1. Field of the Invention
The present invention relates to a device for adjusting an ink supply gap for an ink fountain apparatus of a printing press, and more particularly to a device for adjusting an ink supply gap adapted to move blade segments toward or away from an ink fountain roller so as to adjust the width of the ink supply gap.
2. Description of the Related Art
In an ink fountain apparatus for an inking arrangement of a printing press, ink is stored in an elongated space of a substantially V-shaped cross section, which is formed by the peripheral surface of an ink fountain roller, the bottom portion of the ink fountain apparatus having its forward edge located in proximity to the peripheral surface of the ink fountain roller with an appropriate gap therebetween, and a pair of side plates, each disposed at one lateral end of the bottom portion. When the ink fountain roller is rotated, the ink stored in the elongated space is withdrawn through an ink supply port, i.e., a gap between the peripheral surface of the ink fountain roller and the forward edge of the bottom portion of the ink fountain apparatus.
To control the amount of ink withdrawn through the ink supply port, i.e., the supply of ink, the ink fountain apparatus has a blade for adjusting ink supply located at its bottom portion and a device for adjusting an ink supply gap. The device for adjusting the ink supply gap causes the blade to advance or retract so that the forward edge of the blade moves toward or away from the peripheral surface of the ink fountain roller, thereby adjusting the opening of the ink supply port.
Such conventional devices for adjusting an ink supply gap are disclosed in, for example, Japanese Patent Application Laid-Open (kokai) Nos. 7-246699 and 8-230161.
According to "Blade Adjusting Device for Ink Fountain of Printing Press" disclosed in Japanese Patent Application Laid-Open (kokai) No. 7-246699, in order to adjust the width of a gap between an ink fountain roller provided in an ink fountain of a printing press and each of a plurality of blade segments, a gap adjust device is provided for each of the blade segments. The gap adjustment device includes pushing means for continuously urging a blade segment toward its base end by means of a compression coil spring; a push rod disposed in contact with the base end of the blade segment and adapted to move the blade segment; a front cam whose support shaft is disposed in parallel with the moving direction of the blade segment and whose face moves in parallel with the moving direction of the blade segment and is in contact with the base end of the push rod; position adjustment means for moving the support shaft of the front cam axially so as to adjust the axial position of the front cam; and drive means for rotating the front cam.
In order to adjust the initial position of each blade segment, the corresponding drive means is operated to rotate the corresponding front cam until the blade segment advances to a foremost position closest to the ink fountain roller. Then, the position adjustment means is operated to axially move the support shaft of the front cam, thereby adjusting the axial position of the front cam so as to bring the forward edge of the blade segment into contact with the ink fountain roller. In this state, the position adjustment means is locked to thereby set the blade segment to its initial position.
During printing, according to the amount of ink required at a widthwise position of a printing surface, the gap between a corresponding blade segment and the ink fountain roller is adjusted in the following manner. The drive means is operated to rotate the front cam in such a direction that the blade segment moves away from the ink fountain roller. Since the pushing means pushes the blade segment toward the front cam, the forward edge of the blade segment moves from the position of contact with the ink fountain roller to an appropriate position located away from the ink fountain roller.
According to "Regulating Device for Opening of Ink Key" disclosed in Japanese Patent Application Laid-Open (kokai) No. 8-230161, in order to adjust a gap between an ink fountain roller provided in an ink fountain of a printing press and each of a plurality of ink keys (corresponding to blade segments in the present invention), a gap adjustment device is provided for each ink key. The gap adjustment device includes a first hydraulic cylinder equipped with a piston connected to an ink key; a second hydraulic cylinder connected to the first hydraulic cylinder via an oil line and serving as drive means; and a third hydraulic cylinder provided in an oil line branching from the oil line which connects the first hydraulic cylinder and the second hydraulic cylinder and serves as adjustment means.
In order to move the ink key to its initial position, where the upper forward edge of the ink key is in contact with the peripheral surface of the ink fountain roller, the second hydraulic cylinder serving as drive means is locked, and the piston of the third hydraulic cylinder serving as adjustment means is moved to thereby move the piston of the first hydraulic cylinder. As a result, the ink key connected to the piston of the first hydraulic cylinder is moved accordingly.
The third hydraulic cylinder serving as adjustment means is locked, and the piston of the second hydraulic cylinder serving as drive means is moved by a drive device to thereby move the piston of the first hydraulic cylinder by means of oil contained in the oil line. As a result, the ink key connected to the piston of the first hydraulic cylinder is moved accordingly.
Notably, the cross sectional area of the pistons increases in sequence of the piston of the third hydraulic cylinder, that of the second hydraulic cylinder, and that of the first hydraulic cylinder. According to Pascal's principle, the stroke of the piston of the first hydraulic cylinder connected to the ink key becomes very small as compared to that of the second hydraulic cylinder serving as drive means and that of the third hydraulic cylinder serving as adjustment means. Accordingly, the movement of the ink key can be finely adjusted.
The above-described conventional gap adjustment devices involve drawbacks.
Specifically, in "Blade Adjusting Device for Ink Fountain of Printing Press" disclosed in Japanese Patent Application Laid-Open No. 7-246699, a plurality of blade segments are each provided with a motor and a plurality of gears which constitute the drive means; shafts, a cam, and a push rod which constitute the position adjustment means; and a compression coil spring serving as the pushing means. Thus, a large number of parts are used, and the mechanism of the device is complex. As a result, the frequency of failure is high, and maintenance and inspection are time consuming.
Accuracy in adjusting the gap between the ink fountain roller and a blade segment cannot be improved due to the backlash between gears and the influence of machining accuracy of the cam face.
In "Regulating Device for Opening of Ink Key" disclosed in Japanese Patent Application Laid-Open No. 8-230161, each of a plurality of ink keys must be provided with hydraulic piping; thus, complex piping is involved. Further, each ink key must be provided with a plurality of hydraulic cylinders, including a cylinder for moving the ink key, a cylinder for driving the ink key, and a cylinder for adjusting the ink key. Thus, the device assumes a large-scaled configuration, resulting in an increased manufacturing cost. Also, use of hydraulic oil involves a potential for oil leakage.