| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable to adjust resistance of a door closer depending on a size of the door and a degree of an external force acting in the closing direction by making a relief valve selectively switchable. Ž<P>SOLUTION: High-pressure and low-pressure chambers A and B are ordinarily shut off by the relief valve 39. The relief valve 39, which communicates the high-pressure chamber A and the low-pressure chamber B and discharges a hydraulic fluid in the high-pressure chamber A into the low-pressure chamber B, can be switched between the opening/closing operable state and the opening inoperable state when the external force in the closing direction acts on the door while the door is in process of closing, and is stored in a housing 3. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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