How to Write a Patent - Anatomy of A Patent Application
Updated: Apr 14, 2022
This is part of a series on writing patents for the layperson. We'll show here how to draft a patent application for the familiar object shown above.
Step 1 - Search
The first step is generally a search, which you'll want to do to get a lay of the land - what already exists and what may be new under the sun. You can do this on your own with a google patent search or get a search done by a patent firm - there are firms that specialize in searches but most patent firms will do searches as well. Investors may want a professional search for obvious reasons. You may also want to do a 'freedom-to-operate' analysis  and/or a patentability analysis.
The easiest search is by keyword, while more advanced searches use a set of subject codes developed independently by various patent offices such as the USPTO and WIPO, and finally a few AI-based searches have started to appear.
There are some cases where inventors skip the search - if you are familiar enough with the field that you already know what's out there, or if your goal is simply to reach 'patent pending' status as quickly as possible, trusting that you'll be able to invent your way out of any problems arising from prior art - a risky but fast approach.
You can search also search through 'freepatentsonline' as in the search box below:
Step 2 - Describe Your Idea
Try to describe the heart of your patent in a single sentence. This can form the basis of a claim later on. A reasonable one-sentence description of a pencil might be:
An outer cylindrical wooden shell surrounding an inner graphite rod.
Now try to 'reduce to practice' - describe clearly how to build your device or execute your method to an imaginary engineer who has access to all possible resources. You can use any building block that a skilled engineer would recognize. This imaginary fellow is an important figure - he is the person 'skilled in the art' for whom a patent application is ideally written. He has absorbed all published knowledge and is familiar with all engineering techniques and methods. A reduction to practice for producing a pencil might be:
A wooden cylinder of radius 5-15mm is obtained. A channel is milled into the cylinder, for instance by use of an end mill. A graphite rod is inserted into the channel, and is entirely covered by a wooden insert of appropriate cross section that is glued or attached to the rest of the cylinder. By sharpening one end of the cylinder into a cone, a section of graphite is exposed that is mechanically supported by the wood against breakage. The exposed section of graphite is useful for making marks upon paper or other surfaces.
Step 3 - Choose a Destination : Provisional or PCT
Patents can be written in several different ways and have different requirements depending on where they're being submitted and what they're trying to cover.
The basic choice here is between a provisional patent application and a PCT patent application.
The provisional patent is easiest to write - there are no requirements for claims, no requirement for oath or declaration, and you don't have to list any prior art you may have found. You can submit this yourself rather easily, for $75 in most cases .
In a provisional, you've got to describe the invention clearly enough, and completely enough, for a technologically savvy person to produce the device or carry out the method - that's it. Figures can (and probably should) be included, but they need not fit any particular style or standard. The usual is to use black and white line drawings (color and photographs will require special permissions so avoid them if possible).
The PCT format is good for submission to all the countries that signed a certain patent treaty (the Patent Cooperation Treaty of 1970, not the Paris Convention Treaty of 1883 as one might think).
If you write your patent in this format it will be acceptable as a nonprovisional or PCT patent pretty much anywhere in the world. 
Write it in English and you'll likewise be able to submit where you see fit, although translations are required for some countries .
The PCT format generally used is :
Field of the Invention
Detailed Description - possibly broken into sections such as:
Problem to be solved
Solution of the invention
Advantages of the Invention
Description of the Drawings
Description of various embodiments
The title should be a short description which is easily understood, e.g.
An Improved Device for Writing
The field of the invention is a short description of the technical field in which the invention lies; for instance:
The invention relates to writing devices, in particular to those not requiring ink.
The background generally goes over the most relevant prior art (things that have already been published or patented) , often pointing out the deficiencies and drawbacks of what's out there currently.
The summary is a brief description of the invention, going over the main points but without the full detail - that goes into the detailed description.
The detailed description often has several subsections, although this isn't strictly necessary. The point of this section is to lay out the invention in sufficient detail that the person 'skilled in the art' (ie an expert in whatever field the patent is in) can understand how to make the device or practice the method of the invention. This is generally done with reference to the figures. The invention can be described in terms of a problem to be solved and the solution of the invention although this also isn't strictly necessary (this is actually how a Japanese patent is always laid out, and in my opinion its an effective way to describe an invention).
Usually several embodiments (or examples of different versions of the invention) are described, with one or more versions listed as a 'preferred embodiment'. For instance in the case of the pencil, different embodiments might include a wooden body, a plastic body, and a metal body, or a round cross section and a hexagonal cross section.
The claims are each a single sentence. Each claim is a brief description of the invention pointing out a novel feature or features; it should define exactly the novelty that the invention covers, and what the inventor wants to be protected. Each claim should clearly lay down what the patent does and does not cover. The claims determine what the patent 'really' covers, and in case of a lawsuit the judge and lawyers will be looking at the claims to see what the patent is staking out. You can think of the claims as being like surveyor lines defining an area which a certain property owner owns - an 'intellectual property line', if you will.
Claim 1. A cylindrical rod of radius 5-15mm, having a channel milled into it, into which a graphite rod is inserted and covered by a wooden insert glued into place, wherein said rod may be sharpened to reveal a length of said graphite, and be used to form marks upon paper and other surfaces.
There are some rules concerning the claims and how they are constructed, which change from time to time and from country to country.
The abstract is a brief recap of the invention, in informal language, and is often used in a one-page shortened publication of the patent. This is the first thing people will read when searching for patents.
The drawings are generally black and white line drawings. The elements in the drawing should be labelled by use of letters (as in the figure above) or (more commonly today) numbers.
That's it! The devil of course lies in the details - there are rules concerning each of the sections mentioned, and the 'Manual of Patent Examination Practice' for instance (the US list of rules concerning patent practice) and from the size of the books below you can get a feel for what's involved. Add to this the fact that each country has its own variations of laws governing patents and acceptable practice for writing patents, and you'll see why generally people go to patent attorneys.
To be able to submit this application to the USPTO electronic filing system, save it .as a pdf (with fonts embedded and PDF/A-1a (ISO 19005-1) if you have those options). You should restrict yourself to Times New Roman or other common font to avoid problems down the road.
Now that you've got your patent written , you can submit it - here's a post on how to submit a provisional patent to the USPTO yourself (something written in PCT format can also be submitted as a provisional).
 A small entity has 500 or fewer employees + affiliates.
A micro entity qualifies as small entity and also has a gross income less than three times the current gross median income.
 watch this space for an article on how to submit a provisional patent application yourself.
 China, Japan, and Korea for instance require translations.
Pencil patent - https://patents.google.com/patent/US19783