Switch for detecting erroneous erase protection fin of tape cassette

A switch for detecting an erroneous erase protection fin provided on a side wall of a video tape cassette including a stationary contact strip made of electrically conductive metal, a movable contact strip made of electrically conductive metal, and a main body formed by an integral molding of electrically insurating synthetic resin. The main body includes a base portion for supporting the stationary and movable contact strips such that they are aligned in a direction in which they are resiliently deformable, a first actuation portion which is engaged with the stationary and movable contact strips, a first flexible portion provided between the base portion and the first actuation portion, a second actuation portion which is engaged with the movable contact portion, and a second flexible portion which is provided between the base portion and the second actuation portion. When the cassette has the fin, the first and second actuation portions are pushed and the stationary and movable contact strips are placed in contact with each other, but when the fin has been removed from the cassette, the second actuation portion is not pushed and the movable contact strip is separated from the stationary contact strip.

BACKGROUND OF THE INVENTION 
Field of the Invention and Related Art Statement 
The present invention relates to a switch for detecting an erroneous erase 
protection fin provided on a tape casette such as a video tape cassette 
and an audio tape cassette. 
FIG. 1 is a schematic cross sectional view illustrating the construction of 
a switch for detecting the existence of the erroneous erase protection fin 
of tape cassette. The switch comprises a stationary contact strip 1, a 
movable contact strip 2, both made of a resilient metal, and a main body 3 
made of electrically insulating synthetic resin. The switch further 
includes a first actuation member 4 which is secured to the main body 3 
rotatably about a shaft 5, and a second actuation member 7 secured to a 
free end of movable contact strip 2. The second actuation member 7 is 
arranged within a space 6 formed in the first actuation member 4. It 
should be noted that the second actuation member 7 has a substantially 
triangular cross section and its apex portion is projected beyond the 
first actuation member 4. A reference numeral 8 denotes a stopper for 
restricting the rotation of the first and second actuation members 4 and 7 
in the clockwise direction, and a reference numeral 9 represents a stopper 
for preventing the counter-clockwise rotation of the second actuation 
member 7. 
As shown in FIG. 1, the known switch is consisting of the five parts, i.e. 
stationary contact strip 1, movable contact strip 2, main body 3, first 
actuation member 4 and second actuation member 7. Therefore, the cost for 
preparing the parts is liable to be increased and the number of assembling 
steps becomes large. Further, the force of restitution of the switch is 
generated only by the resilient force of metal strips 1 and 2, so that the 
strips are liable to be fatigued and the durability of the switch is 
short. 
SUMMARY OF THE INVENTION 
The present invention has for its object to provide a novel and useful 
switch for detecting the erroneous erase protection fin of tape cassette, 
which can be manufactured simply from a smaller number of parts and the 
force of restitution can be generated not only by the resiliency of the 
contact strips, but also by the resiliency of synthetic resin material 
forming the main body. 
According to the invention, a switch for detecting an erroneous erase 
protection fin provided on a tape cassette comprises a stationary contact 
strip made of electrically conductive metal, a movable contact strip made 
of electrically conductive metal, said movable contact strip being aligned 
with said stationary contact strip viewed in a direction in which they are 
deformable, and a main body made of electrically insulating material and 
having a base portion for supporting said stationary and movable contact 
strips, a first actuation portion which is engaged with the stationary and 
a tip of the movable contact strips, a first flexible portion provided 
between the base portion and the first actuation portion, a second 
actuation portion which is engaged with the movable contact strip, and a 
second flexible portion provided between the second actuation portion and 
the base portion, whereby when the cassette has the fin, the first and 
second actuation portions are moved to place the stationary and movable 
contact strips into contact with each other, but when the cassette does 
not have the fin, the second actuation portion is not pushed by the fin so 
that the movable contact strip is separated from the stationary contact 
strip.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 2 is a cross sectional view showing the construction of an embodiment 
of the switch according to the invention. The switch is mainly consisting 
of three parts, i.e. a stationary contact strip 11, a movable contact 
strip 12 and a main body 13 made of electrically insulating synthetic 
resin material, said stationary and movable contact strips being made of 
electrically conductive metal. According to the invention, a first 
actuation member 14 for actuating both the stationary and movable contact 
strips 11 and 12 and a second actuation member 15 for driving only the 
movable contact strip 12 are formed integrally with the main body 13. 
FIG. 3 is a perspective view illustrating the construction of the 
stationary contact strip 11. The stationary contact strip 11 comprises a 
pair of contact portions 11a, a pair of arm portions 11b formed at a free 
end portion thereof and a terminal portion 11c formed at a root portion 
thereof. The contact portions 11a are curved such that they project toward 
the movable contact strip 12. 
FIG. 4 is a perspective view depicting the detailed construction of the 
movable contact strip 12. The movable contact strip 12 has a contact 
portion 12a, a lag portion 12b and a terminal portion 12c. When the 
movable contact 12 is assembled in the main body 13, the lag portion 12b 
is projected into a hole formed in the main body as shown in FIG. 2, so 
that the movable contact strip is prevented from being removed out of the 
main body. Further, the terminal portion 12c is brought into contact with 
the bottom surface of main body 13. 
FIGS. 5 to 9 show the detailed construction of the main body 13 of the 
switch and FIGS. 5 and 6 are front and rear views, respectively viewed 
from directions C and D in FIG. 2 FIG. 7 is a side view and FIGS. 8 and 9 
are plan and bottom views of the main body. The main body 13 includes a 
base portion 16 and a frame portion 18 which are coupled with each other 
by means of a first flexible portion 17. At an upper part of the frame 
portion 18 there is integrally formed a first actuation portion 14. On an 
inner surface of the frame portion 18 there is integrally formed a second 
actuation portion 15 by means of a second flexible portion 19. In the 
second actuation portion 15 there is formed an opening 20 through which 
the movable contact strip 12 is passed. On an inner surface of the first 
actuation portion 14 there is formed a flat portion 21 against which the 
free end of movable contact strip 12 is resiliently urged. 
The first and second flexible portions 17 and 19 are formed in the thin 
plate which can be resiliently bent so that they can produce the force of 
restitution. In order to prevent the first and second actuation portions 
14 and 15 from being rotated in the clockwise direction in FIG. 2, a 
stopper portion 22 is integrally formed with the main body 13 by means of 
a hinge portion 23 which is shaped in the formed of a thin strip. The 
hinge portion 23 is formed at a tip of a first side wall portion 24a. 
Upon assembling, the movable contact strip 12 is inserted into a recess 28 
formed in the base portion 16 of the main body 13 and then the stationary 
contact strip 11 is inserted into a recess 27 formed in the base portion 
16. After that, the stopper 22 is rotated by 180.degree. in the direction 
shown by an arrow E in FIG. 5 until a tip 22a of the stopper is engaged 
with a recess 25 formed in a top of a second wall portion 24b. In this 
manner, the switch can be assembled very simply. 
In order to prevent the first actuation portion 14 from being rotated 
excessively in the direction shown by an arrow A in FIG. 2, there is 
formed a pair of projections 26 integrally with the frame portion 18, said 
projections is engaged with the arm portions 11b of the stationary contact 
strip 11. In FIGS. 8 and 9, there are shown the recess 27 into which the 
stationary contact strip 11 is to be inserted, and the recess 28 into 
which the movable contact strip 12 is to be inserted. In FIGS. 8 and 9, a 
reference numeral 29 denotes a recess into which the terminal portion 12c 
of movable contact strip 12 is clamped, and a reference numeral 30 
represents a hole through which a screw for fixing the switch to an 
electric device using the tape cassette is passed. 
When the first actuating portion 14 is pushed in the direction A in FIG. 2, 
the movable contact strip 12 is pushed by the flat portion 21 of the first 
actuation portion, and at the same time the second actuation portion 15 is 
also moved. In this condition, the force of restitution is generated by 
the first and second flexible portions 17 and 19 in addition to the 
stationary and movable contact strips 11 and 12. When the second actuation 
portion 15 is pushed in the direction C in FIG. 2, only the movable 
contact strip 12 is moved so that these contact strips 11 and 12 are 
remained in contact with each other and the force of restitution is 
produced not only by the movable contact strip 12 but also by the second 
flexible portion 19. 
The switch is secured to a video deck at a video tape cassette installing 
portion with the aid of the hole 30. When the video tape cassette is 
inserted in the direction shown by an arrow B in FIG. 2, the first and 
second actuation portions 14 and 15 are engaged with the cassette and both 
the contact strips 11 and 12 are pushed in the direction A. When the 
cassette has the erroneous erase protection fin left unbroken, the second 
actuation portion 15 is urged against the fin and the movable contact 
strip 12 is pushed in the direction A and thus the switch is remained on. 
When the cassette has no erroneous erase protection fin, the apex portion 
of the second actuation portion 15 protrudes into a recess formed in the 
wall of cassette, so that the switch is made off. This will be further 
explained with reference to FIGS. 10(a) and 10(b). 
When the erroneous erase protection fin 32 is remained in the cassette 31 
as illustrated in FIG. 10(a), the second actuation portion 15 is pushed 
rightward by the fin, and therefore the movable contact strip 12 is also 
pushed and the contact portion 12a of movable contact strip 12 is urged 
against the contact portions 11a of stationary contact strip 11. In this 
manner the switch is driven into the ON condition, and the video deck 
recognizes that the cassette can be erased, if desired. Contrary to this, 
when the fin 32 is broken off as shown in FIG. 10(b), the second actuation 
portion 15 is projected into the space 33 formed in the cassette 31 upon 
the insertion of the cassette into the video deck, the switch is changed 
in the OFF condition and the video deck recognizes that the cassette could 
not be erased and the electronic circuit in the video deck is driven into 
such a condition that the recording could not be effected. 
As explained above, the switch for detecting the erroneous erase protection 
fin according to the present invention can be constructed from a smaller 
number of parts because the first and second actuation portions are 
integrally formed with the main body. Further the switch according to the 
invention can be assembled very simply and thus the cost of the switch can 
be reduced materially. Moreover, the force of restitution is generated not 
only by the contact strips made of metal plate, but also by the flexible 
portions integrally formed with the main body, so that the large force of 
restitution can be obtained and the fatigue of the switch is reduced. 
Therefore, the switch according to the invention can be used for a very 
long time in a reliable manner.