JP2825601B2 - Automatic printing defect inspection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention mainly relates to the dropping or missing of letters and symbols indicating product names, lot numbers, expiration dates, etc., which are printed on solid preparations, cartons or bottle containers. The present invention relates to an automatic print defect inspection apparatus capable of automatically inspecting for defects such as cuts or ink stains and automatically cleaning a print roller for removing the cause of the defect based on the inspection result.

<Prior Art> It is required by law such as the Pharmaceutical Affairs Law to print and display the product name, lot number, expiration date, etc. on solid preparations such as tablets, capsules, caplets, and cartons or medicine containers. Common printing means for these are:
The printing ink in the ink reservoir is supplied to the printing roller by the design roller, and the printing roller, which is in contact with the supply drum, transfers the printing ink to a printing material such as a tablet fed by the supply drum to perform required printing. Configuration.

In continuous printing by such transfer, excessive ink remains on the print roller over time, causing printing stains, or fine particles coming out of the printing material such as tablets, etc., resulting in print blurring and character breakage and character loss. Alternatively, printing defects such as missing characters occur.

Therefore, various devices for automatically inspecting for the presence or absence of such print defects have been devised. However, if the accuracy of detection of print defects is increased, slight printing that is merely a variation and cannot be called a print defect is considered. Detecting a defect also lowers the yield, and conversely, if the detection accuracy is lowered, the detection becomes coarse and the defective product cannot be reliably selected. For this reason, in reality, a print defect automatic inspection apparatus that meets user needs has not been put into practical use, and at present, print defects are constantly selected by visual inspection.

<Problems to be Solved by the Invention> However, in the above-described inspection of print defects by visual inspection, there is a problem that there is a large variation in inspection accuracy due to individual differences and print quality is not stable. In addition, inspection work is extremely inefficient and requires a large number of skilled inspectors,
These are factors that increase costs.

On the other hand, in continuous printing by transfer, as described above, excess ink remains on the print roller or accumulation of fine powder coming out of the tablet which causes a print defect occurs with time, so the print roller is cleaned each time. Unless it is possible, the cause of printing defects cannot be eliminated. Therefore, the same applicant as the present application has devised an apparatus for automatically cleaning the print roller (see Japanese Patent Application Laid-Open No. 67-10457). However, since the printing defects are visually inspected, cleaning cannot be automatically performed in association with the inspection results of the printing defects. , There is a concern that the efficiency of the printing operation may be reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and various printing defects can be detected reliably and with good yield, and a printing operation can be performed efficiently by effectively cleaning a printing roller. An object of the present invention is to provide a print defect automatic inspection apparatus.

<Means for Solving the Problems> In the present invention, as a technical means for achieving the above-described problems, a printing defect is inspected by the following means. That is, a supply means for transferring the printing material, a printing roller for sequentially transferring and transferring the printing ink to each printing material transferred by the supply means, and a cleaning position for bringing the printing roller into contact with and separating from the supply means. A printing roller position switching unit for switching to a printing position; a cleaning mechanism for pressing a cleaning member against the printing roller at the cleaning position; and a printing unit for transferring characters and symbols of a printed material transferred by the supply unit. And a total number of dots corresponding to the plasticity of the printing portion of the binary signal and the number of connected components in which the dots are continuous as a group. And the number of dots corresponding to the pixels of the printing section for each block obtained by dividing the inspection mask surrounding the printing section into N pieces. A print quality determination unit for determining at least two types of the cleaning mechanism and comparing them with a reference range, and outputting a failure detection signal when at least one of the types is out of the reference. The drive unit is configured to be driven and controlled.

<Operation> For example, in the inspection of a printing defect of a tablet, a printing roller rolls and transfers printing ink to a tablet which is sucked in alignment with a supply drum of a supply unit and is transported with the rotation of the supply drum. After printing is performed, the printing portion of the printed tablet is imaged by a camera or the like, and this video signal is converted into a binary signal, and the total number of dots corresponding to the pixels of the printing portion,
At least two of the number of connected components and the number of dots corresponding to the pixels of the printing unit for each divided block are obtained, and it is determined whether or not these are within the reference range.

First, by determining whether or not the total number of dots corresponding to the pixels of the printing unit is within the range of the reference total number of dots, it is possible to detect ink stains in the vicinity of the printing unit without increasing detection accuracy so much. Can be reliably detected.

Also, by determining whether the number of connected components is within the range of the reference number of connected components, it is possible to eliminate printing (omission), print out,
Ink stains and the like in the printing unit can be detected.

Furthermore, by individually determining whether or not the number of dots corresponding to the pixels of the printing unit in each block obtained by further dividing the inside of the inspection mask surrounding only the printing unit is within the range of the reference dot number for each divided block. In addition to missing prints, missing prints, and ink smears in the printing section, it is possible to reliably detect missing prints, different types of characters, and the like without significantly increasing the detection accuracy.

Therefore, by combining at least two of the above three types of inspection and determining that one of them is out of print when any one is out of the standard, a print defect can be detected with good yield and reliably. Since the print roller is cleaned by the cleaning mechanism according to the occurrence rate of the print defect, the print roller can be cleaned without deteriorating the printing efficiency, and the printing, the inspection of the print defect, and the cleaning of the print roller can be performed. Integrated operation can be performed by unmanned automatic operation.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention illustrating the case of a tablet 1 as a print material, and FIG. 2 is a block configuration diagram of a print quality determination unit. First, the outline will be described with reference to FIG. 1. A tablet 1, which is a printing material, is passed through a primary hopper 2 and a secondary hopper 3 to a first supply drum 4, a second supply drum 5, and a third supply drum 6. The printing ink is transferred by the printing roller 7 at the contact position with the printing roller 7 and transferred (printed) at the position of contact with the printing roller 7 when the third supply drum 6 is transferred, and further, the optical fiber (endoscope) is transferred. 8 is inspected at the inspection position opposite to the leading end of 8 to determine whether there is a printing defect. A non-defective product determined to have no printing defect by this inspection is dropped onto the discharge conveyor 9 and discharged, and a defective product having a printing defect Are collected in the defective product storage unit 10. The cleaning mechanism K is actuated in accordance with the frequency of occurrence of the printing defects, and stains on the transfer surface of the printing roller 7 are removed.

The tablet 1 is adsorbed to the first supply drum 4 with the surface facing outward, is transferred by the rotation of the supply drum 4, is irradiated by the lamp unit 11 when passing through the inspection position, and is irradiated by the camera 12. The tablet 1 is processed by processing the image signal.
An inspection is performed to determine whether a foreign substance is present on the surface of the device. Then, at the position where the first supply drum 4 is in contact with the second supply drum 5, the tablet 1 is adsorbed from the first supply drum 4 to the second supply drum 5 with the back surface facing outward. In the same manner as described above, the light is illuminated by the lamp unit 13 when passing through the inspection position and is imaged by the camera 14, and the image signal is processed to determine whether or not a foreign substance is present on the back surface of the tablet 1. Is performed.

Thereafter, the second supply drum 5 is moved to the third supply drum 6.
The tablet 1 is aligned with the outer peripheral surface of the second supply drum 5 from the second supply drum 5 to the third supply drum 6 as shown in FIG. The drum 6 is successively fitted into the pocket 6 'recessed in the state by a suction force of a vacuum suction device (not shown), and is transferred as the drum 6 rotates.

The printing unit P supplies the printing ink in the ink reservoir 15 to the printing roller 7 by the design roller 16, and the printing roller 7
The printing ink is transferred to a predetermined portion of the surface of the tablet 1 and printed directly. The printing roller 7 has a printing position in contact with both the design roller 16 and the third supply roller 6 shown by a dashed line in FIG. 1, and a print position between the design roller 16 and the third supply roller 6 shown by a solid line in FIG. An air cylinder (not shown) can be used to selectively switch to a cleaning position that separates from both.
At the cleaning position, the transfer surface is cleaned by the cleaning mechanism K to remove dirt and the like.

The cleaning mechanism K includes, for example, a cleaning belt 17 in which gauze is laminated on one side of a core belt made of twill-woven fibers.
And a solvent nozzle 18 for injecting a solvent to the cleaning belt 17, an air cylinder 19 for moving these to and from a solid line position and an alternate long and short dash line position, and a solvent drying unit 20. When cleaning is performed, the air cylinder 19 is operated by a solenoid valve (not shown) to move to the solid line position, the cleaning belt 17 is pressed against the printing roller 7 at the cleaning position, and the cleaning is performed from the solvent nozzle 18. A solvent is sprayed on the belt 17, and the printing roller 7 rotates while contacting the cleaning belt 17.
The surface of the printing roller 7 wet by the solvent is dried by the dry air blown from the drying unit 20.

When the cleaning operation is completed, the air cylinder 19 retracts to the position indicated by the one-dot chain line and separates from the printing roller 7.
On the other hand, the printing roller 7 is also moved to the dashed line position and contacts the third supply drum 6 and the design roller 16, and the printing operation is restarted.

At the print defect inspection position along the third supply drum 6,
The tip of the optical fiber 8 is arranged, and
As shown in FIG. 2, a synchronization sensor 21 is disposed at a stage subsequent to the print defect inspection position in the rotation direction of the third supply drum 6, and is provided for the third supply drum 6 rotated at a constant speed. The passage of the tablet 1 is detected, and a detection signal is output to the inspection synchronization signal generation circuit 22.
Outputs a test synchronization signal by synchronizing the detection signal from the synchronization sensor 21 with the horizontal synchronization signal and the vertical synchronization signal from the horizontal / vertical synchronization signal generation circuit 23.

Then, when the printed tablet 1 is transported with the rotation of the third supply drum 6 and reaches the print defect inspection position, the strobe light 24 is turned on at the output timing of the inspection synchronization signal to irradiate the tablet 1. At the same time, the reflected light from the tablet 1 is incident on the CCD camera 25 through the optical fiber 8, is photoelectrically converted by the CCD solid-state imaging device of the CCD camera 25, and is a still image of the tablet 1 at the moment when the tablet 1 passes the print defect inspection position. A signal is obtained, and the image signal is subjected to signal processing by the print quality determination unit 26.

Next, the print quality determination unit 26 will be described with reference to FIG. The video signal of the single tablet 1 from the CCD camera 25 is decomposed into horizontal-vertical 512 × 512 pixels by a horizontal synchronizing signal and a vertical synchronizing signal, and is converted into an 8-bit digital signal by an A / D conversion circuit 27. That is, after being converted into a 256-level digital signal corresponding to the gray level, the image digital signal for one tablet 1 is stored in the image frame memory.
28 is temporarily stored in a dot matrix. FIG. 4 schematically shows an image stored in the image frame memory 28, and FIG. 3 shows a screen M of a monitor 29 by an image digital signal of the image frame memory 28. 5 shows an image in which a symbol combining a square and a triangle and three numbers are printed in the center thereof.

This image digital signal is used as a binarized reference level setting circuit.
A signal corresponding to a print portion such as a print character or a symbol is extracted from the image digital signal by comparing with a reference value of 0 to 255 steps for binarization which is externally set in advance at 30. It is converted into a digitized signal and stored in a 512 × 512 binarized frame memory 32 in a matrix form, that is, at a predetermined address corresponding to the coordinate position of the image by the horizontal and vertical synchronization signals. FIG. 5 schematically shows the storage state of the binarized frame memory 32.

Since the binarized signal stored in the binarized frame memory 32 is also a signal at a horizontal-vertical coordinate position,
In the inspection mask base point detection circuit 33 and the inspection mask size setting unit 32, a window which becomes an inspection range based on each specific coordinate position of a vertical signal and a horizontal signal in the binarized signal read from the binarized frame memory 14. And an inspection mask are set.

First, to describe the setting of the window W ₁ shown in FIG. 6, the minimum coordinate position V ₁ initially manifested among the vertical signal of the image e of the tablet 1 in the matrix to stored image digital signal in the image frame memory 28 and thereby detecting the respective first minimum coordinate position H ₁ appearing among the horizontal signal, the two detecting minimum coordinate position V _1, respectively H ₁ predetermined offset value V _0, H ₀ respectively summing the vertical and horizontal after setting the window W ₁ which surrounds the printing unit based on the horizontal and vertical lines through each coordinates of the image digital signal of the window W ₁ is binarized, the 2
From the digitized signal, the total number of dots corresponding to the pixels of the printing section and the number of connected components in which the dots corresponding to the pixels of the printing section of the binarized signal continue as a group are calculated. Incidentally, the number of connected components in this embodiment is "4" by a symbol and three numbers.

Subsequently explained setting of the inspection mask W ₂ shown in FIG. 7, in the inspection mask base point detecting circuit 33, among the first occurrence of minimum coordinate positions V ₂ and a horizontal signal among the vertical signal of the printed portion of the image A horizontal line passing through the vertical and horizontal coordinates obtained by adding the predetermined offset values V ₃ and H ₃ to the two detected minimum coordinate positions V ₂ and H ₂ respectively while detecting the minimum coordinate position H ₂ that appears first. And the intersection of the vertical line and the coordinate position of this intersection is set as the base point of the inspection mask. On the other hand, the inspection mask size corresponding to the object to be inspected is set in advance in the inspection mask size setting unit 34, and the base point of the set inspection mask size is set to the coordinate position of the base point set by the above-described inspection mask base point detection circuit 33. inspection mask W ₂ to be inspected range is matched is automatically set. Then, the inspection mask W _2, (in the figure 5 × 5) a predetermined number as shown in Figure 8 is divided into blocks of, determine the number of dots corresponding to the pixels of the printing unit for each the divided block.

It should be noted that the inspection mask size can be arbitrarily variably adjusted by the inspection mask size setting unit corresponding to the inspection object. The reason for this is that the inspection object such as the tablet 1 is often transported by the third supply drum 6 while being fixed at a position shifted from the predetermined position of the pocket 6 ′.
When the position of the W ₂ thereby fixed setting, a part such as a print character becomes be located outside the test mask, resulting determines inconvenience erroneously good and defective products. In order to solve this problem, the inspection mask is set to a floating type and the inspection mask is automatically set by detecting a base point from a printed portion of the inspection object.

In addition, the reference width setting unit 35, the inspection and the total number of dots and connected components number corresponding to a pixel of the printed portion of the window W ₁ based on the print good average tablet 1 of a predetermined number mask W ₂
Are set in advance with three types of reference widths corresponding to the number of dots corresponding to the pixels of the printing unit for each divided block. Then, the microcomputer 36 is a control unit, the total number of dots in the window W ₁ corresponding to the pixel of the printing portion detected from the binary signal read from the binary frame memory 14 at the timing of the test synchronization signals and connected Number of components and inspection mask
The number of dots and corresponding to the pixels of the printing unit of each divided block in W _2, in contrast to the three kinds of reference width of the aforementioned set in the reference width setting unit 35, if not enter the reference width defect detecting A signal is output to drop the tablet 1 from the third supply roller 6 to the defective product storage section.

Quality decision by the total number of dots of the aforementioned printing unit, the aims of detecting a test mask W ₂ outside the printing stain NG1 the like shown in FIG. 8, which reference total dot number range may be coarse detection accuracy .

In the pass / fail determination based on the number of connected components corresponding to the pixels of the printing unit, the number of connected components in this embodiment is “4”, but the number of cut-out NG2 or “9” such as the number “1” in FIG. If print omission NG3 or print smudge NG1 such as a number exists, the number of connected components increases or decreases, so that it is determined that the print defect exists.

In the pass / fail determination based on the number of dots corresponding to the pixels of the printing unit for each divided block, the inspection mask W ₂ surrounding only the printing unit in addition to the print stain NG1, the print cut NG2, and the print omission NG3.
Since the inside is further divided into blocks and inspected for each detail, it is possible to reliably detect missing prints NG4 and heterogeneous characters such as the numeral “3” in FIG. 8 without increasing the inspection accuracy so much.

A defect detection signal is output when any one of the inspection results of the three types of printing defects is out of the standard, and when the rate of occurrence of the defect detection signal exceeds a set value, the cleaning mechanism unit K is operated. Alternatively, when the cleaning mechanism K operates at regular intervals, the operation of the cleaning mechanism K is stopped when the rate of occurrence of the failure detection signal is equal to or less than a set value, thereby improving the efficiency of the cleaning operation. In addition to performing the printing operation efficiently, the printing operation, the inspection of the printing defects, and the cleaning operation of the printing roller based on the inspection result can be performed by the unmanned automatic operation.

<Effect of the Invention> As described above, according to the automatic printing defect inspection apparatus of the present invention, the total number of dots corresponding to the pixels of the printing section and the continuous connection of the dots corresponding to the pixels of the printing section in the portion including the printing section. The print defect is inspected by combining at least two of the three types of inspection items of the number of components and the number of dots corresponding to the pixels of the printing unit for each block obtained by dividing the inside of the inspection mask surrounding only the printing unit. Printing defects can be detected well and reliably.

Further, since the cleaning of the print roller is automatically performed based on the inspection result of the print defect, the cleaning can be effectively performed without lowering the printing efficiency, and the printing, the inspection of the print defect, and the cleaning of the print roller can be performed. Cleaning can be performed by unmanned automatic operation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment of the present invention, FIG. 2 is a block diagram of a print quality judgment unit in FIG. 1, FIG. 3 is a diagram showing a screen of a monitor in FIG. 2, and FIG. FIG. 5 is a schematic diagram of the storage state of the image frame memory of FIG. 2, FIG. 5 is a schematic diagram of the storage state of the binarized frame memory of FIG. 2, FIG. FIG. 7 is an explanatory diagram of the setting of the inspection mask of FIG. 2, and FIG. 8 is an explanatory diagram of a printing defect. 1 tablet (substrate to be printed) 6 third supply roller (supply unit) 7 printing roller 17 cleaning belt (cleaning unit) 25 CCD camera (imaging unit) 26 printing quality judgment unit K ...... cleaning mechanism W ₂ ...... inspection mask

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41F 33 / 14,35 / 02,17 / 36 G01N 21/89 G06F 15/62

Claims (1)

(57) [Claims] 1. A supply means for transferring a printing material, a printing roller for transferring the printing ink by sequentially rolling and contacting each printing material transferred by the supply means, and bringing the printing roller into and out of contact with the supply means. A printing roller position switching means for switching between a cleaning position and a printing position; a cleaning mechanism for pressing a cleaning member against the printing roller at the cleaning position; characters and symbols of a printed material transferred by the supply means; Imaging means for outputting a video signal of the printing section, and the video signal is converted into a binary signal, and the total number of dots corresponding to the pixels of the printing section of the binary signal and the dots are continuous as a group Three types of inspections, the number of connected components and the number of dots corresponding to the pixels of the printing unit for each block obtained by dividing the inspection mask surrounding the printing unit into N blocks A print quality determination unit that obtains at least two types of eyes, compares them with a reference range, and outputs a failure detection signal when at least one of the eyes is out of a reference. An automatic print defect inspection apparatus, wherein the cleaning mechanism is driven and controlled.