Gear pump is a rotary pump that transfers liquid or pressurizes it depending on the change and movement of the working volume formed between the pump cylinder and the meshing gear. The two enclosed spaces are composed of two gears, the pump body and the front and rear covers. When the gears rotate, the volume of the space on the disengaged side of the gears becomes larger from small to form a vacuum. The liquid is sucked in, the volume of the space on the meshing side of the gears becomes smaller from large to small, and the liquid is squeezed into the pipeline. The suction chamber and the discharge chamber are separated by the meshing lines of the two gears. The pressure at the outlet of the gear pump depends entirely on the resistance at the pump outlet.
The concept of gear pump is very simple. Its most basic form is that two gears of the same size mesh and rotate with each other in a closely matched housing. The interior of the housing is similar to an "8" shape. The two gears are installed inside. The outer diameter and both sides of the gear are closely matched with the housing. The material from the extruder enters between the two gears at the suction port and fills the space. It moves along the shell with the rotation of the teeth and is finally discharged when the two teeth mesh.
In terms, the gear pump is also called a positive displacement device, that is, like a piston in a cylinder barrel, when one tooth enters the fluid space of another tooth, because the liquid is incompressible, the liquid and the tooth cannot occupy the same space at the same time, so the liquid will be mechanically squeezed out. Due to the continuous meshing of the teeth, this phenomenon occurs continuously. Therefore, a continuous discharge quantity is provided at the outlet of the pump. The discharge quantity is the same for each revolution of the pump. With the continuous rotation of the drive shaft, the pump will discharge the fluid continuously. The flow of the pump is directly related to the speed of the pump.
In fact, there is a small amount of fluid loss in the pump, because these fluids are used to lubricate both sides of the bearings and gears, and the pump body can never be fitted without clearance, so the fluid cannot be discharged from the outlet 100%, so a small amount of fluid loss is inevitable, which makes the pump's operating efficiency unable to reach 100%. However, the pump can still operate well, and for most extruded materials, the efficiency can still reach 93% ~ 98%.
For the fluid whose viscosity or density changes in the process, the pump will not be affected much. If there is a damper, such as a strainer or a limiter on the discharge side, the pump will push the fluid through them. If the damper changes during operation, that is, if the filter screen becomes dirty, blocked, or the back pressure of the limiter increases, the pump will still maintain a constant flow until the mechanical limit of the weakest component in the device is reached (usually equipped with a torque limiter).
