This type of rotary gear pump moves liquid
in the same direction regardless of the direction the gears turn. |
The valves (shown in yellow in this drawing) are forced open and closed by the difference in pressure on the input and output sides.
In this drawing, fluid in the higher-pressure output side is shown in light blue while fluid in the lower-pressure input side is dark blue.
Notice that when the green gear starts moving clockwise, the fluid in the outer circular tubes changes pressure but stops flowing, and fluid flows more or less straight up.
When the red gear is moving clockwise, fluid travels in a sideways 'S' shape through the outer circular tubes.
The pump in this drawing reverses direction about every 8 seconds.
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