Q: i have an idea to modify and existing patent. can i patent my modified design?
A: Yes, you can. Patents are granted on new things, but on improvement on existing things. For example, Alexander Graham Bell invented the telephone, but people are still making improvements to telephones and getting patents for them.
A: Mr. Mlynek's answer is correct but I want to make sure you understand the consequences of the path you choose.
Let me step through the basic process. Assume that the existing patent covers a WIDGET and you have an improved WIDGET.
1) You do not infringe a patent. You infringe one or more specific independent claims (ones that start with no reference to another claim) and possibly some dependent claims (a claim that adds additional limitations to at least one other claim).
2) You infringe a claim under the all elements rule by having every noun, every verb, and every relationship required by the claim. In some special circumstances some nouns or verbs are stretched to include some alternatives that achieve substantially the same function in substantially the same way to achieve substantially the same result. (sorting out these close calls under the "doctrine of equivalents" will require a patent attorney).
3) Thus, if you provide the same sort of benefits with your WIDGET as another provider does but no claim in their patent has a good match for all the required elements in that claim to your product, you are not infringing. You are simply competing which is encouraged.
4) If you are infringing one of their patent claims but add some bells and whistles to your WIDGET to add another feature, then you are still infringing. You may be able to get your own patent on a WIDGET with that added features and prevent the first company from adding that feature. You might be able to cross license patent rights with the first company to trade access to your patent to access to their patent (and possibly some money paid to them as they have the broader patent).
As you can see, this gets complicated quickly. You will need help from a competent patent attorney to lead you forward. The good news is that patent attorneys help people get patents under a federal license so you can chose a patent attorney to help you get patents from anywhere in the country.
I think you would benefit from going through my slide set to teach entrepreneurs about basic patent concepts as you seem to have a thirst for understanding - not just simple answers. http://bit.ly/Protecting_Advantages
You may also benefit from tips on patent searching in this slide set http://bit.ly/Patent_Searching
If you found this answer helpful, you may want to look at my answers to other questions about patent law are available at the bottom of my profile page at
Kevin E Flynn
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