Photocopying – Contact printing – Light boxes
Patent
1989-10-05
1991-08-06
Grimley, A. T.
Photocopying
Contact printing
Light boxes
29123, 29130, G03G 500
Patent
active
050381725
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a mechanism for releasable fastening of a drum fashioned as intermediate carrier of a non-mechanical printer or copier device.
2. Description of the Prior Art
A prior art mechanism is disclosed by German published application 27 17 055 and corresponding U.S. Pat. No. 4,134,669 . In that mechanism, the photo-conductive drum includes turned-out cylindrical carriers at both ends that cooperate with corresponding necks of drum receptacle flanges that are arranged on the drive shaft. One drum receptacle flange is rigidly connected to the drive shaft while other can be detachably slipped onto the drive shaft via a through bore. A clamp mechanism that is screwed to the drive shaft presses the releasable drum receptacle flange resiliently against the drum which is then pressed against the stationary drum receptacle flange.
The concentric running precision of the photo-conductive drum that can be obtained with such a mechanism is dependent on the differential play between the drum receptacle flanges and the inside diameter of the photo-conductive drum, on the differential play between the through bore of the releasable drum receptacle flange and the drive shaft and on the actual concentricity precision of the drive shaft.
In printer equipment operating with intermediate carriers, such as electro-photographic printer equipment or magnetic printer equipment, a high concentricity precision of the drum-like intermediate carrier is extremely important for good print quality. This is particularly true when printing is to be carried out with a high character resolution. When a number of printed apparatuses are coupled together to produce multi-color printing or front and backside printing, the concentricity precisions of each printer apparatus participating in the printing add up.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a mechanism for releasably fastening a photo-conductive drum such that a high concentricity precision is achieved while easy replaceability of the drum-shaped intermediate carrier is maintained. Damage to and deterioration of the surface of the drum-shaped intermediate carrier is avoided.
The object is achieved according to the principles of the present invention.
Spreader elements, that spread when the clamp mechanism is screwed to the drive shaft, are arranged between the drive shaft and the drum receptacle flange for centering the second, replaceably fashioned drum receptacle flange on the drive shaft. These spreader elements are composed, for example, of conical spring washers, the drum receptacle flange is exactly centered on the drive shaft and free of bearing play. Due to the additional measure of the conical design of the ends of the drum and of the drum receptacle flange, bearing play can not occur between the drum receptacle flanges and the drum.
In a preferred embodiment of the invention, the first drum receptacle flange is connected to the drive shaft via ribs that extend along the inside wall of the drum and are designed as pre-centering elements for the drum. These ribs penetrate through the replaceable drum receptacle flange at openings provided therefor, so that an easy replacement of the drum is possible when the drum receptacle flange is taken off. To avoid damage to the surface of the drum, it can first be put in place onto the rib-shaped pre-centering elements. The fine centering then ensues by screwing the clamp mechanism in and by clamping the drum between the drum receptacles flanges.
In another embodiment of the invention that also suppresses the concentricity imprecision of the drive shaft, the drive shaft is seated at both ends, via a bearing fixed to the housing at one end and via a removeable bearing at the other end. The bearing is advantageously arranged at the inside of an end shield that can be screwed to the housing. The built-in end shield is designed such that it covers the access region for the drum a completely dust-free and contact-proof fashion.
DETAIL
REFERENCES:
patent: 3926515 (1975-12-01), Nagahara
patent: 4120576 (1978-10-01), Babish
patent: 4134667 (1979-01-01), Schnall
patent: 4134669 (1979-01-01), Reitner
patent: 4527883 (1985-07-01), Kamiyama
Grimley A. T.
Horgan Christopher
Siemens Aktiengesellschaft
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