No, you do not need a working prototype of your invention in order to successfully file for a patent with the USPTO. However, there are several probing questions an inventor needs to answer in order to cross the finish line. These answer(s) will determine if you are far enough along with your idea to even seek patent protection. After you initiate contact with myself by email, phone or in person I will ask you to complete a confidential Invention Disclosure Worksheet which should not take you no more than 15 minutes to complete. The questionnaire will also require a preliminary sketch, nothing too formal, which can be done on paper or on a computer. I go over these points in the video below. Please contact me if you have any urgent questions.
Tough Questions Inventors Need to Ask Themselves
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I will be glad to offer you my advice and experience.