Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
2000-03-24
2001-05-29
Chen, Sophia S. (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S159000
Reexamination Certificate
active
06240267
ABSTRACT:
The invention concerns a printing apparatus and, more particularly, an apparatus and method using a sleeved printer drum.
The invention is applicable to printing presses and other fields of printing, including electrography, electrophotography and magnetography.
In the fields of electrography, electrophotography, or magnetography, electrical or magnetic magnitudes are distributed in recording materials in accordance with a printed image. Electrophotography uses photoconductor drums on whose respective enveloping surfaces is applied a photoconductive layer that is discharged in response to light in a manner equivalent to the image. The recording materials have only a limited service life, which is why in the case of high-production printing apparatuses, the entire cylinder or layer support for the recording material must be replaced relatively frequently. In multi-color printing apparatuses, replacing the recording materials is particularly time-consuming. Recording materials are particularly sensitive. The recording materials must not be touched, and must not be exposed to ambient light for longer than necessary. Photoconductor drums are therefore equipped with special protective coverings and with handles for installation in a printing apparatus. For physical reasons, a photoconductor drum is often installed in an arrangement parallel with the rotation axis of the drum.
In the case of rotation printing presses, it is known from U.S. Pat. No. 5,241,905 to replace a sleeve-shaped rubber printing blanket laterally through a side wall in which the cylinder carrying the rubber blanket is mounted (DE 43 32 364 A1). With this approach, an opening that is closed off during printing by a door is provided in the side wall. The housing of the cylinder bearing is clamped in place on the door. The external dimensions of the bearing are smaller than the inside diameter of the sleeve-shaped rubber blanket. In order to replace the rubber blanket, the clamped attachment of the bearing on the door is released, and the door is swung aside in front of the opening. The rubber blanket can be removed by hand, through the side door, by way of the bearing which remains in place on the bearing journal of the cylinder, and then reinstalled. The rubber blanket is of elastic configuration and insensitive to contact. During printing, the rubber blanket cylinder has associated with it a cleaning apparatus with which the surface of the rubber blanket is cleaned before printing.
It is an object of the invention to develop a printing apparatus and method in which the replacement of a sleeve-shaped sheath is simplified, and the danger of damage to the sheath is reduced.
The object is achieved in accordance with a first aspect of the invention. There is provided a printing apparatus comprising a cylinder mounted between side walls and having a sleeve-shaped sheath that can be replaced through an opening on one of the side walls, wherein the sheath is detachable from the cylinder and has a projecting part that projects laterally from the cylinder on the side toward the opening, the sheath being supported on an enveloping surface of the cylinder, a holding apparatus which can be set against and moved away from the interior of the projecting part of the sheath, the holding apparatus being physically integrated with a bearing element of the cylinder, and in order to replace the sheath, the bearing element can be positioned in a location which uncovers the opening.
According to the invention, several precautions are taken to ensure that the sheath can be installed without damage. The sleeve-shaped sheath possesses, in addition to the actual functional surface used during printing, a clamping surface on its projecting part that can have a smaller diameter than the outer enveloping surface of the functional surface. Engaging onto the projecting part is a holding or clamping apparatus for the sheath which takes effect when the frictional or positive engagement between the sheath and the enveloping surface of a cylinder that carries the sheath is abolished, for example by the generation of an air cushion. While the sheath is being expanded, for example by the air cushion, the sheath can be held on the projecting part by the holding apparatus, by the fact that there acts on the interior of the projecting part a clamping apparatus that includes elements which are movable toward the outside, so that the projecting part is expanded sufficiently that it rests at the outer circumference against a clamping surface that is incorporated into a bearing element for the cylinder in a side wall of a printing apparatus. The use of an air cushion between the inner side of the sheath and the outer side of the cylinder is mentioned only by way of example. All that is important is that the holding forces between the sheath and the cylinder are temporarily abolished, which in the case of a ferrous-metal sheath and magnetic clamping can occur by abolishing the magnetic field, or by extending rolling elements, so that the large holding friction between the sheath and cylinder is replaced by a small rolling friction. Actuation of the clamping apparatus for the rim of the sheath can be accomplished manually by actuating a positioning lever that is easily accessible from outside. It is also possible to provide holding or clamping apparatus whose holding or clamping forces are generated by a pneumatic or hydraulic system. As a result of the physical unification of the holding apparatus and the bearing element, the bearing element that is removable from the side wall serves simultaneously as an installation aid when replacing the sheath. The bearing element is completely removed, together with the sheath, from the side wall and from the bearing journal of the cylinder.
Sheath replacement can be performed completely automatically if manipulation apparatuses which displace the bearing element laterally in the direction of the rotation axis are provided on the exterior of the printing apparatus.
Because the sheath is handled gently, the invention is applicable in particular to printing apparatuses in which the sheath has a charge-accepting layer. In the case of printing apparatuses having an image cylinder and a transfer cylinder for toner, each possessing a sheath, the holding apparatuses for the sheaths can be provided on a shared bearing element. As a result, the two sheaths can be replaced simultaneously. In the case of multi-cylinder arrangements, it is possible to provide apparatuses which move the cylinders apart from one another prior to sheath replacement.
REFERENCES:
patent: 4134667 (1979-01-01), Schnall et al.
patent: 4823160 (1989-04-01), Ikuta et al.
patent: 5130751 (1992-07-01), Sato et al.
patent: 5722013 (1998-02-01), Nagase et al.
Chen Sophia S.
Kessler Lawrence P.
Nexpress Solutions LLC
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