Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DEVICE FOR POSITIONING THE SHEETS INTO AN INTRODUCTION
STATION OF A PROCESSING MACHINE
The present invention refers to a device for positioning the sheets
into an introduction station of a processing machine, comprising a feed table
with drive means for said sheets, at least one positioning front stop for
stopping
the leading edges of said sheets, means for registering the lateral position
of
said sheets, means for comparing said position to a reference position, means
for transversely driving said sheets and control means for controlling said
drive
1 o means in dependence on the direction and the space between the registered
lateral position of said sheet and said reference position and for stopping
the
latter when the sheet meets with said reference position.
In the positioning devices usually used 'for machines processing
paperboard, solid board, corrugated board sheets, such as converting presses
comprising a plurality of stations, the positioning of the sheets must be very
accurate as well in a longitudinal direction as in a transverse direction at
each
station they cross. To this end, the sheets are regularly infed by a feeder
towards the feed table, shingling the sheets and enabling their seizing by the
gripper bar as well as their. conveying towards the subsequent stations.
2 o The sheet is usually aligned on the feed table first of all against
front stops and then against lateral stops by means of advance rollers or
plastic
foils supporting downwards on the table. When processing thin sheets, since
the latter are often injured when they reach the stops, they can generate thus
a
positioning error and their edges are marked.
The problem arising in the sheet positioning is also especially
delicate when the sheet performed several operations such as printing, folding
lines creasing, diecutting, since said operations must be carried out the most
exactly depending on the preceding operation. In spite of all cautions, errors
or
drifts in position of the processed portion with respect to the leading and
lateral
3 0 edges of the sheet are issued, for example, from successive alignments at
different locations of a sheet edge being not exactly rectilinear, or from
systematic alignments at the same locations while leaving a mark. However, the
diecutting of pre-printed elements do not allow any positioning error so as to
reach the desired quality of the manufactured product.
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US 6'264'196 relates to a specification wherein, when the sheet
reaches front stops mounted on a cylinder, it is seized by means of a gripper
of
a gripping device arranged on a carriage laterally held by two opposed
compression springs. One of the latter being coaxial to a rod and compressed
between the end of the carriage and one rod shoulder. The end of said rod
helds a pressure roller actuated against a cam section, located between two
standby areas 41, 42. When the sheets reach the front stops, it is seized by
the
gripping device and the rod roller rests in the standby area of the cam. Once
the grippers close, the pivoting cylinder drives the roller into a cam section
while
laterally moving the carriage and thus the sheet itself. When the detector
registers said sheet edge, a brake is actuated to stop the carriage. The
remaining travel of the rod is absorbed by the spring.
One notes thus that in said abovementioned document, the register
position is not compared with a reference one for moving the sheet into one
direction and with a distance corresponding to the space between the
registered lateral position of the aligning mark and the reference position.
No
comparison is effectively carried out and the original position of the sheet
is not
registered. One simply moves the sheet until its lateral edge reaches the
desired position. The displacement applied by the cam remains the same and
2 o is not related to the registered error, since the latter is unknown. One
simply
stops the carriage when the sheet edge is registered by a detector. However,
the front stops are not fixed, but fixedly attached to the cylinder.
US 4'989'855 described a positioning device wherein the stops are
motorized in order to modify their position. Said device comprises means for
registering an aligning mark on the sheets to be aligned, comparing it with a
reference position and adjusting the stops for correcting the sheet position.
Such a device works like a common device and owns the same risks, namely
as far as the lateral aligning is concerned.
One proposed in EP 669'274 an aligning device wherein the sheet
3 o to align is actuated against the front lays, is then laterally moved
against side
guides by means of a pull rod and a pad between which the sheet is seized.
The sheet is stopped moving by side guides and the pull rod ends its motion
sliding with respect to the flat element. Such a device is more particularly
adapted for relative rigid sheets such as corrugated ones.
EP 1'044'908 describes a positioning device with no pad,
comprising a movable shelf with temporary fastening means for the sheet to
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align, that, on the one hand, is longitudinally moved by a back-and-forth
motion
and, on the second hand, by correction motions about three vertical studs
being
each fixedly attached to a carriage, a central carriage sliding into a
longitudinal
guide and two lateral carriages sliding into transverse guides. The correction
motions of said shelf are produced by three linear motors controlled by opto-
electronic registering means. The correction is carried out during the sheet
conveying by the movable shelf, in order to drive the leading edge of the
sheet
in the grippers of a gripper bar in an accurate reference position, so that
the
temporary fastening means of the shelf can free the sheet and the shelf can be
brought back in its origin position for restarting with a new sheet. Said
device
saves the time needed for sheets alignment, increasing thus appreciably the
processing machine rate.
EP 1'151'833 refers to a closely related device, wherein a sheet
gripping device is connected to the movable shelf by at least one link
comprising a plurality of levers forming a parallelogram that can be put out
of
shape about an horizontal swiveling axis in order to impede the arrival of a
component of horizontal strength issued from the opening levers of the
temporary fastening grippers of one sheet edge on the shelf.
Both abovementioned devices are very efficient as well as the
positioning accuracy as the rate increasing of said positioned sheets are
concerned. The alternative of an uninterrupted positioning of the conveyed
sheet effectively enables saving the time needed for a common alignment.
However, the resulting productivity increase requires then a huge investment.
The cost increase between a common registering system and an uninterrupted
positioning device like the one described in EP 1'044'908 and EP 1'151'833 is
effectively appreciable and economically justified only for some kind of
machines.
One described lastly in EP 1'308'406 a device for registering a
lateral edge of a sheet in an introduction station. According to the device of
the
3 0 invention, one compares the registered position of one lateral edge of the
sheet
with the desired position, one produces a correction signal that generates an
adjusting signal transmitted to an adjusting member for moving said lateral
edge to the desired position. One operates thus directly on the conveyed sheet
with respect to the measured space between the registered position and the
desired position. On the other hand, said document includes no detail about
how to perform the method.
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The present invention has an aim to obviate, at least partly, the
usual drawbacks of the common sheet aligning devices, without resulting in a
considerable increased cost of the processing machine, to which the sheets
positioning device is related.
To this end, the present invention relates first to a sheet positioning
device into an introduction station of a processing machine according to claim
1.
The main advantage of the present invention is to join two aligning
methods. To align the sheet leading edge, it uses, likes for common
positioning
1 o devices, front lays against which the sheet is conveyed by means of the
feed
table, since said method of positioning the leading edges of the sheets is
liable,
simple and owns no appreciable drawback. Said front lays can be fixed or
adjustable. For lateral alignment, one uses a method wherein sheets driving
means are controlled by opto-electronic means, without using thus side guides
owning drawbacks, i.e. especially when processing with flexible sheets. Since
the lateral alignment is achieved, as it is the same case for common
positioning
systems, once the leading edge of the sheet is aligned by the front lays, the
single movement to apply to the sheet for laterally aligroing it is a
rectilinear one,
which means an appreciable simplification, as well as 'the mechanical design
or
2 o the electronical control are concerned, with respect to a movable device
according to three vertical axis, like for abovementioned devices. Another
important advantage of the present invention is due t~o the fact that the
lateral
alignment enables a sheets displacement in both directions, whereas a
mechanical positioning allows only to pull or to push, while moving the sheet
in
only one direction.
Finally, whereas the devices for a single mechanical positioning
only can align the sheets depending on the sheet edge, the device according to
the invention can achieve said positioning according to a printed aligning
mark.
It enables preventing from errors repetition between the print of the sheets
3 o printed in reels and their edges sectionally diecut by the reel, while
using the
print and not the diecut sheet edge as a reference and whose angle of the
leading edge of the sheet to align can vary of several degrees with respect to
the perpendicular axis.
Further features and advantages of this invention will become
evident from the reading of the following descriptiorn and from the enclosed
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drawings illustrating, schematically and by way of example, an embodiment of
the device for positioning according to the present invention in which
Fig. 1 is a perspective view illustrating the method of positioning of
the invention;
Fig. 2 is a transverse elevation view of the positioning device;
Fig. 3 is a sectional view according to the line lll-III of fig. 2;
Fig. 4 is a sectional view according to the line IV-IV of fig. 2;
Fig. 5 is the same view as fig. 2, illustrating an alternative;
Fig. 6 is a sectional view according to the line Vi-VI of fig. 5;
l0 Fig. 7 is a sectional and partially enlarged view of the inner part of
the ring VII of fig. 5;
Fig. 8 is a data-processing diagram of the control device of the
method of positioning.
The method of positioning is illustrated on figs. 1 to 8. The sheet 1
to align is conveyed by a feed table T of a sheets processing machine, like a
diecutting press, a printing machine, wherein the sheet that just went through
a
printing or diecutting operation must be accurately positioned with a view to
a
subsequent operation, so as to ensure a same reference position of the sheet
for the successive operations, so that the print or diecutting position, for
2 o example, is not shifted with respect to the preceding diecutting or
printing
operation.
To this end, after the first operation, the sheet 1 is conveyed in the
direction of arrow F by the feed table T against a range of front lays 2,
whose
position could be adjustable. In this example, this operation is preferably
carried
2 5 out by means of at least one pressure roller 3, controlled by a cam or a
pneumatic cylinder (not shown), pressing the sheet 1 against a transverse
slide
4, arranged between the feed table T and the front lava 2. Said pressure
roller 3
could also be a gripping device, namely a suction pipe arranged on the
transverse sliding and connected to a suction supply. A photoelectric cell or
a
3 o camera 5 is adapted to register a lateral edge of the sheet 1 or,
preferably, an
aligning mark, whose position is typically the one of the printing or
diecutting of
said sheet 1 and to compare said position to a relference one. Said cell is
connected to an input of a control station 6, of which one output is connected
to
an actuator, namely a linear motor 7 for driving the transverse slide 4 with
35 respect to the space between the measured lateral position of the sheet and
the reference position. Said control station 6 produces a supply current of a
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linear motor 7 in dependence with the direction into ~rvhich the linear motor
7
moves to bring the edge of the sheet 1 in the reference position.
Figs. 2 to 4 illustrate the device for positioning the sheets into an
introduction station of a processing machine. Said device comprises in its
centre a transverse support 8 fixedly attached to the frame 9 of the
processing
machine extending to both ends of the transverse support 8. The latter
comprises in its centre a linear motor 7, of which a U-shaped magnet rail 10
is
fastened by means of screws 11 to said transverse support 8. A reel 12,
arranged into the magnet rail 10 of the linear motor 7, is fastened to a
movable
section 13 of said linear motor 7 by means of screws 16. Said reef 12 is
connected to an output of the control station 6 (Fig. 1 ). The movable section
13,
acting like a transverse slide, is connected to the transverse support 8 by
two
carriages 14a, 14b arranged on both sides of the linear motor 10, 12. Each
carriage 14a, 14b is coupled to two parallel guiding slides 15a, 15b (Fig. 3).
The
upper surface of said transverse slide, made up of the movable section 13, is
fixedly attached to an aluminum section 17 covered 'with a material owning a
high friction coefficient such as polyurethane, or presenting a rough surface.
The positioning device comprises also a transverse profile 18
fixedly attached to two vertical slides 19a, 19b, mounted in two vertical
guides
20a, 20b fixedly attached to the frame 9. The bottom of each vertical slide
19a,
19b is pressed by a spring 21 a, 21 b against a roller 22a, 22b, assembled
swiveling at the end of an arm of a swing 23a, 23b rotatable in its centre on
the
frame 9. Another roller, of which only the roller 24a is shown on fig. 4, is
assembled swiveling at the other arm end of each swing 23a, 23b. Said rollers
of the swings 23a, 23b being pressed against two related cams, of which only
the cam 25a is shown on Fig. 4, are fixedly attached to a control shaft 26
kinematically linked to the drive mechanism {not shown) of the processing
machine for the sheets 1.
Two pairs of pressure rollers 27a, 27b are freely swiveling about
3o axis perpendicular to the transverse section 18, i.e. parallel to the
advance
direction F of the sheet 1 and fixedly attached to two supports 28a,
respectively
28b. Each support 28a, 28b comprise two adjusting units 29a, 29b, 30a, 30b to
adjust the height, respectively the lateral position of each support 28a, 28b.
Each turn about the control shaft 26 is related to a working cycle of
the positioning device during which the cams 25a, 25b are pivoting the swings
23a, 23b, driving thus the rollers 27a, 27b downwards against the aluminum
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section 17, seizing thus the sheet 1 between said section 17 and the rollers
27a, 27b after said sheet is supporting against the front lays 2. The register
cell
registers the position of the lateral edge of the sheet 1 or of an aligning
mark
on said sheet and sends the value as well as the direction of the measured
5 space to the control station 6. The latter sends an electric current to the
reel 12
of the linear motor for moving the transverse slide 13, forming the movable
part
of the linear motor, in the desired direction until the position registered by
the
register cell refers about the lateral position of the sheet 1 as being
related to
the reference position.
Said operation of lateral displacement of the sheet 1 by the linear
motor is achieved in synchronism with the rotation of the control shaft 26, so
that when the correction is over, the cams 25a, 25b, connected to the control
shaft 26, are swiveling the swings 23a, 23b (Fig. 4) in the anticlockwise
direction, while raising the slides 19a, 19b and the rollers 27a, 27b. The
sheet 1
is thus free and the cycle can re-start with a new sheet 1. The means used for
stripping the positioned sheet comprise a common gripper bar. The latter is
not
shown insofar it is not mentioned in the present invention and is of no use
for its
understanding.
According to the alternative of the device illustrated on figs. 5 to 7,
instead of joining the transverse section 18 to vertical slides 19a, 19b, said
alternative comprises a transverse section 31 fixedly attached by its both
ends
to the frame 9. Each pair of pressure rollers or shoes 27a, 27b is then
fixedly
attached to the rod of a cylinder 32a, 32b, as well ass to two guide rods 33a,
33b, arranged sliding inside the cylinder 32a, 32b, so that said rollers or
shoes
27a, 27b are applied against the sheet 1 supporting on the movable section 13
of the linear motor at the time of its lateral alignment by means of the
cylinders
32a, 32b. Such an alternative is more advantageous than the embodiment
illustrated by fig. 2, since less expensive.
