Electrocoagulation printing apparatus

Details Electrocoagulation printing apparatus Electrocoagulation printing apparatus

1999-04-01

2001-02-20

Gorgos, Kathryn (Department: 1741)

Chemistry: electrical and wave energy

Apparatus

Electrophoretic or electro-osmotic apparatus

C204S622000, C101SDIG029

Reexamination Certificate

active

06190527

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an electrocoagulation printing apparatus for reproducing an image by electrocoagulation of ink and transferring the image thus reproduced onto a substrate.
U.S. Pat. No. 4,895,629, discloses an electrocoagulation printing apparatus including opposed frames, a cylindrical positive electrode, coating means, ink feed means, a printing head, and a pressure roller.
The positive electrode is rotatably supported between the frames. The positive electrode is provided at its outer peripheral surface with a passivated surface defining a positive electrode active surface.
A printing head includes pin-like negative electrodes, and is supported between supporting bars extending upward from the frames. A gap of about 50 &mgr;m is formed between the outer peripheral surfaces of the negative electrode of the printing head and an outer peripheral surface of the positive electrode.
The coating means coats oily material on the surface of the positive electrode. The electrocoagulation printing ink which includes the coloring agent is injected into the gap from the ink feed means. When the negative electrode is electrically energized, multivalent metal ions are generated from the positive electrode, and dots of the coagulated ink representing a desired image are formed on the surface of the positive electrode.
The pressure roller is rotatably supported between brackets extending from the frames in a lateral direction, and transfers the coagulated ink from the surface of the positive electrode to a paper web, thereby printing the desired image on the web.
SUMMARY OF THE INVENTION
For example, a preferable size of the gap under a certain condition is very small and is about 50 &mgr;m. Since the size of the gap affects the print image, it is necessary to keep the gap within a range of 50 &mgr;m±5 &mgr;m. For example, if the gap is 40 &mgr;m or less, there is a possibility that a void in a highly density region is generated due to shortage of ink. If the gap is 60 &mgr;m or greater, there is a possibility that unclear image is printed due to bad dot formation. When the gap is greater than a distance between the negative electrodes, there is a possibility that the negative electrodes are damaged due to electricity flowing between the negative electrodes. In order to prevent such an inconvenience, an operator needs to frequently adjust the size of the gap using a precision screw, which is troublesome.
Further, the size of the gap may be varied because constituent elements of the apparatus are expanded or contracted due to variation in temperature or load. For example, assuming that a distance from the surface of the positive electrode to the supporting portion of the printing head is 170 mm, the frames and the supporting bars are made of stainless steel, and the temperature is varied by 10° C., it is known that the size of the gap is varied by about 28 &mgr;m. Therefore, in order to keep the quality of the printed image constant, it is necessary to frequently adjust the gap during the printing operation. However, since the gap can not be adjusted when the apparatus is operated continuously, and the apparatus must be interrupted for adjusting the gap, it is difficult to enhance both the quality and the quantity of print.
It is an object of the present invention to provide an electrocoagulation printing apparatus capable of stably obtaining an image of high quality without interrupting the operation of the apparatus.
To achieve the above object, an electrocoagulation printing apparatus of the invention comprises: a positive electrode having a positive electrode active surface; a printing head having a negative electrode spaced from the positive electrode active surface by a gap; feed means for supplying ink into the gap, dots of coagulated ink for representing a desired image produced from the ink on the positive electrode active surface as the negative electrode is electrically energized; removing means for removing any non-coagulated ink from the positive electrode active surface; transfer means for bringing a substrate into contact with the dots of coagulated ink to cause transfer of the coagulated ink from the positive electrode active surface onto the substrate and thereby imprint the substrate with the image; gap measurement means for measuring the gap between the positive electrode active surface and the negative electrode; and gap control means for controlling the gap according to output from the gap measurement means.
With the above structure, the ink is supplied from the feed means into the gap, and if the negative electrode is electrically energized, the dots of the coagulated ink representing the desired image is produced on the positive electrode active surface. After the non-coagulated ink on the positive electrode active surface is removed by the removing means, the dots of the coagulated ink are transferred to the substrate by the transfer means, thereby imprint the substrate with the desired image.
The gap between the positive electrode active surface and the negative electrode is measured by the gap measurement means, and the measured value is sequentially output to gap control means. The gap control means controls the size of the gap in accordance with the input measured value. If the gap is changed during the operation of the apparatus, the gap control means sequentially controls the size of the gap appropriately.
Therefore, since the size of the gap during the operation is appropriately maintained automatically, it is possible to stably obtain an image of high quality without interrupting the apparatus.
The gap measurement means may include a gap measurement sensor, the gap control means may include a driving arrangement, and the driving arrangement may move the negative electrode so that a measured value by the gap measurement sensor falls within an established value.
With the above structure, if the size of the gap is changed, and the measured value by the gap measurement sensor falls out of the established value, the gap control means operates the driving arrangement to move the negative electrode. With this operation, the measured value falls within the established value.
The electrocoagulation printing apparatus may further include a movable unit with the printing head and the gap measurement sensor, and the positive electrode maybe rotatably connected to a frame body, the movable unit may be movably connected to the frame body, and the driving arrangement may move the movable unit.
With the above structure, if the measured value falls out of the established value, the gap control means operates the driving arrangement to move the movable unit. With this operation, the negative electrode is moved and the measured value falls within the established value.
The movable unit may include a supporting axis, a rotary axis and a lever, the printing head and the gap measurement sensor may be fixed with respect to the supporting axis, the supporting axis may be fixed with respect to the rotary axis, the rotary axis may be rotatably connected to the frame body, the lever may be projected from the rotary axis, the driving arrangement may include a push bar, a drive transmission mechanism, and a driving motor, the push bar may be movable up and down and may come in engagable contact with the lever for moving the lever, and the driving motor may be linked to the push bar via the drive transmission mechanism.
With the above structure, if the measured value falls out of the established value, the gap control means operates the driving motor. With this operation, the push bar moves up or down, the rotary axis rotates, the supporting axis is moved up or down, the negative electrode moves and the measured value falls within the established value.
The drive transmission mechanism may include a nut member, a vertical ball screw and a second abutment portion, the nut member may be fixed with respect to the push bar, the ball screw may be screwed with the nut member, and the second abutment portion may be provided below the lever.
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