TAPE REEL CHUCKING MEANS WITH CONTROLLED FORCE OF MAGNETIC ATTRACTION

Abstract: A recording and/or reproducing apparatus (1) can hold a magnetic-tape cassette (2), which accommodates a supply reel (3) including a first magnetic circuit element (42) and has a disc-shaped drive member (47) including a second magnetic circuit element (49), the two magnetic circuit elements (42, 49) forming magnetically acting holding means (43) for holding the supply reel (3) in the apparatus (1) and the disc-shaped drive member (47) having magnetic-force-of-attraction limiting means (51) which serve to and are adapted to cooperate with the first magnetic circuit element (42) and which enable the magnetic force of attraction produced between the two magnetic circuit elements (42, 49) to be limited.

Description: TAPE REEL CHUCKING MEANS WITH CONTROLLED FORCE OF MAGNETIC ATTRACTION The invention relates to a recording and/or reproducing apparatus as defined in the opening part of claim 1. Information about a known recording and/or reproducing apparatus as defined in the opening part of claim 1 and information about a cassette with a magnetic tape as record carrier tape for such a recording and/or reproducing apparatus is obtainable via the internet, namely at the internet address "www.lto-technology.com". In connection with the known recording and/or reproducing apparatus and the known cassette reference may also be made to the two patent documents WO 98/44506 A2 and WO 98/44499 Al. In the known recording and/or reproducing apparatus the disc-shaped drive member has drive teeth which form reel drive means at the drive member side and which serve and are configured to cooperate in a driving fashion with reel teeth of the supply reel of a cassette, which reel teeth form reel drive means at the reel side. During operation, when the cassette has been loaded into the recording and/or reproducing apparatus, the reel teeth and the drive teeth axially abut against one another, which is caused by the magnetic force of attraction of the magnetically acting holding means. The geometric distance in an axial direction between the first magnetic circuit element connected to the supply reel and the second magnetic circuit element connected to the disc-shaped drive member is in the first place dictated by the drive teeth and the reel teeth, but in the second place it also depends on the tolerances of said teeth as well as the tolerances of the axial dimensions of the two magnetic circuit elements and on the tolerances of the assembly dimensions of the two magnetic circuit elements. However, as a result of this dependence of the axial distance between the two magnetic circuit elements the magnetic force of attraction that occurs between the two magnetic circuit elements, which force depends on this axial distance, may vary comparatively strongly, which results either in a magnetic force of attraction which is inadequate for properly holding the supply reel on the disc-shaped drive member or in an excessive magnetic force of attraction, which may lead to problems when the supply reel is to be disengaged from the disc-shaped drive member, which disengagement is necessary when a cassette is moved out of the recording and/or reproducing apparatus. Tests have shown that in the case of an inadequate axial distance between the two magnetic circuit elements such a large magnetic force of attraction may occur that the supply reel of a cassette is no longer disengageable from the reel-shaped dnve member of the recording and/or reproducing apparatus, or that such a large magnetic force of attraction is exerted on the first magnetic circuit element connected to the supply reel that the first magnetic circuit element may become disengaged from the supply reel. In both problem situations mentioned above the recording and/or reproducing apparatus requires a repair, which is unfavorable and undesirable. It is an object of the invention to preclude the af ore-mentioned problems with the aid of simple and reliable means and at low cost and to provide an improved recording and/or reproducing apparatus in which the occurrence of an undesirably large magnetic force of attraction between the first magnetic circuit element of a supply reel of a cassette and the second magnetic circuit element of the disc-shaped dnve member is avoided. To achieve this object, according to the invention, the charactenstic features defined in the charactenzing part of claim 1 are provided in a recording and/or reproducing apparatus as defined in the opening part of claim 1 Owing to the provision of the charactenstic features in accordance with the invention it is achieved in a simple manner that the magnetic force of attraction that occurs in operation between the first magnetic circuit element of the supply reel of a cassette and the second magnetic circuit element of the disc-shaped dnve member of a recording and/or reproducing apparatus in accordance with the invention can never exceed a given value which can be defined by a suitable configuration of the magnetic-force-of-attraction limiting means, which consequently precludes the problems descnbed hereinbefore for the known recording and/or reproducing apparatus. In a recording and/or reproducing apparatus in accordance with the invention the magnetic-force-of-attraction limiting means may be formed, for example, by a separate element connected to the disc-shaped dnve member, which connection may, for example, take the form of an adhesive joint Such a construction is of particular advantage when the disc-shaped dnve member is made of a magnetic or magnetizable mateπal. However, in a recording and/or reproducing apparatus in accordance with the invention it has also proved to be very advantageous when, in addition, the charactenstic features defined in claim 2 are provided. Such an embodiment has the advantage that it can be manufactured simply and has a high reliability. Such an embodiment, in which the magnetic-force-of-attraction limiting means are integral with the disc-shaped dnve member, is particularly advantageous when the disc-shaped dnve member is made of a non-magnetic or non-magnetizable matenal, notably when the disc-shaped dnve member is made of a plastic. In a recording and/or reproducing apparatus in accordance with the invention having at least one such projection it has proved to be particularly advantageous when, in addition, the charactenstic features defined in claim 3 are provided. This guarantees an unambiguous, reliable and stable conformity with a given minimum distance between the first magnetic circuit element and the second magnetic circuit element. In a recording and/or reproducing apparatus in accordance with the invention it has further proved to be very advantageous when, in addition, the charactenstic features defined in claim 4 are provided. Such an embodiment has proved to be very advantageous in practice. Such an embodiment further has the advantages that as a result of the provision of the third magnetic circuit element the stray field of the magnetically acting holding means is kept comparatively small and that, in addition, a high efficiency of the magnetically acting holding means is achieved. The above-mentioned as well as further aspects of the invention will become apparent from the embodiments descnbed hereinafter by way of example and will be elucidated with reference to these examples. The invention will now be descnbed in more detail with reference to the drawings, which show an embodiment given by way of example but to which the invention is not limited Fig. 1 is a plan view which shows a recording and/or reproducing apparatus in accordance with an embodiment of the invention, which apparatus includes a disc-shaped dnve member for dnving a supply reel Fig. 2 shows in an oblique view from underneath the disc-shaped dnve member of the recording and/or reproducing apparatus shown in Fig. 1 and a supply reel placed on the dnve member. Fig 3 shows, in a manner similar to Fig. 2, the disc-shaped dnve member and the supply reel of Fig. 2, the supply reel being shown in a situation in which it is lifted off the dnve member Fig. 4 is an oblique plan view which shows the disc-shaped drive member of Figs. 2 and 3. Fig. 5 is a cross-sectional view which shows the disc-shaped drive member of Figs. 2, 3 and 4 and the supply reel of Figs. 2 and 3, the relative axial position of the supply reel with respect to the disc-shaped drive member being defined by drive teeth. Fig. 6 shows a part of Fig. 5 to an enlarged scale in comparison with Fig. 5. Fig. 7 shows the disc-shaped drive member and the supply reel in a manner similar to Fig. 5, the relative axial position of the supply reel with respect to the disc-shaped drive member being defined by three projections of the disc-shaped drive member. Fig. 8 shows a part of Fig. 7 in a manner similar to Fig. 6. Fig. 1 shows a recording and reproducing apparatus 1 which serves to 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 12 November 1998. Said recording and reproducing apparatus was already shown at the Comdex fair of Las Vegas in the USA from 15 November 1998 and is consequently known. The disclosure represented by the exhibited recording and reproducing apparatus and for a substantial part contained in the nine afore- mentioned 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 11 November 1999. The storage apparatus is adapted to hold a cassette 2, which is shown only in dash-dot lines in Fig. 1. The cassette 2 accommodates a supply reel 3, which is rotationally drivable with respect to a reel axis 3A and which serves to and is adapted to take up (wind) a magnetic tape 4, which tape as well as the supply reel 3 are shown merely as dash-dot lines in Fig. 1. 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 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. Thus, the supply reel 3 also forms a part of the drive means 19. The two kinds of gear teeth will be described in greater detail hereinafter. 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 tape guide rollers 23 and 24. Each of the two tape guide rollers 23 and 24 has a guide shafts, 25 and 26 respectively, which are stationarily connected to the chassis 5, and a guide surface, 27 and 28 respectively, which is cylindrical with respect to the respective guide shaft 25 or 26. Further, each of the two tape guide rollers 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 cylindrical guide surfaces 27 and 28, which end flanges extend transversely to the respective guide shafts 25 and 26. 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 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 3. As already stated hereinbefore, the storage apparatus 1 further includes a second motor, of which only the stator section 20 is shown in Fig. 1. The second motor forms a part of a reel drive device 35 which serves to and is adapted to rotationally drive the supply reel 3 of the cassette 2. As regards the supply reel 3 it is to be mentioned in addition (see Figs. 2 to 8) that the supply reel 3 consists of a plastic and has a substantially pot-shaped hub portion 36 which is integral with a first reel flange 37 and a second reel flange 38. The pot-shaped hub portion 36 has a bottom wall 39 and a cylindrical circumferential wall 40. In a manner not shown the magnetic tape 4 has one end attached to the circumferential wall 40 and is subsequently wound up, the tape spool thus formed being disposed between the two reel flanges 37 and 38. In the area of the bottom wall 39 the supply reel 3 is connected to, i.e. is integral with, a reel-side reel dnve means 41. Here, the reel-side reel dnve means 41 is formed by reel teeth 41. In the area of its bottom wall 39 the supply reel 3 is further connected to a first magnetic circuit element 42, which serves to form magnetically acting holding means 43 for holding the supply reel 3 the storage apparatus 1. The first magnetic circuit element 42 is formed by a circular disc, which forms a magnetic yoke and which consists of a low-carbon steel having a nickel cladding to protect it The first magnetic circuit element 42 has a total of three angularly equispaced bores 44, which are each engaged by a projection 45 which extends from the bottom wall 39. The first magnetic circuit element 42 is connected to the bottom wall 39 of the supply reel 3 by insert-molding The reel dnve device 35 has a disc-shaped dnve member 47 which is rotationally dnvable with respect to a disc axis 46 and which is shown only as a dash-dot line in Fig. 1. The disc-shaped dnve member 47 has a dnve-member-side reel dnve means 48, which in the present case is formed by dnve teeth 48. The dnve teeth 48 serve to and are adapted to cooperate in a dnving fashion with the reel teeth 41, i.e. with the reel-side reel dnve means 41. The dnve teeth 48 are integral with the dnve member 47. The dnve member 47, just as the supply reel 3, is made of a plastic. The dnve members 47 is connected to a second magnetic circuit element 49 provided with the magnetically acting holding means 43 for holding the supply reel in the storage apparatus 1. Here, the second magnetic circuit element 49 is formed by an annular magnet 49 The magnet 49 consists of a neodymium-iron-boron compound. Furthermore, a third magnetic circuit element 50 is connected to the discshaped dnve member 47, the connection being made by insert-molding. The third magnetic circuit element 50 is basically annular and also forms a magnetic yoke. The third magnetic circuit element 50 consists of a stainless steel. The provision of the third magnetic circuit element 50 results in a small stray field and a high efficiency of the magnetically acting holding means 43. It is to be noted that the second magnetic circuit element 49, which is formed by a magnet, and the third magnetic circuit element 50 are connected to one another by the magnetic force of attraction In addition, an adhesive joint, not shown in the Figures, is provided between the second magnetic circuit element 49 and the third magnetic circuit element 50, in order to guarantee an increased reliability for the connection between the second magnetic circuit element 49 and the third magnetic circuit element 50 In the storage apparatus 1 the disc-shaped dnve member 47 is advantageously provided with magnetic-force-of-attraction limiting means 51 which serve to and are adapted to cooperate with the first magnetic circuit element 42 With the aid of the magnetic-force-of- attraction limiting means 51 the magnetic force of attraction produced between the first magnetic circuit element 42 and the second magnetic circuit element 49 can be limited to a given value This given value is dictated by a given minimum axial distance between the first magnetic circuit element 42 and the second magnetic circuit element 49. In the storage apparatus 1, i.e. in the disc-shaped dnve member 47 the magnetic-force-of-attraction limiting means 51 are formed by three projections 52, 53 and 54, which project from the dnve member 47 in the direction of the disc axis 46. The three projections 52, 53 and 54 are situated on a circle which is coaxial with the disc axis 46 and are angularly equispaced The construction of the three projections 52, 53 and 54 is apparent from Figs 4 to 8. Each of the three projections 52, 53 and 54 consists of a block-shaped basic portion 55, 56 and 57, respectively, and of a stud portion 58, 59 and 60, respectively Each of the three basic portions 55, 56 and 57, as is shown for the second projection 53 in Figs. 5 to 8, is integrally connected to the disc-shaped dnve member 47 via a limb 61. Figs. 5 and 6 illustrate a normal operating situation, in which the first magnetic circuit element 42 of the supply reel 3 is properly and faultlessly connected to the bottom wall 39 of the supply reel 3 In this normal operating situation the three projections 52, 53 and 54 have no effect, as is apparent particularly from Fig 6. In fact, the three projections 52, 53 and 54 do not come into contact with the first magnetic circuit element 42. Therefore, the relative axial position of the supply reel 3 and, consequently, of the first magnetic circuit element 42 with respect to the disc-shaped dnve member 47 and, consequently, with respect to the second magnetic circuit element 49 is determined by the reel teeth 41 and the dnve teeth 48, which teeth 41 and 48, l e their tooth flanks, intermesh under the influence of the force exerted by the magnetically acting holding means 43 Thus, in this normal operating situation the magnetic force of attraction between the first magnetic circuit element 42 and the second magnetic circuit element 49 is determined by the axial distance between the first magnetic circuit element 42 and the second magnetic circuit element 49, which distance is defined by means of the reel teeth 41 and the dnve teeth 48 Figs 7 and 8 show a supply reel 3, whose first magnetic circuit element 42 - whatever the cause - does not occupy a specified correct position on the supply reel 3 As is apparent from Figs. 7 and 8, the first magnetic circuit element 42 shown in Figs. 7 and 8 has too large an axial distance from the bottom wall 39 of the supply reel 3. This excessive distance may have originated during the production of the supply reel 3. Alternatively, the excessive distance may have arisen after frequent use of the supply reel 3 or rather of the cassette 2 including the supply reel 3. When the supply reel shown in Figs. 7 and 8 has been loaded into the storage apparatus 1 shown in Fig. 1 and no precautionary measures in the form of the magnetic- force-of-attraction limiting means 51 had been provided in the storage apparatus 1 and the disc-shaped drive member 47 of the storage apparatus 1, this would result in the first magnetic circuit element 42 being situated at such a small axial distance from the second magnetic circuit element 49 that a given maximum permissible magnetic force of attraction between the first magnetic circuit element 42 and the second magnetic circuit element 49 would be exceeded. The result of this might be that the first magnetic circuit element 42 could no longer be detached from the second magnetic circuit element 49 or could be detached only through an undesired separation of the connection between the first magnetic circuit element 42 and the bottom wall 39 of the supply reel 3, which is obviously undesirable. The provision of the magnetic-force-of-attraction limiting means 51 precludes the undesirable situation described above in the storage apparatus 1 and the disc-shaped drive member 47 in an advantageous manner, namely in that - as is apparent in particular from Fig. 8 - the three projections 52, 53 and 54 operatively engage with the first magnetic circuit element 42, as a result of which the first magnetic circuit element 42 abuts with the stud portions 58, 59 and 60 in this operating situation. This guarantees that the axial distance between the first magnetic circuit element 42 and the second magnetic circuit element 49 is determined by the difference in axial level between the free ends of the stud portions 58, 59 and 60 and the free end surface of the second magnetic circuit element 49. Thus, it is guaranteed by simple means and in a very reliable manner that the distance between the first magnetic circuit element 42 and the second magnetic circuit element 49 defined by said difference in level can never become smaller, as a result of which the magnetic force of attraction between the two magnetic circuit elements 42 and 43 can never exceed a given value. Thus, undesirably high magnetic forces of attraction are precluded in a reliable manner. It is to be noted that the measures in accordance with the invention may also be applied to a recording and/or reproducing apparatus having two juxtaposed disc-shaped drive members, the two drive members serving to and being adapted to cooperate with two reels accommodated in a cassette. A disc-shaped drive member and a reel need not cooperate in a driving fashion via teeth but alternatively other reel drive means may be provided, for example winding mandrels and the like.

Claims: CLAIMS 1 A recording and or reproducing apparatus (1) adapted to hold a cassette (2) which includes a supply reel (3) which is rotationally dnvable with respect to a reel axis (3 A), which supply reel serves to and is adapted to take up a record earner (4) in the form of a tape and which is connected to a reel- side reel dnve means (41) and which is connected to a first magnetic circuit element (42), which magnetic circuit element serves to form magnetically acting holding means (43) for holding the supply reel (3) in the recording and/or reproducing apparatus (1), and having a reel dnve device (35) for rotationally dnving the supply reel (3), which reel dnve device (35) has a disc-shaped dnve member (47), which is rotationally dnvable with respect to a disc axis (46), which dnve member (47) has a dnve-member-side reel dnve means (48), which means serves to and is adapted to cooperate in a dnving fashion with the reel-side reel dnve means (41), and which dnve member (47) is connected to a second magnetic circuit element (49), which serves to form the magnetically acting holding means (43) for holding the supply reel (3) in the recording and/or reproducing apparatus (1 ), charactenzed m that the disc-shaped dnve member (47) has magnetic-force-of-attraction limiting means (51), and the magnetic-force-of-attraction limiting means (51) serve to and are adapted to cooperate with the first magnetic circuit element (42) of the supply reel (3), and the magnetic-force-of-attraction limiting means (51) enable the magnetic force of attraction produced between the first magnetic circuit element (42) and the second magnetic circuit element (49) to be limited to a given value 2 A recording and/or reproducing apparatus (1) as claimed m claim 1, charactenzed m that the magnetic-force-of-attraction limiting means (51) are formed by at least one projection (52, 53, 54) which projects from the dnve member (47) in the direction 3. A recording and/or reproducing apparatus (1) as claimed in claim 2, characterized in that the magnetic-force-of-attraction limiting means (51) include three projections (52, 53, 54) which are situated on a circle which is coaxial with the disc axis (46) and which are angularly equispaced from one another. 4. A recording and/or reproducing apparatus (1) as claimed in claim 1, characterized in that the second magnetic circuit element (49) is formed by an annular magnet, and a third magnetic circuit element (50), which is also annular and also forms a magnetic yoke, is connected to the disc-shaped drive member (47).

Inventors: HUETTENEGGER HEIMO, KLETZL FRANZ, HUETTENEGGER, HEIMO, KLETZL, FRANZ
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 2001
Main classification: G11B17
IPC codes: G11B15, G11B23