Mode detecting apparatus for a video cassette recorder

A new mode detecting apparatus for video cassette recorder which is capable of linearly directly controlling the mode position is disclosed. A light emitting diode is installed under a main deck. A mode driving plate is provided with a plurality of holes for selectively passing the light from the light emitting diode. The light which have passed through the holes of the mode driving plate are sensed by photo transistors which then generates electrical signals. The signals are sent to a microcomputer which then detects the mode of the deck. The constitution of the gears is simplified, and the mode can be recognized and controlled by the mode driving plate directly and linearly.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a mode detecting apparatus for a video 
cassette recorder. More particularly, the present invention relates to a 
mode detecting apparatus in which the mode can be linearly accurately 
detected for controlling the operating mode of deck of the video cassette 
recorder. 
2. Description of the Prior Art 
In a video cassette recorder, the mode represents the operating state 
between the circuits and the mechanism, and the mode is classified 
generally into a play mode, a still mode, a recording mode, a fast forward 
winding mode, a rewinding mode, etc. According to the kind of modes, the 
respective components of the circuits and the mechanisms have to be 
positioned at the predetermined positions, and therefore, the detecting 
and controlling of the mode are known to be important matters. 
FIG. 1 is a schematic view showing a constitution of a conventional deck 
mechanism. Referring to FIG. 1, when a loading motor 1 is driven, the 
driving force of loading motor 1 is transmitted through a worm gear 3 to a 
cam gear 5 to rotate cam gear 5. The rotation force of cam gear 5 is 
transmitted through a relay plate 11 (having a rack portion 11a on a side 
surface thereof) and a relay gear 13 (meshed with rack portion 11a of 
relay plate 11) to a mode driving plate 15. Mode driving plate 15 operates 
the drive-related components of the video cassette recorder in such a 
manner that the are operated at the predetermined positions. 
FIG. 2 is a schematic view for showing the constitution of the mode driving 
section for illustrating in more detail the operation of mode driving 
plate 15. A mode driving plate 15A is a detailed illustration of mode 
driving plate 15 of FIG. 1. Mode driving plate 15A is provided with a rack 
portion 15B on an outer peripheral portion thereof, and rack portion 15B 
is meshed with relay gear 13. Mode driving plate 15A has an elongate form 
extending across the deck, and various cam portions are disposed on mode 
driving plate 15A for controlling various components connected to mode 
driving plate 15A. The reason why mode driving plate 15A has an elongate 
form is that mode driving plate 15A receives the driving force from 
loading motor 1 through cam gear 5, relay plate 11 and the relay gear 13 
of FIG. 1, thereby controlling various driving components for driving a 
tape such as a brake opening and closing device, a tension lever, and a 
review lever. 
FIG. 3 is a schematic view for illustrating the position of mode driving 
plate 15A within the video cassette recorder. As shown in FIG. 3, mode 
driving plate 15A is generally provided between a main deck 17 and a main 
circuit board 19. 
When the deck part of a video cassette recorder is driven through mode 
driving plate 15A, the various mode positions can be detected by a mode 
switch 7 which is connected to cam gear 5. The detected signals are 
inputted into a microcomputer (hereinafter, referred to as "micom") 9, and 
then, the signals are fed back to loading motor 1. 
FIG. 4A is a schematic view for illustrating the mode detecting principle 
in mode switch 7. As illustrated in the drawing, mode switch 7 includes a 
switching disc 7A and a brush supporting member 7B. Switching disc 7A is 
provided with a plurality of tracks which are divided into the conductive 
portions and non-conductive portions, while the brush supporting member 7B 
supports a plurality of brushes 9a, 9b, 9c and 9d which contact with the 
tracks of switching disc 7A. The number of tracks and the brushes is 
generally 3 to 5. 
FIG. 4B is a plan view of switching disc 7A. Referring to FIG. 4B, a 
hatched portion 8a is a conductive portion, while a non-hatched portion 8b 
is a non-conductive portion. On the switching disc 7A shown in the 
drawing, there are four tracks T1, T2, T3 and T4 which have conductive 
portions 8a and non-conductive portions 8b. Correspondingly to four tracks 
T1, T2, T3 and T4, there are provided first, second, third and fourth 
brushes 9a, 9b, 9c and 9d on the bottom of brush supporting member 7B. 
These brushes 9a, 9b, 9c and 9d contact with the tracks T1, T2, T3 and T4 
at predetermined positions, thereby producing the on and off signals in 
each of the brushes. The produced signals are sent to the micom (9 of FIG. 
1) so as to detect the mode of the video cassette recorder. 
In the case where there are four brushes, the four brushes 9a, 9b, 9c and 
9d are capable of detecting 2.sup.4 -1=15 modes excluding the off state of 
all four brushes 9a, 9b, 9c and 9d. For example, when the brushes 9a, 9b, 
9c and 9d are contacted with the line A--A of FIG. 4B, the first, third 
and fourth brushes 9a, 9c and 9d generate "0" signals which are off 
signals. The second brush 9b generates an "1" signal which is an on 
signal, and thus, the combined signals "0100" are transmitted to micom 9. 
Micom 9 compares the received signals with reference signals, thereby 
discriminating the current deck mode. 
In the conventional mode detecting apparatus described above, a rotary type 
is adopted using various components such as loading motor 1, cam gear 5, 
switching disc 7A, and a plurality of brushes. Therefore, not only the 
mechanism is complicated, but also various indirect components such as the 
switching disc and the brushes are used, with the result that the 
manufacturing cost is increased. Further, the mode switch is disposed on 
the cam gear, and therefore, the bulk of the cam gear is increased, and 
the shape of the cam becomes complicated. 
Further, the areas of the conductive portion is different from the 
peripheral portion to the central portion, and therefore, the conductive 
contacting areas of the brushes become different, with the result that it 
becomes difficult to obtain a combined mode signal at the accurate 
position. Therefore, it may be difficult to detect and to control the deck 
mode of the video cassette recorder. 
SUMMARY OF THE INVENTION 
The present invention is intended to overcome the above described 
disadvantages of the conventional techniques. 
Therefore, it is an object of the present invention to provide a mode 
detecting apparatus for a video cassette recorder, in which a linearly and 
directly positional control can be carried out. 
For achieving the above object, the mode detecting apparatus of a video 
cassette recorder according to the present invention includes: 
a means for generating a light installed under a main deck; 
a mode driving plate provided with a plurality of holes for selectively 
passing the light from the light generating means in accordance with a 
deck mode, and for transmitting a driving power of a loading motor to 
components of the main deck to drive them; 
a means for sensing the light passed through said holes of the mode driving 
plate to generate a signal; and 
a means for detecting the signal of the light sensing means, and for 
comparing the signal with a reference signal to thereby recognize a mode 
of the video cassette recorder. 
According to one embodiment of the present invention, the mode detecting 
apparatus includes a light dispersing means for dispersing the light of 
the light emitting means into a plurality of rays (or beams) to be 
irradiated onto the mode driving plate. As the light dispersing means, for 
example a prism may be mentioned. 
As the light generating means, for example, a light emitting diode may be 
mentioned, and as the light sensing means a photo transistor or a photo 
diode may be mentioned. 
The light which is generated by the light generating means are irradiated 
onto the mode driving plate, and the light selectively passes through the 
holes of the mode driving plate and is irradiated into the plurality of 
the light sensing means, thereby generating electrical signals. The 
electrical signals are added together to form combined signals. The 
combined signals are inputted into the mode detecting means, so that the 
mode of the deck of the video cassette recorder can be discriminated, and 
that the mode of the deck may be converted, when necessary. 
According to the present invention, the conventional mode detecting device 
which includes a switching disc and brushes is not required, and 
therefore, the constitution of the cam gear is simplified so as to save 
the manufacturing cost. Further, as the mode detecting device is installed 
on the mode driving plate, the mode on the mode driving plate can be 
directly and linearly recognized, with the result that the mode can be 
recognized accurately without any error.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Hereinafter, the present invention will be explained with reference to the 
accompanying drawings. 
FIG. 5 is a schematic view showing the constitution of the deck mechanism 
of a video cassette recorder according to one embodiment of the present 
invention. In the video cassette recorder according to the present 
invention, similarly to the conventional video cassette recorder as shown 
in FIG. 1, when a loading motor 21 is driven, the driving force of loading 
motor 1 is transmitted through a worm gear 23 to a cam gear 25, with the 
result that cam gear 25 is rotated. The driving force of cam gear 25 is 
transmitted through a relay plate 31 and a relay gear 33 to a mode driving 
plate 35, and relay plate 31 is provided with a rack portion 31a on a side 
thereof, while relay gear 33 is meshed with rack portion 31a of relay 
plate 31. Mode driving plate 35 operates various drive-related components 
of the video cassette recorder, which are connected to mode driving plate 
35, so that they may be operated at the predetermined positions under the 
respective mode state. 
At a portion of mode driving plate 35, there are formed a plurality of 
holes 27 through which light rays pass in a selective manner in accordance 
with the mode of the video cassette recorder. As in mode driving plate 15A 
of FIG. 3, mode driving plate 35 has an elongate form extending across 
main deck 17 and is provided with various cams for driving various 
components which are installed on a main deck 17. In the same manner as in 
FIG. 3, mode driving plate 35 is disposed between main deck 17 and a main 
circuit board 19. Mode driving plate 35 receives the driving force from 
driving motor 21 through relay gear 33 so as to move left and right. 
A light emitting diode 41 as a light generating device is installed under 
main deck 17 and above the portion where holes 27 of mode driving plate 36 
are formed. In the present embodiment of the present invention, the light 
emitting diode 41 is used as the light generating device, but any device 
which can emit light rays to be converted to electrical signals may be 
acceptable without any limitation. Between light emitting diode 41 and 
mode driving plate 35, there is installed a prism 43 as a light dispersing 
device for dispersing the light from light emitting diode into a plurality 
of light rays. 
On main circuit board 19, there are disposed a photo transistors 39 as a 
light sensing device for sensing the light rays passing through holes 27 
of mode driving plate 35. When the light rays which are generated by light 
emitting diode 27 are irradiated onto photo transistor 39 after passing 
through prism 43 and holes 27, photo transistor 39 is turned on. On the 
other hand, when the light rays do not pass through holes 27 and therefore 
shielded by mode driving plate 35, the photo transistor 39 is in the off 
state. Photo transistors 39 are provided in a proper number on main 
circuit board 19 in accordance with the arrangement of holes 27. For 
example, when the number of the mode in the video cassette recorder is 
less than 7, holes 27 are arranged in a 3-column and 7-row matrix form 
based on the moving direction of mode driving plate 35, so that 7 
different combined signals may be formed. 
When the deck part of the video cassette recorder is driven through mode 
driving plate 35, the light which is generated from light emitting diode 
41 are irradiated onto mode driving plate 35 after passing through the 
prism 43. The light pass through holes 27 of mode driving plate 35 in a 
selective manner to be inputted into photo transistors 39 which then 
generate electrical signals. Photo transistors 39 are provided in a proper 
number by taking into account the arrangement of holes 27. In the case 
where a 3-column and 7-row matrix is formed as mentioned above, three 
photo transistors 39 are provided. 
When the light rays which have passed through prism 43 are irradiated onto 
mode driving plate 35, and when the light rays which have passed through 
the holes 27 are irradiated onto photo transistors 39 to turn on them, 
with the result that an electrical signal "1" is generated. On the other 
hand, when the light rays are shielded by mode driving plate 35, then 
photo transistors are turned off, with the result that an electrical 
signal "0" is generated. 
The above described electrical signals are summed together to form a 
combined signal. The combined signals are inputted into a micom 49 as a 
means for detecting the mode which have stored certain reference signals 
in accordance with the deck modes respectively. Micom 49 compares the 
received combined signals with the reference signals, thereby judging the 
current mode of the deck of the video cassette recorder. Further, based on 
the command of the user, driving signals are fed back into driving motor 
21, so that the mode of the deck of the video cassette recorder can be 
converted depending on the need. 
FIG. 6 is a schematic sectional view for illustrating in more detail the 
mode detecting apparatus according to the present invention and FIG. 7 is 
a partial plan view showing the portion of mode driving plate 35 of FIG. 6 
where holes 27 are formed. 
As shown in FIG. 7, at the portion of mode driving plate 35 where holes 27 
are formed, a plurality of holes 27 are arranged in 3-columns in parallel 
with the movement of mode driving plate 35, in such a manner that 3-column 
on/off combined signals should be generated. Excluding the case where all 
the three columns generate off-signals, 2.sup.3 -1=7 kinds of combined 
signals can be generated, and therefore, 7 kinds of modes can be detected 
in a video cassette recorder. Mode driving plate 35 can move to left and 
right (in the direction of an arrow mark C) so as to drive various 
components on the main deck 17, and so as to enable the light generated 
from light emitting diode 41 to selectively pass through holes 27. 
As shown in FIG. 6, in accordance with the arrangement of holes 27, three 
photo transistors, i.e., a first, a second and a third photo transistors 
39a, 39b and 39c are provided on main circuit board 19. On a corresponding 
portion under main deck 17 to photo transistors 39a, 39b and 39c, a light 
emitting diode 41 is installed. Between light emitting diode 41 and mode 
driving plate 35, there is provided a prism 43 which disperses the light 
generated from light emitting diode 41 into three separate light rays 
corresponding to three columns of holes 27 of mode driving plate 35. In 
the preferred embodiment of the present invention, one light emitting 
diode 41 and one prism 43 is used for dividing the light generated 
therefrom into three light rays are used, but in replacement of these 
three light emitting diodes 41 can be used to irradiate the light rays 
directly onto mode driving plate 35. 
In the video cassette using the mode detecting device, in accordance with 
the commands of the user, when loading motor 21 is driven by receiving a 
command from micom 49, the driving force of loading motor 21 is 
transmitted through worm gear 23 to cam gear 25 to rotate cam gear 25. The 
driving force of cam gear 25 is transmitted through relay plate 31 and 
relay gear 33 to mode driving plate 35, so that mode driving plate 35 
would perform reciprocating movements over a certain distance. Mode 
driving plate 35 drives various mode-driving related components connected 
therewith of the video cassette recorder so that they are driven in each 
mode states at predetermined positions. 
At this time, light emitting diode 41 generates a light, and this light 
passes through prism 43 where it is dispersed into three light rays which 
are to be irradiated onto mode driving plate 35. The irradiated light rays 
pass through holes 27 of mode driving plate 35 in a selective manner. The 
light rays which have passed through holes 27 are irradiated onto first, 
second and third photo transistors 39a, 39b and 39c, formed on main 
circuit board 19 to thereby generate electrical signals. For example, as 
shown in FIG. 7, when the portion B of mode driving plate 35 having holes 
27 comes to be positioned below prism 43, the outer two rays among the 
three rays pass through the holes 27, so that first and third photo 
transistors 39a and 39c would be turned on by receiving the light rays, 
and that electrical signals "1" would be generated. On the other hand, the 
central ray is shielded by mode driving plate 35, with the result that 
second photo transistor 39b is turned off, and that an electrical signal 
"0" is generated. The electrical signals generated from first, second and 
third photo transistors 39a, 39b and 39c are combined together to form a 
combined signal "101". The combined signal is transmitted to micom 49, 
which compares the combined signal with a reference signal to make a 
judgment on the mode of the deck of the video cassette recorder. When the 
mode of the deck does not correspond with the selection of the user, the 
mode of the deck is converted by driving the loading motor. This operation 
is repeated, thereby accurately detecting and controlling the mode of the 
deck. 
When the mode detecting apparatus according to the present invention is 
used, the conventional mode detecting device which includes a switching 
disc and brushes is not required, and therefore, the constitution of the 
cam gear is simplified, with the result that the manufacturing cost is 
saved. 
Further, the mode detecting devices is installed on the mode driving plate, 
and therefore the mode can be directly and linearly detected and 
controlled, so that the mode can be accurately detected and controlled 
without error. 
While the present invention has been particularly shown and described with 
reference to particular embodiments thereof, it will be understood by 
those skilled in the art that various changes in form and details may be 
effected therein without departing from the spirit and scope of the 
invention as defined by the appended claims.