FIELD OF THE INVENTION
The invention relates to wound multi-ply tubes and to a process for
BACKGROUND OF THE INVENTION
Spirally wound paperboard tubes and paperboard composite tubes (tubes
having one or more layers of paper and/or non-paper sheet material such as plastic,
foil, or the like), are used in a wide variety of applications throughout numerous
industries. For example, spirally wound tubes are used as winding cores for winding
filamentary materials such as yams, threads and the like, and for various disposable
sheet goods such as toilet tissue, paper towels, gift-wrap, aluminum foil and other
materials. Spirally wound multi-layer tubes are also used as containers for food
products such as frozen juices, bread doughs, and snack products, and as forms in
the building industry, e.g., for forming concrete columns and the like.
Spirally wound tubes are traditionally produced by winding continuous
plies of paperboard or other sheet material around a stationary mandrel. A plurality
of strips or plies are fed onto the exterior of the mandrel in a radially layered
relationship. The individual plies are coated on one or both faces with glue so
that each layer is adhered to each radially adjacent layer to form a cylindrical
tube wall. A rotating belt contacts the exterior of the layered tube as it is formed
on the mandrel and rotates the tube so that it moves spirally and longitudinally
down the mandrel.
Conventionally, a liquid glue or adhesive is applied to one or both
faces of a paperboard ply as the ply is advanced to the mandrel. Ply guides and
tension devices guide the ply to the glue applicators and ultimately to the mandrel.
Proper functioning of the glue applicator operation is essential to ensure that
the liquid adhesive is applied to each ply in the appropriate amount and only in
the appropriate locations. Any malfunction may result in significant material scrap
and assembly line downtime. When such liquid adhesives are used, newly formed tubes
tend to be relatively weak until the adhesive is fully dried, which can take up
to 24 hours or more. Accordingly, it is necessary in some cases to store newly formed
tubes for a period of time to allow them to fully dry thereby ensuring that radially
adjacent plies adhere strongly to each other. If a newly formed tube is not adequately
dried before subsequent operations are performed on the tube, the relative weakness
of the tube can cause problems.
As noted, spirally wound paperboard tubes are widely used as cores
for consumer rolls of various products such as toilet paper, paper towels, and others.
Frequently, the manufacturer or converter of such products also makes the cores
onto which the products are wound. In some cases, the manufacturer may not have
particular expertise in making spirally wound cores because that is not the manufacturer's
primary business. It is not uncommon for such manufacturers to employ ply guides
and glue applicators that are not state-of-the-art and are not very reliable; as
a result, frequent breakdowns occur during the core-making operation. It would be
desirable to simplify the core-making operation so that it can be less susceptible
to breaking down.
SUMMARY OF THE INVENTION
The present invention addresses the above needs and achieves other
advantages by providing a wound tube and tube manufacturing process wherein the
plies are joined together with a cold seal adhesive, also referred to herein as
cohesive. The cold seal adhesive is pre-applied to the plies and thus eliminates
the need for an in-line adhesive application station. Such plies having pre-applied
cold seal adhesive are referred to herein as "pre-adhered" plies. The use of pre-adhered
plies simplifies the tube forming process and accordingly, the process is less susceptible
to malfunction. The invention is particularly applicable to paperboard tubes, but
can be applied to tubes formed partly or entirely of non-paperboard material.
Cold seal adhesives or cohesives are bonding compounds that adhere
only to other surfaces coated with the same compound. The cohesive is applied to
a surface and is allowed to dry. Once dried, the cohesive is no longer "tacky" and
may contact a variety of other materials without sticking. When bonding with another
surface is desired the other surface is coated with the cohesive, allowed to dry
and then is pressed against the first surface. The cohesive layers adhere to one
another, joining the surfaces. Cohesives are traditionally used in such applications
as cereal boxes, candy bar wrappers, self-seal envelopes and protective packaging.
In accordance with one preferred embodiment of the invention, a single-ply
spirally wound tube is formed by winding a ply such that opposite edge portions
of the ply overlap to form a helical overlapping joint. Cohesive is disposed on
one surface of the ply at one edge portion and on the opposite surface of the ply
at the other edge portion. Coating the edges of the ply in this fashion allows the
pre-adhered ply to be provided in the form of a roll without bonding or blocking.
During tube assembly the ply is drawn from the supply roll and wound about the mandrel
with the edge portions overlapping and bonding to form a cylindrical tube.
In a second preferred embodiment of the invention, a tube has two
plies. At least one surface of each ply is coated partially or completely with cohesive
such that when a similarly coated ply is introduced the two plies may be wound together
forming a rigid tube. Coating the entire surface of a ply may be advantageous because
accurately applying cohesive to only a portion of a surface may slow production.
Preferably, in this preferred embodiment only a single side of each of the plies
is coated so that the plies can be rolled upon themselves to form supply rolls without
To produce a tube in accordance with this embodiment, a first ply
is drawn from a supply roll thereof and spirally wound about a stationary mandrel.
This first ply is positioned such that the cohesive coated side faces outward, away
from the mandrel. A second ply is then drawn from a second supply roll and wrapped
about the mandrel, directly on top of the first ply. The second ply is positioned
such that its cohesive coated side faces inward toward the first ply. The plies
of the first and second layers may be offset to ensure that seams of the first layer
do not align with seams of the second layer. As with the first preferred embodiment,
the rotating belt draws the plies from their supply rolls and then spirally winds
them about the mandrel. When the coated surfaces of the two plies make contact,
their cohesive coatings form a bond that adheres the two plies together. Once formed,
the resulting elongate tube may be cut into a plurality of smaller tubes of desired
In a third preferred embodiment of the invention, a tube comprises
three or more plies. In this embodiment at least one of the plies is radially positioned
between two other plies and therefore must have cohesive on both of its surfaces.
A ply coated with cohesive completely on both surfaces could not be stored in roll
form without blocking. As a result, in the present invention the cohesive preferably
is applied to both surfaces of a ply in a pattern of strips, boxes, circles, ovals,
etc., which allows the ply to readily be stored in roll form. To accomplish this,
the cohesive patterns disposed on the opposite surfaces of the ply are offset relative
to each other so as to allow the ply to be rolled about a spindle such that the
cohesive areas on one surface align with uncoated areas on radially adjacent surfaces.
To produce multi-layer tubes in accordance with this embodiment, a
first pre-adhered ply having cohesive on only one side is drawn from the supply
roll and spirally wound about a stationary mandrel. A second pre-adhered ply having
cohesive on both sides is then drawn from a second supply roll and is wound onto
and bonded to the first ply. A third pre-adhered ply is then drawn from its supply
roll and wound onto the second ply. The third ply is axially positioned relative
to the second ply so that the coated areas of the second ply align with the coated
areas of the third ply. A rotating belt contacts the exterior of the layered tube
as it is formed on the mandrel and rotates the tube so that it moves spirally down
the mandrel. Placing additional ply supply rolls at different points along the mandrel
allows for further layering of the tube, providing greater wall thickness and increased
tube wall strength. Once formed, the resulting elongate tube may be cut into a plurality
of tubes of desired length.
There are several advantages to the present invention. Most notably,
the use of plies having pre-applied cohesive eliminates the need for a conventional,
liquid adhesive application station. Applying the cohesive in a controlled environment,
designed solely for applying adhesives, can result in a more-uniform and consistent
application than can typically be achieved when applying adhesive in a conventional
in-line tube assembly process. This reliability can produce tubes with improved
bond uniformity between plies. Additionally, the removal of the in-line glue applicators
may reduce overall assembly line downtime by eliminating a source of assembly malfunction.
Also, tubes formed in accordance with the invention have full strength as soon as
they are made; no drying period is required to produce adequate tube wall strength
as is required during conventional tube forming processes. The present invention
introduces the pre-adhered plies to the assembly line in a fully dried state and
thereby accelerates the overall rate of tube production.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
Having thus described the invention in general terms, reference will
now be made to the accompanying drawings, which are not necessarily drawn to scale,
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
- FIG. 1 is a perspective view of a single-layer tube in accordance with
one embodiment of the present invention;
- FIG. 2 is a sectional view of the cohesively bonded single-layer tube
ofFIG. 1 taken along section line 2-2;
- FIG. 3 is top view of a single ply of the present invention illustrating
cohesive coating on opposing edges for winding into a single-layer tube;
- FIG. 4 is a perspective view of a double-layer tube in accordance with
another embodiment of the present invention;
- FIG. 5 is a sectional view of the cohesively bonded double-layer tube
ofFIG. 4 taken along section line 5-5;
- FIG. 6 is a perspective view of a multi-layer tube in accordance with
another embodiment of the present invention;
- FIG. 7 is a sectional view of the cohesively bonded multi-layer tube
ofFIG. 6 taken along section line 7-7;
- FIG. 8 is a schematic illustration of one preferred multi-layer tube
forming operation of the invention providing pre-applied cohesive plies; and
- FIG. 9 is a partially exploded view of one preferred multi-layer tube
ofFIG. 6 particularly showing the interface between pre-applied cohesive
strips and spirally wrapped paperboard plies.
The present inventions now will be described more fully hereinafter
with reference to the accompanying drawings, in which some but not all embodiments
of the invention are shown. Indeed, these inventions may be embodied in many different
forms and should not be construed as limited to the embodiments set forth herein;
rather, these embodiments are provided so that this disclosure will satisfy applicable
legal requirements. Like numbers refer to like elements throughout.
FIG. 1 illustrates one preferred embodiment of a single-layer
tube 10 produced from a single ply 11. The tube 10 is formed
by winding a single ply 11 such that opposite edge portions of the ply overlap
to form a helical overlapping joint 13. FIG. 2 is a section view depicting
this overlapping joint 13 in which a lower layer 11 and an upper layer
11' of the same ply are bonded at their edge portions with cohesive
12. FIG. 3 more clearly depicts the configuration of the cohesive
coating 12, which is disposed on one side of the ply at an edge portion and
on the opposite side of the ply at the other edge portion.
FIGS. 4 and 5 illustrate another embodiment of the invention
in the form of a double-layer tube 15 comprising a first ply 16 and
a second ply 16'. A cold seal adhesive layer 17 is provided on each
of the first and second plies. The cold seal adhesive layers 17 are pressed
together to bind the spirally wound first ply 16 to the second ply
16' forming the cylindrical double-layer tube 15.
FIG. 5 is a section view of the double-layer tube
15 showing the cohesive layers 17 bonding the first ply
16 and the second ply 16' together, and showing the butt joint or
seam 18 created during the spiral winding of each ply. It should be noted
that the seams of the first ply 18 and the second ply 18' are offset
relative to one another to ensure adequate structural integrity of the tube
FIG. 6 illustrates a multi-layer tube 20 in accordance
with another embodiment of the present invention. The multi-layer tube
20 has three plies 21,21', 21"; however, tubes of the
present invention are not limited to three plies and may include additional plies.
The plies are adhered together by cohesive strips 22 disposed on the opposing
surfaces of each ply.
FIG. 7 is a section view of the preferred multi-layer tube
20 of FIG. 6 showing the cohesive areas or strips 22 disposed
on radially adjacent surfaces of the plies. The cohesive areas are depicted in
FIG. 7 as strips, but the present invention may include other patterns of
cohesively coated areas including boxes, circles, ovals, etc. The middle ply
21 has cohesive areas 22 on both of its opposite surfaces. Advantageously,
to allow the middle ply to be rolled into a supply roll, the cohesive areas on one
side of the ply are offset from those on the other side of the ply, as shown in
FIG. 7, so that when the ply is rolled the cohesive areas on one side do
not contact cohesive areas on the other side. 'In the illustrated embodiment the
cohesive is not disposed on the outer surface of the outermost ply21"; however,
the present invention may include tubes with an adhesive or cohesive disposed on
this outer surface. Such an adhesive might be used to engage a first layer of paper
or non-paper sheet material, which is to be wrapped about the tube. The outermost
and innermost plies are shown as having cohesive 22 covering only part of
their surfaces, but these plies could instead have cohesive entirely covering their
surfaces that bond to the intermediate ply 21.
FIG. 8 illustrates a preferred multi-layer tube forming process
in accordance with the present invention. A first supply roll 30 of pre-adhered
material is introduced to the tube forming assembly line. An individual first ply
31 is advanced from the first supply roll 30 and wound about a stationary
mandrel 33. As noted above, the first play 31 could have cohesive
covering its entire outer surface rather than strips as shown. This first ply
31 is situated as shown in FIG. 9, such that its cohesive strips
31' are facing outward, away from the mandrel 33. A second ply
34 is drawn from a second supply roll 35 of pre-adhered material and
wrapped about the mandrel 33, directly on top of the first ply
31. The second ply34 is situated as shown in FIG. 9, having
both surfaces coated with cohesive strips34'. The second ply 34 is
axially positioned such that its cohesive strips 34' align with the corresponding
strips of the outer surface of the first ply 31'. A rotating belt
32 contacts the exterior of the layered tube as it is formed on the mandrel
and rotates the tube 38 so that it moves spirally down the mandrel
33, thereby spirally winding the plies while simultaneously drawing the plies
from their respective supply rolls.
A plurality of additional plies 37 may be drawn from supply
rolls situated downstream of the second ply supply roll 35 and may be subsequently
wrapped about the mandrel 33. These additional plies 37 are wrapped
directly upon radially adjacent plies such that their cohesive strips align with
the cohesive strips of the radially adjacent plies. An outermost or final ply
36, is then drawn from a supply roll and wrapped about the mandrel
33. The final ply 36 may have cohesive strips on its lower surface
or may have cohesive covering the entire lower surface. If the final ply
36 has strips of cohesive, it is wrapped such that its inwardly facing cohesive
strips 36' are aligned with the corresponding strips of the radially adjacent
ply. The formed elongate tube 38 is then cut by a cutting apparatus
39 into a plurality of tubes of desired length.
Single-ply tubes 10 and two-ply tubes 15 of the present
invention may be produced by a tube forming process similar to that described in
connection withFIG. 8, using the appropriate number and types of plies.
Many modifications and other embodiments of the inventions set forth
herein will come to mind to one skilled in the art to which these inventions pertain
having the benefit of the teachings presented in the foregoing descriptions and
the associated drawings. Therefore, it is to be understood that the inventions are
not to be limited to the specific embodiments disclosed and that modifications and
other embodiments are intended to be included within the scope of the appended claims.
Although specific terms are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.