Note: Descriptions are shown in the official language in which they were submitted.
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~I~LE: COLL~PSI8LE CORE ADHESIVE ROL~S
CR05S REFERENC~ TO ~ELATED APPLICATION
This application i8 a continuation-in-part of Serial
No. 252,196 filed September 30, 1988,
BACKGROUND OF THE INVENTION
This invention relates to the art of manufacturing
rolls of adhesive tape and, more particularly, to the
core or hollow cylindrical member on which lengths of
adhesive tape are traditionally wound.
Adhesive tapes a-e customarily prepared by forming a
sheet or length of tape appreciably wider than the
ultimate tape widths and then passing this tape through a
slitting operation.to provide a plurality of rolls of a
given width, e.g. 3/4", 1", 2", etc.
The tape may be formed by first applying an adhesive
layer to the desired backing to form an elongated strip
of adhesive-coated backing which may, for example, be on
the order of 30-50 inches wide X 70 or more yards long.
Following application of the adhesive layer, the
resulting tape is generally wound on a master or jumbo
roll and then transmitted in due course to the slitting
operation.
There are basis~tty ~ ~ e ~S ~ t~.g
to form a roll of tape of the desired width. In the
first and most common procedure which may be referred to
as "baloney slicing", the tape of the desired length is
wound on a single core of the same width as the tape from
the feed roll for the slitting operation and is then
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slit, a~ one envisions slicing baloney, into individual
rolls of the desired width. Typlcally, this iB done by
passing the core on which the desired length of adhesive
tape is wound through a slitting operation consisting of
a plurality of slitting knives spaced apart to provide
individual rolls of the desired width.
In the second or alternate method which from a
manufacturing standpoint may be more desirable, the web
of tape from the master (feed) roll is first slit to the
desired width and then taken up on individual cores of
the same width which are then ready for packaging and
shipment.
In either case, a manufacturing problem referred to
as "telescoping" occurs. [see Figure 3 of the
illustrative drawings.] In essence, telescoping is the
fanning out of overlapping portions of the tape roll
beyond the width of the core on which the tape is wound.
Telescoped rolls will be rejected during guality control
inspection in the manufacturing process, requiring either
discarding or rewinding of the roll.
In the so-called baloney slicing method for tape
manufacture, telescoping is not as severe a problem due
to the fact that the narrow slit tape width i8 not
elongated prior to winding it on a core.
The task of the present invention, simply stated, is
to understand the cause of the problem Xnown as
telescoping and, once understood, to find a solution to
the problem which is cost-effecti~e a-ld otlle~wlse ~able
from a commercial manufacturing standpoint.
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BRI~F DESC~IPTION OF T~E INVENTION
In accordance with the present invention it has been
determined that the cause of the problem is the stress
recovery that the tape undergoes after slitting and
winding on the core (as will be described in more detail
hereinafter~ and that the problem may be obviated by
employing what is defined as a "collapsible core" so that
the stress recovery phenomenon collapses the core rather
than causing telescoping or sliding of the tape away from
the core.
B~I~F ~S~IpTXO~ OF DR~NÇ~
Figure 1 i8 a perspective view of a conventional
core for adhesive rolls according to the prior art:
Figure 2 is a schematic view illustrating the
conventional slitting operation and tape roll formation;
Figure 3 is a perspective view of a roll of tape of
the prior art illustrating the telescoping problem to
which the present invention is directed;
Figure 4 is a perspective view of a collapsible core
according to this invention;
Figure 5 iB a perspective view of an alternate
embodiment of a collapsible core according to this
invention; and
Figure 6 is a perspective view illustrating a roll
of tape prepared with a collapsible core of this
invention.
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DETAILED DESC~IPTION OF THE INV~NTION
As was previously alluded to, conventional method~
of roll tape manufacture start with the coating operation
at which an adhesive layer is applied to at least one
side of a suitable backing material, e.g. by calendering,
extrusion coating, casting, etc. to provide a long web of
adhesive-coated backing. This web is taken up on rolls
which then form the feed rolls for the slitting operation
wherein the web is slit widthwise to provide tapes of the
desired width, e.g. 3/4", ln~ 2", etc. The web is also
cut to the desired length and wound on cores to provide
the rolls of tape which are subsequently marketed.
In general, two alternate slitting processes are
known, namely the "baloney slicing" technique and the
shear slitting technique. In the former, tape of the
desired length i8 wound on a core whose width
approximately equals the width of the adhesive web. The
resulting "elongated" roll of tape is then slit into a
plurality of rolls of the desired width and then conveyed
to the packaging and distribution stations. Slitting is
customarily done in a single step by passing the roll of
tape through a series of parallel slitting knives spaced
apart to provide the desired widths.
In the shear slitting technique, the web is first
slit to the desired width and length and taken up on
individual cores for packaging and distribution.
- ~ e~her case, the core members on whr~k ~e ~ ~e~
1s wound are continuous cylindrical cores made of a
semi-rigid material such as cardboard, plastic, paper,
laminates thereof, etc.
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Irrespective of the slitting technique employed, the
aforementioned problem of telescoping is a frequent
occurrence, thereby adversely affecting manufacturing
costs.
As was previously stated, the problem is not as
severe in the baloney slicing procedure. However, it i8
a very serious problem in the aforementioned alternate
slicing procedure. Accordingly, while this alternate
procedure has certain manufacturing advantages which may
render it more cost effective than baloney slicing, the
telescoping problem may preclude its use in large scale
industrial manufacture.
The problem of telescoping, which, simply stated, is
the task of this invention nay best be understood by
reference to Figures 1-3 of the accompanying drawing.
Figure 2 illustrates schematically the shear
slitting technique wherein a web of adhesive tape 20 from
a master roll (not shown) is passed between a plurality
of slitting knives and superposed rollers, only one of
which knives 30 and rollers 40 are shown. The severed
lengths of tape 20 are then vound on individual
semi-rigid cores 10 which may be defined, for purposes of
understanding the present invention, as being continuous
or endless cylindrical bodies, as is best seen in Figure
1.
In operation, the leading end of the tape web is
wound onto the cores, and it is the drive action of the
s~ O n ~ corcs are placed which drives thc ~b
through the slitting knives 30.
This drive action pulling the tape web through the
knives and superposed rollers produces a pulling action
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which create~ tension which in turn create~ a stres~ or
stretching as the slit tape is wound onto the core.
Since the tapes are flexible to varying degrees,
they possess an elastic memory. Accordingly, after being
wound on their cores, they undergo stress recovery and it
is this stress recovery which has been determined to
cause the migration off the core, which migration is what
is termed "telescoping", as seen in Figure 3. The time
in which telescoping occurs has been found to be directly
proportional to the ambient temperature, so that
increased ambient temperatures have been observed to
initiate and/or accelerate roll telescoping.
Initial efforts to avoid roll telescoping, in
accordance with this invention, were directed to lowering
the tension or stress as the tape i5 pulled through the
knives and wound on the core. However, at least some
tension is inherent in the manufacturing process and even
when minimal tension is used, roll telescoping was still
observed. Accordingly, another means had to be found to
obviate the telescoping problem.
In accordance with the present invention, the
telescoping problem may be obviated or, at least, reduced
materially to an acceptable occurrence level, by
employing what may be described as a "collapsible core".
If the core i8 collapsible, the stress recovery
phenomenon will cause the core to collapse or deform
rather than causing the tape to telescope or slide off
~e, ~;.c"~e.......................................... . ..
The preferred method for providing a collapsible
core in accordance with this invention i9 illustrated in
Figure 4. As shown therein, a thin section i9 removed
along the length of the cylindrical core, providing two
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free ends 50, 50 in closed proximity but spaced apart in
what then may be defined as a discontinuous cylindrlcal
core. While the section remsved i8 shown to be
substantially perpendicular to the ends, it will be
appreciated that removal of the section may also be made
by cutting at an angle.
In general, the space provided between ends 50, 50 .
should be such that, upon stress recovery, the core
collapses so that the ends are substantially abutting.
If the space is too great, the respective ends will not
meet and the modified tdiscontinuous) core will be
noticeable. On the other hand, if too little is removed,
some telescoping may still occur since the core does not
collapse sufficiently to prevent the tape from migrating
off the core.
The exact amount of space to be provided by severing
a section of the core will at least in part be dependent
upon the degree of stress relaxation of the tape and this
will in part be dependent upon the elasticity of the
particular tape and the degree of stress or stretching to
which it has been subjected during manufacture.
Accordingly, the space to be provided between ends 50, 50
of the discontinuous cores of this invention may vary
somewhat from tape-to-tape and/or to the degree of
tension applied. For this reason, it is not capable of
preci6e numerical definition.
However, by way of illustration, with the
~o~c~ t~ ~V~`A14~ es-~Nh~ch Applicant has tested,
a space of from about 1/8 to about 1/4 of an inch
provides optimum results.
Still a further embodiment of the invention produces
a collapsible effect by enveloping the outer surface of a
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non-severed core with foam, 60 tFig. 5). By way of
illustration and not limltation mention may be made of
the fQllowing flexible foam materials: polyurethane,
rubber latex, polyethylene and vinyl polymers. The foam
may be secured to the core by per se known adhesive
means, e.g. a pressure-sensitive adhesive.
The choice of the specific foam material and its
thickness will vary according to the predicted amount of
stress recovery. Thus a tape which is expected by the
ordinary skilled person in the art to recover
substantially will require a foam material of equal
flexibility to prevent telescoping. ~y way of
illustration, a polyurethane foam may be on the order of
1-3 mms. thic~.
Figure 6 illu6trates the aesthetic result desired if
the core of Figure 4 collapses to the proper degree. As
shown, the edges of the tape are uniform with no
telescoping and the free ends 50, 50 are substantially
abutting 80 that the core is essentially cylindrical in
configuration.
The core materials employed in the practice of this
invention may in general be any of the semi-rigid
materials heretofore employed in roll tape manufacture.
Such materials will posses the rigidity and dimensional
stability to retain their shape under the weight of the
adhesive wound thereon but will have sufficient
flexibility to collapse slightly under the stress
rel~R~D~ c~ r d~S~ ~ iypically, such cores
are made from cardboard or other paper-based laminates.
In any event, the selection of particular core material~
per se comprises no part of thi~ invention and will
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accordingly be a matter of individual choice within the
expected ~udgement of the skilled worker.
In like manner, for purposes of this invention, the
adhesives and backings employed to prepare the tape are
immaterial. Typically, they will comprise a
pressure-sensitive adhesive, e.g. an acrylic or
rubber-based adhesive comprising at least one natural or
synthetic rubbery elastomer and one or more tackifying
resin coated onto a polyolefinic, e.g. polyethylene, or
other plastic sheet material. So-called two-faced tapes
having an adhesive layer on each side of the backing are
also contemplated, as are duct tapes and the like having
a reinforcing cloth material disposed between the backing
and the adhesive layer. While pressure-sensitive
adhesive rolls are by far the most common, it will be
appreciated that the invention is egually applicable to
other types of adhesives, e.g. heat- or water activated
adhesive tapes, as well. In general, typical tapes
contemplated for use with the present invention may be
characterized as comprising flexible polymer films with
.
slow stress recovery.
It will also be appreciated that the width and
length of the tapes is also immaterial. However,
typically the rolls will be 0.75 to 2.5 inches wide and
the lengths will range from about 15 to about 60 feet.
:
The following examples show by way of illustration
~; and not be way of limitation the practice of this
in~entLGn.
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~ X A ~ P L ~
A slitting device as previously described having
twelve slitting knive~ in parallel and spaced apart to
provide 3/4 inch tapes was employed in conjunction with
3/4 inch cores in order to provide twelve 3/4 inch tapes.
The cores in the 2, 4, 6, 8, 10 and 12 positions were
conventional continuous cardboard cores; while the cores
in the 1, 3, 5, 7, 9 and 11 position on the drive shaft
were discontinuous cores in accordance with this
invention having a 1/4 inch gap between the free ends of
the cores. A web of commercially available butyl
rubber-based pressure-sensitive adhesive on a plastic
bacXing was employed to form twelve rolls of tape on the
3/4 inch cores. The resulting tapes were measured to
determine the maximum widths from one edge of the rolls
to the other [In theory, the maximum widths should be
approximately the 3/4 inch of the tape and core.] Of the
six continuouæ (control) cores, those in the 4, 8, 10 and
12 positions measured over 1.5 inches, indicating severe
telescoping to over twice the core width. The continucus
core in the two position telescoped appreciably less and
the continuous core in the 6 or middle position
unaccountably did not telescope at all. of the six
discontinuous (experi~ental) tapes, the widths increased
0.07, 0.08, 0.07, 0.05, 0.06 and 0.03 inch, respectively,
which from a commercial viewpoint were all fully
acceptable rolL~ e~h:lbLtin~ ~o ~les~opin9. ~ ach
instance with the tape wound on collapsible cores, the
gap between the core ends did not close completely,
leaving an average gap of 0.13 inch, thus indicating that
a smaller gap could have been used. Even with this
remaining thin gap, the roll i~ substantially
cylindrical, aesthetically plea~ing, and therefore
acceptable.
Since certain changes may be made without departing
from the scope of the invention herein involved, it is
intended that all matter contained in the above
description and the accompanying drawing shall be
interpreted as illustrative and not in a limiting sense.
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