Patent application title: DRILL HEAD
Volker Boike (Lennestadt, DE)
Tracto-Technik GmbH & Co. KG
IPC8 Class: AE21B4702FI
Class name: Boring or penetrating the earth with signaling, indicating, testing or measuring tool position direction or inclination measuring or indicating within the bore
Publication date: 2012-01-12
Patent application number: 20120006597
A drill head, particularly for a horizontal drilling device, includes a
housing and a radar unit disposed within the housing. The radar unit
generates electromagnetic waves that exit the housing. The housing of the
drill head is made of a dielectric material at least in the region where
the electromagnetic waves exit the housing.
8. A drill head, comprising: a housing; and a radar unit arranged within the housing and constructed to produce electromagnetic waves which issue out from the housing, wherein the housing is made of a dielectric material at least in a region in which the electromagnetic waves issue out therefrom.
9. The drill head of claim 8 for application in a horizontal drilling device,
10. The drill head of claim 8, wherein a remainder of the housing is made of a metallic material.
11. The drill head of claim 10, wherein the metallic material is steel.
12. The drill head of claim 8, wherein the region of dielectric material is located in an area of an end face of the drill head.
13. The drill head of claim 8, wherein the dielectric material is a ceramic material.
14. The drill head of claim 8, wherein the ceramic material includes an oxide ceramics.
15. The drill head of claim 8, further comprising a plate of dielectric material connected to the housing for covering an opening in the region of the housing.
16. The drill head of claim 15, wherein the plate is constructed for detachable connection with the housing.
17. The drill head of claim 15, wherein the plate is arranged in a depression of the housing so that an outer surface of the plate is flush or recessed in relation with a surface of the housing.
 The invention relates to a drill head, and in particular to a drill
head for a horizontal drilling device.
 Obstacles in front of the drill head of the drilling device pose a problem in the horizontal drilling technique. Such obstacles may for example involve boulders of hard rock that oftentimes cannot be crushed by the used drilling devices. Furthermore, water, gas, telephone, or power lines can be located in regions near the earth's surface and may not be destroyed during drilling.
 This problem led to the development of steerable horizontal drilling devices. Such drilling devices, designated HDD (Horizontal Directional Drilling), render it possible to navigate around obstacles. It is further known to sort obstacles by means of georadar survey in order to enable to circumnavigate obstacles in view of the location determination.
 U.S. Pat. No. 7,143,844 B2 discloses a horizontal drilling device with a radar unit which is integrated in a sensor housing of the drill head. Obstacles in the earth are normally detected reliably by the radar unit in that electromagnetic waves radiating from the radar unit are reflected from electrically conductive parts of the obstacles and received again by the radar unit. By analyzing the received electromagnetic waves, it is possible i.a. to determine the position, i.e. the direction of the obstacle in relation to the drill head, and the distance thereto, and to use it for a course correction of the drilling device.
 The integration of a radar unit in a horizontal drilling device represents however a major problem. Since the radar unit normally is used to monitor the region in front of the drill head, it is sensible to arrange the radar unit in the drill head in order to preclude the horizontal drilling device itself from interfering with the electromagnetic waves.
 In a horizontal drilling device, the drill head represents however a component that is subject to most intense stress because it transmits to the earth the static and dynamic (when a percussion device is involved) drilling forces, generated by a drive unit of the horizontal drilling device. As a consequence of the high stress to which the drill head is subject during drilling operation, the drill head is virtually exclusively made of high-alloy steel because this material has the required properties as far as hardness, strength, wear-resistance, and ductility are concerned and is also inexpensive.
 Steel constitutes however an electrically conductive material so that electromagnetic waves which radiate from the radar unit are reflected. Integration of a radar unit in a drill head of a horizontal drilling device poses a great challenge because the radar unit should be integrated into the housing of the drill head in order to protect it, but the use of steel or also a different electrically conductive, in particular metallic material for the housing prevents the electromagnetic waves from radiating through the housing wall as a consequence of a reflection on the inner housing side.
 Even though U.S. Pat. No. 7,143,844 B2 mentions the integration of a radar unit into the housing of a drill head of a horizontal drilling device, there is no disclosure that allows solution to the afore-described problem.
 Starting from this prior art, the invention is based on the object to provide an advantageous possibility to integrate a radar unit in a drill head.
 This object is solved by a drill head according to patent claim 1. Advantageous embodiments are the subject matter of the dependent patent claims.
 The essence of the invention resides in the manufacture of at least the one region of the housing of a drill head according to the invention in which the electromagnetic waves radiating from a radar unit that is integrated in the drill head emerge from the housing, from a dielectric, i.e. electrically non-conductive, material. Such a material does not reflect the electromagnetic waves so as to enable a nearly uninhibited emergence from the drill head.
 A drill head according to the invention, provided in particular for a horizontal drilling device, thus includes at least a housing as well as a radar unit arranged within the housing to produce electromagnetic waves that are capable of issuing out of the housing, wherein the housing is made at least in part of dielectric material at least in the region in which the electromagnetic waves exit therefrom.
 A basic construction of a radar unit and in particular of a georadar unit designed for application in a drilling device is sufficiently known in the prior art, whereby for sake of completeness it should be noted that such a radar unit includes at least a transmitter unit for sending out electromagnetic waves, a receiver unit for receiving electromagnetic waves, in particular the electromagnetic waves previously transmitted and reflected from an object. Furthermore, the radar unit can include a transmission device for transmitting signals of the receiver unit to an evaluation unit, wherein the evaluation unit may be arranged within the drilling device as well as also outside thereof and in particular in a control device positioned at ground surface. The evaluation unit may further be connected to a display unit to indicate information about obstacles situated in the earth and detected by the radar unit, in particular about distance, location (i.e. direction in relation to the drilling device), size and shape. The evaluation unit may further be connected with a control unit which is able to automatically execute a course correction for the drill head of the drilling device to prevent a collision with the detected obstacle.
 The configuration of a drill head according to the invention enables further the manufacture of the housing of the drill head from a material especially suitable for this, in particular steel, and the manufacture of only a defined region, preferably of a size large enough to allow electromagnetic waves of the radar unit to unimpededly issue out of the housing of the drill head, from a material which optionally may satisfy to a lesser degree the demands required from a material for the housing of a drill head, but has dielectric (and therefore does not reflect electromagnetic waves of a radar unit) characteristics.
 According to a preferred embodiment of the present invention, it is provided to make a region of the end face of the drill head of dielectric material. This configuration permits a targeted transmission of the electromagnetic waves of the radar unit in the drilling device because the region of the earth should normally be monitored for obstacles in drilling direction, i.e. in the area in front of the drill head.
 According to a preferred embodiment of the present invention, the dielectric material is ceramics, in particular oxide ceramics because these materials are characterized by a very high wear resistance that is advantageous for a material for manufacturing the housing of a drill head, and have of course the required dielectric property.
 Advantageously, the integration into the housing of the drill head may include the manufacture thereof from a suitable material, e.g. steel, and the provision of an opening in the region which should be made of a dielectric material, with the opening being covered subsequently by a plate of such a dielectric material.
 According to an especially preferred embodiment, it can be provided to detachably secure the plate on the remainder of the housing of the drill head so that replacement, for example for repair purposes, is rendered possible in a simple manner. This can be of advantage because even though ceramic materials for example exhibit a very high wear resistance, they still have a relative low ductility so that it may happen that the plate cracks in the event of an impact. Of course, it may also be provided to mount the plate on the remainder of the housing in a non-detachable manner.
 The plate may, for example, be connected with the remainder of the housing of the drill head through bonding, whereby the connection may be detachable or non-detachable depending on the selection of the adhesive. A bonded joint that is detachable can be loosened by heating the adhesive for example.
 It may further be suitable to arrange the plate of dielectric material in a depression of the housing so that the outer surface thereof is flush or recessed in relation to the surface of the remainder of the housing. As a result, the plate of dielectric material can be substantially protected by the remainder of the housing of the drill head.
 Exemplary embodiments of the invention will now be described in greater detail with reference to the drawings.
 It is shown in the drawings:
 FIG. 1 a horizontal drilling device with a drill head according to the invention,
 FIG. 2 a first embodiment of a drill head according to the invention, and
 FIG. 3 a second embodiment of a drill head according to the invention.
 FIG. 1 shows by way of a simplified illustration the application of a steerable horizontal drilling device which is also called a HDD drilling device. HDD is short for "Horizontal Directional Drilling". The horizontal drilling device includes a drill head 1 which involves a drill head 1 according to the invention. The drill head 1 is mounted to the leading end of a drill rod 2, with the drill rod 2 comprised of a plurality of rod sections 3 that are connected to one another via screw threads. The trailing end of the drill rod 2 is connected to a drive unit 4 by which forces in longitudinal direction of the drill rod 2 as well as a torque can be transmitted to the drill rod. By means of the drive unit 4, the drill rod 2 including the attached drill head 1 can be driven in thrust direction and pull direction as well as rotated.
 The drill head 1 involved is a so-called steerable drill head having an end face 5 which is slanted at least in some areas in relation to the own longitudinal axis and thus in relation to the drilling direction. The slanted surface causes a deflective force that is directed to the side during propulsion and results in curved drilling pattern when the drill head 1 is driven statically, i.e. does not rotate. A drilling in a straight line is possible with such a controlled drill head by operating the drill head in propulsion direction as well as rotating it so that the deflective forces compensate over a complete revolution.
 In the horizontal drilling device of FIG. 1, the drive unit 4 is placed stationary on the earth's surface. The drilling operation thus starts also from the earth's surface, whereby initially it is drilled at a slant into the ground and after reaching the desired depth, the course of drilling is changed until reaching the horizontal, and then drilling continues in a substantially horizontal manner.
 Deviations from the straight-lined drilling course may become necessary when obstacles (not shown) are encountered in the earth that cannot be drilled through (e.g. bedrock) or must not be drilled through (e.g. power, gas, or water lines). To detect such obstacles in the ground, the drill head is provided with a radar unit 6 which radiates electromagnetic waves and receives these waves after the latter have been reflected from an electrically conductive object, so as to be able to calculate distance, shape, size, and location of the object.
 FIGS. 2 and 3 show two embodiments of a drill head 1 according to the invention with integrated radar unit 6 and useable in a horizontal drilling device as shown in FIG. 1.
 The drill heads 1 of FIGS. 2 and 3 have a cylindrical shaft 7 which is formed on its trailing end in drilling direction with a locking system by which it can be secured to the leading end of the drill rod 2. Provided on the leading end of the drill head 1 is a drill head front 8 having a shape configured for maximum propulsion. For this purpose, the drill head front includes various hard metal elements 9 which provide for a good cutting action in the earth and moreover are extremely wear-resistant. The afore-mentioned slanted surface 10 produces during propulsion in the earth a laterally directed deflection that allows steerability of the horizontal drilling device. Integrated in the slanted surface 10 are in addition two nozzles 11 for bentonite flushing by which bentonite, conducted to the drill head 1 via an external feed (not shown) and via the interior of the hollow drill rod 2, exits under high pressure from the drill head and improves the drilling propulsion by the hydraulic cutting action on one hand and a softening of the earth in front of the drill head 1 on the other hand.
 The radar unit 6 is arranged in the cylindrical shaft 7 of the drill head 1 and includes a transmitter unit 21 for emitting electromagnetic waves, a receiver unit 12 for receiving the reflected electromagnetic waves, as well as a transmission device 13 for transmission of signals from the receiver unit 12 to an evaluation unit 14 which is connected with the drive unit 4. The evaluation unit 14 includes a display device 15 which can indicate information about distance, location, size, and shape of obstacles located in the earth. The evaluation unit 14 is further connected with a control unit 16 which enables navigation around the obstacles by respectively operating the drive unit 4.
 The radar unit 6 sends out the electromagnetic waves in a defined direction, whereby the region of the housing of the drill head 1 from which region the electromagnetic waves emerge, is covered by a plate 17 which is made of oxide ceramics, a dielectric material. In contrast thereto, the remainder of the housing of the drill head 1 is made of steel and thus of electrically conductive material. The plate 17 of oxide ceramics ensures a sufficient passage of the electromagnetic waves through the housing of the drill head 1 so as to enable a monitoring of the earth in front of and/or to the side of the drill head 1. As can be best seen in FIGS. 2 and 3, the plate 17 is arranged in a depression of the housing so as to be flush-mounted with the housing.
 An essential difference between the drill heads 1 of FIGS. 2 and 3 is the location of the plate 17 of oxide ceramics. In the configuration of FIG. 2, the plate is arranged within the slanted surface 10 and thus directly in drilling direction, whereas in the configuration of FIG. 3 the plate is located in a section of the cylindrical casing of the shaft 7. The arrangement illustrated in FIG. 2 has the advantage that the electromagnetic waves are able to emerge from the housing of the drill head 1 directly in drilling direction. A drawback is however that the slanted surface 10 belongs to those regions of a drill head that are exposed to greatest stress so that the risk is greater that the plate 17 which is made of oxide ceramics and thus has a low ductility is destroyed. The arrangement selected in the configuration of FIG. 3 better protects the plate because it is shielded by the drill head front that is greater in diameter.
 The drill heads 1 illustrated in FIGS. 2 and 3 are configured essentially in three parts, comprised of a shaft end 18 (not shown in FIG. 2) for attachment to the leading end of the drill rod 2, the drill head front 8 whose shape is designed for optimum drilling propulsion, as well as a radar housing 19 arranged between these components of the drill head and forming part of the shaft 7 of the drill head 1. The radar unit 6, and also the plate 17 of oxide ceramics according to the drill head 1 of FIG. 3, is arranged in the radar housing 19. The connection between the three parts of the drill head 1 is implemented by a quick-acting closure system with locking elements 20. The three-part configuration of the drill head 1 allows optional installation of the radar unit 6 so that the drill head front 8 can also be directly connected with the shaft end 18. Depending on the earth in which drilling takes place, there may be situation in which radar monitoring may not be required and since the radar unit is also fairly expensive, the optional installation of the radar unit 6 serves only to improve effectiveness because in some cases fewer radar units may be purchased than drill heads.
Patent applications by Volker Boike, Lennestadt DE
Patent applications by Tracto-Technik GmbH & Co. KG
Patent applications in class Tool position direction or inclination measuring or indicating within the bore
Patent applications in all subclasses Tool position direction or inclination measuring or indicating within the bore