It's a property developer's dilemma: The taller a building, the more space there is to rent out--but with all that space come people who need quick transportation to their floors. That requires more elevators, which means less space available to rent. "Any company that can develop a system that saves space in a building would have an advantage in the marketplace," says Bob Caporale, an elevator engineer for 40 years who's also editor-in-chief of the industry bible Elevator World.
Well, how about this: an elevator system that allows six to eight cars to circulate in a continuous loop in the space normally occupied by just two. As each car reaches the top (or bottom) of the loop, it shifts sideways before descending (or ascending).
Hitachi, which has been designing elevators for more than 70 years, took inspiration from the paternoster lift, which was popular in Europe in the early 1900s. The paternoster's single-drive system moved several open-faced cars in a loop; passengers stepped on and off without interrupting the motion of the cars. Sadly, it was doomed by safety concerns and an inability to accommodate wheelchairs. But Hitachi's elevator (or at least, its one-tenth-scale prototype) solves those short-comings, and more. Its cars (complete with doors) operate in pairs, each with an independent-drive system that lets one car stop at a floor while the other is still moving. Each pair travels on its own within the loop, starting and stopping without interrupting the motion of the other cars. A computer monitors each car's position and controls its speed to prevent one pair from crashing into another.
Hitachi's engineers also figured out how to safely move passengers sideways between ascent and descent, with rails and guides that provide stability. "We assume some passengers will not get off at the top or bottom," says Takashi Teramoto, senior researcher of Hitachi's Mechanical Engineering Research Laboratory. This could be so much fun, some people might never get off.