Patent ID: 7967980

Claim:
A construction machine having a working oil tank, said working oil tank comprising: a tank main body defining complementary compartments, said complementary compartments comprising: an outer compartment for storing working oil; and, an inner compartment for filtering return oil, and wherein said inner compartment is a cylindrical filter case comprising: a bottom wall; a side wall; a return filter for filtering return oil above said bottom wall and inside said side wall; a filter receiving plate provided in a lower part within said filter case, wherein said return filter is disposed on and above said filter receiving plate which defines an upper space above said return filter within said inner compartment, and said filter receiving plate is located above said bottom wall of said filter case which defines a continuous lower gap between said filter receiving plate and said bottom wall of said filter case; and, wherein said bottom wall and said side wall partition said outer compartment from said inner compartment; a plurality of return tubes connected to said side wall of said filter case for returning working oil from said outer compartment to said inner compartment, said return tubes including an upper tube and a lower tube; and, wherein said lower tube is connected to said side wall of said filter case below said filter receiving plate so as to communicate with said continuous lower gap, while said upper tube is connected to said side wall of said filter case above said return filter so as to communicate with said upper space.