Motor control device for sound motion picture camera

In a sound motion picture camera of the type adapted for selective use of a sound magazine and a silent magazine and having separate drives for intermittent advancement and constant-speed transport of the film respectively on an exposure station and a sound recording station, the speed of rotation of a motor for the intermittent film drive is adjusted in accordance with the preselected value of picture frame speed when the used magazine is of the silent type, and varied as taking either of two discrete values faster and slower than the normal picture frame speed, depending upon whether a slack loop of the film formed between the exposure station and the sound recording station is decreased or increased from the predetermined length thereof, when the used magazine is of the sound type.

BACKGROUND OF THE INVENTION 
In the sound motion picture camera for use with a cartridge type sound 
magazine there are provided a film motor for driving film and the like and 
a capstan motor for continuously driving the film at a constant speed past 
a sound recording station in combination with a drive control circuit for 
actuation, release and rotation of these motors. The film motor drives 
mechanisms for film winding up, rotation of a shutter disc and 
intermittent advancement of the film frame-by-frame, while the capstan 
motor is used to continuously rotate a capstan, pinch roller and the like 
by which a sound track on the film is passed at a constant speed in 
contact with a sound recording head in the sound recording position of the 
magazine. These motors are actuated and released by manipulation of a 
common switch almost simultaneously. 
In making sound-accompanied picture taking exposure sequences with a sound 
magazine loaded in the camera, as the position of an aperture for taking 
pictures is different from the position of the sound head for sound 
recordings by a separation of a certain number of frames, and the film 
must be advanced intermittently in the picture taking station but 
continuously in the sound recording station, there is need to provide a 
certain amount of slack loop of the film between these stations. 
In the conventional motor control device for the sound motion picture 
camera, the amount of slack loop of the film between the aperture position 
for taking motion picture and the sound recording head contact position 
was adjusted by On-Off control of the motor driving. 
However, as the field of application and the performance of the motion 
picture camera are increased, the motor control device is required to have 
functions such as of selectively controlling the frame speed while still 
maintaining unchanged the amount of slack loop of the film necessary when 
the frame speed is changed, and of operating the camera with either one of 
the sound cartridge and silent cartridge. 
SUMMARY OF THE INVENTION 
An object of the present invention is to control the speed of rotation of 
the motor in response to detection of the amount of slack loop of the film 
and the speed of rotation of the motor so as to maintain the constant 
amount of loop of the film. 
Another object of the present invention is to maintain the constant amount 
of slack loop of the film by controlling the speed of rotation of the film 
motor based on the amount of film transported by the capstan motor. 
Still another object of the present invention is to provide a motor control 
device for a sound motion picture camera capable of accommodation for 
either of a sound cartridge and a silent cartridge. 
A further object of the present invention is to provide a motor control 
device which makes it possible to perform normal sound-accompanied picture 
taking sequences even when the taking of pictures is performed with change 
in frame speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a super 8 sound cartridge as an example of the sound cartridge 
having a pair of side panels 1, an aperture abutment 2 (exposure station) 
a cutout 4 for receiving a sound recording mechanism and a film takeup 
spool 5, A photographic film strip 3 having perforations 3.sub.1 and a 
magnetic track 3.sub.2 is arranged to travel past the exposure aperture 2 
and the sound recording station space 4 to the takeup spool 5. The 
location at which a film spool detecting mechanism is positioned is 
indicated at 6. 
FIG. 2 shows an example of a silent cartridge which lacks a cutout 
corresponding to that of FIG. 1 and of which the housing 7 is shortened in 
the vertical direction as compared with the magazine of FIG. 1 so that no 
mechanical interference between the magazine housing 7 and the sound 
recording mechanism occurs when this silent magazine is used in a sound 
motion picture camera. 
FIG. 3 shows the basic parts of a sound motion picture camera employing one 
form of the present invention in an operative position where the sound 
cartridge of FIG. 1 is rendered effective. In front of the cartridge 1, 
there is shown an objective lens 9 by which a beam of light forming an 
image of a scene to be photographed is projected through the exposure 
aperture 2 onto the film 3. The camera further includes a first motor 21 
for the film 3 with its output shaft fixedly carrying a pulley 22 for an 
endless drive belt 11. Motion of the first motor 21 is transmitted through 
the belt 11 to a pulley 10 fixedly mounted on a common shaft for a rotary 
member 12 of a pull-down claw 13, a drive gear 14 of a shutter blade 15 
and a gear train 16 of a takeup spool 17. The operation of these 
mechanisms is well known in the art, and therefore its explanation is 
omitted. 
A second motor 32 is provided to transport the film 3 past a sound 
recording station where a sound recording head 19 mounted on a vertically 
slidable support 18 is acted on a magnetic track of the film 3, and a 
pinch roller 20 made of rubber urges the film 3 to driving contact against 
a capstan 29 which is connected to the output shaft of the motor 32 
through an endless belt 28 trained between two pulleys 30 and 33 of the 
capstan shaft and the output shaft of the motor 32 respectively, thereby 
the film 3 is transported at a constant speed. A flywheel 31 is fixedly 
mounted on the capstan shaft. 
A film slack loop detecting mechanism includes a resilient arm 24 extending 
transversely of the film path and arranged forwardly of the sound head 19 
to detect a slack loop of the film between the exposure station and the 
sound recording station. The arm 24 is pivoted about a shaft 25 and 
connected to a lever 26 which is biased upwardly by a spring 27 to urge 
the arm 24 toward the lower surface of the film 3 and which extends into 
the path of movement of a movable contact of a switch 23 so that when the 
slack loop is increased to push down the detecting arm 24, the switch 23 
is opened. 
Referring now to FIG. 4, one embodiment of a speed control circuit for a 
sound motion picture camera of the type described according to the 
invention comprises first and second drive circuits for the film motor 21 
and capstan motor 32 respectively, first and second tachometers 
cooperative with the respective motors 21 and 32 for generating A.C. 
signals each of which after rectified to produce a D.C. voltage is applied 
to a voltage divider, and a logic circuit responsive to three switches 36, 
23 and 37 in combination for controlling the output of the one of the two 
voltage dividers on which the speed of rotation of the film motor 21 
depends, while the output of the other voltage divider for the capstan 
motor 32 is dependent upon the switched position of the third switch 36. 
The first drive circuit includes a first transistor 64 having a base 
connected to the output of the voltage divider, having an emitter 
connected to the negative terminal of an electrical power source or 
battery 35 and having a collector connected through a resistor 66 and 
through a main switch 34 to the positive terminal of the battery 35, and a 
second transistor 65 having a base connected to the collector of the first 
transistor 64, having an emitter connected to the negative terminal of the 
battery 35 and having a collector connected to a winding of the film motor 
21 at one end thereof, the opposite end of which is connected to the 
positive bus. The first tacho-generator 62 is coupled to the rotating 
shaft of the motor 21 to generate an A.C. signal which is a function of 
the actual motor speed and which is rectified by a diode 63 to produce a 
D.C. voltage which is applied to a voltage divider comprised of a fixed 
resistor 59 and one of a plurality of resistors 53 to 58 which is selected 
by the logic circuit. Connected between the cathode of the diode 63 and 
the negative bus are a resistor 60 for adjustment of the output of the 
tacho-generator 62 and the first condenser 61 connected in parallel with 
each other. If this tacho-generator 62 is replaced by a D.C. 
tacho-generator, the rectifying diode 63 and the first condenser 61 may be 
omitted. 
The second drive circuit includes a third transistor 76 having a base 
connected to the output of the second voltage divider, having an emitter 
connected to the negative terminal of the battery 35 and having a 
collector connected through a resistor 78 and through the main switch 34 
to the positive terminal of the battery 35, and a fourth transistor 77 
having a base connected to the collector of the third transistor 76, 
having an emitter connected to the negative terminal of the battery 35 and 
having a collector connected to a winding of the capstan motor 32 at one 
end thereof, the opposite end of which is connected to the positive 
terminal of the battery 35 through the switch 34. The second 
tacho-generator 74 is coupled to the rotating shaft of the motor 32 to 
generate an A.C. signal which is rectified by a diode 75 to produce a D.C. 
voltage which is applied to the second voltage divider composed of a fixed 
resistor 71 and the one of resistors 69 and 70 which is selected by the 
third switch 36. The rectifying diode 75 is biased by an adjusting 
resistor 72 and the second condenser 73 connected in parallel with each 
other. If this tacho-generator 74 is replaced by a D.C. tacho-generator, 
the diode 75 and the second condenser 73 may be omitted. 
To selectively connect either one of the resistors 69 and 70 in series with 
the resistor 71, there are provided two transistors 67 and 68 having 
collectors connected to the respective resistors 69 and 70, having 
emitters connected to the negative bus and having bases connected to the 
third switch 36 directly and through a Not circuit 38 respectively. This 
third switch 36 is arranged to be manually operable between a closed 
position for a film speed of 18 frames/sec. and an open position for 24 
frames/sec. 
The logic circuit includes six AND circuits 41 to 46 each having three 
input terminals connected to the respective switches 36, 23 and 27 either 
directly or through respective Not circuits 38, 39 and 40 and having one 
output terminals connected to respective bases of NPN type transistors 47 
to 52 with their emitters connected to the common negative bus and with 
their collectors connected to respective resistors 53 to 58 and therefrom 
connected by way of a common lead to the base of the transistor 64 of the 
drive circuit. 
The operation of the motor control circuit of FIG. 4 is next explained. 
When the main switch 34 is closed, a base current is caused to flow 
through the resistor 66 to the transistor 65, so that the film motor 21 
start to rotate along with the tacho-generator 62. The potential V.sub.A 
at a point A may be expressed as: 
EQU V.sub.A =K.multidot.n 
wherein K is constant; and n is the number of revolutions of the film motor 
21. As the output voltage V.sub.A of the tacho-generator 62 is divided by 
the resistance value R59 of the resistor 59 and a resistance value Rx of 
the selected one of the resistor 53 to 58, this divided voltage V.sub.B 
may be expressed as: 
##EQU1## 
When V.sub.B &gt;0.6 volt, the first transistor 64 is in a conducting state, 
while the second transistor 65 is in a non-conducting state, thereby no 
current is allowed to flow through the winding of the motor 21 with the 
resulting speed of rotation of the motor 21 being decreased with decrease 
in the output voltage V.sub.A of the tacho-generator 62. When V.sub.B &lt;0.6 
volt, the first transistor 64 is rendered non-conducting, while the second 
transistor 65 is rendered conducting to energize the motor 21. As the 
speed of rotation of the motor 21 is increased, the output voltage V.sub.A 
of the tacho-generator 62 is increased with increase in the divided 
voltage V.sub.B. Upon attainment to stabilization of the motor speed 
control, the divided voltage V.sub.B is maintained at about 0.6 volt. 
Therefore, the number of revolutions of the film motor 21 is adjusted to a 
value defined by the following formula: 
##EQU2## 
Thus, it is possible to vary the adjusted number of revolutions of the 
film motor 21 by varying the resistance value Rx with selection of any one 
of the resistors R53 to R58. 
The speed control of the capstan motor 32 for constant-speed film drive can 
be performed in synchronism with that of the film motor 21 provided that 
the design parameters of the first and second drive circuits are identical 
to each other. In this connection, it is to be noted that the resistors 69 
and 70 correspond to the resistors 54 and 57. 
When the frame speed selector switch 36 is closed, the transistor 67 is 
rendered conducting with the resulting frame speed being 18 frames/sec. 
Upon opening of the switch 36, a high level voltage signal is produced 
from the Not circuit 38, causing conduction of the transistor 68 with the 
resulting frame speed being 24 frames/sec. 
The six AND gates 41 to 46 are selectively gated on to render one of the 
six transistors 47 to 52 conducting depending upon the corresponding one 
of the combinations of the switched positions of the first or film slack 
loop detecting switch 23, the second or magazine type detecting switch 37 
and the third or frame speed selecting switch 36 as summarized in Table 1 
below: 
Table 1 
__________________________________________________________________________ 
SW36 SW23 SW37 47 48 49 50 51 52 67 68 
__________________________________________________________________________ 
OFF OFF ON -- -- -- -- -- ON -- ON 
OFF ON OFF -- -- -- -- ON -- -- ON 
OFF ON ON -- -- -- ON -- -- -- ON 
ON OFF ON -- -- ON -- -- -- ON -- 
ON ON OFF -- ON -- -- -- -- ON -- 
ON ON ON ON -- -- -- -- -- ON -- 
__________________________________________________________________________ 
Note: Symbol, --, represents the open position or non-conducting state. 
The predetermined speed of rotation of the film motor 21 depends upon the 
combination of the switched positions of the first, second and third 
switches with selection of one of the resistors 53 to 58 as summarized in 
Table 2 below. 
Table 2 
______________________________________ 
SW36 SW23 SW37 Speed of Motor 21 
______________________________________ 
OFF OFF ON 26 frames/sec. 
OFF ON OFF 24 
OFF ON ON 22 
ON OFF ON 20 
ON ON OFF 18 
ON ON ON 16 
______________________________________ 
When a silent cartridge is loaded into a cartridge receiving chamber within 
the camera housing not shown, the second switch 37 is automatically 
opened, while the first switch 23 is permitted to remain in the closed 
position. Further when the frame speed switch 36 is opened, the AND 
circuit 45 is gated on and the transistor 51 is actuated for conduction 
with selection of the resistor 57 so that the film motor 21 is driven for 
rotation at a speed corresponding to a frame speed of 24 frames/sec. 
With the silent cartridge loaded, when the frame speed switch 36 is closed, 
the AND circuit 42 is acted on instead of the AND circuit 45, and the 
transistor 48 is rendered conducting, while the transistor 51 is rendered 
non-conducting, so that the resistor 54 is selected instead of the 
resistor 57, causing the speed of the film motor 21 to take on a value 
corresponding to 18 frames/sec. 
When a sound cartridge is loaded into the chamber, and when the frame speed 
switch 36 is opened to select 24 frames/sec., the transistor 68 is 
rendered conducting to select the resistor 70 for cooperation with the 
second drive circuit for the capstan motor 32. When the actual length of a 
slack loop of the film as detected by the detecting arm 24 of FIG. 3 is 
shorter than the predetermined length, the first switch 23 is in the 
closed position. As a result, the AND circuit 46 is gated on, and the 
transistor 52 is rendered conducting so that the speed of the film motor 
21 is adjusted to 26 frames/sec. This faster speed of the film motor 21 
than that of the capstan motor 32 leads to increases in the length of the 
slack loop of the film. When the actual length of the film slack loop has 
reached the predetermined length, the first switch 23 is opened, thereby 
the AND circuit 44 is acted on and the transistor 50 is rendered 
conducting to select the resistor 56 by which the speed of the film motor 
21 is adjusted to 22 frames/sec. In a short time interval, the actual 
length of the film slack loop falls below the predetermined length with 
simultaneous occurrence of closure of the first switch 23. 
With the sound cartridge loaded, when the frame speed switch is set to the 
position for 18 frames/sec., the transistor 67 is rendered conducting to 
select the resistor 69 by which the speed of the capstan motor 32 is 
adjusted to 18 frames/sec. When the actual length of the film slack loop 
in the cutout 4 for the sounding recording station is shorter than the 
predetermined length, the first switch 23 is closed, thereby the AND 
circuit 43 is acted on and the transistor 49 is rendered conducting to 
select the resistor 55 by which the speed of the film motor 21 is adjusted 
to 20 frames/sec. 
As the length of the film slack loop is increased to the predetermined 
length, the first switch 23 is opened, thereby the AND circuit 41 is acted 
on and the transistor 47 is rendered conducting to select the resistor 53 
by which the speed of the film motor 21 is adjusted to 16 frames/sec. 
It will be seen from the foregoing that the present invention provides a 
motor control device capable of selective speed control of intermittent 
and constant-speed film drives between common two frame speeds of 18 and 
24 frames/sec. by the frame speed selecting switch 36 and further capable 
of varying the speed of rotation of a separate motor for the intermittent 
film drive in accordance with the output of the logic circuit depending 
upon the particular combination of the switched positions of the frame 
speed selecting switch 36, the cartridge type responsive switch 37 and the 
film slack loop responsive switch 23. This is done while still maintaining 
the speed of the capstan motor at the constant normal level. Thus, it is 
possible to achieve accurate control of sound-accompanied motion picture 
taking operation at any one of two available frame speeds.