JPH04260557A - Method of setting signal receiving voltage serving as criteria for determination of detection for ultrasonic two sheet detector - Google Patents

Abstract

PURPOSE:To reduce the percentage of erroneous detection by fixing the voltage of a transmitted wave sensor to a high transmission voltage from which a mean value of received signal voltages is obtained when two sheets are set on a received signal sensor, and by multiplying the mean value with a constant value so as to minimize the percentage of erroneous detection in order to set a threshold value. CONSTITUTION:Upon initial setting of a two sheets detector 21, the voltage of a transmitted signal sensor 23 is at first fixed to a transmission voltage which is as high as possible in consideration with the functions of the transmitted signal sensor 23 and a received signal sensor 24. Then, two sheets are set on the received signal sensor 24 so as to perform sampling of received signal voltages by several times. Further, the mean value of received signal voltages is computed, and is then multiplied by a constant value which is determined theoretically and empirically in order to minimize the percentage of erroneous detection, thereby a threshold value is determined.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a two-sheet detector installed in a sheet-fed machine and used for registering paper, plastic sheets, etc. cut to a certain length. This invention relates to a method of setting a received wave voltage (threshold) that is a criterion.

0002

2. Description of the Related Art As an example of a sheet-fed press, an offset sheet-fed printing press will be described, which is comprised of a paper feed section 1, two printing units 2, and a paper discharge section 3, as shown in FIG. In FIGS. 3 and 4, the sheets taken out one by one from the paper feed section 1 are
The swing gripper 11 is placed on the endless tape 5 on the feeder board 4, and its position in the advancing direction is regulated by the front stop 7 provided on the front stop device 6, and its lateral position is regulated by the horizontal needle. The leading edge of the paper is bitten by the paper, and sent to the printing unit 2, which is the post-processing section, where it is printed.
The paper is discharged through the paper discharge section 3. As shown in FIG. 4 as an example, the detector holder 10 attached to the front plate 9 has various detectors, namely a register detector 12, a horizontal needle detector 13, and a two-sheet detector 21 (a, b, c) and an overshoot detector 15, etc. are arranged.

FIG. 2 shows an ultrasonic type two-sheet detector 21. Ultrasonic waves (
200K hertz) is transmitted via the cord 22 from the wave transmitting sensor 23 attached to the detector bracket 19,
The signal is sent to a receiving sensor 24 installed on the detector holder 18. As shown by the solid line on this ultrasonic transport path, the paper is
When a sheet of paper is fed and when two sheets of paper are fed as shown by the one-point gold coin line, when the wave height of the ultrasonic wave emitted from the wave transmitting sensor 23 is received by the receiving sensor 24, the solid line and the one-point gold coin line indicate It looks like a gold coin line, and the wave height of the one-point gold coin line is significantly lower than that of the solid line. This state is sent to the determination device 26 of the control device 20 by the code 25, and
It is determined whether or not a sheet is being fed. Note that the detection timing is matched to the regular timing at which sheets of paper are fed one by one from the paper feed section. A plurality of two-sheet detectors 21 are installed at the positions shown in FIG. 4, and as shown by thin solid lines and broken lines in FIG. Slope salary [shown by dashed line (a≧δ1 >o
)] Sometimes, the two-sheet detectors 21a and 21b operate,
The feeding timing of two sheets of paper is greatly different (b≧δ2
>a) When the second sheet is fed parallel and at an angle (
The two-sheet detector 21c is activated at ◎ mark) (δ1, δ2
is the distance at which the timing is off).

Furthermore, when the paper thickness changes, when the paper is placed on the wave receiving sensor 24, the detection wave height level (threshold) is automatically set by the detection wave height level setting circuit 28 of the control device 20. Furthermore, the wave height level transmitted by the wave transmitting sensor 23 can be adjusted simply by using the knob 29 when the two-sheet detector 21 is set in the front device 6 (initial set).

[0005]

[Problem to be Solved by the Invention] When using the ultrasonic two-sheet detector as described above, even if the same paper is used, the reception level of the reception sensor, i.e. The received voltage varies within a wide area between one sheet of paper and two sheets of paper, as shown by the shaded area in Figure 1, and the interval between the two areas (received voltage difference), that is, the dead zone, is It becomes narrower in the low transmission voltage range.

[0006] The present invention reduces the variation in the reception level of the reception sensor and reduces the false positive rate by increasing the reception voltage (threshold value) which is the detection criterion in the ultrasonic dual-sensor detector.
The purpose of this study is to propose a method for setting the .

[0007]

[Means for solving the problem] 1. Detection is performed in a high transmission voltage range. 2. With a fixed high transmission voltage, the received wave level from the same paper is sampled many times to obtain an average value, and this is multiplied by a constant to set a threshold value (detection criterion received wave voltage).

[0008]

[Effect] 1. Since detection is performed using a high transmission voltage, a wide dead zone can be obtained. 2. When there is a downward variation exceeding the lower limit shown in Figure 1 when using one sheet of paper, or when there is an upward variation exceeding the upper limit shown in Figure 1 when using two sheets of paper (because sampling is a finite number of times), Since the threshold value is calculated by multiplying the average value of the received voltage obtained by multiple samplings of the same paper by a constant set based on theory and experience, the false detection rate is minimized.

[0009]

[Embodiment] A threshold setting method for an ultrasonic two-sheet detector according to the present invention will be explained with reference to FIGS. 1 and 2. As the ultrasonic two-sheet detector, one shown by reference numeral 21 in FIG. 2 is used, and this two-sheet detector 21 is designed to be linked with a computer (not shown). A sensor 24 receives a piece of paper.
When placed on the top, the constant wave transmission voltage V from the wave transmission sensor 23
The wave receiving voltage V2 of the wave receiving sensor 24 relative to 1 varies within an area T (roughly shaded area) surrounded by straight lines P and Q even on the same paper. On the other hand, when two sheets of paper are placed on the wave receiving sensor 24, the wave receiving voltage V2 of the wave receiving sensor 24 relative to the wave transmitting voltage V1 from the wave transmitting sensor 23 is the area U surrounded by the straight lines R and S, even for the same paper. (densely shaded area). This variation is much smaller in area U than in area T. To make the initial settings for this two-piece detector 21, first, while considering the performance of the wave transmitting sensor 23 and the wave receiving sensor 24,
Fix the transmitting voltage V1h as high as possible. Next, under this high transmission voltage V1h, two sheets of paper are placed on the wave receiving sensor 24.
The received wave level, that is, the received wave voltage V2, is sampled many times, and the average value V2A is calculated and determined by the computer. This average value V2A is multiplied by a constant m to obtain a threshold value V2B. (This constant will be explained later). Next, the received voltage between the received voltage V2C at the intersection with the straight line Q below the area T and the received voltage V2D at the intersection with the straight line R above the area U for the fixed high transmission voltage V1h. The difference C+D becomes a dead zone, which can be wider than the low transmission voltage V1l. Within this dead zone, from straight lines Q and R (even on the same paper,
When the receiving wave level is 1 or 2 sheets, the receiving wave voltage V2C of the straight line Q
Theoretical calculation (probability) is calculated so that the false positive rate is the lowest even if the received wave level fluctuates downward or upward (sometimes it fluctuates slightly to a lower level or higher than the received wave voltage V2D). Determine the constant m based on and empirical data,
This is multiplied by V2A obtained by sampling to determine the threshold value V2B.

0010

[Effects of the Invention] The present invention is installed in a front device installed in a portion of a sheet-fed machine that transfers sheets from a sheet feeding section to a post-processing section, and arranged above and below with the sheets in between. Ultrasonic type 2 consisting of an ultrasonic transmitting sensor and a receiving sensor, a receiving circuit connected to the transmitting sensor, a determining device connected to the receiving sensor, and a detection wave height level setting circuit connected to the determining device.
In the sheet detector, the voltage of the wave transmitting sensor is fixed at a high wave transmitting voltage, and when two sheets are placed on the wave receiving sensor with this high wave transmitting voltage, the wave receiving level of the wave receiving sensor is measured. By multiplying the average value obtained by sampling the received wave voltage shown multiple times by a constant to minimize the false detection rate and setting the received wave voltage, that is, the threshold value, which is the detection criterion, the following can be achieved. have an effect.

[0011] Initial settings are simplified, a dead zone is widened, and by determining an appropriate threshold value, the false detection rate is minimized and stable two-sheet detection is possible. Furthermore, errors caused by mounting errors (parallelism of mounting intervals) of the transmitting and receiving sensors are almost eliminated.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between transmitting voltage and receiving voltage for explaining the principle of the present invention.

FIG. 2 is a configuration diagram showing a state in which an ultrasonic two-sheet detector is installed in the front-end device.

FIG. 3 is a side view showing the layout of an offset sheet-fed printing press.

FIG. 4 is a layout diagram of various detectors in the preliminary device.

[Explanation of symbols]

21 Ultrasonic two-piece detector 23 Transmission sensor 24 Wave reception sensor 26 Judgment device 27 Transmission circuit 28 Detection wave height level setting circuit

Claims (1)

[Claims] Claim 1: An ultrasonic transmitter that is attached to a pre-equipment device installed in a section where sheets are transferred from a sheet feeder to a post-processing section of a sheet-fed machine, and that is placed above and below the sheet with the sheet in between. In an ultrasonic two-piece detector consisting of a wave sensor, a wave reception sensor, a reception circuit connected to the wave transmission sensor, a determination device connected to the reception wave sensor, and a detection wave height level setting circuit connected to the determination device, Fix the voltage of the transmitter sensor to a high transmitter voltage,
When two sheets of paper are placed on the receiving sensor at this high transmitting voltage, the average value obtained by sampling the receiving voltage many times, which indicates the receiving level of the receiving sensor when two sheets of paper are placed on the receiving sensor, is falsely detected. The received wave voltage, which is the detection criterion for the ultrasonic dual-sheet detector, is set by multiplying it by a constant so that the ratio is minimized, that is, the threshold voltage, which is the detection criterion. Method.