2 step auto stroke type hyraulic breaker

A two-step auto stroke hydraulic breaker, comprising:

• a cylinder including a high-low pressure chamber at an upper portion thereof, a high pressure chamber at a lower portion thereof, and a pressure converting chamber disposed between the high-low pressure chamber and the high pressure chamber and including a sensing port, a first connecting port, an oil tank port, a long stroke port, and a short stroke port;
• a piston movably disposed in the cylinder, and including a small diameter portion, a large diameter portion, and a sensing fluid groove being a concave shape on an outer circumferential surface of the large diameter portion of the piston;
• a return fluid groove being a concave shape on the large diameter portion of the piston in a longitudinal direction of the piston;
• a high pressure connecting path configured to supply a fluid pressure from the high pressure chamber to the sensing port;
• a fluid circuit unit configured to control a supply direction of a fluid supplied into an inside of the cylinder, and configured to provide the fluid pressure to selectively change a stroke according to a kind of a bedrock;
• and
• a chisel configured to break the bedrock when a lower portion of the piston descends to impact the chisel during a descending operation,
• wherein the fluid circuit unit comprises:
• a control valve disposed on a plurality of fluid paths between the cylinder and a pump to control the supply direction of the fluid;
• a stroke converting valve having an upper portion connected to a first fluid path, which is a connecting path to the sensing port, and a lower portion connected to an elastic member having an elastic force relatively greater than the fluid pressure of the first fluid path in a normal state, so that the control valve is connected to the third fluid path connected to the short stroke port of the cylinder;
• a fourth fluid path configured to connect the long stroke port and the control valve;
• a bypass fluid path configured to connect the first fluid path and a return fluid path, and
• an orifice disposed in the bypass fluid path.

A two-step auto stroke hydraulic breaker, comprising:

• a cylinder including a high-low pressure chamber at an upper portion thereof, a high pressure chamber at a lower portion thereof, and a pressure converting chamber which is disposed between the high-low pressure chamber and the high pressure chamber and includes a sensing port, a first connecting port, an oil tank port, a long stroke port, and a short stroke port;
• a piston movably disposed in the cylinder, and including a small diameter portion, a large diameter portion, and a sensing fluid groove formed as a concave shape on an outer circumferential surface of the large diameter portion of the piston;
• a return fluid groove formed as a concave groove on the large diameter portion in an axial direction of the piston;
• a high pressure connecting path configured to supply a fluid pressure from the high pressure chamber to the sensing port;
• a fluid circuit unit configured to control a supply direction of the fluid supplied into an inside of the cylinder, and configured to provide the fluid pressure to selectively change a stroke according to a kind of a bedrock;
• and
• a chisel configured to break the bedrock when a lower portion of the piston descends to impact the chisel during a descending operation,
• wherein the fluid circuit unit comprises:
• a control valve disposed between the cylinder and a pump to control the supply direction of the fluid;
• a stroke converting valve including an upper portion connected to a first fluid path, which is a connecting path to the sensing port, and a lower portion connected to an elastic member and a return fluid path through which the fluid thereof is returned to an oil tank, so that the third fluid path is selectively connected to the control valve;
• a fourth fluid path configured to connect the long stroke port and the control valve;
• a bypass fluid path configured to connect the first fluid path and the return fluid path, and
• an orifice disposed in the bypass fluid path.

The hydraulic breaker of claim 18, wherein:

• the oil tank port is disposed below the sensing port;
• the long stroke port is disposed below the oil tank port;
• and
• the short stroke port is disposed below the long stroke port.