Note: Descriptions are shown in the official language in which they were submitted.
CA 0220~622 1997-0~-16
METHOD AND APPARATUS FOR REMOVING WASTE
WINDOWS FROM WEB CARTON MATERIAL
This invention relates generally to a rotary mech~ni~m that is used to remove
5 waste sections of die-cut material that are retained within a continuously moving
web of carton board material.
BACKGROUND OF THIS INVENTION
Rotary window stripping is a widely used method for removing die-cut waste
10 sections from carton board web. In a conventional web fed carton press, web is
unwound, fed through a series of print heads, die-cut, stripped, separated and
finally, stacked. This invention pertains specifically to the ~lippillg function of the
overall board converting process.
Window ~ pillg of die-cut board stock is done in order to remove the
15 waste die-cut apellLlles from the web. The waste window pieces are retained in the
die-cut web by means of 'nicks' that tie the window to its adjacent web. Each nick
is like a minute bridge of material linking the window and the web, and forms as the
result of a small discontinuity in the cutting edge of the die rule. Each window can
have several nicks. The 'window' knockouts are typically used as hook holes or
20 viewing windows in a carton box. If used as an actual window, then the aperture is
typically later covered by an adhesive-applied ~ldl~lJalclll plastic panel.
There are two main methods of window stripping: flat and rotary. The flat
method consists of a reciprocating platen that contains suitably located knockout
tooling and moves perpendicular to the direction of web motion. This type of
25 stripper requires that the web be momentarily stopped in order that the tool set can
penetrate the web without ripping it. Rotary strippers, on the other hand, are used
with continuously moving webs and thus are able to operate at higher line speedsthan flat strippers. Conventional rotary ~ pel~ are often referred to as 'rotary pin
Jpels' because of the unique pin shaped tooling they use to spear the window
30 scrap.
CA 0220~622 1997-0~-16
GENERAL DESCRIPTION OF THIS INVENTION
The proposed invention is novel in that instead of using pins, a mP~hing set
of raised image plates (typically, though not l-~cess~ily, of flexible photopolymer
construction), one male, the other female, is engaged in a rotary manner so as to
5 eject the scrap material. Each plate is mounted on the surface of a separate cylinder
such that the resulting composite cir~;ull,ferellce m~trhPs that of the print repeat of
the parts being stripped. The two cylinders are positioned relative to each other and
to the web by the ~LIipping ~-~Pch~ m so as to achieve synchronized registry of the
raised images with the window parts to be removed from the die-cut web.
According to a first embodiment of the proposed system, a continuous die-
cut web replete with nicked waste parts (windows) is passed between the mating set
of imaged plates carried on two cylinders. The male and female plate images match
the shapes of the waste parts to be removed from the cartons, except that they are
slightly mis-sized so as to allow for mis-registration, clearance and draft angles on
the shoulders of the mating plate images. Typically, the male plate is mounted on
the cylinder above the web and the female beneath, with possible vacuum assist
being coupled into the female plate to permit a boost to the extraction process.Nicks linking the window waste to the parts must be broken and the mPshing action
of eng~ging imaged plates provides the positional action to do this. By this process,
waste parts are knocked out of the moving web and held in the cavities of the female
plate until such time as the cylinder on which the female plate is mounted rotates to
a position where the waste parts can fall out of, or be ejected from, the female plate
cavities. Waste parts thus deposited can be gathered and removed from the stripper
mechanism by a suitable means, e.g. conveyor, air stream or vacuum a~pa~alus.
In accordance with a second embodiment of the proposed system, the male
plate is llnrh~nged but the female plate, instead of providing defined apellu,es in
registry with raised portions of the male plate, has an outer layer of substantially
unirollll thicknPss made of resilient polymeric material, which is adapted, when the
raised male portion pushes out a waste window, to be el~ctir~lly distorted
sufficiently to receive at least part of the ~ulwardly protruding part of the male
plate, along with the waste window.
~ CA 0220~622 1997-0~-16
Benefits of the proposed system relative to existing methods:
- the required tooling for the system (drums, plates, etc.) is less expensive
than the tooling required for either conventional flat or rotary stripping systems;
- can operate at a higher speed than the flat system;
- less change-over time required between jobs;
- takes up less space than conventional systems;
- less time required to fabricate the tooling, therefore, lead times can be
reduced Similarly, changes/repairs to the tooling can be done faster and at lesscost.
- more positive means of stripping than pins - window parts are positively
displaced as opposed to being speared.
- on-the-fly tool-to-tool registration, both lateral and longi~ in~l.
In the proposed design, the rotary stripper unit can be powered and
registered to the main press by any number of types of mech~nic~l/electrical/servo
systems.
More particularly, this invention provides a method of removing waste die-
cut windows from continuously moving carton board web material, comprising the
steps:
providing a pair of juxtaposed parallel cylinders with their axes transverse to
the direction of web movement,
passing the web material between the cylinders,
using radially ~ulwardly protruding means on one cylinder to push against
and dislodge said waste windows in the direction toward the other cylinder, and
rece;ving the waste windows in the outer layer of the said other cylinder.
Further, this invention provides an appalalus for removing waste die-cut
windows from continuously moving carton board web material, the appalalus
comprlsmg:
a pair of juxtaposed parallel cylinders with their axes disposed transverse to
the direction of web movement,
guide means for passing the web material between the cylinders,
~ CA 0220~622 1997-0~-16
one of said cylinders having oulw~rdly protruding means for pushing against
and dislodging said waste windows in the direction toward the other cylinder, and
means in the outer layer of the other cylinder adapted for receiving the waste
windows.
GENERAL DESCRIPTION OF THE DRAWINGS
One embodiment of this invention is illustrated in the accompanying
drawings in which like numerals denote like parts throughout the several views, and
in which:
Figure 1 is a perspective view showing the cu~ onell~ of a typical die-cut
carton web.
Figures 2 and 2A are perspective and side elevational views, respectively, of
the first embodiment of this invention, concicting of an upper cylinder plate with its
raised image area matching the window/scrap sections of the carton. The lower
15 cylinder has a female plate witn recesses that mate with the male upper cylinder
plate.
Figures 3 and 3A are perspective and side elevational views, respectively, of
a variant of the first embodiment, consisting of an upper cylinder plate with its
raised image area matching the window/scrap sections of the carton and the scrap20 matrix. The lower cylinder has a plate with raised image areas that match the shape
of the carton. R~cesse,c (or lower washed-out elevations) in each plate mate with the
male areas of the other mating plate.
Figures 4 and 4A are perspective and side elevational views, respectively, of
the second embodiment of this invention, consisting of an upper cylinder plate with
25 its raised image area matching the window/scrap sections of the carton. The lower
cylinder has an elastic, continuous polymeric coating.
DETAILED DESCRIPTION OF THE DRAWINGS
As previously pointed out, the purpose of the device herein disclosed is to
30 remove the scrap window areas from a die-cut web.
CA 0220~622 1997-0~-16
Figure 1 shows a typical die-cut carton 2, still retained in its host web 4.
The window sections 6 are shown still retained in the web. Item 8 is a waste
window after it has been removed from the web. The continuous longitu-lin~l and
short lateral pieces of scrap web 10 are referred to as matrix, and are typically
removed from the individual cartons at a station subsequent to the rotary stripper.
The overall shape of the matrix is typically that of a ladder.
Figure 2 shows a first embodiment of this invention, in which an upper
cylinder 12 with an att~rl-~d raised image plate (male) 14 engages with a lower
cylinder 16 having an att~rh~d raised image plate (female) 18. The two plates are
10 formed such that their raised image surfaces and recessed pockets are
complementary. This allows m~shing of the two surfaces without hlLelr~ ce. In
the case where photopolymer plates are ~ltili7rd, ~tt~rhm~nt of the plates to their
respective cylinders is accomplished by using double-sided tape (referred to in the
printing trade as 'sticky back'). The raised images 20 on the upper plate 14 are15 shaped to match the waste window areas to be removed from the cartons. Similarly,
the pockets 22 on the lower plate 18 are shaped to match the waste windows. The
pockets are typically sized to allow some edge clealallce with the mating male
images. At the beginning of the operation, the upper and lower cylinders, 12 and16, are indexed apart from each other in order to allow free passage of the die-cut
20 web 24. Once the two cylinders are ~yllchroni~ed with each other, and registered as
a pair to the web images, they are then brought into engagement with each other
such that the raised (male) images 20 located on the upper cylinder penel.dL~ the
web line and drive the waste window pieces 26 into the m~tçh~d recessed pockets 22
located in the lower plate 18. Each stripped (removed) window 26 is retained in a
25 lower plate pocket until its position on the lower cylinder has rotated through
approximately half a revolution. At this point, the waste window is removed fromthe pocket either by gravity and/or air jet stream. Being rotary, this process of
sequential waste window removal continues unilllellu~led. After leaving their
pockets, parts can be extracted by a vacuum system or dropped into a bin/conveyor.
The window-stripping plates can be made of any suitable material, e.g. steel,
al~",i,..-.,-, polymer, etc. However, there will be a real advantage in using UV-
CA 0220~622 1997-0~-16
exposed photopolymer plates, since the exposure and development techniques for
these materials are common to the printing industry. In fact, the same materialsused for the printing plates would be used for window-~Lli~pillg.
Subsequent to window ~Llippillg, the matrix, complete with retained cartons,
5 continues in a straight path to a pair of driven nips, specifically top nip 28 and
bottom nip 30, at which point the matrix 32 is pulled down over the lower nip and
drawn into a shredding device. The individual cartons are simultaneously drawn
ahead by a conveying mPch~ni~m (not shown) that serves to:
a) provide tension to the cartons to break the nicks ret~ining the cartons
within the matrix, and
b) convey the sepal~t~d cartons 34 to the next stage of processing, typically
conveying/spreading/stacking .
The post-stripping nip pair 28 and 30 is preferably driven, and the plane
between the longib-clin~l axes of the two nips can be rotated +/- through an arc in
15 order to facilitate the ~Llipping of the cartons from the matrix. It is believed that the
"kicking" action resulting from tilting the nip set will aid ~llippillg. It is expected
that the ability to vary the speed of the ~llippillg nip set relative to the speed of the
window stripping cylinders will be of advantage.
AlLelllati~ely, the matrix may be stripped directly off the lower stripping
20 cylinder, as shown by dashed line 36 (in Figure 2).
Figure 3 illustrates an alternative arrangement whereby the profile of the
lower female plate is such as not only to receive the stripped-out windows, but as
well to serve to 'kick-up' the cartons while the matrix is being stripped off the lower
cylinder. Thus two actions siml-lt~n~ously result from the ~Lli~phlg action of the
25 plates:
a) removal of the waste windows from the cartons, and
b) ~Lli~pillg of the cartons from the matrix.
As a result, no secondary nipping set is required to achieve matrix ~llippillg.
In effect, the lower plate acts as both a female and male, depending on the nature
30 (i.e. window/carton/matrix) of a specific area of the web. In this arlangell~ent, the
matrix is stripped off the female cylinder at the same diametral depth as the recessed
CA 0220~622 1997-0~-16
pocket base; whereas in the assembly shown in Figure 2, the matrix, if stripped
from the lower cylinder, is removed from the outer ~ m~ter of the plate, i.e. the
non-recessed area. Disposal of the waste windows is the same as for the
arrangement shown in Figure 2.
Figure 4 shows a second embodiment of this invention, in which the upper
cylinder with its att~r~Pd male plate acts against a lower cylinder having an elastic
continuous polymer coating 38 in place of a female plate. In this instance, the
raised image areas 20 of the upper plate 14 act to depress the window areas into the
soft polymer surface of the lower cylinder. Non-window areas in the web are not
10 acted upon by the male plate and are supported by the polymer surface of the lower
cylinder. This results in a displacing action in which the window nicks are broken
and the window pieces 26 are separated from their host carton pieces. Upon exiting
from the ~llippillg line between the two cylinders, the window waste tends to adhere
to the polymer surface of the lower cylinder through static attraction. These pieces
15 can then be removed from the lower cylinder surface by any number of means, for
example, lltili7in~ an anti-static bar and air jet, or using an annularly grooved
profile for the lower cylinder surface in conjunction with a comb whose teeth track
through the annular grooves (without touching them) and scrape off the window
pieces.
In this embodiment, the matrix 32 can be stripped from the cartons at a
separate nip set, or directly from the lower cylinder, as previously described.
With this embodiment, several advantages relative to the previously
described versions are realized:
a) the variable cost of a lower (female) plate is elimin~t~d. In addition, the
polymer-coated lower cylinder can be used for all print repeats, unlike
the plated version which requires a dirÇclcl~ mPter cylinder for each
print repeat. Tooling costs are greatly reduced.
b) because the lower cylinder is smooth, it need not be lowered so as to be
disengaged from the upper cylinder male plate. Equipment for
positioning the lower cylinder is thus greatly simplified and lower in
cost.
~ CA 0220~622 1997-0~-16
c) because of the action of the male raised images on the polymer surface of
the lower cylinder, it is not n~cess~ry to drive the lower cylinder in
synch with the upper cylinder; in fact, the lower cylinder can be an idler.
If desired, it can also be driven. Again, cost reduction is reali7e~1
S d) window waste is more easily removed from a smooth cylinder surface
than from the recessed pockets in a lower female plate as used in the
arrangements depicted in Figures 2 and 3.
Although the foregoing disclosure describes a window-~L~ippi,lg arrangement
in which the window pieces are stripped out against a lower cylinder mounted
beneath the web, it is expected that ~Lli~l?illg could also occur against the upper
cylinder, but such an arrangement is not expected to be of great benefit, since the
position of the waste parts would be acting against gravity.
One possible material for the outer layer carried on the lower cylinder is
Nitrile, although it is expected that some wear resistance benefit will be gained from
using polymers such as polyurethane. The Nitrile used has a hardness of 35 ShoreA.
Experimental plates of various durometers and thicknesses were utilized on
the upper cylinder in developing this invention. Specifically, plate thicknessesbetween 0.067" to 0.125" were tried, with success. It is expected, however, thatthe plate thickness could be outside this range. During these trials, plate durometers
of 45 to 90 Shore A+ were utilized.
It is of advantage to be able to vary the depth of engagement between the two
window-~l,ipping plates during operation, in order to achieve oplilllulll
performance. For example, too much engagement (i.e. h~L~,re,e,1ce) can result inthe entire web being trapped between the two cylinders with the result that the
window ~Lli~pillg cylinder acts has a nip. This can cause misregistration and web
breakage. The objective is to have the male images "poke out" the windows from
the web.
While several embodiments of this invention have been described
hereinabove and illustrated in the accoln~al~ g drawings, it will be evident to those
~ CA 02205622 1997-05-16
skilled in the art that changes and modifications may be made therein, without
departing from the essence of this invention, as set forth in the appended claims.
