Cassette structure with lid

Abstract: A recording/reproducing tape cassette with a lid has a cassette body accommodating therein a cassette tape, a part of which is exposed outside and a rotatable lid mechanism (109,115,118) for clamping the exposed part of the tape. The lid mechanism is provided with a rotary shaft (113A) including a guide portion (114) eccentric therewith and a torsion coil spring (121) fitted on the guide portion (114). When the rotary shaft rotates (113A), the guide portion (114) rotates eccentric therewith and the torsion coil spring (121) moves in a direction in which it does not interfere with a tape end detecting optical path (122) located near the rotary shaft so that the torque on the torsion coil spring (121) can be increased smoothly to open and close the lid. Further, the rotary shaft (113A) may be provided with a rib so that a lid spring for constantly urging the lid in a direction in which the lid is closed may engage the rib without bending thereby reducing the space to be occupied by the spring.

Description: The present invention relates to a recording/reproducing tape cassette with a lid. With reference to Figures 7 to 12 of the accompanying drawings, a prior art recording/reproducing tape cassette 60 attached with a lid comprises a substantially square upper shell 2, a reel portion 5 comprised of a pair of reels 4 around which a tape 3 is wound, a lid mechanism 61 including a rotatable lid for clamping the upper and rear surfaces of a part of the tape exposed outside the cassette 60 and a substantially square lower shell 37 capable of engaging the upper shell, as shown in Fig. 9. As shown in Fig. 7, the upper shell 2 is formed of a substantially square insulating member and is provided with a pair of top-lid guide grooves 7, respectively, which are formed on both longitudinal side surfaces thereof so as to extend rearwardly from the front surface, a pair of front-lid rotating shaft bearing portions 8, a pair of tubular lower shell engagement projections 9 and a back-lid engagement portion 10 of a predetermined length formed by recessing the central portion of the front edge of the upper shell 2. The lid mechanism 61 comprises a top-lid 12, a back-lid 17, a front-lid 21 and a lid spring 65 in the form of an elastic torsion coil spring. The lid mechanism 61 operates such that when the cassette 60 is in use, it leaves away from the tape 3 as it opens to release the tape clamped thereby. As shown in Fig. 7, the top-lid 12 is rectangular and comprises two longitudinal side walls 13, a pair of front-lid engagement holes 14 formed inside the side walls 13 in opposite relationship with each other with each being in the form of a partly recessed blind hole, a pair of upper shell engagement projections 15 respectively formed on the side walls 13 at positions behind the front-lid engagement holes 14 so as to be guided by the top-lid guide grooves 7 and a pair of back-lid engagement projections 16 formed on the inner surface of the top-lid 12 in spaced apart relationship with each other inwardly of the side walls 13 so as to engage the back-lid 17. As shown in Fig. 7, the back-lid 17 has a horizontally elongate triangular lower portion and an elongate platelike tape retaining surface 18A for clamping the exposed portion of the tape 3. Further, one side surface of the triangular lower portion of the back-lid 17 is provided with a lower shell guide projection 19 interlocking with the tape clamping and unclamping operations and the upper end of the tape retaining surface 18A is provided at both ends thereof with a pair of top-lid engagement projections 20. As shown in Fig. 7, the front-lid 21 comprises an elongate flat base plate portion 22, a pair of front-lid retaining portions 23 extending from both ends of the base plate portion 22 in a direction intersecting the longitudinal direction of the latter, a pair of top-lid engagement projections 20A to engage the top-lid 12 and a tape retaining surface 18B formed on the rear side of the base plate portion 22 so as to clamp the tape. The front-lid retaining portions 23 are provided with lid-rotating shafts 62 and 35, respectively, which are different in structure and which face each other inwardly right and left and are also provided with tongue-like lid-engagement pieces 26 at positions near the free ends thereof, respectively. As shown in Figs. 8 and 9, the lid rotating shaft bearing portion 62 (see the leftside of Fig. 7) is an engagement portion for the lid mechanism 6 and comprises a axial portion 27 rotatably engageable with a front-lid rotating shaft bearing portion 8 and a front-lid engagement portion 41, a support shaft 63 coaxial with the axial portion 27 for mounting a lid spring 65 thereon and a flange portion 64 of an enlarged diameter provided between the axial portion 27 and the support shaft 63. The support shaft 63 has a diameter smaller than the inner diameter of an end turn 66 of the lid spring 65 and is provided with a flange portion 64 projecting from a portion of the support shaft 63 in a direction intersecting at right angles with the axis of the support shaft 63. As shown in Figs. 10 and 11, the lid spring 65 may comprise the end turn 66 wound in the form of a torsion coil spring, an arm portion 67 formed by linearly expanding one end of the end turn 66 and a semi-circular hook portion 66 formed by raising the end turn portion 66 of a diameter Dc upward by 90°. In that case, the distance between the end turn portion 66 and the free end of the hook portion 68 is dc and it is therefore necessary to increase the width wa for accommodating the lid spring 65 shown in Fig. 8. Therefore, as shown in Fig. 11, the hook portion 69 is made to have a limited height Y in such a manner that after a wire having an end turn is raised upward by 90", the wire is reprocessed to reduce the diameter dh of the semi-circular portion of the wire. Thus, the width wb can be increased to allow the lid spring 65 to be mounted on the front-lid rotating shaft bearing portion 8 support shaft 63. The lid rotating shaft 35 (the right side in Fig. 7) comprises a shaft 36 rotatably engageable with the front-lid rotating shaft bearing portion 8 of the upper shell 2 and the front-lid rotating shaft engagement portion 41 of the lower shell 37. As shown in Fig. 7, the lower shell 37 is substantially square in shape so as to engage the upper shell 2 and is provided with a pair of lid engagement portions 40 on both shorter sides thereof. The assembly of the tape cassette 60 having a lid comprising the various kinds of parts described above is performed in such a manner that the pair of reels 4 having the tape wound therearound are first mounted in the lower shell 37, then the back-lid 17, the top-lid 12 and the front-lid 21 are brought into engagement with one another and then with the upper shell 2 and the lid spring 65 is fitted on the support shaft 63 to thereby complete the lid mechanism 61. Then the lid mechanism 61 is placed over the lower shell 37 while it is kept opened against the force of the lid spring 65 to thereby complete the assembly of the cassette 60. Further, as shown in Fig. 12, a prior art recording/reproducing cassette with a lid is provided with a lid mechanism comprising, in combination, a top lid 118, a front lid 109 and a back lid 115 and provided on the front surface of a combined structure of an upper shell 102A and a lower shell 102B. These lids 118, 109 and 115 are made to open and close in interlocking relationships with one another as they are guided by grooves formed in the shells 102A and 102B such that when the cassette 1 is not in use, the tape is protected by being clamped between the front lid 109 and the back lid 115 while when the cassette 1 is in use, the lids move upward as they release the tape from its clamped state allowing a part of the tape to become exposed outside completely. The closing operation of the lids 118, 109 and 115 is effected by the elastic force of a torsion coil spring 121 fitted on a guide portion 114A coaxial with a lid rotating shaft 113A of the lid mechanism. Further, the position of the guide portion 114A is close to a tape end detecting optical path 122 and usually it is substantially the same size as the lid rotating shaft 113A for rotating the lid mechanism. Further, the distance between the guide portion 114A and the tape end detecting optical path 122 is, as shown in Fig. 21, formed to a size such that when the torsion coil spring 121 is mounted, the end of the spring 121 does not block at least the tape end detecting optical path 122. Accordingly, the torsion coil spring 121 is made to have a predetermined outer diameter. United Kingdom Patent Specification No. 2 187 711 discloses a cassette having a spring biased front cover wherein one end of the spring is "U" shaped and mateable with a projection on the cover. United Kingdom Patent Specification No. 2 248 823 discloses a tape cassette having a spring for biasing a dust lid and lid latch. Both ends of the spring are bent, one to fit within a channel formed in a rotary number about which the dust lid rotates. European Patent Specification No. 0 287 664 discloses a tape cassette having a spring biased front cover wherein the spring comprises a leaf spring with bent ends, one end being bent back upon itself to fit around, and mate with, a channel in a rotary member. As prior art cassette techniques, the following three patent applications are proposed by the present applicant. 1.USP4,989,111 2.USP5,024,394 3.Japanese Patent Application No. H05010347 (Note: Each of the above applications is owned by the assignee of the present invention.) However, the structure of the above-described prior art tape cassette has had the problems that since the diameter of the hook portion 69 of the lid spring 65 has to be reduced after once raising up the end turn portion of the spring by 90°, the bending process for the spring becomes complicated and the workability of the spring becomes bad. Further, the prior art structure has also had the problem that in order to reduce the diameter of the hook portion 69, if the diameter of the end turn of the lid spring 65 is made equal to the diameter of the hook portion 69, the magnitude of the force of the spring 65 required for closing the lid mechanism becomes weak failing to obtain the maximum stress to be applied on the spring. Accordingly, it has been demanded to provide a lid spring structure which has a reduced height while keeping the maximum stress to be applied on the conventional spring. However, the above-described prior art tape cassette attached with the lid mechanism has had the problem that the torsion coil spring guide portion is formed coaxial with the rotary shaft for opening and closing the lid mechanism and therefore, when the diameter of the torsion coil spring blocks the tape end detecting optical path so that the torsion coil spring can not have sufficient force to close the lid mechanism. Accordingly, for solving the above problem, it has been necessary to provide a lid structure in which the diameter of the torsion coil spring can be varied while keeping the lid mechanism rotating shaft positioned close to the tape end detecting optical path. Patent Specifications EP-A 169 544, EP-A 614 185 and EP-A 0 88 438 all show tape cassettes with openable lid members with torsion springs with a central coiled portion and unbent ends, the unbent ends being supported against portions of the lid members and cassette housings respectively. According to the present invention there is provided a tape cassette comprising: a cassette body formed of an upper and a lower square shell; a tape accommodated partly within said cassette body and partly outside of the cassette body; a lid mechanism comprising a lid rotatable about a rotary shaft from a closed position covering the part of the tape outside of the cassette body to an open position exposing the tape; and a torsion spring for constantly urging said rotatable lid toward the closed position, the spring having unbent ends with one unbent end of said spring abutting against the upper shell; characterised in that the other unbent end abuts against an engagement portion provided on the periphery of said rotary shaft. Preferably said rotary shaft comprises an axial portion connected to a portion of said lid and a support shaft formed as a coaxial extension of said axial portion and capable of having said lid spring mounted thereon. Advantageously said engagement portion comprises a flange extending perpendicularly from the rotary shaft and a rib extending perpendicularly from the flange. With such an arrangement it is possible to reduce the height of the spring thereby reducing the mounting space for the spring. Since the lid spring is not required to have a hook portion, the shape of the spring can be simple and the dispersion of the effective opening angle of the spring can be reduced. In addition, since the size of the width of the spring is not limited, it is possible to reduce the stress to be applied on the spring by increasing the diameter of the wire material for the spring and the number of windings of the spring. As described above, the tape cassette according to the present invention can have an extremely excellent effect that since one end of the lid spring for always urging the rotatable lid of the lid mechanism toward its closed state is held in engagement with the engagement portion provided on the lid rotating shaft without bending that end, the spring is not required to have a hook portion as has been required in the prior art device so that the installation space for the spring can be reduced. The tape cassette of the present invention can have also another extremely excellent effect that since the lid spring has no hook portion, it becomes no more necessary to raise any hook portion from the end turn of the spring resulting in improving productivity and reducing the manufacturing cost. Further, the tape cassette of the present invention can have a still another excellent effect that since a sufficient space is obtained in the direction of the width of the lid spring when the lid spring is mounted on the engagement portion, it is possible to reduce the stress to be piled on the spring by enlarging the diameter of the spring wire material and increasing the number of windings and also to reduce the manufacturing cost by using an inexpensive material having a small allowable stress. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:- Fig. 1 is a perspective view of a tape cassette with a lid in its entireties according to the present invention; Fig. 2 is an exploded perspective view of the tape cassette shown in Fig. 1; Fig. 3 is a plan view of a lid spring used in the cassette shown in Fig. 1; Fig. 4 is a side view of the lid spring shown in Fig. 3; Fig. 5 is a schematic illustrative view of a portion of the tape cassette in which the lid spring of Fig. 3 is mounted; Fig. 6 is a schematic illustrative view of a spring engagement portion of the cassette tape shown in Fig. 5; Fig. 7 is an exploded perspective view of a prior art tape cassette with a lid; Fig. 8 is a schematic illustrative view of a portion of a lid spring engagement portion of the prior art tape cassette; Fig. 9 is an illustrative view of a portion of the lid spring engagement portion of the prior art tape cassette; Fig. 10 is a plan view of a lid spring of the prior art tape cassette; Fig. 11 is a side view of the lid spring shown in Fig. 10; and Fig. 12 is an illustrative view of a portion of a lid mechanism of the prior art tape cassette when the lid mechanism is closed. A preferred embodiment of a tape cassette with a lid according to the present invention will now be described by referring to the accompanying drawings wherein like parts are designated by like reference numerals with respect to a prior art tape cassette in order for the structure of the tape cassette to be easily understood. As shown in Figs. 1 to 6, a tape cassette 1 is square in shape and comprises an upper shell 2, a rotatable lid mechanism for keeping the cassette in its closed state by the action of a lid spring 28 when the cassette 1 is not in use, a reel portion 5 comprised of a pair of tape reels 4 housed within the cassette 1 and around which a recording/reproducing tape 3 is wound, a lower shell 37 and a lid engagement member 47 for locking the lid mechanism in its closed state. The tape cassette 1 of the above-described structure protects the tape 3 in such a manner that the tape 3 which is partly exposed outside the front surface of the cassette 1 is clamped by the force of the lid spring 28. Further, when the cassette 1 is in use, the lid mechanism 11 is moved upward against the force of the lid spring 28 to release the clamped tape to become exposed outside the cassette 1. As shown in Fig. 2, the upper shell 2 is made of a substantially square insulating member and a rectangular transparent member 6 occupying the central portion thereof so as to allow the movement of the reel 5 comprised of the pair of tape reels 4 to be easily observed from outside. Further, on both longitudinal side surfaces of the tape cassette 1 there are provided a pair of top-lid guide grooves 7 extending rearwardly from the front surface of the upper shell 2, a pair of semicircular front lid rotating shaft bearing portions 8 arranged close to the top-lid guide grooves 7, respectively, and a pair of tubular lower shell engagement projections 9. Further, there are provided a pair of back-lid engagement portions 10 formed by recessing the central portion of the front edge of the upper shell 2. As shown in Fig. 2, the lid mechanism 11 guides the tape 3 into a recording/reproducing mechanism of an electronic device such as a Digital VTR by opening and closing when the cassette 1 is mounted in the device. It comprises a top-lid 12, a back-lid 17, a front lid 21 and a torsion coillike lid spring 28. As shown in Fig. 2, the top-lid 12 is rectangular and comprises both side walls 13, a pair of front-lid engagement projection holes 14 each in the form of a recessed blind-hole and provided on the internal surfaces of the side walls 13, respectively, in opposite relationship with each other, a pair of upper shell engagement projections 15 provided on the side walls 13 at positions behind the engagement projection holes 14, respectively, so as to be guided by the top-lid guide grooves 7, respectively, and a pair of back-lid engagement projections 16 provided inwardly of the side walls 13 in spaced apart relationship with each other so as to engage the back-lid 17. As shown in Fig. 2, the back-lid 17 is elongated in shape with the lower portion thereof being substantially triangular and the surface thereof forms itself an elongated tape retaining surface 18A for clamping the rear surface of the portion of the tape 3 exposed outside from the upper and lower shells 2 and 37, in cooperation with the tape retaining surface 18B of the front-lid 21 when the cassette 1 is not in use. On one of the side surfaces of the triangular portion there is formed a pair of lower shell guide projections 19 interlocking with the opening and closing operations of the clamped tape 3 by being guided by the lower shell 37 and the upper edge of the tape retaining surface 18A is provided with a pair of rodlike top-lid engagement projections 20 at both ends thereof so as to engage the top-lid 12. As shown in Fig. 2, the front-lid 21 comprises an elongated flat base plate 22, a pair of front-lid retaining portions 23 provided at both ends of the flat base plate 22 so as to extend in a direction intersecting the longitudinal direction of the base plate, a pair of top-lid engagement projections 20A provided at both ends of the front-lid retaining portions 23 so as to engage the top-lid 12 and a tape retaining surface 18 forming the rear surface of the flat base plate 22 and adapted to clamp the tape 3 in cooperation with the back-lid 17. The front-lid retaining portions 23 are provided with lid rotating shafts portions 24 and 35 of different structures on the inner surfaces thereof, respectively, in opposite relationship with each other, light-path holes 25 and tongue-like lid engagement strips 26 near the free ends thereof and outside the light-path holes. As shown in Figs. 5 and 6, the lid rotating shaft portion 24 (left side in Fig. 2) comprises an axial portion 27 rotatably engaging the front-lid rotating shaft bearing portion 8 of the upper shell 2 and the front-lid rotating shaft engagement portion 41, a support shaft 32 coaxially extending from the axial portion 27 so as to mount the lid spring 28 thereon and a flange 33 provided between the axial portion 27 and the support shaft 32. As shown in Figs. 3 and 4, the lid spring 28 is a so called torsion spring and comprises a coiled end turn portion 29, a first arm 30 linearly extending from one side of the end turn portion 29 and a second arm 31 extending from other side of the end turn portion 29 in a direction at a certain angle with respect to the direction of extension of the first arm 30 with the arm 30 being longer than the arm 31. The lid spring of the above-described structure has the function such that when the ringlike end turn portion 29 is fitted about the support shaft 32, the free end of the first arm 30 is held in engagement with the top shell 2 (not shown) and the free end of the second arm 31 is held in engagement with an engagement rib 34 of the flange 33 of the front-lid retaining portion 23, the lid mechanism 11 is constantly urged toward the direction in which it is closed. As shown in Fig. 5 and 6, the support shaft 32 is a coaxial extension of the axial portion 27 separated by the flange 33 and the diameter thereof is smaller than the inner diameter of the end turn portion 29 and the height thereof is sufficiently larger than the width of the end turn portion 29, for example, about two times the latter. As shown in Figs. 5 and 6, the flange 33 is provided between the axial portion 27 and the support shaft 32 with a portion thereof extending in a direction intersecting at right angles with the support shaft and the engagement rib 34 is provided at the projecting end so as to run parallel to the support shaft 32. The engagement rib 34 is spaced from the support shaft 32 by a distance W. On such flange 33, the end turn 29 of the lid spring 28 is loosely fitted about the support shaft 32, the second arm 31 of the lid spring 28 is hooked on the engagement rib 34 and the first arm 30 is hooked on the front lid 21 as it is biased. In this case, the relationship between the support shaft 32 and the end turn 29 is such that unlike the conventional practice of providing a width Y (see Fig. 11) between the end turn 29 and the second arm 31 is not required but only the provision of a width X of the end turn 29 (see Fig. 4) is sufficient so that the height of the support shaft 32 can be reduced by a length corresponding to the width Y or it is possible to obtain a sufficient fitting condition of the lid spring 28. The lid rotating shaft 35 (rightside in Fig. 2) comprises an axial portion 36 rotatably engaging the front-lid rotating shaft bearing portion 8 of the upper shell 2 and the front-lid rotating shaft engagement portion 41, a right-angled dustproof rib 43 adjacent to the axial portion 36, a light-path hole 25 and a lid engagement strip 26. As shown in Fig. 2, the lower shell 37 is square in shape so as to engage the upper shell 2, and comprises an external terminal connecting portion 38 at one end of the rear side surface thereof, a reel lock mechanism 39 provided at the center of the rear side surface thereof, a pair of lid engagement portions 41 each defined substantially triangular from nearly the center of each of both sides toward the front, a pair of optical path recessed portions 42, a pair of dustproof ribs 43, a pair of upper shell engagement projections 44, a light source insert portion 45 provided at the center of the front side thereof and having a hole for receiving a light source from outside and a pair of back-lid guide portions 46 provided on both sides of the light source insert portion 45. As shown in Figs. 2, 5 and 6, the lid engagement member 47 comprises a lid engagement claw 48 and a flat leaf spring 49 whose one end is U-shaped. The lid engagement claw member 48 comprises a rotary shaft 50 extending horizontally on both sides thereof and a claw 51 provided at the lower end thereof with the tip of the claw facing upward at an angle of about 45 degrees. The lid engagement member 47 and the leaf spring 49 are so arranged that the rotary shaft 50 is hung over the lid engagement portions 40 of the lower shell 37 with the claw 51 held downward and the upper portion of the engagement claw portion is compressed to constantly thrust the claw 51 forward by the other end of the leaf spring 49. The assembly of the tape cassette comprising the above-described various kinds of parts is performed as follows. First, the pair of reels 4 having the tape 3 wound therearound are mounted on the lower shell 37. Then the back-lid 17 is engaged with the top-lid 12 and the latter is engaged with the front-lid 21. These lids may be assembled from the beginning. Next, the lid assembly is engaged with the upper shell 2 and the lid spring 28 is fitted about the support shaft 34 of the front-lid 21 thereby completing the assembly of the lid mechanism 11. Then the lid mechanism 11 is held open against the force of the lid spring 28 and caused to cover the lower shell 37 thereby completing the assembly of the cassette 1. The lid spring 28 constituting the lid rotating shaft 24 housed in the assembled cassette 1 includes two linear portions, namely, the first arm 30 to be fixed to the upper shell 2 and the second arm 31 to be fixed to the lid in contrast to the prior art cassette in which the terminating end of the spring to be fixed to the lid is in the shape of a semicircular hook. Consequently, it is possible to reduce the space for accommodating the spring and at the same time, prevent the maximum stress applied on the spring from becoming deteriorated. Further, the shape of the lid spring can be simple thereby reducing the dispersion of the effective opening angle of the spring. Further, the lid spring 28 of such structure has a reduced width X (see Fig. 4) so that it is possible to reduce the stress to be applied on the spring by enlarging the diameter of the spring wire material and increasing the number of windings of the spring to that degree and at the same time, to reduce the manufacturing cost by using an inexpensive material having a small allowable stress.

Claims: A tape cassette (1) comprising: a cassette body formed of an upper (2) and a lower (37) square shell; a tape (3) accommodated partly within said cassette body and partly outside of the cassette body; a lid mechanism (11) comprising a lid (12, 17, 21) rotatable about a rotary shaft (24) from a closed position covering the part of the tape (3) outside of the cassette body (2,37) to an open position exposing the tape (3); and a torsion spring (28) for constantly urging said rotatable lid (12, 17, 21) toward the closed position, the spring (28) having unbent ends with one unbent end (30) of said spring (28) abutting against the upper shell (2); characterised in that the other unbent end (31) abuts against an engagement portion provided on the periphery of said rotary shaft (24). A tape cassette according to Claim 1, wherein said rotary shaft comprises an axial portion (27) connected to a portion of said lid (12, 17, 21) and a support shaft (32) formed as a coaxial extension of said axial portion (27) and capable of having said lid spring (28) mounted thereon. A tape cassette according to Claim 1 or Claim 2, wherein said engagement portion comprises a flange (33) extending perpendicularly from the rotary shaft (24) and a rib (34) extending perpendicularly from the flange (33). A tape cassette according to any preceding claim, wherein said lid comprises a top lid (12) connectable to the upper cassette shell (2), and a back lid (17) and a front lid (21) both connectable to the top lid (12). A tape cassette according to any preceding claim wherein said cassette is a digital video tape cassette.

Inventors: TAGUCHI OSAMU, TAGUCHI, OSAMU, TAGUCHI, OSAMU, C/O INTELLECTUAL PROPERTY DIV.
Applicants: SONY CORP, SONY CORPORATION
Application year: 1995
Main classification: G11B23
IPC codes: G11B23