The doctrine of equivalents (DOE) allows for a finding of direct infringement even if not every element of a claim is literally present in the accused device or activity. The accused device or activity is deemed equivalent to the patented claim if every element of the claim is present either literally or equivalently in the accused device or activity. There are two tests for determining whether the DOE applies.
Doctrine of Equivalents (DOE)
Under the insubstantial-differences test, the DOE applies if differences between the elements of the claim and the accused product or process are insubstantial.
The rights of a patentee are to exclude anyone from making, using, offering to sell, selling, and importing the patented invention within (or into) the United States. If during a term of a patent, someone commits one of these acts with respect to any particular claim in the patent, and does so without permission, that person has infringed the patent.
Direct infringement is strict liability. This means that even if a person is not aware of a patent, that person is still liable if he commits direct infringement.
Literal infringement occurs when every limitation, exactly as described in a claim, is found in an accused device or activity. The claim exactly matches the device or activity.
Rights of Patentee
The exhaustion doctrine precludes a patentee from exercising rights to a particular patented product after the first authorized sale of that product.
Under the function-way-result test, the DOE applies if the accused product or process performs substantially the same function in substantially the same way to obtain substantially the same result. This test compares the function of a claim element, the way the element performs, and the result of the use of that element with that of the corresponding element in the accused product or process.
Prosecution History Estoppel
The doctrine of prosecution history estoppel (PHE) limits application of the DOE. If a patentee has made an amendment to his claims in response to the PTO, the amendment presumptively precludes a finding of infringement under the DOE. Simply put, if the prosecution history indicates that a claim has been narrowed for purposes of patentability, the doctrine of equivalents cannot apply absent a rare exception.
Indirect infringement is possible where a person either induces someone else to directly infringe or contributes toward someone else’s direct infringement.
To be liable for inducing infringement, a person must actively induce another to infringe, and that other person must directly infringe. The person must take active steps to encourage the act of infringement. This might include advertising an infringing use or requesting someone to do the infringing act.
To be liable for inducing infringement, a defendant must know that the activity that he encourages actually infringes on another’s patent. The requisite knowledge may be imputed to a defendant who is willfully blind. To be willfully blind, a defendant must subjectively believe that there is a high probability that the activities infringe a patent; and the defendant must take deliberate actions to avoid actual knowledge of the infringing nature of the activities.
Contributory infringement is based on the act of selling or offering to sell something that contributes to direct infringement. Five elements must exist for contributory infringement:
(1) the defendant made an offer to sell or sold (within the U.S.)
(2) a component of an infringing product, or a material or apparatus in an infringing process,
(3) that constitutes a material part of the invention,
(4) knowing that the component or material or apparatus is made or adapted for use in an infringement of a patent, and
(5) the component, material, or apparatus is not a staple article of commerce suitable for substantial non-infringing use.
If the component is good for nothing else except to for infringing the patent, the knowledge element will be presumed.
To directly infringe a patent, a person must be responsible for committing all the acts necessary to infringe, either personally or vicariously.
Borus has been working on an invention for 10 years. Finally, in July 2016, he perfects it, making a working model. Borus files for a patent application that same month. However, he then discovers that another inventor, Kyle, had already filed for a patent on the same invention, and the patent issued to Kyle two years earlier.
Question: Has Borus infringed Kyle’s invention?
Doug has patented his invention—tint for windows that eliminate sunray glare. Emily has invented an aerodynamic window design for cars. Her window design is novel, useful, and non-obvious. She would like to use Doug’s tint in the car windows with her design when she makes a model window.
Questions: Can Emily obtain a patent on a claim for her aerodynamic window that incorporates Doug’s tint (without obtaining Doug’s permission)? If Emily does obtain a patent, will this entitle her to make a model of the claimed window using the tint?
Lonnie purchases a new car from Ford Motor Company that contains many parts that are patented by Ford. Three years later, Lonnie sells the car to Beatrice. Lonnie never obtained permission from Ford to sell the patented parts that are part of the car.
Question: Has Lonnie infringed the patents of Ford?
Molly creates a novel skin ointment that helps heal skin abrasions. She receives a patent for the ointment based on the following claim: “A skin ointment that heals abrasions, comprising 10 g of Chemical X, 16 g of Chemical Y, 1 cup of rose petals, and 3 cups water.” In her written description, Molly describes how the rose petals function by reacting with the other ingredients to provide a pleasant aroma during the healing process. She receives a patent for this claim. Her competitor, Taylor, makes the same ointment using the same ingredients and proportions, except that he replaces the rose petals with daisy petals. (The daisy petals also interact with the other ingredients to provide a pleasant aroma during the healing process.) Taylor is thrilled to discover that his daisy-petal ointment has the same effect on skin abrasions as Molly’s rose-petal ointment does.
Question: Has Taylor directly infringed the patent of Molly?
Answer to Question 1
Yes. When Borus made a working model of the invention, Kyle had a patent on that invention. Kyle’s patent includes a right to exclude others from making the invention. Borus did not have permission from Kyle to make the invention. The fact that Borus did not know of Kyle’s patent is no defense.
Answer to Question 2
Doug’s patent on the tint does not preclude Emily from obtaining a patent on a window that incorporates his tint. Doug does not have a right to preclude someone from referring to his patented tint. However, his right to exclude others from making, using, and selling the tint does mean that Emily is not entitled to make a model of the claimed window using the tint, even if the PTO grants her a patent.
Answer to Question 3
No. The exhaustion doctrine precludes a patentee from exercising patent rights over a particular product after the first authorized sale of that product. Ford’s right to sell the patented parts ceases once it sells those parts (or authorizes a car dealer to sell the parts). Lonnie can re-sell the car without infringing.
Answer to Question 4
Likely yes under the doctrine of equivalents. Taylor has not literally infringed her patent because his ointment lacks one of the limitations in Molly’s claim—rose petals. However, Taylor may have infringed under the doctrine of equivalents. Under the function-way-result test, the daisy petals appear to perform substantially the same function (providing a pleasant aroma) in substantially the same way (reacting with the other ingredients) to obtain substantially the same result (an ointment that heals skin abrasions while giving off a pleasant aroma).
Under the insubstantial differences test, the only difference between any element of Molly’s claim and Taylor’s ointment is the replacement of rose petals with daisy petals. Although ultimately the distinction between rose and daisy petals must be decided from the perspective of a PHOSITA, it seems likely that the difference is insubstantial given that they are both flower petals.
Hence, Taylor likely directly infringed Molly’s claim under the doctrine of equivalents.
Amy raises chickens and is tired of having to close the door to the chicken coop each night. So Amy invents a chicken coop that has a door that closes automatically. The coop door has a closing mechanism that is activated once all the chickens are in their nests. She initially files for a patent by claiming the following:
An animal housing unit with an automatic door-closing device comprising:
a housing unit for an animal;
a door on the housing unit that closes automatically when a wireless apparatus triggers a closing mechanism on the door; and
an individual weight sensor under the resting place of any animal in the housing unit, wherein the weight sensor communicates with the wireless apparatus.
The prior art includes a publication describing a dog house with an automatic-closing door that employs the same sort of technology. The PTO therefore rejects the claim based on the prior art. Amy then amends her claim to state the following (deleting the highlighted verbiage):
An animal housing unit chicken coop with an automatic door-closing device comprising:
a housing unit for an animal chicken coop;
a door on the housing unit chicken coop that closes automatically when a wireless apparatus triggers a closing mechanism on the door; and
an individual weight sensor under the resting place of each chicken in the housing unit coop, wherein the weight sensor communicates with the wireless apparatus.
Based on this amendment, the PTO grants her patent. Two years later, David starts selling pig pens with automatic closing doors, employing the same technology that Amy used—sensors that trigger the door once the pig lies down on its bed of straw.
Question: Has David infringed Amy’s patent?
RESLA is a company that specializes in producing battery-powered automobiles. Recently, RESLA patented a battery technology that will enable a car to travel 1,000 miles before needing a re-charge of its battery.
Katie learns of RESLA’s patent and asks her friend, Aaron, to build her such a car. Katie explains the new technology to Aaron, and Aaron, it turns out, is a near genius, able to build anything, including batteries and automobiles. However, Aaron does not know that RESLA holds a patent on this technology. Aaron proceeds to build the car with the patented battery technology. He sells the car to Katie.
Question: Is either Katie or Aaron liable for infringement?
Justin sells microchips to Bethany, who sells radar guns. Bethany sells a radar gun that infringes a patent that Bradley owns (the Bradley patent). The infringing radar gun requires a certain type of microchip that can only be used in that particular radar gun. Justin knows that Bethany uses his microchips to infringe the Bradley patent. The microchip itself, however, does not infringe the Bradley patent. Other people sell the microchip to Bethany as well.
Question: Is Justin liable for infringing Bradley’s patent?
Answer to Question 5
No. David has not literally infringed Amy’s claim because in his pig pen he does not build a “chicken coop.” Amy may argue infringement under the doctrine of equivalents, but prosecution history estoppel is likely to preclude that argument. During the prosecution history, Amy amended her claim to include the limitation of a chicken coop rather than a housing unit for an animal. That claim limitation is narrowing. Moreover, Amy included the amendment in order to distinguish her invention from prior art (i.e., the dog-house reference), and therefore it was for purposes of patentability. None of the rare exceptions apply. Prosecution history estoppel therefore bars her from proving infringement under the doctrine of equivalents. Thus, David’s pig pen does not infringe.
Answer to Question 6
Yes; both Katie and Aaron have infringed RESLA’s patent. Aaron is a direct infringer. He both made and sold the patented battery technology, two actions that infringe the rights of RESLA, so he has directly (and literally) infringed. The fact that Aaron did not know about RESLA’s patent does not matter because direct infringement is a strict liability offense.
Katie is liable for inducing Aaron’s infringement. She actively encouraged his building and selling the battery technology, taking the affirmative steps of telling him the details of the technology and asking Aaron to build her a car with that technology. Furthermore, she has knowledge of RESLA’s patent, having learned of the patent. Katie, however, is not liable as a contributory infringer because she did not sell any component to Aaron.
Answer to Question 7
Yes. Justin is indirectly liable under the doctrine of contributory infringement. He has contributed to Bethany’s direct infringement. Specifically, Justin has sold to Bethany a component of the infringing radar gun—the microchip—that is material to the radar gun given that the gun cannot operate without it. Justin has knowledge that the microchip will go in the radar gun that infringes the Bradley patent. The microchip itself is not a staple article of commerce because it has no substantial non-infringing uses. The fact that other people sell the microchip to Bethany merely means that those other people may also be contributorily infringing the Bradley patent.