Patent ID: 7121089

Claim:
A hydraulic cylinder comprising: a cylinder piston that is inserted into a cylinder and divides the cylinder into a first cylinder chamber and a second cylinder chamber; and a cylinder rod having the cylinder piston fixed to one end thereof, and a rod head fixed to another end of the cylinder rod, wherein: the cylinder rod is of a concentric triple tube structure comprising a first guide tube, a second guide tube surrounding the first guide tube, and a third guide tube surrounding the second guide tube; the first guide tube has one end that is communicated with the second cylinder chamber, and another end that is communicated with a head side port formed in the rod head, and the second guide tube has one end that is communicated with the first cylinder chamber and another end that is communicated with a bottom side port formed in the rod head; and the third guide tube has in an interior thereof an accumulator comprising an accumulator piston that is inserted into the third guide tube and divides the interior of the third guide tube into a first cylinder rod chamber and a second cylinder rod chamber, compressive gas that is charged into the second cylinder rod chamber, and an accumulation port that is formed in the rod head and communicated with the first cylinder rod chamber.