Steerable drilling mole

Abstract: Steerable drilling mole (3) which includes a round, hollow body (13), a spraying device (10) situated in front of this body (13) and a high pressure pipe (15) which connects to the spraying device (10), characterised in that the high pressure pipe (15) is at least flexible in the body (13) but nevertheless relatively stiff and it is so held fast in front and at a distance more toward the back by a support (14 and 16) central in the body (13), while the drilling mole (3) has means (22) for bending the high pressure pipe (15) outward in relation to the longitudinal axis of the body (13) between the support in front (14) and the rear support (16) so that the front extremity of the high pressure pipe (15) and therefore the spraying device (10) mounted thereon change direction.

Description: The invention relates to a steerable drilling mole which includes a hollow round body, a spraying device situated at one end of this body, a pipe for drilling liquid under pressure, which connects to the spraying device, which is supported in the body and which is flexible at least in the body, and at least one moving device situated between the inner side of the body and the pipe. A steerable drilling mole of this kind is disclosed in US-A-4 396 073. The spraying device is mounted in a head which is pivotable mounted by means of a spherical surface element in the front part of the body. A hose for water under high pressure, extending through the body, ends in the rear end of the head and directs water under pressure into a central passage way trough this head. Four piston/cylinder units disposed inside the body around the water hose acts directly on the tapered circumferential surface of the inner end of the head for determining the direction of the head. Due to the use a pivotable head and piston/cylinder units for pivoting this head, the construction of this known drilling mole is relatively complicated. The invention has the purpose of remedying this disadvantage and to provide a steerable drilling mole of the type referred to above of which the construction is very simple and which can be steered in a simple manner. For this purpose the pipe is supported centrally in the body adjacent the spraying device, respectively at a distance therefrom, by supports and is flexible in such a way that, when the part between the supports bends in one direction, the end of said pipe connected to the spraying device deviates in the opposite direction, and the mole includes at least three moving devices which are arranged between the inner wall of the body and the part of the pipe between the supports, spread over the periphery of the high pressure pipe, for bending the pipe in different directions. With this use is made of the finding that, when a flexible pipe of the above type bends in one direction, the extremities situated outside the supports, at least if they are free, are going to deviate in the opposite direction form the normal longitudinal direction. By making use of this for directing the front extremity of the pipe and thus the spraying device mounted thereupon a rather simple construction is obtained while the spraying direction and thus the drilling direction can nevertheless be accurately determined. WO-A-8 600 111 discloses a directional drilling tool comprising a round body, a bendable pipe supported at both ends therein and a moving device acting on this pipe. However, this tool is a so-called drilling sub for drilling oil wells carrying on its end a drill bit for loosening the formation and is not a mole carrying on its end a spraying device for spraying drilling liquid under pressure. In the drilling sub, the bendable pipe is a driving shaft which is hollow to provide for a mud flow passage. Bending of the driving shaft is only possible in one direction. The use of three moving devices for outlining a tool is known as such from FR-A-2 118 328. This tool is however not a drilling tool but a perforating tool and it has neither a spraying device nor a flexible pipe. The three moving devices move radially a rigid perforating element inside a hollow body, without bending this element. In a particular embodiment of the invention, each of said moving devices includes an expandable container and means for filling this container separately with fluid under pressure so that it expands. Through the choice of container which is filled while the others are not filled, a bending outward of the high pressure pipe in one or another direction is obtained. The container can be filled with the same fluid that is also supplied to the spraying device or another fluid under pressure. The means for filling the container can therefore apart from a source of fluid under pressure also include valves, which are mounted for that purpose either on the containers or on separate supply pipes. In a suitable embodiment of the invention the supports for the pipe are elastically deformable. Advantageously one of the supports of the flexible pipe iis formed by a support for the spraying device. The extremity of the body adjecent to the spraying device is preferably sealed around this spraying device by an elastic seal. This elastic seal may advantageously form one of the supports. In order to show better the characteristics according to the present invention, a preferred embodiment of a steerable drilling mole according to the invention is described hereafter, as example without any restrictive character, with reference to the enclosed drawings, in which: Figure 1 is a schematic representation of a device for making a tunnel in the ground provided with a steerable drilling mole according to the invention; figure 2 represents a longitudinal cross-section of the steerable drilling mole according to the invention from the device according to figure 1; figure 3 represents a detail from figure 2 drawn on a larger scale; figure 4 represents a cross-section of the drilling mole taken at the location of the line IV-IV from figure 2; figure 5 represents a longitudinal cross-section of the drilling mole according to the invention analogue to that from figure 2 but in relation to another position of the spraying device. As illustrated in figure 1 a tunnel 1 is made in the ground with assistance of a steerable drilling mole 3 according to the invention which drilling mole is mounted upon a flexible drilling pipe 4. The supple drilling pipe 4 is unwound from a drum 5 which is erected above the ground. This drilling pipe 4 has a smaller diameter than the drilling mole 3. The drilling mole 3 and subsequently the drilling pipe 4 enter the ground 2 through a tank 6 with rinsing liquid or water for the supply of hydraulic pressure in the tunnel 1. This tank 6 is mounted over an opening 7 in a plate 8 which lies on the ground 2. An inflated ring 9 which surrounds the opening 7 in the plate 8 and the mouth of the tunnel 1 on the surface of the ground, is placed between the plate 8 and the surface of the ground. The drilling mole 3 is provided with a high pressure spraying device 10 for drilling into the ground. The high pressure fluid for this spraying device 10 is pumped through the flexible drilling pipe 4 by means of a high pressure pump 11. The depth of the drilling mole 3 in the ground can be read from a translucent upper extremity of a pipe 12 situated above the ground 2 which extends along the flexible drilling pipe 4 in the tunnel 1 and with its lower, closed extremity is situated on the front extremity of the drilling mole 3. This pipe 12 is filled with liquid upon which thus on top the atmospheric pressure acts. The level of the liquid in the upper translucent and vertically directed part of the pipe 12 changes in function of the depth of the drilling mole. For the sake of clarity this pipe 12 is not represented in the figures 2 through 5 in which the drilling mole 3 is completely represented in detail. As appears from these figures, the drilling mole 3 according to the invention includes a cylindrical body 13. The spraying device 10, that is itself of a known construction, is mounted centrally in a rubber support 14 which seals off the front extremity of the body 13 and through elastic formation allows the directing of the spraying device 10. This spraying device 10 connects to a flexible but nevertheless relatively stiff high pressure pipe 15 of polyethylene reinforced with fabric. Halfway along the body 13 this flexible high pressure pipe 15 is centrally supported by a support 16 in the form of a rubber wall which is directed diagonally to the longitudinal axis of the body 13. A separation wall 17 situated on the rear of the support 16 further holds fast the high pressure pipe 15 in its place in the middle of the body 13. From there the pipe extends out axially into the chamber 18 which is formed on the rear extremity in the body 13 and in which measurement apparatus 19, 20 21 are disposed. This chamber 18 connects to the drilling pipe 4. The flexible high pressure pipe 15 is as a result supported in the front part of the body 13, in front by intervention of the spraying device 10 by the support 14 and further to the back, by the support 16. Between these two supports 14 and 16 the high pressure pipe 15 is surrounded by four inflatable containers 22 which extend in the longitudinal direction of the body 13, between the pipe 15 and the inner side of the body 13. Two compressed air pipes connect onto the extremity situated behind of each container 22, namely a supply pipe 23 and a drainage pipe 24. In each of these pipes 23 and 24 a solenoid valve 25 is mounted which can be controlled from above the ground. The pipes 23 and 24 of all the containers 22 come together in the body 13, extend into the wall of the chamber 18 and further extend through the drilling pipe 14 out to above the ground where the supply pipes 23 connect to a source of compressed air. These pipes 23 and 24 can even just extend out through the pipe 4 or can extend through a second flexible pipe which extends coaxially in the drilling pipe 4. The electric wires for the operation of the solenoid valves 25, which wires are not represented in the figures for the sake of simplicity, follow the same route as the pipes 23 and 24. At the location of the drilling pipe 4 these electric wires can also extend into the wall of the drilling pipe 4 or into the coaxial pipe situated therein. When the solenoid valves 25 in the supply pipes 23 are closed and the solenoid valves 25 in the drainage pipes 24 are open the containers 22 are in unexpanded state as represented in the figure 2 and 3. The containers 22 exert no pressure on the part of the high pressure pipe 15 that is situated between the supports 14 and 16 or all four exert the same small pressure, all of which such that the high pressure pipe 15 extends axially. The spraying device 10 is therefore also directed axially and the drilling mole 3 will move in the ground a straight line according to its axis direction when fluid under high pressure is pumped through the pressure pipe 15 and the spraying device 10. When the solenoid valve 25 in the supply pipe 23 of one of the inflatable containers 22 is opened and at the same time the solenoid valve 25 in the drainage pipe 24 of this container is closed, compressed air will enter into the container and this container will expand and therefore push away the high pressure pipe 15 from the inner side of the body 15. In figure 5 the container 22 situated above is represented in expanded state. Because the valve in the drainage pipe 24 situated opposite container 22 is still open and the valve 25 in the supply pipe 23 is still shut, this container 22 will be pressed flat. All this gives the result that the part of the high pressure pipe situated between the supports 14 and 16 is pushed away sideways and therefore becomes bent as appears from figure 4. Because this high pressure pipe is relatively stiff the front extremity of the high pressure pipe 15 that is situated in front of the containers 22 will also change direction and be directed in the opposite sense to the bending of the high pressure pipe 15 caused by the inflated container 22. This deviation in direction of the front extremity of the high pressure pipe 15 is possible because the front support 14 is elastically transformable. Through this change of direction of the front extremity of the high pressure pipe 15 the direction of the spraying device 10 mounted on the extremity also changes so that the spraying direction also changes and will deviate from the axial direction of the drilling mole. This drilling mole 3 will now move in the ground in the spraying direction in other words deviates from its original direction. It is clear that two or even three containers 22 can be inflated simultaneously which can be controlled from above the ground by operating the appropriate valves 25. In any case through the inflation of one or several containers 22 depending on the choice of these containers 22 the direction of the bending out of the high pressure pipe 15 and as a result also the spraying direction of the spraying device 10 can be accurately adjusted. In order to steer the drilling mole 3 accurately it is not sufficient to be able to adjust accurately the direction of the spraying device 10 in relation to the axis of the drilling mole 3, the position of the drilling mole 3 around its longitudinal axis and the position in the ground must also be known accurately. Therefore, as already mentioned, three measuring instruments are built into the chamber 18, namely an clinometer 19, a torsion meter 20 and a compass 21. The clinometer 19 and the torsion meter 20 of which the operation is based on the capacitance theory, whereby the clinometer 19 is arranged parallel to a vertical symmetric surface of the drilling mole 3 in its neutral position and therefore measures the incline of the axis of the drilling mole 3, and the torsion meter 20 is arranged diagonally to the longitudinal axis of the drilling mole 3 and measures the incline of this plane of symmetry in relation to its vertical starting position. Clinometers of this type are placed on the market by Sperry Corporation and are among others described in the article "Capacitance-based angular measurement" by Tom Donahoe published in the November 1985 issue of "Sensor Magazine". In principle such a clinometer consists of a condenser plate which is divided into two parts and contained between two halves of zinc which form earthing plates. The space between the latter plates is half filled with a dielectric liquid and for the rest with an inert gas. Depending on the incline one half of the condenser plate is immersed to a lesser or greater degree in the liquid which gives a change in its capacitance. The compass 21 can be a so-called "fluxgate" compass. Such compasses are on the market and in principle contain a toroidal coil through which an alternating current is sent in order to sense the magnetic field of the earth. The unit is built into a sealed ring of plastic in which this unit flows on a liquid in order more or less to absorb the swing and other movements of the drilling mole 3. The coil is directed horizontally and with rotations it detects very accurately the changes in the magnetic lines of force. These changes are electronically amplified and shown on a screen that is disposed above the ground and is connected to the compass 21 by means of wires not shown in the figures. The compass 21 can also be a stationary compass that consists of three very sensitive magnet sensors which correctly indicate changes in direction according to the azimuth plane, by vector analysis in relation to the drilling plane and by their 120 degree rotation in relation to the axis. The three measuring instruments 19, 20 and 21 are in the chamber 8 still surrounded by a housing 26 of nonmagnetic metal. The construction of the above described drilling mole 3 is relatively simple, but it can be accurately steered and positioned. The present invention is in no way restricted to the embodiment described and shown, but such drilling mole can be implemented in different forms and dimensions without departing from the scope of the present invention. In particular the containers need not necessarily be inflated with compressed air. They can also be pumped up with liquid under pressure. The drainage pipes of the containers can be partly common and also the supply pipes can be partly common. The valves on these pipes need not necessarily be of the known type. They can for that matter also be mounted above the ground on the pipes instead of in the drilling mole, in which case the pipes must then be separate. The spraying device is also not necessarily a hydraulic spraying device. It can also be a pneumatic spraying device in which case no liquid under pressure but then air under pressure is pumped through the high pressure pipes.

Claims: Steerable drilling mole (3) which includes a round, hollow body (13), a spraying device (10) situated at one end of this body (13), a pipe (15) for drilling liquid under pressure, which connects to the spraying device (10), which is supported in the body (13) and which is flexible at least in the body (13), and at least one moving device (22) situated between the inner side of the body (13) and the pipe (15), characterised in that the pipe (15) is supported centrally in the body (13), adjacent to the spraying device (10), respectively at a distance therefrom, by supports (14 and 16) and is flexible in such a way that, when the part between the supports (14 and 16) bends in one direction, the end of said pipe (15) connecting to the spraying device (10) deviates in the opposite direction, and in that it includes at least three moving devices (22) which are arranged between the inner wall of the body (13) and the part of the high pressure pipe (15) between the supports (14 and 16), spread over the periphery of the high pressure pipe (15), for bending the pipe (15) in different directions. Steerable drilling mole (3) according to claim 1, characterised in that each of said moving devices (22) includes an expandable container (22) and means (23,24,25) for filling this container (22) separately with fluid under pressure so that it expands. Steerable drilling mole (3) according to claim 2, characterised in that it includes four expandable containers (22) which are located in the body (13) along the pipe (15) and between the supports (14 and 16), while means are provided for filling one to three containers (22) so that they expand, while the remaining container or containers can be compressed. Steerable drilling mole (3) according to either one of claims 1 to 3, characterised in that the supports (14 and 16) are elastically deformable. Steerable drilling mole (3) according to either one of claims 1 to 4, characterised in that the extremity of the body (13) adjacent to the spraying device (10) is sealed around this spraying device (10) by an elastic seal (14). Steerable drilling mole (3) according to either one of claims 1 to 5, characterised in that one of the supports (14) of the flexible pipe (15) is formed by a support for the spraying device (10). Steerable drilling mole (3) according to claims 5 and 6, characterised in that the elastic seal (14) forms one of the supports. Steerable drilling mole (3) according to either one of claims 1 to 7, characterised in that in the body (13), a clinometer (19), a torsion meter (20) and a compas (21) are mounted. Steerable drilling mole (3) according to claim 8, characterised in that at least one of the meters formed by the clinometer (19) and the torsion meter (20) is formed by a clinometer of the capacitive type. Steerable drilling mole (3) according to claim 8, characterised in that the compass (21) is a "fluxgate" compass.

Inventors: SMET MARC JOZEF MARIA, SMET, MARC JOZEF MARIA
Applicants: SMET MARC JOZEF MARIA, SMET, MARC JOZEF MARIA
Application year: 1990
Main classification: E21B7
IPC codes: E21B7