The working principle of gear pump
Gear pump concept is very simple, that is, it is the most basic form of two gears of the same size in the case of a tightly meshed rotating, the Interior of the shell is similar to the "8"-shaped, two gears on the inside, the outside diameter of the gear and work closely together with the shell on both sides. From extruder material at the entrance between two gears, and fill this space with rotation along the shell of the tooth movement, culminating in two when the tooth out.
in terms of speaking, gear pumps are positive displacement devices, namely, like a piston in a cylinder, when a tooth into another gear when fluid spaces, liquid was squeezed out by mechanical. Because liquids are incompressible, so the liquid and teeth cannot occupy the same space at the same time, so that the liquid has been removed. Due to the continuous engagement of the teeth, this phenomenon will occur in a row, thus also excluded in exports provide a continuum of pumps, pump each take a turn, exhaust is the same. With continuously rotating the drive shaft, the pump is continuously discharged fluid. Flow rate of the pump is directly associated with the pump speed.
in fact, very small amounts of fluid loss in the pump, the efficiency of the pump not 100%, because the fluid is used to lubricate the bearings and the gears on both sides, and the pump body is impossible without clearance, it is not 100% from the fluid egress, so a small amount of fluid loss is inevitable. Pumps can be run well, however, for most of the extrusion material, you can still achieve the efficiency of 93%~98%.
for the viscosity or density changes in the process fluid, the pump will not be much affected. If you have a damper, like put a filter on the outlet side or a limiter, pump will push the fluid passing through them. If the damper changes at work, that is if the filter gets dirty, clogged or limiter increased back pressure, the pump will still maintain a constant flow until it reaches the mechanical limits the weakest parts in the appliance (typically equipped with a torque limiter).
for a pump speed is actually limited, it depends on the process fluid, if the transmission is oil pump appear to rotate at very high speed, but when the fluid is a high viscosity of the polymer melt, this limitation will be significantly reduced.
high viscous fluid into the suction side of the two very important tooth space, if this space is not filled, the pump cannot be discharged flow of accurate, so the PV value (pressure x velocity) is also a limiting factor, but also a process variable. Because of these limitations, gear pump manufacturer will provide a range of products, that is, different specifications and displacement (discharge per round). These pumps will dovetail with specific applications of technology, to make the system capabilities and achieve optimal price.

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