JPS6139261B2 - - Google Patents

Description

[Detailed description of the invention] In currently known printing machines and copying machines,
Cut sheets are often used as paper for printing, but depending on the quality of the paper or the way the sheets overlap in the paper feeding device, two or more sheets may be fed at the same time during paper feeding. This is generally referred to as double shipping, but
At present, it is difficult to avoid this double feeding as long as cut sheets are fed. If it is a low-speed printing or copying machine with a small number of copies, such as a general office machine, there is no problem if a person directly checks it, but if it is used as a high-speed and unmanned output device, such as a computer output terminal. In a high-speed printing device, double feeding during paper feeding causes blurred or omitted characters, which greatly affects the reliability of the device, and it is extremely difficult to detect misaligned or omitted characters. Furthermore, even if a problem is found, reprinting only that part will be a huge waste, which is a fatal defect for an output device. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an abnormal transfer detection device for detecting the occurrence of abnormal transfer such as double feeding in a printing machine or a copying machine, which overcomes the drawbacks of the prior art described above.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows a block diagram of this device. Reference numeral 11 denotes a detection circuit that converts the degree of overlapping of fed sheets into an electrical signal.The output of this detection circuit 11 is held in a sample and hold circuit 12 in response to a trigger pulse from a gate circuit 10. Reference numeral 13 denotes an attenuator that attenuates the output signal of the sample and hold circuit. The output signal from this attenuator 13 and the signal from the detection circuit 11 are compared in a comparator circuit, and the output signal of the comparator circuit is used for multiple transmission. It is possible to know whether or not this has occurred. Note that 15 indicates the comparison circuit 14.
This is an alarm circuit that notifies you that double feeding is occurring by outputting an output. Reference numeral 16 indicates a reference signal generation circuit that generates a timing pulse for instructing paper feeding, and the timing pulse derived from this circuit is passed through a gate circuit 10 consisting of an AND gate with the output of the comparator circuit 14 printed on one end thereof. The output of the gate circuit 10 is applied to the sample hold circuit 12 as a trigger signal for sampling as described above.

In other words, the detection output currently detected by the detection circuit is applied to the terminal 14-1 of the comparison circuit 14, and the detection output of the previous sheet or the previous one is applied to the terminal 14-2. A comparative output is derived by comparing signals, and furthermore,
In order to be able to detect double feeding without any problem even if double feeding occurs continuously, the output of the gate circuit 10 is used as a trigger signal for the sample hold circuit 12, so that when double feeding occurs, no new sample is performed. It is something that

FIG. 2 shows in more detail the case where the abnormal transfer detection device shown in FIG. 1 is applied to an electronic copying apparatus that records information using a laser beam. The paper feed cassette is indicated by 17.
This paper feed cassette 17 has a bottom plate 19 pressed upward by a spring 18, and papers (sheets of paper) 20 stacked on the bottom plate 19.

Above the paper feed cassette 17, a roller 21 that is constantly rotating in the direction of arrow S is mounted on a plunger 2.
2 is provided with a feeding roller 23 which can press onto the paper 20 or pull it away from the paper 20 as shown by the solid line.

The paper 2 at the upper end of the paper feed cassette is moved by this roller 21.
0, the sheet of paper 20-1 is transferred to the right in FIG.
5, and its tip is inserted into a pair of timing rollers 26 and 27, which normally do not rotate.

After the paper 20-1 fed out in this way is inserted between the timing rollers 26 and 27, the plunger 22 is driven to pull up the roller 21, and the timing rollers 26 and 27 are driven to immediately release the paper 20-1. 1 is now in a state where it can be transferred to the right.

Note that in order to pull up the roller 21 after the paper 20-1 reaches a predetermined position, the roller 21 may be pressed against the paper 20-1 by a timer for the time required for the paper 20-1 to reach the state shown in the figure. Alternatively, the insertion of the paper 20-1 into the timing rollers 26 and 27 may be detected by a light emitter and a light receiver (not shown), and the roller 21 may be pulled up.

When the timing rollers 26 and 27 are driven in the direction of the arrow in this state, the paper 20-1 is moved to the guide plate 2.
The toner reaches the photosensitive drum 30 through the paper 20-1 and is transferred onto the photosensitive drum 30 by a developing device 30-1 of a known electrophotographic device onto the paper 20-1. 30-2. It goes without saying that the paper 20-2 to which the toner has been transferred in this manner is fixed by a fixing device (not shown).

Since the photosensitive drum 30 is irradiated with a laser beam 31 that is ON-OFF modulated according to recorded information in order to form an electrostatic latent image, (this laser beam is directed in a direction perpendicular to the plane of the paper). The driving of the timing rollers 26 and 27 must be started in correlation with the start of writing of certain information by the laser beam 31 (assumed to be deflected at a constant period). (Photosensitive drum 30
is driven at a constant speed) In other words, the paper 2 is driven by the timing rollers 26 and 27.
Assuming that the feeding speed of 0-1 is equal to the circumferential speed of the photosensitive drum 30, when the leading edge of the paper sent in the direction of the photosensitive drum between the guide plates 28 and 29 by the timing rollers 26 and 27 reaches the photosensitive drum 30. The leading edge of the information recorded on the photosensitive drum by the laser beam 31 must reach the location indicated by arrow A.

At this time, the area between arrows A and B will form a top margin formed at the top of the paper. In this embodiment, the timing rollers 26, 2
Since the length of the path of the paper from 7 to the point indicated by the arrow on the photosensitive drum 30 and the distance between the arrows A and C on the photosensitive drum 20 are equal, the laser beam 31 causes the paper to pass on the photosensitive drum 30. Simultaneously with starting recording of a page, a paper feed timing pulse is generated to start driving the timing rollers 26 and 27. In addition, this timing roller 26, 2
The plunger 22 of the feeding roller 23 is controlled so that its driving is stopped when there is no more paper between the timing rollers 26 and 27.
Assume that once both timing rollers 26 and 27 start driving, the roller 11 is pushed down after a certain period of time to transport a sheet of paper to the right in the figure.

Through holes 34 and 35 are provided at opposing positions of the guide plates 28 and 29 as described above, respectively, and a light emitter 32 and a light receiver 33 are provided in each of the through holes.

Such a light emitter 32 and a light receiver 33 are provided as shown in FIG. 3 which shows FIG. 1 in more detail, respectively.
The paper 20-1 travels in the direction of arrow P during this time.

Therefore, when the fed paper 20-1 passes between the light emitter 32 and the light receiver 33, the amount of light reaching the light receiver 32 changes, and the resistance value of the light receiver 32 changes.

Note that an ultrasonic generator and a sound receiver may be used instead of the light emitter and receiver, as long as they can substantially measure the thickness of the paper.

Since a constant voltage is applied to one end of the resistor 33, a voltage signal corresponding to the amount of light received by the light receiver 33 can be obtained at point a in FIG.

This signal is applied to a normal operational amplifier 39, which is used as a voltage follower to provide high input impedance and low output impedance characteristics.

The output of the operational amplifier 39 is connected to a capacitor 41 via a transistor 40.
The signal when the torque transistor 40 is turned on is held in the capacitor 41.

As mentioned above, the operational amplifier 39 is used as a voltage follower so that the charge up of the capacitor 41 is instantaneous, and so as not to affect the light amount-to-electrical conversion section formed by the photodetector 33 and the resistor 38. It is something.

The voltage signal held in the capacitor 41 in this way is further applied to an ordinary operational amplifier 42 (used as a voltage follower in the same way as described above), and the output of the operational amplifier 42 is divided by a resistor 44 to be attenuated. After that, it is applied to one input terminal 45-1 of an operational amplifier 455 constituting a comparison circuit.

By connecting the other terminal 45-2 of the operational amplifier 45 to the point a, the signals applied to both terminals are compared, and the level of the signal applied to the terminal 45-1 is higher than the level of the signal applied to the terminal 45-1. When the signal level applied to terminal 45-2 is low, there is no output signal, and when the signal level applied to terminal 45-2 is high, a positive output signal is derived.

As mentioned above, 16 is a reference signal generation circuit that generates a pulse signal (timing pulse) that instructs, for example, to start driving the timing rollers 26 and 27.
The timing pulse from 6 is not directly applied as a trigger pulse for turning on the transistor 40, but is applied via the gate circuit 10.

Since the output of the operational amplifier 45 is applied to this gate circuit 10, only when the operational amplifier 45 is deriving a positive output, that is, only when double feeding is not detected. A timing pulse from the reference signal generation circuit 46 is applied to the transistor 40 as a trigger signal.

The operation of the abnormal transfer detecting device constructed as above will be explained in more detail using the waveform diagram of FIG. 4.

Here, it is assumed that the paper fed between the light emitter 32 and the light receiver 33 of the device shown in FIG. 3 passes at timing P in FIG. 4, and P ₁ , P ₂ , P ₃ , _P6 ,
Assume that _P7 indicates that the paper is being fed normally, and _P4 and _P5 indicate that the paper is being fed multiple times. Then, the voltage waveform shown in FIG. 4a is obtained at point a. Here, the voltage levels at the points corresponding to P ₁ , P ₂ , P ₃ , P ₆ , and P ₇ are determined by the fact that since there is only one sheet of paper that blocks light, some light may reach the light receiver 33. At the locations corresponding to P ₄ and P 5 , almost no light can reach the light receiver 33 due to the plurality of sheets of paper blocking the light, and the locations corresponding to P 4 and P ₅ are lower. Note that the voltage levels V ₁ to _{V 3} , V ₆ , and V ₇ are different because even if the paper is transferred normally, the paper type, thickness, etc. are slightly different. This shows that the amount of light emitted is different.
Note that if abnormal transfer is detected after inputting the type and thickness of the paper, abnormal transfer can be detected more quickly.

Note that the reason why the levels of V ₄ and V ₅ are different is due to the same reason.

Reference numeral b indicates timing pulses (TP1 to TP7) derived from the reference signal generation circuit 16, but these pulses are not directly applied to the transistor 40, but are applied at point c in FIG. As shown in Figure C, the gate circuit 10 is closed during the double feed period, so that the voltage is applied except during the double feed period.

Therefore, TP1 to TP3, TP6, and TP7 are applied as trigger pulses to the transistor 40, the transistor 40 is turned on only during this period, and the output voltage of the operational amplifier 39 when the trigger pulse is applied is changed to the next trigger pulse. Since the signal is held in the gong capacitor 41 until it is applied, a signal as shown in Fig. d can be obtained at point d in Fig. 3.

Therefore, the voltage corresponding to P ₄ and P ₅ where double feeding occurred
V ₄ and V ₅ are not sampled and held, and this period is
The voltage V ₃ corresponding to P ₃ is continuously maintained.

The voltage sampled and held in this way is applied to the attenuator composed of resistors 43 and 44 via the operational amplifier 42, so at the terminal 45-1 in FIG. 3, the voltage shown by the solid line in FIG. It is possible to obtain a signal such as that shown in FIG. d, and a signal whose level is attenuated by R ₄₃ /R ₄₂ +R ₄₃ times. Note that the operational amplifier 3
The explanation is given assuming that the gain of 9 and 42 is 1. On the other hand, at the terminal 45-2 of the operational amplifier 45,
The signal at point a is applied as is through the signal line 47, and for ease of understanding, the signal waveform at point a is shown by a dotted line in Figure e.

As mentioned above, the operational amplifier 45 outputs a positive output when the voltage applied to the terminal 45-2 is higher than the voltage applied to the terminal 45-1, and outputs no output when it is lower. The double feed detection output waveform at point f in FIG. 3 is as shown in f in FIG. 4.

Therefore, if the warning circuit 15 has a built-in flip-flop that is set at the falling edge of the output waveform, and the output of this flip-flop is configured to drive a lamp or a buzzer, the occurrence of double feeding can be visually detected. It is possible to notify visually or audibly.

In addition to reporting in this way, the operational amplifier 4
The output of step 5 may drive a mechanism for removing double-fed paper, or the output may simultaneously instruct the photosensitive drum to repeatedly record the same information. Of course it's good.

In the abnormal transfer detection device shown in Figs. 1 and 3, the output of the reference signal generation circuit is not directly applied to the sample and hold circuit, but is applied via a gate circuit to which the output of the comparison circuit is applied to one end. was applied to the sample and hold circuit,
If you only want to notify that a multi-feed has started,
The configuration may be such that the output of the reference signal generating circuit 16 is directly applied to the sample hold.

However, with this configuration, even if multiple feeds occur consecutively, only the first double feed can be detected.
At the same time as double feeding is detected, measures must be taken to substantially stop the device.

Furthermore, although in the above embodiments abnormal transfer is detected by processing analog signals, it is also possible to detect abnormal transfer by processing digital signals based on exactly the same concept.

That is, when processing with a digital signal, the output of the detection circuit 11 in FIG. The latch circuit (corresponding to the sample-and-hold circuit in FIG. 1) latches only when this occurs. After that, a subtracter subtracts the output of the latch circuit from the output of the A-D converter, and a discriminator (the pre-subtractor and discriminator (corresponding to the comparison circuit 14 in FIG. 1), double feeding can be detected.

As described above, the abnormal transfer detection device according to the present invention does not detect double feeding based only on the thickness of the object being transferred, but detects abnormal transfer by comparing the reference signal. Therefore, abnormal transfer can be detected extremely accurately.

Also, by configuring as shown in Figures 1 and 3,
Since a detection output can always be obtained depending on the object being transported abnormally, such detection output can be used to eliminate double-feeding paper or to repeatedly write the same information on the photosensitive drum. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the abnormal transfer detection device according to the present invention, FIG. 2 is a side view of main parts when the present invention is applied to a copying machine, and FIG. 3 is a circuit diagram of the abnormal transfer detection device according to the present invention. , and FIG. 4 is a waveform diagram at each part of FIG. 3. Here, 11 is a detection circuit, 12 is a sample hold circuit, 14 is a comparison circuit, and 16 is a reference signal generation circuit.

Claims (1)

[Claims] 1 comprises a detection means for detecting the thickness of the first object to be transported, and a holding means for holding the detection output by the detection means at a predetermined timing synchronized with the transfer of the first object to be transported, and the first object is held by the holding means. and a damping means for attenuating the detected output amount to a predetermined value according to the detected output amount, the output of the attenuating means and a second transported object to be transferred next to the first transported object. a comparison means for detecting double feeding of objects to be transported by comparing the output from the detection means according to the thickness of the object, and when double feeding is detected by the output of the comparison means, the An abnormal transfer detection device characterized by comprising a control means for prohibiting the holding means from holding the detection output by the detection means.