Abstract:
The invention relates to a securing device for at least one circular data carrier, comprising a central opening arranged in a housing, said housing comprising a central section on which a ring of tongue-like elements is secured, said elements engaging in an elastic manner in the central opening of the at least one data carrier. 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 comprises an inner area which is essentially circular in shape and wherein the tongue-like elements are secured on the inner edge at a certain distance so that gaps remain between the tongue-like elements and that the inner area comprises means which enable a highly elastic movement of the ring of tongue-like elements relative to the housing.

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to a fastening device or securing device for at least one circular data carrier, comprising a central opening, arranged in a housing or cassette, comprising a central section or middle part on which a ring or crown of tongue-like elements is secured, said tongues engaging in an elastic manner in the central opening of the at least one data carrier.  
         BACKGROUND OF THE INVENTION  
         [0002]    For safe storage of data carriers like CDs or DVDs commonly cassettes are used, into which the data carriers are put. The data carriers are being fastened in the housing of the cassette by means of a fastening device. The fastening device may either grip or fix the data carrier on its peripheral outer border, or, and this version is more commonly used, the fastening device comprises means to insert into the central opening of the data carrier (if need be in combination with an additional peripheral fixation). Such central fastening devices, usually comprising a crown of flexible tongues, which are elastically insertable into the central opening of the data carrier, are described in a large number of documents, such as for example in WO 01/39193, EP 0817196, EP 0762425, DE 4107218 or in U.S. Pat. No. 5,785,172.  
           [0003]    Usually such cassettes are being produced by using thermoplastic material, that is plastics with a flow transition above the usual temperature of use. Of particular interest in this respect are plastics which are available on the market for cheap prices, such as Polyethylene (PE), particularly LDPE (Low Density Polyethylene) and HDPE (High Density Polyethylene), Polyvinylchloride (PVC), Polystyrene (PS) or Polypropylene (PP). When using such materials, usually the whole cassette is made from such a material in a forming process, it is however also possible to use combinations of different materials, wherein for example the outer part of the housing is made from one material, and the insert, i.e. the middle part, on which the fastening device is provided, is made from another material.  
           [0004]    One problem in the context of such fastening devices is very often that they have the tendency to, for example if a cassette is dropped, break apart at least partially. In particular if Polystyrene is used for the fastening device, it is possible that if the cassette is dropped in a direction parallel to the plane of the CD fastened within the cassette one, or more of the tongues of the crown break out, the reason for which is that Polystyrene is stiff and rather brittle. To avoid such breaking out of the tongues, for example the document EP 0692791 proposes to provide a support surface for the CD which is provided with undercut sections of the tongues, wherein these tongues are unsupportedly extending with a radial arm and an axial arm and wherein there is a continuous arched transition or connection, respectively, between the radial and the axial arm. This design allows a good fastening as well as a sufficient toughness of the tongue, because the tongues have an increased elasticity and due to the undercut support the shearing forces at the tongues are well distributed.  
           [0005]    Also problematic in the context of such fastening devices is the fact that if such a cassette is dropped, the data carrier very often jumps out of the fastening device and is subsequently loose in the cassette. This may, in particular if the loose data carrier is not noticed, and the cassette with the loose data carrier is being moved, lead to irreversible damage of the data carrier. This problem can for example be solved in that the fastening device for the data carrier works with a larger force, which for example can be achieved by an increased stiffness, by means of additional peripheral fastening means, or by means of more pronounced retaining noses. All these measures however have the drawback, that accordingly to remove the data carrier from the cassette, an increased force has to be used, and that it is in particular more difficult, to release the data carrier from the cassette, or out of the fastening device, respectively. This may even go as far as that there is a realistic danger to damage the data carrier when removing it from the cassette.  
         SUMMARY OF THE INVENTION  
         [0006]    That is where the present invention provides a solution. The objective problem underlying the present invention is therefore to provide a fastening device for at least one disc shaped data carrier with a central opening in a cassette, which sufficiently fastens the data carrier but at the same time allows comfortable removal of the data carrier from the cassette. The cassette comprises a middle part on which means are provided that are elastically insertable into the central opening of the data carrier. These means are preferentially designed in the form of a crown or ring of tongues, which are elastically insertable into the central opening of the at least one data carrier. The disc shaped data carrier may in particular be a CD or a DVD.  
           [0007]    The present invention solves the problem in that, the middle part comprises an inner, substantially disc shaped part on the inner edge of which the tongues are mounted spaced from each other such that between the tongues there is slots, and in that the inner part is provided with means allowing an increased elastic mobility of the crown of tongues with respect to the cassette.  
           [0008]    The key element of the invention in other words resides in the fact that on the radial outer side of the crown of tongues in the middle part, which commonly is given as a surface substantially made of plastics, an area is provided, which allows an increased elastic mobility of the crown. The aim is to keep the tongues as they are with respect to the elasticity of the tongues as necessary for keeping and fixing the data carrier, such as to maintain the same comfort for removal of the data carrier, and to maintain good fixation of the data carrier by the crown. In other words, the increased mobility does not relate to the mobility of the tongues but to the mobility of the whole crown with respect to the cassette, that is relative to the regions of the middle part, which are radially exterior to the inner part.  
           [0009]    Accordingly, the slots between the tongues do not extend into this inner part with increased flexibility. This is for example in contrast to the so called Z-shaped tongues, as they are for example described in EP0692791, which comprise a pronounced radial portion, and where the slots between the tongues extend far out radially. The tongues considered here may also be Z-shaped, but with a substantially shorter radial portion, and that&#39;s why in the present context the tongues are described as L-shaped. In any case, the slots between the tongues do not extend into the inner part, that is this inner part does act in the sense of a membrane, which is disc shaped, and which is provided on the radial outer side on the adjacent portion of the middle part, and which on its radial inner side carries the crown. Middle part and tongues may be made from one single thermal plastic material (PE, LDPE, HDPE, PVC, PS, PP), in particular Polypropylene is suitable.  
           [0010]    Surprisingly, it can be shown that the increased mobility provided by these means leads to the fact that while keeping the same comfort of removal of the data carrier, for example if the cassette is dropped, it has a substantially lower tendency that the data carrier jumps out of the fastening device and is subsequently loose in the cassette.  
           [0011]    Preferentially, the means allowing an increased elastic mobility of the crown are provided such that the increased mobility of the crown of tongues is allowed in a direction substantially perpendicular to the plane of the data carrier. The increased mobility in this direction in particular leads to the fact that if the cassette is for example dropped in a direction substantially perpendicular to the plane of the data carrier i.e. in the direction of removal, the data carrier is not kicked out of the fastening device. This is related to the fact that the inner mobile part allows an elastic motion of the crown together with the at least one data carrier fastened by this crown, and that the impulse present in the fall is taken up by the membrane, i.e. is elastically taken up. If, as given in the state of the art, the crown is stiffly connected with the middle part, the impulse generated in such a fall can not be elastically taken up but directly leads to the conversion of the kinetic energy of the fall into a deformation of the tongues, and correspondingly the data carrier is loosened from the crown.  
           [0012]    According to another preferred embodiment of the present invention the means are provided in the form of a, preferentially circumferential, recessed region. In other words the inner part is provided with a lower thickness of the material than the other parts of the middle portion. This reduced, thickness of the material increases the elasticity of the inner part and allows the so called membrane effect of this inner region. A corresponding membrane effect can also be reached in that the inner part additionally or alternatively is provided with a preferentially circumferential, rippled design. The increased elasticity of the inner part can also be effected in that this region is generally weakened, which is for example possible by means of a provision of holes in the inner part. However, such holes are not connected with the slots between the tongues, since in this case additionally the elasticity of the crown of tongues would be influenced, which is not wanted in the present case.  
           [0013]    According to another preferred embodiment of the present invention, the middle part comprises on the radial outer side of the inner part a substantially circumferential supporting ring for supporting the data carrier. Preferably, the means for increasing the mobility of the inner part are provided substantially on the radial inner side of said supporting ring. The supporting ring, should have a low diameter such that the information carrying region of the data carrier does not come to lie on this supporting ring.  
           [0014]    Another preferred embodiment of the present invention is characterised in that the fastening device is made of Polypropylene. Polypropylene shows a high toughness and ability to restore and a high stiffness, without showing the brittle characteristic as seen with Polystyrene. These properties of Polypropylene lead to the fact that if it is used, and if no increased elasticity of the crown relative to the cassette is provided, the data carrier easily jumps out of the crown, if the cassette is dropped. If Polypropylene is used, the means are preferentially given in the form of a circumferential, uninterrupted recessed region with reduced thickness, wherein the thickness of the material is reduced with respect to the other regions of the middle part by 20-70%, particularly by 30-50%. This for example at a typical thickness of the middle part (not within the recessed region) in the range of 1 to 1.5 mm.  
           [0015]    The recessed portion can be designed as a planar disc shape, it is however also possible to provide it as a cone converging towards the nose, or as a cone downwards sloping towards the noses. The inner portion in the region of the reduced thickness typically has a thickness in the range of 0.5 to 0.9 mm, preferably in the range of 0.7 mm, and in particular this region of reduced thickness preferably has a radial width (width of the ring of the disc shape) in the range of 2 to 8 mm, preferably in the range of 4 to 5 mm; it can be shown that if using such dimensions of the recessed region, a sufficient elastic effect can be provided, and that still a supporting ring can be provided which does not touch a data carrying region of the data carrier.  
           [0016]    According to another preferred embodiment the crown carries 8 tongues, it is however also possible to have a crown with 4 to 10 tongues. Preferably, not every tongue is provided with noses or projections, respectively, for axial fixation of the data carrier, but alternatingly only every second tongue carries such a tongue.  
           [0017]    Another preferred embodiment is characterised in that the tongues are designed to take up two data carriers, on top of each other, wherein in particular preferably alternatingly only every second tongue is provided with a nose for axial fixation of the data carrier, while the other tongues are provided with ribs for keeping the data carriers at a defined distance.  
           [0018]    Since possibly the restoring force of the tongues is not sufficient in a design as proposed here for fixing a CD or maybe two CDs, it is possible, according to another preferred embodiment of the present invention, connect at least two of the tongues of the crown in certain regions in an elastic manner. By means of these connections of the tongues which each other, i.e. bridging the slots, the fixing force of the crown can be increased without much effort and in a manner which can easily be realised, such that the data carrier is held more firmly in the cassette. Preferably, this connection can be provided by means of spring elements, which preferably connect adjacent tongues in a manner such that the slots are bridged. With respect to the production but also with respect to the actual effect it proves to be advantageous to provide the spring elements as one piece with the tongues in the form of flexible, planar lamellae between the tongues, these lamellae do not necessarily have to be planar, but they can also have a zic-zac structure or a rippled form. If such lamellae are designed in a planar manner, there results the advantage (which advantage is not only present in the context of the design according to the invention, in which an increased elastic mobility of the whole crown of tongues is allowed by means of for example a recessed region), that in a first moment of time, if for example due to a fall of the cassette the CD is just about to fall out of the crown with its opening, due to the initially planar position of the lamellae the restoring force due to these spring elements is very large and can efficiently prevent the falling out of the data carrier. If however the lamellae are slightly deformed when the CD is inserted into the crown, the restoring force is immediately reduced as soon as the lamellae are not planar anymore, which facilitates insertion of the data carrier. These lamellae are advantageously provided with a width of 0.8 to 3 mm, preferentially in the range of 1 to 2 mm and with a thickness of 0.1 to 0.4 mm, preferentially with a thickness of 0.2 to 0.3 mm. By means of the thickness as well as of the width and of the number of tongues connected by such lamellae the restoring force of the crown can be increased and adjusted. Preferentially, the lamellae are provided at the central tips of the radial arms of the tongues, it is however also possible to locate them in other portions of the slots between the tongues.  
           [0019]    Another preferred embodiment of the present invention is characterised in that all tongues are connected with each other. Alternatively it is possible to, for example in case of  8  tongues of the whole crown, connect three opposing tongues by means of two spring elements in the range of the central tips of the radial arms of the tongues.  
           [0020]    Further preferred embodiments of the present invention are outlined in the depending claims. 
       
    
    
     SHORT DESCRIPTION OF THE FIGURES  
       [0021]    The present invention shall be illustrated with the aid of the examples in the context of the drawings which show the following:  
         [0022]    [0022]FIG. 1 a top view onto a fastening device;  
         [0023]    [0023]FIG. 2 a cut along the line A-A in FIG. 1;  
         [0024]    [0024]FIG. 3 a cut along the line B-B in FIG. 1;  
         [0025]    [0025]FIG. 4, a top view onto another fastening device;  
         [0026]    [0026]FIG. 5  a )- c ) further examples of cuts according to FIG. ; 2   
         [0027]    [0027]FIG. 6 a top view onto a fastening device for two CDs;  
         [0028]    [0028]FIG. 7 a cut along the line A-A in FIG. 6;  
         [0029]    [0029]FIG. 8 a cut along the line B-B in FIG. 6;  
         [0030]    [0030]FIG. 9 a) a top view onto a fastening device with spring elements; b) a cut along the line A-A in FIG. 9 a ) in relaxed position; c) a cut along the line A-A in FIG. 9 a ) if the, spring elements are compressed; and  
         [0031]    [0031]FIG. 10 a top view onto a fastening device with alternative arrangements of spring elements.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    A first embodiment of the present invention is shown in FIG. 1 to  3 . FIG. 1 shows a top view onto a fastening device. All the elements shown are made of polypropylene. The fastening device is fastened in a cassette or forms integral part of such a cassette. Of the cassette only the middle part  1  is shown, which generally is given as a planar surface made of plastics, and which comes to lie underneath the CD. Generally speaking, such a fastening device is capable of taking up data carriers like CDs of DVDs with a central opening, as an example in the following only CDs however shall be discussed. It shall furthermore be pointed out, that such fastening devices can be combined with additional clamps or means, which grip a CD on its peripheral border. The plane forming the middle part  1  has a thickness of 1.4 mm. The fastening device is additionally provided with a supporting ring  8 , on which the CD, if it is fastened comes to lie, or onto which in case of several CDs the lowermost CD comes to lie. The supporting ring  8  has a diameter of 30 mm, such that the CD does not touch the supporting ring with its data carrying area. The supporting ring  8  has a width of approximately 1 mm. Immediately adjacent to the supporting ring  8  on its radial inner side there is provided an inner disc shaped area  10 , which in the middle carries a crown of  8  tongues,  3 ,  3 ′. These tongues are alternatingly provided with noses  6 , with which the CD is retained. Between the tongues  3 , 3 ′ there is slots  4 , which however only extend to the foot of the tongues, and do not extend into the inner region  10 .  
         [0033]    The inner part  10  is in particular provided with a recessed part  11  with reduced thickness, which is disc shaped, and which is located immediately adjacent to the supporting ring on its radial inner side. The recessed region  11  has a thickness of 0.7 mm and a width of approximately 4 mm, and the recessed region  11  is bordered toward its inner side by means of a boundary  12  (given in a dashed line in FIG. 1). In FIG. 2 the region of reduced thickness is realised in that from the bottom side there is provided a disc shaped recessed area. Alternatively it is possible to provide this recessed area from the upper side, i.e. on the side of the CD. At the radial inner boundary  12  the inner part  10  increases in thickness to a thickness of 1.2 mm. Thereby it is made sure that the mobility of the tongues  3 , 3 ′ is not influenced by the region of reduced thickness  11 .  
         [0034]    The tongues  3 , 3 ′ are provided with a radial arm  13 , which among other things can be used for facilitating removal of the CD. To this end one presses with the thumb onto the arms  13 , such that the tongues  3 , 3 ′ slightly tilt towards the inner side, and thereby also the noses  6  recede, and the CD can easily be removed.  
         [0035]    [0035]FIG. 2 shows a cut along line A-A through a fastening device according to FIG. 1. The cut in particular shows those tongues  3 , which are provided with noses  6 . In this cut it is visible that the middle part  1  is provided with a so to speak cylindrical, axial part  9 , which ends in the supporting surface or the supporting ring  8 , respectively. The axial part  9  provides a distance between the CD  2  from the surface of the middle part  1  in the region (not displayed) of the CD, where effectively data are stored. FIG. 2 shows, how the tongues  3  are L-shaped, and are provided with a groove  7 , into which the inner diameter of the central opening of the CD comes to lie. This groove  7  results from the noses  6 , at the location of which the tongues are protruding slightly towards the radial outer side.  
         [0036]    From FIG. 2 it among other things becomes clear how the crown of tongues, which is fastened on a ring (on the inner side of the boundary  12 ) with large thickness of the material, forms a so to speak stiff unit, which by means of the flexible portion  11  is connected with the outer portion of the middle part  1 . If a cassette with such a fastening device is dropped in a direction as indicated with the reference numeral  30 , the unit given by the CD  2  and the crown of tongues  3 , 3 ′ can yield elastically, and the energy of the fall, or the moment exerted by the CD, respectively can thus not act onto the elasticity of the tongues, and correspondingly the CD cannot jump out of the crown.  
         [0037]    [0037]FIG. 3 shows another cut indicated in FIG. 1, namely the cut along the line B-B, i.e. through tongues  3 ′, which do not carry noses  6 . From FIG. 3 it becomes clear that these tongues  3 ′ are only there to support the CD in radial direction but not in axial direction.  
         [0038]    [0038]FIG. 4 shows a top view onto another example of the present invention. In this case the means for increasing the flexibility of the inner part  10  are provided as holes  18 . These holes do not have to, as indicated in FIG. 4, be of circular shape, but may also be provided in the form of slots, straight or bent and/or there maybe provided a much larger number of such holes. Such holes  18  may also be combined with recessed regions as indicated in FIG. 1- 3 .  
         [0039]    [0039]FIG. 5 illustrates further examples for designing the means for increasing the flexibility. FIG. 5 a ) shows that for example in the inner part  10  there may be provided a rippled portion  14 , which also allows an increased mobility of the crown relative to the cassette. Such a rippled portion may, as indicated in FIG. 5 a ), be combined with a recessed portion.  
         [0040]    The FIG. 5 b ) and  c ) show two further examples, in which the recessed portion is provided as a cone, wherein the slope of the cone is possible in both directions.  
         [0041]    [0041]FIG. 6 to  8  again, show an example, in which there is provided the possibility to stack two CDs on top of each other on the crown of tongues. In this case L-shaped tongues  19  provided with noses  20 , are alternating with tongues  21  without noses. Due to the stacked CDs  2  accordingly the axial portion  9  of the middle part  1  has to be designed more shortly. The tongues  21  without noses are mi particular provided with ribs  22  for keeping the distance of the  2  CDs stacked on top of each other, as visible in FIG. 8. Such ribs also allow the at least provisional fixation of a single CD in such a fastening device. Furthermore FIG. 6 shows how the radial arm  13  may also have another, shorter form. Such a form of the arm  13  would also be possible within the scope of FIG. 1- 5 . Analogously it is also possible to provide such fastening device for more than two CDs (with correspondingly higher design of the tongues).  
         [0042]    [0042]FIG. 9 shows another example, in which individual tongues are at, least partially stabilised with respect to each other for increasing their restoring force and thus the holding force of the crown. It shows sometimes that the restoring force of a crown in the proposed construction if need be has to be increased for avoiding the loosening of the CD if the cassette is dropped. This can either be achieved by providing tongues with a thicker structure. Such measures however prove not to be advantageous from a production point of view, since in the production large volumes have to be avoided. Correspondingly in the example as shown in FIG. 9 the restoring force is increased by means of connecting individual tongues  3  with each other.  
         [0043]    In FIG. 9 a ) there is displayed a top view onto an example, in which respectively  3  tongues  3  are connected with each other by means of spring elements  31  which are lamellae or strips. These two spring elements  31  are displayed in a hatched manner in case of the upper three connected tongues  3  for better visibility. The spring elements  31  are given as strips in the region of the slots  4  with a width (i.e. in radial direction, with respect to the crown towards the outer side) of 1.5 mm. The spring elements  31  are provided on the inner tip of the radial arm  13  of the tongues  3  and flush with these tips.  
         [0044]    [0044]FIG. 9 b ) shows cut along the line A-A in FIG. 9 a ). In this case the crown is shown in relaxed position, i.e. the spring elements  31  are planar. The spring elements  31  are designed as one piece with the connected tongues and have a thickness of 0.2 to 0.3 mm. The increase of the restoring force due to the spring elements  31  may either be effected by means of an increase of their width or of an increase of their thickness.  
         [0045]    [0045]FIG. 9 c ) shows a cut according to FIG. 9 b ), wherein however a CD is just being put onto the crown. As a consequence the tongues  3  are tilted towards the inner side. Accordingly, a force is acting onto the spring elements, and these spring elements  32  are being deformed out of their planar position. As displayed in FIG. 9 c ) these spring elements  32  bend, for example in a U-shape towards the lower side. As already mentioned above, it is possible to provide the spring elements not as planar strips but already as for example V-shapes or U-shapes in relaxed positions. This however then has as a consequence that the restoring force as affected by these spring elements does not have the same advantageous characteristics as in case of a planar design. In case of a planar design the restoring force in an initial moment of time, i.e. if the tongues  3  are not yet deformed, has a high value, however, as soon as the spring elements have once been brought out of their plane, the force decreases or becomes lower, respectively.  
         [0046]    [0046]FIG. 10 shows further variants of spring elements. In the upper half again three tongues are connected by means of two spring elements  32  in the region of the tips of the tongues. Another possibility of placement is shown on the left side, where two tongues  3  are connected in the middle part of the slot  4 , i.e. approximately at half distance of the radial arm  13 , by means of a spring element  33  in the form of a strip. The spring element  33  is again 1.5 mm wide and the restoring force can not only be adjusted by means of the thickness and the width of the spring element  33  but also by means of its position along the radial arm  13 .  
         [0047]    A further alternative is displayed in the lower portion on the left side where a spring element  34  is arranged vertically in the region of the axial arm  5  of the tongue  3 . The spring element  34  may either be at the height of the groove  7  or at the height of the nose  6  or may even extend over these two regions. Principally such spring elements may be located at any position along the slot  4 .  
         [0048]    List of Reference Numerals  
         [0049]    [0049] 1  middle part of the CD-cassette  
         [0050]    [0050] 2  CD  
         [0051]    [0051] 3  L-shaped tongues  
         [0052]    [0052] 4  slot between the tongues  
         [0053]    [0053] 5  axial part of  3   
         [0054]    [0054] 6  nose of  5   
         [0055]    [0055] 7  groove for  2   
         [0056]    [0056] 8  supporting ring for  2   
         [0057]    [0057] 9  axial part of  1   
         [0058]    [0058] 10  inner disc shaped part of  1   
         [0059]    [0059] 11  part of  10  with reduced thickness  
         [0060]    [0060] 12  radial inner boundary of  11   
         [0061]    [0061] 13  radial arm of  3   
         [0062]    [0062] 14  rippled portion of  10   
         [0063]    [0063] 15  recessed and sloped portion of  10  (conically converging towards the top)  
         [0064]    [0064] 16  recessed and sloped portion of  10  (conically converging towards the bottom)  
         [0065]    [0065] 17  radial inner boundary of  15   
         [0066]    [0066] 18  holes in  10   
         [0067]    [0067] 19  L-shaped tongue for two CDs with nose located on the upper side  
         [0068]    [0068] 20  nose on  19   
         [0069]    [0069] 21  L-shaped tongue for two CDs, with rib for keeping the distance  
         [0070]    [0070] 22  rib for keeping the distance between the CDs  
         [0071]    [0071] 30  direction of the fall  
         [0072]    [0072] 31  spring element (relaxed state)  
         [0073]    [0073] 32  spring element (compressed)  
         [0074]    [0074] 33  spring element at the middle radial art  13  of  3   
         [0075]    [0075] 34  spring element at the axial arm of  3