United States Patent Number 4,725,006 issued on February 16, 1988 for an APPARATUS FOR CONVEYING SEWAGE. The patent application was filed in May 1986–and will expire this month making the patent part of the public domain. The patent relates to a rotary pump and a rotary cutting device run off of a common drive shaft. The cutting device is positioned at a water inlet upstream from the pump. The cutting device is used for cutting solid materials that are part of waste water to reduce their size in order for the materials to be able to pass through the pump. Using this apparatus is definitely a dirty job. Now, everyone can do it.
Filed under: Dead Patents by lbarbin