James, from what I've heard from some members of the Inventors Association I belong to is to ask for their product development or new product department and tell them you're a "product developer," not an inventor. Don't just send a prototype unless they ask for it. Ask them to send a NDA before you send them info about your idea. (Some large companies won't sign a NDA, so it's up to you whether you want to take the chance. You can always research the company, or a patent agent or attorney.  If there's an inventor association near you, it will be helpful overall to attend some meetings and learn from others.  There's also a ton of info on the EN site.  Good luck!