The R series pumps with internal gear drive are self-priming positive displacement rotary pumps. The fluid is conveyed by two gears, one of which is the rotor and the other the pinion. The rotor drives the gear inside it. The fluid is sucked into the free space between the gear teeth and then gently moved to the discharge side of the pump, where a spacer or so-called "crescent" closes the free space between the gear teeth.

Thanks to the unique design of the pump, the gears, which engage each other, guide the liquid to the pump outlet. This ensures that the pumped liquid flows evenly and without pulsations.