Abstract:
A recording and/or reproducing apparatus having at least one guide arrangement that facilitates recording and reproduction even when a tape edge comes into contact with an end flange of the guide arrangement. The guide arrangement structure preferable is in the form of a tape guide roller, for guiding a record carrier in the guide arrangement. There is at least one damping projection in the area of the guide surface. The damping projection extends in tangential directions of the guide surface and is adapted to damp axial relative movements of the record carrier with respect to the guide arrangement.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a recording and/or reproducing apparatus, and particularly relates to a guide arrangement. 
     2. Description of the Related Art 
     Such a recording and/or reproducing apparatus (hereinafter briefly referred to as the apparatus) and such a guide arrangement are known, for example from the patent document WO 98/44499 A1. The known apparatus is a so-called data streamer intended and constructed for the storage of large amounts of data on a magnetic tape. For this purpose, the known apparatus has drive means with the aid of which a magnetic tape is driven with a comparatively high transport speed, as a result of which a more or less satisfactory air film is formed between the magnetic tape and the guide surfaces of two guide arrangements, i.e. two tape guide rollers. Said apparatus further has a multi-track magnetic head whose relative position, i.e. its height position, with respect to a magnetic tape is controllable with the aid of an actuator device, so as to enable a plurality of predefined mutually parallel tracks on the magnetic tape to be followed as exactly as possible and thus always enable a correct recording and reproduction to be achieved. In the known apparatus external influences on the magnetic tape, but also internal conditions in the magnetic tape, may result in the magnetic tape being subjected to forces which cause the magnetic tape to be deflected transversely to the transport direction of the magnetic tape, as a result of which at least one tape edge of the magnetic tape comes into contact with an end flange of at least one of the two tape guide rollers. This contact of a tape edge of the magnetic tape with an end flange, in its turn, leads to variations of comparatively high frequency in the height position of the magnetic tape, which height variations lie in a frequency range of approximately 500 Hz and even higher. However, these high frequency variations in the height position of the magnetic tape occur not only in the area of the tape guide rollers but also in the area of the multi-track magnetic head, which as already stated is movable in height with the aid of the actuator device in order to always guarantee a correct tracking. However, with the aid of the actuator device in the known apparatus the multi-track magnetic head is only capable of following those variations in the height position of the magnetic tape whose frequency is lower than the frequency of the variations in the height position of the magnetic tape which are caused by the magnetic tape coming into contact with an end flange. With the aid of the actuator device the magnetic head can follow only variations in the height position of the magnetic head which have a frequency of approximately 200 Hz but not the afore-mentioned variations having a frequency of at least 500 Hz. However, this means that as a result of an undesired but frequently inevitable contact of at least one of the tape edges of the magnetic tape with an end flange a correct tracking is no longer guaranteed and, consequently, a correct recording and reproduction is no longer guaranteed. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to preclude the afore-mentioned problems and to provide an improved recording and/or reproducing apparatus and an improved guide arrangement, which improved embodiments always ensure a correct recording and/or reproduction even when a tape edge of a magnetic tape comes into contact with an end flange of a guide arrangement. 
     To achieve this object, according to the invention, the characteristics features are provided in a recording and/or reproducing apparatus. 
     To achieve the object, according to the invention, the characteristics features are provided in a guide arrangement. 
     Owing to the provision of the characteristic features in accordance with the invention it is achieved by simple means that there is a direct mechanical contact between the at least one damping projection of the at least one guide arrangement and the record carrier tape guided by means of this guide arrangement, i.e. no air film is formed between the guide surface of the guide arrangement and the record carrier tape at this location, as a result of which in the area of the damping projection a friction effect is produced between the record carrier tape and the damping projection, by means of which a damping of axial relative movements of the record carrier tape with respect to the guide arrangement is achieved. This guarantees that excursions of the driven record carrier tape in an axial direction of a guide arrangement, which excursions are caused by external influences on the magnetic tape as well as by internal conditions in the magnetic tape, are damped to such an extent by the at least one damping projection of the guide arrangement that at least one tape edge of the record carrier tape does not or only to a greatly weakened extent come into contact with an end flange of the guide arrangement, as a result of which no or hardly any high frequency variations in the height position of the record carrier tape occur and, as a consequence, such high frequency variations occur neither at the location of the magnetic head and therefore always a correct recording and/or reproduction by means of the magnetic head is guaranteed. 
     In a recording and/or reproducing apparatus in accordance with the invention and in a guide arrangement in accordance with the invention the use of one damping projection is adequate. However, in practice it has been advantageous to provide two damping projections that are axially spaced apart a distance from one another. It is to be noted that an embodiment of the invention may alternatively have more than two damping projections, for example, three, four, or five of such damping projections according to need. The number of damping projections also depends on the axial dimension of a guide arrangement. 
     In a recording and/or reproducing apparatus in accordance with the invention the at least one damping projection may extend parallel to a plane which is inclined with respect to the guide axis of the guide arrangement. The at least one damping projection may then in itself by slightly undulate. However, in practice it is has been advantageous when a recording and/or reproducing apparatus in accordance with the invention and a guide arrangement in accordance with the invention utilizes a damping projection extending parallel to a plane that extends perpendicularly to the guide shaft of the guide arrangement. This arrangement has proved to be advantageous in view of a construction which is as simple as possible and in view of a production which is as simple as possible. 
     In a recording and/or reproducing apparatus in accordance with the invention and in a guide arrangement in accordance with the invention, the at least one damping projection may be rectangular or trapezoidal or substantially triangular with one rounded free corner in a radial cross-sectional view. However, it has been particularly advantageous when a recording and/or reproducing apparatus in accordance with the invention and a guide arrangement in accordance with the invention has a dome-shaped damping projection when view in a radial cross section. Such an embodiment has proved to be advantageous in view of a simple production but primarily in view of cooperation as gentle as possible with a record carrier tape. 
     In a recording and/or reproducing apparatus in accordance with the invention and in a guide arrangement in accordance with the invention it has been proved to be very advantageous when the height of the damping projection is based on the speed of the transport of record carrier and the curvature of the guide surface of the guide arrangement. These embodiments have proved to be advantageous in tests carried out during the development of a recording and/or reproducing apparatus in accordance with the invention and a guide arrangement in accordance with the invention. 
     In a recording and/or reproducing apparatus in accordance with the invention and a guide arrangement in accordance with the invention it has proved to be particularly advantageous when, in addition, the characteristic features are provided. Such an embodiment has the advantage that the tape guide roller provided as guide arrangement is moved along by a record carrier tape when this record carrier is driven, as a result of which hardly any relative movement in a circumferential direction occurs between the record carrier tape and the at least one damping projection of the tape guide roller, which provides a particularly high damping effect of the at least one damping projection on axial excursions of the record carrier tape. 
     However, it is emphasized that a guide arrangement in accordance with the invention may alternatively have a curved and, preferably, cylindrical guide surface, which may be supported so as to be stationary or rotatable with respect to its guide axis, which guide surface may have an end flange in the area of each of its two axial ends, which flange does not have a direct mechanical connection with the guide surface. This makes it possible, for example, to combine a rotatably supported cylindrical guide surface of a guide arrangement with stationary end flanges of this guide arrangement. 
     The above-mentioned as well as further aspects of the invention will become apparent from the embodiments described hereinafter by way of example and will be elucidated with reference to these examples. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail with reference to the drawings, which shows some embodiments given by way of example but to which the invention is not limited. 
     FIG. 1 is a plan view which shows a recording and reproducing apparatus in accordance with an embodiment of the invention, which apparatus includes two guide arrangements which serve for guiding a magnetic tape and which are each formed by a tape guide roller. 
     FIG. 2 is an axial cross-sectional view of a tape guide roller of the apparatus shown in FIG.  1 . 
     FIG. 3 shows a detail of the tape guide roller shown in FIG. 2, which detail is situated in an area marked by two circles III in FIG.  2 . 
     FIG. 4 shows a further detail of the tape guide roller shown in FIG. 2, which further detail is situated in an area marked by a circle IV in FIG.  2 . 
     FIG. 5 diagrammatically illustrates the principle of the construction of the tape guide roller shown in FIG.  2 . 
     FIG. 6 illustrates, in a manner similar to FIG. 5, the principle of a further tape guide roller which can be used in an apparatus as shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIG. 1 shows a recording and reproducing apparatus  1  which serves and is configured for the recording and reproduction of digital data and by means of which a large amount of data can be stored. The recording and reproducing apparatus  1  is briefly referred to hereinafter as the storage apparatus  1 . 
     The storage apparatus  1  is a development of a recording and reproducing apparatus which includes features forming the subject matter of nine patent applications in total, namely the European priority patent applications bearing the application numbers 98 890 332.4, 98 890 333.2, 98 890 334.0, 98 890 335.7, 98 890 336.5, 98 890 337.3, 98 890 338.1, 98 890 339.9 and 98 890 340.7 filed on Nov. 12, 1998. Said recording and reproducing apparatus was already shown at the Comdex fair of Las Vegas in the USA from Nov. 15, 1998 and is consequently known. The disclosure represented by the exhibited recording and reproducing apparatus and for a substantial part contained in the nine aforementioned European priority patent applications is incorporated herein by reference. For this reason, the remainder of the description of the storage apparatus shown in FIG. 1 is limited to only those areas and parts which are relevant in the present context. Furthermore, in the present context reference is also made to the two European priority patent applications bearing the application numbers 99 890 360.3 and 99 890 361.1, both filed on Nov. 11, 1999. 
     A cassette  2 , which is shown only in dash-dot lines in FIG. 1, can be loaded into the storage apparatus  1 . The cassette  2  accommodates a supply reel  3 , on which a magnetic tape  4  is wound, which tape as well as the supply reel  3  are shown merely as dash-dot lines in FIG.  2 . The magnetic tape  4  can be scanned along a plurality of tracks which extend in the longitudinal direction of the magnetic tape  4 , in order to record or reproduce digital data. 
     The storage apparatus  1  has a chassis  5  which carries the individual constructional units and parts of the storage apparatus  1 . Hereinafter, only those of the constructional units and parts are mentioned which are relevant in the present context. 
     For holding a cassette  2  and moving it from a loading position into an operating position in the storage apparatus  1  the storage apparatus  1  has a movable cassette holder  6 . The movable cassette holder  6  is movable along an L-shaped path of movement between a loading position, in which a cassette  2  can be inserted into the cassette holder  6 , and an operating position, in which an inserted cassette  2  is in its operating position. 
     To move the cassette holder  6  and further movable apparatus parts of the storage apparatus  1  the storage apparatus  1  has drive means  7 . The drive means  7  include a motor  8  and a gear mechanism  9 , by means of which a ring-shaped drive gear wheel  10  is drivable. With the aid of the ring-shaped drive gear wheel  10  cam devices, by means of which the movable cassette holder  6  is movable, can be driven via gear racks. 
     When the cassette holder  6  is in its operating position a cassette  2  loaded into the cassette holder  6  is also in its operating position. As already stated, the cassette  2  accommodates a supply reel  3  on which the magnetic tape  4  is wound. At the free end of the magnetic tape  4  the magnetic tape  4  is connected to a coupling pin  11 . In the operating position of the cassette  2  pull-out means  12  can be coupled to the coupling pin  11 , which means include a pull-out element  13  and a pull-out tape  14 . For the clarity of the drawing the pull-out tape  14  is shown as a dash-dot line in FIG.  1 . The pull-out tape  14  is passed from pull-out element  13  to a take-up reel  15  and is fixedly connected to a hub portion  16  of the take-up reel  15 . The hub portion  16  has a recess  17  which is adapted to receive the pull-out element  13 . By means of a first motor, not shown, of the storage apparatus  1  the take-up reel  15  is rotationally drivable in a direction indicated by an arrow  18 . The rotational drive of the take-up reel  15  enables the pull-out tape  14  and, consequently, the pull-out element  13  to be driven, as a result of which, after coupling of the pull-out element  13  to the coupling pin  11 , the magnetic tape  4  can be pulled out of the cassette  2  with the aid of the pull-out tape  14  and can be moved up to the take-up reel  15  and can be wound onto the take-up reel  15 , upon which recording on or reproducing from the magnetic tape  4  is possible. 
     The storage apparatus  1  has drive means  19  for driving the magnetic tape  4 . The drive means  19  include the first motor, not shown, which has been provided in the storage apparatus  1  in order to drive the take-up reel  15  and which drives the take-up reel  15  with the aid of a drive member, not shown, which also forms a part of the drive means  19 . The drive means  19  further include a second motor, which is not shown completely. FIG. 1 only shows a stator section  20  of the second motor, which stator section carries excitation coils, not shown, by means of which a rotor, not shown, of this second motor can be driven. The second motor can drive crown-like gear teeth which mesh with crown-like mating gear teeth provided on the supply reel  3 , the supply reel  3  thus being drivable in a direction indicated by an arrow  21  by means of the second motor to wind the magnetic tape  4  onto the supply reel  3 . 
     The storage apparatus  1  further has guide means  22  for guiding the magnetic tape  3 . In the present case the guide means  22  include two guide arrangements  23  and  24 . Each of the two guide arrangements  23  and  24  has a guide shafts,  25  and  26  respectively. Each of the two guide arrangements  23  and  24  further has a guide surface,  27  and  28  respectively, which is curved with respect to the respective guide shaft  25  or  26 . Finally, each of the two guide arrangements  23  and  24  has an end flange,  29 ,  30  and  31 ,  32  respectively, in the area of each of the two axial ends of the respective guide surfaces  27  and  28 , which end flanges extend transversely to the respective guide shafts  25  and  26 , as is illustrated for the guide arrangement  24  in FIG.  2 . In the present case, the two guide arrangements (or two tape guide roller)  23  and  24 , which are rotatable about the respective guide shafts  25  and  26 . The guide shaft  25  or  26  is stationarily connected to the chassis  5 . 
     The storage apparatus  1  further has a multi-track magnetic head  33  which serves for scanning the magnetic tape  4 . The magnetic head  33  is mounted on an actuator device  34  by means of which the magnetic head  33  is movable in a direction perpendicular to the longitudinal direction of the magnetic tape  4  to keep the individual magnet systems of the multi-track magnetic head  33  constantly aligned with respect to the scanning tracks of the magnetic tape  4 , so as to guarantee an exact tracking. The magnetic head  33  is arranged in the area between the two guide arrangements  23  and  24 , i.e. between the two tape guide rollers  23  and  24 . With the aid of the actuating device  34  the magnetic head  33  can follow variations in the height position of the magnetic tape  4 , namely those variations in the height position whose frequency is of the order of magnitude of approximately 200 Hz. 
     As is apparent from FIG. 2, the guide arrangement  24 , which is also referred to hereinafter as the tape guide roller, comprises an outer part  35  whose circumferential bounding surface forms the guide surface  28  and whose axial end portions form the end flanges  31  and  32 . The outer part  35  has a central bore  36  having at each of its axial ends a respective bore portion  37  or  38  whose diameter is larger than that of the portion of the bore  36  situated between them. The bore  36  accommodates two ball-bearings, of which only the outer rings  39  and  40  are shown in FIG.  2 . The parts of the two ball-bearings situated between the outer rings  39  and  40  in a radial direction are not shown. The ball-bearings support the guide arrangement  24  so as to be rotatable with respect to the guide shaft  26 , which is not shown in FIG. 2 but which is only represented diagrammatically as a dash-dot line. 
     In the area of its guide surface  28  the guide arrangement  24  has two damping projections  41  and  42 , which are spaced at a distance D 1  from one another and which are adapted to damp axial relative movements of the magnetic tape  4  with respect to the guide arrangement  24 . Owing to the small size of the damping projections  41  and  42  the two damping projections  41  and  42  are hardly visible in FIG.  2  and can only be seen in FIG. 3, which shows a part of the guide surface  28  of the guide arrangement  24 , which part carries one of the two damping projections  41 ( 42 ). The two damping projections  41  and  42  each extend parallel to a plane  43  or  44 , which plane extends perpendicularly to the guide shaft  26  and is shown as a dash-dot line in FIGS. 2 and 3. 
     As is apparent from FIG. 3, the two damping projections  41  and  42  are dome-shaped in a radial cross-section. This is achieved in that the two damping projections  41  and  42  have a central portion  45  having a radius R 1  of, for example, 3±0.2 mm, which central portion  45  is bounded by two edge portions  46  and  47 , each having a radius R 2  of 1±0.2 mm. Each of the two damping projections  41  and  42  has a height H 1  with respect to the remainder of the guide surface  28 , which height has a value of approximately 0.02±0.005 mm and preferably a highly accurate value of 0.02 mm. 
     With respect to the value of the height H 1  it is to be noted that the value of the height H 1  of the two damping projections  41  and  42  is defined in dependence on the speed of transport of the magnetic tape  4  and the curvature of the guide surface  28  of the tape guide roller  42 . In the case of the present storage apparatus  1 , in which the speed of transport of the magnetic tape  4  is approximately 4.0 m/s and the curvature of the guide surface  28  is defined by the radius of curvature of the guide surface  28 , i.e. by the diameter of the tape guide roller  24  in the area of its guide surface  28 , which radius of curvature has a value of 10 mm, the advantageous value of the height H 1  lies in the range of 0.02±0.005 mm. 
     For the construction of the guide arrangement  24  in the area of the two end flanges  31  and  32  reference is also made to FIG. 4 which is a representation to a larger scale than in FIG.  2 . As can be seen in FIG. 4, a receding portion  48  is provided in the area of the transition between the guide surface  28  and the end flange  32 . Starting from the recessed portion  48  the bounding surface of the end flange  32  first has a bounding portion  49  adjoined by a bounding portion  50  which is inclined with respect to the guide shaft  26 . A similar construction is also used in the area of the other end flange  31  of the guide arrangement  24 . 
     The construction of the tape guide roller  24  described above is identical for the other tape guide roller  23 . 
     FIG. 5 illustrates the principle of the construction of the guide arrangement  24 . 
     FIG. 6 illustrates the principle of a further tape guide roller  24 . The tape guide roller  24  shown in FIG. 6 has only one damping projection  41 . 
     It is to be noted that tape guide rollers as well as differently constructed guide arrangements may alternatively have more than one damping projection and more than two damping projections, for example three, four or five damping projections. The number of damping projection depends in particular on the axial dimension of the tape guide surface of a guide arrangement.