A mechanical pump consists of two main parts: a motor and a pump body. In a standard mechanical pump, the motor drives the pump shaft through a belt; in a direct-coupled mechanical pump, the motor is connected directly to the pump shaft without any intermediate components. Mechanical pumps work on the principle of gas expansion, compression, and discharge to extract gas from a container. They're called mechanical pumps because they use mechanical means to periodically change the volume of the intake chamber in the pump, allowing gas from the container to continuously expand through the pump's intake into the intake chamber, and then get compressed and discharged out of the pump through the exhaust port. The ways to change the volume in the intake chamber include piston reciprocating, fixed vanes, and rotary vanes, which are known as reciprocating mechanical pumps, vane-type mechanical pumps, and rotary vane mechanical pumps, respectively. In practical applications, rotary vane mechanical pumps are more commonly used, so let's take them as an example to explain their working principle.