How to Read Patents

In Part I of this article we discussed how to read the front page of a patent. In this Part II we will look at the drawings, specification and claims.


Most utility patents include a number of drawings following the front page of the patent. These drawings are used to describe the invention. A small percentage of utility patents do not include drawings. These patents tend to be for inventions that do not lend themselves to drawings, such as chemical inventions.

Many different kinds of drawings can be used in patents. Patents related to mechanical inventions can have different types of mechanical drawing drawings, such as isometric, plan, exploded, and cross-sectional views. Patents related to software, processes and methods tend to have flow charts. Patents related to electrical inventions tend to have schematic circuit diagrams. Patents can also include graphs, charts and conceptual diagrams. Almost any kind of drawing that is useful to describe an invention can be used in a patent.


How to read patents


Drawings usually have reference numbers that point to specific elements or parts of an invention. Each of these parts are described or referenced in the written description that follows. The reference numbers help make it clear what part is being discussed.

Design patents protect the appearance of an object. Therefore, almost all design patents have drawings that communicate the appearance of an invention. Plant patents also have drawings of the plants that are the subject of the patent.


How to Read Patents


Navigating the Specification with Columns (17) and Line Numbers (18)

Patents are usually printed in columns (17) that contain line numbers (18) running down the side. These numbers are very useful for anyone who needs to work with a patent. Sections of a patent can be referred to easily and unambiguously by specifying a range of columns and line numbers.

Background of the Invention (19)

The Background of the Invention (19) typically includes two sections. The first section describes the Field of Invention (20). The Field of Invention is the industry or technology to which the invention relates.

The Background of the Invention (19) may also contain a description of the related art (not shown). This section describes what was known in the field of the invention at the time the inventor conceived of his invention. Often, this section is used to describe problems with existing technology or disadvantages encountered with prior products or processes. Generally, this section describes what was already known, rather than the new invention.

Summary of the Invention (21)

How to Read Patents


The Summary of the Invention (21) describes the specific nature of the claimed invention, as well as its method of operation and purpose. Typically, this section will also list advantages (22) the invention offers. The Summary also contains a Brief Description of the Invention (23), which provides an intermediate level of detail between the Summary of the Invention and the Detailed Description (25).

Brief Description of the Drawings (24)

How to Read Patents

Description of Drawings

The Brief Description of the Drawings (24) provides a very general description of what is depicted in the drawings and the way it is depicted.

Detailed Description (25)

How to Read Patents

Detailed Description

The detailed description (25) is an in-depth discussion of the invention that should enable a person of ordinary skill in the field of the invention to make and use the invention. This section generally contains a detailed discussion of the drawings and explains the invention with reference to the reference numbers included on the drawings.


Claims (26) always receive a great deal of attention during licensing and litigation. The scope of protection provided by a patent is mostly determined by the patent’s claims. In a way, claims are similar to a metes and bounds description in a property deed.

Although applicants want to obtain broad claims for a potentially more valuable monopoly, it is important that the claims be specific enough to be valid. Occasionally, an applicant obtains a patent from the Patent Office only to have the patent invalidated by a court during litigation.

Patent law has evolved in such a way that claims are confusing to non-patent attorneys. For example, each claim is written as a single sentence and some claims have dozens of clauses and parts.

Non-patent attorneys sometimes make the mistake of interpreting the scope of a patent based only on part of the patent (e.g., the title or abstract). However, the scope of a patent is determined by the claims as they are interpreted using the entire patent as well as its prosecution history in the Patent Office. In addition, claims do not always mean what they say. There are a number of legal doctrines that could lead to a much narrower or broader interpretation than their apparent meaning.

How to Read Patents


Claims can be broken into two general groups: dependent claims and independent claims. Independent claims are those that stand by themselves; they do not incorporate other claims. For example, claim 1 of the ‘593 patent is an independent claim. Dependent claims are those that refer to and incorporate at least one other claim. A dependent claim contains all the elements of the dependent claim itself, and those of any other claim it depends upon, including at least one independent claim. Although it is not common in the U.S., some claims can depend on more than one claim.

You can think of independent and dependent claims as a tree. The independent claim is the trunk and the dependent claims are the branches and twigs. Since the independent claim includes the fewest elements, it is the broadest and provides the strongest protection. Each dependent claim branch adds at least one element to the invention and provides narrower protection.

Two Minute Patent Review

A patent can sometimes seem impenetrably dense and confusing. However, a brief review can reveal important information from even the most complex patents.

If time or attention span is in short supply, follow these steps for a two minute patent review: 1) Read the filing date and the date of grant to determine the age of the patent. From this you can determine if the patent has expired. 2) Read the title and abstract of the patent to get an idea of the subject matter. But do not assume that this determines the scope of the patent. 3) Read the independent claims of the patent to get a feel for the scope of the patent. After this review, you should have a basic understanding of the patent. Care should of course be taken not to reach any important conclusions without consulting patent counsel.

Please call us if you need help with a patent issue.

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