| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic cylinder capable of controlling oil leakage in a simple structure and an impact tester having the hydraulic cylinder. SOLUTION: A dust seal 30 is arranged closer to a tip side of a piston rod rather than a location of a U packing 20. A sliding portion 31 of the dust seal 30 receives force with a direction of increasing sealing performance of the dust seal 30 from a piston rod 12 when the piston rod is expanded. The sliding portion 31 of the dust seal 30 receives force with a direction of relieving sealing performance when the piston rod is contracted. Consequently, thickness of an oil film stuck on the piston rod 12 becomes thinner when the piston rod 12 is expanded, and the amount of oil scraped by the dust seal 30 is reduced when the piston rod 12 is contracted. Accordingly, oil leakage can be controlled. COPYRIGHT: (C)2004,JPO&NCIPI
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