This dual output permanent magnet DC (PMDC) planetary gearmotor drives two hinged arms on an automated surgical table used in orthopedic surgery. It was designed so that the two hinged arms would be positionally aligned and their movement synchronized at all times. It was designed to eliminate the need for link chains or belts – and provide a positive mechanical actuation interface.

Design Significance

The traditional solution of link chains, belts, and pulleys has a greater margin of operational error and it is significantly more difficult to synchronize the movement and alignment of the two hinged arms. This design provided the desired operational performance, AND it eliminated the need for two separate motors – which are also difficult to synchronize and are a more expensive solution.

Design Innovations

This is a custom‐designed, high torque, fractional HP PMDC motor with two planetary speed reducers, one on each end, driven by the same motor shaft. Because the same motor drives both outputs there is both mechanical AND electrical “linkage”. If two separate motors were used, a more complex common control would be required to achieve the same positioning and synchronized movement. In addition to eliminating the need for two separate motors, this design essentially eliminates the need for a more complex (and expensive) control scheme to provide electrical linkage.

Pictured: Two low-noise high torque planetary speed reducers driven by a common motor shaft