Application: Pump, Steam engine, water motor.
This device was invented by one Behrens, a partner in the firm of Dart and Co. of New York, around 1867. This firm produced at least one in the form of a 12 hp steam engine.

It can be used as either a pump or a water motor, because surface contact exists between the mating surfaces and leakage can be kept low.

The profile of the surface art the end of the moving members is that of a curtate epitrochoid. When a circle rolls upon the outside of a fixed circle, a point on the radius of the rolling circle (but not on the circumference) describes a curve called the epitrochoid. A curtate epitrochoid is a small section of the whole curve.

H. Roehl 1950-00-00