CYLINDER UNIT

PURPOSE:To reduce the consumption of working fluid by forming a cylinder in such a configuration as to operate by means of only a piston of a small diameter during a stroke motion while a piston of a large diameter is not connected to a piston rod until said rod comes up close to the position where it sends out a required power. CONSTITUTION:When a piston 16 of a small diameter advances up to the stroke end, a taper part 17c of a cushion ring 17a touches a ball 28 and a mechanical valve 27 makes an opening action. Then an operate valve 31 makes an offset action to a position B and air is supplied into a chamber R5 of each minicylinder 20 through a port 36, and passage 37. This causes click pieces 26 to advance all together toward a piston rod 15 to be engaged with a circular groove 25. As a result, air is also supplied into a chamber R1 on the rod side of a cylinder tube 11 of a large diameter simultaneously with connection of the piston rod 15 to a piston 18 of a large diameter.