Hydraulic Hammering Device

A hydraulic hammering device, comprising:

• a cylinder;
• a piston slidably fitted into the cylinder in such a manner as to be capable of advancing and retracting;
• a first control valve to control advancing and retracting movements of the piston;
• an auto-stroke mechanism configured to switch a piston stroke of the piston between a regular stroke and a short stroke shorter than the regular stroke;
• an idle strike prevention mechanism configured to decompress an inside of a circuit configured to hydraulically drive the piston to lower than a working pressure;
• and
• a second control valve to select either mode of the auto-stroke mechanism and the idle strike prevention mechanism, wherein:
• to the second control valve, a shared spool including an auto-stroke setting portion and an idle strike prevention setting portion at the same time is slidably fitted,
• a mode selection means for allowing and cutting off both of supply of pressurized oil to the auto-stroke setting portion and discharge of pressurized oil from the idle strike prevention setting portion is disposed, and
• the mode selection means is configured in such a way that:
• when, while allowing pressurized oil to be supplied to the auto-stroke setting portion, prohibiting pressurized oil from being discharged from the idle strike prevention setting portion, the auto-stroke mechanism is selected, and
• when, while prohibiting pressurized oil from being supplied to the auto-stroke setting portion, allowing pressurized oil to be discharged from the idle strike prevention setting portion, the idle strike prevention mechanism is selected.