Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Patent
1997-08-08
1998-11-17
Le, Que
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
25055943, 356430, G01N 2186
Patent
active
058380175
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a control device for monitoring the passage of two superimposed paper webs in a paper processing machine, with photoelectric sensors, whose light beams are directed on to the surfaces of the paper webs.
In some paper processing machines, e.g. in an automatic account processing installation which follows a laser printer, the passage of two superimposed paper webs has to be monitored. The account processing installation has a so-called slitter/merger unit. In this unit a wide paper web is firstly divided along the middle by longitudinal cutter knives, so that two half-width paper webs result. These two paper webs are then placed one on the other and fed on superimposed with their edges aligned. Since the wide paper web is already provided with transverse perforations which are arranged with the spacing of the format height, it can happen that one of the paper webs tears and is not fed on with the second paper web. A control device is necessary for this reason, which monitors the presence of two superimposed paper webs. A known control device operates with a light barrier which illuminates both paper webs simultaneously. The light barrier must be so adjusted that no light falls on the receiving photocell in the presence of two paper webs, while the light beam penetrates the remaining paper web when one paper web is missing, and falls on the receiving photocell. For this system to function, the light barrier must adjusted by the person running the machine for the transparency of the current paper webs. If this is forgotten, the control device no longer responds when processing a paper quality of lower transparency or no longer responds reliably. The known control device is not suitable at all for thicker papers or those of low transparency.
A paper feed device for a printer is known from U.S. Pat. No. 4,467,949, in which the paper web is driven by a motorised drive roller. In order to monitor the paper web a light-emitting diode is provided behind the drive roller with a photo-transistor optically aligned opposite thereto. When no paper web is present between the diode and photo-transistor, the latter is turned on, whereas when a paper web is present between the two, it interrupts the light emitted by the diode and the photo-transistor is turned off. This device is only suitable for monitoring a single paper web and not for monitoring two superimposed paper webs, since the light beam is already interrupted by a single paper web, even if the second paper web is no longer present.
The invention is therefore based on the object of providing a control device for monitoring the passage of two superimposed paper webs in a paper processing machine, of the kind initially referred to, which makes it possible with a simple structure to monitor reliably paper webs of any transparency, without adjusting operations being necessary when there is a change in paper quality.
This is achieved by the features set out in claim 1 or 5.
The invention is thus based on the concept of monitoring the passage of each individual paper web by its own photoelectric sensor responding to reflection. With passage free from disturbance the light beam emitted by each sensor is reflected by the associated paper web and received by the receiver part thereof. If however the associated paper web tears in a region preceding the plate, the surface of the plate facing the torn paper web is no longer covered by the paper web, as soon as the end of the torn paper web adjoining the tear has passed the plate. Since the surface of the plate has different reflective properties than the paper web, the sensor associated with the torn paper web responds and issues a corresponding signal. The surfaces of the plate can be so chosen that they guarantee different reflection properties from all the kinds of paper which will pass through the paper processing machine. As a result the photoelectric sensors always react only when no or too little light is reflected from the paper surface in the absence of one paper web. The control device acco
REFERENCES:
patent: 5095214 (1992-03-01), Eder
Boewe Systec AG
Le Que
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