Photocopying – Contact printing – Light boxes
Patent
1994-09-08
1996-12-10
Braun, Fred L.
Photocopying
Contact printing
Light boxes
355285, 492 21, 492 45, G03G 1520, G03G 2100
Patent
active
055836240
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
It is standard in electrophotographic printer or copier devices to fix the toner-coated recording medium in a thermal fixing station. Such thermal fixing stations generally contain electrically heated fixing drums with applicable pressure rollers that can be pivoted in and out. For fixing, the recording medium is conducted past between the fixing drum and the pressure roller. The toner is fixed on the recording medium due to the application of heat from the side of the fixing drum. Since the toner must be brought to melting temperature during the short contacting distance of the recording medium with the fixing drum, a high heating capacity on the part of the fixing drum is necessary. For this purpose it is standard to install halogen radiators having a high heating capacity in the hollow fixing drum. Both the halogen radiators in the fixing drum as well as the fixing drum itself are subject to wear, so that it is necessary from time to time to replace the halogen radiators and the fixing drum.
In order to be able to replace the fixing drum in its hot condition as well, PCT WO 91/09 351 discloses that the fixing drum be seated in bearing flanges, whereby the one bearing flange is permanently secured and the other bearing flange is releasably secured in the device. The releasable bearing flange comprises holder elements for the fixing drum as well as a gripping member with which the bearing flange together with the fixing drum appended thereto can be removed from the fixing station. The releasable bearing flange is then separated from the worn fixing drum and is put in place on a new, replacement fixing drum which is then introduced into the fixing station via the bearing flange.
It has proven disadvantageous given this known apparatus to introduce the cold, new fixing drum into the fixing station via the releasable bearing flange since this can be done only after a cool-down time. Due to the relatively high thermal capacity of the fixing station, cools only slowly after shut-off, so that the bearing flange remaining in the fixing station is more greatly expanded due to the heat than the new, cold fixing drum. It is thus not possible during the cool-down time to put the new fixing drum in place on the bearing flange situated in the fixing station. Smaller problems arise in conjunction with the releasable bearing flange when put in place onto the new fixing drum. Here, too, it is necessary to allow the releasable bearing flange to cool.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to offer a device for the releasable fastening of a fixing drum on bearing flanges of a fixing station in an electrophotographic printer or copier device which enables the bearing flanges and fixing drum to be joined to one another or, respectively, to be released from one another even when the fixing drum and the bearing flange have different temperatures.
In an apparatus of this type, this object is achieved by providing a cone-shaped spreader element allocated to the bearing flange of the fixing station. A resiliently designed receptacle bushing having an inwardly disposed counter-cone is provided that embraces the spreader element like a collet chuck and has an outwardly disposed seating surface for seating of the receptacle bushing at an inside radius of the fixing drum. The spreader element spreads the receptacle bushing for fastening the fixing drum on the bearing flange and thus presses it against the inside radius.
According to the invention, receptacle bushings like collet chucks are allocated to the fixing drum receptacle flanges, these receptacle bushings having an inwardly disposed, conical bore. The receptacle bushings are seated on a spreader element in the form of a counter-cone that enters into the conical bores. A straining ring that embraces the receptacle bushings presses the receptacle bushings radially resiliently against the counter-cone of the spreader elements. The receptacle bushings themselves in turn have an outwardly disposed seating surface for sea
REFERENCES:
patent: 3794417 (1974-02-01), Machmer
patent: 3989372 (1976-11-01), Davidge et al.
patent: 3990391 (1976-11-01), Singh
patent: 4229950 (1980-10-01), Fessenden
patent: 4800644 (1989-01-01), Muellenberg
patent: 4890372 (1990-01-01), Halttula
Braun Fred L.
Siemens Nixdorf Informationssysteme Aktiengesellschaft
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