JPS6251454A - Device for checking upside and face side of paper - Google Patents

Abstract

PURPOSE:To perform accurate examinations by detecting the density of a predetermined spot of a printed surface and the availability of printed matter for the comparison of densities of printed matters in synchronization with a timing signal transmitted when printed sheets are fed to a detection position, and display the comparison results. CONSTITUTION:Printed matter with reverse sides printed is delivered from a stack 8 and fed to a check position 12 through a conveyor 11, and brought to a stop by a stopper 13. While a timing signal is generated by a signal generation device 2, synchronized to a moment where printed matter is halted instantaneously, the reflection density of the reverse side of printed matter is measured by a density sensor 3. Then the density value measured is stored into a memory of a processor 5. When no printed matter is detected by a printed matter sensor 4, the measured value is cancelled. This measured value is processed by the processor 5 according to a program. When some measured value beyond the limits of a predetermined boundary value has been input, an alarm is sounded by an alarm device 17 or a notice is displayed on a display unit 6. The measured value is evaluated by the comparison for judgement of measured values of the first printed sheet with the next one. Thus correct checking of printed matter is assured.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] This invention is a method for correcting the upside-down and reverse-whiteness of the first printing surface, which is the already printed surface, when performing top-side printing on a sheet-fed printing press. This invention relates to an upside-down/back-white inspection device for inspection.

In a sheet-fed printing press, in order to perform correct up-side printing, feed the sheet with the up-side facing toward the printing plate and the top, bottom, right and left sides of the paper in the correct orientation, and keep the paper at the required distance from the initial printing surface. It is necessary to feed the sheets to the printing press while maintaining the same relationship, and for this purpose, it is necessary to detect the upside down and whiteness of the first printing surface of the fed sheets before they enter the printing press.

[Prior art] In order to detect upside down and reverse white on the upper surface of such a sheet, conventionally, as shown in Japanese Patent Publication No. 58-51825, inspection tools were installed at designated locations on all sheets. The method used was to print a mark and read this mark with a sensor.

[Problems to be Solved by the Invention] However, in this conventional technique, the space for printing the inspection mark is limited to a part of the printed sheet,
For example, it is necessary to prepare the edges of the paper, which is a constraint when composing the printed design, and it takes time and effort to print the mark.Also, the printed design covers the entire surface of the paper, and there is no space for printing the mark. Sometimes there is no. Furthermore, the position of the mark may shift due to a change in paper size, and the mark may be beyond the range of position movement of the detection sensor and cannot be detected. Making and printing marks at predetermined positions in this way has a strong tendency to save paper space, making management difficult, and it is desired to develop techniques to address these problems.

This invention was made in view of the above circumstances, and there is no need to print an inspection mark on printed matter, and therefore there is no need to provide a space for an inspection mark, which is a constraint when configuring a printed pattern. The purpose of the present invention is to provide an upside-down/back-white inspection device that can be applied to prints of any size, can reliably inspect upside-down/back-white, and has a structure with a spacing wheel for reliable operation. That is.

(B) Means for constructing the invention and solving the problem] In response to this object, the upside-down/back-white inspection device of the present invention detects that a sheet-fed printed matter is supplied to an inspection position and generates a timing signal. a timing signal generator that generates
a density detection sensor that operates in synchronization with the timing signal to detect the density of a predetermined portion of the already printed surface of the sheet-fed printed matter; and a printed matter detection sensor that operates in synchronization with the timing signal to detect the presence or absence of the printed matter. , a comparison device that compares the density of the printed material with the density of other printed materials, and a display device that displays the results of comparison by the comparison device.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

As shown in FIG. 1, the inspection device 1 includes a timing signal generator 2, a density detection sensor 3, a printed matter detection sensor 4, a processing device 5, and a display device 6.

The timing signal generator 2 is used to generate a timing signal for the operation of the inspection device 1, and includes a sensor, such as a proximity switch or a limit switch, installed on a rotating part that can provide timing once per rotation of the machine. It is composed of a rotating detecting body, such as a timing cam, and when the rotating detecting body overlaps the sensor position, it generates a timing signal and inputs it to the processing device via the input/output section.

The density detection sensor 3 is used to determine whether the printed matter 7 is upside down or with the reverse side white by measuring the reflection density of the surface of the printed matter. The density at an arbitrary location is detected using reflected light, and an output signal is input to the processing device 5 via the AD converter 16.

The printed matter detection sensor 4 detects whether the printed matter 7 is at the detection position as a condition for detecting the whiteness of the top and bottom of the printed matter, and is installed near the inspection position 12 to detect the amount of light reflected from the surface of the printed matter. If the amount of light is sufficient for the output (ON) of the sensor, it is assumed that there is paper, and if the amount of light is small, it is assumed that there is no paper and no output signal is output. However, if the paper surface has a particularly small amount of reflection, it may be used in the opposite manner (off with paper present).

The processing device 5 includes a comparison device which inputs the signals from each of the sensors and compares the inverse 11FI density of the printed material sent from the density detection sensor with the reflection density of the previous and subsequent printed materials, and the comparison results obtained by the comparison device. It is equipped with a display device that displays the number of defective sheets and a measured value, and a control device that controls the operation of each of the devices based on signals sent from each sensor.

[Function] The function of the detection device 1 configured as described above is as follows.

The printed matter after printing on the back side that comes out from the top of the stack 8 accumulated on the paper stacker of the printing machine feeder is conveyed to the conveyor 11.
It reaches the inspection position 12, stops at the front stop 13,
The vertical positioning is performed, and then the horizontal positioning is performed using the horizontal needle, and the timing signal generating device 2 generates a timing signal in synchronization with the moment when the printed material temporarily stops. While this timing signal is being generated, the density detection sensor 3 measures the reflection density on the back side of the printed matter 7, and the measured value is converted into digital data by the A/D converter 16 and stored in the memory of the processing device 5. Ru. Further, the presence or absence of a printed matter is checked by the printed matter detection sensor 4, and if there is no printed matter, the measurement value is canceled. The above measured values are processed by the processing device 5 according to the program 1, and when a measured value that deviates from a boundary value that is different from the measured value by a predetermined ratio is input, the display device 6 and the alarm device 17 An alarm is outputted by , and the number of defective sheets (the number of abnormal measurement values that have occurred until reset) is displayed on the display device 6 each time. The quality of the measured values is determined by comparing the measured values of the first printed material and the next printed material in succession.

The theory of judgment is as follows.

As shown in FIG. 3, which is a perspective view of the printed matter seen from the back side, if the printed matter 7a, 7b, and 7c are successively flowing, the parts in the soil are the same as those of the respective printed matter 7a, 76.7c. This is the measurement position of the point.

If the printed matter 7a and 7G are normal, the printed matter 7b will flow with the pattern upside down, and the measurement position will be at a location where the pattern is different. Therefore, the difference between the density measurement value at the inspection position of the printed matter 7a and the density measurement value at the inspection position of the printed matter 7b, which is a reference value, exceeds the set boundary value and is determined to be abnormal. It is possible to inspect upside down printing and reverse whitening. Also, the 'mm degree of the printed matter 7b is canceled so that the density of the printed matter 7b is not updated as the reference value. Printed matter 7C
The density is compared with the density of the printed matter 7a and determined to be normal.

(c) Effects of the invention In this way, the inspection apparatus of the present invention uses the printed matter 7a.

The measured value at the measurement position of 7C and the measurement value at the measurement position of printed material 7b are thicker than the boundary value set in the program (by selecting different locations in advance, a specific detection mark is not required. Since it is possible to inspect the upside-down printing and reverse whiteness of the pattern using the already printed pattern, there is no need to print inspection marks on the printed material, which is a constraint when configuring the printed pattern. Therefore, it can be applied to printed matter of any size in which the proportion of the printed design occupies the printed matter, it is possible to reliably inspect upside down and reverse side whiteness, and the structure is simple. It is possible to obtain an upside-down and reverse-side white inspection device that can be operated reliably.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an inspection device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the arrangement of sensors in the inspection device, and Fig. 3 is a perspective view from the bottom showing the principle of pass/fail judgment. It is an explanatory diagram. 1... Inspection device 2... Timing signal generator 3... Density detection sensor 4... Printed matter detection sensor 5... Processing device 6... Display @ 7... Printed material 8... Accumulation 11... Conveyor 12.
...Inspection position 13... Front cover 14... Input/output section 15... Processing device 16... A/D converter 17... Alarm device

Claims (1)

[Claims] a timing signal generating device that detects that a sheet-fed printed material is supplied to an inspection position and generates a timing signal; and a timing signal generator that operates periodically in response to the timing signal to detect the density of a predetermined location on the already printed surface of the sheet-fed printed material. a density detection sensor that operates in synchronization with the timing signal to detect the presence or absence of the printed matter; a comparison device that compares the density of the printed matter with the density of other printed matter; 1. An upside-down/back-white inspection device comprising: a display device that displays the results of comparison by a comparison device.