 72 is moved, much of the tored volume of air in chamber R 98 is simply transferred to 14.

chamber A 97, thus leaving a relatively small "operable volume," of, for example, only about 200 cubic inches, or less, in chamber R 98 when the brakes are fully applied. In contrast, the operable volume of a conventional brake cylinder can typically be more than 600 cubic inches. After the piston 72 has been moved to apply the brakes, the pressure of the relatively small remaining volume in chamber R 98 can be incrementally increased, ar reduced; to gradually adjust braking force by essentially any degree desired. Moreover, this can all be accomplished using relatively little compressed air.
In one embodiment; shown best in Figure 5, the electronic control valve portion 66 can include four small, electrically operated valves, for example miniature solenoid valves V 1-V4. Each valve V 1-V4 can be paired with, and can also serve as a pilot to, separate pneumatic booster valves B1-B4 having higher air flow capacities than the mailer solenoid valves V 1-V4: The electronic control valve portion 66 also can include a charging check-valve I l 1,. a pneumatic interlock valve I 14 (which can be configured for automatic actuation in response to movement of the piston 72);
and a cut-off valve 116 that can serve to cut off the exhaust of application chamber pressure in the event of a substantial loss of brake pipe 10 pressure. In one;
illustrated in Figure 4, a full stroke of the piston 72 can automatically actuate the pneumatic interlock valve 114:
Solenoid valve Vl and its diaphragm booster valve BI can control air communication between the reservoir 75 and chamber R 98. The reservoir pressure 75 can serve as a source for pilot air pressure, which normally holds booster diaphragm valve B1 closed. When solenoid valve V1 is;energized, it opens to quickly exhaust the I 5.

pilot pressure against a very small feed choke 117, allowing pressure in the reservoir 75 and chamber R 98 to 'force the diaphragm of booster valve B 1 off its seat, against a light spring 120, and connect chamber R 98 with the reservoir 75.
Solenoid valve V2 audits diaphragm booster valve B2 can control the flow of air under pressure from chamber A 97 to atmosphere via passage 109.
When energized, valve V2 isolates chamber A 97 from the atmosphere, and when de-energized connects it. Reservoir 7~ air is used as the pilot pressure, which is admitted by solenoid valve V2, when energized, to close the diaphragm booster valve B2.
The pilot pressure is open fo a small bleed hole I23, which introduces a very small amount of leakage flow against an essentially overwhelming supply when valve V2 is activated, but exhausts the small pilot volume quickly once the valve V2 is closed.
Solenoid valve V3, in conjunction with its: diaphragm booster valve B3, can control air communication between the reservoir 75 and chamber A 97. Brake pipe 10 pressure can be used as the source for pilot air pressure for valve V3, which normally holds the diaphragm booster valve B3: closed, disconnecting chamber A

from the reservoir 75. When valve V3 is energized, it exhausts the pilot pressure against a small feed choke 124; allowing booster valve V3 to open and connect chamber A 97 to the reservoir 75: It is also noteworthy that the loss of brake pipe 10 pressure, even without energization of valve V3, will cause the pilot pressure to be lost and allow booster valve B3 to open.
Solenoid valve V4 and its diaphragm booster valve B4 can control the flow of air under pressure from chamber R 98 to the atmosphere via passage 109.
When de-energized, valve V4 isolates chamber R 98 from the atmosphere, and when 16.

energized connects it. Similarly to valve V3; pressure in the brake pipe 10 can be used as the source of pilot air pressure to normally hold booster valve B4 closed, and thus the depletion of brake pipe pressure will allow booster valve B4 to open even without energization of valve V4.
A piston-travel interlock valve 114 can be designed to work in concert with booster valves B3 and B4 of solenoid valves V3 and V4 to bring about an automatic full application of the brakes responsive to a loss of pressure in the brake pipe 10. Such an application requires no electronic valve actuation.
The,piston-travel interlock valve 114 acts in parallel with valve V 1 to connect the reservoir 75 with chamber R 98 in release position, and in series with valve V4 to control the exhaust of chamber R 98 fo atmosphere in the applied position. Reservoir 75 pressure can communicate with the top of the interlock valve 114 and a beveled stem 126 can actuate the interlock valve 114. The beveled stem l26 can be positioned laterally perpendicular to and abutting the end of the interlock operating valve stem 129. The beveled stem 126 protrudes into the:release chamber R 98 of the brake cylinder 63 and is contacted and driven forward by the piston 72 when full piston travel is approached;
as shown in Figure 4. When the piston 72 is in its noanal release position; a spring 132 forces the beveled stem 126 outward, causing a ramp profile 13S on the beveled stem 126 to laterally displace the interlock valve stem 129. As it moves, the interlock valve stem 129 first seats on the interlock check valve member 137, cutting off the connection of chamber R 98 from atmosphere, and then forces open the check valve member 137 from its stationary eat, :connecting chamber R 98 to the reservoir 75.
When brakes on the railcar are applied and the piston ?2 approaches its full travel, it 17.

contacts and forces the protruding beveled stem 126 to retract: The beveled stem 126 then allows the interlock valve stem 129 to be displaced downward by the interlock check valve spring 138, permitting the interlock check valve member 137 to re-seat, cutting off the reservoir 75 from chamber R 98. The interlock valve stern 129 is also free to then be forced away from the interlock check valve member137 under the influence of the check valve spring 138, thus connecting chamber R 98 to booster valve B4, and to atmosphere if B4 is also open. Because the interlock valve 114 is arranged in series with booster valve B4; no-; air :pressure can be exhausted from chamber R 98 unless both the interlock valve I 14:. and booster valve B4 are open. The interlock valve 114 is only open when the piston 72 is in applied position. Booster valve B4 can be opened either as a result of V4 being energized under electronic control or by the eternal depletion of brake pipe pressure from the pilot chamber of valve B4.
Solenoid valve V l, which controls communication between chamber R
and the reservoir 75, can also be used in combination with the piston-travel interlock valve 114 to perform electronic graduated release. Additionally, a simple brake cylinder release :valve (not shown) could also be employed to allow manual brake cylinder release by venting chamber A 97 to drain off air pressure without electrical control.
Because valve V2 must be energized in order to isolate chamber A 97 from exhaust and retain pressure'dur~ng an application; a pneumatic cut-off valve 116 can be provided in series with booster valve B2. Brake pipe 10 pressure communicates on one side of the pneumatic cut-off valve I 16 and holds the valve open to connect chamber A to atmosphere. , with V2;controlling the connection of chamber A to cut-18.

off valve 116. In the event of a power failure, V2 ,would connect chamber A to exhaust. i-Iowever, in such case cut-off valve 116 can block the exhaust of chamber A 97 when brake pipe 10 pressure is depleted, thereby permitting retention of chamber A 97 pressure during the pneumatic application. If a power failure should occur during a brake application, and brake pipe pressure were not depleted, V 2 would exhaust chamber A. All of this can be best understood from Figure 4. Releasing the brakes on an individual railcar experiencing a.power failure can be the desired fault condition.
However, if this condition were to occur on the whole train of railcars, or a certain number of railcars'in the train, an emergency application could be commanded.
A loss of brake pipe pressure would automatically close the cut-off valve 116, cutting off chamber A from atmosphere, and: would also automatically open booster valve B3, thereby eonnecting: chamber A to the reservoir.
As a general principle of operation; the unitized brake equipment 64 relies on he control of pressures that act on unequal effective areas across the piston 72 to apply and release the brakes on the railcar. Referring back to Figure 2, in release position chamber A 97 is vented to atmosphere, which allows the return spring 90 and the pressure in chamber R 98 to force the piston 72 to its fully retracted position.
When the brakes are to be applied, first the reservoir 75 pressure is admitted to chamber A 97 via valve V3. Because the reservoir 75 is also connected to chamber R 98 at this time via valve V 1, all three chambers 75, 97, 98 will tend to equalize in pressure. Based on selected design volumes for the three chambers 75, 97, 98 and the specific area unbalance, full equalization would generally cause a reduction of pressure in the reservoir 75 and chamber It 98.on the order of about 5 psi. Therefore, if the 19.

initial operating pressure were 90psi, for example; the pressure in all three chambers 75, 97; 98 would equalize at about 85 psi; if allowed to do so.
Because the .hollow piston rod 81 is sealed where it passes through the front cover 64 of the brake cylinder b3; chamber A 97 pressure acts on the piston head 78 with a larger effective area than the opposing chamber R 98 pressure.
The difference in the area acted on by pressure on the face 79 of the piston head 78 and the area acted on by the pressure on the back side 80 of the piston head 78 is commonly referred to ws the "area offset." Referring to Figures 6a and 6b; dl could represent the diameter of the face 79 of the piston head 78 and d2 could represent the diameter of sliding air seal 96., The area of d2 would be the "offset area," since this is the area not acted upon by pressure in the release chamber R. Depending upon the actual areas selected, some minimum pressure, such as, for example, l0 to 20 psi, will be required on the effective: offset area to produce sufficient force to overcome the resistance of the return spring 90 and sliding friction; causing full travel or extension of the piston 72.
At the equalized pressure, such as, for example, 85 psi, the total output force of the piston 72 will be generally about equivalent to that of a heavy minimum service reduction with a conventional brake arrangement; again, depending on the specific area offset.
It should be noted that; during piston 72 movement, chambers A 97and R 98 remain connected, by way of the reservoir 75, via valves V 1 and V3, and most of the volume of air originally residing in chamber R 98 is effectively transferred across the piston to expanded chamberA 97; vriith only a modest increase in total volume and therefore minimal loss of initial pressure. The increase in pressurized volume in going 20.

from release to applied position consists of the clearance volume of chamberA
97 (in release) plus the area offset multiplied by the piston. stroke. The relatively small volume made up of the area offset multiplied by the piston stroke represents the displacement volume (theoretically pressurized: from a complete vacuum created by piston displacement). In this case, the area offset is equal to the area of the front seal 96 on the push rod 81, because that is the area not acted upon by the pressure in chamber R 98 in opposition to chamber A 97. Also, the relatively large brake cylinder 63 can reduce the overall rigging lever ratio required to achieve the desired braking ratio, in turn minimizing the piston stroke necessary to take up a given brake shae-to-wheel clearance.
Once the piston travel has been completed and the minimum braking force established, valve V 1 can be operated to isolate chamber R 98 from the reservoir 75; and thus chamberA 97. In this applied position, the volume remaining in chamber R 98 can be minimal as a result of the piston 72 travel. In order to exert increasing braking force, the pressure in this small volume of chamber R 98 can be exhausted via valve V4 to atmosphere, to whatever extent is needed or desired.
It should be noted that at this degree of piston travel the piston-travel interlock valve 114 is open, connecting chamber R fo valve V4. If chamber R 98 pressure is completely exhausted, as it could be during an emergency application, the maximum effective pressure acting across the full area of the face of the piston head 78 will be the original equalization pressure, or about 85 psi. This is comparable to the maximum emergency brake cylinder pressure of about 78 psi produced with a conventional reservoir and brake cylinder.
21.

For any application heavier than a minimum application, chamber R 98 pressure can be supplied or exhausted to maintain a target pressure, which can be a function of chamber A 97 pressure and the degree of application commanded.
During a brake application, the pressure in the reservoir 75 can be continuously charged from the brake pipe 10 via charging check valve 111 to raise it back to about 90 psi and generally maintain it at that pressure. Valve V3 can be used to either maintain chamber A 97 at 85 psi,.or to gradually increase it back to 90 psi during a sustained brake application by connecting chamber A 97 to fhe reservoir 75 via valve V3. If such recharge is desired in system design; chamber:R 98 pressure could also be recharged to a controlled degree; by connecting chamber R 98 to the reservoir 75 via valve V 1, in order to maintain the desired cylinder output force while recharging chamber A
97.
This may be different during an emergency application.
In order to graduate brake pressure off, to reduce the effective braking force, it can be necessary only to re-charge chamber R 98 to whatever degree is desired, which can be accomplished using valve V 1. The system can be very efficient in terms of minimiaang compressed air usage due to the relatively small volume of chamber R 98 when the piston 72 is in the applied position: The effective braking force may be reduced from any point, up to and including a maximum application, all the way down to essentially zero braking force, simply by restoring chamber R

pressure to the extent needed to obtain the particular level of braking desired. Unless chamber R 98 pressure is increased somewhat above that of chamber A 97, the piston will remain in the applied position due to the effective area advantage of chamber A 97 over chamber R 98. Braking force may, in fact, be repeatedly graduated on and off to 22.

any desired degree simply by exhausting and recharging the small chamber R 98 volume.
When a complete release to a fully retracted running position is desired, chamber R 98 can be recoupled with the reservoir 75, and chamber A 97 pressure can be isolated and reduced by connecting it to exhaust. This step can result in amore significant air loss than any other, because the substantial volume of applied chamber A 97 must be exhausted to below 40 psi in order to fully retract the piston 72 under the influence of the return spring 90. Consequently, a full release would be made only when it is anticipated that there will be no need for subsequent brake applications for some time. As long as a very minimal application is maintained, so that the piston 72 does not retract, higher braking forces can be reapplied with only minimal air usage from the system.
According to one embodiment, four valve operating positions are provided: release, transition; application and application lap. Transition occurs both during piston movement from release to applied position when an application is initiated, and during graduated release. In transition, the positions of all valves V I -V4 are intermittently the same regardless of which transition condition is occurring, but the effect differs due to the prevailing pressures. The following chartindicates the individual valve positions for each of these conditions.
23.

Reservvoir ZS Chamber A 97 Atmosphere Chamber R 98 r ~~
V2 Open Full Release ( ) V 1 Open Transition V3 Qpen V 1 Open Application [ 1 [ ) V3 Open V4 Open Application [ ) Lap V3 Open In release position chamber9 97 is opened to atmosphere, allowing the return spring 90 to: move the piston 72 to its fully retracted position. The reservoir 75 is connected to chamber R
98 and both are fully charged to the operating brake. pipe 10 pressure.
Transition position applies to both initial piston 72 movement and o graduated relcsase: Piston 72 movement is initiated when an application is made, by connecting the reservoir 75 to chamberA 97 while still connected to chamber R 98. The pressure in chamber A 97 is increased sufficiently to fully displace the piston 72 and drive the brake shoes against the wheels: Because of the effective area advantage of chamber A
97 over chamber R 98, full piston 72 movement can occur before chamber A 97 pressure is increased to that of chamber R
98. Depending on the prevailing pressures; the charging of chamber A 97 can be controlled to produce he exact amount of desired cylinder output force; even for light minimum applications. At higher prevailing pressures; minimum application forces will be reached priorto equalizing chamberA
97 with chamber R 98, whereas at lower pressures or for heavier applications, it may be necessaryto equalize the pressures and possibly reduce chamber It 98 pressure o meet force requirements. During graduated release, transition position charges chamber R 9& instead of chamber A 97.
~ Application position connects chamberA 97 to the reservoir 75 to .increase the pressure in chamber A 9? to the desired 24.

application force. Additionally, chamber R 98 is isolated from the reservoir 75 and opened to exhaust; as needed, to reduce chamber R 98 pressure to derive the desired application force.
'The pneumatic interlock valve 114 is arranged in series with solenoid V4; so that chamber R 98 pressure cannot be exhausted until the piston 72 movement has been essentially completed.
~ In application lap; the chamber R 98 exhaust is closed and target pressures are maintained.
The unitized brake equipment 60 can also be more efficient in the application of air pressure to produce braking force. From any given pressure, the unitized brake equipment 60 with a selfaetuating brake cylinder 63 can be capable of generating approximately 9% higher maximum (emergency) effective brake cylinder pressure, in substantially larger brake cylinders, with only about one-third as much stored air volume as conventional reservoirs. Furthermore; using a 12-inch diameter brake cylinder 63 with a 5- to 6-inch piston stroke; the 2000 cubic inch volume of stored air in the unitized brake equipment 60 can produce more than SO°1o higher maximum cylinder output force than the conventional brake equipment produces with a 10-inch brake cylinder. Using a reduced-rigging lever ratio ('tn conjunction with the shorter piston stroke); the maximum net brake shoe force on the railcar would still be approximately 35% higher using the unitized brake equipment 60. This would enable higher loaded car braking ratios, which would not cause excessive in-train forces with electronic signal transmission.
A train of railcars equipped with the unitized brake equipment 60 can provide the capability for fully graduable brake applications and releases, while utilizing far less compressed air than a conventionally equipped train.
Because much less cumulative air volume would need to be delivered through the train brake pipe 10 25:

using the unitized brake equipment 60, train charging times could also be dramatically reduced.
In'a certain embodiment, pressures in the reservoir 75 and both chambers A 97 and R 98 can be controlled electronically by the four solenoid valves V2-V4, for example, under the direction of a CGD 38 which receives command signals 48 from a controller 49 via the wire line 11 or RF. communication system 12, as described previously in connection with Figure lb: The CGD 38, and/or the controller, can be a computer or other processing equipment. Valve leads L1-L4 can be electrically connected in a known manner to the CCD 38 actuating the corresponding solenoid valves Vl-V4. Alternatively; the valve leads L1-L4 could be simply be hardwired to an interface provided onboard the railcar, and the interface could be connected to the controller 49 via the wireline 11 or 1tF communication system I 2. In any case, it is to be understood that: various ways of communicating with and controlling the solenoid valves V1-V4 on the railcars; whether using both a and controller 49, or simply hardwiring the electrically operated valves V 1-V4 for direct control by the controller 48; can be accomplished employing conventional methods such as currently being used in prior art ECP braking systems like that described above in connection with Figure 1b. Moreover, feedback from one or more sensors 150, 153, 156, for example pressure transducers, can also be provided to either or both the CCD 38 and the controller 49. Like the electrical leads L1-L4 of the solenoid valves V l-V4; leads 160, 163 and 166 of the pressure sensors 15U, 153, 156, can be similarly connected to the CCD 38 or controller 49 to provide feedback regarding the prevailing pressure in each of the air volumes 75, 97, 98, or other 26.

pressures, such as in the brake pipe 10, in order to implement what is commonly referred to as "closed-loop" control over the braking functions on the railcars.
In accord with AAR practice, brake commands to each car can call for (1) a brake release, (2) a percentage of fuel service; ar (3) an emergency application, the maximum brake available. These commands can be interpreted and translated into a net shoe force requirement on each car. The proper pressures in chambers A 97 and R 98 can then be determined based upon appropriate equations. Whatever type of controller or control devices are utilized; it could be programmed with the appropriate equations for calculating the desired shoe force, and for controlling the electronic control valve portion to provide the proper pressure in the various chambers and reservoir. Various equations for making-such calculations are provided below;
near the end of the description.
The following tables are spreadsheet calculations of chambers A 97 and R 98 pressures and' corresponding output forces for the a preferred 12-inch brake cylinder b9. Table I shows the brake cylinder output forces for pressure equalization of chambersA 97 and R 98, as well.as the maximum cylinder output force, for various piston offset areas, from 5 to l3 square inches. These calculations are based on 90 psi initial pressure. The equivalent pressure required in a standard I O-inch brake cylinder with a conventional brake equipment is also shown for both the light applications derived from equal pressures in A 97 and R 98 and for maximum applications.
Additionally, Table 1 shows the theoretical equalization pressure required to yield 300 pounds cylinder output force with the various unbalanced piston areas.
27.

When equaftzationof chamber R 98 with the reservoir 75 and chamber A 97 is used as a minimum or light service application, the equivalent lU-inch cylinder pressure varies from 3.63 to 11.3 psi, as the piston offset area is increased from S to 13 square inches,; respectively. This suggests that; if it is desired to use a simple pressure equalization for minimum applications; the offset area should be approximately square inches, yielding a braking force equal to that which would be obtained with about 8:5 psi in a conventional 10-cylinder. This equalization force output would vary some, however, if initial pressures other than 90 psi were used.
Table 2 fixes the piston offset area at 12.566 square inches, representing a 4-inch diameter seal on the push rod 81. This piston offset area was found to be an optimum balance for minimizing air usage on one hand; and both for providing application capability at the lowest charge pressure and providing a rapid piston movement in emergency on the other hand. Preferably, the pressure in chamber R

should not be reduced to provide high emergency braking force until full piston travel has been completed. This is because that exhat,sting chamber R 98 to produce high braking forces, prior to full piston travel, would waste much air, and thus reduce the available chamber A 97 pressures that could otherwise be provided. Therefore, the only force available to actually move the piston 72 is the offset piston area times the equalized pressure in both chambers A 97 and R 98: It is also desirable to move the piston 72 as fast as possible during an emergency application. Table 2 also shows the brake cylinder output force for light applications, where chamber A 97 pressure is charged to a range of pressures from 80 psi up to 85.2 psi, rwhich is the equalization prESSUre from 90 psi. The net cylinder force varies from 218 pounds up to 1070.8 28.

pounds, respectively. Equivalent pressures for a conventional 10-inch cylinder are also shown for each case. Using this cylinder arrangement, the ideal chamber A 97 pressure for a light minimum application would be 83:5 to 84 psi, which is below the full equalization pressure of 85.2 psi.
Table 3 shows the chamber A 97 pressure required o produce approximately 7U~ pounds cyti~der output force for initial pressures ranging from SQ
to 110 psi. Table 4 is a worksheet, and Table 5 shows the chamber A 97 pressures which will produce nominally 600 pounds cylinder output force. It is believed that 600 pounds net cylinder output force is about ideal far a true minimum application with electronic brakes.
Table 6 is a worksheet used to derive an equation to closely approxirn:ate the ideally desired chamber A 97 pressure with this cylinder arrangement ( 12-inch main piston 72 with 4-inch push rod 81 ) for any initial pressure.
The equation is intended to matchthe chamber A 97 pressures indicated on the previous third chart, and it is:
Pp = Pe * (2000'-P;)/1950 Where: PA = Chamber A pressure Pe = equalization pressure P; = initial pressure at time of application The equalization pressure, Pe; is easily calculated from the initial pressure and the pressure-volume relationships That exist: The equation is only applied for initial pressures above 70 psi; where equalization would produce excessive cylinder output force. Below this pressure; chamber A 97 is allowed to equalize with the reservoir 75 and chamber R 98. Chamber R 98 pressure can be exhausted as needed to 29.

produce the target force output of 600 pounds. As indicated, at initial pressures of 70 and 80 psi the equation derived yields values lightly lower than the exact theoretically desired PA pressure, which produces cylinder::forces of 562 and 587.5 pounds;
respectively. These forces are within 10% of the target and are considered acceptable for minimum applications, since they can be increased as desired by the operator simply by commanding a slightly heavier service application.
Table 7 illustrates equalization pressures and chamber R 98 pressures for full service and emergency applications, for initial pressures ranging from SU to 110 psi. In emergency, chamber R 98 is exhausted to zero (gauge) or atmospheric pressure, producing the maximum available cylinder output force. For the maximum service application, chamber R 98 pressure is exhausted to a pressure required to produce 19%
lower cylinder output force than the corresponding emergency application.
Tahle 8 compares the target pressure in chamber R 98 to the pressure computed by the derived equation, and Table 9 simply shows the equalization pressure for various initial pressures and' the corresponding chamber A 97 pressure required to derive just sufficient force to bring abut full piston travel. This is significant, because chamber R 98 should not be exhausted to produce high braking forces until full piston travel has been completed. Otherwise, much air would be wasted and available chamber A 97 pressures reduced. The chart shows that with the selected area offset, the full piston travel can be obtained with an initial pressure as low as l2 psi, providing an equalization pressure of 10'.9 psi. Finally; Table l0 duplicates the information in Table 7, except that the simplified equation Pi/4:4 is used for P~.
30.

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- Equations-Cylinder equalization pressure:
(l.) Pe;= (2000*(P~+14:7)+V~* 14:7)/(2000+PT*a+V~)-14.7 Where: Pe = equalization pressure for the reservoir and chamber A with R
V~ = total clearance-volume (ctlamber A in release) PT -- piston travel (typically 6 inches) a = area of push rod seal (offset piston area - 12:566 sq. in.) Chamber A pressure for minimum applications:
(2.) PA =Pe*(200fl-P;)/1950 Where: PA = chamber A pressure Pe = equalization pressure (from equation ( 1:)) P; = initial pressure Chamber A pressure for all other app~tcateons, including emergency:
~3,) pA = p~
Where: PA = chamber A pressure Pe _ equalization pressure Chamber R Pressure for minimum applications:
(4.) pR = (2000*(P~+14.7)+Ve*14.7-(A'*PT+s)*(pA+14.7)/(2004-PT*(A-a)-14.7 Where: PR = chamber R pressure P; = initial pressure V~ = clearance volume (24 cubic inches) PA = chamber A pressure PT = piston travel (typically 6 inches) A = main' piston area ( 113.09 sq. in; far 12" cylinder) a = area of push rod seal (offset area -12.566 sq. in.) Note: This pressure can be calculated, but need not be for brake applications.
It is the pressure in chamber R that will result from feeding reservoir and chamber R
into chamber A to charge chamber A to less than egualization:
Chamber R pressure for all service-applications heavier than minimum and lighter than full service:
(5.) pR = (pA*A-F)/(A-a) Where: PR = chamber R pressure . PA = chamber A pressure A = main piston area (113.097 sq. in.) 32.

a = push .rod seal area (12:566 sq. in.) F = cylinder output' force Chamber R pressure for full service apgtications:
(6.) PR = P;/4:4 Where: PR = chamber R pressure P; = initial pressure Net cylinder output force:
(7:) F = pA*A_PR*(A_a)_FS
Where: F = cylinder output force..in pounds PA = chamber A pressure PR = chamber R pressure A = main piston area (113.097 sq. in.) a = push rod seal area (12.566 sg. in:~
FS = return spring force (nominally 120 lbs.) Although certain embodiments of the invention have been described in detail;
it will be appreciated by those skilled in the art that various modifications to those details could be developed in light of the overall teaching of the disclosure.
Accordingly, the particular embodiments disclosed herein are intended to be illustrative only and not limiting to the scope of the invention which should be awarded the full breadth of the following claims and any and all embodiments thereof.
33:

Claims (52)

1. Unitized brake equipment for a railcar comprising:
a. a brake cylinder;
b. a single piston having a piston head end movably housed in said brake cylinder and a piston rod end connectable to a brake member movable in an application direction to increase braking force and a release direction to decrease braking force;
c. a first volume communicating on the entire first side of said piston head, pressurization of said first volume causing said single piston to move in the application direction;
d. a second volume communicating on a portion of a second side of said piston head comprising a smaller effective surface area than on said first side, pressurization of said second volume tending to cause said single piston to move in the release direction; and e. a plurality of valves controllable responsive to an electrical brake signal selectively coupling at least one of said first and second volumes with at least one of each other, a source of pressure, and the atmosphere to control pressure in said first and second volumes and move said single piston to control braking force on said railcar in a gradual manner.

2. The unitized brake equipment of claim 1 further comprising a reservoir connectable via said plurality of valves to said first volume and said second volume.

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3. The unitized brake equipment of claim 2 wherein said reservoir comprises a third volume integrally formed with said brake cylinder.

4. The unitized brake equipment of claim 2 wherein said source of pressure is a brake pipe and comprising at least one valve of said plurality of valves connecting said first volume to said reservoir responsive to a predetermined pressure loss in said brake pipe.

5. The unitized brake equipment of claim 2 further comprising said plurality of valves having at least one valve having a normally open state wherein said first volume is connected to atmosphere and isolating said first volume from atmosphere when in an activated state.

6. The unitized brake equipment of claim 5 comprising a cut-off valve connected in series with said at least one valve, said cut-off valve held normally open to atmosphere by said source of pressure, said cut-off valve isolating said first volume from atmosphere responsive to a predetermined loss of pressure in said source of pressure notwithstanding the state of said at least one valve.

7. The unitized brake equipment of claim 2 comprising a piston travel interlock valve, said piston travel interlock valve movable between first and second positions responsive to travel of said single piston, said piston travel interlock valve isolating said second volume from at least one valve of said plurality of valves connected to the atmosphere in said first position and connecting said second volume to said at 35.

least one valve in said second position, said second position corresponding to a predetermined amount of travel of said single piston in said application direction.

8. The unitized brake equipment of claim 7 further comprising:
a. said piston travel interlock valve having an operating valve stem;
b. a beveled stem having a first end projecting into said second volume and a second end abutting an end of said operating valve stem, said second end having a beveled portion; and c. said first end of said beveled stem engagable by said piston after said predetermined amount of travel of said single piston, said beveled portion causing movement of said operating valve stem responsive to said piston moving said beveled stem, movement of said operating valve stem causing said piston travel interlock valve to move between said first and second positions.

9. The unitized brake equipment of claim 1 further comprising:
a. a local brake control device located on said railcar, said local brake control device controlling said at least one valve; and b. a remotely located brake control device controlling said local brake control device via at least one of wire and wireless signals.

10. The unitized brake equipment of claim 2 comprising said at least one of said plurality of vavles controllable to connect said first and second volumes to said reservoir to 36.

effectively transfer pressure between said first and second volumes to increase said braking force.

11. The unitized brake equipment of claim 10 comprising at least one of said plurality of valves controllable to connect said second volume to atmosphere to further increase said braking force.

12. The unitized brake equipment of claim 11 comprising at least one of said plurality of valves controllable to connect said first volume to atmosphere to reduce said braking force.

13 The unitized brake equipment of claim 1 wherein said said plurality of valves are pilot valves and further comprising booster valves activated by said pilotvalves.

14. The unitized brake equipment of claim 2 wherein said plurality of valves comprise:
a. a first valve controllable to connect said first volume with at least said reservoir to pressurize said first volume;
b. a second valve controllable to connect said second volume with at least said reservoir to pressurize said second volume;
c. a third valve controllable to connect said first volume to the atmosphere to depressurize said first volume; and 37.

d. a fourth valve controllable to connect said second volume to the atmosphere to depressurize said second volume.

15. The unitized brake equipment of claim 14 wherein said first through fourth valves are first through fourth electrically controlled pilot valves and further comprising:
a. a first booster valve associated said first pilot valve and said source of pressure providing pilot pressure;
b. a second booster valve associated said second pilot valve, said reservoir providing pilot pressure;
c. a third booster valve associated said third pilot valve, said reservoir providing pilot pressure; and d. a fourth booster valve associated said fourth pilot valve, said source of pressure providing pilot pressure.

16. The unitized brake equipment of claim 15 further comprising said third booster valve connecting said first volume with atmosphere when said third pilot valve is energized and isolating said first volume from atmosphere when said third pilot valve is de-energized.

17. The unitized brake equipment of claim 16 further comprising a cut-off valve connected in series with said third booster valve, said cut-off valve held normally open to atmosphere by said source of pressure, said cut-off valve isolating said third valve 38.

from atmosphere responsive to a predetermined loss of pressure in said source of pressure.

18. The unitized brake equipment of claim 15 further comprising a piston travel interlock valve connected in series with said fourth booster valve, said piston travel interlock valve movable between first and second positions responsive to travel of said single piston, said piston travel interlock valve isolating said second volume from said fourth booster valve in said first position and connecting said second volume to said fourth booster valve in said second position, said second position corresponding to a predetermined amount of travel of said single piston in said first direction.

19. The unitized brake equipment of claim 18 further comprising:
a. said piston travel interlock valve having an operating valve stem;
b. a beveled stem having a first end projecting into said second volume and a second end abutting an end of said operating valve stem, said second end having a beveled portion; and c. said first end of said beveled stem engagable by said piston after said predetermined amount of travel of said single piston, said beveled portion causing movement of said operating valve stem responsive to said piston moving said beveled stem, movement of said operating valve stem causing said-piston travel interlock valve to move between said first and second positions.

39.

20. The unitized brake equipment of claim 15 comprising said first booster valve connecting said first volume to said reservoir responsive to a predetermined pressure loss in said source of pressure notwithstanding an operating condition of said third pilot valve.

21. The unitized brake equipment of claim 14 comprising said first and second valves controllable to connect said first and second volumes to said reservoir to effectively transfer pressure between said first and second volumes to increase said braking force.

22. The unitized brake equipment of claim 21 comprising said fourth valve controllable to connected said second volume to atmosphere to further increase said braking force.

23. The unitized brake equipment of claim 22 comprising said third valve controllable to connect said first volume to atmosphere to reduce said braking force.

24. Unitized brake equipment for a railcar comprising:
a. a brake cylinder;
b. a single piston having a piston head movably housed in said brake cylinder and a piston rod end connectable to a brake member movable in an application direction to increase braking force and a release direction to decrease braking force;

40.

c. a first volume communicating on the entire first side of said piston head, pressurization of said first volume causing said single piston to move in the application direction;
d. a second volume communicating a portion of a second side of said piston head comprising a smaller effective surface area than on said first side, pressurization of said second volume causing said single piston to move in a second direction to decrease said braking force;
e. a third volume connectable to a source of pressure;
f. a first electrically controllable valve to selectively couple said first volume with at least said third volume to gradually pressurize said first volume;
g. a second electrically controllable valve to selectively couple said second volume with at least said third volume to gradually pressurize said second volume;
h. a third electrically controllable valve to selectively couple said first volume to the atmosphere to gradually depressurize said first volume; and i. a fourth electrically controllable valve to selectively couple said second volume to the atmosphere to gradually depressurize said second volume.

25. The unitized brake equipment of claim 24 wherein said first through fourth electrically controllable valves are first through fourth electrically controllable pilot valves and further comprising:
a. a first booster valve associated said first pilot valve and said source of pressure providing pilot pressure;
b. a second booster valve associated with said second pilot valve, said third volume providing pilot pressure;

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c. a third booster valve associated said third pilot valve, said third volume providing pilot pressure; and d. a fourth booster valve associated said fourth pilot valve, said source of pressure providing pilot pressure.

26. The unitized brake equipment of claim 25 further comprising said third booster valve connecting said first volume with atmosphere when said third-pilot valve is energized and isolating said first volume from atmosphere when said third pilot valve is de-energized.

27. The unitized brake equipment of claim 26 further comprising a cut-off valve connected in series with said third booster valve, said cut-off valve held normally open to atmosphere by said source of pressure, said cut-off valve isolating said third valve from atmosphere responsive to a predetermined loss of pressure in said source of pressure.

28. The unitized brake equipment of claim 25 further comprising a piston travel interlock valve connected in series with said fourth booster valve, said piston travel interlock valve movable between first and second positions responsive to travel of said single piston, aid piston travel interlock valve isolating said second volume from said fourth booster valve in said first position and connecting said second volume to said fourth booster valve in said second position, said second position corresponding to a predetermined amount of travel of said single piston in said first direction.

42.

29. The unitized brake equipment of claim 28 further comprising:
a. said piston travel interlock valve having an operating valve stem;
b. a beveled stem having a first end projecting into said second volume and a second end abutting an end of said operating valve stem, said second end having a beveled portion; and c. said first end of said beveled stem engagable by said piston after said predetermined amount of travel of said single piston, said beveled portion causing movement of said operating valve stem responsive to said piston moving said beveled stem, movement of said operating valve stem causing said piston travel interlock valve to move between said first and second positions.

30. The unitized brake equipment of claim 25 further comprising said first booster valve connecting said first volume to said third volume responsive to a predetermined pressure loss in said source of pressure notwithstanding an operating condition of said third pilot valve.

31. The unitized brake equipment of claim 24 further comprising:
a. a local brake control device located on said railcar, said local brake control device controlling at least one of said first through fourth valves;
and b. a remotely located brake control device controlling said local brake control device via at least one of wired and wireless signals.

43.

32. The unitized brake equipment of claim 24 further comprising said first and second valves controllable to connect said first and second volumes to said third volume to effective transfer pressure between said first and second volumes to increase said braking force.

33. The unitized brake equipment of claim 32 further comprising said fourth valve controllable to connect said second volume to atmosphere to further increase said braking force.

34. The unitized brake equipment of claim 33 further comprising said third valve controllable to connect said first volume to atmosphere to reduce said braking force.

35. A method of controlling braking force on a railcar comprising:
a. controlling movement of a single piston having a piston head end slidably disposed in a brake cylinder and a rod end connectable to a brake movable in an application direction to increase braking force and a release direction to decrease braking force;
b. providing a first volume acting on the entire first side of said piston head and a second volume acting on a second side of said piston head having a smaller effective surface area than said first side;
c. at least one of selectively connecting said first volume to a source of pressure and selectively connecting said second volume to the atmosphere to control movement of said single piston to gradually increase said braking force;

44.

d. at least one of selectively connecting said second volume to a source of pressure and selectively connecting said first volume to the atmosphere to control movement of said single piston to gradually reduce said braking force; and e. at least one of:
i. isolating said first volume from atmosphere responsive to a pressure reduction in said source of pressure, and ii. isolating said second volume from the atmosphere while connecting said first volume to said source of pressure to increase said braking force until a predetermined amount of travel of said single piston has occurred, and thereafter selectively connecting said second volume to atmosphere to gradually reduce pressure in said second volume to further increase said braking force.

36. The method of claim 35 further comprising selectively connecting said first and second volumes to transfer pressure therebetween to increase said braking force.

37. The method of claim 36 further comprising connecting said second volume to atmosphere to further increase said braking force.

38. The method of claim 37 further comprising connecting said first volume to atmosphere to decrease said braking force.

39. The method of claim 36 further comprising:
a. providing a third volume integral with said brake cylinder;

45.

b. connecting said third volume with said source of pressure; and c. transferring pressure between aid first and second volumes by connecting both of said first and second volumes to said third volume.

40. The method of claim 39 further comprising controlling pressure in said first and second volumes using at least one electrically operated valve.

41. The method of claim 40 wherein said at least one electrically operated valve is a plurality of electrically operated valves and further comprising:
a. connecting said first volume with at least said third volume to pressurize said first volume using a first electrically operated valve;
b. connecting said second volume with at least said third volume to pressurize said second volume using a second electrically operated valve;
c. connecting said first volume to the atmosphere to depressurize said first volume using a third electrically operated valve; and d. connecting said second volume to the atmosphere to depressurize said second volume using a fourth electrically operated valve.

42. The method of claim 41 wherein said first through fourth electrically operated valves are first through fourth electrically operated pilot valves, and further comprising:
a, controlling a first booster valve with said first pilot valve and using said source of pressure as a source of pilot pressure;

46.

b. controlling a second booster valve with said second pilot valve and using said third volume as a source of pilot pressure;
c. controlling a third booster valve with said third pilot valve and using said third volume as a source of pilot pressure; and d. controlling a fourth booster valve with said fourth pilot valve and using said source of pressure as a source of pilot pressure.

43. The method of claim 42 further comprising connecting said first volume with atmosphere when said third pilot valve is energized and isolating said first volume from atmosphere when said third pilot valve is de-energized.

44. The method of claim 43 further comprising:
a. connecting a cut-off valve in series with said third booster valve;
b. holding said cut-off valve open to connect said first volume to atmosphere using pressure from said source of pressure; and c, closing said cut-off valve to isolate said first volume from atmosphere responsive to a predetermined loss of pressure in said source of pressure.

45. The method of claim 42 further comprising:
a. connecting a piston travel interlock valve in series between said fourth booster valve and said second volume, said piston travel interlock valve movable between first and second positions responsive to travel of said single piston;
and 47.

b. said piston travel interlock valve isolating said second volume from said fourth booster valve in said first position and connecting said second volume to said fourth booster valve in said second position, said second position corresponding to a predetermined amount of travel of said single piston in said first direction.

46. The method of claim 45 further comprising:
a. using a beveled stem to move said piston travel interlock valve between said first and second positions;
b. said piston moving said beveled stem responsive to said predetermined amount of travel of said single piston;
c. using a beveled portion of said beveled stem which abuts an end of an operating valve stem of said piston travel interlock valve to move said piston travel interlock valve between said first and second positions responsive to said travel of said single piston.

47. The method of claim 42 further comprising said first booster valve connecting said first volume to said third volume responsive to a predetermined pressure loss in said source of pressure notwithstanding an operating condition of said third pilot valve.

48. The method of claim 41 further comprising transfer pressure between said first and second volumes by connecting said first and second volumes to said third volume using said first and second valves to increase said braking force.

48.

49. The method of claim 48 further comprising connecting said second volume to atmosphere using said fourth valve to further increase said braking force.

50. The method of claim 49 further comprising connecting said first volume to atmosphere using said third valve to reduce said braking force.

51. The method of claim 35 further comprising controlling pressure in said first and second volumes using a local brake control device on said railcar.

52. The method of claim 51 further comprising remotely controlling said local brake control device via at least one of wired and wireless signals from a remotely located brake control device.

49.