Screws, applications, methods and systems

Abstract

The invention relates to a screw (10) having a screw head (12) and a screw shank (16), wherein the screw head is provided with a drive structure (14) and the screw shank is provided at least sectionally with a thread, wherein the screw shank has a cylindrical holding section (20) and an end section (22) tapering towards the screw end, wherein the thread is configured as a standard thread, in particular a metric thread, in the holding section, wherein the holding section has a circular cross section, wherein the end section tapers from the holding section, wherein the end section is provided with at least two thread leads configured as self-cutting threads, wherein the end section has a multi-lobed cross section, and wherein the screw shank is hardened in the holding section and in the end section.

Description

Technical Field

[0001] This invention relates to a screw having a head and a shank, wherein the head is provided with a drive mechanism and the shank is at least partially threaded, wherein the shank has a cylindrical retaining section and a tapering end section toward the screw tip, wherein the thread in the retaining section is a standard thread, particularly a metric thread, and wherein the retaining section has a circular cross-section. The invention also relates to the application of the screw according to the invention. The invention further relates to a system and method for screwing in a screw according to the invention. Background Technology

[0002] On the one hand, screws for screwing into existing internal threads are known. Such screws have a screw head and a screw shank, wherein the screw head is provided with a drive structure and the screw shank is at least partially threaded, wherein the screw shank has a cylindrical retaining section and a tapering end section toward the screw tip, wherein the thread in the retaining section is a standard thread, especially a metric thread. The tapering end section simplifies insertion into existing internal threads.

[0003] Furthermore, the so-called self-tapping screw (Furchschraube) is known. Self-tapping screws are used to drive threads into existing holes (e.g., through-holes in sheet metal). For this purpose, the tapered end section of the screw has a self-tapping thread. Then, a retaining thread is provided in the cylindrical retaining section, which is optimized for optimal screw retention within the workpiece. Summary of the Invention

[0004] The present invention should improve a screw, an application of a screw, a system for screwing in a screw, and a method for screwing in a screw.

[0005] According to the invention, for this purpose, there is provided a screw having the features of claim 1, an application of the screw according to the invention having the features of claim 14, a system for screwing in the screw according to the invention having the features of claim 15, and a method having the features of claim 16.

[0006] This invention is based on the understanding that, unexpectedly, the same screw can be screwed not only into holes with existing internal threads but also into holes without internal threads. This provides unexpected advantages in terms of storage, dokumentation, and process reliability during the screwing process. Specifically, a screw suitable for use as a self-tapping screw is provided, having a tapering end section extending from a retaining section, wherein the end section has at least two thread leads configured as self-tapping threads, wherein the end section has a multi-leaf-shaped cross-section at least in the region of the self-tapping threads, and wherein the screw shank is hardened in the retaining section and the end section. Due to the hardened end section with a multi-leaf-shaped cross-section (having at least two thread leads of self-tapping threads and tapering from a columnar retaining section), this screw is suitable as a self-tapping screw, and can be used to tap threads into existing holes without internal threads. It is advantageous within the scope of this invention to provide two to six thread leads of self-tapping threads. Because the threaded construction in the cylindrical retaining section with a circular cross-section is a standard thread, the screw can also be screwed into existing standard internal threads. The same screw can be used regardless of whether the hole has internal threads and therefore requires a screw to be tapped into them, or whether the hole has internal threads.

[0007] First, this simplifies storage, because the same screw can be screwed not only into holes with internal threads but also into holes without internal threads. Obviously, a disadvantage here is that the screws according to the invention are more expensive to manufacture than conventional standard threaded screws. However, unexpectedly, these cost disadvantages are compensated for, and even overcompensated for, by the simplified storage possible, the ability to produce screws according to the invention in very large quantities, the simplification of the storage required during screwing, and, in particular, a significant improvement in the reliability of the screwing process. Confusion is avoided because the same screw is used to screw into both holes without internal threads and holes with internal threads. Screws are typically relatively small components, and while conventional screws with standard threads are technically distinct from self-tapping screws used for threading, they are only subtly different visually. Confusion can occur because the two types of screws have very similar external dimensions. This could even lead to an automatic screwing device designed for self-tapping screws failing to recognize that it is filled with a conventional screw with standard threads. During production, i.e., during screwing, the defect that screws with standard threads break during threading can occur. However, a significantly more serious situation arises where the screw fails to break during threading, resulting in the production of workpieces with insufficiently strong screws. The use of the same screws throughout simplifies the documentation of the screwing process. Furthermore, process reliability is significantly improved by eliminating the possibility of confusion between different screws.

[0008] In an improved embodiment of the invention, the end section is constructed as an ogivalspitze, wherein the ogivalspitze is particularly flat or rounded.

[0009] The end section preferably has the shape of a pointed arch (in other words, a pointed dome), the top of which may be flat or rounded. The transition from the top of the pointed arch to the columnar retaining section can be achieved tangentially (i.e. without visible or perceptible edges), or similarly, by constructing an edge in the profile of the screw and thus the top of the pointed arch enters the columnar retaining section non-tangentially.

[0010] In an improved embodiment of the invention, the end section is constructed as a truncated cone section, particularly having a rounded end.

[0011] In an improved embodiment of the present invention, the end segment terminates at the end face.

[0012] In the screw according to the invention, there is no need to construct a top, because the screw according to the invention is designed to be screwed into an existing hole in the workpiece.

[0013] In an improved embodiment of the invention, when viewed perpendicular to the longitudinal axis of the screw, the diameter of the end face is between 70% and 80%, particularly 75%, of the diameter of the retaining section.

[0014] In such dimensions, particularly for the preferred use of the pointed arch area, it is possible to achieve simplified hole discovery during the automated processing of the screw according to the invention, and the threading can also be carried out in a reliable and procedurally reliable manner.

[0015] In an improved embodiment of the invention, the end section has a rounded search top.

[0016] In this way, screws can be introduced into existing holes in a very simple manner, even when component tolerances are foreseeable, for example.

[0017] In an improved version of the invention, the top is constructed without threads.

[0018] This makes it easier to spot drill holes with tolerances.

[0019] In an improved embodiment of the invention, the search top has a circular cross-section.

[0020] This also makes it easier to insert screws into existing drill holes. For example, the first turn (Umdrehung) can be used to properly position the screw relative to a smooth drill hole or a drill hole with existing threads before the self-tapping threads are engaged.

[0021] In an improved version of the invention, the end section has multiple leaf-shaped cross sections only in the area of ​​the self-tapping thread.

[0022] In this way, threads can be tapped, making the screw suitable for use in smooth drilled holes without internal threads. However, very high pull-out force is achieved by retaining the section. Similarly, the circular search section in the cross-section (i.e., the area between the screw's self-tapping thread and the free end) facilitates the insertion of the screw into existing drilled holes, with or without internal threads.

[0023] In an improved embodiment of the present invention, the self-tapping thread is constructed as a circular thread in the end section.

[0024] In this way, it is easy to tap the thread, as with placing a screw. In the case of a round thread, not only the thread tip but also the thread valley is rounded, and not only the thread lead but also the core has a rounded profile (Rundprofil).

[0025] In an improved embodiment of the invention, in addition to the self-tapping thread, the end section also has an additional thread lead constructed as a circular thread.

[0026] When screwing the screw into the existing internal thread, the internal thread is thus easily visible. Circular threads can also have rounded thread tips and rounded valleys, resulting in a circular profile at the thread lead and in the core.

[0027] In an improved version of the invention, the standard thread structure in the section is maintained as a trapezoidal thread.

[0028] In this way, very good pull-out force is achieved. In other words, the thread construction is kept as a top thread with a flat valley and a top. The angle between the thread flanges is typically 60°.

[0029] In an improved embodiment of the invention, the threads on the screw shank have a continuous, imaginary envelope curve (Hüllkurve) in the side view, extending to the free end of the screw shank.

[0030] In other words, the self-tapping thread does not extend beyond the envelope curve. Instead, in the region of the radially farthest protruding area of ​​the self-tapping thread implemented with a multi-leaf cross-section, the thread tip only contacts the continuous envelope curve and does not extend beyond it.

[0031] In an improved embodiment of the invention, at least the end sections are additionally partially, and particularly inductively, hardened.

[0032] Through partial, and especially induced, hardening, at least the end section can be constructed such that it withstands mechanical and thermal loads during threading. The greatest mechanical and thermal loads occur in the region of the end section, therefore, it is generally sufficient to inducedly and partially harden the end section. In particular, only a region of the end section is partially and additionally hardened from the surface to a predetermined depth. It is not necessary to partially and additionally harden the entire cross-section of the end section, because according to the invention, the retaining section is already hardened.

[0033] In an improved version of the invention, the screw is hardened to a strength grade of 8.8, 10.9, 12.9 or to an ultra-high strength range.

[0034] These strength grades have proven extremely advantageous for screws according to the invention. Furthermore, the tapped end section can be partially and additionally hardened. The hardening method for screws according to the invention can be bainitrification or surface hardening, with subsequent tempering. In particular, bainitic structures possess high strength and very high toughness. Bainitic structures are produced in carbon steel through special cooling in a salt bath. Bainitic structures have proven extremely advantageous for screws according to the invention.

[0035] In an improved embodiment of the invention, the tensile strength of the screw is at least 800 N / mm². 2 .

[0036] For example, the screw construction according to the invention is a so-called 8.8 screw, and preferably the screw construction according to the invention is a 10.9 screw.

[0037] In an improved embodiment of the invention, the 0.2% elongation limit of the screw is at least 640 N / mm. 2 Especially at least 900 N / mm 2 Especially at least 1040 N / mm 2 .

[0038] For example, screws are constructed with a strength of 8.8 or greater, especially in the ultra-high strength range.

[0039] In an improved embodiment of the invention, before the end section terminates at the transition to the retaining section, at least the last complete thread lead of the self-tapping thread is constructed in terms of thread size as a standard thread in the retaining section.

[0040] Besides the different cross-sections, the final thread lead of the self-tapping thread corresponds to the standard thread in the retaining section in terms of thread dimensions (i.e., in terms of outer diameter and core diameter) because the retaining section has a circular cross-section and the end section has a multi-leaf cross-section. Unlike common self-tapping threads with a diameter slightly larger than the standard thread, the self-tapping thread in the screw according to the invention is not implemented with an interference fit relative to the standard thread in the retaining section. This has a significant advantage that the screw according to the invention can be screwed into existing internal threads corresponding to the standard without any problems. It has also been unexpectedly proven that, although the self-tapping thread is manufactured without an interference fit relative to the standard thread in the retaining section, the screw according to the invention can also be screwed into holes without internal threads, where tapping must therefore be done first by means of the self-tapping thread. The maximum screwing torque preset by the material and dimensions can be maintained. The thread dimensions here involve the outer diameter and core diameter, and especially the flank diameter, the thread pitch, and the flank angle. Due to the multi-leaf cross-section of the end section, the outer diameter, core diameter, and flank diameter must be measured as the maximum diameter of the final thread lead of the self-tapping thread. Only when the multi-leaf cross-section is implemented with the same thickness can the outer diameter, core diameter, and flank diameter of the final thread lead of a self-tapping thread be measured independently of the angular position. For example, the standard thread in the retaining section can be implemented as a metric or imperial thread. In the case of a metric M5 thread, the outer diameter of the standard thread in the retaining section is between 4.790 mm and 5.0 mm, referring to DIN 13-20:2000-08 / M5-4H-6G-6E. Commonly used self-tapping threads for tapping metric M5 threads are typically designated by a nominal size greater than 5.0 mm, either the outer diameter of at least one section with a tolerance range or the circumcircle of the polygonal cross-section. According to the invention, the final thread lead of the self-tapping thread, or at least the self-tapping thread at the transition between the end section and the retaining section, is implemented with an outer diameter corresponding to the standard thread (i.e., between 4.790 mm and 5.0 mm). 4.790 mm corresponds to the minimum size of an M5 screw according to tolerance class 6E.

[0041] The present invention also relates to the application of the screw according to the invention as a tapping screw in a first application case or as a screw for screwing into existing internal threads in a second application case.

[0042] Therefore, by using the screw according to the invention both as a tapping screw and as a screw screwed into existing internal threads, the same screw can be used for different applications. This simplifies warehousing, enables larger quantities of screws, simplifies the archiving of the screwing process, and, in particular, avoids defects in workpiece manufacturing that may arise from confusing different screws. By using the screw according to the invention not only as a tapping screw but also as a screw screwed into existing internal threads, potential safety-related defects in workpiece manufacturing can be avoided, and the higher manufacturing cost of the screw according to the invention compared to conventional screws with standard threads can be compensated for or even over-compensated.

[0043] The present invention allows selection of the maximum driving torque for screws according to the invention. First, it checks whether an existing hole in one or more workpieces has an internal thread. If an internal thread is present, a first maximum driving torque is selected; if no internal thread is present, a second maximum driving torque is selected, wherein the first driving torque is less than the second driving torque. In this way, screws according to the invention can be used not only for tapping internal threads but also for screwing into existing internal threads. By selecting a smaller maximum driving torque when screwing into existing internal threads compared to when tapping, it is possible to reliably determine whether the screw gets stuck or other defects occur when screwing into existing internal threads. The present invention can also reduce the driving torque in the case of tapping, which can also be applied to screw connections with existing nut threads. In existing nut threads, preferably metric, only a very small driving torque occurs when screwing in with a metric screw. When screwing a commonly used tapped screw into an existing nut thread, an increased tightening torque may occur because the commonly used tapped screw has an interference fit on the entire thread or at least a section of the thread. The screw according to the invention thus reduces the tightening torque. Generally, when screwing a tapped screw into an existing nut thread, there is a risk of cross-threading, in other words, the risk of tapping a second thread lead, thereby damaging or destroying the nut thread. The risk of cross-threading is caused by the furchzone at the tapped screw. In practice, when an increased tightening torque occurs when a tapped screw is screwed into an existing thread, it is indistinguishable whether this increased tightening torque is due to cross-threading or due to the interference fit of the tapped screw and therefore through re-tapping. The screw according to the invention ensures that when the screw is directly inserted into the existing nut thread (in other words, when the nut thread is found and no cross-threading occurs), the tightening torque is at an extremely low level and is typically close to zero. Therefore, the screw according to the invention can be used to detect potential mis-threading in the case of mis-threading, since mis-threading is accompanied by an increased tightening torque. Consequently, the process reliability is significantly greater when using the screw according to the invention. Consequently, it can make a significant contribution to quality improvement when assembling the threaded screw into existing, preferably metric, nut threads. Consequently, by using the universal self-tapping screw according to the invention not only for threading but also for tightening into existing threads, the strategy of reducing part types can be significantly better realized in practice.

[0044] The problem upon which this invention is based is also solved by a system for screwing in a screw according to the invention, wherein a device is provided for determining whether an existing hole has internal threads and wherein a setting device is provided to cause the screw to be screwed in with different maximum screwing torques depending on whether the existing hole has internal threads.

[0045] The problem upon which this invention is based is also addressed by a method for screwing in screws, wherein steps are included to detect the screwing torque during screwing into an existing nut thread and to detect incorrect screwing when the screwing torque exceeds a predetermined value.

[0046] Unlike conventional self-tapping screws, in screws according to the invention, it is possible to distinguish whether the screw is correctly screwed into existing internal threads, or whether so-called thread misalignment has occurred, i.e., the screw inserts additional threads into existing threads. In common self-tapping screws, the screwing torque is very large when screwed into existing internal threads because, for example, the outer diameter of a conventional self-tapping screw is larger than the outer diameter of the screw designed for screwing into existing internal threads. For this reason, it is not possible, or under no circumstances, to reliably distinguish between correct screwing into existing internal threads and thread misalignment in conventional self-tapping screws. Now, screws according to the invention can be screwed into existing internal threads with a relatively small screwing torque. If thread misalignment occurs, this manifests as a significantly larger screwing torque, for example, up to 10 times the increased screwing torque relative to correct screwing. This can be detected and identified, and thus incorrect screwing can be identified, and if necessary, the screwing can then be repaired. Attached Figure Description

[0047] Further features and advantages of the invention will become apparent from the claims and the following description of a preferred embodiment of the invention, taken in conjunction with the accompanying drawings. Wherein:

[0048] Figure 1 A side view of the screw according to the invention is shown.

[0049] Figure 2 The first workpiece is shown, which has an existing hole with a partial section of internal thread.

[0050] Figure 3 It shows in Figure 2 In the screw-in state of the workpiece Figure 1 screws,

[0051] Figure 4 Another workpiece is shown, which has an existing hole without internal threads.

[0052] Figure 5 It shows in Figure 4 In the screw-in state of the workpiece Figure 1 screws,

[0053] Figure 6 A schematic diagram of a system for screwing in screws according to the present invention is shown.

[0054] Figure 7 Another workpiece is shown, which has an existing hole without internal threads.

[0055] Figure 8 Another workpiece is shown, which has an existing hole without internal threads.

[0056] Figure 9 It shows Figure 8 The workpiece having a screw screwed in according to the invention,

[0057] Figure 10 A partial diagram of a screw according to another embodiment of the invention is shown from a rearward angle, wherein a screw without a screw head is shown.

[0058] Figure 11 Shown from the diagonal front Figure 10 screws,

[0059] Figure 12 The view from the free end is shown from the front. Figure 10 screws,

[0060] Figure 13 Shown in side view Figure 10 screws,

[0061] Figure 14 A partial diagram of a screw according to another embodiment of the invention is shown from a rearward angle, wherein a screw without a screw head is shown.

[0062] Figure 15 Shown from the diagonal front Figure 14 screws,

[0063] Figure 16 As shown from the front Figure 14 The screw, in which the observer's line of sight points towards the free end of the screw.

[0064] Figure 17 It shows Figure 14 A side view of the screw in its first rotational position about the screw's central longitudinal axis.

[0065] Figure 18 The other side view of the screw is shown, where the screw is relative to... Figure 17 The diagram is rotated 90° around the central longitudinal axis.

[0066] Figure 19 It shows Figure 14A cross-sectional view of the screw.

[0067] Figure 20 It shows Figure 14 Another cross-sectional view of the screw, wherein the cutting plane is relative to Figure 19 The diagram is rotated 90°.

[0068] Figure 21 It shows Figure 14 The cross-section of the screw in the area at the top of the unthreaded search.

[0069] Figure 22 As shown from the front Figure 21 The cross-section,

[0070] Figure 23 It shows Figure 14 The screw in another cross-section of the self-tapping thread area.

[0071] Figure 24 As shown from the front Figure 23 The cross-section,

[0072] Figure 25 It shows Figure 14 The screw has another cross-section in the area where the thread is retained.

[0073] Figure 26 As shown from the front Figure 25 The cross-section, and

[0074] Figure 27 An exemplary torque-rotation angle curve is shown when screwing in a screw according to the invention. Detailed Implementation

[0075] Figure 1 A screw 10 according to a preferred embodiment of the invention is shown. The screw has a... Figure 1 The screw head 12 and screw shank 16 of the drive structure 14 are not visible in the image. The screw shank has threads 18 running approximately along its entire length. Figure 1 It is shown only schematically.

[0076] The screw shank has a columnar retaining section 20 and an end section 22 connected to the retaining section 20 in a direction away from the screw head 12. The end section 22 tapers in a direction away from the retaining section 20.

[0077] The retaining section 20 is provided with a standard thread, such as a metric thread. The end section 22 is provided with at least five thread leads of a self-tapping thread. The thread flank height in the end section 22 corresponds to the thread height of the standard thread in the retaining section 20 at the transition from the retaining section 20 to the end section 22, and then decreases towards the free end of the end section 22. The thread height at the free end of the end section 22 is, for example, about 50% of the thread height of the end section 22 at the transition to the retaining section 22.

[0078] End section 22 has a flattened, pointed arch top shape. End section 22 in... Figure 1 The visible outer contour is formed by an arc that transitions tangentially into the cylindrical outer contour of the retaining section 20 on one hand, and terminates on the other hand at an end face 26 arranged perpendicular to the central longitudinal axis 24 of the screw 10. The end section further has... Figure 1 The end section 22 has a multi-lobed cross-section 221 on the right side, while the retaining section 20 has a columnar cross-section 201. In the illustrated embodiment, the cross-section 221 of the end section 22 has three rounded corners 221a, 221b, 221c and three convex, curved side edges 221d, 221e, 221f that connect the rounded corners to each other. This can also be referred to as trilobal. In the illustrated embodiment, the cross section 221 is implemented with a uniform thickness. Therefore, the outer diameter of the cross section 221 is always the same, independent of the angular position. However, within the scope of the invention, the multi-leaf-shaped cross section 221 of the end section 22 may also have an outer diameter that varies according to the angular position.

[0079] On the upper side of the screw head 12, the number 10.9 can be seen. The number 10.9 indicates the screw strength. The tensile strength of the screw is at least 1000 N / mm². 2 Furthermore, the 0.2% elongation limit of screw 10 is at least 900 N / mm. 2 Within the scope of this invention, such a so-called 10.9 screw is a preferred embodiment.

[0080] In end section 22, screw 10 is inductively hardened. This is in Figure 1 The hardened region 28, indicated by dashed lines 28, is schematically represented in the diagram. Through inductive hardening, the fully formed self-tapping thread is hardened from the surface of the end section 22, and the region 28, extending slightly beyond the bottom of the thread towards the central longitudinal axis 24, is hardened. The initial region of the retaining section 20 is also inductively hardened. This ensures that at least five thread leads of the self-tapping thread in the end section 22 are fully hardened. In particular, the fully formed thread lead must lie within the inductively hardened region 28, so that the thread in the retaining section 20 no longer needs to perform a self-tapping function.

[0081] Figure 2 A workpiece 30 with a hole 32 is shown in partial view. The workpiece consists of a cover plate 34 with a hole drilled in the area of ​​the hole 32 and a second plate 36 with a press-fit nut 38. The press-fit nut 38 is shown schematically, and in particular, how the press-fit nut 38 is pressed into and anchored to the plate 36 is not shown. By providing the press-fit nut 38, the hole 32 has an existing internal thread in the area of ​​the press-fit nut 38.

[0082] Figure 3 The screw-in state is shown. Figure 1 The screw 10. The lower side of the screw head 12 is positioned on the upper side of the cover plate 34, and the thread 16 in the retaining section 20 engages with the internal thread of the press-fit nut 38. Thus, the cover plate 34 and the plate 36 are pre-tightened to each other by means of the screw 10 and the press-fit nut 38.

[0083] When screwing in screw 10, the tapered end section 22 simplifies the introduction of screw 10 into hole 32, and also simplifies the placement and screwing of thread 16 into the internal thread of press-fit nut 38.

[0084] Therefore, the screw 10 according to the invention can be easily screwed into existing internal threads, in this case, into the existing internal threads of the press-fit nut 38. Since the thread 16 in the retaining section 20 is constructed as a standard thread, the thread 16 reliably engages with the threads of the press-fit nut 38.

[0085] Figure 4 A second workpiece 40 with a hole 42 is shown, which has no internal thread. The workpiece 40 also has a cover plate 44 and another plate 46 arranged below the cover plate 44, wherein the cover plate 44 and the other plate 46 are only shown in partial sections. The other plate 46 has a through-pull portion 48, which forms an extension of the hole 42.

[0086] Figure 5 The screw-in state in hole 42 is shown. Figure 1 Screw 10. Screw 10 is positioned such that end section 22 is partially inserted into hole 42 and through pull portion 48. Figure 4After the upper end portion is placed, the screw 10 is rotated, and the self-tapping thread in the end section 22 is screwed into the hole 42 in the pull portion 48, whereby its self-tapping action creates an internal thread in the pull portion 48. The end section has at least five thread leads of self-tapping threads, which, as explained, have an increasing thread flank height from the beginning of the end section 22 to the transition in the columnar retaining section 20. Therefore, during the screwing of the end section 22 into the pull portion 48, the internal thread in the end section 48 is constructed to such an extent that it corresponds to a standardized internal thread that mates with the standard thread in the columnar retaining section 20.

[0087] The multi-leaf-shaped end section 22 in the cross-section reduces the screwing torque when the thread is introduced, because only the rounded corners of the multi-leaf-shaped cross-section abut against the inner wall of the pull section 48, or only in the areas of these rounded corners, is the increased pressing force applied outward to the inner wall of the pull section 48. Once the introduction section 22 is screwed into the pull section 48 until its termination (i.e., the transition to the holding section 20), the pull section 48... Figure 5 At least one thread lead of the fully constructed internal thread at the upper end is available for use, its dimensions corresponding to the standard, and therefore adapted to the standard thread in the retaining section 20. Thus, the retaining section 20 can be screwed into the pull-through portion 48. Figure 5 In this state, the screw 10 is fully screwed into the pull part 48, thereby pre-tightening the plate 46 and the cover plate 44 against each other.

[0088] Therefore, the screw 10 according to the invention can also be used to introduce threads into a hole 42 that does not have existing internal threads.

[0089] Figure 6 A system 50 is shown for screwing the screw 10 according to the invention into different workpieces 30, 40 and 60. Workpiece 30 has been designed according to... Figure 2 To explain, workpiece 40 has been based on Figure 4 To explain. Workpiece 60 and Figure 2 The only difference of workpiece 30 is that it is provided with a plastic plate 64 instead of a cover plate, and the hole 62 is limited by a brass sleeve 66 inserted into the plastic plate 64. The plastic plate 64 is arranged above the plate 36 having a press-fit nut 38.

[0090] System 50 is designed to screw the same screw 10 into different workpieces 30, 40, and 60. The screw 10 is arranged at an automatic screw-in device 70, schematically shown, whose shaft 72 is rotatable in the screw-in direction. A maximum screw-in torque can be preset here. The automatic screw-in device 70 can move in the longitudinal direction of the screw and perpendicular to the longitudinal direction; in other words, in three spatial directions, to guide the screw 10 into one of the holes 32, 42, and 62. The automatic screw-in device is equipped with a camera 74 oriented toward the workpieces 30, 40, and 62 and connected via at least one data line to a control unit (not shown) within the automatic screw-in device 70. By means of the camera 74 or another suitable sensor, the presence of internal threads in the corresponding holes 32, 42, and 62 can be determined. Based on whether internal threads are determined to be present, the maximum screw-in torque for screwing in the screw 10 is set by means of the automatic screw-in device 70.

[0091] The hole 32 of the first workpiece 30 has internal threads in the area where the nut 38 is pressed in. Therefore, a first tightening torque is set when the screw 10 is screwed into the hole 32. This first tightening torque is selected, for example, in a manner that corresponds to the commonly used tightening torque when screwing a standard threaded screw into an existing internal thread.

[0092] When screwing screw 10 into hole 42 (which has no internal thread, nor in the area of ​​the through-hole 48 of the sheet metal), a second maximum screwing torque is set, which is sufficient to tap threads in the through-hole 48. The second maximum screwing torque is higher than the first maximum screwing torque.

[0093] In the hole 62 of the third workpiece 60, there is an internal thread in the area where the nut 38 is pressed in. Therefore, when the screw 10 is screwed into the hole 62, a first maximum screwing torque is set, which is lower than the second maximum screwing torque.

[0094] Therefore, when using the system 50 according to the invention to screw the same screw 10 into different workpieces 30, 40, 60 or into the same workpiece (e.g., a motor vehicle body) with holes of different constructions, confusion between different screw types can be avoided because the same screw 10 is always used regardless of whether the hole into which the screw is to be screwed has internal threads. This significantly improves the process reliability of the screwing process. Because the same screw 10 is always used, the record-keeping of the screwing process is also simplified.

[0095] use Figure 6 The system 50 shown can also be fitted with the same screw 10. Figure 7 and Figure 8 Among the workpieces 70 and 80 shown. Figure 7A workpiece 70 with a drilled core hole 72 is shown, the core hole being cylindrically constructed. The core hole 72 has no internal threads, and a screw 10 according to the invention can be inserted into the core hole 72, wherein the screw 10 taps threads on the wall of the core hole 72 when screwed into it.

[0096] Figure 8 The workpiece 80 shown has a cast conical core hole 82. The core hole 82 is implemented in a truncated conical shape, and therefore in its... Figure 8 The open end shown in the upper middle part has a larger diameter than its lower part. Figure 8 The diameter is larger at the lower middle part.

[0097] Figure 9 The screw 10 according to the invention is shown in its screwed-in state into the core hole 82 in the workpiece 80. Another component 90 is fastened to the workpiece 80 using the screw 10. Figure 9 As can be seen, screw 10 is threaded into core hole 82. Screw 10 terminates before the bottom of core hole 82, which is constructed as a blind hole, thus leaving a gap (Zwischenraum) 84 between the end of screw 10 and the bottom of blind hole.

[0098] Figure 10 Another screw 100 according to the invention is shown in a partial section of the illustration in a rearward oblique view. The screw 100 has a screw head (not shown) with a drive structure, for example... Figure 1 The screw head 12 is shown. For clarity, in Figure 10 The screw head is omitted from the illustration. The screw head will be placed in... Figure 10 The screw 100 is positioned on the end facing the observer, i.e., on the cutting surface 102. Within the scope of the invention, the cutting surface 102 also immediately follows another section of the shank 116 of the screw 100. The screw 100 has screw threads 118 along its entire length on the screw shank 116, which are constructed as standard threads, particularly trapezoidal threads, in the retaining section 120 and as round threads in the end section 122. Figure 10 As can be seen in the view, the end section has a self-tapping section 123 with a multi-lobed cross-section, particularly a trilobed cross-section, and at the free end of the screw 120 (i.e., at the end section 122) Figure 10 The end facing away from the observer also has a search section 124 with a circular cross-section. The holding section 120 also has a circular cross-section. Self-tapping threads with a total of four thread leads are arranged in the self-tapping section 123.

[0099] Figure 11 Shown from the diagonal front Figure 10 A view of screw 100, in which the screw head is omitted. Figure 11As can be seen in the view, in the search section 124, the only thread lead found there has a circular cross-section and is constructed as a circular thread. The four thread leads in the self-tapping section 123 are constructed on the trilobed cross-section of the rod 116 and are also constructed as circular threads. In the retaining section 120, which immediately follows the self-tapping section 123, a standard thread constructed as a 60° trapezoidal thread is again constructed on the circular cross-section of the rod 116. It can be seen that in the retaining section 120, the thread has a flat thread tip. The search section 124 and the self-tapping section 123 together form the end section 122.

[0100] exist Figure 11 In the illustration, regions 126 can be seen at the final thread lead of the self-tapping section 123 and at the first thread lead of the retaining section 120, where the threads are constructed slightly differently. These regions are not implemented with flat but rounded thread tips and are only used to ensure that the trilobed cross-section of the self-tapping thread 123 smoothly transitions into the thread of the retaining section, which has a circular cross-section.

[0101] Figure 12 As shown in the front view Figure 10 Screw 100, wherein the screw head is omitted. Figure 12 In the middle, the line of sight is directed towards the end section 122. Figure 12 As can be seen, the first thread lead 128 of the end section 122 also has an approximately circular cross-section. Then, this first thread lead 128 is immediately followed by four thread leads of a self-tapping thread 123 with a three-lobed cross-section. Following the self-tapping thread 123, a retaining section 120 with a standard thread having a circular cross-section can be seen. Figure 12 It is clearly shown that the self-tapping thread 123 does not extend beyond the cross-section of the retaining thread in the retaining section 120. In other words, the region of the self-tapping thread 123 located at its farthest radial outer edge also does not extend beyond the profile of the retaining thread in the retaining section 120.

[0102] Figure 13 It shows Figure 10 A side view of screw 100, wherein the screw head is omitted. It can be clearly seen that in the end section 122, the thread configuration is a circular thread with a rounded thread tip. Within the scope of the invention, the thread valley may also be rounded. Conversely, in the retaining section 120, the thread configuration is a trapezoidal thread with a flat thread tip and a flat thread valley.

[0103] Figure 14Another embodiment of the screw 200 according to the invention is shown. The screw 200 has a screw shank 216 and is shown only in partial sections. In particular, the screw head, which rests on the cut surface 202, is not shown. The screw shank 216 may also extend beyond the cut surface 202. For example, Figure 1 The screw head 12 shown can be placed at the cut surface 202.

[0104] Screw 200 has a retaining section 220 and an end section 222. End section 222 has four leads of self-tapping thread 223 and a threadless search tip 224. The threadless search tip 224 is rounded at its free end and gradually increases in diameter to the first thread lead of the self-tapping thread. Search tip 224 has a circular cross-section. In the region of self-tapping thread 223, the shank 216 has a trilobal cross-section. In retaining section 220, the thread configuration is a standard thread, and specifically a 60° trapezoidal thread with a flat thread tip and a flat thread trough.

[0105] Figure 15 As shown in the front view Figure 14 Screw 200. The circular cross-section of the search top 224 and the trilobal cross-section of the self-tapping thread 223 can be clearly seen. In addition, the circular cross-section of the thread in the retaining section 220 can be seen.

[0106] Figure 16 The screw 200 is shown in a front view, where the screw head is omitted. The circular cross-section of the search tip 224, the three-lobed cross-section of the thread lead of the self-tapping thread 223, and the circular cross-section of the thread in the retaining section 220 are clearly visible. Figure 16 It can be seen that the thread lead of the self-tapping thread 223 does not extend beyond the profile of the retaining thread in the retaining section 220.

[0107] Figure 17 It shows Figure 14 A side view of screw 200 in its first rotational position about its central longitudinal axis. In the area of ​​the self-tapping thread 123, the thread tip is rounded. (Compared to...) Figure 17 Unlike the illustrations, the valley of the thread can also be rounded.

[0108] Figure 18 Another side view of screw 200 is shown, in which the screw is relative to... Figure 17 The diagram rotates 90° around the central longitudinal axis.

[0109] Figure 19 A cross-sectional view of screw 200 is shown, and Figure 20 Another cross-sectional view of screw 200 is shown, in which, Figure 20 The cutting plane relative to Figure 19 The cutting plane rotates 90° around the central longitudinal axis.

[0110] Figure 21 A cross-sectional view of screw 200 in the area of ​​the top 224 of the search is shown. Figure 22 Shown from the front Figure 21 A sectional view. The circular cross-section of the search top is clearly visible, which is smoothly constructed without threads and has rounded ends.

[0111] Figure 23 Another sectional view of screw 200 is shown, in which the cutting plane is placed in the region of self-tapping thread 223. The multi-lobed cross-section with three poles, or in other words, the trilobed cross-section, can be clearly seen. Figure 24 Shown from the front Figure 23 A sectional view.

[0112] Figure 25 Another cross-sectional view of the screw 200 in the region of the retaining section 220 is shown. The circular cross-section of the screw shank in the retaining section 220 is clearly visible. (Seen from the front) Figure 25 The view Figure 26 It should also be noted that, Figure 25 and Figure 26 The cutting plane extends perpendicular to the central longitudinal axis of the screw, while maintaining the slant angle of the thread lead. For this reason, Figure 25 and Figure 26 The cutting plane extends through the thread valley on one hand and through the thread crest on the other. This explains the slight deviation from a strictly circular shape.

[0113] also, Figures 10 to 26 The screws 100 and 200 are hardened and have a bainitic structure. As a result, high strength and, in particular, very high toughness can be obtained.

[0114] Figure 27 An exemplary illustration shows the torque-rotation angle curve when a screw according to the invention is screwed into an existing thread. Here, a curve corresponding to... Figures 14 to 26 The screw, obviously, has a screw head with a drive structure. The screw according to the invention has a diameter of 6 mm and therefore has an M6 thread in the retaining section. As illustrated, a circular thread exists in the end section 122. When properly screwed into an existing M6 nut thread, a torque of no more than 0.1 Nm is generated at rotation angles exceeding 2000°, corresponding to curves CRV001, CRV002, and CRV003. Therefore, the screw according to the invention can be easily and smoothly screwed into existing nut threads.

[0115] The two curves, CRV0004 and CRV0005, illustrate screwing into an M6 nut thread, where the screw is intentionally placed at an angle to induce thread stripping, i.e., cutting additional threads into the existing nut thread. It can be seen that within the first rotation (i.e., within the rotation angle range of 0 to 360°), the required torque has already increased significantly to a value exceeding 1 Nm. That is, if thread stripping occurs, the screw according to the invention requires at least ten times the torque required for proper screwing. Therefore, the screw according to the invention can be used to very easily detect whether the screw is properly screwed into the existing thread or whether thread stripping has occurred. This can be achieved simply by detecting the torque required for screwing and detecting exceeding a predetermined torque limit. Figure 27 In the torque-rotation angle curve shown, the limit value can be set, for example, to 0.2 Nm. If the torque required to screw the screw according to the invention into an existing thread exceeds 0.2 Nm, a so-called thread roll is present. The component and screw must then be inspected and repaired if necessary. As already explained, the torque required in a conventional self-tapping screw to screw into an existing nut thread is within the same order of magnitude not only when screwed in correctly but also when thread roll occurs. Therefore, similar detection of incorrect screwing or thread roll is not possible in conventional self-tapping screws.

Claims

1. A screw having a screw head and a screw shank, wherein, The screw head has a drive structure and the screw shank is at least partially threaded, wherein the screw shank has a columnar retaining section and a tapering end section toward the screw tip, wherein the thread in the retaining section is a standard thread, wherein the retaining section has a circular cross-section, wherein the end section tapers from the retaining section, wherein the end section has at least two thread leads configured as self-tapping threads, wherein the end section has a multi-leaf cross-section at least in the region of the self-tapping threads, and wherein the screw shank is hardened in the retaining section and the end section, wherein the self-tapping thread in the end section is a circular thread, and wherein the standard thread in the retaining section is a trapezoidal thread.

2. The screw according to claim 1, characterized in that, The end section has a rounded search top.

3. The screw according to claim 2, characterized in that, The search top has an unthreaded construction.

4. The screw according to claim 2 or 3, characterized in that, The top of the search bar has a circular cross-section.

5. The screw according to any one of claims 1 to 3, characterized in that, The end section has multiple leaf-shaped cross sections only in the area of ​​the self-tapping thread.

6. The screw according to claim 1, characterized in that, In addition to the self-tapping thread, the end section also has an additional thread lead constructed as a circular thread.

7. The screw according to any one of claims 1 to 3, characterized in that, In the side view, the thread on the screw shank has a continuous, imaginary envelope curve extending to the free end of the screw shank.

8. The screw according to any one of claims 1 to 3, characterized in that, At least the end sections are additionally partially hardened.

9. The screw according to any one of claims 1 to 3, characterized in that, The tensile strength of the screw is at least 800 N / mm². 2 .

10. The screw according to any one of claims 1 to 3, characterized in that, The screw has a 0.2% elongation limit of at least 640 N / mm. 2 .

11. The screw according to any one of claims 1 to 3, characterized in that, Before the end section terminates at the transition to the retaining section, at least the last complete thread lead of the self-tapping thread is constructed in terms of thread size as the standard thread in the retaining section.

12. The screw according to claim 1, characterized in that, The thread configuration in the retaining section is a metric thread.

13. The screw according to claim 9, characterized in that, The tensile strength of the screw is at least 1040 N / mm². 2 .

14. The screw according to claim 10, characterized in that, The screw has a 0.2% elongation limit of at least 900 N / mm. 2 .

15. The screw according to at least one of claims 1 to 14 is used as a tapping screw in a first application or as a screw for screwing into existing internal threads in a second application.

16. A system for screwing in a screw according to any one of claims 1 to 14, characterized in that the device is used to determine whether an existing hole has internal threads, and to screw in the screw with different maximum screwing torques depending on whether the existing hole has internal threads.

17. A method for screwing in a screw according to any one of claims 1 to 14, characterized in that, The screwing torque is detected during screwing into the existing nut thread, and incorrect screwing is detected when the screwing torque exceeds a predetermined value.

Images