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DC647 2013-03-18

Innovations include snap electrodes for clean exhaust

Innovations include snap electrodes for clean exhaust

In Schwieberdingen near Stuttgart, Dietmar Steiner from Robert Bosch GmbH shows the snap electrode he invented.

Stuttgart/Munich/Brussels – The European Patent Office in Brussels announced on Wednesday that Bosch was ranked first for patents in Europe in 2012, with 838 patents granted to the company over the course of the year. The company currently holds a portfolio of more than 90,000 active industrial property rights. In total, Bosch filed more than 4,700 patents in 2012. The European Patent Office regulates the granting of property rights in the 38 member states of the European Patent Organization (EPOrg).

Bosch spends more than 8 percent of its sales on research and development, with R&D expenditure reaching 4.5 billion euros in 2012. More than 42,000 associates work in R&D worldwide, 20,700 of them in Germany. Patents protect the company’s innovations from being imitated, while licensing allows third parties to benefit from Bosch’s technological edge.

From patent to product: a long and winding road

Not every good idea leads to a patent, and not all patents go on to become products. The process is generally a long one. “One example is the snap electrode, which is part of our particulate filter for the clean combustion of biomass in the wood-burning stoves of private households,” says Dietmar Steiner, one of the inventors at Bosch.

High-voltage dust-catcher: While heating with renewable materials such as briquettes or wood pellets is carbon-neutral, the exhaust gas contains unwanted particulate matter. However, it can be removed by means of a particle separator. Steiner, a physicist in the research department in Schwieberdingen close to Stuttgart, explains how this works: a strong electric field is created in the exhaust pipe, as a result of which free charge carriers attach themselves to the dust. An electrode then attracts the charged dust particles, which stick to it.

Longer maintenance cycles thanks to snap electrodes: At some point, the electrode is so covered in dust that it has to be cleaned. Steiner and his project team first began to devise solutions in 2006. The dusty electrode can be briefly shaken by a bimetal element that folds over (“snaps”) as the stove heats up. As a result, the dust is shaken off the electrode into the stove’s ash pan.

“Our aim was to have a filter that required maintenance only twice a year, and we have achieved this,” Steiner says. The filter prevents more than 85 percent of particulate matter from being emitted. By using mass-produced parts that Bosch is able to manufacture in large numbers and to high quality standards, costs were significantly reduced. Lower limits on particulate matter will take effect in Germany from 2015. The new filter will make it possible to comply with them.

The first prototypes were built in 2006, and a patent was filed in 2008. In 2010, the snap electrode patent was published. It was then legally granted in 2011. A number of other companies in the heating industry have expressed interest in the technology, and licensing negotiations are currently underway.

Background information on patent statistics:: The statistics include all patents granted between January 1 and December 31, 2012.


  • For more information on the European Patent Organisation click here
  • For more information on patents at Bosch click here
  • Directive for small and medium-sized wood-burning stoves click here

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