Lobe Pumps

The lobe pump receives the name from the rounded shape of the rotor radial surfaces that provide the rotor to be continuously in contact with each other as they rotate. Lobe pump can be either single or multiple lobe pumps and carry fluid between their rotor lobes much in the same way a gear pump does.

Unlike gear pumps, however neither the number of lobes nor their shape permit one rotor to drive the other, and so all true pumps require timing gear. The body surfaces, rotor surfaces, the contact between rotors, and the contact between rotor lobe end and the pump body define the OTI of a pump. The contact between the lobe ends and the body wall and the adjoining body wall and lobe surfaces define the OTI volume. The body walls, rotor surfaces, lobe to body wall contacts, and the lobe to lobe contacts define the OTO volume.

In the two rotor lobe pumps, the torque is shared by both rotors with the proportional amount of torque dependent on the position of the rotor to rotor contact point on the rotor contact locus. When the contact point is at the major locus radius (maximum lobe radius of one rotor in contact with the minimum lobe radius of an adjoining rotor), one rotor sees the full pumping torque, while the other rotor feels a balanced as many times in each complete revolution of a rotor as there are lobes on the rotor.

An internal lobe, or gorotor pump has a single rotor with a lobe like peripheral shape. It moves in a combination of rotations and gyrations about its centre of rotation in a body with internal, lobe shaped contours in such away that the rotor always touches the body or more locations to preserve the fluid seal between OTI and OTO volumes. The outer rotor surface, and the fluid seal points between two adjacent fluid seal points define the CTIO volume. The outer rotor surface, inner body surface, and the rotor to body fluid sealing define the OTO volume.

Most pumps of this type have one fewer rotor lobe than an internal body lobe cavity and the term progressing tooth gear pump is sometimes used. The full pumping torque is seen by the single rotor, but the torque is cyclic. It is a function of the position of the rotor and its sealing arrangement with the pump body, while the number of torque cycles per rotor revolution is equal to the number of lobes on the rotor.

Lobe pumps are capable of flows up to about 1,000 gpm (3.785 l/min) and pressures up to 125 lb/in2 (8.6 bar). They are commonly used to pump single sludge in waste water treatment plants and in stainless steel systems for handling foodstuffs in the food, baverage, dairy, and pharmaceutical industries.