Drill head of a ground drilling device, method for producing a drill head of a ground drilling device, and use of a drill head of a ground drilling device

Abstract

The invention relates to a drill head of a ground drilling device having a drill bit and an attachment which can be fastened to the drill bit, wherein at least one dowel pin is provided for holding the attachment on the drill bit, and the drill bit has one or more receptacles for a dowel pin, wherein the receptacle is enlarged with respect to the radius of the dowel pin.

Claims

1. Drill head of a ground drilling device (1) having a drill bit (2) and an attachment (3) which can be fastened to the drill bit (2), wherein at least one dowel pin (7) is provided for holding the attachment (3) on the drill bit (2), and the drill bit (2) has one or more receptacles (6) for a dowel pin (7), wherein the receptacle (6) is designed enlarged with respect to the radius of the dowel pin (7).

2. Drill head according to claim 1, wherein the receptacle (6) has a contour (K) with a first portion (20) that is adapted to the radius of the dowel pin (7), wherein the contour (K) of the receptacle (6) has a further portion (21) that has a design that is enlarged with respect to the first portion (20).

3. Drill head according to claim 1, wherein the distance between a first portion (20) of the contour (K) and the center point of the receptacle (6) is smaller than the distance between the contour (K) in a further portion (21) and said center point.

4. Drill head according to claim 1, wherein the receptacle (6) has a radius in a first portion (20), which radius is smaller than the radius of a further portion (21).

5. Drill head according to claim 1, wherein different portions (20, 21) of the contour (K) of the receptacle (6) are adjacent.

6. Drill head according to claim 1, wherein an enlargement of the receptacle (6) is present in a portion (21) of the receptacle (6), which enlargement is arranged in the longitudinal direction (L) of the drill bit (2) closer to the drill bit tip (11).

7. Drill head according to claim 1, wherein an enlargement of the receptacle (6) is designed as a straight line (12) which is inclined in particular with respect to the longitudinal direction (L) of the drill bit (2).

8. Drill head according to claim 7, wherein the inclination of the straight line (12) with respect to the longitudinal direction has an angle of between 5° and 20°, in particular between 10° and 20°, in particular between 12° and 18°, in particular between 14° and 18°.

9. A method for producing a drill head of a ground drilling device (1), wherein the drill head has a drill bit (2) and an attachment (3) which can be fastened to the drill bit (2), wherein the attachment (3) can be held on the drill bit (2) by means of at least one dowel pin (7), and the drill bit (2) has one or more receptacles (6) for the dowel pin (7), wherein the receptacle (6) is designed enlarged with respect to the radius of the dowel pin (7).

10. Use of a drill head of a ground drilling device (1), wherein the drill head has a drill bit (2) and an attachment (3) which can be fastened to the drill bit (2), wherein a dowel pin (7) is used to hold the attachment (3) on the drill bit (2), and the drill bit (2) has one or more receptacles (6) for the dowel pin (7), wherein a design of the receptacle (6) is used, which design is enlarged with respect to the radius of the dowel pin (7).

Description

[0049] The invention is explained in more detail below with reference to an embodiment shown in the drawings in which:

[0050] FIG. 1 is a sectional view of a ground drilling device;

[0051] FIG. 2 is an enlarged view of the fastening of an attachment to a drill bit according to the prior art with a further enlarged view in the region of a receptacle for a dowel pin;

[0052] FIG. 3 is an enlarged view of the fastening of an attachment to a drill bit with an enlarged receptacle in contrast to FIG. 2;

[0053] FIG. 4 shows the attachment fastened to the drill bit of FIG. 3 after relative movement of the attachment with respect to the drill bit;

[0054] FIG. 5 is an enlarged view in the front-side region of the receptacle of FIGS. 3 and 4; and

[0055] FIG. 6 is a further embodiment with an enlarged receptacle in contrast to FIG. 2.

[0056] FIG. 1 shows an example of a ground drilling device 1 which is designed as a self-propelled impact device. A drill bit 2, which is part of a drill head 102, protrudes from a housing 100. The drill bit 2 has a drill bit tip 11. In the housing 100, the drill bit 2 can be acted upon at the end side by means of an impact piston 14 moving back and forth in the housing 100. The impact piston hits the end which is at a distance from the drill bit tip 11 in a pulsed manner.

[0057] The drill head 102 has the drill bit 2 and an attachment 3 fastened to the drill bit 2.

[0058] FIG. 2 is an enlarged view of the fastening of the attachment 3 on the drill bit 2, as previously done: The attachment 3 has a conical (central) bore 8 with which the attachment 3 is pressed onto the drill bit 2 which has a conical outer face 9. The conical contact surfaces of the bore 8 and the outer face 9 are adapted to each other. The connection is secured by means of a plurality of dowel pins 7 (four are selected in the embodiment shown) under a defined preload which braces the attachment 3 against the drill bit 2. In the prior art, as shown in FIG. 2, very narrow tolerances have to be observed. This applies to the cone angle 10 and a cone diameter 4 of the attachment 3 and the drill bit 2, as well as to the positions of receptacles or bores 5 for the dowel pin in the attachment 3 and of receptacles or round grooves 6 on the drill bit 2 in the direction of the longitudinal axis L of the drill bit 2 or of the attachment 3. Compliance with the tolerances served to achieve a defined preload between the attachment 3 and the drill bit 2. The entire contour of the receptacle 6 is adapted to the diameter of the dowel pin 7; the contour K of the receptacle 6 is formed in its the entirety by means of one and the same portion 20 which, as a radius portion, is adapted to the diameter of the dowel pin 7.

[0059] FIG. 3 shows a preferred embodiment of a design of the receptacle 6 now provided on the drill bit 2: The attachment 3 is in this case in a marginal (extreme) position on the drill bit 2; the dowel pins 7 create a preload between the attachment 3 and the drill bit 2. The attachment 3 is shown in an unloaded state, i.e., free from external forces. The receptacles 6 on the drill bit 2 have a portion 20 having a contour K (adapted or suitable radius) adapted to the dowel pin 7. In addition, there is another portion 21 of the contour K of the receptacle 6, which portion is designed as a straight line 12 that rises toward the drill bit tip 11 (in this case at an angle of 16° to the longitudinal axis L of the drill bit 2).

[0060] FIGS. 4 and 5 describe the connection between a possible displacement ΔS and the resulting diameter difference ΔD for the dowel pin 7 in the event that the front-side portion 21 causing the enlargement of the receptacle 6 is designed as a straight line 12:

ΔD=b−a=ΔS×(tan α+tan β)

[0061] For example, a displacement of the dowel pin 7 in the direction of the drill bit tip of ΔS=1 mm and a possible cone angle 10 of the attachment 3 and the drill bit 2 of α=2° and an angle of the straight line 12 of the contour K of the receptacle 6 of

[0062] β=16° results in a diameter difference of the dowel pin 7 in the amount of ΔD=1 mm×(tan 2°+tan 16°)=0.32 mm. It can be seen from FIG. 4 that a displacement of the attachment 3 is possible by 1 mm without the dowel pin 7 being fully compressed. A further displacement of the attachment 3 in the direction of the drill bit tip is readily possible with regard to a compression of the dowel pin 7.

[0063] FIG. 6 shows a further preferred embodiment of a design of the receptacle 6 on the drill bit 2: The attachment 3 is in an unloaded state on the drill bit 2, i.e., free from external forces, similar to the situation according to FIG. 3. The contour K of the receptacle 6 on the drill bit 2 has the portion 20 which is adapted to the dowel pin 7. In addition, there are two further portions 21 of the contour K of the receptacle 6, with which portions the receptacle 7 is designed to be enlarged. In addition to the straight line 12, a portion 22 is designed at a distance from the drill bit tip, which portion has a larger radius than the radius of the portion 20 adapted to the dowel pin 7.