I think we all know that a patent is enforced by suing the copy-cat for infringement. However, what may look like copying, may not be infringement. Similar, what you may believe to be new and different, may actually be copying all the elements of an existing patents. When your device or method contains all the elements of an existing patent, even if used differently or for a different purpose, it may be infringing. Even if your device or method contains features not disclosed in an existing patent, it may still be infringing.
The important thing to understand when discussing whether or not infringement exists is to understand the function of the CLAIMS of the patent. Every patent consists of three parts. The patent contains an abstract (summary) and a specification (detailed description explaining the invention and how it works). The specification may be supplemented by drawings. The third element of every patent is the claims.
In almost all cases, there are multiple claims. Each claim provides a complete definition of a variation (“embodiment”) of the invention.
A useful analogy is that each claim describes the boundary lines of one embodiment of the invention. (The invention can be described in multiple ways, with each way containing different or additional components.)
First, you really need an experienced patent attorney to draft the claims for your patent application. The inventor can certainly write a specification (detailed description) with accompanying drawings. The inventor can of course write the abstract (summary). But the claims are different. If the claims are too narrow or specific, it will be easy for others to create a device or method that skips some of the steps of your method or omit components of your device.
Simply stated, if the claims of a patent (Jones patent) describes a device containing the defined components A, B, C & D, a competing device (Smith device) comprised of elements A, C, D, & E (where each letter denotes a separate and distinct component), the competing device will not infringe the Jones patent. This is because Smith’s device does not contain all the components required of the Jones patent claim, i.e., Smith’s device does not contain component B. However, if the Smith device comprises the components A, B, C, D, & E, the Smith device does infringe the Jones patent. This is because Smith device contains all the components of the Jones patent, i.e., components A, B, C, & D. The fact that the Smith device also contains component E is irrelevant for purposes of determining infringement.
It gets more complicated. If the Jones patent is for a bicycle and Smith is selling a tricycle, the Smith tricycle may infringe the bicycle patent, depending upon the wording of the claims of the Jones patent.
If Jones claims: “A device that may be propelled across a ground surfaces comprising two or more wheels and a pedal that when rotated, causes at least one wheel to rotate over the ground surface.”
This is a very broad claim for a bicycle. However, a tricycle is covered by this claim description. (In patent parlance, the Jones claim “reads on” the Smith tricycle.) The Smith tricycle infringes upon the Jones bicycle patent since a tricycle also has “two or more wheels” and “a pedal that rotated, causes at least one wheel to rotate”.
If Jones, however, drafted the claim with more specificity, the claim may not be infringed by the Smith tricycle. If Jones’ claim states: “A device that may be propelled across a ground surfaces comprising two or more wheels, a pedal and a chain component that connects the pedal to a wheel that when the pedal is rotated, at least one wheel is caused to rotate over the ground surface.”
In this case, the bicycle contains of two or more wheels (Component A) and a pedal (Component B) and a chain (Component C). However the Smith tricycle does not include a chain, Element C. (Recall that the tricycle pedal is directly connected to the front wheel.) Since Smith does not contain a chain, it does not infringe the more specific Jones patent claim.
What this simple example shows is that it is very important how each patent claim is worded. Depending upon the text of the patent claim(s), there may or may not be a case of infringement.