Accumulator station with stack height control

Details Accumulator station with stack height control Accumulator station with stack height control

2000-05-26

2001-07-10

Ellis, Christopher P. (Department: 3651)

Sheet feeding or delivering

Delivering to stack and feeding therefrom

Feeding from bottom of stack

C271S003070, C271S003010, C493S416000

Reexamination Certificate

active

06257568

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention is directed to an apparatus adapted to be used for the automatic transfer of sheets from which leaflets are formed from a printing press to a folder.
Leaflets may be formed by printing a paper web with printed subject matter, separating the web into individual sheets, transferring the individual sheets to a folder, and then folding the individual sheets into leaflets. As disclosed in U.S. Pat. No. 4,616,815 to Michael Vijuk, printed and cut shingled sheets were previously transferred manually from a web printing press to an automatic folding machine used for folding the sheets to form leaflets. The invention disclosed in that Vijuk patent is advantageous in that allows the previously manual transfer of sheets to be automated, which is particularly advantageous in view of the relatively high output of sheets from a web printing press, which may be on the order of 40,000 sheets per hour or more.
As shown in
FIG. 1
, the Vijuk patent discloses a printing press
15
which applies printed subject matter to a paper web and cuts the paper web into individual sheets to generate a shingled stream of sheets. The sheets are conveyed by a sheet transfer conveyor
16
to a stacking station
18
where sheets may accumulate in a vertical stack. Sheets are periodically removed from the bottom of the stack of sheets at the stacking station
18
by a rotatable vacuum cylinder
40
(shown in
FIG. 6
) and transferred to an alignment conveyor
22
for subsequent transfer to a folding station
14
.
A prior art apparatus for automatically transferring sheets from a web printer to a folding machine generally in accordance with the disclosure of the Vijuk patent controlled the vacuum cylinder so that its rotational speed varied in response to the height of the stack of sheets in the stacking station, with the height of the stack of sheets being detected by a sensor positioned adjacent the stack. The prior art apparatus also included a sensor for sensing whether the height of the stack of sheets was below a minimum height. In that case, a visual message would be displayed to prompt the operator to place additional sheets in the stack at the stacking station. The prior art apparatus also controlled when a vacuum was provided to the interior of the vacuum cylinder was selectively opening and closing a pneumatic valve that fluidly coupled the vacuum cylinder to a vacuum pump.
The prior art apparatus described above included a batch control module that allowed the operator to input a desired number of sheets which was to be transferred as a batch, along with a desired time delay between batches of sheets. The prior art apparatus also included a rate control module that allowed the operator to input a desired distance or gap between adjacent sheets as they are fed by the vacuum cylinder, as well as the time duration for which the pneumatic valve was opened and closed. Based upon those parameters entered by the operator, the batch control module and rate control module controlled the time periods when the pneumatic valve was on and off, and thus the removal of the sheets from the stack by the vacuum cylinder.
SUMMARY OF THE INVENTION
The invention is directed to an apparatus adapted to be used for the automatic handling of sheets from which leaflets are formed. The apparatus includes a transfer unit for conveying sheets, an accumulator station disposed adjacent the transfer unit and being adapted to receive sheets from the transfer unit and to accumulate the sheets in a stack, a sensor associated with the accumulator station and being adapted to generate a signal indicative of whether the height of the stack of sheets in the accumulator station is at least equal to a minimum height, a sheet feeder adapted to periodically remove sheets from the stack of sheets, and a control mechanism operatively coupled to the sensor and the sheet feeder. The control mechanism is adapted to cause the sheet feeder to remove the sheets from the accumulator station as long as the height of the stack of sheets is at least the minimum height as determined by the sensor, and the control mechanism is adapted to cause the sheet feeder to cease removal of the sheets from the accumulator station if the height of the stack of sheets falls below the minimum height as determined by the sensor.
The transfer unit may include a first set of conveyor belts, a second set of conveyor belts, and a support structure for supporting the first and second sets of conveyor belts, the support structure being adapted to cause a stream of sheets to be received between the first set of conveyor belts and a second set of conveyor belts. The accumulator station may be provided with a plurality of air-pressure apertures to supply pressurized air against a portion of the stack of sheets.
The sheet feeder may include a rotatable vacuum roll adapted to remove a sheet from the bottom of the stack of sheets at the accumulator station, vacuum means operatively coupled to the vacuum roll for creating a suction pressure within an interior portion of the vacuum roll, and a motor for causing the vacuum roll to be rotatably driven at a substantially constant rate, and the control mechanism may include an actuator mechanism operatively coupled to the vacuum means for selectively eliminating the suction pressure, in response to the signal generated by the sensor, while the vacuum roll is being rotatably driven by the motor.
The vacuum means may include a vacuum pump, a conduit pneumatically connecting the vacuum pump to the interior portion of the vacuum roll, and a valve operatively coupled to the conduit and being capable of selectively closing the conduit in response to the signal generated by the sensor.
The control mechanism may include a pulse-shaping circuit, operatively coupled to receive the signal from the sensor, that causes the sheet feeder to cease removal of the sheets from the accumulator station for a minimum period of time after the height of the stack of sheets falls below the minimum height as determined by the sensor. The control mechanism may also include means for limiting the rate at which the sheet feeder transitions between an on state in which the sheet feeder removes sheets from the accumulator station and an off state in which the sheet feeder does not remove sheets from the accumulator station.
In another aspect, the invention is directed to an apparatus adapted to be used for the automatic handling of sheets from which leaflets are formed. The apparatus includes a transfer unit for conveying sheets, an accumulator station disposed adjacent the transfer unit and being adapted to receive sheets from the transfer unit and to accumulate the sheets in a stack, a sensor associated with the accumulator station and being adapted to generate a signal indicative of whether the height of the stack of sheets in the accumulator station reaches a maximum height, a sheet feeder adapted to periodically remove sheets from the stack of sheets, and a control mechanism which is adapted to cause the sheet feeder to alter the rate at which the sheets are removed from the accumulator station in response to the height of the stack of sheets reaching the maximum height as determined by the sensor. The apparatus may also include a rate control module adapted to control a gap between at least two batches of sheets, and the control mechanism may include means for reducing the duration of the gap in response to the stack of sheets reaching the maximum height as determined by the sensor.


REFERENCES:
patent: 3044767 (1962-07-01), Winkler et al.
patent: 3599965 (1971-08-01), Humphrey et al.
patent: 4018434 (1977-04-01), Mitchell et al.
patent: 4436297 (1984-03-01), Chandhoke
patent: 4524963 (1985-06-01), D'Angelo et al.
patent: 4579330 (1986-04-01), Lehmann
patent: 4616815 (1986-10-01), Vijuk
patent: 4771896 (1988-09-01), Newsome
patent: 4850583 (1989-07-01), Monday
patent: 5121914 (1992-06-01), Hargreaves
patent: 5150891 (1992-09-01), Svyatsky et al.
patent: 5197726 (1993-03-01), Nogami
patent: 5295678 (1994-03-01), Lin

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