Electrophotography – Image formation – Fixing
Reexamination Certificate
2001-03-02
2002-09-10
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Fixing
Reexamination Certificate
active
06449458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a fixing station for fixing toner images on a carrier material, having a heating device with at least one radiant heat source that emits radiation in the direction of the carrier material, and having a cover device with which an undesired incidence of radiation onto the carrier material can be prevented.
2. Description of the Related Art
In electrographic printers or copiers, the toner image transferred from an intermediate carrier, generally a photoconductor, onto the carrier material, generally paper, must be fixed, i.e. it must be joined so as to be smear-proof and abrasion-proof to the carrier material. Heat/pressure fixing is currently usually utilized in electrophotography. When no pre-heating, for example with the assistance of a heating saddle, of the carrier material is undertaken, this is usually limited to approximately 0.5 m/s through 0.7 m/s in terms of processing speed. In the duplex printing mode wherein the front side and the back side of a carrier material are printed, the fixing process is relatively difficult because both sides are still covered with smearable toner images. A high fixing quality given simultaneous fixing of the front side and of the back side of the carrier material can only be achieved with relatively soft fixing drums, for example silicone drums. These fixing drums have a low service life and are uneconomical. Such soft fixing drums are therefore only utilized given printers having a relative low printing volume. Since soft fixing drums are utilized at both sides of the carrier material, the guidance of the carrier material becomes problematical. Such fixing drums are therefore not suited in the further-processing of continuous form paper.
For said reasons, it is desirable to fix toner images contact-free, whereby a relatively broad spectrum of carrier material can be utilized. Another goal of contact-free fixing is comprised in achieving a high fixing quality without smearing effects.
A contact-free fixing method is known wherein the toner material is softened with the assistance of a solvent material, so that it unites better with the fibers of the carrier material. When, however, chromatic toner is employed, it can occur that the color pigments are dissolved to different extents, which can potentially lead to a color-dependent smearing of the toner images. Moreover, the known environmental problems given the utilization of solvents arise.
Another known fixing method that works contact-free is what is referred to as photoflash fixing, whereby the toner is fixed on the carrier material with the assistance of high-energy light pulses. The wavelength of the radiation usually lies in the visible through ultraviolet range of the spectrum. Since the various color toners absorb to different extents in this wavelength range, a photoflash fixing is not suitable for multi-color printing.
Another fixing station is disclosed by European Patent Document EP-A-0 629 930. The fixing station is employed for an electrostatic printer in order to fix toner material on paper. The cover device serves the purpose of preventing the incidence of radiation during a heating-up phase or during a standstill of the carrier material. In the closed condition of the cover device, the active surfaces of the radiant heat source emitting thermal radiation face away from the carrier material. In this condition, the cover device surrounds the radiant heat source, so that the heating-up phase is shortened. During normal operation wherein the toner material is fixed on the carrier material as a consequence of the incident radiant heat, the radiant heat source faces toward the carrier material and the radiation can impinge the carrier material unimpeded.
Japanese Patent Document JP-A-62-055685 discloses a fixing device wherein a cover device can be moved into the beam path between a radiant heat source and a carrier material. The cover device comprises a plate of heat-resistant material. The cover device is removed from the beam path in the normal operating condition. Given an abnormal operating condition, the cover plate is shoved between the carrier material and radiant heat source.
The Japanese Patent document JP-A-60-014268 is directed to a fixing device wherein a cover plate can be moved into the beam path between a radiant heat source and a carrier material. The intensity of the fixing is set with the assistance of this cover plate dependent on the paper thickness of the carrier material. A detector thereby determines the paper thickness, whereupon the cover plate is swivelled. The fixing device can be set to different paper thicknesses relatively fast in this way.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fixing station that works with high processing speed and assures a high print quality.
This object is achieved by a fixing station for fixing toner images on a carrier material, including a heating device with at least one radiant heat source that emits radiation in the direction of the carrier material, and having a cover device movable essentially parallel to the moving direction of the carrier material and that can be moved in to the beam path between radiant heat source and carrier material, in that, given a stop of the carrier material, the cover device is moved with the velocity V
R
, according to the relationship: V
R
=−V
P
, wherein vp is the transport velocity of the carrier material; and in that, given continued transport of the carrier material with the velocity V
P
, the cover device is moved with the velocity V
R
, according to the relationship: V
R
=V
P
. Advantageous developments provided by the cover device having at least the width of the carrier material. Specifically, the cover device is flexible as viewed in moving direction of the carrier material. In one embodiment, the cover device contains a band. Alternately, the cover device contains a plurality of strip-shaped lamellae that form a window blind, whereby adjoining lamellae preferably overlap. The band or, respectively, the lamellae can be wound up in the fashion of a winding.
In a preferred embodiment, an endless deflection means is arranged around the heating device; and the band or, respectively, the window blind can be moved along the deflection device. The deflection device may contain a tensing mechanism that keeps the band or, respectively, the window blind in a tensed condition. A feature of the invention provides that the cover device has a length that is adequate in order to cover the entire radiation of the radiant heat source in the direction of the carrier material. The cover device may contain a rigid plate for covering the radiation.
The fixing station of one embodiment has a radiant heat source with a radiation temperature in the range from 500° C. through 800° C. and the maximum intensity of the radiation lies at a wavelength greater than 2 &mgr;m. In one embodiment, a respective heating device each having at least one radiant heat source is arranged at both sides of the carrier material, whereby a respective cover device can be moved into the beam path between radiant heat source and carrier material, whereby both cover devices are preferably moved by a common drive. Such a fixing station may be employed for a printer device or copier device that works in duplex printing mode.
A ceramic flat radiator, a crystal radiator or, in particular, a foil radiator can be employed as the radiant heat source. In one aspect of the invention, the radiant heat source is pre-heated. Specifically, the radiant heat source is pre-heated to a temperature above 200° C.
Advantages of the invention are realized when a temperature Tm is established in the steady state at the carrier material given an operation of the radiant heat source with nominal power NL; and the radiant heat source is preheated such that a temperature of approximately 0.45 Tm is established on the carrier material. A further feature of the invention is that a temperature sensor acquires the temp
Eckardt Andreas
Fuchs Werner
Goldmann Gerd
Lang Robert
Rosenstock Günter
Brase Sandra
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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