US 4,896,605 AGranted

Method of cut position determination for printing machines

AssigneeAsea Brown Boveri AG

InventorThomas Schroder

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Abstract

A method of cut position determination for printing machines, wherein in order to ensure a synchronous running of the paper webs (P1-P4) to be folded and cut into newspapers (16) on a printing machine for rotary offset printing or rotary letter press printing, main and secondary registers (5, 7) are controlled in their position by means of servomotors (M1-M4) as a function of actuating signals (S.sub.M1 -S.sub.M4). Above each former-introduction guide roller (10), 4 photocells (11) are arranged equally spaced next to one another, which detect brightness signals (H.sub.A1 -H.sub.D4) from the printed surface of these paper webs at a scanning frequency of 20 khz. These brightness signals are subjected to a Fourier analysis in a microprocessor. The fundamental oscillation is evaluated, the fundamental oscillation with the greatest amplitude being selected from the 4 fundamental oscillations of each paper web. The phase position signal associated with the selected fundamental oscillation is used for calculation of one of the actuating signals (S.sub.M1 -S.sub.M4). Consequently, the cut position of the paper webs (P1-P4) can be determined without socalled register marks or register-keeping marks made on them.

Claims9

Dependent claims

A method of cut position determination for printing machines, having at least one, to be synchronously guided, printed paper web (P1-P4), identical printed product pages following directly or at periodic intervals one after the other on each paper web, wherein,

(a) print-dependent brightness signals (H.sub.A1 -H.sub.D4) are derived by at least 2 photodetectors, which are arranged for each paper web (P1-P4) next to each other with respect to the direction of transport of the latter,
(b) at least a 1st oscillation signal of definable frequency (f1) is derived as a function of each of these brightness signals, provided these brightness signals are not constant,
(c) the amplitude (a.sub.A1 -a.sub.D1) is determined as a function of each of these 1st oscillation signals,
(d) of the 1st oscillation signals, the one with the greatest amplitude is selected,
(e) from this selected 1st oscillation signal, the current phase position (.phi..sub.x,.phi..sub.A1 -.phi..sub.D1) with respect to a predeterminable synchronizing signal (S.sub.syn) is determined and stored as reference phase position (.phi..sub.ref),
(f) the phase difference (.DELTA..phi.n) between the current phase position (.phi..sub.x) and the reference phase position (.phi..sub.ref) is determined at an interval of at least one printed product page, and
(g) at least one register of the printing machine is controlled as a function of this phase difference (.DELTA..phi.n) such that the phase difference becomes at least approximately =0.

4 more elements

Dependencies are inferred from the claim text.