Operating mode switching mechanism for a tape recorder

An operating mode switching mechanism for a tape recorder for effecting various operations in response to operation of manually operating keys comprises a single solenoid for causing a rotary wheel to start rotating so that various operations are selectively performed depending on the duration for which the solenoid is energized by moving a carrier plate carrying thereon an electromagnetic transducer head, between first and second positions. The rotational angle of the rotary wheel is detected by a photo sensing means, and the detected angle will be used in an electrical circuit in which three different pulses for energizing the solenoid are selectively produced in accordance with the selected operating key and the detected rotational angle of the rotary wheel. Energization interval of the solenoid is, thus synchronized with the rotation of the solenoid thereby providing accurate operating mode switching operations.

FIELD OF THE INVENTION 
This invention generally relates to tape recording and reproducing 
apparatus, and more particularly, the present invention relates to an 
operating mode switching mechanism for tape recorders, which mechanism is 
arranged to operate by energizing a single solenoid. 
BACKGROUND OF THE INVENTION 
Electrically operated mode switching mechanisms are often used in tape 
recorders in place of conventional mechanically controlled mode switching 
mechanisms. Since a mode switching mechanism of the electrically operated 
type permits selection of a desired mode in response to a featherly touch 
on the associated key or button, it has gained wide popularity among 
users. However, the conventional electrically operated mode switching 
mechanism employs a plurality of solenoids which are associated with 
different operating keys. This requires a substantial amount of power for 
operating various mechanical elements particularly because the circuitry 
is designed so that the solenoids remain energized during the time the 
recorder is being operated. Although this continuous power operation may 
find use in applications where the power is supplied from an external A.C. 
source, application to battery powered portable tape recorders is not 
possible due to its power consumption. Furthermore, the use of a plurality 
of solenoids results in a relatively large size and a high manufacturing 
cost. 
The inventor of the present invention divised, prior to the present 
invention, a pulse-operated mode switching mechanism for tape recorders 
and filed patent applications Ser. No. 54-38006 in Japan, 134,990 in the 
United States, now U.S. Pat. No. 4,336,560, 8010392 in United Kingdom, and 
P 3012196.1 in West Germany. According to the technique of the prior 
applications by the present inventor, a pulse operated mode switching 
mechanism for tape recorders comprises a single solenoid which is operated 
in response to a pusle of different periods depending on the function of 
the operating key. A rotary control wheel is driven by a motor to provide 
a 360 degree revolution in response to the energization of the solenoid. 
Electromagnetic transducer head(s) and an erase head are mounted on a 
carrier plate which is movable between a first position in which the heads 
are remote from the magnetic tape and a second position in which the tape 
is in cotact with the heads. A pinch roller or idler is arranged to be 
biased toward the capstan to drive the tape when the carrier plate assumes 
the first position. The carrier plate is moved from the first to second 
position by the rotation of the rotary control wheel when the solenoid is 
energized for an interval greater than a first predetermined interval so 
that playback or recording is performed. Energization of the solenoid for 
an interval smaller than a second predetermined interval, which is smaller 
than the first predetermined interval, during playback or recording mode 
causes the carrier plate to return to the first position so that movement 
of the tape terminates to assume stop mode. On the other hand, when the 
solenoid is energized for an interval greater than the second interval but 
smaller than the first interval, the carrier plate is arranged to be 
locked at an intermediate position between the first and second positions 
causing the idler to be remote from the capstan, resulting in pause 
operation. Namely, in accordance with the technique of the prior invention 
of the present inventor, the position of the carrier plate is controlled 
by the rotation of the control wheel in response to the operation of the 
solenoid, where the duration of the pulse applied to the solenoid 
determines the mode to be assumed. To this end one of three pulses having 
different intervals is selected in accordance with a selected key, such as 
playback key, record key, stop key, fast forward key, rewind key, and 
pause key. The three different intervals are all predetermined so that 
desired operations are respectively performed. 
However, the above-described pulse-operated mode switching mechanism has 
suffered from the following disadvantages and drawbacks. Namely, timing 
error between the operation of the solenoid and the control wheel is apt 
to occur because of the variations in the predetermined intervals, and 
because of variations in the rotational speed of the control wheel. In 
detail, each of the predetermined intervals is defined by a time constant 
circuit having resistor(s) and capacitor(s), and it is difficult to obtain 
a uniform time constant throughout a number of cirucits because of 
variations in resistances and capacitances. In addition, when a D.C. motor 
is used for driving the control wheel, the rotational speed of the control 
wheel is apt to vary as the amount of load varies. The above-mentioned 
timing error corresponds to the product of the error of the predetermined 
interval and the error of the rotational speed of the control wheel. 
The timing error between the operating period of the solenoid and 
rotational angle of the control wheel results in malfunction of the 
operating mode switching mechanism, and in the worst case, changeover 
between operating modes cannot be performed. 
SUMMARY OF THE INVENTION 
The present invention has been developed in the order to remove the 
disadvantages and drawbacks inherent to the above-mentioned pulse-operated 
mode switching mechanism for tape recorders. 
It is, therefore, an object of the present invention to provide an 
operating mode switching mechanism for a tape recorder which mechanism is 
capable of performing accurately mode switching operations irrespectively 
of the variations in energizing intervals of a single solenoid and of the 
variations in the rotational speed of a rotary control wheel, which 
controls the position of the carrier plate carrying the magnetic heads, in 
response to the operation of the solenoid. 
A feature of the present invention is to employ an arrangement that the 
single solenoid is energized for one of three different intervals which 
are respectively defined by the rotational angle of the control wheel 
which is driven by a motor to move the carrier plate between two 
positions. 
In accordance with the present invention there is provided an operating 
mode switching mechanism for a tape recorder having a movable carrier 
member carrying thereon an electromagnetic transducer and movable between 
first and second positions, a tape driving mechanism arranged to drive a 
magnetic tape at a constant speed when said carrier member assumes said 
second position, a plurality of manually operating keys for effecting 
various oeprations, and a motor, comprising: (a) a single solenoid 
arranged to be energized by pulses applied thereto in response to the 
operation of said operating keys; (b) a rotary wheel; (c) means for 
locking said rotary wheel at a predetermined angular position and for 
unlocking the same in response to the energization of said solenoid; (d) 
means for rotating said rotary wheel after unlocked so that said rotary 
wheel provides a 360 degree revolution from said predetermined angular 
position; (e) means responsive to the rotation of said roatry wheel for 
causing said carrier member to move from said first position to said 
second position against a biasing force only when said solenoid is being 
energized until said rotary wheel is rotated by a first predetermined 
angle; (f) means responsive to the rotation of said rotary wheel for 
locking said carreir member in an intermediate position between said first 
and second positions only when said solenoid is being energized during the 
time said carrier member assumes said second position until said rotary 
wheel is rotated by a second predetermined angle which is smaller than 
said first predetermined angle; (g) means responsive to the rotation of 
said rotary wheel for causing said carrier member to move from said second 
position to said first position when said solenoid is being energized 
until said rotary wheel is rotated by a third predetermined angle which is 
smaller than said second predetermined angle; (h) means for detecting the 
rotational angle of said rotary member; and (i) means responsive to the 
detected angle of said rotary wheel for deenergizing said solenoid when 
said rotary wheel is rotated by one of said first to third predetermined 
angles, which has been selected in accordance with said selected operating 
key.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is made to FIG. 1 which shows a schematic top plan view of a tape 
recorder to which an embodiment of the present invention is adapted. The 
operating mode switching mechanism for a tape recorder according to the 
present invention generally comprises a mechanical control portion shown 
in FIG. 1 and an electrical control portion shown in FIG. 6 which will be 
described hereinlater. The tape recorder is arragned to switch or change 
its operating modes, such as playback, stop, fast forward etc. by 
manipulating a selected key or button which is normally-open electrical 
switch. 
In FIG. 1, a pay off or supply reel wheel 35 and a take up reel wheel 36 
are shown, and these wheels 35 and 36 are respectively arranged to be 
driven by an unshown motor. A numeral 1 is a flywheel; 2, a capstan 
equipped with the flywheel; 3, a flywheel gear coaxially connected to the 
capstan 2, and these members 1 to 3 are rotatably supported on an unshown 
chassis where the flywheel 1 is driven via a belt 5, which is partially 
wrapped around the flywheel 1, by means of a motor 4. A rotary control 
wheel 6 has a toothed portion along the periphery thereof except for a 
portion, which is referred to as a nontoothed portion 18. The toothed 
portion of the control wheel 6 is arranged to be engaged with the flywheel 
gear 3. Since the diameter of the control wheel 6 is much greater than 
that of the flywheel gerar 3, the control wheel 6 is driven at a reduced 
speed. The control wheel 6 will be rotated by the flywheel gear 3 only 
when the toothed portion thereof is engaged with the flywheel gear 3 so 
that mode switching operation is performed as will be described later 
using a driving force from the control wheel 6. The control wheel 6 may be 
called, therefore, a dirve gear. The control wheel 6 is rotatably mounted 
on the chassis, and is normally prevented from rotating by a stop lever 16 
as will be described later. A slide bar 7 is slidably mounted on the 
chassis, and is movable in the directions A and B indicated by arrows. The 
slide bar 7 is biased toward the direction A by a force of a return spring 
8 which is interposed between the slide bar 7 and the chassis. The slide 
bar 7 has a rotary member or pin 30 which projects from the rear surface 
thereof. The rotary member 30 is positioned so that it comes into contact 
with the periphery of a cam 9 connected to or integrally formed with the 
control wheel 6. Although the rotary member 30 is shown to be remote from 
the cam 9 in FIG. 1, when the slide bar 7 is moved to the direction A, the 
rotary member 30 abuts against the cam 9, and thus the slide bar 7 will 
move in the direction B against the force of the return spring 8 as the 
cam 9 rotates clockwise together with the control wheel 6. 
A carrier plate 10 is slidably mounted on the chassis to move in the 
direcitions X and Y indicated by arrows. The carrier plate 10 carries 
magnetic transducer head(s), such as record/reproduce head, and an erase 
haed, which are not shown for simplicity. A pinch roller or idler which is 
also not shown, is arranged to be pressed toward the capstan 2 when the 
carrier plate 10 is moved in the direction Y. The position of the carrier 
plate 10 shown in FIG. 1 is referred to as a first position and the 
position of hte same of FIG. 4 is referred to as a second position. 
Namely, the first position of FIG. 1 is a stop/fast forward/rewind 
position, while the second posiiton of FIG. 4 is a playback/record 
position. With the carreir plate 10 at the first position, the magnetic 
heads are remote from the tape, while the idler is spaced from the capstan 
2. On the other hand, when the carrier plate 10 is at the second position, 
the magnetic heads are in contact with the tape and the tape is engaged 
between the capstan 2 and the idler so that the tape is driven at a 
constant playback or recording speed. 
The above-mentioned carrier plate 10 is moved by the rotational movement of 
a bell crank 11 pivoted at a point 11b. In detail, the bell crank 11 has, 
at one end, a projection or pin 11a which is received in a through-hole 
made in the carrier plate 10. The carrier plate 10 is biased in the 
direction X to normally assume the first position by a force of a return 
spring 33 which is connected to the chassis. The bell crank 11 can be 
rotated by the movement of the slide bar 7 against the spring 33 connected 
to the carrier plate 10 as will be described later so that the carrier 
plate 10 moves between the first and second positions in the directions X 
and Y. 
An arm 12 is rotatably moutned on the slide bar 7, and has a left end 12b 
arranged to be pulled by a plunger 23a of a solenoid 23 so that the arm 12 
rotates clockwise. The right end 12a of the arm 12 is arranged to be 
engaged with the bell crank 11 to rotate the same counterclockwise as the 
slide bar 7 moves in the direction B as will be described later. The 
structure of the arm 12 is partially shown in FIG. 1 for simplicity. 
Furthermore, although the arm 12 is shown to be a single member in FIG. 1, 
it actually comprises an arm body 12c and a lost motion member 12d as 
shown in FIG. 2. 
FIG. 2 is an enlarged perspective view showing the relationship between the 
arm 12 and the bell crank 11. The arm body 12c and the lost motion member 
24 are coaxially mounted on the slide bar 7 of FIG. 1. The arm body 12c is 
biased in the counterclockwise direction by means of a return spring 31 
which is connected to the slide bar 7 at its one end, while the lost 
motion member 12d is biased in the clockwise direction by means of a 
spring 12f connected between the lost motion member 12d and the arm body 
12c. The arm body 12c has a projection 12g which is arranged to rotated 
the lost motion member 12d counterclockwise when the arm body 12c rotates 
counterclockwise. The lost motion member has a tip portion which 
corresponds to the above-mentioned right end 12a of the arm 12. When the 
arm body 12c rotates clockwise, the lost motion member 12d also rotates 
clockwise by the spring 12f if the lost motion member 12d is not prevented 
from rotating by the bell crank 11. Namely, when the lost motion member 
12d is prevented from rotating as will be described later, only the arm 
body 12c can be rotated in the clockwise direction. 
The bell crank 11 has a deep recess 11c and a contact portion 11d which is 
semispherically recessed. When the slide bar 7 moves to the right with the 
arm 12 rotated counterclockwise by the spring 31, a portion of the lost 
motion member 12d including the tip portion 12a is received in the deep 
recess 11c of the bell crank 11, as shown in FIG. 1, so that rightward 
movement of the slide bar 7 does not cause the bell crank 11 to rotate 
counterclockwise. On the contrary, when the slide bar 7 moves to the right 
with the arm 12 rotated clockwise by the plunger 23a of the solenoid 22, 
the tip portion 12a of the lost motion member abuts against the 
semispherically recessed portion 11d as known in FIG. 2. Namely, as the 
slide bar 7 moves rightwards, the tip portion 12a is engaged with the 
semispherically recessed portion 11d so that the rightward movement of the 
slide bar 7 causes the bell crank 11 to rotate counterclockwise. 
As described in the above, the slide bar 7 is movable between two positions 
in the directions A and B, and when the slide bar 7 moves to the left to 
assume its left most position, the tip portion 12a of the lost motion 
member 12d will be spaced from the bell crank 11. 
Turning back to FIG. 1, a kick arm 13 is pivotally supported on the 
chassis, and has a portion abutting against a recessed portion 14 of the 
control wheel 6. The kick arm 13 is biased by means of a spring 15 so that 
the kick arm 13 tends to rotate clockwise applying a clockwise force to 
the control wheel 6. The control wheel 6 has an annular wall (not shown 
for simplicity) along the circumpherence on the upper surface thereof, and 
the recessed portion 14 is made at a portion of the annular wall. The kick 
arm 13 is arranged to be normally received in the recessed portion 14, and 
slides along the outer surface of the annular wall as the control wheel 6 
rotates. 
Since the lower or right end 16a of the stop lever 16 abuts against a lug 
17 which projects from the annular wall of the control wheel 6, the 
control wheel 6 is prevented from rotating. With the control wheel 6 in 
this position, the flywheel gear 3 faces the nontoothed portion 18 of the 
control wheel 6 so that driving force from the flywheel gear 3 is not 
applied to the control wheel 6 keeping the same stationary. 
A lock lever 19 is pivotally mounted on the chassis, and is biased 
counterclockwise by the spring 15 which is connected to the 
above-mentioned kick lever 13 at one end thereof. The lock lever 19 has a 
right end 19b arranged to be engaged with a stepped portion 7a of the 
slide bar 7, and a left end 19a arranged to be kicked by a lug 20 provided 
on the upper surface of the control wheel 6. Namely, the lock lever 19 
locks the slide bar 7 at its right-most position as shown in FIG. 1 
because the lock lever 19 is biased by the spring 15 counterclockwise. As 
will be described later, when the control wheel 6 rotates clockwise, the 
lug 20 comes into contact with the left end 19a of the lock lever 19 to 
kick the same causing the lock lever 19 to rotate clockwise, and thus the 
right end 19b of the lock lever 19 will be disengaged from the stepped 
portion 7a of the slide bar 7. As a result, the locking of the slide bar 7 
is cancelled so that the slide bar 7 moves to the left, i.e. in the 
direction A, by the force of the return spring 8. 
A latch lever 21 and a latch-release lever 22 are rotatably supported on 
the chassis coaxially with the stop lever 16. A spring 32 is connected 
between the stop lever 16 and the latch-release lever 22 so that the 
latch-release lever 22 is biased clockwise with respect to the stop lever 
16. The latch-release lever 22 has a pin engaged with a slot made in the 
latch lever 21 which is biased counterclockwise by a spring (not shown). 
The latch lever 21 has a rotary pin 21a at its tip portion which can be 
engaged with a stepped portion 34 of the carrier plate 10. The latch lever 
21 will hold the carrier plate 10 at an intermediate position between the 
first and second positions so that the tape recorder assumes pause mode as 
will be described later. Unless the stop lever 16 is in clockwise rotated 
position, the latch-release lever 22 is arranged to be kicked by the lug 
20 of the control wheel 6 as the control wheel 6 rotates to cause the 
latch lever 21 to rotate counterclockwise so that the rotary pin 21a of 
the latch lever 21 is remote from the stepped portion 34 of the carrier 
plate 10. 
The above-mentioned stop lever 16 which prevents the control wheel 6 from 
rotating clockwise, is rotatably supported on the chassis coaxially with 
the latch lever 21 and the latch-release lever 22, and is biased 
counterclockwise by a spring 29. The stop lever 16 has a left end arranged 
to be engaged with the plunger 23a of the solenoid 23, and the 
above-mentioned right end 16a arranged to come into contact with the lug 
17 of the control wheel 6. While the solenoid 23 is being deenergized, the 
stop lever 16 assumes the position illustrated in FIG. 1, abutting against 
the lug 17 to prevent the control wheel 6 from rotating clockwise agaisnt 
the force of the spring 15, which force is applied via the kick arm 13. 
The solenoid 23 is mounted on the chassis and is arranged to be energized 
in response to a pulse applied thereto. As the solenoid 23 is energized, 
the plunger 23a thereof is attracted toward the solenoid body to rotate 
both the stop lever 16 and the arm 12 clockwise. As the stop lever 16 
rotates clockwise, the latch-release lever 22 is pulled by the spring 32 
to rotate clockwise. The latch lever 21 is also pulled by the 
latch-release lever, thus the pin 21a of the latch lever 21 rotates 
clockwise. As soon as the stop lever 16 starts rotating clockwise, the 
right end 16a is disengaged from the lug 17 of the control wheel 6, and 
thus the control wheel 6 is kicked by the kick arm 13 to rotate a given 
angle. The toothed portion of the control wheel 6 thus engages with the 
flywheel gear 3 to receive a continuous rotational force from the motor 4 
via the flywheel 1. As a result, the control wheel 6 rotates fully once 
until the nontoothed portion 18 again faces the flywheel gear 3. 
Reference is now made to FIG. 3 which is a bottom plan view of the control 
wheel 6. The control wheel 6 has a light-receiving disk 24 with 
light-reflecting portion 25, and a plurality of light-absorbing or 
non-reflecting portions 26.sub.1 to 26.sub.3. The light-receiving disk 24 
is attached to the lower surface of the control wheel 6. The reflecting 
portion 25 is metallic lustered, while the nonreflecting portions 26.sub.1 
to 26.sub.3 are black. A light-emitting diode 27, which functions as a 
light source, and a photo transistor 28, which functions as a detector, 
are respectively disposed on the chassis so as to face the light-receiving 
disk 24. A light beam emitted from the light-emitting diode 27 will be 
reflected at the reflecting portion 25 of the disk 24, and thus the 
reflected beam will be received by the photo transistor 28. The 
combination of the light-emitting diode 27, the light-receiving disk 24 
and the photo transistor 28 is used for detecting the rotational angle of 
the control wheel 6 as will be described later. 
Referring to FIG. 6, which shows a schematic block diagram of the 
electrical circuit which is a part of the operating mode switching 
mechanism according to the present invention, the above-mentioned 
light-emitting diode 27 is supplied with power via an unshown switch to 
emit light. The light beam emitted from the diode 27 is then reflected at 
the disk 24 of the control wheel 6 so as to be received by the photo 
transistor 28. The output signal of the photo transistor 28 is supplied to 
a waveform shaping circuit 40 in which a pulse is generated as each of the 
nonreflecting portions 26.sub.1 to 26.sub.3 passes through the light beam 
from the light-emitting diode 27. Namely, the number of pulses emitted 
from the shaping circuit 40 during the full turn of the control wheel 6 is 
one of 1, 2 and 3 depending on the rotational angle thereof. A counter 42 
is responsive to the output pulse or pulses from the waveform shaping 
circuit 40 to count the number thereof, and has three output terminals 
42a, 42b and 42c. When a first pulse is detected, the logic level at the 
first output terminal 42a turns to logic "1". In the same manner, as the 
second and third pulses are detected, the logic levels at the second and 
third output terminals 42b and 42c respectively turn to logic "1". The 
three output terminals of the counter 42 are respectively connected to 
input terminals of three AND gates 66, 68 and 70. 
On the other hand, six push-button types normally-open keys or switches 44, 
46, 48, 50, 52 and 54 are provided, where one terminal of each of the keys 
44 to 54 is connected to a power supply +Vcc. These keys 44 to 54 are used 
to select a desired operating mode of the tape recorder, and are 
respectively named stop key, first forward (EF) key, rewind(REW) key, 
pause key, playback(PB) key, and record(REC) key. The other terminal of 
each of the keys 44 and 54 is connected to an unshown circuit which 
controls the operation of the motor 4, the aformentioned another motor for 
driving the take up and pay off reel wheels 36 and 35, and the 
recording/reproducing amplifier or the like. The stop key 44, fast forward 
key 46 and the rewind key 48 are respectively connected to input terminals 
of an OR gate 56, while the playback key 52 and record key 54 are 
respectively connected input terminals of another OR gate 58. The output 
terminals of the OR gate 56 and 58 are respectively connected to set input 
terminals S of first and third flip-flops 60 and 64, while the pause key 
50 is directly connected to a set input terminal S of a second flip-flop 
62. The output terminals of the flip-flop 60 to 64 are respectively 
connected to the other input terminal of the respective AND gates 66 to 
70, and are further connected respectively to input terminals of an OR 
gate 72. The output terminals of the AND gates 66 to 70 are connected to 
input terminals of an OR gate 74 whose output terminal is connected to a 
reset terminal R of a flip-flop 76, and to reset terminals R of the 
flip-flops 60 to 64. The output terminal of the OR gate 72 is connected to 
a set terminal of the flip-flop 76 whose output terminals is connected to 
a drive circuit 78 arranged to drive the solenoid 23. 
The circuit of FIG. 6 operates as follows. Assuming that the tape recorder 
is first in a playback mode, and now a stop key 44 is depressed, a logic 
"1" signal is applied via the OR gate 56 to the set terminal S of the 
flip-flop 60. Thus the flip-flop 60 produces a logic "1" output signal, 
which is applied via the OR gate 72 to the set terminal S of the flip-flop 
76. Accordingly, the flip-flop 76 produces a logic "1" output signal to 
trigger the drive circuit 78. With this operation, the solenoid 23 is 
energized to rotate the stop lever 16 clockwise. Accordingly, the control 
wheel 6 starts rotating clockwise. When the control wheel 6 is stationary 
as shown in FIG. 1 and FIG. 3, the light-emitting diode 27 and the photo 
transistor 28 both face the nonreflecting portion 26.sub.1. Therefore, the 
output signal level of the photo transistor 28 is kept low before the 
control wheel 6 starts rotating. As the control wheel 6 has rotated a 
given angle corresponding to the arc of the nonreflecting portion 
26.sub.1, and as soon as the reflecting portion 25 faces the 
light-emitting diode 27 and the photo transistor 28, the output signal 
level of the photo transistor 28 turns high. Thus a single pulse is 
applied to the counter 42 causing a logic "1" signal to be applied to the 
AND gate 66 from the first output terminal 42a. The AND gate 66 is thus 
enabled to transmit a logic "1" signal via the OR gate 74 to the reset 
terminal R of the flip-flop 76. The flip-flop 76 as well as the flip-flop 
60 is reset to produce a logic "0" output signal. The drive circuit 78 
deenergizes the solenoid 23 in response to the logic "0" signal from the 
flip-flop 76. 
From the above, it will be understood that the solenoid 23 is energized for 
an interval defined by the duration of logic "1" or on-state of the 
flip-flop 76. Namely, the solenoid 23 is energized immediately after the 
stop key 44 is manipulated, and is deenergized when the control wheel 6 
has rotated a predetermined angle. When the fast forward key 46 or the 
rewind key 48 is manipulated, the exact the same operation as described in 
the above will be performed. In the same manner, if one of the remaining 
keys 46 to 54 is manipulated, the solenoid 23 is immediately energized to 
cause the rotary control wheel 6 to start rotating. However, the solenoid 
23 will be continuously energized until a second pulse from the shaping 
circuit 40 is applied to the counter 42 in the case of the pause key 50, 
and until a third pulse is applied to the same in the case of the playback 
key 52 or record key 54. In other words, the solenoid 23 is deenergized 
when the second nonreflecting portion 26.sub.2 of the control wheel 6 has 
passed through the light beam after the pause key 50 is operated. In the 
case of the playback key 52 or record key 54, the solenoid 23 is 
deenergized when the third nonreflecting portion 26.sub.3 has passed 
through the light beam. 
Summarizing the operation of the circuit of FIG. 6, the solenoid 23 is 
energized as soon as of the keys 44 to 54 is manipulated to cause the 
control wheel 6 to start rotating. If the manipulated key is one of the 
stop key 44, fast forward key 46 and rewind key 46, the solenoid 23 is 
deenergized when the control wheel 6 has rotated a first predetermined 
angle. If the manipulated key is the pause key 50, the solenoid 23 is 
deenergized when the control wheel 6 has rotated a second predetermined 
angle which is greater than the first predetermined angle. Furthermore, if 
the manipulated key is the playback key 52 or record key 54, the solenoid 
23 is deenergized when the control wheel 6 has rotated a third 
predetermined angle which is greater than the second predetermined angle. 
FIG. 7 is a timing chart showing the output pulses of the waveform shaping 
circuit 40 of FIG. 6 and respective intervals for which the solenoid 23 is 
being energized depending on the selected key. The output signal of the 
shaping circuit 40 assumes a low level L when the light-emitting diode 27 
and the photo transistor 28 of FIGS. 3 and 6 face the nonreflecting 
portion 26.sub.1, 26.sub.2, or 26.sub.3 and assumes a high level H when 
facing the reflecting portion 25. Solenoid energizing intervals are 
respectively represented by three lines 80, 82 and 84. In detail, for 
setting the tape recorder in stop, fast forward or rewind mode the 
solenoid 23 is energized for a short period of time, such as 0.1 second; 
for setting in pause mode, for an intermediate period of time, such as 
0.25 second; and for setting in playback or record mode, for a long period 
of time, such as 0.4 second. The above values of respective intervals, 
however, are variable in accordance with the rotational speed of the 
control wheel 6 and the pattern of the light-receiving disk 24. 
The mechanical operation of the operating mode switching mechanism will be 
described with reference to FIGS. 4 and 5. FIG. 4 shows the tape recorder 
which is in playback mode. Let us assume that the playback key 52 of FIG. 
6 is manipulated when the tape recorder is in stop mode shown in FIG. 1. 
The solenoid 23 is immediately energized as described in the above causing 
the stop lever 16 to rotate clockwise against the return spring 29 so that 
the right or lower end 16a of the stop lever 16 disengages from the lug 17 
provided on the upper surface of the control wheel 6. Accordingly, the 
control wheel is rotated clockwise by the kick arm 13, and subsequently, 
it rotates because of the rotational force applied from the flywheel gear 
3. As the control wheel 6 rotates, the lug 20 on the upper surface of the 
control wheel 6 kicks the left end 19a of the lock lever 19 to rotate the 
same clockwise. As a result, the right end 19b of the lock lever 19 is 
disengaged from the stepped portion 7a of the slide bar 7 so that the 
slide bar 7 returns in the direction A by the force of the return spring 
8. When the slide bar 7 reaches its left-most position, the pin 30 of the 
slide bar 7 is in contact with the cam 9 of the control wheel 6. As the 
control wheel 6 keeps rotating, the pin 30 is depressed rightwards by the 
periphery of the cam 9. Namely, the slide bar 7 is moved to the right, 
i.e. in the direction B. After the slide bar 7 is moved to the right-most 
position of FIG. 3, the slide bar 7 is again locked by the lock lever 19. 
On the other hand, turning back to the point of energization of the 
solenoid 23, the arm body 12c of the arm 12 is rotated clockwise by the 
plunger 23a of the solenoid 23 (see FIG. 2). At this time, the tip portion 
12a of the lost motion member 12d is received in the deep recess 11c of 
the bell crank 11, and therefore, the lost motion member 12d does not 
rotate. However, when the slide bar 7 assumes its left-most position as 
described in the above, the tip portion 12a of the lost motion member 12d 
leaves from the recess 11c. As soon as the tip portion 12a gets out of the 
recess 11c, the lost motion member 12d rotates clockwise by the spring 12f 
to assume the position of FIG. 2. As the slide bar 7 moves rightwards by 
the rotation of the cam 9, the tip portion 12a comes into contact with the 
semispherical recess 11d of the bell crank 11. The slide bar 7 further 
moves rightwards so that the bell crank 11 is rotated counterclockwise by 
the arm 12 which also moves rightwards. The pin 11a of the bell crank 11 
is engaged with the carrier plate 10 so that the carrier plate 10 slides 
in the direction Y as the bell crank 11 rotates counterclockwise. When the 
slide bar 7 has been moved to the right-most position, the carrier plate 
10 assumes the aforementioned second position in which playback or 
recording operation can be performed. 
In the above operation, after the lug 20 kicks the left end 19a of the lock 
lever 19, the same lug 20 also kicks the right end of the latch-release 
lever 22 causing the latch-release lever 22 and therefore the latch lever 
21 to rotate counterclockwise temporarily. After the lug 20 has passed the 
right end of the latch-release lever 22, both the latch lever 21 and the 
latch-release lever 22 rotate clockwise by the force of the spring 32. 
However, the above-described movement of the latch lever 21 and the 
latch-release lever 22 does not affect the movement of the carrier plate 
10 in the direction Y. 
It will be understood from the above, that the solenoid 23 is energized for 
a relatively long period of time, such as 0.4 second, for setting the tape 
recorder in playback or record mode. This interval should be longer than 
an interval in which the tip portion 12a of the lost motion member 12d of 
the arm 12 abuts against the semispherical recess 11d of the bell crank 11 
after the slide bar 7 has started moving rightwards. If the energizing 
interval were shorter than the above-mentioned interval, namely, if the 
solenoid 23 where deenergized before the tip portion 12a comes into 
contact with the semispherical recess 11d, the tip portion 12a would enter 
into the deep recess 11c and thus the bell crank 11 would remain 
stationary. 
Now, let us assume that the stop key 44 is manipulated during playback or 
record mode. The solenoid 23 is energized to rotate the stop lever 16 
clockwise in the same manner as described in the above. The control wheel 
6 starts rotating clockwise so that the lug 20 kicks the lock lever 19, 
and thus the slide bar 7 rapidly returns to the left-most position 
temporarily. With the leftward movement of the slide bar 7, the arm 12 is 
disengaged from the semispherical recess 11d of the bell crank 11, and 
thus the carrier plate 10 returns to the first position in the direction 
of X by the spring 33. After disengaged from the semispherical recess 11d, 
the arm body 12c and the lost motion member 12d of the arm 12 are rotated 
counterclockwise by the spring 31. Therefore, when the slide bar 7 moves 
to the right by the rotation of the cam 9 of the control wheel 6, the tip 
portion 12a of the lost motion member 12d does not engage with the 
semispherical recess 11d but enters into the deep recess 11c. As a result, 
the bell crank 11 and therefore the carrier plate 10 does not move by the 
rightward movement of the slide bar 7. From the above, it will be 
understood that in order to set the tape recorder in stop mode from 
playback or record mode all required is to energize the solenoid 23 for a 
relatively short period of time, such as 0.1 second, so that the right end 
12a of the stop lever 12 disengages from the lug 17 to make the control 
wheel rotate clockwise. 
Let us suppose that it is intended to set the tape recorder in pause mode 
from playback or record mode. The pause key 54 of FIG. 6 is first operated 
to energize the solenoid 23. The solenoid 23 is thus energized for an 
interval which is longer than the above-mentioned short period of time but 
is shorter than the above-mentioned long period of time. In this 
embodiment, the solenoid 23 is energized for an intermediate interval, 
such as 0.25 second. With this operation, the latch-release lever 22 and 
the latch-lever 21 are both held at the clockwise rotated position until 
the left end 19a of the lock lever 19 is kicked by the lug 20 of the 
control wheel 6. Therefore, although the carrier plate 10 tends to return 
to the first position as described in the above, the pin 21a of the latch 
lever 21 is located at such a position that the stepped portion 34 of the 
carrier plate 10 abuts thereagainst. As a result, the carrier plate 10 is 
prevented from returning to the first position on the way thereto. 
Furthermore, the energization of the solenoid 23 is kept so that the 
latch-release lever 22 is evacuated from the locus of the lug 20. 
Therefore, the latch-release lever 22 is not kicked by the lug 20, thus 
pause condition is maintained as illustrated in FIG. 5. On pause mode, the 
carrier plate 10 is at an intermediate position between the first and 
second positions so that the idler is remote from the capstan 2 preventing 
the magnetic tape from running. Other mechanical operation is the same as 
the operation described in connection with the case of setting the tape 
recorder in stop mode. The above-mentioned intermediate interval for 
setting the tape recorder in pause mode substantially corresponds to an 
interval in which the control wheel 6 rotates a given angle, the slide bar 
7 rapidly returns to the left-most position, the carrier plate 10 is held 
by the latch lever 21 on the way to the first position, and the 
latch-release lever 22 is evacuated from the locus of the lug 20. 
In the above-description, it has been described how the tape recorder is 
set in playback or record mode from stop mode, and is set in stop or pause 
mode form playback or record mode. When it is intended to set the tape 
recorder in fast forward mode or rewind mode, the corresponding key 46 or 
48 of FIG. 6 is manipulated. In order to perform fast forward reeling or 
rewinding operation the carrier plate 10 is located at the same position 
as in stop mode. Namely, the solenoid 23 is energized for the short period 
of time to perform fast forward reeling or rewinding operation in the same 
manner as in stop mode, while the one of the reel wheels 35 and 36 is 
rotated at a high speed by means of an unshown separate drive mechanism. 
As described in the above, in the embodiment of the operating mode 
switching mechanism for a tape recorder according to the present 
invention, the solenoid 23 is energized for a relatively long period of 
time for setting the tape recorder in playback or record mode, for an 
intermediate period for setting the same in pause mode, and for a 
relatively short period for stopping the same, or setting in either fast 
forward or rewind mode. Namely, one of three different kinds of pulses is 
selectively applied to the solenoid 23 in accordance with the selected 
key, where the interval of each of the pulses is controlled by detecting 
the rotational angle of the control wheel 6 by using the aforementioned 
light-emittind diode 27, the light-receiving disk 24 and the photo 
transistor 28. With this arrangement, the energization interval of the 
solenoid 23 is synchronized with the rotational angle of the control wheel 
6. Consequently, the aforementioned various disadvantages and drawbacks 
inherent to the technique of the prior application by the inventor are 
removed. 
The above-described embodiment is just an example of the invention, and 
therefore, it will be understood for those skilled in the art that many 
modifications and variations may be made without departing from the spirit 
of the present invention.