Two-piston hydraulic striking device

A two-piston hydraulic striking device comprising:

• a striking mechanism configured to strike one transfer member with two pistons, wherein
• the striking mechanism includes a first striking mechanism and a second striking mechanism, and the first striking mechanism and the second striking mechanism are arranged in series in front and rear direction in such a way that striking axes are coaxial with each other and the second striking mechanism is positioned on a side where the one transfer member is located,
• the first striking mechanism includes:
• a first cylinder;
• a first piston configured to be slidably fitted into the first cylinder in such a manner as to be able to advance and retract, the first piston having a first striking portion for striking the one transfer member at a tip portion of the first piston;
• and a first switching valve configured to switch advancing and retracting movements of the first piston,
• the second striking mechanism includes:
• a second cylinder;
• a second piston configured to be slidably fitted into the second cylinder in such a manner as to be able to advance and retract, the second piston having a second striking portion for striking the one transfer member at a tip portion of the second piston;
• and
• a second switching valve configured to switch advancing and retracting movements of the second piston,
• only either the first striking mechanism or the second striking mechanism includes a valve controller for controlling operation of both the first switching valve and the second switching valve,
• of the two pistons, at least the second piston is formed into a hollow shape and the first piston is inserted into inside of the second piston in such a way that the first striking portion extends in such a manner as to be able to strike the one transfer member, and
• a pressure receiving area ratio between front and rear of the first piston and a pressure receiving area ratio between front and rear of the second piston are set to satisfy a formula below:
• [t1a+t1c]=t1b=[t2a+t2c]=t2b (Formula),
• where t1a, t1b, t1c, t2a, t2b, and t2c represent an advance time of the first piston, a retraction acceleration time of the first piston, a retraction deceleration time of the first piston, an advance time of the second piston, a retraction acceleration time of the second piston, and a retraction deceleration time of the second piston, respectively,
• the first piston has a first piston medium diameter portion, a first piston small diameter portion, and a first piston large diameter portion formed between the first piston medium diameter portion and the first piston small diameter portion,
• the second piston has a second piston medium diameter portion, a second piston small diameter portion, and a second piston large diameter portion formed between the second piston medium diameter portion and the second piston small diameter portion,
• the pressure receiving area ratio of the first piston is a ratio between a difference between a cross-sectional area of the first piston large diameter portion and a cross-sectional area of the first piston medium diameter portion and a difference between the cross-sectional area of the first piston large diameter portion and a cross-sectional area of the first piston small diameter portion, and
• the pressure receiving area ratio of the second piston is a ratio between a difference between a cross-sectional area of the second piston large diameter portion and a cross-sectional area of the second piston medium diameter portion and a difference between the cross-sectional area of the second piston large diameter portion and a cross-sectional area of the second piston small diameter portion.