Imaging apparatus and improved exit device therefor

Details Imaging apparatus and improved exit device therefor Imaging apparatus and improved exit device therefor

1998-03-04

2000-12-19

Beatty, Robert

Electrophotography

Image formation

Transfer

399397, G03G 1516

Patent

active

061636762

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates generally to imaging systems and, more particularly, to printed substrate exit devices of imaging systems.


BACKGROUND OF THE INVENTION

Printed substrate exit devices for imaging and printing systems, such as electrophotographic imaging and printing systems, are known in the art. Exit devices are designed to provide efficient, controlled, exit of the printed substrate from a printing site of the imaging system. The printing site is typically an impression region between the substrate and a member carrying a toner or ink image. In many existing systems, an impression roller provides positive contact between the image carrying member and the substrate.
To provide efficient, slip-free, removal of the printed substrate from the impression region, a portion of the exit device must be urged against the printed side of the substrate. However, to avoid deformation of the yet incompletely fixed image upon exit from the impression region, the exit device preferably includes a smooth surface and the area of contact between the exit device and the printed surface is preferably minimized. Thus, existing exit devices include rigid, smooth elements, for example a plurality of narrow rollers, contacting only a portion of the width of the printed surface. This structure results in slight image deformation, such as loss of glossiness, in the form of streaks corresponding to the regions of contact between the rollers and the printed surface.
PCT Publication WO 93/04409 describes a duplex imaging system having such an exit device. The exit device used in WO 93/04409 includes a pair of thin, rigid, rollers which urge the printed substrate against the impression roller, downstream of the impression region. The exit rollers are rotatably mounted on an axle which is also utilized as part of a substrate deflection arrangement of the duplex imaging system.
Substrate feeder rollers for feeding printing substrate into the impression region are known in the art. Since there is no image on the substrate being fed, there are no particular restrictions on the contact area between the feeding roller and the substrate. Therefore, the feeding roller is typically in contact substantially with the entire width of the substrate. U.S. Pat. No. 4,287,649 describes a substrate feeder-roller which contacts the entire width of the printing substrate. The roller of U.S. Pat. No. 4,287,649 is formed of a thick, spongy, interior coated with a thin, smooth or textured, outer shell.


SUMMARY OF THE INVENTION

The present invention seeks to provide an improved exit device which guides image bearing substrates, out of an image impression region of imaging apparatus, efficiently and substantially without causing deformation of the images printed on the substrates.
The exit device of the present invention includes an elongate exit roller which urges substantially the entire width of the image bearing substrate against the impression roller. The exit roller preferably has a layered structure, including a relatively thick, resilient, relatively soft, inner layer and a thin, rigid, relatively hard, outer layer having a smooth outer surface. During operation of the exit device, the outer surface of the outer layer engages substantially the entire width of the image bearing surface of the substrate. The smoothness of the outer surface and the resilience provided thereto by the inner layer prevent deformation of the unfixed, typically still warm and relatively soft, image impressed on the substrate at the impression region. The large area of contact between the outer surface and the image bearing substrate ensures controlled exit of the image bearing substrate from the impression region.
In one preferred embodiment of the present invention, the exit device is adapted for use with a duplex imaging system, whereby an axis on which the exit roller is mounted is also utilized by a substrate deflection arrangement of the duplex imaging system.
In accordance with a preferred embodiment of the present invention, t

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