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).
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. The band, ring or plunger is moved away from its engagement with the piston when the pressure acting against the piston becomes greater than a preset pressure to vent the moisture and liquid to the vehicle brakes. An upper portion of the piston may be concave to funnel any liquid or moisture present therein into the sump.
An electropneumatic regulating valve for an air brake system of a motor vehicle, with a valve seat assembly which switches compressed air flow between at least one external brake line connection, a feed pressure connection, and a venting port, the valve seat assembly including a coaxial valve seat assembly with external and internal valve seats and a pot-like sealing cup with a coaxial passage. A ring-shaped, surface of the sealing cup seals between the exterior and interior valve seats. The opposing face of the ring-shaped surface has two coaxial sealing lip segments projecting away from the ring-shaped surface and forming an annular space therebetween. The sealing cup includes a reinforcing insert with a U-shaped cross-section located in the annular space which reinforces the ring-shaped surface and the sealing lip segments. The insert also has a molded-on shoulder which reinforces the inside radial area of the sealing area.
An improved relay valve (10) having a supply port (16), a delivery port (18), an exhaust port (20), a control port (17), a relay piston (14) controlling communication between the supply port (16), the delivery port (18), and the exhaust port (20) in response to a pneumatic signal applied to the control port (17) and including a passage (40) extending through the piston (14) to the exhaust port (20) for draining to atmosphere moisture and other contaminants which build up on the top of the piston (14). A diaphragm element (30) having a cylindrical protrusion portion (36) is disposed in the piston (14) above the passage (40) to act as a check valve and seal the passage (40) when a pneumatic signal is applied to control port (17). The diaphragm element includes a top resilient portion (32) which serves as a spring to open the drain passage when no signal is applied to control port (17). Two flat areas (34) are provided on the top resilient portion (32) which prevents the diaphragm element (30) from prematurely sealing the drain hole (40). The cylindrical protrusion (36) keeps the diaphragm element (30) properly aligned in the tapered bore (44) leading to drain hole (40). A retaining ring (42) keeps diaphragm element (30) within the bore (44).
A braking system is able to meet emergency stopping distance requirements associated with a failed rear axle service control line by modifying the service relay valve. The service relay valve incorporates a biased double check valve so that an additional or secondary control line from the foot control valve communicates with the service port of the relay valve. If the primary circuit is operational, a biasing force imposed on the double check valve permits normal operation via the primary service line. On the other hand, if the primary service line is lost, the biasing force is overcome and communication between the secondary service line and the service port of the relay valve is established.
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.
