Film transfer device used in a camera

A film transfer device of a camera, which consists of a charging means for controlling one frame transfer of a film. The charging means is engaged with a winding part and a rewind spindle RS. A sprocket is designed to rotate independently from the winding part and the rewind spindle RS. A second clutch means is provided to compensate for the speed difference between the sprocket and the winding part on film winding or between the sprocket and the rewind spindle on film rewinding.

BACKGROUND OF THE INVENTION 
The present invention concerns a camera, and more particularly a film 
transfer device used in a camera. 
Generally, there are two kinds of cameras, of which one is manually 
operated for loading a film on a take-up spool, and the other 
automatically operated by means of a drive means such as a motor. 
Referring to FIG. 8, the drive means includes a motor 50, a planetary gear 
part 51 connected to the motor, a winding part 52 engaged with the 
planetary gear part 51, a charging part 53 intermittently engaged with the 
planetary gear part 51, and a rewind part 54 intermittently engaged with 
the planetary part 51. 
The film is wound one by frame (interval) at a time according to the 
rotation of the motor 50. The rotation of the motor 50 causes the 
planetary gear part 51 to engageably rotate with the charging part 53 to 
operatively work a charging lever (not shown). Simultaneously with the 
working of the charging lever is rotated the winding part 52 to wind the 
film on the take-up spool (not shown), and the motor 50 is stopped at one 
frame advanced position for transferring the film by one frame. The rewind 
part 54 is driven to rewind the film to the cartridge. To this end, the 
motor 50 is reversely rotated to cause the planetary gear part 51 to be 
engaged with the rewind part 54 to rotate a rewind spindle (now shown) for 
rewinding the film to the cartridge. 
As described above, since the winding part 52 has the rewind part 54 and 
the charging part 53 separately mounted, it is intended to prevent the 
slow down of the rewind speed when the winding part 52 simultaneously 
drives the charging part 53 and the rewind part 54, and, further, to 
secure the winding of the film on the film winding parts. However, the 
separate mounting of the winding and the rewind part 52 and 54 requires a 
plurality of idle gears to adjust the speed reduction ratio, thereby 
complicating the structure. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a simple structure for 
a film transfer device of a camera. 
According to the present invention, a film transfer device of a camera 
comprises a charging means for controlling one frame transfer of a film. 
The charging means is engaged with a winding part and a rewind spindle RS. 
A sprocket is designed to rotate independently from the winding part and 
the rewind spindle RS. A second clutch means is provided to compensate for 
the speed difference between the sprocket and the winding part on film 
winding or between the sprocket and the rewind spindle on film rewinding. 
The present invention will not be described more specifically with 
reference to the drawings attached only by way of example.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 1, a winding part 52 is engaged with a motor 50. A 
charging part is connectably disposed between the winding part 52 and a 
rewind spindle RS to control one frame transfer of a film. The rotating 
speed of a sprocket 1 is to compensate for the speed difference between 
the winding part 52 and the rewind spindle RS. The charging part is 
separated from the rewind spindle RS while rotating in a forward direction 
and engaged with the rewind spindle RS while rotating in a reverse 
direction. 
The charging part, as collectively shown in FIGS. 1-3, preferably includes 
a charging cam 2 connected with the sprocket 1 and a first clutch part, 
and a charging gear 4 associated with a winding base 3 having a shaft 58 
with a gear 56 attached thereto. Also connected with the charging part 4 
are the sprocket 1, a second clutch part, the winding part 52, and a 
planetary gear part 51. The first clutch part is preferably composed of a 
first cam 5 formed on the upper surface of the sprocket 1, a first 
resilient plate 7 with a pair of cut flaps 6 resiliently contacting the 
first cam 5, and a pair of perforations 8 formed in the first resilient 
plate 7 to hold a pair of projections 9 formed on the charging cam 2. The 
first cam 5 is interlocked with the first resilient plate 7 on the forward 
rotation of the sprocket 1. The second clutch part is preferably composed 
of a second resilient plate 14 and a second cam 15. The second resilient 
plate has a pair of holes 11 respectively receiving a pair of projections 
10 formed on the shaft of the sprocket, so that it may be rotated 
integrally with the sprocket 1. The second resilient plate 14 also has a 
pair of cut flaps 13 with an end bend 12. The second cam 15 is provided on 
the bottom surface of the charging gear 4, so that the second resilient 
plate 14 may be interlocked with or slip on the charging gear 4 depending 
on whether the forward or reverse rotation is made. 
A one-step frame device provided in the charging cam 2 is preferably 
composed of a third cam 16 formed on the perimeter of the charging cam 2, 
a one-step frame switch 17, a semicircular fourth cam 18 formed on the 
upper surface of the charging cam 2, and a charging lever 20 mounted by 
means of a hinge to contact the fourth cam 18. The charging lever 20 is 
resiliently supported by means of a spring to press the fourth cam 18. The 
sprocket 1 is rotatably mounted on a boss now shown. 
In operation, when the back cover (not shown) of a camera is opened, a film 
is loaded, and the back cover is consequently closed, the motor 50 is 
activated by a switch (not shown) to rotate the winding part 52 to wind 
the film, and the charging gear 4, which is engaged with the winding part 
52, is also rotated. Then, as shown in FIG. 5, the second cam 15 of the 
charging gear 4 is rotated interlockedly with the cut flaps 13 of the 
second resilient plate 14, resulting in the rotation of the sprocket 1. 
When the sprocket 1 is rotated, since the first cam 5 of the sprocket 1 is 
interlocked with the cut flaps 6 of the first resilient plate 7, as shown 
in FIG. 6, the first resilient plate 7 is also rotated, and the charging 
cam 2, which projections 9 formed thereon are engaged with perforations 8 
formed in the plate 7, is also rotated. When the charge cam 2 is rotated, 
as shown in FIGS. 7A and 7B, one-step frame switch 17 becomes separated 
from the third cam 16 and removed from contact therewith by the third cam 
16, and the fourth cam 18 causes the charging lever 20 to rotate to charge 
the shutter (not shown). When the charging cam 2 continues to rotate to 
cause the frame switch 17 again to be positioned to contact the third cam 
16, so that the motor is stopped to transfer the film by one frame. The 
third cams 16 are formed with an interval of 180 .degree. to rotate the 
sprocket 1 by exactly one frame, and the charging lever 20 returns to the 
original position by the spring 21 and stands by for the next rotation. 
When the sprocket I is rotated at a speed greater than that of the winding 
part 52, the charging gear 4 rotates more slowly than the sprocket 1 with 
respect to the position of the second resilient plate 14, so that the cut 
flaps 13 slip over the second cam 15. Namely, if the second resilient 
plate 14 slips over the charging gear 4, the sprocket 1 cannot transfer 
the film subjected to a given pressure by the pressure plate (not shown) 
mounted on the back cover of the camera only by the rotational force of 
the sprocket 1, so that the film is transferred according to the 
rotational speed of the winding part 52, thus preventing the winding error 
of the film. In addition, if the sprocket 1 is loaded excessively, the 
first clutch 14 slips over the charging gear 4 with the help of end bends 
12, so that the winding part 52 is prevented from receiving an excessive 
force, thus protecting the gear. 
As explained above, the film is completely used to take pictures, the motor 
is reversely rotated by activating a rewind switch to rotate the charging 
gear 4, when the charging gear 4 is rotated, it causes the planetary gear 
part 51 to engage with the rewind spindle RS, thus rotating the rewind 
spindle RS at a given speed. With respect to the relationship between the 
first resilient plate 7 and the sprocket, as shown in FIG. 6, when winding 
the first cam 5 of the sprocket 1 pushes the cut flaps 6 of the first 
resilient plate 7 to rotate. Further, when rewinding, since the direction 
is opposite, the first resilient plate 7 and the first cam 5 of the 
sprocket 1 are rotated by the frictional force therebetween. Hence, as 
shown in FIG. 7B, since the one-step frame switch 17 is separated while 
the above rotate by the frictional force, when the fourth cam 18 contacts 
the charging lever 20, the rotation is stopped, which is maintained until 
the rewinding is completed. 
At this time, since the rotational speed of the rewind spindle RS should be 
greater than that of the charging gear 4 in order to secure a smooth 
rewinding, a constant speed ratio is provided via the planetary gear part 
51, so that the film is quickly wound by the rewind spindle RS and the 
sprocket 1 is rotated more rapidly than the charging gear 4. Consequently, 
the rotational speed of the second resilient plate 14 becomes different 
from that of the charging gear 4. Namely, since the second resilient plate 
14 is rotated faster than the charging gear 4, the end bends 12 slip over 
the second cam 15. Thus, the speed difference between the rewind spindle 
RS and the charging gear 4 is compensated. 
After retracting the rewound film, the planetary gear part 51 is separated 
from the rewind spindle RS in order to load a new film. To this end, when 
the back cover of the camera is opened and film is loaded, a sensing 
switch (not shown) automatically turns on the motor 50 to rotate the 
charging gear 4 as shown in FIG. 7A, so that the forward rotational 
position is resumed to load the new film. Thus, the single charging gear 
compensates for the rotational speed difference occurring in the forward 
and the reverse rotation.