DE29818143U1 - Security key - Google Patents

Description

08.10.1998

Security key

The invention relates to a security key according to the preamble of claim 1.
15

EP 0 651 117 discloses a security key for locking cylinders, the key back of which is formed by two parallel circular cylinders. The locking recesses are truncated cone-shaped depressions in a cylinder surface, with the cone axis of the locking recesses being perpendicular to the cylinder axis. The locking recesses can be distributed essentially over the entire circumference of the security key. They are set back behind the outer contour surface of the key back. The conical surfaces in the longitudinal direction form inclined flanks for a core pin, which can slide over these inclined flanks into and out of the locking recess as the key passes. Each of the locking recesses has a centrally located locking surface. This locking surface is used to align the height of the core pin. The locking surfaces form a depth coding in interaction with the core pin and housing pin, so that in the release position, when the core pin and housing pin have fallen into the locking recess, the gap between the core pin and housing pin lies exactly in the separating gap between the core and housing 5 of the locking cylinder and thus releases the rotation of the core in the housing.

The locking devices are spring-loaded on the outside of the housing pin to ensure positive scanning of the locking recesses. When inserting the safety

When the security key is inserted, the locking recesses move past the core pins, whereby the core pins move over all the inclined flanks and locking recesses arranged in front of them, until the security key has reached its end position. Several locking recesses can also move under the core pins if the locking recesses are located one behind the other in the direction of insertion. When the key is removed, the static friction of the core pin in the locking recess must first be overcome. The locking recesses then move under the core pins and impose an upward, inclined movement on them that corresponds to the geometry of the inclined flanks.

When the security key is inserted and removed, a sequence of radial movements predetermined by the order of the passing locking recesses is impressed on the core pin in its radial guide bore, namely against the spring force of the tumblers when rising from a locking recess and in the direction of the spring force when plunging into a locking recess.

Due to the truncated cone shape of the locking recesses, the base of the core pin, which is usually chamfered, has to follow the transition from the locking surface to the inclined flank. When sliding out of a locking recess, a quasi-singular stress occurs there. During the sliding movement over the locking surface, which is wider in the sliding direction than the base of the core pin, the key only moves relative to the core pin in the longitudinal direction of the key. At the point where it hits the inclined flank, the core pin is forced into a radial movement by the inclined flank almost seamlessly. The geometry of the transition therefore requires very tight tolerances for the edge curvature of the base of the core pin and the edge of the locking recesses in order to avoid wear caused by using the security key. If this aspect is neglected, which occasionally happens with duplicate keys copied by third parties, these unauthorized copies often tend to "hook" in the locking cylinder after some time when one or more core pins hit a beveled flank and are lifted

·

This makes operation more difficult and less safe over time, as both the core pins of the locking cylinder and the bevelled flanks of the security key are subjected to axial strain due to the tendency to become jammed.

This problem only occurs after some time and often leads to the locking cylinder falling into disrepute, even though the poorly copied duplicate key is the cause.

The object of the invention is therefore to design a security key of the type mentioned at the beginning in such a way that even a copied security key slides practically without hindrance when inserted and removed and that the wear of the security key and the core pins of the locking cylinder remains so low that the locking cylinder cannot be brought into disrepute by copied duplicate keys.

The problem is solved by the features of the main claim.

The invention offers the advantage that the core pins continuously and thus without inhibition dip into the locking recesses and rise from them according to the geometry of the locking recesses. The invention is based on the finding that

With the conventional geometry of the locking recesses, a certain amount of inhibition of the core pin occurs when its chamfered surface runs onto the inclined flank. These inhibition points are eliminated by the invention.
30

The inhibiting points - the transitions between the locking surface and its inclined flanks - are designed as concavely rounded sliding surfaces. The concave rounding excludes singularities - such as corners or edges - on the sliding line of the transition.

In addition, the sliding surfaces in the longitudinal direction of the key back nestle tangentially against both the inclined flanks and the locking surface. This ensures that the gearing implementation of the pure

Longitudinal movement of the key back to the purely radial movement of the core pin occurs continuously and steadily, without load peaks occurring, although the key back and core pin basically form a link mechanism in which two link blocks are guided on longitudinal paths that are perpendicular to each other and the movement of one link block (= key back) should be converted into the perpendicular movement of the other link block (= core pin) with as little friction as possible and with a continuous transition.

The penetration of the core pins into and emergence from the locking recess is facilitated by the special geometry of the sliding surface in conjunction with the friction properties of the sliding pair. The force in the longitudinal direction of the key back with which the security key is inserted and pulled out is always outside the friction cone, particularly in the area of the beveled flanks. This requirement prevents the key from self-locking. This requirement is automatically met by the suggested 0 rounding and the tangential fit for the sliding surfaces as well. The angular distance of the force in the longitudinal direction from the friction cone is a measure of the expected wear. In the area of the sliding surfaces, this is always greater than or equal to the angular distance in the area of the 5 beveled flanks and approaches the value in the area of the beveled flanks.

The base of the core pin is always in a continuous 0 sliding friction state during insertion or removal. The usual breakaway torque at the point of contact with the inclined flank, caused by the singular transition, is avoided with the invention.

The core pins and thus also the tumblers are exposed to practically only low axial forces. They cannot tilt and are only subjected to a small amount of axial stress. This means that the stress on the base of the core pin and thus the wear there is minimal. The locking recesses are also subjected to less stress thanks to the proposed design in the above sense.

The key slides in and out of the locking cylinder with reduced sliding resistance, which makes it easier to use and increases operating safety. The user also has the impression that the locking pairs are working perfectly without the key catching at all. The invention therefore offers the highest level of operating comfort with a reliable and low-wear interaction between the security key and the locking cylinder.

The precise, geometric positions of the locking surfaces of the security key are blurred by the rounding of the transitions from the locking surface to the sliding flank. They can therefore only be measured imprecisely by scanning. In order to copy these quasi-curved locking recesses, increased scanning accuracy and possibly an additional degree of freedom of the copying machine is required to precisely scan the trajectory.

The sliding surfaces can be designed inconspicuously. They are then barely perceptible to an uninformed expert, so that he usually copies the security key without the corresponding sliding surfaces. A key copied without the trajectory of the locking recesses is comparatively easy to identify as a counterfeit, since it differs from the original with the trajectory on closer visual inspection. In addition, such a counterfeit does not run over the core pins as easily from the first moment as the original or a permissible copy 0 in accordance with the present invention.

Preferred embodiments of the invention are described in the subclaims.

If all of the locking recesses spaced apart along a longitudinal line of the key back have a concavely rounded sliding surface at each of the transitions from the locking surface to one of the beveled flanks, each locking surface extends over one beveled flank on the key tip side and one beveled flank on the key shoulder side

into the respective sliding surface. Each locking recess always consists of inclined flanks and a locking surface located within the inclined flanks. In the described design, a core pin passes through several locking recesses until it reaches its end position. The inhibiting points are eliminated by the described design.

In addition to this, it is proposed that the transitions between the inclined flanks and the outer contour surface of the key back are designed as convexly rounded sliding surfaces which, in the longitudinal direction of the key back, nestle tangentially against both the inclined flanks and the outer contour surface of the key back. The transitions are therefore concave on the locking surfaces and convex on the key back. All transitions are scanned with little sliding resistance because they are designed without singularities. The transitions mentioned, which are radially outward with respect to a conical locking recess, for example, will not generally lead to an impediment to the key, but they are noticeable when the key is operated and thus also influence the operation of the locking pair. The proposed design therefore creates a smooth-running security key which is functionally reliable and practically even reduces or even prevents the impression of mechanical actuation of the tumblers.

It is further proposed that adjacent locking recesses overlap with their beveled flanks and that the transitions between the respective overlapping beveled flanks are designed as convexly rounded sliding surfaces which tangentially fit the respective beveled flanks in the longitudinal direction of the key back. The invention offers the advantage that locking recesses which are closely spaced - as occur in locking cylinders with a high degree of security - can also benefit from the invention.

The transitions mentioned are convex rounded areas. During production, this has the advantage that each recess

The design allows the recesses to be milled practically continuously in the form of a curve. All transitions are in the form of fillets, so that synergy effects play a role in production. The transitions (two or four different types) only have to be programmed once, for example in a CNC machine, and can then be used for each locking recess. For this purpose, the locking recesses, with the exception of the locking surfaces, are designed as continuously rounded curved paths in the longitudinal direction of the key spine. Only the run-out zone of the locking recess located on the outermost side on the key bow can be excluded from this. The sloping flank of this locking recess facing away from the key bow is never impacted by a core pin during normal use.

The position of the locking surfaces and the distances between the locking recesses in the longitudinal direction of the key back are blurred if two opposing sliding surfaces of a locking recess are curved with different radii of curvature. The center of the locking surface is then no longer exactly the middle of the locking recess, since the sliding surfaces of a locking recess have different radii of curvature and therefore usually also different longitudinal extensions. When attempting to copy, the locking surface or the position of the corresponding tumbler pins can no longer be determined by determining the center of the locking recess due to the asymmetrical design of the locking recess. The distances between the locking recesses can then also no longer be determined by their edge distances.

The proposed design offers the advantage that the sliding of locking recesses that are essentially equidistant on a longitudinal line does not occur synchronously for all corresponding core pins. The multiplication of the 5 mechanical forces when the core pin slopes come into contact with the sloped flanks of the locking recesses of a conventional key is replaced by the addition of smaller mechanical forces. The security key slides more smoothly overall.

In order to ensure that the core pins slide freely across their entire width when the key is moved, it is suggested that the width of the sliding surface in the transverse direction of the key is greater than the width of the contact zone of the base of a core pin with the sliding surface in the position where the core pin comes into contact with the sliding surface. The sliding surface should not be less than the specified width over its entire length. It is particularly important that the width of the sliding surface in the transverse direction of the key at the transition from the locking surface to the sliding surface is greater than the specified width of the contact zone of the base of a core pin. The specified widths are the transverse dimensions projected onto the transverse direction of the back of the key. The design described above ensures that the core pin slides freely along the sliding surface. To do this, it is sufficient to design the width of the contact zone - as specified - of the core pin with the sliding surface accordingly. This width of the contact zone can differ from the width of the base of a core pin. This is the case, for example, if the locking recess is essentially truncated cone-shaped. With a cylindrical core pin, the curvature of the base circle of the core pin can deviate from the curvature of the outer circle of the truncated cone at the level of the locking surface. In this case, the contact zone - with a smaller base circle of the core pin - is smaller than the width of the core pin as a whole.

The unhindered running is always automatically achieved when the width of the sliding surface in the cross-key direction is greater than or equal to the width of the base of the core pin. Then the contact zone of the base of the core pin with the sliding surface in the running position of the core pin must always be within the width of the sliding surface in the cross-key direction. This ensures unhindered sliding. Preferably, the width of the sliding surface over the entire longitudinal extension of the sliding surface is greater than or equal to the width of the base of a core pin. Then mechanical inhibition points within the sliding surface are also excluded.

It is intended that the locking recess has a truncated cone-shaped inclined flank with a cone angle ß measured in the longitudinal direction (6) of the key symbol (5) and that, with respect to the longitudinal section, the tangent angle to the concave surface, measured in the longitudinal direction of the key back, is always smaller than the cone angle ß. When milling the locking recesses, for example with an end mill, the cone angle ß is the bevel angle of the end mill head. The locking recess can then be milled in a simple manufacturing process by continuously guiding the milling head along a curved path with a component in the longitudinal direction when plunging into the material of the key back and when emerging from the milled locking recess. An additional degree of freedom of the milling machine is required for this.

The mechanical inhibition during sliding of the surfaces of the locking recess and core pin is further reduced by the fact that the smallest radius of curvature of the sliding surface is greater than or equal to the associated radius of curvature of the core pin at the point where it is in contact with the sliding surface.

The invention is explained in more detail using embodiments shown in the drawings. They show:

Fig.la a longitudinal section through a locking recess in the
key back,

Fig.Ib the flank angle profile of the key head end of the locking recess of Fig.la,

Fig.2a a longitudinal section through a key back

with several locking recesses and cylinder core and housing with several locking mechanisms,

Fig.2b a detail of Fig.2a,

Fig.3 a plan view of a locking recess,

Fig.4a a security key according to the invention in
side view,

Fig.4b shows a section through the security key of Fig.4a seen in the direction of arrows IVb.

δ I

r ·

10

Unless otherwise stated below, all reference symbols always refer to all figures.

Fig.la shows a locking recess 3 in section in the longitudinal direction of the key 6. This locking recess 3 is incorporated in a security key 1 for a locking cylinder 2. The locking recess 3 projects behind the outer contour surface 4 of the key back 5. The outer contour surface 4 is the shape of the key back corresponding to the profile of the locking core.

The locking recess 3 has sloping flanks 7 running in the longitudinal direction 6 of the key back 5. These sloping flanks 7 slide under a core pin 9 when the security key 1 is inserted into or removed from the locking cylinder 2. The sloping flanks 7 serve to ensure that the core pin 9 is guided between a locking surface 11 and the outer contour surface 4. Each of the locking recesses 3 has such a locking surface 11. The locking surface 11 serves to align the tumblers 8 consisting of the core pin 9 and the housing pin 10. The foot sits on the locking surface 11.

12 of an associated core pin 9. When the security key 1 is fully inserted, the foot 12 of an associated core pin 9 rests on its locking surface 11 so that the locking cylinder 5 assumes its release position.

The transition areas between the locking surface 11 and its inclined flanks 7 are designed as concavely rounded sliding surfaces

13. These sliding surfaces 13 extend in

0 longitudinal direction 6 of the key back 5 and nestle tangentially against both the beveled flanks 7 and the locking surface 11. This reduces the mechanical inhibition, which occurs more frequently, for example, with a seamless beveled flank 33 - as shown in dashed lines in Fig.la 5. The beveled flank 7 merges smoothly and continuously into the locking surface 11.

In addition, in the embodiment shown

also the transitions between the beveled flanks 7 and the outer contour surface 4 of the key back 5 are rounded as convex

formed sliding surfaces 13, which also tangentially conform to both the inclined flanks 7 and the outer contour surface 4 of the key back 5 in the longitudinal direction 6 of the key back 5. As a result, the locking recess 3 conforms uniformly to the locking or outer contours in a curved manner without any mechanical hindrances. There can be a turning point at the transition from the concavely rounded sliding surface 13 to the convexly rounded sliding surface 13, provided that the concave and convex sliding surfaces then touch each other.

In order to fully ensure this effect when a locking recess 3 moves away from under a core pin 9, the locking recess 3 has a sliding surface 13 both at its end 26 on the key tip side and at its end 27 on the key bow side. This is particularly important in view of the fact that several core pins 9 can be arranged on the same longitudinal line 42, so that the corresponding locking recess slides away under several core pins 9■ and at least under one core pin 9 with its entire longitudinal extent. The sliding surfaces 13 mean preferred transitions from the locking surface 11 to the inclined flank 7. These are crucial for mechanically unrestrained sliding. The transitions from the inclined flank 7 to the outer contour surface 4 or to another locking surface 11 (see below) are then preferably also designed as sliding surfaces 13 in the sense of the invention.

It is preferred that each of the locking recesses 3 has at least two sliding surfaces 13. This in turn applies to the transitions between the locking surface 11 and the inclined flank 7.

In the other case, each of the locking recesses 3 has at least four sliding surfaces 13 - as shown.

Fig.Ib shows the course of the flank angle α of a seamless oblique flank 33 in dashed lines and the course of the tangent angle α" of the embodiment of Fig.la in solid lines as a function of the distance L in the longitudinal direction 6 of the key back. The seamless oblique flank 3 3 has a practically rectangular course of the flank angle α.

The flank angle α suddenly takes on a constant value in the flank area 34 and returns to practically zero when leaving the flank area 34.

In contrast, the tangent angle α" initially increases steadily and slowly in the transition region 35. The gradient then increases until it again approaches the value zero in the flank region 34. Here, the sliding surface 7 according to the invention also has a substantially constant gradient, so that a flank region 34 can be assumed. To the right of the flank region 34, the tangent angle α' decreases again in the transition region 35 until the angle zero is assumed when the locking surface 11 is reached.

The invention is characterized by the continuous course α' of the tangent angle. Any course of the inclined flanks 7 of a locking recess 3 that is rounded off smoothly in this way is covered by the invention. This applies provided that the rounding and thus the curved course of the tangent angle α' is not merely due to manufacturing tolerances.

Overall, the locking recess 3 has a truncated cone-shaped cross-section. The inclined flanks 7 are at the cone angle ß with respect to the longitudinal line 42. With respect to the longitudinal section, the tangent angle α' to the sliding surface 13, measured to the longitudinal direction 6 of the key back 5, is smaller than the cone angle ß. This is achieved by curved path milling with an end mill with a milling head chamfered at the angle β when the milling head is subjected to a continuous transverse movement in the area of the inclined flanks 7 during its longitudinal movement.

Fig.2a shows a longitudinal section through the key back 5. The longitudinal section includes the core 28 and housing 29 of a locking cylinder 2 with corresponding tumblers 8. There are locking recesses 3 arranged at a distance from each other. At the same time, locking recesses 3 are provided which overlap with their beveled flanks 7. In Fig.2a, these are the two locking recesses on the right-hand side.

3. All locking recesses 3 have sliding surfaces 13 according to the invention. The two right-hand locking recesses 3 merge into one another. The transition between the locking surface 11 of the left-hand locking recess 3 and the inclined flank 7 of the right-hand locking recess 3 is also designed as a convex sliding surface 13 in accordance with the invention.

The core 28 is connected to the key back 5 in the transverse direction 16 of the key. It has 8 core pins 9 seated in the core bores 3. The core pins 9 rest with their feet 12 on the associated locking surfaces 11 (see also Fig. 1). The separating joint 30 between the core 28 and the housing 29 is arranged exactly between the core pins 9 and the housing pins 10, so that the rotation of the core 28 is possible.

The safety lock is thus shown in the release position.

. Fig.2b shows a detailed view of Fig.2a shown enlarged. Here, a chamfer 31 of the foot 12 of the core pin 9 is particularly clearly visible. The chamfer angle 32 is preferably larger than the flank angle α shown, so that the core pin 9 always slides with its underside along the sliding surface 13 and the inclined flank 7.

The curvature of the sliding surface 13 can be described by local radii of curvature 21. As an example, a radius of curvature 21 of the sliding surface 13 is shown together with a dashed circle of curvature. The radius 21 of this circle of curvature is larger than the associated radius of curvature 22 of the outer edge 23 of the base of the core pin 9 at the point of contact. Core pin-sliding surface pairs that are dimensioned in this way always slide on one another without hindrance. The radius of curvature 21 is preferably at least twice as large as the radius of curvature 22 in order to exclude hindrance.

Fig.3 shows a top view of the locking recess 3. The locking recess 3 is elongated to oval in the longitudinal direction 6 of the key. The ends of the locking recess 3 are rounded and merge into the inclined flanks 7. The locking recess 3 is therefore surrounded by a self-contained,

• · · ϕ ϕ t

• · · ϕ ϕ
φ φφφ φ ·

running slope. The slope has two parallel side flanks 14, the ends of which are connected by the sloping flanks 7 running at 180°. "Light edges" are shown at the transition 40 of the sloping flanks 7 into the locking surface 11. These transitions 40 correspond to the sliding surfaces 13 in a top view. In the embodiment shown, the locking surface 11 is elongated and oval. The locking surface 11 can also wind around the key back 5 in a spiral or partially spiral shape and thus run with components both in the longitudinal direction 6 and in the transverse direction 16 of the key back 5.

The outline of the foot 12 of the core pin 9 is shown resting on the locking surface 11, which runs straight onto the sliding surface 13 of the inclined flank 7. The foot 12 of the core pin 9 has a smaller width 20 than the width 15 of the sliding surface 13. This is equal to the width of the locking surface 11, so that the foot 12 does not touch any of the side flanks 14. The outline of the foot 12 of the cylindrical core pin 9 is circular. The radius of this circle is smaller than the radius of curvature of an imaginary "light edge" between the sliding surface 13 and the locking surface 11. As a result, the width 17 of the contact zone 18 of the foot 12 of the core pin 9 with the sliding surface 13 in the sliding position 19 of the core pin 9 on the sliding surface 13 is smaller than the width of the foot 12 of the core pin 9. The width 15 of the sliding surface 13 in the cross-key direction 16 is larger than the width 17 of the aforementioned contact zone 18. This ensures that the sliding surface slides smoothly onto the core pin 9.

For this purpose, it is also sufficient that the width 15 of the sliding surface 13 in the key transverse direction 16 is greater than or equal to the width 20 of the foot 12 of the core pin 9.

Fig.4a shows a security key 1 in an overall view. The security key 1 has locking recesses 3. These are partially curved as described above. They are incorporated into the outer contour surface 4 of the key back 5. They are all located between

Key tip 24 and key head 25. Each locking recess 3 therefore has an end 26 on the key tip side and an end 27 on the key head side. Several locking recesses 3 are located on the longitudinal line 42 shown. The longitudinal distance 43 between the locking recesses 3 is given by the center distance of the respective locking recesses 3. This longitudinal distance 43 can also be unequal to the distance between the corresponding core pins 9, since one of the locking recesses 3 is elongated with the locking surface 11. The position of the core pins 9 cannot therefore be determined even with precise knowledge of only the relative position of the locking recesses 3.

Fig. 4b shows the section of Fig. 4a, which is indicated there with IVb. The section runs through a locking recess 3. The key back 5 consists of two parallel solid cylinders 36, which are connected by means of a connecting web 37. The locking recesses 3 are made on each of the two solid cylinders 36 radially to the respective cylinder axis 41 or secantial to it. They can also run completely or partially on the connecting web 37.

This means that the entire circumference of the key back 5 is available for the arrangement of the locking recesses 3. To increase security, a large number of locking recesses 3 are generally provided and thus also the same number of core pins 9. However, this also means an increased number of transitions and inhibition points. With such a security key 1, the reduction in inhibition at the numerous inhibition points also brings a correspondingly large improvement in sliding and a reduction in wear.

The locking recesses 3 can be arranged distributed practically over the entire circumference of the solid cylinders 3 6. This means that a very large surface is available for attaching the locking recesses 3. Since the locking recesses 3 can be designed with rounded sliding surfaces 13 and with a curved path, their space requirement is greater than that of conventional locking recesses 3. Despite the increased space requirement, the available space can be increased.

large surface of such security keys 1, many locking recesses 3 according to this invention can be provided.

08.10.1998

Reference list:

1 security key

2 locking cylinders

3 locking recess

4 Outer contour surface

5 key backs

6 Longitudinal direction

7 Very rag flank

8 Locking mechanism 9 Core pin

10 Housing pin

11 Rest area

12 feet of the core pin

13 Sliding surface 14 Side flank

15 Width of the sliding surface

16 Key cross direction

17 Width of the contact zone

18 touches

19 Sliding position of the core pin

20 Width of the base of the core pin

21 smallest radius of curvature of the sliding surface

22 Radius of curvature of the outer edge of the core pin

23 Outer edge of the core pin 24 Key tip

25 Key head

26 Key tip end of the locking recess

27 Key head end of the locking recess

28 core

5 29 Housing

3 0 Separation joint

31 chamfer

3 2 Chamfer angle

33 seamless sliding flank

34 flank area

3 5 Transition area

3 6 Solid cylinder

37 Connecting bridge

3 8 Core drilling

3 9 Housing bore

40 Transition

41 Cylinder axis

42 Longitudinal line

43 Longitudinal distance of the locking recesses α flank angle

α' tangent angle

β cone angle

L Distance in longitudinal direction

Claims (8)

1. Security key ( 1 ) for locking cylinders ( 2 ), wherein the security key ( 1 ) has locking recesses ( 3 ) which are set back behind the outer contour surface ( 4 ) of the key back ( 5 ) and have inclined flanks ( 7 ) running in the longitudinal direction ( 6 ) of the key back ( 5 ), and wherein each of the locking recesses ( 3 ) has a locking surface ( 11 ) for aligning its locking element ( 8 ) consisting of core pin ( 9 ) and housing pin ( 10 ), on which the foot ( 12 ) of the associated core pin ( 9 ) rests, characterized in that the transitions between the locking surface ( 11 ) and its inclined flanks ( 7 ) are designed as concavely rounded sliding surfaces ( 13 ) which extend in the longitudinal direction ( 6 ) of the key back ( 5 ) both to the The inclined flanks ( 7 ) as well as the locking surface ( 11 ) each fit tangentially. 2. Security key according to claim 1, characterized in that of all the locking recesses ( 3 ) spaced apart from one another along a longitudinal line of the key back, each has a concavely rounded sliding surface ( 13 ) at each of the transitions from the locking surface ( 11 ) to one of the inclined flanks ( 7 ). 3. Security key according to claim 1 or 2, characterized in that the transitions between the inclined flanks ( 7 ) and the outer contour surface ( 4 ) of the key back ( 5 ) are designed as convexly rounded sliding surfaces ( 13 ) which, in the longitudinal direction ( 6 ) of the key back ( 5 ), nestle tangentially both against the inclined flanks ( 7 ) and against the outer contour surface ( 4 ) of the key back ( 5 ). 4. Security key according to claim 2 or 3, characterized in that adjacent locking recesses ( 3 ) overlap with their inclined flanks ( 7 ) and that the transitions between the respectively overlapping inclined flanks ( 7 ) are designed as convexly rounded sliding surfaces ( 13 ) which tangentially conform to the respectively involved inclined flanks ( 7 ) in the longitudinal direction ( 6 ) of the key back ( 5 ). 5. Security key according to one of claims 1 to 4, characterized in that two opposing sliding surfaces ( 13 ) of a locking recess ( 3 ) are curved with different radii of curvature. 6. Security key according to one of claims 1 to 5, characterized in that the locking recesses ( 3 ), with the exception of the locking surfaces ( 11 ), are designed as curved tracks which are continuously rounded in the longitudinal direction ( 6 ) of the key back ( 5 ). 7. Security key according to one of claims 1 to 6, characterized in that the locking recess ( 3 ) has a truncated cone-shaped beveled edge ( 7 ) with a cone angle (β) measured to the longitudinal direction ( 6 ) of the key symbol ( 5 ) and that with respect to the longitudinal section all tangent angles (α') to the concave sliding surface ( 13 ), measured to the longitudinal direction ( 6 ) of the key back ( 5 ), are smaller than the cone angle (β). 8. Security key according to one of claims 1 to 7, characterized in that the smallest radius of curvature ( 21 ) of the sliding surface ( 13 ) is greater than or equal to the associated radius of curvature ( 22 ) of the core pin ( 9 ) at its point in contact with the sliding surface ( 13 ).