Hydraulic hammering device

A hydraulic hammering device comprising:

• a cylinder;
• a piston that is slidably fitted into the inside of the cylinder;
• a piston front chamber and a piston rear chamber that are defined between an outer peripheral surface of the piston and an inner peripheral surface of the cylinder and are arranged separated from each other in axially front and rear direction;
• and
• a switching valve mechanism configured to switch each of the piston front chamber and the piston rear chamber into communication with either a high pressure circuit or a low pressure circuit in an interchanging manner;
• and which is configured to hammer a rod to be hammered, by making the piston advance and retract in the cylinder,
• wherein the piston has a large-diameter section, small-diameter sections that are individually disposed in front and the rear of the large-diameter section, and a valve switching groove that is formed substantially at an axially middle portion of the large-diameter section,
• the switching valve mechanism has a valve chamber that is formed in the cylinder in a non-concentric manner with the piston, a valve that is slidably fitted into the valve chamber and has a piston high/low pressure switching section formed that is configured to, by the valve advancing or retracting, switch each of the piston front chamber and the piston rear chamber into communication with either the high pressure circuit or the low pressure circuit in an interchanging manner, a valve presser that always presses the valve in either of advancing and retracting directions, and a valve controller configured to, when pressurized oil is supplied, move the valve to an opposite direction against pressing force by the valve presser,
• the cylinder has three control ports including, in order from the front, a piston retraction control port, a valve control port, and a piston advance control port, between the piston front chamber and the piston rear chamber,
• the valve control port is in communication with the valve controller in such a way as to be able to supply and discharge the pressurized oil and is always isolated from respective ones of the piston front chamber and the piston rear chamber, and
• the piston retraction control port and the piston advance control port are configured to cause, in association with an advance of the piston, the valve switching groove to communicate with the piston retraction control port and the valve control port and the pressurized oil to be supplied to the valve controller to make the valve retract and, in association with a retraction of the piston, the valve switching groove to communicate with the piston advance control port and the valve control port and the pressurized oil to be discharged from the valve controller to make the valve advance, and the switching valve mechanism switches each of the piston front chamber and the piston rear chamber into communication with either the high pressure circuit or the low pressure circuit in an interchanging manner depending on an advancing or a retracting movement of the piston high/low pressure switching section in association with an advance or a retraction of the valve to supply and discharge hydraulic oil so that an advance and a retraction of the piston can be repeated.