FLOATING TYPE CUSHION DEVICE OF HYDRAULIC CYLINDER

摘要

PROBLEM TO BE SOLVED: To increase the cushion performance in a floating type cushion device of a hydraulic cylinder by preventing the change of the circular gap of a cushion passage due to the back pressure to control the back pressure properly. SOLUTION: Passages continuously open are formed with a plurality of concave grooves 30a on an end face on the side of a cushion passage 32 on a cushion ring 30 loosely fitted with a ring inserting part of a piston rod 3. A plurality of notches 30d are formed open from the periphery to near the center of the wall of the end face on the opposite side. A switching ring 31 is insertingly fit for telescopic action in the radial direction between the end face of that cushion ring and a piston end face 4a. The switch ring 31 closes a passage between the cushion ring end face and the piston end face 4a when the external diameter side pressure (a rod room 7a) is higher than the internal diameter side pressure (a circular passage 30c), and opens the flow passage when the internal diameter side pressure is higher than the external diameter side pressure.