Reel brake operable from both sides of magnetic tape cassette

A magnetic tape cassette incorporates therein a braking member which brakes reel hubs when the magnetic tape cassette is not in use, so that the reel hubs are prevented from being rotated. The braking member can be operated to release the reel hubs from their locked conditions from any side of the upper and lower parts of the cassette casing. Thus, the magnetic tape cassette of this invention can correspond with a tape cassette of the double-sided use kind, in which a cassette casing is turned over and the recording and reproduction can be performed in a cited fashion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to magnetic tape cassettes and, 
more particularly, to a magnetic tape cassette having a braking member 
which locks a reel hub so that the reel hub can be inhibited from being 
rotated uselessly when the magnetic tape cassette is not in use. 
2. Description of the Prior Art 
Conventionally, in a magnetic tape cassette for accommodating therein a 
magnetic tape on which a signal such as a video signal, a PCM (pulse code 
modulated) signal or the like is recorded at high density, various 
magnetic tape cassettes are now available on the market. Each of these 
magnetic tape cassettes incorporates therein a braking member to lock the 
reel hub so that the reel hub is inhibited from being rotated uselessly in 
order to prevent the magnetic tape from slackening when the magnetic tape 
cassette is not in use. These conventional magnetic tape cassettes might 
be, for example, a 1/2-inch video tape cassette, an 8 mm video tape 
cassette or the like. 
More specifically, when this magnetic tape cassette is not in use, this 
braking member is biased by the spring-biasing force of a spring in a 
direction so that it is urged against the reel hub, thereby locking the 
reel hub so that the reel hub cannot be rotated. When the magnetic tape 
cassette is in use, the braking member is moved to the direction in which 
it is isolated from the reel hub by a lock releasing pin inserted thereto 
from the outside of the cassette casing. Thus, the locking of the reel hub 
is released. 
The magnetic tape cassette having such braking member is of the type of a 
so-called one side use so that only one side of the magnetic tape can be 
recorded and reproduced, that is, the tape cassette cannot be turned over 
in use. For this reason, the braking member is adapted to perform the lock 
releasing operation only from one of the upper and lower parts of the 
cassette casing. For example, when the magnetic tape cassette is loaded 
onto a cassette tape recorder, the lock releasing pin is inserted into the 
magnetic tape cassette from its lower part side and the hub lock releasing 
operation of the braking member is performed by this lock releasing pin. 
However, in a magnetic tape cassette in which a PCM signal is recorded on a 
magnetic tape at high recording density, a novel tape cassette of a 
double-sided use type has been developed recently, in which the two sides 
of the magnetic tape can be recorded and reproduced. In that case, since 
the cassette casing is turned over to use the two sides of the magnetic 
tape, the hub lock releasing operation of the braking member cannot be 
performed by the conventional braking member which performs the hub lock 
releasing operation only from the one side of the cassette casing. 
Therefore, a magnetic tape cassette is required in which the braking member 
can be operated from two sides of the cassette casing. All of the existing 
magnetic tape cassettes are of the above-mentioned type so that the 
braking member can be operated only from the one side of the cassette 
casing. Thus, a magnetic tape cassette in which the hub lock releasing 
operation can be performed from the two sides of the cassette casing is 
not yet proposed. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
improved magnetic tape cassette which can eliminate the aforenoted 
shortcomings and disadvantages encountered with the prior art. 
More specifically, it is an object of the present invention to provide a 
magnetic tape cassette in which a hub lock releasing operation of a 
braking member can be performed from any one of upper and lower parts of a 
cassette casing. 
It is another object of the present invention to provide a magnetic tape 
cassette which can be applied to a magnetic tape cassette of a 
double-sided type in which a cassette casing is turned over and the 
recording and reproduction can be performed in a reciprocating fashion. 
It is still another object of the present invention to provide a magnetic 
tape cassette in which a space of a cassette casing can be saved from a 
design standpoint. 
It is a further object of the present invention to provide a magnetic tape 
cassette which can reduce the number of parts of a cassette tape recorder 
and also can simplify the mechanism of the cassette tape recorder. 
It is yet a further object of the present invention to provide a magnetic 
tape cassette in which a hub lock releasing operation can be performed 
positively. 
It is still a further object of the present invention to provide a magnetic 
tape cassette in which a magnetic tape can be transported stably. 
It is still a further object of the present invention to provide a magnetic 
tape cassette which is high in reliability. 
As an aspect of the present invention, a magnetic tape cassette is 
comprised of a braking member provided within a cassette casing so that 
the braking member is brought in contact with or is isolated from 
peripheral surfaces of a pair of reel hubs around which a magnetic tape is 
wrapped and the braking member is always spring-biased in the locking 
direction in which the braking member is urged against the reel hubs, 
wherein symmetrical inclined cam surfaces are formed on the upper and 
lower sides of the braking member and a hub lock releasing operation of 
the braking member is performed by pressing the inclined cam surfaces by a 
pin inserted from any one of insertion apertures formed on the upper and 
lower parts of the cassette casing. 
The above, and other objects, features and advantages of the present 
invention will be apparent in the following detailed description of an 
illustrative embodiment when read in conjunction with the accompanying 
drawings, in which like reference numerals are used to identify the same 
or similar parts in the several views.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the magnetic tape cassette according to the present 
invention will now be described with reference to FIGS. 1 to 6. The 
magnetic tape cassette of this embodiment is constructed as an extremely 
small magnetic tape cassette. 
In FIGS. 4 to 6, reference numeral 1 generally designates a a cassette 
casing which accommodates therein a magnetic tape on and from which, for 
example, a PCM signal is recorded and reproduced. This cassette casing 1 
is formed by fastening an upper half or upper part 2 and a lower half or 
lower part 3 by screws 4, and a lid 6 is rotatably supported to the 
cassette casing so as to open and close an opening portion 5 formed on the 
front surface sides of both the upper and lower parts 2 and 3. 
A magnetic tape T is accommodated within the cassette casing 1, i.e. 
between the upper and lower parts 2 and 3 under the condition such that 
the magnetic tape T is wound around a pair of reel hubs 7 and 8 provided 
in correspondence with hub drive shaft insertion apertures 2a, 2b and 3a, 
3b. One portion of the magnetic tape T is exposed to the front surface 
side opening portion 5 under the condition such that the magnetic tape T 
is extended between pinch rollers 9 and 10 serving as guide rollers 
rotationally supported at both sides of the opening portion 5. 
A braking mechanism 11 is provided within the cassette casing 1 to brake 
the two reel hubs 7 and 8 when this magnetic tape cassette is not in use. 
Mis-erase preventing mechanisms 12 and 13 are provided at the upper and 
lower surface sides of the cassette casing 1 at its two rear corner 
portions so as to communicate with the upper and lower parts 2 and 3. 
Positioning reference apertures 14, 15 and 16, 17 are formed through the 
cassette casing 1 at its central front and back portions in the front to 
back direction and at its two rear side portions in the lateral direction. 
A plurality of predetermined detection apertures 18 and 19 are formed 
through the cassette casing at its rear edge portion in the lateral 
direction. Further, grip portions 20 and 21 are formed on the rear 
portions of two side walls of the cassette casing 1. 
An engaging portion 23 for a cassette changer is formed along a guide 
groove 22 extending along the width direction of the lid 6 which opens and 
closes the front surface side opening portion 5 of the cassette casing 1. 
In the magnetic tape cassette thus arranged, the magnetic tape T 
accommodated within the cassette casing 1 is recorded and/or reproduced by 
a rotary head in a helical scan fashion. 
More specifically, as shown in FIG. 5, a rotary head 41 is rotated at a 
predetermined slant angle relative to a head drum 42, and the head drum 42 
is partly inserted into the front surface side opening portion 5 which is 
opened by rotating the lid 6 of the cassette casing 1 in the upper or 
lower direction. The magnetic tape T extended across the opening portion 5 
is slidably moved so as to be wound around the insertion side peripheral 
surface of the head drum 42. Thus, when the rotary head 41 is rotated, 
slant tracks across the magnetic tape T are formed on the magnetic tape T. 
In this embodiment, in order to ensure that the magnetic tape T is brought 
in slidable contact with the head drum 42 in a helical scan fashion, as 
shown in FIG. 6, a pair of tape guide members 24 and 25 whose guide 
portions are inclined in the opposite direction are disposed in the 
insertion portion of the opening portion 5 of the cassette casing 1 for 
the head drum 42 at their positions inside the guide rollers 9 and 10 such 
that the tape guide members 24 and 25 can be vibrated and moved in the 
lateral direction in an opposing fashion. When the head drum 42 is 
inserted into the opening portion 5, the tape guide members 24 and 25 come 
in contact with the peripheral surface of the head drum 42, and guide the 
magnetic tape T under the condition such that the magnetic tape T is 
sandwiched between them and the peripheral surface of the head drum 42. 
Further, as shown in FIG. 5, the head drum 42 has at its both side portions 
formed wing guides 43 and 44 which are inserted between the pinch rollers 
9, 10 and the tape guide members 24, 25 in both side portions of the 
opening portion 5 of the cassette casing 1. Rollers 43a and 44a are 
mounted on the front end portions of the two wing guides 43 and 44, and 
brought in slidable contact with the magnetic tape T, urging the magnetic 
tape T against the tape guide members 24 and 25. 
The wing guides 43 and 44 are inserted into the opening portion 5 of the 
cassette casing 1 such that they are located between supporting members 26 
and 27 provided near the inside of the opening portion 5 and tape 
projection preventing guide protrusions 28, 29 positioned between the 
supporting members 26 and 27 and the pinch rollers 9 and 10. 
The arrangement of the braking mechanism 11 in the thus arranged magnetic 
tape cassette will be explained with reference to FIGS. 1 to 3A and 3B. 
As illustrated, a recess portion 30 of substantially rectangular 
configuration is formed on the bottom surface of the lower part 3 at its 
rear central portion. A braking member 31 is accommodated within this 
recess portion 30 such that the braking member 31 can be freely moved in 
the front to back direction, that is, in the direction in which the 
braking member 31 approaches or moves away from the reel hubs 7 and 8. 
As shown in the figures, this braking member 31 is composed of a flat plate 
portion 31a which is flush with the bottom surface of the recess portion 
30 and a vertically-protruded wall portion 31b erected from the rear 
portion of the flat plate portion 31a. A pair of protruded nail members 
31a1 and 31a2 are protruded from the front portion of the flat plate 
portion 31a so as to correspond with the two reel hubs 7 and 8 as shown in 
FIG. 2. The top portions of the protruded nail members 31a1 and 31a2 are 
urged against the reel hubs 7 and 8, thereby the two reel hubs 7 and 8 
being locked, as will be described later. 
The reel hubs 7 and 8 are comprised of inner hubs 7a and 8a with which hub 
drive shafts are engaged and outer hubs 7b and 8b which can be moved in 
the axial directions relative to the inner hubs 7a and 8a and which can be 
engaged with the inner hubs 7a and 8a in the circumferential direction 
thereof. The protruded nail members 31a1 and 31a2 of the braking member 31 
are urged against the peripheral surfaces of the inner hubs 7a and 8a 
protruded from the lower surfaces of the outer hubs 7b and 8b, 
respectively. 
A pair of left and right guide slits 32a and 32b of recess configurations 
are formed on the central portion of the flat plate portion 31a so as to 
extend from the front edge of the flat plate portion 31a to its rear 
direction. A pair of guide pins 33a and 33b are projected from the bottom 
surface of the recess portion 30 in correspondence with the pair of guide 
slits 32a and 32b. The guide slits 32a and 32b are guided by the guide 
pins 33a and 33b, whereby the moving direction of the braking member 31 is 
restricted. 
A plate spring 34 is provided at the rear side of the braking member 31 to 
spring-bias the braking member 31. This plate spring 34 is composed of a 
main plate portion 34a and an arm portion 34b erected from the central 
portion of the main plate portion 34a. The main plate portion 34a is 
engaged with a spring accommodating portion 35 provided at the rear side 
wall inner surface side of the lower part 3, and the arm portion 34b is 
engaged at its top portion with a concave portion 36 formed on the rear 
surface side of the vertically-projected portion 31b as shown in FIG. 2. 
Thus, the braking member 31 is always spring-biased in the forward 
direction, i.e. in the direction in which the protruded nail members 31a1 
and 31a2 are urged against the peripheral surfaces of the inner hubs 7a 
and 7b. 
The vertically-protruded wall portion 31b of the braking member 31 has on 
its central front surface side formed a pressing operation portion 37 
which allows the braking member 31 to perform the hub lock releasing 
operation. This pressing operation portion 37 is formed as a 
mountain-configuration whose central portion is high in cross-sectional 
side view, that is, this pressing operation portion 37 has inclined cam 
surfaces 37a and 37b whose cam surfaces are symmetrically inclined 
rearwardly toward the upper to lower sides from the central portion. When 
this pressing operation portion 37 is pressed by the lock releasing pin 
inserted from the insertion aperture bored through the two upper and lower 
parts 2 and 3, the braking member 31 is moved in the rear direction, 
thereby the reel hubs being released from their locked conditions. 
In this embodiment, one of the positioning reference apertures of the 
cassette casing 1, i.e. the reference aperture 15 at the rear and central 
portion of the cassette casing 1 in its front to back direction so that, 
when this magnetic tape cassette is loaded onto the cassette tape 
recorder, a cassette tape recorder side positioning pin 50 inserted into 
the reference aperture 15 is used as the lock releasing pin, so that the 
hub lock releasing operation of this braking member 31 is performed by 
this positioning pin 50. 
An opening 38 elongated in the front to back direction is formed through 
the central portion of the flat plate portion 31a of the braking member 31 
in correspondence with the reference aperture (insertion aperture) 15, and 
this opening 38 permits locking member 31 to slide when the positioning 
pin (lock releasing pin) 50 is inserted from the lower half 3 side. 
A pair of left and right protruded portions 39a and 39b are symmetrically 
protruded from both sides of the flat plate portion 31a of the braking 
member 31 at its rear portion in the lateral direction. The protruded 
portions 39a and 39b are made to have a predetermined resiliency so that, 
if the braking member 31 is abnormally skewed in the hub lock releasing 
operation, any one of top circular-shaped portions 39a1 and 39b1 of the 
two protruded portions 39a and 39b comes in contact with a rear side edge 
surface 30a of the recess portion 30, thus the braking member 31 is 
returned to the normal hub lock releasing condition, as will be described 
later. 
In this braking mechanism 11, as shown in FIG. 3A, a supporting column 
member 40 projects from the inner surface side of the upper part 2 
downwardly and the lower end face of the support column member 40 is 
facing to the central portion of the flat plate portion 31a of the braking 
member 31. The braking member 31 is restricted by this support column 
member 40 so that it is prevented from being disengaged from the recess 
30. 
As will be clear from the above-mentioned arrangement, according to the 
braking mechanism 11 of the magnetic tape cassette of this embodiment, in 
the normal condition, or when the magnetic tape cassette is not in use, 
the protruded nail members 31a1 and 31a2 of the braking member 31 are 
urged against the peripheral surfaces of the inner hubs 7a and 8a of the 
two reel hubs 7 and 8 by the spring-biasing force of the plate spring 34, 
whereby the two reel hubs 7 and 8 are located and hence they can be 
prevented from being rotated by a certain amount of shock (see FIGS. 3A 
and 6). 
When the magnetic tape cassette is loaded onto the cassette tape recorder, 
the cassette tape recorder side positioning pin 50 is inserted into the 
reference aperture 15 (in actual practice, the cassette casing 1 is 
lowered and the reference aperture 15 is engaged with the positioning pin 
50), the positioning of the cassette casing 1 is performed and the hub 
lock releasing operation by the braking member 31 is simultaneously 
performed. 
The hub lock releasing operation by the braking member 31 can be performed 
from any side of the upper part 2 and the lower part 3. That is, when the 
magnetic tape cassette is loaded onto the cassette tape recorder under the 
condition such that the upper part 2 side (so-called side A) thereof is 
oriented above as shown in FIG. 3, the positioning pin 50 inserted into 
the reference aperture 15 of the lower part 3 side presses the inclined 
cam surface 37b (lower side in FIG. 3) of the pressing operation portion 
37 so that the braking member 31 is moved rearwards against the 
spring-biasing force of the plate spring 34, that is, the braking member 
31 is moved in the direction in which the protruded nail members 31a1 and 
31a2 come away from the inner hubs 7a and 8a of the reel hubs 7 and 8 (see 
FIGS. 3B and 2). Conversely, when the magnetic tape cassette is loaded 
onto the cassette tape recorder under the condition such that the cassette 
casing 1 is turned over and the lower part 3 side is oriented above, the 
positioning pin 50 inserted into the reference aperture 15 of the upper 
part 2 side presses the inclined surface 37a of the other side of the 
pressing operation portion 37, whereby the the braking member 31 is moved 
in the rear direction similarly as described above, thus the reel hubs 7 
and 8 being released from their locked conditions the reel hubs 7 and 8 
being allowed to rotate freely. 
In the hub lock releasing operation of the braking member 31, the braking 
member 31 is operated by pressing one point of the central portion of the 
braking member 31. There is then the substantial risk that the braking 
member 31 is frequently operated in an unbalanced fashion and is moved in 
the inclined condition as shown by a two-dot chain line in FIG. 2, thus 
the braking member 31 being placed in a so-called deviated skewed 
condition where only one protruded nail member is brought in contact with 
the reel hub and does not come apart from the reel hub. In that case, 
according to the magnetic tape cassette of this embodiment, the 
circular-shaped portion of any one of the left and right protruded 
portions (the circular-shaped portion 39b1 of the right protruded portion 
39b in the example of FIG. 2) comes in contact with the rear side edge 
surface 30a of the recess 30, whereby the braking member 31 is returned to 
the normal condition that the two protruded nail members 31a1 and 31a2 
correspond with the reel hubs 7 and 8 in a well-balanced condition by 
virtue of cushion-action of the protruded portion. Thus, the two protruded 
nail members 31a1 and 31a2 come away from the reel hubs 7 and 8 together, 
so that the braking member 31 can be protected from the above-mentioned 
defect and the two reel hubs 7 and 8 can be released from their locked 
conditions. 
Under the condition that the reel hubs 7 and 8 are positively released from 
being locked by the braking member 31, the reel hubs 7 and 8 are rotated 
by the hub drive shafts (not shown) of the cassette tape recorder, whereby 
the magnetic tape T being transported. 
As described above, according to the magnetic tape cassette of this 
embodiment, the hub lock releasing operation by the braking member can be 
performed from either the upper part 2 side or the lower part 3 side of 
the cassette casing 1. Therefore, the magnetic tape cassette of this 
invention can be applied to a double-sided use cassette where the cassette 
casing 1 is turned over and the recording and reproduction can be 
performed in a two-sided fashion. 
Since the positioning reference aperture 15 of the cassette casing 1 is 
utilized as the pin insertion aperture into which the pin 50 for operating 
the braking member 31 is inserted, insertion apertures need not be bored 
respectively through the upper and lower parts 2 and 3 of the cassette 
casing 1, which saves the space of the cassette casing 1 from a design 
standpoint. This is very effective for the extremely small magnetic tape 
cassette of this embodiment in which the space of the cassette casing 1 is 
restricted. Also, in the cassette tape recorder side, special lock 
releasing pin for operating the braking member 31 is not needed and the 
positioning of the cassette casing 1 and the hub lock releasing operation 
of the braking member 50 are simultaneously performed by the positioning 
pin 50 which performs the positioning of the cassette casing 1. Therefore, 
the assembly parts on the cassette tape recorder side can be reduced and 
the mechanism of the cassette tape recorder can be simplified. 
Further, if the braking member 31 is abnormally operated in the skewed 
condition during the hub lock releasing operation, the braking member 31 
can be returned to the normal condition by the cushion action of any one 
of the left and right protruded portions 39a and 39b, thereby ensuring 
that the hub lock releasing operation is always performed positively. 
Therefore, in the recording or reproducing operation, the reel hubs 7 and 
8 can be smoothly rotated without any resistance to ensure that the 
magnetic tape T can be stably transported. Thus, the magnetic tape 
cassette of the present invention can bring about various advantages 
unlike the prior art. 
While the present invention is applied to the extremely small magnetic tape 
cassette for recording a PCM signal in the above-mentioned embodiment, the 
present invention is not limited thereto and can be applied to a wide 
variety of tape cassettes such as a standard audio compact tape cassette 
and other tape cassette of the double-sided type. 
As set forth above, according to the present invention, it is possible to 
provide a novel magnetic tape cassette in which the hub lock releasing 
operation by the braking member can be performed from any one of the upper 
and lower parts of the cassette casing. Therefore, the magnetic tape 
cassette of the present invention can be applied to a magnetic tape 
cassette of the double-sided type in which the cassette casing is turned 
over and the recording and reproducing operations can be effected in a 
two-sided fashion. 
Since the insertion aperture into which the pin is inserted also serves as 
the positioning reference aperture of the cassette casing, the space of 
the cassette casing can be saved and this can achieve a remarkable effect 
in the extremely small magnetic tape cassette in which the space of the 
cassette casing is restricted. 
Furthermore, since the pair of protruded portions are provided at the left 
and right portions of the braking member to thereby avoid the defect that 
only one reel is released, the braking member can always be operated 
accurately to thereby positively release the reel hubs from being locked. 
Accordingly, it is possible to provide a magnetic tape cassette of high 
reliability. 
Having described a preferred embodiment of the invention with reference to 
the accompanying drawings, it is to be understood that the invention is 
not limited to that precise embodiment and that various changes and 
modifications thereof could be effected by one skilled in the art without 
departing from the spirit or scope of the novel concepts of the invention 
as defined in the appended claims.