In 1995, two Virginia inventors patented a method to get cats to exercise by chasing a laser beam.

That's an example of a frivolous patent, according to Phil Dowd, who said there would be no way to prove someone had infringed on it. Nor would it make money, he said, because anyone could do the same thing.

"Without understanding ... how you could market (an invention), you could end up with a frivolous patent," said Dowd, technology manager at Arizona Technology Enterprises, which helps bring the inventions of Arizona State University researchers to the marketplace.

The example illustrates key lessons for entrepreneurs who think they have a patentable invention.

"Just because it's patentable doesn't mean it could generate some revenue," said Dave Cormier, a board member of the Henrietta, N.Y.-based United Inventors Association.

The purpose of a patent is to protect an invention that could give the applicant a competitive advantage in the marketplace.

But the process of obtaining a patent is time consuming and costly, especially for inventors who lack the financial arsenals of Microsoft, Google and other intellectual-property powerhouses.

That is why doing your homework is important.

"Anytime you're considering patenting something you need to assess whether having an exclusive position on the technology or invention is going to give you a significant advantage in the marketplace, enough so to make up the cost of patenting," said Brad Hartman, a Phoenix attorney specializing in intellectual-property issues.

"If your competition can do it a better way and still compete with you without missing a beat, then how valuable is this patent to you?"

The patent process can cost anywhere from $5,000 to $20,000, or more.

Costs include filing fees, attorney fees and costs associated with actually writing the application, an endeavor that requires a skilled wordsmith.

James Xia knows the expensive process firsthand. He estimates that his 20-employee company, GenoSensor Corp. in Tempe, Ariz., has spent more than $100,000 seeking patents.

The company, which Xia founded in 2003, develops products used for genetic testing, including a kit that identifies micro-RNA strands found in human cells that can trigger the onset of certain diseases. It currently has three patents pending.

Although the process is expensive, Xia said patenting is important for companies such as his, which depend on having a robust intellectual-property portfolio to attract potential partners.

Conducting research in advance of filing a patent was and still is a significant part of the patenting process, he said.

"I could not have filed a patent until I proved this could work," Xia said. "That took me a whole year to prove that everything worked."

U.S. patent law requires inventors to file a patent application within 12 months of selling the invention, disclosing it in a printed publication and engaging in other activities related to marketing the product.

Missing that deadline typically means forfeiting the right to seek a patent.

Once a patent application is filed, it can take as long as 18 months for the applicant to receive a response from a patent examiner.

Often the initial response an applicant receives is a rejection. That is because writing a patent requires perfect phrasing.

"You want to write in a way that avoids what's already out there but still gives your company that broad protection it needs to get the competitive advantage it wants," said Hartman, the Phoenix attorney.

"Words are important. There's an art to drafting a patent application."