InfringementWorked examplesClaim analysis

Patent infringement examples

By Ipiry TeamPublished August 31, 20269 min read

Short answer

The clearest way to understand infringement is element by element. A product infringes when every element of a claim is present, so a product with extra features still infringes while a product missing one element does not, however similar it looks. The examples below work through literal infringement, a missing element, an equivalents argument, a divided method claim, indirect liability and exhaustion.

Patent infringement examples are best understood one element at a time, because that is how the analysis actually works.

Every claimed element must be present. Not most of them, not the significant ones — every one.

Which produces two results that surprise people. A product with far more features than the patent describes still infringes. A product that looks nearly identical, missing one claimed element, does not.

The examples below all use the same method: claim elements in one column, the accused product in another, compared row by row.

The reference claim

Most examples here use one claim, so the comparisons are easy to follow.

Claim 1. A pressure relief valve assembly comprising: a housing; a spring-biased poppet disposed within the housing; and a bypass channel positioned to equalise pressure across the poppet during transition.

Element	Shorthand
A housing	A
A spring-biased poppet within it	B
A bypass channel equalising pressure during transition	C

"Comprising" is the transition word, and it is open. Extra elements do not avoid infringement.

Example 1: literal infringement

Element	Accused product
A — housing	Present
B — spring-biased poppet	Present
C — bypass channel	Present
Also has	Digital sensor, alloy body, service port
Result	Infringes

The extra features are irrelevant. The claim says comprising, so a product containing A, B and C plus anything else still contains A, B and C.

Knowledge is irrelevant too. The manufacturer may never have heard of the patent. Direct infringement is strict liability.

Example 2: a missing element

Element	Accused product
A — housing	Present
B — spring-biased poppet	Present
C — bypass channel	Absent — no bypass at all
Overall similarity	Very high
Result	Does not literally infringe

This is the all-elements rule doing its work. The products look alike and perform similarly, and one element is simply not there.

No doctrine bridges a wholly absent element. Equivalents substitutes a different element for a claimed one; it does not excuse having none.

Example 3: equivalents

Element	Accused product
A — housing	Present
B — spring-biased poppet	Magnetically biased poppet
C — bypass channel	Present
Literal infringement	No
Equivalents question	Is magnetic bias insubstantially different from spring bias?

Function-way-result: does the magnetic bias perform substantially the same function, in substantially the same way, to achieve substantially the same result? Arguably yes.

Then check the file history.

Prosecution fact	Effect
Claim originally recited "a biased poppet"	—
Amended to "spring-biased" to overcome prior art	Estoppel
Result	Equivalents argument likely barred

Prosecution history estoppel is what usually decides equivalents cases. Scope surrendered to get the patent generally cannot be recaptured. See doctrine of equivalents.

Example 4: a method claim performed by one party

Claim 8. A method comprising: sampling a pressure signal; comparing the sample against a threshold; and actuating a valve when the threshold is exceeded.

Step	Performed by
Sampling	The accused controller
Comparing	The accused controller
Actuating	The accused controller
Result	Infringes — one actor performs every step

Method claims are infringed by performance, not by sale. Selling the controller is not itself infringement of a method claim, though it may induce infringement by whoever operates it.

Example 5: divided infringement

Same method claim, different architecture.

Step	Performed by
Sampling	The customer's on-site sensor
Comparing	The vendor's cloud service
Actuating	The customer's equipment
One party performs all steps?	No
Direction or control?	Contractual service, no control over the customer
Result	Likely no direct infringement by either party

Divided infringement is a real defence. Liability generally requires one party to direct or control the others' performance, and an ordinary vendor-customer relationship does not meet that.

It is also a drafting lesson. A method claim written so a single actor performs every step is far more enforceable than one splitting steps across parties.

Example 5b: a system claim across two parties

Claim 12. A system comprising: a sensor configured to sample pressure; a processor configured to compare the sample against a threshold; and an actuator responsive to the comparison.

Component	Located at
Sensor	Customer site
Processor	Vendor's cloud
Actuator	Customer site
One party makes or uses the whole system?	Arguable

System claims are treated differently from method claims. Using a system can be infringement where a party puts the whole system into service and benefits from it, even if components sit in different places.

Which is why claim drafters often include both apparatus and method versions. The system claim may reach a distributed arrangement the method claim cannot.

Example 6: induced infringement

Fact	Effect
Vendor sells a controller that does not infringe alone	No direct infringement by the vendor
Vendor publishes instructions to configure it in the claimed way	—
Customers follow them and directly infringe	Direct infringement by customers
Vendor knew of the patent	Knowledge established
Result	Induced infringement under §271(b)

Inducement requires an underlying direct infringement. If no customer ever configures it that way, there is nothing to induce.

Knowledge and intent are both required, which is what distinguishes indirect from direct liability. See contributory patent infringement.

Example 7: exhaustion

Fact	Effect
Patent holder sells the valve to a distributor	Authorised first sale
Distributor resells to an end user	Rights exhausted in that item
End user operates it	No infringement
End user resells it	No infringement
A third party makes a copy	Infringes — exhaustion attaches to the item, not the design

Exhaustion follows the article, not the technology. Buying one authorised unit gives no right to make more.

International sales exhaust US rights since Impression Products v. Lexmark, so an authorised sale abroad exhausts the holder's rights in that item on import.

Example 8: repair versus reconstruction

Activity	Generally
Replacing a worn spring	Permitted repair
Replacing the poppet	Usually repair
Replacing the housing and reusing the internals	Arguable
Rebuilding the assembly from spent parts	Reconstruction — infringes

The line is fact-specific. Courts look at whether the article was spent as a whole and whether what was done amounts to making a new one.

Single-use restrictions do not survive exhaustion as a patent matter, though they may be enforceable as contract terms.

Example 9: territorial limits

Fact	Infringes a US patent?
Manufactured in Country X, sold in Country X	No
Manufactured in Country X, imported to the US	Yes
Offered for sale in the US, made abroad	Yes
Components supplied from the US for assembly abroad	Possibly — §271(f)
Product made abroad by a patented US process, imported	Possibly — §271(g)

Rights are national. A US patent covers acts in the US, which is why patent families are filed country by country and why most inventions are protected in only one or two markets.

Example 10: an expired patent

Fact	Effect
Patent granted 2013	—
Second maintenance fee missed 2021	Grace period expired
Status	Expired — public domain
Product launched 2023 containing A, B and C	No infringement

This is the most common real-world answer and the one people check last.

Ipiry Patent Survival Curve v1.0	Rate
Survive the 3.5-year fee (2022 cohort)	85.8%
Survive the 7.5-year fee (2018 cohort)	64.6%
Reach full term (2014 cohort)	41.4%
Abandoned before full term	58.6%

Computed from 27,273,654 USPTO maintenance fee records covering 8,262,336 US utility patents — see the patent survival curve.

Nearly three in five utility patents lapse before term. Checking status takes minutes and answers the question outright more often than any other single step.

Example 11: a narrow claim and a redesign

Element	Original product	Redesigned product
A — housing	Present	Present
B — spring-biased poppet	Present	Present
C — bypass channel equalising during transition	Present	Channel present but equalises continuously
Result	Infringes	Arguably outside the claim

The claim recites a functional limitation — equalising during transition — and a channel that equalises continuously may fall outside it.

This is what design-around looks like in practice. Not removing a component, but changing how it behaves so it no longer meets the functional language.

Check the prosecution history before relying on it. If "during transition" was added to overcome prior art, the estoppel protects the redesign; if it was there from the start, an equivalents argument remains open.

Building your own comparison

Column	Contains
Claim element	Exact words, one element per row
Accused feature	The specific corresponding feature
Evidence	Manual page, teardown photo, specification
Present?	Yes / no / arguable

One row per element, always. The discipline prevents overall-similarity reasoning, which is what produces wrong answers in both directions.

Cite evidence rather than asserting. Public documentation carries weight; a conclusion does not. See patent claim chart.

What none of these examples decide

A mapping documents a comparison; it does not decide infringement.

Question	Decided by
What do the claim words mean?	The court, at claim construction
Is the element present?	Fact, from evidence
Is the difference insubstantial?	Fact, with estoppel as a legal limit
Is the claim valid?	Separate question entirely

Claim construction comes first and changes everything. A term construed broadly or narrowly moves several rows at once, which is why the same product can be analysed two ways in good faith.

Patent infringement examples: the checklist

Check the patent is in force first. It is the fastest possible answer.
Work from the claims, never the title or abstract.
Identify the transition word. "Comprising" means extra features never help.
List the elements and compare one row at a time.
A single missing element defeats literal infringement, however similar the products are.
Extra features never avoid infringement.
Check the prosecution history before relying on an equivalents argument.
For method claims, ask who performs each step, since divided performance frequently defeats liability.
Check exhaustion where the item came from an authorised source.
Confirm the acts happened in the US, since rights are national and a foreign product sold abroad infringes nothing here.

Common questions

What is an example of patent infringement?

A competitor manufactures a valve containing a housing, a spring-biased poppet and a bypass channel, where a live patent claims exactly those three elements in combination. Every claimed element is present, so the product literally infringes regardless of what else it contains or whether the maker knew of the patent.

Does adding features avoid infringement?

No. If a product contains every element of a claim plus additional features, it still infringes. Claims almost always use the open transition word comprising, which means extra elements are irrelevant. This is the most common misunderstanding about infringement.

Can a product be similar and not infringe?

Yes, and this is the normal case. If one claimed element is absent, there is no literal infringement however closely the products resemble each other overall. Similarity is not the test; presence of every claim element is.

What is an example of the doctrine of equivalents?

A claim recites a spring-biased component and the accused product uses a magnetic bias achieving the same result the same way. That may infringe under equivalents if the difference is insubstantial — unless the applicant narrowed the claim to spring-biased during prosecution, which usually estops the argument.

How does infringement work for method claims?

Performing every step infringes. Where different parties perform different steps, liability usually requires one party to direct or control the others, which is a high bar. A method split between a server operator and an end user frequently escapes liability for this reason.

What is an example of induced infringement?

A company sells a component that is not itself patented, along with instructions telling customers to combine it in a way that infringes a patent it knows about. The customer directly infringes; the seller induces. Knowledge and intent are required.

Does buying a patented product make me an infringer?

Not if it was sold with authorisation. Patent exhaustion means an authorised first sale exhausts the holder's rights in that item, so using or reselling it is permitted. If the seller was not authorised, exhaustion does not apply and use can infringe.

Is repairing a patented product infringement?

Repair is generally permitted; reconstruction is not. Replacing a worn part is repair. Rebuilding the article essentially anew amounts to making a new infringing product. The line is fact-specific and frequently litigated.

Can I infringe a patent I have never heard of?

Yes. Direct infringement is strict liability, so knowledge and intent are irrelevant. Knowledge matters only for indirect infringement, which requires it, and for willfulness, which can increase damages up to three times.

What if the product is made abroad?

Making and selling entirely outside the US does not infringe a US patent, because rights are national. Importing into the US infringes, as does selling here. Supplying components abroad for assembly can create liability under 35 U.S.C. 271(f).

How do I document a suspected infringement?

Build a claim chart: each claim element in one column, the corresponding product feature in another, with cited evidence such as manual pages, teardown photographs or specification sheets. Credibility rests on the evidence, not on the argument.

Does infringement depend on commercial scale?

No. Making one unit for internal use infringes. Scale affects damages rather than liability, and small-scale infringement is frequently not worth pursuing for that reason rather than because it is lawful.

What it takes to infringe a patent

What legally counts as infringing a patent — the all-elements rule, direct and indirect liability, the acts covered, the defences available, and why similarity is not the test.

Patent claim chart: how to build one

A claim chart maps every element of a patent claim to a feature of an accused product or a prior art reference. How to build one, what makes it credible, and where they are used.

Doctrine of equivalents: how it works and what limits it

The doctrine extends claims beyond their literal wording. How the function-way-result and insubstantial-differences tests work, and how prosecution history estoppel constrains them.

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