Abstract: A control valve for applying a spring-loaded brake pressure to spring-loaded parts of a rear-axle wheel brake is pneumatically activated as a function of a parking-brake braking demand and a service-brake braking demand. A first control chamber is connected via a first control piston to a control arrangement in the control valve. During an adjustment of the first control chamber via the service-brake control pressure, the spring-loaded brake pressure at the working output is a function of the service-brake control pressure or of the parking-brake control pressure. The first control piston is connected to a third control chamber, wherein the pressure in the first control chamber acts on the first control piston in one direction, and the pressure in the third control chamber acts on the first control piston in the opposite direction. The first control chamber is selectively connectable to the third control chamber via a switchable bypass valve.

Abstract: A control valve for applying a spring-loaded brake pressure to spring-loaded parts of a rear-axle wheel brake is pneumatically activated as a function of a parking-brake braking demand and a service-brake braking demand. A first control chamber is connected via a first control piston to a control arrangement in the control valve. During an adjustment of the first control chamber via the service-brake control pressure, the spring-loaded brake pressure at the working output is a function of the service-brake control pressure or of the parking-brake control pressure. The first control piston is connected to a third control chamber, wherein the pressure in the first control chamber acts on the first control piston in one direction, and the pressure in the third control chamber acts on the first control piston in the opposite direction. The first control chamber is selectively connectable to the third control chamber via a switchable bypass valve.

Abstract: A pressure regulating module for regulating the pressure of a first fluid using a reference pressure of a second fluid. A pressure transfer assembly including a piston slidably disposed within a cylinder bore between a control fluid chamber and a reference fluid chamber is dimensioned to provide a predefined radial clearance between at least a portion of the outer side wall and the inner circumferential surface of the housing along a predefined axial length of the main body. The predefined radial clearance and predefined axial length are dimensioned to control the flow rate and amount of fluid along one or more fluid communication passages formed between at least a portion of the piston and the housing inner circumferential surface from one or more high pressure fluid zones to a lower pressure fluid zone which can include a leak and/or weep orifice directing fluid to a drain and/or vent circuit.

Abstract: A controller includes a foot brake valve electrical input port, which is capable of receiving an electrical signal indicative of a foot brake delivery pressure, and a trailer brake valve electrical input port, which is capable of receiving an electrical signal indicative of a trailer brake delivery pressure. The controller also includes control logic that is capable of receiving the electrical signal indicative of the foot brake delivery pressure, receiving the electrical signal indicative of the trailer brake delivery pressure, based on an electrical level of the electrical signal indicative of the foot brake delivery pressure, determining if the foot brake delivery pressure is above a predetermined threshold pressure, and based on a presence of the electrical signal indicative of the trailer brake delivery pressure, determining if the trailer brake delivery pressure is above the predetermined threshold pressure.

Abstract: An abnormal detecting system for a pneumatic brake includes a pedal stroke sensor, a front chamber pressure sensor, a rear chamber pressure sensor, a storage unit pressure sensor, a parking brake switch and an abnormal detecting circuit. A pedal stroke signal, a front chamber pressure signal, a rear chamber pressure signal, an air storage unit pressure and a parking brake control signal are output. The abnormal detecting circuit receives the pedal stroke signal, the front chamber pressure signal, the rear chamber pressure signal, the air storage unit pressure signal and the parking brake control signal. The abnormal detecting circuit compares the pedal stroke signal with the front chamber pressure signal or the rear chamber pressure signal and then outputs a first abnormal signal; and the abnormal detecting circuit compares the parking brake control signal and then outputs a second abnormal signal.

Abstract: A compressed air supply apparatus includes a control unit configured to operate an air compressor when a measurement value of a pressure measurement unit reaches a first pressure or less, and configured to stop the air compressor when the measurement value reaches a second pressure higher than the first pressure, and a plurality of relief valve apparatuses installed in each of the connection flow path between the air compressor and each of a plurality of air tanks, wherein each of the plurality of relief valve apparatuses is configured to open the connection flow path to the atmosphere when the measurement value reaches a third pressure higher than the second pressure and close the connection flow path when the measurement value reaches a fourth pressure higher than the second pressure and lower than the third pressure after the opening.

Abstract: A valve assembly including a housing and a first movable member which divides the housing into a control chamber and a main chamber. A second movable member has a first valve part and a second valve part and is movable to engage the first valve part with a corresponding inlet valve part to substantially prevent flow of fluid into the main chamber via an inlet port. The first movable member is provided with an exhaust valve part and is movable to engage the second valve part of the second movable member to substantially prevent flow of pressurised fluid out of the main chamber via an exhaust port. A support part is secured relative to the housing, there being a first seal between the second movable member and the support part and a second seal between the support part and the first movable member.

Abstract: A brake cylinder maintaining valve feeds brake pipe (BP) pressure through a choke to replenish and maintain brake cylinder (BC) pressure up, when the pressure in the brake cylinder drops below its original set pressure. In one embodiment, the brake cylinder maintaining valve may be a differential type valve having an input diaphragm and an output diaphragm having different surface areas.

Abstract: A valve for use in a pneumatic system of a truck-trailer having a source of air under pressure, a reservoir, at least one spring brake unit and a brake service line is provided. The valve includes a housing, a pressure protection valve portion, a spring brake actuation valve portion and an anti-compounding valve portion. The housing has a supply passage in communication with the source of air under pressure. The pressure protection valve portion is disposed within a first chamber of the housing. The first chamber has an inlet in communication with the supply passage and an outlet in communication with the reservoir. The pressure protection valve portion is configured to selectively block the flow of pressurized air from the supply passage to the reservoir through the first chamber. The spring brake actuation valve portion is disposed within a second chamber of the housing.

Abstract: A locking control valve is provided. This control valve includes a valve body that further includes a first locking member, and a handle attached to the valve body. The handle is moveable between a first position and a second position for controlling the operation of the valve and further includes a second locking member. The first locking member and the second locking member cooperate with one another to retain the handle in the second position when so desired by the operator of the vehicle.

Abstract: An electronic vehicle service braking system having at least one braking cylinder and a pressure control module with a control chamber and a working chamber. The working chamber is connected to an air supply via a supply line, the control chamber is connected to the air supply via a connecting line and an inlet valve and to the atmosphere via an outlet valve. The control chamber is also connected to a back-up braking system via a back-up line and a back-up valve, and a control system is provided for controlling at least the inlet valve and the back-up valve. The control system controls the valves such that the back-up valve is opened together with the inlet valve, enabling air to flow into the control chamber when an ABS signal for a rise in pressure follows a drop in pressure.

Abstract: A valve for use in a pneumatic system of a truck-trailer having a source of air under pressure, a reservoir, at least one spring brake unit and a brake service line is provided. The valve comprises a housing, a pressure protection valve portion, a spring brake actuation valve portion and an anti-compounding valve portion. The housing has a supply passage in communication with the source of air under pressure. The pressure protection valve portion is operably disposed within a first chamber of the housing. The first chamber has an inlet in communication with the supply passage and an outlet in communication with the reservoir. The pressure protection valve portion is configured to selectively block the flow of pressurized air from the supply passage to the reservoir through the first chamber until a predetermined pressure is reached. The spring brake actuation valve portion is operably disposed within a second chamber of the housing.

Abstract: The present invention includes a pneumatic system for an agro-industrial vehicle including an air compressor, a dual circuit foot valve connected to the air compressor, and at least two air storage tanks connected to said dual circuit foot valve. The operation of the dual circuit valve establishes an air pressure link from the storage tanks to a rear air chamber as well as to a front air chamber. Each storage tank fills the rear or front air chambers and the movement of the rear air chamber and the front air chamber activate a brake device.

Abstract: A combined spring brake modulating relay valve integrates the functions of a relay valve and a modulating valve. The housing includes a valve assembly movable in response to air pressure provided to selected ports in the housing. A relay piston selectively communicates with a control port and a primary brake circuit port. A modulating piston includes surfaces selectively pressurized by the primary brake circuit port and a secondary brake circuit port. This modulates the pressure from the delivery port to thereby selectively apply the associated spring brakes if a failure is detected at the primary brake circuit port. The exhaust member selectively controls communication between the supply and delivery ports as necessary.

Abstract: The invention relates to a control device for compressed-air brakes having a control valve, comprising a housing, a piston rod, a piston, a second piston, a double-seat valve, having a control element, having a supply air reservoir, having a control chamber, having a main air pipe; one side of the piston being connected in a compressed-air carrying manner with the main air pipe; the other side of the piston being connected in a compressed-air carrying manner with the control chamber; one side of the second piston having a compressed-air connection to a brake cylinder or a brake cylinder pilot chamber; the double-seat valve being connected between a compressed-air connection of the supply air reservoir and the compressed-air connection to the brake cylinder or to the brake cylinder pilot chamber.

Abstract: An actuating device for a brake unit of a vehicle EBS includes a tappet positioned in a housing of the brake unit for actuating a piston to operate a brake valve. A displacement sensor slide measures axial movement of the tappet. So that moving parts of the actuating device are guided with minimal friction and that torque acting on the tappet is compensated for, the tappet includes a cylindrical attachment having a bottom with holes and a shell, a groove on the outer surface of the shell having openings, a spacer ring in the cylindrical attachment between the tappet and the piston having projections which extend into the holes, a guide ring in the groove having raised portions on its inner surface which extend into the openings and a window on its outer surface protruding through an opening into a slit on the housing to receive the displacement sensor slide.

Abstract: A combined spring brake modulating relay valve integrates the functions of a relay valve and a modulating valve. The housing includes a valve assembly movable in response to air pressure provided to selected ports in the housing. A relay piston selectively communicates with a control port and a primary brake circuit port. A modulating piston includes surfaces selectively pressurized by the primary brake circuit port and a secondary brake circuit port. This modulates the pressure from the delivery port to thereby selectively apply the associated spring brakes if a failure is detected at the primary brake circuit port. The exhaust member selectively controls communication between the supply and delivery ports as necessary.

Abstract: A combined spring brake modulating relay valve integrates the functions of a relay valve and a modulating valve. The housing includes a valve assembly movable in response to air pressure provided to selected ports in the housing. A relay piston selectively communicates with a control port and a primary brake circuit port. A modulating piston includes surfaces selectively pressurized by the primary brake circuit port and a secondary brake circuit port. This modulates the pressure from the delivery port to thereby selectively apply the associated spring brakes if a failure is detected at the primary brake circuit port. The exhaust member selectively controls communication between the supply and delivery ports as necessary.

Abstract: A combined spring brake modulating relay valve integrates the functions of a relay valve and a modulating valve. The housing includes a valve assembly movable in response to air pressure provided to selected ports in the housing. A relay piston selectively communicates with a control port and a primary brake circuit port. A modulating piston includes surfaces selectively pressurized by the primary brake circuit port and a secondary brake circuit port. This modulates the pressure from the delivery port to thereby selectively apply the associated spring brakes if a failure is detected at the primary brake circuit port. The exhaust member selectively controls communication between the supply and delivery ports as necessary.

Abstract: The present invention is a valve system for exhausting air from a brakepipe in a remote portion of a train. It has a pressure containment structure having a cylindrical bore and a piston mounted in the bore. A first valve chamber is on one side of the piston and a second valve chamber on a second side. A diaphragm seals between piston and bore, the diaphragm having an annular fold for permitting movement of the piston within the bore. The system has a first brakepipe pressure passageway for conveying air from the brakepipe to the first valve chamber and a control pressure connection for conveying air from a control chamber to the second valve chamber. A biasing means is provided for urging the piston toward the first valve chamber.

Abstract: Method and apparatus for limiting brake cylinder pressure in emergency braking of a locomotive consist connected to a train of railway cars. The apparatus includes a manifold device connected to a reservoir of pressurized fluid for operating pneumatic brakes of the locomotive consist. A first magnet valve is connected to the manifold device for supplying fluid pressure from such device to a brake actuating pipe when an operating coil of the first magnet valve is energized. A second magnet valve having an operating coil is connected to the manifold device for supplying fluid pressure from the reservoir to an adjustable pressure regulator connecting an independent application and release pipe to the manifold device. A relay is connected to receive an emergency brake signal and conduct emergency power to the operating coils of the first and second valves whereby fluid pressure is supplied to the brake actuating pipe and to the adjustable pressure regulator from the manifold device.

Abstract: A braking system for a vehicle includes a pressure relief valve which rids the -system of moisture and liquid therein. The braking system includes a controller which is in fluid communication with the vehicle brakes, an air source, and an air signal that is supplied by the application of the vehicle's brakes. The controller includes piston structure therein which can be moved relative thereto to selectively allow the air from the source to be supplied to the vehicle brakes when a preset air pressure acts against the piston. The piston has a sump therein for collecting any moisture or liquid present in the structure. In an embodiment, the valve includes a vent hole through the piston and a band or ring which overlies the vent hole. The band or ring is preferably positioned around a necked-down portion of the piston. In another embodiment, the sump is effectively eliminated by a plug which overlays the sump and the valve includes a vent hole through an upper portion of the piston and a spring-biased plunger.

Abstract: A pilot operated relay valve (10) for an air pressure braking system includes a relay piston (16) which is responsive to the pressure at a control port (20) to open the valve (10) so that it's inlet port (38) is in free communication with it's outlet port (24). The relay piston (16) includes a balance orifice (26) which permits the outlet port (24) to communicate with the control port (20) to equalized or balance the pressure differential therebetween. A shut off valve arrangement (80,82) or a check value (90 or 92) is provided to shutoff or control flow through the balance orifice during rapid release modulation of the pressure signal for braking applied to the control port (20).

Abstract: A brake pipe pressure control system for a railroad train including a regulating valve device under control of a microprocessor wherein the regulating valve device is housed in the existing end-of-train device and effects service and emergency reductions of brake pipe pressure from the rear end of the train in correspondence with service and emergency reductions initiated at the locomotive.

Abstract: A simplified integrated full-function valve for heavy duty brake systems comprising a valve body having individual ports for fluid communication with spring brake chambers, service brake chambers, pressurized-air reservoir and exhaust and for receiving pressurized control and supply air from respective sources thereof; internal passageways within the valve body providing selected fluid communication with the various ports; a plurality of valve modules within the valve body comprising a spring brake valve module, a relay valve module and a biased one-way pressure protection valve module, and disposed to selectively determine the fluid communications within the internal passageways and ports responsive to the respective positions of the valve modules; the port and related internal passageways for the spring brake chambers being fluid-communicatively-isolated from the reservoir, the service brake chambers and the control air, whereby the number of the internal passageways within the valve body is minimized; the

Abstract: A work brake system applies a reduced air pressure service brake application as a work brake to hold a heavy duty vehicle in place without actuation of conventional spring brakes during frequent start-and-stop operations of the vehicle, such as in refuse collection. The work brake system includes fail safe features to prevent vehicle roll in the event of loss of air pressure, by providing separate primary and secondary sources of pressurized air, and by automatically diverting to application of spring brakes in the event of primary pressure or signal loss.

Abstract: A relay valve device for a relayed type brake system in which the compressed air of the auxiliary reservoir is connected to an equalizing reservoir instead of directly to the brake cylinder, as in a conventional system. Since the equalizing reservoir volume is fixed, as compared to the brake cylinder volume which varies with piston displacement, the equalizing reservoir volume must be greater than the final brake cylinder volume in order to obtain a full equalization pressure that matches the full service application pressure in a conventional brake system. The relay valve device employs a control piston that is subject opposingly to the equalizing reservoir pressure and the effective brake cylinder pressure delivered by the relay valve device.

Abstract: A full function skid control valve assembly for use in an air brake system which provides for brake control utilizing a compact single assembly. The system provides for the maintenance of certain minimum operating pressures so that, when the air pressure within the vehicle brake system falls below predetermined levels, the valve assembly automatically partially or entirely exhausts the air pressure sometimes causing the spring parking brakes to engage. Once the air pressure within the brake system returns to predetermined levels, the valve assembly will allow a reservoir to be charged and the spring brakes to be deactuated. During operation, the assembly provides control of the service brakes while preventing undesired skid conditions.

Abstract: A fluid pressure responsive valve includes a valve member mounted on a guide pin slidably carried by a piston. A valve guide is engaged by one side of the valve element, and the piston engages the opposite side. The piston controls the valve member. The valve guide acts as a stop for a check valve element that controls communication through the inlet port, and also guides and supports the spring controlling the check valve element.

Abstract: A diaphragm-type of variable load control valve device having a diaphragm piston assembly for effectively providing pressurized fluid to the brake cylinders of a railway vehicle in accordance with the brake demand established by a vehicle operator and at a pressure level in conformance with the load condition of the vehicle.

Abstract: A fluid pressure braking system for a tractor-trailer combination vehicle includes a proportioning relay valve which controls communication to the rear wheel brakes of the tractor. When the tractor pulls a trailer, the proportioning control within the relay valve is disabled, but when the vehicle is operated in the "bobtail" mode without pulling a trailer a proportioned brake application is effected in which the braking pressure communicated to the rear brake actuator is a predetermined percentage of that in the front wheel braking circuit. The proportioning mechanism is also disabled when the front axle braking circuit malfunctions, so that upon loss of pressure of the front axle system, the driver effects a non-proportioned rear brake application.

Abstract: A spool type valve arrangement in which a booster spring is employed to overcome static friction of the spool valve O-rings and thereby assure prompt actuation of the spool valve member. The arrangement is such that the booster spring is only active through a limited distance of travel from release position toward application position, this limited distance of spool valve travel being selected so as to occur prior to any transition of the port connections controlled by the spool valve. In this manner, the spool valve return spring force need not be increased in order to reset the spool valve sufficiently to reestablish the original spool valve port connections.

Abstract: An electrically actuated valve for regulating a working pressure of a closed volume load includes an inlet valve (24) for controlling fluid flow between a supply port (16) and a working port (18) and an outlet valve (26) for controlling fluid flow between the working port (18) and an exhaust port (20). A solenoid actuator (70) applies an adjustable force to a movable valve element (44) for closing the outlet valve (26) and opening the inlet valve (24). The adjustable force is opposed by a reactionary force that is generated by the working pressure. The movable element (44) includes opposing areas exposed to the working pressure for scaling the reactionary force to the working pressure.

Abstract: A relay valve arrangement useful in an ABS system comprises a relay valve, a source of control pressure, a control pressure circuit, a control chamber which receives the control pressure from the control pressure circuit and thereby determines the configuration of the relay valve, a control valve through which the control pressure is delivered to the control chamber, and a return valve connecting the control chamber to the control pressure circuit so as to by-pass the control valve to deaerate the control chamber when the control pressure in the control chamber is greater than the control pressure in the control pressure circuit. The control valve includes a solenoid-actuated inlet valve having an armature, and a solenoid-actuated outlet valve. The return valve is designed so that at least part of it constitutes an armature support for the armature of the solenoid-actuated inlet valve and is coaxial with this armature.

Abstract: A relay valve for a fluid pressure braking system includes a relay piston and a load piston which is responsive to the pressure at the inlet port of the relay valve to exert a biasing force on the relay piston loading the latter against the inlet/exhaust valve. The biasing force is opposed by fluid pressure at the inlet port acting across the effective area of the inlet/exhaust valve. The biasing force is greater than the spring force holding the inlet/exhaust valve closed, so that the valve responds immediately to pressure signals transmitted through the control port of the relay valve.

Abstract: The preferred embodiment of the invention is a brake system comprised of a primary source of air under pressure, and independent secondary source of air under pressure, a primary relay, a secondary relay valve, a device for actuating the service brakes, a device for actuating the park brakes and a control device, and a plurality of brake assemblies. The primary relay receives air under pressure only from the primary source and the secondary relay receives air under pressure only from the secondary source, but the other components are so arranges as to achieve complete system redundancy in operation at the source level, the brake level, the hose level, and at the actuation level.

Abstract: A pneumatic braking system for a tractor and trailer which delivers air to the trailer substantially first and in a greater amount than to the tractor but which continues to deliver to the tractor until the pressure at the tractor approaches the pressure at the trailer. This gives better control and substantially avoids jack-knifing. A valve is also provided to lessen the time factor of air to the tractor when a greater braking pressure is applied. Also when "bob-tailing" only substantially 50% of air is delivered to the tractor to prevent over-braking.

Abstract: A pressurized fluid control module is provided for a tractor-trailer brake system to effect the appropriate braking function.

Abstract: A vehicle braking system wherein, for avoiding serious brake unbalance under fault conditions which would cause either loss of braking or excessive braking at one wheel, a small bore link pipe is arranged to connect the pressure control elements, for example solenoid actuated relay valves, of respective brake circuits associated with the two wheels at opposite ends of an axle whereby the pressure control elements in each electronically controlled pressure adjustment channel are influenced in such a manner that a correctly functioning channel attempts to influence a faulty channel in such a direction as to reduce the pressure unbalance.

Abstract: A valve including a housing in which is disposed a relay piston. The relay piston has an upper control surface adjacent a control chamber leading to a control connection. The underside of the relay piston is in communication with a reaction chamber leading to a working pressure connection. An outlet valve seat is formed on the lower extremity of the relay piston. A multistage hollow graduated piston disposed within a graduated bore formed in the housing. The graduated piston has a tapered edge extending downwardly to form an inlet valve seat. A hollow valve element is cooperatively associated with the inlet and outlet valve seats to form inlet and outlet valves. The underside of the graduated piston a reaction chamber which is connected to a second control pressure connection.

Abstract: A valve including a housing in which is disposed a relay piston. The relay piston has an upper control surface adjacent a control chamber leading to a control connection. The underside of the relay piston is in communication with a reaction chamber leading to a working pressure connection. An outlet valve seat is formed on the lower extremity of the relay piston. A multistage hollow graduated piston disposed within a graduated bore formed in the housing. The graduated piston has a tapered edge extending downwardly to form an inlet valve seat. A hollow valve element is cooperatively associated with the inlet and outlet valve seats to form inlet and outlet valves. The underside of the graduated piston is located in a reaction chamber which is connected to a second control pressure connection.

Abstract: The compact, integrated, multi-function valve employed in semi-trailer brake systems having a plurality of pressurized air reservoirs comprise a plurality of internal passageways and ports communicating externally, a plurality of internal control means for interrupting or establishing fluid communication between the various internal passageways and a plurality of one-way means to ensure the integrity of the brake system in the event of leakage problems with one or the other of the pressurized air reservoirs. A preferred embodiment of the brake valve employs four sets of internal passageways and ports, two control means and two multi-function one-way means. As compared with the prior art, the improved brake valve protects the integrity of the brake system with less complexity, fewer components and the potential for enhanced reliability, reduced maintenance and overall lower costs.

Abstract: A relay valve apparatus having two relay valves are located in a single housing with their longitudinal axes parallel to one another. The two relay valves each include a double seat valve and a relay piston. The two relay valves are located one behind the other in the direction along their longitudinal axes so that the two double seat valves are located between the relay pistons. An outlet chamber of the first double seat valve and an outlet chamber of a second double seat valve empty into a common fluid pressure outlet leading to the atmosphere.

Abstract: The relay valve employs a body preferably of metal defining a central exhaust port and a pair of delivery ports on the bottom of the valve body as well as a supply port on the side thereof. The body defines a cylinder in which a spool or shuttle moves toward and away from the exhaust port. A cover seals the upper open end of the body and defines a second cylinder in which a large piston moves from an upward, non operative position to a lower, operated position in engagement with the spool. The cover includes a control line port through which control pressure is applied to the valve. Service brake delivery pressure for the brake system is available at the supply port of the relay valve and sealed from the two or more delivery ports by a pair of O rings sealing the spool to shuttle in the body.

Abstract: A brake pressure control valve for regulating the braking pressure in the trailer brake system of a tractor-trailer vehicle, so as to develop the trailer brake pressure to a preset level ahead of the braking pressure in the tractor brake system during a pilot phase of brake operation. The preset level of this advance trailer brake pressure can be selected by an adjustable member that forms a part of the auxiliary valving that controls the point at which the pilot phase of operation is terminated. A limit stop is cooperatively arranged with this adjustable member in order to provide a means for limiting the point beyond which the auxiliary valving is activated, to thereby prevent the advance trailer brake pressure from exceeding a specified safe maximum value.

Abstract: A relay valve is provided within a single housing and includes a brake cylinder relay valve with combined highway override, a dual pressure brake cylinder limiting valve responsive to load, highway supply line and rail supply line charge check valves and a rail reservoir protection valve. The brake cylinder relay valve includes a valve spool positioned by a first piston responsive to the control signal from a control valve to determine the flow to the brake cylinder and a second piston responsive to the highway supply line to connect the brake cylinder to exhaust. The limiting valve includes a first piston responsive to load signals to define the first set of limits and a second piston in tandem with the first piston responsive to load signals and emergency brake signal in the brake pipe for increasing the response of the first piston to the load signals in response to an emergency signal on the brake pipe.

Abstract: An apparatus is disclosed for the control of brake pressure in a trailer pulled by a tractor. The apparatus includes a two-circuit controllable relay valve as the trailer control valve. The first circuit is controlled by the brake valve of the tractor with the pressure from the brake apparatus of such tractor. The second circuit can be optionally-connected to a distribution valve with a pressure medium source with a specified pressure or with atmosphere. Activation of the distribution valve is controlled so that the distribution valve connects the second circuit with the pressure medium source before or at the beginning of the activation of the first circuit. With this apparatus, the brake pressure can be increased in the brake apparatus of the trailer prior to increase of the brake pressure in the brake apparatus of the tractor. The level of brake pressure increased first in the brake unit of the trailer can be regulated by a set screw acting on the trailer control valve.

Abstract: A braking system for railroad freight trains and a novel relay valve for use in the system are disclosed. The relay valve permits the brake system to be configured so that the requirement for expensive control valves is minimized. The novel relay valve is interposed between the control valve and a number of brake cylinders. Upon a signal from the control valve, the relay valve delivers brake air to the cylinders from a pre-charged reservoir or other source. The novel relay valve includes primary and secondary flow valves to cause air to be delivered to the brakes in a controlled manner. An exhaust valve arrangement in the relay valve permits the brakes to be released.

Abstract: A relay valve for use with a railroad car braking system includes a housing in which a control chamber is disposed between a delivery chamber on an upper side and an exhaust chamber on a lower side. A supply chamber is disposed above the delivery chamber. A control piston disposed in the control chamber is reciprocally-movable as a function of the balance of forces acting on opposing sides of the piston. In order to achieve the desired balance of control fluid pressure to delivery fluid pressure, the surface areas of the piston on which these pressures are exerted are equalized by way of a hollow rod extension coaxially-disposed on the piston, and extending from the lower exhaust chamber to the upper delivery chamber.

Abstract: A proportioning control valve for a fluid pressure braking system for a tractor-trailer combination vehicle permits unproportioned communication of control pressure when the tractor is pulling a trailer but proportions communication of control pressure when the tractor is operated without a trailer to establish a proportonally lower pressure level at the outlet of the valve. The control valve, when operating in the proportioning mode, is also responsive to pressure in the brake reservoir. When pressure in the reservoir drops below a predetermined level, the control valve proportions at a rate which increases the pressure level at the outlet at a rate greater than the rate of increase of control pressure until the unproportioned pressure level is attained.