An example of an asymmetric tooth application in an experimental medical gear pump.

Medical applications set performance specs that differ greatly from traditional gear applications, such as automotive transmissions. Performance priorities in medical devices include space limitations (miniature gear drives), extremely high speeds, low or no-noise operation, restricted use of lubricants, and the potential need for making gears disposable. Hence, designs for these tasks are made from nontraditional gear materials that range from polymers to stainless alloys.

Alexander Kapelevich, owner of AKGears LLC, Shoreview, Minn., and Thomas McNamara, research and development director at Thermotech Co., Hopkins, Minn., have a few ideas for better medical gears. Their ideas center around the “Direct Gear Design,” an alternative design method that doesn’t use the basic rack parameters. Instead, it uses the required performance parameters and operating conditions to define the needed gear shape.

A detailed account of Kapelevich’s and McNamara’s ideas is in their white paper, “Optimal Gear Design for Medical Applications.”