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A Comparative Analysis regarding Patent
Claim Construction : The English Purposive
Construction and the US Doctrine of
Equivalents
Dr Jakkrit Kuanpoth
Tilleke & Gibbins International
Patent infringement

Lessons from validity


It’s the claim that counts!
Comparing claim to [reference] = comparing
claim to [accused product]
The Telephone Cases (1888)
Bangkok | Phuket | Hanoi | Ho Chi Minh City

Claim at issue: “The method of, and apparatus for,
transmitting vocal or other sounds telegraphically, as
herein described, by causing electrical undulations,
similar in form to the vibrations of the air
accompanying the said vocal or other sounds,
substantially as set forth.”
พระราชบัญญัตสิ ิทธิบตั ร พ.ศ. ๒๕๒๒
มาตรา ๓๖ ทวิ

“สิทธิของผูท้ รงสิทธิบตั รตามมาตรา ๓๖ ในการประดิษฐ์ที่ได้รบั สิทธิบตั รมี
ขอบเขตดังระบุในข้อถือสิทธิ ในการวินิจฉัยขอบเขตของการประดิษฐ์ตามข้อถือ
สิทธิ ให้พิจารณาลักษณะของการประดิษฐ์ที่ระบุในรายละเอียดการประดิษฐ์
และรูปเขียนประกอบด้วย ขอบเขตของการประดิษฐ์ที่ได้รบั ความคุม้ ครองย่อม
คลุมถึงลักษณะของการประดิษฐ์ที่แม้จะมิได้ระบุในข้อถือสิทธิโดย
เฉพาะเจาะจง แต่เป็ นสิ่งที่มีคุณสมบัติประโยชน์ใช้สอย และทาให้เกิดผล
ทานองเดียวกับลักษณะของการประดิษฐ์ที่ระบุไว้ในข้อถือสิทธิตามความเห็น
ของบุคคลที่มีความชานาญในระดับสามัญในศิลปะหรือวิทยาการที่เกี่ยวข้องกับ
การประดิษฐ์น้ัน”
Comparison of:
Claimed Invention and Accused Device
• Literal (Purposive Construction)
• Non-Literal (Doctrine of Equivalents)
Electric and Musical Industries, Ltd. et al
v. Lissen, Ltd. et al (1939)
 Lord
Russell:
“The function of the claims is to define clearly and with precision the
monopoly claimed, so that others may know the exact boundaries of
the area within which they will be trespassers. Their primary object is
to limit and not to extend the monopoly. What is not claimed is
disclaimed.
The claims must undoubtedly be read as part of the entire document,
and not as a separate document; but the forbidden field must be
found in the language of the claims and not elsewhere. It is not
permissible, in my opinion, by reference to some language used in
the earlier part of the specification to change a claim which by its
own language is a claim for one subject-matter into a claim for
another...
A patentee who describes an invention in the body of a specification
obtains no monopoly unless it is claimed in the claims. As Lord
Cairns said, there is no such thing as infringement of the equity
of a patent (Dudgeon v. Thomson, L.R. 3 App. Cas. 34).”
Literal Infringement Analysis

“Applying the Properly Construed Claims to the Accused
Product or Process”

The question of infringement is a question of fact for a
judge/jury.

Each and every element must read on the accused device


Under literal infringement, in effect, all claim elements were
considered to be essential to the invention and thus, the absence of
any claimed element resulted in a finding of no literal infringement.

It was therefore called an ‘all elements’ test.
Infringement:

The accused device must perform the identical function required
by the claim limitation, and must have identical structure to that
disclosed in the specification.
Intrinsic ------- Extrinsic evidence
“Although we have emphasized the importance of
intrinsic evidence in claim construction, we have
also authorized district courts to rely on extrinsic
evidence, which “consists of all evidence external
to the patent and prosecution history, including
expert and inventor testimony, dictionaries, and
learned treatises.” Markman, 52 F.3d at 980.
Intrinsic --------- Extrinsic

Claim language

Dictionaries

Specification

Expert witness
testimony

Prosecution History

Papers generated
during prosecution

The role of an expert
is to assist in putting
the Court in the
position of a person
skilled in the art as of
the relevant time.
9
Literal Infringement
Interactive Gift Express, Inc. v. CompuServe Inc. (1998)

Facts:
Claims cover system for reproducing information at
“point of sale locations”
 Accused process – sale of software and documents
online


Issue – is a sale made to a consumer using a
computer at home conducted at a “point of sale
location”?
Literal Infringement – Compuserve
Case

Analysis
 Intrinsic evidence evaluated first
 Look to plain language of claim limitation first
 If claim language is clear, look to specification and prosecution
history only to determine if a deviation from the plain language
is required.
 Do not read limitations appearing in the specification into the
claims; specification is used only to help determine what the
inventor meant by using the claim terms.
 Only took to extrinsic evidence to construe claim terms if the
claim language remains genuinely ambiguous after considering
intrinsic evidence
 Extrinsic evidence can never be used to vary or contradict the
claim terms
 But extrinsic evidence may always be consulted to assist in
understanding the underlying technology.
 Perspective from which claims are interpreted is the person of
ordinary skill in the art.
Literal Infringement – Compuserve
Case

Analysis
 Specification
defines “point of sale location” as “a
location where a consumer goes to purchase
material objects embodying predetermined or
preselected information.”
 Court of First Instance: defined this not to exclude
a home.
 Appeal: nothing in the intrinsic evidence excludes
a home as a point of sale location.
 No need for extrinsic evidence
U.S. claim construction
jurisprudence
Markman hearings

Herbert Markman and Positek Inc. v. Westview
Instruments Inc. and Althon Enterprises Inc. (1996),
US Supreme Court ruled that

“Claim construction is a matter of law that should be
decided by a judge alone.”
This conclusion paved the way for “Markman
hearings” where the judge construes the claims of a
patent without any consideration of infringement or
validity issues.
 Claim construction has been done in a pre-trial
proceeding called a “Markman hearing”.

Balancing Tensions: The Doctrine
of Equivalents
•
Ensuring the notice function of a patent

“[I]t is only fair (and statutorily required) that competitors
be able to ascertain to a reasonable degree the scope of
the patentee’s right to exclude.”*
Versus
•
Giving a patent owner a fair and reasonable scope
of protection
Markman v. Westview, 523 F.3d 967 (Fed. Cir. 1995)
Warner-Jenkinson Company v. Hilton Davis
Chemical Co.

The Doctrine of Equivalents
Defendant can be liable for patent infringement even
though the infringing device or process does not fall
within the literal scope of a patent claim.
 “… [A] product or process that does not literally
infringe upon the express terms of a patent claim may
nonetheless be found to infringe if there is
‘equivalence’ between the elements of the accused
product or process and the claimed elements of the
patented invention.”

16
Graver Tank & Manufacturing Co. v.
Linde Air Products Co. (1950)

Graver test (FUNCTION-WAY-RESULT):
It performs substantially the same function
 In substantially the same way
 To yield substantially the same result.


Graver Tank: “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.”
17
Infringement under Doctrine of
Equivalents

Equitable Doctrine

Adheres to literalism yet evolve a doctrine which supplements
the claims by extending protection to equivalents.

Affords protection to inventions where a product avoids the
literal language of the claim by making a noncritical change

Each element contained in a patent claim is deemed material
to defining the scope of the patented invention

Determine if the differences between the elements of the
claimed invention and the suspect infringing device or
process are “insubstantial”

Question of Fact
Johnson & Johnson Associates
Inc. v R.E. Service Co. Inc.

Facts
Claims for printed
circuit board with
aluminum substrate
that protects the thin
copper foil
 Specification states
that “other metals,
such as stainless
steel or nickel alloys,
may be used.”
 Accused devices
uses thin sheet of
steel as substrate

J&J Case
Issue – can P (J&J) claim the steel substrate by
equivalents or was steel substrate dedicated to
the public by disclosing in specification but not
claiming
 Analysis

Maxwell case (F. Cir.)– subject matter disclosed but
not claimed is dedicated to the public domain b/c the
patent office does not have an opportunity to review it
 YBM Magnex case (F. Cir.) – Maxwell is limited to
situations where the disclosed but unclaimed matter is
distinct from what is claimed; unclaimed equivalents
disclosed in the specification are not dedicated to the
public domain

J&J Case

Analysis
Infringement analysis proceeds by comparing accused
device to the claims, not to preferred embodiments in
the specification
 Disclosure of an embodiment without claiming it
dedicates that embodiment to the public domain

 Contrary
rule would encourage narrow
claims with broad disclosures to limit the
PTO’s role

Rader concurrence
any foreseeable equivalent should be claimed;
 equivalents that are unforseeable at the time of the
application should be allowed.

U.K. purposive construction
jurisprudence
UK developments

UK courts used ‘literal approach’ until the current
law entered into force in 1977.


Conforming to EPC, Art. 69
The courts have recognised that patents must be
interpreted purposively.



House of Lords 1982 – Catnic v Hill and Smith
Lord Diplock – Claims be read through the eyes of the
person skilled in the art, and the purpose or function of the
invention should be borne in mind when the patent is
interpreted.
Catnic was confirmed by: Improver Corporation v.
Remington Consumer Products Ltd. [1990]
Fact of Catnic
Catnic Components Ltd. v. Hill & Smith Ltd.
(1982)
Catnic’s patent claimed a lintel (the bar that spans
the top of a window to support the weight of the
bricks laid above it) having a rear wall member
‘extending vertically’.
 Hill’s lintel differed from what was illustrated in the
Catnic patent in that the rear wall was inclined 6 or
8 degrees off vertical, as shown and highlighted in
Figure 4 above. The sloping of the rear wall made
the Hill lintels 0.6 to 1.2% weaker in their load
bearing capacities than the Catnic lintels.
 Functionally, it was a negligible difference.

Catnic Patent Drawing
Hill’s Lintel
The trial judge, Whitford J., held that there was
no literal infringement but there was
infringement under the ‘pith and marrow’
doctrine.
 The Court of Appeal held that the limitation that
the rear member should ‘extend vertically’ was
an essential feature and, being changed or
absent, there could be no infringement of the
‘pith and marrow’.
 The House of Lords overturned and found there
to be infringement.

Lord Diplock: ‘Purposive
Construction’
“My Lords, a patent specification is a unilateral statement by
the patentee, in words of his own choosing, addressed to
those likely to have a practical interest in the subject matter of
his invention (i.e. "skilled in the art"),
A patent specification should be given a purposive construction
rather than a purely literal one ...
The question in each case is: whether persons with
practical knowledge and experience of the kind of work in
which the invention was intended to be used, would
understand that strict compliance with a particular
descriptive word or phrase appearing in a claim was
intended by the patentee to be an essential requirement
of the invention so that any variant would fall outside the
monopoly claimed, even though it could have no material
effect upon the way the invention worked.”

“The question, of course, does not arise where
the variant would in fact have a material effect
upon the way the invention worked. Nor does it
arise unless at the date of publication of the
specification it would be obvious to the informed
reader that this was so.
Where it is not obvious, in the light of then-existing
knowledge, the reader is entitled to assume that
the patentee thought at the time of the
specification that he had good reason for
limiting his monopoly so strictly and had
intended to do so, even though subsequent work
by him or others in the field of the invention might
show the limitation to have been unnecessary.”


“… it seems to me that the expression
‘extending vertically’ as descriptive of the
position of what in use will be the upright
member of a trapezoid-shaped box girder, is
perfectly capable of meaning positioned
near enough to the exact geometrical
vertical to enable it in actual use to perform
satisfactorily all the functions that it could
perform if it were precisely vertical.
Infringement under “Purposive”
construction


Purposive construction is not unique to patent law and has
had a long history in contract law and statutory construction.
Purposive construction does not ask:


Rather:



“What was the inventor trying to say?” or
"What would a skilled reader have understood the patentee to have
been trying to say?”
Purposive construction should not allow a patentee to
broaden or expand the scope of a claim.



"What did the patentee say?" which might be a literal interpretation.
It does not ask “What should the patentee have said?”
If a patentee failed to claim as broadly as he or she could have,
purposive construction should be of no assistance.
The last point makes the “Purposive construction” different
from the “US Doctrine of Equivalents”.
How the UK purposive
construction applies?

What would a person skilled in the art have
understood the patentee to have used the
language of the claim to mean?
UK (Catnic Test) - Lord Diplock in Catnic
Does the variant have a material effect upon the
way the invention works?
yes
No
Would this have been obvious to a person skilled in
the art at the publication date?
No
yes
Would a person skilled in the art have understood from
the language of the claim that the patentee intended that
strict compliance with the primary meaning was an
essential requirement of the invention?
yes
No
Infringement (purposive)
No
infringement
A Chair With Wheels
Allegedly-infringing
products
A
Claimed invention
A
B
B
C
B
C
C
D
E
The following
variants:
A?
A and E ?
D
D
Variant A has no material effect upon the way invention
works, but it seems obvious to person skilled –
infringement.
Variant E has material effect upon the way invention works,
non-obvious; no strict compliance required – No
infringement.
Summary – UK Purposive
approach






A patent specification must be read as a whole
The description and drawings shall be used to interpret
the claims
The claims must be interpreted as part of the entire
documents
The court can hear expert evidence on the meaning of
technical terms.
The prosecution history (information exchanged
between the applicant and the Patent Office during the
grant process) can be used to interpret the claims
Patent document is read from the point of view of a
person skilled in the art and is understood at the time of
the priority date.
‘Purposive construction’ ----------‘Doctrine of Equivalents’
Doctrine of Equivalents protects “substance of the
invention”.
 “Purposive Construction”:





Patents protect only the literal meaning of the claims.
The patent protects only the invention described in the
claims, as understood by a workman skilled in the trade, as
of the date of the patent.
But the a literal interpretation is based on the construction
of ‘the intent of the inventor’ manifested in the patent
claims.
It does not extend protection to the “substance of the
invention”.
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