Designer's Corner

Leveling valve

Air springs control ride-height and load compensation on most heavy trucks today. An engine-driven air compressor maintains constant line pressure. As the distance between the axle and the frame decreases to less than a permissible minimum, a mechanical linkage actuates the air-leveling valve that admits air into the bladder. The same valve exhausts air when the distance between the frame and axle becomes excessive.

With no reservoirs to leak and no poppets to jam, the compact valve is unaffected by normal contamination. Of rotary design and containing only one moving part, the valve relies on lapped surfaces to affect a seal. Compressed air does not flow across sealing surfaces, but directly through the inside diameter of the seal. The relative movement of two circular, overlapping ports affects valve operation to ramp the flow rate and eliminate full-on/full-off behavior.

A 1.58 deadband prevents nuisance valve actuation during normal suspension travel. Exhaust and fill times are 11/2 to 21/2 times quicker than those of other systems. And an integral fast-flow dump port permits 10-sec system depressurization prior to driving away from parked trailers.

Paul O'Reilly
Barksdale Inc.
3211 Fruitland Ave.
Los Angeles, CA 90058
(800) 835-1060