PRINT-REGISTRATION INDEXING DEVICE
Field Of The Invention This invention relates to the assembly line printing of information on compact discs during their manufacture in an on-line process. In particular it relates to printing registration to enable multiple color printing stages.
Background Of The Invention Compact discs are optical recording media that are read by a laser through one transparent surface of the disc. The optical data are pits that are too small to be seen by unaided eye, although they cause some diffraction that is visible. The data is recorded in a spiral from the inside outwardly, beginning a certain distance from a central hole in the disc. For identification purposes visible text is made to appear around the circumference of the central hole at a radius less that the start radius for the optical data.
Typically, compact discs have information printed on the surface that is not required to be transparent to a reading laser. The printing method usually employed is screen printing. Printing is usually accomplished by multiple print heads and/or multiple passes through the printing station of an assembly line. Brief Description Of The Invention The Print-Registration Indexing Device provides the means for removing an optical disc from a printing line, placing it in a storage buffer, and then returning it to the printing line in the exact angular orientation that it originally possessed prior to its first removal from the printing line. Such steps may be repeated an endless number of times. Usage of such a device allows an optical disc printer to apply a theoretically endless number of ink passes to a disc, while using a printer with a small number of printing heads.
Brief Description Of The Drawings Figure 1 is a side cutaway view of the spindle and robot of the invention. Figure 2 is a top view of the printer machine conveyer of the invention.
Figure 3 is side view of the present invention. Figure 4 is top view of a disc having an identification band.
Detailed Description Of A Preferred Embodiment
The purpose of the Print Registration Indexing Device is to allow a printer with any number of print heads to apply an unlimited amount of ink patterns to an optical disc, where the disc is removed from the printer's conveyor in between printer passes and returned to the printer with its previous angular orientation.
The registration task is achieved as follows. Optical discs 1. stacked on spindles 3_ are placed on the printer machine conveyor 5_ by means of a robot arm 1_ . The angular orientation of these discs is truly random, in that the standard identification markings in the identification band of the disc reside at differing angles when comparing disc to disc. A few positions away from the entrance to the conveyor exists the registration module a mechanical assembly which provides the actual registration of each disc. As discs pass under the registration module, a vacuum lifts the disc approximately one centimeter upward such that the disc becomes attached to a solid circular gripping region 11.
With the vacuum remaining intact, a steppe motor 1_3 soon activates to spin the optical disc at a constant velocity, during the spin, a beam of light 1_5 originating from a laser diode 1_7 strikes the identification band 1_9 of the disc. The reflected light reaches a photodetector 21_, whose electrical output is sent to a computer 23 for analysis.
At the computer, an algorithm analyzes the electrical output of the photodetector. Since the - -
identification band 1_9 of the optical disc is annular in shape, an endless circular array of data must be analyzed. The algorithm sets a reference point in the identification band where the stepper motor is given a signal to stop rotating. A minimum of two rotations is required so that the laser diode beam passes through the entire identification band with no breaks at the endpoints of the identification band. Each optical disc at the registration module will stop at the same reference point, affording an identical registration for each disc in the production run.
Once the stepper motor 1_3 stops at the reference position, the registration module places the disc back on the printer conveyor, where the vacuum 2_5 of the printer conveyor resumes its grip on the disc, holding it in place on the conveyor during printing until the exit robot J_ removes the disc from the line. This process can be run continuously for as many printer passes as the particular artwork requires.
While there have been shown and described and pointed out the fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention, which is expressed in the following claims.