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With the increasing application of milling technology in near-horizontal directional drilling stuck/buried drilling accidents in coal mines, the probability of second stuck/buried drilling accidents with milling tools increases. To solve this problem, based on the conventional hydraulic mechanical internal cutter, a ratchet type two-stage positioning small diameter internal cutter was designed for the milling tool of near-horizontal directional drilling in underground coal mine; the displacement relationship between the push device and the cutting tool was obtained by establishing the geometric model, and the technical parameters of the ratchet two-stage positioning small diameter internal cutter were determined. In the field application, the casing milling drill pipe with a diameter of 114 mm was cut off successfully at 446.5 m. The results show that the piston and the throttle needle cooperate to cut the signal function; the ratchet mechanism with positioning function is adopted to reduce the dependence on continuous water pressure and reduce the operation difficulty. Using spring energy storage to provide flexible thrust force for cutting tool rotation, the thrust is continuous and stable, and the impact of water pressure fluctuation on tool tip is eliminated.

The basic design principles and structural characteristics of the feeding device of drilling rig in underground coal mine are analyzed. According to the demand of long-stroke, a feeding device by the series and parallel combination cylinder is developed, the theoretical calculation method of key parameters of the feeding device is given, and the changes of effective feeding force and pulling force are analyzed by fitting curve. The analysis shows that the effective feeding force and pulling force decrease with the increase of wear. The maximum feeding force and pulling force of the drilling rig were tested, and the validity of the theoretical calculation method was verified.

In order to realize the coal mine drilling hole sealing automation, according to the “13th Five-Year” key research and development project “gas control drilling and hole sealing robot” requirements, we put forward the integral multi-channel automatic hole sealing device overall scheme, designed the automatic hole sealing control method, and studied and designed the parameters of grouting channel and hole sealing channel. Finite element method was used to analyze the setting dynamics of the hole sealing device, and the drilling setting and grouting simulation tests were carried out on the prototype of the hole sealing device. The research shows that the whole structure of the hole sealing device can be equipped with the drilling robot to grasp, install and switch the channel automatically to seal the hole automatically. It can meet the requirements of sealing holes with different sealing lengths and different inclination angles. The three-way structure can meet the requirements of setting, exhaust, grouting, gas extraction and other technological processes on pressure and pressure loss; according to the dynamic analysis of the contact stress between the setting seal capsule and the hole wall, the axial friction resistance between the setting seal capsule and the hole wall, as well as the simulation experiment results of sealing the hole, when the setting grouting pressure of the device is 6 MPa, the grouting pressure of the sealing hole can reach 3 MPa, which fully meets the technical requirements of “two blocks and one grouting” sealing hole in the coal mine, and the negative pressure loss of the extraction channel is less than 2 kPa. By meansof sensors and instruments, the monitoring of setting pressure, sealing grouting pressure, extraction flow, pressure and other parameters can be realized.