SCREW CONNECTION ELEMENT WITH EXTERNAL MULTI-SOCKET DRIVE

Description

[0001] The invention relates to a screw connection element with an external polygon drive for driving with a polygon socket wrench, wherein the screw connection element, which is designed in the form of a screw nut or screw, is particularly suitable for screw connections that are to be assembled or disassembled in hard-to-reach places or in a confined working space.

[0002] External polygon drives for screw fasteners, i.e., nuts or bolts, are among the most well-known, conventional screw drives. These fasteners have a polygonal section formed on the nut or bolt head, onto which a wrench with a size matching the polygonal section of the fastener is placed.

[0003] One of the most common drive types is the hexagonal drive. When the nuts or bolt heads have an external hexagon, open-end, ring, or socket wrenches are typically used as turning tools to operate the screw drive. Conventional hexagonal screws or nuts, as standardized, for example, in DIN EN ISO 4017 or DIN EN ISO 4032, have the basic shape of a straight hexagonal prism, the cylindrical surfaces of which form the wrench flats where the wrench engages to tighten or loosen the fastener. Conventional socket wrenches for driving hexagonal nuts or screws usually have a hexagonal recess with the basic shape of a straight hexagonal prism, i.e., a straight external hexagon; they must therefore be positioned axially straight onto the hexagonal section of the fastener in order to turn the fastener to tighten or loosen it.While open-end wrenches can be used by changing the angle, they require a large turning radius when rotating the fastener, unlike socket wrenches. For assembling or disassembling bolted connections in confined spaces—that is, where there is limited space around the nut or bolt head for positioning the tool—socket wrenches, due to their axial length, and open-end and ring wrenches, due to their turning radius, may not be usable or may only be usable with considerable difficulty.

[0004] For tightening or loosening socket head cap screws in confined spaces, ball-end hex keys can be used. These ball-end hex keys are known, for example, from DE 20 2009 015 275 U1 or US 9 763 754 B2. They allow the screw head to be turned even with an angled socket wrench inserted. The internal hexagon socket recess in the screw head of conventional socket head cap screws has the basic shape of a straight hexagonal prism.

[0005] A further known patent from WO 2014 / 012970 A1 is an abutment screw for jaw implants, which has a ball-head external hexagon drive on the screw head, similar to ball-head hex keys for tightening or loosening socket head cap screws, and which is actuated by means of a special multi-sided socket tool that can also be attached at an angle. Screws with ball-head external hexagon drives are also known from DE 298 19 955 U1. US 2003 / 077113 A1 discloses a screw connection element according to the preamble of claim 1.

[0006] A disadvantage of ball-end hex drives is the higher flank load on the wrench flats and the associated risk of edge damage, which is particularly pronounced with frequent tightening or loosening. The use of ball-end hex drives is therefore limited to the tool side, which is more easily adapted to the higher flank and edge loads in terms of the tool material, or to special screws, such as those used in orthodontics – i.e., screws that typically only need to be tightened or loosened rarely.

[0007] The invention is based on the objective of overcoming the aforementioned disadvantages and providing a screw connection element with an optimized external polygon drive for actuation with a conventional polygon socket wrench as a turning tool, wherein the external polygon drive should enable the screw connection element, which is preferably designed as an otherwise conventionally constructed screw or nut, to be actuated by means of the angled turning tool. The optimized external polygon drive should also ensure good, edge-protecting power transmission from the turning tool to the screw connection element, even when the polygon socket wrench is attached at an angle.

[0008] This problem is solved by a screw connection element with an external polygon drive and the features according to claim 1; advantageous embodiments and further developments of the invention are described in claims 2 to 10.

[0009] According to the invention, the screw connection element with external polygon drive is designed in the form of a nut or a screw. A conventional polygon wrench, in particular a conventional polygon socket wrench, i.e., a socket wrench having a polygonal recess with the basic shape of a straight prism or with a straight external polygon, is intended to serve as the turning tool for actuating the external polygonal drive of the screw connection element.

[0010] In a generally known manner, the screw connection element has a threaded section extending axially along a central axis of the screw connection element, a polygonal section formed on the outer circumference of the nut or on the outer circumference of a screw head to form the external polygonal drive, a flat end face arranged at the tool-side axial end region of the polygonal section and oriented perpendicular to the central axis, and a bearing plane arranged at the mating-side axial end region of the polygonal section and oriented perpendicular to the central axis. The end face extends in a plane that is also referred to as the end plane. A free surface, then referred to as the bearing surface, may be formed on the screw connection element in the bearing plane. However, the bearing plane may also be located inside the screw connection element, for example, if a collar is formed at the mating-side end region.The axial end region on the mounting side, as defined in this description, is the side of the screw connection element that rests against the workpiece to be joined. The exposed end face, onto which the socket wrench is placed to actuate or turn the screw connection element, is located on the end region opposite the axial end region on the mounting side.

[0011] The polygonal section extends between the end face (or end plane) and the mounting plane over a predetermined polygonal axial length. The axial distance of a cross-sectional plane located within the polygonal section and oriented perpendicular to the central axis from the end face is called the end face distance.

[0012] The polygonal section has several key surfaces, each extending from the end face to the mounting plane. Each intersection of one of the key surfaces with a cross-sectional plane oriented perpendicular to the central axis of the screw connection element forms a key surface cross contour line. According to the invention, all key surfaces are designed such that each of these key surface cross contour lines is straight.

[0013] The fully adjoining key surfaces of the polygonal section form a cross-sectional contour in the shape of a convex polygon in all cross-sectional planes oriented perpendicular to the central axis of the screw connection element, where the number of vertices of this polygonal cross-sectional contour, i.e. the convex polygon, corresponds to the number of key surfaces of the polygonal section.

[0014] The fully adjacent key surfaces of the polygonal section form edges of the polygonal section at their lines of contact, each of which runs completely in an axial section plane of the screw connection element containing the central axis.

[0015] Each key surface has a key surface axial contour line extending from the end face to the mounting plane. This line represents the intersection of the respective key surface with an axial section plane that includes the central axis and is perpendicular to the key surface transverse contour lines of the respective key surface. The distance of a specific point on the key surface axial contour line perpendicular to the central axis is called the axial contour height.

[0016] According to the invention, the polygonal section of the screw connection element has a first axial sub-section and a second axial sub-section, wherein the first axial sub-section extends from the end face to a transition plane oriented perpendicular to the central axis, and the second axial sub-section extends from the transition plane to the contact plane. Each of the wrench flats has a first wrench flat section located within the first axial sub-section and a second wrench flat section located within the second axial sub-section.

[0017] The first axial section of the polygonal segment is dome-shaped, meaning it bulges radially in a dome-like or spherical shape and is axially flattened by the end face. This dome-shaped form of the first axial section of the polygonal segment can be roughly compared to the shape of bulbous tower domes, for example, the Welsche Haube (Italianate dome) of Munich's Frauenkirche (Cathedral of Our Lady). Each key face, and thus its respective key face axial contour line, is convexly curved outwards within the first key face segment – ​​in axial extension. The curvature of the key face axial contour line exhibits a maximum curvature with a maximum axial contour height at a distance between the end face and the transition plane where the curvature maximum lies.

[0018] The second axial section of the polygonal portion is formed as a straight truncated pyramid, tapering from the transition plane to the contact plane; the key surface axial contour line is a straight line within the second key surface section for each of the key surfaces. This straight segment of the key surface axial contour line within the second key surface section forms an angle of inclination between 10° and 40° with the central axis.

[0019] According to the invention, the axial contour line of each key surface has a continuous curve over its entire length; that is, the curve of the axial contour line is free of jumps and kinks. In particular, at the transition from the first axial section to the second axial section of the polygonal segment, i.e., when passing through the transition plane, the axial contour line of the key surface is free of discontinuities, such as jumps or kinks.

[0020] Using the screw connection element according to the invention, screw connections can be tightened or loosened in confined working spaces by placing the socket wrench at an angle onto the screw connection element. When using the screw connection element, screw connections can be tightened securely and firmly at an angle of up to approximately 30° between the socket wrench's axis of rotation and the central axis of the screw connection element. The multi-sided socket wrench used as a turning tool for tightening or loosening has an internal polygon shaped in a generally known manner, which matches the polygonal section of the screw connection element. The force or torque transmission is achieved through the positive locking of the corresponding geometric elements.For the screw connection elements according to the invention, the multi-sided socket wrench is dimensioned slightly larger than the multi-sided section of the screw connection element in the region of the maximum curvature of the wrench surface axial contour line, or the screw connection element is adapted to the dimensions of the multi-sided socket wrench in the region of the maximum curvature of the wrench surface axial contour line. This means that the screw connection elements can be operated with conventionally available socket wrenches, for example, socket sockets or pipe wrenches. Special tools are not required. Tightening or loosening the screw connection elements can also be carried out with other commercially available wrenches, such as open-end wrenches, ring wrenches, ratchets, or similar hand tools.

[0021] The external multi-point drive is generally compatible with screws or nuts of common wrench sizes, allowing the use of standard (metric or imperial) socket sets for tightening or loosening the fasteners. The fasteners can be manufactured from various materials, particularly the materials commonly used for standard screws or nuts. Furthermore, the fastener can be manufactured with threads in all common sizes and types.

[0022] In the screw connection elements according to the invention, force and torque transmission occurs primarily in the area of ​​the dome-shaped first axial section of the polygonal portion, particularly in the area of ​​the maximum curvature of the wrench flat axial contour line. Compared to conventional, i.e., straight, external polygonal drives, the force transmission from the wrench polygon to the polygonal portion of the screw connection element, to enable angled tightening and loosening, necessarily occurs in the screw connection elements according to the invention via a smaller proportion of contacting wrench flat areas and thus higher flank and edge loads.A particular advantage of the screw connection element designed according to the invention is that, when tightening or loosening at an angle, the wrench surfaces in the second axial part of the multi-sided section also make contact along the edges of individual wrench surfaces where an angled, attached multi-sided wrench rests, and contribute to force transmission, so that the higher flank and edge load of the wrench surfaces is at least partially compensated.

[0023] The described external polygonal drive can be implemented on both the screw head of screws and on screw nuts. The screw connection elements according to the invention are particularly suitable for screw connections where, due to confined working spaces, the straight insertion of socket wrenches is restricted or not permitted, but which can be easily assembled or disassembled using angled socket wrenches.

[0024] Due to the aesthetically pleasing shape of the polygonal section compared to conventional screw head or screw nut shapes, the screw connection elements according to the invention can also be used as decorative screws or decorative nuts.

[0025] According to one embodiment of the screw connection element, the preferred end face distance of the transition plane is in the range of 60% ± 5% of the polygon axial length.

[0026] The bulging or protrusion of the first axial sub-section of the polygonal segment is preferably designed such that the distance between the end faces of the maximum bulging is 40% ± 5% of the polygonal axial length.

[0027] Furthermore, it may be provided that within the second key surface section of each key surface, the included angle of inclination between the key surface axial contour line running straight in this section and the central axis is in the range of 25° ± 5°.

[0028] The polygonal section of the screw connection element is preferably dimensioned such that the maximum axial contour height of the wrench surface axial contour line is in the range of 65% ± 5% of the polygonal axial length of the polygonal section.

[0029] According to one embodiment, the key surface axial contour line within the first key surface segment of each key surface has a parabolic curve. That is, the functional relationship between axial contour height and end face distance, whose function graph is represented by the key surface axial contour line, can be expressed as a second-order polynomial in the first key surface segment.

[0030] The contour height of the key surface axial contour line within the first key surface section of each of the key surfaces, for a given polygon axial length, preferably lies within a range of ± 5% of the value determined by the function. Konturh ö he = − 4 5 Stirnfl ä chenabstand Mehrkantaxiall ä nge 2 + 5 8 Stirnfl ä chenabstand Mehrkantaxiall ä nge + 2 7 ⋅ Mehrkantaxiall ä nge determined contour height.

[0031] Preferably, the fully adjoining key surfaces of the polygonal section form a cross-sectional contour in all cross-sectional planes oriented perpendicular to the central axis of the screw connection element, with the shape of a convex polygon rotationally symmetric about the central axis.

[0032] It can be provided that the polygonal section has an even number of key faces, resulting in cross-sectional contours with even-fold rotational symmetry. Particularly suitable are polygonal cross-sectional contours with two-, four-, six-, or eight-fold rotational symmetry, where the polygonal section is simultaneously designed as either a square, hexagonal, or octagonal section.

[0033] Particularly preferably, the fully adjoining key surfaces of the polygonal section form a cross-sectional contour in the shape of a regular convex hexagon in all cross-sectional planes oriented perpendicular to the central axis of the screw connection element. The polygonal section is thus designed as a hexagonal section, and the external polygonal drive of the screw connection element is correspondingly designed as an external hexagonal drive.

[0034] According to the described configuration of the polygonal section with an even number of wrench flats, the polygonal section designed as an external polygonal drive has at least one wrench width that corresponds to the sum of the maximum axial contour heights of two opposing, parallel wrench flats. That is, the wrench width, or one of the wrench widths, of the external polygonal drive corresponds to the distance between the respective opposing, parallel wrench flats in the cross-sectional plane oriented perpendicular to the central axis at the maximum curvature of the first axial sub-section of the polygonal section.

[0035] It can further be provided that the screw connection element has a collar on the contact side, which is generally designed as a circular disc. The collar connects axially to the second axial section of the polygonal segment at the contact plane. The collar forms – in a generally known manner – a washer integrated into the screw connection element. In conjunction with the polygonal segment of the screw connection element designed according to the invention, the collar has proven to be particularly advantageous, since a comparatively small contact area results when the screw connection element is designed without a collar due to the tapering of the second section of the polygonal segment at the contact plane.By attaching the collar, the material stress in the area of ​​the mounting plane is significantly reduced and also made more uniform, since the integral collar also avoids mounting inaccuracies that would occur when using a collarless screw connection element in conjunction with a separate washer.

[0036] The invention is explained in more detail below with reference to exemplary embodiments and the schematic drawings, wherein identical or similar features are provided with the same reference numerals; to this end, the following are shown: Fig. 1: A first embodiment of the screw connection element as a nut in two perspective views; Fig. 2: A longitudinal half-section of the screw connection element according to the first embodiment in axial section view and end face view; Fig. 3: A second embodiment of the screw connection element as a collared nut in two perspective views; Fig. 4: A longitudinal half-section of the screw connection element according to the second embodiment in end face view (a), axial section view (b) and view of the collar (c); Fig. 5: A third embodiment of the screw connection element as a bolt with a collared head in perspective view; Fig. 6: A longitudinal half-section of the bolt head (without collar) of the screw connection element according to the third embodiment in perspective view; and Fig.7: The longitudinal half-section of the screw head (without collar) of the screw connection element according to the third embodiment in axial section view (a) and end face view (b).

[0037] The screw connection element according to the two views (a) and (b) of the Fig. 1 It is designed as a flangeless hexagonal nut with the threaded section 9 extending along the central axis 8. The screw connection element has six identical wrench flats 2 and correspondingly six identical edges 3.

[0038] The view (a) of Fig. 1 The visible flat end face 6 is exposed when the screw connection element is tightened. During intended use, the turning tool, preferably a conventional hexagonal socket wrench, is placed on the screw connection element on the side of the end face 6; this axial end region of the screw connection element is therefore also referred to as the tool-side end region.

[0039] The view (b) of Fig. 1 The visible flat contact surface extends in the contact plane 7. When used as intended, the contact surface makes contact with one of the workpieces to be joined, i.e., the contact surface rests on or against its surface; this axial end region of the screw connection element is therefore also referred to as the contact-side end region.

[0040] The polygonal section 1 of the screw connection element extends from the end face 6 to the contact plane 7; it is axially subdivided into the first axial, dome-shaped sub-section 1.1 (from the end face 6 to the transition plane 1.3) and the second axial, truncated pyramid-shaped sub-section 1.2 (from the transition plane 1.3 to the contact plane 7). The first wrench flat section 2.1 of each wrench flat 2 lies in the first axial sub-section 1.1, and the second wrench flat section 2.2 of each wrench flat 2 lies accordingly in the second axial sub-section 1.2.

[0041] The key surface cross contour lines 4, which each represent the intersection lines of one of the key surfaces 2 with a cross-sectional plane oriented perpendicular to the central axis 8, are always formed as straight lines.

[0042] The key surface axial contour lines 5 each represent the course of the section line of the respective key surface 2 with an axial section plane within this axial section plane, containing the central axis 8 and perpendicular to the key surface transverse contour lines 4 of the respective key surface 2. As can be seen from views (a) and (b) of the Fig. 1 As can be seen, the key surface axial contour lines 5 therefore run centrally in the respective key surface 2.

[0043] The two views of Fig. 2 illustrate the shape of polygonal section 1 using the example in view (a) of the Fig. 2 visible axial section contours and based on the view (b) of the Fig. 2visible cross-sectional contours.

[0044] Each point shown in view (a) of the Fig. 2 The wrench surface axial contour line 5, shown as an example, can be described by its end-face distance a and its axial contour height r associated with this end-face distance a. The course of the wrench surface axial contour line 5 can be mathematically represented as a function of the axial contour height r as a function of the end-face distance a. In the first axial section 1.1 of the polygonal segment 1 (from the end face 6 to the transition plane 1.3), the wrench surface axial contour line 5 is parabolic; in the second axial section 1.2 of the polygonal segment 1 (from the transition plane 1.3 to the contact plane 7), the wrench surface axial contour line 5 is linear, i.e., a straight line. The latter is connected to the central axis 8 in the exemplary embodiment according to Figs. 1 and 2 enters a tilt angle of 25°.

[0045] The axial position of the transition plane 1.3 is characterized by the end-face distance at of the transition plane 1.3. This end-face distance at of the transition plane 1.3 lies for the in the Figs. 1 and 2 The first embodiment of the screw connection element shown is at 60% of the polygonal axial length m, which corresponds to the end face distance r of the contact plane 7.

[0046] In the first axial sub-section 1.1 of the polygonal section 1, the wrench surface axial contour line 5 has a maximum curvature, the axial position of which is characterized by the end-face distance a rmax of the maximum curvature and its radial height by the maximum axial contour height rmax. The wrench size S of the screw connection element designed as a hexagonal nut corresponds to twice the axial contour height rmax.

[0047] The Figs. 3 and 4Their illustrations show a second embodiment of the screw connection element as a hexagonal flange screw nut. With respect to thread section 9 and polygon section 1, the screw connection element largely corresponds to the first embodiment according to the Figs. 1 and 2 The collar 10, designed as a ring washer, connects axially directly to the polygonal section 1 in the area of ​​the contact plane 7. In this embodiment of the screw connection element as a collared screw nut, the contact surface with a workpiece is located, as usual, on the collar 10 of the screw connection element.

[0048] The third, in Fig. 5 The illustrated embodiment of the screw connection element as a hexagon screw has the threaded section 9 and a screw head with the collar 10 and the polygonal section 1. The collar 10 and the polygonal section 1 of the hexagon screw according to Fig. 5are comparable to the collar 10 and the polygonal section 1 of the hexagonal collar screw nut according to the second, in the Figs. 3 and 4 The design shown is as follows. Figs. 6 and 7 The details of polygonal section 1 of the screw head are shown. The course of the [unclear] in view (a) of the Fig. 7 The key surface axial contour line 5 shown corresponds to the one in view (a) of the Fig. 2 . Reference symbol list

[0049] 1. Polygonal section 1.1 First axial section 1.2 Second axial section 1.3 Transition plane 2. Wrench surface 2.1 First wrench surface section (tool side) 2.2 Second wrench surface section (contact side) 3. Edge 4. Wrench surface transverse contour line 5. Wrench surface axial contour line 6. End face 7. Contact plane 8. Center axis 9. Threaded section 10. Collar a. End face spacing a. rmax. End face spacing of the maximum curvature at. End face spacing of the transition plane m. Polygonal axial length r. Axial contour height rmax. Maximum axial contour height (at the maximum curvature) S. Wrench size

Claims

1. Screw connection element with an external polygonal drive for driving by means of a polygonal socket wrench, wherein the screw connection element, formed as a nut or a screw, comprises: - a thread section (9) extending axially along a central axis (8) of the screw connection element, - a polygonal section (1) formed on the outer circumference of the nut or on the outer circumference of a screw head of the screw for forming the external polygonal drive, - a planar end face (6) arranged at the tool-side axial end region of the polygonal section (1) and oriented perpendicularly to the central axis (8), and a contact plane (7) arranged at the contact-side axial end region of the polygonal section (1) and oriented perpendicularly to the central axis (8), wherein the polygonal section (1) extends between the end face (6) and the contact plane (7) over a predetermined polygonal section axial length (m), and wherein the axial distance of a cross-sectional plane arranged within the polygonal section (1) and oriented perpendicularly to the central axis (8) from the end face (6) is defined as the end face distance (a), wherein the polygonal section (1) comprises a plurality of wrenching surfaces (2) each extending from the end face (6) to the contact plane (7), and wherein the line of intersection of each wrenching surface (2) with a cross-sectional plane oriented perpendicularly to the central axis (8) of the screw connection element forms a wrenching surface transverse contour line (4), and wherein the wrenching surfaces (2) are formed such that all wrenching surface transverse contour lines (4) extend straight, wherein the circumferentially adjacent wrenching surfaces (2) of the polygonal section (1) form, in all cross-sectional planes oriented perpendicularly to the central axis (8) of the screw connection element, a cross-sectional contour in the form of a convex polygon, and wherein the number of corner points of this polygonal cross-sectional contour corresponds to the number of wrenching surfaces (2) of the polygonal section (1), wherein each wrenching surface (2) has a wrenching surface axial contour line (5) extending from the end face (6) to the contact plane (7), which represents, within an axial section plane containing the central axis (8) and oriented perpendicularly to the wrenching surface transverse contour lines (4) of the respective wrenching surface (2), the course of the line of intersection of the respective wrenching surface (2) with said axial section plane, wherein the distance of a point of the wrenching surface axial contour line (5) from the central axis (8) being defined as the axial contour height (r), wherein - the polygonal section (1) comprises a first axial partial section (1.1) extending from the end face (6) to a transition plane (1.3) oriented perpendicularly to the central axis (8), and a second axial partial section (1.2) extending from the transition plane (1.3) to the contact plane (7), wherein each wrenching surface (2) having a first wrenching surface section (2.1) lying within the first axial partial section (1.1) and a second wrenching surface section (2.2) lying within the second axial partial section (1.2), - the first axial partial section (1.1) of the polygonal section (1) is dome-shaped, wherein the wrenching surface axial contour line (5) within the first wrenching surface section (2.1) of each wrenching surface (2) is outwardly convexly curved, and wherein the curvature has a maximum curvature with a maximum axial contour height (rmax) at an end face distance (armax) of the maximum curvature located between the end face (6) and the transition plane (1.3), - the wrenching surface axial contour line (5) of each wrenching surface (2) has a continuous curve profile over its entire length, characterised in that - the second axial partial section (1.2) of the polygonal section (1) is formed as a straight truncated pyramid tapering from the transition plane (1.3) towards the contact plane (7), wherein the wrenching surface axial contour line (5) within the second wrenching surface section (2.2) of each wrenching surface (2) is a straight line and encloses with the central axis (8) an inclination angle in the range of 10° to 40°.

2. Screw connection element according to claim 1, characterised in that the end face distance (at) of the transition plane (1.3) is 60 % ± 5 % of the polygonal section axial length (m).

3. Screw connection element according to claim 1 or 2, characterised in that the end face distance (armax) of the maximum curvature is 40 % ± 5 % of the polygonal section axial length (m).

4. Screw connection element according to any one of claims 1 to 3, characterised in that, within the second wrenching surface section (2.2) of each wrenching surface (2), the inclination angle enclosed between the wrenching surface axial contour line (5) and the central axis (8) lies within a range of 25° ± 5°.

5. Screw connection element according to any one of claims 1 to 4, characterised in that the maximum axial contour height (rmax) of the wrenching surface axial contour line (5) lies within a range of 65 % ± 5 % of the polygonal section axial length (m).

6. Screw connection element according to any one of claims 1 to 5, characterised in that the wrenching surface axial contour line (5) within the first wrenching surface section (2.1) of each wrenching surface (2) has a parabolic curve profile.

7. Screw connection element according to any one of claims 1 to 6, characterised in that the contour height (r) of the wrenching surface axial contour line (5) within the first wrenching surface section (2.1) of each wrenching surface (2), for a given polygonal section axial length (m), lies within a range of ± 5 % of the contour height (r) determined according to the function contour height r = − 4 5 end face distance a polygonal section axial lenght m 2 + 5 8 end face distance a polygonal section axial lenght m + 2 7 ⋅ polygonal section axial lenght m 8. Screw connection element according to any one of claims 1 to 7, characterised in that the circumferentially adjacent wrenching surfaces (2) of the polygonal section (1) form, in all cross-sectional planes oriented perpendicularly to the central axis (8) of the screw connection element, a cross-sectional contour in the form of a convex polygon that is rotationally symmetrical about the central axis (8).

9. Screw connection element according to claim 8, characterised in that the polygonal section (1) has an even number of wrenching surfaces (2).

10. Screw connection element according to claim 9, characterised in that the circumferentially adjacent wrenching surfaces (2) of the polygonal section (1) form, in all cross-sectional planes oriented perpendicularly to the central axis (8) of the screw connection element, a cross-sectional contour in the form of a regular convex hexagon.