EP3310513A1

EP3310513A1 - Drill bit and production method

Info

Publication number: EP3310513A1
Application number: EP16730794.1A
Authority: EP
Inventors: Guenter Domani; Carsten Peters; Florian Schroeder
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2015-06-17
Filing date: 2016-06-14
Publication date: 2018-04-25
Also published as: US20180171721A1; WO2016202768A1; CN107690364A; EP3106253A1

Abstract

A drill bit (1) has, along a drill-bit axis (6), a drilling head (2), a multi-start helix (3), made of two or more helical coils (12), and an insertion end (4). The helix (3) has a helix slope (19) and a pitch (20) in a delivery region (15). In an outlet region (17) of the helix (3), said outlet region being directed towards the insertion end (4), the helical coils (12) merge continuously, within a first portion (26), from orientation in alignment with the helix slope (19) into orientation parallel to the drill-bit axis (6). A length (30) of the portion (26) is at least quarter the pitch (20) of the delivery region (15). The helical coils (12), in a second portion (27), are oriented parallel to the drill-bit axis (6).

Description

Drill and manufacturing process

FIELD OF THE INVENTION

The present invention relates to a drill, in particular for the mining of mineral materials, and a method of manufacturing the drill.

A drill for mining mineral building materials, e.g. US 7,628,232, has a drill bit with a chisel edge. The chisel edge is beaten periodically against the building material by a striking mechanism of a hand-held power tool. The material is crushed. The drill is continuously rotated about its drill axis, whereby the bit edge is rotated by one angle from one beat to the next. The drill head may additionally break material from the borehole wall as it rotates, resulting in an approximately circular borehole. The helix is subject to high mechanical loads, especially when the user cross-loads the drill during drilling.

DISCLOSURE OF THE INVENTION

The drill according to the invention, which is preferably designed for a beating processing of mineral and reinforced building materials, has along a drill axis a drill head, a multi-turn helix of two or more helical webs and a spigot. The helix has a spiral pitch and a pitch in a conveying area. In an end region of the helix facing the insertion end, the helix webs continuously transition within a first section from an orientation with the helix pitch into an alignment parallel to the drill axis. A length of the section is at least a quarter of the pitch of the conveyor area. The spiral webs are aligned in a second section parallel to the drill axis. The run-out area with the weakly curved first section and the rectilinear second section proves to be helpful in absorbing bending loads and damping the bending stresses between the drill head and the insertion end.

An embodiment provides that a cross section in the first section and the conveying region is constant. The cross section has only one due to the helical shape of the Spiral orientation changing along the drill axis. However, the cross-section can be made to coincide completely anywhere within the first section and the conveyor section by suitable rotation about the axis. The helix thus continues into the outlet area, but increases its helical pitch and reaches 90 degrees. The spiral webs do not change their dimensions, ie height and strength. Bending stresses can be introduced evenly and do not produce local peaks.

An embodiment provides that the helical grooves in the delivery region and the first section have a constant depth.

One embodiment provides that in the first region, the helical pitch of the helical webs relative to the drill axis decreases at a rate between 0.25 degrees and 2 degrees per degree in the direction of rotation of the helix. The helix pitch preferably changes continuously over the entire length of the first region. The spiral pitch can be in the range of between 30 degrees and 70 degrees, the helical pitch in the first region continuously decreases until this helix pitch is reached. An embodiment provides that a length of the second section is between a quarter and three times the pitch of the conveyor region. The second section extends the drill unnecessarily, also has no and only a very small effect on the drilling dust. However, this second section can increase the fatigue strength of the drill. A cross section of the second portion may be constant over at least half of the second portion.

A method of making the drill may include the following steps. In a cylindrical blank a plurality of rectilinear, parallel to the axis of the blank aligned longitudinal grooves are formed. The longitudinal grooves are twisted with a twisting tool. A portion of the longitudinal grooves is twisted so that the longitudinal grooves of the blank are continuously deformed from the alignment parallel to the axis in the orientation according to the helical pitch in the conveying region. The first section has a length which corresponds to at least a quarter of the pitch. A second section of the longitudinal grooves is excluded from the twisting.

The longitudinal grooves are preferably formed by a longitudinal rollers. BRIEF DESCRIPTION OF THE FIGURES

The following description explains the invention with reference to exemplary embodiments and figures. In the figures show:

Fig. 1 a drill

2 shows a cross section through the drill in the plane II-II. FIG. 3 shows a cross section through the drill in the plane III-III. FIG. 4 shows a cross section through the drill in the plane IV-IV. FIG. 5 shows a cross section through the drill in the level VV

6 shows a cross section through the drill in the plane Vl-Vl FIG. 7 shows a longitudinal section through a straight section of the helix, FIG. 8 unrolled view of the helix FIG. 9 rolling a blank FIG. 10 shows a cross section to FIG. 9

Fig. 1 1 a halfling

Fig. 12 Reshaping of the halfling with a rotating die Fig. 13 Cross-section through a support die Fig. 14 Cross-section through a die

Identical or functionally identical elements are indicated by the same reference numerals in the figures, unless stated otherwise.

EMBODIMENTS OF THE INVENTION 1 shows an exemplary drill 1. The drill 1 has a drill head 2, a helix 3 and an insertion end 4. The drill 1 is designed for example for the mining of mineral materials, eg reinforced concrete. The drill 1 is rotated in operation in a direction of rotation 5 about its longitudinal axis 6 (drill axis). The drill 1 can be used for this purpose in a hand tool, which has a corresponding rotary drive. A striking mechanism of the power tool periodically strikes the free end 7 of the insertion end 4. The shock wave of the blows passes through the coil 3 in the direction of impact 8 to the drill head 2. The drill head 2 shatters the material. Firstly, the rotational movement ensures that the drill head 2 strikes the ground at different orientations and the borehole is evenly knocked out, and secondly causes the bored material to be removed from the borehole by means of the filament 3. The exemplary boring head 2 has four bit edges 9. The bit edges 9 converge at a tip 10 on the drill axis 6. The tip 10 is preferably the highest point in the direction of impact 8, which thus first contacts the material during drilling. The chisel edges 9 can rise in the radial direction from the outside to the drill axis 6 along the direction of impact 8. The chisel edges 9 all point in the direction of impact 8. The chisel edge 9 is formed by a facet leading in the direction of rotation and a trailing facet, both facing in the direction of impact 8. The two facets are inclined to each other, the roof angle at the chisel edge 9 is greater than 45 degrees, preferably greater than 60 degrees and less than 120 degrees. The chisel edges 9 can all be the same or be different in pairs. The drill head 2 has four demolition edges 11, which run parallel to the drill axis 6. The demolition edges 11 go over into the chisel edges 9. The demolition edges 11 define the diameter of the drill head 2. The number of chisel edges 9 and the demolition edges 11 may be selected depending on the diameter of the drill 1. For example, in a small diameter drill bit 1, the drill head 2 may have two bit edges 9, a large diameter drill bit 2 may have more than four bit edges 9 and corresponding number of breakaway edges 11.

The drill head 2 is preferably made of a sintered material, in particular tungsten carbide. The chisel edges 9 and the demolition edges 11 are preferably connected monolithically contiguous, in particular without joining zone. The helix 3 of the drill 1 has, for example four spiral webs 12. The number of helical webs 12 is preferably equal to the number of chisel edges 9. The helical webs 12 run along the drill axis 6 several times around this drill axis 6. The spiral webs 12 describe when rotating the drill 1, a cylindrical envelope 13. Each adjacent Wendelstege 12 include between them a helical groove 14, which is viewed in the radial direction by the envelope 13 as geometrically limited. The drill cuttings are transported in the helical grooves 14 through the helix webs 12 along the drill axis 6. The helix 3 has along the drill axis 6 different sections that differ to meet different requirements, differ in the pitch of the spiral webs 12. A conveyor section 15 is the dominant section and serves to convey the cuttings. The conveying region 15 typically extends over more than 80% of the length of the helix 3. The conveying region 15 can adjoin the drill head 2 directly, alternatively between the drill head 2 and the drill head 2 a fastening region 16 which meets special requirements for the attachment of the Drill head 2 is designed to the coil 3. The helix 3 terminates at its end 7 facing the insertion end 4 with an outlet region 17. The outlet region 17 merges into the cylindrical shank 18 of the insertion end 4.

In the conveying region 15 is a helical pitch 19 of the coil webs 12, ie an inclination of the coil webs 12 relative to a plane perpendicular to the drill axis 6, in a range between 35 degrees and 70 degrees. The spiral pitch 19 of the spiral webs 12 is preferably constant over the entire conveying region 15. The constant spiral pitch 19 ensures a uniform transport of the cuttings in the coil 3. The constant spiral pitch 19 causes a constant pitch 20 of the helix 3. In an alternative embodiment, the spiral pitch 19 and the pitch 20 may increase in the direction of impact 8. The helix 3 has, in the conveying area 15, a cross section (FIG. 3) which is constant along the drill axis 6 and which rotates continuously around the drill axis 6. The cross section may be described, inter alia, by the helical diameter 21, a core diameter 22, a height of the spiral webs 12 and depth 23 of the helical grooves 14, an average thickness 24 of the helical webs 12 and an average width 25 of the helical grooves 14. The helical diameter 22 is the diameter of the drill 1 or the envelope 13 of the helix 3, ie the smallest hollow cylinder, in which the helix 3 can be rotated about its drill axis 6. The core diameter 22 is the diameter of the largest circle that can be completely inscribed in the cross section of the helix 3. The average thickness 24 and the average width 25 can for Example halfway up the spiral webs 12 are determined. The core diameter 22, the height of the spiral webs 12 and the depth 23 of the helical grooves 14 remain constant along the entire conveying region 15. Preferably, the average thickness 24 of the spiral webs 12 and the average width 25 of the spiral grooves 14 remain constant along the entire conveying region 15.

In the case of the drill 1 illustrated by way of example, the conveyor region 15 merges in the direction of impact 8 into the fastening region 16. The drill head 2 is soldered or welded on the preferably flat front side of the attachment region 16. The spiral pitch 19 increases continuously in the attachment area 16. Preferably, the helical pitch 19 merges into an orientation parallel to the drill axis 6. The cross section of the helix 3 in the attachment region 16 can remain constant over its entire length. Preferably, the cross section of the attachment region 16 is congruent to the cross section in the delivery region 15. In particular, preferably the core diameter 22, the height of the spiral webs 12 and the depth 23 of the helical grooves 14 are constant.

In the outlet region 17 of the helix 3, the spiral webs 12 pass from the conveying region 15 into the cylindrical insertion end 4. The outlet region 17 is divided along the drill axis 6 into a curved section 26 and a rectilinear section 27. The curved portion 26 adjoins the conveying area 15, the rectilinear portion 27 adjoins the cylindrical insertion end 4. Fig. 4 shows a cross section through the curved portion 26 in the plane IV-IV, Fig. 5 shows a first cross section through the rectilinear portion 27 in the plane VV and Fig. 6 shows a second cross section through the rectilinear portion 27 in the plane VI-VI. The cross sections are on a scale of 2: 1 compared to the representation of FIG. 1. Fig. 7 shows a longitudinal section along the drill axis 6 through the outlet region 17bz.

The spiral webs 12 extend in the straight section 27 continuously parallel to the drill axis 6, ie with a helical pitch 19 of 90 degrees. The spiral webs 12 and the helical grooves 14 form their shape in the rectilinear portion 27. The height of the spiral webs 12 and the depth 18 of the helical grooves 14 reach the values of the conveying region 15 in the straight section 27. The adjacent shaft 18 is cylindrical with a shaft diameter 28. The helical webs 12 rise in relation to the shaft diameter 28 and the bottoms of the helical grooves 14 decrease relative to the shaft diameter 28 in the direction of impact 8 from. The helix 3 already reaches within the rectilinear section 27 the cross section, which continues in the conveying region 15. In particular, the cross section reaches the helical diameter 21, the Core diameter 22 and the depth 18 of the helical grooves 14. The height of the spiral webs 12 and the depth 18 of the helical grooves 14, for example, between 20% and 25% of the helical diameter 21. The straight section 27 preferably has a length 29, which is between a quarter and 3 times the pitch 20 in the conveying region 15, preferably the length 29 is greater than the pitch 20. The parallel to the drill axis 6 and rectilinear spiral webs 12 prove to be favorable for the stability of the drill 1 against bending loads. The bending loads occur, for example, when the user does not guide the drill 1 exclusively parallel to the drill axis 6 but, for example, due to the weight of the drilling machine, causes the drill 1 to hang transversely to the drill axis 6.

In the curved portion 26 of the outlet region 17 continuously reduces the helical pitch 19. The helical webs 12 go from the parallel to the drill axis 6 alignment in the rectilinear portion 27 in the inclined orientation of the conveyor region 15 over. The change in the spiral pitch 19 is illustrated in FIG. 8 in a rolled-up illustration of the four-turn helix 3. The length 30 of the curved portion 27 is greater than 25% of the pitch 20, preferably greater than 50% of the pitch 20. The slow adjustment of the helical pitch 19 improves the bending capacity of the helix 3. The length 30 is preferably less than 100% of the pitch 20. The change in the helical pitch 19 can be given in relation to the rotational angle of the helical web 12 in the direction of rotation 5. The helical pitch 19 preferably increases between 0.5 degrees and 2 degrees for each degree that the helical land 12 winds around the drill axis 6. The rate of change can be constant. The exemplary male end 4 of the drill 1 is designed for the use of hand tool lathe chisels. The insertion end 4 has two closed grooves 31, in which locking elements of the power tool radially engage and can slide along the drill axis 6. To the drill axis 6 longitudinally aligned webs 32 allow introduction of a torque from the power tool.

An exemplary manufacturing process begins with a rod-shaped and cylindrical blank 33. The blank preferably has a cross-sectional area that is approximately equal to or up to 50% greater than the cross-sectional area of the helix 3. The length of the blank 33 is for example approximately in the range between the length 34 of the helix 3 and the length of the drill 1. The blank 33 is preferably made of a low-alloy steel. The blank 33 is fed to a first rolling stand and formed into a halfling 34 (FIG. 9). The rolling stand has a plurality of rollers 35 which roll parallel to the axis 36 of the blank 33. The rollers 35 rotate about corresponding to the feed direction 37 and axis 36 vertical axes of rotation 38. The rollers 35 generate to the axis 36 parallel longitudinal grooves 39 in the halfling 34th

The exemplary rollers 35 have along their circumference a circular segment 40 for forming the blank 33 and a flat segment 41. The rollers 35 are aligned with the flat segments 41 facing the blank 33. The distance of the flat segments to the axis 36 is greater than the radius of the blank 33. so that the blank 33 can be inserted between the rollers 35 along the axis 36 without being reshaped. The blank 33 is pushed in between the rollers 35 for a predetermined distance. The rollers 35 are now pivoted, whereby the circular segments engage in the blank 33 and deform the blank 33. The distance between the circular segments to the axis 36 is correspondingly smaller than the radius of the blank 33. The rollers 35 drive the blank 33 in the feed direction 37 until the blank 33 falls between the rollers 35.

The longitudinal grooves 39 are introduced into a section 42 of the blank 33 to be formed. An unchanged left to leave section 43 of the blank 33 remains unprocessed. The longitudinal grooves 39 have a transition region 44 between the deformed portion 43 and the unaltered portion 43. In the transition region 44, the cross section of the deformed portion 42 continuously changes to the unaltered portion 43. The depth 45 is reached over a distance 46 which corresponds to one-fifth to one-half of the depth 45.

As an alternative to rolling, the longitudinal grooves can be introduced into the blank by means of extrusion. A die has a funnel-shaped opening. The opening tapers to a cross-section corresponding to the complementary to the first section of the halfling. The funnel shape of the die is complementary to the transition region. The matrix is thus at least as long as the transition region. The groove bottom preferably continuously increases continuously in the transition region. The shape of the groove bottom along the axis may be circular-segment-shaped or rectilinearly rising steadily.

The halfling 35 is then twisted exclusively in the deformed section 42. The twisting takes place for example with a die 47 and a Stützmatrize 48. The to be formed portion 42 of the half-ring 35 is inserted into the die 47 and the support die 48. The die 47 has a distance 49 to the unchanged portion 43. The distance may be, for example, between one to three times the later pitch 20 of the coil 3. A portion 50 of the deformed portion 42 is not twisted, but retains its straight longitudinal grooves 39. The portion 50 includes at least the transition region 44, preferably, the portion 50 is longer than the transition region. The longitudinal grooves 51 reach already in the section 50 their full depth 45. The die 47 is pivoted relative to the support die 48 in the direction of rotation 5 of the coil 3 by a pivoting angle. Subsequently, the halfling 35 is pulled out of the die 47 and the support die 48, whereby the portion 42 to be formed is twisted into the helix 3. The pivot angle is initially increased within a second section 52 continuously up to a desired value and then kept constant. The length 53 of the second section 52 is between one quarter and one pitch 20 of the helix 3 to be produced. The setpoint value for the pivoting, together with the internal geometry of the die 47, predetermines the spiral pitch 19. The helical pitch 19 changes in the second section 52 at a low rate along the drill axis 6 or the sense of rotation 5 of the helix 3. The rate is preferably in the range between 0.25 degrees and 2.0 degrees with each degree being the helix 3 around the drill axis 6 winds. For example, the helical pitch 19 changes from 90 degrees to 45 degrees within an eighth turn of the helix 3, ie at an average rate of 1.0 degrees per degree. The support die 48 has a prismatic passage opening 54 (FIG. 13). The hollow cross section of the passage opening preferably corresponds to the cross section of the deformed portion 27 of the halfling 35 or the cross section of the helix 3 correspond. The support die 48 can be slidingly slid onto the halfling 35 without reshaping it and preferably with little play. The inner surfaces of the support die 48 are preferably parallel to the axis 36.

The die 47 has a through hole 54 which allows the halfling 35 to be inserted into the die 47 without any effort (FIG. 14). The passage opening 54 comprises a prismatic cavity whose hollow cross section corresponds to the cross section of the deformed portion 27 of the halfling 35, ergo the cross section of the helix 3. The directions of rotation 5 facing away from the inner surfaces 55 are inclined so that the cross-section along the withdrawal direction 56 tapers. When swiveling the die 47 The inclined inner surfaces 55 press on the rectilinear webs 57 of the Halblings 35. The webs 57 are supported in the support die 48, whereby the webs 32 mainly within the die 47 transform. The die 47 serves only to the straight webs 32 to twist, the depth 45 of the longitudinal grooves 39 is largely retained and transmits to the depth of the helical grooves 14. The direction of rotation 5 facing inner surfaces 58 are preferably parallel to the axis 36th

The one end of the halfling 35 on the side of the die 47 rotates due to the forming relative to the support die 48 and the other end 59 of the halfling 35. A drive can assist the rotational movement.

A drill head 2, preferably of tungsten carbide, is welded or soldered to the free end 59 of the halfling 35.

Claims

Drill (1) having along a drill axis (6) a drill head (2), a multi-turn coil (3) of two or more spiral webs (12) and a spigot (4), wherein the coil (3) in a conveyor region ( 15) has a helical pitch (19) and a pitch (20), characterized in that

in a run-out region (17) of the helix (3) facing the insertion end (4), the helix webs (12) continuously transition within a first section (26) from alignment with the helix pitch (19) into alignment parallel to the drill axis (6) wherein a length (30) of the portion (26) is at least a quarter of the pitch (20) of the conveyor section (15) and the coil webs (12) are aligned in a second section (27) parallel to the drill axis (6).

Drill (1) according to claim 1, characterized in that the conveying region (15) and the first portion (26) of the outlet region (17) have a constant except for the orientation with respect to the drill axis (6) cross-section.

Drill (1) according to claim 1 or 2, characterized in that the helical grooves (14) in the conveying region (15) and the first portion (26) have a constant depth (23).

Drill (1) according to one of the preceding claims, characterized in that in the first section (26) the spiral pitch (19) of the spiral webs (12) relative to the drill axis (6) at a rate between 0.25 degrees and 2 degrees per one Degrees in the direction of rotation (5) of the coil (3) decreases.

Drill (1) according to claim 4, characterized in that in the first region, the helical pitch (19) in the direction of rotation (5) of the helix (3) continuously at the rate of a spiral pitch (19) of 90 degrees to a helical pitch (19 ) drops between 30 degrees and 70 degrees.

Drill (1) according to one of the preceding claims, characterized in that a length (29) of the second section (27) lies between one fourth and three times the pitch (20) of the conveying region (15).

7. drill (1) according to any one of the preceding claims, characterized in that a cross section of the second portion (27) over at least the half of the second portion (27) is constant.

8. drill (1) according to any one of the preceding claims, characterized in that the drill head (2) is made of a sintered hard metal.

Drill (1) according to claim 8, characterized in that the drill head (2) to the drill axis (6) parallel demolition edges (1 1).

Manufacturing method for a drill with a multi-turn helix (3) and a shank (4) with the steps:

Forming a cylindrical blank (33) by forming a plurality of rectilinear longitudinal grooves (39) aligned parallel to the axis (36) of the blank (33) in the blank (33),

Twisting of the rectilinear longitudinal grooves (39) by means of a twisting tool (47) for producing a helix (3) with a helical pitch (19) and a pitch (20) in a conveying region (15), wherein in a first section (52) of the longitudinal grooves ( 39) whose length (30) corresponds to at least a quarter of the pitch (20), the longitudinal grooves (39) of the blank (33) from the alignment parallel to the axis (36) in the orientation according to the helical pitch (19) in the conveying region (15) are continuously formed and a second portion (50) of the longitudinal grooves (51) is excluded from the twisting.

A manufacturing method according to claim 10, characterized in that a length (49) of the second portion (50) is between a quarter and three times the pitch (20) of the conveying area (15).

Manufacturing method according to claim 10 or 11, characterized in that the longitudinal grooves (39) are formed by rolling (35) along the axis (36) of the blank (33).