JPS647940B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a web feeding device that feeds a web such as a microfilm tape from a supply reel to a take-up reel and winds it onto the take-up reel.

When winding up a web such as photographic paper or film stored in a roll in a supply unit such as a cartridge or supply reel onto a take-up reel, the web is fed by rotating the take-up reel with a motor. I have to.

In a search device for finding specific information from a film containing a large amount of information, the film is wound onto a take-up reel and rewound into a supply section at high speed. For example, the film used in such a search device has frame marks attached to the side of the film corresponding to the frames of the film, and the feeding of the film is controlled by detecting these marks. ing. The area near the end of the film is usually a part where nothing is recorded, and this part is called a trailer part, and the end of the film is usually fixed to the core of the supply part.

Therefore, when searching for a desired frame on a film, after detecting the last frame of the film,
It is necessary to reverse the film to rewind or stop it, but if the film is fed at high speed to the end of the film on the supply side, a strong impact force will be applied to the end of the film that is fixed to the supply section. There was a risk of damaging mechanical parts or cutting the film.

Conventionally, in order to detect the end of the film, an end mark is provided near the end of the film, that is, in the trailer section, and the film is stopped using the detection signal.However, a special mark is placed on the film. This method requires a lot of effort, has poor workability, and has the disadvantage that it cannot be applied to films without end marks.

SUMMARY OF THE INVENTION An object of the present invention is to provide a web feeding device that eliminates the above-mentioned drawbacks.

Another object of the present invention is to prevent the web from being cut by preventing strong impact from being applied to the end of the web.

Still another object of the present invention is to easily detect when the web has been fed near the end, even when using a web without markings, thereby preventing damage to the apparatus.

The present invention will be explained below using specific examples shown in the drawings.

FIG. 1 shows a microfilm reader to which the present invention is applied, in which drive motors 3 and 4 are connected to opposing film reels 1 and 2, respectively, and by switching the drive of both motors, the supply reel 1 is moved from the take-up reel 2 to the take-up reel 2.
In this configuration, the film F is transferred from the take-up reel 2 to the supply reel 1.

For example, if 1 is a supply reel and 2 is a take-up reel, the motor 4 is driven to rotate to feed the film in the direction of the arrow and wind it onto the reel 2. The film F, which passes through the focal point of the imaging lens 21 by the guides 20 and 20, is illuminated by an illumination source (lamp) 22 and projected onto a screen 25. 23, 24
26 is a reflecting mirror, 26 is a condensing lens, and 27 and 28 are transparent glass plates placed opposite each other across the film transport path.

The motor 3 is connected to the shaft of the supply reel 1 and is capable of forward and reverse rotation, and the motor 4 is connected to the shaft of the take-up reel 2.
The motor is connected to the shaft of the motor and can be rotated in forward and reverse directions, and both motors are DC motors.

When winding the film onto the take-up reel 2, the motor 4 is rotated to rotate the reel 2 clockwise.
reel 1 when rewinding to supply reel 1.
Motor 3 rotates counterclockwise.
to drive.

The terminal end of the film F is fixed to the core of the reel 1.

FIG. 2 shows a drive control circuit for the motor 4 when winding the film onto the take-up reel 2, where Tr is a transistor, R1 and R2 are resistors for changing the base current of the transistor Tr, D is a diode, Vcc is the motor drive power supply, S is the resistance R1, R
This is a switch that connects either one of 2 to the base of the transistor Tr. Transistor Tr and resistors R1 and R2 constitute a current limiting circuit, and motor 4
The current flowing through the motor 4, that is, the drive current of the motor 4 is controlled.

The emitter of the transistor Tr is connected to the power supply Vcc, and the collector is connected to the motor 4 via the diode D.
The base is grounded via a resistor R1 or R2.

The collector current Ic flowing from the emitter to the collector of the transistor Tr is the drive current of the motor 4, and the torque of the motor 4 is determined by the collector current Ic.

R3 is the voltage corresponding to the drive current Ic of motor 4
A resistor for detecting Vc, 31 is a voltage Vc detected by resistor R3 and a preset reference voltage Vs.
This comparator consists of an operational amplifier and detects when the film winding diameter of the take-up reel has reached the set value. The resistance value of the resistor R1 is set to be smaller than that of the resistor R2. The switch S normally connects a resistor R1 to the base of the transistor Tr.

The relationship between the base current IB flowing from the emitter to the base of the transistor Tr and the collector current Ic is Ic=h·I _B (1). h represents the current amplification factor, which is determined by the transistor used. Therefore, collector current Ic is determined by base current _IB .

Further, the base current I _B becomes I _B = (Vcc - V _BE )/R (2) where V _BE is the voltage between the base and emitter. R is a resistor (R1 or R2 in FIG. 2) connected to the base of the transistor Tr.

As is clear from equations (1) and (2), since Vcc and V _BE are constant, the base current I _B depends on the value of the resistor R.
is determined, and once the base current is determined, the collector current is determined. Therefore, if the resistance R is set to an appropriate value, the maximum drive current of the motor 4 during winding
Icmax is determined, and the drive current of the motor 4 does not exceed the set current Icmax even if a strong load is applied to the motor.

When the film F on the supply reel 1 is fed to the end, the film diameter on the take-up reel 2 reaches its maximum, but the take-up reel 2 is driven to rotate at such a speed that no strong impact is applied to the film at that time. The resistance value of the resistor R2 is set so that the drive current is sufficient to obtain the torque that can be achieved. The resistor R2 is configured as a variable resistor, and when the maximum winding diameter of the film on the take-up reel changes, the value is changed accordingly. The maximum drive current Icmax of the motor is determined by resistor R1. If the variation range of the maximum winding diameter is not very large, there is no problem even if the resistance value of the resistor R2 is kept constant.

FIG. 3 is a graph showing the relationship between the film winding diameter D of the take-up reel 2, the drive current Ic of the motor 4, and the film feeding speed U. The solid line Ic' shows the change in the drive current Ic with respect to the winding diameter D, and the broken line U' shows the change in the film feeding speed U with respect to the winding diameter D.

In addition, in FIG. 2, the diode 5 functions to prevent the back electromotive force generated by the motor 4.

When the film feeding device is operated to wind the film onto the take-up reel 2 using the circuit configured as described above, the following will occur.

When the take-up reel 2 starts winding the film F, as the winding diameter D of the take-up reel 2 increases, the load on the motor 4 increases, and the current Ic flowing through the motor 4 increases accordingly. . That is, as shown by the solid line Ic' in FIG. 3, as the winding diameter D (horizontal axis) increases, the drive current Ic increases.

In FIG. 2, at the beginning of winding, that is, when the film winding diameter of the take-up reel 2 is small, the output of the comparator 31 connects the resistor R1 to the base of the transistor Tr via the switch S, and the film is wound on the take-up reel 4. As the diameter increases, the motor drive current increases and the voltage Vc increases, and when the winding diameter reaches a certain value (smaller than the maximum winding diameter), the voltage Vc becomes the reference voltage.
Becomes equal to Vs. At this time, the switch S is switched by the signal output from the comparator 31, and the resistor R
2 is connected to the base of the transistor Tr. As a result, the driving current of the motor 4 decreases, and the film feeding speed becomes slower than the maximum feeding speed. From then on,
The film is subsequently wound up, but as the winding diameter increases, the feeding speed decreases and the impact applied to the film is weakened when the film is fed out to the end. According to this embodiment, the film can be fed at high speed until near the end of the film, and when the film is near the end, the speed is reduced to prevent the film from breaking.

In addition, although the example in which the winding core is rotationally driven by a DC motor has been described above, the same application is possible with an AC motor.

As described above, as the film approaches the end, the film transport speed decreases, so the impact when the film F is wound to the end is weakened, and there is no risk of the film being cut or the drive system being damaged. . After winding to the end, the power is cut off using an automatic or manual switch (not shown) to complete feeding of the film. As mentioned above, in this film feeding device, when the load increases for some reason, the impact applied to the film F is weakened.
Prevents film breakage. It operates reliably and is effective especially when the film is wound to the end. According to experiments, if the drive current of the motor 4 is maximized when the winding diameter of the take-up reel becomes 10 to 20% smaller than the maximum winding diameter, the winding speed will not be reduced too much. It is possible to prevent the film from breaking without causing any damage.

As described above, according to the present invention, impact accidents at the end of web winding can be prevented.
Furthermore, the device has a simple structure and can be manufactured at low cost, which is advantageous in practical terms.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a film reader to which the present invention is applied, FIG. 2 is a control circuit diagram of a film feeding device, and FIG. 3 is a graph showing the relationship between drive current and film transport speed. 1, 2...Reel, 3, 4...Motor, 21...
...Lens, 22...Lamp.

Claims (1)

[Claims] 1 a motor 4 that rotationally drives a web take-up shaft; a power supply means VCC that supplies power to the motor;
a transistor Tr connected to the power supply means and the motor and controlling a drive current of the motor;
and comparing means 31 for comparing a voltage according to the drive current of the motor with a reference voltage and outputting a signal when the two match, and controlling the base current of the transistor by the signal output from the comparing means. A web feeding device comprising means S, R1, and R2 for limiting the driving current of the motor to a constant value.