Theory of Machines: How do Hydraulic Gear Pumps Work?

Internal & External Gear Pumps There are a lot of different types of hydraulic pumps. One type of pump is a gear pump, and there are two types of gear pumps. One is an external gear pump, and one is an internal gear pump. When we say external or internal, we're not referring to the gears with reference to the housing (or the material that hold it all together); we're talking about the gears in reference to each other, so external gear pumps are going to have gears that pass by each other, whereas internal gear pumps are going to have one gear within another gear. When we look at this graphic of the external gear pump we can see that the flow is coming in from the low pressure left Inlet and it's flowing out through the higher pressure right outlet. With the internal gear pump we can see that the fluid is flowing through the low pressure left input or Inlet and out through the high pressure outlet which is out through the top