U.S. patent application number 15/330527 was filed with the patent office on 2017-02-02 for conveyors for box making machines.
This patent application is currently assigned to SUN AUTOMATION, INC.. The applicant listed for this patent is Robert Michael Hershfeld. Invention is credited to Robert Michael Hershfeld.
Application Number | 20170028744 15/330527 |
Document ID | / |
Family ID | 52003688 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170028744 |
Kind Code |
A1 |
Hershfeld; Robert Michael |
February 2, 2017 |
Conveyors for box making machines
Abstract
A vacuum belt conveyor sequentially delivers sheet articles to a
digital printer. The sheets are held in position by vacuum on the
underside of the sheets through apertures in the belts and covered
by the sheets. A plurality of independent plenums on the underside
of the belt have chambers respectively communicating with rows of
apertures extending along the belt. Vacuum is selectively applied
from a manifold only to the plenum chambers that supply apertures
that are covered by the sheets so that the ink from the printer
will not be directed from its intended position on the sheet by
vacuum from adjacent uncovered belt apertures. The sheets are fed
to the conveyor in synchronism with the conveyor speed by a timed
feeder so that the sheets are carried by the conveyor with a
predetermined gap between the sheets and no belt apertures in the
gap. A sensor counts the apertures in the belt and activates the
feeder at predetermined time intervals.
Inventors: |
Hershfeld; Robert Michael;
(Parkton, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hershfeld; Robert Michael |
Parkton |
MD |
US |
|
|
Assignee: |
SUN AUTOMATION, INC.
Sparks
MD
|
Family ID: |
52003688 |
Appl. No.: |
15/330527 |
Filed: |
October 4, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13999578 |
Mar 11, 2014 |
9493307 |
|
|
15330527 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 2511/10 20130101;
B31B 50/88 20170801; B65H 7/02 20130101; B65H 2406/362 20130101;
B31B 50/07 20170801; B41F 17/24 20130101; B31B 2110/35 20170801;
B65H 2513/514 20130101; B65H 2701/1764 20130101; B65H 2511/22
20130101; B31B 50/042 20170801; B41J 11/0085 20130101; B65H 2511/31
20130101; B65H 2511/514 20130101; B41J 11/007 20130101; B31B
2100/00 20170801; B65H 2406/42 20130101; B65H 5/224 20130101; B65H
11/005 20130101; B65H 2513/10 20130101; B65H 2511/10 20130101; B65H
2220/01 20130101; B65H 2511/514 20130101; B65H 2220/01 20130101;
B65H 2220/11 20130101; B65H 2513/514 20130101; B65H 2220/02
20130101; B65H 2513/10 20130101; B65H 2220/01 20130101; B65H
2511/31 20130101; B65H 2220/01 20130101; B65H 2511/22 20130101;
B65H 2220/02 20130101 |
International
Class: |
B41J 11/00 20060101
B41J011/00; B31B 1/88 20060101 B31B001/88; B65H 7/02 20060101
B65H007/02; B65H 5/06 20060101 B65H005/06; B65H 5/22 20060101
B65H005/22 |
Claims
1. Apparatus for digital printing of planar articles comprising in
combination: a digital printer, a conveyor having a conveyor belt
movable along a generally horizontal path for moving planar
articles with a gap between the articles along said path to said
printer, said belt having a plurality of apertures for introducing
a vacuum to the underside of articles on said belt to hold the
articles on the belt, means for opening a number of said apertures
to a source of vacuum and for closing other apertures in the belt
to a source of vacuum while said first number of apertures are open
to said vacuum source, and sensor means for sensing the apertures
in the belt as the belt is moving along said path and for sending a
signal for feeding articles to the conveyor in a predetermined
position relative to the apertures.
2. Apparatus defined in claim 1 including: a feeder for feeding
articles on said belt in a timed manner, a computer for controlling
said feeder, and wherein said sensor means sends said signal to
said computer for feeding articles to the conveyor in a
predetermined position relative to said apertures for printing the
articles.
3. Apparatus defined in claim 1 wherein said sensor means counts
the apertures in the belt.
4. Apparatus defined in claim 3 wherein said apertures are provided
in rows in the belt extending along said path.
5. Apparatus defined in claim 1 wherein said sensing means senses
the position of said apertures as the conveyor belt moves along
said path.
6. Apparatus defined in claim 5 including means for shifting the
position of said conveyor belt in response to the position of said
belt apertures as sensed by said sensing means.
7. A method of printing planar articles with a digital printer
positioned along a generally horizontal path of conveyance of the
articles including the steps of: sequentially conveying the
articles along the path with a vacuum belt conveyor having a belt
including apertures in the belt for holding the articles on the
belt by a vacuum applied to apertures covered by the articles,
sensing the apertures in the belt as the belt moves along said
path, and feeding the articles along said path in a predetermined
position relative to said apertures in accordance with the sensing
of the apertures.
8. The method defined in claim 7 including the step of counting the
apertures with a sensor as the belt moves along said path, and
sending a signal with the sensor for feeding the articles on the
conveyor.
9. The method defined in claim 7 including the step of sensing the
position of the apertures in the belt as the belt moves along said
path, sending a signal for feeding the articles on the belt in a
predetermined position in accordance with the position of the
apertures as sensed.
Description
FIELD OF THE PRESENT INVENTION
[0001] The present invention generally relates to conveyors and
methods of conveying articles such as sheets, and more particularly
in a preferred form, to conveyors for box making machines where the
articles are typically corrugated cardboard sheets called "boards"
or "corrugated boards" or even "corrugated" alone.
BACKGROUND OF THE INVENTION
[0002] In the field of box-making, sheets, typically corrugated
boards, are sequentially conveyed along a horizontal path to one or
more stations along the path where operations like cleaning,
printing, cutting, slotting or scoring are performed on the boards
in a timed sequence. It is essential that the boards arrive at each
of the aforementioned work stations in "registration", that is, in
a predetermined timed sequence. Various examples of corrugated
board conveyors including timed feeders may be found in U.S. Pat.
Nos. 4,045,015; 4,494,745; 4,632,378; 4,681,311; 4,889,331;
5,184,811 and, 7,635,124 B2.
[0003] Several methods of conveying the boards to the various
stations along the path are presently in use in the industry. One
uses opposed pull rolls which pull the boards through the nip
between the rolls. Another method uses rotatable friction rolls
made, for example, with a urethane surface on which the boards are
maintained by vacuum. This method which is disclosed in U.S. Pat.
Nos. 7,096,529 B2, and 5,004,221, is sometimes referred to as
"vacuum transfer".
[0004] Another vacuum transfer method employs a belt conveyor which
supports the boards while they are held on the conveyor belt by
vacuum. This type of conveyance is sometimes referred to as a
"vacuum belt conveyor", and one example of such is disclosed in
U.S. Pat. No. 5,163,891.
[0005] The above methods have been and still are satisfactory where
the boards are printed by passage between opposed rolls or
cylinders, one being an "impression" roll and the other, a "print"
roll having a printing plate and ink to transfer the image of the
plate to the board in well-known fashion. However when a digital
printer is used instead of the above system, a problem may arise
when the boards are conveyed to the printer by a vacuum belt
conveyor. In one form of this system, a vacuum transfer unit is
used and the conveyor belt is perforated to Provide a plurality of
holes or apertures that communicate the vacuum with the board to
hold the board on the belt. If any of the belt apertures adjacent
to the edges of the boards is not covered or closed by the board,
ink emitted from these apertures is subject to deviation
("windage") from its intended position on the image being printed
on the board. It is understood that the digital printer includes a
print head having a plurality of ink discharge ports or nozzles
from which the inks are deposited to form the image on the board.
If the vacuum used to hold the boards on the conveyor belt is free
to divert the flow of ink from the print head to the board to form
the desired image, the resulting image will be adversely
affected--smudged, distorted, off-color, etc. Such a result is of
course not acceptable in the printing industry.
OBJECTS OF THE PRESENT INVENTION
[0006] One of the objects of the present invention is to provide
novel methods and apparatus for digital printing of articles such
as sheets or boards sequentially conveyed along a path, typically a
horizontal path. Included herein is the provision of such methods
and apparatus that are particularly useful in the digital printing
of corrugated boards, for example, in a box-making machine.
[0007] A further object of the present invention is to provide a
novel vacuum transfer conveyor for use in moving sheet-like
articles along a path to be printed by a digital printer positioned
at a station along the path. Included herein is such a conveyor
that is particularly useful in a box-making machine.
[0008] Another object of the present invention is to provide a
novel vacuum transfer conveyor for digital printing of sheets which
are delivered to a digital printer by a conveyor belt but without
adversely affecting the quality of the image printed on the sheets.
Included herein is the provision of such a conveyor that will
substantially reduce if not solve the problem identified above.
[0009] Another object of the present invention is to provide a
novel and improved conveyor belt for use in a vacuum transfer
conveyor for sequentially feeding sheets to a digital printer for
printing on the sheets.
[0010] A further object of the present invention is to provide a
novel vacuum control system for a vacuum conveyor for controlling
the distribution or communication of vacuum to the conveyor belt
for holding the sheets on the belt but without adversely affecting
digital printing of the sheets at a station along the conveyor.
SUMMARY OF PREFERRED METHODS AND APPARATUS OF THE PRESENT
INVENTION
[0011] A conveyor having a horizontal endless belt movable along a
horizontal path to sequentially deliver sheets, for example
corrugated boards, to a digital print station for printing a
predetermined, desired image on the boards. The image can of course
include numbers, letters, words, designs, shapes, characters, etc.
of virtually any type. The printer includes a print head located
typically above the conveyor path and including a plurality of ink
discharge ports or nozzles for directing ink to the sheets to form
the desired image. A vacuum is applied under the top run of the
conveyor belt for communication with the sheets through holes or
apertures in the belt. A vacuum control system is provided below a
section of the belt at a location along the path below the print
head so that the flow or communication of the vacuum with each belt
aperture may be selectively closed or opened. The operator of the
apparatus will open the vacuum (suction) to the apertures covered
by the sheets to hold the sheets on the belt but will close the
vacuum to the apertures that are not covered by the sheets and are
close enough to the edges of the sheet and would otherwise
communicate the vacuum with the ink discharged by the print head to
possibly cause unwanted deviation of the ink on the sheet being
printed.
[0012] In one preferred embodiment, the vacuum control system
includes a plurality of independent plenums each having a vacuum
chamber in communication with a vacuum manifold having a vacuum
chamber communicating with a vacuum source such as a suitable
blower. The plenums underlie the conveyor belt and are respectively
in communication with the rows of apertures in the belt through,
for example, conduits extending between the plenum and manifold
chambers. A control member such as a piston-like diverter member is
movable to selectively place vacuum in the manifold chamber in
communication with one or more plenum chambers to apply vacuum only
to the apertures in communication with those plenum chambers.
[0013] In one preferred system and method, the sheets are delivered
on the conveyor belt offset to one side of the belt so that side of
the sheets covers all of the adjacent or nearby apertures of the
conveyor belt on that side of the conveyor belt. If the belt
apertures on the opposite side of the belt are open (not covered by
the sheets), the operator will, through the vacuum control system,
block or close the vacuum suction to those apertures so that they
cannot communicate the vacuum with the ink being discharged on the
sheet by the nozzles to form the desired image. In addition, the
vacuum conveyor is supplied with the sheets to be printed by a
timed feeder such as, for example, described in U.S. Pat. No.
7,635,124 B2. This feeder times the delivery of the sheets on the
vacuum conveyor which moves at a constant speed for a given job or
operation, such that the gaps between successive sheets on the belt
of the vacuum conveyor do not have any apertures thereby avoiding
the possibility of the vacuum reaching through the belt at the
sheet edges at the opposite ends of the sheet to deviate or draw
the ink from its intended path during a printing operation. To this
end the distance or "pitch" between the conveyor belt apertures
measured in the direction of sheet travel along the conveyor path,
is selected such that the length of the sheet (measured in the
direction of sheet travel along the path) plus the gap dimension
between successive sheets equals a multiple of the pitch of the
belt apertures. Once the desired gap between the sheets is
selected, the time cycle of the feeder (see U.S. Pat. No. 7,635,124
B2) may be easily adjusted to deposit each sheet on the belt
conveyor at the same predetermined interval of time to form the
desired gap between the sheets being conveyed by the vacuum
conveyor to the digital printer. In one preferred embodiment, a
photoelectric sensor is used to count the belt apertures as they
pass the sensor for a given belt speed. Knowing the pitch of the
apertures and the length of each sheet, the number of apertures
that need to be covered by each sheet fed on the conveyor belt may
be determined as well as the amount of the sheet that will extend
beyond the forward most and rearward most apertures covered by the
sheet.
DRAWINGS
[0014] Other objects and advantages of the present invention will
become apparent from the following more detailed description of the
present invention taken in conjunction with the accompanying
drawings in which:
[0015] FIG. 1 is an elevational view of a box-making apparatus
including a feeder and a belt conveyor for delivering corrugated
boards to a digital printer for printing the boards;
[0016] FIG. 2 is a plan view of the apparatus of FIG. 1;
[0017] FIGS. 3 to 5 are plan views of sections of the conveyor belt
with three different size boards being transported by the belt to
the printer (not shown);
[0018] FIG. 6 is an enlarged cross-sectional view taken
transversely of the belt conveyor;
[0019] FIG. 7 is a plan view in perspective of a system of vacuum
plenums underlying the top run of the belt conveyor for supporting
the belt and supplying vacuum to the sheets through apertures in
the belt;
[0020] FIG. 8 is a perspective view of one of the plenums shown in
FIG. 7 to an enlarged scale;
[0021] FIG. 9 is a schematic view of a circuit including a sensor
for sensing the apertures in the belt and controlling the actuation
of the feeder which feeds the sheets to the conveyor belt;
[0022] FIG. 10 is a graph of the input shaft position (angle)
versus its velocity of a feeder for delivering sheets to a belt
conveyor in accordance with a preferred form of the present
invention;
[0023] FIG. 11 is a graph similar to FIG. 10 for short sheets being
fed;
[0024] FIG. 12 is a graph similar to those above except it is for
long sheets being fed; and
[0025] FIG. 13 is a graph similar to those above except it shows a
time delay for shifting the position of the sheet relative to the
apertures in the conveyor belt.
DETAILED DESCRIPTION
[0026] Referring to the drawings in detail and initially to FIGS.
1-5, there is shown for illustrative purposes only, one preferred
embodiment of the present invention including a belt conveyor 10
for sequentially feeding sheets such as corrugated boards 12 one
behind the other in horizontal planes along a horizontal path to a
digital printer 14 for printing an image on the top surface of the
boards 12 when they arrive below the printer 14. Also shown is a
feeder 16 for feeding the boards 12 one by one in a predetermined
timed fashion to conveyor 10 from a stack of boards. Feeder 16 is a
timed feeder such as described in U.S. Pat. No. 7,635,124 B2 to
Sardella whose disclosure is hereby incorporated by reference into
the present application as part hereof. For a particular job,
feeder 16 delivers a board 12 to conveyor 10 at a predetermined
interval of time so that the boards 12 are transported to the
printer 14 with the same predetermined space or gap 18 between
successive boards, one gap being shown in FIG. 5. Conveyor 10
includes a perforated belt 20 with holes or apertures arranged in
rows as shown in FIGS. 3, 4 and 5 which illustrate three different
sizes of boards 12a, 12b, and 12c that may be processed for
printing in accordance with the present invention.
[0027] Feeder 16 in the specific embodiment is a vacuum conveyor
and may use a series of conveyor belts or driven rolls engageable
with the underside of the boards to drive them under a gate 24 and
to the nip of a pair of pull rolls 26 which in turn drive the
boards on to the inlet end surface of conveyor belt 20. The latter
is driven at a constant speed to sequentially deliver the boards to
the printer 14. Boards 12 are positively held on the conveyor belt
20 by vacuum supplied by a vacuum control system generally
designated 28 to the underside of the boards 12 through the belt
apertures 22. FIG. 2 shows the blowers 30 and their motors 32 which
remove air from below the boards 12 on the conveyor belt 20 and
through the belt apertures 22 and conduits 34 thereby producing a
vacuum for positively holding the boards 12 on the conveyor belt as
the latter transports them along the conveyor path. FIG. 2 also
shows a motor 36 for driving the downstream end sprocket 38 of the
conveyor 10 through any suitable transmission. In addition, FIG. 2
shows a servo motor and a transmission generally at numeral 40 for
driving the feeder 16 in a timed fashion as will be further
described below. In the embodiment of the feeder 16 which utilizes
a vacuum to hold the boards 12 on the transport rolls or endless
belts, a blower such as shown in FIG. 2 at 44 may be used to
produce the vacuum under the boards 12. A more detailed description
of feeder 16 including its transmission 40 is disclosed in
above-identified U.S. Pat. No. 7,635,124 B2.
The Printer
[0028] Printer 14 is a commercially available ink jet printer
including a plurality of print heads for four colors. For example,
one printer could have twenty (20) print heads with five (5) heads
per color. A larger printer for printing larger sheets could have
forty-eight (48) print heads with twelve (12) heads per color. All
of the heads for each color are assembled together into a print
bar. Printer 14 of the shown embodiment has four (4) print bars 15
shown in FIGS. 1 and 2. The print heads of course have nozzles for
discharging ink on the sheet to form the desired image, character
or any desired indicia, etc. on the sheets. A print head could have
as many as 2,656 nozzles. Also the nozzles can be spaced from the
sheet being printed in a range of 1 to 4 mm. but when printing
corrugated board a spacing of 3 mm. is preferred. In the specific
embodiment shown, print bars 15 are mounted for movement in a
holder 17 between an operative position shown in FIG. 2 for
printing the sheets 12 and in inoperative position on the drive
side of the conveyor 10 as shown in phantom lines in FIG. 2. The
printer may be slid along holder 17 into any desired position over
the sheet 12 in order to print the desired image at the desired
location on the sheet 12. Various printer sizes can be used
depending on the size of the sheet. A maximum sheet size for one
machine could be for example 1000 mm. (width--across the machine)
by 1600 mm. A minimum sheet width could be for example 250 mm. The
print width equals the sum of the print width of all heads of a
single color. For a five head system this amounts to a print width
of about 23'' (inches) and for a twelve head system a print width
of about 53'' (inches). One preferred method that may be used to
practice the present invention uses a drop on demand ink jet print
head which can print at speeds up to 200 meters per minute at
600.times.480 dpi. In addition to the print head described above,
printer 14 includes pumps and a controller including a computer for
controlling the print head and sending image data in accordance
with a print program. The entire printer, also termed "print
engine" in the art, is commercially available.
Vacuum Control System
[0029] Referring to FIGS. 6-8, a vacuum control system is provided
for controlling the vacuum applied to the apertures 22 of the
conveyor belt 20 to hold the sheets in position on the conveyor
belt 20. Vacuum blowers 30 respectively driven by motors 32 shown
in FIG. 1 produce a vacuum or suction in conduits 34 (see FIG. 2)
which communicate with a vacuum manifold 51 (see FIG. 6) through
conduits such as hoses. Manifold 51 encloses a vacuum chamber 53
from which a plurality of conduits such as hoses 54 extend to
communicate the manifold chamber 53 with a plurality of independent
plenums 55 shown in FIGS. 7 and 8. In the preferred embodiment
shown, plenums 55 provide the support surface of the upper run of
the belt 20 of conveyor 11. Plenums 55 extend longitudinally along
the conveyor path and are assembled to and fixed on, in side by
side abutting relationship, underlying base pieces 56 which in turn
are fixed through flanges 59 to opposite sides of the conveyor
frame generally designated 11 at an upper portion thereof Plenums
55 are each elongated and hollow to provide independent elongated
vacuum chambers 58 which respectively communicate with the rows of
belt apertures 22 extending along the path of conveyor belt 20. To
that end, plenums 55 each have a slot 62 (see FIG. 6) in its top
wall communicating with only one row of belt apertures 22.
Therefore each row of belt apertures 22 extending along the
conveyor path is in communication with plenum chamber 58. Plenums
55 may be molded or otherwise made from any suitable metallic
material, and in the specific embodiment shown, include a depending
pin 57 for locating the plenum in position in a top frame portion
of conveyor 10. Although only one plenum assembly 70 is shown in
FIG. 7 it will be understood that a plurality of plenum assemblies
may be used in continuous fashion under the conveyor belt 20
throughout the entire length of the conveyor belt or throughout a
length sufficient to accommodate and print any size of sheet
without vacuum interference with the flow of ink at the edge areas
of the sheet. Also in other forms of the invention, the plenums can
be combined with the manifold in one unit or can be directly
supplied with vacuum from other sources.
[0030] In order to block or close the vacuum at certain apertures
for example apertures 22b in FIG. 2 or 22a in FIGS. 3-5, the
operator rotates hand wheel 50 to rotate screw rod 49 to axially
move diverter 52 along the manifold chamber 53 until vacuum in
chamber 53 is blocked from the appropriate conduit 54 leading to
the plenum chamber 58 which communicates with the row of apertures
22b or 22a whichever the case may be. It will be seen that one or
more plenum chambers 53 may be blocked from vacuum in the manifold
51 by the same position of diverter 52 in the manifold chamber, it
being understood that each plenum 55 communicates or is in registry
with only one row of apertures 22 that extend in the longitudinal
direction of conveyor belt 20.
Operation
[0031] Depending on the size of the boards 12 being processed, the
timing of the deposit of the boards 12 on the conveyor 10 is
selected such that the gap 18 (see FIG. 5) between successive
boards 12 as they are being conveyed on the conveyor 10 will not
overlie any of the belt apertures 22 so that the printing ink
issuing from the printer 14 will not be distorted, diverted or
deviate into the marginal areas of the boards at the edges adjacent
the gaps 18. To that end the gap 18 is selected so that the length
of the board (measured in the direction of the travel path) plus
the size of the gap (measured in the direction of the travel path)
will equal a multiple of the "pitch" of the belt apertures (where
the pitch is the distance between adjacent apertures 22 measured in
the direction of sheet travel. FIGS. 3-5 illustrate three different
size boards 12a, 12b and 12c as they would appear on the conveyor
belt 20. In each case, the gaps 18 between the boards do not
overlie any of the belt apertures 22. Also it should be noted that
the boards 12a, 12b, and 12c are offset or "justified" towards one
side of the conveyor belt 20 so that there are no belt apertures 22
in the marginal areas 20a between the boards and the edges of the
belt on that side. Preferably that side of the conveyor is the
"drive side" where the motors and drive 40 of the feeder 16, vacuum
blowers 32, 34 and drive 38 for conveyor 10 are located. The
opposite side is termed the "operator side" where the operator
controls and oversees the operation of the machine. Referring to
FIG. 1, standing on the operator side, the operator closes the flow
of vacuum to the apertures 22a by rotating the spindle 50 to move
the diverter 52 to block the vacuum flow to apertures 22a so that
the ink being deposited on the boards will not deviate or otherwise
be diverted from its intended path in the formation of the desired
printed image on the board. FIG. 2 shows a conveyor belt 20 having
a different size than the belt in FIGS. 3-5. The belt 20 in FIG. 2
also has more apertures 22 than the belt shown in FIGS. 3-5. The
operator will block off the vacuum to the apertures 22b on the
operator's side of the conveyor of FIG. 2 in the area of the
printer 14.
[0032] The feeder 16 and the conveyor belt 20 must be in time or
synchronized so that sheets 12 can be fed on and carried by the
belt at a calculated position relative to the belt apertures 22. In
order to arrive at a gap 18 between successive sheets 12, the
length or dimension of the sheet 12 (measured in the direction of
the conveyor path) and the dimension of the gap (measured in the
direction of the conveyor path) must add up to a multiple of the
pitch of the belt apertures 22 which are equally spaced from each
other in each of the rows of apertures. Knowing the length of the
sheet 12, plus the number and pitch of the belt apertures 22 in a
row, and the speed of the conveyor belt 20, the computer 42 (FIG.
9) can calculate the distance the sheet will extend beyond the
covered apertures 22 at each end of the sheet in order to center
the sheet over the apertures 22 that the sheet covers. A
photoelectric sensor 60 shown in FIG. 9 counts the apertures 22 as
they pass the photoelectric cell and sends it to the computer 42 to
activate the feeder 16 after, a certain interval of time which has
been calculated, taking into account the known factors described
above. The feeder 16 then feeds a sheet to the conveyor 20, and the
process is repeated and a sheet 12 is fed to the conveyor 20 at the
same intervals of time until the job is completed or otherwise
terminated. When a new printing operation is to be run on sheets 12
of a different size, the interval of operation (the time cycle) of
feeder 16 can be easily adjusted as taught in U.S. Pat. No.
7,635,124 B2 to suit the different size of the sheets 12. This is a
significant advancement in the box-making art since the repeat time
or time cycle of operation of conventional feeders is constant
regardless of the size of the boards being processed.
[0033] In the form of the invention just described above, the
initiation of the feed of sheets 12 to conveyor 10 is limed based
on the pitch or distance between the holes or apertures 22 in a
conveyor belt where the holes are equally spaced from each other in
the longitudinal and transverse directions of the belt. However in
another and preferred method of the present invention, initiation
of the feed is not dependent on a predetermined pitch or spacing
between the apertures 22. Rather it is based on the actual position
of the apertures 22 during operation and will therefore not be
affected if the actual pitch of the apertures is different than the
predetermined pitch of the apertures or if the apertures are not
equally spaced from each other. In the present method, the feeder
16 is reregistered to the true position of the apertures 22 in the
conveyor belt on each and every feed of sheet, and therefore
requires that initiation of the feed of each sheet 12 by feeder 16
occur at the same position (angle) of the input shaft of feeder 16
every time. After each sheet feed, the transmission of feeder 16
always returns to its starting position and stops. In this
preferred method of the present invention, the input motion profile
over the 360.degree. transmission cycle is not a function of sheet
size and the input velocity is scaled up or down based on machine
speed, as shown in FIG. 10. A dwell is added between each cycle of
the feeder 16 to allow for different sheet sizes. FIGS. 11 and 12
show how this dwell changes for short sheets and long sheets. For
the shortest sheet that can be fed there is almost no dwell time.
In all cases the feeder input shaft returns to a stop after feeding
each sheet. A servo motor is used in feeder 16 to achieve this
motion profile.
[0034] When the feed cycle is initiated in response to the actual
position of holes 22 in the belt, the position of the sheet
relative to the holes in the belt is shifted to the desired
position through a time delay. FIG. 13 shows how the calculated
time delay is used to shift the actual feeding of the sheet
relative to the trigger signal from the belt hole sensor 60. This
could also be done by using an encoder that is measuring the
position of the conveyor belt. Instead of applying a time delay to
shift the feed cycle, it could wait a certain number of encoder
counts after seeing a hole in the belt to start the feed cycle.
Each method provides the same result.
[0035] Although the belt conveyor 10 shown and described above
includes a single belt 20, it will be understood that it may
include two or more belts (not shown) arranged in side by side
relationship.
[0036] Although preferred forms of the method and apparatus of the
present invention have been shown and described above, variations
of the present inventions will become apparent to those skilled in
the art but without departing from the scope of the invention
appearing in the following claims.
* * * * *