EP2775090A2 - Drill bit - Google Patents

Abstract

The drill bit (1) has a smaller radial extension portion provided with a first cutting edge (3) extending over entire drill bit diameter. The first cutting edge is arranged along an outer circumference of an end surface (2). A second cutting edge (5) protruding from the first cutting edge is located in a region of the end surface and is tilted in the region of a drill bit shaft (4) such that an acute angle is formed between the first cutting edge and a rotational axis (6).

Description

The present invention relates to a drill bit for a device for drilling holes in soft soil or rock material having a plurality of blades extending at least over one end face of the drill bit, which blades have at least two mutually different "radial" extensions as well as two mutually different "axial" extensions are formed in the direction of a rotation axis of the drill bit, and at least one opening for discharging flushing fluid.

The formation of holes in soft or mild soil or rock material is usually achieved with a rotating or a rotating and beating drilling method, in which by a rotary motion or by a simultaneous rotational movement and impact movement of the drill bit by means of the formed thereon or fixed cutting Borehole is formed. Drill bits for the formation of holes in soft soil or rock material are for this purpose equipped with cutting strips, which extend at least over a diameter of a central part of the drill bit and which are often formed a plurality of intersecting or an angle with each other enclosing cutting. The cutting bars or cutting edges can continue to project beyond the end face of the drill bit and at least partially have a non-planar contour of the cutting bar when viewed with respect to the bore hole interior.

For example, from the EP 1 045 112 B1 A1 a rock drill or a drill bit for such a rock drill has become known, in which the cutting bar or the cutting bars have a sloping contour, in particular have such a sloping contour that the cutting strips are formed substantially in the shape of a roof whose ridge furthest designed directed to the borehole interior.

Another form of drill bit for an anchor intended for the formation of holes in soft or loamy rocks is the DE 197 12 181 A1 to see which drill bit has substantially two mutually normal cutting edges, one of which rises above the end face of the drill bit and the other is formed substantially in the plane of the end face of the drill bit, both Cutting symmetrical to each other are formed and project beyond the circumference of the drill bit.

A disadvantage of such known drill bits on the one hand, that due to the symmetrically formed over the circumference of the drill bit cutting strips, especially those cutting strips, which further protrude to the borehole interior, are rapidly worn and other cutting strips, which are located further away from the borehole interior, to the formation of the Borehole have only a minor or low proportion, so that the cutting strips of one and the same drill bit usually have different lengths of life.

The present invention now aims to develop such drill bits to the effect that on the one hand with such a drill bit rapid drilling progress can be achieved and also the most uniform wear of the cutting strips can be provided and thereby the service life of the drill bit compared to conventional drill bits are significantly increased can.

To solve this problem, the drill bit according to the invention is essentially characterized in that a first radial extent having a first cutting edge extends over the entire Bohrkronendurchmesser that on the lower radial extent having first cutting edge two over an outer periphery of the end face of the drill bit further than first cutting edge projecting second cutting are provided and that the second cutting edges in the region of the end face of the drill bit and / or inclined in the region of the drill bit shank, with the first cutting edge and / or with the axis of rotation of the drill bit formed an acute angle. In that the drill bit has two mutually different shapes of blades, one that substantially accomplishes the drilling progress toward the well bore and provides a smaller diameter of bore and at least one second blade that extends beyond the outer periphery of the face of the drill bit than the drill bit projecting first cutting edge is provided, which is thus provided essentially for the formation of the desired diameter of the borehole, it is ensured that on the one hand a sufficiently rapid rate of penetration is achieved and on the other hand a substantially uniform wear of the cutting is ensured. Furthermore, since the second cutting edges in the area of the end face and / or of the drill bit shaft are inclined with the axis of rotation of the drill bit at an acute angle, the drill bit can be screwed into the ground in the manner of a screw. or rock material are driven in and thus not only a rapid rate of penetration is provided, but it is also due to the geometric design, in particular the inclination of the second cutting in the region of the face and / or the Bohrkronenschafts a rapid and complete removal of the cuttings from the Ensured area of the drill bit. Finally, such a drill bit can not only be used for a rotary drilling, but it is also used for a rotating and beating drilling due to their special geometry.

According to one embodiment of the invention, the inclination of the second cutting is in this case designed so that upon rotation of the drill bit, the second cutting first arrive with its adjacent to the first cutting edge areas in engagement with the rock to be dissolved. During a rotation of the drill bit, the second cutting edges first come into engagement with the stone to be loosened with their regions adjacent to the first cutting edge, the stone to be loosened is loosened in the manner of a helical drill first and then safely and reliably from the drill bit region conveyed away, so that laying of the cutting or slowing down the progress of drilling due to excessive amounts of cuttings inside the well is certainly lagged. Preferably, in this case, as in a further development of the invention, the second cutting edges with the axis of rotation of the drill bit form an angle of 2 ° to 15 °, in particular 5 ° to 10 °. By such a design on the one hand ensures that the cutting edge contribute evenly to the release work and on the other hand causes already by the geometry of the cutting a removal of the cuttings toward a borehole exterior.

By, as this corresponds to a development of the invention, the drill bit is formed so that a cutting surface of the blades is inclined at an angle to the horizontal, in particular by an angle of 1 to 10 ° to the horizontal and in particular so further developed that one in the direction of rotation the drill bit leading edge is located higher than a trailing edge in the direction of rotation of the drill bit, the leading in the direction of rotation of the drill bit cutting edge is first brought into use with the rock to be dissolved, so that a rapid and safe cutting of the cutting edges of the drill bit in the rock to be dissolved is ensured. In particular, by tilting the cutters at an angle to the horizontal of 1 ° to 10 °, it is further ensured that not only the leading edge comes into engagement with the rock to be loosened, but that at a deep cutting the blades also with their entire cutting surface can be used and thus a particularly rapid Ensure drilling progress. Furthermore, it is ensured with such a design of a cutting edge that the blades resharpen itself and thus a particularly long service life of the drill bit is guaranteed.

According to one embodiment of the invention, the drill bit is formed so that the first cutting edge in the axial direction of the drill bit is substantially sawtooth formed with two outer periphery of the drill bit cross over the axis of rotation of the drill bit extending vertical areas. Characterized in that the first cutting edge in the axial direction of the drill bit substantially sawtooth formed with two outer periphery of the drill bit, extending along the axis of rotation of the drill bit, vertical areas, on the one hand a first diameter of a borehole formed by the first cutting and on the other hand ensured in that, due to the sawtooth-shaped contour of this first cutting edge, a region of the sawtooth-shaped profile projecting farthest to the bore-hole first engages and performs a first release work, after which, after penetration of this first region, the further regions of the sawtooth-shaped profile engage successively and the first diameter of the borehole without requiring excessive force and without the first blade being excessively worn. In particular, the force can be reduced by the fact that the most projecting portions of the sawtooth-shaped profile form a first release work, whereupon adjacent portions of the first incision are more easily solvable, since they have already experienced some relaxation by engaging the most projecting portion.

By, as in a further development of the invention, the sawtooth-shaped portion of the first cutting edge has flats at its furthest projecting into the well interior, a substantially annular profile is degraded farthest in a borehole interior, whereby not only the entire release work is facilitated but also the removal of the cuttings is facilitated.

By, as corresponds to a development of the invention, the drill bit is formed so that the trailing edges in the direction of rotation of the second cutting at its inflection point between the end face of the drill bit and the drill bit shank on a common axis passing through a drill bit center and that articulation of the second Cutting the first cutting edge let the center of the drill bit, it is ensured that on the one hand by the second cutting, in particular the entire diameter of a borehole to be achieved is swept over and the second cutting edges contribute sufficiently to the dissolving work and, on the other hand, ensures that the special cross section of the drill bit reliably and reliably removes cuttings. Furthermore succeeds with such a training succeeds a safe and reliable release of the rock throughout the drill bit cross-section and also a rapid rate of penetration is achieved with the least possible wear of the cutting.

In order to reduce the wear of the drill bit still further and to increase the service life, the invention is preferably developed such that the first and the second cutting edges of the drill bit are hardened on their areas reaching into the rock to be loosened and / or with one Hard material or hard metal cladding are provided.

For a further increase in the service life of the drill bit, and in particular to ensure the largest possible and particularly uniform borehole diameter, the invention is preferably developed so that the areas of the second cutting edges inclined in the region of the drill bit shaft are substantially wedge-shaped from a borehole interior to a borehole exterior are formed. By making the sloped portion of the second blades substantially wedge-shaped from a wellbore to a wellbore exterior, it is ensured that in the region of the second cutters where they are performing the bulk solving work, the second cutters have a larger diameter and thus increased strength or have service life.

For improved removal of the drill cuttings in the direction of a borehole exterior, the contour of the second cutting edges is substantially formed so that the leading edge of the substantially wedge-shaped region of the second cutting edges is curved. Such a curved contour of at least parts of the second cutting edges ensures a uniform removal of the drill cuttings along the area of the cutting edges during drilling, and thus reliably prevents laying or excessive accumulation of drill cuttings in the area of the end face of the drill bit.

In particular, a tearing or canceling over a diameter of the drill bit and in particular over the diameter of the Bohrkronenschafts protruding

In order to withstand certain areas of the first and second cutting edges, the invention is preferably developed in such a way that reinforcing ribs, in particular reinforcing ribs running essentially helically around the drill bit shank, are formed between the regions of the first and second cutting edges projecting beyond the drill bit shank.

Furthermore, by providing reinforcing ribs, the projecting portion of the first and second blades, and particularly those of the second blades, can be made relatively large relative to the diameter of the bit shank and thus the achievable bore diameter can be significantly increased over that of conventional bit shells.

In order to further accelerate the removal of the cuttings and in particular to complete, the drill bit according to the invention is further developed such that in addition at least two offset by about 90 ° to the Spülkanälen, with a horizontal between 10 and 45 ° enclosing angle in the direction are provided to a borehole outer inclined flushing channels. In particular, by forming backward flushing passages in the bit shank for dispensing flushing fluid within the drill bit shank, drill cuttings located in the area of the bit shank between the projecting portions of the blades and the bit shank are safely removed to a drill bit outer and cuttings of drill cuttings undermined prevents the drill bit. In the case of particularly unstable conditions in a borehole, rinsing with a cement suspension, in particular a strongly diluted cement suspension, can be carried out with which, in addition to rinsing the borehole, the wall thereof can be at least partially solidified.

By, as this corresponds to a development of the invention, the flushing channel is an angle with the horizontal between 2 ° and 10 ° includes, the flushing fluid is applied especially in the direction of a bore hole inside and thus the area of the end face of the drill bit or to a Rinsed outside of the wellbore outer surface of the drill bit shank, whereupon cuttings along the helical shape of the projecting over the drill bit shank portions of the first and in particular the second cutting to a borehole exterior is washed away.

By finally, as corresponds to a development of the invention, the drill bit is further developed so that two flushing channels are provided and that the scavenging channels on the reinforcing ribs and adjacent the leading cutting edge of the inclined portion of the second cut open on the one hand, a swirling of the flushing fluid in the Ensures face of the drill bit and thus transported away any cuttings from this area and also ensures that the cuttings continue to be transported along the inclined portions of the second cutting towards a borehole exterior.

By, as this corresponds to a development of the invention, the (the) flushing channel (channels) is provided at their lying on an outer side of the drill bit mouths in particular releasably definable flush valves (are), it is possible, the amount or the exit velocity of the flushing fluid To control or, which is achieved, for example, in a sharper jet of flushing fluid even more complete and faster removal of the cuttings from the field of the drill bit and the entire borehole, but also, for example, in cases of rocks, in which a drilling and a simultaneous flushing with water could be unfavorable, by closing the flush valve, the escape of flushing fluid can be completely obstructed.

Further, by further developing the invention such that the valves are substantially cap-shaped flow-through valves, the cap-shaped area of which is carbide-cemented or carbide-plated, eliminating the valves during operation and thereby wearing them down, thereby either the outlet is much too large or clogged by abraded metal chips or the like. So that a targeted discharge of flushing fluid does not seem possible. In addition, by the cap-shaped flow control valves are formed of hard metal, these valves can perform dissolution work especially in sharp-edged protruding rock residues. For this purpose, for example, the cap-shaped surfaces of the carbide valves could be formed contoured. In order to increase the service life of the valves further, in this case the valves can be formed in their entirety of hard metal.

• Fig. 1 eine Seitenansicht einer Bohrkrone gemäß der Erfindung,
• Fig. 2 eine Draufsicht auf die Bohrkrone von Fig. 1,
• Fig. 3 einen Schnitt durch eine Bohrkrone gemäß der Erfindung entlang der Linie A-A von Fig. 2,
• Fig. 4 eine perspektivische Ansicht einer Bohrkrone gemäß der Erfindung von der Seite,
• Fig. 5 eine perspektivische Ansicht der Bohrkrone von Fig. 4 in einer um 90° um eine Drehachse der Bohrkrone gedrehten Position,
• Fig. 6 einen Längsschnitt durch eine Bohrkrone gemäß der Erfindung entsprechend der
• Fig. 4, in welchem in einem im Schnitt dargestellten Spülkanal ein Gewindeanschluss für ein Ventil gezeichnet ist und im anderen Spülkanal schematisch ein Ventil aufgeschraubt dargestellt ist, und
• Fig. 7 eine perspektivische Ansicht einer Variante eines Ventils mit einem kappenförmigen aus Hartmetall ausgebildeten Bereich.

The invention will be explained in more detail with reference to embodiments shown in the drawing. In these show:

• Fig. 1 a side view of a drill bit according to the invention,
• Fig. 2 a top view of the drill bit of Fig. 1 .
• Fig. 3 a section through a drill bit according to the invention along the line AA of Fig. 2 .
• Fig. 4 a perspective view of a drill bit according to the invention from the side,
• Fig. 5 a perspective view of the drill bit of Fig. 4 in a position rotated by 90 ° about an axis of rotation of the drill bit,
• Fig. 6 a longitudinal section through a drill bit according to the invention according to the
• Fig. 4 in which a threaded connection for a valve is shown in a scavenging duct, which is shown in section, and a valve is shown screwed on schematically in the other scavenging duct, and
• Fig. 7 a perspective view of a variant of a valve with a cap-shaped formed from hard metal area.

In detail is in Fig. 1 a drill bit 1 is shown, which has at least one extending over the end face 2 first cutting edge 3. The first cutting edge 3 is in this case substantially sawtooth-shaped and extends slightly beyond the outer diameter a of the drill bit 1 or of the drill bit shank 4. At least one second cutting edge 5, which extends on the one hand over the end face 2 of the drill bit 1 and, on the other hand, is pulled down laterally at least partially over the drill bit shank 4, is formed substantially normal to the sawtooth-shaped cutting edge 3. The entire blade 5 is in this case inclined to a rotational axis 6 of the drill bit 1 and closes with this axis of rotation 6 of the drill bit 1 an angle α. Both the cutting edge 3 and the cutting edge 5 had a diameter b, which can be substantially equal for both cutting edges. At an outwardly, ie to a borehole interior and a borehole facing portion of the cutting edges 3 and 5, the cutting edges 3 and 5 are provided with a hard metal plating 7, as shown schematically by the hatched area of the cutting edges 3 and 5. The provided with the hard metal plating 7 surface of the cutting edges 3 and 5 is in this case further inclined to a horizontal inclined so that in the direction of rotation, which is indicated by the arrow 8, the drill bit 1 leading edge 9 at a rotary drilling a drill bit 1 first in Engagement with a rock to be loosened and a trailing in the direction of rotation 8 edge 12 of the cutting edges 3 and 5, the actual release work only comes at a later date, in particular only auxiliary used.

The inclination angle ß of the cutting edges 3, 5 is in this case selected so that the surface of the cutting edges 3 and 5 with the horizontal angle between 1 ° and 10 ° include further wherein the maximum inclination is selected such that the hard metal cladding 7 of the cutting. 3 and 5 extending straight line represents a tangent to the peripheral edge adjacent the end face of the drill bit. However, it also follows that the inclination of the blades can be changed over the length of the blades.

Finally, the cutting edges 3 and 5 are designed such that they protrude in the region of the drill bit shank 4 over its outer diameter a, in particular by a different amount from each other. Between the projecting portions of the cutting edges 3 and 5 are in this case, in order to prevent inadvertent breaking or breaking out of the cutting edges 3 and 5 with certainty, reinforcing ribs 10 are provided. The reinforcing ribs 10 are formed so that they are arranged substantially helically around the drill bit shank 4.

In order to ensure a safe removal of cuttings formed during drilling from a borehole, flushing channels 15 and flushing openings 11 are formed in the bit shaft 4. The flushing channels 15 in this case extend on the one hand along the axis of rotation 6 in the interior of the drill bit 1, as is apparent Fig. 3 can be seen, and by the material of the drill bit substantially normal to the axis of rotation. 6

In Fig. 2 is a plan view of the drill bit 1 of Fig. 1 4, wherein it can be seen that the cutting edge 3 is a cutting edge 3 which extends essentially over the entire diameter a of the drill bit 1, wherein the cutting edge 3 additionally engages over the drill bit shank 4 of the drill bit 1 substantially concurrently with the axis of rotation 6 of the drill bit 1 , Furthermore, in Fig. 2 to see that in the direction of rotation 8 of the drill bit 1 leading edge 9 of the cutting edge 3 when turning the drill bit 1 in the direction of the arrow 8 first comes into engagement with the rock to be dissolved. The second cutting edge 5 is formed in two parts, wherein the cutting edges 5 are each arranged eccentrically from the axis of rotation 6 of the drill bit 1 on the end face 2 of the drill bit 1. The cutting edges 5 are formed so that they are also formed inclined over the end face 2 of the drill bit 1. In the area of the drill bit shank 4, the cutters 5 are in this case designed such that they are inclined by an angle .alpha Fig. 1 is shown, with respect to the axis of rotation 6 of the drill bit 1 are formed inclined by between 2 ° and 15 °, so that upon rotation of the drill bit 1 in the direction of the arrow 8 first one Part of the cutting edge 5 comes into engagement with the rock to be dissolved, which is closest to the cutting edge 3 and last that portion of the cutting edge 5 comes into engagement, which furthest from a bore hole inside, ie farthest from the end face 2 of the drill bit 1 is arranged. At the same time, the cutting edges 3, 5 are designed such that they rest on their area which overlaps the end face 2 of the drill bit and abut against the borehole wall and, in particular, form the definitive and desired borehole cross section or diameter of the borehole. With such a training, all areas of the cutting edges 3, 5 and 5 contribute uniformly to the formation of the borehole and are therefore evenly worn, which increases the overall service life of the drill bit 1.

Instead of a uniform inclination of the blades 3, 5 by the angle α, these, in particular their leading edge 9 may also be curved to be even clearer or more complete of the desired helical shape to follow for an improved removal of cuttings.

Finally, in the presentation of Fig. 2 still recognizable that the end face 2 of the drill bit 1 is substantially formed of 2 semicircular elements 13, which semi-circular elements 13 are offset from each other with respect to the cutting edge 3. Furthermore, in order to avoid accidental breaking off or damaging of the cutters 3 and 5 projecting beyond the drill bit diameter a, reinforcing ribs 10, which are not provided with a hard material cladding 7, are formed in the region of the drill bit shank 4. The hard metal claddings 7 are also in Fig. 2 shown as dark hatched areas 7.

In Fig. 3 , which is a longitudinal section through the drill bit 1 along the line AA of Fig. 2 represents, it is seen that in the interior of the drill bit 1 on the one hand, a thread 14 is provided, for example, insert a drill rod or an adapter, not shown, and set the drill bit 1 on a device for drilling holes, not shown, and on the other hand, that inside the Drill bit 1 is further a flushing channel 15 is guided, which opens into a flushing opening 11 on the outside of the drill bit 1 in the region between the reinforcing ribs 10 and the inclined blades 5. The flushing channel 15 is in this case formed substantially normal to the axis of rotation 6 of the drill bit 1, wherein it usually includes an angle between 2 ° and 10 ° with the horizontal and are directed in the direction of the end face 2 of the drill bit 1. With such a design is in the application of flushing fluid, which in known Can be made of water, air or mixtures thereof, ensures that especially in the area of the end face 2 of the drill bit 1 accumulated cuttings swirled with certainty and along the substantially spiral formation of both the reinforcing ribs and the blades 5 backwards in the direction a borehole exterior is transported away. In this case, the flushing opening 11 preferably has a diameter d which is essentially the same size as the diameter or the thickness of the cutters 3 and 5.

In Fig. 4 , which is a perspective side view of the drill bit of Fig. 1 shows, the reference numerals of Fig. 1 to 3 maintained as much as possible.

In the presentation of Fig. 4 It can be seen that the cutting edge 3 extends substantially over the entire diameter a of the drill bit shank 4 and that over the outer periphery of the drill shank 4 projecting portions 16 of the cutting edge 3 are provided in its upper region with a hard metal cladding and in the area which further from facing away from a bore hole inside, the cutting edge 3 is formed without Hartmaterialplattierung 7. Between the cutting edge 3 and the cutting edge 5, a reinforcing rib 10 is provided which extends substantially below the edge of the end face 2 of the drill bit 1 facing a borehole exterior. The dimensioning of the reinforcing rib 10 or reinforcing ribs 10 is chosen so that it is ensured that in a practical use tearing of the thereby supported or held cutting edge 3 5 is reliably prevented.

The second cutting edges 5 are mounted on the end face 2 of the drill bit 1 in such a way that the substantially sawtooth-shaped cutting edge 3 has its lowest point 17 in the immediate vicinity of an articulation point of the trailing edge 12 of the cutting edge 5 against the cutting edge 3. Furthermore, the cutting edge 5 is formed inclined so that it extends substantially in the manner of one of the rotational movement of the drill bit according to the arrow 8 following spiral to at least a portion of the circumference of the shaft 4. This means that the cutting edges 5 are provided with a "crown" in the direction of the arrow 8.

Needless to say in this context, that in each case the entire cutting edges 3, 5 may be formed of hardened material or hard material, in particular to increase the service life of the drill bit 1 further or this also for a Drilling, especially rotating or rotating and beating drilling in moderately hard rock to apply.

The representation of Fig. 5 is essentially the same as the representation of Fig. 4 , wherein the drill bit was rotated only by 90 ° in the direction of arrow 8. In Fig. 5 Therefore, not only is a reinforcing rib 10 to be seen between the cutting edge 3 and the cutting edges 5, but it can be seen that the reinforcing ribs 10 extend substantially in the manner of a spiral around the circumference of the shaft 4 of the drill bit 1. Finally, the presentation of Fig. 5 it can be seen that this outlet opening 11 opens substantially in the region of the interface between the cutting edge 5 and a reinforcing rib 10, so that the exiting flushing fluid is forcibly guided and in particular the area of the drill bit 1, which to a Drilling hole inside facing, certainly rinsed free of cuttings.

In Fig. 6 is a section through a drill bit 1 according to the invention, in the interior of a thread 14 is provided for connection with, for example, an adapter and which thread 14 is hollow and through which a flushing fluid is passed. The inclined by an angle γ of up to 45 ° in the direction of a borehole outer flushing channels 20 are in this case provided with a schematically indicated thread, in particular an internal thread 18, as the right side of Fig. 6 can be seen. In this internal thread 18 can, as shown schematically on the left side of the Fig. 6 is shown, a releasably fixable flush valve 19 may be used. Similar flushing valves 19 may be used, for example, formed in the flushing channels 15. By providing backward flushing channels 20 and rinsing valves 19 inserted therein, it is possible to flush any rock out of the borehole and also safely carry off any packed rock that has already been packed together.

Furthermore, a further branch channel 23 of the flushing channel 15 is provided, which extends substantially to the center of the drill bit 1, which lies closest to the wells. With this flushing channel 23 cuttings can be removed from the area of the cutting edges 3 and 5.

The exact configuration of the purge valves 19 can be chosen arbitrarily here. Such is the use of valves whose outlet can be throttled as desired, or can also be completely closed, as also covered by the invention, as the use of flush valves, which have an always constant passage cross-section. Also, the pressure with which the flushing fluid is discharged, can be freely selected depending on the given conditions. In the case of very brittle rocks, the spray jet can be chosen so that the flushing fluid is discharged under high pressure, which allows it to perform additional work of dissolution.

The purge valves 19 are preferably designed as substantially cap-shaped flow valves, as for example in Fig. 7 is shown. Such a flush valve 19 in this case has, for example, a cap 20 made of hard material, in which the flushing channel 15 opens. The carbide cap 25 may be either, as shown in FIG Fig. 7 is shown to be completely smooth, or contoured, in particular to be able to perform release work when the pins project sufficiently and, in particular, as may often be the case in soft or mild rock, the borehole wall is irregular or already broken rock under the cutting edges 3, 5 of the drill bit 1 has packed together. The hard metal cap 25 is in this case fixed on a base body 21, for example by plating or welding, wherein the base body 21 has an external thread 22 which can be brought into engagement with, for example, the internal thread 18 in the flushing channel 15. In this way, the flush valves 19 can be exchanged as needed or, for example, a plug can be set, if a flush could be disadvantageous, for example due to the rock type to be degraded. In this connection, reference is made, for example, to the setting of anchors in loam, in which loam, after setting the anchor, a hardening medium can only be introduced when the loam is dry.

It is needless to say that, of course, the purge valves 19 may be arbitrarily formed, in particular further protruding or less far from the surface of the drill bit 1 can be formed projecting, depending on whether it is desired that the purge valves 19 only rinsing or increased participate in the dissolution work in the rock. In particular, when the purge valves also participate in the release work, they are preferably designed so that they protrude at least to the level of the blades 3, in particular the blades 5, in any case project beyond the area 16 of the blades 3 to sufficiently with the rock or to engage with already dissolved, but for example packed together rock. In such a case, it is preferable that the flush valves are made entirely of hard metal so as not to fear unintentional flaking of the plating from the base 21.

If in particular long service lives of the drill bits are desired, in this case also all parts of the drill bit can be made of one and the same hard material, or hardened in a single common step, in particular to avoid interfaces between differently hard materials.

Claims (18)

A drill bit (1) for a device for drilling holes in soft soil or rock material having a plurality of cutting edges extending at least over an end face (2) of the drill bit (1), said cutting edges (3, 5) having both at least two mutually different "radial" extensions and two mutually different "axial" extensions in the direction of an axis of rotation (6) of the drill bit (1) are formed, and at least one opening (11) for discharging flushing fluid, characterized in that a smaller one radial extension extending first cutting edge (3) extends over the entire Bohrkronendurchmesser (a) that on the smaller radial extent having first cutting edge (3) two over an outer periphery of the end face (2) of the drill bit (1) further than the first cutting edge (3) projecting second cutting edges (5) are provided and that the second cutting edges (5) in the region of the end face (2) of the drill bit (1) un D / or in the region of a drill bit shank (4) inclined, with the first cutting edge (3) and / or with the axis of rotation (6) of the drill bit (1) an acute angle (α) are formed enclosing. A drill bit according to claim 1, characterized in that the inclination of the second blades (5) is such that upon rotation of the drill bit (1), the second blades (5) first engage with their portions adjacent to the first blade (3) reach the rock to be dissolved. Drill bit (1) according to claim 1 or 2, characterized in that the second cutting edges (5) with the axis of rotation of the drill bit (1) form an angle (α of 2 ° to 15 °, in particular 5 ° to 10 °. Drill bit (1) according to claim 1, 2 or 3, characterized in that a cutting surface of the cutting edges (5) is inclined by an angle (β) to the horizontal, in particular by an angle (β) of 1 to 10 ° to the horizontal. Drill bit (1) according to claim 4, characterized in that in the direction of rotation (8) of the drill bit (1) leading cutting edge (9) is higher than in the direction of rotation (8) of the drill bit (1) trailing edge (12). Drill bit (1) according to one of claims 1 to 5, characterized in that the first cutting edge (3) in the axial direction of the drill bit (1) is substantially sawtooth-shaped is formed with two the outer periphery of the drill bit (1) cross over the axis of rotation (6) of the drill bit (1) extending vertical areas. Drill bit (1) according to claim 6, characterized in that the sawtooth-shaped region of the first cutting edge (3) has flattenings at its regions projecting furthest into a borehole interior. Drill bit (1) according to one of claims 1 to 7, characterized in that in the direction of rotation (8) trailing edges (12) of the second cutting edges (5) at its inflection point between the end face (2) of the drill bit (1) and the drill bit shank (4) lie on a common axis (AA) passing through a bit center and that articulation areas of the second blades (5) to the first blade (3) leave the bit center free. Drill bit (1) according to one of claims 1 to 8, characterized in that the first and the second cutting edges (3, 5) of the drill bit (1) are hardened in their areas reaching into the rock to be loosened and / or with a Hard material or hard metal cladding (7) are provided. Drill bit (1) according to any one of claims 1 to 9, characterized in that in the region of the drill bit shank (4) inclined areas of the second cutting edges (5) are formed from a well interior to a borehole outer substantially wedge-shaped. Drill bit (1) according to claim 10, characterized in that the leading edge (9) of the substantially wedge-shaped portion of the second cutting edges (5) is curved. Drill bit (1) according to one of claims 1 to 11, characterized in that between the over the Bohrkronenschaft (4) projecting portions (16) of the first and second cutting edges (3, 5) reinforcing ribs (10), in particular substantially helically around the Bohrkronenschaft (4) extending reinforcing ribs (10) are formed. Drill bit (1) according to one of claims 1 to 12, characterized in that at least one, substantially normal to the axis of rotation (6) of the drill bit (1) standing flushing channel (15) for discharging flushing fluid in the drill bit shank (4) is formed , Drill bit (1) according to claim 13, characterized in that the flushing channel (15) is inclined by an angle between the horizontal of 2 and 10 ° angle (α) towards a borehole interior. Drill bit (1) according to claim 13, characterized in that additionally at least two by about 90 ° to the flushing channels (15) offset, one with the horizontal between 10 and 45 ° enclosing angle (γ) inclined towards a borehole exterior Flushing channels (20) are provided. The drill bit (1) according to one of claims 14 or 15, characterized in that two flushing passages (15) are provided and that the flushing passages (15) are located above the reinforcing ribs (10) and adjacent the leading cutting edge (9) of the inclined portion of the second blades (5) result. Drill bit (1) according to any one of claims 14, 15 or 16, characterized in that the (the) flushing channel (channels) (15) at their to an outer side of the drill bit (1) lying mouths provided in particular releasably fixable flush valves (19) are. The drill bit (1) according to claim 17, characterized in that the flushing valves (19) have substantially cap-shaped flow valves whose cap-shaped region (24) enclosing a flow opening (15) is made of hard metal or have a hard metal cladding.

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