With an improvement patent, you add improvements to a previously patented invention. If you are not the owner of the previous patent, you might be able to get a patent but not be able to sell the product related to the patent because you would be infringing on the original patent.
Under pressure to fight counterfeit products on its online platform and those accused of violating third-party patents, Amazon created its APEX program. It’s sort of an intramural arbitration process whereby someone claiming its patents were being infringed upon by an article sold on the Amazon website could—for a $4,000 fee—file a complaint and be bound by the final decision of the patent specialist retained by Amazon.