Patent ID: 7438091

Claim:
A construction machine comprising: a lower traveling body and an upper rotating body rotatably mounted on the lower traveling body, said upper rotating body having a rotating frame; a working oil tank; a switching valve adapted to open and close a pilot line of a hydraulic pressure control system that controls an operation of the construction machine, wherein said switching valve is provided at a position lower than said working oil tank and is at an outer peripheral part of said rotating frame; a return pipe for a passage of a return oil from said switching valve, the return oil being put back to said working oil tank through said return pipe; a drain pipe branched from a portion of said return pipe, said portion of said return pipe being located at a lower position than that of said working oil tank and lower than a position of said switching valve; and an opening and closing means provided at an outlet of said drain pipe to open and close said drain pipe such that the oil can be drained from the working oil tank, switching valve, return pipe and drain pipe via the outlet of said drain pipe.