Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Utility Patent
1998-07-28
2001-01-02
Lee, Susan S. Y. (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S118000, C347S129000, C347S134000, C347S139000
Utility Patent
active
06169558
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns to a process for high speed laser printing as well as to an apparatus intended for carrying out this process.
2. Description of the Prior Art
As known, within the laser printers a rotary light sensitive roller is employed, which is activated by points of a laser beam having a suitable wave length, that generates on the surface of the light sensitive roller a pattern of positively charged points forming the image to be printed. The light sensitive roller is partially immersed in a liquid toner containing tiny negatively charged particles of colored powder kept suspended in a liquid whose nature is such as not to wet the light sensitive roller. The particles of negatively charged toner powder adhere therefore to the positively charged points of the light sensitive roller, which then by rotating transfers the image onto a band to be printed, for example a band of paper. Then, heating means cause the toner powders deposited on the band to melt, thus fixing the printed image. For a polychromatic printing, such process is repeated by using, in subsequent stations, toners containing powders of different colors.
In the known systems, the light sensitive roller is directly charged by a laser beam coming from a dot-shaped source controlled by a computer, and this beam has to charge for each turn of the light sensitive roller, namely for each printing operation, a very large number of points which corresponds to the number of pixels by which the image is defined, a number which may amount to millions or billions. Notwithstanding the high processing power of the modern computers, the very large number of operations to be repetitively effected for each turn of the light sensitive roller limits the printing speed. A limitation to the printing speed also results from the mechanical displacements that the laser unit should effect in order to scan each generatrix of the light sensitive roller. For these reasons the laser printing process cannot be suitably adopted for of massive productions, as for example those of the food packing or the magazine printing industries. Another unfavorable consequence of the limitations to the printing speed is that, in order to obviate therefor, one is sometimes led to limit the image definition, and therefore the number of pixels defining the image.
SUMMARY OF THE INVENTION
The object of this invention is therefore to provide a new laser printing process, and the apparatus intended to carry out the same, which should not be subjected to the said speed limitation, or may be subjected thereto in a substantially lower measure, and which, therefore, are suitable for being adopted for massive productions too, without reducing or even by increasing the image definition.
This object is attained, according to the invention, by a laser printing process using a rotary light sensitive roller electrically charged by points by a laser beam and intended for receiving onto the charged points a toner powder and then transferring the same onto a band to be printed, which comprises a first step wherein the image to be printed is stored, by a first laser beam coming from a first dot-shaped source controlled by a computer, onto a rotary memory roller whose surface is covered with a layer of a material capable of assuming either an amorphous or a crystalline structure, said structure being convertible under the action of a laser beam, said material showing a high difference in reflecting ability according to whether it assumes the one or the other of said structures, and comprises a second step wherein the thus stored image is transferred, by means of the optical reflection of second laser beams coming from a second source having in its whole a linear character, onto the light sensitive roller intended to receive the toner and to transfer the image onto the band to be printed.
Substantially, the process usually employed for charging an image by a pattern of single points, under the control of a computer, onto the light sensitive roller, is instead employed according to the invention for storing the image onto a memory roller. During this operation, the usual limitations to the operating speed are encountered. However, this operation has not to be repeated for each printing operation, but it has only to be effected once at the start of a repetitive print cycle of the same image, whereby the time spended for this operation has no importance. On the contrary, the printing speed is only influenced by the time needed for transferring the image from the memory roller onto the light sensitive roller, and this time may be radically reduced because this operation does not require any processing and it is effected by a standing unit, through the optical reflection of an entire series of points, by action of the second laser beams coming from a source which is linear in its whole. This second laser beam may cover the entire width of the light sensitive roller and therefore of the band to be printed. As a consequence it is possible to attain printing speeds which are much larger than the usual ones, and are suitable for massive productions too.
Correspondingly, the apparatus intended for carrying out the process according to the invention includes a rotary light sensitive roller, a toner distributing means co-operating with said light sensitive roller, means for advancing a band along a trajectory to co-operate with said rotary light sensitive roller in order to be printed, a rotary memory roller, a layer of a memory material covering the surface of said rotary memory roller, said memory material being capable of assuming either an amorphous or a crystalline structure, said structure being convertible under the action of a laser beam, and said memory material showing a high difference in reflecting ability according to whether it assumes the one or the other of said structures, a first laser beam emitting device including a first dot-shaped source, a computer controlling said first dot-shaped source and a first optical system arranged for forming onto said rotary memory roller an image to be printed, and a transfer device including a second source of second laser beams, which is linear in its whole, a second optical system arranged for focusing said second laser beams onto a generatrix of said rotary memory roller, from which they are reflected, and a third optical system arranged for projecting onto a generatrix of said light sensitive roller the laser beams reflected by said generatrix of said rotary memory roller onto which said second laser beams have been focused.
Said first laser beam emitting device includes a first dot-shaped source, a computer controlling said first dot-shaped source and a first optical system arranged for forming onto said rotary memory roller an image to be printed, all these components substantially conforming the corresponding components usually employed for forming an image onto the surface of a rotary light sensitive roller.
Said second source of second laser beams may be linear in the whole of its own extension, or it may be formed by a series of juxtaposed linear sources of more reduced extension or dot-shaped sources, arranged in line in order to form in their whole an extended linear source.
Said second and third optical systems may be partially combined with each other and comprise a semi-reflecting surface arranged for deviating towards said rotary light sensitive roller the laser beams reflected by said rotary memory roller.
Preferably, said memory material covering said rotary memory roller is an amorphous/crystalline material of a type suitable for being written repeatedly. Said memory material covering said rotary memory roller may be formed of Te/TeO
x
, In/InO
x
, Cu/CuN
x
or Sb
2
/Se
3
. The subscript “x” represents any numeral compatible with the indicated chemical formula.
Said rotary light-sensitive roller and said rotary memory roller may be actuated in solid manner or be synchronized in a rigid manner, but preferably they have independent actuation means. In this l
Melotti Renzo
Molino Sergio
Lee Susan S. Y.
Valmet Rotomec S.p.A.
Young & Thompson
LandOfFree
Process and apparatus for high speed laser printing using a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and apparatus for high speed laser printing using a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and apparatus for high speed laser printing using a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2445288