DAMODARAM SANJIVAYYA NATIONAL LAW UNIVERSITY

VISAKHAPATNAM, A.P., INDIA

Doctrine Of Equivalent And Prior History

Estoppel – A Critical Analysis

SUBJECT
Intellectual Property Rights

NAME OF THE FACULTY

Dr.P.Sree Sudha

Name of the Candidate: - Shaik MD Umar Abdullah

Roll No: - 2017084

Semester: - V
 ACKNOWLEDGMENT
I would sincerely like to put forward my heartfelt appreciation to our respected Intellectual
Property Rights professor- Dr.P.Sree Sudha for giving me a golden opportunity to take up
this project regarding ― “Doctrine Of Equivalence And Prior History- A Critical
Analysis.” I have tried my best to collect information about the project in various possible
ways to depict clear picture about the given project topic.

2
 Abstract

Doctrine Of Equivalence And Prior History Estoppel – A Critical Analysis

Patents are acknowledged to be one of the most difficult legal instruments to draw with
accuracy. Perhaps it is the level of technical detail and the need to capture a multitude of
permutations employing a single basic idea that most complicates the crafting of claims. Or,
the difficulty may stern from the fact that patents may issue only for "novel" ideas that have
yet to work their way into the common vernacular, forcing the draftsperson to strain the
meanings of well-known terms to articulate best the core inventive notion. Perhaps in
recognition of these difficulties, the patent law includes a collection of interpretive doctrines,
some statutory and some judicially developed, that allow courts to look beyond the literal
language of the claims. Every patentee may be his own lexicographer, and thus is free to
define claim terms in the body of the specification. Similarly, if the court is uncertain as to
the meaning of a claim, it "must look to the language of the claim, and the patent's
specification and prosecution history to properly interpret the scope of a patent claim.”

The modern doctrine of equivalents lacks theoretical justification, imposes high costs on
society, and likely impedes innovation and also needlessly conflicts with other patent law
doctrines and complicates patent law procedures. These adverse effects are cumulatively
imposed over time in regard to every issued and litigated patent for its entire term. The
doctrine of equivalents should be restored to its historic forming patent protection to the
scope of application of the patent claims' construed language. As under the European Patent
Convention, any residual fairness concerns would be addressed better by non literally
interpreting claim language than by applying the modern doctrine of equivalents.

This researcher in this project discusses the lack of theoretical justification for the modern
doctrine of equivalents, the complexity that it creates and explains how the modern conflicts
with substantive standards and generates needless complexity. Further the arguments by court
through which the doctrine is evolved are critically analyzed

3
Doctrine Of Equivalence And Prior History Estoppel – A Critical Analysis

Project synopsis

INTRODUCTION
Patents are acknowledged to be one of the most difficult legal instruments to draw with
accuracy. Perhaps it is the level of technical detail and the need to capture a multitude of
permutations employing a single basic idea that most complicates the crafting of claims. Or,
the difficulty may stern from the fact that patents may issue only for "novel" ideas that have
yet to work their way into the common vernacular, forcing the draftsperson to strain the
meanings of well-known terms to articulate best the core inventive notion. Perhaps in
recognition of these difficulties, the patent law includes a collection of interpretive doctrines,
some statutory and some judicially developed, that allow courts to look beyond the literal
language of the claims. Every patentee may be his own lexicographer, and thus is free to
define claim terms in the body of the specification. Similarly, if the court is uncertain as to
the meaning of a claim, it "must look to the language of the claim, and the patent's
specification and prosecution history to properly interpret the scope of a patent claim.”

The modern doctrine of equivalents lacks theoretical justification, imposes high costs on
society, and likely impedes innovation and also needlessly conflicts with other patent law
doctrines and complicates patent law procedures. These adverse effects are cumulatively
imposed over time in regard to every issued and litigated patent for its entire term. The
doctrine of equivalents should be restored to its historic forming patent protection to the
scope of application of the patent claims construed language. As under the European Patent
Convention, any residual fairness concerns would be addressed better by non literally
interpreting claim language than by applying the modern doctrine of equivalents.

AIM/OBJECTIVE
To critically analyze the doctrine of equivalence and prior history estoppels and examine the
relevant case law in an effort to highlight the issues that factor into the doctrine of equivalents
analysis, and also to assess whether the courts have developed a coherent framework for
implementing the doctrine and to explore in detail the practical difficulties inherent in the
application of the tripartite test.

4
 SIGNIFANCE OF THE PROJECT
The modern doctrine of equivalents lacks theoretical justification, imposes high costs on
society, and likely impedes innovation and also needlessly conflicts with other patent law
doctrines and complicates patent law procedures. These adverse effects are cumulatively
imposed over time in regard to every issued and litigated patent for its entire term. The
doctrine of equivalents should be restored to its historic forming patent protection to the
scope of application of the patent claims construed language. Therefore the researcher in this
project would analyze the uncertainty of the doctrine and determine the scope of this doctrine
in light of relevant case laws. This project would bring into limelight as to why the present
doctrine is irrelevant and should be abolished.

SCOPE OF THE PROJECT

The scope of this research is limited to critically analyzing the doctrine of equivalence and
prior history estoppels in light of relevant case laws and development of scope of patent law

RESEARCH QUESTION
1. Whether the modern doctrine lacks theoretical justification and conflicts with other
doctrines?

HYPOTHESIS
That the modern doctrine expands and renders more uncertain over time of patent protection
and is conflicts with substantive standards and generates needless complexity.

LITERATURE REVIEW
1. Martin J. Adelmant And Gary L. Francione “The Doctrine Of Equivalents In Patent
Law” 137 UPLR 674 (1989)
Part I of this Article provides a brief introduction to the role of the doctrine of equivalents in
patent law. Part II reviews the Pennwalt decision and argues that it did not substantially
reduce the tensions in patent law stemming from the doctrine of equivalents. Part III
canvasses the modern articulation of the doctrine of equivalents and argues that the doctrine
has become the patent law analogue to the "substantial similarity" concept in copyright law.
After a review of the primary uses and legitimacy of the uses of the doctrine of equivalents,
Part IV proposes that there is, at best, a very limited need for the doctrine of equivalents.

5
2. Kurt L. Glitzenstein “A Normative And Positive Analysis Of The Scope Of Doctrine Of
Equivalents” 7 HJLT 282 (1994)
This article explores in detail the practical difficulties inherent in the application of the
tripartite test. Further attempts to unravel the myriad justifications militating in favor of and
against application of the doctrine. Finally, it undertakes a constitutionally-founded
normative study of the doctrine, focusing in particular on the scope of equivalents protection
afforded a patent holder.

3. Joshua D. “Sarnoff Abolishing the Doctrine of Equivalents and Claiming the Future
After Festo” 19 BTLJ 1157-1225 (2004)
This Article argues that the Supreme Court or Congress should abolish patent law's modern
doctrine of equivalence as it lacks theoretical justification and imposes high costs on the
society. These articles seek to encourage and contextualize discussions of abolishing the
modern doctrine

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CONTENTS
1. INTRODUCTION ……………………………………………………………………8
2. NATURE OF DOCTRINE …………………………………………………………..9
3. WHAT CONSTITUTES EQUIVALENT ………………………………………….11
4. SCOPE OF THE DOCTRINE ………………………………………………………12
5. THE TESTES OF EQUIVALENCE ………………………………………….…….12
(i) All elements rule,
(ii) Tri-partite test: Function, way, result
(iii) Insubstantial differences test
(iv)Obviousness test
(v) Known interchangeability test
6. LEGAL BARS TO THE APPLICATION OF THE DOCTRINE………………. 17
6.1. Prosecution history estoppel
6.1.1. Impact of Festo on prosecution history estoppel
6.2. Public dedication,
6.3. After arising equivalents for means-plus-function claims, and
6.4. Prior art patentability.
6.5. The obviousness bar
7. THE INADEQUATE JUSTIFICATIONS FOR THE MODERN DOCTRINE….22
A. Graver Tank's, Rationales ……………………………………………………..….23
1. Fairness and Copying
a) Limits to Broad Claims
b) Limits to and Costs of Specific Claims
c) Mistakes
2. Limits to Language
3. Encouraging Disclosures
B. Warner-Jenkinson's Rationales …………………………………………..…….27
1. Factual Equivalency
a) Construction and Application Versus
b) Time of Infringement and Historic
2. Implied Claim Terms
3. Avoiding Implied Disclaimers
C. Festo's Rationales …………………………………………………………...……..28
8.CONCLUSION ………………………………………………………..……………..29

7
INTRODUCTION
The scope of a patent is not limited to its literal terms, but instead embraces all equivalents to
claims described in a patent application. Limiting the scope of a patent to its literal elements,
would allow a competitor to make an unimportant or insubstantial change to the patented
invention and thereby defeat the patent. The doctrine of equivalents is an important tool of
law (developed by the courts of United States) to determine infringement in cases of non-
literal infringement. The doctrine removes unfairness that could result from an overemphasis
on the literal language of patent claims, and thereby affords protection accorded to the patent.
The doctrine strikes a balance between a fair scope for the patent and the notice the patent
provides for the public, along with a balance between incentives to innovate and costs of
uncertainty.
It is not always that the nature of language in a patent application reflects the true essence of
an invention. The inventor who chooses to patent an invention and discloses it to the public,
rather than exploit it in secret, bears the risk that others will devote their efforts towards
exploiting the patent beyond the limits of its language. ‘An invention exists most importantly
as a tangible structure or a series of drawings. A verbal portrayal is usually an afterthought
written to satisfy the requirements of patent law. This conversion of machine to words allows
for unintended idea gaps which cannot be satisfactorily filled. Often the invention is novel
and words do not exist to describe it. The dictionary does not always keep abreast of the
inventor. It cannot. Things are not made for the sake of words, but words for things.1

It was because of this difficulty that the US Supreme Court expressed, as early in 1853, that a
patent covers ‘not only the precise forms the patentee has described, but all other forms
which embody his or her invention.’2 Pronouncing a preference for substance over form, the
Court said: ‘Where form and substance are inseparable, it is enough to look at the form only.
Where they are separable; where the whole substance of the invention may be copied in a
different form, it is the duty of courts and juries to look through the form for the substance of
the invention--for that which entitled the inventor to his or her patent, and which the patent
was designed to secure; where that is found, there is an infringement……’3 The Court further

1
Festo Corp v Shoketsu Kinzoku Kogyo Kabushiki Co Ltd, 535 US 722, 731-32 (2002) (quoting: Autogiro Co of
America v United States, 384 F 2d 391, 397 (Ct Cl 1967).
2
ibid
3
Stating the comparison as one between the claim and the accused product is preferable to stating it as one
between the claimed product and the accused product. The former makes it clearer that the accused product is
not compared to a particular embodiment of the claim but rather to the claim itself. A claim could include any
number of products, all of which could be called claimed products. Another preferable option would be to
compare the claimed invention and the accused product.

8
highlighted that a patent is an exclusive right that ‘is not secured, if the public are at liberty to
make substantial copies of it, varying its form or proportions.4

If the proposition that the scope of a patent is limited to its literal elements is accepted, it
would allow a competitor to make an unimportant or insubstantial change to a patented
invention and thereby defeat the patent.5 Instead, the scope of a patent is not limited to its
literal terms but instead embraces all equivalents to the claims described.6 This forms the
basis of the ‘doctrine of equivalents’, which was first adopted by the Supreme Court of US in
1854.7

In short, the doctrine mandates that in the absence of literal infringement, a product may be
found to infringe a patented product if it is found to be its substantial equivalent. A non-literal
infringer infringes a patent by practicing the invention. However, in the non-literal
infringement analysis, practicing the invention involves a product that does not literally meet
at least one claim limitation but either literally meets or contains an equivalent to all claim
limitations of at least one claim of the patent.

For example, the claim reading ‘a device comprising A + B + C’ would be (non-literally)

infringed by a product consisted of A + B + D, if D is an equivalent of C.

‘DOCTRINE OF EQUIVALENTS’: NATURE OF THE DOCTRINE

The ‘Doctrine of Equivalents’ proposes that despite an absence of literal infringement of
express terms of a patent claim, the infringement can still be proven if an element of an
accused product or service and a claimed element of patented invention are found to be
legally equivalent.8 In other words, the doctrine expands the protection an inventor receives
for his invention (based on the literal wording of the claims in a patent application), as the
doctrine holds that a patentee can claim rights to inconsequential alterations to the thing
patented, which are not literally covered by the original claims, but which could be achieved

4
Michel, The role and responsibility of patent attorneys in improving the Doctrine of Equivalents, IDEA: The
Journal of Law and Technology, 40 (2000) 123, 128-129, Zimmerman Scott P, The Doctrine of Equivalents: A
call for congressional reinvigoration, IDEA: The Journal of Law and Technology, 40 (2000) 599 (calling for the
obviousness test to be made the test for equivalence under the doctrine of equivalents through legislative
intervention). Siekman Michael T, The expanded hypothetical claim test: A better test for infringement for
biotechnology patents under the Doctrine of equivalents, Boston University Journal of Science & Technology
Law, 2 (1996) 6.
5
Supra at 1
6
ibid
7
ibid
8
Hsing Benjamin, Practicing Law Institute/ Patent Litigation 115 (2002)

9
with little effort. It ‘prevents a person from practicing a fraud on a patent by substituting
obvious equivalents for elements in the claims in order to avoid their literal language.’9

A patent owner may invoke the doctrine of equivalents in an infringement suit if the allegedly
infringing device ‘performs substantially the same function in substantially the same way to
obtain the same result.’ 10 In simpler words, it protects a patentee from infringement by a
person who makes insubstantial changes to the patented invention by taking a new device out
of the literal realm of the claims, yet basically embodying the same invention.11

The doctrine also recognizes that ‘to permit imitation of a patented invention which does not
copy every literal detail would be to convert the protection of the patent grant into a hollow
and useless thing.’12

The doctrine serves to ‘temper unsparing logic and prevent an infringer from stealing the
benefit of the invention.’13 The existence, scope and extent of the doctrine of equivalents
represents a balance between a fair scope for the patent and the notice the patent provides for
the public, along with a balance between incentives to innovate and the costs of uncertainty.14
It removes the unfairness that could result from an overemphasis on the literal language of
patent claims, and thereby ensures protection accorded by the patent.

On the other hand, guiding rules, i.e. all elements rule; tri-partite test (function, way, result);
insubstantial differences test; obviousness test, and known interchangeability tests, limit the
application of the doctrine. They ensure that the doctrine does not take on ‘a life of its own,
unbounded by the patent claim’ to provide protection not within the scope of the patent, and
would thereby eliminate an important function of patents: clear public notice of patentee's
scope of exclusive right.15 It is a measure of law that strikes a balance between the interest of
the inventor to maintain a temporary monopoly, with the interest of the general public to
‘pursue innovations, creations, and new ideas beyond the inventor's exclusive rights.’

9
Chisum Donald S, Chisum on Patents (LexisNexis, New York), 2002 at G1-3.
10
Supra at 8
11
‘The Supreme Court in Graver Tank ... made insubstantial differences the necessary predicate for
infringement under the doctrine of equivalence.’ Hilton Davis Chemical Co v Warner-Jenkinson Co Inc, 62 F
3d 1512, 1517 (Fed Cir 1995). The Court in Hilton Davis went on to explicitly hold that ‘the application of the
doctrine of equivalents rests on the substantiality of the differences between the claimed and the accused
products or processes, assessed according to an objective standard.’ Hilton Davis Chemical Co v Warner-
Jenkinson Co Inc, 62 F 3d 1512, 1518 (Fed Cir 1995).
12
Supra at 4
13
Royal Typewriter Co v Remington Rand Inc, 168 F 2d 691, 692 (2d Cir 1948).
14
Royal Typewriter Co v Remington Rand Inc, 168 F 2d 691, 692 (2d Cir 1948). Warner-Jenkinson v Hilton
Davis Chemical Co, 520 US at 36.
15
Johnson & Johnston Assocs Inc v R E Service Co, 285 F 3d 1054 (Fed Cir 2002) (en banc).

10
However, the doctrine does not encompass equivalents that belong to the state of the art or
which are obvious to the state of the art.16

WHAT CONSTITUTES ‘EQUIVALENTS’

It was proposed in Graver Tank that ‘a patentee may invoke this doctrine to proceed against
the producer of a device ‘if it performs substantially the same function in substantially the
same way to obtain the same result.’17 Further, the Court stated that ‘it’ means the device as a
whole and that ‘the theory on which it is founded is that 'if two devices do the same work in
substantially the same way, and accomplish substantially the same result, they are the same,
even though they differ in name, form, or shape.’18

The post-Graver Tank environment has been tumultuous. The reason being that the key
question of ‘what constitutes an equivalent?’ has never been answered with certainty.19 It is
submitted that the ‘finding of equivalence is a finding of fact’. 20 It must be noted that
infringement exists where the alleged device copies the patented mode of operation, even
where the copy is ‘totally unlike the original in form or proportions.’21 Furthermore, where a
patentee describes his invention and claims it ‘in that form, which most perfectly embodies
it,’ he is ‘deemed to claim every form in which his invention may be copied, unless he
manifests an intention to disclaim some of those forms.’22

In Warner-Jenkinson, it has been proposed that ‘equivalency must be determined against the
context of the patent, the prior art, and the particular circumstances of the case. Equivalence,
in the patent law, is not a prisoner of a formula and is not an absolute to be considered in a
vacuum.’23 It does not require complete identity for every purpose and in every respect. In
determining equivalents consideration must be given to the purpose for which an ingredient is
used in a patent, the qualities it possesses when combined with the other ingredients, and the
function which it is intended to perform.

16
White Katherine E, Festo: A case contravening the convergence of Doctrine of Equivalents jurisprudence in
Germany, the United Kingdom, and the United States, Michigan Telecommunication & Technology Law
Review, 8 (2001-2002) 1.
17
Sanitary Refrigerator Co v Winters, 280 US 30, 42 (1929
18
Union Paper-Bag Mach Co v Murphy, 97 US 120, 125 (1877
19
Chisum Donald S, The scope of protection for patents after the Supreme Court's Warner-Jenkinson decision:
The fair protection-certainty conundrum, Santa Clara Computer & High Technology Law Journal, 14 (1998) 1,
15; Adelman Martin J & Francione Gary L, The Doctrine of Equivalents in patent law: Questions that Pennwalt
did not answer, University
20
Winans v Denmead, 56 US (15 How) at 609, 612, 614.
21
Ibid at 342
22
Ibid 343
23
Hilton Davis Chemical Co v Warner-Jenkinson Co Inc, 520 US at 24-25.

11
Another important factor to determine equivalents should be: whether a person reasonably
skilled in the art would have known of the interchangeability of an ingredient not
contained in the patent with one that was.24

Furthermore, it is submitted that the doctrine should not be limited to those equivalents which
were known at the time the patent was issued, or, more strictly, to those that were disclosed
within the patent itself. In this regard, the Court in Warner-Jenkinson held that ‘the proper
time for evaluating equivalency is at the time of infringement.’25

SCOPE OF THE DOCTRINE

The determination of the scope of the doctrine rests upon two factors.

(i) The test for equivalence, and

(ii) The legal bars to equivalents.26

It is submitted that both these steps must be undertaken to determine whether a particular
element of the accused product is equivalent to a particular claim limitation as a particular
element might meet a test for equivalents and yet still not be considered equivalent because it
fails one of the legal bars. For example, the element might perform substantially the same
function in substantially the same way to obtain the same result and yet might be barred from
equivalents by prosecution history estoppel. Conversely, a particular element might not fail
any of the legal bars and still not be equivalent because it does not meet the test for
equivalence. Of course, the need for a court to examine either step depends on the arguments
put forth by the parties.

THE TESTS OF EQUIVALENCE

To restrain the application of the doctrine, the courts have developed five legal tests:

(i) All elements rule,

(ii) Tri-partite test: Function, way, result,

(iii) Insubstantial differences test,

24
Winans v Denmead, 56 US (15 How) at 609.
25
Hilton Davis Chemical Co v Warner-Jenkinson Co Inc, 520 US at 37.
26
IDEA: The Journal of Law and Technology. The Honorable Paul R Michel, The role and responsibility of
patent attorneys in improving the doctrine of equivalents, IDEA: The Journal of Law and Technology, 40 (2000)
123, 124.

12
(iv) Obviousness test, and

(v) Known interchangeability test.

These tests have been developed by the judiciary in different cases and are now ‘crystallized’
of sorts.

All-Elements Rule27
To place some limitation on the doctrine of equivalents, the Federal Circuit in Pennwalt and
subsequently, the Supreme Court in Warner- Jenkinson adopted the so-called ‘All Elements
Rule.’

The Court in Pennwalt stated:

‘Under the doctrine of equivalents, infringement may be found (but not

necessarily) if an accused device performs substantially the same overall
function or work, in substantially the same way, to obtain substantially the same
overall result as the claimed invention. That formulation, however, does not
mean one can ignore claim limitations.... In applying the doctrine of
equivalents, each limitation must be viewed in the context of the entire claim....
To be a ‘substantial equivalent,’ the element substituted in the accused device
for the element set forth in the claim must not be such as would substantially
change the way in which the function of the claimed invention is performed ....’

It is clear from this that the district court correctly relied on an element-by-element
comparison to conclude that there was no infringement under the doctrine of equivalents,
because the accused devices did not perform substantially the same functions as the Pennwalt
invention.28

‘Each element contained in a patent claim is deemed material to defining the scope of the
patented invention, and thus the doctrine of equivalents must be applied to individual
elements of the claim, not to the invention as a whole. It is important to ensure that the

27
Pennwalt Corp v Durand-Wayland Inc, 833 F 2d 931 (Fed Cir 1987); Hilton Davis Chemical Co v Warner-
Jenkinson Co Inc, 520 US at 21.
28
Ibid at 29

13
application of the doctrine, even to an individual element, is not allowed such broad play as
to effectively eliminate that element in its entirety’.29

The all-elements rule is not a test in itself, but rather a rule for how the test for equivalents
under the doctrine of equivalents is to be applied. The rule states that the test for equivalents
must be applied on an element-by element basis. 30 For each limitation in the claim, the
product must have an element that reads on the limitation either literally or equivalently. If
the product does not contain a literal or equivalent element for each claim limitation, then
there can be no infringement.

The ‘all elements rule’ after Warner-Jenkinson is illustrated by the statements of Judge Plager
that one must apply either the function/way/result or the insubstantial difference test to each
element and check if the claimed and equivalent elements have an insubstantial difference or
the claimed and equivalent elements perform substantially the same function, in substantially
the same way, to produce substantially the same result. However, a careful reading of
Pennwalt suggests that in carrying out the element by- element analysis one should examine
the effect on the accused product or process as a whole on substituting only one element with
a corresponding claimed element. In short while determining equivalence each claim of the
infringed and infringing patent must be transposed with each other. Besides, one should not
examine the effect of substituting several elements of the accused product or process with
several claimed elements.

The all-elements rule serves to increase the amount of notice provided by the claims.31 By
requiring that the accused product contain an equivalent element for each claim limitation,
instead of requiring that the accused product be equivalent ‘as a whole,’ the all elements rule
provides potential infringers with more notice of what may or may not be an infringement of
the patent under the doctrine of equivalents. It is submitted that the all elements rule requires
that all of the elements of a patent claim must be present in an accused product or service,
though it need be present only equivalently, to support a finding of patent
infringement.32According to this rule, the doctrine of equivalents may not be used to supply
limitations that are wholly missing from an accused product or service. 33 Because the all

29
Hilton Davis Chemical Co v Warner-Jenkinson Co Inc, 520 US at 29.
30
Ibid at 40
31
Supra at 27
32
Ethicon Edo-Surgery Inc v US Surgical Corp, 149 F 3d 1309, 1329-30 (Fed Cir 1998).
33
SciMed Life Systems Inc v Advanced Cardiovascular Systems Inc, 242 F 3d 1337, 1347 (Fed Cir 2001).

14
elements rule protects the materiality of each claim limitation, it is also often described as a
rule against vitiating a limitation.34

Tri-Partite Test: Function, Way, Result35

The tri-partite test, or function-way-result test, is the most traditional test for determining
what is equivalent under the doctrine of equivalents. The tri-partite test states that an accused
product infringes under the doctrine of equivalents if it ‘performs substantially the same
function in substantially the same way to obtain the same result’ as the claimed invention.10
‘It is an offshoot of the ‘all elements rule’

A combination of the test with the all-elements rule, states that the accused product must
contain an element that performs substantially the same function in substantially the same
way to obtain the same result for each claim limitation, in order for the accused product to
infringe under the doctrine of equivalents.36

Insubstantial Differences Test

The Federal Circuit Court interpreted Graver Tank and other precedents as establishing an
ultimate test of equivalents: the insubstantial differences test. The substantiality of the
differences between the claim and accused product is the ultimate question under the doctrine
of equivalents. A finding of infringement under the doctrine of equivalents requires proof of
insubstantial differences between the claimed and accused products or processes.’

When combined with the all-elements rule, the test states that a finding of infringement under
the doctrine of equivalents requires proof of insubstantial differences between each claim
limitation and the corresponding element of the accused product or processes.

Obviousness Test37
The obviousness test for equivalents under the doctrine of equivalents has never been used or
even recognized in a majority court opinion, but it has been proposed by one Federal Circuit

34
Gross David J F & Gordon Shawn T, Claim construction, patent infringement, and the growing importance of
the claim vitiation defense, Practicing Law Institute /Patent Litigation, 841 (2005) 45,75.
35
Robert Greene Sterne & McPhail Donald R, The Doctrine of Equivalents, American Law Institute-ABA CLE,
18 (2000) 105, 111-118.
36
Industrias Metalicas Marva v Empresas Lausell, 1997 WL 557626 at 30.
37
Michel, IDEA: The Journal of Law and Technology, 40 (2000) 123, 128-29.

15
judge in a concurring opinion,38 mentioned as a possibility worth consideration by another
Federal Circuit judge,39 and championed by at least one commentator.40

Essentially, the proposed test would involve the use of the test for non-obviousness to
determine if the differences between the accused product and the claimed invention are
substantial. If the differences meet the test for non-obviousness, then the differences are
substantial and the accused product does not infringe under the doctrine of equivalents. If the
differences do not meet the test for non obviousness, then the differences are insubstantial
and the accused product infringes under the doctrine of equivalents.41

One advantage of using the obviousness test for determining equivalents under the doctrine
of equivalents is that the test is a well-understood, well developed test, with which judges and
practitioners are comfortable.42 Furthermore, the obviousness test has greater predictive value
than either the tri-partite test or the insubstantial differences test, because the obviousness test
refers to prior art instead of referring to abstractions.43 Finally, because the overall conclusion
of obviousness is a matter of law, using the obviousness test to determine equivalents under
the doctrine of equivalents would gain the benefits to accuracy and predictability that come
with deciding issues as legal questions as opposed to deciding them as factual questions.44

Known Interchangeability Test

The concept of ‘known interchangeability’ has been used in the doctrine of equivalents
analysis for some time. 45 It has long been considered a possible factor to examine when
determining equivalents. 46 This factor could be developed into a test. 47 Such a known
interchangeability test could state that proof of known interchangeability would either be
necessary or sufficient to prove equivalents under the doctrine of equivalents. As a necessary
test, a patent holder would have the burden of showing that the element in question was
known to be interchangeable with the claim limitation in order to prove infringement under
the doctrine of equivalents. As a sufficient test, a showing of known interchangeability would

38
Roton Barrier Inc v Stanley Works, 79 F 3d 1112, 1128 (1996) (Nies J, concurring).
39
Michel Paul R, The role and responsibility of patent attorneys in improving the doctrine of equivalents, IDEA:
The Journal of Law and Technology, 40 (2000) 123, 128-129.
40
Zimmerman Scott P, The Doctrine of Equivalents: A call for congressional reinvigoration, IDEA: The Journal
of Law and Technology, 40 (2000) 599.
41
Roton Barrier Inc v Stanley Works, 79 F 3d at 1128
42
Supra at 39
43
ibid
44
Tec Air Inc v Denso Mfg Mich Inc, 192 F 3d 1353, 1359 (Fed Cir 1999)
45
Graver Tank & Mfg Co v Linde Air Prods Co, 339 US at 609
46
Autogiro Co of America v United States, 384 F 2d 391, 397 (Ct Cl 1967)
47
Supra at 44

16
establish that the relevant element and the claim limitation were equivalent, but a showing of
known interchangeability would not be the only way for the patent holder to prove
equivalents.

LEGAL BARS TO THE APPLICATION OF THE DOCTRINE OF EQUIVALENTS

In addition, legal equivalency requires the patent owner's assertion of infringement to fall
outside various legal defenses to the doctrine. Legal bars define an area or products that lie
outside the scope of the patent. They do not define what is within the scope of a patent; that is
the function fulfilled by the test for equivalents. The legal bars and the test do not create one
co-extensive line dividing what is and what is not equivalent. An element of an accused
product that is not placed outside the range of equivalents by a legal bar might nonetheless
fail to meet the test for equivalents. Conversely, an element that meets the test for equivalents
might be placed outside the scope of the doctrine of equivalents by a legal bar. Thus, in order
to determine if a particular element is equivalent to a claim limitation, the test for equivalents
must be applied, and the legal bars to equivalents must be examined. The courts have
recognized four legal bars: prosecution history estoppel, public dedication, after arising
equivalents for means-plus-function claims, and prior art patentability.48

Prosecution History Estoppel

The price of broadening of a patentee's rights enabled under the doctrine of equivalents is
uncertainty.49 Innovators and competitors are left without a clear indication of what is and is
not covered by a patent. One helpful source of clarity has been the prosecution history of the
patent. Prosecution history estoppel dictates that the claims of a patent must be interpreted in
the light of prosecution history, or the process through which USPTO issued the patent based
on a submitted application.50 More specifically, the claims must be interpreted in the light of
their rejections, cancellations and amendments. A patentee is estopped from asserting
equivalents for a claim element when, for the purpose of patentability, he has amended a
claim in a way that surrenders the subject matter that he is now alleging is an equivalent.51

48
Michel Paul R, The role and responsibility of patent attorneys in improving the doctrine of equivalents, IDEA:
The Journal of Law and Technology, 40 (2000) 123, 125.
49
Shepard v Carrigan [116 US 530, at 593 (1886)]
50
Miller Jennifer, Festo: Blessing to patent holders or thorn in their sides? Duke Law & Technology Review,
(2002) 17 para 12.
51
ibid

17
As an estoppel doctrine, prosecution history estoppel prevents a litigant from denying an
earlier admission when another has relied upon it.52 In the context of patent prosecution, ‘the
admission is the applicant's surrender of claim scope to acquire a patent.

Prosecution history estoppel applies both 'to claim amendments to overcome rejections and
to arguments submitted to obtain the patent.53 Thus, the scope of the surrender, normally,
must be determined before the estoppel applies. The Court in Warner-Jenkinson, noted that
prosecution history estoppel most frequently arises when the applicant narrows a claim to
overcome a rejection based on the prior art. It was held:

‘Prosecution history estoppel continues to be available as a defense to

infringement, but if the patent-holder demonstrates that an amendment required
during prosecution had a purpose unrelated to patentability, a court must
consider that purpose in order to decide whether an estoppel is precluded.’

The Court stated that the better rule would allow the patent holder to demonstrate that an
amendment was made for a purpose unrelated to patentability. 54 If, however, the patent
holder is unable to establish such a purpose, the court should presume that prosecution
history estoppel applies.55

Prosecution history estoppel has received a great deal of attention from the courts recently.
This bar prevents a patent holder from reclaiming, through the doctrine of equivalents,
subject matter that was given up during prosecution of the patent. A claim amendment, claim
cancellation, or argument in support of patentability can create an estoppel. A claim
amendment creates a presumption that the change was made for reasons of patentability. This
presumption is refutable if the patent holder can show that the change was made for reasons
other than patentability. Prosecution history estoppel is strongly linked to the notice function
of the patent. The arguments and amendments made during prosecution of the patent serve as
sources of notice as to what the patent covers in addition to the notice provided by the issued
patent and its claims. Prosecution history estoppel has been treated as a way to limit the range
of equivalents, and not as a method to entirely eliminate the doctrine of equivalents as a form

52
Bonito Boats Inc v Thunder Craft Boats Inc, 489 US 141, 146-47 (1989).
53
Townsend Eng'g Co v HiTec Co, 829 F 2d 1086, 1090 (Fed Cir 1987) (quoting Hughes Aircraft v United
States, 717 F 2d 1351, 1362 (Fed Cir 1983)).
54
Hilton Davis Chemical Co v Warner-Jenkinson Co Inc, 520 US at 33-34
55
ibid

18
of infringement.56 In keeping with this tradition, prosecution history estoppel should remain
subservient to the doctrine of equivalents. This limitation has been altered by Festo Corp v
Shoketsu Kinzoku Kogyo Kabushiki Co Ltd.

Impact of Festo on Prosecution History Estoppel

In Festo, the Supreme Court of the United States, while continuing its support for the
doctrine, unanimously agreed with the decision of Federal Circuit on the point ‘that
prosecution history estoppel may apply any time an amendment is made to the application for
reasons of patentability, not just when the amendment is made to avoid the prior art’. 57
However, the Court rejected an attempt by the Federal Circuit to severely restrict application
of the doctrine of equivalents in situations where prosecution history estoppel applies. It held
that a presumption exists that prosecution history estoppel bars a finding of equivalence, but
the patentee may rebut that presumption. In order to rebut the presumption, a patentee ‘must
show that at the time of the amendment one skilled in the art could not reasonably be
expected to have drafted a claim that would have literally encompassed the alleged
equivalent.’ The Court further held that not only is the burden on the patentee to show that
an amendment was not made for the purpose of patentability, but he or she must also show
that the amendment does not surrender the particular equivalent in question.
The Supreme Court recognized that usually a ‘patentee's decision to narrow his claims
through amendment should be presumed to be a general disclaimer of the territory between
the original claim and the amended claim.’ However, even if a patentee narrows a claim, he
may rebut the presumption by showing that ‘at the time of the amendment one skilled in the
art could not reasonably be expected to have drafted a claim that would have literally
encompassed the alleged equivalent.’ 58 Specifically, the Court states that the patentee can
rebut the presumption that prosecution history estoppel bars a finding of equivalents if:
“the equivalent may have been unforeseeable at the time of the application; the rationale
underlying the amendment may bear no more than a tangential relation to the equivalent in
question; or there may be some other reason suggesting that the patentee could not reasonably
be expected to have described the insubstantial substitute in question.”59

56
Haynes Int'l Inc v Jessop Steel Co, 8 F 3d 1573, 1581 (Fed Cir 1993)
57
Festo Corp v Shoketsu Kinzoku Kogyo Kabushiki Co Ltd, No. 00-1543.
58
Ibid
59
Ibid

19
In this regard, it is submitted that the complete bar would have had enormous consequences if
it had been allowed to stand. As a matter of fact very few patents are issued in which the
claims are not amended during prosecution.60

Public Dedication61
The public dedication bar blocks the application of the doctrine of equivalents to cover an
embodiment that was disclosed in the patent but not claimed. As the Federal Circuit has
stated, ‘subject matter disclosed in the specification, but not claimed, is dedicated to the
public.’ 62 Subject matter that has been dedicated to the public cannot be the basis for
infringement under the doctrine of equivalents. The bar has been limited to specific factual
situations in which a distinct alternative embodiment has been disclosed but not claimed.63
Put another way, the bar does not exclude all subject matter disclosed but not claimed from
equivalency.64 Disclosed subject matter can actually form the basis for equivalency under the
doctrine of equivalents, even if the subject matter is not literally claimed.
Like prosecution history estoppel, the public dedication bar is strongly linked to the notice
function of the patent. By disclosing but not claiming subject matter, a patentee tells the
public that that subject matter is not covered by the patent; instead, it is dedicated to the
public. By reading the patent and the file history, a member of the public can identify subject
matter that has been disclosed but not claimed, and can, therefore, practice that subject matter
with the knowledge that it is outside the scope of the patent. Application of the doctrine of
equivalents to recapture subject matter deliberately left unclaimed is ‘contrary to our system
of patent examination, in which a patent is granted following careful examination of that
which an applicant claims as her invention.’65

After-Arising Requirement for Equivalents for Means-Plus- Function Claims

This bar affects the application of the doctrine of equivalents to a specific type of claim
limitation, namely, means-plus-function limitations allowed under 35 USC § 112, paragraph
6. Equivalence, for the purpose of the doctrine of equivalents, is limited to those elements

60
Winans v Denmead, 56 US (15 How) at 609, 612, 614
61
Phillips Matthew C, Taking a step beyond Maxwell to tame the Doctrine of Equivalents, Fordham Intellectual
Property
Media & Entertainment Law Journal, 11 (2000) 155.
62
Maxwell v J Baker Inc 86 F 3d 1098, 1107 (Fed Cir 1996), certiorari denied, 520 US 1115 (1997).
63
Chisum Donald S, Chisum on Patents (LexisNexis, New York), 2001 § 18.04(d)
64
YBM Magnex Inc v US Intl Trade Commn, 145 F 3d 1317, 1320- 21 (Fed Cir 1998).
65
Maxwell v J Baker Inc, 86 F 3d at 1107.

20
developed after the patent was granted.66 An equivalent element, for the purposes of literal
interpretation of the claims under § 112, paragraph 6, must have arisen before grant of the
patent.67 Thus, if the element arose before the grant of the patent, infringement under the
doctrine of equivalents is barred. It is submitted that this bar is an application of the principle
of estoppel. It recognizes that a known equivalent element not claimed at the time of filing
the patent application is deemed to be disclaimed, and cannot be claimed with the help of the
doctrine.
This bar is indirectly linked to the notice function. The rule as to what can be an equivalent
for the purposes of literal interpretation of the claims under § 112, paragraph 6 is designed to
give notice to the public about what the means-plus-function limitation covers. The after-
arising bar to the doctrine of equivalents is a corollary to this rule.

Prior Art Patentability

The Court in Graver Tank said that an important factor for determining equivalency is
whether persons reasonably skilled in the art would have known of the interchangeability of
an ingredient not contained in the patent with one that was. The existence of prior art also
limits the application of the doctrine of equivalents to extend a patentee's protection beyond
literal claims. The doctrine of equivalents exists to prevent a fraud on a patent, not to give a
patentee something which he could not lawfully have obtained from the PTO had he tried.
Thus, since prior art always limits what an inventor could have claimed; it limits the range of
permissible equivalents of a claim.68 The scope of equivalents cannot be taken in a vacuum,
free from the prior art.69 When a question of equivalency is under study, it is also necessary
to know if the patent is a pioneer in a whole new field or if the patent shows only a narrow
improvement of a subject that is well known.70 Typically, pioneer patents will be given a
broader range of protection than an improvement patent under the doctrine of equivalents.71
If an accused product is found in the prior art, or is obvious in the light of prior art, then the
product cannot be infringing under the doctrine of equivalents.72 To allow such a product to
be covered under the doctrine of equivalents would allow the patent holder to gain rights to

66
Chiuminatta Concrete Concepts Inc v Cardinal Indus Inc, 145 F 3d 1303 (Fed Cir 1998).
67
Al-Site Corp v VSI Intl Inc, 174 F 3d 1308 (Fed Cir 1999).
68
Wilson Sporting Goods Co v David Geoffrey & Associates, 904 F 2d 677, 684 (Fed Cir 1990).
69
Ibid
70
Hsing Benjamin C, Proof of Equivalence after Festo, Practicing Law Institute/Patent Litigation, 725 (2002)
115, 127.
71
ibid
72
Streamfeeder LLC v Sure-Feed Sys Inc, 175 F 3d 974, 982- 84 (Fed Cir 1999);

21
something which he could not lawfully have obtained rights to in the first place during
prosecution of the patent in the Patent Office.73 In applying the prior art patentability bar, the
court must look at the product as a whole to determine if that product, or a hypothetical claim
covering the product, would have been un-patentable in light of the prior art.
Unlike the previous bars, the prior art patentability bar is not based on the notice function of
patents. This bar is instead based on the concept of what is patentable, because it essentially
says that products that would not have been patentable at the time of filing cannot be a part of
the invention and therefore cannot be covered under the doctrine of equivalents.

The Obviousness Bar

The obviousness test has been proposed as a test for equivalence under the doctrine of
equivalents, but perhaps makes more sense as a legal bar to the application of the doctrine.
The rationale for using the obviousness test in conjunction with the doctrine of equivalents is
summed up by a single statement: “A substitution in a patented invention cannot be both non-
obvious and insubstantial.”
What follows naturally from this statement is the following: If a substitution is non-obvious,
then that substitution is not insubstantial. If the differences between the accused product and
the claim are non-obvious, then the differences are not insubstantial, and the product
therefore does not infringe under the doctrine of equivalents.
Regardless of from where the problem stems, the doctrine of equivalents is an attempted
solution for the inherent imperfection in the ability of language to define an invention
perfectly. This imperfection of language as a means for defining an invention plays a
significant role in the failures of past attempts to improve the doctrine of equivalents and will
be important in fashioning improvements in the future.

THE INADEQUATE JUSTIFICATIONS FOR THE MODERN DOCTRINE

In establishing and upholding the modern doctrine of equivalents, Supreme Court has
articulated several rationales for extending patent protection beyond the scope of direct
application of construed claim language.74 Each of these rationales is analyzed below.

73
Conroy v Reebok Intl Ltd, 14 F 3d 1570, 1576-77 (Fed Cir 1994).
74
Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 731 32 (2002); Warner-Jenkinson Co.
v. Hilton Davis Chem. Co., 520 U.S. 17, 35-37 (1997); Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339
U.S. 605, 607 (1950).

22
Graver Tank’ s Rationales

The theoretical foundation for the modern doctrine of equivalents articulated at the time of its
creation in Graver Tank. In an earlier decision in the same action, the Supreme Court had
invalidated broader composition claims that would have literally applied to the allegedly-
infringing manganese fluxes at issue.75 The Court apparently could not liberally construe the
remaining composition claims (which included a limitation alkaline earth metals) to apply to
the manganese fluxes (as manganese not an alkaline earth metal).76 The Court likely strove to
find infringement because of the importance of the invention and because the patentee not
intended-in-fact to disclaim coverage when seeking and broader but invalid flux claims.77
The Court thus extended patent protection beyond the scope of application of the literally
construed the valid claims.

To reach its finding of infringement, the Court mischaracterized the history and nature of the
doctrine of equivalents. The Court stated that the doctrine of equivalents:

(1) Had evolved in response to the experience of unscrupulous copying and piracy

(2) Had as its essence that one may not practice a fraud upon the patent

(3) Originated in Winans v. Denmead,78 and had been consistently applied by the Court
and lower courts and

(4) Was available to temper unsparing logic and prevent an infringer from stealing the
benefit of the invention

In fact, the doctrine: (1) had evolved as a necessary construct for determining the scope of
patent protection before and after requiring use of formal claims; (2) had, as its essence, a
required judicial judgment on the level of generality of the patented principle of invention
and, after claims were required, the level of generality that permissibly had been claimed; (3)
originated before Winans, which had reinforced that the doctrine was limited to the scope of

75
Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 607 (1950).
76
Graver Tank, 339 U.S. at 612. The Court had earlier preserved the validity of alkaline earth metal flux claims
based on their exclusion of inoperative embodiments, and had refused to import limitations into other, broader
composition claims in' order to preserve their validity. See Graver Tank, 336 U.S. at 273-77. Further, claims that
would have explicitly recited manganese fluxes would likely have been held invalid. (Douglas, J., dissenting)
(noting that a claim to the manganese flux composition could not have been patented because it was already
disclosed in a prior art patent); Janicke, supra note 22, at 121 n.444 (discussing invalidity of the alkaline earth
metal claim were it to apply directly to the manganese flux).
77
Supra at 15
78
56 U.S. (15 How.) 330 (1853).

23
application of construed claims; and (4) was available only within the scope of application of
construed claims in order to assure notice to the public and to prevent fraud on the Patent
Office, requiring the patentee to timely seek a reissued patent to protect any disclosed scope
patentable invention that had not validly been claimed.79

The Supreme Court articulated three separate justifications the doctrine of equivalents and
extending protection beyond application of the claim limitations selected by the patentee by
the public. First, the Court argued that extra-claim protection needed to assure fairness to
patentees and to protect the monetary patents from inevitable copying of principles of
invention that are encompassed by claim language. The Court stated:

To permit imitation of a patented invention which does copy every literal detail
would be to convert the protection of patent grant into a hollow and useless
thing. Such a limitation would leave room for—indeed encourage—the
unscrupulous copyist to make unimportant and insubstantial changes and sub-
situations in the patent which, though adding nothing, would enough to take the
copied matter outside the claim, and hence outside the reach of law. One who
seeks to pirate an invention, like one who seeks to pirate a copyrighted book or
play, may expected to introduce minor variations to conceal and shelter the
piracy. 80

Second, the Supreme Court criticized linguistic formalism. "To prohibit no other would
place the inventor at the mercy of verbalism and would be subordinating substance to
form."81 The Court thus implicitly suggested that limits exist in the ability of language to
fully describe and thus to disclose and claim an invented principle.

Third, the Court argued that limiting protection to claim language would discourage inventors
from disclosing their inventions, stating "it would deprive him of the benefit of his invention
and would foster concealment rather than disclosure of inventions, which is one of the
primary purposes of the patent system."82

These rationales clearly overlap. If claim language were able to fully describe inventions,
additional protection would not be required for fairness nor needed to prevent copying. If

79
Darcy A. Paul, The Judicial Doctrine of Equivalents, 17 Harv. J.L. & Tech. 247, 254-61 (2003)
80
Graver Tank, 339 U.S. at
81
Graver Tank, 339 U.S. at
82
ibid

24
fairness was assured and copying was prohibited by claim language, additional protection
would needed to induce and might not induce any additional disclosure.

1. Fairness and Copying

Without a doctrine of equivalents, patentees may be deprived of protection for their

inventions that even a liberal claim construction affords. This would leave the public and
competitors free to copy portion of the invented subject matter and to use it without paying
the patentee for the privilege of doing so.83 But some additional, extrinsic standard of fairness
is required to establish that any limits to the scope of application of patent claims is unfair
and that any such copying is a fraud on a patent84. For the public, the additional protection
may constitute an unwarranted restriction of the public domain; for the patentee, the
additional protection may provide an unjust enrichment.

Absent an external criterion to delimit the scope of an inventor's rights, the Supreme Court's
fairness and copying rationales may reflect only judicial hostility to competition or to
85
"designing around" patent claims. Accordingly, the Federal Circuit and some
commentators have suggested that the modern doctrine of equivalents is an equitable
doctrine, requiring more explicit consideration of extrinsic fairness criteria.

Limiting a patent to direct applications of the construed language claims may be thought to
be unfair for at least three reasons. First claim language and claim validity doctrines might
unfairly exclude some existing and future embodiments of the invention—notwithstanding
the broad scope of claims currently allowed for pioneering inventions the ability of patentees
to use generic or functional language foreseeable (and block non obvious) later-arising
improvements vented principle. 86 Second, unfairness might result from legal or practical
difficulties and costs associated with more claiming embodiments of the invented principle.87
Third, unfairness might result from holding patentees to any "mistakes" that they made
language of the claims actually adopted. The Supreme Court in Graver did not identify
which, if any, of these three fairness criteria when referring to copying of unclaimed or
invalidly claimed subject matter as piracy and fraud. But whatever the Court intended, each
criteria would have conflicted with established patent law principles.

83
Supra at 26
84
Libel flarshiem Co. Vs. Medrad Inc. 358 F.38 89, 911 (Fed. Circuit 2004)
85
mark A. Lemley, THE ECONOMICS OF IMPROVENT IN INTELLECTUAL PROPERTY LAW 75 Tex. L.
REV. 989, 999 n47 (1997)
86
Noelle v. Lederman, 355 F.3d 1343, 1348-
87
SmithKline Beecham Corp. v. Excel Pharms., Inc., 356 F.3d 1357, 1364 (Fed. Cir. 2004)

25
2. Limits to Language
The preceding analysis was premised on patentees choosing (expressly or mistakenly) to
claim less than they had invented or disclosed. But the same analysis applies even more
strongly if patentees cannot fully or claims what they invent, based on the limits of language
used inventions.88 If they cannot fully disclose their inventions, patentees never fulfill the
quid pro quo of a written description that would them to complete protection. Conversely, if
they can fully disclose cannot fully claim their inventions, patentees would necessarily such
broader inventive principles at the risk of an implied disclaimer. Absent a mistake, the
patentee would make its choice to seek patent protection advisedly. There is nothing
inherently unfair about holding to their conscious choices whether or not mistaken. However,
considerations such as encouraging disclosure might provide reasons waive strict compliance.

Further, assuming that there are limits to language that prevent claiming the full scope of an
invention, the modern doctrine of equivalents not a necessary or inevitable means of assuring
a fair scope of for inventors.

The limits-to-language rationale of Graver Tank thus reflects policy judgment: the cost of
drafting broader or more precise risk of inadequate protection from any inability to do so
should not by the inventor but rather by the public. For this reason, many judges and
commentators suggested the modern doctrine should be limited in its application seeable
later-arising technologies that could not be claimed with increased expenditures on claim
drafting89. Counter-intuitively, application of the modern doctrine of equivalents to such later
arising technologies is not justifiable on utilitarian grounds, because refinement costs or
significantly improves cases.

3. Encouraging Disclosures
The Supreme Court in Graver Tank failed to supply any theory or empirical data to ground its
argument that the modern needed to encourage the disclosure of inventions. The implied
premise the argument (in crude form) is that reducing the scope of protection eliminating the
modern doctrine would decrease the value of which in turn would decrease ex ante incentives
either to invent what could be disclosed or to disclose inventions through patents. Thus, any
purported benefits of encouraging invention or disclosure provided by the modern doctrine

88
Autogiro Co. of Am. v. United States, 384 F.2d 391, 396 (Ct. (converting physical inventions to words
"allows for unintended idea gaps be satisfactorily filled," because the invention is new and words do not
describe it)
89
Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558, 619 (Fed. Cir. 2000) (en

26
must be evaluated along with the social costs that the modern doctrine imposes, including but
not limited to discouragement of sequential invention and disclosure.

B. Warner-Jenkinson 's Rationales

In Warner-Jenkinson Co. v. Hilton Davis Chemical Co.90 the Supreme Court articulated two
related reasons why patent protection should extend beyond the scope of application of
construed claim language. The first rationale is based on the philosophical belief that
equivalents to embodiments of claimed inventions are factually the same thing claimed
inventions. The second rationale is based on the belief claim language contains an "implied
term" that includes as embodiments all factual equivalents of the claimed, enumerated
embodiments. Third rationale is based on the doctrinal policy that patent law should finding
implied-in-law disclaimers of disclosed, patentable subject matter.

1. Factual Equivalency
In Warner-Jenkinson91, the Court authorized patent under the modern doctrine of equivalents
based on the factual the accused product or process to the embodied limitations construed
claims. The Court focused on the knowledge of interchangeability of elements as a factual
matter, and on "what it tells the fact-the similarities or differences between those elements.
Thus, the Supreme Court treated equivalency judgments based on factual similarity to be the
same as category judgments of identity based on the application of the construed claim
language. The Court thereby changed the role of the jury and the question that it must answer
to determine infringement, 92 but also potentially shifted the theoretical providing patent
protection. Under the Court's rationale, juries corporate into their factual similarity judgments
perceptions of the fairness of extending patent protection. Although it may be difficult to
define the philosophical differences between factual and theoretical knowledge, there are at
least clear practical differences between and legal judgments.

2.Implied Claim Terms

As further justification for extending equivalents protection scope of application of construed
claims, the Supreme Court in Warner-Jenkinson suggested that the modern doctrine of
equivalents is result of:

90
102. 520 U.S. 17(1997).
91
ibid
92
, William R. Zimmerman, Unifying Markman and Warner-Jenkinson: Revised Approach to the Doctrine of
Equivalents, 11 Harv. J.L. & TECH. 185, 260-(1997)

27
 a legally implied term in each patent claim that "the claim tends to the thing
patented, however its form or proportions be varied." Under that view,
application of the doctrine equivalents involves determining whether a
particular accused product or process infringes upon the patent claim, where
claim takes the form—half express, half implied—of "X and equivalents."

The Court thereby denied any difference in treatment between claim construction and direct
application on the one hand and equivalents on the other. There is a substantial difference
between that are embodiments of the construed claim language and the construed claims do
not directly apply. Claims are to be construed in light of the specification, claim language
having a meaning that varies from the specification be given effect93. Clear or ambiguous but
definitively construed language thus should apply directly only to factual equivalents
embodiments of such language, and could not contain any implied that would extend to
factual equivalents that are not embodiments. Rather the application of patents to such
equivalents should necessarily vitiate the meaning of clear claim language, and ambiguous
claim language should not be allowed.94

Further, claims are to be interpreted for validity based on their meaning at the time of filing.
In unpredictable arts, claims for pioneering inventions containing such implied terms
necessarily should be invalid. This is because the claims would be understood at the time of
filing to apply to all sorts of un-claimable equivalents that had not yet been invented, were
not yet enabled, and could not be described without adding new matter (that had not been
invented by the applicant or anyone else). 95 Finally, unless the scope of equivalents
encompassed by such an implied term were foreseeable, including the implied term within
the claim would violate the spirit of public notice that animates these claim-language and
claim-scope doctrines.

Festo’s Rationales
In Festo, the Court articulated similar reasons to those to support protection for equivalents
that were not and could not be claimed by the patentee.

93
g., Keystone Bridge Co. v. Phoenix Iron Co., 95 U.S. 274, 275-
94
United Carbon Co. v. Binney & Smith Co., 317 U.S. 228, 236
95
Cf. Edison Elec. Light Co. v. Boston Incandescent Lamp Co., 62 F. 397, 398-99 (C.C.D. Mass. 1894)
(holding that newly discovered substances or devices substituting for previously known elements are within the
scope of pioneering claims because "it is difficult to point out in this class of cases what known equivalents
existed at the date of the patent, for the reason that the combination of elements in which the invention is
embodied was first made known by the patentee").

28
As in Graver Tank, the Supreme Court in Festo focused on the decreased value of patents
resulting from copying and on the limits of the language. The Court, however, apparently
converted Graver concerns for placing inventors "at the mercy of verbalism"96 rationale into
an efficiency rationale. The Court also focused Festo on judicial efficiency than on social
efficiency.

The Court's nearly exclusive concern to protect the patentee preserve the value of inventions
is deeply troubling. It fails to balance the rights of the public and eliminates from efficiency
analyses all costs to the public, including but not limited to the tax on sequential posed by the
modern doctrine. The Court's approach thus may impermissibly conflict with the utilitarian
premises of the Constitution's patent power and certainly reverses course from the Court's
earlier assuring both notice to and fairness for the public.

Further, the Supreme Court's justification for the modern equivalents reflects two serious
errors of analysis. The court may have been correct that claim language will not always an
invented principle. But the Court's conclusion that the scope of the patent therefore
"embraces all equivalents" of the claims is the non sequitur and conflicts with the Court's
prior limits on claim scope and with its vitiation standard for the modern doctrine. The
Court's analysis also to be based on the false premise that patent claims must be interpreted
by their literal terms. Whatever the degree to which it has been used past, non-literal
interpretation of claim language is a permissible alternative to the modern of equivalents if
additional, fairness-based protection is thought needed.

CONCLUSION
In Pennwalt, the Federal Circuit in banc purported to decide an issue crucial to the scope of
patent protection: Does the doctrine of equivalents apply on an element-by-element basis or
on an entirety basis? The majority chose the element-by-element approach in an apparent
attempt to limit the reach of the doctrine of equivalents. Although both the majority and the
dissent obviously thought that the debate was important, the crucial issue involved in the
doctrine of equivalents is not the question that the court answered, but the one that it did not:
What is an equivalent? The Federal Circuit seems prepared to allow the doctrine of
equivalents to play a major role as a factual issue to be decided in every case, but the court
has yet to address the meaning of this fundamental concept.

96
Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339

29
The doctrine of equivalents was originally intended to prevent "fraud on the patent," but the
doctrine presently mirrors the "substantial similarity" concept in copyright law. The
differences between the two types of intellectual property raise serious questions about
whether the "substantial similarity" standard should be applied to the claiming system of
patent law, the sole function of which is to ensure that inventions are described with
particularity and specificity. The doctrine of equivalents serves two roles in patent law. First,
it allows a patentee to cover an accused device when the patentee has omitted to claim what
her patent enabled. Second, it ensures that patent protection is not eviscerated by technology
developed after the patent issues when claims that would cover the technology literally are
unavailable under reissue and were unavailable during the original prosecution. The second
purpose, applied only in special circumstances, represents the sole legitimate function of the
doctrine. In other circumstances, the balance should be drawn in favor of the public.
Inventors need to know with some certainty what they .can and cannot do. The law should
seek to accommodate this interest so long as it can be done while doing justice.

It is to be remembered that grant of a patent and disclosure of the patented invention is quid-
pro-quo. A patentee discloses his invention to the world and that in turn entitles him to enjoy
a monopoly over the invention. Conversely, grant of monopoly in favour of the patentee,
demands disclosure of the invention by him. However this monopoly is only for a limited
period of time. Once the monopoly gets over, the invention falls in public domain so that the
public could be benefited from it. This is the rationale behind the law of patents. In this
regard, it is submitted that if the courts had accepted the proposition that the scope of a
patented invention is limited to the literal interpretation of its claims, it would have not only
been unfair to a patentee, but would have also deterred any inventor from revealing his
invention to the world. In the absence of the doctrine, the scope of a patent would have been
of no great significance. The doctrine of equivalence widens the scope of a patent and
prevents any infringement made in the garb of an insubstantial alteration or substitution.

The doctrine certainly strikes a balance between a fair scope for the patent and the notice the
patent provides for the public, along with a balance between incentives to innovate and the
costs of uncertainty. The doctrine is further justified in that it is not absolute but well guided
by the legal bars imposed on it, which see to it that the doctrine does not take on ‘a life of its
own, unbounded by the patent claim’ providing for protection not within the scope of the
patent, and thereby eliminating an important function of patents: clear public notice of
patentee's scope of exclusive right.

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