Electrophotography – Image formation – Fixing
Reexamination Certificate
2001-12-18
2004-01-06
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Fixing
Reexamination Certificate
active
06674990
ABSTRACT:
FIELD OF THE INVENTION
The invention involves a digital printer or copier machine with an overheating protection device.
BACKGROUND OF THE INVENTION
For certain commercial printer or copier machines, a latent electrostatic image is developed by charged toner particles. These particles are transferred onto an image receiving substrate, hereinafter referred to simply as “substrate”. Afterwards, the developed image that has been transferred onto the substrate is fixed by the toner particles being fused by supplying them with heat. This operation occurs in a fixing device.
Fixing devices are known in which hot cylinders or rollers are used to fix the toner onto the substrate or in order to preheat the substrate that may already have the toner image. The heating of the hot, customarily hollow cylindrical fixing rollers is done from the inside via their inner sheath surface and/or from the outside using at least one heated auxiliary roller that is in rolling contact with the fixing roller, or at least one radiation device that impinges the fixing roller with electromagnetic radiation. Furthermore, fixing devices are known in which the fixing of the toner image and possibly, the preheating of the substrate, is started directly by a radiation device without an intermediate connection of fixing rollers, and by using them, the toner can be fused in a non-contact manner.
The known radiation devices have at least one lamp that, for example, radiates ultraviolet light and visible or infrared light. The known lamps customarily have a quartz glass bulb that can heat up to 800° C. when the radiation device is turned on. Furthermore, ceramic radiators are known that have temperatures up to 1200° C. on their outer side. Disadvantageous in the previously described radiation devices based on their very high temperatures is that there is a danger of fire. This danger occurs especially during a paper jam, when the substrate that consists of paper, for example, is arranged opposite the radiation device (then turned off) and exposed to its heat radiation. The paper can start to arch as a result so that it comes into contact with the lamp, or parts heated up by it, and can ignite in the process. Furthermore, there is the possibility that the paper has a deformation, such as a dog-ear, whereby contact can also occur between the paper and the radiation device.
DESCRIPTION RELATIVE TO THE PRIOR ART
In order to prevent contact between the paper and the radiation device, devices are used to protect the substrate from excessive heating. From the U.S. Pat. No. 5,068,684, a protection device is provided with flaps arranged in a radiation path of a radiation source. These flaps can be moved into an open and closed position. As soon as the radiation source is turned off, the flaps are closed in order to shield the paper arranged in the radiation path from the heat radiation.
A protection device with rotationally movable sealing flaps and/or screens is provided in U.S. Pat. No. 6,085,060.
From the patent DE 2298 18 588 U1, a fixing device for an electrophotographic printer or copier device is known, in which to protect the paper to be printed from excessive heating, a radiation device is used which is constructed in two parts. The two parts are constructed so that they can be positioned crosswise to the paper transport device. The fixing device is controlled in such a way that during a paper stop, the two parts of the radiation device are driven far enough apart from each other in opposite directions, so that the paper no longer is impinged by their heat radiation.
Based on the constructive embodiment, in particular because of their movable screens, flaps, and/or parts of the radiation devices, the previously described protection devices have an expensive and thus cost intensive design. Furthermore, they are susceptible to damage and require an increased maintenance expense.
From U.S. Pat. No. 4,019,054, a fixing device that has a radiation device is known in which a fixed metal plate arranged opposite the radiation device is located in the radiation path. The metal plate, which is completely solid, has a prearranged intake area, as seen in the transport direction of the substrate that is passed by it. In the intake area, the substrate should be preheated. An outlet area follows this, in which many throughput openings that have a large open cross section are made in the metal plate, so that the electromagnetic radiation penetrates the metal plate in an almost unhindered manner and the substrate with the toner image can heat up. It is a disadvantage in this device that the metal plate is heated so much by the radiation device that the paper can ignite upon contact with it.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a printer or copier machine and a protection device, in which a contact between the substrate and the radiation device can be practically ruled out. Furthermore, the protection device should have a simple and thus cost effective design.
In order to achieve this purpose, a printer or copier machine is proposed which has a fixing device for fixing a toner image onto a substrate, for example a paper sheet or a paper web, and is guided along a transport path. The fixing device contains at least one radiation device, by the use of which at least one side of the substrate can be impinged with electromagnetic radiation. Finally, a device for protection against excessive heating of the substrate, especially during an interruption of the substrate transport, is provided. The printer or copier machine is characterized in that the protection device has at least one stopper arranged fixed in the radiation path between the radiation device and the transport path of the substrate, which prevents a contact between the substrate and the radiation device. The stopper is thus constructed in such a manner according to the invention that, for example, when the substrate arches up in the direction of the radiation device or if there is a bend in the substrate, it stops on the stopper. In this way, it can be ensured that the substrate cannot ignite on the turned off radiation device or by parts of the machine heated by it during its normal operation.
In relation to the invention presented, the term “fixed” is understood to mean that the stopper is installed in a housing or the like in such a way that its position does not change within the printer or copier machine. This means the stopper can not be moved relative to the substrate transport plane and the radiation device, but instead is arranged fixed in location and thus in the installed condition is always located in the radiation path, both during the fixing of the toner image on the substrate and during an interruption of the substrate transport. The protection device, differing from the known protection devices, has no movable parts in the sense of, for example, parts that can rotate or tilt, and thus represents a passively acting solution for the protection of the substrate against excessive heating and ignition as a result of a contact between the substrate and the radiation device and/or parts heated by it. Because of its simple construction, the protection device according to the invention can be manufactured in a cost effective manner. Moreover, a compact and space saving construction is possible.
It is noted that an ignition of the substrate can only be ruled out with certainty if the radiation device is turned off quickly and safely during a substrate stop and if necessary, when the speed of the substrate has fallen below a certain, preferably adjustable, substrate transport speed. This is usually done automatically. As of that moment, the stopper and the substrate arranged in the radiation path are then only still impinged with the heat radiated off of the hot parts of the radiation device or other structural parts of the machine heated in the operation of the radiation device.
The stopper arranged in the radiation path is constructed in such a way in a preferred embodiment form that it does not prevent the fusing of the toner image. F
Bartscher Gerhard
Morgenweck Frank-Michael
Rohde Domingo
Kessler Lawrence P.
NexPress Solutions LLC
Royer William J.
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