Patent ID: 8267374

Claim:
A multi-turn hydraulic actuator comprising: a hydraulic motor installed at a front end of one side of a housing of a drive part, to operate a motor disk so as to rotate by hydraulic pressure generated in a hydraulic pressure generator; a decelerator installed in the middle of the housing of the drive part and including a worm, a worm shaft, a driving shaft and a worm wheel, wherein the worm shaft with the worm is installed to be rotatable, and the worm is engaged with the worm wheel connected to the driving shaft in a single unit, to reduce a speed of a rotational force of the worm and transmit the rotational force of the worm to the driving shaft at the reduced speed; a moving shaft penetrating the worm shaft and connected to the worm shaft, to operatively rotate together and to selectively slide left or right; an automatic disk connected to one side of the moving shaft and operatively rotated by a number of rotation pins selectively meeting rotation pins of the motor disk; a manual disk connected to the other side of the moving shaft; a manual mode switch including a release bar positioned between the motor disk and the automatic disk, wherein the release bar is pivoted when a manual mode button is operated and then the release bar moves the automatic disk so as not to interfere with the motor disk, to switch an automatic mode of the worm shaft to a manual mode; and a manual handle installed at the other side of the housing of the drive part and including a handle shaft, rotation pins and a handle disk, wherein the rotation pins of the handle disk installed at a front end of the handle shaft selectively meet rotation pins of the manual disk, to manually rotate the worm shaft.