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American Bar Association - Defending Liberty, Pursuing Justice

Spring 2009

Vol. 5, No. 3


Business Law


The Patent Lawyer’s Mission—Isolate the Inventive Concept

For most people, an invention is something tangible. One thinks of mechanical devices like the zipper or manufactured substances like tetracycline. Even process inventions, like pasteurization, evoke the physical reality of the milk being heated.

For patent lawyers, however, an invention is not something physical, but a concept. Indeed, the patent attorney’s primary mission is to discover the inventive concept underlying the specific “embodiment” that the inventor designed, and then to articulate that concept in what is called a patent “claim.” To fail in that mission is to open the door for a competitor to take advantage of the inventor’s contribution to the art while avoiding liability under the patent.

Consider John Loud’s invention of the ballpoint pen, patented in 1888. 1 Loud’s “embodiment” is shown in the figure. The ball L is held against the contracted mouth f of tube A by spring S, which pushes against rod G, bearing H and antifriction balls K. The spring yields when the ball is pressed against paper, thereby regulating the flow of ink onto the ball and from there onto the paper as the pen is moved.

Loud Ballpoint Pen
John Loud’s ballpoint pen

Here is a patent “claim” defining Loud’s ballpoint pen

1. A pen comprising a tube having a contracted mouth and adapted to hold ink, a spheroidal marking point projecting from the mouth, and an ink regulator for resiliently holding the marking point against the mouth.

It is desirable for a claim to be as broad (think “terse”) as possible because a patent covers a competitor’s product only if that product meets every word of the claim. If there’s something in the claim that the competitor’s product doesn’t have, the competitor is free of liability under the patent, even if the competitor’s product clearly takes advantage of the patentee’s underlying teachings or discovery. On the other hand, there must be something new in the claim in order for the patent examiner to accept it. Thus if Loud’s patent application had presented a claim like

2. A writing implement having a tip that transfers ink from an ink reservoir to a writing surface

the patent examiner would have rejected it because claim 2 not only defines, or “reads on,” Loud’s ballpoint pen, but also “reads on” the theretofore already invented fountain pen. Claim 2 is inappropriately broad; it doesn’t define anything new.

So claim 1 seems pretty good. Desirably, the claim even reads on the pen empty of ink because the claim calls for a tube adapted to hold ink, but does not include the ink itself as an element of the patented subject matter. As such, the claim reads on pens in their manufactured form and could be asserted against manufacturers who might have sold the pen without ink, like fountain pens of the day.

Yet claim 1 would be of little value if Loud’s patent were still in force. Modern ballpoint pens do not have anything like Loud’s “apparatus for resiliently holding the marking point against the mouth.” Instead, the ink is kept from leaking out by virtue of a tight fit between the ball and its socket and by using an ink having just the right level of viscosity.

Granted, it would have required a visionary of considerable insight to have anticipated the advent of the technology required to manufacture today’s modern ballpoint pens. However, it does not require a visionary to recognize that advances do occur. Indeed, the patent attorney’s task is to draft claims that preserve a patent’s value despite such advances if improved devices embody the inventor’s original work.

Loud’s attorney, William Dowss, was, in fact, up to the task. Claim 1 is not Dowss’s claim, but was written by the author for purposes of our discussion here. If the Loud patent were still in force, Dowss’s claims would command a royalty for every ballpoint pen on the market because Dowss successfully isolated—in a ten-word claim—the concept that underlies every ballpoint pen:

3. A pen having a spheroidal marking-point, substantially as described.

There are myriad ballpoint pens on the market. Yet each implements the concept that Loud was the first to embody in a pen and that Dowss was skilled enough to claim. Loud’s embodiment did not have a replaceable cartridge, a plastic barrel or a retractable tip. The technology needed to create the tiny balls and tight-fitting sockets used in modern fine-line ballpoint pens probably did not exist in 1888. Today’s metals, plastics and ink compositions were not available. Nonetheless, every ballpoint pen produced since Loud’s original embodies a concept that transcends these embodiment details—the concept of a pen “having a spheroidal marking-point.”

It is easy enough now to recognize the shortcomings of claim 1. But how would one know that it is not the broadest definition of the invention? How did patent attorney Dowss have the insight to foresee in 1888 that future pens would not need claim 1’s spring-loaded “ink regulator?”
Dowss may not have had that insight. But Dowss’s claims clearly evince his understanding that implementational details—like an ink regulator or a tube with a contracted mouth—were irrelevant to the essence of Loud’s invention.

How did Dowss come to that understanding? And how can the practicing patent attorney today know when the inventive concept has truly been found and properly claimed?

The path to the inventive concept begins with the problem that the inventor solved. The inventive concept is the inventor’s solutionto that problem, when broadly articulated at a conceptual level. Given any detail in the inventor’s “embodiment”—a physical element, a method step, a particular functionality or a specific relationship among these—one can ask whether that detail is essential to solving the problem to at least some extent. If not, that detail is not intrinsic to the inventive concept.

The problem Loud addressed was that existing (fountain and quill) pens could not write on rough surfaces, such as wood or leather. Central to his solution is the ball itself. Problem solved. Claim 1’s ink regulator tells how such a pen could be constructed, not about how the problem of writing on rough surfaces can be solved. If the ink could somehow regulate itself, we would still have a pen of the type Loud envisioned. Never mind that Loud probably never considered whether such an ink could exist. It is possible to formulate a statement of something new—a pen with a spherical marking-point—without having to describe how such a pen might be constructed.

Perhaps somewhat more subtle is the question of the contracted mouth of the pen barrel, which one might think is absolutely required. How else could the ball be held in place?

It doesn’t matter.

Imagine a tiny genie whose job is to hold the ball in place. Loud’s spherical marking-point pen would still be a novel writing implement, even with that genie hanging on for dear life as the pen wiggles across the paper. Distinguishing Loud’s pen from those that came before it does not require that the pen has a contracted mouth or an ink regulator. Advantageous or not, these are only implementational details not going to the essence of solving the problem of writing on rough surfaces.

In short, whether something seems required to implement an inventive concept is irrelevant to the task of claiming it.


1 United States Patent No. 392,046

Ronald Slusky mentored dozens of attorneys in “old school” invention analysis and claiming principles over a 31-year career at Bell Laboratories. He is now in private practice in New York City. This article is adapted from his book I nvention Analysis and Claiming: A Patent Lawyer’s Guide (American Bar Association 2007). His monthly column, Invention Analysis and Claiming, appears in Intellectual Property Today. Slusky also teaches a two-day seminar based on this book ( He can be reached at 212-246-4546 and

Invention Analysis and Claiming: A Patent Lawyer’s Guide

Did you find this article helpful? Do you need more information regarding inventions or patent law? To provide some basic assistance in this area, we are pleased to introduce the Invention Analysis and Claiming: A Patent Lawyer’s Guide. This book should provide attorneys with some basic knowledge that will allow them to get started with preparing patent applications.It can be purchased at:

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