JPH072543B2 - Sheet double feed detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a double feed detection device in a sheet feeding mechanism.

[Prior art and its problems]

For example, in a sheet-fed printing press, since printing is performed on each printing paper, it is necessary to feed the printing paper one by one.
It is necessary to prevent double feed. Therefore, conventionally, various means have been provided for detecting the two-sheet stack.

However, these are all unsatisfactory.

[Object of the Invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide an apparatus capable of surely detecting a double-feed state regardless of the paper quality, paper thickness, and number of overlapping sheets.

[Outline of Invention]

In order to achieve this object, in the present invention, firstly, a zero adjusting circuit is provided to set the normal maximum thickness of the target feeding as a zero state, and to detect a paper thickness change due to feeding abnormality with respect to this zero state. Secondly, the paper thickness measuring means for the sample paper is provided, and the gain of the target paper feeding thickness measuring means is adjusted according to the paper thickness.

〔Example〕

Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a circuit configuration of an embodiment of the present invention, and FIG. 2 shows a detecting portion of a thickness detecting device combined with a paper feeding mechanism.

First, the paper feed mechanism and the paper feed detection operation during feeding will be described with reference to FIG. Reference numeral 1 denotes a paper stack, in which sheets 100 are stacked and stored, sequentially pushed up, and sent out from an upper end to a paper feed path on the left side in the drawing by means not shown.

The fed-out paper is sent to the receiving stand 3 by the sending roller 2, and is sent from the receiving stand 3 to the printing machine (not shown) by the belt mechanism 4. The feed roller 2 is in contact with the lower surface of the paper feed, but a detection roller 11 is provided so as to face the feed roller 2 with the paper feed interposed therebetween. This roller 11 is a swing arm
It is provided at one end of 12 and a displacement sensor 13 is attached to the other end to form a displacement detector 10.

As a result, when the sheet 100 is fed, the displacement sensor 13 outputs a signal whose size changes according to the change in the distance between the feed roller 2 and the detection roller 11. Since the sheets are fed on top of each other, the sheets are fed between the detection roller 11 and the feed roller 2 with a periodical change in the number of sheets, for example, one or two sheets, two sheets or three sheets. Sandwiched. Therefore, the detection signal of the displacement sensor 13 also changes periodically.

Next, FIG. 1 will be described. In FIG. 1, 10 is the displacement detector described with reference to FIG. 2, and this detection signal is given to the head amplifier AMP2 via the sensor amplifier AMP1. The gain controller 20 is connected to the input end of the head amplifier AMP2, and the detection signal from the sensor amplifier AMP1 is amplified by the head amplifier AMP2 with an amplification gain determined by the operation of the gain controller 20. Here, the gain adjuster 20 will be described.

The gain adjuster 20 is separate from the displacement sensor 13 and is the same paper as the paper stored in the paper feed stack 1 by the displacement sensor 22 provided on the sample table 21 apart from the feeding path.
A 100X thickness is measured and a gain control signal is formed based on this measured signal. That is, the detection signal of the displacement sensor 22 is given to the amplifier AMP7 of the gain controller for base paper and the amplifier AMP8 of the gain controller for thin paper. Amplifier AMP8 for thin paper has a characteristic that output is saturated with a small input, whereas amplifier AMP7 for thick paper can respond to a large input. Therefore, if thin paper with a thickness of 0.2 mm or less is sample paper, amplifier A
MP8 produces output Amplifier AMP7 produces no output. As a result, the photocoupler PC2 transmits and receives signals, but the PC1 does not. The photo coupler is a combination of an LED and a CdS element, and the CdS element of PC2 shows low resistance, but PC1
The CdS element remains high resistance.

On the other hand, for example, when a thick paper having a thickness of more than 0.2 mm is given as a sample, both the amplifiers AP8 and AMP7 generate outputs, and the CdS elements of both the photocouplers PC1 and PC2 have low resistance. This resistance value depends on the thickness of the sample paper 100X. Since the amplifier and the photocoupler are divided into those for thick paper and those for thin paper, it is possible to cope with a very wide range of paper thickness.

Due to the change of the resistance value according to the paper thickness of the sample paper, the detection signal whose size is adjusted according to the paper thickness is given to the input of the head amplifier AMP2. The output of the head amplifier AMP2 is always directly to the buffer amplifier AMP3 via the changeover switch SW, and at the time of zero adjustment, it also passes through the peak hold circuit PH.
Given to AMP3. The output of the buffer amplifier AMP3 is given to the auto-zeroing circuit ZA. This auto-zeroing circuit ZA is an amplifier AM
It has P4, feedback amplifier FA and switching element, and performs automatic zero adjustment operation during the output period of timer T2 based on the operation of push button switch PB. During the output period of the timer T1 based on this, the peak hold operation is performed by the cooperation of the switch SW and the peak hold circuit PH.

The output of the auto-zeroing circuit ZA is given to the display LED by the amplifier AMP5 as a detection signal. A reference signal is given to the amplifier AMP5 as another input by the potentiometer VR, and the display LED supports how the detected signal has a magnitude relationship with the reference signal.

This display LED displays the paper thickness of the feeding path by the number of LED lights, and displays the maximum thickness in the normal state as zero state.
In order to make the maximum thickness in this normal state zero, the auto-zeroing circuit ZA
Is adjusted.

The same signal as that given to the display LED is given to the output circuit OUT via the amplifier AMP6, and when an excessive signal is given, the feed mechanism is stopped and an alarm is given as a contact output.

Next, the operation will be described.

It is assumed that the sheet 100 is being fed by the sheet feeding mechanism. The sheet 100X of this sheet is set on the displacement sensor 22 of the gain adjuster 20 and the sheet thickness is measured. As a result, the gain of the head amplifier AMP2 was adjusted.
As long as 100X is set, it is adjusted to the same gain.

Next, when the push button switch PB is pressed, the timer T1 produces an output of 5 seconds and the timer T2 produces an output of slightly shorter than 5 seconds. The timer T1 switches the switch SW to the broken line side in the figure to give the output of the head amplifier AMP2 to the peak hold circuit PH. As a result, if the displacement detector 10 detects one or two sheets, the sheet thickness of two sheets is held in the capacitor C of the peak hold circuit, and this holding signal is automatically zeroed via the buffer amplifier AMP3. It is given to the tuning circuit ZA.

The auto-zeroing circuit ZA performs the auto-zeroing operation while the output of the timer T2 is given. The output of the timer T2 is given to the switching element Q of the auto-zeroing circuit ZA. This turns on the switching element Q and sets the control terminal T of the feedback amplifier FA to the ground potential. As a result, the feedback amplifier FA becomes the amplifier AM.
Takes in the output of P4 and performs operation to set the output of amplifier AMP4 to the zero state. The feedback amplifier FA has, for example, an A / D converter in the input section and a D / A converter in the output section, and an up / down counter is provided between these converters.
The zero state of the amplifier AMP4 is set to the count value obtained by up-counting or down-counting by the up-down counter according to the output state of P4. As a result, the amplifier AMP4 maintains the same zero adjustment state even after the time limit of the timer T2 has passed and the switching element Q is turned off and the zero adjustment operation by the feedback amplifier FA is completed.

As a result, the apparatus of the present invention is in a state in which double feeding can be detected. If there is no paper feeding error, the display LED will be lit repeatedly with zero and one less than that, and if there is an error, that is, double feeding, the display LED will be displayed and the output circuit OUT will stop the paper feed mechanism and the buzzer will sound. An alarm is given.

[Modification]

The displacement sensor in the above embodiment may be replaced by a photoelectric sensor or an electrostatic capacitance sensor.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

First, since a zero adjustment circuit for setting the normal maximum thickness of the target paper feed as a zero state is provided, it is possible to cope with any thickness of paper fed in any state. Double feed detection can be performed.

Secondly, the paper thickness signal of the sample paper taken out by the paper thickness measuring means is applied to the two sets of circuits for thick paper and thin paper to form the gain adjustment signal, so that it is possible to cope with a very wide range of paper thickness. Therefore, it is possible to detect double feeding of various types of paper.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of one embodiment of the present invention, and FIG. 2 is an explanatory diagram of a paper feed mechanism to which the present invention is applied. 10 …… Displacement detector, 11 …… Detection roller, 13,22 …… Displacement sensor, 20 …… Gain adjuster. AMP ... Amplifier, SW ... Switch, PH ... Peak hold circuit, ZA ... Auto-zeroing circuit, LED ... Display, O
UT: output circuit, T: timer.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-56-88040 (JP, A) JP-A-60-36249 (JP, A) JP-A-55-44412 (JP, A) JP-A-46- 4186 (JP, A) Actually opened Sho 57-126453 (JP, U) Japanese Patent Sho 59-12579 (JP, B2)

Claims (2)

[Claims] 1. A paper thickness sensor which is provided in a paper feeding path of a paper feeding mechanism for sequentially feeding sheets and which forms a signal according to a change in thickness of the paper being fed, and an output of the paper thickness sensor. It has a gain variable amplifier that amplifies with a gain determined according to the control signal, a changeover switch and a peak hold circuit, and outputs the gain variable amplifier when the changeover switch is in one of the switching positions when a command is given. A peak detection circuit that outputs a peak hold value and outputs a signal that does not pass through the peak hold circuit when the changeover switch is in the other switching position due to the absence of the command; When the command is given, the output is adjusted so that the peak hold value from the peak detection circuit is set to the zero state, and the output is generated around the zero state even after the command disappears. A zero adjustment circuit, a deviation detection circuit that compares the output of the zero adjustment circuit with a preset reference value and outputs the deviation, and an output that stops the paper feed mechanism according to the output of the deviation detection circuit. A sheet double feed detection circuit with a circuit. 2. A paper thickness sensor which is provided in a paper feeding path of a paper feeding mechanism for sequentially feeding sheets and which forms a signal according to a change in thickness of the paper being fed, and an output of the paper thickness sensor. A gain variable amplifier that amplifies with a gain determined according to the control signal, a sample paper thickness detector that detects the thickness of the sample paper having the same thickness as the fed paper, a gain controller for thick paper, and a gain controller for thin paper When the output of the sample paper thickness detector is equal to or less than a predetermined value, only the thin paper gain controller produces an output, and when the output exceeds the predetermined value, the thick paper gain controller also produces an output. It has a gain controller for controlling the gain of the amplifier, a changeover switch and a peak hold circuit, and when the changeover switch is in one of the switching positions by receiving a command, A peak that outputs the peak hold value by applying the output of an in-variable amplifier to the peak hold circuit, and outputs a signal that does not pass through the peak hold circuit when the changeover switch is in the other switching position due to the absence of the command. A detection circuit, and a zero adjustment circuit that outputs an output centering on the zero state even after the disappearance of the command by adjusting the output so that the peak hold value from the peak detection circuit becomes zero when the command is given. A deviation detection circuit for comparing the output of the zero adjustment circuit with a preset reference value and outputting the deviation thereof, and an output circuit for stopping the sheet feeding mechanism according to the output of the deviation detection circuit are provided. Sheet double feed detection circuit.