Sheet feeding or delivering – Delivering – With transfer means between conveyor and receiver
Reexamination Certificate
1999-07-06
2001-03-13
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Delivering
With transfer means between conveyor and receiver
C271S265020, C271S273000, C162S271000, C399S406000, C242S563000, C242S566000
Reexamination Certificate
active
06199859
ABSTRACT:
The present invention is directed to a decurling unit according to the preamble of claim
1
for decurling carrier material.
In electrophotographic high-performance printers, the paper employed as carrier material curves concavely through convexly in the toner fixing due to the influence of pressure and heat. This curvature (curling in English) is thereby dependent on the paper quality, which is mainly defined by thickness, moisture and the manufacture, as well as on the number of fixings, i.e. of the selecting printing mode. Disproportionately much moisture is withdrawn from the paper in the first fixing. An especially pronounced curling of the paper therefore occurs therein compared to the second, third, etc., fixing. In a recent printing system having two printing units, for example, the number of fixings is dependent on the printing mode such as simplex, duplex, spot-color simplex, spot-color duplex printing.
The paper quality can be assumed to be constant within a paper stack but the plurality of fixings per sheet or per page cannot be assumed to be constant. Given employment of roll paper that, for example, is cut to format and the printer input given automatic delivery into a single sheet printer, the curvature of the supplied paper changing with the rolled diameter must be taken into consideration.
Decurling units (also known as “decurler” in German usage) are thus known, wherein the paper having only one deformation direction can be smoothed, i.e. concave or convex curvature. Such a known decurling unit bends the paper opposite the deformation direction. Given non-deformed, i.e. flat paper, this decurling unit dare not be used because would otherwise be deformed in it. A paper transport of smooth paper through such a decurling unit is therefore not possible.
U.S. Pat. No. 4,360,356 discloses a decurling means that optionally smooths concavely or convexly curved paper or through which smooth paper can be conducted without the paper being bent. The decurling means has two ledges proceeding parallel to one another that extend transverse to the conveying direction of the paper, as well as two drums extending parallel to the two ledges that are arranged immediately following the two ledges as viewed in conveying direction. The ledges and the drums are secured to a common swivelling means with which they can be swivelled in common around an axis proceeding transverse to the conveying direction. The paper is conducted through between the two ledges and the two drums, whereby respectively one ledge with the drum arranged diametrically opposite forms a decurling unit with which the convexly or, respectively, concavely curved paper can be smoothed. For smoothing the paper, the ledges and the drums are swivelled in common around the axis such that the paper running through the decurling means lies against one of the two ledges as well as the drum arranged diametrically opposite this under tension and is thereby decurled. When a smooth paper passes through the decurling means, the swivel means is placed such that the paper passes through between the ledges and the drums without touching these.
U.S. Pat. No. 5,565,971 discloses a decurling unit with which concavely or convexly curved carrier material can be optionally smoothed. To this end, the decurling unit has a stationary, first drum proceeding transverse to the conveying direction of the carrier material as well as a driven, rubberized, second drum proceeding parallel to the former, whereby both drums are secured to a common base plate. For smoothing a concavely curved carrier material, a conveyor belt is pressed against the first drum with the assistance of a swivel means. An elastic conveying nip through which the carrier material to be smoothed is transported thereby forms between the conveyor belt and the drum. The decurled carrier material emerging from the elastic conveying nip is conducted past the second drum without touching it. In order to decurl a convexly curved carrier material, the carrier material is conducted past the revolving, second drum with the assistance of a deflection plate likewise provided at the swivel means, as a result whereof the carrier material is bent. In this position of the swivel means, the conveyor belt interacting with the first drum is deactivated, so that the carrier material is in fact conducted part the drum but without being bent by the conveyor belt and the first drum. Given this known decurling unit, there is then the problem that it can only be traversed by convexly or concavely curved carrier material. Smooth carrier material that is not deformed, by contrast, is unintentionally deformed by the decurling unit, so that the decurling unit is not suited for the employment of undeformed carrier material.
The invention is thus based on the object of offering a decurling unit that enables a smoothing of the carrier material independently of the deformation direction. In particular, carrier material without deformation should be capable of being smoothed by the decurling unit in addition to carrier material having a concave or a convex deformation.
This object is achieved with the decurling unit of the species initially cited on the basis of the characterizing features of claim
1
. Advantageous developments derive from the subclaims.
Given the inventive decurling unit, the element for eliminating convexity is functionally coupled such to the element for eliminating concavity that, on the one hand, a decrease in the influence of the element for eliminating concavity occurs given an increase in the effect of the element for eliminating convexity and, on the other hand, an increase in the effect of the element for eliminating concavity occurs given a decrease in the effect of the element for eliminating convexity. This enables a continuous or graduated setting of the decurling unit between two extreme positions for eliminating extreme concavity or, respectively, extreme convexity.
In a specific development, the element for eliminating concavity is a decurling shaft having a rotational axis extending perpendicular to the conveying direction of the carrier material, whereby the decurling shaft can be immersed into one or more stretchable decurling belts that are arranged parallel to one another and drive it by static friction, said decurling belts being stretched between a drive roller and a deflection roller for the decurling belt or belts in conveying direction of the carrier material, whereby the rotational axes of the drive roller and of the deflection roller likewise extend perpendicular to the conveying direction of the carrier material, so that the decurling belt or belts lies or, respectively, lie against the decurling shaft in convex form. The elimination of the concavity ensues in that the concavely curved carrier material to be smoother is ceased between the decurling belt or belts and the decurling shaft immersed there into with a suitable emersion depth t and is convexly, oppositely bent between the belt and shaft.
Expediently, the element for eliminating convexity is a discharge contour shaped concavely in conveying direction of the carrier material that can be swiveled into the paper path around an angle. The convex paper is deformed in opposite direction by the concavely curved discharge contour that is pivoted out by a suitable pivot angle &ggr;, a smoothing being achieved as a result thereof.
In an especially advantageous development, the element for eliminating concavity and the element for eliminating convexity are rigidly connected by a rodding and are pivotable together around a common rotational axis A.
As a result thereof, a mechanical drive of the rodding can simultaneously adjust the immersion depth t of the decurling shaft into the decurling belt and the swivel angle &ggr; of the discharge contour. Given a swivel of the rodding in one direction, the immersion depth t and the swivel angle &ggr; thereby increase, as a result whereof the concavity decurling is enhanced and the convexity decurling is reduced. Given an opposite pivot of the rodding, the immersion dept
Boehmer Georg
Naesser Helmut
Schauer Christian
Oce Printing Systems GmbH
Schiff & Hardin & Waite
Skaggs H. Grant
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