Patent ID: 6889730

Claim:
A hydraulic drive system for driving a processing apparatus ( 10 , 20 , 30 ), comprising a high-pressure liquid generating apparatus ( 40 ), a main tank ( 41 ) communicating with a liquid inlet of the high-pressure liquid generating apparatus, an accessory tank ( 54 ) with a side exposed to ambient atmosphere, a liquid processing apparatus ( 56 ), a high-pressure liquid feed path ( 51 ) through which a high-pressure liquid outlet of the high-pressure liquid generating apparatus is communicated with a high-pressure liquid inlet of the processing apparatus, a first return path ( 52 ) through which a liquid outlet of the processing apparatus is communicated with the accessory tank, a second return path ( 53 ) through which the accessory tank is communicated with the liquid processing apparatus, a third return path ( 57 ) through which the liquid processing apparatus is communicated with the main tank, and a pump ( 55 ) for returning the liquid in the accessory tank ( 54 ) to the main tank ( 41 ) through the liquid processing apparatus ( 56 ).