EP1504455A1

EP1504455A1 - Securing device for data carriers

Info

Publication number: EP1504455A1
Application number: EP03711783A
Authority: EP
Inventors: Josef Krummenacher
Original assignee: AWM Mold Tech AG
Current assignee: AWM Mold Tech AG
Priority date: 2002-05-03
Filing date: 2003-04-23
Publication date: 2005-02-09
Also published as: AU2003218596A1; WO2003094168A1; US20040163976A1

Abstract

The invention relates to a securing device for at least one circular data carrier (2), comprising a central opening arranged in a housing, said housing comprising a central section (1) on which a ring of tongue-like elements (3,3', 19,21) is secured, said elements engaging in an elastic manner in the central opening of the at least one data carrier (2). The aim of the invention is to prevent the data carriers, e.g. CDs or DVDs, from falling out of the housing. This is achieved by virtue of the fact that the central part (1) comprises an inner area (10) which is essentially circular in shape and whereon the tongue-like elements (3,3', 19,21) are secured on the inner edge at a certain distance so that gaps remain between the tongue-like elements (4) and that the inner area (10) comprises means (11, 14, 15, 16, 18) which enable a highly elastic movement of the ring of tongue-like elements (3,3', 19,21) relative to the housing.

Description

DESCRIPTION

TITLE

FASTENING DEVICE FOR MEDIA,

TECHNICAL AREA

The present invention relates to a fastening device for at least one circular data carrier with a central opening in a cassette, the cassette having a central part to which a ring of tongues which engage resiliently in the central opening of the at least one data carrier is fastened.

STATE OF THE ART

For the secure storage of data carriers such as CDs or DVDs, cassettes are usually provided in which the data carriers are inserted can. The data carriers are fastened in the cassette with a fastening device on the housing. The fastening device can either encompass or hold the peripheral edge of the data carrier or else, and this is the more frequently chosen variant, the fastening device engages in the central opening of the data carrier (optionally in combination with an additional peripheral holder). Such central fastening devices, which usually comprise a ring of flexible teeth which engage resiliently in the central opening, can be found in a large number of documents, such as e.g. B. in WO 01/39193, EP 0817196, EP 0762425, DE 4107218, or US 5,785,172.

Thermoplastics are usually used for the production of such cassettes, i. H. Plastics with a flow transition area above the service temperature. In particular, the plastics available on the market such as polyethylene (PE), in particular LDPE (Low Density Polyethylene) and HDPE (High Density Polyethylene), polyvinyl chloride (PVC), polystyrene (PS) or polypropylene (PP) come into question. The entire cassette is made of this material, but combinations of materials can also be used. B. the outer shell is made of one material, and the insert, d. H. the middle part, on which the fastening device is arranged, is made of a different material.

Often problematic in connection with such fastening devices is that these fastening devices tend to e.g. B. partially broken when the cassette is dropped. In particular, when polystyrene is used as the material for the fastening device, if the cassette falls parallel to the plane of the CD fastened therein, one or more of the teeth of the ring break off, which is due to the fact that polystyrene is stiff and rather brittle. In order to prevent such teeth breaking, z. B. EP 0692791 proposes to undercut the support surface for the CD on the teeth and to form the cantilever teeth with one radial arm and one axial arm, with a continuous transition or connecting arch is provided between the radial and the axial arm. This ensures both good retention and sufficient strength of the retaining tongues, since the retaining tongues have an increased elasticity and shear forces are well distributed through the undercut bearing surface on the teeth.

Another problem with fastening devices of this type is the fact that when the cassette is dropped, the data carrier often detaches from the fastening device and then flies loosely in the cassette. In this case, especially if this is not noticed and the cassette is moved with the data carrier lying loosely in it, the data carrier can be irreversibly damaged. This problem can e.g. B. be solved in that the fastening device simply holds the data carrier with a greater force, which, for. B. can be achieved by greater rigidity, by additional peripheral brackets, or by more pronounced retaining lugs. However, all of these measures have the disadvantage that it also requires a greater effort to insert the data carrier into the cassette, and that it is in particular also more difficult to detach the data carrier from the cassette or from the fastening device. This can go so far that there is a risk of damaging the data carrier when it is removed.

PRESENTATION OF THE INVENTION

This is where the invention intervenes. The invention is therefore based on the object of providing a fastening device for at least one circular data carrier with a central opening in a cassette, in which the data carrier is stably held in the cassette with good removal convenience. The cassette has a central part, to which resilient means, which engage in the central opening of the data carrier, are fastened. These means are designed in particular in the form of a ring of tongues which engage resiliently in the central opening of the at least one data carrier. The circular data carrier can in particular be a CD or a DVD. This object is achieved in that the central part has an inner, substantially circular-disk-shaped area, on the inner edge of which the tongues are fastened at a distance such that gaps remain between the tongues, and that the inner area has means which have an increased resilient Allow the ring of tongues to move relative to the cassette.

In other words, the essence of the invention is to provide an area radially outside the ring of tongues in the middle part, which is usually essentially a plane made of plastic, which permits increased resilient mobility of the ring. The aim is to leave the ring of tongues unchanged with regard to the elasticity of the tongues, which is necessary for gripping the data carrier, so that the ease of removal is retained and the data carrier is nevertheless held well by the ring. In other words, the increased mobility does not affect the mobility of the tongues, but the mobility of the entire ring relative to the cassette, i. H. relative to the areas of the central part which are arranged radially outside the inner area.

Accordingly, the gaps between the tongues do not extend into this inner area with increased flexibility. This z. B. in contrast to the so-called Z-shaped tongues, as described, for example, in EP 0692791, which comprise a pronounced radial part, and where the gaps between the tongues extend radially outward. The tongues considered here may also be Z-shaped, but with a much shorter radial part, which is why the tongues are referred to as L-shaped in this context. In any case, the gaps between the tongues do not protrude into the inner area, i. H. Rather, this inner area acts in the sense of a membrane which is designed in the form of a circular disk and is fastened radially on the outside to the adjacent area of the central part and carries the ring radially on the inside. The middle part and teeth can be made from a single thermoplastic (PE, LDPE, HDPE, PVC, PS, PP), and polypropylene is particularly suitable.

Surprisingly, it has been shown that the increased mobility guaranteed by the means leads to the data carrier having the same ease of removal z. B. if the cassette is dropped, it has a much lower tendency to detach itself from the fastening device and then lie loosely in the cassette.

The means which ensure the increased resilient mobility of the ring are preferably designed in such a way that increased mobility of the ring of tongues is permitted in a substantially perpendicular direction to the data carrier. The increased mobility in this direction leads in particular to the fact that when the cassette z. B. is dropped in a direction substantially perpendicular to the plane of the data carrier in the removal direction of the data carrier, the data carrier is not knocked out of the fastening device. This is due to the fact that the movable inner area allows a resilient movement of the ring together with the at least one data carrier held by it, and thus the impulse occurring during the fall is intercepted by the membrane. can be cushioned. If, in contrast, as in the prior art, the ring is rigidly connected to the middle part, the impulse that occurs during such a fall cannot be cushioned but instead leads directly to the fact that the falling energy leads to a deformation of the teeth and the data carrier from the ring solves.

According to a preferred embodiment of the present invention, the means are designed in the form of a taper, which is particularly preferably circumferential. In other words, the inner area has a lower material thickness than the other areas of the middle part. This lower material thickness increases the elasticity of the inner area and allows the membrane effect of this inner area. A corresponding membrane effect can also be achieved by additionally or alternatively shaping the inner region in the form of a, in particular preferably circumferential, corrugated configuration. The increased elasticity of the inner area can also be brought about by weakening this area in general, which, for. B. is possible by making holes in the inner area. However, this is by no means holes that are connected to the gaps between the teeth, since otherwise the elasticity of the ring is influenced by teeth, which is not wanted. According to another preferred embodiment of the present invention, the central part on the radial outside of the inner region has an essentially circumferential support ring for supporting the data carrier. The means for increasing the mobility of the inner region are particularly preferably arranged essentially radially on the inside on the support ring. The support ring should have such a small diameter that the area of the data carrier carrying the information does not come to rest on this support ring.

Another preferred embodiment of the present invention is characterized in that the fastening device consists of polypropylene. Polypropylene has great hardness and resilience and rigidity, without showing the brittle properties that occur with polystyrene, for example. However, these properties of polypropylene mean that, particularly when using this material, if no increased elasticity of the ring is provided relative to the cassette, the data carrier is very easily knocked out of the ring if the cassette is dropped. When polypropylene is used, the agents are particularly preferably in the form of a continuous, uninterrupted taper, the taper should have a 20 to 70%, particularly preferably 30 to 50% less material thickness than other areas of the central part. This z. B. at a typical thickness of the central part (outside the inner region) of in the range of 1 to 1.5 mm.

The tapering can be designed as a flat circular disk, but it is also possible to design the tapering as a cone tapering towards the lugs or as a cone dropping towards the lugs. The inner area typically has a thickness in the range from 0.5 to 0.9 mm, in particular in the range from 0.7 mm, and particularly preferably the taper has a radial width (width of the circular disc) of in the range from 2 to 8 mm, preferably in the range from 4 to 5 mm. It is shown that with such a dimensioning of the taper, a sufficient resilient effect can be guaranteed, and that a support ring which does not touch the data area of the data carrier can still be arranged in this way. According to a further preferred embodiment, the ring has 8 tongues, but it is also possible to provide a ring with 4 to 10 tongues. Particularly preferably, lugs or projections for axially holding the data carrier are not attached to each tongue, but alternately only on every second tongue.

Another preferred embodiment is characterized in that the tongues are designed to accommodate two data carriers lying one on top of the other, particularly preferably alternately only a nose for axially holding the data carrier is provided on every second tongue, and a spacer rib on the other tongues for controlled spacing the disk is arranged.

Since the restoring force of the tongues may not be sufficient in the proposed construction for a sufficient mounting of the CD or the 2 CDs, according to a further preferred embodiment of the present invention, at least two of the tongues of the ring can be connected to one another in a resilient manner. By connecting the tongues together z. B. across the columns, the holding force of the ring can be increased in a simple manner that can be realized with little effort in relation to the production of such frames, so that the data carriers are held better. The connection can preferably be ensured by spring elements, which particularly preferably connect adjacent tongues in the gaps (4) to bridge one another. With regard to the production but also with regard to the mode of operation, it proves to be particularly advantageous to design the spring elements in one piece with the tongues in the form of flexible, flat slats between the tongues. The slats do not necessarily have to be flat, but can also already have a zigzag structure or a corrugated shape. With a flat design of the lamellae, however, there is the advantage (not only in connection with the construction according to the invention, in which there is increased resilient mobility of the entire ring of tongues over, for example, a tapered area) that in the first moment when e.g. , B. if the cassette falls, a CD threatens to fall out of the wreath with its opening, as a result of the initially flat location of the lamellae, the restoring force is very large due to these spring elements and can thus efficiently prevent them from falling out. On the other hand, if the lamellae are slightly deformed when the CD is pressed into the rim, a lower restoring force results as soon as the lamellae are no longer flat, which makes insertion easier. The lamellae are advantageously formed with a width in the range of 0.8 to 3 mm, preferably in the range of 1 to 2 mm and a thickness of 0.1 to 0.4 mm, preferably with a thickness of 0.2 to 0.3 mm. The increase in the restoring force of the ring can be adjusted by the thickness and the width as well as by the number of tongues connected with slats. The lamellae are advantageously arranged in the region of the central tips of the radial arms of the tongues, but it is also possible to arrange them in other regions of the slots between the tongues.

A further preferred embodiment of the present invention is characterized in that all tongues are connected to one another. Alternatively, it is possible that e.g. B. with 8 tongues of the entire ring three opposite tongues are connected via two spring elements in the region of the central tips of the radial arms of the teeth.

Further preferred embodiments of the present invention are described in the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

The invention will be explained in more detail below using exemplary embodiments in conjunction with the drawings. Show it:

Figure 1 is a plan view of a fastening device.

Fig. 2 is a section along the line A-A in Fig. 1;

Fig. 3 is a section along the line B-B in Fig. 1;

4 shows a plan view of a further fastening device;

5 a) -c) further exemplary embodiments of a section according to FIG. 2; Fig. 6 is a plan view of a fastening device for two CDs;

Fig. 7 is a section along the line A-A in Fig. 6;

Fig. 8 is a section along the line B-B in Fig. 6;

9 a) a top view of a fastening device with spring elements; b) a section along the line A-A in Fig. 9a) in the rest position; c) a section along the line A-A in Fig. 9a) when the spring elements are compressed; and

Fig. 10 is a plan view of a fastening device with alternative arrangements of spring elements.

WAYS OF CARRYING OUT THE INVENTION

A first exemplary embodiment of the present invention is shown in FIGS. 1 to 3. Fig. 1 shows a plan view of a fastening device. All elements shown are made of polypropylene. The fastening device is fastened in a cassette or forms an integral part of such a cassette. Of the cassette, only the middle part 1 is shown, which is usually designed as a flat surface made of plastic, and which comes to lie below the CD. In general, such a fastening device is suitable for receiving data carriers such as CDs or DVDs with a central opening, but in the following, for example, only CDs will be discussed. It should also be pointed out that such a fastening device can be combined with additional clamps which grip the CD at the peripheral edge. The plane which forms the middle part 1 has a thickness of 1.4 mm. The fastening device also has a support ring 8, on which the CD rests when it is fastened, or on which, in the case of several CDs, the bottom CD comes to rest. The support ring 8 has a diameter of 30 mm, so that the CD with the data area does not touch the support ring. The support ring 8 has a width of approximately 1 mm. Immediately radially inward adjoining the support ring 8 is an inner circular disk-shaped area 10, which has a ring of 8 in the middle Teeth 3,3 '. These teeth alternately have noses 6 with which the CD is retained. There are gaps 4 between the teeth 3, 3 ', which, however, only extend to the base of the teeth and do not protrude into the inner region 10.

The inner region 10 now has, in particular, a tapered region 11 which is in the form of a circular disk and directly adjoins the support ring 8 radially. The tapered region 11 has a thickness of 0.7 mm and a width b of approximately 4 mm, and the tapered region 11 is delimited inwards by the boundary 12 (indicated by dashed lines in FIG. 1). 2, the tapering is achieved by providing a circular disk-shaped recess from below. Alternatively, it is also possible to form this recess from the upper side facing the CD. At the boundary 12, the inner region 10 again thickens to a thickness of 1.2 mm. This ensures that the mobility of the teeth 3, 3 'is not influenced by the taper 11.

The teeth 3, 3 'have a radial arm 13 which, among other things, can be used to facilitate the removal of the CD. To do this, press with your thumb on the arms 13 so that the teeth 3, 3 'tilt slightly inwards and thus also the noses 6 retreat and the CD can be easily removed.

FIG. 2 shows a section along the line A-A through a fastening device according to FIG. 1. The section thus shows in particular those teeth 3 which have lugs 6. In this section it can be seen that the central part 1 has a somewhat cylindrical, axially extending section 9, which ends in the support surface or the support ring 8. Section 9 ensures that the CD 2 is spaced from the plane of the central part 1 in that area (not shown) of the CD where data is effectively stored. 2 shows how the teeth 3 are L-shaped and have a groove 7 in which the inside diameter of the central opening of the CD comes to rest. This groove 7 results from the lugs 6, in which the teeth are slightly thickened radially outwards.

From Fig. 2 it can be seen, among other things, how the ring of teeth, which is attached to a ring (within the boundary 12) with a large material thickness, one to a certain extent forms a rigid unit which is connected to the outer region of the central part 1 via the flexible region 11. If a cassette, which has such a fastening device, falls in the direction of the arrow designated by the reference symbol 30, the unit of CD 2 and the ring of tongues 3, 3 'can spring back and the falling energy or the moment exerted by the CD can so do not affect the elasticity of the tongues and accordingly do not remove the CD from the wreath.

Fig. 3 shows one of the cuts indicated in Fig. 1, namely the section along the line B-B, i.e. H. by tongues 3 ', which have no lugs 6. From Fig. 3 it can be seen that these tongues 3 'serve only to support the CD in the radial direction, but not in the axial direction.

4 shows a top view of a further exemplary embodiment of the present invention. In this case, the means for increasing the flexibility of the inner region 10 are designed by the provision of holes 18. The holes do not have to be circular, as indicated in FIG. 4, but can also be designed in the form of slots, straight or curved, and / or it can be a much larger number of holes. Holes 18 of this type can also be used in combination with a taper, as shown in FIGS. 1-3.

5 illustrates further exemplary embodiments for designing the means for increasing flexibility. Fig. 5a) shows that e.g. B. a corrugated area 14 can be provided in the inner area 10, which also allows increased mobility of the ring relative to the cassette. Such a corrugation can, as shown in Fig. 5a), be combined with a taper.

FIGS. 5 b) and c) show two further exemplary embodiments in which the tapered region is conical, the cone being able to be inclined in both directions.

Figures 6 to 8 again show an embodiment in which there is now the possibility of two CDs one above the other on the ring of tongues sit up. L-shaped tongues 19, which have a nose 20, alternate with tongues 21 without lugs. As a result of the CDs 2 lying one above the other, the axial section 9 of the central part 1 must also be made shorter. The tongues 21 without lugs have spacer ribs 22 visible in particular in FIG. 8, which ensure a controlled spacing of the two CDs lying one above the other and also allow the at least provisional mounting of a single CD in such a fastening device. 6 also shows how the radial arm 13 can also have a different, shorter shape. Such a shape of the arm 13 would also be possible in the context of FIGS. 1 to 5. In an analogous manner, it is also possible to implement such a fastening device for more than 2 CDs (with a correspondingly higher configuration of the tongues).

Fig. 9 shows a further embodiment, in which the individual tongues are partially stabilized with each other in order to increase their restoring force and thus the holding force of the ring. It can be seen that the restoring force of a ring in the proposed design may have to be increased in order to prevent the CD from falling out if the cassette falls. This can either be done by simply making the structure of the tongues thicker. However, such measures prove to be disadvantageous in terms of production technology, since volumes which are too large must be avoided in the production process. Correspondingly, in the exemplary embodiment according to FIG. 9, the restoring force is increased in that individual tongues 3 are connected to one another.

9a) shows a top view of an exemplary embodiment in which three tongues 3 are connected to one another by lamellae or webs designed as spring elements 31. These two spring elements 31 are shown hatched in the upper three connected tongues 3 for better visibility. The spring elements 31 are arranged as webs in the area of the gaps 4 with a width (i.e. in the radial direction, with respect to the rim towards the outside) of 1.5 mm. The spring elements 31 are arranged on the inner tip of the radial arm 13 of the tongues 3 and are flush with these tips.

Fig. 9b) shows a section along the line AA in Fig. 9a). The wreath is in Rest position shown, ie the spring elements 31 are flat. The spring elements 31 are formed in one piece with the connected teeth and have a thickness of 0.2 to 0.3 mm. The increase in the restoring force due to the spring elements 31 can be brought about either by increasing their width or by increasing their thickness.

Fig. 9c) shows a section corresponding to Fig. 9b), but a CD 2 is just being placed on the rim. As a result, the tongues 3 are pressed inwards. Accordingly, pressure acts on the spring elements and these spring elements 32 are deformed out of their flat position. As shown in Fig. 9c), the spring elements 32 bend z. B. in the form of a U down. As already mentioned above, it is possible not to design the spring elements as flat webs, but already z. B. V-shaped or U-shaped in the rest position. However, this has the consequence that the restoring force caused by the spring elements does not have the same advantageous characteristic as in the case of a flat design. With a planned training, the restoring force is at the beginning, i.e. H. if the tongues 3 are not yet deformed, have a high value, but as soon as the spring elements have been deformed a little out of their plane, the force will decrease or be less.

10 shows further variants of spring elements. In the upper half, three tongues are in turn connected to one another by two spring elements 31 in the region of the tips of the tongues. Another possible arrangement is shown on the left, where two tongues 3 in the central region of the gap 4, d. H. approximately in half of the radial arm 13, are connected by a spring element 33 in the form of a web. The spring element 33 is again 1.5 mm wide, and the restoring force can be adjusted not only by the thickness and the width of the spring element 33, but also by its positioning along the radial arm 13.

Another alternative is shown at the bottom left, where a spring element 34 is arranged vertically in the region of the axial arm 5 of the tongues 3. The spring element 34 can lie at the level of the groove 7 or at the level of the nose 6 or can even extend over these two areas. Basically, the spring elements be arranged at any point along the gap 4.

LIST OF REFERENCE NUMBERS

1 middle section of the CD cassette

2 CD

3 L-shaped tongues

4 gap between the tongues

5 axial arm of 3

6 nose to 5

7 groove for 2

8 support ring for 2

9 axial section of 1

10 inner circular disk-shaped area of 1

11 tapered area of 10

12 radially inner boundary of 11

13 radial arm of 3

14 wavy area of 10

15 tapered and beveled area of 10 (tapering upwards)

16 tapered and beveled area of 10 (tapering downwards)

17 radially inner boundary of 15

18 holes in 10

19 L-shaped tongue for two CDs, with nose on top

20 nose to 19

21 L-shaped tongue for two CDs, with spacer rib

22 Spacer rib 30 Fall direction Spring element (at rest) Spring element (compressed) Spring element on the central radial arm 13 of 3 Spring element on the axial arm of 3

Claims

1. Fastening device for at least one circular data carrier (2) with a central opening in a cassette, the cassette having a central part (1) on which a ring of tongues (3, 3 ', 19, 21) resiliently in the central The opening of the at least one data carrier (2) engages, is fastened, characterized in that the central part (1) has an inner, essentially circular disk-shaped area (10), on the inner edge of which the tongues (3, 3 ', 19, 21) are attached at a distance such that gaps (4) remain between the tongues and that the inner region (10) has means (11, 14, 15, 16, 18) which increase the resilient mobility of the ring of tongues (3, 3 ', 19, 21) relative to the cassette.

2. Fastening device according to claim 1, characterized in that the circular data carrier (2) is a CD or a DVD.

3. Fastening device according to one of claims 1 or 2, characterized in that the means (11, 14, 15, 16, 18) an increased mobility of the ring of tongues (3,3 ', 19,21) in a substantially vertical direction allow to disk (2).

4. Fastening device according to claim 3, characterized in that the means (11, 14, 15, 16, 18) in the form of a, particularly preferably circumferential, taper (11, 15, 16), and / or in the form of a, particularly preferred circumferential, corrugated configuration (14), and / or in the form of holes (18) in the inner region (10).

5. Fastening device according to one of the preceding claims, characterized characterized in that the central part (1) on the radial outside of the inner region (10) has an essentially circumferential support ring (8) for supporting the data carrier (2), and that the means (11, 14, 15, 16, 18) are arranged essentially radially on the inside on the support ring (8).

Fastening device according to one of claims 3 to 5, characterized in that the fastening device consists of polypropylene, that the means (11, 14, 15, 16, 18) are designed in the form of a circumferential, uninterrupted taper (11, 15, 16), and that, compared to other areas of the middle part (2), the taper (11, 15, 16) has a material thickness that is 20 to 70%, particularly preferably 30 to 50% less.

Fastening device according to claim 6, characterized in that the taper is designed as a flat circular disc (11), as a cone (15) tapering towards the lugs or as a cone (16) sloping towards the lugs.

Fastening device according to one of claims 6 or 7, characterized in that the inner region (10) has a thickness during the tapering in the range from 0.5 to 0.9 mm, in particular in the range from 0.7 mm, and that the taper particularly preferably has a radial width (b) of in the range from 2 to 8 mm, preferably in the range from 4 to 5 mm.

9. Fastening device according to one of the preceding claims, characterized in that the ring comprises 8 tongues (3, 3 ', 19, 21), and that in particular preferably alternately only on every second tongue (3) a nose (6, 20) for axial mounting of the data carrier (2) is provided.

10. Fastening device according to one of the preceding claims, characterized in that the tongues (19, 21) are designed to accommodate two data carriers (2) lying one above the other, with a nose (20) particularly preferably alternatingly only on every second tongue (19). is provided for the axial mounting of the data carrier (2), and a spacer rib (22) for controlled spacing of the data carriers (2) is arranged on the other tongues (21).

11. Fastening device according to one of the preceding claims, characterized in that at least two of the tongues (3, 3 ', 19, 21) of the ring are connected to one another in regions in a resilient manner.

12. Fastening device according to claim 11, characterized in that the connection is ensured by spring elements (31, 32, 33, 34), which particularly preferably bridging adjacent tongues (3, 3 ', 19, 21) into the gaps (4) connect with each other.

13. Fastening device according to claim 12, characterized in that the spring elements (31, 32, 33, 34) in one piece with the tongues (3, 3 ', 19,21) in the form of flexible, flat slats with a width in the range of 0.8 to 3 mm, preferably in the range from 1 to 2 mm and a thickness of 0.1 to 0.4 mm, preferably with a thickness of 0.2 to 0.3 mm.

14. Fastening device according to one of the preceding claims, characterized in that all tongues (3, 3 ', 19, 21) are connected to one another, or that with 8 tongues (3, 3', 19, 21) three opposing tongues each have two Spring elements (31, 32, 33, 34) in the area of the central tips of the radial arms (13) of the teeth (3, 3 ', 19, 21) are connected.