John and Andrew Doney invented a hard-bearing device for balancing rotors. Although they obtained a patent for their invention from the U.S. Patent and Trademark Office, it was never used as an automobile wheel balancer. Some time later, Exetron Corp. produced an automobile wheel balancer that used a hard-bearing device with a support plate similar to that of the Doneys' device. Given that the Doneys had not used their device for automobile wheel balancing, does Exetron's use of a similar device infringe on the Doneys' patent? Why or why not?