Abstract: A push-pull force control method for a horizontal directional drilling machine with the following steps is provided. According to a correspondence relationship between a motor displacement and a maximum push-pull force of a drilling machine, the motor displacement is first adjusted, so that the required push-pull force can be obtained through the adjustment of the subsequent steps. Then, an oil feeding pressure of the motor is controlled according to a relationship between the push-pull force and the working pressure difference of the motor. Finally, the push-pull force of the motor is controlled in real time according to the oil feeding pressure of the motor to be equal to the required push-pull force value.

Abstract: A double-walled drill pipe includes an outer drill pipe, an inner drill pipe and a drill pipe sealing apparatus. The outer drill pipe includes an axial through hole and a wall surface through hole, and the wall surface through hole is disposed in a wall surface of the outer drill pipe to connect the outside of the double-walled drill pipe and the axial through hole. The inner drill pipe is rotatably disposed in the axial through hole, and includes a fluid guiding hole connected to the wall surface through hole. The drill pipe sealing apparatus is disposed between the outer drill pipe and the inner drill pipe. The drill pipe sealing apparatus is axially located between a driving end and a connecting port of the wall surface through hole connected to the axial through hole. A drilling machine including the double-walled drill pipe is also provided.

Abstract: A push-pull force control method for a horizontal directional drilling machine and a horizontal directional drilling machine are provided. The control method includes: adjusting a working displacement of a motor to enable a maximum push-pull force Fmax corresponding to the working displacement to be greater than a set push-pull force Ft; calculating a working pressure difference ?P of the motor according to the set push-pull force Ft; calculating a working pressure required by the motor according to the working pressure difference ?P and a collected first oil return back pressure of the motor; and adjusting an oil feeding pressure of the motor to enable the oil feeding pressure of the motor to be equal to the working pressure required by the motor. The method accurately and fast controls the push-pull force of the horizontal directional drilling machine.

Abstract: A double-walled drill pipe includes an outer drill pipe, an inner drill pipe and a drill pipe sealing apparatus. The outer drill pipe includes an axial through hole and a wall surface through hole, and the wall surface through hole is disposed in a wall surface of the outer drill pipe to connect the outside of the double-walled drill pipe and the axial through hole. The inner drill pipe is rotatably disposed in the axial through hole, and includes a fluid guiding hole connected to the wall surface through hole. The drill pipe sealing apparatus is disposed between the outer drill pipe and the inner drill pipe. The drill pipe sealing apparatus is axially located between a driving end and a connecting port of the wall surface through hole connected to the axial through hole. A drilling machine including the double-walled drill pipe is also provided.