The Simplex, or Single-Cylinder Double Acting,
Pump was invented in 1840 by Henry R. Worthington. A Simplex Pump is a reciprocating
pump. This pump has a single liquid cylinder which forces liquid out through the
top outlet on both the in and the out stroke (here up and down.)
This basic
type of pump might be used for Air Pumps, Feed Pumps for the furnace, Fire, Bilge,
and Fuel Oil Service. All might rely on this fundamental pump.
The DUPLEX
PUMP is similar to the Simplex pump, having two pistons instead of one, providing
smoother operation. From the outside a simplex pump can take many forms but the
basic concept follows this illustration.
(This is a 32-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
(and are larger).)) 
