Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF ATTACHING WHEEL OVERLAYS
FIELD OF THE INVENTION
[0001] The invention relates to improved methods for assembling vehicle wheels
having decorative and/or protective claddings, where an overlay is attached to
a wheel
using an adhesive.
DISCUSSION OF THE RELATED ART
[0002] One method currently employed for manufacturing vehicle wheels involves
attaching a relatively thin decorative and/or protective overlay (sometimes
referred to as a
"cladding") comprised of plastic, chrome-plated plastic, stainless steel or
the like to a
functional wheel which is constructed of steel, aluminum alloy or other such
metal. The
overlay provides an attractive, durable finish to the wheel, generally at a
lower overall cost
than an alloy wheel having an exposed surface that has to be specially
finished in multiple
steps to provide comparable appearance and performance. Clad wheels are also
preferred
over wheels having non-permanently attached wheel covers which are secured to
the
wheel by retention clips or the like, but which can be readily detached from
the wheel if
the vehicle hits a pothole or other obstacle in the road or by a thief.
[0003] Many different wheel cladding methods have already been proposed,
including the techniques described in the following United States patents:
3,669,501;
3,915,502; 4,416,926; 5,368,370; 5,564,791; 5,577,809; 5,597,213; 5,630,654;
5,636,906;
5,845,973; 6,082,829; 6,346,159; 6,547,341; 6,637,832; 6,729,695; 6,755,485;
6,779,852;
6,932,435; 6,991,299; 6,998,001; 6,955,405; 7,025,426; 7,025,844; 7,097,730;
7,204,562;
and 7,044,524. Other methods are described in WO 2007/092201 and WO
2007/098157,
each incorporated herein by reference in its entirety.
[0004] Currently utilized methods for bonding overlays to wheels generally use
one of three different types of adhesive systems: beads of one component
adhesives, beads
of two component adhesives, and two component polyurethane foams injected
behind the
overlay (cladding). In each case, the adhesive is applied in the form of a
flowable liquid
material. The adhesives applied as beads are effective at bonding the overlay,
but tend to
exhibit very poor acoustic properties (e.g., it is clearly evident from the
sound
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characteristics of the clad wheel that the overlay is a thin covering simply
glued to the
wheel). The two component polyurethane foams injected between the cladding and
the
wheel not only provide effective bonding but also improved acoustic
performance as
compared to the adhesives applied as beads. However, the utilization of such
foams has
the disadvantage that the wheel assembly operation will require a foaming and
fixturing
system for each wheel/cladding combination, which is a significant capital
investment. In
addition, such polyurethane foam systems are messy and require special safety
precautions
to protect workers from the isocyanate-containing components that must be
used.
[0005] It is therefore clear that the development of alternative, improved
wheel
cladding methods is still needed.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention provides a method for attaching an overlay to a
wheel. The method comprises the steps of:
a). providing a wheel having an outboard surface;
b). providing an overlay having an inboard surface;
c). applying at least one preformed, solid, dimensionally stable, heat-
activatable adhesive body to at least one of the outboard surface of the wheel
or the
inboard surface of the overlay;
d). positioning the wheel and the overlay so that the outboard surface of
the wheel faces the inboard surface of the overlay; and
e). heating the at least one adhesive body to a temperature effective to
cause said at least one adhesive body to join the wheel and the overlay.
[0007] This method provides a means to effectively bond and seal the area
between the cladding and the wheel, without the need for specialized, costly
fixtures and
without having to deal with the mess that can be created utilizing
conventional wheel
cladding adhesives that are applied as flowable liquids. This approach has the
further
significant advantages of providing acoustic performance that is enhanced as
compared to
the bead-applied adhesives and facilitating the changeover during a
manufacturing
operation from one type of wheel/cladding combination to another.
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DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
[0008] The present invention utilizes one or more preformed, solid,
dimensionally
stable, heat-activatable adhesive bodies to secure together the outboard
surface of the
wheel and the inboard surface of the overlay, thereby attaching the overlay to
the wheel in
a permanent manner. The term "preformed" means that the adhesive body has been
formed into the desired shape before being applied to the outboard surface of
the wheel or
the inboard surface of the overlay. Preferably, the adhesive body is
unsupported; that is, it
is not supported by or attached to any type of carrier or other structure
priot to being
positioned between the wheel and the overlay. The desired shape will vary
depending
upon the particular application. For example, the width and length of the
adhesive body
will be selected based upon the extent to which it is desired to cover the
surfaces of the
outboard surface of the wheel and the inboard surface of the overlay once the
adhesive
body has been activated by heating. The dimensions and overall shape of the
adhesive
body will also generally be selected to avoid having any adhesive visible to
an observer
looking at the outboard surface of the overlay once the wheel and overlay have
been
assembled. For example, if the overlay and wheel have holes or openings in
them that are
aligned in the assembled wheel, the adhesive body should be configured and
positioned to
avoid having any of the adhesive body extend into such openings. Typically,
the
thickness of the adhesive body is sufficient to permit essentially the entire
gap between the
overlay and the wheel to be filled with adhesive once the adhesive body has
been activated
by heating, thereby providing a secure adhesive bond between these components
and also
providing good acoustic properties. As will be explained further in more
detail, filling of
the gap may also be facilitated by the use of a heat-expandable (foamable)
adhesive body.
The adhesive body may be uniform in thickness (e.g., 0.5 to 20 mm thick) or
may contain
portions of varying thickness. In certain embodiments, the adhesive body is
relatively
thin; e.g., the thickest dimension may be less than 30% or less than 20% or
less than 10%
of the width or length of the adhesive body at its narrowest or shortest
point. The
adhesive body may be continuous in structure or may contain one or more
through holes.
The through holes may be configured to align with openings in the wheel or
overlay when
the adhesive body is applied to the wheel or overlay, for example. The
adhesive body may
be planar (flat) or curved or otherwise configured to match the contours of
the wheel or
overlay surface to which it is applied. In one embodiment, the adhesive body
may initially
be planar but is sufficiently flexible (either at room temperature or a
moderately elevated
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temperature, e.g., up to about 50 degrees C) to permit it to be conformed
closely to the
contours of the wheel or overlay surface. The overall shape of the adhesive
body is varied
as may be needed for a particular application; the adhesive body may, for
example, be in
the form of a circle, rectangular, square, triangle, ring, cross, oval, or
other geometric
shape or may be irregular in shape. In other embodiments, the adhesive body
may be
elongated with a relatively small cross-sectional area; e.g., the adhesive
body may be in
the form of a rod having a substantially circular cross-section or a cross-
section which is
partially curved and flat on one side or a substantially square or rectangular
cross-section.
The elongated adhesive body may be formulated to be sufficiently flexible at
room
temperature or a moderately elevated temperature to permit it to be readily
bent, curved or
otherwise shaped into the desired configuration when applied to the overlay or
wheel. For
example, the adhesive body may be a flexible rod approximately 0.5 to 10 mm in
diameter.
[0009] The edges of the adhesive body may be of any suitable shape such as,
for
example, straight, rounded, chamfered, tapered, angled, notched or the like.
[0010] A single adhesive body or a plurality of adhesive bodies having the
same
shape or different shapes may be used to join a wheel to an overlay. Where a
plurality of
adhesive bodies is employed, the adhesive bodies may be positioned adjacent to
each other
and/or spaced apart from each other.
[0011] The adhesive body should be solid (i.e., not a liquid, gel or paste)
and
dimensionally stable, meaning that it does not flow or change in shape at room
temperature (15 to 25 degrees C) in the absence of any forces other than
gravity and
maintains its dimensions under such conditions. Preferably, the adhesive body
does not
readily distort when subjected to manipulation by hand, although some
flexibility may be
desirable where the adhesive body is to be conformed to a surface having a
contour
different from that of the surface of the adhesive body. Such characteristics
facilitate the
fabrication, storage, handling and application of the adhesive body and thus
help avoid
some of the problems associated with the adhesives conventionally used in
wheel cladding
manufacture. In one embodiment of the invention, all the outer surfaces of the
adhesive
body are non-tacky at room temperature. In other embodiments, however, one or
more
outer surfaces of the adhesive body are tacky at room temperature. A tacky
surface may
be utilized to position and attach the adhesive body where desired on the
wheel or overlay
surface, but such tacky surface may need to be temporarily protected by a
release film,
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release paper or the like to avoid contamination of the surface with dirt or
dust and/or to
facilitate processing, storage, and handling. The release film or release
paper is removed
from the tacky surface prior to applying the adhesive body to the wheel or
overlay. In one
embodiment of the invention, only the surface to be applied to the overlay or
wheel
surface is tacky, with the other surfaces being non-tacky. A layer of a
pressure sensitive
adhesive or the like may be applied to the surface of an otherwise non-tacky
surface to
render it tacky, if so desired. Alternatively, an adhesive body having
surfaces that are
initially all tacky may be treated to render only certain of such surfaces or
only certain
portions of a surface non-tacky, through the application of an anti-blocking
substance or
the like. In yet another embodiment, all surfaces of the adhesive body are non-
tacky and
the adhesive body is held in the desired position and orientation relative to
the overlay
and/or wheel by mechanical means such as a clip, pin or bracket.
[0012] The adhesive body is also heat-activatable, meaning that the adhesive
bond
between the wheel and the overlay is created or enhanced when heat is applied
to the
adhesive body. In one embodiment, the adhesive body softens and flows when
heated,
thereby filling a space between the outer surface of the adhesive body and the
other
component of the wheel assembly (e.g., either the inboard surface of the
overlay where the
adhesive body has initially been applied to the outboard surface of the wheel
or the
outboard surface of the wheel where the adhesive body has initially been
applied to the
inboard surface of the overlay). Even where a surface of the adhesive body is
initially in
at least partial contact with a wheel or overlay surface when the wheel and
the overlay are
positioned so that the outboard surface of the wheel faces the inboard surface
of the
overlay, the adhesive bond between such surfaces is often significantly
enhanced by the
softening and flowing of the adhesive body whereby more intimate contact
between the
adhesive body and the wheel or overlay surface, with the adhesive body surface
remaining
adhered to the other surface when the adhesive body is subsequently cooled to
room
temperature (the adhesive body thus, in a sense, functions as a hot melt
adhesive). In a
particularly preferred embodiment of the invention, the adhesive body is at
least in part
expandable, that is, capable of being expanded when heated. Such heat-
activated
expansion may be effected through the use of one or more latent chemical
and/or physical
blowing agents, for example, which are stable at room temperature but release
gas (by
chemical decomposition, for example) or otherwise induce expansion (by
expansion of
hollow thermoplastic microspheres, for example) when heated to an elevated
temperature.
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Sufficient blowing agent may be utilized to cause the adhesive body to expand
at least
10% or at least 20% or at least 50% or at least 100% or at least 250% or at
least 500% or
at least 1000% or more in volume. In still another embodiment of the
invention, the
adhesive body may contain one or more latent curing agents (which may also be
referred
to as crosslinking agents) that induce curing and/or crosslinking of one or
more
components (e.g., polymers and/or polymer precursors) present in the adhesive
body.
Such latent curing agents (which are generally stable at room temperature)
thus may
render an initially thermoplastic material used to fabricate the adhesive body
at least
partially thermoset (crosslinked) in character after activation and thus more
heat resistant
(other properties of the adhesive body, such as its sound or vibration
dampening
properties, may similarly be manipulated or altered as desired through the use
of such
heat-activated curing agents).
[0013] The adhesive body may be uniform in composition, that is, formed of a
single material (it being understood that such material may itself be an
admixture of two
or more components, such as one or more polymers (e.g., a thermoplastic such
as a
polyolefin or a copolymer of an olefin with one or more other types of
monomers), one or
more polymer precursors (e.g., an epoxy resin or other functionalized monomer,
oligomer
or prepolymer capable of forming a polymer when reacted), one or more fillers,
one or
more curing agents (especially latent curing agents), one or more blowing
agents
(especially latent blowing agents), one or more plasticizers, one or more
pigments, one or
more tackifiers and/or one or more stabilizers or a plurality of different
materials. For
example, the adhesive body may be laminar and contain two or more layers
having
different compositions and properties. For example, the adhesive body may have
a core
layer having one composition with an additional outer layer on either side,
with the outer
layers having the same or different compositions as each other. One layer, for
example,
may be rubbery or elastomeric in character, with another layer being a more
rigid
thermoplastic or thermosettable material. In another embodiment, at least one
layer is
expandable with at least one layer being non-expandable. In still another
embodiment,
different regions of the adhesive body may be comprised of different materials
(e.g., a first
material may be in a ring around the perimeter of the adhesive body, with a
second
material being present within the ring defined by the first material). The
adhesive body
may be formulated to contain components capable of being cured or crosslinked
through
exposure to radiation such as ultraviolet light or electron beam radiation,
with the adhesive
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body (or certain sections or areas of the adhesive body) being irradiated so
as to impart
certain desired characteristics to the adhesive body.
[0014] Heat activation of the adhesive body may be selected to occur at any
desired temperature through the choice of the components used to formulate the
adhesive,
e.g., the polymers, polymer precursors, blowing agents, curing agents and the
like.
Typically, the components of the formulation are chosen so that the adhesive
body is heat-
activatable at a temperature of at least 50 C or at least 100 C but not more
than 250 C or
not more than 200 C.
[0015] Heating of the adhesive body may be accomplished by any suitable means
such as, for example, baking in an oven (e.g., a paint cure oven) or induction
heating.
Continuous as well as batch heating processes may be employed. If the
activation
temperature of the adhesive body is the same as or greater than the
temperature at which
the overlay would begin to exhibit heat-related damage (distortion or
discoloration, for
example), the wheel may be pre-heated in the absence of any adhesive bodies to
a
temperature greater than (e.g., at least about 10 degrees C or at least about
20 degrees C
greater than, but preferably not more than about 50 degrees C or at least
about 60 degrees
greater than) the activation temperature of the adhesive body and then
assembled together
with the adhesive body and the overlay. The residual heat in the pre-heated
wheel can be
sufficient to cause the adhesive body to activate, thereby bonding the overlay
to the wheel.
In this embodiment, the adhesive body can be pre-attached to the overlay,
thereby
reducing the assembly time required when forming the sandwich structure
wheel/adhesive
body/overlay.
[0016] Suitable foamable materials useful in constructing adhesive bodies
suitable
for use in the present invention are also available commercially, such as, for
example, the
TEROPHON, TEROCORE and ORB NV products sold by Henkel AG & Co. KGaA and
its affiliates.
[0017] The adhesive bodies may be shaped or formed using any suitable method,
including, but not limited to, injection molding, compression molding,
extrusion molding
or other molding techniques. For example, a sheet comprised of a suitable
material as
described previously and having the thickness desired in the final adhesive
body is first
formed by extrusion of the material (heated to a temperature effective to
soften the
material, thereby permitting it to flow under pressure) through a slit die or
the like, with
the adhesive bodies being thereafter die cut from the sheet using a die such
as a rotary die
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corresponding in shape to the desired shape of the adhesive body. If the
adhesive body
shape desired is that of a simple rectangle or ribbon, the sheet may be slit
and cut after it
emerges from the slit die into adhesive bodies having the desired width and
length.
Alternatively, granules of such suitable material may be placed into a hopper
which feeds
into a heated injection unit. A reciprocating screw pushes the granules
through a long
heating chamber, where the granules are softened to a flowable state. At the
end of this
chamber there is a nozzle which abuts firmly against an opening into a
relatively cool,
closed mold having a cavity with the same dimensions as the desired adhesive
body. The
heated, flowable material is forced at high pressure through the nozzle into
the mold
cavity. A series of clamps holds the mold halves together. Once the material
has cooled
to a solid state, the mold is opened and the injection molded adhesive body
ejected.
During such molding and shaping operations, it will generally be desirable to
maintain the
material being used to form the adhesive body at a temperature below which
expansion of
the material begins to take place (if the material is heat expandable) and
curing/crosslinking of the material begins to take place (if the material is
heat-curable).
[0018] Where the adhesive body is laminar (multi-layer) in structure or
otherwise
contains regions having different compositions, techniques such as
coextrusion,
overmolding, comolding and lamination may be utilized to prepare the adhesive
body.
[00191 Where the adhesive body is in the form of a flexible rod or other
elongated
relatively narrow shape, it may be convenient to manufacture a spool or reel
having a
long, continuous tape, rope or ribbon wound thereon and then unwind such tape,
rope or
ribbon from such spool or reel and cut the adhesive body to length as needed
prior to or
after applying it to the wheel or overlay surface.
[0020] The present invention may be readily adapted for use in cladding any
type
of wheel, including the various types conventionally used in vehicles such as
automobiles,
trucks and so forth. Generally, such wheels are metallic and may be comprised
of a metal
or metal alloy such as steel, aluminum alloys, magnesium alloys and the like.
Composite
plastic wheels may also be clad in accordance with the present invention,
however. It
may be desirable to treat the outboard surface of the wheel before bonding it
to the inboard
surface of the overlay using the adhesive body. Such pretreatment may include,
for
example, subjecting the surface to conversion coating (e.g., chemically
reacting the
surface to enhance its corrosion resistance and/or adhesiveness), placing a
layer of primer
or paint on the surface (to improve its corrosion resistance and/or
adhesiveness), and/or
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cleaning the surface (to remove contaminants that might otherwise adversely
affect the
adhesive bond created between the wheel and the overlay). One advantage of the
present
invention, however, is that a decorative finish need not be put on the
outboard wheel
surface, since such surface will be effectively hidden by the overlay once the
wheel has
been clad. For example, the outboard wheel surface may be left in rough,
unpolished
form, thereby simplifying the wheel manufacturing process and reducing its
overall costs;
a rough wheel surface may actually enhance the strength of the adhesive bond
formed.
[0021] The overlay (cladding) may be constructed of any desired materials and
can
have any desired configuration, with the materials and configuration typically
being
selected to provide an attractive finish to the wheel. Generally, the overlay
is relatively
thin (e.g., 0.5 to 5 mm) and can be comprised of plastic (e.g., polycarbonate,
polycarbonate alloys, acrylonitrile-butadiene-styrene polymers, polyamides,
polyurethanes, aromatic polyethers, polyesters and the like, including both
thermoplastic
and thermoset materials, with the overlay optionally also comprising one or
more fillers,
plasticizers, pigments, reinforcing agents, adhesion promoters, stabilizers,
and the like) or
metal (e.g., aluminum, stainless steel, chrome-plated stainless steel). Metal-
plated plastics
or metal-plastic laminates may also be employed. The inboard surface of the
overlay may,
if desired, be pretreated before being brought into contact with the adhesive
body, with
exemplary pretreatments including cleaning, priming, flame treatment,
ozonation and the
like. Such pretreatments may help to maximize the strength of the adhesive
bond
ultimately formed between the wheel and the overlay upon activation of the
adhesive
body.
[0022] As mentioned previously, the adhesive body may be initially attached to
the surface of the wheel or overlay by means of a tacky surface provided on
the adhesive
body, such tacky surface being provided through the use of a composition in
preparing the
adhesive body that is inherently tacky at room temperature or by application
of a layer of a
tacky substance, for example a pressure sensitive adhesive, onto the non-tacky
surface of
an adhesive body. In another embodiment, however, the surface of the adhesive
body that
is to be applied to the wheel or overlay is formulated so as to function as a
hot melt
adhesive. That is, the adhesive body surface is warmed to a temperature
effective to
render it soft and tacky and then applied while still warm to the wheel or
overlay surface.
An adhesive bond between the adhesive body surface and the wheel or overlay
surface is
retained upon cooling and resolidification of the adhesive body surface.
Alternatively, the
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wheel or overlay may be heated and the adhesive body surface applied thereto,
wherein
the heated wheel or overlay surface is at a temperature effective to soften
the adhesive
body surface, thereby forming an adhesive bond upon cooling. In still another
embodiment, however, the adhesive body is retained in the desired position on
the wheel
or overlay surface by means of one or more mechanical fasteners such as clips,
pins or
retaining tabs.
[0023] Although the adhesive body may be applied to the wheel or overlay
surface
by automated and/or mechanized means (e.g., through the use of a programmed
robotic
applicator), in other embodiments such application is performed by hand.
[0024] Once the adhesive body (or multiple adhesive bodies) has (have) been
applied, the wheel and the overlay are positioned relative to each other so
that the
outboard surface of the wheel faces the inboard surface of the overlay with
the adhesive
body or bodies therebetween. Generally speaking the exposed surface of the
adhesive
body is brought into close proximity to the surface of the other component.
The surfaces
may actually be in contact with each other or spaced slightly apart from each
other (e.g.,
0.1 to 5 mm). For example, where the adhesive body has been applied to the
outboard
surface of the wheel, the surface of the adhesive body facing away from such
outboard
surface is positioned so that it is adjacent to the inboard surface of the
overlay. Typically,
such positioning also includes aligning any openings or other features in the
wheel and
overlay as desired. It will generally be advantageous to provide some form of
mechanical
interlocking, permanent or temporary, that assists in holding the wheel and
overlay in the
desired alignment at least until the adhesive bodies are activated by heating.
For example,
the wheel and overlay may be temporarily held together using one or more
clamps, fixing
elements and/or jigs.
[0025] In one embodiment of the invention, adhesive bodies are applied to both
the inboard surface of the overlay and the outboard surface of the wheel, in a
staggered
and/or aligned manner. That is, the outboard surface of a,n adhesive body
applied to the
wheel outboard surface may, for example, face the inboard surface of the
overlay or the
inboard surface of a second adhesive body that has been applied to the overlay
inboard
surface.
[0026] Once the desired alignment is achieved, the adhesive body is heated to
a
temperature effective to cause the adhesive body to join the wheel and the
overlay by one
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or more of a) softening and flowing of the adhesive body, b) expansion
(foaming) of the
adhesive body, and/or c) curing/crosslinking of the adhesive body. As
explained earlier,
the effective temperature will vary depending upon the components selected for
use in the
adhesive body, but will typically be at least 50 C or at least 100 C but not
more than
250 C or not more than 200 C. The assembled wheel is thereafter cooled to room
temperature, resulting in a secure adhesive bond between the wheel and the
overlay.
[0027] The present invention has the advantage of permitting more complete
control over placement of the adhesive that joins the wheel and overlay. The
size, shape
and position of the adhesive bodies may be varied as may be needed to achieve
the desired
characteristics in the assembled wheel, such characteristics including,
without limitation,
the strength of the adhesive bond created, sealing of the assembled wheel to
limit ingress
of water or other elements, sound/vibration dampening properties, aesthetic
properties
(e.g., avoidance of visible adhesive in the assembled wheel), and the like.
[0028] For example, the method of the present invention can be practiced such
that
the adhesive body (or adhesive bodies), when activated, occupies/occupy at
least 10%, or
at least 25%, or at least 50% or at least 75% or at least 90% of both the
outboard surface
of the wheel and the inboard surface of the overlay. The size and/or number of
adhesive
bodies may be selected such that the adhesive body or bodies, when activated,
occupies or
occupy no more than 20% or no more than 40% or no more than 80% of both the
outboard
surface of the wheel and the inboard surface of the overlay. In another
embodiment,
essentially all of both the wheel outboard surface and the inboard overlay
surface is
occupied by the activated adhesive body or bodies. The method of the present
invention
can also be practiced using an expandable adhesive body or plurality of
adhesive bodies
wherein such adhesive bodies, when activated by heating, expand to occupy at
least 25%
or at least 50% or at least 75% or at least 90% of the volume between the
outboard surface
of the wheel and the inboard surface of the overlay. In certain embodiments,
however, no
more than 25% or no more than 50% or no more than 75% or no more than 90% of
the
volume between the outboard surface of the wheel and the inboard surface of
the overlay
is occupied by the expanded adhesive body or bodies. In another embodiment,
essentially
all of the volume between the outboard surface of the wheel and the inboard
surface of the
overlay is occupied by the expanded adhesive body or bodies.
