The patent from 1949

Since the invention of the circulation accelerator in 1928, Wilo had focused increasingly and with great success on the production of pumps in addition to building heating systems. In an effort to make the new development on the heating market even more efficient and reliable, Louis and Wilhelm Opländer had worked tirelessly on improvements and technical innovations. For although the circulation accelerator was a pioneering piece of technology, it did have some minor disadvantages.

The circulation accelerator was equipped with a stuffing box whose bearing had to be lubricated with oil and therefore required a great deal of maintenance. While the circulation accelerator was relatively quiet thanks to the oil lubrication, the dry-running electric motor still generated noise. In addition, the stuffing box was not hermetically sealed, as a result of which the system lost water that had to be refilled frequently.

Louis Opländer had already been considering designing an electric motor with a water-lubricated rotor since the 1930s in order to alleviate the disadvantages described above. There were a number of drafts for a glandless pump (in contrast to the glanded pump) where the engine was to be lubricated not with oil, but with the water that was present anyway.

Over the coming years, Wilhelm Opländer used these ideas as a basis for his own deliberations. In his patent from 1949, he described a first water-based circulation accelerator with a glandless motor. What makes this design special is that the rotor of the motor is located and moves in the water to be conveyed. The rotor chamber is separated from the current-carrying part of the motor (stator) by a watertight can.

The wet and dry chambers are separated by an extremely thin wall measuring just a few tenths of a millimetre – an idea that has been used since the introduction of the Wilo-Perfecta in 1953 and is still used successfully in pump production today. While a thin metal foil was used at the beginning, plastic is the material used for this sophisticated technology today. This reduces vortex losses and increases the efficiency of the pump considerably.

Patent DE 807589 A, 19 March 1949 Wilhelm Opländer

Water circulation accelerator for heating and cooling systems. Issue of patent DE 807589 C, 19 April 1951

Patent claims:

1. Electrically operated circulation accelerator to be installed in the piping, especially in heat- ing systems in which a propeller arm moves the water, characterised by the fact that the drive motor (m, n) is installed in the piping itself in such a way that the motor armature (m) surrounds the propeller arm (f) in the form of a ring and circulates in the water with it while the stator (n) of the motor is installed in a chamber that is sealed off from the water.

The development of the glandless pump was a milestone, and not only for the Dortmund-based company. Its basic functional principle is still relevant for heating technology all over Europe and many countries of the world today.