According to Donald Grant Kelly, director of the Office of Independent Inventor Programs at the U.S. Patent and Trademark Office (PTO, www.uspto.gov), broad vs. narrow is really an issue of establishing barriers to market entry by competitors. The issue relates to a patent's claims, which are the heart of a patent.
A patent claim presents details of the invention. Just how precise those details are determines whether a patent is broad or narrow. For example, says Kelly, broad claim language would be a phrase like "container of fruit," while narrower claim language would be "a bowl of apples."
The problem for Demon and other inventors is that the PTO doesn't like to issue patents with broad claims. "When an inventor succeeds in gaining a patent on an invention, this means that the other 250 million Americans will be excluded," says Kelly. "There's an important line that must be drawn by the patent examiner [that] delineates the inventor's right to a newly developed and precisely defined invention and the right of the general public to freely enjoy that which is already in the public domain. If the inventor's claim is too broad, it will impinge on that technology that is already owned." Since the concept of cushioning shoe soles was already known, the patent office is going to restrict Demon's patents to specific claims.