Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
2000-06-26
2001-08-07
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Feeding
By means to convey sheet
C271S194000, C271S196000
Reexamination Certificate
active
06270075
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a vacuum transport for moving sheets, such as paper sheets, within a xerographic printing apparatus, such as a copier or “laser printer.”
BACKGROUND OF THE INVENTION
Electrostatographic or xerographic printing devices, such as copiers or digital “laser printers,” are well known. In many types of apparatus, a key area from a reliability standpoint is the zone between the charge-retentive member, such as a photoreceptor, and the fuser. The sheet that receives an image from the photoreceptor in a transfer step must be pulled from the photoreceptor (which is typically in the form of a rotating drum or belt) and, as smoothly as possible, directed to a fuser, which typically comprises two rollers forming a nip therebetween. The length of the gap between the photoreceptor and the fuser is crucial when the machine is handling short sheets as the photoreceptor may not ensure continuous drive to deliver the sheet to the fuser, causing a paper jam. If the sheet is caused to jam very close to the fuser, heat from the fuser is liable to create a dangerous situation. Further, because the toner image on the sheet as it passes from the photoreceptor to the fuser is only loosely attached to the sheet, any irregularities in the paper feeding between the photoreceptor and the fuser are likely to cause unacceptable smearing of the image.
In many designs of copiers or printers, particularly of the high-speed variety, the preferred device for moving a sheet from the photoreceptor to the fuser is a vacuum transport. A typical design of a vacuum transport is shown in FIG.
4
. As shown in the Figure, the vacuum transport generally indicated as
100
is disposed within a copier or printer between a photoreceptor
102
and the fuser rolls
104
. Vacuum transport
100
itself typically comprises a belt
110
which is entrained about two rollers
112
,
114
. This belt
110
typically defines a number of small holes therein (not shown). Disposed inside the belt
110
is a vacuum chamber
116
. The vacuum chamber
116
is an actuated by a motor (not shown) and thereby draws air through the holes in belt
110
particularly in the area where a sheet moving in a process direction in is passing over the belt
110
. In this way, vacuum chamber
116
holds a sheet against the outer surface of belt
110
, while belt
110
moves that sheet from photoreceptor
100
toward the nip of fuser rolls
104
.
While the vacuum transport of the general design shown in the Figure has long been proven to be effective, it suffers from various impracticalities. For instance, transport
100
tends to be heavy and expensive, and the belt
110
may require replacement over the life of the machine. The large size of the vacuum transport tends to preclude its use in compact printers and copiers. The present invention is directed toward a small, low-cost, yet effective vacuum transport.
SUMMARY OF THE INVENTION
The present invention is a vacuum transport for conveying a sheet in a process direction within a printing apparatus. A chamber defines an external surface, the external surface defining a full width perpendicular to the process direction. A first plurality of openings is defined in the external surface. A first plurality of ribs protrude from the external surface, the ribs being disposed between pairs of openings of the first plurality of openings, the ribs being oriented along the process direction. An axle is rotatably mounted within the chamber, and a plurality of rollers are disposed on the axle, whereby a portion of each roller protrudes through one of the first plurality of openings, and a gap is defined between a surface of each roller and an edge of the opening.
REFERENCES:
patent: 4889331 (1989-12-01), Sardella
patent: 5127329 (1992-07-01), DeMoore et al.
patent: 5344133 (1994-09-01), Jantsch et al.
patent: 5520382 (1996-05-01), Nakajima
Korhonen John V.
Mayfield Peter A.
Muggleworth Simon
Partridge Colin
Bollinger David H.
Hutter R.
Xerox Corporation
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