Hydraulic striking device

A hydraulic striking device comprising:

• a cylinder;
• a piston slidably fitted in an inside of the cylinder;
• a piston front chamber and a piston rear chamber defined between an outer peripheral surface of the piston and an inner peripheral surface of the cylinder and arranged separated from each other in axially front and rear directions;
• and
• a switching valve mechanism configured to switch the piston front chamber and the piston rear chamber into a high pressure state and a low pressure state in an interchanging manner, the piston being advanced and retracted in the cylinder to strike a rod for striking, wherein:
• the switching valve mechanism includes a valve chamber formed in the cylinder in a non-concentric manner with the piston, a valve slidably fitted in the valve chamber and to which a high/low pressure switching portion for switching the piston front chamber and the piston rear chamber into a high pressure state and a low pressure state in an interchanging manner is formed, a valve biasing portion configured to constantly bias the valve forward, and a valve control portion configured to, when pressurized oil is supplied, move the valve rearward against biasing force by the valve biasing portion,
• to the switching valve mechanism, a reverse operation circuit and a forward operation circuit are connected and connection states of the reverse operation circuit and the forward operation circuit to a high pressure circuit and a low pressure circuit are interchangeable by means of an operation switching valve,
• the valve biasing portion includes a reverse operation biasing portion configured to operate when the reverse operation circuit is connected to the high pressure circuit and a forward operation biasing portion configured to operate when the forward operation circuit is connected to the high pressure circuit,
• the hydraulic striking device is configured to, through operation of the operation switching valve, be selectable between a reverse operation mode in which the valve and the piston are operated in opposite phases and a forward operation mode in which the valve and the piston are operated in the same phase, and
• to the high/low pressure switching portion, a shortening portion is disposed, the shortening portion reducing a switching time taken to switch the piston front chamber and the piston rear chamber between the high pressure state and the low pressure state by retraction of the valve to be shorter than a switching time taken to switch the piston front chamber and the piston rear chamber between the high pressure state and the low pressure state by advancement of the valve.