Drill bit with an exchangeable cutting portion

Abstract

A drill bit is disclosed. The drill bit has a cutting portion having an annular portion, where the annular portion has a first end on which is disposed a cutting element and a second end that includes an outer insertion element and a stop shoulder. The drill bit has a drill shaft portion having a cylindrical drill shaft, where the drill shaft has an inner insertion element with an end face on a side of the drill shaft facing the cutting portion. The outer insertion element and the inner insertion element together form a plug connection in an insertion direction that is parallel to the axis of rotation and the insertion elements are connectable to each other via a pin element that is movable into a slot-shaped recess. The pin element is attached to an outside of the inner insertion element and the outer insertion element has the slot-shaped recess.

Claims

1. A drill bit that is rotatable in a rotational direction around an axis of rotation, comprising: a cutting portion having an annular portion, a cutting element, an outer insertion element, and an annular limit stop shoulder, wherein the cutting element is disposed on a first end of the annular portion, wherein the outer insertion element is disposed on a second end of the annular portion, and wherein the annular limit stop shoulder is disposed at a transition from the annular portion to the outer insertion element; and a drill shaft portion having a cylindrical drill shaft and an inner insertion element, wherein the inner insertion element is connected to the cylindrical drill shaft on a first end of the inner insertion element and has an end face on a second end of the inner insertion element facing the cutting portion; wherein the outer insertion element and the inner insertion element together form a plug connection in an insertion direction that is parallel to the axis of rotation and wherein the outer insertion element and the inner insertion element are connectable to each other via a pin element that is movable into a slot-shaped recess; wherein the pin element is attached to an outside of the inner insertion element, wherein the slot-shaped recess is formed in the outer insertion element, and wherein in a connected state of the drill bit, the end face of the inner insertion element is in contact with the annular limit stop shoulder of the cutting portion; and wherein a lug is disposed on the outside of the inner insertion element, wherein the outer insertion element has a groove, and wherein the lug and the groove form a form-fitting connection in a connected state in an axial direction.

2. The drill bit according to claim 1, wherein a length of the inner insertion element is greater than a length of the outer insertion element.

3. The drill bit according to claim 2, wherein the length of the outer insertion element is at least 18 mm.

4. The drill bit according to claim 3, wherein the length of the outer insertion element is no greater than 28 mm.

5. The drill bit according to claim 1, wherein the outer insertion element and the inner insertion element are formed as a ring, wherein a difference between an inside diameter of the outer insertion element and an outside diameter of the inner insertion element is greater than 0.11 mm.

6. The drill bit according to claim 1, wherein one or more additional pin elements are attached to the outside of the inner insertion element, wherein the outer insertion element has one or more additional slot-shaped recesses, and wherein a number of the slot-shaped recesses is greater than or equal to a number of the pin elements.

7. The drill bit according to claim 1, wherein the pin element has a pin height perpendicular to the axis of rotation that is between 68% and 89% of a width of the drill shaft.

8. The drill bit according to claim 1, wherein the pin element is a circular cylinder with a pin radius that is between 2.5 and 5 mm.

9. The drill bit according to claim 1, wherein the slot-shaped recess has a cross-slot perpendicular to the axis of rotation and wherein the cross-slot is connected to an upper edge of the outer insertion element via a connecting slot.

10. The drill bit according to claim 9, wherein the cross-slot has a distance parallel to the axis of rotation from an edge of the annular portion of at least 3 mm.

11. The drill bit according to claim 10, wherein the distance is no greater than 5 mm.

12. The drill bit according to claim 9, wherein a height of the connecting slot parallel to the axis of rotation is at least 10 mm.

13. The drill bit according to claim 12, wherein the height of the connecting slot parallel to the axis of rotation is no greater than 13 mm.

14. The drill bit according to claim 9, wherein the cross-slot has a follower region and a securing region, wherein the follower region is disposed on a first side of the connecting slot and wherein the securing region is disposed on a second side of the connecting slot.

15. The drill bit according to claim 14, wherein a width of the follower region is no less than a radius of the pin element plus 1.5 mm.

16. The drill bit according to claim 15, wherein the width of the follower region is no greater than the radius of the pin element plus 3 mm.

17. The drill bit according to claim 14, wherein a width of the follower region and a width of the securing region are equal.

18. The drill bit according to claim 14, wherein a width of the follower region is greater than a width of the securing region.

19. The drill bit according to claim 1, wherein the annular portion has a guide portion, wherein the guide portion is in flush contact with an outer edge, an inner edge, or the outer edge and the inner edge of the cutting element parallel to the longitudinal axis.

20. The drill bit according to claim 19, wherein a length of the guide portion is less than 4 mm parallel to the axis of rotation.

21. The drill bit according to claim 1, wherein the lug is disposed between the pin element and the drill shaft in the axial direction and wherein the groove is disposed at a height of the slot-shaped recess in the axial direction.

22. The drill bit according to claim 1, wherein the groove is ring-shaped and is disposed in a plane perpendicular to the axis of rotation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A, B illustrate a drill bit according to the invention, having a cutting portion and a drill shaft portion in an unconnected state (FIG. 1A) and in a connected state (FIG. 1B);

(2) FIGS. 2A, B illustrate the drill shaft portion of the drill bit shown in FIG. 1 in a longitudinal section along the sectional plane A-A in FIG. 1A (FIG. 2A) and the insertion element of the drill shaft portion in an enlarged diagram (FIG. 2B);

(3) FIGS. 3A, B illustrate the cutting portion of the drill bit shown in FIG. 1 in a longitudinal section (FIG. 3A) and the insertion element of the cutting portion in an enlarged diagram (FIG. 3B);

(4) FIGS. 4A, B illustrate the cutting portion in an a longitudinal section along the sectional plane B-B in FIG. 1A (FIG. 4A) and along the sectional plane C-C in FIG. 1B (FIG. 4B); and

(5) FIG. 5 illustrates another embodiment of a drill bit according to the invention having a cutting portion and a drill shaft portion which are connected in the axial direction by means of an additional form-fitting connection as a withdrawal safety device.

DETAILED DESCRIPTION OF THE DRAWINGS

(6) FIGS. 1A, B show a drill bit 10 according to the invention with a cutting portion 11 that is connected by a releasable plug-twist connection to a drill shaft portion 12. FIG. 1A shows the cutting portion 11 and the drill shaft portion 12 in the unconnected state with the plug-twist connection opened, and FIG. 1B shows the cutting portion 11 and the drill shaft portion 12 in the connected state with the plug-twist connection closed.

(7) The cutting portion 11 comprises an annular portion 13, which is connected to a plurality of cutting elements 14 at its first end and has a first insertion element 15 at its second end. The first insertion element is designed as an outer insertion element 15. The cutting elements 14 are welded, soldered or screwed onto the annular portion 13 or they are attached to the annular portion 13 by some other suitable form of attachment. The cutting portion 11 may also have a single cutting element, which is designed as a cutting sleeve and is connected to the annular portion 13, in addition to having a plurality of cutting elements 14.

(8) The drill shaft portion 12 comprises a cylindrical drill shaft 16 having a second insertion element 17 on an end facing the cutting portion 11 and connected to a receiving portion 18 on an end facing away from the cutting portion 11. The second insertion element is designed as the inner insertion element 17. The receiving portion 18 comprises a cover 19 and an insertion end 20. The drill bit 10 is fastened in the tool receptacle of a core drilling device by means of the insertion end 20. During drilling operation the drill bit 10 is driven by the core drilling device about an axis of rotation 22 in a direction of rotation 21 and is advanced into the substrate to be worked in a drilling direction 23 parallel to the axis of rotation 22. The axis of rotation 22 runs coaxially with a longitudinal axis of the drill shaft 16 and a longitudinal axis of the annular portion 13. The drill bit 10 has a circular cross section perpendicular to the axis of rotation 22. Alternatively, drill bits according to the invention may have other suitable cross sections, for example, a polygonal cross section.

(9) The cutting portion 11 is connected to the drill shaft portion 12 by way of a plug-twist connection 24 (FIG. 1B). Connections of two connecting elements which form a plug connection in at least one direction are referred to as plug-twist connections, such that the connecting elements plugged together are additionally connected by a twist connection. The plug connection and the twist connection may be closed one after the other or simultaneously. The plug-twist connection 24 must connect the cutting portion 11 and the drill shaft portion 12 to one another in all directions of translation and rotation. The cutting portion 11 must be secured against translation in the drilling direction 23, opposite the drilling direction 23 and radially to the drilling direction 23 as well as being secured against rotation about the axis of rotation 22.

(10) The cutting portion 11 is plugged together with the outer insertion element 15 onto the inner insertion element 17 of the drill shaft portion 12, wherein the insertion direction of the plug connection runs parallel to the axis of rotation 22. The plug connection of the insertion elements 15, 17 secures the cutting portion 11 against translational movements opposite the drilling direction 23 and radially to the axis of rotation 22. The cutting portion 11 must be secured by means of the rotational connection of the insertion elements 15, 17 to prevent rotation about the axis of rotation 22 and to prevent translational movements in the drilling direction 23. The rotational connection comprises six pin elements 25, which are inserted into six slot-shaped recesses 26. The six pin elements 25 are attached to the outside 27 of the inner insertion element 17, and the six slot-shaped recesses 26 are provided in the outer insertion element 15. The pin elements 25 and the recesses 26 are arranged so that they are distributed uniformly around the axis of rotation 22. Due to the uniform distribution, there is no assignment between the pin elements 25 and the recesses 26, and a pin element 25 can be inserted into any recess 26.

(11) The cutting portion 11 can be connected easily and quickly to the drill shaft portion 12 by the operator. To do so, the cutting portion 11 together with the outer insertion element 15 is plugged onto the inner insertion element 17 of the drilling shaft portion 12 so that the pin elements 25 are arranged in the slot-shaped recesses 26. The cutting portion 11 is moved in the plug-in direction and then is secured by rotation about the axis of rotation 22.

(12) FIGS. 2A, B show the drill shaft portion 12 of the drill bit 10 according to the invention in a longitudinal section along the sectional plane A-A in FIG. 1A. FIG. 2A shows the drill shaft portion 12, and FIG. 2B shows the second insertion element 17, which is designed as an internal insertion element, in an enlarged diagram.

(13) The drill shaft portion 12 comprises the cylindrical drill shaft 16 and the inner insertion element 17 which are designed monolithically. As an alternative to the monolithic design, the inner insertion element 17 may be designed as a separate part and is then connected to the drill shaft 16. The pin elements 25 are attached to the outside 27 of the inner insertion element 17. The pin elements 25 and the inner insertion elements 17 may be manufactured from different materials and connected to one another or they are made of the same material, and the pin elements 25 are created by molding methods such as embossing or interpenetrating.

(14) The drill shaft 16 has an outside diameter d.sub.a and an inside diameter d.sub.i perpendicular to the axis of rotation 22 and a drill shaft width b, b=(d.sub.A?d.sub.I)/2. The inner insertion element 17 has an outside diameter d.sub.2,a and an inside diameter d.sub.2,i perpendicular to the axis of rotation 22. The inside diameter d.sub.2i of the inner insertion element 17 corresponds to the inside diameter d.sub.i of the drill shaft 16, and the outside diameter d.sub.2a of the inner plug element 17 is smaller than the outside diameter d.sub.a of the drill shaft 16, so that an annular step is formed on the outside of the drill shaft portion 12.

(15) FIG. 2B shows the inner insertion element 17 in an enlarged diagram. The inner insertion element 17 comprises an outer lateral surface 31, an inner lateral surface 32 and an end face 33. There is an annular stop shoulder 34 at the transition from the drill shaft 16 to the inner insertion element 17.

(16) The inner insertion element 17 has a length l parallel to the axis of rotation 22 and a width b.sub.2 perpendicular to the axis of rotation 22. The pin element 25 has a circular cylindrical shape with a pin radius R.sub.z parallel to the axis of rotation 22 and a pin height H.sub.z perpendicular to the axis of rotation 22. The lower edge of the pin element 25 runs parallel to the axis of rotation 22 at a distance A.sub.z from the end face 33 of the inner insertion element 17.

(17) FIGS. 3A, B show the cutting portion 11 of the drill bit 10 shown in FIG. 1 in a longitudinal section parallel to the plane of the drawing in FIG. 1A. FIG. 3A shows the entire cutting portion 11, and FIG. 3B shows a slot-shaped recess 26 in the outer insertion element 15 in an enlarged diagram.

(18) The cutting portion 11 comprises the annular portion 13, the cutting elements 14 and the outer insertion element 15. The annular portion 13 and the outer insertion element 15 are designed to be monolithic in the embodiment shown here. As an alternative to the monolithic design, the outer insertion element 15 may be designed as a separate part and then connected to the annular portion 13.

(19) The cutting elements 14 are arranged in a ring shape around the annular portion 13 in a plane perpendicular to the axis of rotation 22, and each has an outer edge 41 and an inner edge 42. The outer edges 41 of the cutting elements 14 form an outer circle with an outside diameter D.sub.a and the inner edges form an inner circle with an inside diameter D.sub.i. The cutting elements 14 create a borehole in the substrate having a borehole diameter that corresponds to the outside diameter D.sub.a. In the interior of the drill bit 10, a drill core with a drill core diameter corresponding to the inside diameter D.sub.i is formed. The outer insertion element 15 has an outside diameter d.sub.1,a and an inside diameter d.sub.1,i perpendicular to the axis of rotation 22. The outside diameter d.sub.1,a of the outer insertion element 15 is smaller than the outside diameter D.sub.a, and the inside diameter d.sub.1,i of the outer insertion element 15 is larger than the inside diameter D.sub.i.

(20) FIG. 3B shows a slot-shaped recess 26 in the outer insertion element 15 in an enlarged diagram. The slot-shaped recess 26 consists of a cross-slot 43, which is arranged perpendicular to the axis of rotation 22, and a connecting slot 44, which is arranged parallel to the axis of rotation 22. The connecting slot 44 connects the cross-slot 43 to an upper edge 45 of the outer insertion element 15, which is designed to be open on the upper edge 45 in the region of the connecting slot 44. The pin elements 25 are inserted into the slot-shaped recess 26 through the connecting slot 44 and are shifted into the cross-slot 43 by turning them around the axis of rotation 22. The torque is transferred from the pin element 25 to the outer insertion element 15 in the cross-slot 43.

(21) The outer insertion element 15 has a length l.sub.1 parallel to the axis of rotation 22 and a width b.sub.1 perpendicular to the axis of rotation 22 (FIG. 4A). The cross-slot 43 has a width B perpendicular to the axis of rotation 22 and a height H parallel to the axis of rotation 22. The connecting slot 44 has a width b perpendicular to the axis of rotation 22 and a height h parallel to the axis of rotation 22. The width b of the connecting slot 44 is greater than the pin diameter 2R.sub.z of the pin elements 25, so that the pin elements 25 can be inserted easily into the connecting slot 44. The insertion of the pin elements 25 can be facilitated by an insertion bevel 46 on the upper edge 45. The height h of the connecting slot 44 is selected, so that the cutting portion 11 has a sufficient durability with respect to tensile loads when loosening a jammed drill bit. If the selected height h is too small, there is the risk of deformation of the outer insertion element 15.

(22) The cross-slot 43 has a lower distance A.sub.1,u from the annular portion 13 and an upper distance from the upper edge 45 parallel to the axis of rotation 22, wherein the upper distance corresponds to the height h of the connecting slot 44. The lower distance A.sub.1,u from the annular portion 13 is selected, so that, due to the drill stand, the cutting portion 11 has a sufficient durability with respect to tensile loads. If the selected lower distance A.sub.1,u is too small, there is the risk of deformation of the outer insertion element 15.

(23) The cross-slot 43 comprises a follower region 47, a securing region 48 and a transitional region 49. The follower region 47 and the securing region 48 are arranged on different sides of the connecting slot 44, based on the direction of rotation 21 of the drill bit 10, wherein the follower region 47 and the securing region 48 are connected to the connecting slot 44 by means of the transitional region 49. The follower region 47 is arranged on the side of the connecting slot 44 facing the direction of rotation 21, and the securing region 48 is arranged on the side facing away from the direction of rotation 21. The transfer of torque from the drill shaft portion 12 to the cutting portion 11 takes place by way of the pin elements 25 and the follower region 47. The securing region 48 reduces the risk that the plug-twist connection 24 between the drill shaft portion 12 and the cutting portion 11 is opened unintentionally when loosening a jammed drill bit out of the substrate.

(24) The follower region 47 has a width B.sub.1 perpendicular to the axis of rotation 22, the height of the follower region 47 corresponds to the height H of the cross-slit 43. The securing region 48 has a width B.sub.2 perpendicular to the axis of rotation 22 and the height of the securing region 48 corresponds to the height H of the cross-slot 43. The widths B.sub.1, B.sub.2 of the follower region 47 and of the securing region 48 are selected so that the pin elements 25 are held in the cross-slot 43 when there is a tensile load and do not break out.

(25) FIGS. 4A, B show the cutting portion 11 of the drill bit 10 according to the invention in a longitudinal section along the sectional plane B-B in FIG. 1A (FIG. 4A) and along the cutting plane C-C in FIG. 1B (FIG. 4B). The cutting portion 11 comprises the annular portion 13, the cutting elements 14 and the outer insertion element 15.

(26) The cutting elements 14 are constructed of a matrix zone 51 and a neutral zone 52, wherein the matrix zone 51 consists of a powder material mixed with abrasive particles and the neutral zone 52 consists of a weldable powder material without any abrasive particles. The two-part design of the cutting elements 14 is necessary to be able to weld the cutting elements 14 to the annular portion 13. The annular portion 13 forms a flush connection to the inner edge 42 of the cutting element 14 and has a setback 53 with respect to the outer edge 41 of the cutting element 14.

(27) The annular portion 13 comprises a guide portion 54 and a core removal section 55 on the inside. The core removal section 55 has an inside diameter which decreases in the direction of the cutting elements 14, and the inclined face of the core removal section 55 supports the removal of the drill core. The guide portion 54 is in flush contact with the cutting element 14 and forms a guide for the cutting elements 14 during drilling, and the guide portion 54 has a length m parallel to the axis of rotation 22. As an alternative to guidance on the inside of the drill bit 10, the guide portion may also be arranged on the outside or on the outside and inside. The length m of the guide portion 54 is smaller than 4 mm. A guide portion smaller than 4 mm causes little or no hindrance to the supply of a cooling and rinsing medium.

(28) The outer insertion element 15 comprises an outer lateral surface 56, an inner lateral surface 57 and an end face 58. At the transition from the annular portion 13 to the outer insertion element 15 there is an annular stop shoulder 59. With the cutting portion 11 shown in FIG. 4A, the outer insertion element 15 additionally has an inclined outer face 60 whose diameter increases in the direction of the cutting elements 14.

(29) FIG. 4B shows the cutting portion 11 and the drill shaft portion 12 which are connected via the plug-twist connection 24, wherein the pin element 25 is arranged in the securing region 48 of the cross-slot 43. In the connected state the drill shaft portion 12 is in contact with the stop shoulder 59 of the cutting portion 11 at its end face 33. Between the inner lateral surface 57 of the outer insertion element 15 and the outer lateral surface 31 of the inner insertion element 17 there is a radial clearance 61. The different ?.sub.radial between the inside diameter d.sub.1,i of the outer insertion element 15 and the outside diameter d.sub.2,a of the inner insertion element 17 is larger than 0.11 mm for all diameters. The length l.sub.2 of the inner insertion element 17 is greater than the length l.sub.1 of the outer insertion element 15, so that an axial clearance 62 of the clearance width ?.sub.axial is formed between the end face 58 of the outer insertion element 15 and the stop shoulder 34 of the inner insertion element 17. The radial clearance 61 and the axial clearance 62 ensure that the end face 33 of the inner insertion element 17 is in contact with the stop shoulder 59 of the outer insertion element 15 and during drilling there is a defined transfer of force from the drill shaft portion to the cutting portion.

(30) FIG. 5 shows another embodiment of a drill bit 70 according to the invention with a cutting portion 71 and a drill shaft portion 72. The drill bit 70 differs from the drill bit 10 in that an additional form-fitting connection is provided in the axial direction, making it difficult for the cutting portion 71 to be loosened unintentionally from the drill shaft portion 72.

(31) The cutting portion 71 has a first connecting device 73 in addition to the outer insertion element 15 and the slot-shaped recesses 26, and the drill shaft portion 72 has a second connecting device 74 in addition to the inner insertion element 17 and the pin elements 25. The first connecting device 73 comprises a groove 75, which is arranged on the inside 57 of the outer insertion element 15. The second connecting device 74 comprises a lug 76, which is arranged on the outside 28 of the inner insertion element 17 and extends radially outward. In the connected state of the drill bit 70, the lug 76 and the groove 75 form a form-fitting connection between the cutting portion 71 and the drill shaft portion 72 in the axial direction, i.e., in the drilling direction 23. The cutting portion 71 is secured by means of the lug 76 and the groove 75 to prevent the drill shaft portion 72 from being pulled away from the cutting portion 71.

(32) The lug 76 is arranged between the pin elements 25 and the drill shaft 16 in the axial direction. To remove the drill shaft portion 72 from the cutting portion 71, a force is exerted on the end face of the outer insertion element 15 with the help of a tool. By the action of the force, the elastic section of the outer plug element 15 is deflected and the form-fitting connection between the lug 76 and the groove 75 can be released. The greater the distance between the lug 76 and the end face 33 of the inner insertion element 17, the greater is the deflection of the elastic section. The groove 75 is designed in a ring shape and arranged in a plane perpendicular to the axis of rotation 22. A groove with an annular design, arranged in the axial direction at the height of the slot-shaped recesses 26, supports the spring action of the sections of the outer insertion element 15 between the slot-shaped recesses 26.

(33) The holding force which the lug 76 and the groove 75 withstand can be adapted via the geometry of the lug 76 and the groove 75. The engagement of the lug 76 in the groove 75 should be as convenient as possible for the operator and an incline facilitates this engagement. For example, the radial height of the lug 76, i.e., its height in the radial direction, the contact area between the lug 76 and the inner insertion element 17 and the angle of inclination are all suitable as geometric parameters for adjusting the holding force.