Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
2000-03-02
2002-04-30
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Feeding
By means to convey sheet
C271S202000
Reexamination Certificate
active
06378864
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a stacker for stacking and holding a multiplicity of printed printing papers delivered from a printer.
2. Background Art
A stacker adapted to be arranged adjacent to a paper delivery port of a printer, for sequentially taking in a multiplicity of printed printing papers (or sheets) delivered from the printer and for stacking and holding the papers thus taken in on a tray and in order, is known. In this type of stacker, in order to smoothly take in and carry a large number of papers delivered at a predetermined rate from the printer, a paper carrying speed in a stacker body is normally set at a paper intake speed (equal to the paper delivery speed of the printer) or higher. Especially, in order to shorten a time required for taking in the paper and stacking it on the tray, the conventional stacker has set the paper carrying speed at a sufficiently high level as compared with the paper intake speed.
Under this speed setting, when the stacker is used for a high-speed printer (referred to as, e.g., a high-speed page printer) capable of printing dozens of papers per minute, the paper carrying speed tends to reach a high level such as several hundreds of mm/s. The papers carried at high speed are discharged from an outlet port provided on the back side of the stacker to fly above the tray extending rearward of the stacker, and freely fall on the tray to be stacked one by one. The tray is usually provided with a paper support surface inclined in such a manner that the proximal end thereof adjacent to the stacker body is positioned lower than the distal end thereof. Thus, the paper that has first fallen on the tray slides downward on the support surface by its own weight, and bumps against a back plate of the stacker body to come to a stop at a predetermined position. The paper that has subsequently fallen on the tray slips downward on the first paper, and it also bumps against the back plate of the stacker body to come to a stop at a predetermined position. In this way, a multiplicity of papers are stacked with the edges thereof aligned with one another.
Incidentally, if a speed at which the paper is discharged from the outlet port is excessively high, the flying distance of the paper may be increased and thus the sliding distance on the tray may be increased. In this case, it is often difficult to stack a large number of papers in a mutually exact alignment on the tray. In view of this, in the conventional stacker adapted to be used for the high-speed printer, a paper discharge speed is set lower than a paper carrying speed, so as to prevent the excessive flying of the paper.
FIG. 13
is a velocity diagram showing one example of a paper-transfer velocity change between the paper intake and the paper discharge in the conventional stacker used for the high-speed printer. In
FIG. 13
, a horizontal axis represents a time (ms) and a vertical axis represents the peripheral velocity (mm/s) of an eject roller installed at the outlet port of the stacker. The eject roller is one of drive rollers for transferring the papers delivered from the high speed printer inside the stacker body. The rotational speed of the eject roller is controlled by stages over a time period T
1
for taking the paper into the stacker body, a time period T
2
for carrying the paper in the stacker body and a time period T
3
for discharging the paper above the tray.
In the illustrated example, when the stacker receives a paper delivery signal from the high-speed printer, the eject roller first starts to rotate at a peripheral velocity of 180 mm/s identical to the paper delivery speed of the printer (the intake time T
1
). The paper is transferred at this intake speed v
1
to the eject roller along a paper guide in the stacker body. When the paper arrives at a predetermined position at [t
01
], the eject roller increases the peripheral velocity to 750 mm/s, and catches the paper to transfer it to the outlet port at this carrying speed v
2
(the carrying time T
2
). When the leading portion of the paper protrudes from the outlet port by a predetermined length at [t
02
], the eject roller decreases the peripheral velocity to 400 mm/s, and acts to discharge the paper from the outlet port at this discharge speed V
3
above the tray to make it fly thereabove (the discharge time T
3
). After that, at [t
03
], the eject roller is returned to the intake speed V
1
and waits for the next paper.
Also for the next paper, the peripheral velocity of the eject roller is controlled in the same way, i.e., to the intake speed v
1
=180 mm/s from t
03
to t
11
, to the carrying speed v
2
=750 mm/s from t
11
to t
12
, and to the discharge speed V
3
=400 mm/s from t
12
to t
13
. Subsequently, the printed papers are discharged successively from the printer at the speed of, e.g., 42 sheets per minute (the cycle of 1430 ms). Thus, the eject roller changes the peripheral velocity thereof by stages in the same way, and repeats the intake, carry and discharge of the paper, so as to stack a large number of papers on the tray.
The above-described stacker for the high-speed printer is required to be able to automatically and accurately stack and hold several thousand papers on the tray, so as to cope with the automatic operation of the printer. For this purpose, this type of stacker generally incorporates therein an automatic lift mechanism of the tray. The automatic lift mechanism includes a paper stack sensor of a reflection type arranged at a predetermined position on a back plate below the outlet port of a stacker back-side, and a tray drive mechanism activated in accordance with a sensing signal of the paper stack sensor. When a paper stack piled on the tray closes the front side of the paper stack sensor, the paper stack sensor outputs the sensing signal, and thereby the tray drive mechanism is activated to move the tray downward. Consequently, the position of the top surface of the paper stack on the tray is held at a substantially constant height in the vicinity of the paper stack sensor. When the tray moves downward in accordance with the increase in the number of stacked papers and reaches a lowest position with several thousand (e.g., three thousand or more) papers being piled thereon, a limiter placed at the lowest position of the tray detects the tray and outputs a stop signal to the control section of the printer and stacker. As a result, the printer and stacker come to a stop, and thereby a printing and paper stacking operation is completed.
In the conventional stacker having the above configuration, a circumstance may arise wherein a paper, expected to fly and fall toward the tray, falls, contrary to expectations, along the back plate of the stacker body while coming into partially contact therewith. In this case, the paper cannot be laid in flat on the tray or on the previously formed paper stack, but tends to lean at a part thereof against the back plate of the stacker body.
One of the factors of this falling behavior of the paper is an adsorbing action due to static electricity charged on the paper in the printer. If the paper is considerably charged, the paper cannot sufficiently fly after it is discharged from the outlet port of the stacker, but is adsorbed to the back plate of the stacker due to an electrostatic absorbing force. Therefore, in order to eliminate the static electricity charged on the paper, the conventional stacker is constituted such that a charge-eliminating brush is placed around the outlet port and the paper is discharged above the tray from the outlet port after any charge is eliminated by coming into contact with the charge-eliminating brush. The charge-eliminating brush can exhibit a charge-eliminating effect to some degree by optimizing the dimensions and location thereof, but is difficult to perform perfect charge-elimination, and thereby the paper is actually discharged with the static electricity of 1 kV to 2 kV remaining on the paper. An effective method for completely eliminating th
Bollinger David H.
Bower Kenneth W.
Citizen Watch Co., LTD
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
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