Document-printing arrangement with document-collection station

Details Document-printing arrangement with document-collection station Document-printing arrangement with document-collection station

1999-04-05

2000-10-17

Yan, Ren

Typewriting machines

Sheet or web

For feeding web record-medium

101227, 101409, B41J 1170

Patent

active

061321214

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION



Technical Field

The invention relates to a document-printing arrangement.


Prior Art

A prior art document-printing arrangement is disclosed in the international patent application WO 94/22117 A1. In this document, use is made of a document collection station which is designed as a drum, as is described in German Offenlegungsschrift DE 42 25 418 A1. The drum is only set rotating when a document has been transported under the clamping elements by the paper transport arrangement. In this case, the document is pushed against the operating levers of the clamping elements, which levers project from the interior of the drum, which is still at rest, and is compressed, which leads to buckling of the document between the printing station and the drum. Since the cutting arrangement is also arranged in the buckling area, the buckling of the document leads to an unacceptably high tolerance on the cut length.


SUMMARY OF THE INVENTION

The object of the present invention is a document-printing arrangement of the above-mentioned type in which buckling of the document is avoided.
The invention is based on the consideration that buckling of the document is avoided if, at the moment at which the leading edge of the continuous paper web arrives tangentially on the outer surface of the drum, the circumferential speed of the drum corresponds to the advance speed of the continuous paper web, that is to say the operating levers of the clamping elements lead the forwardly transported paper edge by a short distance.
To this end, a light barrier that responds to the leading edge of the continuous paper web is arranged in the paper path and, in its rest position, the drum assumes a second angular position which--as viewed in the direction of rotation of the drum--is set back by a prescribable angular dimension with respect to a first angular position. Starting from the second angular position, when the leading edge of the continuous paper web is reported by the light barrier, the drum is accelerated in such a way that, at the moment at which the leading edge of the continuous paper web runs into the transfer position, said drum has reached the first angular position and the circumferential speed of the drum corresponds to the transport speed of the continuous paper web. This achieves the situation in which the leading edge of the continuous paper web no longer collides with the operating levers of the clamping elements. Compression of the paper edge and buckling in the document are therefore prevented. It is therefore possible for even particularly brittle papers or those having a low inherent stiffness to be processed.
A further advantage of the document-printing arrangement according to the invention is to be seen in the fact that it is also possible to use printing processes having a high paper advance speed, and those having a continuous paper advance. In a development of the invention, use is made of this advantage by the printing station having a thermal printing bar.
Displacing the clamping elements between their releasing position and their clamping position during the rotation of the drum can be implemented in a particularly simple way by the displacement being carried out by means of an electric motor provided specifically for this.
In an advantageous development of the invention, the electric motors are designed as stepping motors. The paper advance speed is known from the stepping pulse sequence of the electric motor which drives the impression roll. It is therefore simply possible to apply stepping pulses to the electric motor of the drum, these pulses defining an acceleration ramp which is matched to the circumferential speed of the impression roll--conveying the continuous paper web through the printing station--the electric motor of the drum being started at the point where the leading edge of the continuous paper web is detected by the light barrier. Starting from the leading edge of the continuous paper web, the current length of a document can be determined at the same time from

REFERENCES:
patent: 4132403 (1979-01-01), Weisbach et al.
patent: 4594597 (1986-06-01), Lin et al.
patent: 4766463 (1988-08-01), Watanuki et al.
patent: 5390908 (1995-02-01), Luxem
patent: 5606913 (1997-03-01), Kowalewski
patent: 5699741 (1997-12-01), Schmidt et al.
patent: 5768675 (1998-06-01), Estabrooks

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