Technical - Valve Operation

How does an Air Suspension work? (Why is a valve necessary?)

Air suspensions use air springs or air shocks to support all or part of a vehicle’s (or other equipment’s) weight. These air springs are inflated with compressed air to raise the load. Under varying load, air springs change in height to a considerable degree; as the load increases, the spring lowers, as the load is reduced, the spring raises. If there is any variation in the load applied to the air spring, it will be necessary to include a valve in the air spring circuit to control the height of the vehicle suspension. This valve is typically mounted to the vehicle frame and connects to the suspension lower member with a signal link. As the suspension raises and lowers, the valve ‘reads’ the height of the suspension and adds air to or removes air from the air springs.

Why a Delay Valve?

The valve/air spring circuit forms a closed-loop control system for suspension height. This closed loop system responds directly to the valve input. When the valve is shifted from ‘raise’ to ‘lower’ or vice-versa, each movement adds or removes air from the air springs. If the vehicle is traveling on a rough road or the equipment has a variable load (ex: washing machinery), the valve is constantly shifting, and constantly using air from the supply.

By incorporating a delay mechanism into the valve, the minor excursions of the valve control input will not result in any air usage as these signals will simply be ignored. If the valve control link is moved rapidly from ‘raise’ to ‘lower’, the delay will prevent the valve from actuating until the average input is shifted away from the valve center position. Once this occurs, the valve will begin to respond by moving to bring the valve center position in line with the new signal input.

The King of the Road integral delay valve reduces unnecessary valve actuation and can significantly reduce air consumption.

What is Dead-band?

The dead-band is the portion of the valve operation stroke where both the intake and exhaust valves are closed and the air spring is isolated from the supply. When the valve is at the dead-band point the vehicle or equipment is at the regulated height. The width of the dead-band affects the accuracy of the regulated height. As the suspension approaches the dead-band from one direction, the valve will settle at that end of the dead-band. As the suspension approaches the dead-band from the other direction, the valve will settle at the other end of the dead-band.

If the dead-band is made narrower to provide a more accurate regulated height, air consumption will increase because the intake and exhaust valves will open more frequently. Incorporating a delay into the valve allows adjustment of a tighter dead-band with lower air consumption. The King of the Road valve incorporates a delay mechanism that can be set during the manufacturing process from zero to over 30 seconds to provide the proper delay time for your application.

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