But this typically forces the manufacturer to assemble an array of pneumatic valves, connectors, and other components into a customized system.
Cleveland-based Parker Hannifin (parker.com), has developed a Kneeling Module that integrates the pneumatic components, simplifying installation and maintenance while providing a range of kneeling capabilities on large passenger vehicles.
The new module consists of a durable, lightweight manifold with a machined-aluminum anodized body. It houses four pneumatic poppet valves that inflate and exhaust air bags mounted on the vehicle axles. Depending on system requirements, at the flick of a switch the unit routes compressed air to provide split-level kneeling, left or right tilting, complete kneeling, or a "high-boy" position that elevates the bus or motor coach for over-the-road travel.
Standard 22-mm grommet-style P2F Series mobile solenoids actuate the valves. The combination of a solid housing, poppet valves, and heavy-duty solenoids results in a durable unit that stands up well to dirt, water, and salt that the vehicles commonly see, says Paxton Augustine, a product manager with Parker's Pneumatic Div.
Exhaust protectors — flapper-type devices on the manifold — permit unrestricted airflow out but keep contaminants from entering the valve, adding to system reliability, says Augustine.
The system also features Viton seals designed for temperatures from -40 to 122°F. The Kneeling Module operates at pressures from 60 to 150 psi, and coil voltages are available in 12 or 24-Vdc versions.