Note: Descriptions are shown in the official language in which they were submitted.
~33~ 71087-28
This invention relates yenerally to hollow plas-tic
parts and particularly to a vehicle air foil.
Air foils are frequent]y mounted on the rear deck lid
of a vehicle. Such foils usually serve a functional purpose in
connection with the air currents over the top of the vehicle and,
in the opinion ofmany, also enhance the appearance of the vehicle.
Vehicle ai`r toils are usually formed as hollow tubular members
having a streamllned cross section. They extend transversely of
the vehicle and have upright stanchions at the opposite ends for
mounting on the rear deck lid of the vehicle. Such air foils
usually comprise two thin, injection molded, plastic half sections
which are cemented together at their mating peripheral edges to
form a hollow light-weight structure.
As presently constructed, such air foils have several
disadvantages. Since the half sections are rather flimsy and
their mating edges are relatively long and very narrow, it is dif-
icult to mold the two half sections so that, when assembled, the
edges mate perfectly around the entire periphery of the air foil.
us a result, it is sometimes extremely difficult to obtain a con-
tinuous, permanent seal when these edges are cemented together. Itis noi uncommon to observe small gaps between edge portions of the
two half sections. When this occurs water will seep into the in-
terior of the air foil. Furthermore, because of their light
weight and hollow construction, such air foils are normally rela-
tively flimsy and flexible, even when assembled As a consequence,
they tend to distort and flutter excessively at high vehicle speeds.
Because of their hollow construction they are also noisy. In add-
ition, because the bonding surfaces of such foils are very narrow,
separation of the bonded edges frequently results.
,. . .
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710~7-28
The primary object of the present invention is -to pro-
vide vehicle air foils of rigid construction without unduly in-
creasing the cost thereof.
According to one aspect of the invetnion there is pro-
vided an air foil for an automobile comprisirlg:
an elongated, hollow structural body defining an aero-
dynamically desirable shape adapted to be mounted on the auto-
mobile transverse to the longitudinal axis of the automobile,
said body including first and second plastic shell sections join-
ed in mating relation;
a semi-rigid foam core molded in situ filling substan-
tially all of the interior volume of the hollow structural body
and in adhesive contact with the interior walls of the shell
sections to provide a unitary assembly; and
mounting means, connected to the body, for mounting the
body on the automobile.
Other objects, features and advantages of the present
invention will become apparent from the following description
and accompanying drawing, in which:
FIGURE 1 is a perspective view of the rear end of a
vehicle having an air foil mounted thereon;
FIGURE 2 is a plan view of one end portion of the air
foil;
2 -
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FIGURE 3 is an end view of the air foil;
FIGURE 4 is a sectional view taken along the
line 4-4 in FIG. 2; and
FIGURE 5 is a sectional view taken along the
line 5-5 in FIG. 2.
In FIG. 1 there is illustrated a vehicle 10
having an air foil 12 mounted thereon. In the embodi-
ment illustrated air foil 12 is mounted on the rear deck
lid 14 of a hatchback type vehicle. An air spoiler 16
is mounted on the rear deck lid 14 at a position below
and rearwardly of air foil 12. From the standpoint of
functionality, air foil 12 is designed to direct air
downwardly against spoiler 16 and thus apply a downward,
road-hugging force at the rear end of the vehicle.
- Air foil 12 has a generally flat and thin hollow
portion 18 which extends transversely across the vehicle.
At each end the hollow section 18 is formed with stanchions
20 by means of which the air foil is adapted to be mounted
on the vehicle, as by fasteners through mounting openings
21. The central portion 18 and preferably also the stan-
chions 20 are formed as upper and lower half sections 22,
24 which are injection molded from a suitable plastic
material and joined together around their peripheral edges
26. At the present time it is preferred to injection
mold these half sections from a polycarbonate resin.
In accordance with the -,l~s-nt invention the
two half sections 22S24 which are relatively thin and,
when assembled, impart to the central portion 18 of the
air foil a tubular configuration, are filled with a plas-
tic foam, preerably of the self-skinning type so that the
two half sections enclose a foam core 25. The plastic
foam presently preferred is of the pGlyurethane type.
The air foil is filled with the foamable plastic either
by pouring a predetermined amount in one of the half sec-
tions and then clamping the otherhalf section to it sothat, when the foam expands, it substantially fills the
hollow space between the two half sections. Alternative-
ly, the two half sections can be assembled together,
plugged at one end if necessary and a predetermined amount
of molten foamable plastic poured into the open end of the
air foil.
Most plastic foams are compatible with many in-
jection molded resins in the sense that they become inte-
grally bonded thereto. This is true, for example1 in the
case of polyurethane foam and a polycarbonate molded part.
When the half sections 22,24 are injection molded from a
resin to which the foam readily bonds, there is no need
to apply adhesive to either the peripheral edges 26 or to
theinterior surfaces of the two half sections. On the
other hand, if the half sections are molded from resins
such as polypropylene or polyethylene to which plastic
~2~
foams do not readily adhere, then the inner surf,~_es of
these half sections are preferably treated in a suitable
manner so that the foam will bond to these surfaces or, in
the alternative, these inner surfaces should have an adhe-
sive applied thereto. Many such adhesives are available
Resins to which foams do not readily bond can be rendered
bondable by surface treatments such as oxidizing or by
the applieation of a suitable primer.
The rigidity of the foam core 25 can be varied
as desired through the use of conventional additives to
the foamable plastic composition. A semi-rigid foam core
is preferred because it adds stiffness to the air foil
and thereby imparts sufficient rigidity to prevent it
from fluttering at high speeds. A highly rigid structur-
al foam is not normally recommended because the air foilthen becomes too stiff and will break too readily.
In the case of vehicle air foils and other pro-
ducts where the external appearance and ornamentation is
extremely important a self-skinning foam is preferred.
When a self-skinning foam is employed, if there are any
gaps between the mating edges of the two half sections
(it is sometimes impossible or impractical to assemble
the two half sections so that there is no separation
between the mating edges), the foam will flow into the
gaps, such as illustrated at 28 in FIG. 4, and present
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a ~nse solid surface at the exterior of the air foil
that can be finished and decorated, such as by sanding,
painting, etc., so that the gap 28 at the separated
edges of the two half sections is imperceptible in the
S finished product.
In some cases, depending upon the size and shape
of the air foil, the shrinkage of the foam core bonded to
the outer shell has a tendency to cause broad flat surfaces
on the half sections to become depressed and, thusl form a
concavity on the outer surface of the air foil. In the
embodiment illustrated the section 22 has such a broad flat
surface. To overcorne this problem, either, and preferably
both, half sections are molded with opposed ribs 30,32
which, when the sections are assembled, form a reinforcing
strut which extends between the opposed walls of the air
foil and prevent them from collapsing.
It therefore follows from the above that the
present invention is admirably suitable for application
to hollow parts formed of two half sections and especial-
ly suited to the manufacture of vehicle air foils. Whenthe hollow part is filled with a plastic foam as describ-
ed, it substantially increases the inherent rigidity of
the part. This is extremely important in the case of air
foils. Any foam that expands into gaps between the mating
edges of the two half sections effectively seals the air
33~
oil against the insress of water. In addition, when the
foam is o the self-s~inning type, any foam that expands
into spaces between separated edge portions of the two
half sections can be finished and decorated in a very
simple manner so that the ornamental appearance of the
par is not affected by such gaps in the mating edges.
