U.S. patent application number 10/668417 was filed with the patent office on 2004-04-01 for method for controlling stack-advancing in a reproduction aparatus.
Invention is credited to Dobbertin, Michael T., Sciurba, Thomas K., Zimmer, James A. JR..
Application Number | 20040061280 10/668417 |
Document ID | / |
Family ID | 31978788 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040061280 |
Kind Code |
A1 |
Sciurba, Thomas K. ; et
al. |
April 1, 2004 |
Method for controlling stack-advancing in a reproduction
aparatus
Abstract
The present invention relates to a method for providing paper
stack level calibration in a reproduction apparatus. According to
various aspects of the invention, methods are provided for
continuous feeding with a transition from one supply to another,
and leaving a controlled number of sheets in the prior supply.
Inventors: |
Sciurba, Thomas K.;
(Webster, NY) ; Zimmer, James A. JR.; (Gates,
NY) ; Dobbertin, Michael T.; (Honeoye, NY) |
Correspondence
Address: |
Kevin L. Leffel
Heidelberg Digital L.L.C.
2600 Manitou Road
Rochester
NY
14624
US
|
Family ID: |
31978788 |
Appl. No.: |
10/668417 |
Filed: |
September 23, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60413898 |
Sep 26, 2002 |
|
|
|
Current U.S.
Class: |
271/152 |
Current CPC
Class: |
B65H 2511/22 20130101;
B65H 3/44 20130101; B65H 2511/13 20130101; B65H 2511/22 20130101;
B65H 1/18 20130101; B65H 2511/13 20130101; B65H 2511/30 20130101;
B65H 2511/30 20130101; B65H 7/02 20130101; B65H 2220/01 20130101;
B65H 2220/11 20130101; B65H 2220/03 20130101; B65H 2220/03
20130101 |
Class at
Publication: |
271/152 |
International
Class: |
B65H 001/18 |
Claims
What is claimed is:
1. A method for controlling sheet stack advancing, comprising:
determining a distance of a platform relative to a feedhead
corresponding to a predetermined number of sheets to be left in a
sheet supply, said sheets resting upon said platform; switching to
another sheet supply when said platform is said distance from said
feedhead thereby leaving said predetermined number of sheets in
said sheet supply, said predetermined number remaining unchanged
regardless of a sheet thickness.
2. The method of claim 1, further comprising driving said platform
with a stepper motor, and expressing said distance as stepper motor
counts.
3. The method of claim 1, further comprising determining said
distance prior to said platform being at said distance relative to
said feedhead.
4. The method of claim 1, further comprising storing said distance
in memory.
5. A method for controlling sheet stack advancing, comprising:
determining a sheet thickness by measuring a displacement of a
platform corresponding to a known number of sheet feeds by said
feedhead, said sheets resting upon said platform; determining a
distance of said platform relative to a feedhead corresponding to a
predetermined number of sheets having said sheet thickness to be
left in a sheet supply; switching scheduling of future feeds to
another sheet supply when said platform is said distance from said
feedhead.
6. The method of claim 5, further comprising driving said platform
with a stepper motor, and expressing said distance as stepper motor
counts.
7. The method of claim 5, further comprising determining said
distance prior to said platform being at said distance relative to
said feedhead.
8. The method of claim 5, further comprising storing said distance
in memory.
9. A method for controlling sheet stack advancing, comprising:
determining a maximum travel of a platform and storing it in a
memory, said sheet stack resting upon said platform; advancing said
platform with a motor from a bottom-most to a top-most height
position and performing sheet separating and feeding; determining a
current platform travel before every feed; saving said current
platform travel in said memory and comparing said current platform
travel with a nominal platform travel, and updating said maximum
travel in memory each time said platform is completely emptied of
sheets.
10. The method of 9, further comprising generating an error signal
if a difference between said current platform travel and said
nominal platform travel is greater than a predetermined value.
11. A method for controlling stack advancing in a reproduction
apparatus, comprising: determining maximum platform displacement,
N.sub.T, and storing it in memory, a stack of sheets resting on
said platform; advancing said platform and performing sheet
separating and feeding for K sheets; recording a current platform
displacement, N.sub.K, that occurred during feeding said K sheets;
and, calculating a paper low displacement N.sub.L=N.sub.T-N.sub.K
and storing N.sub.L in memory.
12. The method of claim 11, further comprising initializing N.sub.L
to a nominal value and storing it in memory.
13. The method of claim 11, wherein reaching N.sub.L initiates
switching over to feed from another stack loaded with the same
sheet attributes.
14. The method of claim 11, comprising initializing N.sub.L if a
renewal of the stack occurs.
15. The method of claim 11, further comprising initializing N.sub.L
in response to a change of sheet attributes.
16. The method of claim 11, further comprising initializing N.sub.L
to a nominal value, storing it in memory, and replacing it with a
determined N.sub.L for that stack.
17. The method of claim 11, further comprising driving said
platform with a stepper motor, and expressing said displacement as
stepper motor counts.
18. A method for controlling stack-advancing in a reproduction
apparatus, comprising: driving a platform in steps with a lifting
motor and performing sheet separating and feeding; initializing a
paper-low displacement, N.sub.L, of said platform to a nominal
number of said steps and storing it in memory; determining a number
of steps of said lifting motor to achieve movement from a bottom
position to a top position of said platform, N.sub.T, and storing
it in a memory; separating and feeding K sheets and recording in
memory an actual number of said steps corresponding to feeding said
K sheets, N.sub.K; replacing said nominal number of steps with
N.sub.T-N.sub.K in memory.
19. The method of claim 18, wherein reaching N.sub.L initiates
switching over to feed from another stack loaded with the same
sheet attributes.
20. The method of claim 18, comprising initializing N.sub.L if a
renewal of the stack occurs.
21. The method of claim 18, further comprising initializing N.sub.L
in response to a change of sheet attributes.
23. The method of claim 18, further comprising initializing N.sub.L
to a nominal value, storing it in memory, and replacing it with a
determined N.sub.L for that stack.
24. A method for controlling sheet stack advancing, comprising:
determining a distance of a platform relative to a feedhead
corresponding to a predetermined number of sheets K to be left in a
sheet supply, said sheets resting upon said platform; determining a
number of feeds J already scheduled from said sheets when said
platform is said distance from said feedhead; scheduling up to K-J
more feeds from said sheets, and switching further scheduling to
another sheet supply.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for providing
paper stack level calibration in a reproduction apparatus.
BACKGROUND OF THE INVENTION
[0002] In typical reproduction devices, such as copiers or
printers, for example, information is reproduced on individual cut
sheets of receiver material such as plain bond or transparencies.
Receiver sheets of the various types are stored in stacks and
respectively fed seriatim from such stacks when copies are to be
reproduced thereon. The sheet feeder for the reproduction devices
should be able to handle a wide range of sheet types and sizes
reliably and without damage. Desirably, the sheets are accurately
fed individually from the sheet stack without misfeeds or
multifeeds.
[0003] Reproduction device sheet feeders are typically of two
types, vacuum feeders or friction feeders. An exemplary vacuum
sheet feeder is shown in U.S. Pat. No. 5,344,133, issued Sep. 6,
1994, in the name of Jantsch et al. In such an apparatus, a stack
of sheets is stored in a supply hopper. A sheet feed head assembly,
including a plenum, a vacuum source in flow communication with the
plenum, and a mechanism, such as a feed belt associated with the
plenum, transports a sheet acquired by vacuum in a sheet feeding
direction away from the sheet supply stack.
[0004] Typically, in most vacuum sheet feeders, the sheet supply
stack is supported to maintain the topmost sheet at the feed head
assembly. A first positive air supply then directs a flow of air at
the sheet supply stack to levitate the top several sheets in the
supply stack to an elevation enabling the topmost sheet to be
acquired by vacuum from the sheet feed head assembly plenum.
Additionally, a second positive air supply typically directs a flow
of air at an acquired sheet to assure separation of any additional
sheets adhering to such topmost sheet.
[0005] It is clear that the sheet stack should be maintained in a
particular positional relation with the sheet feed head assembly to
assure desired feed from the stack. An exemplary control of a sheet
stack is shown in U.S. Pat. No. 5,823,527, issued Oct. 20, 1998, in
the name of Burlew et al. In such an apparatus, a sheet feeder is
disclosed having a platform for supporting a stack of sheets, a
feed head assembly for feeding sheets seriatim from the top of a
sheet supply stack on the platform, a mechanism for moving the
platform relative to the feed head assembly, and device for
controlling operation of the platform moving mechanism. The control
device can determine a selected parameter in response to
examination of sheet stack parameters, and consequently produce a
signal corresponding thereto. The speed of the platform moving
mechanism is then set based on the parameter signal.
[0006] Modern reproduction devices have more than one sheet feeder
to store different types of sheets. When running large print jobs
without any stop page there is a need to switch over from one
feeder to another. Normally the first stack is not run empty before
switching over to the next stack. It is preferred to leave the
minimum number of sheets necessary to insure that the feed source
will not run out prior to switching. This maximizes the effective
capacity of the supplies and minimizes the number of sheets that
are likely to be exposed to undesirable environments for an
extended period of time as a result of being left behind. Normally,
feeding is switched to another feed source when a paper low
condition is signaled. This is typically determined by sensing that
the platform has reached a certain position, either through action
of a switch, or feedback from a platform travel monitor, such as an
encoder, potentiometer or step count from a step motor. The
actuation point for this paper low condition is selected to insure
that a sufficient number of receiver sheets is present to allow
switching under all conditions. Due to the system architecture, the
system tolerances and differences in the receiver sheet thickness,
this actuation point is selected conservatively. This results in an
excessive number of sheets remaining under most conditions.
[0007] The stack advancing is often performed with stepper motors.
The height position of the stack is proportional to the number of
steps a stepper motor is triggered. The paper supply controller
needs data relating to the displacement of the stack supporting
platform relative to a down switch for several reasons. The
displacement data is used to determine the paper low status as well
as enabling the paper out check and other functions. The paper low
displacement is one parameter that determines how many sheets are
left behind in a supply hopper after a continuous mode swap,
wherein paper supplies are switched and filled alternately in order
to provide continuous stream of sheets to the marking engine. As
mentioned before, the displacement can be measured in terms of
stepper motor steps applied. The mechanical tolerances in the stack
advancing mechanism are such that no nominal value for each of
these displacements would give an acceptable performance for all
supplies of the reproduction apparatus. Although it is possible to
manually calibrate the total possible displacement of an elevator,
it is inconvenient to manually calibrate for paper thickness.
[0008] The embodiments described herein allow for more effectively
controlling the level of a sheet stack and the switching over to
the next stack.
SUMMARY OF THE INVENTION
[0009] According to various aspects of the invention, methods are
provided for continuous feeding with a transition from one supply
to another, and leaving a controlled number of sheets in the prior
supply.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a side elevational view of an exemplary receiver
sheet supply and feeding apparatus.
[0011] FIG. 2 is a top plan view of the receiver sheet supply and
feeding apparatus of FIG. 1, with portions removed or broken away
to facilitate viewing.
[0012] FIG. 3 is a side elevational view of a cross-section of the
receiver sheet supply and feeding apparatus taken along lines 3-3
of FIG. 2, particularly showing the platform elevating
mechanism.
[0013] FIG. 4 is an end view, on an enlarged scale and with
portions removed, of a portion of the receiver sheet supply and
feeding apparatus, particularly showing the feed head assembly
thereof, taken along the lines 4-4 of FIG. 3.
[0014] FIG. 5 is a schematic illustration of an exemplary
reproduction device with two feeding apparatuses.
[0015] FIGS. 6-9 present a schematic illustrations of a different
stack advancing scenes according to further aspects of the
invention.
DETAILED DESCRIPTION
[0016] Addressing the problems with paper feeder supplies in
reproduction devices described above, the present embodiments
provide effective control of a paper stack in a reproduction
apparatus with the capability of increasing the effective receiver
sheet capacity.
[0017] According to an aspect of the present invention, the control
of stack-advancing may be characterized by an elevator step
calibration management system whereby each supply will calibrate
itself for both the total possible displacement and the paper low
displacement of a stack supporting platform. The calibration occurs
in a fashion that is both continuous and independent from the user.
The calibration procedure could be performed every time a stack has
been renewed or the sheet attributes were changed.
[0018] According to another aspect of the invention, the number of
elevator steps counted during the calibration procedure could be
checked with preset values to eliminate malfunctions in the stack
advancing control and devices.
[0019] According to another aspect of the invention the data
derived from the calibration procedure could be used to control the
switching over to the next stack and to calculate the limits for
declaring elevator movement problems.
[0020] The present invention provides a number of advantages and
applications as will be readily apparent to those skilled in the
art. Utilizing the disclosed methods, the present invention allows
increased effective receiver capacity without increasing the risk
of running out of paper while feeding sheets and switching over to
another stack.
[0021] The present embodiments described herein, provide the
ability to more effectively control a paper stack in a reproduction
device. The system and method have been implemented in a
reproduction device utilizing a top feed vacuum feeder. However, it
should be understood that the present embodiments can be
implemented in a reproduction device that utilizes other types of
feeders, including variations of the vacuum feeder or a friction
feeder. Thus, the exemplary embodiments disclose a system and
method that can be utilized to increase the efficiency for any type
of reproduction machine.
[0022] FIG. 1 is a side elevational view of an exemplary receiver
sheet supply and feeding apparatus according to one aspect of the
invention. The receiver sheet supply and feeding apparatus 10
generally includes an open hopper 12 and an elevating platform 14
for supporting a stack of sheets. The sheet stack (not shown in
FIG. 1) supported on the platform 14 contains individual sheets
suitable, for example, for serving as receiver sheets for having
reproductions formed thereon in a copier or printer device. Sheets
for receiving reproductions may be selected from a wide variety of
materials and sizes, which altogether define the sheet attributes.
For example, the sheets may be of a weight in the range of 49 grams
per square meter ("gsm") to 300 gsm index, and a size in the range
of 8.times.10 inches to 14.times.18 inches, or larger, or smaller,
depending upon the application.
[0023] The sheet stack supporting platform 14 is supported within
the hopper 12 for substantially vertical elevational movement by a
lifting mechanism ("L"). Preferably, the lifting mechanism L serves
to raise the platform 14 to an elevation for maintaining the
topmost sheet in the stack at a predetermined level during
operation of the receiver sheet supply and feeding apparatus 10,
and to lower the platform to permit adding sheets thereto. The
lifting mechanism L may include a motor ("M.sub.1"), attached to
the outside of the upstanding front wall of the hopper 12.
Preferably, the motor M.sub.1 rotates a gear set 16 mounted on a
shaft 18 extending from the upstanding rear wall of the hopper 12.
A pair of sprocket mounted lifting chains 20 are respectively
interconnected by gears with the shaft 18 to be moved about a
closed loop path when the shaft 18 is rotated by the motor M.sub.1.
As shown in FIG. 1, the sheet stack supporting platform 14 is shown
in its lowest position in phantom. This most bottom position of the
platform 14 is detected with a down switch 21.
[0024] FIG. 2 is a top plan view of the receiver sheet supply and
feeding apparatus 10 of FIG. 1, with portions removed or broken
away to facilitate viewing of a sheet feed head assembly 30. The
sheet feed head assembly 30 is generally located in association
with the hopper 12, so as to extend over a portion of the platform
14 in spaced relation to a sheet stack 50 supported thereon. The
sheet feed head assembly 30 includes a ported plenum 32 connected
to a vacuum source V, and an air jet device 40 connected to a
positive pressure air source P. Preferably, the positive pressure
air jet from the air jet device 40 levitates the top several sheets
in the supported sheet stack 50, while the vacuum at the plenum 32
is effective through its ports to cause the topmost levitated sheet
from the stack 50 to thereafter be acquired at the plenum 32 for
separation from the sheet stack 50. Additional positive pressure
air jets from the air jet device 40 helps to assure separation of
subsequent sheets from the acquired topmost sheet. To further
assure separation of sheets from the sheet stack, the lifting
mechanism (for example, L in FIG. 1) preferably presents the top
sheet a specified distance from the vacuum plenum 32.
[0025] FIG. 3 is a side elevational view of a cross-section of the
exemplary receiver sheet supply and feeding apparatus 10 taken
along lines 3-3 of FIG. 2, particularly showing the platform 14
lifting mechanism. Each of the lifting chains have a link 22
extending through respective slots 12a (FIG. 1) in the front and
rear upstanding walls of the hopper 12. The links 22 are connected
to a shaft 24a supported in brackets 24b extending from the
underside of the platform 14. Tension cables 26 are respectively
connected, at the ends 26a, 26b thereof, to the front and rear
upstanding wall of the hopper 12. The cables 26 are respectively
threaded over their associated first pulleys 24 and under second
pulleys 28 mounted on a shaft 28a supported in the brackets 28b
extending from the underside of the platform 14.
[0026] In FIG. 3, the sheet stack supporting platform 14 is shown
in its most elevated position in solid lines, and in its lowest
position in phantom. During the operation of the lifting mechanism
L, an appropriate signal to the motor M.sub.1 causes the motor to
rotate the gear set 16 (FIG. 1), such as either clockwise to lower
the platform 14 toward the lowest position or counterclockwise to
raise the platform toward its most elevated position. Rotation of
the gear set 16 moves the lifting chains 20 (FIG. 1) in their
closed loop paths, thereby imparting vertical movement to the links
22. This movement, in turn, moves the shaft 24a, and thus the
platform 14, and as well as its brackets 24b and first pulleys 24.
The platform 14 is maintained substantially level in its movement
by the action of the tension cables 26, which cooperatively move
the second pulleys 28, and thus, the shaft 28a and the brackets 28b
of the platform 14.
[0027] FIG. 4 is an end view, on an enlarged scale and with
portions removed, of a portion of the receiver sheet supply and
feeding apparatus 10, particularly showing the feed head assembly
30 thereof, taken along the lines 4-4 of FIG. 3. Preferably,
maintaining the topmost sheet 51 at the predetermined level is
accomplished by one or more sheet detecting switches 80, which
controls the operation of the motor M.sub.1 for actuating the
lifting mechanism L, (more described below), to raise the platform
14 through a predetermined increment. On the other hand, lowering
of the platform 14 is usually accomplished by some externally
produced signal to the motor which tells the motor to rotate until
the platform 14 reaches the down switch 21 that signals the motor
M.sub.1 to stop, often bringing the platform 14 to its lowest
position.
[0028] Of course, other precisely controllable lifting mechanisms,
such as worm gears, lead screws, or scissors linkages are suitable
for use in the elevation control for the sheet stack supporting
platform 14 according to these embodiments, and other suitable
mechanisms without limitation.
[0029] Preferably, the lower surface 32a of the plenum 32 of the
sheet feed head assembly 30 has a particularly configured shape, so
as to provide for a specific corrugation of an acquired sheet 51.
As the top sheets 51 in the supported sheet stack 50 are levitated,
the topmost sheet 51 preferably contacts the outer winged portions
32b of the surface 32a. A minimal pressure is exerted on the sheet
51 to help in forming a controlled corrugation to the sheet 51.
This establishes a consistent spacing for the center portion of the
sheet 51 from the center portion of the plenum 32. As such, the
access time for a sheet 51 to be acquired at the plenum 32 is often
repeatably consistent and readily predictable.
[0030] The interactions of the plenum 32 and the air jet device 40
attempt to assure that control over the sheet 51, as it is acquired
at the plenum 32, is not lost. Further, corrugation of the sheet 51
contorts the sheet 51 in an unnatural manner. Since subsequent
sheets 51 are not subjected to the same forces, at the same time,
as is the topmost sheet 51, such subsequent sheets 51 are unable to
contort in the same manner. Accordingly, the subsequent sheets 51
are effectively separated from the topmost sheet 51 as it is being
acquired at the plenum 32.
[0031] As noted above, it is important for proper operation of the
sheet supply and feeding apparatus 10, according to this
embodiment, for the level of the topmost sheet 51 in the stack 50
supported on the platform 14 to be maintained at a predetermined
height relative to the plenum 32. The level is selected to be in a
range where the topmost sheet 51, when levitated by the first air
jet arrangement 42, is close enough to the plenum 32 to be readily
acquired by the vacuum forces from the plenum 32, within a
repeatable time frame, but yet far enough away from the plenum 32
to assure that the sheet being acquired is not pinned against the
plenum 32.
[0032] Preferably, each of the switches 80, as noted above, are
designed to detect the level of the topmost sheet 51. Such switches
80, as known in the art, could be for example, a paper guide that
rides against the sheet 51 with very little downward pressure, at
the highest level of acceptable corrugation, as found in U.S. Pat.
No. 5,823,527, in the name of Burlew et al. Additionally, paper
level actuators could be integrated into an optical switch so as to
cause limited pressure on the sheet 51. The switches 80 can be read
during the feed interval, and if necessary, will transmit a signal
to the lifting mechanism L to raise the platform 14 in one or more
increments. Preferably the increments can maintain the proper sheet
level. The location of the switches 80 at the highest level of
acceptable corrugation is an advantage in that each of the switches
80 can sense the location of sheets 51 which may be severely curled
and still not pin the sheet 51 to the plenum 32.
[0033] Referring back to FIG. 1, to further assure separation of
sheets from the sheet stack and the switching over to another
stack, the lifting mechanism L can present the top sheet a
desirable distance from the vacuum plenum, in response to a second
signal that originates from a secondary source other than the
switches 80, such as by a microprocessor 90 executing source code,
or hardware logic.
[0034] FIG. 5 is a scheme illustrating an exemplary reproduction
device 500 with two feeding apparatuses 502, 504 similar as
described above with FIGS. 1-4. In each of feeding apparatus 502,
504 there is a platform 506, 508 supporting stack 510, 512. The
platform 506, 508 is coupled with an elevating stepper motor 514,
516. Sheets 518, 520 in a stack 510, 512 are separated and
transported by a feed head assembly 522, 524. The stack height is
measured with level sensors 526, 528. An additional paper out
sensor 527, 529 gives a signal if no sheet 518, 520 is remaining on
the platform 506, 508. A reference position of the platform 506,
508 is detected with down switches 530, 532. To count the number of
separated and transported sheets 518, 520 an optical edge sensor
534, 536 is arranged in the transport path 538, 540. The sheets
518, 520 are transported to a printing unit 542. After printing the
sheets 518, 520 are discarded in a piling apparatus 544. The piling
apparatus contains a platform 546 to discard the sheets 518, 520 in
a stack 548. The stack 548 is lowered with the help of a stepper
motor 550 whereby the bottom position is detected with a down
switch 552.
[0035] As shown in FIG. 5 all active and sensor elements are
connected to a control system 554 for the reproduction device 500.
To input, process and display data the control system 554 is
connected to a computer system 556 with a keyboard 558 and a
monitor 560. Preferably, software for controlling feeding, of types
known in the art, is modified in accordance with the present
invention to provide the functionality described herein.
[0036] With FIGS. 6-9 it will be described below how the
stack-advancing may be performed according to various further
aspects of the invention. Referring now to FIG. 6 (with reference
to FIG. 5), a first procedure is presented wherein a number of
steps needed to advance the stacks 510, 512 from a bottom most to a
top most position is determined. This procedure is preferably done
when the printing unit 500 is manufactured and the feeding
apparatuses 502, 504 are mounted, or by field service if they have
to be changed or repaired. After starting the procedure by calling
up a program in the computer system 556, first a total possible
displacement count is initialized to a nominal value N.sub.T. The
initialized value N.sub.T is stored in Non-Volatile Memory ("NVM",
for example battery-backed memory, flash memory, etc.), also
referred to herein as "persistent memory", within the control
system 554. Next a complete stack 510, 512 is advanced stepwise
with the stepper motor 514, 516 while sheets 518, 520 are separated
with the head assembly 522, 524. This is performed with the control
system 554. Just before every feed the current step count N.sub.T,C
of the motor 514, 516 is recorded. A successful feed is verified
with a signal from the edge sensor 534, 536. This procedure goes on
until the paper out sensor 527, 529 generates a paper out signal.
If so, the current step count N.sub.T,C, which is the total number
of steps needed to feed a stack of sheets starting from the initial
lowest position of platform 506, 508, is saved as the new total
possible displacement count N.sub.T in the NVM memory, thereby
overwriting the nominal initialized value N.sub.T.
[0037] In FIG. 6 there is shown a platform 506, 508 in a
bottom-most position (solid lines) and a top-most position (dashed
lines). The just-described procedure starts at the bottom-most
position where the platform 506, 508 closes the down switch 530,
532. This responds to the reference position with the step count
zero. In vertical direction the step count is shown. After feeding
all sheets 510, 512 the empty platform 506, 508 would activate the
level sensor 526, 528 in the top-most position. In this position
the step count reaches N.sub.T.
[0038] The new total possible displacement count N.sub.T may be
checked to determine whether it lies in a predetermined range of
values. If not an error message may be displayed on the monitor
560. In this case a service person could do further checking.
[0039] Referring now to FIGS. 5 and 6, the number of steps needed
for the stepper motor 514 (FIG. 5) to advance the stack 510 for
feeding K sheets may be determined, wherein K is the number of
sheets 518 that should remain in the stack 510 before the
scheduling of future feeding goes to the other stack 512 in a
continuous mode. For example, K may be the maximum number of sheets
that can potentially be scheduled in advance. This paper low
displacement procedure is automatically realized by recording the
number of steps N.sub.K required to feed K sheets at some point
during the reproduction process before only K sheets are left in
the stack 510, 512.
[0040] A paper-low value, N.sub.L, may be determined by subtracting
N.sub.K from N.sub.T. N.sub.L may be used to signal a user that
paper is almost out in a particular hopper, or it may be used to
initiate transfer to another paper supply when paper is feeding in
continuous mode. Preferably, K corresponds to a number of sheet
feeds already fed from a corresponding supply before N.sub.L is
reached. This value N.sub.L is also stored in the memory,
preferably volatile Random Access Memory (RAM) rather than NVM.
[0041] The system may be initialized with a value N.sub.L that
represents a nominal paper-low value. For example, if it is
determined that an access to the hopper 12 of apparatus 502 or 504
or a paper attributes change occurred, a paper-low displacement
count may be initialized to a nominal low paper value N.sub.L.
N.sub.L may be chosen to either correspond to a thickest possible
paper to ensure that paper will never run out in a drawer or
N.sub.L may be chosen to correspond to a thinnest possible paper to
ensure that excess paper is not left in a drawer.
[0042] With the motor 514 the stack is advanced up to the level of
the feed-head assembly 522, as shown in FIG. 7. The arrival at the
feed-head assembly is confirmed by the level sensor 526. After the
level sensor 526 is activated the current step count is recorded as
N.sub.0 in the memory. K sheets are fed, and the corresponding step
count N.sub.1 is recorded. The number of step counts corresponding
to K sheets is N.sub.K=N.sub.1-N.sub.0. Finally a new paper low
nominal value N.sub.L may be calculated as the difference between
the total possible displacement N.sub.T and N.sub.K,
N.sub.L=N.sub.T-N.sub.K. The stack 510 has now the position shown
in FIG. 8.
[0043] After determining the paper low value, N.sub.L, feeding may
continue until the actual step count reaches N.sub.L. The platform
506 has then the level shown in FIG. 9. The scheduling from stack
510 will be stopped and is continued with feeding apparatus 504
activated with the control system 554. The feeding out of apparatus
504 is done in the same way as described with feeding apparatus
502.
[0044] While the switching over from one feeding apparatus 502 to
the next feeding apparatus 504 has been described with the
remaining sheet number K, it should be clear that the switching
over could be delayed by feeding J additional sheets with the
feeding apparatus 502. For example, after paper low N.sub.L is
reached, allow scheduling of J additional feeds in a manner to
insure that not more than K feeds occur from that point prior to
switching the supplies. I.e., if six additional feeds (J) are
scheduled when paper low N.sub.L is reached, allow K-6 (k-J) more
feeds to be scheduled prior to switching to feeding apparatus
504.
[0045] The present embodiments described herein, provide the
ability to more effectively and reliably control stack-advancing in
a reproduction device, by automatically calibrating the counts for
the stepper motors M1, 514, 516. Although described in the setting
of a reproduction device utilizing a top feed vacuum feeder 502,
504 and switches 80, 526, 528 that generate a signal to indicate an
increment, it should be understood that the present embodiments
could be implemented in a reproduction device that utilizes other
types of feeders and switches, or in an off-line configuration (a
paper supply not connected to a reproduction device), or with a
post-fuser inserter.
[0046] The disclosed method provides a number of advantages and
applications. Utilizing the disclosed embodiments, the present
invention allows better control over the number of sheets remaining
during a continuous mode swap even if the sheet attributes and the
mechanical tolerances change or vary from stack to stack.
[0047] It should also be understood that the programs, processes,
methods and systems described herein are not related or limited to
any particular type of hardware, such as TTL logic or computer
software, or both. Various types of general purpose or specialized
processors, such as microcontrollers may be used with or perform
operations in accordance with the teachings described herein.
[0048] In view of the wide variety of embodiments to which the
principles of the present invention can be applied, it should be
understood that the illustrated embodiments are exemplary only, and
should not be taken as limiting the scope of the present invention.
For example, more or fewer elements may be used in the drawings and
signals may include analog, digital, or both. While various
elements of the preferred embodiments have been described as being
implemented in hardware, in other embodiments in software
implementations may alternatively be used, and vice-versa. For
example, the said stepper motor, could be any type of motor with
feedback for platform movement such as an encoder or a
potentiometer.
[0049] Although the invention has been described and illustrated
with reference to specific illustrative embodiments thereof, it is
not intended that the invention be limited to those illustrative
embodiments. Those skilled in the art will recognize that
variations and modifications can be made without departing from the
true scope and spirit of the invention as defined by the claims
that follow. It is therefore intended to include within the
invention all such variations and modifications as fall within the
scope of the appended claims and equivalents thereof.
* * * * *