Tape cartridge reel lock mechanism

A magnetic tape cartridge, particularly for use in a digital audio tape player, which includes a lock mechanism for avoiding an arbitrary motion of any one of the reels within the cartridge so as to avoid an undesirable loosening of a length of the magnetic tape extending between the reels, the lock mechanism including a lock member normally biased to a lock position and having lock pawls normally engaged with toothed lock wheels integral with the respective reels, at least one stopper rod protruding from one end of the lock member and terminating in alignment with a free end of a corresponding one of hinge arms integral with a front cover used to selectively open and close a front opening of the cartridge such that so long as the front cover is in position to close the front opening, the free end of the stopper rod is positioned in close proximity to the corresponding hinge arm to keep the lock member immovable even when a drastic impact acts on the tape cartridge tending the lock member to move from the locked position towards an unlocked position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a tape cartridge accommodating a rolled 
length of magnetic recording tape and, more particularly, to a tape 
cartridge having a reel lock mechanism to keep reels immovable when the 
tape cartridge is not in use. 
2. Description of the Related Art 
DAT tape cartridges, that is, tape cartridges specifically designed for use 
with a digital audio tape (DAT) player, are generally provided with a reel 
lock mechanism to keep reels immovable when the tape cartridge is not in 
use. This type of reel lock mechanism is disclosed in, for example, 
Japanese Laid-open Utility Model Publication No. 63-191483, published in 
1988, and this known reel lock mechanism will now be discussed with the 
aid of FIG. 20a and 20b of the drawings annexed hereto. 
As is well known, the tape cartridge of the type to which the present 
invention pertains is generally standardized in size and configuration so 
that it can be used with the commercially available digital audio tape 
player. This tape cartridge comprises a generally rectangular box-like 
casing 1 including rectangular top and bottom walls and a peripheral wall 
disposed between the top and bottom walls to keep the top and bottom walls 
spaced apart a distance enough to accommodate a length of magnetic 
recording tape within the casing, the peripheral wall including a hingedly 
supported front wall section or front cover 6, a rear wall section 
opposite to the front cover and a pair of side wall sections, all 
assembled together with the top and bottom walls to render the cartridge 
to represent a generally rectangular, generally flattened box-like 
configuration. 
In practice, the casing 1 is divided into two casing halves along a plane 
generally intermediate of the thickness of the peripheral wall. 
within the casing 1, there is disposed a pair of freely rotatable reels 3, 
each generally in the form of a cylindrical hub, to which opposite ends of 
the length of magnetic recording tape 2 are anchored respectively, and a 
pair of guide rollers 5 rotatably disposed within the casing 1 at 
respective corner areas adjacent the front cover 6 so as to permit a 
portion of the length of magnetic recording tape 2 between the guide 
rollers 5 to extend generally parallel to the front cover 6. 
As shown in FIGS. 20a and 20b, the reel lock mechanism employed in the 
prior art DAT tape cartridge is housed within the casing 1 and is 
cooperable with any one of toothed lock wheels 8 each formed integrally 
with one end of the associated reel 3. This reel lock mechanism includes a 
generally elongated, thin-walled lock member 9 extending widthwise of the 
casing 1 and between the opposite side wall sections of the casing 1 for 
movement between unlocked and locked positions in a direction 
perpendicular to the lengthwise direction of the lock member 9. The lock 
member 9 has lock pawls 11 formed integrally therewith so as to protrude 
outwardly therefrom for engagement with the corresponding toothed lock 
wheels 8 integral with the respective reels 3. 
The lock member 9 is normally biased towards the lock position by a wire 
spring 10 and has its opposite ends connected or integrally formed with 
respective traction arms 12 extending perpendicular to the lock member 9. 
Respective free ends of the traction arms 12 are operatively associated 
with the front cover 6 so that, when the front cover 6 is opened to allow 
that portion of the length of magnetic recording tape 2 to be exposed to 
the outside, the lock member 9 can be retraced against the resiliency of 
the wire spring 10 towards the unlock position with the lock pawls 11 
consequently disengaging from the associated toothed lock wheels 8, but 
when the front cover 6 is closed to conceal that portion of the length of 
magnetic recording tape 2, the lock member 9 can be urged by the wire 
spring 10 to the lock position with the lock pawls 11 consequently engaged 
with the toothed lock wheels 8. 
To operatively couple the free ends of the front cover 6, respective hinge 
arms 6b protruding transversely from opposite ends of the front cover 6 
have their inner surfaces formed with associated operating ribs 16. So 
long as the lock member 9 is held in the lock position, the lock pawls 11 
are engaged with the associated toothed lock wheels 8 integral with the 
reels 3 and, therefore, the reels 3 are held immovable to avoid any 
possible loosening of the length of magnetic recording tape 2. 
With the reel lock mechanism wherein the biasing force of the wire spring 
10 is utilized to keep the lock member 9 in the lock position, the lock 
pawls 11 integral with the lock member 9 will not disengage from the 
associated toothed lock wheels 8 so long as the tape cartridge is handled 
normally. However, when an excessive external force such as an impact on 
the tape cartridge as a result of, for example, an accidental fall of the 
tape cartridge onto an indoor or outdoor ground surface, the reels 3 may 
be instantaneously rattled enough to cause the lock member 9 to be 
undesirably displaced against the resiliency of the wire spring 10. Once 
this occur, the lock pawls 11 are disengaged from the associated toothed 
lock wheels 8, permitting the reels 3 to rotate idle, resulting in a 
loosening of the length of magnetic recording tape 2 that is turned around 
those reels 3. 
When the tape cartridge in which the length of magnetic recording tape 2 
has been loosened in the manner described above is loaded into a digital 
audio tape player, the length of magnetic recording tape may be 
undesirably bent and/or caught by loading pins employed in the digital 
audio tape player to pull that portion of the length of magnetic recording 
tape outwardly from the casing, eventually resulting in a detrimental 
problem in that the tape cartridge may be no longer usable and/or a tape 
loading mechanism in the digital audio tape player may be impaired. 
SUMMARY OF THE INVENTION 
The present invention is therefore intended to provide an improved tape 
cartridge wherein, even though an external force such as an impact acts on 
the tape cartridge, the lock member will not be undesirably displaced 
towards the unlock position unless the front cover is operated, thereby to 
avoid any possible undesirable loosening of the length of magnetic 
recording tape within the tape cartridge when the tape cartridge is not in 
use. 
To this end, the present invention provides a tape cartridge which 
comprises a generally rectangular box-like casing including rectangular 
top and bottom walls, a pair of side walls and a rear wall, all assembled 
together to represent a generally rectangular flat box-like configuration 
with a tape chamber defined therein, and having a front opening defined 
therein so as to confront the rear wall. The casing also includes a front 
cover hinge supported having a pair of hinge arms pivotally coupled to the 
respective side walls for pivotal movement between an opened position, in 
which the front cover opens the front opening, and a closed position in 
which the front cover closes the front opening. 
First and second reels are rotatably housed within the tape chamber, 
opposite ends of the length of magnetic tape being secured to the first 
and second reels, respectively. Each reel has a toothed lock wheel 
rotatable together therewith. 
The tape cartridge also comprises a hub lock mechanism housed within the 
tape chamber and including a generally elongated lock member movable 
between locked and unlocked positions in a direction transverse to the 
front cover, and a spring element for biasing the lock member towards the 
locked position. The lock member has lock pawls engageable with the 
toothed lock wheels to lock the respective reels when the lock member is 
in the lock position and also has traction arms protruding from opposite 
ends of the lock member in a direction perpendicular to the lock member 
and towards the hinge arms, the traction arms being operatively coupled 
with the hinge arms such that, as the front cover is pivoted from the 
closed position towards the opened position, the lock member is pulled 
from the lock position towards the unlock position against the spring 
element. 
The tape cartridge further comprises at least one stopper rod protruding 
from a corresponding one of the opposite ends of the lock member in a 
direction perpendicular to the lock member and towards the front opening 
in alignment with a corresponding one of the hinge arms, the stopper rod 
having a free end positioned in close proximity of a free end of the 
corresponding hinge arm, when the front cover is in the closed position 
thereby to keep the lock member immovable. 
A lateral displacement suppressing means may be employed in the tape 
cartridge of the present invention. This lateral displacement suppressing 
means may be defined in part in the free end of the stopper rod and in 
part in the free end of the corresponding hinge arm for avoiding a 
deformation of stopper rod inwardly of the casing. 
Preferably, the lateral displacement suppressing means may comprise a first 
lateral engagement defined in the free end of the stopper rod and a second 
lateral engagement defined in the free end of the corresponding hinge 
arms, the first and second lateral engagements being laterally offset in 
position relative to each other with respect to a longitudinal axis of any 
one of the stopper rod and the corresponding hinge arm. 
Alternatively, the lateral displacement suppressing means may comprise a 
first inclined face defined at the free end of the stopper rod and a 
second inclined face defined at the free end of the corresponding hinge 
arm, the first and second inclined faces being complemental to each other 
and inclined relative to a longitudinal axis of any one of the stopper rod 
and the corresponding hinge arm. 
Also alternatively, the lateral displacement suppressing means may comprise 
a protuberance protruding outwardly from one of the free ends of the 
stopper rod and the corresponding hinge arm and a pocket defined in the 
other of the free ends of the stopper rod and the corresponding hinge arm 
for receiving the protuberance therein. 
Preferably, the casing may include an inner side wall segment for 
restricting an inward displacement of any one of the stopper rod and each 
hinge arm when the front cover is in the closed position. 
Also preferably, the casing may include an outer side wall segment for 
restricting an outer displacement of any one of the stopper rod and each 
hinge arm when the front cover is in the closed position. 
Again preferably, the tape cartridge may further comprise a generally 
U-sectioned slider forming a front area of the bottom panel and supported 
for movement in a direction perpendicular to the front cover for 
selectively opening and closing a bottom region of the front opening, the 
slider having upright side wall elements aligned with the respective hinge 
arms integral with the front cover, each of the side wall elements having 
a first engagement defined therein while each of the hinge arms has a 
second engagement defined therein for engagement with the first engagement 
to prevent the hinge arms from being outwardly deformed.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIGS. 1, 2, 4 and 5 showing a first preferred embodiment 
of the present invention, the tape cartridge shown therein is so designed 
and so structured as to meet the DAT standards so that it can be used with 
the commercially available digital audio tape player of any make. This 
tape cartridge comprises a generally rectangular box-like casing 1. The 
casing 1 includes rectangular top and bottom walls and a peripheral wall 
disposed between the top and bottom walls to keep the top and bottom walls 
spaced apart a distance enough to accommodate a length of magnetic 
recording tape 2 within the casing 1 and including a hinged supported 
front wall section or front cover 6, a rear wall section opposite to the 
front cover and a pair of side wall sections, all assembled together with 
the top and bottom walls to render the cartridge to represent a generally 
rectangular, generally flattened box-like configuration. 
In practice, the casing 1 is comprised of upper and lower casing halves 1a 
and 1b separate from each other along a plane generally intermediate of 
the thickness of the peripheral wall, which casing halves 1a and 1b are 
placed one above the other and then bonded or rigidly connected together 
to complete the casing 1. 
Within the casing 1, there is disposed a pair of freely rotatable reels 3, 
each generally in the form of a cylindrical hub, to which opposite ends of 
the length of magnetic recording tape 2 are anchored respectively, and a 
pair of guide rollers 5 rotatably disposed within the casing 1 at 
respective corner areas adjacent the front cover 6 so as to permit a 
portion of the length of magnetic recording tape 2 between the guide 
rollers 5 to extend generally parallel to a plane of a transverse front 
window 4 adapted to be selectively opened and closed by the front cover 6. 
In practice, the length of magnetic recording tape 2 when the tape 
cassette is in use within the digital audio player travels from one reel 3 
to the other reel 3 via the guide rollers 5 with that portion of the 
magnetic recording tape 2 pulled outwardly through the transverse front 
window 4 for sliding engagement with a magnetic recording and/or 
reproducing head. At this time the front cover 6 is held in an open 
position to permit that portion of the length of magnetic recording tape 2 
to be pulled outwardly through the transverse front window 4. 
The front cover 6 includes a generally elongated front flap 6a extending a 
distance sufficient to close the entire width of the front window 4 and 
hinge arms 6b secured to, or otherwise formed integrally with, respective 
opposite ends of the front cover 6 so as to protrude transversely 
therefrom. Free ends of the hinge arms 6b remote from the front flap 6a 
are pivotally connected to the side wall sections of the casing 1 by means 
of associated pivot pins 15 so that the front cover 6 can pivot about a 
common axis of the pivot pins 15 between a closed position, in which the 
front window 4 is closed to protect that portion of the length of magnetic 
recording tape, and an opened position in which that portion of the length 
of magnetic recording tape 2 is exposed to the outside through the front 
window 4. It is, however, to be noted that the front cover 6 is normally 
biased by a spring element (not shown) so as to assume the closed 
position. 
The tape cartridge carries a slider 7 which forms a front part of the 
bottom wall thereof adjacent the transverse front window 4 and which is 
supported for movement in a direction perpendicular to the widthwise 
direction of the casing 1 for selectively opening and closing a bottom 
region of the transverse front window 4. This slider 7 is normally biased 
by a biasing spring 17 towards a projected position to close the bottom 
region of the transverse front window 4. 
A reel lock mechanism operable to avoid an arbitrary rotation of any one of 
the reels 3 within the casing 1 when the tape cartridge is not in use is 
housed within the casing 1 and cooperates with any one of toothed lock 
wheels 8 each formed integrally with one end of the associated reel 3. 
This reel lock mechanism includes a generally elongated, thin-walled lock 
member 9 extending widthwise of the casing 1 and between the opposite side 
wall sections of the casing 1 for movement between unlocked and locked 
positions in a direction perpendicular to the lengthwise direction of the 
lock member 9. The lock member 9 has lock pawls 11 formed integrally 
therewith so as to protrude outwardly therefrom for engagement with the 
corresponding toothed lock wheels 8 integral with the respective reels 3. 
The lock member 9 is normally biased towards the lock position by a wire 
spring 10 and has its opposite ends connected or integrally formed with 
respective traction arms 12 extending perpendicular to the lock member 9. 
Respective free ends of the traction arms 12 are operatively associated 
with the front cover 6 so that, when the front cover 6 is opened to allow 
that portion of the length of magnetic recording tape 2 to be exposed to 
the outside, the lock member 9 can be retraced against the resiliency of 
the wire spring 10 towards the unlocked position with the lock pawls 11 
consequently disengaged from the associated toothed lock wheels 8, but 
when the front cover 6 is closed to conceal that portion of the length of 
magnetic recording tape 2, the lock member 9 can be urged by the wire 
spring 10 to the lock position with the lock pawls 11 consequently engaged 
with the toothed lock wheels 8. 
As best shown in FIG. 4, the lock member 9 is made of plastic by the use of 
a plastics molding techniques and is therefore of one-piece construction 
including side plates 9a and a generally elongated, thin-walled bridge 
plate 9b extending between the side plates 9a, lock pawls 11 positioned 
generally intermediate of the length of the bridge plate 9b and protruding 
laterally outwardly therefrom so as to confront the associated toothed 
lock wheels 8, and traction arms 12 protruding from the respective side 
plates 9a in a direction counter to the direction of extension of the lock 
pawls 11 and positioned offset relative to the bridge plate 9b. Respective 
free ends of the traction arms 12 are formed integrally with engagement 
pawls 13 protruding laterally outwardly in respective directions opposite 
to each other. 
The lock member 9 also includes stopper rods 14 secured to the respective 
side plates 9a at a location intermediate between the bridge plate 9b and 
the traction arms 12 so as to protrude parallel to the associated traction 
arms 12 in a direction conforming to the direction of extension of the 
traction arms 12, but terminating a distance inwardly from the free ends 
of the traction arms 12. Since the lock member 9 is normally biased by the 
wire spring 10 towards the lock position as briefly described, the bridge 
plate 9b has a pair of fingers 9c formed therein at a location generally 
intermediate of the length of the bridge plate 9b so as to confront in a 
direction counter to the direction of extension of the lock pawls 11 for 
engagement with opposite ends of the wire spring 10 while the wire spring 
10 having an intermediate eye defined therein is supported in position 
with the eye mounted on a support boss 18 integral with the top wall of 
the upper casing half 1a. 
As best shown in FIG. 5, to operatively couple the front cover 6 with the 
lock member 9, the hinge arms 6b of the front cover 6 which protrude 
transversely from opposite ends of the front cover 6 have their inner 
surfaces formed with associated operating ribs 16. So long as the lock 
member 9 is held in the lock position as biased by the wire spring 10, the 
lock pawls 11 are engaged with the associated toothed lock wheels 8 
integral with the reels 3 to keep the reels 3 immovable thereby to avoid 
any possible loosening of the length of magnetic recording tape 2 within 
the casing 1. At this time, the front cover 6 is held in the closed 
position, in which condition respective free end faces of the hinge arms 
6b remote from the front flap 6a are held in contact with side walls 7b of 
the slider 7, as shown in FIG. 2. The condition shown in FIG. 2 
illustrates when the tape cartridge is not in use. 
Referring still to FIG. 5, the stopper rods 14 secured to the respective 
side plates 9a of the lock member 9 have their free end portions exposed 
to the outside of the casing 1 through associated side openings 19 defined 
at stepped shoulders in opposite side walls of the upper casing half 1a. 
The stopper rods 14 are so sized and so configured that, when and so long 
as the lock member 9 is held in the lock position with the front cover 6 
held in the closed position, respective free ends of the stopper rods 14 
terminate at a location spaced a distance from the associated free end 
faces of the hinge arms 6b of the front cover 6 while forming a gap G 
therebetween, as best shown in FIG. 3(b). The gaps G between the free ends 
of the stopper rods 14 and the free end faces of the hinge arms 6b of the 
front cover 6 are secured for the purpose of permitting the front cover 6 
to pivot from the closed position towards the opened position without 
receiving any resistance which would be imposed on the front cover 6 if a 
sliding contact took place therebetween. Care must, however, be taken that 
any movement of the lock member 9 integral with the stopper rods 14 over 
the distance corresponding to each gap G does not result in a 
disengagement of the lock pawls 11 from the associated toothed lock wheels 
8 integral with the reels 3. This can be accomplished by choosing the size 
of each gap G to a value smaller than the depth of engagement of each lock 
pawl 11 into any one of the tooth grooves in the respective toothed lock 
wheel 8. 
The provision of the stopper rods 14 in the lock member 9 as described 
hereinabove is effective to avoid an undesirable movement of the lock 
member 9 towards the unlock position while the front cover 6 is held in 
the closed position, that is, while the tape cartridge is not in use, 
because a corresponding movement of the stopper rods 14 is barred by the 
free end faces of the hinge arms 6b of the front cover 6 then held in the 
closed position. In other words, even though the lock member 9 tends to 
move towards the unlocked position against the resiliency of the wire 
spring 10 under the influence of an external force, such as an impact 
acting on the tape cartridge as a result of, for example, a fall of the 
tape cartridge onto a ground surface, or even though an arbitrary motion 
of one or both of the reels 3, as a result of the application of the 
external force thereto, tends to cause the lock member 9 to move towards 
the unlock position, the movement of the lock member 9 over the distance 
which would result in the disengagement of the lock pawls 11 from the 
associated toothed lock wheels 8 is hampered by the engagement of the free 
ends of the stopper rods 14 against the free end faces of the hinge arms 
6b of the front cover 6 then held in the closed position. Therefore, so 
long as the front cover 6 is held in the closed position, that is, the 
tape cartridge is not in use, the reels 3 can advantageously be locked in 
position with the lock pawls 11 engaged with the associated toothed lock 
wheels 8 integral with the reels 3. 
On the other hand, when the tape cartridge is in use, i.e., the tape 
cartridge is loaded in the digital audio tape player, the slider 7 is 
moved from the projected position, as shown in FIG. 1, towards the 
retracted position against the biasing spring 17, opening the bottom 
region of the transverse front window 4 and the front cover 6 is 
subsequently pivoted about the common axis of the pivot pins 15 from the 
closed position towards the opened position. As the front cover 6 so 
pivoted approaches the opened position, the operating ribs 16 are brought 
into abutment with the engagement pawls 13 and the continued pivot of the 
front cover 6 towards the opened position results in a pull of the 
traction arms 12 in a direction close towards the front window 4 and, 
therefore, the lock member 9 integral with the traction arms 12 is moved 
from the lock position towards the unlock position against the wire spring 
10. It is to be noted that, since each of the free ends of the hinge arms 
6b of the front cover is partially inclined or rounded, as shown by 6d in 
FIG. 1 so, as to permit the free end of the associated stopper rod 14 to 
provide no obstruction to the passage of the free end of the corresponding 
hinge arm 6b, the pivotal movement of the front cover 6 from the closed 
position towards the opened position will not be hampered. 
It may, however occur, that, when the tape cartridge is inadvertently 
dropped onto the ground surface, one or both of the free ends of the 
stopper rods 14 may slide along the free end faces of the respective hinge 
arms 6b of the front cover 6 and then protrude into gaps each between the 
associated hinge arm 6b and the adjacent side wall section of the casing 
1. Once this occurs, the free end portions of the hinge arms 6b may be 
undesirably deformed outwardly of the casing 1. This possibility can be 
advantageously eliminated according to a second preferred embodiment of 
the present invention which will now be described with particular 
reference to FIGS. 6 to 9. 
According to the second preferred embodiment of the present invention, the 
tape cartridge is provided with means 22 for suppressing a lateral 
displacement of the free ends of the stopper rods 14 relative to the 
associated free ends of the hinge arms 6b. So far, as illustrated in FIGS. 
6 to 9, this lateral displacement suppressing means 22 comprises a first 
lateral protuberance 20 formed on each of the free ends of the stopper 
rods 14 so as to protrude along an axis laterally offset from the 
longitudinal axis of the respective stopper rod 14, and a second lateral 
protuberance 21 formed on each of the free ends of the hinge arms 6b so as 
to protrude along an axis laterally offset from the longitudinal axis of 
the respective hinge arm 6b, but in a sense opposite to the axis along 
which the first lateral protuberance 20 protrudes. 
Thus, it will readily be understood that, not only can the lateral 
displacement of the stopper rods 14 in a direction laterally inwardly of 
the casing 1 be blocked by the second lateral protuberances 21 then 
receiving the first lateral protuberances 20, but the lateral displacement 
of the hinge arms 6b integral with the front cover 6 in a direction 
laterally outwardly of the casing 1 can also be blocked by the lateral 
protuberances 20 then receiving the second lateral protuberances 21. 
Therefore, even though an intense impact acts on the tape cartridge, the 
possibility of one or both of the free ends of the stopper rods 14 
plunging into the gaps each between the associated hinge arm 6b and the 
adjacent side wall section of the casing 1 can advantageously be 
minimized. 
Each of the side openings 19 through which the associated stopper rods 14 
move during the movement of the lock member 9 between the unlocked and 
locked positions has been described as defined at the stepped shoulder in 
each side wall of at least the upper casing half la. Specifically, as best 
shown in FIGS. 7 and 10, each of the side wall of the upper casing 1a is, 
when viewed from top as shown in FIG. 7, constituted by an inner side wall 
segment 23 adjacent the front window 4 and an outer side wall segment 24 
extending parallel to, but offset laterally relative to the inner side 
wall segment 23, and a gate wall g lying parallel to any one of the inner 
and outer side wall segments 23 and 24 and connecting the both together. 
The gate wall g has the side openings 19 defined therein for the passage 
of the corresponding stopper rod 14 therethrough. 
The position of the gate wall g in each of the side walls of the upper 
casing 1a is so chosen that, so long as the tape cartridge is not in use 
with the lock member 9 held in the lock position, the free end of each 
stopper rod 14 is situated within the respective side opening 19. In this 
case, the extent to which the inner and outer side wall segments 23 and 24 
are laterally offset relative to each other is so chosen as to correspond 
to the thickness of each stopper rod 14 or, alternatively, each side 
opening 19 may be so chosen as to have a width corresponding to the 
thickness of the associated stopper rod 14, thereby to avoid any lateral 
rattling motion of the stopper rod 14 within the associated side opening 
19. 
Each side opening 19 may be of a generally closed rectangular configuration 
or, alternatively, it may be of a generally U-shaped configuration opening 
downwardly towards the corresponding side wall of the lower casing 1b. In 
the illustrated embodiments, the side opening 19 is of the generally 
U-shaped configuration opening downwardly towards the corresponding side 
wall of the lower casing 1b and, therefore, in the event that the free 
ends of the stopper rods 14 abruptly and vigorously abut against the free 
end faces of the hinge arms 6b of the front cover 6, a bending moment 
indicated by M in FIG. 6 acts to bend the free ends of the hinge arms 6b 
downwardly towards the lower casing half 1b. To avoid this possibility, a 
bench piece 26 is formed on an upper edge of each side wall of the lower 
casing 1b at a location immediately below the associated side opening 19 
to support the associated stopper rod 14 from below thereby to avoid any 
possible bending of the support rod 14. 
It is to be noted that, although in any one of the foregoing embodiments of 
the present invention, the stopper rods 14 have been described as employed 
for each side of the tape cartridge, only one stopper rod 14 may be 
employed for either side of the tape cartridge. It is also to be noted 
that an undesirable movement of the lock member 9 towards the unlock 
position may also be suppressed even when at least a similar bench piece 
is formed on the associated operating rib 16 integral with the front cover 
6. 
While respective mating faces of the first and second lateral protuberances 
20 and 21 forming the lateral displacement suppressing means 22, which 
confront with each other in a direction transverse to the associated side 
wall of the casing 1, are inclined so as to extend parallel to each other, 
as best shown in FIG. 7, the mating faces of the first and second lateral 
protuberances 20 and 21 may be right-angled relative to the associated 
stopper rod 14 and the associated hinge arm 6b, as best shown in FIG. 11. 
Alternatively, as shown in FIGS. 12 and 13, the lateral displacement 
suppressing means 22 may be constituted by a first inclined end face 27 
defined in the free end face of the stopper rod 14 and a second inclined 
end face 28 defined in the free end face of the hinge arm 6b and extending 
parallel to the first inclined end face 27. 
Again alternatively, as best shown in FIGS. 14 and 15, the lateral 
displacement suppressing means 22 may be constituted by a semi-spherical 
or conical protuberance 29 formed on the free end face of one of the 
stopper rod 14 and the hinge arm 6b so as to protrude towards the 
associated hinge arm 6b or the associated stopper rod 14, and a pocket 30 
formed on the free end face of the other of the stopper rod 14 and the 
free end face of the hinge arm 6b and having a shape complemental to the 
shape of the semi-spherical or conical protuberance 29. The lateral 
displacement suppressing means 22 constituted by the shaped protuberance 
29 and the complementally shaped pocket 30, as shown in FIGS. 16 and 17, 
is particularly advantageous in that, even though the free end of the 
stopper rod 14 is substantially displaced laterally relative to the free 
end of the associated hinge arm 6b at the moment the stopper rod 14 is 
brought into abutment with the associated hinge arm 6b, the shaped 
protuberance 29 is received within the complementally shaped pocket 30 
thereby to assuredly avoid any possible plunging of the stopper rod 14 
into the gap between the associated hinge arm 6b and the adjoining side 
wall (inner side wall segment 23) of the upper casing half 1b. 
In an embodiment shown in FIGS. 16 and 17, the free end of the hinge arm 6b 
integral with the front cover 6 is formed with a thin-walled extension 6c 
protruding outwardly therefrom towards the associated stopper rod 14 so 
that, so long as the front cover 6 is held in the closed position, the 
extension 6c is received within the side opening 19 together with the free 
end of the associated stopper rod 14. According to the embodiment of the 
lateral displacement suppressing means 22, shown in FIGS. 16 and 17, so 
long as the tape cassette is not in use with the front cover 6 
consequently held in the closed position, any undesirable lateral 
displacement of both of the respective free ends of the stopper rod 14 and 
the corresponding hinge arm 6b can advantageously minimized or 
substantially eliminated since both of the free end of the stopper rod 14 
and the extension 6c of the corresponding hinge arm 6b are enclosed within 
the associated side opening 19. 
FIG. 18 illustrates a modified form of a deformation preventing means for 
preventing any possible deformation of each of the hinge arms 6b of the 
front cover 6. This deformation preventing means exhibits its function and 
effect when the tape cassette is not in use, that is, when the front cover 
6 is held in the closed position and the slider 7 is held in the projected 
position. As shown therein, a lower face of the respective hinge arm 6b is 
formed with a generally L-sectioned groove 31a while an upper face of the 
side wall 7b of the slider 7 is formed with a mating rib 31b engageable in 
said L-sectioned groove 31a, thereby to avoid any possible lateral 
deformation of one of the hinge arm 6b and the side wall 7b relative to 
the other of the hinge arm 6b and the side wall 7b. 
The effect to avoid the possible lateral deformation of one of the hinge 
arm 6b and the side wall 7b relative to the other of the hinge arm 6b and 
the side wall 7b can be advantageously enhanced if, as shown in FIG. 19, 
that portion of the hinge arm 6b where the L-shaped groove 31a is formed 
and confronts the rib 31b is thick-walled to have an increased thickness. 
Thus, according to the present invention, the stopper rods 14 protruding 
from the side plates 9a of the lock member 9 are designed to receive the 
rear end faces of the respective hinge arms 6b integral with the front 
cover 4 so as to avoid an arbitrary movement of the lock member 9 towards 
the unlock position when the front cover 4 is in the closed position. 
Accordingly, when the tape cartridge is inadvertently dropped onto the 
ground surface with a drastic impact consequently acting thereon, the lock 
pawls 11 will not disengage from the associated toothed lock wheels 8 and, 
therefore, any possible loosening of the length of magnetic tape can 
advantageously be avoided. This in turn substantially eliminates the 
possibility of the digital audio tape player malfunctioning as a result of 
entanglement of the loosened length of magnetic tape around component 
parts of the player and/or by any other reason. 
The provision of the lateral displacement suppressing means 22 defined in 
the free end faces of the stopper rods 14 and the mating free end faces of 
the hinge arms 6b integral with the front cover 4 makes it possible to 
avoid any possible lateral displacement of the stopper rods 14 relative to 
the associated hinge arms 6b which would otherwise result in an 
undesirable plunge of the stopper rods 14 into gaps between the hinge arms 
9b and the side walls of the tape cartridge and/or an undesirable lateral 
deformation of the hinge arms 6b. 
The use of each side wall of the tape cartridge which is comprised of the 
inner and outer wall segments 23 and 24 with the respective side opening 
19 defined therebetween ensures any possible lateral displacement of one 
or both of the hinge arms 6b and the stopper rods 14 inwardly for 
outwardly with respect to the tape cartridge. 
Also, according to the present invention, the possible lateral deformation 
of one of the hinge arm 6b and the side wall 7b relative to the other of 
the hinge arm 6b and the side wall 7b can be substantially eliminated by 
the use of the L-shaped groove 31a, formed in one of the hinge arm 6b and 
the side wall 7b, and the rib 31b formed in the other of the hinge arm 6b 
and the side wall 7b, thereby to ensure an constant alignment of the 
respective stopper rod 14 with the associated hinge arm 6b which is 
necessary to assuredly avoid the undesirable movement of the lock member 9 
towards the unlock position. 
Although the present invention has been described in connection with the 
preferred embodiments thereof with reference to the accompanying drawings, 
it is to be noted that various changes and modifications are apparent to 
those skilled in the art. Such changes and modifications are to be 
understood as included within the scope of the present invention as 
defined by the appended claims, unless they depart therefrom.