WO1999045541A1

WO1999045541A1 - Magnetic tape cassette

Info

Publication number: WO1999045541A1
Application number: PCT/JP1999/000996
Authority: WO
Inventors: Teruo Ashikawa; Atusi Takano
Original assignee: Fuji Photo Film Co., Ltd.
Priority date: 1998-03-04
Filing date: 1999-03-02
Publication date: 1999-09-10
Also published as: JPH11250613A; EP1058929A1

Abstract

A magnetic tape cassette in which a lid lock spring will not be disengaged from a lower half and the lid lock is maintained at an appropriate position when the magnetic tape cassette is being assembled. In the magnetic tape cassette, a lid lock spring has a coil part to be attached onto an attachment pin formed on the lower half and a free end engaging with the lid lock, a spring holder rib for retaining the coil part is formed in a space between the attachment pin and a sidewall of the lower half confronting the attachment pin. In this case, a height of the coil part is larger than a space that is formed when the upper and lower halves are assembled. Alternatively, a lid lock spring may include a coil part fastened to the lower half, and guide members may be respectively provided in the upper and lower halves and have guide grooves for guiding the lid lock spring to a position which applies a force to the lid lock. In this case, the guide members are located at different positions along an extending direction of the lid lock spring, and the guide members are superposed as viewed from the extending direction when assembling the upper and lower halves. Alternatively, the lid lock may have projecting parts provided at opposite ends thereof and loosely fitted in grooves formed in the lower half, and a stopper rib may be formed on the upper half. In this case, the stopper rib restrains the projecting parts to the grooves in recoverable positions thereof when the upper half is assembled with the lower half and is tightened with screws.

Description

DESCRIPTION

MAGNETIC TAPE CASSETTE

[Technical Field]

The present invention relates to a magnetic tape cassette which is favorably applied to video tape cassettes etc. More specifically, the present invention relates to a magnetic tape cassette which includes a cassette case, a lid that can open and close an opening formed at a front end of the cassette case, and a lid lock for locking the lid in the closed state.

The present application is based on Japanese Patent Applications Nos. Hei. 10-52250, 10-52251 and 10-52252, the contents of which are incorporated herein by reference.

[Background Art] Various modes of magnetic tape cassettes have been known. For example, comparatively, a digital video cassette (DVC) was recently developed. Fig. 1 is an exploded perspective view showing a magnetic tape cassette 60 which is utilized as a digital video cassette (DVC) . Fig. 1 shows the aforementioned magnetic tape 60 wherein a pair of reels 62 and 63 which include upper and lower flanges are housed so as to be able to rotate inside a lower half 61 which constitutes a half of the cassette case body and a magnetic tape (not shown) is wound around such reels 62 and 63. Each of the reels 62 and 63 includes an upper flange 184 or 185 and a lower flange 70 or 71, and engagement teeth are formed on the entire circumferences of the rims of these flanges 70 and 71. The reels 62 and 63 are applied with forces toward the lower half 61 side by leaf springs 51 and 52. The magnetic tape is guided by tape guides 65 and 66 to the front of the cassette (the left side in Fig. 3) and on both the right and left sides so as to pass through an opening 67 on the front side of the lower half 61.

A lid 69 which covers the magnetic tape that passes through the opening 67 on the front side of the cassette is attached, so as to be able to rotate, to an upper half 75 which constitutes the other half of the cassette case body together with the aforementioned lower half 61. Such lid 69 includes three members: an outer lid 76, a top lid 77 and an inner lid 78.

A lock pin 80 is provided so as to protrude on the inner side of a side plate 79 of the aforementioned outer lid 76. A lid lock 82, which locks such lock pin 80 so as to secure the lid 69 in the closing direction of the aforementioned opening 67, is attached to a side plate 87 of the lower half 61 so as to be able to rotate. Additionally, a lid lock spring 83 which applies a force to such lid lock 82 in the closing direction of the lid 69 is provided on the cassette- rear-side of such lid lock 82. As shown in Fig. 2, the lid lock spring 83, which is a wire spring 83a with a ring part 83b formed at one end thereof, is attached to the lower half 61 in such manner that the ring part 83b is mounted on an attachment pin 84a of a cylindrical boss 84 which is formed on the lower half 61 while an intermediate part of a free end of the wire spring 83a is engaged in a guide groove 87a that is formed at an upper end of a guide member 87 which is provided at a part of the side wall so as to apply a force to the lid lock 82 in a locking direction A. Since the aforementioned wire spring 83a is engaged in this manner, the aforementioned attachment pin 84a is provided with a sufficient height for temporary attachment till the lower half 61 is covered with the upper half 75.

When the lower half 61 is covered with the upper half 75, a guide groove 72a of a guide member 72 which protrudes from the inner wall surface of the upper half 75 comes to be engaged, from the upper side, with the intermediate part of the wire spring 83a which bridges over both the cylindrical boss 84 and the guide member 87 that is provided on a part of the side wall of the cylindrical boss 84 so that such wire spring 83a is positioned. Then, the aforementioned wire spring 83a is engaged with the lid lock 82 from the upper half 75 side (upper side), at the free end thereof, applying the force so as to be in the closed sate.

In the state wherein the aforementioned lid lock 82 is mounted on the lower half, the upper half 75 is assembled onto the upper side of the lower half 61 and then, after the cassette case is turned over, screws 90 which are shown in Fig. 1 are tightened with a screwdriver etc. in the state wherein the lower half 61 is up to complete the assembling process . As shown in Fig. 2, the lid lock 82 are provided at the upper part thereof with projections 82a protruding in both sides. The projections 82a are adapted to be loosely fitted in grooves 61a formed in the upper end parts of the side plate 87.

The upper half 75 is assembled with the lower half 61 in the state where the lid locks 82 are loosely fitted, and then screws 90 shown in Fig. 1 are tightened with a screwdriver etc. in the state where the cassette case is turned over so that the lower half 61 is upside. Thus, the assembling process is completed. Herein, since the opening of the groove 61a of the lower half 61 is covered by the upper half 75, the lid lock 82 does not slip out.

However, in the state wherein the cassette case is turned over so that the lower half 61 is up, a very narrow space is left since the lower half 61 is floated a little above the upper half 75 by the force applied by the leaf spring 51 before the upper half 75 and the lower half 61 are tightened with the screws 90. There will be no problem if the ring part 83b of the lid lock spring 83 is tightly fitted on the attachment pin 84a, but it has happened sometimes that a manufactural allowance of error etc . causes the ring part 83b to be loosely fitted on the attachment pin 84a. This case may result with such a problem that the ring part 83b is disengaged from the attachment pin 84a if the wound coil height of the ring part 83b of the lid lock spring 83 is small or that vibration etc. causes revolutions of the wire spring 83a with the attachment pin 84a as the center thereof. Furthermore, the ring part 83b may be disengaged from the attachment pin 84a in the state wherein the lower half 61 is floated above the upper half 75.

Since the aforementioned guide grooves 72a and 87a are positioned slightly deviated from each other in the extended direction of the wire spring, some space is formed in horizontal direction between the guide grooves 72a and 87a in the state wherein the lower half 61 is floated above the upper half 75. Therefore, if once the wire spring 83a is revolved by the vibration etc . result with disengagement from the guide grooves 72a and 87a, the wire spring 83a cannot be reset in the guide grooves 72a and 87a when the upper half 75 and the lower half 61 are tried to be tightened with screws and thus assembling process cannot be continued appropriately.

Even after completion of assembling process, the wire spring 83a can be disengaged from the guide grooves 72a and 87a by an impulse given at a fall of the cassette.

These problems can be prevented from happening if the fitting of the ring part 83b and the attachment pin 84a are made so as not to be disengaged but, to realize this, precision forming of the ring part 83b and the attachment pin 84a is needed.

Furthermore, the lower half 61 is floated by the force applied by the leaf spring 51 before tightening with screws. Therefore, since the projections 82a of the lid lock 82 are loosely fitted in the grooves 61a, the lid lock 82 may slip out of the grooves 61a. [Disclosure of the Invention]

In order to eliminate the above-described problems, it is an object of the present invention to provide a magnetic tape cassette wherein, when the magnetic tape cassette is being assembled, the lid lock spring will not be disengaged from the appropriate mounting position of the lower half, and further, the lid lock is maintained at an appropriate position.

To achieve the above object, according to the first aspect of the present invention, there is provided a magnetic tape cassette which comprises: a cassette case including an upper half and a lower half, and having an opening at a front end thereof for drawing a magnetic tape out; a reel accommodated in the cassette case so as to be able to rotate while a force is applied to the reel toward the lower half by a leaf spring, wherein the magnetic tape is wound around the reel; a lid attached to the cassette case in order to open and close the opening; a lid lock that can lock the lid so as to close the opening; an attachment pin formed on a bottom wall of the lower half; a lid lock spring including a coil part to be attached onto the attachment pin, wherein a free end of the lid lock spring engages with the lid lock so that the lid lock spring applies a force to the lid lock to close the opening; and a spring holder rib formed in a space between the attachment pin and a sidewall of the lower half that confronts the attachment pin, wherein the coil part is retained by the spring holder rib, wherein a height of the coil part is larger than a space that is formed when the upper and lower halves are assembled. Preferably, the spring holder rib has a substantially triangular shape. More specifically, a width of the spring holder rib gradually increases from a distal end to a proximal end thereof. According to the first aspect of the present invention, even if any space is created between the upper and lower halves by the force applied on the aforementioned half side by the leaf spring when, after the lower half is assembled onto the upper half, the screws are driven with the cassette case reversed so that the lower half will be up, the lid lock spring which comprises a long coil with a height of the wound coil part larger than the aforementioned space cannot be disengaged through the space.

Additionally, since the holder rib is provided in the space between the attachment pin of the lower half and the sidewall of the lower half that confronts such attachment pin, the coil part is sure to be retained on the attachment pin and the revolutions of the lid lock spring with the attachment pin as the center thereof will not occur. Therefore, the assembling efficiency is improved since the magnetic tape cassette is assembled while the upper and lower halves are appropriately tightened with the screws .

Furthermore, a highly reliable lid lock can be assured since the lid lock spring cannot be disengaged from the mounted part by an impulse given at a fall of the cassette after completion thereof.

Further, in order to achieve the above object, according to the second aspect of the present invention, there is provided a magnetic tape cassette which comprises: a cassette case including an upper half and a lower half, and having an opening at a front end thereof for drawing a magnetic tape out; a reel accommodated in the cassette case so as to be able to rotate while a force is applied to the reel toward the lower half by a leaf spring, wherein the magnetic tape is wound around the reel; a lid attached to the cassette case in order to open and close the opening; a lid lock that can lock the lid so as to close the opening; a lid lock spring including a coil part fastened to the lower half, wherein a free end of the lid lock spring engages with the lid lock so that the lid lock spring applies a force to the lid lock to close the opening; and guide members respectively provided in the upper and lower halves, the guide members having guide grooves for guiding the lid lock spring to a position which applies a force to the lid lock, the guide members being located at different positions along an extending direction of the lid lock spring, wherein the guide members are superposed as viewed from the extending direction when assembling the upper and lower halves . Preferably, each of the guide grooves is defined by three surfaces. More specifically, the three surfaces are two inclined surfaces and a plane located between the inclined surfaces . According to the second aspect of the present invention, when the upper half is assembled onto the lower half and the cassette case is turned over so that the lower half is upside for tightening with screws, even if any space is created

8 between the upper and lower halves by the force applied on the side of the aforementioned half by the leaf spring, and since the guide members for guiding the lid lock spring are present at different positions along an extending direction of the lid lock spring and are superposed seeing from the extending direction, no space occurs along a horizontal direction between the guide members. Therefore, the lid lock spring supported in a cantilevered manner is not disengaged from the guide grooves even if a revolution is caused within the horizontal surface due to vibrations etc . , and the upper and lower halves are tightened appropriately with screws and the magnetic tape cassette is assembled. Thus the assembling property is improved.

Furthermore, a highly reliable lid lock can be assured since the lid lock spring cannot be disengaged from the mounted part by an impulse given at a fall of the cassette after completion thereof .

In addition, it is not necessary to form fitting parts at high precision not to disengage the lid lock spring at a fitting and attaching part, and the productivity of the lid lock spring is not decreased.

The lid lock spring of the present invention is supported in a cantilevered manner, and there are, as the lid lock spring, the above mentioned wire spring or plate spring. Still further, in order to achieve the above object, according to the third aspect of the present invention, there is provided a magnetic tape cassette which comprises: a cassette case including a lower half in which grooves are formed and an upper half, and having an opening at a front end thereof for drawing a magnetic tape out; a reel accommodated in the cassette case so as to be able to rotate while a force is applied to the reel toward the lower half by a leaf spring, wherein the magnetic tape is wound around the reel; a lid attached to the cassette case in order to open and close the opening; a lid lock that can lock the lid so as to close the opening, the lid lock having projecting parts provided at opposite ends thereof, the projecting parts being loosely fitted in the grooves, respectively; and a stopper rib formed on the upper half, the stopper rib restraining the projecting parts of the lid lock to the grooves in recoverable positions thereof when the upper half is assembled with the lower half and is tightened with screws in a state where the cassette case is turned over so that the lower half is upside.

According to the third aspect of the present invention, when the upper half is assembled with the lower half and is tightened with screws in the state where the cassette case is turned over so that the lower half is upside, even if the lower half is applied with the force by the leaf spring, the stopper rib provided at the upper half restrains the projections of the lid lock in the recoverable position. Therefore, even if the projections of the lid lock somewhat are disengaged from the grooves of the lower half, since they can go back into the grooves and be maintained in the proper position, it is possible to improve the assembling property of the magnetic tape cassette.

10 [Brief Description of Drawings]

Fig. 1 is an exploded perspective view of a magnetic tape cassette of the background art;

Fig. 2 is an exploded perspective view in the vicinity of a lid lock shown in Fig. 1;

Fig. 3 is an exploded perspective view showing significant parts in the vicinity of a lid lock of a magnetic tape cassette related to a first embodiment of the present invention; Fig. 4 is a partial cross-sectional view showing a state of completion of assembling in Fig. 3;

Fig. 5 is a side view of an element of the magnetic tape cassette according to a second embodiment of the present invention; Figs. 6A-6C show assembling procedure of upper and lower halves, wherein Fig. 6A is before assembling, Fig. 6B is before tightening with screws after assembling the upper and lower halves, and Fig. 6C is after tightening the upper and lower halves with screws ; Fig. 7A is a side view of an upper half of the magnetic tape cassette according to a third embodiment of the present invention;

Fig. 7B is an inner view of Fig. 7A;

Fig. 8A is a side view of a lower half of the magnetic tape cassette according to the third embodiment of the present invention;

Fig. 8B is an inner view of Fig. 8A;

11 Fig. 9 shows a partially cross sectional view of the state where the upper and lower halves are assembled; and

Fig. 10 shows a partially cross sectional view of the state where the upper and lower halves are turned over.

[Best Mode for Carrying Out the Invention] First Embodiment

A first embodiment of the present invention will now be described in detail with references to Figs . 3 and 4. As for the same components as of the magnetic tape cassette shown in Figs. 1 and 2 are described with use of the same symbols. Fig. 3 is an exploded perspective view showing the vicinity of a lid lock of a magnetic tape cassette according to the first embodiment of the present invention before the upper and lower halves are assembled. Fig. 4 is a partial cross- sectional view showing the vicinity of the lid lock after the upper and lower halves in Fig. 3 have been assembled.

As shown in Fig. 3, the lid lock 82 is pivotably mounted while being supported at projections 82a by grooves 61a which are formed in the sidewalls of a guide member 87 of the lower half 61. An insertion rib 118 which comes into contact with inner circumferential surfaces of a later-described lid lock spring is provided on a sidewall of a square-prism-shaped attachment pin 116 which is provided on a bottom wall of the lower half 61. A wedge-shaped spring holder rib 120 is formed in some space between a sidewall of the guide member 87 and the attachment pin 116. As shown in Fig. 4, the width of the spring holder rib 120 gradually increases from the

12 distal end thereof toward the proximal end thereof. The clearance S between the bottom end part of this spring holder rib 120 and the attachment pin 116 is almost the same as the diameter of the wire which forms the lid lock spring. Although the attachment pin 116 in the first embodiment is formed from the bottom wall of the lower half 61, an alternative structure is an attachment pin which is formed on a boss part that is formed on the bottom wall.

The lid lock spring 110 includes a long wire spring 112 and a ring part 114 of a coil spring shape. A free end of the wire spring 112 which comes into contact with a projecting part 82c inside a vertical slit 82b that is formed in the lid lock 82 applies a force to the lid lock 82 in locking direction A while the ring part 114 is fitted on the attachment pin 116. Since a height of the wound coil part of the ring part 114 is set up to be larger than the space which is formed between the upper and lower halves when the upper and lower halves are assembled, disengagement through this space will not occur. Assembling procedures of the above described magnetic tape cassette are now described (see Fig. 1). Firstly, after reels and other components are housed inside the lower half 61, the projections 82a of the lid lock 82 are respectively fitted into the grooves 61a in the guide member 87, and then the ring part 114 of the lid lock spring 110 is fitted on the attachment pin 116. At this time, since the internal circumferential surface of the ring part 114 comes into contact with the upper surface of the spring insertion rib

13 118 while being inserted, the assembling operation is easier. Moreover, since the bottom end of the ring part 114 is engaged in the space between the bottom end part of the holder rib 120 and the attachment pin 116, the lid lock spring 110 cannot be easily disengaged from the attachment pin 116.

Furthermore, since the tip part of the wire spring 112 of the lid lock spring 110 which comes into contact with the projecting part 82c inside the slit 82b in the lid lock 82 applies the force to the lid lock 82 in direction A so as to lock the lid 69 in the closed state.

Next, the upper half 75 wherein the lid 69 have been assembled is assembled with the lower half 61. The cassette case is then turned over and the screws 90 are tightened with the lower half 61 up. When the leaf springs 51 and 52 which are attached to the upper half 75 apply forces to the lower half 61 side at this moment, the lower half 61 is floated and a very narrow space is created between the sidewalls of the upper half 75 and the sidewalls of the lower half 61. However, the height of the wound coil part of the ring part 114 of the lid lock spring 110 is set so as to prevent an easy disengagement from the attachment pin 116 through the aforementioned very narrow space or even a larger space which may be created by a warp etc. in either the upper half 75 or the lower half 61 at least. Therefore, the lid lock spring 110 will not be disengaged through the space.

The guide grooves 72a and 87a in the guide members 72 and 87 of the upper and lower halves 75 and 61 confront the

14 wire spring 112 and the horizontal position of the wire spring 112 is approximately controlled by housing the wire spring 112 inside the guide grooves 72a and 87a. When the screws 90 are tightened after joining the upper and lower halves 75 and 61, the vertical position of the wire spring 112 is also approximately controlled.

Therefore, when the upper and lower halves 75 and 61 are turned over to tighten the upper and lower halves 75 and 61 with screws 90, even if some space is formed between the sidewalls of the upper and lower halves 75 and 61 by actions of the leaf springs 51 and 52 and if a force in the revolving direction acts on the wire spring 112 at this moment, the wire spring 112 of the lid lock spring 110 will not be disengaged from the guide grooves 72a and 87a but retained in the appropriate position. That is, since the lid lock spring will not be disengaged from the attached part even if the upper and lower halves 75 and 61 during assembly of the cassette, the efficiency of the assembling operations can be improved .

Second Embodiment

A second embodiment of the present invention will now be described in detail with reference to Figs . 5 and 6. As for the same components as of the magnetic tape cassette shown in Figs. 1 and 3 are described with use of the same symbols. Fig. 5 shows a partially sectional view in the vicinity of the lid lock in the state where the upper and lower halves are assembled with screws, the halves being element parts of

15 the magnetic tape cassette according to the second embodiment of the present invention.

As shown in Fig. 5, the lid lock 82 is pivotably mounted while being supported at projections 82a by grooves 61a which are formed in the sidewalls of the lower half 61. An attachment pin 84a of a cylindrical boss 84 provided in the lower half 61 is attached into a ring part 83a of the lid lock spring 83. The free end of the lid lock spring 83 acts on a projection 82c inside a slit 82b formed in a vertical direction in the lid lock 82, and the lid lock 82 is supported at a shaft portion 82a and receives a force at the projection 82c from the wire spring 83a so that the lid lock is applied with the force in a locking direction A.

The intermediate portion of the wire spring 83a is regulated with respect to the position thereof by a guide member 100 formed in the upper half 75 and a guide member 102 formed in the lower half 61. Namely, the guide member 100 of the upper half 75 is formed with a guide groove 104 (see Figs. 6A-6C) shaped in trapezoid facing downward for guiding and regulating the wire spring, while the guide member 102 of the lower half 61 is formed with a guide groove 106 (see Figs. 6A-6C) shaped in trapezoid facing upward for guiding and regulating the wire spring 83a, and the wire spring 83a is held within both grooves 104, 106 and regulated with respect to the position.

Herein, the guide member 100 of the upper half 75 and the guide member 102 of the lower half 61 are located at different positions along the extending direction of the wire

16 spring 83a, and are not opposite each other but are superposed seeing from the extending direction of the wire spring 83a (seeing from the left direction of Fig. 5). This superposing state is also maintained during setting up the assembled cassette with the upper and lower halves 75, 61.

Assembling procedures of the above mentioned magnetic tape cassette will now be described. First, the reel, lid lock 82 and other component parts are accommodated in the lower half 61. Next, the upper half 75 incorporated with the lid 69 is assembled onto the lower half 61. Thus, the upper half 75 and the lower half 61 are assembled as shown in Fig. 5.

Afterwards, the cassette case is turned over and is attached by utilizing the screws in the state where the lower half 61 is upside. Herein, the force is applied to the side of the lower half 61 by the leaf springs 51, 52 attached to the upper half 75, and the lower half 61 is floated so that a little space is created between the upper half 75 and the lower half 61. However, since the guide members 100, 102 formed with the guide grooves 104, 106 for regulating the position of the wire spring 83a are superposed, seeing from the extending direction of the wire spring 83a, no space occurs in a horizontal direction between end points of the guide members 100, 102. Figs. 6A-6C show the front views of the guide members

100, 102, seeing from the extending direction of the wire spring 83a. Fig. 6A is a state before assembling the upper and lower halves, Fig. 6B is a state assembling and before

17 tightening the upper and lower halves, and Fig. 6C is a state after tightening with screws. Fig. 6B shows that the upper half is upside, but when tightening the screws, the upper and lower halves are turned over . The guide members 100, 102 of the upper and lower halves

75, 61 are opposite at the guide grooves 104, 106 with respect to the wire spring 83a, and the wire spring 83a is housed in the guide grooves 104, 106, thereby almost regulating the position of the wire spring 83a in the horizontal direction, and when the upper and lower halves 75, 61 are assembled and tightened with screws, the wire spring 83a is regulated in the position of the vertical direction as shown in Fig. 6C.

Herein, in the state where the upper and lower halves 75, 61 are only assembled as shown in Fig. 6B, the space is, as the above, created between the upper and lower halves 75, 61 due to the action of the leaf springs 51, 52 provided in the upper half 75, and a space in the vertical direction of an area partitioned by the guide grooves 104, 106 is also slightly widened. However, since the area partitioned by the guide grooves 104, 106 defines a closed space in a state seeing from the extending direction of the wire spring 83a, the wire spring 83a does not deviate from the guide grooves 104, 106. Therefore, when the upper and lower halves 75, 61 are turned over for tightening them with screws, so that the space is created between the side walls of the upper and lower halves 75, 61 due to the action of the leaf springs 51,

18 52, if the wire spring is then effected with a force in a revolution direction, the wire spring 83a of the lid lock spring 83 is not disengaged from the guide grooves 104, 106, and is maintained in a proper position. Namely, when the upper and lower halves 75, 61 are turned over during setting up the cassette, the lid lock spring 83 is not disengaged from the attaching part. Thus, the assembling property is improved.

The superposing margin h of the guide members 100, 102 of the upper and lower halves 75, 61 is, as shown in Fig. 6C, made larger than the space created between the side walls of the upper and lower halves 75, 61 when they are tightened with screws .

Although the second embodiment of the present invention has been described above, the present invention is not restricted thereto or thereby but possible to be embodied in other modes with appropriate changes . The shape of the guide groove for holding the wire spring is not restricted to the shown trapezoid shape that has two inclined surfaces and a plane located between the inclined surfaces. For example, the shape of the guide groove may be V, U or circular shapes. If the shapes of the guide member are these as the, the wire spring in the state of tightening the upper and lower halves is regulated with respect to the appropriate position in the vertical direction, and the position in the horizontal direction is effected with centering within the guide grooves, and the wire spring is regulated in the appropriate position.

19 The lid lock spring is not limited to the wire spring as shown in Figs. 5-6C, but may be a plate spring.

Third Embodiment

A third embodiment of the present invention will now be described in detail with reference to Figs. 7A-10. As for the same components as the magnetic tape cassette shown in Figs. 1 and 2, the explanation thereof is omitted. Fig. 7A shows a side view of the upper half of the magnetic tape cassette according to the third embodiment of the present invention, and Fig. 7B shows the inner view thereof.

As shown in Figs. 7A and 7B, the upper half 1 has a substantially rectangular shape. On the upper half 1, there are provided projections 2a, 2b at a front side thereof, projections 3a, 3b at a rear side of the same and a projection 4 nearly at a center, and each of the projections 2a, 2b has a hollow cylindrical shape. The upper half 1 is attached with a pair of leaf springs 5a, 5b which apply force to a reel toward the lower half side.

The upper half 1 is provided at both side plates with concaves 6a, 6b for housing upper end parts of the lid locks. The concaves 6a, 6b are provided with stopper ribs 7a, 7b for regulating positions of a lid lock 30 (described later) . The positions of the stopper ribs 7a, 7b do not interfere with sliding area of the lid lock and positioning area of a lid lock spring.

Fig. 8A shows a side view of the lower half 10 of the magnetic tape cassette according to the third embodiment of

20 the present invention, and Fig. 8B shows the inner view thereof. As shown in Figs. 8A and 8B, the lower half 10 has a rectangular shape similar to the upper half 1. On the lower half 10, there are provided hole parts 12a, 12b at a front side thereof, hole parts 13a, 13b at a rear side of the same and a hole part 14 nearly at a center, and each of the projections includes a hollow cylindrical form.

The projections 2a, 2b provided at the front side of the upper half 1, the projections 3a, 3b at the rear side of the same and the projection 4 near at the center correspond respectively to the projections 12a, 12b provided at the front side of the lower half, the projections 13a, 13b at the rear side of the same and the projection 14 near at the center, and are attached by utilizing screws etc. At both side plates of the lower half 10, grooves 16a, 16b are formed in which the projections 33 protruding in both sides of a later mentioned lid lock 30 are fitted loosely.

Assembling procedures of the above mentioned magnetic tape cassette will now be described. First, the reels, the lid lock 30 and other components are accommodated in the lower half 10. Next, the upper half assembled with the lid is assembled with the lower half. As shown in Fig. 9 (but the lid is not shown), the upper half 1 and the lower half 10 are assembled. Afterwards, as shown in Fig. 10, the cassette case is turned over and is attached by utilizing the screws in the state where the lower half 10 is upside. Herein, the force is applied to the side of the lower half 10 by the leaf

21 springs 5a, 5b attached to the upper half 1, and the lower half 10 is floated so that a space t is created between the upper half 1 and the lower half 10. However, the stopper ribs 7a, 7b provided in the upper half 1 control the position of the lid lock 30 at its upper end 30a, and support the lid locks 30 at two points together with side walls 18a, 18b provided to the lower half 10. Since a pair of projections 33 of the lid locks 30 are regulated with respect to the recoverable position where the projections 33 is not disengaged from the grooves 16a, 16b. As a result, since the lid locks can be maintained at the proper position, it is possible to improve the assembling property of the magnetic tape cassette.

Although the preferred embodiments of the present invention have been described above, the present invention is not restricted to the above-described embodiments but possible to be embodied in other modes with appropriate changes. For example, the magnetic tape cassette is not restricted to the DVC but applicable to various types of cassettes which have a structure wherein the wire spring position is controlled by the upper and lower halves .

The present invention is not restricted to the third embodiment but possible to be embodied in other modes with appropriate changes or improvements. For example, when the shapes of the lid locks are changed, it is necessary to appropriately change the shapes, positions etc. of a stopper rib in accordance with changes of the lid locks.

22 [Industrial Applicability]

As described above, according to the present invention, the one end of the lid lock spring comprises the long coil to be fitted onto the attachment pin that is formed on the bottom wall of the lower half and the height of such wound coil part is set up to be larger than some space that is formed when the upper and lower halves are assembled while the coil part is retained by the spring holder rib that is provided in some space between the attachment pin of the lower half and the sidewall of the lower half that confronts such attachment pin.

Therefore, even if any space is created between the upper and lower halves by the force applied on the half side by the leaf spring, the lid lock spring cannot be disengaged through the space .

Additionally, since the coil part is sure to be retained on the attachment pin, the revolutions of the lid lock spring with the attachment pin as the center thereof will not occur and, since the magnetic tape cassette is assembled while the upper and lower halves are appropriately tightened with the screws, the assembling efficiency is improved.

Furthermore, the highly reliable lid lock can be assured since the lid lock spring cannot be disengaged from the mounted part by the impulse given at the fall of the cassette after completion thereof .

According to the present invention, when the lower half is assembled onto the upper half and the cassette is turned over, and is tightened with screws in the state where the

23 lower half is upside, even if the space exists between the side walls of the upper and lower halves, since the guide grooves provided in the guide members regulating the wire spring are present at the different positions along the extending direction of the wire spring, and are superposed seeing from the extending direction of the wire spring, no space is created in the horizontal direction between the guide members , and the wire spring does not deviate from the attaching position. Therefore, the working is not interrupted by the disengagement of the spring during setting up the cassette, and it is possible to improve the setting property of the magnetic tape cassette.

In addition, the lid lock spring is not disengaged from the attaching part by shocks when dropping, it is possible to secure the lid lock of high reliability.

Further, it is possible to prevent the lid lock from disengagement without forming the lid lock spring and the attachment part thereof at high precision. According to the present invention, when the upper half is assembled with the lower half and is tightened with screws in the state where the cassette case is turned over so that the lower half is upside, since the stopper rib is provided at the upper half, which regulates the projections of the lid lock in the recoverable positions of the grooves of the lower half, even if the lower half is applied with the force by the leaf spring and the projections of the lid lock are somewhat disengaged from the grooves of the lower half, they can go

24 back into the grooves and be maintained in the proper position thereof, and thus it is possible to improve the assembling property of the magnetic tape cassette.

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Claims

1. A magnetic tape cassette, comprising: a cassette case including an upper half and a lower half, and having an opening at a front end thereof for drawing a magnetic tape out; a reel accommodated in the cassette case so as to be able to rotate while a force is applied to the reel toward the lower half by a leaf spring, wherein the magnetic tape is wound around the reel; a lid attached to the cassette case in order to open and close the opening; a lid lock that can lock the lid so as to close the opening; an attachment pin formed on a bottom wall of the lower half; a lid lock spring including a coil part to be attached onto the attachment pin, wherein a free end of the lid lock spring engages with the lid lock so that the lid lock spring applies a force to the lid lock to close the opening; and a spring holder rib formed in a space between the attachment pin and a sidewall of the lower half that confronts the attachment pin, wherein the coil part is retained by the spring holder rib, wherein a height of the coil part is larger than a space that is formed when the upper and lower halves are assembled.

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2. The magnetic tape cassette of claim 1, wherein the spring holder rib has a substantially triangular shape.

3. The magnetic tape cassette of claim 1, wherein the 5 spring holder rib is formed on the lower half, and wherein a width of the spring holder rib gradually increases from a distal end to a proximal end thereof.

4. A magnetic tape cassette, comprising: o a cassette case including an upper half and a lower half, and having an opening at a front end thereof for drawing a magnetic tape out; a reel accommodated in the cassette case so as to be able to rotate while a force is applied to the reel toward s the lower half by a leaf spring, wherein the magnetic tape is wound around the reel; a lid attached to the cassette case in order to open and close the opening; a lid lock that can lock the lid so as to close the o opening; a lid lock spring including a coil part fastened to the lower half, wherein a free end of the lid lock spring engages with the lid lock so that the lid lock spring applies a force to the lid lock to close the opening; and 5 guide members respectively provided in the upper and lower halves , the guide members having guide grooves for guiding the lid lock spring to a position which applies a force to the lid lock, the guide members being located at

27 different positions along an extending direction of the lid lock spring, wherein the guide members are superposed as viewed from the extending direction when assembling the upper and lower halves .

5

5. The magnetic tape cassette of claim 4, wherein each of the guide grooves is defined by three surfaces .

6. The magnetic tape cassette of claim 5, wherein the three o surfaces are two inclined surfaces and a plane located between the inclined surfaces .

7. A magnetic tape cassette, comprising: a cassette case including a lower half in which grooves s are formed and an upper half, and having an opening at a front end thereof for drawing a magnetic tape out; a reel accommodated in the cassette case so as to be able to rotate while a force is applied to the reel toward the lower half by a leaf spring, wherein the magnetic tape is o wound around the reel; a lid attached to the cassette case in order to open and close the opening; a lid lock that can lock the lid so as to close the opening, the lid lock having projecting parts provided at 5 opposite ends thereof, the projecting parts being loosely fitted in the grooves, respectively; and a stopper rib formed on the upper half, the stopper rib restraining the projecting parts of the lid lock to the

28 grooves in recoverable positions thereof when the upper half is assembled with the lower half and is tightened with screws in a state where the cassette case is turned over so that the lower half is upside.

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