WO2016003351A1

WO2016003351A1 - Indexing hydraulic dth rock drill by intermittent pressure

Info

Publication number: WO2016003351A1
Application number: PCT/SE2015/050639
Authority: WO
Inventors: Fredrik EGERSTRÖM
Original assignee: Lkab Wassara Ab
Priority date: 2014-07-04
Filing date: 2015-06-02
Publication date: 2016-01-07
Also published as: SE538237C2; SE1450845A1

Abstract

The present invention concerns a down-the-hole drill that is driven via a drill string by a flow of fluid. It comprises a housing with an impact mechanism, a drill bit that is mounted such that it can be axially displaced in a driver chuck that is mounted in bearings in the housing such that it can be rotated, the impact mechanism being arranged with a hammer piston with a piston surface arranged to impact onto a neck at the drill bit, and a valve to control the hammer piston backwards and forwards between an initial position and an end position, whereby the valve of the hammer piston alternately places under pressure and removes the pressure from a pressure chamber that drives the hammer piston forwards when placed under pressure, the housing further comprising a fluid-driven rotation motor of vane motor type comprising pressure chambers with vanes that rotate the drill bit when placed under pressure. A flow pathway for the flow to the pressure chambers of the rotation motor is opened by the valve of the hammer piston when the valve closes the flow pathway to the pressure chambers of the hammer piston.

Description

INDEXING HYDRAULIC DTH ROCK DRILL BY INTERMITTENT PRESSURE TECHNICAL AREA

The present invention concerns a fluid-driven down-the-hole drill comprising a housing, a drill bit mounted in a driver chuck in a manner that does not allow it to rotate, an impact mechanism with a hammer piston arranged to impact on a neck of the drill bit, and a fluid-driven vane motor arranged at the housing for rotation of the drill bit.

BACKGROUND

Fluid-driven down-the-hole drills of this type are often used with drill rods that are joined together. The fluid that drives the impacts and the rotation is led through the rods. Another manner to lead the driving fluid is through what is known as "coiled tubing", a flexible drill tubing that is unreeled from a roll. The advantage of using flexible tubing is that the direction of the drilling can be controlled, and that the drilling proceeds more rapidly, due to the fact that the tube does not require joining.

The disadvantage of this type of fluid-driven down-the-hole drill is that complicated valve systems must be used in order to achieve a percussion and rotating motion. A further disadvantage is that the drill bit can, with such a motion, take drilling residue, known as "drilling cuttings" with it into the rotation, which means that the drill bit is severely worn, and that there is a risk that the drill bit gets stuck.

SUMMARY OF THE INVENTION The purpose of the present invention is to offer a fluid-driven down-the-hole drill of the type that has an intermittently rotating motor that is placed under pressure by the flow from the impact mechanism.

This purpose is achieved through the rotation motor and the impact mechanism being built together in a machine housing to which the flow is led and intermittently places the rotation motor under pressure through valves.

DESCRIPTION OF DRAWINGS

Figure 1 shows a side view of a down-the-hole drill according to the invention.

Figure 2 shows a section through the rotation motor of the down-the-hole drill from Figure 1. DESCRIPTION OF EMBODIMENTS

The fluid-driven down-the-hole drill 1 that is shown in Figure 1 demonstrates a machine housing 2 with an impact mechanism 3, a rotation motor 4 and a drill bit 5. The machine housing 2 comprises an extended pipe with a coupling part or connection 6 to which a drill string, not shown in the drawings, in the form of, for example, a drill rod or a coil, is connected. A fluid under pressure, such as water, air or mud, which will below be referred to as the "fluid", is led from a source, not shown in the drawings, through the drill string into the connection 6 for the driving of the down-the-hole drill 1. Thus, during drilling, the complete machine housing 2 is introduced into the borehole with the drill bit directed towards the bottom of the borehole and the drill string extending from the borehole connected to a source of a fluid under pressure.

An impact mechanism 3 is arranged at one end 7 of the machine housing 2, in connection with the coupling part 6. The impact mechanism 3 comprises a hammer piston 8 that is driven by the flow of fluid. The hammer piston 8 is designed as a shaft with an impact surface A and a penetrating passage 9. The flow of fluid is led through a valve 10 that alternately opens and closes the flow when the hammer piston 8 is displaced between its initial position 11 and its end position 12, and in this way alternately places under pressure and releases the pressure from a pressure chamber 13. The valve 10 may comprise a slide valve, but also other types of valve may be used. A port may, for example, be opened by the hammer piston when the hammer piston is caused to move. The pressure chamber 13 is so designed that the pressure from the fluid drives the hammer piston 8 against the drill bit 5. The hammer piston 8 is axially controlled with the aid of, for example, bushings 14 that permit the hammer piston 8 to be displaced between its initial position 11 and its end position 12. The end position 12 demonstrates a seating S, against which the striking surface of the hammer piston ends its displacement.

A drill bit 5 is arranged at the second end 15 of the machine housing 2 with a neck 16 that protrudes into the machine housing 2. The neck 16 of the drill bit 5 demonstrates a penetrating axial passage 17 and is terminated by a neck 18. The hammer piston 8 demonstrates a piston surface 19 and is arranged in an axially displaceable manner to impact the neck 18 of the drill bit 5. The hammer piston 8 is connected to the flow of fluid that alternately fills and empties through the valve 10 one or several pressure chambers 13 with fluid under pressure, and that impacts the piston 8 onto the neck 18 of the drill bit 5 through the piston surface 19. The drill bit 5 is equipped at its end that faces the rock with outlets 31 for the return flow. When the hammer piston has completed its impact against the drill bit, the pressure chamber 13 is placed under low pressure, whereby the hammer piston is caused to carry out its return motion and return to its initial position 11.

The neck 16 of the drill bit 5 has a splined connection 20 with a drill bit chuck 21, which gives a guided reciprocating motion to the drill bit 5 as shown by the arrow in Figure 1, and it is mounted in bearings in such a manner that the neck 16 of the drill bit 5 can rotate inside the machine housing 2 and accompany the rotation of the rotation motor 4. The bearing 22 of the drill bit chuck 21 is fixed screwed, fixed pressed or fixed attached in another manner at the machine housing 2. The neck 16 of the drill bit 5 is mounted in the drill bit chuck 21 after which a stop ring 23 is mounted onto the neck 16 of the drill bit 5 in order to prevent the drill bit 5 being able to fall out from the chuck 21. The drill bit chuck 21 is subsequently mounted at the end 7 of the machine housing 2. The drill bit 5 may, in another embodiment, be equipped with only one groove to guide the reciprocating motion.

The rotation motor 4, which is shown in cut-through view in Figure 2, is located between the drill bit 5 and the impact mechanism 3 in such a manner that the neck 16 of the drill bit 5 runs axially through the centre 24 of the rotation motor 4. The valve 10 at the connection 6 demonstrates passages 25 through which the flow is led when the valve 10 opens the flow pathway to the passages 25 that lead the flow to the rotation motor 4. The rotation motor 4 comprises a generally known vane motor of the type that comprises a housing H with radially displaceable vanes 26 arranged on a rotor shaft 27 surrounded by a pressure chamber 28. It is an advantage that the pressure chamber be formed by the housing H and the jacket surface M of the rotation shaft. The centre 24 of the rotation shaft 27 is designed with splines or grooves 29 corresponding to the splines or grooves 20 at the drill bit 5, such that the neck 16 of the drill bit 5 can move forwards and backwards in a controlled manner and accompany the rotation.

The pressure chambers 28 are so designed that the volume increases at the start of the rotation, and subsequently decreases at the end of the rotation. Due to the fact that the vanes 26 are radially displaceable, the vanes 26 follow the form of the pressure chambers 28 and obtain in this way an area that increases, and subsequently obtain an area that decreases at the end of the rotation. When the fluid under pressure is led into the pressure chambers 28, it presses the vane in front of it, whereby the rotation is achieved. It is an advantage if the pressure chambers are located symmetrically around the rotor. The fluid is led in on both sides of the rotor shaft 27, and in this way uneven loading is avoided. When the rotation motor 4 rotates, the drill bit 5 accompanies it in the rotation. The penetrating passages 9, 17 of the drill bit 5 and the hammer piston 8 lead the return flow from the pressure chambers 13 of the hammer piston 8 to the drill bit 5 in order to rinse the drilled region. The rotation motor 4 comprises further a separate outlet 30 for the return flow of the fluid. The outlet 30 is located between the connection 6 and the drill bit 5. This gives the advantage that the return flow, which cleans the borehole from drilling cuttings, is supplied from two directions. One supply is from the return flow 31 of the drill bit, which cleans also the region in the immediate vicinity of the drill bit, while the second supply is from the return flow outlet 30 of the rotation motor, which gives an effective cleaning of the borehole.

The flow of fluid to the rotation motor 4 is started when the hammer piston 8 is located at its initial position 11, the position at which the piston 8 is located closest to the connection 6. The drill bit 5 in this position is not in pressure-bearing contact with the bottom of the borehole. When the flow of fluid under pressure reaches the hammer piston 8, the valve 10 that leads a part of the flow to the rotation motor 4 is opened, whereby the motor 4 rotates and takes with it the drill bit 5 into the rotation. The remaining part of the flow is thus led to the hammer piston 8, which impacts onto the neck 18 of the drill bit. When the hammer piston 8 leaves its initial position 1 1 during its motion towards its end position 12, the valve 10 closes the passages 25 to the pressure chambers 28 of the rotation motor, whereby the rotation motor stops. When the rotation motor is stationary, the hammer piston 8 carries out its working impacts and hammers the piston surface 19 of the hammer piston 8 against the neck 18 of the drill bit 5, whereby the drill bit 5 impacts against the rock. When the hammer piston 8 moves backwards in the direction towards its initial position 11 , the drill bit 5 lifts away from the rock, and when the hammer piston 8 reaches its initial position 11, the valve 10 opens and the flow is led to the rotation motor 4.

In a second embodiment, the flow under pressure is led to the hammer piston 8, which drives the drill bit 5 against the rock. When the drill bit 5 has carried out its impact, and the hammer piston 8 is moving back towards its initial position 11, the valve 10 is opened, whereby the rotation motor 4 rotates, and takes with it the drill bit 5 into the rotation. When the hammer piston 8 reaches its initial position 11 , the valve 10 is closed, whereby the rotation stops. This is repeated as long as the flow of fluid under pressure is led down through the drill string from the source of the fluid under pressure (not shown in the drawings). These two embodiments give a form of indexing drilling or motion, in which the drill bit impacts against the rock at the bottom of the borehole at a new, undisturbed location each time. The connection is arranged with nozzles, not shown in the drawings, in the flow pathway in order to control the rate of rotation of the engine by limiting the flow.

The present invention is not limited to what has been described above and shown in the drawings: it can be changed and modified in several different ways within the scope of the innovative concept defined by the attached patent claims.

Claims

1. A down-the-hole drill (1) that is driven via a drill string by a flow of fluid, comprising a housing (2) with an impact mechanism (3), a drill bit (5) that is mounted such that it can be axially displaced in a driver chuck (21) that is mounted in bearings in the housing (2) such that it can be rotated, the impact mechanism (3) being arranged with a hammer piston (8) with a piston surface (19) arranged to impact onto a neck (18) at the drill bit (5), and a valve (10) to control the hammer piston (8) backwards and forwards between an initial position (11) and an end position (12), whereby the valve (10) of the hammer piston (8) alternately places under pressure and removes the pressure from a pressure chamber (13) that drives the hammer piston (8) forwards when placed under pressure, the housing (2) further comprising a fluid-driven rotation motor (4) of vane motor type comprising pressure chambers (28) with vanes (26) that rotate the drill bit (5) when placed under pressure, c h a r a c t e r i s e d i n that it comprises a flow pathway (25) for the flow to the pressure chambers (28) of the rotation motor that are opened by the valve (10) of the hammer piston when the valve (10) closes the flow pathway to the pressure chambers (13) of the hammer piston (8).

2. The down-the-hole drill according to any one of the preceding claims, whereby the valve (10) is arranged in association with the hammer piston (8).

3. The down-the-hole drill according to any one of the preceding claims, whereby the valve (10) opens the flow pathway (25) to the rotation motor (4) when the hammer piston (8) is located at an end position (12) when the hammer piston (8) has carried out its working impact.

4. The down-the-hole drill according to any one of the preceding claims, whereby the valve (10) closes the flow pathway (25) to the rotation motor (4) when the hammer piston (8) leaves its end position (12) during its motion in a direction back towards its initial position (11).

5. The down-the-hole drill according to claim 2, whereby the valve (10) opens the flow pathway (25) to the rotation motor (4) during the displacement of the hammer piston (8) in a direction towards its initial position (11).

6. The down-the-hole drill according to claim 5, whereby the valve (10) closes the flow pathway (25) to the rotation motor (4) when the hammer piston (8) reaches its initial position (11).

7. The down-the-hole drill according to claim 1, whereby the drill bit (5) comprises a neck (16) equipped with grooves or splines (20).

8. The down-the-hole drill according to claim 8, whereby the neck (16) of the drill bit extends axially through the rotation shaft (27) of the rotation motor (4), which shaft (27) is equipped with grooves or splines (29) corresponding to the grooves (20) in the neck (16) of the drill bit (5).