One of the important scientific instruments in use is the rotary vain pump. It is a positive-displacement pump, which includes vanes mounted to a rotor that rotates inside of a hollow. In some of the rotary vain pumps these vanes can be inconsistent length and/or tensioned to maintain contact with the walls as the pump rotates. The simplest rotary vain pump is a circular rotor rotating inside of a larger circular cavity. Eccentricity is caused as the centers of these two circles offset. The rotary vanes are allowed to glide in and out of the rotor and seal on all edges, creating vane chambers that do the pumping work. When the pump is on the intake, the vane chambers increase in volume. These increasing volume vane chambers are crammed with fluid forced in by the inlet pressure. This inlet pressure is often nothing more than pressure from the atmosphere. When the pump is on discharge, the vane chambers decrease in volume, forcing fluids out of the pump. This action of the vane drives out the same volume of fluid with each rotation.
The most common uses of vane pumps include high-pressure hydraulic pumps and automotive uses including power steering and automatic transmission pumps. There are also rotary vain pumps for mid-range pressures, which are designed for applications such as carbonators for fountain soft drink dispensers and espresso coffee machines. They are also often used as vacuum pumps for providing braking assistance in diesel vehicles.
