Patent ID: 7614170

Claim:
An extendable excavating screw unit having a spiral screw on outer circumference of an excavating shaft is operated by a hydraulic pressure, the excavating screw unit comprising: an extension unit ( 10 ) having a pair of auxiliary excavating blades ( 11 , 11 ′), cylinder mounting holes ( 12 , 12 ′), built-in fluid passages in the extension unit ( 15 , 15 ′), hydraulic cylinders ( 16 ) and pistons ( 17 ), piston shafts ( 18 ) with end flanges and flange mounting seats, an excavation column ( 20 ) having a square-shape hollow center, a bottom end of said excavation column ( 20 ) mounted on top of said extension unit ( 10 ), an extension rod ( 30 ) having an outer square-shape to fit into said excavation column ( 20 ), a pair of built-in hydraulic tube ( 14 , 14 ′) in the extension rod, the hydraulic passages at top portion of the extension rod ( 30 ) bent right angle to form an inlet and outlet ( 32 , 32 ′) for connecting to hydraulic hose ( 33 ), wherein said extension rod ( 30 ) is inserted into said excavation column ( 20 ) for extending or retracting, a pair of valve mounting seats ( 40 , 40 ′) formed transversely inner top portion of the extension unit ( 10 ), double pilot check valves ( 41 , 41 ′) mounted on the valve mounting seats ( 40 , 40 ′), said double pilot check valves ( 41 , 41 ′) are connected to the built-in fluid passages in the extension unit ( 15 , 15 ′) and the fluid passage in the guiding rod ( 19 a , 19 b ), so that the extended excavating auxiliary blades ( 11 , 11 ′) is maintained by the pressurized fluid for preventing to be retracted by the digging resistance during the excavating operation, and a mounting plate ( 50 ) and a pair of flexible hydraulic hoses ( 51 , 51 ′) for fixing and connecting to said pair of built-in hydraulic tube ( 14 , 14 ′) in the extension rod ( 30 ) and the built-in fluid passages ( 15 , 15 ′) in the extension unit ( 10 ).