Patent ID: 6164186
Filing Date: 2000-12-26
Classification: F15B

Abstract:
A jack comprising:a jack body with a peripheral wall which forms a jack chamber in which first and second pistons are displaced in combination with a piston rod, the pistons being movable along the piston rod and relative to each other;a locking means for automatically locking the first and second pistons and the piston rod in first and second extreme positions of the piston rod, respectively, said locking taking place automatically in response to movement of the piston rod to either of the extreme positions, the locking means including:first and second locking grooves in the piston rod adjacent the first and second pistons, respectively;at least first and second locking elements which interact with the first and second locking grooves respectively, in the piston rod, the first locking element interacting with the first locking groove to lock the piston rod in the first extreme position and the second locking element interacting with the second locking groove to lock the piston rod in the second extreme position;a resilient biasing device which urges the first and second pistons apart from each other against two stops;first and second drive elements for longitudinally displacing the first and second pistons, respectively, longitudinally away from the first and second locking elements; and,first and second unlocking collars rotatably mounted around each extremity of the body of the jack, each unlocking collar being manually rotatable, the rotation of each of the unlocking collars causing longitudinal displacement of the corresponding locking member and piston releasing the piston rod from the corresponding locking element.