Note: Descriptions are shown in the official language in which they were submitted.
132S034
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related in subject matter to -
Canadian patent application No. 574,743 filed August 15, 1988.
TECHNICAL FIELD
This invention relates to an extrusion method and
apparatus and molding strip produced thereby and, in particular,
to an extrusion method and apparatus for producing a molding strip ;
which includes an outer plastic layer interbonded with a plastic
body by interfusion. ~
BACKGROUND ART -
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Plastic side .~olding strips are provided for various
manufactured articles such as appliances and motor vehicles in
order to minimize damage to a side body panel of the article from ~ -
inadvertent, slight contact. In order to enhance the appearance ~
of such molding strips, it is desirable to have the color of the - -
molding strip match the color of the side body panel. ;
Frequently, a clear PVC totally encapsulates the molding
strip in order to prevent separation between the underlying
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plastic body and the clear PVC. However, total encapsulation of
the plastic body by the clear PVC is undesirable for a number of -~
reasons including inefficient use of the clear PVC.
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One proposed alternative to total encapsulation is to --
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use multiple dies, the last one of which
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applies a top coat of clear PVC to the extruded
plastic body.
One disadvantage of this method is that the
clear plastic layer has a tendency to separate from
its underlying plastic body during use of the
molding strip, especially when the molding strip
encounters impact at extreme temperatures or when
the molding strip is used around corners having a
relatively small radius. -
The U.S. Patents to Angioletti et al 4,087, -
223, Gans et al 4,269,897, Azzola 4,381,273, Preis
4,470,943, Zoller 4,563,141, Adell 4,581,807 and
Paul 4,643,659 all deal with extrusion of more than
one type of plastic to form a resulting plastic
part. For example, the U.S. Patent to Azzola
discloses a sealing strip, including a channel-
shaped attachment profile of rubber in which a
metallic reenforcement strip is embedded. The
profile has an external coating layer of sponge
rubber with an outer surface rendered velvety by
abrasion.
DISCLOSURE OF THE INVENTION
An object of the present invention is to
provide an improved method and apparatus for
continuous composite molding of a molding strip
which includes a plastic layer interbonded to an
underlying plastic body by interfusion and wherein a
single die is utilized to produce the molding strip.
Another object of the present invention is to
provide an improved method and apparatus for
continuous composite molding of a molding strip
havinq a plastic layer interbonded to an underlying
plastic body by interfusion and wherein the molding
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is performed in such a fashion so that the plastic
layer does not separate from the plastic body during
use of the molding strip.
Yet still another object of the present
invention is to provide an improved method and
apparatus for continuous composite molding of a
molding strip including a polyurethane plastic layer
and an underlying flexible PVC plastic body wherein
the molding strip is produced in a relatively cost-
efficient fashion (i.e. it is not necessary nor
desirable to totally encapsulate the PVC plastic
body with the polyurethane plastic).
In carrying out the above objects and other
objects of the present invention, a method for
continuously forming a composite molding strip is
provided. The method utilizes a single extrusion
die which includes first and second passages
communicating the outer surface of the die with a
common bonding chamber formed in the die. The
method includes the steps of extruding a molten
flexible PVC plastic through the first pa~sage and
into a bottom portion of the bonding chamber and
extending a molten, polyurethane plastic through the
second passage and into the top portion of the
bonding chamber. The PVC plastic has an outer
surface and the polyurethane plastic has an inner
surface in the bonding chamber. The PVC plastic is
interbonded with the polyurethane plastic by
interfusion between the surfaces while in the molten
state to form the molding strip.
Further in carrying out the above objects and
other ob~ects of the present invention, an extrusion
die for use in forming the continuous composite
molding strip along a forming axis is provided. The
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molding strip has a flexible PVC plastic body having
an outer surface and an outer polyurethane plastic
layer having an inner surface. The die includes a
bonding chamber therewithin and a first passage
extending from the outer surface of the die and into
a bottom portion of the bonding chamber to receive
the flexible PVC plastic in molten form. A second
passage extends from the outer surface of the die
into a top portion of the bonding chamber to
receive the polyurethane plastic. The die further
includes a means or mechanism for directing the flow
of the molten polyurethane plastic from the second
passage into the bonding chamber in a direction
parallel to the forming axis. A bottom portion of
the mechanism at least partially defines an opening
extending along the forming axis and communicating
the first passage with the bonding chamber. The PVC
plastic and the polyurethane plastic are interbonded
by interfusion between the surfaces within the
bonding chamber to form the molding strip.
Still further in carrying out the above
objects and other ob~ects o~ the present lnvention,
a continuous composite molding strip is provided.
The molding strip includes a body of PVC plastic
having an outer surface and a polyurethane plastic
layer having an inner surface overlying the outer
surface of the PVC body. The plastic polyurethane
layer is interbonded with the PVC plastic body by
interfusion between the surfaces while in a molten
state to form the molding strip.
Preferably, a third passage communicates the
outer surface of the die with the comman bonding
chamber to allow the feeding of a reenforcing strip
through the third passage and into the lower portion
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of the bonding chamber while the PVC plastic is in
the molten state to provide added strength to the
molding strip. ;
Also, preferably, the polyurethane plastic -
layer is clear and may be painted to match the
color of the side body panel to which the molding
strip is to be attached. One outer surface of the
plastic body is free of the plastic layer to provide
a surface for the adhesive binding of the molding ;
strip to the side body panel. The body of the --~
molding strip is formed from flexible PVC plastic. ` -
The above extrusion method and apparatus and -
molding strip provide numerous advantages. For ;`
example, the molding strip is produced with a single
die. Also, the plastic layer does not separate from ~`
the plastic body during use of the molding strip.
Furthermore, the molding strip can be produced in a
cost-efficient fashion without wasting plastic
material~ - -
Other advantages of the present invention can
be readily appreciated as the same becomes better
understood by reference to the following detailed
description when considered in connection with the
accompanying drawings. ~;
BRIEF DES~RJPTION OF THE INVENTION
FIGURE 1 is a perspective, broken-away view -
of a molding strip constructed in accordance with
the method and apparatus of the present invention;
FIGURE 2 is a first end view of the die for
making the molding strip of FIGURE 1;
FIGURE 3 is a sidé sectional view of the die
utilized in accordance with the method of the
present invention;
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:,
FIGURE 4 is a side elevational view of the
die of FIGURE 3 with various apertures indicated by
phantom lines;
FIGURE 5 is a second end view of the die:
FIGURE 6 is a side elevational view of a part
of the die of FIGURES 3, 4 and 5: and
FIGURE 7 is an inner end view of a plate of
the die of FIGURES 3, 4 and 5.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawing figures, there
is illustratPd in FIGURE 1 a continuous, composite
molding strip, generally indicated at 10, con-
structed in accordance with the present invention.
The molding strip 10 may be utilized as a vehicle
body side molding to protect a vehicle side body
panel, for example. However, it is to be understood
that the molding strip 10 can also be used on other
products and goods, such as appliances and the like.
The molding strip 10 includes a body,
generally indicated at 12, preferably of a black
plastic, such as black flexible PVC, BOCMS 2-8 Type
VI grade EU30L. However, it is to be understood
that a different flexible plastic, such as polyure-
thane, can also be utilized with the present
2~ invention.
The molding strip 10 also preferably includes
a top layer, generally indicated at 16, of a clear
plastic such as polyurethane (and has the grade
EUC). The plastic top layer 16 is interbonded to
the plastic body 12 by interfusion between a bottom
or inner surface 18 of the top layer 16 and a top or
outer surface 20 of the plastic body 12 while both
plastics are in the molten state.
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Bonding by interfusion between the surfaces
18 and 20, in effect, causes the top plastic layer
16 and the plastic body 12 to act as a single piece
of resilient plastic and is thereby effective to
absorb shocks to the top or outer surface 14 of the
top layer 16 without damage to the molding strip 10.
The molding strip 10 also includes a
reenforcing strip 22 which extends along the
longitudinal length or axis of the molding strip 10
and is embedded within the plastic body 12 to
thereby strengthen the molding strip 10. The strip
22 is preferably an aluminum metal strip. ~
Referring now to FIGURES 2 through 7, there
is illustrated an extrusion die, generally indicated
at 24, for forming the molding strip 10 along a
: forming axi~ 26. The extrusion die 24 includes a
crosshead, generally indicated at 28, first and
second extrusion plates 30 and 32, respectively, and
an extrusion block 33, all of which are held
together by bolts 34 and dowels 35 (only one of
which is shown). Bolts ~not shown) extend through
holes 39 for securing the crosshead 28 and,
consequently, the die 24 to the discharge end of the
extruder (not shown) for the molten PVC plastic for
the body 12.
The crosshead 28 includes a first passage,
generally indicated at 36 in FIGURE 4, which extends
from an outer surface 38 of the crosshead 28 into a
- bottom portion of a bonding chamber 40 formed in
the second plate 32.
The die 24 also includes a tube or snorkel,
generally indicated at 42. A head portion 44 of the
snorkel 42 is secured by bolts 46 to the crosshead
28 to retain the snorkel 42 against an inner
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cylindrical surface 48 formed in the crosshead 28.
The outer periphery of a cylindrical portion 49 of
the snorkel 42 cooperates with the inner surface 48
of the crosshead 28 to define a circular groove 50
for receiving and directing the molten PVC plastic
from a direction transverse the forming axis 26 to a
direction parallel with the forming axis 26.
The snorkel 42 also includes a hollow end cap
member 52 which is fitted at one end of the snor~el
42 and further defines a passage 54 formed in the
snorkel 42 along the forming axis 26. The end cap
member 52 directs the molten plastic thereover along
the passage 36 and into the molding or bonding
chamber 40.
The passage 54 extends through the snor~el 42
to receive and direct the metal strip 22 from the
exterior of the die 24, through the hollow end cap
member 52 and into the chamber 40.
Another passage 56 is cooperatively formed by
~o the first plate 30 and the ~econd plate 32 to
communicate the top outer surface 58 o~ the first
plate 30 with the bonding chamber 40. The first
plate 30 includes a directing means or mechanism,
generally indicated at 60 which has an aperture,
generally indicated at 62 which communicates the
passage 56 with the bonding chamber 40. The
aperture 62 extends in a direction perpendicular to
the forming axis 26 to permit the passage of the
clear molten polyurethane plastic therethrough and
into a top portion of the bonding chamber 40.
The aperture 62 includes side branches 65 and
an interconnecting middle branch 63 which are
definPd by the opposing surfaces of the first and
second plates 30 and 32, respectively. The branches
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63 and 65 allow for the even distribution of clear
molten plastic over the top and side surfaces of a
lower portion 68 of the directing mechanism 60. The
lower portion 68 of the directing mechanism 60
directs the flow of the clear molten plastic from
its downwardly flowing direction in the passage 62
to a direction parallel to the forming axis 26.
The bottom surface of the lower portion 68 of
the directing mechanism 60 at least partially
defines an opening 72 which extends along the
forming axis 26 and communicates the first passage
36 with the bonding chamber 40.
Within the bonding chamber 40 the molten PVC
plastic and the clear molten polyurethane plastic
are interbonded by interfusion between their
contacting inner and outer surfaces respectively, to
form the molding strip 10 of FIGURE 1.
The advantages accruing to the use of the
present invention are numerous. For example, a
single die is utilized to produce the molding strip
10. Also, the plastic body 12 and the plastic layer
16 are interbonded in such a fashion such that the
layer 16 and the body 12 do not separate during use
of the molding strip 10. Furthermore, it is not
necessary, nor desirable, to fully encapsulate the
plastic body 12 with the plastic layer 16 to form a
shock-absorbing molding strip. Plastic material is
saved and the plastic layer 16 may be painted to the
same color as the side body panel to which the strip
10 is secured. The strip 10 is adhesively secured
to the panel lo at the unencapsulated surface of the
plastic body 12.
While the best mode for carrying out the
invention has been described in detail, those
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familiar with the art to which this invention ~:
relates will recognize various alternative designs :
and embodiments for practicing the invention as
defined by the following claims.
