Full-function valve for heavy duty semi-trailer brake systems

A unitary full-function valve capable of meeting the emergency and service requirements of a tandem axle air brake system comprising a full-function valve body with multiple ports, including individual ports for fluid communication to spring brake chambers, to service brake chambers, to reservoir means and to exhaust;

• and for receiving pressurized control and supply air from respective sources thereof;
• said ports and related passageways within said valve body being disposed so as to communicate the control air for service brake control, and the supply air to and from the reservoir means, to and from the spring brake and service brake chambers of the air brake system, and to exhaust, the communications being selectively responsive to the positions of a plurality of valve modules within said full-function valve body;
• the supply air being communicated to the spring brake chambers only when supply air is also communicated to the reservoir means;
• said plurality of valve modules comprising:
• (a) a spring brake valve module within said full-function valve body providing (i) fluid communication from spring brake ports of said valve body to exhaust ports when air pressure at the supply port is less than a first predetermined pressure, and (ii) fluid communication from the reservoir port of said valve body to the spring brake ports when the air pressure at the supply port is at or higher than said first predetermined pressure;
• (b) a relay valve module within said full-function valve body for selectively employing supply air to actuate the service brakes responsive to control air signals received at the control port of said valve body;
• and
• (c) a biased one-way pressure protection valve module within said full-function valve body providing fluid communication from the supply port to the reservoir port, to the spring brake valve module and to the relay valve module at or above a second higher predetermined air pressure at the supply port.

A unitary full-function valve capable of meeting the emergency and service requirements of a tandem axle air brake system comprising a full-function valve body with multiple ports, including individual ports for fluid communication to spring brake chambers, to service brake chambers, to reservoir means and to exhaust;

• and for receiving pressurized control and supply air from respective sources thereof;
• said ports and related passageways within said valve body being disposed so as to communicate the control air for service brake control, and the supply air to and from the reservoir means, to and from the spring brake and service brake chambers of the air brake system, and to exhaust, the communications being selectively responsive to the positions of a plurality of valve modules within said full-function valve body;
• the supply air being communicated to the spring brake chambers only when supply air is also communicated to the reservoir means;
• said plurality of valve modules comprising:
• (a) a spring brake valve module within said full-function valve body providing (i) fluid communication from spring brake ports of said valve body to exhaust ports when air pressure at the supply port is less than a first predetermined pressure, and (ii) fluid communication from the reservoir port of said valve body to the spring brake ports when the air pressure at the supply port is at or higher than said first predetermined pressure;
• said spring brake valve module having a one-way check valve associated therewith whereby fluid communication from the reservoir port to the spring brake ports is one-way;
• (b) a relay valve module within said full-function valve body for selectively employing supply air to actuate the service brakes responsive to control air signals received at the control port of said valve body;
• said relay valve module (i) in a first mode providing fluid communication between the service brake ports of said full-function valve body and an exhaust port in response to decreasing pressure and zero pressure at said control port;
• (ii) in a second mode providing one-way fluid communication from said supply port and fluid communication from said reservoir port to said service brake ports in response to increasing pressure at said control port;
• and (iii) in a third mode blocking fluid communication to and from said service brake port in response to a stabilized elevated pressure at said control port;
• and
• (c) a biased one-way pressure protection valve module within said full-function valve body providing fluid communication from the supply port to the reservoir port, to the spring brake valve module and to the relay valve module at or above a second higher predetermined air pressure at the supply port;
• said biased one-way pressure protection valve having a consistently-disposed unbiased one-way check valve associated therewith.