W. Henry Nichols was the first to develop gerotor production techniques back in the 1920's. His vision and genius transformed the W.H. Nichols Company from a small machine shop in Waltham, Massachusetts into the world's largest manufacturer of gerotors; a distinction which Nichols Portland enjoys to this very day. The word "gerotor" was coined by scholar Myron Hill, and is a contraction of the two works GEnerated ROTOR. Simply put, it means that one of the components is formed (generated) by the shape of the other. A pumping or motor element gerotor consists of two components, an inner rotor and an outer rotor. The inner has one less tooth than the outer. For a pump, the inner has its centerline positioned at a fixed eccentricity from the centerline of the outer rotor. The gerotor pumping principle is shown below. For information related to gerotor motors, kindly contact the Nichols Product Engineering Department. A more detailed history is available by clicking here.

The gerotor is a positive displacement pumping unit consisting of just two elements; an inner rotor and an outer rotor. The outer rotor has one more tooth than the inner rotor and has its centerline positioned at a fixed eccentricity from the centerline of the inner rotor and shaft.

Although gerotors come in a variety of geometric configurations, materials, and sizes, all gerotor set share the basic principle of having conjungately-generated tooth profiles which provide continuous fluid-tight sealing during operation.

As the rotors rotate about their respective axes, fluid is drawn into the enlarging chamger to a maximum volume. As rotation continues, chamber volume decreases, forcing fluid out of the chamber. The process occurs constantly for each chamber, providing a smooth pumping action.