Dr. Ing. Rudolf Hell Gmbh

Juergen Doelves

Dieter Herforth

Wolfgang Schroedter

A method and circuit for driving a stepping motor which is driven by a motor clock output having a time variable frequency. So as to generate the time varying frequency, the constant frequency of a basic clock output is divided by constant first factor and is multiplied by a time variable second factor which is in the range between zero and the first factor. A transfer clock sequence is derived from the basic clock output by a division factor. The second factor is changed by a prescribed increment with the frequency of the transfer clock output at the respective clock times and this prescribed increment determines the frequency change of the motor clock output per clock interval. In this manner, the unavoidable frequency discontinuities can be maintained small and constant over the full frequency range of the motor clock output even by when the frequency of the basic clock output is not high whereby a reliable run-up and a reliable braking of the stepping motor are assured without stepping errors.

Method and circuit for driving a stepping motor

In a picture-element-by-picture-element and picture-line-by-picture-line recording of printing forms, at least two picture signal sequences are acquired, and the picture signal sequences are influenced by mask signals. A recording signal sequence for the control of a recording element for the printing form is generated with the assistance of the influenced picture signal sequences. A signal sequence is acquired from every picture signal sequence, this signal sequence containing the picture signal values of the corresponding picture sequence to be recorded for picture elements lying within a sub-area of the printing form to be recorded and in which the picture signal values of the corresponding picture signal sequence which are not to be recorded for picture elements lying outside of the sub-area are respectively replaced by a mask signal value. The signal sequences are combined to form a resulting signal sequence. The possible signal value combinations of the resulting signal sequence have recording signal values allocated to them, which, during recording of the printing form, are called in by the respective signal value combinations as a recording signal sequence.

Method for recording printing forms

Method for engraving printing cylinders having seamless joints within

A method for the improved reproduction of edges by engraving of screened printing forms by an electro-magnetic engraving member. The engraving member is controlled by a signal obtained by superposition of an image signal and a screening signal. The image signal is derived from scanning an image pattern with a resolution which is twice as great in the scanning direction as that of the printing screen. Based on the higher resolution the image signal is converted into digital principal image values and additional intermediate image values. The principal and the intermediate image values are superimposed onto the screening signal after being converted back into an analog image signal, whereby the principal image values are superimposed at the instances of periodically recurrent amplitude values of the screening signal when the tool of the engraving member has its largest deflections in the direction of the printing form for engraving the cups arranged in the printing screen. Thus, the engraving information for each cup consists of two image values, whereby the cups representing a sharp charge in tone density in the pattern are shifted relatively to the printing screen toward the higher level of density so as to accomplish improved reproduction of edges.

Method for improved reproduction of edges formed by engraving of

A method for the improved reproduction of edges associated with sharp changes in tone density during the engraving of screened printing forms with an engraving tool. The engraving tool is controlled by an engraving signal obtained from superposition of an image signal and a screening signal. The image signal is derived from scanning an original with a resolution which is twice as large in the scanning direction as that of the printing screen. Based on the higher resolution the image signal is digitalized into principal image values and additional intermediate image values. If a sharp change in the density defined as an edge occurs in the original a principal image value and the associated intermediate image values are combined into one memory word after the image values have been recoded into values of shorter word lengths and intermediately stored. If no edge is present in the original only the principal image values are intermediately stored as memory words. The combined memory words are separated into the principal image values and the intermediate image values when read out of the memory. The principal image values are superimposed onto the screening signal at the instants of periodically recurrent amplitude values of the screening signal, when the engraving tool cuts the cups and the associated intermediate image values are superimposed before said instants. Thus, the engraving information for each cup consists of two image values, whereby the cups for a sharp change in tone density are shifted relatively to the printing screen toward a higher density level so as to accomplish improved reproduction of the edges. Storing the image values as described allows the capacity of the memory to remain constant although a bigger number of image values are processed.

Method for improved reproduction of edges by engraving screened printing

Apparatus and method for exactly locating and adjusting the beginning and end of reproduction of an image pattern reproduced from a master picture attached to a rotating scanning cylinder which is reproduced on a rotating printing cylinder and wherein the adjustment is made by a circumferential pulse adjustment movable relative to a permanent circumferential mark in which process the image pattern is optoelectronically scanned, dot and image-line wise, to convert the image pattern into an electrical image signal and wherein the analog image signal is converted into a digital signal with the aid of a scanning pulse sequence device and the data obtained is stored into a memory after which the information is read from the memory with the aid of a recording pulse device and reconverted into an analog image signal and during the process of recording on the printing cylinder the timing of the recording pulse sequence train controls an engraving device and the movement of an engraving member, whereas the timing of the scanning pulse sequence train controls a scanning device and the movement of a scanning member. The movements are carried out in the axial direction of the cylinders.

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Heikendorf, Germany

Juergen Doelves