DRILLING ROBOT

Description

TECHNICAL FIELD

The invention relates to a drilling robot for drilling a borehole. The drilling robot is purely electrically driven. It comprises a movement unit for moving the drilling robot through the borehole and a rotary hammer unit. The rotary hammer unit comprises a drill head, a rotating system and a hammering system. The rotating system is adapted to rotate the drill head. The hammering system is adapted to hammer with the drill head.

BACKGROUND ART

Heat generation through geothermal energy plays a crucial role in worldwide successful heat transition. Boreholes for geothermal probes are traditionally drilled with a pneumatic hammer drill, wherein a compressor and a drill rig are arranged outside the borehole and the drill energy is transferred to the drill head inside the borehole via a drill pipe. Cuttings are flushed out of the borehole. With increasing depth of the borehole, the pressure drop of the compressed air immensely increases along the drill pipe. A very large compressor is needed to generate the necessary pressure and flow volume.

Such a drill system requires a lot of space. The process in energy-intensive, expensive, imprecise, causes noise and massive damage to the landscape. As a result, many buildings cannot benefit from geothermal heat or are equipped with other heating systems.

DISCLOSURE OF THE INVENTION

The problem to be solved by the present invention is therefore to provide a compact drilling robot for drilling a borehole which can be operated with low energy consumption.

This problem is solved by the drilling robot according to the independent claim. According to this, a purely electrically driven drilling robot comprises a movement unit, a rotary hammer unit with a drill head, a rotating system and a hammering system. The movement unit moves and stabilizes the drilling robot inside the borehole. The rotating system is adapted to rotate the drill head. The hammering system is adapted to hammer with the drill head and to operate according to an electro-pneumatic principle in order to generate an electro-pneumatic stroke. In particular, the hammering system comprises a piston compressing and expanding air between itself and a weight, in particular a cylindric weight, in particular without touching the weight.

The advantage of such a drilling robot is that the drill rig is located directly in the borehole and a drill pipe or other large equipment is not required. Construction costs are substantially reduced due to the autonomous and energy-efficient mode of operation. A purely electrically driven drilling robot does not cause uncomfortable noise.

Advantageously, the drilling robot comprises at least one, in particular two, electric motors. In particular, a first of the at least one electric motors drives the rotating system and a second of the at least two electric motors drives the hammering system.

The first electric motor generates the torque and might have a power of approximately 0.6 kW or more, in particular more than 1 kW. The second electric motor generates the strokes and might have a power of approximately 0.95 kW. The resulting impact energy breaks the rock.

In particular, the drilling robot has a cylindrical shape with a diameter smaller than 250 mm, in particular smaller than 200 mm, in particular smaller than 150 mm, in particular smaller than 100 mm, in particular smaller than 90 mm. Much less material has to be disposed of compared to today's drilling equipment. Drilling such a small borehole is energy-and cost-efficient.

Advantageously, no part of the drilling robot protrudes from the cylindrical shape. I.e. the diameter of the cylindrical shape defines the diameter of the borehole. For example, if the diameter of the drilling robot is 80 mm, the diameter of the resulting borehole is approximately 90 mm.

Advantageously, the first electric motor and the second electric motor are arranged within the cylindrical shape. The full power of the drilling robot is generated within the compact cylindrical shape. The drilling robot moves through the borehole like a worm.

In particular, the first electric motor is further away from the drill head than the second motor. I.e. the power of the rotating system is generated further away from the drill head than the power of the hammering system. A compact drilling robot can only be reached if the electric motors are arranged in a row. The torque generated by the first electric motor is transferred from the first electric motor to the drill head via a bypass shaft arranged in longitudinal direction on the side of, in particular parallel to, the second electric motor. This results in a compact drilling robot with an optimized relation between size and power of the drilling robot.

Advantageously, the bypass shaft rotates with a frequency higher than 30%, in particular higher than 50%, in particular higher than 100%, in particular higher than 120%, of the rotation frequency of the first electric motor. With other words, the high rotational speed of the first electric motor is only substantially converted to a lower rotational speed with a higher torque after it has bypassed the second electric motor, i.e. between the second electric motor and the drill head. Bypassing the second electric motor with a high rotational speed has the advantage that the bypass shaft can be dimensioned with a small diameter. This is an imported aspect, since the dimensions of both the second electric motor and the bypass shaft determine the diameter of the drilling robot.

Preferably, the drill head comprises reamers rotating with a frequency at least 10 times, in particular 20 times, lower than the rotation frequency of the first electric motor. This frequency conversion is reached by a gearbox arranged between the drill head and the second electric motor providing a frequency conversion for the rotating system with a conversion factor of at least 8, in particular at least 10, in particular at least 20, in particular at least 40.

Advantageously, the rotating system comprises an epicyclic gear train, i.e. a planetary gearset, or a cycloidal drive. In particular, the epicyclic gear train or the cycloidal drive is arranged between the drill head and the second electric motor.

In a preferred embodiment, the hammering system generates strokes, wherein the strokes travel through the sun of the epicyclic gear train to the drill head. Such a design has the advantage of an optimal dimensioning and arrangement of the electric motors and the gearbox. In an efficient manner, strokes can be transferred from the second electric motor to the drill head and power of the rotational system can be converted to a low rotational speed with a high torque.

In particular, the hammering system comprises a piston, compressing and expanding air between the piston and a cylindric weight without touching the cylindric weight.

In a further preferred embodiment, the drilling robot comprises a water-based flushing system for flushing cuttings away from the drill head to the surface of the borehole.

Cuttings might be separated from the water by a special filter system, which reuses the water for flushing. In particular, sensors detect the water level, which allows either water to be added or removed.

Advantageously, the hammering unit is adapted to operate with a hammer energy in relation to the diameter of the cylindrically shaped drilling robot of at least 0.08 J/mm, in particular of at least 0.1 J/mm, in particular 0.12 J/mm. For example, if the hammer unit operates with a hammer energy of 11 J and the cylindrically shaped drilling robot has a diameter of 80 mm, it results a relation of 0.1375 J/mm.

Other advantageous embodiments are listed in the dependent claims as well as in the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above will become apparent from the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:

FIG. 1 shows a general illustration of a system for drilling a borehole;

FIG. 2 shows an overview of the drilling robot working inside the borehole;

FIG. 3a shows the drilling robot from the outside;

FIG. 3b shows the drilling robot of FIG. 3a, wherein the housing of the drilling robot is not shown;

FIG. 3c shows a sectional view through the drilling robot.

MODE FOR CARRYING OUT THE INVENTION

It follows a description of a specific embodiment. The technical data given are merely exemplary and does not limit the scope of the claims.

FIG. 1 shows a one family house and equipment for drilling a borehole 1. Borehole 1 is drilled in order to heat the house by geothermal energy. The drilling equipment comprises a drilling robot 2 autonomously operating inside the borehole 1. I.e. the drill rig is located directly in the borehole 1 and does not require a drill pipe. The drilling robot 2 is connected with a power and water source via connection 3. A container 4 is arranged on the surface 5 for collecting cuttings from the drilling robot 2. The drilling robot can drill boreholes for geothermal probes up to a depth of at least 250 meters or maximally 500 meters.

FIG. 2 shows the drilling robot 2 operating inside the borehole 1 in a more detailed view. The drilling robot 2 comprises a drilling unit 3, a movement unit 4 and a control unit 5. Furthermore, a support system (not shown in detail) is arranged inside the borehole 1 following the drilling robot 2.

The movement unit 4 moves the drilling robot 2 through the borehole 1. While drilling, the movement unit 4 clamps against the drill wall 6 of the borehole 1 in order to absorb all forces of the drilling process. The control unit 5 controls the drilling process of the drilling robot 2 and delivers information to the operating user at the surface 5. The support system supports the drill wall 6. Especially in loose rock, without a support system, rocks, sand, clay etc. would fall into the borehole and cause it to collapse. The support system prevents this.

A water-based flushing system 8 efficiently flushes cuttings 9 to the surface 5. The water-based flushing system 8 is connected to a water source 10. The flushing is done by a pump 11 that can produce a volume flow of about 5 m³/h at a pressure of 15 bar. The water is then pumped to the surface 5.

The water-based flushing system 8 separates the cuttings 9 from the water by a special filter system 12, which reuses the water for flushing. The separated cuttings 9 are stored in container 4. Sensors detect the water level, which allows either water to be added or removed.

The drilling robot 2 is purely electrically driven and powered by a power source 13. Furthermore, the drilling robot 2 has a cylindrical shape with a diameter D₁ of 80 mm and the borehole 1 has a diameter D₂ of 90 mm.

FIG. 3a shows the drilling robot 2 from the outside and FIG. 3b shows the drilling robot 2 without the housing 20 sealing the drilling robot 2. FIG. 3c shows a sectional view of the drilling robot 2.

The drilling robot 2 comprises a rotary hammer unit with a drill head 21, a rotating system 22 and a hammering system 23. The drill head 21 is designed as an overburden system and comprises a pilot bit 25 and three reamers 26. The drill head 21 is rotated by the rotating system 22. Drill head 21 is responsible for demolishing rock and removing cuttings 9 underneath the drill head 21. Therefore, making room for the drilling robot 2 to advance in depth. The rotary hammer unit, including the drill head 21, is designed so that it can be operated in different rock formations by varying the rotary and hammer movement.

The rotating system 22 comprises a first and upper electric motor 27 which are water-cooled. The first electric motor 27 provides the torque needed to turn the drill head 21 through multiple cylindrical gear pairs 28, a bypass shaft 29 and a planetary gearset 30, also called an epicyclic gear train. A slip clutch 31 then transmits the power to the main shaft 32.

The first electric motor 27 rotates with a speed of 3k rpm and operates with a power of 0.6 kW. Cylindrical gear pairs 28 convert the rotation of the electric motor 27 to a higher speed of rotation which is further transferred by the bypass shaft 29 to the main shaft 32. With other words, the bypass shaft 29 rotates with a frequency higher than 100% of the rotation frequency of the first electric motor 27. The planetary gearset 30, which is part of a gearbox of the rotating system together with a cylindrical gear pair 36, arranged between the drill head 21 and the second electric motor 31, substantially reduces the rotational speed such that the reamers 26 are operated with a rotational speed of about 100 rpm and a corresponding torque. Reamers 26 rotate with a frequency 30 times lower than the first electric motor 27 and 40 times lower than the bypass shaft 29.

The hammering system 23 comprises a second and lower electric motor 31. The second electric motor 31 is less far away from the drill head 21 than the first electric motor 27. The second electric motor 31 powers a piston 32 driven by a bevel gear 35. The piston 32 compresses and expands air 33 between itself and a cylindric weight 34 but doesn't touch the cylindric weight 34. Moved by air 33, the cylindric weight 34 hits the main shaft 32 with its kinetic energy several times a second, providing a stroke that travels down to the drill head 21. This principle is called an electro-pneumatic stroke. The main shaft 32 extends through the sun 33 of the planetary gearset 30.

The second electric motor 31 rotates with a speed of about 13k rpm and operates with a power of about 0.7 kW. The speed of rotation is reduced by the bevel gear 22 such that the piston operates with about 2.5k rpm.

Finally, the drilling head 21 operates with a torque of 57 Nm, a rotational speed of 100 rpm, a hammer energy of 11 J and with 2.5k strokes per minute.

The bypass shaft 29 transferring the torque from the first electric motor 27 to the drill head 21 is arranged in longitudinal direction 37 on the side of, in particular parallel to, the second electric motor 31.

Underneath the impact, a rotary and translational feedthrough of the water-based flushing system 8 is at work. It allows water to enter the flushing channel 8 in the centre of the main shaft 32. The water then travels down to the drill head 21.

The housing 20 consists of multiple parts that are sealed against outside pressure and held together by metal straps.