US 5,375,348 AGranted

Deep excavator

AssigneeJapanic Corporation

InventorMitsuhiro Kishi

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Abstract

A stretchable arm of a deep excavator comprises top, middle and base arms wherein a bucket is suspended from the top arm and a working unit is fixed to the middle arm. Two hydraulic cylinders constituting the working unit are arranged in parallel with each other while cylinder rods thereof are oppositely directed, wherein the cylinder rod of one hydraulic cylinder is coupled to the base arm and the cylinder rod of the other hydraulic cylinder is coupled to the top arm. It is possible to extend and contract each arm of the stretchable arm synchronously with one another at higher speed compared with a conventional deep excavator having a single hydraulic cylinder. The oil under pressure which flows out from the discharge chamber of each hydraulic cylinder can be merged into the oil under pressure for extending each hydraulic cylinder so that the amount of oil to be supplied to the pressure chamber is increased.

Claims16

Dependent claims

A deep excavator comprising a chassis, a turntable disposed on the chassis, a boom which is pivotally supported on the turntable and is vertically swingable, a telescoping arm which is mounted on the boom and is telescoping in the longitudinal direction and comprises a plurality of telescopically assembled base, middle and top arms, and a bucket which is attached to the top arm for excavating and holding earth or sand, the deep excavator further comprising:

a working unit which is fixed to the middle arm and is operable by hydraulic power to telescopically extend or contract the telescoping arm, said working unit comprising a pair of hydraulic cylinders which are arranged physically in parallel with each other with cylinder rods thereof disposed to extend in opposite directions, wherein the cylinder rod of one hydraulic cylinder is connected to the base arm and the cylinder rod of the other hydraulic cylinder is connected to the top arm and fluid connecting passages joining pressure and discharge chambers of said one cylinder to respective pressure and discharge chambers of said other cylinder to cause synchronous extension and retraction of said cylinder rods of said pair of cylinders.

Dependencies are inferred from the claim text.