1. Field of the Invention
The present invention relates to an apparatus and a method for extracting an uppermost printing plate from a stack of printing plates accommodated in a cassette and conveying the extracted printing plate to a processing section.
2. Description of the Related Art
Apparatus have been developed in which it has become possible to quickly and directly record, by exposure with a laser beam or the like, an image on a printing plate comprising a support having disposed thereon an image forming layer. Such apparatus typically include a cassette that accommodates a stack of printing plates. The cassette is disposed substantially parallel to a surface on which the apparatus is placed, with the printing plates being stacked on a base of the cassette.
The printing plates are extracted from the cassette one at a time and conveyed to a section where the printing plates are exposed. In order to extract the uppermost printing plate from the cassette, the uppermost printing plate is usually sucked by suckers and guided along guide rails to the exposure section.
In this case, it is necessary to uniformly arrange and dispose the suckers substantially parallel to the surface of the uppermost printing plate, and move the suckers so that the uppermost printing plate is evenly sucked and lifted. However, the following problems arise.
Firstly, the area of contact between adjacent printing plates is large and the contact is close. Therefore, when the uppermost printing plate is to be separated from the underlying printing plate, an excessive amount of sucking force is necessary. It is also necessary to ensure that the uppermost printing plate is separated from the underlying printing plate by, for example, swinging the uppermost printing plate after it has been sucked and slightly lifted by the suckers.
Secondly, the path along which the extracted printing plate is conveyed to the exposure section is not only long, but must be disposed with a plurality of rollers, which leads to an increase in the number of parts necessary for the apparatus.
Additionally, depending on the printing plate, it is not always possible for the printing plate to be suckingly extracted by the suckers due to the vulnerability of the image forming layer. In order to cope with this problem, the printing plates are stacked so that surfaces opposite to the surfaces on which the image forming layers are disposed face up, so that the surface of the printing plate that is sucked by the suckers is the surface of the printing plate opposite to the surface on which the image forming layer is formed.
In this case, however, the extracted printing plate needs to be inverted during conveyance to the exposure section. If extraction, inversion, and conveyance of the printing plates are separately controlled, systems for driving and controlling these operations become complicated.
In view of the above-described facts, an object of the present invention is to obtain an apparatus and a method for extracting an uppermost printing plate from a stack of printing plates accommodated in a cassette and conveying the extracted printing plate by rollers or the like along a shorter conveyance path to a processing section without scratches being formed on an image forming layer of the printing plate.
Another object of the present invention is to obtain an apparatus and a method for extracting and conveying a printing plate in which the printing plate can be extracted, inverted, and conveyed to a processing section in one operation.
A first aspect of the present invention is an apparatus for extracting an uppermost printing plate from a cassette in which printing plates are stacked and conveying the extracted printing plate to a processing section, the apparatus comprising: movable bodies, each of which are movable along a guide rail disposed between the cassette and the processing section; a holding member disposed at each of the movable bodies and movable towards and away from ends of the printing plates in the cassette opposite to ends disposed near the processing section, the holding member holding the uppermost printing plate as the holding member is moved towards the uppermost printing plate and separating the uppermost printing plate from an underlying printing plate as the holding member is moved away; separation members provided at end corners of the cassette opposite to end corners disposed near the processing section, the separation members curving the uppermost printing plate while the holding member separates the uppermost printing plate from the underlying printing plate; a moving device for moving each of the movable bodies along the guide rail to the processing section while the holding member holds the uppermost printing plate; and a rotation device for rotating the uppermost printing plate held by the holding member at a predetermined radius of curvature while the movable bodies are moved by the moving device, such that the uppermost printing plate is inverted.
According to the apparatus of the first aspect, the movable bodies are moved along the guide rails and made to face the cassette. The holding member approaches the stack of the printing plates accommodated in the cassette, holds the uppermost printing paper, and is moved away from the stack while holding the uppermost printing plate. At this time, the printing plate interferes with the separation members and is curved, for example. Because of this curve, air enters between the uppermost printing plate and the underlying printing plate. As a result, separation of the uppermost printing plate from the underlying printing plate is improved, and only the uppermost printing plate is reliably extracted from the cassette.
The extracted printing plate is conveyed to the processing section by the movable bodies being moved along the guide rails. Along with this movement, the holding member is rotated at a predetermined radius of curvature. By the rotation of the holding member, the printing plate is taken out so that the end of the printing plate opposite to the end near the processing section is lifted, and the printing plate is inverted and sent into the processing section. Due to the inversion, the surface of the printing plate opposite to the surface on which the image forming layer is formed can be held by the holding member, and the image forming layer can be prevented from being scratched by the holding member.
Further, immediately after the holding member holds the printing plate, the printing plate is still supported by the underlying printing plate except for the portion held by the holding member, namely, the end opposite to the end near the processing section, and the area of the printing plate supported by the underlying printing plate is gradually decreased. Therefore, holding power of the holding member does not need to be increased more than necessary.
Furthermore, the printing plate is conveyed along with the rotational movement of the rotation device. Accordingly, the path along which the printing plate held by the holding member is conveyed can be shortened.
In the apparatus of the first aspect, plural cassettes are preferably stacked in a direction that is the same as the direction in which the printing plates are stacked, and the apparatus further includes a device for retracting cassettes accommodating printing plates not in use, such that the cassette accommodating printing plates to be used faces the holding member.
According to the apparatus of the first aspect, plural cassettes are stacked in the direction which is the same as the direction in which the printing plates are stacked. For example, when the cassettes are disposed parallel to a surface on which the apparatus is placed, the cassettes except the uppermost cassette are hidden by cassettes disposed above them. Therefore, cassettes other than the cassette accommodating printing plates to be conveyed to the processing section are retracted such that the cassette accommodating printing plates to be used faces the holding member. Namely, the cassette in use is not moved.
When the cassettes are stacked parallel to the surface on which the apparatus is placed as described above, it suffices if the cassettes accommodating printing plates not in use are moved parallel to the surface on which the apparatus is placed.
A second aspect of the present invention is an apparatus for extracting an uppermost printing plate from a cassette, in which printing plates and interleaf sheets for protecting image forming surfaces of the printing plates are alternately stacked, and conveying the extracted printing plate to a processing section, the apparatus comprising: an interleaf sheet removal device that is actuated when an interleaf sheet is disposed at the top of the stack and removes the interleaf sheet; movable bodies, each of which are movable along a guide rail disposed between the cassette and the processing section; a holding member disposed at each of the movable bodies and movable towards and away from ends of the printing plates in the cassette opposite to ends disposed near the processing section, the holding member holding the uppermost printing plate as the holding member is moved towards the uppermost printing plate and separating the uppermost printing plate from an underlying printing plate as the holding member is moved away; separation members provided at end corners of the cassette opposite to end corners disposed near the processing section, the separation members curving the uppermost printing plate while the holding member separates the uppermost printing plate from the underlying printing plate, and making air enter between the uppermost printing plate and the underlying printing plate, thereby improving separation of the uppermost plate from the underlying plate; a moving device for moving each of the movable bodies along the guide rail to the processing section while the holding member holds the uppermost printing plate; and a rotation device for rotating the uppermost printing plate held by the holding member at a predetermined radius of curvature while the movable bodies are moved by the moving device, such that the uppermost printing plate is inverted.
According to the apparatus of the second aspect, interleaf sheets and printing plates are alternately stacked in the cassette. Because of this structure, the printing plates and the interleaf sheets are alternately extracted. It suffices if the interleaf sheet removal device, which is actuated when the interleaf sheet is disposed at the top of the stack and removes the interleaf sheet, is added to the apparatus of the first aspect.
In the apparatus of the second aspect, plural cassettes are preferably stacked in a direction that is the same as the direction in which the printing plates and the interleaf sheets are stacked, and further comprising a device for retracting cassettes accommodating printing plates not in use, such that the cassette accommodating printing plates to be used faces the holding member or the interleaf sheet removal device.
In the apparatus of the second aspect, plural cassettes are stacked in the direction which is the same as the direction in which the printing plates are stacked. For example, when the cassettes are disposed parallel to a surface on which the apparatus is placed, the cassettes except the uppermost cassette are hidden by cassettes disposed above them. Therefore, cassettes other than the cassette accommodating printing plates to be conveyed to the processing section are retracted such that the cassette accommodating printing plates to be used faces the holding member. Namely, the cassette in use is not moved.
When the cassettes are stacked parallel to the surface on which the apparatus is placed as described above, it suffices if the cassettes accommodating printing plates not in use are moved parallel to the surface on which the apparatus is placed.
A third aspect of the present invention is a method for extracting and conveying a printing plate, comprising the steps of: (a) determining the size of a printing plate to be processed and selecting a cassette in which printing plates of the determined size are stacked; (b) controlling suckers for sucking and lifting an uppermost printing plate from the cassette; and (c) controlling a conveyance unit disposed near the cassette such that the printing plate is inverted and conveyed to a processing section.