Many prospective patent applicants are eager to know if they are already infringing on an existing product before pursuing a patent application of their own. Most of the time, clients will come to me with pictures of competing products or a link to online stores carrying the competing products.
While it is helpful to look at competing products to see how one invention differs from another invention, it is often not easy to tell if one invention infringes upon the other. To do this, you have to look at a registered patent disclosing the inventions at issue.
Without a registered patent, there is no infringing. So if your competitor does not own a patent, then you can stop right there and stop worrying about infringing, because you're not. Copying, maybe, but not infringing. To find out whether your competitor owns a patent, or multiple patents for that matter, you have to conduct a patent search. Most likely, the patent would be assigned to a company, and not to an individual person. So it is helpful to know what company makes the product at issue.
Once you find relevant patents, you have to look at the claims portion of the patents. Just because something was disclosed in the specification, abstract, or the drawings does not mean that it is necessarily "protected." You can only find infringement if you can show that the alleged infringing products meet every element of the claims as recited in a registered patent (not a published patent application). This means that you may have a non-infringing product that shares some of the elements of a claim, but not all.
Alternatively, you may see an invention with a very specific configuration in the specification, but with very broad claims. For instance, a patent may disclose a swivel armchair that can spin, rock, and recline, so that it is different from a conventional rocking chair or a recliner. However, the patent may claim a chair that can move relative to its base. So, even though the patent disclosed a very specific chair, the claim would include a rocking chair, a recliner, and other types of chairs that can be adjusted.
Although the scenario above is unlikely, it just goes to show you how important it is to review the claims and interpret it in light of the specification to understand what is protected and what is not.