This pump consists of two rotating gears;
an Internal Gear with the teeth on the outside, and an External gear with the
teeth on the inside. The External Gear is larger and has more teeth, but the teeth
are the same size. As the teeth separate (lower left side in this drawing)
they pass over the intake hole (shown behind the gears in black on the left).
They "suck" in fluid, then the gears are separated by a Crescent Seal (shown in
brown.)
When the teeth start to come together again (upper right here) they
squeeze the fluid through the outlet hole (shown in black at the top center of
this drawing.)
Normally the inner gear is attached to a drive shaft and the
outer gear is turned by the inner gear at the point of contact (upper left area
of this drawing.)
Advantages of the crescent pump include its simple design
and low maintenance requirements. The crescent pump is common in many applications
including automatic transmissions.
(This is a 20-frame
animation, converted to animated GIF format and then super-compressed 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.))
