Magnetic tape cassette

A magnetic tape cassette for use in a magnetic recording/reproducing apparatus has a sliding plate provided on a lower surface to selectively cover and expose insertion apertures that open into the interior of the cassette. A front lid is provided which may be pivoted to either expose or cover a front opening in the cassette through which tape may be withdrawn for a recording/reproducing operation. When the front lid is in its closed position and the sliding plate covers the insertion apertures, the front lid is locked in its closed position. The magnetic tape cassette is thereby closed to prevent dust, oil and other contaminants from damaging the magnetic tape within.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to magnetic tape cassettes and more 
particularly is directed to a magnetic tape cassette suitable for use in a 
recording/reproducing apparatus for recording digital signals, for example 
pulse code modulated signals. 
2. Description of the Prior Art 
Magnetic recording/reproducing apparatus for recording signals on and 
reproducing signals from magnetic tape are well known in the art. In such 
apparatus, an analog signal, such as an audio signal, is converted into a 
digital signal, which may be a pulse code modulated (PCM) signal, and then 
recorded at a high density on a magnetic tape contained in a cassette by 
means of a rotary magnetic head. Upon a recording or reproducing 
operation, the magnetic tape is withdrawn from the cassette and wound 
around the periphery of a rotary drum within which the rotary head is 
provided. An opening at the front of the cassette is provided for 
permitting withdrawal of the tape from the cassette. 
In addition, the tape is wound about two reel hubs within the cassette, 
which receive drive shafts of the recording/reproducing apparatus when the 
cassette is inserted therein for winding or rewinding the tape. In order 
to permit the reel shafts to be inserted into the reel hubs, the cassette 
has insertion apertures which receive the reel hubs with a small degree of 
clearance, so that the hubs may be smoothly rotated. 
It is very important in such a cassette that the magnetic tape be protected 
from contamination by oil or dust. If the tape is contaminated, the signal 
cannot properly be reproduced and a drop-out in the reproduced signal 
occurs, leading to reduced quality in the reproduced audio signal. 
Therefore, to prevent such contamination, as from fingerprints or dust and 
pollution in the atmosphere, the magnetic surface of the tape should 
ideally be maintained sealed within the cassette. However, the front 
opening and apertures described above constitute openings through which 
dust and unwary fingers may enter to damage the tape. 
In order to close the front opening in a cassette of this type, there has 
been proposed a cassette with a pivotable front lid which covers the front 
of the cassette. This rotatable front lid can cover either the front 
surface or the magnetic surface of the magnetic tape, and an opening is 
provided in the front lid for inserting therethrough a tape guide system 
for withdrawing the magnetic tape from the tape cassette. 
However, with this proposed tape cassette, it is still possible for the 
magnetic tape to be touched or contaminated through the space through 
which the tape guide system is inserted. Moreover, although the magnetic 
surface of the tape is covered by the front lid, there is still a small 
clearance between the front lid and the magnetic surface of the tape, so 
that dust and contamination may still reach the magnetic surface of the 
tape and adhere thereto. 
Therefore, it has been further proposed that an inner lid be provided 
inside the front lid to cover the tape surface opposed to the magnetic 
surface, so that the magnetic tape will be enclosed between the front lid 
and the inner lid. Although in such a tape cassette the magnetic tape is 
protected, this construction is relatively complicated and assembly 
thereof may be quite difficult. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
improved magnetic tape cassette which avoids the difficulties of the prior 
art. 
It is another object of the present invention to provide a magnetic tape 
cassette having a simple construction which can be assembled with ease. 
It is a further object of the present invention to provide a magnetic tape 
cassette having a construction which prevents dust and contamination from 
reaching the magnetic tape and which further prevents touching of the 
magnetic tape by fingers, or other objects. 
It is another object of the present invention to provide a magnetic tape 
cassette in which the front lid is locked against inadvertent opening when 
the cassette is not in use. 
It is yet another object of the present invention to provide a magnetic 
tape cassette of the above type suitable for use in an apparatus for 
recording and reproducing a digital signal, for example a pulse code 
modulated signal. 
Therefore, in accordance with one aspect of the present invention, there is 
provided a magnetic tape cassette which comprises a casing enclosing first 
and second reel hubs adapted to have a magnetic tape wound thereabout, a 
first surface of the casing having first and second reel shaft insertion 
apertures into which the first and second reel hubs are inserted, 
respectively, with a small degree of clearance, and a cut-out portion 
through which the magnetic tape may be withdrawn from the cassette, and 
sliding plate means provided on the first surface and freely slidable 
between first and second positions thereon, so that, in the first position 
of the sliding plate means, the first and second insertion apertures and 
the cut-out portion are exposed for respectively receiving first and 
second reel shafts and tape withdrawing means and, in the second position, 
the sliding plate means covers the first and second insertion apertures 
and the cut-out portion, whereby the magnetic tape in the cassette is 
protected from external contamination. The magnetic tape cassette 
according to the present invention has a simple construction and may be 
assembled with ease. Furthermore, the construction of the magnetic tape 
cassette according to the present invention prevents dust and other 
contaminants from reaching the magnetic tape to adhere thereto and further 
prevents fingers and other objects from touching the magnetic tape. 
According to another aspect of the present invention, the magnetic tape 
cassette is further provided with means for locking a front lid against 
rotation when the tape cassette is not inserted in the 
recording/reproducing apparatus, so that the front lid is prevented from 
being opened unintentionally. 
These and other objects, features and advantages of the present invention 
will become apparent from the following detailed description taken in 
conjunction with the accompanying drawings, throughout which like 
references designate like elements and parts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The illustrated embodiments of the invention differ only slightly, namely 
with respect to the rounding or squaring of the corners of arms 9a, 9a'. 
Either construction can be used, as long as the arms 9a, 9a' cooperate 
with a sliding plate 10 to lock a front lid 9 in the closed position in 
the matter described below. 
A preferred embodiment of the magnetic tape cassette according to the 
present invention will now be described with reference to the drawings, 
and initially with reference to FIGS. 1 and 2 thereof. As illustrated 
therein, the magnetic tape cassette according to the present invention has 
a casing 1 with an front opening 1a (FIG. 2) at the front portion of 
casing 1. Casing 1 has an upper half portion 2 and a lower half portion 3 
which may be manufactured separately and joined together by means of 
screws, bolts, or the like (not illustrated), and front opening 1a is 
constituted by the opening defined between upper half portion 2 and lower 
half portion 3 when they are joined together. Upper half portion 2 has a 
transparent window portion 2a in an upper wall 2b, right and left upper 
side walls 2c, 2c' and a rear wall 2d. Upper side walls 2c, 2c' have 
indented stepped portions 2e, 2e', with a predetermined depth to provide a 
smooth exterior wall of the complete magnetic tape cassette when 
assembled, as will be discussed in detail later. 
Lower half portion 3 includes a cut-out portion 3a which is formed by 
cutting away a portion of a bottom wall 3b in a rectangular shape. 
Together, front opening 1a and cut-out portion 3a form an L-shaped space 
through which the tape may be withdrawn. That is, when the tape cassette 
according to the present invention is inserted in a recording/reproducing 
apparatus, a tape guide system (not illustrated) is inserted into casing 1 
through cut-out portion 3a. During a recording or reproducing operation 
this tape guide system withdraws the tape from casing 1 through front 
opening 1a. 
First and second reel hubs 4a, 4b (FIG. 1) held within casing 1 are 
inserted into a corresponding pair of reel shaft insertion apertures 5 and 
6 (FIG. 2), formed in the bottom wall 3b of lower half portion 3. A 
magnetic tape 7 is wound about reel hubs 4a, 4b. Again, it is contemplated 
that when the cassette is inserted into the recording/reproducing 
apparatus, a pair of drive shafts (not illustrated) will extend through 
insertion apertures 5, 6 to drivingly engage reel hubs 4a, 4b for winding 
and rewinding magnetic tape 7. Therefore, reel hubs 4a, 4b are designed to 
have a small degree of clearance within insertion apertures 5 and 6, so 
that they may be freely driven by the drive shafts. 
Also in the bottom surface wall 3b are a pair of positioning apertures 8a 
and 8b at predetermined positions located closer to front opening 1a and 
spaced apart farther than insertion apertures 5, 6. Positioning apertures 
8a, 8b are adapted to be engaged by positioning members (not illustrated) 
with the recording/reproducing apparatus for holding the cassette in a 
stable position during operation. Lower half portion 3 further includes 
right and left lower side walls 3c, 3c', respectively corresponding to and 
aligned with left and right upper side walls 2c, 2c' of upper half portion 
2. A stop flange 3d is provided on lower wall 3b at the rear portion of 
housing 1 and runs the entire width of the cassette. 
Located at the front portion of housing 1 is a front lid 9, having a 
U-shaped configuration when viewed from above and an L-shaped 
configuration when viewed from the side, which is rotatably pivoted to 
upper side walls 2c, 2c' of casing 1 at indented stepped portions 2e, 2e'. 
Front lid 9 is formed of a plate member 9b having approximately the same 
rectangular shape as the front opening 1a of casing 1, such that when 
front lid 9 is rotated to overlie front opening 1a, front opening 1a is 
completely covered. Front lid 9 further has arm members 9a, 9a' which are 
extensions of plate member 9b bent at right angles thereto. Arm members 
9a, 9a' are pivotally connected through shafts 9c, 9c' to side walls 2c, 
2c' at stepped portions 2e, 2e', respectively. 
Front lid 9 can be rotatably positioned in closed and opened positions. In 
its closed position, front lid 9 covers front opening 1a to protect 
magnetic tape 7 from contamination when the cassette is not in use, that 
is, when it is not within the recording/reproducing apparatus. When front 
lid 9 is rotated to its closed position to cover front opening 1a, arm 
members 9a, 9a' overlie only the stepped portions 2e, 2e' of upper side 
walls 2c, 2c'. In its open position, to which it is rotated when within 
the recording/reproducing apparatus, front lid 9 is rotated upwardly to 
expose front opening 1a, so that magnetic tape 7 may be withdrawn from the 
cassette. 
Provided on the bottom wall 3b is a sliding plate 10 having a substantially 
U-shaped cross-section, which opposes and slides along the bottom wall 3b 
of lower half portion 3 in both the forward and rearward direction between 
a first, forewardmost position and a second, rearmost position. Sliding 
plate 10 includes a lower plate 10a with the same width as lower wall 3b, 
but with a lesser extent in the forward and backward direction. Side 
plates 10b, 10b', extend from the right and left edges of lower plate 10a 
and overlie lower side walls 3c, 3c', respectively. Guide runners 10c, 
10c' extend inwardly from side plates 10b, 10b', respectively. 
In order that sliding plate 10 may be freely slid in the forward and 
rearward direction of casing 1 between its first and second positions, 
guide grooves 11, 11' are respectively formed by a spacing between upper 
and lower right side walls 2c, 3c and upper and lower left side walls 2c', 
3c' over the desired sliding range of sliding plate 10. Guide runners 10c, 
10c' respectively engage guide grooves 11, 11' for guiding the sliding 
plate 10 along its path. 
A rectangular groove or slit 12 (FIG. 2) is formed in the center of bottom 
wall 3b of lower half portion 3 so that its longitudinal direction is 
coincident with the direction along which sliding plate 10 travels. A 
return spring 13 located within rectangular groove 12 is fixed at one end 
13a to the portion of bottom wall 3b at the front of rectangular groove 
12. The other end 13b of return spring 13 is adapted to be engaged by a 
spring engaging member 14 (FIG. 4) on sliding plate 10 to bias sliding 
plate 10 into its second position, i.e. towards the front portion of the 
housing 1. 
Sliding plate 10 embodies an important aspect of the present invention, in 
that it provides the means by which the apertures in casing 1, that is, 
insertion apertures 5, 6 and positioning apertures 8a, 8b, are covered 
when the cassette is not in use and exposed when the cassette is in use. 
In accordance with this important aspect of the present invention, 
apertures 5', 6', 8a', and 8b' are provided in lower plate 10a of sliding 
plate 10, which respectively correspond to insertion apertures 5, 6 and 
positioning apertures 8a, 8b of lower wall 3b. These apertures are located 
on lower plate 10a, so that, when sliding plate 10 is positioned on lower 
wall 3b in its first position (FIG. 8), apertures 5', 6', 8a', 8b' will 
respectively overlie apertures 5, 6, 8a, 8b to form continuous apertures 
through which the drive shafts and positioning members may be inserted. 
Conversely, when sliding plate 10 is in its second position (FIG. 5), 
insertion apertures 5, 6, positioning apertures 8a, 8b, and cut-out 
portion 3a are covered by solid portions of sliding plate 10, while 
apertures 5', 6', 8a', 8b' all overlie solid portions of lower wall 3b. 
Thus, in the second position, sliding plate 10 forms a protective barrier 
to prevent the entry of dust or fingers which might damage magnetic tape 
7. 
When front lid 9 is in its closed position, sliding plate 10 may be slid 
forward to its second position where the front edge of sliding plate 10 
contacts plate member 9b of front lid 9. The results in the highly 
advantageous feature that front lid 9 is now locked against inadvertant 
opening, as will be discussed below. When sliding plate 10 is slid to its 
first position where its rearmost edge abuts stop flange 3d, front lid 9 
is released. Thus, sliding plate 10 may be slid between its first and 
second positions for producing the advantageous features of the present 
invention. 
In order that the cassette according to the present invention may have 
smooth, planar exterior walls, as illustrated in FIGS. 1 and 3, it may be 
seen that stepped portions 2e, 2e' have a depth equal to the thickness of 
arm members 9a, 9a' of front lid 9 (FIG. 1). In addition, right and left 
lower side walls 3c, 3c' are similarly reduced in thickness by the 
thickness of side plates 10b, 10b' of sliding plate 10 (FIG. 3). By this 
means the exterior surface of upper side walls 2c, 2c' form a smooth plane 
with the exterior surfaces of side plates 10b, 10b' and arm members 9a, 
9a', respectively. Similarly, stop flange 3d extends below lower wall 3b 
by a thickness equal to that of lower wall 10a (FIG. 9), so that when 
sliding plate 10 has been slid to its second position to abut stop flange 
3d, the exterior surfaces of stop flange 3 d and lower wall 10a form 
another smooth plane. Thus, stop flange 3d not only serves to limit the 
rearward sliding of sliding plate 10, but also creates a smooth exterior 
wall with the sliding plate 10. 
The operation of the magnetic tape cassette according to the present 
invention will now be described in detail with reference to FIGS. 5 to 13, 
and initially with reference to FIGS. 5 to 7, which show different views 
of the magnetic tape cassette when it is not in use and removed from the 
recording/reproducing apparatus. As illustrated, when the cassette is not 
in use, front lid 9 is in its closed position to cover front opening 1a 
and sliding plate 10 is in its second, or forwardmost, position with the 
front edge of sliding plate 10 abutting front plate member 9b of front lid 
9. In this initial state, it may be seen from FIG. 7 that apertures 5', 6' 
do not overlie insertion apertures 5, 6, nor do apertures 8a', 8b' overlie 
positioning apertures 8a, 8b. Rather, these apertures are respectively 
displaced from each other, so that lower wall 3a and sliding plate 10 form 
a continuous barrier along the lower surface of the tape cassette to 
prevent dust, oil, and other contaminants from entering the cassette and 
damaging magnetic tape 7. It will be further noted that sliding plate 10 
also overlies and covers cut-out portion 3a, indicated in dotted lines in 
FIG. 7, so that this portion also is covered and protected. It is to this 
end that positioning apertures 8a and 8b are located forwardly and to the 
sides of insertion apertures 5, 6, so that corresponding apertures 8a', 
8b' may be located on sliding plate 10 on either side of the portion of 
sliding plate 10 adapted to overlie cut-out portion 3a. Therefore, all 
openings into the cassette are completely covered and sealed against 
contamination. That is, front opening 1a, cut-out portion 3a, insertion 
apertures 5 and 6 and positioning apertures 8a and 8b are all covered by 
the front lid 9 and sliding plate 10. 
A further advantageous feature of the magnetic tape cassette according to 
the present invention may be clearly seen from FIG. 6. As illustrated 
there, when front lid 9 is in its closed position and sliding plate 10 is 
in its second position, side plates 10b of sliding plate 10 are positioned 
directly beneath arm members 9a of front lid 9 and the upper edges of the 
side plates 10b closely oppose the lower edges of arm members 9a. 
Accordingly, even if front lid 9 were loosely connected to casing 1 so 
that it had a tendency to rotate, or if a user attempted to manually 
rotate front lid 9, side plates 10b would prevent the rotation of front 
lid 9, thus locking front lid 9 against rotation to further insure the 
closure of the tape cassette against contaminants. When the cassette is 
fully assembled, spring engaging member 14 engages return spring 13 at its 
end 13b such that sliding plate member 10 is yieldingly retained in its 
second position abutting front lid 9. Thus, when the tape cassette 
according to the present invention is not in use, it presents a continuous 
closed surface surrounding the tape, such that magnetic tape 7 is not 
exposed to contaminants or rough handling. 
FIGS. 8 to 10 illustrate an intermediate state of the novel tape cassette 
as it is being inserted into the recording/reproducing apparatus. As the 
cassette is inserted, sliding plate 10 is engaged by an engaging member of 
the recording/reproducing apparatus (not illustrated) and is slid 
rearwardly against the biasing force of return spring 13 to its first 
position abutting stop flange 3d (FIG. 9). In this intermediate state, as 
clearly seen in FIG. 10, apertures 5', 6', 8a' and 8b' respectively 
overlie insertion apertures 5, 6 and positioning apertures 8a, 8b, so that 
the reel shafts and positioning members of the recording/reproducing 
apparatus may extend therethrough to engage with the cassette, as is 
conventional. In addition, cut-out portion 3a is also exposed so that the 
tape guide system for drawing out magnetic tape 7 may be inserted into 
casing 1 through cut-out portion 3a. When the tape case cassette is within 
the recording/reproducing apparatus, it is protected by the apparatus 
itself from contaminants in the air and inexpert handling. Then, the 
necessary apertures to the interior of the cassette may be safely exposed 
for operation. 
It should be noted that in this intermediate position, side plates 10b, 
10b' no longer oppose arm members 9a, 9a' of front lid 9. Thus, front lid 
9 is released from its locked state. 
Thereafter, in a final state of the cassette as illustrated in FIGS. 11 to 
13, front lid 9 is rotated upwardly to its open position by the action of 
further engaging members (not illustrated) within the 
recording/reproducing apparatus. Once front opening 1a of casing 1 is thus 
exposed and magnetic tape 7 is presented at the front of casing 1, 
magnetic tape 7 may be drawn forward by the tape guide system, inserted 
through cut-out portion 3a, as is conventional. Thus, the magnetic tape 
cassette according to the present invention has been transformed from a 
completely closed, sealed box while not in use protecting magnetic tape 7 
from contaminants to a fully operational and functional cassette within 
the recording/reproducing apparatus. 
When it is desired to remove the magnetic tape cassette from the 
recording/reproducing apparatus, the operation is simply the reverse of 
the above-described steps from the final state to the intermediate state 
to the initial state. That is, upon actuation of an appropriate mechanism 
on the recording/reproducing apparatus, magnetic tape 7 is returned to the 
cassette by the tape guide system. Front lid 9 is then rotated to its 
closed position to cover front opening 1a. Then the tape guide system, the 
engaging members for engaging apertures 8a, 8b and the reel shafts are 
withdrawn from the cassette and the cassette itself is withdrawn from the 
recording/reproducing apparatus. As the tape cassette is withdrawn, the 
operation of return spring 13 causes sliding plate 10 to be returned to 
its second, forwardmost position to cover apertures 5, 6, 8a, and 8b and 
to seal magnetic tape 7 once again against contamination. 
Thus, in the above-described embodiment of the magnetic tape cassette 
according to the present invention, the magnetic tape contained therein is 
at all times protected from contamination from dust, oil from touching, or 
physical damage to the tape. That is, when the novel tape cassette 
according to the present invention is outside the recording/reproducing 
apparatus and is not in use, all apertures into the interior of the casing 
are covered by sliding plate 10 and front lid 9. Alternatively, when the 
cassette is in use within the recording/reproducing apparatus and the 
apertures are exposed, the recording/reproducing apparatus itself forms a 
protective shield about the tape. In addition, when the sliding plate is 
in its second, forwardmost position, front lid 9 is locked against 
rotation, so that it may not be inadvertently opened with consequent 
damage to the tape. 
The above description is given for a single preferred embodiment of the 
invention, but it will be apparent that many modifications and variations 
may be effected by those skilled in the art with departing from the spirit 
or scope of the present invention as defined in the appended claims.