Magnetic Stirrer Presented by Alan Spannagel

Introduction Inventor and Patent Award Product Design How the Product Works Manufacturer Problems and Societal Affects References

Inventor and Patent Arthur Rosinger of Newwark, New Jersey, U.S.A. filed a patent application on 5 October 1942. The United States Patent Office awarded US Patent 2,350,534, titled Magnetic Stirrer on 6 June 1944. Rosinger described it as a mixing device using magnetic action in a novel and efficient manner.

Parts and Design An electric motor with wire connections and rheostat. A horseshoe shaped permament magnet. A box shaped casing with a removable top. A Teflon-coated magnetic bar.

Parts and Design Secure the electric motor in the center of the casing. Attach the magnet to the shaft of the motor. Secure the top of the casing to the box and seal the exit for the wiring.

Parts and Design Place the magnetic bar in a beaker of fluid on top of the magnetic stirrer. Plug in the stirrer and adjust the settings on the rheostat until the rotating magnetic field spins the magnetic bar at the desired rate.

Some magnetic stirrers are made by Hanna Instruments in Woonsocket, Rhode Island.

Problems and Societal Affects Mixing different substances together is often a vital step in many Engineering and Scientific processes. Before the invention of the magnetic stirrer, mixing substances was often an inefficient and time consuming step. Despite its efficiency, thermal conductivity from the electric motor can be a problem for substances sensitive to heat.

Problems and Societal Affects Adding a fan to the casing or using the mixer in a refrigerator or cold room often solves the thermal conductivity problem. Magnetic Stirrers usually last about 15 years with thermal breakdown of the electric motor being the primary cause of equipment failure. Every 20oC increase in temperature will decrease longevity by 1/2.

References https://google.com/patents/US2350534. https://www,catscientific.com/ www.aiche.org/cep https://tutorialtub.com/info/build-a-magnetic-stirrer-from-an-old-computer https://www.practicalmachinist.com/vb/general/electric-motor-life-expectancy