Patent ID: 6959466

Claim:
A street sweeper comprising: a variable speed engine; an engine speed sensor coupled to the engine for providing engine speed information to a control unit; a hydraulic pump operatively coupled to the engine; a sweeping mechanism powered by the hydraulic pump and including a main pickup brush and a debris conveyer; a vacuum system including a vacuum fan motor powered by the hydraulic pump, said vacuum system for creating an airflow within the street sweeper; an electric proportional valve coupled between the hydraulic pump and the vacuum fan motor, said valve for selectively restricting a flow rate of hydraulic fluid to the vacuum fan motor; and the control unit operatively coupled to the engine speed sensor and the proportional valve, said control unit receiving the engine speed information from the engine speed sensor and communicating a control signal to the proportional valve to control the flow rate of hydraulic fluid to the vacuum fan motor as a function of engine speed.