Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-07-15
2001-03-06
Brase, Sandra (Department: 2852)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S117000
Reexamination Certificate
active
06198496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to printers and facsimile machines, and more particularly to a printer where multiplexed print data is transferred from control circuits to corresponding one of a plurality of print heads via a common bus line.
2. Description of Related Art
An electrophotographic color printer incorporates a series of print engines of the same construction. Each print engine operates for a corresponding one of yellow, magenta, cyan, and black images. Such a system is referred to as tandem system. An LED array illuminates a photoconductive drum to form an electrostatic latent image of a corresponding color on the surface of the drum. The electrostatic latent image is then developed with a corresponding colored toner into a colored toner image. The colored toner image is then transferred to a print medium. As the print medium passes through the series of print engines, yellow, magenta, cyan, and black toner images are transferred one over the other on the print medium, thereby producing a full color image.
However, a tandem system requires a large number of interface cables which increase manufacturing cost. For example, a control circuit generates image data for each color and transfers the image data to a corresponding LED print head. Therefore, in order to communicate image data and associated control signals, a total of four sets of cables are connected between the respective LED print heads and the circuit board on which the control circuits are built.
A large number of cables necessarily increases the number of connectors and the number of pins of LSIs that connect cables, and therefore requires large circuit boards. This increases the total cost of the printer. In addition, a large number of wires radiate more noise, and therefore requires some measure for addressing increased noise radiation.
The aforementioned problems exist not only in a printer having a plurality of LED heads but in thermal transfer type printers, ink jet type printers and the like having a plurality of print heads.
SUMMARY OF THE INVENTION
An object of the invention is to provide a printer which minimizes the number of cables required for transferring image data and associated control signals such as clock, strobe, and latch.
A printer of the invention includes a plurality of LED heads or the like and a plurality of head controllers. Each head controller transfers a plurality of items of data, including image data and control signals associated with the image data, to a corresponding one of the plurality of heads over a set of common buses. Each LED head has a receiver that is activated by a corresponding head selecting signal and receives the plurality of items of data.
In the first embodiment, the image data DD is transferred over the data bus and the control signals (clock DK, strobe DS, and latch DL) are transferred over corresponding lines of the set of common buses.
In the second embodiment, the set of common buses include a selector bus over which the selector signal DC is transferred and a data bus over which the image data DD and the a group of signals (strobe DS and latch DL) are alternately transferred. The group of signals includes a latch signal DL for latching the image data DD into a corresponding head strobe signals DS for driving a corresponding head in accordance with the image data DD. The selector signal DC indicates which of the image data DD and the group of signals is transferred over the data bus.
In the third embodiment, encoding the control signals reduces the number of bus lines of the set of common buses. In the fourth embodiment, the control signals include a group of signals (strobe DS and latch DL), an image clock, and a control clock. The set of common buses include an image clock bus over which the image clock GK is transferred, a control clock bus over which the control clock SK is transferred, and a data bus over which the image data DD and the group of signals are alternately transferred. The group of signals is attended by the control clock SK and the image data is attended by the image clock GK.
In the fifth embodiment, the image data DD includes a train of image data in which first image data and second image data appear alternately. One of two receivers receives the first image data on the rising edges of the image clock GK and the other receivers receives the second image data on the falling edges of the image clock GK.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4455578 (1984-06-01), Fearnside
patent: 5179392 (1993-01-01), Kawaguchi
patent: 5339150 (1994-08-01), Hubble, III et al.
patent: 5751327 (1998-05-01), De Cock et al.
patent: 5754218 (1998-05-01), Baek et al.
patent: 5809216 (1998-09-01), Ng
Akin Gump Strauss Hauer & Feld L.L.P.
Brase Sandra
Oki Data Corporation
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