Data processing: measuring – calibrating – or testing – Measurement system – Density
Reexamination Certificate
1999-01-22
2001-07-17
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Density
C101S119000
Reexamination Certificate
active
06263296
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for predicting a printing density under a desired printing condition and a method for predicting a printing condition under which a desired printing density is achieved, and also relates to devices for the same.
BACKGROUND OF THE INVENTION
Well known in the art is a stencil printing device in which a perforated stencil sheet is wound around a circumferential surface of a cylindrical printing drum with an ink supplied thereto, and in which the ink is transferred from the printing drum to a printing sheet through the perforated stencil sheet by pressing the printing sheet to the printing drum while the drum is rotated.
In a stencil printing above, it has been proposed in Japanese patent laid open publication (Kokai) No. 62-127276 that the printing density of an image to be printed on a printing sheet is variably set by variably setting a pressing force to be applied to the printing sheet against the printing drum, in accordance with the printing density information given by a means for setting printing density information, for instance, a printing density set up key provided on an operation panel.
Furthermore, since the printing density in stencil printing changes with printing speed, Japanese patent laid open publication (Kokai) No. 06-155880 has already proposed a method for implementing stencil printing at a desired density irrespective of the change in printing speed. This method comprises variably setting a pressing force applied to the printing sheet against the printing drum, in accordance with printing speed information given by a means for setting printing speed information, for instance, a printing speed set up key provided on an operation panel.
With recent diversification in quality of printing paper and originals, there is a demand on a stencil printing device which can more widely and finely control printing density. Particularly, in case stencil printing is performed using a photograph as an original, reproduction of a wide range of gradation is desired; hence, the printing density must be set properly in accordance with quality of printing paper to obtain a desired gradation range. Furthermore, in order to reproduce a desired color hue in case of multicolor printing, density of each of colors to be mixed together should be accurately controlled. Besides, in case printing is overlaid on a sheet in the same color, printed product would be messy in appearance if printing density of the second printing is different from that of the first printing. Thus, the printing densities of the first and second printing must be matched accurately.
In case of the conventional printers described above, however, even if the same printing density is set by the printing density set up key of the printer, actual printing density differs depending on printing paper because the printing density is largely influenced by quality of printing paper. Moreover, degree of pressing force that compensates for a change in printing speed to obtain the same printing density had to be determined only by experience. Thus, to obtain the same printing density in the actual printing performed at a high speed as that realized in trial printing carried out at a lower printing speed, trial printing had to be carried out repeatedly, and much experience was necessary. Needless to say, it has been furthermore difficult to accurately predict printing densities at various combinations of printing speed and pressing force.
BRIEF SUMMARY OF THE INVENTION
In view of the above problems, an object of the present invention is to provide a method and a device for predicting printing density in stencil printing, which are capable of, not only finely and widely varying printing density under various printing conditions, but also accurately predicting printing density at a desired printing speed and a desired pressing force, or displaying a printing condition that provides a desired printing density, by merely performing several times of trial printing using printing sheets to be printed.
As a result of the present inventor's intensive studies under the above object, it has been found that quantity of ink transferred to paper, i.e., printing density, depends on a value of F/f (where F is a pressing force at which a printing sheet is pressed to a printing drum, and f is a rotation speed of the drum), and more particularly, that the quantity is approximately proportional to the value of {square root over ( )}(F/f). This means that, even if rotation speed of the drum is varied, the same printing density can be obtained by performing stencil printing using a pressing force which yields the same value of F/f. Thus, the present inventor has found that a function for predicting a printing density can be obtained by measuring printing densities under conditions of different F/f as samples, followed by statistically processing the thus-obtained data on printing density, and thus it is possible to predict a printing density under a desired printing condition without undue times of trial printings.
In accordance with one aspect of the present invention, there is provided, in a stencil printing in which a perforated stencil sheet is wound around a circumferential surface of a printing drum to which an ink is supplied, and the ink is transferred from the printing drum to a printing sheet through the perforated stencil sheet by pressing the printing sheet and the printing drum against each other while the drum is rotated, a method for predicting a printing density which comprises:
(a) a first step of measuring printing densities on at least two copies of print at corresponding printed portions thereof, said copies of print being obtained under different conditions of F/f, in which F is a pressing force at which the printing sheet is pressed to the drum and f is a rotation speed of the drum,
(b) a second step of statistically processing said printing densities measured in the first step, in order to obtain a function of printing density and F/f value, and
(c) a third step of calculating a printing density at a desired pressing force and a desired rotation speed based on the function obtained in the second step.
In accordance with another aspect of the present invention, there is provided, in a stencil printing in which a perforated stencil sheet is wound around a circumferential surface of a printing drum to which an ink is supplied, and the ink is transferred from the printing drum to a printing sheet through the perforated stencil sheet by pressing the printing sheet and the printing drum against each other while the drum is rotated, a method for calculating a printing condition, which comprises:
(a) a first step of measuring printing densities on at least two copies of print at corresponding printed portions thereof, said copies of print being obtained under different conditions of F/f, in which F is a pressing force at which the printing sheet is pressed to the drum and f is a rotation speed of the drum,
(b) a second step of statistically processing said printing densities measured in the first step, in order to obtain a function of printing density and F/f value, and
(c) a third step of calculating a combination of a pressing force and a rotation speed at a desired printing density based on the function obtained in the second step.
According to a yet other aspect of the present invention, there is provided a device for predicting a printing density for use in stencil printing in which a perforated stencil sheet is wound around a circumferential surface of a printing drum to which an ink is supplied, and the ink is transferred from the printing drum to a printing sheet through the perforated stencil sheet by pressing the printing sheet and the printing drum against each other while the drum is rotated, which comprises
(a) a first means for measuring printing densities on at least two copies of print at corresponding printed portions thereof, said copies of print being obtained under different conditions of F/f, in which F is a pressing force at which the printing sheet
Hoff Marc S.
Pillsbury & Winthrop LLP
Raymond Edward
Riso Kagaku Corporation
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