Drill bit with improved removal of the drill core

Abstract

Drill bit (20) including a drilling shaft and a cutting portion having a first drilling segment (23-1) and a second drilling segment (23-2). The first drilling segment (23-1) has a first inner lateral surface (28-1) with a first inner distance (B.sub.1(, h)), and the second drilling segment (23-2) has a second inner lateral surface (28-2) with a second inner distance (B.sub.2(, h)) from the longitudinal axis (24) of the drilling shaft. The first inner distance (B.sub.1(, h)) varies between a first maximum value (B.sub.max,1) and a first minimum value (B.sub.min,1) over the circumference of the first drilling segment (23-1) and has precisely one first absolute minimum value (B.sub.min,1). The second inner distance (B.sub.2(, h)) is greater than or equal to the first absolute minimum value (B.sub.min,1) over the circumference of the second drilling segment (23-2).

Claims

1-14. (canceled)

15: A drill bit comprising: a drilling shaft having a cylinder with a longitudinal axis, wherein the cylinder has, in a plane perpendicular to the longitudinal axis, an outside diameter, an inside diameter and a shaft width, and two drilling segments spaced apart from one another in a circumferential direction and fastened by an underside to the drilling shaft, wherein the two drilling segments include a first drilling segment with a first inner lateral surface having a first inner distance from the longitudinal axis perpendicular to the longitudinal axis, and a second drilling segment with a second inner lateral surface having a second inner distance from the longitudinal axis perpendicular to the longitudinal axis, the first inner distance varying between a first maximum value and a first minimum value and having precisely one first absolute minimum value over the circumference of the first drilling segment, the second inner distance being greater than or equal to the first absolute minimum value over the circumference of the second drilling segment.

16: The drill bit as recited in claim 15 wherein the first inner distance has two first maximum values over the circumference of the first drilling segment, wherein the first absolute minimum value is arranged between the first maximum values in the circumferential direction.

17: The drill bit as recited in claim 15 wherein the first inner distance follows, over the circumference of the first drilling segment, a strictly monotonic profile in the region of the first absolute minimum value.

18: The drill bit as recited in claim 17 wherein the second inner distance varies between a second maximum value and a second minimum value and has precisely one second absolute minimum value over the circumference of the second drilling segment.

19: The drill bit as recited in claim 18 wherein the second inner distance has two second maximum values over the circumference of the second drilling segment, wherein the second absolute minimum value is arranged between the second maximum values in the circumferential direction.

20: The drill bit as recited in claim 18 wherein the second inner distance follows, over the circumference of the second drilling segment, a strictly monotonic profile in the region of the second absolute minimum value.

21: The drill bit as recited in claim 18 wherein the first absolute minimum value of the first drilling segment and the second absolute minimum value of the second drilling segment are offset from one another by about 180 in the circumferential direction.

22: The drill bit as recited in claim 15 wherein the first inner lateral surface is formed as a portion of a first cylinder, and the second inner lateral surface is formed as a portion of a second cylinder.

23: The drill bit as recited in claim 22 wherein the first cylinder has a first base surface differing from a circular shape, or the second cylinder has a second base surface differing from a circular shape.

24: The drill bit as recited in claim 15 wherein the first inner lateral surface is formed as a portion of a first inner cone tapering in the direction of a first upper side opposite to the underside of the first drilling segment, and the second inner lateral surface is formed as a portion of a second inner cone tapering in the direction of a second upper side opposite to the underside of the second drilling segment.

25: The drill bit as recited in claim 24 wherein the first inner cone has a first base surface differing from a circular shape, or the second inner cone has a second base surface differing from a circular shape.

26: The drill bit as recited in claim 15 wherein the first drilling segment and the second drilling segment are of identical design.

27: The drill bit as recited in claim 15 wherein the first inner lateral surface is formed as a portion of a first inner cone tapering in the direction of a first upper side opposite to the underside of the first drilling segment, and the second inner lateral surface is formed as a portion of a second cylinder.

28: The drill bit as recited in claim 27 wherein the first inner cone has a first base surface which differs from a circular shape, or the second cylinder has a second base surface differing from a circular shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Exemplary embodiments of the invention are described hereinafter with reference to the drawing. It is not necessarily intended for this to illustrate the exemplary embodiments to scale; rather, the drawing is produced in a schematic and/or slightly distorted form where this is useful for purposes of explanation. It should be taken into account here that various modifications and alterations relating to the form and detail of an embodiment may be undertaken without departing from the general concept of the invention. The general concept of the invention is not limited to the exact form or the detail of the preferred embodiment shown and described hereinafter or limited to subject matter that would be restricted compared with the subject matter claimed in the claims. For given dimensioning ranges, values within the stated limits should also be disclosed as limit values and should be able to be used and claimed as desired. For the sake of simplicity, the same reference signs are used hereinafter for identical or similar parts or parts having an identical or similar function.

[0026] In the drawing:

[0027] FIG. 1 shows a drill bit having a drilling shaft and two drilling segments which are fastened to the drilling shaft;

[0028] FIGS. 2A, B show a first embodiment of a drill bit according to the invention having a drilling shaft and two drilling segments in a three-dimensional view (FIG. 2A) and in a longitudinal section parallel to the longitudinal axis of the drilling shaft (FIG. 2B):

[0029] FIGS. 3A, B show the drill bit of FIG. 2A in a view of the upper side of the drilling segments (FIG. 3A) and the drilling segments in a longitudinal section parallel to the longitudinal axis of the drilling shaft (FIG. 3B);

[0030] FIGS. 4A, B show a second embodiment of a drill bit according to the invention having a drilling shaft and two drilling segments in a three-dimensional view (FIG. 4A) and in a longitudinal section parallel to the longitudinal axis of the drilling shaft (FIG. 4B);

[0031] FIGS. 5A, B show the drill bit of FIG. 4A in a view of the upper side of the drilling segments (FIG. 5A) and the drilling segments in a longitudinal section parallel to the longitudinal axis of the drilling shaft (FIG. 5B); and

[0032] FIG. 6 shows a third embodiment of a drill bit according to the invention having a drilling shaft and two drilling segments in a view of the upper side of the drilling segments.

DETAILED DESCRIPTION

[0033] FIG. 1 shows a drill bit 10 which has a drilling shaft 11 having a shank 12 and a cutting portion 13 having a first drilling segment 14-1 and a second drilling segment 14-2. The drill bit 10 is fastened in the tool fitting of a core drilling device via the shank 12 and, during the drilling operation, is driven by the core drilling device about an axis of rotation which runs coaxially to the longitudinal axis 15 of the drilling shaft 11.

[0034] FIGS. 2A, B show a first embodiment of a drill bit 20 according to the invention which has a drilling shaft 21 and a cutting portion 22 having a first drilling segment 23-1 and a second drilling segment 23-2. In this case, FIG. 2A shows the drill bit 20 in a three-dimensional view and FIG. 2B shows the drill bit 20 in a longitudinal section parallel to the longitudinal axis 24 of the drilling shaft 21.

[0035] The drilling shaft 21 comprises a cylinder 25 which, in a plane 26 perpendicular to the cylinder axis, which defines the longitudinal axis 24 of the drilling shaft 21, has an outside diameter d.sub.A, an inside diameter d.sub.I and a shaft width b. In the exemplary embodiment, the inside diameter d.sub.I, the outside diameter d.sub.A and the shaft width b are constant both in a circumferential direction and in a height direction h. Alternatively, the inside diameter, the outside diameter and/or the shaft width can vary in the circumferential direction and/or the height direction h.

[0036] The first drilling segment 23-1 comprises a first inner lateral surface 28-1, a first outer lateral surface 29-1, a first underside 31-1 and a first upper side 32-1, and the second drilling segment 23-2 comprises a second inner lateral surface 28-2, a second outer lateral surface 29-2, a second underside 31-2 and a second upper side 32-2. Here, the first underside 31-1 of the first drilling segment 23-1 and the second underside 31-2 of the second drilling segment 23-2 are fastened to an end face of the drilling shaft 21.

[0037] The first inner lateral surface 28-1 of the first drilling segment 23-1 is formed as a portion of a first cylinder 34-1, and the second inner lateral surface 28-2 of the second drilling segment 23-2 is formed as a portion of a second cylinder 34-2. The formation of the first and second inner lateral surface 28-1, 28-2 as a portion of a first or second cylinder 34-1, 34-2 has the advantage that the abrasive removal properties of the first and second drilling segment 23-1, 23-2 are constant over the height.

[0038] FIGS. 3A, B show the drill bit 20 according to the invention of FIG. 2A in a view of the upper side of the drilling segments 23-1, 23-2 (FIG. 3A) and the drilling segments 23-1, 23-2 in a longitudinal section parallel to the longitudinal axis 24 of the drilling shaft 21 (FIG. 3B).

[0039] The first inner lateral surface 28-1 has, in the plane 26 perpendicular to the longitudinal axis 24, a first inner distance B.sub.1(, h) from the longitudinal axis 24. Here, the first inner distance B.sub.1(, h) defines a first mathematical function which describes the profile of the first inner distance over the circumference and the height of the first drilling segment 23-1.

[0040] The first inner distance B.sub.1(, h) varies between a first minimum value B.sub.min,1 and a first maximum value B.sub.max,1 in the circumferential direction over the circumference of the first drilling segment 23-1; the first inner distance B.sub.1(, h) is constant in the height direction h. The first inner distance B.sub.1(, h) has a further first maximum value B.sub.max,1, wherein the first absolute minimum value B.sub.min,1 is arranged between the two first maximum values in the circumferential direction . The first inner distance B.sub.1(, h) follows a strictly monotonic profile in the region of the first absolute minimum value B.sub.min,1 in the plane 26 perpendicular to the longitudinal axis 24.

[0041] The distribution of the first maximum values B.sub.max,1 and of the first absolute minimum value B.sub.min,1 over the circumference of the first drilling segment 23-1 and the strictly monotonic profile of the first inner distance B.sub.1(, h) in the region of the first absolute minimum value B.sub.min,1 allow the production of a first drilling segment 23-1 with a small contact surface with respect to the drill core 35. The first drilling segment 23-1 can be in contact with the drill core 35 only in the region of the first absolute minimum value B.sub.min,1, with all remaining regions of the first inner lateral surface 28-1 having a gap with respect to the drill core 35.

[0042] The second inner lateral surface 28-2 has, in the plane 26 perpendicular to the longitudinal axis 24, a second inner distance B.sub.2(, h) from the longitudinal axis 24. Here, the second inner distance B.sub.2(, h) defines a second mathematical function which describes the profile of the second inner distance over the circumference and the height of the second drilling segment 23-2.

[0043] The second inner distance B.sub.2(, h) varies between a second minimum value B.sub.min,2 and a second maximum value B.sub.max,2 in the circumferential direction over the circumference of the second drilling segment 23-2; the second inner distance B.sub.2(, h) is constant in the height direction h. The second inner distance B.sub.2(, h) has a further second maximum value B.sub.max,2, wherein the second absolute minimum value B.sub.min,2 is arranged between the two second maximum values B.sub.max,2 in the circumferential direction . The second inner distance B.sub.2(, h) follows a strictly monotonic profile in the region of the second absolute minimum value B.sub.min,2 in the plane 26 perpendicular to the longitudinal axis 24.

[0044] The distribution of the second maximum values B.sub.max,2 and of the second absolute minimum value B.sub.min,2 over the circumference of the second drilling segment 23-2 and the strictly monotonic profile of the second inner distance B.sub.2(, h) in the region of the second absolute minimum value B.sub.min,2 allow the production of a second drilling segment 23-2 with a small contact surface with respect to the drill core 35. The second drilling segment 23-2 can be in contact with the drill core 35 only in the region of the second absolute minimum value B.sub.min,2, with all remaining regions of the second inner lateral surface 28-2 having a gap with respect to the drill core 35.

[0045] In the exemplary embodiment, the first drilling segment 23-1 and second drilling segment 23-2 are of identical design within production tolerances and are offset from one another by about 180 in the circumferential direction . With an offset of about 180, the first absolute minimum value B.sub.min,1 and second absolute minimum value B.sub.min,2 are opposite one another in the circumferential direction and lead to a mirror-symmetrical design of the drill bit 20. The mirror-symmetrical design allows vibrations of the drill bit 20 to be reduced during the drilling operation and the running smoothness of the drill bit 20 to be improved.

[0046] The first cylinder 34-1 has a first base surface which differs from a circular shape and which is formed as a first elliptical shape in the exemplary embodiment, and the second cylinder 34-2 has a second base surface which differs from a circular shape and which is formed as a second elliptical shape in the exemplary embodiment. The first drilling segment 23-1 and second drilling segment 23-2 are arranged in such a way that the first absolute minimum value B.sub.min,1 of the first drilling segment 23-1 and the second absolute minimum value B.sub.min,2 of the second drilling segment 23-2 form the short semiaxis of the elliptical shape.

[0047] FIGS. 4A, B show a second embodiment of a drill bit 40 according to the invention which has a drilling shaft 41 and a cutting portion 42 having a first drilling segment 43-1 and a second drilling segment 43-2. In this case, FIG. 4A shows the drill bit 40 in a three-dimensional view and FIG. 4B shows the drill bit 40 in a longitudinal section parallel to the longitudinal axis 44 of the drilling shaft 41.

[0048] The drilling shaft 41 comprises a cylinder 45 which, in a plane 46 perpendicular to the cylinder axis, which defines the longitudinal axis 44 of the drilling shaft 41, has an outside diameter d.sub.A, an inside diameter d.sub.I and a shaft width b. In the exemplary embodiment, the inside diameter d.sub.I, the outside diameter d.sub.A and the shaft width b are constant both in the circumferential direction and in the height direction h. Alternatively, the inside diameter, the outside diameter and/or the shaft width can vary in the circumferential direction and/or the height direction h.

[0049] The first drilling segment 43-1 comprises a first inner lateral surface 48-1, a first outer lateral surface 49-1, a first underside 51-1 and a first upper side 52-2, and the second drilling segment 43-2 comprises a second inner lateral surface 48-2, a second outer lateral surface 49-2, a second underside 51-2 and a second upper side 52-2. Here, the first underside 51-1 of the first drilling segment 43-1 and the second underside 51-2 of the second drilling segment 43-2 are fastened to an end face of the drilling shaft 41.

[0050] The first inner lateral surface 48-1 of the first drilling segment 43-1 is formed as a portion of a first inner cone 54-1 which tapers in the direction of the first upper side 52-1 of the first drilling segment 43-1, and the second inner lateral surface 48-2 of the second drilling segment 43-2 is formed as a portion of a second inner cone 54-2 which tapers in the direction of the second upper side 52-2 of the second drilling segment 43-2.

[0051] FIGS. 5A, B show the drill bit 40 according to the invention of FIG. 4A in a view of the upper side of the drilling segments 43-1, 43-2 (FIG. 5A) and the drilling segments 43-1, 43-2 in a longitudinal section parallel to the longitudinal axis 44 of the drilling shaft 41 (FIG. 5B).

[0052] The first inner lateral surface 48-1 has, in the plane 46 perpendicular to the longitudinal axis 44, a first inner distance B.sub.1(, h) from the longitudinal axis 44. Here, the first inner distance B.sub.1(, h) defines a first mathematical function which describes the profile of the first inner distance over the circumference and the height of the first drilling segment 43-1.

[0053] The first inner distance B.sub.1(, h) varies between a first minimum value B.sub.min,1 and a first maximum value B.sub.max,1 in the circumferential direction over the circumference of the first drilling segment 43-1; the first inner distance B.sub.1(, h) varies in the height direction h and decreases in the direction of the first upper side 52-1 of the first drilling segment 43-1. The first inner distance B.sub.1(, h) has a further first maximum value B.sub.max,1, wherein the first absolute minimum value B.sub.min,1 is arranged between the two first maximum values in the circumferential direction . The first inner distance B.sub.1(, h) follows a strictly monotonic profile in the region of the first absolute minimum value B.sub.min,1 in the plane 46 perpendicular to the longitudinal axis 44.

[0054] The distribution of the first maximum values B.sub.max,1 and of the first absolute minimum value B.sub.min,1 over the circumference of the first drilling segment 43-1, the strictly monotonic profile of the first inner distance B.sub.1(, h) in the region of the first absolute minimum value B.sub.min,1 and the variation of the first inner distance B.sub.1(, h) in the height direction h allow the production of a first drilling segment 43-1 with a small contact surface with respect to the drill core 55. The first drilling segment 43-1 can be in contact with the drill core 55 only in the region of the first absolute minimum value B.sub.min,1, with all remaining regions of the first inner lateral surface 48-1 having a gap with respect to the drill core 55.

[0055] The second inner lateral surface 48-2 has, in the plane 46 perpendicular to the longitudinal axis 44, a second inner distance B.sub.2(, h) from the longitudinal axis 44. Here, the second inner distance B.sub.2(, h) defines a second mathematical function which describes the profile of the second inner distance over the circumference and the height of the second drilling segment 43-2.

[0056] The second inner distance B.sub.2(, h) varies between a second minimum value B.sub.min,2 and a second maximum value B.sub.max,2 in the circumferential direction over the circumference of the second drilling segment 43-2; the second inner distance B.sub.2(, h) varies in the height direction h and decreases in the direction of the second upper side 52-2 of the second drilling segment 43-2. The second inner distance B.sub.2(, h) has a further second maximum value B.sub.max,2, wherein the second absolute minimum value B.sub.min,2 is arranged between the two second maximum values in the circumferential direction . The second inner distance B.sub.2(, h) follows a strictly monotonic profile in the region of the second absolute minimum value B.sub.min,2 in the plane 46 perpendicular to the longitudinal axis 44.

[0057] The distribution of the second maximum values B.sub.max,2 and of the second absolute minimum value B.sub.min,2 over the circumference of the second drilling segment 43-2, the strictly monotonic profile of the second inner distance B.sub.2(, h) in the region of the second absolute minimum value B.sub.min,2 and the variation of the second inner distance B.sub.2(, h) in the height direction h allow the production of a second drilling segment 43-2 with a small contact surface with respect to the drill core 55. The second drilling segment 43-2 can be in contact with the drill core 55 only in the region of the second absolute minimum value B.sub.min,2, with all remaining regions of the second inner lateral surface 48-2 having a gap with respect to the drill core 55.

[0058] In the exemplary embodiment, the first drilling segment 43-1 and second drilling segment 43-2 are of identical design within production tolerances and are offset from one another by about 180 in the circumferential direction . With an offset of about 180, the first absolute minimum value B.sub.min,1 and second absolute minimum value B.sub.min,2 are opposite one another in the circumferential direction and lead to a mirror-symmetrical design of the drill bit 40. The mirror-symmetrical design allows vibrations of the drill bit 40 to be reduced during the drilling operation and the running smoothness of the drill bit 40 to be improved.

[0059] The first inner cone 54-1 has a first base surface which differs from a circular shape and which is formed as a first elliptical shape in the exemplary embodiment, and the second inner cone 54-2 has a second base surface which differs from a circular shape and which is formed as a second elliptical shape in the exemplary embodiment. The first drilling segment 43-1 and second drilling segment 43-2 are arranged in such a way that the first absolute minimum value B.sub.min,1 of the first drilling segment 43-1 and the second absolute minimum value B.sub.min,2 of the second drilling segment 43-2 form the short semiaxis of the elliptical shape.

[0060] The drill bit 20 of FIG. 2A comprises a first and second drilling segment 23-1, 23-2 having inner lateral surfaces 28-1, 28-2 which are formed as a portion of a first cylinder 34-1 or second cylinder 34-2, and the drill bit of FIG. 4A comprises a first and second drilling segment 43-1, 43-2 having inner lateral surfaces 48-1, 48-2 which are formed as a portion of a first inner cone 54-1 or second inner cone 54-2. Alternatively, a drill bit according to the invention can have a first drilling segment having an inner lateral surface which is formed as a portion of an inner cone, and a second drilling segment having an inner lateral surface which is formed as a portion of a cylinder. For this purpose, in the drill bit 20 of FIG. 2A, the first drilling segment 23-1 is replaced by the first drilling segment 43-1 of the drill bit of FIG. 4A, or, in the drill bit 40 of FIG. 4A, the second drilling segment 43-2 is replaced by the second drilling segment 23-2 of the drill bit 20 of FIG. 2A.

[0061] FIG. 6 shows a third embodiment of a drill bit 60 according to the invention which has a drilling shaft 61 and a cutting portion having a first drilling segment 63-1 and a second drilling segment 63-2, in a view of the upper side of the drilling segments 63-1, 63-2.

[0062] The first drilling segment 63-1 is designed to be identical to the first drilling segment 23-1 of the drill bit 20 or to the first drilling segment 43-1 of the drill bit 40. The drill bit 60 differs from the drill bit 20 of FIG. 2A and the drill bit 40 of FIG. 4A in that the first drilling segment 63-1 and second drilling segment 63-2 are designed to be different. The drilling shaft 61 is designed analogously to the drilling shaft 21 of the drill bit 20 and to the drilling shaft 41 of the drill bit 40. The drilling shaft 61 comprises a cylinder having a cylinder axis which defines a longitudinal axis 64 of the drilling shaft 61.

[0063] The first drilling segment 63-1 comprises a first inner lateral surface 68-1, a first outer lateral surface 69-1, a first underside 51 and a first upper side, and the second drilling segment 63-2 comprises a second inner lateral surface 68-2, a second outer lateral surface 69-2, a second underside and a second upper side. Here, the first underside of the first drilling segment 63-1 and the second underside of the second drilling segment 63-2 are fastened to the drilling shaft 61.

[0064] The first inner lateral surface 68-1 has, perpendicular to the longitudinal axis 64 of the drilling shaft 61, a first inner distance B.sub.1(, h) from the longitudinal axis 64. Here, the first inner distance B.sub.1(, h) defines a first mathematical function which describes the profile of the first inner distance over the circumference and the height of the first drilling segment 63-1.

[0065] The first inner distance B.sub.1(, h) varies between a first minimum value B.sub.min,1 and a first maximum value B.sub.max,1 over the circumference of the first drilling segment 63-1. The first inner distance B.sub.1(, h) has a further first maximum value B.sub.max,1, wherein the first absolute minimum value B.sub.min,1 is arranged between the two first maximum values in the circumferential direction . The first inner distance B.sub.1(, h) follows a strictly monotonic profile in the region of the first absolute minimum value B.sub.min,1 in the plane perpendicular to the longitudinal axis 64.

[0066] The first inner lateral surface 68-1 can, like the first inner lateral surface 28-1, be formed as a portion of a first cylinder or, like the first inner lateral surface 48-1, be formed as a portion of a first inner cone which tapers in the direction of the first upper side of the first drilling segment 63-1.

[0067] The second inner lateral surface 68-2 has, perpendicular to the longitudinal axis 64 of the drilling shaft 61, a second inner distance B.sub.2(, h) from the longitudinal axis 64. Here, the second inner distance B.sub.2(, h) defines a second mathematical function which describes the profile of the second inner distance over the circumference and the height of the second drilling segment 63-2.

[0068] The second inner distance B.sub.2(, h) varies between a second minimum value B.sub.min,2 and a second maximum value B.sub.max,2 over the circumference of the second drilling segment 63-2. The second inner distance B.sub.2(, h) has a further second maximum value B.sub.max,2, wherein the second absolute minimum value B.sub.min,2 is arranged between the two second maximum values in the circumferential direction . The second inner distance B.sub.2(, h) follows a strictly monotonic profile in the region of the second absolute minimum value B.sub.min,2 in the plane perpendicular to the longitudinal axis 64.

[0069] The second inner lateral surface 68-2 can, like the second inner lateral surface 28-2, be formed as a portion of a second cylinder or, like the second inner lateral surface 48-2, be formed as a portion of a second inner cone which tapers in the direction of the second upper side of the second drilling segment 63-2.

[0070] In the exemplary embodiment of FIG. 6, the second drilling segment 63-2 differs from the first drilling segment 63-1 in that the first absolute minimum value B.sub.min,1 is less than the second absolute minimum value B.sub.min,2. This means that the second drilling segment 63-2 does not have a contact surface with respect to the drill core 75. The contact surface between the drilling segments 63-1, 63-2 and the drill core 75 is limited to the region of the first absolute minimum value B.sub.min,1.