Both Dow and AVI manufacture and sell plastic packaging
materials, including plastic foam. Plastic foam is made by mixing
a polymer resin with a blowing agent and other additives. The
mixture is melted and blended in a pressurized environment before
the mixture is pushed through a die into the non-pressurized
atmosphere where it expands. The plastic foam is then allowed to
cure such that the hot plastic cools and hardens.
A blowing agent is a chemical that produces a superatmospheric
pressure inside the cells of the polymer, causing its individual
cells to grow. The principal purpose of the blowing agent is to
bring about the formation and inflation of the cells that
comprise the plastic foam. For years, manufacturers of plastic
foam used chlorofluorocarbon ("CFC") blowing agents. Recently,
however, concern over the impact of CFCs on the earth's ozone
layer has caused foam manufacturers to replace CFC blowing agents
with hydrocarbon and other blowing agents. Although the use of
these alternative blowing agents has reduced or eliminated the
problems associated with the use of CFCs, they present their own
One problem associated with blowing agents is that they diffuse
out of the foam too quickly during the aging period, causing the
foam to experience unacceptable shrinkage. Specifically, once the
foam is formed, the gaseous blowing agent begins to permeate out
of the foam, and air begins to permeate in. If the blowing agent
permeates out more quickly that the air permeates in, the foam
can shrink because the pressure inside the cells of the foam
become less than the atmospheric pressure. Thus, manufacturers
have attempted to find a blowing agent that can form and inflate
the cells of the plastic foam, yet which also exhibits a high
degree of dimensional stability with minimal shrinkage during
aging. A stability control agent helps to control this shrinkage
by slowing the rate of release of the blowing agent from the foam
until air can permeate into the foam to balance the pressure
inside the foam's cells.
Dow owns five patents related to the manufacture of plastic
foam. In the first set of patents, there are three related
patents directed to the use of isobutane as a blowing agent in
creating foam structures: U.S. Patent No. 4,640,933 ("the '933
patent"), U.S. Patent No. 4,694,027 ("the '027 patent"), and U.S.
Patent No. 4,663,361 ("the '361 patent") (collectively, the
"isobutane patents"). The isobutane patents derive from the
original application filed on December 24, 1985, and each
describes an invention comprising three elements: (1) an olefin
polymer resin, (2) a stability control agent, and (3) a blowing
agent consisting of isobutant or certain mixtures of isobutane
and other blowing agents. Specifically, the '933 patent, which
issued on February 3, 1987, describes the foam made with those
elements; the '361 patent, which issued on May 5, 1987, describes
a foamable polymer composition for making foam using those
elements; and the '027 patent, which issued on September 15,
1987, describes the process for making foam with those elements.
In the second set of patents, there are two related patents
directed to the perforation of plastic foam: U.S. Patent No.
5,424,016 ("the '016 patent"), and U.S. Patent No. 5,585,058
("the '058 patent") (collectively, the "perforation patents").
The perforation patents cover a method of accelerating the
release of a blowing agent from plastic foam. The purpose of
perforation is to create channels in the foam to allow the
blowing agent to escape more readily to the outside atmosphere
than if the blowing agent was forced to permeate only through the
cell walls of the plastic foam.
B. Procedural History
On September 21, 1995, Dow commenced this action against AVI,
the infringement of its isobutane and perforation patents. AVI
now moves for the construction of various claim terms in the
patents. Specifically, with respect to the isobutane patents, it
seeks the construction of the terms (1) "polyolefin foam,"
"polymeric composition" and "olefin polymer foam." As to the
perforation patents, it seeks the construction of the terms (2)
"plastic foam" and "polyethylene foam," (3) "accelerated
release," (4) "perforating," and (5) "extruded." On November 9,
1998, a Markman Hearing*fn1 was held at which the parties
presented oral argument on the construction of the disputed claim
terms and background expert testimony relating to the
manufacturing process of plastic foam. The following discussion
contains the Court's construction of the disputed claim terms.
A. Standard for Claim Construction
A patent infringement analysis involves two steps: first, a
court determines the scope and meaning of a patent claim; and
second, the construed claim is compared to the allegedly
infringing product or process. Markman, 517 U.S. at 390, 116
S.Ct. 1384; Cybor Corp. v. FAS Technologies, Inc.,
138 F.3d 1448, 1454 (Fed.Cir. 1998) (en banc). The first step presents a
question of law exclusively for the court; the second step a
question of fact generally for the jury. Markman, 517 U.S. at
390, 116 S.Ct. 1384; Intervet Am., Inc. v. Kee-Vet Labs., Inc.,
887 F.2d 1050, 1053 (Fed.Cir. 1989).
In determining the scope of a claim, the starting point is the
claim language. See Comark Communications, Inc. v. Harris
Corp., 156 F.3d 1182, 1186 (Fed.Cir. 1998); Fromson v. Advance
Offset Plate, Inc., 720 F.2d 1565, 1571 (Fed. Cir. 1983); see
also Lindemann Maschinenfabrik GMBH v. American Hoist and Derrick
Co., 730 F.2d 1452, 1459 (Fed.Cir. 1984). The claim language
should be construed in context, however, and the other claims,
the patent specification and the prosecution history must be
considered in determining what the claim means. See, e.g.,
Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582
(Fed.Cir. 1996); SRI Int'l v. Matsushita Elec. Corp.,
775 F.2d 1107 (Fed.Cir. 1985).
B. The Isobutane Patents
With respect to the isobutane patents, AVI seeks the
construction of the claim terms "polyolefin foam" in the '933
patent, "polymeric composition" in the '361 patent and "olefin
polymer foam" in the '027 patent. As these terms are not
meaningfully different for purposes of construction, I will
follow the lead of the parties and refer to them collectively as
According to AVI, foam should be construed to require foam that
is "dimensionally stable." As support, AVI relies heavily on the
prosecution history, in which it asserts that DOW narrowed its
claims before the Patent Trade Office ("PTO") to foam having
dimensional stability to distinguish its claims from prior art.
AVI asserts that Dow's test data submitted to the PTO emphasized
this distinction and that without it, Dow's isobutane patents add
nothing to the prior art and thus would be unpatentable. AVI also
relies on the specification sections of the patents, which it
asserts repeatedly emphasize the criticality of dimensional
stability. Further, it cites to the claim language itself, which
requires a stability control agent as a component of the claimed
foam composition. This is significant, according to AVI, because
the purpose of the stability control agent is to render the foam
AVI's construction is flawed. The term "dimensional stability"
appears in only four dependent claims of the '933 patent and in
the preamble of the '027 patent; it does not appear in any of the
claim terms that AVI now seeks to add it too. Simply put, while
AVI seemingly requests the construction of the term foam, it is
not attempting to define this commonly understood term. Rather,
it seeks to interject into foam the requirement of dimensional
stability. Essentially, AVI endeavors to add words —
dimensionally stable — to all of the isobutane patents claims
that use the claim terms foam but which do not contain this
requirement. Thus properly understood, AVI is not attempting to
construe existing claim language; it is attempting to limit the
scope of the invention itself by adding a requirement not found
AVI's construction is contrary to existing precedent. As
explained in Autogiro Co. of Am. v. United States, 181 Ct.Cl.
55, 384 F.2d 391, 395-96 (Ct.Cl. 1967):
The claims of the patent provide the concise formal
definition of the invention. They are the numbered
paragraphs which particularly [point] out and
distinctly [claim] the subject matter which the
applicant regards as his invention. It is to these
wordings that one must look to determine whether
there has been infringement. Courts can neither
broaden nor narrow the claims to give the patentee
something different than what he has set forth. No
matter how great the temptations of fairness or
policy making, courts do not rework claims. They only
See also E.I. du Pont de Nemours & Co. v. Phillips Petroleum
Co., 849 F.2d 1430, 1433 (Fed.Cir.) (citing Autogiro), cert.
denied, 488 U.S. 986, 109 S.Ct. 542, 102 L.Ed.2d 572 (1988);
McCarty v. Lehigh Valley R. Co., 160 U.S. 110, 116, 16 S.Ct.
240, 40 L.Ed. 358 (1895) ("[W]e know of no principle of law which
would authorize us to read into a claim an element which is not
present. . . ."). Here, the plain language of the claims does not
require dimensional stability. As such, to read this requirement
into them would be error. See du Pont, 849 F.2d at 1433
(discussed below); American Standard Inc. v. Pfizer Inc.,
722 F. Supp. 86, 93 (D.Del. 1989) (refusing to read requirement of
"bone growth" into patent); Procter & Gamble Co. v. Nabisco
Brands, Inc., 711 F. Supp. 759, 764-65 (D.Del. 1989).
Furthermore, the examiner in charge of prosecution of the
isobutane patents specifically treated the term "dimensionally
stable" numerous times and allowed claims both with and without
this language. If the examiner wanted the requirement of
dimensionally stable in the claims, he presumably would have
ensured that it appeared there. AVI thus, in effect, asks the
Court to hold the examiner incompetent to understand this
distinction among Dow's claims. Additionally, it seeks to have
this Court substitute its judgment for the PTO by having the
claims limited by the language dimensionally stable. This is not
appropriate. See Intervet, 887 F.2d at 1054 ("The presumption
of validity under 35 U.S.C. § 282 carries with it a presumption
the examiner did his duty and knew what claims he was allowing.
In any event, the claims as allowed are what we have to deal with
and it is not for the courts to say that they contain limitations
which are not in them.") (citations omitted).
AVI's construction also is at odds with the doctrine of claim
differentiation, which presumes that there is a difference in
scope among the claims of a patent. See, e.g., United States v.
Telectronics, Inc., 857 F.2d 778, 783-84 (Fed.Cir. 1988), cert.
denied, 490 U.S. 1046, 109 S.Ct. 1954, 104 L.Ed.2d 423 (1989).
Simply stated, by reading the requirement of dimensionally stable
foam from the narrower dependent claims of the isobutane patents
into the broader independent claims, AVI renders
the dependent claims superfluous.*fn2 See id.; Beachcombers v.
WildeWood Creative Products, Inc., 31 F.3d 1154, 1162 (Fed. Cir.
1994) (stating that it is "presumptively unreasonable" to
interpret different claims as having the same scope); Specialty
Composites v. Cabot Corp., 845 F.2d 981, 987 (Fed.Cir. 1988)
("Where some claims are broad and others narrow, the narrow claim
limitations cannot be read into the broad whether to avoid
invalidity or escape infringement.") (quoting Kalman v.
Kimberly-Clark Corp., 713 F.2d 760, 770, (Fed. Cir. 1983),
cert. denied, 465 U.S. 1026, 104 S.Ct. 1284, 79 L.Ed.2d 687
AVI advances several arguments that merit discussion. First,
AVI relies on the specifications of the isobutane patents, which
speak of dimensional stabile foam. Its mistake here, however, is
that while dimensional stability is undeniably an advantage of
the isobutane patents as recited in the specifications, it is
improper to read this advantage from the specification sections
into the claims as a requirement of the inventions themselves.
Comark Communications, Inc., 156 F.3d at 1186 (noting that
Federal Circuit has repeatedly held "limitations from the
specification are not to be read into the claims"); Vehicular
Techs. Corp. v. Titan Wheel Int'l, Inc., 141 F.3d 1084, 1096
(Fed.Cir. 1998) (Newman J., dissenting) ("Advantages described in
the body of the specification, if not included in the claims, are
not per se limitations to the claimed invention."); Hoganas AB
v. Dresser Indus., Inc., 9 F.3d 948, 950 (Fed.Cir. 1993)
(finding that district court erred in interpreting "
`straw-shaped, channel-forming element' limitation to mean
`straw-sized' . . . because [the claim] does not impose any
requirement as to size."); du Pont, 849 F.2d at 1433 (Fed. Cir.
1988) ("It is entirely proper to use the specification to
interpret what the patentee meant by a word or phrase in the
claim. But this is not to be confused with adding an extraneous
limitation appearing in the specification, which is improper.")
(internal citation omitted).
Second, AVI relies on the prosecution history to support its
construction. However, the preceding principle applies equally
here; that is, while the prosecution history is relevant to
interpreting the claim language, see Laitram Corp. v. Morehouse
Ind., Inc., 143 F.3d 1456, 1463 (Fed.Cir. 1998), it cannot be
used to rewrite claims to impose a requirement not found in the
claim language. See Intervet, 887 F.2d at 1053 (stressing the
"impropriety of injecting into claims limitations from the
prosecution history"). At bottom, AVI is not using the
prosecution history to aid in the interpretation of a term
already in the claim — which would be entirely permissible.
Rather, it is using the prosecution history to import an
additional property into the claim — an entirely inappropriate
tactic. See id.
The du Pont case is instructive in this regard. In that case,
the district court interpreted the claims as including two
properties or advantages of the claimed inventions — "superior
environmental stress crack resistance and impact strength." 849
F.2d at 1433. The Federal Circuit reversed, holding that
"[c]ourts can neither broaden nor narrow the claims to give the
patentee something different than what he has set forth. No
matter how great the temptations of fairness or policy making,
courts do not rework claims. They only interpret them." Id.
(quoting Autogiro, 384 F.2d at 395-96). Like the du Pont
defendants, AVI seeks to add a property to claims that contain no
such property. du Pont teaches this would be error.
Third, AVI contends that the claim language itself supports its
construction because the claim language includes the term
"stability control agent," which has as its basic purpose to
allow for dimensional stable foam. The flaw here, however, is
that while dimensional stability is obviously an intended
advantage or purpose of the patents as expressed by the stability
control agent component, it is not a requirement contained in the
claims themselves. In other words, the isobutane patent claims in
question do not claim dimensionally stable foam. See, e.g., du
Pont, 849 F.2d at 1433; American Standard Inc., 722 F. Supp. at
93. This distinction between an advantage and a limitation is
illustrated by an example offered by Dow. An engineer invents an
electric car that can travel 100 miles per hour. The engineer
files a patent application claiming an electric car traveling 100
miles per hour comprising an automobile with four wheels, a
battery, an electric motor, and a widget connecting the battery
to the electric motor that increases the motor's efficiency. The
invention is the car — comprised of a body with four wheels, a
battery, an electric motor and a widget — not that the car can
travel 100 miles per hour. The speed of the car is an advantage
of the invention, not a limitation to the claim. In this case,
the invention is the use of a blowing agent in conjunction with a
permeability modifier that allows for dimensionally stable foam;
it is not the advantage of dimensionally stable foam.
Fourth, AVI points to the term "dimensional stability" in the
preamble of the '027 patent, asserting that the preamble of the
claim is a positively stated limitation of the claim. The Federal
Circuit has held that:
A claim preamble has the import that the claim as a
whole suggests for it. Where a patentee uses the
claim preamble to recite structural limitations of
his claimed invention, the PTO and courts give effect
to that usage. Conversely, where a patentee defines a
structurally complete invention in the claim body and
uses the preamble only to state a purpose or intended
use for the invention, the preamble is not a claim
Rowe v. Dror, 112 F.3d 473, 478-79 (Fed. Cir. 1997) (internal
quotations and citations omitted); see also Kropa v. Robie,
187 F.2d 150, 151-52 (Cust. & Pat.App. 1951) (summarizing collection
of cases). In this case, dimensional stability is not a
structural limitation of the claims, but rather, an advantage or
objective of the invention. Moreover, the claim body defines the
structurally complete invention. As such, the preamble of the
'027 patent does not support AVI's construction.
Finally, AVI suggests that without defining foam as
dimensionally stable, the isobutane patents add nothing to the
prior art and thus would be invalid. This stage of the
proceeding, however, is addressed only to the construction phase
of the isobutane patents. See, e.g., Stairmaster Sports/Med.
Prods., Inc. v. Groupe Procycle, Inc., 1998 WL 290296, at *2 n.
5 (D.Del. May 20, 1998); Rohm and Haas Co. v. Lonza Inc.,
997 F. Supp. 635, 639-40 (E.D.Pa. 1998). Inasmuch as AVI relies on the
"language in [prior] decisions [that] may have given the
perception that claims are to be `saved' from invalidity by
reading extraneous limitations into them, [the Federal Circuit's]
consistent approach in interpreting claims, and in rejecting
resort to extraneous limitations from the specification, should
have negated that perception by now." du Pont, 849 F.2d at 1434
(internal citations omitted).
It also is significant that aside from being incorrect as a
matter of patent interpretation, AVI'S construction is incorrect
as a factual matter. As noted by Dow, the isobutane patents do
not always result in dimensionally stable foam as defined by AVI.
Thus, to say foam means dimensionally stable foam is
inaccurate, and does not reflect the invention as set forth in
For all these reasons, I cannot accept AVI's proposed
construction that adds the requirement of "dimensionally stable"
the claim terms "polyolefin foam" in the '933 patent, "polymeric
composition" in the '361 patent and "olefin polymer foam" in the
C. The Perforation Patents
Turning now to the perforation patents, AVI seeks the
construction of the following terms: (1) "plastic foam" in the
'016 patent and "polyethylene foam" in the '058 patent; (2)
"accelerated release" in both patents; (3) "perforating" in both
patents; and (4) "extruded" in independent claim 1 of the '016
patent and independent claim 44 of the '058 patent. Each will be
addressed in turn.
1. Plastic Foam and Polyethylene Foam
AVI contends that "plastic foam" and "polyethylene foam" means
foam product of any thickness, and therefore, encompasses both
plank and sheet foam thickness.
Dow, in response, concedes that the terms refer to foam product
regardless of thickness. Nonetheless, it asserts that when used
in the context of the invention, which accelerates the release of
a blowing agent, the terms refer to polyethylene foam containing
a permeability modifier and a blowing agent.
I disagree with this last part of Dow's construction. First,
limiting plastic foam to polyethylene foam is incorrect, as
polyethylene is only one of the potential plastic resins listed
in the '016 patent. Second, while admittedly the foam must
contain a blowing agent and a permeability modifier, those are
additional undisputed limitations already existing in the claim.
Thus, they are unnecessary to the construction of the above
2. Accelerated Release
The next term at issue is the preamble term "accelerated
release." In this regard, AVI mounts a two-tiered attack. As an
initial matter, it argues that construction of the preamble claim
term accelerated release is unnecessary because it should not be
read to limit the claims as it relates to only the purpose of the
patent rather than a structural limitation. Alternatively, it
asserts that accelerated release means that the rate of release
of the blowing agent occurs more quickly than what the rate of
release would be without channels perforating the foam. Oddly,
Dow skips over AVI's first tier of argument and proceeds to the
second, to which it counters that accelerated release means that
the rate or release of the blowing agent over time, after
perforating, is increased so that the time required to cure the
foam is substantially reduced relative to the time required to
cure the foam without perforation.
As to AVI's first point that the preamble term accelerated
release is not a claim limitation, I disagree. As previously
explained, a preamble is a claim limitation if it is necessary to
provide meaning to the claimed invention. Rowe, 112 F.3d at
478-79; In re Paulsen, 30 F.3d 1475, 1479 (Fed.Cir. 1994).
Conversely, it is not a limitation if the claimed invention is
complete and the preamble only states a purpose or intended use
of the invention. Rowe, 112 F.3d at 478-79. Here, the preamble
states as follows: "A method for providing accelerated release of
a blowing agent from an extruded plastic foam. . . ." Accelerated
release is thus more than just a mere statement of the purpose of
the perforation patents; it is essential to breath life, meaning,
and vitality to the claims. See In re Paulsen, 30 F.3d at 1479;
Bell Communications Research, Inc. v. Vitalink Communications
Corp., 55 F.3d 615, 620 (Fed. Cir. 1995); Porter v. Farmers
Supply Serv., Inc., 790 F.2d 882, 885 (Fed.Cir. 1986) (stating
that preamble "gives meaning to other elements of the claimed
invention"); see generally 2 DONALD S. CHISUM,
PATENTS § 8.06[d] (1998). Further, in light of the
specification and prosecution histories, it is plain that the
claims require accelerated release. See Rowe, 112 F.3d at
Turning to the construction of that term, I agree with AVI that
it means that the rate of release of the blowing agent occurs
more quickly than what the rate of release would be without
channels perforating the foam. Interpretation begins with the
words in a claim, which should generally be ascribed their
ordinary and customary meaning. See, e.g., Bell Communications
Research, Inc., 55 F.3d at 620. The ordinary meaning of the word
accelerated is to increase over what would otherwise be the case.
This comports with AVI's construction.
In addition to examining ordinary meaning, "it is always
necessary to review the specification to determine whether the
inventor has used any terms in a manner inconsistent with their
ordinary meaning. The specification acts as a dictionary when it
expressly defines terms used in the claims or when it defines
terms by implication." Vitronics, 90 F.3d at 1582 (citing
Markman, 52 F.3d at 979); Hormone Research Found., Inc. v.
Genentech, Inc., 904 F.2d 1558, 1563 (Fed.Cir. 1990) ("[A]
patentee is free to be his or her own lexicographer and thus may
use terms in a manner contrary to or inconsistent with one or
more of their ordinary meanings.").
In the case at bar, the specification defines the term to mean
that "[t]he blowing agent permeates from the foam into channels
to accelerate the release of blowing agent from what the rate
would be without channels." See the '016 patent, at 3:20-24
(emphasis added). Again, this comports with AVI's construction.
See Vitronics, 90 F.3d at 1582 (espousing that specification is
generally dispositive and "is the single best guide to the
meaning of a disputed claim term"). Conversely, noticeably absent
from this specification definition is any adjective like
"substantially" to support Dow's construction. Nor is there any
rate or quantity of release of blowing agent from the foam after
perforation is set forth, other than a rate a release greater
than a foam with no channels.
For these reasons, I agree with AVI's construction of
The next claim term at issue is "perforating." AVI construes
perforating to mean using any device that creates "channels" in
the foam, which channels may be any cross-sectional shape,
including rectangular. Dow does not disagree with that definition
insofar as it goes; however, it seeks to add a functional
limitation that the channels formed must "allow accelerated
release of the blowing agent so that the cure time is
As I have already noted, accelerated release is to be read into
the claim to the extent stated above. Accordingly, I construe
"perforating" to mean using any device that creates "channels" in
the foam, which channels may be any cross-sectional shape,
including rectangular, that allow for the accelerated release of
a blowing agent.
The final claim term in dispute is "extruded." According to
AVI, extruded means foam created by using the wellknown extruder
apparatus that uses a screw-device to continuously force
pressurized polymer gel through a die into a lower pressure area.
Dow's definition, by contrast, is that of forcing a polymer gel
through a die under a compressive force.
Essentially, the point of disagreement between the parties is
whether extruded should be limit to any one type of process or to
the use of any specific apparatus. As to this construction issue,
I side with Dow. The language in the specifications of the
perforation patents does not limit the term extruded to a
specific type of process and apparatus. See du Pont, 849 F.2d
at 1433; American Standard Inc., 722 F. Supp. at
93; Hoganas 9 F.3d at 950. Rather, the specifications state, in
Providing the plastic foam comprises blending of
various components, including a resinous melt of a
foamable polymer and a blowing agent, under pressure
to form a foamable plastic gel and extruding the
foamable gel through a conventional die (not shown)
to a region of lower pressure to form the foam. The
blending of various components of the foamable gel
may be accomplished according to known techniques in
the art. Suitably a mixer, extruder, or other
suitable blending device (not shown) may be
emphasized to obtain homogeneous gel. The molten
foamable gel is then be [sic] passed through
conventional dies to form the foam.
'016 patent, col. 4, lines 16-27 and '058 patent, col. 4, lines
33-44 (emphasis added). Furthermore, no limitation on the term is
provided anywhere in the patents or the prosecution histories.
Although the example in the '016 patent utilizes an extruder
apparatus that appears to be of a conventional screw-type, it is
improper to read this extraneous limitation in the specification
into the claims. See, e.g., du Pont, 849 F.2d at 1432;
Intervet, 887 F.2d at 1056.
Accordingly, I find that extruded means forcing a polymer gel
through a die under a compressive force.
For the reasons stated above, I hold that: (1) "polyolefin
foam" in the '933 patent, "polymeric composition" in the '361
patent and "olefin polymer foam" in the '027 patent do not
require dimensional stability, and that the preamble of the '027
patent does not limit the claim to foams that have dimensional
stability; (2) "plastic foam" in the '016 patent and
"polyethylene foam" in the '058 patent mean foam product of any
thickness; (3) "accelerated release" in both perforation patents
means that the rate of release of the blowing agent occurs more
quickly than what the rate of release would be without channels
perforating the foam; (3) "perforating" in both perforation
patents means using any device that creates "channels" in the
foam, which channels may be any cross-sectional shape, including
rectangular, that allow for the accelerated release of the
blowing agent; and (5) "extruded" in independent claim 1 of the
'016 patent and independent claim 44 of the '058 patent means
forcing a polymer gel through a die under a compressive force.
IT IS SO ORDERED.