US Patent 7559733 Hydraulic control system for refuse collection vehicle

A front loading refuse vehicle includes at least one positive displacement pump having an associated valve system in fluid communication with drive mechanism that operates a lifting arm, packer, a rear door of the vehicle, and a hoist for a refuse storage body. The valve system includes at least one closed-centered valve with a spool mechanism having a pressure compensator to maintain a constant flow rate of fluid through the valve regardless of differential in pressure across the valve for any given position of the spool mechanism. Two pumps with two separate hydraulic control systems are used with a side loading refuse vehicle. An electrical/electronic control system including a microprocessor operates the valve systems for each vehicle.