JPH06344541A - Method of inspecting printing quality - Google Patents

Abstract

PURPOSE: To provide a printing quality inspecting method for excluding dangerousness such that a printed object bad in quality is sent to a consumer. CONSTITUTION: In a method for inspecting the printing quality on an object 4, especially, a cup or a cover, printing is performed by an offset cylinder 1 and a plate cylinder 2 equipped with an ink supply mechanism 3 cooperating during the passage of the object 4 through a printer and a video camera 9 combined with a stroboscope 5 is adapted in order to observe the certain selected position 21 of the printing on each of a series of the objects 4. The signal supplied by the video camera 9 is converted to the image 13 of a video monitor 14 by a first device 11 and converted to a parameter related to the color characteristics of printing by a second device 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset cylinder and a plate cylinder provided with an ink supply mechanism which cooperates while passing an object through a printing apparatus, and particularly to objects such as cups and covers. On the method of inspecting the print quality of.

[0002]

2. Description of the Prior Art In known methods, printed objects are optionally continuously removed and visually inspected. This work requires the expertise and attention of the person performing the inspection. There is always the possibility that poor quality prints will escape attention and be sent to the consumer during this operation.

[0003]

The present invention eliminates this problem.

[0004]

To this end, a video camera in combination with a stroboscope has been applied to observe certain selected positions of the print on a series of objects and is supplied by the video camera. The converted signal is converted by the first device into an image on a video monitor, and converted by the second device into a parameter relating to the color characteristics of printing.

Therefore, a visual inspection of the printing of the object can be carried out during the production process, the quality of the printing can be expressed by a number, and as a result the requirements of the inspector's expertise are low, Actions can be taken earlier if print quality is poor.

Through the image of the video monitor, it is possible to adjust the position and size of the portion of the print to be inspected.

In this way, it is possible to inspect various positions of the print, while also adjusting the size of those positions.

In particular, the parameters relate to the color itself, the saturation and the intensity of the color.

This therefore means that always three types of parameters are provided. In particular, said parameters are compared with the desired color supplied to the first device, for example in the form of a quality-checked image.

Furthermore, parameter tolerances are determined for positions with certain tolerances, and warning signals are provided if these tolerances are exceeded. Through this, the inspection of print quality can be greatly automated.

According to another development of the invention, the measured parameters can be used to adjust a part of the printing device, for example to adjust the speed of the motor driving the rollers of the ink supply mechanism. .

When the term color itself is used as mentioned above, this should be understood to mean comparing the color with a base color, for example pure red, pure yellow or the like. "saturation"
The term is understood to mean the purity of a color. Highly saturated colors are vibrant, less saturated colors are dull, ie the "intensity" of the light shade is related to the relative brightness of the print and represents a measure of the amount of light rays reflected by the print. High strength prints appear whiter and low strength prints appear blacker.

The present invention will be described in detail with reference to the drawings shown in the accompanying drawings.

[0014]

The figure shows an offset cylinder 1 provided with one of a number of plate cylinders 2 in its vicinity. Each plate cylinder cooperates with the ink supply mechanism 3. further,
The object 4 to be printed is shown.

The lamp of the stroboscope 5 is aimed at the object 4, said stroboscope being connected via a line 6 to a synchronizing pulse generator 7. Information about the position of the offset cylinder 1 and thus of the object 4 is sent to the generator 7 via the line 8.

A video camera 9 is also aimed at the object 4, said camera being connected by line 10 to a first device 11, said device being connected by line 12 to a monitor 14.
At 13, an image 13 is generated. The device 11 is also connected to the generator 7 by a line 15. The device 11 may be constituted by a so-called "frame grabber".

The device 11 is a second device 1 which can be constituted by a personal computer or the like via a line 16.
Connected to 7. The device 17 is connected to the text monitor 19 by a line 18 and to the generator 7 by a line 20. When a signal is provided via lines 8 and 20, the generator 7 causes a start pulse for the flash of the stroboscope 5 and a start pulse for starting the recording of a single image by the device 11 at the correct moment. To supply. The signal supplied through the line 20 contains information from the device 17 in the part of the object 4 which is made visible.

The text monitor 19 shows the color itself, such as those mentioned above, and the parameters providing the saturation and intensity indications.

The monitor 14 shows an overall image 13 of the object, for example a printing cup made of plastic. However, in general, a portion of the print is inspected, especially as indicated by the dotted line. The value of the parameter for this part then appears on the text monitor 19.

As already mentioned, the value of the parameter can be compared with the desired value supplied to the first device 11. Some tolerance is allowed. However, if the tolerance exceeds the tolerance, it is possible to supply a signal via line 22 to a so-called interface 23, which can provide the signal to a part of the printing device, which is the plate. It is possible to consider changing the speed of the motor that drives the roller of the ink supply mechanism 3 of the cylinder 2.

Obviously, it is not necessary to inspect each printed object, and the inspection can be limited to one in a series of objects.

The application of the method of the invention is also of particular importance when the prints on the object are dried directly and when the object is automatically packaged immediately after leaving the printing device. In that case, it is not necessary to interrupt the process of the invention in order to retrieve an object for inspection.

Therefore, it is possible to significantly limit the amount of waste and shorten the adjustment time of this device.

While only one embodiment of the method according to the invention has been shown and described, it will be clear that many modifications can be made without departing from the concept of the invention.

[Brief description of drawings]

FIG. 1 is a diagram showing the present invention.

[Explanation of symbols]

 1 Offset Cylinder 2 Plate Cylinder 3 Ink Supply Mechanism 4 Object 5 Stroboscope 9 Video Camera 11 First Device 13 Image 14 Video Monitor 17 Second Device 21 Position of Printing Part

Claims (6)

[Claims] 1. A method for inspecting print quality on an object (4), in particular a cup, cover or the like, said offset cylinder (1) and said offset cylinder during the passage of the object (4) through a printing device. Printing is carried out by means of a plate cylinder (2) with an ink supply mechanism co-operating with the printing system, and printing at a selected position (2) on a series of objects (4).
A video camera (9) in combination with a stroboscope (5) is applied to observe 1), and the signal provided by the video camera (9) is displayed on the video monitor (14) by the first device (11). A method for inspecting print quality, which is converted into an image and converted into a parameter relating to a color characteristic of print by a second device (17). 2. A method according to claim 1, characterized in that the position and the size of the part of the print to be inspected are adjusted through the image (13) of the video monitor (14). 3. A method according to claim 1 or 2, characterized in that the parameters relate to the color itself, the saturation and the intensity for the color. 4. Parameter according to any one of claims 1 to 3, characterized in that the parameter is compared with a desired value supplied to the first device (11), for example in the form of an image whose quality is examined. The method described in the section. 5. A parameter according to claim 1, characterized in that the tolerances of the parameters are determined with respect to a certain position and that a warning signal is provided if these tolerances are exceeded.
The method described in the section. 6. The measured parameter can be used to adjust a part of the printing device, for example to adjust the speed of a motor driving a roller of the ink supply mechanism (3). The method according to any one of claims 1 to 5.