| 摘要 |
A breaker, used for breaking target hard objects, such as reinforced concrete structures, rocks or hard soil, using pneumatic and hydraulic pressure, is disclosed. In the breaker, the piston is multi-stepped to form first, second and third oil chambers between the piston and the cylinder. First, second, third and fourth oil paths are formed in the sidewall of the cylinder. The first oil path extends from the oil inlet port to the first chamber, thus feeding pressurized oil from an external oil source to the first chamber. A valve chamber is formed in the sidewall of the cylinder. The second oil path allows the valve chamber to selectively communicate with the second chamber. A directional control valve unit is installed within the valve chamber, and selectively returns the pressurized oil from the first chamber to the valve chamber prior to feeding the oil from the valve chamber to the second chamber through a plurality of oil ports and the second oil path. The third oil path selectively communicates with the valve chamber through the valve unit when the piston axially moves within the cylinder. The fourth oil path discharges the pressurized oil from the third chamber through an oil drain path, thus making the pressure of the third chamber become zero and initializing the pressure of the third chamber.
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