ROUNDED CUTTER POCKET HAVING REDUCED STRESSED CONCENTRATION

Description

BACKGROUND

1. Field of Invention

[0001] The disclosure herein relates to contoured cutting teeth for use with a drilling bit. More specifically, the present disclosure concerns inserts having a spherical shaped rear portion disposed in a correspondingly formed pocket, wherein the pocket is situated on the cutting surface of a drag bit. The present disclosure also concerns a method for forming the pockets on the face of a drill bit.

2. Description of Prior Art

[0002] Earth boring bits for drilling wellbores into subterranean formations include roller cone bits and drag bits. The earth boring bits are typically connectable to a drilling system via a threaded connection disposed on the bottom portion of the bit. Drag type bits includes blades formed on the lower surface of the bit. The blades comprise a raised portion of material having a generally rectangular cross-section extending roughly from the center portion of the bit surface and radially outward along a side of the bit. Cutter pockets are formed on the upper surface of the blade, wherein the respective axes of the pockets are generally parallel with other pockets on the individual blade. Typically, the pockets comprise a hollowed out trough portion of the upper surface of the blade, wherein the pockets are formed to receive a cutting element therein.

[0003] The cutting elements can be attached in any number of ways, such as welding and brazing or other attachment means. The cutting element has a generally cylindrical shape with a cutting face on one end and planar on its other end. It is well known in the prior art to add polycrystalline diamond compact, i.e., PDC, on the face of the cutting element. The cutting element body is typically formed of a relatively hard material such as sintered tungsten carbide. The PDC layer may be mounted directly on the mounting body or on an intermediate carrier also generally made from a sintered tungsten carbide.

[0004] The bit body is usually comprised of either a tungsten carbide matrix or various forms of steel. Drilling systems typically utilize the weight on bit to press down into the rock that combined with the torque crushes the rock which causes the drilling action. Continued turning of the drill string pushes the teeth through the rock by the combined forces of the weight on bit and the torque.

[0005] Known displacements have planar ends that form cutter pockets with corresponding flat bottoms. During use of bit bodies having flat bottom cutter pockets, the geometry produces high stresses in the bit body adjacent the cutter pocket bottom. The high stresses can initiate cracking in the bit body thereby reducing bit life.

[0006] US 6 823 952 B1 discloses A method of forming a bit body for an earth boring drill bit in which bit body raw materials and a displacement are combined into a bit body casting form. The rounded end of the displacement is oriented to extend into the bit body materials. Then the materials are processed in the casting form to form a bit body, wherein the presence of the displacement extending into the bit body raw materials during the step of processing the materials forms a cutter pocket in the bit body. The displacement is integrally made of removable material and removed after processing in the casting form to form a cutter pocket.

[0007] The object of the invention is to provide a method for forming a bit body having an increased bit life.

[0008] This object is achieved by a method comprising the method steps of claim 1. Preferred ways to carry out the method of the invention are claimed in claims 2 to 8.

[0009] An earth boring bit having an increased bit life is claimed in claim 9. Preferred embodiments of the earth boring bit of the invention are claimed in claims 10 to 13.

SUMMARY OF INVENTION

[0010] Disclosed herein is a drag bit and a method for creating a drag bit. In one embodiment, the drag bit comprises a blade on its cutting face, with a series of pockets on the blade formed using displacements. In one embodiment, the displacement comprises an insert on one end with removable displacement material on the other. The insert end opposite the displacement is rounded and oriented to be at the cutter pocket bottom while forming the bit. The insert and displacement converge at a planar surface. After the displacement material is removed from the insert, a cutting element may be attached to the end of the insert. A method is included herein for forming the pockets on the blade of the drag bit. The method involves forming the cutter pocket with the displacement having an insert with a rounded shaped end to form a rounded cutter pocket bottom, cleaning the removable portion of the displacement, and adding a cutting element to the end of the insert.

BRIEF DESCRIPTION OF DRAWINGS

[0011] Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

[0012] Figure 1 is a bottom view of a drill bit shown during the formation process.

[0013] Figure 2 is a side view of an example of a displacement for forming a cutter pocket.

[0014] Figure 3 is a side view of a displacement for forming a cutter pocket having an insert on one end.

[0015] Figure 4 is a partial cutaway view of a displacement forming a cutter pocket having an insert.

[0016] Figure 5 is a partial cutaway view of a cutting element comprising an insert on one end.

[0017] Figure 6 is a partial sectional view of a displacement in a bit body having an elliptical end.

[0018] Figure 7 is a partial sectional view of a displacement in a bit body having an elliptical end.

[0019] Figure 8 is a partial sectional view of a displacement in a bit body having a frusto-conical end.

[0020] Figure 9 is a partial sectional view of an example of a drilling system employing a drill bit having a cutter pocket with a rounded bottom.

[0021] Figure 10 is a partial cutaway view of a cutting element with a rounded end in a bit body.

[0022] While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the scope of the invention as defined by the appended claims.

DETAILLED DESCRIPTION OF INVENTION

[0023] The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

[0024] It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

[0025] Disclosed herein is a device and method regarding forming cutter pockets and cutting elements of a drag bit. In one embodiment, a cutter pocket is formed using a displacement comprising removable displacement material and a non-removal insert having a rounded end. The displacement is oriented within a bit body casting form so when the bit body is formed, the rounded ended of the insert is integral within the bit body with the removable displacement between the insert and the bit outer surface. After removing the displacement material from the insert a cutting element can be attached to the insert's free end. Another way to form a rounded cutter element to bit body interface, which does not form part of the present invention, is to form a bit body using a rounded end displacement, wherein the entire displacement comprises removable material. In one embodiment, the cutter element(s) to bit body interface describes the contact surface between the cutter element and the bit body: The cutter element(s)/bit body interface also describes the forces and/or force distributions transferred between the cutter element(s) and the bit body. The interface can describe a single cutting element and bit body, a plurality of cutting elements and the bit body, or all cutting elements and the bit body. After casting the bit and then cleaning the displacement from the cutter pocket, a cutting element with a correspondingly rounded bottom can be affixed in the rounded bottom cutter pocket. One of the advantages of having a rounded cutter element to bit body interface is the forces experienced by the cutting element during cutting are transferred to the bit body through the insert (or cutter element) rounded end. A rounded interface has a greater area than traditional planar or flat bit body/cutting element interfaces, thus stresses imparted by the cutting element to the bit body are more evenly distributed throughout the bit body. More even stress distribution thereby minimizes stress concentrations in the bit body. Additionally, the improvement disclosed herein removes sharp corners in the cutter pocket rear portion. In contrast, some diamond fixed cutter bits have experienced primary cutter pocket cracking, especially for the cutters located proximate to the bit axis. These cracks initiate from the joint of the cutter pocket seat and propagate down towards the nozzle and/or front blade root.

[0026] Figure 1 illustrates a bottom view of an example of a bit body 10, which does not form part of the present invention, being formed in accordance with the present disclosure. The bit body 10 comprises a series of blades 12 formed on the bit face 14, wherein the blades 12 radially extend outward from the center towards the outer radius of the bit face 14. Cutter pockets 13 are generally formed along the upper or outer edge of the blade for receiving cutting elements within the pockets. Displacements may be used in forming these cutter pockets by positioning the displacements inside a form as the bit body is being cast. One example of this novel process is provided in Figure 1 where displacements 16 were situated in a casting form before bit body raw materials were added. The displacements 16 were kept in place in the casting form during the casting process and integrated with the bit body 10. Examples of bit body raw materials include a hard material, such as tungsten or tungsten carbide, and binder constituents. Binder constituents include copper, nickel, other soft metals, and combinations thereof. Processing the bit body raw materials within the casting form may comprise heating to soften and/or melt the binder enabling the softened binder material to migrate within the hard material, and when cooled will bind the hard materials together. However the scope of the present disclosure is not limited to a high temperature forming process, but instead other processing methods can be employed with the forming method described herein, such as a high pressure forming process, or a combination of increased pressure and increased temperature.

[0027] In one example the displacements 16 in Figure 1 comprise a material that retains its shape during the bit casting process, but are removable and can be cleaned away after the bit body 10 is removed from the form. Examples of materials for the displacements 16 include generally, graphite silicon carbide, refractory materials, compressed particulate matter, combinations thereof, and similar substances. Sand blasting is one example method that can be employed for cleaning displacement material from within the cutter pocket 13. Accordingly the displacement(s) 16 may optionally comprise erodible materials removable with some applied impact, such as by particles (for example sand), water air, or any other stream comprising matter directed at the displacement. In this example, one end of the displacement 16 is shown protruding away from the cutter face. The rearward end, or the displacement rear portion 18 (forming the cutter pocket 13) is shown in a dashed outline on the blade face 12. Optionally, use of the stress minimizing cutter pockets can be limited to the portions of the bit face having cutters exposed to localized high stresses.

[0028] Figure 2 provides a side view of an example of a displacement 24 such as used to form a cutter pocket 13 in the bit body 10 of Figure 1. The displacement 24 comprises a rear section 26, a front section 28, and an indicator groove 30. A groove 30, formed proximate to the front 28 circumscribes the displacement 24 outer periphery. The displacement 24 rear section 26 is rounded for forming a shaped cutter pocket with a rounded bottom. Optionally, the rear section 26 of this displacement 24 may be hemi-spherical, oval, or have any radial shape, with or without tapers. Examples of displacements 24 having an end with an elliptical shape are provided in a side partial sectional view in Figures 6 and 7. An example of displacements 24 having an end with a fructo-conical shape is provided in a side partial sectional view in Figure 8. In other examples, the front section 28 may be flat, elliptical, chamfered, or have a chisel shape. The present method also includes orienting a displacement having a rounded end within a bit body casting form so the rounded end is used to shape the bottom end 15 of a cutter pocket 13. The optional groove 30 is formed to indicate displacement position and to allow manufacturing personnel to properly align displacements 24 with the face of the blade 14. Optionally, the cutter can be formed as a unibody assembly having a rounded rear portion, in this embodiment the cutter would not have an added insert.

[0029] Figure 3 provides a side view of displacement 42 embodiment. The displacement 42 of Figure 3 comprises an insert 46 rounded on its free or bottom end (i.e. the end inserted into a rounded bottom cutter pocket 13). The displacement 42 further includes a cylindrically shaped mid section 45 attached to the insert 46. A front section 44 is shown on the mid section 45 opposite the insert 46. The mid section 45 and front section 44 may comprise above described displacement material such as graphite or silicon carbide. The insert 46 may be glued to the mid section 45 prior to being placed in the mold. Forming a bit body 10 with the displacement 42 of Figure 3 includes removing the front portion 44 and mid section 45 after the casting process. The step of removing may include the displacement cleaning/removal method as described above. Removing the mid section 45 leaves the insert 46 within the cutter pocket 13. As discussed below and illustrated in Figure 5, a cutter element having a rounded end and a cutter face can be affixed to the insert 46 within the cutter pocket. Typical methods of adhering cutter elements in formed pockets exist, such as welding, brazing and possibly gluing. Accordingly, using the insert 46 results in cutter forces being more evenly distributed from the cutter element to the cutter blades 12 and bit 10. The insert 46 may comprise mild carbon steel, such as 1018 carbon steel, tungsten carbide, alloys, sintered tungsten carbide, low carbon alloy steels, or combinations thereof. Cutter pockets formed using displacements 42 that comprise an insert 46 may optionally be described as extending from the flat or planar surface of the insert 46 to the cutter pocket opening on the bit body surface. When described in this fashion, the insert 46 would not be in the cutter pocket and the cutter pocket would have a flat bottom defined by the insert 46 upper surface. Optionally, the cutter pocket can be described as extending to the rounded interface between the insert 46 and bit body 12, thus the insert 46 would be in the bottom of the cutter pocket. Irrespective of how a cutter pocket is described, inserts 46 having a rounded end provide a rounded cutting element to bit body interface.

[0030] Figure 4 illustrates a side partial sectional view of the displacement 42 of Figure 3 disposed in a bit body 12 cutter pocket 13. This illustrates an example of a displacement 42 combined with the bit body 12 during the casting process. The front portion 44 is removable, such as by using the above described process, thereby leaving the insert 46 within the pocket 13. The cutter pocket bottom 15 rounded configuration with the correspondingly contoured insert 46 forms a rounded cutter element to bit body interface to better distribute bit body 12 stress than the traditional flat or planar cutter element to bit body interfaces. Unlike the bit bodies having high stress concentrations from flat bottom cutting elements; earth boring bit bodies formed using the displacements (24, 42) described herein will experience a substantially equal cutter element to bit body stress distribution. Reducing stress concentration in the bit body reduces a likelihood of crack initiation and/or crack growth, thereby increasing useful bit life.

[0031] After removing the front portion 44 of Figure 4, a cutting element 35 may be secured onto the insert 46. One example is provided in Figure 5 that illustrates a side view of the cutting element 35 comprising a cutter body 36 secured to the insert 46 within the cutter pocket 13. Here the cutting element 35 is attached to the insert 46 within the cutter pocket 13 created by the mid section 45 (Figure 4) and includes a cutter tip 38 on its outwardly facing surface. As is known, the cutter tip 38 may be a polycrystalline diamond compact (PDC) and include hard or super hard materials.

[0032] With regard to the displacement 24 shown in Figure 2, after forming a bit body 10 using a casting process, then blast removing the displacement material, a cutting element 31 (Figure 10) having a rounded bottom 32 and a cutting tip 33 is illustrated attached in the rounded bottom pocket 13. Brazing or some other means of attachment can be employed for securing the cutting element 31 within the pocket 13.

[0033] Figure 9 illustrates an embodiment of a drilling system 50 comprising the bit body 10 having a cutter pocket 13 with a rounded bottom. Here the bit body 10 is deployed on a drill string 52 and connected to a top drive 58 for rotating the drill string 52 and bit 10.

Claims

1. A method of forming a bit body (10) for an earth boring drill bit comprising:

providing a displacement (42) having a portion with a rounded end that defines an insert (46);

combining bit body raw materials and the displacement (42) into a bit body casting form;

orienting the rounded end of the displacement (42) to extend into the bit body materials; and

processing the materials in the casting form to form a bit body (10), wherein the presence of the displacement (42) extending into the bit body raw materials during the step of processing the materials forms a cutter pocket (13) in the bit body (10) and wherein the insert (46) is not removable from the cutter pocket (13).

2. The method of claim 1 further comprising, separating the portion of the displacement (42) that defines the insert (46) from the remaining portion (44, 45)and removing the remaining portion (44, 45) of the displacement (42) from the cutter pocket (13).

3. The method of claim 1, wherein the displacement (42) comprises a portion (44, 45) formed from an erodible material and an insert portion (46) comprising the rounded end.

4. The method of claim 3, wherein the insert (46) is integrally formed in the bit body (10), the method further comprising removing the erodible portion, and affixing a cutting element to the insert (46).

5. The method of claim 1, wherein the raw materials comprise tungsten and a binder.

6. The method of claim 2, further comprising, affixing a cutting element onto the insert (46) in the cutter pocket (13).

7. The method of claim 1, wherein the displacement (42) comprises material selected from the group consisting of graphite, silicone carbide, refractory materials, compressed particles, and combinations thereof.

8. The method of claim 1 further comprising, removing at least a portion of the displacement (42) from the formed bit body (10), affixing a cutting element within the cutter pocket (13), coupling the bit body (10) with insert (46) to a drill pipe, boring a wellbore with the bit body (10) and drill pipe.

9. An earth boring bit formed using a casting process, the bit attachable to a drill string for forming a subterranean wellbore, the bit comprising:

a bit body (10);

a blade extending from the bit body (10); and

a cutter pocket (13) having a rounded bottom end formed in the blade during the casting process, wherein the rounded bottom end is formed using a displacement (42) having a front section (44) and an insert section (46) with a rounded end that is integrally formed in that pocket (13).

10. The earth boring bit of claim 9, wherein the front section (44) of the displacement (42) is formed using an erodible material.

11. The earth boring bit of claim 9, wherein the displacement (42) further comprises a mid section (45) between insert section (46) and front section (44), wherein the mid section (45) is formed from an erodible material.

12. The earth boring bit of claim 9, wherein the displacement (42) rounded end is orientable in a bit body casting mold to form a cutter pocket (13) having a rounded bottom.

13. The earth boring bit of claim 10, wherein the displacement (42) comprises material selected from the group consisting of graphite and silicone carbide, refractory materials, compressed particles, and combinations thereof.

Ansprüche

1. Verfahren zur Bildung eines Meißelkörpers (10) für einen Erdbohrmeißel, das umfasst,

- dass ein Verdrängungsteil (42) bereitgestellt wird, das einen Abschnitt mit einem gerundeten Ende aufweist, der einen Einsatz (46) bildet;

- dass Meißelkörperrohmaterialien und das Verdrängungsteil (42) in eine Meißelkörpergussform kombiniert werden;

- dass das gerundete Endes des Verdrängungsteils (42) so ausgerichtet wird, dass es sich in die Meißelkörpermaterialien erstreckt; und

- dass die Materialien in der Gussform zur Bildung eines Meißelkörpers (10) verarbeitet werden, wobei das Vorhandensein des sich während des Schritts der Verarbeitung der Materialien in die Meißelkörperrohmaterialien erstreckenden Verdrängungsteils (42) eine Schneidelementtasche (13) in dem Meißelkörper (10) bildet und wobei der Einsatz (46) aus der Schneidelementtasche (13) nicht entfernbar ist.

2. Verfahren nach Anspruch 1, das weiterhin umfasst, dass der Abschnitt des Verdrängungsteils (42), der den Einsatz (46) bildet, von dem verbleibenden Abschnitt (44, 45) getrennt und der verbleibende Abschnitt (44, 45) des Verdrängungsteils (42) aus der Schneidelementtasche (13) entfernt wird.

3. Verfahren nach Anspruch 1, wobei das Verdrängungsteil (42) einen Abschnitt (44, 45), der aus einem erodierbaren Material gebildet wird, und einen Einsatzabschnitt (46) umfasst, der das gerundete Ende umfasst.

4. Verfahren nach Anspruch 3, wobei der Einsatz (46) in dem Meißelkörper (10) einstückig ausgebildet wird, wobei das Verfahren weiterhin umfasst, dass der erodierbare Abschnitt entfernt und ein Schneidelement an dem Einsatz (46) befestigt wird.

5. Verfahren nach Anspruch 1, wobei die Rohmaterialien Wolfram und ein Bindemittel umfassen.

6. Verfahren nach Anspruch 2, das weiterhin umfasst, dass ein Schneidelement auf dem Einsatz (46) in der Schneidelementtasche (13) befestigt wird.

7. Verfahren nach Anspruch 1, wobei das Verdrängungsteil (42) Material umfasst, das aus der Gruppe ausgewählt wird, die aus Graphit, Siliciumcarbid, refraktorischen Materialien, komprimierten Partikeln und Kombinationen daraus besteht.

8. Verfahren nach Anspruch 1, das weiterhin umfasst, dass wenigstens ein Abschnitt des Verdrängungsteils (42) aus dem gebildeten Meißelkörper (10) entfernt, ein Schneidelement innerhalb der Schneidelementtasche (13) befestigt, der Meißelkörper (10) mit dem Einsatz (46) an ein Bohrrohr gekoppelt und ein Bohrloch mit dem Meißelkörper (10) und dem Bohrrohr gebohrt wird.

9. Unter Verwendung eines Gießprozesses gebildeter Erdbohrmeißel, wobei der Meißel zur Bildung eines unterirdischen Bohrlochs an einem Bohrstrang befestigbar ist, wobei der Meißel

- einen Meißelkörper (10);

- ein sich von dem Meißelkörper (10) erstreckendes Blatt; und

- eine Schneidelementtasche (13) umfasst, die ein gerundetes unteres Ende aufweist, das während des Gießprozesses in dem Blatt gebildet wurde, wobei das gerundete untere Ende unter Verwendung eines Verdrängungsteils (42) gebildet wird, das einen vorderen Abschnitt (44) und einen Einsatzabschnitt (46) mit einem gerundeten Ende aufweist, der in der Tasche (13) einstückig ausgebildet ist.

10. Erdbohrmeißel nach Anspruch 9, wobei der vordere Abschnitt (44) des Verdrängungsteils (42) unter Verwendung eines erodierbaren Materials gebildet wird.

11. Erdbohrmeißel nach Anspruch 9, wobei das Verdrängungsteil (42) weiterhin einen mittleren Abschnitt (45) zwischen dem Einsatzabschnitt (46) und dem vorderen Abschnitt (44) umfasst, wobei der mittlere Abschnitt (45) aus einem erodierbaren Material gebildet ist.

12. Erdbohrmeißel nach Anspruch 9, wobei das gerundete Ende des Verdrängungsteils (42) in einer Meißelkörpergussform so ausrichtbar ist, dass eine Schneidtasche (13) mit einem gerundeten Boden ausgebildet wird.

13. Erdbohrmeißel nach Anspruch 10, wobei das Verdrängungsteil (42) Material umfasst, das aus der Gruppe ausgewählt ist, die aus Graphit und Siliciumcarbid, refraktorischen Materialien, komprimierten Partikeln und Kombinationen daraus besteht.

Revendications

1. Procédé de formation d'un corps de trépan (10) pour un trépan de forage terrestre comprenant :

la prévision d'un déplaçeur (42) ayant une partie avec une extrémité arrondie qui définit un insert (46) ;

la combinaison de matières premières de corps de trépan et du déplaçeur(42) en une forme de moulage de corps de trépan ;

l'orientation de l'extrémité arrondie du déplaçeur(42) pour qu'elle s'étende à l'intérieur des matières de corps de trépan ; et

le traitement des matières à la forme de moulage pour former un corps de trépan (10), dans lequel la présence du déplaçeur(42) s'étendant à l'intérieur des matières premières de corps de trépan pendant l'étape de traitement des matières forme un logement d'outil de coupe (13) dans le corps de trépan (10) et dans lequel l'insert (46) ne peut être enlevé du logement d'outil de coupe (13).

2. Procédé selon la revendication 1 comprenant en outre la séparation de la partie du déplaçeur(42) qui définit l'insert (46) de la partie restante (44, 45) et l'enlèvement de la partie restante (44, 45) du déplaçeur(42) du logement d'outil de coupe (13).

3. Procédé selon la revendication 1, dans lequel le déplaçeur(42) comprend une partie (44, 45) formée à partir d'un matériau érodable et une partie d'insert (46) comprenant l'extrémité arrondie.

4. Procédé selon la revendication 3, dans lequel l'insert (46) est formé de façon intégrale dans le corps de trépan (10), le procédé comprenant en outre l'enlèvement de la partie érodable, et la fixation d'un élément de coupe sur l'insert (46).

5. Procédé selon la revendication 1, dans lequel les matières premières comprennent du tungstène et un liant.

6. Procédé selon la revendication 2, comprenant en outre la fixation d'un élément de coupe sur l'insert (46) dans le logement d'outil de coupe (13).

7. Procédé selon la revendication 1, dans lequel le déplaçeur(42) comprend un matériau choisi parmi le groupe consistant en le graphite, le carbure de silicium, des matériaux réfractaires, des particules compressées, et des combinaisons de ceux-ci.

8. Procédé selon la revendication 1 comprenant en outre l'enlèvement d'au moins une partie du déplaçeur(42) du corps de trépan (10) formé, la fixation d'un élément de coupe à l'intérieur du logement d'outil de coupe (13), le couplage du corps de trépan (10) avec un insert (46) à une tige de forage, le forage d'un puits avec le corps de trépan (10) et la tige de forage.

9. Trépan de forage terrestre formé en utilisant un procédé de moulage, le trépan pouvant être fixé à un train de tiges de forage pour former un puits de forage souterrain, le trépan comprenant :

un corps de trépan (10) ;

une lame s'étendant à partir du corps de trépan (10) ; et

un logement d'outil de coupe (13) ayant une extrémité de fond arrondie formée dans la lame pendant le procédé de moulage, dans lequel l'extrémité de fond arrondie est formée en utilisant un déplaçeur(42) ayant une section avant (44) et une section d'insert (46) avec une extrémité arrondie qui est formée de façon intégrale dans ce logement (13).

10. Trépan de forage terrestre selon la revendication 9, dans lequel la section avant (44) du déplaçeur(42) est formée en utilisant un matériau érodable.

11. Trépan de forage terrestre selon la revendication 9, dans lequel le déplaçeur(42) comprend en outre une section médiane (45) entre la section d'insert (46) et la section avant (44), dans lequel la section médiane (45) est formée à partir d'un matériau érodable.

12. Trépan de forage terrestre selon la revendication 9, dans lequel l'extrémité arrondie du déplaçeur(42) est orientable dans un moule de corps de trépan pour former un logement d'outil de coupe (13) ayant un fond arrondi.

13. Trépan de forage terrestre selon la revendication 10, dans lequel le déplaçeur(42) comprend un matériau choisi parmi le groupe consistant en le graphite et le carbure de silicium, des matériaux réfractaires, des particules compressées, et des combinaisons de ceux-ci.

Drawing