Ways to Infringe a Patent
A patent can be infringed in two basic ways: directly and indirectly.
These different ways of infringing are important to understand by
anyone wanting to enforce patents and by anyone wanting to avoid
infringing a patent.
A patent claim is directly infringed by some product when that
product practices each limitation of the claim when
the claim is a method claim, or includes a structure equivalent
to each limitation of the claim when the claim is an
apparatus claim, or does both in the case of a means-plus-function
claim. The term limitation is used by lawyers and those
in the know to mean the step or steps spelled out in the patent
There is another way of directly infringing known as the doctrine
of equivalents. If a product doesn't perfectly meet the limitations
of a claim, it may still infringe on the patent if it does something
that a person of ordinary skill in the art (POSITA or
OOSITA) would know was equivalent. While this may seem
like a loophole, its actually quite fair. Suppose someone
patents a glass bulb containing a filament that produces light
when an electric current is sent through it. The inventor
may not realize that a bulb made of specially treated plastic would
also work. The key to the invention isn't the material from which
the bulb is made. Thus a plastic bulb could infringe on the patent
because of the doctrine of equivalents.
If a product doesn't directly infringe a patent, it may also indirectly
infringe. There are two types of indirect infringement: induced
infringement and contributory infringement. Encouraging others to
infringe a patent is called induced infringement. When
two products working together infringe on a patent, thats
called contributory infringement.
Induced infringement occurs when some party purposefully causes
or encourages another party to infringe a patent. The key work here
is purposely. Induced infringement must meet these criteria:
- The infringer actively encouraged or instructed another party
on how to use a product or perform a process in a way that infringes
the patent claims.
- The infringer knew of the patent.
- The infringer knew or should have known that the encouragement
or instructions would induce infringement of the patent.
- The other party actually infringed the patent.
So induced infringement requires that the infringer purposely got
another party to infringe a patent. Lets say you have a software
company that produces word processing software, and your competitor
has a patent on checking the spelling of words in a document and
putting a squiggly red line under misspelled words. You need a spell
checker, but you dont want to infringe, so your product outputs
misspelled words to a separate file and you recommend that your
customers buy third-party software that reads in that separate file
and puts squiggly red lines in the documents. You may be inducing
infringement by encouraging your customers to perform the patented
method. And dont try to use an orange line or a chartreuse
line, because youll probably still be infringing under the
doctrine of equivalents.
Contributory infringement occurs when one party who knows about
the patent supplies a component to another party to use in an infringing
product. Contributory infringement occurs if the party who received
the component directly infringes the patent and if the component
has the following characteristics:
- The component is a significant part of the invention.
- The component is especially made for use in a way that infringes
- The supplier knows that the component was especially made for
- The component doesn't have any substantial non-infringing use.
So contributory infringement requires that the infringer knowingly
supplied another party with a product that was incorporated into
a second product, causing the combination to infringe a patent.
Lets take the example again of your word processing company.
Suppose your word processing company decides to buy the third-party
squiggle generator software to incorporate into your word processor.
You meet with the head of the squiggler company and tell her that
your word processor doesn't infringe on your competitors product
and the squiggler doesn't infringe. You want to embed the squiggler
into the word processor. At that point you've just lost the game,
because the squiggler company knows that the combination infringes
and so they can be found to be contributory infringers. Because
its your product, you can be liable for direct infringement
in this scenario.
However, if the squiggler can be used to underline important words,
hyperlinks, and naughty words in addition to misspelled words, then
the squiggler company may be OK because the component has significant
uses that are non-infringing.