GB1391344A - Printing apparatus - Google Patents

Abstract

1391344 Printing apparatus NIPPON STEEL CORP and SAGINOMIYA SEISA. KUSHO KK 12 June 1972 [11 June 1971] 27429/72 Heading B6C [Also in Division G3] Printing apparatus comprises a conveyer belt 2 feeding steel or veneer sheets 1 to a print drum 16 carrying a printing plate 17 and rotating at a speed determined by a directlycoupled hydraulic drive motor 19 whose servovalve 14 is controlled by the circuit shown in Fig. 2, whereby for each fed sheet the drum is rotated one revolution, is started when the sheet is at a predetermined position from the drum and is accelerated to a speed to equalize the speed of its plate 17 with the speed of the sheet 1. In a typical one-off operation, a member 8 (photo-cell or a magnetic or capacitance detector) detects the leading edge of the sheet 1 and actuates a monostable vibrator 9 to open a gate circuit 7 and so allow the output of a pulse generator 5, representative of the speed of conveyer 2, to pass to a register 11, the vibrator 9 being adjustable to variably delay the opening of the gate circuit and thus vary the position of engagement of members 1, 17. The register 11 is part of an analyser 10 having a second register 12 receiving the output of a pulse generator 20 representative of the speed of the drum, a comparator producing an output representative of the difference between registers 11, 12 and a digital-to-analogue converter receiving this output and producing a control signal modified as necessary to allow for variable parameters such as print drum diameter. This signal is applied to a servo-amplifier 13 controlling the servo-valve 14, whereby the drum is accelerated to the correct speed before engagement of members 1, 17 and maintained at this speed during printing, after which the generator 20 produces a timing pulse to close the gate circuit 7 and clear the registers 11, 12 to respectively stop the motor and reset the analyser 10. The described operation also occurs for sheets fed almost continuously, although in this case the drum rotation does not stop completely.