| 摘要 |
The present invention relates to a double hammer type underground drilling machine. More specifically, internal and external pistons are installed inside a housing combined with a top sub, and the opening and closing operation of air is automatically circulated by pressure of injected air while the internal and external pistons hit internal and external bits, and therefore, noise from a ground hit is reduced as a hit part is distributed to the internal and external bits when the ground is drilled. The number of times, hitting the bits, is guaranteed according to the number of times, moving up and down the internal and external pistons, as a direction of the injected air is switched, and therefore, power is concentrated on one of the bits to prevent damage to the bits and abrasion thereof and improve the reliability of ground drilling work. |
