U.S. patent application number 11/364645 was filed with the patent office on 2006-08-10 for activator means for pre-applied adhesives.
Invention is credited to Frederick Edward Charles Lidington, John Lazar, Todd Schwantes.
Application Number | 20060177634 11/364645 |
Document ID | / |
Family ID | 46124101 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060177634 |
Kind Code |
A1 |
Lazar; John ; et
al. |
August 10, 2006 |
Activator means for pre-applied adhesives
Abstract
An activator means for use in activating or re-activating
adhesive and sealant compositions that have been pre-applied to a
bonding surface prior to mating said bonding surface said means
having a plurality of features for directly acting upon the
pre-applied composition.
Inventors: |
Lazar; John; (Custer,
WI) ; Schwantes; Todd; (Lena, WI) ; Charles
Lidington; Frederick Edward; (Custer, WI) |
Correspondence
Address: |
EDWARD K. WELCH II;IP&L Solution
4558 Ashton Court
Naples
FL
34112
US
|
Family ID: |
46124101 |
Appl. No.: |
11/364645 |
Filed: |
February 28, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11216516 |
Aug 31, 2005 |
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11364645 |
Feb 28, 2006 |
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60606720 |
Sep 1, 2004 |
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60665134 |
Mar 25, 2005 |
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60692008 |
Jun 17, 2005 |
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Current U.S.
Class: |
428/156 |
Current CPC
Class: |
C08J 3/241 20130101;
B05D 3/12 20130101; B32B 37/12 20130101; Y10T 156/1798 20150115;
C08J 3/24 20130101; B01J 13/02 20130101; C09J 5/00 20130101; B32B
2037/1269 20130101; Y10T 428/24479 20150115 |
Class at
Publication: |
428/156 |
International
Class: |
B32B 3/00 20060101
B32B003/00 |
Claims
1. An activator means capable of lifting an inactive pre-applied
adhesive from a substrate surface and depositing said adhesive in
an activated state onto said substrate surface, said activator
means having a centerline axis and, perpendicular thereto, a
transverse axis, said centerline axis being parallel to and aligned
with direction of the relative movement of the activator means to
the substrate upon which it acts during activation of the
pre-applied adhesive, said activator means comprising an activator
body having at least one activator face, said activator face having
(a) a surface, which surface, in use, opposes the substrate surface
to be acted upon, and (b) a plurality of projections extending from
said surface, which projections, in use, engage the pre-applied
adhesive, thereby lifting the adhesive, and deposit the adhesive in
an activated state in a predetermined pattern or configuration,
provided that when at least one of the projections is a linear
projection which is perpendicular to the centerline axis, the
length of that projection is substantially less than the width of
the pre-applied adhesive to be acted upon.
2. The activator means of claim 1 wherein, in use, the pre-applied
adhesive is activated concurrent with the engagement of the
projections with the pre-applied adhesive.
3. The activator means of claim 1 wherein the surface of the
activator face is contoured to mimic the contour of the substrate
surface upon which it is intended to act.
4. The activator means of claim 1 wherein when the surface of the
activator face is viewed in the direction of its centerline at its
axis, the projections appear to form a solid wall which wall
corresponds to the width of the pre-applied adhesive to be acted
upon by the activator face.
5. The activator means of claim 1 wherein when the surface of the
activator face is viewed in the direction of its centerline at its
axis, the projections appear to form a wall extending between the
two projections situated the furthest from and on opposite sides of
the centerline axis which wall has one or more gaps.
6. The activator means of claim 5 further comprising a
reciprocating means which reciprocating means moves the activator
face back and forth along the transverse axis.
7. The activator means of claim 6 wherein the extent of the
movement off the centerline axis imparted to the activator face by
the reciprocating means is about one-half the width of the gap in
each direction.
8. The activator means of claim 1 wherein the projections are
selected from linear dams and ridges, chevrons, herringbones,
inverted "V" shaped or crescent shaped dams or ridges, pyramids,
hemispheres, hemispheroids, and cylinders and combinations
thereof.
9. The activator means of claim 1 wherein the projections are in a
staggered relationship along the centerline axis, but not
necessarily intersecting the centerline axis, such that at least a
portion of one projection overlaps with a portion of another
projection when viewed in the direction of the centerline axis.
10. The activator means of claim 1 having at least one linear
projection or projection having linear extensions posterior to one
or more other substantially non-linear projections.
11. The activator means of claim 1 wherein the substantially
non-linear projections are selected from the group consisting of
inverted crescents, small inverted "V"s, hemispheres,
hemispheroids, pyramids and cylinders.
12. The activator means of claim 1 wherein at least one of the
projections is a linear projection or a projection having linear
extensions or arms.
13. The activator means of claim 12 wherein the linear projection
or extension is set at an angle relative to the centerline axis,
which angle is from about 20.degree. to about 70.degree..
14. The activator means of claim 12 wherein the linear projection
or extension is set at an angle relative to the centerline axis,
which angle is from about 30.degree. to about 60.degree..
15. The activator means of claim 1 wherein the projections are
aligned in a linear relationship parallel to the transverse
axis.
16. The activator means of claim 1 wherein the projections are
aligned in a plurality of rows, each row parallel to the transverse
axis.
17. The activator means of claim 16 wherein the projections in one
row are staggered relative to the projections in the
neighboring.
18. The activator means of claim 1 wherein the activator face
further includes one or more channels posterior to the
projections.
19. The activator means of claim 18 wherein the forward face of the
elements defining the channel also serve as projections lifting and
moving the adhesive material.
20. The activator means of claim 18 wherein the depth and width of
the channel(s) are predetermined to extrude a bead of activated
adhesive of a desired width and height.
21. The activator means of claim 1 wherein the projections are
selected from the group consisting of linear projections,
diversionary projections and splitters and combinations
thereof.
22. The activator means of claim 1 wherein the activator face is
composed a metal, plastic, carbide or ceramic.
23. The activator means of claim 1 wherein the activator face is
composed of a material that is heat resistant and has good heat
transfer capabilities.
24. The activator means of claim 1 wherein the surface of the
activator face, including the projections, has a coating thereon
which coating is inert to the adhesive material to be
activated.
25. The activator means of claim 24 wherein the coating is selected
from polytetrafluoroethylene and a silicone material.
26. The activator means of claim 1 wherein the activator face is
integral with the activator body.
27. The activator means of claim 1 wherein the activator face is
attached to the activator body.
28. The activator means of claim 1 further comprising heating
means.
29. The activator means of claim 1 in which the activator face is
in a heat transfer relationship with a heating means.
30. The activator means of claim 1 further comprising a
reciprocating means for providing reciprocating movement to the
activator face.
31. The activator means of claim 1 which is associated with a
reciprocating means for providing reciprocating movement to the
activator face.
32. The activator means of claim 1 further comprising or being
associated with a lift means for adjusting the distance between the
activator face and the substrate upon which it is to work.
33. The activator means of claim 32 further comprising a sensing
means which sensor means detects variations in the height of the
substrate surface upon which the activator face is to work relative
to the positioning of the activator face so as to enable the
adjustment of the activator means.
34. The activator means of claim 1 further comprising an attachment
means for integrating the activator means into an apparatus for the
in-line activation of a pre-applied adhesive.
35. The activator means of claim 1 wherein the projections and any
channels, if present, are molded into the activator face concurrent
with the manufacture of the activator face.
36. The activator means of claim 1 wherein the activator face is
made of a stock material wherein the projections and any channels,
if present, are milled into stock material.
37. An activator means capable of lifting an inactive pre-applied
adhesive from a substrate surface and depositing said adhesive in
an activated state onto said substrate surface, said activator
means having a centerline axis and, perpendicular thereto, a
transverse axis, said centerline axis being parallel to and aligned
with direction of the relative movement of the activator means to
the substrate upon which it acts during activation of the
pre-applied adhesive, and said activator means comprising (a) an
activator body having at least one activator face, said activator
face having a surface, which surface, in use, opposes the substrate
surface to be acted upon, and a linear projection extending from
said activator face surface and (b) a reciprocating means for
effecting a secondary movement of the activator face along the
transverse axis; wherein when said linear projection is
substantially perpendicular to the centerline axis, the length of
the linear projection is shorter than the width of the pattern of
the pre-applied adhesive on the substrate surface and the movement
of the activator face along the transverse axis is sufficient to
allow an effective amount of adhesive to pass the linear projection
as the activator means, relative to the substrate surface, moves
along the centerline axis; and wherein when said linear projection
is substantially parallel with the centerline axis, the movement of
the activator face along the transverse axis is sufficient to act
upon an effective amount of pre-applied adhesive as the activator
means, relative to the substrate surface, moves along the
centerline axis.
38. The activator means of claim 37 wherein the activator face has
a plurality of linear projections substantially parallel to the
centerline axis.
39. The activator means of claim 37 wherein the activator face has
a plurality of linear projections substantially perpendicular to
the centerline axis, wherein said linear projections are co-linear
or staggered along, but not necessarily intersecting with, the
centerline axis, or both.
40. The activator means of claim 37 wherein the activator face has
a plurality of linear projections substantially perpendicular to
the centerline axis, wherein said linear projections are staggered
along, but not necessarily intersecting with, the centerline
axis.
41. An improved method of activating a pre-applied adhesive on the
surface of a substrate said method comprising the steps of passing
an activator means over the pre-applied adhesive wherein the
improvement lies in the use of an activating means having a
centerline axis and, perpendicular thereto, a transverse axis, said
centerline axis being parallel to and aligned with direction of the
relative movement of the activator means to the substrate during
activation, said activator means comprising an activator body
having at least one activator face, said activator face having (a)
a surface, which surface opposes the substrate surface being acted
upon, and (b) a plurality of projections extending from said
surface, which projections engage the pre-applied adhesive, thereby
lifting the adhesive from the substrate and deposit the adhesive in
an activated state in a predetermined pattern or configuration,
provided that when at least one of the projections is a linear
projection which is perpendicular to the centerline axis, the
length of that projection is substantially less than the width of
the pre-applied adhesive to be acted upon.
42. The method of claim 41 wherein the pre-applied adhesive is a
thermoplastic adhesive and the activator means further comprises or
is in a heat transfer relationship with a heating means whereby
heat is transferred from the heating means to the thermoplastic
adhesive by the activator face.
43. The method of claim 41 wherein the pre-applied adhesive is an
encapsulated adhesive wherein the projections fracture the
microcapsules containing the adhesive components and create
sufficient flow within the adhesive mass to effect activation
before depositing the same on the substrate.
Description
[0001] This application is a Continuation-in-Part application of
pending U.S. patent application Ser. No. 11/216,516, filed Aug. 31,
2005, entitled "Encapsulated Cure Systems", which claims the
benefit of U.S. Provisional application No. 60/606,720, filed Sep.
1, 2004, and claims the benefit of the following U.S. Provisional
applications: 60/665,134 filed Mar. 25, 2005 and 60/692,008 filed
Jun. 17, 2005: the contents of all of the foregoing hereby
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is directed to a novel activator means
for use in activating or re-activating adhesive and sealant
compositions that have been pre-applied to a bonding surface or a
substrate prior to mating said bonding surface with the surface or
substrate to which it is to be bonded. In one embodiment, the
activator means is a heated activator means for use with
pre-applied heat activated/re-activated adhesive and sealant
compositions wherein the heat of the activator means transforms the
adhesive or sealant into a flowable state and the features of the
activator face of the activator means serve to lift the flowable
adhesive or sealant from the substrate surface, collect and then
redeposit the same on the substrate surface in the area of the
intended bondline in a defined profile. In a second embodiment, the
activator means has an activator that is not heated or, if heated,
provides minimal heat, and whose activator face has features that
are capable of lifting the adhesive from the surface of the
substrate to which it is pre-applied, mixing and collecting the
pre-applied adhesive material and then re-depositing the same on
the substrate surface in the area of the intended bondline.
Preferably, the activator means is employed with pre-applied,
two-part, curable or polymerizable adhesive or sealant
compositions, especially encapsulated compositions, and has
features on the activator face that are capable of intimately
mixing the two parts to activate the cure or polymerization of the
composition before re-depositing the activated composition on the
substrate surface in the area of the intended bondline. The present
invention is also directed to industrial bonding systems and
apparatus that incorporate said activator means, especially systems
and apparatus for high-speed industrial, automated bonding
applications as well as bonding methods employing the
aforementioned activator means.
[0004] 2. Description of Related Art
[0005] Multi-part adhesive and sealant compositions are widely
known and commercially available for both consumer and industrial
or commercial use. These compositions are typically characterized
as being reactive systems wherein cure or polymerization is
initiated once all of the components of the curable composition are
brought into intimate contact with one another. By far, the most
common multi-part adhesive and sealant compositions are two-part
systems. Two-part adhesive and sealant compositions take many forms
and can be employed in numerous ways. For example, an adhesive or
sealant composition may comprise a first part, Part A, which
includes a liquid curable component, and a second part, Part B,
which includes an activator in an appropriate solvent, which
activator, in the presence of Part A, initiates or effectuates cure
or polymerization of the liquid curable component. In use, one or
both of the surfaces to be bonded is pretreated or primed with Part
B so that when Part A is applied thereto or to the untreated
surface, if one, and the surfaces mated, cure or polymerization is
initiated.
[0006] Alternatively, both Parts A and B may comprise the same or a
different liquid curable component with Part A also containing an
activator which is, by itself, non-reactive with the liquid curable
component of that part, but which is reactive when mixed with Part
B. In this instance the activator may be a chemical additive such
as an initiator, accelerator, catalyst, etc., which effectuates
polymerization or cure but does not itself become chemically
incorporated into the cured or polymerized polymer (though it may
be physically entrained therein) or it may be a component
co-polymerizable with the liquid curable component of Part B, as
for example a cross-linking agent or hardener. Of course, not all
two-part systems are liquid curable or polymerizable systems. For
example, two-part epoxy adhesive and sealant compositions often are
found in the form of ribbons, strings, beads, etc. of the two parts
in a putty-like state, extruded in a side-by-side or concentric
relationship. As with liquid curable or polymerizable systems, cure
or hardening is initiated upon intimate mixing of the two
components.
[0007] In industrial operations, most two-part adhesive and sealant
compositions are applied at the time of use: typically through the
use of expensive, sophisticated dispensing equipment which meters
the relative proportions of the two components and mixes the two
concurrent with or just prior to dispensing. Whether mixing occurs
within the dispensing equipment or upon exiting the same depends
upon the physical nature of the materials as well as their cure
characteristics, especially the speed of cure or pot life of the
activated materials. Such dispensing equipment is often fed from
large containers or reservoirs of the two components or the
dispensing equipment may be constructed so as to receive disposable
cartridges, including cartridges comprising two chambers, e.g.,
double barrel cartridges, each of which is constructed to contain a
predetermined amount of the two components so that the two
materials are dispensed in their proper proportions. The former
allows for continuous, or nearly so, dispensing so long as the
reservoirs are replenished. However, concerns arise relative to
clogging of the dispenser nozzle due to cure of the two-part
compositions in the mixer head or at the nozzle orifice,
particularly in the event of a shut down or temporary stoppage of
the assembly line. The use of the cartridge is especially
beneficial in those systems where it is impractical to employ large
containers or the containers are unable to be located proximate to
the dispenser nozzle. Further, with these systems one has the
benefit of being able to dispose of the spent cartridges and avoid
concerns of contamination, set-up or cure of the large reservoirs.
Furthermore, if a problem arises the unspent cartridge is merely
replaced with a new cartridge; whereas, if a problem arises with
the large reservoir systems, the reservoirs must be emptied and
cleaned and the dispensing system purged before dispensing can be
resumed. With cartridges, one also has the possibility of
integrating the nozzle or mixer head in the cartridge assembly.
Thus, the nozzle or mixer head is replaced with each replacement of
the cartridge. If a problem should arise where the nozzle or mixer
head is clogged, one merely replaces the whole cartridge system and
gets on with the assembly operation. The only loss is the unspent
materials in the cartridge and a minimal delay in the assembly line
process. Despite the attributes of the cartridge systems, with or
without the integrated nozzle or mixer head, the cartridges must be
continually replaced due to the relatively low volume of materials
held within them as compared to the larger reservoirs of the more
sophisticated dispensing equipment. This replacement process
results in a repetitive, though temporary, stoppage of the assembly
line with its concomitant impact on through put.
[0008] Perhaps the greatest disadvantage of the foregoing systems
is the use and application of liquid materials in high-speed
industrial manufacturing lines. Extreme care must be employed to
ensure that the components are mixed in their proper proportions.
Even small variations in the proportions by which the two
components are dispensed may lead to materials that cure too
quickly or too slowly, if at all. Even if cure is unaffected by
such variations, such variations will likely result in adhesives
having different performance characteristics or physical profiles
than would be attained had the dispensing occurred as intended.
Furthermore, because these dispensing systems rely upon pressure,
direct or indirect, to dispense the components, any variation in
pressure may also adversely affect the adhesive and/or bond to be
formed. For example, low pressure or the loss of pressure will
result in the dispensing of insufficient quantities of adhesive or
gaps in the dispensed adhesive leading to poor or failed bonds. Too
much pressure or sudden surges in pressure will lead to the
dispensing of excessive quantities of material rendering the
substrates unsuitable for use or, worse, broadcasting adhesive
material not only onto the substrate but onto proximate components
of the assembly line itself as well. The latter may lead to a shut
down of the assembly line in order to clean it before more, and
oftentimes more significant, problems arise.
[0009] In order to avoid many of the problems associated with
in-line applied liquid adhesive materials, many industrial
processes have employed pre-applied adhesives. The vast majority of
these systems employ thin films of a dry-to-the-touch thermoplastic
(including cooled hot melt) or thermoset adhesive materials that
are activated or re-activated, as the case may be, upon exposure
to, among others, high temperatures, irradiation (e.g., UV, IR,
etc.), electromagnetic fields (e.g., RF, UHF, microwave, etc.)
and/or ultrasound. Though such systems have found broad use, they
too have limitations, particularly with respect to the bonding of
surfaces which are not planar or where gaps may exist. Furthermore,
each presents concerns relative to the generation of the necessary
energy to activate or re-activate the adhesive, not only with
respect to the substrate being acted upon but also the associated
equipment proximate to the activation station of the assembly line
as well as other general health, safety and environmental concerns,
particularly with respect to workers responsible for the operation
and maintenance of the assembly line. For example, high-speed
packaging formation and closing processes typically employ a
pre-applied thermoplastic or thermoset adhesive film applied to the
bonding surface which is heated to its activation or melt
temperature by one or more heater elements that direct a jet of
extremely hot air to the intended bondline.
[0010] Although such jets of hot air can be directed, the greater
the distance from the source to the substrate, the more diffuse
that jet becomes. Also, once the jet hits the substrate, the hot
air then disperses along the surface of the substrate. This can be
a significant problem with many substrates that have heat sensitive
surfaces, coatings and the like. For example, packaging oftentimes
has a coating or varnish and/or printing on its outer surface which
may be adversely affected by the high temperatures needed to
activate or reactive the pre-applied adhesive material,
particularly if the heat cannot be contained to the immediate
bondline area. Furthermore, workers who are called upon to address
problems with the assembly line often come close to or in direct
contact with the heating equipment or the heat generated by the
equipment, particularly the jets of hot air, which heat may cause
severe burns. While safeguards and protective means or design
modifications may be incorporated into the assembly line and the
heating equipment, such requires additional expenditure and adds
more complexity to the system. The same holds true for systems that
rely upon electromagnetic energies, ultraviolet light, etc.; rather
than the direct application of heat. Finally, such systems are
often lengthy, adding further cost, both in terms of equipment and
space, to the process in order to allow sufficient cooling of the
heated adhesive or sealant before the bond is formed or before
sufficient bonding is achieved so that the substrate can move on to
its next workstation.
[0011] Another class of pre-applied materials are those known as
the encapsulated adhesives and sealants. Such encapsulated systems
may comprise a one-part adhesive, such as the encapsulated PSAs of
Schwantes et. al. (U.S. Pat. No. 6,592,990) or the encapsulated
tacky adhesives of Eichel (U.S. Pat. No. 2,986,477), or two- or
more part adhesive systems, such as solvent based encapsulated
adhesive systems as in Roesch et. al. (U.S. Pat. No. 5,922,798) and
Eichel (U.S. Pat. No. 2,907,682) or, more commonly, the liquid
curable systems as in Bachmann et. al. (U.S. Pat. No. 3,814,156 and
U.S. Pat. No. 3,826,756), Chao (U.S. Pat. No. 6,375,872) and Usami
et. al. (U.S. Pat. No. 5,397,812). With the former, crushing the
microcapsules makes the encapsulated adhesive available for
effectuating a bond. In the latter, crushing the microcapsules
merely creates the opportunity for the adhesive to activate or be
formed. For example, in the solvent based systems the microcapsules
may contain, or one type may contain, a solvent that dissolves or
renders tacky an adhesive material that exists in a separate
microcapsule, as a particle or as the binder that holds the
microcapsule to the surface. When the solvent microcapsule is
crushed, the solvent is released so as to `activate` the adhesive.
Alternatively, with the curable systems, cure cannot be initiated
or activated until the necessary curatives, whether they be
activators, catalysts, initiators or whatever, come in contact with
each other and/or the polymerizable components. Crushing the
microcapsules allows for all such constituents to come into contact
so that cure can be effectuated and the adhesive or sealant formed
in-situ.
[0012] As mentioned, the more common of the encapsulated adhesives
are the two-part liquid curable systems. Like the in-line applied
liquid curable systems mentioned previously, these encapsulated
adhesives can be custom formulated to fit any number of particular
applications/end-uses and/or achieve a multitude of performance
properties. Yet, despite their broad properties and performance
profiles, these adhesive have found very limited commercial
applications. By far, the most common use of these materials is in
mechanical fastening applications, either threaded assemblies or in
retaining applications. In the former, activation is achieved by
the threading action. In the latter, activation is achieved as a
result of the assembly of the two parts to be bonded and is most
often associated with insertion assemblies. For example, Bonutti
(U.S. Pat. No. 4,750,457) employs an encapsulated adhesive in the
grooves set in the sidewall of an engine cup plug that is to be
inserted into the receiving hole of an engine block. An
interference fit deforms the grooves leading to the fracturing of
the microcapsules and a flow of the liquid components contained
therein. Similarly, Muller et. al. (U.S. Pat. No. 4,100,954) and
Mederski (U.S. Pat. No. 5,965,866) employ encapsulated adhesives in
the recesses of a body or card wherein the force of inserting a
dowel or microchip, respectively, into the recess crushes the
microcapsules, thereby initiating cure of the adhesive
material.
[0013] The use of encapsulated adhesives has also been found with
the bonding of rigid flat or planar substrates, albeit in very
limited applications. Since activation is initiated by crushing of
the microcapsules and the microcapsules themselves are of extremely
small diameters, their use, in this regard, is limited to
substrates whose bonding surfaces are planar or, if contoured,
whose contours mirror image one another so that the two mate
together with minimal gap at the bondline or bond interface. If
gaps exist which are greater than the diameter of the microcapsules
or, depending upon the fragility or rigidity of the capsule walls,
even greater than three quarters the diameter of the microcapsules,
there may be insufficient release of the curable components so that
no or poor bonding occurs. On the other hand, if the mating is
perfect and no gap exists whatsoever, then there is concern that
all or substantially all of the liquid adhesive material will be
squeezed out under the pressure used to crush the microcapsules.
Here, remnants of the microcapsule walls help maintain a gap
between the mated surfaces to preclude all the adhesive material
from being squeezed out under the mating pressure. Even so, a
substantial amount of adhesive material may be pressed out of the
bondline resulting in poor bond strengths as well as excess
adhesive that must be cleaned up.
[0014] A growing area of use for encapsulated adhesives is in the
bonding of prous or semi-porous, flexible sheet media, especially
paper and paper products as well as woven and non-woven fabrics,
sheets and web type products. For example, Akridge et. al. (U.S.
Pat. No. 5,794,409) and Haugwitz (U.S. Pat. No. 4,961,811) employ
encapsulated liquid curable adhesives in the production and/or
closure of paper envelopes for letters, junk mail and the like.
More recently, Schwantes et. al. (U.S. Pat. No. 6,592,990), employ
encapsulated, in-situ formed PSAs for label bonding applications.
Activation of the adhesive is typically accomplished by passing the
mated surfaces through one or more pinch rollers, under one or more
stationary blades, past a set of rotatable discs or a series of
sets of rotatable discs, or a combination of the foregoing (See,
e.g., Wells et. al., U.S. Pat. No. 6,726,796), which operation
fractures the microcapsules and spreads the adhesive between the
two mated substrates. Alternatively, at least with the in-situ
formed PSAs, the aforementioned activation means may act directly
upon the pre-applied adhesive prior to mating the substrates to be
bonded.
[0015] Despite the success of such systems, these too have
limitations, particularly with respect to the encapsulated liquid
curable adhesives. For example, due to their low viscosity, liquid
curable compositions have a tendency to wick into the porous
substrates leaving little curable material in the bond gap or
interface to create the bond. This is not as significant a problem
with thinner media and very planar surfaces as found with
conventional paper envelopes where the liquid materials often
saturate the immediate surface layer of the paper, which saturation
provides sufficient adhesive material to effectuate the bond.
However, more significant concerns and problems are found with
thicker media such as paperboard and especially cardboard, where
the liquids can be absorbed or wicked deep into the subsurface,
leaving little, if any, liquid curable material at the interface,
and certainly an insufficient amount to address surface
irregularities often found with these materials. On the other hand,
some degree of porosity or surface irregularity may be important
for those substrates wherein the pre-applied adhesive is to be
activated by the use of the aforementioned pinch rollers, blades
and rotatable discs; otherwise, if such pores were not present to
serve as receptacles for the adhesive, such means would have a
tendency to push away, squeeze out or scrape off the adhesive
materials leaving little at the bondline or bond interface.
[0016] Another factor limiting the use of encapsulated adhesives is
the inability to supply sufficient pressure to rupture the
microcapsules and/or the poor efficiency with which the capsules
are ruptured. Exacerbating the problem is the use of thicker
capsule walls as is often found with traditional encapsulated
adhesives and sealants in order to avoid premature fracturing.
These problems are especially problematic with substrates like
paper, cardboard, and the like, especially in thicker sections,
that absorb or cushion the pressure that may otherwise be exerted
by activation means as described above. Making adjustments to
increase the pressure will have the deleterious effect of marring
or otherwise deforming the substrates. Substrates that are rigid
have a similar problem but for a different reason. Specifically,
while the pressure exerted on the rigid substrate passes through to
the bond interface, if the substrate surfaces are irregular, there
may be gaps at the bond interface where no matter how much pressure
is supplied, no fracturing of the microcapsules in the gaps occurs.
Thus, again, poor bonding or areas of no bonding may exist.
[0017] Though some of the aforementioned problems and concerns are
lessened in systems like Wells et. al. wherein a mechanical
activator means is seen acting directly upon the encapsulated
adhesive materials, such a configuration or process is not typical
of nor applicable to the majority of pre-applied encapsulated
adhesives. Like conventional activation apparatus and methods,
Wells et. al. rely upon compressive forces to fracture the
microcapsules; however, since Wells et. al. act directly upon the
adhesive, rather than the mated substrates, additional concerns
arise and accommodations need to be made to avoid scraping or
squeezing all the activated adhesive or sealant off the substrate
surface. Here, the angle of the activator means to the substrate
surface is very low to enable a mashing of the pre-applied adhesive
or sealant as well as allow for the activated adhesive or sealant
to pass under the activator means. In any event, the apparatus of
Wells et. al. is further limited to those applications which can
accommodate or only need a thin film of adhesive for effectuating a
bond.
[0018] Despite the many attributes of encapsulated curable adhesive
systems, particularly with respect to the ability to remove the
dispensing of liquid and/or molten adhesives from assembly lines,
current technology has not advanced to the point where such may be
used across a broad spectrum of substrates and applications. For
example, limitations on microencapsulation technology, particularly
with respect to the difficulty in, if not inability to,
microencapsulate highly viscous materials, effectively restricts
the creation of encapsulated adhesives and sealants to those of low
viscosity liquid materials. Regardless, perhaps the key shortfall
in such technology has been with respect to the activation of
encapsulated adhesives. As noted above, most commercial
applications rely upon the mating of the substrates to effectuate
the bond, either through the rotation or threading action of
threaded assemblies or the forced insertion of one element into
another in the retaining applications. While rollers, blades and/or
rotating discs, as mentioned in Wells et. al. above, facilitate the
use of such encapsulated adhesives on certain substrates, their use
on rigid and/or non-porous substrates is suspect. Furthermore,
because such devices provide only a thin film of adhesive material,
they do not allow for their use on non-planar substrates or
substrates where gaps may exist, either due to design, poor quality
control, or natural flex forces in the materials from which they
are made.
[0019] Thus, it would be desirable to and there is a need in the
industry for a means for activating or re-activating a pre-applied,
heat activated thermoset or thermoplastic adhesive or sealant
composition which means directly transfers heat to the adhesive or
sealant composition without concern for heating, particularly to
adversely high temperatures, areas of the bonding substrate outside
of the bonding area and which means has minimal heated surface area
so as to minimize the possibility that workers in the area or
working on the assembly line will be burned or exposed to the high
temperatures.
[0020] In another respect, it would be desirable to and there is a
need in the industry for a means for activating a pre-applied
adhesive material that does not require the use of heat,
irradiation, ultrasound, electromagnetic energy, etc., for
effecting activation or re-activation of the adhesive composition
and where, if heat were employed, such heating is merely ancillary
to the activation or re-activation of the adhesive and of
relatively low temperature and limited duration.
[0021] Further, it would be desirable and there is a need in the
industry for a means for activating a two-part pre-applied curable
or polymerizable adhesive or sealant composition as well as for
effectively and efficiently releasing an encapsulated adhesive or
sealant composition, which means is simple to employ and cost
effective and which is able to do so in other than as a thin film.
In particular, it would be desirable and there is a need in the
industry for a means for effectively activating a two-part,
pre-applied adhesive or sealant composition, most especially an
encapsulated liquid curable adhesive or sealant composition, that
provides for excellent intermixing of the components thereof,
especially those that are of higher viscosity and/or are
non-flowing under ambient conditions, as well as a high degree of
capsule fracture, where appropriate, while also leaving the
activated adhesive on the substrate in a given profile or bead,
especially one of a thickness that is of the same thickness as or
thicker than the original pre-applied material. In following, it
would be desirable and there is a need for such a means that also
has the ability to deposit the activated adhesive in a customized
bead of a given thickness for the particular end-use application to
which it is applied.
[0022] Finally, it would be desirable and there is a need in the
industry for a bonding method and apparatus which avoids the need
to dispense in-line liquid curable or molten adhesive or sealant
materials and which provides for high speed bonding applications
with minimal capital investment, particularly as compared to
current systems for activating pre-applied adhesive and sealant
compositions. Furthermore, it would be desirable and there is a
need for a high-speed industrial bonding method and apparatus that
is able to employ a pre-applied adhesive or sealant composition,
particularly one of a thin profile or thickness, and create,
in-situ, an activated bead of adhesive or sealant material of a
defined profile and/or thickness so as to accommodate the bonding
of substrates that do not have planar or mating surfaces,
especially those wherein the bonding areas have gaps and/or the
whole of the bondline has a gap.
SUMMARY OF THE INVENTION
[0023] In accordance with the practice of the present invention
there is provided an activator means comprising an activator head
having at least one surface or face thereof . . . an activator
face, having a plurality of features which features engage and lift
a pre-applied adhesive or sealant composition from a substrate,
directly or indirectly activate or re-activate said adhesive or
sealant composition, and direct the flow or movement of the same so
as to redeposit the activated or reactivated adhesive or sealant on
the substrate in a defined pattern. The features on the activator
face are in the form of projections extending from the surface of
the activator face, alone or in combination with one or more
recesses or channels. These projections serve to lift the
pre-applied adhesive or sealant composition from the surface of the
substrate to which it is applied, to disrupt or create shear forces
in the flow of the adhesive or sealant composition in the activator
means, and/or to direct the flow of said adhesive or sealant
composition. The number, shape and size of the projections depend
upon the composition of and the pattern of the pre-applied adhesive
as well as, in part, the desired pattern or profile of activated
adhesive to be left on the substrate following activation. Suitable
shapes for the projections include, for example, linear projections
such as dams, ridges, herringbones, chevrons, etc. as well as
non-linear projections such as hemispheres, hemi-ovals,
crosshatches, etc. When dams and ridges or other linear projections
are employed, it is preferred that they be aligned at an angle
relative to the centerline axis of the activator face to allow for
the continuous flow of the adhesive along and past the projections.
Though any combination of such projections will provide some degree
of activation, it is preferred that the projections include at
least two linear projections, especially in a herringbone pattern,
or at least one linear projection in combination with one or more
other projections. More preferably, the projections will include
two or more linear projections, preferably in a herringbone or
chevron pattern in combination with one or more other type
projections. The use of a plurality of dams and/or ridges alone or
in combination with other profiles is particularly beneficial for
use with pre-applied two-part curable or polymerizable systems,
especially encapsulated systems, as these combinations of features
serve to ensure intimate mixing of the components of the adhesive
or sealant composition and, where applicable, excellent fracturing
of the microcapsules.
[0024] Notwithstanding the foregoing, it is also possible that one
or more linear projections may be aligned perpendicular to the
centerline axis of the activator face provided that either (a) the
projection is of sufficiently short length that adhesive
accumulated in front of the projection as the substrate advances
relative to the activator face is able to flow around and past the
ends of the projection or (b) the activator is a reciprocating
activator wherein the reciprocation is perpendicular to or
essentially perpendicular to the centerline axis so that the
reciprocation motion in combination with the relative lateral
movement of the activator to the substrate facilitates the flow of
the adhesive around and past the ends of the projection. Such
projections, however, though possible, are not preferred.
[0025] Optionally, the features on the activator face may include
one or more recesses which recesses are most often immediately
forward the dams or ridges so as to provide a temporary retention,
collecting and/or mixing area for the adhesive or sealant
composition before exiting the recess. Alternatively or in addition
thereto, the recess may be in the form of one or more defined
channels in the activator face, posterior to the aforementioned
projections, which channels help direct or determine the flow path
of the adhesive or sealant as well as provide additional space in
which the adhesive or sealant composition collects and mixes. These
channels, in combination with the substrate surface, define a die
that corresponds to the adhesive pattern and profile to be left on
the substrate following activation.
[0026] The activator may also have incorporated therein or
associated therewith a sensing and motor means which enables the
activator face to maintain contact with or at a defined distance
from the surface of the substrate upon which it is acting, even if
the substrate thickness varies from one article to another or even
within a given article. In essence, the sensor will detect changes
in the thickness of the substrate or the height of the substrate
surface upon which the adhesive lies and relay those readings to a
processor which, in turn, activates a motor or lift means that then
raises or lowers the activator face, as appropriate. Preferably,
the sensor and motor means maintains the activator face in touch
contact with the substrate, but without a force that may otherwise
result in the activator face marring the substrate surface upon
which it acting or cause the activator face to catch the substrate
causing a jam or temporary snag in the system.
[0027] Depending upon the nature of the adhesive or sealant
composition with which the activator means is to be employed, the
activator face may incorporate a heating means or be in a heat
transfer relationship with a heating means so that the activator
may transfer heat to the adhesive or sealant composition in contact
therewith. In the case of heat activated or re-activatable adhesive
and sealant compositions, the heat to be generated must be high in
order to achieve the heat needed for melting or activating the
adhesive or sealant composition. In the case of curable or
polymerizable adhesive and sealant compositions which do not
require the presence of heat to initiate or activate cure, it may
be desirable to heat the activator face to a low temperature to
facilitate flow of the adhesive and sealant composition through and
past the projections and recesses. In both instances the heating
element may be incorporated into or comprise a part of the
activator means or may be in a heat transfer relationship with the
activator means so long as the needed heat energy is provided to
the activator face.
[0028] The activator of the present invention may be incorporated
into any number of existing bonding apparatus in place of current
activator means and/or in place of liquid or molten adhesive,
especially hot melt adhesive, dispensing means and such apparatus
may be readily modified to accept such activator means. In doing
so, the activator means may be held in a fixed arrangement so that
it does not move relative to the substrate upon which it acts or it
may be attached to a robotic arm or like apparatus that controls
the movement of the activator means relative to the substrate
during the activation process and/or enables the activator means to
be retracted from its fixed active position to a stand-by
position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic representation of the orientation of
the activator means to a substrate during operation.
[0030] FIG. 2 is a perspective plan view of an activator body
having an attached activator face.
[0031] FIG. 3 is a partial plan view of an activator face having
two dams in a herringbone pattern.
[0032] FIG. 4 is a partial plan view of an activator face having
two dams in a herringbone pattern and a plurality of hemispherical
bumps.
[0033] FIG. 5 is a cross-section of the activator face of FIG. 4
taken along line 4-4.
[0034] FIG. 6 is a partial plan view of an activator face having
two dams in a herringbone pattern and a bead splitter.
[0035] FIG. 6(a) is a photo of the adhesive pattern generated by
the activator face of FIG. 6.
[0036] FIG. 7 is a partial plan view of an activator face having a
front inverted "V" dam and two trailing linear dams in a chevron
pattern.
[0037] FIG. 7(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 7.
[0038] FIG. 8 is a partial plan view of an activator face having a
plurality of circular projections, a chevron dam and a bead
splitter.
[0039] FIG. 8(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 8.
[0040] FIG. 9 is a partial plan view of an activator face having a
plurality of ovoid projections, a chevron dam and a bead
splitter.
[0041] FIG. 9(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 9.
[0042] FIG. 10 is a partial plan view of an activator face having a
front semicircular dam and a wide mouth chevron dam.
[0043] FIG. 11 is a partial plan view of an activator face having
semicircular dam, a chevron dam and a wide bead splitter.
[0044] FIG. 11(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 11.
[0045] FIG. 12 is a partial plan view of an activator face having
semicircular dam, a chevron dam and two series of bead
splitters.
[0046] FIG. 12(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 12.
[0047] FIG. 13 is a partial plan view of an activator face having a
plurality of rows of inverted "V" dams in a staggered
relationship.
[0048] FIG. 13(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 13.
[0049] FIG. 14 is a partial plan view of an activator face having a
semicircular dam, a stepped chevron dam and a bead splitter.
[0050] FIG. 15 is a partial plan view of an activator face having a
plurality of repeating splitter and chevron dams.
[0051] FIG. 16 is a partial plan view of an activator face having a
semicircular dam and a chevron dam leading to a broad channel.
[0052] FIG. 17 is a partial plan view of an activator face having a
semicircular dam, a chevron dam and a bead splitter leading to two
channels.
[0053] FIG. 18 is a partial plan view of an activator face having a
single linear dam parallel to the centerline axis of the activator
face.
[0054] FIG. 18(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 18.
[0055] FIG. 19 is a partial plan view of an activator face having a
plurality of linear dams parallel to the centerline axis of the
activator face.
[0056] FIG. 19(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 19.
[0057] FIG. 20 is a partial plan view of an activator face having a
crosshatch pattern projection.
[0058] FIG. 20(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 20.
[0059] FIG. 21 is a partial plan view of an activator face having a
combined crosshatch and chevron pattern projection.
[0060] FIG. 21(a) is a picture of the adhesive pattern generated by
the activator face of FIG. 21.
[0061] FIG. 22 is a picture of an assembly apparatus employing an
activator means in accordance with the present invention.
[0062] FIG. 23 is a picture of the sled means of the assembly
apparatus of FIG. 22.
DETAILED DESCRIPTION
[0063] The present invention is directed to novel activator means
for use in activating pre-applied adhesives. The activator means
may exist in several different configurations or embodiments
depending upon the physical nature, chemical composition and
activation methodology associated with the pre-applied adhesive
composition. For example, as will be discussed in greater detail
below, in one embodiment the activator means may include, or be
associated with, in a heat transfer relationship, a heating means
that generates sufficient heat to activate or re-activate a
pre-applied heat activatable or re-activatable thermoset or
thermoplastic adhesive or sealant composition. On the other hand,
the activator means may be free of any heating means, either as an
integral part thereof or in a heat transfer relationship therewith,
or, if heating is desired, the heating means is only capable of
generating low temperatures that have the ability to enhance flow
of the pre-applied adhesive material past and through the activator
face of the activator means but is otherwise insufficient or
unnecessary to activate or re-activate the pre-applied adhesive.
The activator means may also include or be associated with a
reciprocating means and/or vibratory means for providing movement
to the activation means relative to the substrate surface upon
which it is acting during activation. However, the key element
common to the various embodiments of the activator means of the
present invention is the presence of an activator face which
activator face acts directly upon the pre-applied adhesive or
sealant material and includes a plurality of features in the form
of projections extending from the surface thereof, alone or in
combination and associated with one or more recesses or channels,
which features define a flow path for the activated or re-activated
adhesive or sealant composition.
[0064] FIG. 1 provides a schematic representation of the relative
orientation of the activator means to a substrate upon which it is
it to act. As shown in FIG. 1, the activator means 1 has an
activator face 2 (the underside of the means as shown) having one
or more projections 3 extending from the surface thereof. The
activator means has two axes, a centerline axis A and a transverse
axis B. The substrate 4 to be acted upon has a pre-applied adhesive
band 5. The pre-applied adhesive band 5 has a centerline axis
parallel to the centerline axis A of the activator means. During
activation, the relative motion of the substrate to the activator
means will be in the direction denoted by the arrow C, along the
centerline axis. In certain embodiments, the activator means may
also have a reciprocating motion whereby the activator means also
moves along the transverse axis B, though such movement will be
very small. Where the reciprocating motion is essentially
vibrational in nature, the movement along the transverse axis will
typically be on the order of nanometers. Where the reciprocating
motion is largely responsible for the flow or positioning of the
pre-applied adhesive and, where present, the crushing of the
microcapsules, the movement along the transverse axis will be on
the order of fractions of millimeters to millimeters. In this
circumstance, the extent of the movement from one extreme to the
other will define the bond width. Consequently, it is preferred
that the reciprocation motion be as small as feasible or as needed
for the given bond desired.
[0065] As discussed in more detail below, reciprocation of the
activator means will generally enhance the intermixing of the
components of the adhesive or sealant composition; however,
reciprocation is particularly important for those activator faces
where the projections are aligned in such a manner that gaps exist
between the projections when looking down the activator face
parallel to the centerline axis. The presence of such gaps means
that pre-applied adhesive on a substrate in regions corresponding
to the gaps will not be acted upon absent a transverse movement of
the activator face, preferably transverse movement in each
direction that is at least one-half the width of the gap.
Reciprocation of the activator means is also important, if not
critical, where the projections are linear or, if aligned in a
linear arrangement, non-linear and parallel with or nearly parallel
with the centerline axis. Reciprocation may also be important for
use with those linear projections that are wide and perpendicular,
or nearly perpendicular, to the centerline axis. In this latter
respect, reciprocation will assist with the movement of the
activated adhesive or sealant past the ends of the linear
projection. This is especially important where the projection is
nearly as wide or wider than the band of the pre-applied adhesive
or sealant upon which it is acting. Those skilled in the art will
readily recognize when such reciprocation is needed in light of the
teachings contained herein.
[0066] As noted, the activator means comprises, at a minimum an
activator body and at least one activator face. The activator face
may be integral with and form a part of the activator body or, as
more clearly shown in FIG. 2, it may be a separate element that is
fastened or otherwise bonded to the activator body 6. FIG. 2 shows
an activator face 2 having two linear projections 3 in a
herringbone relationship.
[0067] Although not shown in FIG. 2, the activator body will also
comprise one or more attachment means by which the activator body
is attached to a larger apparatus or component thereof for the
in-line activation of a pre-applied adhesive on a substrate. For
example the activator body may be attached, directly or indirectly,
to a robotic arm or means that advances and retracts the activator
means to and from the active or operational position in an
automated bonding process. Alternatively, the activator body may be
attached, directly or indirectly, to that part of the frame or
superstructure of an automated bonding system and apparatus that is
defined as the activation station. In the latter, during use, the
activator means would be held substantially stationary while the
substrate being acted upon passes the activator face.
[0068] As discussed in greater detail below, the activator means
may also be mounted upon or have associated therewith a manually
operated or motorized lift means, with or without associated sensor
means, that allows for an adjustment of (a) the distance or gap
between the outer surface or peaks of the features or projections
on the activator face and the surface of the substrate upon which
it is to act and upon which the pre-applied adhesive lies or, as
the case may be, (b) the amount of force of such features on the
substrate surface when the two are in a touch relationship.
Alternatively or in addition thereto, as discussed above, the
activator means may be associated with a reciprocating means which
provides reciprocating movement to the activator face which
movement is preferably perpendicular to the centerline axis of the
activator face.
[0069] The activator face and body may be composed of any number of
materials, depending upon the specific nature and use of the
activator means, and may be the same or different materials.
Suitable materials include metals, ceramics, plastics, and
carbides, especially metals like aluminum and anodized aluminum.
The specific selection of the material depends, in part, upon the
particular end-use application for the activator means and the
nature of and sensitivity to or reactivity with the adhesive or
sealant material to be acted upon. For example, if the activator
means is to have heating capability then the activator body and the
activator face must be made of a material that has excellent heat
resistance and heat transfer characteristics so that the requisite
heat is present at the surface of the activator face for transfer
to the pre-applied adhesive or sealant material without affecting
the integrity or life of the activator means.
[0070] On the other hand, if the adhesive or sealant composition is
a redox curable adhesive or sealant composition, it may be
desirable to avoid certain metals, especially those containing or
based on iron or iron compounds, which may cause adhesive or
sealant to bond to the activator face. Alternatively, if such
metals are employed, then it may be desirable to also coat the
activator face with an inert (relative to the curable composition)
coating composition to ensure that the metals or metal ions are not
available to the curable composition. In essence, the selection of
the material comprising the activator head, especially the
activator face, should be such that it, either in its virgin state
or an aged state, does not adversely interfere with the cure or
polymerization of the curable or polymerizable material. In this
regard, it is to be understood that interference could be an
inhibitory or an acceleration effect on cure.
[0071] Another factor to be considered in choosing the composition
of the activator face, especially the projections thereon, is the
physical nature of the adhesive or sealant composition as well as
the abrasiveness of the substrate surface upon which it is to act.
In this respect, remnants of the microcapsule walls in the case of
pre-applied encapsulated adhesives or inorganic fillers of other
adhesives may generate excessive wear on the activator face,
especially those made of plastic materials.
[0072] Finally, as noted above, the activator face may also have a
coating applied thereto. These coatings may serve as a barrier to
prevent exposure of the adhesive composition to the composition of
the activator face and/or have slip or non-bonding characteristics
so that the activated adhesive or sealant flows past and through
the activator face without bonding or clogging the same. For
example, the coating may be a release type coating such as a
silicone material or polytetrafluoroethylene. Typically the coating
will be from about 3 to about 6 mils in thickness; however thinner
coatings are also suitable.
[0073] As previously noted, the activator face may be a part of the
activator means or a separate component that is attached thereto, .
. . mechanically, chemically or otherwise. Where the activator face
is a part of the activator means, the pattern representing the
activator face may be machined into that surface of the activator
means which serves as the activator face. Alternatively, where the
activator means or the body thereof is prepared by a molding
operation, the pattern representative of the activator face may be
formed concurrent with the molding of the activator means. Where
the activator face is a separate component that is attached to the
activator body, the activator face, including the features to be
incorporated thereon or therein, may be machined out of a stock
material or made by a molding process.
[0074] The key or critical aspects of the activator means of the
present invention are the features on or defining the surface of
the activator face. These features are in the form of upwardly
extending projections on the surface of the activator face, alone
or in combination with one or more recesses or channels that
further define the flow path, or a portion thereof, of the adhesive
or sealant material through the activator face. Most critical are
the projections which engage and lift the pre-applied adhesive or
sealant composition from the substrate, directly or indirectly
activate or re-activate said adhesive or sealant composition, and
direct the flow or movement of the same so as to redeposit the
activated or reactivated adhesive or sealant on the substrate. As
used herein, the concept of lifting the adhesive or sealant from
the substrate refers to the mobilization of the same, though it
remains in contact with the substrate surface. Although not
critical, as more clearly described below, the addition of channels
posterior to the aforementioned projections enables one to then
deposit the activated adhesive in a defined pattern and
profile.
[0075] The projections serve many functions depending upon their
shape, size and orientation on the activator face as well as the
nature of the pre-applied adhesive. Foremost, as already noted, the
projections must lift and/or push the pre-applied adhesive or
sealant composition from the surface of the substrate to which it
is applied and, in the case of encapsulated adhesives, help
fracture the microcapsules to release the contents thereof. Where
the adhesive or sealant composition is a curable or polymerizable
composition, the activator face will also preferably include
projections that alter or disrupt the flow path, thereby creating
shear or mixing within the curable or polymerizable composition,
and/or, if appropriate, participate in the fracturing or crushing
of the microcapsules in the case of encapsulated adhesive or
sealant compositions. The activator face may also include one or
more projections that serve to collect and deposit the activated
adhesive into a single bead or, depending upon the number and shape
of such projections, a plurality of beads. In this respect, the
projection may also comprise the forward end of a profile channel,
as discussed below. Alternatively, the activator face may include
one or more projections that divide a single bead into two or more
beads. Of course, it is clear that many of these projections serve
multiple functions at the same time. For example, the projections
that lift and collect the pre-applied adhesive or sealant will most
likely also create a flow within the mass of material collected,
thereby aiding in the mixing of the same.
[0076] Generally speaking, the shape, size, orientation and
position of any given projection on an activator face are dependent
upon the purpose and function that it is to serve. The height of
the features varies depending upon the adhesive, the desired bead
of adhesive arising from the activator means, the line speed, the
substrate being acted upon, etc. The features of an activator means
suitable for use in closing paperboard containers, such as cereal
or cookie boxes, will typically have a height of about 18 mils
whereas features twice that height and more may be necessary for
sealing a corrugated cardboard container. As discussed in greater
detail below, these projections are of three overlapping classes:
linear projections, diversionary projections and splitters. Among
the shapes such projections may take include, but are not limited
to, linear dams and ridges, chevrons, herringbones, "V" shaped or
crescent shaped dams or ridges, pyramids, hemispheres,
hemispheroids, cylinders, etc. Though a given activator face may
have a plurality of identical or like shaped projections, it is
preferred that a combination of different shaped projections be
employed, particularly where the material to be acted upon is an
encapsulated composition. Such variation helps promote good
microcapsule fracturing, intimate mixing of the components thereof,
as well as good bead formation of the activated material. As will
become readily apparent, those skilled in the art and having the
benefit of the teachings herein will readily be able to select the
appropriate projections and design the proper orientation of those
projections to address their particular needs.
[0077] Perhaps the most preferred of the projections to be
incorporated into or onto the activator face are those that are
linear, such as dams and ridges. These linear projections are
especially suited for lifting the pre-applied adhesive or sealant
from the substrate surface and create flow and mixing of the
components as the adhesive passes along the length of the linear
projection. When used alone or posterior to other projections, they
also serve to collect and direct the flow of the activated adhesive
or sealant, preferably creating one or more beads of the activated
adhesive. Though the prior art has employed straight edge blades,
as noted in Wells et. al. above, the linear edge of the blade is
perpendicular to the centerline axis of the adhesive upon which is
acts and is angled relative to the surface of the substrate upon
which it acts so that the microencapsulated adhesive is crushed and
allowed to pass beneath the blade edge. Depending upon the force
applied to the blade edge, fracturing may be poor; however, if one
increases the pressure to ensure good fracturing, then the adhesive
film arising on the posterior side of the blade is thin, most
likely much thinner than the original pre-applied adhesive film
upon which the blade acted. In essence, activation under the prior
art is accomplished by a mashing action that, besides forming thin
films of adhesive, limits the degree of mixing of the components of
the microcapsules. In Wells et. al., for example, the mixing of the
components is dictated solely by the flow generated by the
compressive forces, a flow that is essentially linear extending
outward from and forward of the activator element, e.g., the blade
or roller. This is in stark contrast to the activator means of the
present invention where the various projections create non-linear
flow and shear within the mass of materials lifted from the
substrate surface
[0078] Additionally, in contrast to the prior art technology, the
linear projections according to the present invention are not
aligned perpendicular to the centerline axis or, if one or more is,
their length is less than, preferably substantially less than the
width of the band of the pre-applied adhesive or, if as wide or
nearly so, the activator means has associated therewith
reciprocating means so that the ends of the linear dam at each end
of the reciprocation motion are within the pre-applied adhesive
band and/or the intended bond line. Generally speaking, if such
perpendicular linear dams are present in the activators of the
present invention, even with reciprocation, they will preferably be
very short so as to avoid the build-up of adhesive material on the
forward face thereof, which build-up will lead to poor deposits, at
least until the amount of build-up exceeds that amount the
projection can hold without it spilling past the ends of the
projection. Furthermore, such perpendicular linear projections
would be employed with one or more non-linear projections and/or
one or more angled linear projections. In essence, their primary
function would be to lift the pre-applied adhesive from the
substrate surface, not smear the adhesive as with the prior
art.
[0079] Though not preferred, the linear projections may also be
aligned parallel to the centerline axis of the activator means. As
shown in FIGS. 18 and 19, the activator face may have one or more
linear projections; however, in these cases the activator means
must reciprocate transverse to the centerline axis so that the
linear projections can act upon the pre-applied adhesive band.
Otherwise, only that adhesive in the line of contact between the
linear projection and the pre-applied adhesive will be activated.
The use of such lateral activation creates a bead of adhesive at
the end points of the reciprocation motion of each projection. The
extent of reciprocation, i.e., the size of the movement of the
activator face along the transverse axis, should be sufficient to
ensure that the full width of the band of pre-applied adhesive is
acted upon or, at a minimum, that the desired width of the intended
bondline is achieved. Though, as shown in FIG. 18, a single linear
projection could be employed, it is oftentimes preferable to employ
a plurality of such projections as shown in FIG. 19. This reduces
the extent or length of the reciprocation movement needed and helps
ensure that more adhesive is being activated, especially in
high-speed automated applications. As shown in FIGS. 18(a) and
19(a), while the single linear projection creates two parallel
beads of activated adhesive, a plurality of equally spaced linear
projections will create either X+1 beads or 2X beads, where X
represents the number of linear projections, depending upon the
extent of the reciprocation movement. Where a plurality of such
linear projections is employed, it is preferred that the
reciprocation motion be at least such that the furthest movement of
a projection in one direction overlaps with the furthest movement
of the neighboring projection in the opposite direction, i.e., the
reciprocating motion is such that the extreme edges of their paths
overlap with those of the neighboring projection. This will
generate X+1 beads and allow for a greater build up of the adhesive
beads. A shorter movement, i.e., where the paths do not overlap or
co-terminate, will typically generate 2X beads of lower a profile:
though, depending upon the viscosity of the activated adhesive or
sealant, the beads may flow and commingle to form a low profile,
wide bead.
[0080] Most preferably the linear projections, especially the dams
and ridges, will be set at an angle relative to the centerline axis
of the activator face. The specific angle of the linear projections
will depend upon a number of factors including the adhesive or
sealant to be acted upon, particularly taking into consideration
its flow characteristics and viscosity, as well as the number and
function of the linear projections, etc. Generally speaking, the
angles should not be so low that the width of the adhesive band
acted upon is too small to generate an adhesive bead of sufficient
volume. Conversely, too high an angle, e.g., near or at 90.degree.,
and the dam or ridge, particularly with long linear projections,
will impede the flow of adhesive leading to a buildup of the same
in front of the dam or ridge, which build-up will cause a
significant retention time and, in extreme situations, can cause
the face of the activator means to rise relative to surface of the
packaging substrate upon which is acting. The consequence of this
will likely be an uneven and/or irregular bead of activated
adhesive, including gaps therein, as well as areas of un-activated
pre-applied adhesive. Preferably, the angle of the dams or ridges
relative to the centerline of the pre-applied adhesive band will be
from about 20.degree. to about 70.degree., more preferably from
about 30.degree. to about 60.degree., most preferably from about
40.degree. to about 50.degree.
[0081] The orientation of the linear projections also plays an
important role in the performance and efficacy of the activators of
the present invention. Within limitations, as noted above, they may
be aligned in any number of different configurations, whether used
alone or in combination with other projections. For example, as
shown in FIGS. 3, 4 and 6, the linear projections may be aligned in
a herringbone configuration where the forward end of the posterior
projection overlaps the trailing end of the forward projection.
Alternatively, as shown in, for example, FIGS. 7-10, the linear
projections may be aligned so as to form a chevron. With this
configuration, it is preferred that one or more other projections
exist forward of and/or posterior to the gap at the tail end of the
chevron. These alignments allow for optimal collection and
depositing of one or more, as appropriate, substantially uniform,
linear beads of the activated adhesive or sealant. Alternatively,
as will be discussed below, one or more raised bands or beads of
activated adhesive or sealant may be formed by the selection of
certain chevrons in combination with one or more profile channels
in the activator face. Other alignments/designs for the linear
projections include cross-hatch designs, alone or in combination
with chevron patterns, as shown in FIGS. 20 and 21, respectively;
inverted "V"s, as shown in FIG. 13; and the like. Finally, one may
also employ a plurality of closely laid, stepped chevron dams, each
of which is successively higher than the preceding chevron dam.
This configuration is shown in FIG. 14 and provides excellent shear
and mixing since each successive chevron cuts deeper into the
pre-applied adhesive or sealant and creates high shear and mixing
forces.
[0082] The second type of projections incorporated into or
protruding from the activator face are those hereinafter referred
to as diversionary projections. These diversionary projections may
be of various shapes including, for example, pyramids, hemispheres,
hemispheroids, plateaus, etc. These diversionary projections are
especially suited for removing the pre-applied adhesive from the
substrate surface and for creating disruptions and shear in the
flow of the activated adhesive or sealant materials thereby
inducing more mixing thereof. When employed with encapsulated
adhesives, these diversionary projections also help in fracturing
the microcapsules and the release and intermixing of the
encapsulated materials. When employed with encapsulated materials
of the type wherein a curative is contained within a viscous, solid
or semi-solid carrier material, theses diversionary projections
also help knead and mash the carrier material, thereby exposing or
rendering available the curative contained therein. Compositions of
the latter type are disclosed in co-pending U.S. patent application
Ser. No. 11/216516, filed Aug. 31, 2005, hereinafter Schwantes et.
al., which is hereby incorporated in its entirety by reference.
[0083] Although not necessary, typically and preferably the
diversionary projections will be used in combination with at least
one linear projection, as shown in FIGS. 4, 8 and 9. In each of
these embodiments, the diversionary projections are primarily
responsible for mobilizing the pre-applied adhesive and, as
appropriate, fracturing the microcapsules, while the trailing
linear projections collect and direct the activated adhesive.
However, if the linear projections of the embodiments in FIGS. 4, 8
and 9 were removed, the resultant adhesive pattern would be in the
form of a plurality of low profile beads or ridges of the activated
adhesive. Furthermore, depending upon the alignment of these
diversionary projections, one may have the undesired consequence of
leaving strips of un-activated adhesive or sealant on the substrate
surface. As seen in FIG. 8(a), the lack of staggering and overlap
of the paths of the projections of the activator face in FIG. 8
results in strips of un-activated adhesive, shown as light colored
strips between the darkened activated areas. On the other hand, as
seen in FIG. 9(a), the activation pattern of the activator face of
FIG. 9 shows that all the pre-applied adhesive has been acted upon
as a result of the overlap of the activation paths. Thus, it is
preferred that the diversionary projections be tiered or set in a
plurality of rows each of which is off-set relative to the other so
that the work areas of the diversionary projections have overlap
with one another to ensure that all the pre-applied adhesive is
activated. Of course, another means to achieve this goal would be
to employ an activator means which has associated therewith a
reciprocating means so that the reciprocating motion of the
activator face ensures that all the pre-applied adhesive is acted
upon. Such motion would also increase the mixing of the adhesive
and would provide an adhesive pattern similar to that shown in FIG.
20(a).
[0084] As shown in FIGS. 8 and 9, any given activator face may
employ a plurality of different shaped diversionary projections.
Typically the height of each diversionary projection will be the
same, though such is not required. For instance, should different
diversionary means have different heights, those that are higher
will have a greater role in lifting and/or mobilizing the
pre-applied adhesive from the substrate as well as fracturing the
microcapsules, if present. On the other hand, those that are of a
lower profile will enhance the shear or alteration of the flow of
materials and, if applicable, aid in fracturing the microcapsules
as well as mashing and kneading the contents thereof.
[0085] The third class of projections, and one that overlaps with
the aforementioned classes of projections, especially the linear
projections, is characterized as the splitter projections. These
splitter projections are typically in the shape of crescents,
semicircles, and inverted "V"s and are posterior to either of the
aforementioned linear and/or diversionary projections. They serve
two key functions: to activate any remaining pre-applied adhesive
in its path that has yet to be acted upon and, more importantly, to
divide the activated adhesive bead or, if none, the activated
adhesive film formed in front of it into two or more beads. Of
course, the splitter projections also assist with ensuring fracture
of the microcapsules and creating good flow of the adhesive
materials for intimate mixing. The width of the splitter projection
will determine the spacing between the beads created by that
projection. For example the short crescent projection of FIG. 6
produces two closely arranged parallel beads of activated adhesive
as shown in FIG. 6(a). In contrast, the wide inverted "V" splitter
projection of FIG. 11 produces two widely separated parallel beads
of the activated adhesive as shown in FIG. 11(a). Alternatively, as
shown in FIGS. 12 and 12(a) and FIGS. 13 and 13(a), one may create
a larger number of beads by employing a series of cascading
splitter projections so that each of the split beads arising from
one splitter projection is subsequently split by a trailing
splitter projection.
[0086] The combination, number and/or size or length of the
projections, especially the linear projections, will also play a
role in the efficacy of the activator means. Though more
projections and/or longer linear projections, especially, dams or
ridges, may increase the efficiency with which the adhesive is
lifted from the substrate and increase the degree of mixing of the
components before the activated adhesive is re-deposited on the
substrate, these factors will also affect the dimensions of the
activator face, and thus the activator, and, perhaps more
importantly, the retention time of the adhesive or sealant in the
activator. In this respect, it is especially desirable to keep the
flow path, and thus the retention time, as short as possible: the
shortest possible flow path being a straight line which is only
achieved with projections that are parallel to the centerline axis
and activated by a reciprocation motion. However, since the
preferred embodiments of the present invention involve a transverse
movement of the adhesive material during activation, said
transverse movement, in this respect, being due solely to the
shapes, size, number and orientation of the projections, there is
inherently a displacement of the adhesive from the point at which
it was first acted upon by the activator face to a point further
along, though not necessarily on, the centerline axis. The extent
of this retention time and, thus, the displacement of the adhesive,
will depend upon the complexity of the activator face, especially
the length of transverse movement of the adhesive in the activator
face, and the viscosity of the materials being acted upon. For
example, although the activator face shown in FIG. 15 will provide
much more intimate mixing of the adhesive or sealant composition
than that provided by the similar activator face shown in FIG. 10,
the latter will have a much shorter retention time than that of the
latter. Thus, this aspect must be taken into consideration in
designing an activator face for a given application. For example,
in large applications, e.g., on the flaps of 10 ft.sup.3 bulk
cardboard boxes, a bead displacement of an inch or more is not
critical; however, with small boxes, e.g., a box whose size is on
the order of a package of cigarettes, such a displacement is not
acceptable: though displacements on the order of a half inch or
less could be tolerated.
[0087] Alternatively, or in addition thereto, depending upon the
nature of the activated adhesive and its affinity for the activator
face, the flow path along and past the projections must be primed
before the activated adhesive or sealant finally passes the end of
the last projection and is deposited on the substrate. In this
instance, all or a portion of the pre-applied adhesive from the
first substrate to pass through the activation station may remain
in the activator means until the next substrate with pre-applied
adhesive passes through the activation station whereby the newly
collected adhesive material `pushes` the previously retained
activated material through the activator means and onto the
substrate. In essence, the adhesive material from the first
substrate primes the pump for the next. Here, the retention time is
substantially longer as it not only reflects the delay due to the
transverse motion of the adhesive material within the activator
face but also reflects the time interval between activation on one
substrate to the next. This happenstance is important in selecting
the appropriate pre-applied adhesive composition in order to avoid
premature curing in the activator means.
[0088] Another type of feature that may be incorporated into the
activator face are recesses which may be in the form of pools
and/or channels in and among the projections or profile channels
that define an exit path or exhaust for the adhesive from the
activator face. In the former, these pools and channels lie below
the plane that is defined by the base of the projections and serve
as reservoirs and mixing chambers for the adhesive or sealant
composition as well as pathways for the flow of the activated
adhesive or sealant through and past the projections. Such
channels, if present, are shallow so as to minimize their volume;
thus, reducing their impact on the retention time.
[0089] On the other hand, profile channels that define the exit
path for the activated adhesive or sealant are desirable,
especially when one is endeavoring to create one or more adhesive
or sealant beads of defined geometry or profile. These profile
channels act like funnels, collecting the activated material and
allowing it to pass through as one or more defined beads. Typically
these profile channels will have a chevron or chevron-like shaped
forward end that leads into a narrowed pathway extending the
remaining length of the activator face. The width of the profile
channels and their depth, i.e., the height of the sidewalls, will
define the bead that arises from or is generated by the activator.
Initially the depth of the profile channel at the forward end of
the channel will be co-planar with the base of the projections;
however, as one traverses the length of the profile channel, the
depth may increase or decrease depending upon the ultimate bead or
beads desired. Increasing the depth of the profile channels,
preferably with a narrowing or tapering of the width of the
channels, creates raised or high, narrow beads of the activated
adhesive or sealant. Alternatively, decreasing the depth of the
profile channel, preferably with a broadening of the width of the
channel, creates low, broad bead of the activated adhesive or
sealant.
[0090] Additionally, although the viscosity of the activated
adhesive or sealant will affect its stability, the profile channels
may also be configured to generate beads of defined profiles or
cross-sections. For example, the sidewalls may be angled so that
they meet at the point of maximum depth, thereby generating a bead
of activated material having a triangular profile. Alternatively,
the sidewalls of the profile channels may be rounded so that a
rounded bead is generated. In this latter embodiment, the channel
looks much like a lengthwise cross-section of a typical funnel. In
essence, a cross-section of the profile channel at its tail end,
perpendicular to the centerline axis, defines the die from which
the activated adhesive or sealant is extruded and, therefore, the
beads of the activated adhesive or sealant that results from the
given activator. Of course, the viscosity of the activated adhesive
will also determine how well and long that profile is maintained
following its exit from the activator face. Such may be of little
concern in high speed industrial bonding applications since little
time exists between the time the substrate exits the activator
station and the mating step of the bonding process. Finally,
besides affecting the profile or the bead, the viscosity of the
activated adhesive in combination with its affinity for the surface
of the activator face relative to the substrate surface will also
affect the how well the material transverse through and are
expelled from the channels. In this latter respect, with low
viscosity materials the channel may cause a capillary action
whereby activated adhesive is retained in the channel until the
next charge and/or the combined forces/interactions may cause a
drawdown or stringing of the bead along the surface of the
substrate. Alternatively, with high viscosity materials the
cohesive strength and resistance to flow of the adhesive materials
will also affect retention of the same within the channels and the
need for repetitive charging for optimal dispensing or discharging
of the activated adhesive from the activator face. Again, with
proper selection of the adhesive material, one is able to address
these concerns, to the extent they are of concern.
[0091] As noted, a given activator face may incorporate one or more
profile channels defining the exit pathway. FIG. 16 shows an
activator face having a forward semi-circular or crescent dam
followed by profile channel whose entry is in the form of a
chevron-type dam that also serves as a linear projection that
lifts, collects and moves the adhesive or sealant composition. FIG.
17 depicts an alternate embodiment having two profile channels that
are fed by a chevron projection that is preceded by a semi-circular
or crescent dam. In this embodiment, the forward end of the common
wall of the profile channels acts as a splitter projection,
dividing and feeding the adhesive or sealant composition emanating
from the chevron into the two profile channels. Although, as shown,
the forward end of the channel, e.g., the chevron or chevron-like
entrance or collector, may serve as a linear projection, lifting
and mixing the adhesive or sealant, it is preferred that such
profile channels are employed in combination with one or more of
the other projections mentioned above, especially one or more
linear projections.
[0092] The dimensions of the activator face vary markedly depending
upon the volume or rate of application for the pre-applied adhesive
to be worked upon; the number, type and complexity of design or
pattern of the various features on the activator face; the pattern
and profile of the adhesive to exit the activator face; etc.; all
of which, in turn, are dependent upon the articles to be activated
and the bond or bond area to be formed. Certainly, to optimize the
utilization of a pre-applied adhesive or sealant material, the
width of active region of the activator face, i.e., that distance
along the transverse axis of the activator face from the outermost
projection or portion thereof on one side to the outermost
projection or portion thereof on the opposite side of the activator
face, will be at least as wide as the band or pattern of
pre-applied adhesive or sealant material upon which it is to act.
In high speed automated bonding lines, since there can be no
assurance that the pre-applied adhesive will be in the exact same
location from one lot of substrates to the other or that no
shifting, even minor, of the substrates occurs on the processing
line, the active width of the activator face should be somewhat
wider than the band of pre-applied adhesive to be worked upon.
Alternatively, one may apply a wider band of adhesive material than
is needed to deposit the desired bead to account for such offset
and ensure that enough adhesive material is acted upon.
[0093] The length of the activator face should be as short as
reasonably possible and practical for the given application. In
this respect, the dimension will depend upon the physical
properties of the adhesive or sealant, once activated, including
the cure speed; the type, length, number and complexity of the
features on the work face; the speed of the activation means
relative to the substrates upon which it acts; the amount of mixing
needed to ensure good cure speed and bond strength; the dimensions
and location of the pre-applied adhesive and the intended bondline;
etc. Generally speaking, by minimizing the length of the transverse
flow path, i.e., that distance the materials flow transverse to
centerline axis, and the volume or space of the flow path, one can
reduce the residence or retention time of the adhesive in the
activator face and, consequently, the displacement of the adhesive
along the centerline axis. Again, as noted previously, a reduced
residence time will coincide with minimal shift and, in the case of
curable and thermoset materials, ensure that the composition has
not cured or, since cure will have begun, that the degree of cure
is not beyond the point where the adhesive is no longer useful for
effectuating the bond.
[0094] Generally speaking, the dimensions and design of the
activator face are dependent upon a number of interrelated factors
and parameters. As alluded to previously, the number, type, shape,
orientation or alignment, and pattern of the features, especially
the projections, to be incorporated into any given activator face
depends largely on the chemistry or physical characteristics of the
pre-applied adhesive or sealant material upon which it is to act,
the volume of pre-applied adhesive, the substrates to be bonded and
the bond or bondline desired. Also, as mentioned in the above
paragraphs, the dimensions of the activator face are largely
dependent upon the number, type, shape, orientation or alignment,
and pattern of the features. In essence one needs various features
on an activator face in order to activate a given band of
pre-applied adhesive of a given chemistry and, in following, one
needs adequate space upon which to place the needed features of the
activator face to ensure adequate activation and deposition of the
activated adhesive or sealant.
[0095] For most all applications, the activator face as defined by
the peaks of the projections will be essentially planar; however,
as noted above, it is possible that one or more projections may
have a lower profile or height than others. For example, as
explained with respect to FIG. 14, a series of linear projections
may be employed that are stepped so that successive profiles strip
the pre-applied adhesive or sealant from the substrate one layer at
a time. Similarly, one may employ diversionary projections of
varying heights to create additional shear and mixing around and
under their peaks that may enhance the mashing and kneading of the
contents of encapsulated materials. When the activator face
includes one or more profile channels the tops of the sidewalls of
said profile channels will also be co-planar or substantially
co-planar with the peaks of the projections, or at least the
highest of said peaks.
[0096] Notwithstanding the foregoing, it is also possible for the
activator means and, especially the activator face, to be
configured to work on non-planar surfaces such as tubular or
contoured surfaces. In these instances, the activator face will be
contoured so that the contour of its face matches the contour of
the substrate upon which it is to act. When reference is made
herein to the plane defined by the activator face or the base of
the projections thereon, the plane in those instances will be the
planar arch defined by the same peaks or bases in their contoured
arrangement.
[0097] For certain applications it will be necessary to have heat
present at the activator face. In those instances, the activator
body must include or have incorporated therein a heating means,
such as a resistance wire, ultrasonic horn and the like, or be in a
heat transfer relationship with a heating means whereby the
necessary heat is transferred through the activator body to the
activator face. Unlike conventional heaters for pre-applied
adhesives, especially the hot air heaters, the heating means in
accordance with the present invention are such that the heat
generated is localized at the activator face and/or in the
activator body. Since the activator face is fairly small and the
sides of the activator face and activator body can be encased or
insulated, concern for accidental burning of workers and the like
are avoided. Furthermore, since only the activator face comes in
contact with the substrate surface, any potential for impact of the
heat on the substrate is limited to the bondline. And, in
high-speed processing lines, since the time of contact between the
substrate and the activator face is so small, there is little if
any chance that any substantial amount of heat will actually
transfer from the one to the other. In essence, all or
substantially all heat transfer will be between the activator face
and the adhesive material, with little, if any, heat transfer to
the substrate. Furthermore, since the contact time of the adhesive
with the activator face is so small, especially in high speed
automated applications, there is little if any heat transfer to the
adhesive, except, perhaps, to the monolayer of adhesive material at
the adhesive/activator face interface.
[0098] The activator means of the present invention may also have
incorporated therein or be in a motion transfer relationship with a
reciprocating, oscillating or vibration means which imparts
movement to the activator face. Such means are well known it the
art and will comprise, for example, an electric or pneumatic motor
with an associated cam. As noted above, activator faces wherein the
projections are parallel with or substantially parallel with the
centerline axis or, in the case of long linear projections,
perpendicular to the centerline axis, the extent of the motion of
the reciprocating means will generally be on the order of one
millimeter or more, preferably several millimeters. In most all
other applications, the movement to be imparted to the activator
face is minimal, preferably one millimeter or less, most preferably
less than one-half millimeter. Indeed, for many applications,
movement on the order of nanometers is sufficient as the primary
goal of such motion is to increase the mixing of the adhesive or
sealant composition, including, as appropriate, the mashing and
kneading of any microcapsules and their contents.
[0099] Additionally, the activator means will preferably
incorporate or be associated with an adjustment means which allows
the operator to set the initial relationship, whether a gap or zero
gap, with or without a predetermined compressive force, between the
activator face and the substrate surface upon which it is to act.
Most preferably the adjustment means will accommodate both manual
and automatic adjustments so that the initial or desired height may
be set and then the system automatically makes adjustments to
accommodate changes in the height or thickness of the substrates
upon which it is acting, especially during operation of a fully
automated assembly process. Suitable adjustment means may be simple
in design and construction. For example, the means may comprise a
tension means e.g., springs, which maintains a constant or near
constant force on the activator means so as to maintain pressure
contact with the substrate wherein the tension or force is
sufficient so that the uppermost surface of the projections
maintains contact with the substrate surface even as the activator
face lifts the pre-applied adhesive or sealant material from the
substrate surface, i.e., the tension is preferably sufficient so
that the activator face does not ride above the pre-applied
adhesive or the mass of adhesive built up in front of the
projections. Such tension means will also allow for an adjustment
of the activator means so as to accommodate variations in the
thickness of the substrate or sequential substrates as they pass
through the activator means.
[0100] Alternatively, the adjustment means may be complex and
involve more sophisticated mechanical and/or intricate electronic
systems that include a sensing means which identifies variations in
the height or thickness of the substrate as it enters the activator
means and adjustment means, responsive to the sensing means, that
automatically adjusts the height of the activator face to
accommodate such variations so as to maintain the desired
relationship between the activator face and the substrate surface.
Such systems will accommodate and make adjustments for thickness
variations even on the order of microns.
[0101] As noted above, during operation of the activator means
there may be a gap between the activator face and the substrate
surface upon which it is acting provided that the gap is less than,
preferably no more than one-half, most preferably no more than
one-third, the height or thickness of the pre-applied adhesive or
sealant on the substrate. Otherwise, the amount of adhesive or
sealant activated will likely be insufficient to effectuate a
suitable bond or seal. The concern with gaps is even more
troublesome in the case of encapsulated adhesives and sealants
since gaps exceeding about one-half the average particle size of
the microcapsules will lead to poor and insufficient fracturing of
the encapsulated components and, consequently, insufficient cure
and/or adhesive materials to effectuate a suitable bond or seal.
Furthermore, with compositions like those of Schwantes et, al, such
gaps may result insufficient microcapsule fracture, but
insufficient kneading of the carrier to release or make available
sufficient curative to effectuate a suitable bond or seal.
[0102] In the preferred set-up for use of the activator means of
the present invention, there will be no gap between the activator
face and the substrate surface. Though not required, it is also
desired that the activator body be set so that an interference
exists between the features of the upper surface of the activator
face and the substrate surface upon which it acts. For solid
surfaces, the interference will be negligible or only a touch
interference: most preferably, the activator means will be set to a
depth of from about 0.1 to about 0.5 mils below the substrate
surface, preferably from about 0.1 to about 0.3 mils below the
surface. However, for softer surfaces, like paperboard, cardboard
and the like, a greater interference is desired. Here the activator
body will be set so that the upper surface of the features of the
activator face will be about 10 mils or less below the surface of
the substrate, preferably about 5 mils or less below the surface of
the substrate. Though the interference is not required, it is
preferred that the interference be at least about 0.1 ml, most
preferably 0.3 mils, on softer surfaces. Maintaining a low degree
of interference minimizes any marring or scoring of the substrate
surface while endeavoring to ensure that all of the pre-applied
adhesive or sealant is lifted from the substrate surface. This will
also help ensure that the activator face will not rise relative to
the substrate surface due to a build-up of adhesive or sealant
materials on the forward face of the features on the activator
face. Such a configuration helps maximize the amount of activated
adhesive or sealant available to form the bond or seal as well as
provide a `clean` surface for good wet out of the adhesive directly
on the substrate surface. Furthermore, this setup minimizes and/or
accommodates for any tendency of the activator face to rise
relative to the substrate surface during operation, i.e., the
happenstance of the activator face hydroplaning on the activated
adhesive materials. If a gap exists or the force is insufficient to
guard against the activator face rising relative to the substrate
surface during operation, a thin film of the pre-applied adhesive
or sealant will remain and the activated adhesive or sealant will
then bond to that film rather than the substrate surface itself. At
the same time, as noted above, it is preferable to minimize the
extent to which the activator face is set below the surface of the
substrate, thus the compressive force between the activator face
and the substrate surface, so as to avoid or minimize the
likelihood of a projection or other feature on the activator face
catching on any surface irregularities or imperfections on the
substrate surface or of such projections marring the substrate
surface as well as to avoid or minimize the likelihood that
compressive force will interfere with the substrates, impeding
their progression through the activator means or causing the
substrates to become misaligned. The latter will adversely affect
the through-put rate and, potentially, the quality of the product
formed; whereas the former, especially in high speed automated
operations, may have significant and disastrous consequences
including, for example a complete shutdown of the production line
in which it is integrated. Thus, in general, a light touch contact
is most preferred.
[0103] As noted above, the type, chemistry and dimensions of the
pre-applied adhesive or sealant to be acted upon are, at least in
part, determinative of the selection and positioning or alignment
of the projections on the activator face as well as the other
features or capabilities of the activator means. For example, a
pre-applied heat activated/re-activatable thermoset or
thermoplastic material has very simple needs relative to the
activator face: the presence of a heat source in or in a heat
transfer relationship with the activator face and a single linear
projection, e.g., one that looks and performs much like a snowplow.
If one wanted a plurality of beads for forming the bond, one could
employ an inverted "V" shaped projection. However, if the band of
the pre-applied adhesive or sealant is wide, particularly if the
heated adhesive or sealant is still quite viscous, a single linear
projection may not be suitable. Here, the combined length of the
linear projection and the poor flow of the viscous material would
create a circumstance where a significant retention time exists
before a sufficient bead of activated material exists the end of
the linear projection. Thus, it is preferable to employ a plurality
of shorter linear projections, most preferably either in a
herringbone arrangement, as seen in FIG. 3, or as a chevron. As
seen in FIGS. 7, 7(a), and 10, the chevron configuration will
typically have a forward linear or diversionary projection to
ensure that the gap defined by the trailing ends of the chevron is
activated. Both configurations have the benefit of collecting the
activated adhesive or sealant into a larger mass that then exits
the activator face. The herringbone configuration produces a single
raised bead whereas the chevron will produce two beads or, if the
gap is small enough, a single, broad bead of the activated
adhesive. These raised beads provide excellent bonding capabilities
and expand the number and variety of applications into to which
such pre-applied thermoplastic and thermoset adhesive can be
employed. Indeed, raised beads of activated adhesive allow for the
use of this technology on non-planar surfaces, on more porous
surfaces, and the like.
[0104] Pre-applied encapsulated curable adhesives and sealants, on
the other hand, present a somewhat more difficult circumstance
since the microcapsules must be fractured with high efficiency and
the contents thereof intermixed to ensure good and/or efficient
cure. The former is of utmost concern with encapsulated materials
having thick capsule walls and/or small particle size
microcapsules. The latter is of utmost concern with those
compositions, including the aforementioned Schwantes et. al.
compositions, wherein mere fracturing of the microcapsules fails to
release or make available all of the encapsulated components and/or
a sufficient amount of the critical components otherwise necessary
to initiate full or even satisfactory cure. Consequently, activator
faces for use with curable adhesive and sealant compositions will
typically have more complexity, which complexity is most often
embodied in the use of a plurality of projections and, most
preferably, a combination of different types of such projections.
Such variation will help ensure good mobilization of the adhesive
or sealant, highly efficient microcapsule fracture and increased
shear or mixing of the adhesive or sealant components. Most
preferably, such configurations will include a plurality of linear
projections or one or more linear projections in combination with
one or more diversionary and/or splitter projections.
[0105] Depending upon the nature of the microcapsules and/or their
contents, it may also be preferable, if not necessary, to heat the
activator face for optimal performance of the activator means.
Though the curable compositions are preferably non-heat activated,
as also disclosed in Schwantes et. al., certain carrier materials,
e.g., low melting waxes and the like, may require elevated
temperatures in order to make the curative contained therein
accessible to the other constituents of the curable compositions.
Furthermore, it has been found that low levels of heat, generally
400.degree. F. or less, preferably from about 175.degree. F. to
about 350.degree. F., most preferably from about 200.degree. F. to
about 250.degree. F., help the flow of the activated material along
the activator face and through and past the projections. Of course,
the actual or preferred temperature will depend upon the adhesive
materials used and can be determined by simple trial and error.
Though the exact mechanism is not known, it is thought that the
heat creates a lower viscosity film at the adhesive/activator face
interface: similar in concept to the creation of the water film
between the ice and a blade of an ice skate. As in the skate
example, because the contact time is so short, the heat transfer is
limited to the molecular interface and no heating of the bulk of
the adhesive or sealant is seen.
[0106] Regardless of which adhesive or sealant chemistry or type is
present, when the band or pattern of the pre-applied material to be
acted upon is extremely wide, e.g., more than three quarters of an
inch wide, it may be desirable to employ a plurality of linear
projections, e.g., herringbone or chevron projections, in a
side-by-side relationship, extending across the full width of the
pre-applied adhesive band. Such an arrangement, although employing
side-by-side inverted "V" linear projections in combination with a
plurality of side-by-side inverted "V" splitter projections, is
shown in FIG. 13. This configuration results in the generation of
plurality of parallel beads of the activated composition, as shown
in FIG. 13(a), and minimizes the length of the activator face that
would otherwise be necessary for activating the wide band of
adhesive. Alternatively, the activator face could have a plurality
of diversionary projections extending across the full width of the
band of pre-applied adhesive or sealant, preferably in a staggered
orientation, so that the whole of the pre-applied adhesive is acted
upon. Such an activator face would provide a series of parallel
furrows with raised edges, similar to the pattern generated by
drawing one's fingers through the top inch or so of sand at the
beach. Adding reciprocating motion to this activator face will
create a ribbon-like pattern of a series of parallel furrows with
raised edges or a braided like pattern of the furrows, similar to
the patterns shown in FIGS. 20(a) and 21(a), respectively,
depending upon the spacing and number of rows of the projections.
The reciprocating motion will also help ensure intimate mixing of
the components of the adhesive or sealant compositions should such
be needed.
[0107] Activation of the pre-applied adhesive may be accomplished
manually using a hand-held device that incorporates the activator
body and activator face or, preferably, automatically using
automated machinery that holds or incorporates the activator body
and activator face. Though there is a large zone of overlap in
terms of when each may be used, in the case of curable encapsulated
adhesives and sealants, where the cure speed of the activated
curable composition is very fast, on the order a second or less,
in-line automated activation and assembly will be needed. Slow cure
speeds, e.g., where there is a long open time, are especially
beneficial in manual operations and when the activator means is a
stand-alone apparatus or where the subsequent assembly step is a
manual step as opposed to an automated step or where in an
automated system, the activator means must be retracted from the
activation site before the surfaces to be bonded may be mated.
[0108] In the preferred embodiment, activation of the pre-applied
adhesive will be achieved through an automated activator means,
either as a stand alone apparatus or machinery that merely
activates the pre-applied adhesive or as an in-line activator means
that is integrated into a larger industrial assembly or
manufacturing apparatus. In either situation, the activator means
may be stationary or attached to or part of a robotic arm or like
apparatus. In the latter situation, which is especially suited to
allow for its use with substrates of non-planar shapes or which
have odd shapes whereby an unobstructed path for the activator
means is not present as the substrate passes the activator means.
In this case the activator means is capable of movement from an
active mode where it is in-line in the activation workstation and
an idle mode where it is off-line and retracted from the actual
working site of the activation work station. Alternatively, there
may be situations in which the centerline of the adhesive bead is
perpendicular to the assembly line. In such situations, the
activator means, during the activation step, is not stationary
relative to the assembly line apparatus but moves such that the
activator passes over or swipes across those sections of the
substrate upon which the pre-applied adhesive lies, either in a
continuous or discontinuous fashion. In either respect, these
apparatus are directly integrated into the assembly line and, for
existing lines, can replace those workstations that previously
applied a liquid or flowable adhesive and, if present, cured the
same or, where appropriate, the heating stations employed with
conventional pre-applied heat activated adhesives.
[0109] An especially preferred embodiment of the present invention
is that where the substrate to be acted upon is flat or is such
that it allows for a stationary activator means to act upon the
pre-applied adhesive as the substrate passes through the activator
workstation. In these instances, the process is a continuous one
whose speed or level of output is only limited by the speed or
output of the remaining steps of the assembly or manufacturing
process. In essence, the present invention provides processes where
the adhesive application and/or bonding steps are no longer the
bottlenecks.
[0110] As disclosed in U.S. Provisional Patent Application Nos.
60/665,134 filed Mar. 25, 2005 and 60/692,008 filed Jun. 1, 2005,
both of which are hereby incorporated herein by reference, the
present invention is especially suited for use with stock
materials, most especially stock packaging materials or blanks,
having a pre-applied adhesive or sealant. Due to the planar nature
of such stock packaging materials, or at least the flaps or
portions thereof upon which the adhesive is pre-applied, these
substrates are especially suited for high speed industrial package
forming and/or closing operations. Indeed, it is found that
automated package formation processes employing stock materials in
the form of paperboard blanks may achieve rates of up to 300 feet
per minute and higher when being activated by an activation means
in accordance with the present invention. Even with less than
optimal activation, rates of up to 250 feet per minute or more can
be successfully attained. Such high rates of assembly are in marked
contrast to most traditional, automated assembly operations that
only achieve rates on the order of 150 feet per minute or so.
[0111] While any of the activator face configurations shown in
FIGS. 3 through 21 are efficacious, the efficacy varies, especially
when employed in activating an encapsulated curable adhesive
composition. In order to evaluate relative efficacies of various
activator faces, a test workstation 10, mimicking an in-line, high
speed bonding apparatus, was constructed as shown in FIG. 22. This
apparatus consisted of four workstations: the Loading Station A,
the Activation Station B, the Mating Station C and an End Station
(not shown). A work sled 11 carried a 5 inch by 3.5 inch paperboard
test card along rail 15 through each workstation. The test card had
a 0.5 inch wide, 4 inch long, 18 mil thick band of pre-applied
encapsulated adhesive made in accordance with the teaching of
Schwantes et. al. applied along its centerline beginning at its
forward edge and ending approximately 1 inch from the tail end of
the card. The adhesive was manually applied to the cards using a
coating block.
[0112] As more clearly shown in FIG. 23, the work sled 11 comprises
a base 14 and a platform 16. Integrated into the platform 16 were
four vacuum ports 18 attached to a vacuum means (not shown) through
conduit 19. During testing, at Loading Station A, the card would be
centered on the platform 16, adhesive side up, and the vacuum
applied to hold the card in place. The vacuum was maintained until
the bonded card came to a rest in the End Station. Loading Station
A also incorporated a laser sensor means 13 for detecting the
height of the surface of the card which communicated with a
motorized or, preferably, a hydraulically operated elevator means
22 in the Activation Station B. Attached to the elevator means 22
is activator means 21 having an activator face (not shown) attached
to the underside of the activator means. The elevator means,
responding to the data supplied by the laser sensor means 13, would
adjust the height of the activator means, and thus the activator
face, to ensure that the upper surface of the projections on the
activator face would come into touch contact with the surface of
the paperboard card to which the pre-applied adhesive had been
applied.
[0113] During activation, the sled, and thus the test card, would
traverse through the Activation Station at a rate of 250 feet per
minute. The sled carrying the activated test card would then enter
the Mating Station and stop whereupon mating means 30 would mate a
second 5 inch by 3.5 inch paperboard card to the activated card. In
this respect, mating means 30 includes a work platform 32 and
vacuum ports (not shown) for holding the second card to the
underside of the platform. During the mating step a piston 33 would
lower the work platform 32 until the two cards mated with a
pressure of approximately 5 psi. Thereafter the work platform was
retracted and the work sled moved on to the End Station. The
assembled test card structures were then removed from the sled and
allowed to set. Subsequently, the assembled test card structures
were evaluated for adhesive strength and, for the purpose of this
application, microcapsule fracture. The latter was determined by
solvent extraction on cards subjected to the activator means and
others not so subjected in conjunction with gas chromatography of
the extractions to determine the amount of liquid monomer released
during the activation process versus the total amount of liquid
monomer present in the pre-applied adhesive, except here the
pre-applied adhesive was inactive, i.e., it lacked the curative
ingredient, so that the released liquid would not cure.
[0114] Based on the microcapsule fracture evaluation, it was found
that simple herringbone configurations, with and without splitter,
as shown in FIGS. 3, 4 and 6, only succeeded in achieving rupture
of around 25 to 30 percent of the microcapsules. On the other hand,
the more complex activator faces of FIGS. 8, 9 and 12 having a
plurality of different types of projections achieved much higher
microcapsule fracture, generally on the order of from 50 to 60%,
with the same composition. Based on these findings, other
configurations, such as the crosshatch type activator faces of
FIGS. 20 and 21 may provide good microcapsule rupture, particularly
when combined with reciprocating motion. However, the crosshatch
pattern of these activator faces will likely only result in the
generation of what is essentially a thin film of activated
adhesive.
[0115] Though the numerical values on the extent of microcapsule
fracture noted above appear low, the efficiency of the activator
means of the present invention are comparable with, and in most
instances better than, those achieved with traditional activator
means. Of course, varying the chemistry and make-up of the
encapsulated adhesives will also affect the fracture efficiency.
For example, it is anticipated that higher fracture performance may
be realized with a microencapsulated liquid adhesive as opposed to
the encapsulated solid and semi-solid carriers of Schwantes et. al.
Furthermore, the activator means of the present invention have the
added benefit of providing the requisite degree of kneading and
mashing necessary for effectively employing the encapsulated
materials of Schwantes et. al., which show reduced or poor
performance absent multiple passes with traditional activator
means. More importantly, the activator means of the present
invention allow for the generation of beads of activated adhesive,
rather than thin films, which greatly expand the applications into
which pre-applied adhesive may be employed.
[0116] Activator means in accordance with the present invention
were also evaluated on a modified, automated packaging line, one
typical for the filling and closing of, for example, a cereal box,
with the exception that the apparatus did not employ a hot melt
dispensing station. Such apparatus are well known in the art and
typically comprise a magazine for holding the carton blanks, a
conveyor means for moving the carton blank along the production
line, a feeding means for placing the carton blanks on the conveyor
means, a forming means for squaring the carton blank, an adhesive
dispensing means for applying a hot melt adhesive to the end flaps
of the carton blank and closure means for closing the flaps and
holding them in the close relation to allow the adhesive to cool
and seal the carton. Here, however, instead of the adhesive
dispenser, the apparatus incorporated two activator means in
accordance with the present invention, one on each side of the
conveyor means at a point subsequent to the squaring and/or filling
operation and prior to the closing operation. Also, here the carton
blanks had an encapsulated adhesive pre-applied to the inner
surface of the outer end flaps. Although various techniques could
be and were employed to apply the adhesive, in one series of tests
the encapsulated adhesive was applied via flexographic printing
using an anilox roll and a 0.25 inch thick flexographic plate which
deposited the adhesive in a diamond pattern. As the carton blank
passed the activator means--typically the apparatus was run as a
line speed of about 150 feet per minute, though a 250 feet per
minute speed was also attained--the features on the activator
surface acted upon the pre-applied adhesive. As the carton blank
continued, the closure means closed the end flaps and held the same
in the closed position until the formed carton was expelled from
the apparatus. The expelled cartons were sealed at each end,
demonstrating the effectiveness of the activator means.
[0117] Although the present invention has been described with
respect to specific embodiments and examples, it should be
appreciated that other embodiments utilizing the concepts of the
present invention are possible without departing from the scope of
the invention. Thus present invention is defined by the claimed
elements and any and all modifications, variations, or equivalents
that fall within the spirit and scope of the underlying principles
set forth herein.
* * * * *