Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
1999-02-24
2001-07-10
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
C271S010110, C271S010030, C271S010040, C271S110000, C271S114000, C271S115000, C271S127000, C271S126000, C271S121000, C271S124000, C271S123000, C271S118000
Reexamination Certificate
active
06257569
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to printing systems, and more particularly relates to sheet feeder apparatus for delivery of print media to printers.
BACKGROUND OF THE INVENTION
Sheet media delivery apparatus are used to deliver print media to printers. These apparatus are often incorporated into auxiliary bin sheet feeders, which are typically used to increase the media delivery capacity of nominally low-capacity inkjet or laser printers. They also are commonly used as part of an overall media transport system in large-capacity office printers and copier systems.
Various auxiliary bin sheet feeders were developed for many of the early laser printers, such as the Hewlett-Packard “LASERJET” II and “LASERJET” III printers. Since these printers were fairly large (in comparison to today's laser printers), the overall size of the auxiliary bin sheet feeders could also be fairly large without appearing out of place or taking up excessive room on a desk or printer stand that was sized to accommodate the printer.
Today's contemporary laser printers and inkjet printers are much smaller than their predecessors. However, the demand for increased media-handling capacities remains as strong as ever. In parallel with this reduction in printer size, office and consumer markets have also demanded a reduction in the size of the auxiliary bin sheet feeders that work with the newer printers.
A reduction in overall size of an auxiliary bin sheet feeder requires a reduction in the media delivery system. The media delivery system typically performs two functions. First, a sheet of media must be “picked” off of a stack of media. It is desired to pick a single sheet of media at time, which is known as “singulation.” The second function of the media delivery system is to advance the picked sheet of media into a printer media feed system.
A common problem generally encountered in media delivery systems is “multipicking.” Multi-picking may occur when underlying sheets in the stack are partially “dragged” out of the tray by the picking of sheets above. Many conventional media delivery systems are designed to provide minimal drag on the media sheet after it has entered the feed mechanism of the printer. While minimizing drag improves media alignment and positional accuracy in the printer, retracting the separator pad can create another type of multi-picking known as a “trailing pick.” A trailing pick is caused when an underlying sheet is dragged by a sheet above it (generally the picked sheet) as the picked sheet is transported through the media delivery system.
A common technique for performing the pick operation employs a D-shaped wheel (D-wheel) that is rotated to cause a media sheet pick action. As the D-wheel is rotated, its curved portion contacts the media, urging it forward. As the D-wheel is further rotated it falls out of contact with the media at its flattened portion, allowing an upstream media transport mechanism to advance the media without resistance from the D-wheel. This arrangement is satisfactory so long as the media sheet is not bent around the D-wheel shaft during a feed operation. This situation may occur when the media tray is positioned at an angle relative to the feed mechanism. If the media sheet presses against the D-shaped wheel, significant drag on the media sheet results. Therefore, D-wheel systems are generally impractical for use in feed systems that require the media to be bent as it is fed to the printer, a common condition when auxiliary bin feeders are used with today's smaller printers.
The use of a D-wheel is also impractical for use in a low-profile auxiliary feed system applications that require the sheet media to be advanced a fair distance prior to entering the printer feed mechanism. For instance, a typical feed system may employ a D-wheel with a nominal diameter of about 2 inches (50 mm). Since about ¾ of the perimeter of the D-wheel contacts the media during a feed operation, a D-wheel of this size can advance the media about 5 inches. In comparison, the D-wheel diameter of a low-profile auxiliary feed mechanism may be limited to about half this size. Such a reduced-size wheel can only advance the media about 2.5 inches, which is insufficient in most applications.
Another typical pick and feed arrangement is shown in
FIGS. 1-3
, which illustrate a pick roller system employed in a media sheet feed mechanism manufactured by the Epson Corporation. As shown in
FIG. 1
, the system comprises a pick roller
216
that is driven by a drive gear
210
mounted on a shaft
212
, which in turn is coupled to a drive motor (not shown). A pivot arm
214
is mounted for rotation about shaft
212
and encloses a rubber pick roller
216
. A driven gear
218
mates with drive gear
210
, is rigidly connected to pick roller
216
, and is mounted for rotation on a shaft
220
. A spring washer
222
is positioned between an inner surface of arm
214
and driven gear
218
, and performs a friction clutch function.
The pick and feed system is positioned above a media tray including a pressure plate
224
which supports a stack of media sheets
226
. The tray is biased by a spring
228
into contact with the pick roller
216
. An edge separator
230
is positioned to maintain an uppermost sheet on stack
226
in place until operation of the rubber pick roller
216
.
The pick operation is illustrated in
FIGS. 2 and 3
. To implement a pick operation, drive gear
210
is driven in a counterclockwise (CCW) direction, thereby causing driven gear
218
to rotate in a clockwise (CW) direction. Due to the friction exerted by spring washer
222
, arm
214
and pick roller
216
are caused to rotate in a CCW direction until arm
214
hits stop
232
. This action causes pick roller
216
to come into contact with a top sheet
234
of stack
226
. The top sheet is forced against pick roller
216
through the action of spring
228
on tray
224
. Continued clockwise rotation of the pick roller
216
feeds the top sheet
234
from the stack
226
.
As shown in
FIG. 3
, when the top sheet
234
is grabbed by a pair of feed rollers
236
, the direction of rotation of the driven gear
210
is reversed to a CW direction, thereby causing the arm
214
and pick roller
216
to rotate in a CCW direction and out of engagement with the top sheet. The CCW rotation of pick roller
216
is required as the clutching action of spring washer
222
otherwise would cause pick roller
216
to impede the feeding of the top sheet. The CCW rotation of the arm
214
and pick roller
216
continues until the arm
214
hits a second stop
238
.
The prior art device of
FIGS. 1-3
is generally too large to be used in a low-profile auxiliary bin sheet feeder. In order to meet the height restrictions necessitated by the lower profile, the size of the pick roller and drive gear must be reduced, which adversely impacts the pick and feed performance. Furthermore, the positioning of the feed rollers adds extra length to the overall size of the feed system.
Reduced-size media delivery systems present other problems that are not generally encountered with larger systems. One such problem is that the size (diameter) of the drive motor on these systems may be limited. A drive motor with a 50% reduction in diameter may have 25% of the torque of a comparable full-size motor. As a result, the torque available to drive the system may be dramatically reduced.
In addition to the foregoing problems, the media feed system needs to be able to handle media that is not completely flat. Humidity will often cause media sheets to become corrugated in that the sheets have ripples or waves formed in them and are no longer flat. Corrugated sheets pose a problem for conventional feed systems because they have a tendency to jam, rip or become skewed when they enter a feed-roller assembly subsequent to being picked.
Therefore a need exists for an improved reduced-size auxiliary bin feeder and associated media delivery system. It is further desired to have a media delivery system that reduces multi-picks and
Chen Angela
Rasmussen Steve O
Rhodes John D.
Yraceburu Robert M.
Hewlett--Packard Company
Miller Jonathan R
Walsh Donald P.
LandOfFree
Apparatus and method for delivery of sheet media to a printer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for delivery of sheet media to a printer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for delivery of sheet media to a printer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438410