The CEO of a nearly century-old manufacturer that supplies parts to Caterpillar Inc. and Boeing Co. issued a challenge to his executives 31/2 years ago: Come up with a new and less-cyclical business.

“We wanted to have something that was new to the industry, and new to the world,” recalls Don Washkewicz, chief executive of Parker Hannifin Corp.

Now, the company, whose components and systems have long helped propel construction equipment, factory machinery and airplanes—including Charles Lindbergh’s Spirit of St. Louis—is helping disabled people walk.

The effort is built on a set of motorized robotic braces that support, bend and move the legs of people who can’t walk on their own because of spinal-cord injuries, multiple sclerosis or strokes.

Wearing the device, called Indego, David Carter, a 28-year-old paraplegic from Georgia, took his first steps after years of being confined to a wheelchair.