Air Brake Product Descriptions
Straight Air Brakes
The straight air brake system is typically used on heavy duty commercial vehicles and trailers. Components of the air brake system for trailers are contained within the trailer structure and consist of appropriate compressed air storage tank(s), control valves and hoses to support the number and capacities of the axles used.
Air chambers located on the trailer axles incorporate heavy springs to mechanically apply the trailer brakes for emergency situations and parking. These spring brakes must be released via compressed air in order to move the trailer. The spring brake release system is controlled separately from the service brake system and uses separate valves and hoses, though the air source may be common. The towing vehicle supplies compressed air to the trailer storage tank(s) as well as a modulated control signal through gladhand hose connections mounted on the trailer and tow vehicle.
The operator must first release the parking brakes, this occurs when compressed air is supplied to the trailer system. Once in motion, when the operator applies the tow vehicle service brakes, the tow vehicle air brake system provides a signal pressure in proportion to the tow vehicle's service brake pressure. The trailer control valve receive's this signal and compressed air from the trailer-mounted storage tank, modulated by the trailer control valve(s), is applied to the air chambers located on the trailer axles. The air chambers exert mechanical force to apply the trailer service brakes.
Typical applications for straight air brakes are medium and heavy duty tractor-drawn vans and flat trailers as well as equipment and special purpose trailers. ABS is required by federal statute 571.121. The trailer brakes may be applied independently of the tow vehicle brakes. The spring brakes apply braking force in the event air pressure is lost or the trailer becomes uncoupled from the tow vehicle.
Air Over Hydraulic
The air over hydraulic system is a common application for trailers being towed by light and medium duty commercial vehicles equipped with air brake systems. Components of the air/hydraulic system are trailer-mounted and consist of a compressed air storage tank, a control valve, an air chamber/master cylinder assembly, hydraulic lines and hydraulic disc or drum brakes. The towing vehicle supplies compressed air to the trailer storage tank as well as a modulated control signal through tubing and gladhands or quick connects mounted on the tow vehicle and trailer. When the operator applies the tow vehicle service brakes, the tow vehicle air brake system provides a signal pressure in proportion to the tow vehicle's service brake pressure. The trailer control valve receives this signal and compressed air from the trailer-mounted storage tank, modulated by the trailer control valve, is applied to an air chamber/master cylinder assembly producing a corresponding hydraulic pressure in the trailer brake system. Typical applications for air/hydraulic brake systems are pintle hitch and gooseneck drawn multi-axle equipment and utility trailers towed with air brake equipped vehicles. The trailer brakes may be applied independently of the tow vehicle brakes. ABS and spring actuated emergency braking and parking for FMVSS 571.121 compliance can be incorporated.