parker: Engineering Your Success
 About Gerotors
W. Henry Nichols was the first to develop gerotor mass 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 single manufacturer of gerotors; a distinction which Nichols Portland enjoys to this very day.
What is a gerotor?
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, or the Parker Hydraulic Pump and Motor Division. A more detailed history is available by clicking here.

The Gerotor Principle

The Gerotor Principle
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.

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Nichols Portland · 2400 Congress Street · Portland, Maine 04102 · USA
Tel.: 207-774-6121 · Fax: 207-774-3601 ·