DRILLING SCREW

Abstract

A drilling screw, particularly a two-component steel screw, having a head part and a cutting part, wherein the head part is made of a corrosion-resistant material and comprises a screw head and a shank section, and wherein the cutting part is made of a hardenable material, a cemented carbide, or a technical ceramic, characterized in that an intermediate section made of a corrosion-resistant material is disposed between the shank section and the cutting part, which intermediate section is non-releasably connected to the shank section, wherein the cutting part comprises a peg-like projection or a cup-like recess and wherein the intermediate section comprises a cup-like recess or a peg-like projection, wherein the cup-like recess or a peg-like projection has an engagement profile with multiple engagement sections in its cross section, wherein said peg-like projection is disposed in the cup-like recess and wherein said intermediate section is permanently connected to the cutting part by means of impact extrusion, such that the peg-like projection of the cutting part axially undercuts at least sections of the intermediate section in the region of the cup-like recess or such that the peg-like projection of the intermediate section axially undercuts at least sections of the cutting part in the region of the cup-like recess.

Claims

1. A drilling screw, having a head part and a cutting part, wherein the head part is made of a corrosion-resistant material and comprises a screw head and a shank section, and wherein the cutting part is made of a hardenable material, a cemented carbide, or a technical ceramic, characterized in that an intermediate section made of a corrosion-resistant material is disposed between the shank section and the cutting part, which intermediate section is non-releasably connected to the shank section, wherein the cutting part comprises a peg-like projection or a cup-like recess and wherein the intermediate section comprises a cup-like recess or a peg-like projection, wherein the cup-like recess or a peg-like projection has an engagement profile with multiple engagement sections in its cross section, wherein said peg-like projection is disposed in the cup-like recess and wherein said intermediate section is permanently connected to the cutting part by means of impact extrusion, such that the peg-like projection of the cutting part axially undercuts at least sections of the intermediate section in the region of the cup-like recess or such that the peg-like projection of the intermediate section axially undercuts at least sections of the cutting part in the region of the cup-like recess.

2. The drilling screw according to claim 1, characterized in that the peg-like projection completely fills the cup-like recess or the cup-like recess completely encompasses the peg-like projection.

3. The drilling screw according to claim 1, characterized in that the cutting part is hardened or consists of a hard material and comprises a drill tip.

4. The drilling screw according to claim 3, characterized in that the cutting part comprises a core hole, which leads into the drill tip.

5. The drilling screw according to claim 1, characterized in that the cutting part is made of materials selected from the following group: a high-speed steel (HSS), a heat-treated steel, a cemented carbide, and a technical ceramic.

6. The drilling screw according to claim 1, characterized in that the head part and the intermediate section are made of a stainless steel.

7. The drilling screw according to claim 1, characterized in that the engagement profile is designed as one of the following: a Torx, Torx plus, hexagon, multi-tooth, gearing, and a cross.

8. A method for manufacturing a drilling screw, comprising a head part made of a corrosion-resistant material and having a screw head and a shank section, a cutting part made of a hardenable or hard material, and an intermediate section (16) made of a corrosion-resistant material and disposed between the shank section and the cutting part, the method comprising the following steps: Pressing a cup-like recess of a predetermined depth into the intermediate section or molding a peg-like projection of a predetermined length onto the intermediate section; Producing the cutting part with a peg-like projection or pressing in a cup-like recess into the cutting part; wherein an engagement profile with engagement sections is pressed in or molded on during pressing in the cup-like recess or the peg-like projection; Inserting the projection into the recess and connecting the intermediate section and the cutting part by means of impact extrusion, such that the peg-like projection completely fills out the cup-like recess or the peg-like projection is completely encompassed by the cup-like recess; Welding together the shank section and the intermediate section connected to the cutting part.

9. The method according to claim 8, characterized in that the cup-like recess is pressed into the intermediate section or into the cutting part at an area ratio of about 20% to about 75% relative to the cross-sectional area of the intermediate section.

10. The method according to claim 8, characterized in that the peg-like projection is produced in a circular cylindrical shape or with an engagement profile.

11. The method according to claim 8, characterized in that the intermediate section and the cutting part are brought into axial alignment before being connected.

12. The method according to claim 8, characterized in that the shank section and the intermediate section which is connected to the cutting part are brought into axial alignment before being connected.

13. The method according to claim 8, characterized in that the shank section, the intermediate section, and the cutting part are rolled straight after welding and a thread is then rolled onto the shank section, the intermediate section, and the cutting part.

14. The method according to claim 8, characterized in that manufacturing the cutting part or manufacturing the intermediate section and connecting with the intermediate section or cutting part are performed in a multi-stage press.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further details and advantageous further developments of the invention can be derived from the description below, in which the embodiments of the invention shown in the figures are described and explained in more detail.

[0034] Wherein:

[0035] FIG. 1 shows a drilling screw according to the invention;

[0036] FIG. 2 shows an intermediate section for the drilling screw according to FIG. 1;

[0037] FIG. 3 shows a cutting part for the drilling screw according to FIG. 1;

[0038] FIG. 4 shows an intermediate section and cutting part of the drilling screw according to FIG. 1 in flush alignment prior to an impact extrusion process;

[0039] FIG. 5 shows a detailed view of an intermediate section and a cutting part at the beginning of an impact extrusion process;

[0040] FIG. 6 shows a detailed view of an impact extruded connection after an impact extrusion process;

[0041] FIG. 7 shows a cup-like recess of the intermediate section according to FIG. 2; and

[0042] FIGS. 8 to 13 show further detailed views of embodiments according to the invention.

DETAILED DESCRIPTION

[0043] FIG. 1 shows a drilling screw 10 designed as a two-component steel screw, wherein the drilling screw 10 comprises a head part 12 and a cutting part 14. An intermediate section 16 is disposed in axial alignment with a central longitudinal axis 18 of the drilling screw between the head part 12 and the cutting part 14. The head part 12 further comprises a screw head 20 and a shank section 22. The intermediate section 16 and the cutting part 14 are connected to one another in the region of a joint 24 by means of an impact extrusion process the intermediate section 16, which is connected by impact extrusion to the cutting part 14, is further non-releasably connected to the head part 12 in the region of the shank section 22 in the region of a joint 25. The head part 12 and the intermediate section 16 are made of a stainless steel, wherein the cutting part is made of a hardenable material, a cemented carbide, or a technical ceramic.

[0044] Since the head part 12 and the intermediate section 16 are preferably made of an identical material, the head part 12 and the intermediate section 16 can be welded together easily and securely in the region of the joint 25.

[0045] FIG. 2 shows the intermediate section 16 of the drilling screw 10 shown in FIG. 1. The intermediate section 16 is disposed concentrically with the central longitudinal axis 18. The intermediate section 16 comprises a cup-like recess 26. This cup-like recess 26 has a depth 28, which extends in the axial direction, that is, in the direction of the central longitudinal axis 18. The cup-like recess 26 further has a diameter 30 in FIG. 2. The intermediate section 16 is shaped as a circular cylinder and has a diameter 32. The cup-like recess 26 is preferably provided to the intermediate section 16 using a pressing process. Advantageously, the cup-like recess 26 comprises an engagement profile 70 shown in FIG. 7, which will be described and explained in more detail with reference to FIG. 7.

[0046] FIG. 3 shows cutting part 14 of the drilling screw 10 shown in FIG. 1. The cutting part 14 has a diameter 34, which approximately corresponds to the diameter 32 of the intermediate section 16. The cutting part 14 comprises a peg-like projection 36. The peg-like projection 36 and the cutting part 14 are aligned concentrically with the central longitudinal axis 18. The cutting part 14 has a diameter 38 in the region of the peg-like projection 36. Furthermore, the peg-like projection 36 has a length 40 in the direction of the central longitudinal axis 18.

[0047] The length 40 of the peg-like projection 36 is greater than the depth 28 of the cup-like recess 26 of the intermediate section 16. The diameter 38 of the peg-like projection 36 is smaller than the smallest diameter 30 of the cup-like recess 26.

[0048] This is clearly visible in FIG. 4. FIG. 4 shows an intermediate section 16 and a cutting part 14, wherein the intermediate section 16 and the cutting part 14 are disposed in axial alignment with the central longitudinal axis 18. The peg-like projection 36 of the cutting part 14 is inserted into the cup-like recess 26 of the intermediate section 16. The peg-like projection 36 can be inserted into the cup-like recess 26 in the direction of the arrow 42. It is clearly visible that the peg-like projection 36 has a length 40 which is greater than the depth 28 of the cup-like recess 26. It is further apparent that the cup-like recess 26 has a greater diameter 30 than the diameter 38 of the peg-like projection 36. FIG. 4 shows the intermediate section 16 and the cutting part 14 prior to performing the impact extrusion process.

[0049] FIG. 5 shows an enlarged part of an intermediate section 16, wherein the peg-like projection 36 of the cutting part 14 is inserted in the cup-like recess 26 of the intermediate section 16. The two parts, that is, the intermediate section 16 and the cutting part 14, are disposed in a die 44 of a multi-stage press and rest against a circumferential surface 46 of the die 44. FIG. 5 shows the intermediate section 16 and the cutting part 14 at the beginning of an impact extrusion process. The operating direction of the machine is indicated by the arrow 48. If the cutting part 14 is moved further in the direction of the arrow 48 beyond the position shown in FIG. 4, an end face 50 of the peg-like projection 36 at least partially penetrates into a bottom surface 52 of the cup-like recess 26. Since further axial deflection in the direction of the arrow 48 is limited by the bottom 52 of the cup-like recess 26, material of the peg-like projection 36 can flow radially outwards, that is, transversely to arrow 48, in the direction of the arrow 54 into a void 56 between the intermediate section 16 and the peg-like projection 36 of the cutting part 14.

[0050] FIG. 6 shows an enlarged part of an impact extruded connection at the end of the impact extrusion process. The intermediate section 16 and the cutting part 14 of the drilling screw 10 are still disposed in the die 44 of a multi-stage press and rest against the circumferential surface 46 of said die. It is clearly visible what the extrusion process in the direction of the arrow 54 causes: Material of the peg-like projection 36 can flow transversely to the operating direction of the press, that is, transversely to the direction indicated by the arrow 48. The material flows into the void 56 shown in FIG. 5 and fills it completely.

[0051] Movement of a side wall 58 of the intermediate section 16, which forms the cup-like recess 26, is limited by the circumferential surface 46 of the die 44, since the intermediate section 16 and the cutting part 14 rest against the circumferential surface 46 of the die 44. At the end of the impact extrusion process, the peg-like projection 36 completely fills the cup-like recess 26.

[0052] As can be seen in FIG. 6, the peg-like projection 36 then has a bulge 58. The peg-like projection 36 has a diameter 62 in the region of this bulge 60 after the impact extrusion process. The peg-like projection 36 further has a diameter 66 in the transitional area 64 to the peg-like projection 36. The diameter 62 is greater than the diameter 66, such that the peg-like projection 36 undercuts the cup-like recess 26 in the axial direction. Pulling the peg-like projection 36 out of the cup-like recess 26 in the direction of the arrow 68 is thus no longer possible.

[0053] Since high torques must also be transmitted when producing bores or when using drilling screws 10, the cup-like recess of the intermediate section 16 comprises an engagement profile 70 shown in FIG. 7, as explained above. The engagement profile 70 is formed by circular segments 72 and engagement sections 74 disposed between said circular segments 72. Three circular segments 72 are provided in FIG. 7, such that these are arranged at an angle 76 of about 120 degrees. In the region of the circular segments 72, the cup-like recess 26 has a radius 78, which is constant in the region of the circular segments 72. In the region of the engagement sections 74, the cup-like recess 26 has a radius 80, which steadily decreases towards the centers 82 of the engagement sections 74. This steadily decreasing radius 80 defines the distance, which decreases in the region of the engagement sections 74. The engagement sections 74 are designed as inverse circular segments and can be defined by a radius 86 applied from outside.

[0054] When a cutting part 14 or a peg-like projection 36 of a cutting part 14 is inserted into the cup-like recess 26 of the intermediate section 16 for the impact extrusion process, it is particularly preferred that the diameter 38 of the peg-like projection 36 is selected smaller than, or equal to, the smallest diameter 30 of the cup-like recess 26 in the region of the centers 82 of the engagement sections 74, such that the peg-like projection 36 can easily be inserted into the cup-like recess 26. During the impact extrusion process, the material of the peg-like projection 36 can then deflect into the voids 56, which are defined by the circular segments 72. In addition to the undercuts by the bulge 60, which ensures a connection in the axial direction, torque transmission in the radial direction can be provided due to the engagement profile 70.

[0055] Like the previous explanations and figures, FIGS. 8 to 13 show the various embodiments for cases in which the material of the cutting part 14 cannot be sufficiently formed. In these cases, the filling out is almost exclusively taken over by the intermediate part 16, while the undercuts 88 and 90 on the projection-like peg 36 or in the cup-like recess 26 have already been produced by upstream processes.

[0056] FIG. 8 shows the case in which the cup-like recess 26 with engagement profile 70 as well as the undercut 88 are inserted in the cutting part 14. The projection-like peg 36 has a circular cylindrical shape and, as explained above, is longer than the depth of the cup-like recess 26, while its diameter is smaller than, or equal to, the inner diameter of the undercut 88.

[0057] The variant according to FIG. 9 represents a special case, as the manufacturing process of extruding the cup of the intermediate part 16 and pressing together the intermediate part 16 and the cutting part 14 can be performed in one step, depending on the material of the cutting part 14. The forming is in this case performed by the cutting part 14. In addition, the additional material needed for the bulge is provided in this variant by flowing in material from the upper region of the intermediate part 16. The peg-like projection 36 is in this case attached with the engagement profile 70 and undercut 90 to the cutting part 14 in an upstream process.

[0058] FIG. 10 shows a case like FIG. 5, when the engagement profile 70 and the undercut 88 were previously attached to the cup-like recess 26 on the cutting part 14.

[0059] FIG. 11 shows a case like FIG. 5, when the engagement profile 70 and the undercut 90 were previously attached to the peg-like projection 36 of the cutting part 14.

[0060] FIG. 12 shows a case like FIG. 6, when the engagement profile 70 and the undercut 88 were previously attached to the cup-like recess 26 on the cutting part 14.

[0061] FIG. 13 shows a case like FIG. 6, when the engagement geometry 70 and the undercut 90 were previously attached to the peg-like projection 36 of the cutting part 14.

[0062] After connecting the intermediate section 16 and the cutting part 14 by impact extrusion, the intermediate section 16 connected to the cutting part 14 is welded to the head part 12 in the region of the shank section 22.

[0063] Since a relatively short intermediate section 16 can be used for impact extrusion, a secure connection of cutting part 14 and intermediate section 16 can be achieved on the one hand, wherein on the other hand a reliable non-releasable connection between the intermediate section 16 and the head part 12 can be produced, since the materials of the intermediate section 16 and the head part 12 are of the same type. The screw length can then preferably be defined by defining the length of the shank section 22 of the head part 12.