A hydraulic gear pump works by using the rotation of meshing gears to trap and move fluid from an inlet port to an outlet port, creating flow in a hydraulic system.
Understanding the Basic Mechanism
A typical external gear pump consists of two intermeshing gears housed within a close-fitting casing. One gear is driven by a prime mover (like an electric motor or engine), and it, in turn, drives the other gear.
Here's a simplified breakdown of the process:
- Fluid Entry: Fluid enters the pump through the inlet port.
- Trapping: As the gears rotate away from the inlet, fluid is trapped in the spaces between the gear teeth and the pump casing.
- Transport: The rotating gears carry this trapped fluid around the outer perimeter of the casing towards the outlet port.
- Discharge: As the gear teeth mesh together at the center of the pump, they displace the fluid from the pockets, forcing it out through the outlet port and into the downstream piping.
Because gear pumps are positive displacement pumps, they deliver a relatively constant volume of fluid with each rotation, regardless of pressure changes on the outlet side (within operating limits).
Key Features and Capabilities
The design characteristics of external gear pumps contribute significantly to their performance. As noted in the reference provided:
- Very Tight Clearances: The close fit between the gears and the casing, as well as between the gear teeth themselves, minimizes internal leakage (slip). This tight tolerance is crucial for maintaining efficiency, especially under pressure.
- Gears Supported on Both Sides: Having bearings supporting the gear shafts on both sides of the gears helps the pump withstand hydraulic forces and maintain alignment, contributing to durability and performance under load.
These features collectively enable external gear pumps to be highly capable, particularly for:
- High Pressure Applications: The robust construction and minimal internal leakage allow them to generate and handle high system pressures effectively.
- Thin Liquid Applications: While often used with hydraulic oil, their design allows them to handle fluids with lower viscosity compared to some other pump types, as the tight clearances help prevent excessive leakage.
Practical Applications
Hydraulic gear pumps are widely used in various applications where a reliable and consistent flow rate is required, often at high pressures. Examples include:
- Mobile machinery (construction equipment, agricultural vehicles)
- Industrial power units
- Material handling equipment
- Automotive power steering and transmission systems
Their simplicity, robustness, and capability for high pressure make them a popular choice in fluid power systems.
