Printing – Planographic – Rotary machines
Reexamination Certificate
2000-07-12
2001-10-16
Eickholt, Eugene (Department: 2854)
Printing
Planographic
Rotary machines
C101S183000, C101S216000, C101S247000
Reexamination Certificate
active
06302018
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an offset printer, and more particularly, to a digital offset printer in which rotation of a drive motor is transmitted to a paper feed mechanism and a paper discharge mechanism through an impression cylinder, and also transmitted to an ink reciprocation roller through the impression cylinder, a blanket cylinder and a plate cylinder.
Japanese Patent Application Publication No. 9-510410 discloses an offset printer capable of performing offset printing with four different colors of inks. The printer includes a single impression cylinder, a single paper discharge mechanism, a single paper feed conveyer, a single transfer drum, two blanket cylinders, two plate cylinders and, ink rollers for the four colors. The paper feed conveyer and the transfer drum are adapted for delivering a paper to a surface of the impression cylinder. The paper is mounted on the surface of the impression cylinder. The paper discharge mechanism is adapted to discharge the paper from the impression cylinder. The blanket cylinder is pressed against the paper mounted on the impression cylinder.
The impression cylinder is rotated about its axis by the drive motor. Further, two blanket cylinders have their axes extending in a direction parallel with the axis of the impression cylinder, and the two blanket cylinders are in contact with the impression cylinder and are rotated upon rotation of the impression cylinder. The paper feed conveyer, the transfer drum and the paper discharge mechanism are also driven or rotated by the rotation of the impression cylinder.
Each plate cylinder has a peripheral surface provided with a thin plate where an image to be printed is formed. The two plate cylinders have their axes extending in a direction parallel with the axes of the blanket cylinders. Each plate cylinder is in contact with each blanket cylinder, and each plate cylinder is rotated upon rotation of each blanket cylinder. Each peripheral surface of the plate cylinder is divided into two segments. One of the segments is formed with an image with a single color, and remaining segment is formed with an image with a different color. Accordingly, the two plate cylinders form images of four colors.
The ink roller is adapted for supplying an ink to the plate of the plate cylinder. To this effect, two ink rollers are provided in contact with each plate cylinder so that two different colored inks can be supplied to each plate. Accordingly, totally four ink rollers are provided for four different colors. Axes of the ink rollers extend in parallel with the axis of the plate cylinder. The ink rollers are rotated upon rotation of the plate cylinder.
In the digital offset printer, the plate cylinders must be rotated about their axes so as to form images on the plates. This is similar to a laser printer in which a photo-sensitive drum is rotated so as to form an electro-static latent image on an outer peripheral surface of the drum. The drive motor, which is a single drive source, is driven to rotate the plate cylinder.
SUMMARY OF THE INVENTION
However, in the conventional digital offset printer, driving force of the motor must be transmitted to the plate cylinder by way of the impression cylinder and the blanket cylinders in order to rotate the plate cylinder for image formation thereon. Accordingly, the paper feed conveyer, the transfer drum and paper discharge mechanism are also rotated or driven by the rotation of the impression cylinder. Further, the ink rollers are also rotated upon rotation of the plate cylinders. However, the paper feed conveyer, the transfer drum, the paper discharge mechanism and the ink rollers make no contribution for forming images on the plate cylinders.
Reduction in time period requiring for the image formation is one of the factors in reduction in time period requiring for entire printing operation. In order to reduce the image forming period, the rotation speed of the plate cylinders must be increased. However, the rotation of the plate cylinders also causes rotation or driving of the other components which are not necessary for image formation on the plate. Therefore, high speed rotation of the plate cylinders may not be provided, and otherwise loss in rotation force may be increased, and the main body of the offset printer may be vibrated due to the concurrent rotations or driving.
It is therefore, an object of the present invention to provide an offset printer capable of shutting off the power transmission to components during a process for forming an image on the surface of the plate cylinder, the components being nothing to do with the image formation during this process.
This and other objects of the present invention will be attained by an offset printer including a frame, a drive motor supported on the frame, a drive gear for outputting a rotation force of the drive motor, an impression cylinder, a paper feed mechanism, a paper discharge mechanism, a blanket cylinder, a plate cylinder, an ink supplying mechanism, and a power transmission shut off mechanism. The impression cylinder has an impression cylinder gear provided coaxially and integrally rotatable therewith. The impression cylinder gear is meshedly engaged with the drive gear for rotating the impression cylinder upon rotation of the output gear. The paper feed mechanism includes a paper feed cylinder gear meshedly engaged with the impression cylinder gear, and a paper feed cylinder rotatable coaxially with the paper feed cylinder gear upon rotation of the impression cylinder gear for feeding a paper to a surface of the impression cylinder. The paper discharge mechanism includes a paper discharge gear meshedly engaged with the impression cylinder gear, a paper discharge portion rotatable coaxially with the paper discharge gear, and an endless chain mounted on the paper discharge portion and circularly movable on the paper discharge portion for removing the paper from the impression cylinder. The blanket cylinder is in contact with the surface of the impression cylinder and has a blanket cylinder gear meshedly engaged with the impression cylinder gear. The blanket cylinder gear is rotatable integrally with the blanket cylinder gear upon rotation of the impression cylinder gear. The plate cylinder has a plate cylinder gear meshedly engaged with the blanket cylinder gear. The plate cylinder is rotatable integrally and coaxially with the plate cylinder gear upon rotation of the blanket cylinder gear and in contact with a surface of the blanket cylinder for forming an image on a surface of the plate cylinder. The ink supplying mechanism is driven by the rotation of the plate cylinder for supplying an ink to the surface of the plate cylinder. An inked image is formed on the surface of the plate cylinder by the supplied ink based on an image formed on the surface of the plate cylinder, and the inked image on the plate cylinder is transferred to the surface of the blanket cylinder, and the impression cylinder presses a paper against the surface of the blanket cylinder for transferring the inked image on the blanket cylinder to the paper. The power transmission shut off mechanism is adapted for preventing the rotation force of the drive motor from being transmitted to at least one of the paper feed mechanism, the paper discharge mechanism and the ink supplying mechanism at least during image formation process on the surface of the plate cylinder.
With the structure, because the transmission of rotation force from the drive motor to at least one of the paper feed mechanism, the paper discharge mechanism and the ink supplying mechanism is shut off during the image forming process on the surface of the plate cylinder, it becomes possible to avoid idle driving of at least one of the above described mechanisms which driving is unnecessary for the image formation. For example, if the power transmission from the drive motor to the paper feed mechanism is shut off, the power transmission to the paper feed cylinder can be shut off. If the power transmission from the drive motor to the paper
Aoyama Hideo
Liang Dong
Tahara Naritoshi
Eickholt Eugene
Ryobi Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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