Star Pump (from Internet Glossary of Pumps)
Star Pump
The STAR PUMP consists of a rotating star shaped gear inside of another gear. The inner gear has one less tooth than the outer gear.

The inner gear is usually the drive gear and pushes the outer, larger gear around. A tight fit where the gears mesh keeps fluid advancing around the pump.

In this drawing the dark kidney-shaped hole on the right is the intake and the one on the left is the outlet. As the teeth on the two gears separate the suction draws in the liquid.

This pump is best used for pumping lubricating fluids such as oil because the teeth must rub against each other somewhat. The amount of rubbing is slight but not insignificant.

Star pumps are also called GEROTOR PUMPS and the gears are called gerotor gears.

(This is a 20-frame animation, converted to animated GIF format for Internet transmission. (Note: On some Internet browsers it may be displayed much less smoothly than the CD-ROM version, where the frames are timed to a thousandth of a second.))

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Last modified February, 2002
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