Tape cassette

A tape cassette having a plug for preventing erasure by mistake which may be inserted to make engagement with a recess provided in a peripheral surface of a cassette. The plug has a pair of insertion legs which extend from the ends of a mistake inhibiting web, and engagement portions for engaging mating engagement portions in the engagement recess. The plug may be inserted into the engagement recess from the web side or from the ends of the insertion legs as selected by the user, and the insertion legs will slide along surfaces of the cassette to fill said engagement recess. Different indications may be provided in window openings contiguous to the engagement recess in the cassette proper, according to whether the plug has been inserted from the web side or from the insertion legs, so that the user may know whether the tape cassette is recording correctly or incorrectly.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a tape cassette and, more particularly, to a tape 
cassette including a casing or cassette consisting of upper and lower half 
casing portions integrally connected to each other, and a plug for 
preventing erasure by mistake which separate from said casing. The plug is 
insertable in one or another preselected direction into an engagement 
recess provided in said casing so that the tape cassette may be used for 
recording or to make erasure impossible depending on the selected 
direction in which the plug is introduced into the engagement recess. 
2. Description of the Prior Art 
In many currently used compact type tape cassettes, an opening for 
preventing erasure by mistake is provided on the back side of a cassette 
consisting of interconnected upper and lower half portions. A mistake 
erasure inhibiting tab is implanted on the upper half portion or lower 
half portion so as to cover said inhibiting opening. A mistake erasure 
inhibiting pawl is provided in the tape recorder so as to enter said 
mistake erasure inhibiting opening when the tape cassette is mounted in 
position in the tape recorder. If desired to prevent the tape cassette 
from being erased, that is, to protect the magnetic tape against mistaken 
erasures, the tab is broken off manually to open the mistake erasure 
inhibiting opening so as to permit the mistake erasure inhibiting pawl to 
enter said opening to prevent erasures by mistake of the tape cassette. 
With such conventional tape cassettes, if it is desired to place the tape 
cassette in the recording condition after the pawl has already broken off, 
a piece of tape may be bonded to the opening or the opening may be filled 
with a suitable pad so that the pawl of the tape recorder may not enter 
the erasure inhibiting opening. 
In such prior art devices, it is not possible to completely fill the 
mistake erasure inhibiting opening, which can cause erroneous operations. 
Moreover, the bonded tape pieces or pads may occasionally enter the inside 
of the tape recorder thus causing malfunctions of the device. In addition, 
for certain types of the materials of the cassette, breaking off of the 
projection may involve considerable labor and cause operational 
difficulties. 
In tape cassettes used as recording mediums for e.g. an electronic 
computer, it is also known to use a U-shaped mistake erasure inhibiting 
plug that may be introduced into a mistake erasure inhibiting opening 
provided in the cassette. By selecting the direction in which the plug is 
introduced into the erasure inhibiting opening it may be opened or closed 
so as to make tape cassette recording possible or impossible. 
Such erasure inhibiting devices involve certain inconveniences in that the 
erasure inhibiting opening is provided in the normally invisible back side 
of the cassette so that the user may not realize instantly whether or not 
the tape cassette is recording correctly. Especially, when the tape 
cassette is mounted to the tape recorder, the back side of the tape 
cassette is completely buried in the tape recorder and hidden from the 
user's view. Hence, whenever the tape cassette is used, it may be 
necessary to remove the tape cassette from the tape recorder in order to 
check whether the tape cassette can be used for recording or not, thus 
resulting in inconvenience during operation. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a tape 
cassette free of these shortcomings of the prior art device. 
It is another object of the present invention to provide a tape cassette 
wherein the tape cassette may be fixed so it can be recorded or so it 
cannot be recorded depending on the selected directions in which the 
mistake erasure inhibiting plug is inserted into the engagement recess 
provided in the cassette. 
It is another object of the present invention to provide a tape cassette 
wherein the recording or not recording conditions of the tape cassette may 
be checked with the mistake erasure inhibiting plug mounted on the 
cassette. 
It is another object of the present invention to provide a tape cassette 
wherein the recording or not recording state may be indicated by providing 
different indications in the window openings in the cassette depending on 
the directions in which the mistake erasure inhibiting plug is inserted 
into the mistake erasure inhibiting opening. 
It is still another object of the present invention to provide a tape 
cassette wherein the plug may be accurately positioned in and positively 
engaged with the engagement recess in the cassette proper when the plug is 
introduced into the engagement recess. 
Other objects of the present invention will become apparent from the 
following description and the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The tape cassette of the present invention is formed by a casing or tape 
cassette 11 composed of an upper half casing portion 12 and a lower half 
casing portion 13 conventionally connected integrally to each other. The 
casing has a pair of tape reels on which is wound a magnetic tape. On the 
back surface of the tape cassette 11, that is, on the surface opposite to 
the front surface which has an opening for accommodating the magnetic head 
of the tape recorder, there is provided, as shown in FIG. 1, an engagement 
recess 15 into which a mistake erasure inhibiting plug 14 made of cast 
synthetic material may enter or a mistake erasure inhibiting pawl which 
mounted on the tape recorder may enter. In the present embodiment, there 
is provided a detection opening 16 contiguous to the engagement recess 15 
for allowing the detection of the kind of tape stored in the cassette 
proper 11. 
The plug 14 is adapted to be inserted into and engaged in the engagement 
recess 15 and is U-shaped and has a web 17 and a pair of confronting 
insertion legs 18, 19 which extend from the ends of the web 17, as shown 
in FIGS. 2 and 3. The outer surfaces of the insertion legs 18, 19 are 
formed with a pair of projections 22, 22 adapted to be engaged in recesses 
21, 21 formed in wall surfaces defining the engagement recess 15, when the 
plug 14 is inserted into the engagement recess 15. As shown in FIG. 3, the 
ends of the insertion legs 18, 19 are formed with positioning or stopper 
projections 24, 24 that engage a stepped portion 23 of the engagement 
recess 15. 
The U-shaped plug 14 and the engagement recess 15 are designed with mating 
configurations such that the plug 14 may be inserted into the engagement 
recess 15 only when the insertion legs 18 and 19 are guided along the 
upper and lower walls 15a, 15b of the engagement recess 15 of the cassette 
11, and the plug 14 may be inserted into the engagement recess 15 with the 
web 17 first or with the ends of the insertion legs 18, 19 first, as 
selected by the user. 
When the plug 14 is inserted into the engagement recess 15 with the 
insertion legs 18, 19 first, and the web 17 facing towards the outside of 
the engagement recess 15, the stopper projections 24, 24 engage in the 
stepped portion 23, so that the plug is received and held in the 
engagement recess 15, as shown in FIGS. 5A and B. When the plug 14 is 
inserted in this way so that the engagement recess 15 is closed by the web 
17, the plug 14 is positioned by the step portion 23 and held halfway into 
the engagement recess 15, so that a window opening 25 which is provided in 
the cassette proper 11 contiguous to and communicating with the innermost 
zone of the engagement recess 15 remains open. The purpose of the window 
opening 25 is to allow the user to readily check whether the tape cassette 
is in a record position or in a record preventing position. The window 
opening 25 remains open and indicates if the plug 14 has closed the 
engagement recess 15 and whether the tape cassette is in a record 
condition. 
On the other hand, if the direction of the plug is turned 180.degree. 
relative to the above example before insertion and the plug 14 engages the 
engagement recess 15 with the side of the web 17 leading, the plug 14 will 
no longer be retained by the step portion 23 but may be inserted fully 
into the engagement recess 15, as shown in FIGS. 6A and B. With the plug 
14 inserted in this manner into the engagement recess 15, the recess 15 is 
in the open state, that is, the mistake erasure inhibiting pawl may enter 
the recess 15 and will prevent tape erasure by mistake. At this time, a 
portion of the insertion legs 18 or 19 registers with the window opening 
25. With the portion of the legs 18 or 19 thus in register with the window 
opening 25, it is indicated that the engagement recess 25 is in the open 
position, that is, the tape cassette is in the erasure prevented or in the 
record prevent condition. 
It is to be noted that more positive indication may be obtained by coloring 
the plug 14 with a color different from the main portion of the cassette 
11. Alternatively, an indication that recording is not feasible may be 
provided by the portions of the insertion legs 18, 19 that register with 
the window opening 25. 
When the mistake erasure inhibiting plug 14 is inserted with the web side 
leading as shown in FIGS. 6A and B, the plug 14 may be embedded in the 
recess 15 and thus it may be difficult to extract. In order to facilitate 
extraction, a groove 26 may be provided in the innermost wall surface of 
the recess 15 so that a tool such as screwdriver may be inserted into the 
groove through the window opening 25 of the cassette 11. 
FIG. 7 shows a modified embodiment of the present invention. The mistake 
erasure inhibiting plug 14 of this embodiment has a length l.sub.1 of the 
insertion legs 18, 19 which is equal to the depth d.sub.1 of the 
engagement recess 15. A pair of through-holes 27, 27 are provided in 
positions to register with window openings 25, 25 in the cassette 11 when 
the plug is inserted into the engagement recess 15 with the web side 
leading. 
With such plug 14, the stopper projections 24, 24 and the step portion 23 
of the preceding embodiment may be eliminated. 
When the plug 14 is inserted into the recess 15 with the ends of the 
insertion legs 18, 19 leading so that the engagement recess 15 is closed 
by the web 17, part of the surface of insertion legs 18, 19 may register 
with the window openings 25, while the engagement projections 22, 22 are 
engaged in the window openings 25, 25, as shown in FIGS. 8A and B, thus 
indicating that the tape cassette can be used for recording. 
On the contrary, when the direction of plug insertion is turned 180.degree. 
and the plug 14 inserted with the web 17 leading which allows the 
engagement recess 15 to be visible, the through-holes 27 in the insertion 
legs 18, 19 register with the window openings 25, as shown in FIGS. 9A and 
B, thus indicating that the tape cassette cannot be used for recording. 
It is seen that this invention is simple and provides inexpensive means for 
allowing a tape cassette to be placed in the record or in the record 
preventing condition. The device is simple to use and is fail safe. 
Although the invention has been described with respect to preferred 
embodiments, it is not to be so limited as changes and modifications can 
be made which are within the full intended scope of the invention as 
defined by the appended claims.