Rick Van Anken, who blows the snow from some of Bloomington's 250 miles of sidewalks, used to worry about being injured if his vehicle hit a quarter-inch irregularity in the sidewalk and came to an abrupt dead stop.

"Many times the driver will be thrown into something when the snowblower hits an obstacle," said Van Anken, 26.

No more. Thanks to Minnesota inventor Grant Hanson of Glenwood, commercial snowblowers can now glide over obstacles such as raised sidewalk sections or manhole covers and keep going. That should protect drivers, reduce damage to equipment and, it's hoped, get sidewalks cleared a little faster.

This winter, Bloomington and St. Paul are putting the new mechanical technology, called the Snowalker, to the test. The device is a mechanical connection that sits between a city vehicle and its snowblower. When the snowblower hits an obstacle, the Snowalker redirects the force of the collision to lift the snowblower over the obstacle and give it a push forward, all so quickly that an observer can barely see what happened. Some city workers say the Snowalker may have changed city snow removal forever.

"There is nothing else like it" for the small municipal vehicles used to move snow on sidewalks, trails and parking lots, said John Hall, equipment services manager for St. Paul's Parks and Recreation Department. "I don't expect he'll be in business long, because somebody like a snowblower manufacturer will buy that invention from him. And then it will be part of a snowblower and not a separate attachment. I think Hanson will make himself rich."

Hanson, 63, is a quiet but personable man with a knack for explaining all things mechanical. He's a lifelong mechanical wizard who started out working on farm machinery, while inventing on the side. He's a member of the Minnesota Inventors Congress, which meets each year in Redwood Falls, Minn., and has received some of its awards. The Snowalker grew out of contract work he did for the city of Glenwood.

Hanson invented the Snowalker almost by accident when he tried to protect a small industrial tractor called a payloader that collided with obstacles such as raised sidewalk sections during snow removal. He rejected hydraulics as not strong enough for the job and electronic sensors as too slow to react to a collision, then settled on a mechanical design. But he was surprised when, instead of cushioning the payloader, the device caused the unit to rise up over the obstacle without stopping.

'An original mousetrap'

"It's not a new mousetrap; it's an original mousetrap," Hanson said.

Curtis Hamre, Hanson's patent attorney, says his client is a bit of a throwback to an earlier era of invention.

"Thirty or forty years ago, people with mechanical aptitude were creating inventions and coming in with patent applications," said Hamre, a partner in Minneapolis law firm Hamre, Schumann, Mueller & Larson. "Now it's more electronics and Internet-related. So to see this kind of mechanical invention anymore is unusual."

So intricate is the Snowalker's mechanical design that Hanson and Hamre had to fly to the U.S. Patent and Trademark Office in Alexandria, Va., in mid-2011 to convince a skeptical patent examiner that the device would work. To prove his point, Hanson took along a working scale model to demonstrate the Snowalker's patentable design, which he calls "Safeloader."

"The model really did turn on a light bulb in the examiner's mind," Hamre recalled, and by November 2011, Hanson had a patent.

So far, Hanson has invested $70,000 to $80,000 in developing the product, and has been running the company with $200,000 he got from friendly investors who agreed to let him keep full control of his company, called Glenridge Inc. But revenue hasn't kept pace with expenses. The sale of three Snowalker units to Bloomington brought him just over $14,000.

But the flip side of the relatively low price is that the Snowalker is considered something of a bargain by cities. Dave Hanson (no relation to Grant), Bloomington's park maintenance supervisor, said the Snowalker is a worthwhile investment to protect a 100-horsepower snow-blowing tractor that cost the city $150,000.

In addition to the Bloomington sale, Hanson will, by the end of January, deliver nine more Snowalkers to the city of St. Paul. Previously, he made sales to the Minnesota cities of Chanhassen, Alexandria and Sauk Center, as well as to Fargo, N.D., and the Duluth campus of the University of Minnesota. To drum up business, he goes to trade shows and relies on his website, safeloader.com.

Despite his initial success, Hanson's goal is to get out of the Snowalker business.

"An inventor's dream is to license his product to a manufacturer that can really put it on the map," he said.

Steve Alexander • 612-673-4553