1. Field of the Invention
This invention relates to a plate cylinder for a printing press, and more particularly to a plate cylinder having a positioning means used when a printing plate is set.
2. Description of the Prior Art
Conventional plate cylinders having a positioning means used when a printing plate for a printing press is set include plate cylinders disclosed in, for example, Japanese Patent Laid-Open Nos. 17409/1978 and 116546/1986 and Japanese Utility Model Publication Nos. 18183/1991 and 49880/1991.
Both of the plate cylinders disclosed in Japanese Patent Laid-Open 116546/1986 and Japanese Utility Model Publication No. 18183/1991 have a positioning means provided with a reference surface for aligning a side end of a printing plate therewith, and are capable of positioning a printing plate, when it is set in a printing press, by aligning a side end of the printing plate with the reference surface.
Both of the plate cylinders disclosed in Japanese Patent Laid-Open No. 17409/1978 and Japanese Utility Model Publication No. 49880/1991 are capable of positioning a printing plate when it is set, by engaging a predetermined recess formed in the printing plate with a locking portion of the plate cylinder.
These prior art plate cylinders for printing presses are provided with a reference surface as a positioning means used when a printing plate is set, and a means for aligning a slide end of a printing plate with the reference surface; or a locking portion and a means for engaging a recess in the printing plate with the locking portion. Therefore, these plate cylinders are inconvenient in that a user cannot change the printing plate positioning specifications freely.
When the user's printing plate positioning specifications are changed for unavoidable reasons, a plate cylinder in use has to be subjected to an additional complicated machining process, such as a boring process or a positioning means providing process for the modification thereof. In order to carry out such an additional machining process, it is necessary in some cases that a large-scale operation, such as an operation for removing a plate cylinder from a printing press be carried out.