Power steering units often rely on a vane pump to obtain the pressure needed for the Power Cylinder. Automatic transmissions often use them too.

The vanes are in slots in the rotor. When the rotor spins, centrifugal force pushes the vanes out to touch the casing, where they trap and propel fluid. Sometimes springs also push the vanes outward.

When the vanes reach the return side they are pushed back into the rotor by the casing. Fluid escapes through a channel or groove cut into the casing, shown here on the lower right side in black.

On this vane pump there is considerable unbalanced force on the drive shaft, since the high-pressure, outlet area is all on one side. Vane pumps can be designed in balanced configurations where there are two inlet and two outlet ports, similar to balanced gear pumps.

(This is a still representation and possibly also a low-resolution image of a pump which is fully animated in the CD-ROM version of this glossary.)