AU2022345413A1 - Key, lock system, lock cylinder and production method - Google Patents

Abstract

The flat key (1) comprises a key head (11) and a key shank (12), which extends along a key axis (10) from the key head (11) to a front key tip (23) and has two parallel flat sides (21) and two mutually opposing narrow sides (22). In each case, an edge (25) runs parallel to the key axis (10) between the flat sides and the narrow sides. A series of coding bores (31) is formed parallel to the key axis on at least one of the flat sides. The key also has at least one coding recess (35) in at least one of the edges (25). Said coding recess forms a flank (43), which extends from the flat side towards the narrow side and has a monotonic gradient.

Description

KEY, LOCKING SYSTEM, LOCKING CYLINDER AND METHOD FOR PRODUCING SAME

The invention relates to a locking system with locking cylinder and key as well as a corresponding locking cylinder and a key. Locking cylinders have a stator (sometimes called a "cylinder housing") non-rotatably fastened to a lock and a rotor (sometimes called a "cylinder core") rotatable about the axis of the locking cylinder when a matching key is inserted. The rotation of the rotor moves output means, which are used to actuate a bolt or other means associated with the desired function of the locking cylinder. Many mechanical locking cylinders for reversible flat keys or other flat keys have tumbler-counter-tumbler pairs that query the mechanical coding of the keys. The mechanical codings are designed as bores with different depths depending on the coding on the flat side of the key. The number of possible tumbler lengths, together with the number of bores, determines the number of possible permutations, which should be as large as possible. So-called profile pins or locking pins are also known. Such profile pins are displaceably mounted in pin bores, which open radially inside into the key channel and extend radially outside to the surface of the rotor. In addition, the stator has for each pin bore a radially inner recess, which in the basic state is aligned with the pin bore. The profile pin is overall longer than the pin bore. Rotating the rotor in the stator is therefore only possible if the profile pin can be pressed so far into a corresponding coding groove or other coding bore in the key that it no longer protrudes from the pin bore radially outside. For this purpose, the profile pin has a corresponding, for example rounded, shape at the radially outer end. A further development of the profile pins are the profile wobble pins or pendulum pins. These are also movably mounted in a pin bore. However, they are in two parts with a radially inner part and a radially outer part, with a spring between the radially inner part and the radially outer part pushing the two parts apart and against an inner or outer stop, so that they take up the entire length available to them. Depending on the total length of the profile wobble pin (i.e. depending on how far the two parts are pushed apart), the radially outer part is guided relative to the radially inner part because corresponding parts of the two parts engage with one another or not. When the rotor in the stator is turned away, the profile wobble pin can only be pressed radially inwards as a whole if the parts are guided relative to one another. If this is not the case, the outer part tilts away when turning and can no longer enter the pin bore and thus blocks the rotor. Another possible security feature of locking systems is a profiling: when viewed perpendicular to the key axis, the key shank has a profile that deviates from a rectangular cross-section, for example due to the presence of axially extending grooves or ribs. The key channel of the locking cylinder then has a corresponding profile, at least in sections, so that keys that do not fit cannot be inserted at all. All of these codings for mechanical locking systems have in common that the available space on the key limits the number of possible codings through permutations - i.e. for secure and variable locking systems (e.g. for "master key systems" (MKS) - it is favorable, if there are as many coding positions as possible available. Secondly, these codings have in common that copying is relatively easy using mechanical devices that scan an existing matching key in order to drill or mill coding bores or grooves in a blank, for example. Remedy through sophisticated measures on the key, for example moving parts, or additional electronic coding, is possible, but also very time-consuming. It is an object of the present invention to create a locking system, a corresponding cylinder, and a corresponding key, which overcome the disadvantages of the prior art and which in particular combine good protection against unauthorized key copying with efficient manufacturability. This object is achieved by the invention as defined in the claims. The invention relates to a flat key having a key bow and a key shank extending along a key axis from the key bow to a front key tip with two mutually parallel flat sides and two opposing narrow sides, with an edge parallel to the key axis running between the flat sides and the narrow sides. As is known per se, a row of coding bores parallel to the key axis is formed on at least one of the flat sides. In addition, at least one coding recess is present in at least one of the edges. The coding recess forms a flank which extends from the flat side to the narrow side and which has a monotonous gradient. In this text, "coding bore" refers to a depression in the key, the dimension of which is chosen based on a desired coding. Coding bores can be created by drilling; however, corresponding depressions made using other methods are also referred to here as "coding bores". Firstly, the method according to the invention has the advantage that the positioning on the edge creates an additional position for the coding compared to conventional flat keys. Secondly, there is the following advantage: In contrast to a coding bore in a row of coding bores, the coding recess is less well defined and less easy to copy for the unauthorized key copier. With a coding bore arranged in a row, the position of the row of bores on the flat side (y position) is precisely defined. For copying, only a drilling tool with an approximately matching diameter is required, and the copying machine scans the bore depth as a function of the position along the key axis (x position). This is a standard procedure and easy for the unauthorized key copier. In contrast, with a flank/ramp sloping down towards the narrow side, neither the y position nor a bore depth can be easily read. A key copier must either find a process that accurately records and copies the 3D shape in the region of the coding recess, or they must know information about the manufacturing process, namely the tool and its position and path. The coding recess can in particular extend over a certain axial length, i.e. have an extension in the axial direction that is larger than that of an average coding bore. This can be reflected in the fact that a first transition between the coding recess and the flat side (i.e. a transition that is arranged between the coding recess and the flat side; such a transition can in particular be an edge that forms this transition) forms a (first) section extending substantially parallel to the key axis. Additionally or alternatively, a second transition between the coding recess and the narrow side (i.e. a transition that is arranged between the coding recess and the flat side; in particular an edge that forms this transition) can have a (first) section extending substantially parallel to the key axis. The latter property can be reflected in the fact that the region where the coding recess has the greatest depth (extension perpendicular to the flat side) is extended in the axial direction, i.e. forms a region of constant depth. In this case, the said first section of the first transition, which is substantially parallel to the key axis, and the first section of the second transition, which is substantially parallel to the key axis, can be substantially the same length, i.e. they can match at least 80% or at least 90% or at least 95%, for example even at least 98% in their length. Additionally or alternatively, the said first section of the first transition, which is substantially parallel to the key axis, and the first section of the second transition, which is substantially parallel to the key axis, can be located at substantially the same axial distance from the key tip, i.e. their axial positions can substantially match. The first transition can merge into the edge in a continuous curve or at a flat angle - with the continuous curve or the flat angle being on the flat side (i.e. the first transition runs in particular in a line in the plane defined by the flat side and merges into the edge in this plane). Additionally or alternatively, the second transition, i.e. the transition between the coding recess and the narrow side, can merge into the edge at a flat angle or in a continuous curve, with the flat angle or the continuous curve being located on the narrow side (i.e. the second transition runs in particular in a line in the plane defined by the narrow side and merges into the edge in this plane). According to a first group of embodiments, the flank can form an inclined, step-free surface from the flat side to the narrow side, i.e. the gradient can be strictly monotonic in the mathematical sense. This group of embodiments has the particular advantage that an unauthorized copier does not have any stop at their disposal that would enable them to scan the dimensions of the coding bore. According to a second group of embodiments, the coding recess has, towards the narrow side, a (for example small) flat surface section (bottom") that is approximately parallel to the flat side or at least less downwards sloping than the rest of the flank - then the gradient does not have to be strictly monotonous. However, in the embodiments of the second group, as in other embodiments, there is no undercut neither in the direction perpendicular to the key axis and parallel to the flat side (y direction) nor in the direction perpendicular to the key axis and perpendicular to the flat side (z direction). In particular, the at least one coding recess can be formed by a milled portion on the edge. For example, the coding recess can be produced by a removing tool (drilling and/or milling tool) which rotates about a tool axis perpendicular to the flat side. This results in a substantial advantage in terms of the manufacturing method: The coding recess can be produced in the same operation and possibly with the same tool as the coding bores on the flat side. The key does not need to be reclamped between creating the coding bores and creating the coding recess(s). Through this configuration of the coding recess as a tool acting from the flat side or more generally, one or more of the following features can be implemented: SA closure of the coding recess towards the front and towards the rear is formed by a surface which is curved at least in some areas. This can be concave, for example, or s-shaped in horizontal section (section in a plane parallel to the key axis). In the second case, the coding recess can extend from a first, central middle section towards the front and towards the rear via a truncated cone-like concave surface section, via a flatter surface section and a convexly curved closure. SA region which extends parallel to the key axis has a constant depth (extension perpendicular to the flat side). SA normal to at least one region of the flank is in a plane that is perpendicular to the key axis. * The coding recess is mirror-symmetrical in relation to a plane perpendicular to the key axis. • The location of the coding recess with the greatest depth (extension perpendicular to the flat side; z extension) is in the y direction at the transition to the narrow side. * In particular at the location of the coding recess with the greatest depth (extension perpendicular to the flat side), the coding recess can have a substantially flat first surface section, which can in particular be delimited by parallel straight lines. The substantially flat first surface section can be flat by being produced by a removing tool moved parallel to the key axis, or it can have the shape of a section of a truncated cone, with the extension along the key axis being so small compared to the diameter of the truncated cone, that it acts substantially flat. In this second case, production can be carried out using a removing tool whose position along the key axis (hereinafter: x position) is constant during the production of the first section. The present invention also relates to a locking system with a flat key of the type described and a locking cylinder. Such a device has, in a manner known per se, a stator and a rotor with a key channel. The rotor can be rotated in the stator when the shank of a matching key is inserted into the key channel. The locking cylinder has a pin whose position is such that its radially inner end engages into the coding recess when the flat key is inserted (or hits the key where the coding recess would be if it were present if the key is coded such that it does not have the coding recess). The pin therefore scans the coding recess. Depending on the coding, it enables or does not enable a rotation of the rotor in the stator depending on the presence and dimensions of the coding recess. The pin can be, for example, a profile pin, a tumbler of a spring-loaded tumbler-counter-tumbler pair or a profile wobble pin. In particular, as is known per se, the pin is mounted in the rotor so as to be displaceable along a pin axis. The pin (or its pin axis) can thereby be at an angle to the key that is different from a perpendicular to the flat side and, for example, also different from a normal to the flank. In this way, it can be ensured that the pin does not centrally hit the surface of the key it scans (the flank formed by the coding recess), but rather acentrically. The shape of the radially inner end of the pin, in addition to the coding recess and its dimensions, also affects the position of the pin. This makes the task more difficult for the unauthorized key copier, as it is not enough for them to correctly copy one parameter (the depth of the bore), as is the case with coding bores - rather they have to copy the exact shape of the coding recess in order to be sure that the copied key can unlock the locking cylinder. This generally cannot be accomplished using standard key cutting tools. The pin axis can in particular be at an angle of at least 50, for example at least 100, to the normal to the flank. The subject matter of the invention also relates to a method for producing a flat key of the type described in this text. The coding bores are created on a key blank with the key bow and the key shank using a tool in a machining process. Before or after or in the same operation, the at least one coding recess is also created using a removing tool. This happens in particular with a tool that rotates about an axis perpendicular to the flat side, i.e. the method takes place from the flat side, with the manufacturing advantage discussed above. The method is carried out in particular such that the coding recess is extended in the direction of the key axis, i.e. the tool is moved relative to the key shank during the (milling) process, for example, at least in a direction parallel to the key axis (x direction), with the tool being able to be moved along a three dimensional path to create a recess with parts tapering towards the front and towards the rear. Alternatively, the tool can only be moved during the method in the direction perpendicular to the flat side (z direction) and can be applied several times in succession in immediately adjacent axial positions (x positions).

It can be provided in each case that the tool acts laterally on the key shank, in the sense that the tool axis is always guided next to the key shank throughout the entire machining process, i.e. the (extended imaginary) tool axis does not penetrate the key shank but is not closer to the key axis than the narrow side at any time. In this text, the orientation terms "radial", "radially inner", "axial", etc. generally refer, unless otherwise stated, to the key axis, which also corresponds to the locking cylinder axis in the locking system when the key is inserted. "Front" refers to the position towards the key tip, and "rear" is the position towards the key bow. The subject matter of the invention will be explained in more detail below on the basis of exemplary embodiments and the accompanying drawings. In the drawings, identical reference numerals designate identical or analogous elements. They show: Fig. 1 a perspective view of a key; Fig. 2 an enlarged partial view of the key according to Fig. 1; Fig. 3 a view of a key from the front (from the key tip), with tools for producing the key shown schematically; Fig. 4 a perspective view of another key; Fig. 5 enlarged partial view of the key according to Fig. 1; Fig. 6 a view of a locking cylinder with an inserted key from the rear (from the key bow), with a detail from the interior of the locking cylinder in a sectional representation; Fig. 7 a schematic sectional representation of a locking cylinder with an inserted key; Fig. 8 a detail of Fig. 2; and Fig. 9 a detail of Fig. 5. Figure 1 shows an example of a key 1 with key bow 11 and key shank 12. The key 1 is a flat key in that the key shank is substantially non-square rectangular in cross section perpendicular to a key axis 10, whereby two mutually parallel flat sides 21 and two narrow sides 22 with a smaller area than the flat sides 21 are defined. An edge 25 is formed between the flat sides 21 and the narrow sides 22. Figure 1 also shows the Cartesian coordinate system used in this text, with the x direction running parallel to the key axis and the z direction perpendicular to the flat sides 21. On the key shank 12 there are rows of coding bores 31 (coding bores) running parallel to the key axis 10. In addition to the coding bores, the key in the embodiment represented also has a profiling in the form of grooves 32 running parallel to the key axis. For example, basic profile grooves (which are always the same in the locking system and only exclude keys from other locking systems) and/or variation profile grooves (which form a coding) can be present. The key shown is a reversible key, i.e. the key shank is symmetrical in relation to a rotation of 1800 around the key axis 10, and the codings on the front and rear flat sides 21 are correspondingly identical. In contrast to the illustrated embodiment, the key can also have a different number of rows of coding bores on the flat sides, for example 1, 3, 4, 5 or 6, instead of or in addition to the profiling, and/or it can also have coding bores on the narrow sides 22. Towards the key tip 23, the key has an inlet ramp 24 that slopes down obliquely forward, which enables the locking cylinder to have pins (e.g. tumblers) that scan the coding bores and which protrude further into the key channel than to the central plane, so that the coding bores potentially can have a depth greater than half the thickness of the key. This has a positive effect on the number of possible permutations. In addition to coding bores in the flat side, the prior art also knows those in the narrow side and even bores that were made at an oblique angle (i.e. neither perpendicular nor parallel to the flat sides). In contrast to keys according to the prior art, the key according to Fig. 1 has, in addition to the coding bores, coding recesses 35, one of which is represented enlarged in Figure 8. They are formed by removing material along the edge 25, so that there is a flank 43 which slopes monotonically down from the flat side 21 to the narrow side 22, and there is no undercut, neither when viewed from the narrow side nor when viewed from the flat side. The transition 41 between the coding recess and the flat side 21 as well as the transition 42 between the coding recess and the narrow side 22 each have, in the middle, a substantially straight section 201 or 202 that extends parallel to the key axis, i.e. the coding recess 35 is elongated in relation to the x direction. The coding recess extends towards the front and towards the rear.

In the embodiment represented, the coding recess is also symmetrical in relation to a central plane perpendicular to the key axis 10. In the exemplary embodiment of Figures 1, 2 and 8, the flank 43 is substantially flat in the region between the straight sections 201 and 202 that extend parallel to the key axis. In addition, as is particularly clearly visible in Fig. 2 and 8, such a flat first section 206 can have an extension in the x direction that is substantially constant along the depth, i.e. it can be delimited by two approximately parallel straight lines 203, 204. These straight lines can adjoin the first transition 41 at right angles at the ends of the first section 201 of the first transition 41, in particular in a projection onto the flat side 21. The flat section 206 merges in the axial directions into a second and third section 207, 208, which can be roughly in the shape of a truncated cone-like section (in the example represented with a truncated cone tip towards the narrow side 22). The second and third sections merge into a curved closure 211, 212 of the coding recess 35 via a flatter surface section 209, 210. A property of coding recesses 35 of the type described here is that it can be produced by a machining (in particular cutting) process from a flat side (or possibly a narrow side) with a rotating tool (drill, milling machine). It is therefore possible to produce the coding recesses 35, even though they lie on the edge 25 and thus neither in the flat side nor in the narrow side, in the same operation and, for example, with the same tool as the coding bores 31. This is illustrated in Figure 3, which represents the key 1 clamped between two symbolically represented clamping jaws 51. A drilling and/or milling tool 52, which rotates about a tool axis 53 perpendicular to the flat sides, can produce the coding recesses by removal. Therefore, the key does not have to be reclamped between creating the coding bores 31 and creating the coding recess(s). In particular, it is also possible to use the same drilling and/or milling tool that is used to create the coding bores. When creating the coding recess(es), the tool axis 53 can lie laterally next to the key shank as represented in Fig. 3, i.e. it is offset outwards in the y direction in relation to the corresponding narrow side 22, in the direction away from the key axis. The coding recess is essentially milled, which has the advantages described in this text. The creation of a coding recess as represented in Fig. 1 and 2 is achieved by moving the drilling and/or milling tool, rotating about its tool axis, from above and/or laterally to the key until an initial recess of sufficient depth is created, and it is then moved relative to the key shank in the x direction or x direction and, for example, also in the y direction until the coding recess has its final size. Figures 4 and 5 show an alternative key 1, which differs from that of Fig. 1 and 2 in the shape of the coding recesses 35. In contrast to the embodiment of Figures 1 and 2, the coding recesses 35 each have, towards the narrow side 22, a small flat surface section 45, i.e. approximately parallel to the flat side, (bottom; see also, Figure 9, which represents one of the coding recesses in an enlarged manner). In addition, in contrast to the embodiment of Figures 1 and 2, the coding recesses 35 are concave towards the front and towards the rear, i.e. the truncated cone-like second and third sections 207, 208 extend to the front and rear ends of the recess. In contrast to the embodiment of Figures 1, 2 and 8, the intermediate first section 206 is not completely flat, but only approximately flat. Accordingly, the middle section 201 of the first transition 41 is only approximately parallel to the key axis. Strictly speaking, the middle section 206, like the second and third sections 207, 208, is in the shape of a truncated cone-like section, but can be viewed as approximately flat due to its small extension in the x direction. The coding recess has a shape like that represented in Fig. 4, 5 and 9 if the distance between the drilling and/or milling tool when creating the coding recess has a fixed y position in relation to the key shank and makes a drilling movement (from above) several times at slightly different x positions or is displaced in the x direction after approaching from above, with a fixed y position. In the represented example according to Figures 4, 5 and 9, it is created by moving a drilling and/or milling tool three times to correspondingly different x positions with an identical y position, to create the second section 207, the first section (middle section) 206 and the third section 208. It would also be possible to create the approximately flat middle section of a plurality of adjacent subsections, each with a different x position of the drilling and/or milling tool, so that it would also be approximately flat if, compared to Fig. 4, 5 and 9, it were still elongated in the x direction. The same applies to the embodiments of Figures 4, 5 and 9 as to the coding recesses in Figure 1 and 2, which taper gently towards the front and towards the rear and as generally with a group of embodiments of the invention, however: Also at both transitions from the coding recess towards the edge 25, in the region that is circled in one of the coding recesses in Fig. 5, the recess is open outwards in relation to the key axis and not inwards, i.e. a tangential plane on which the surface delimiting the coding recess at these points points radially outwards in relation to the key axis or is at most parallel to the key axis, but it does not point radially inwards. Correspondingly, a tangent 221 (Fig. 9) will be at an angle 6 of at least 900 to the edge 25 at the transition 41 in the flat side plane at the point of contact with the edge. Therefore, in contrast to a coding bore, the coding recess is not to some extent delimited to the outside, which is why it is not possible for an unauthorized key copier, at least not without great effort, to determine at which y position the tool axis was, i.e. the coding recess was created. This feature, according to which the coding recess is open to the outside, can - and will also be reflected in the embodiments according to Figures 1, 2 and 8 or 4, 5 and 9 - in the fact that the first transition 41 is at a flat angle (Fig. 4, 5 and 9; the angle 6 of the tangent in the flat side plane at the point of contact with the edge 25 is at least the same, in particular greater than 900) or in a continuous curve (Fig. 1, 2 and 8; the curve runs S- shaped and therefore includes a turning point 222) merges into the edge 25. The same applies to the second transition 42 in the exemplary embodiments represented. This also merges - in the plane of the narrow side 22 - into the edge 25 at a flat angle y (Fig. 4, 5 and 9, see Fig. 9) or in a continuous curve with turning point 223 (Fig. 1, 2 and 8). The depth t of the recess (extension in the z direction, i.e. perpendicular to the flat side) is marked in Fig. 5 and is approximately constant over a region b extending in the x direction, just as is the case in Fig. 2. Figures 6 and 7 show, in addition to the key, a locking cylinder 101. The locking cylinder 101 has a stator 103 and a rotor 104 mounted therein in a manner known per se. A key channel for inserting a flat key, for example a reversible key, is formed on the rotor 104. If the key is appropriately coded, the rotor 104 can be rotated relative to the stator 103 (around a locking cylinder axis parallel to the key axis). The output unit, which is not essential to the invention here and with which a bolt or other element is driven by the rotational movement of the rotor, is only partially shown in Fig 6. As illustrated in Fig. 6 and 7, a locking cylinder 100 with the key 1 of the type illustrated in Fig. 1/2 or 4/5 can have at least one pin 111 which is mounted radially displaceably in the rotor 103 of the locking cylinder and which scans the coding recess. In the illustrated exemplary embodiment, the pin 111 is a profile pin (locking pin), which blocks rotation of the rotor 103 of the locking cylinder relative to its stator 104 if the coding recess is not present or is not in the right place or is not sufficiently large or sufficiently wide. However, as mentioned, the principle of the invention can also be applied to other pins, for example tumblers of spring-loaded tumbler-counter-tumbler pairs or profile wobble pins, which also block if the coding recess is too deep, for example (or can block if a coding recess is present where no such coding recess should be present). A special feature of the locking system can be that the pin 111 is at an angle to the key 1, which is both different from a perpendicular to the flat side 21 and different from a normal to the flank 43. In the illustrated exemplary embodiment, the angle a between the pin axis 121 and the flat side 21 is approximately 250, while the normal to the flank 43 is at an angle of approximately 450 thereto. In this way, the result is that the pin 111 does not centrally hit the surface of the key 1 that it scans, but rather acentrically. The shape of the radially inner end of the pin 111 therefore has just as much of an effect on the radial (in relation to the key axis=locking cylinder axis) position of the pin 111 in its scanning position as the shape of the coding recess itself. In the illustrated exemplary embodiments of a key, two coding recesses of the same axial length are shown. The invention is suited to coding through a suitable choice of the number of coding recesses and their dimensions. In addition to varying the number of coding recesses from key to key - even between coding recesses of the same key - the length (extension in the x direction) and/or the depth (extension in the y and z directions) can be varied, under certain circumstances, when using different tools, also the flank angle - even if in many embodiments it is preferred that the flank angle is always the same. The key can in particular - this applies to all embodiments - be a reversible key. In this case, the mechanical codings of each edge 25 corresponds to that of the edge that is diametrically opposite.

Claims (22)

1. A flat key (1), having a key bow (11) and a key shaft (12) extending along a key axis (10) from the key bow (11) to a front key tip (23) with two parallel flat sides (21) and two opposing narrow sides (22), wherein an edge (25) parallel to the key axis (10) extends between the flat sides and the narrow sides, wherein a row of coding bores (31) parallel to the key axis is formed on at least one of the flat sides, characterized by at least one coding recess (35) in at least one of the edges (25), which forms a flank (43) which extends from the flat side to the narrow side and which has a monotonous gradient.

2. The flat key according to claim 1, wherein a first transition (41) between the coding recess (35) and the flat side and/or a second transition (42) between the coding recess (35) and the narrow side has a section (201; 202) extending substantially parallel to the key axis (10).

3. The flat key according to claim 1 or 2, wherein at least one first and one second parallel straight line (203, 204) extend in the flank (43) of the coding recess (35).

4. The flat key according to claim 3 with reference to claim 2, wherein the first and second parallel straight lines (203, 204) join at the ends of said section (201, 202), in particular at right angles in a projection onto the flat side (21).

5. The flat key according to any one of the preceding claims, wherein the coding recess (35) comprises a first surface section (206) which is flat or has the shape of a truncated cone section up to the flat side (21).

6. The flat key according to claim 5 with reference to claim 3 or 4, wherein the first surface section (106) is delimited by the parallel straight lines (103, 104).

7. The flat key according to any one of the preceding claims, wherein the coding recess (35) comprises a first surface section (206) which is flat or has the shape of a truncated cone section and which merges forward and backward into a second and third surface section (207, 208), each of which is designed in the manner of a truncated cone section.

8. The flat key according to any one of the preceding claims, wherein the coding recess (35) comprises at least one concave, truncated cone-like surface section (207, 208) which merges via a flatter surface portion (209, 210) into a convexly curved closure (211, 212) of the coding recess (35).

9. The flat key according to any one of the preceding claims, wherein a first transition (41) between the coding recess (35) and the flat side merges into the edge (25) at a flat angle or in a continuous curve.

10. The flat key according to any one of the preceding claims, wherein a second transition (4) between the coding recess (35) and the flat side merges into the edge (25) at a flat angle or in a continuous curve.

11. The flat key according to any one of the preceding claims, wherein the coding recess can be produced by a removing tool (52) which rotates about a tool axis (53) perpendicular to the flat side (21).

12. The flat key according to claim 11, wherein the tool axis leads past the key shank.

13. The flat key according to any one of the preceding claims, wherein a closure of the coding recess towards the front and towards the rear is formed by a surface which is curved at least in some areas.

14. The flat key according to any one of the preceding claims, wherein there is a region which extends parallel to the key axis (10) in which the coding recess has a constant depth.

15. The flat key according to any one of the preceding claims, wherein a normal to at least one region of the flank (43) is in a plane that is perpendicular to the key axis.

16. The flat key according to any one of the preceding claims, having an inlet ramp (24) which slopes down towards the tip of the key and the depth of which is greater than half the thickness of the key shank.

17. A locking system, having a flat key (1) according to any one of the preceding claims and a locking cylinder (100) having a locking cylinder stator (104) and a locking cylinder rotor (103) with a key channel into which the key shank (12) of the flat key can be inserted, wherein the lock cylinder has a pin (111) which scans the coding recess (35) and enables or does not enable the rotation of the locking cylinder rotor depending on its presence or absence.

18. The locking system according to claim 17, wherein the pin (111) is at an angle to the key (1) which is both different from a perpendicular to the flat side (21) and different from a normal to the flank (43).

19. A method for producing a flat key according to any one of claims 1-16, wherein a key blank having the key bow (11) and the key shank (12) is provided and the coding bores (31) are produced with a tool in a machining process, and wherein the at least one coding recess (35) is also produced in a machining process.

20. The method according to claim 19, wherein the coding recess (35) is produced with a tool (52) which rotates about a tool axis (53) perpendicular to the flat side (21).

21. The method according to claim 19 or 20, wherein the tool (52) is moved relative to the key shank at least in the direction (x) of the key axis (10) during the production of the coding recess (35) while it removes material from the key shank, and/or wherein the tool (52) is applied at different axial positions relative to the key shank (12) in order to produce one and the same coding recess (35).

22. The method according to any one of claims 19 to 21, wherein the tool axis (53) is not closer to the key axis (10) than the narrow side (22) at any time that material of the key shank is removed to create the coding recess (35).