Srikanth Kondragunta IEOR 190G 2/23/2009

 Graver Tank & Manufacturing Co.  Manufacturing company  Designs, manufactures, and erects vessels, storage tanks, stacks, chimney liners, and scrubbers  The Linde Air Products Company  Started in the US as a division of Linde AG, a German company  Eventually acquired by Union Carbide  Involved in making gas production plants

 Welding  Before:  Electric welding which was slow and laborious  Permitted welding of only thin plates  Had hazards such as a dazzling open arc and smoke and splatter which made the operation dangerous

 Electric Arc Welding  Main type of welding due to low capital and running costs  In general terms, electricity is passed through a tip of an electrode to create heat which melts metal  Filler material is added to create a liquid pool of metal  Upon cooling, this liquid metal fuses plates together  Many variations between types of electrodes, fluxes, and shielding equipment

 Jones, Kennedy, and Rothermund in 1935  Patent  Found material that, when added to the process, reduces the amount of mineral-like material that would smother the electric arc present  Part of the electrode  This material included alkaline earth metal silicate and calcium fluoride

 The material controls heat rate as well as rate of penetration in addition to improving the quality of metal as well as purifying and protecting the molten metal  This new process allowed materials up to 2.5 inches thick to be plated in one pass  Obviously improves efficiency

 Graver Tank tried to patent a process initially called the “Hidden Arc”  Note: both the Linde Group and Graver Company’s processes seemed to not have an arc  However, what happens is that voltage is AC; thus, current varies from positive to negative so at times, arc seems to “vanish”  This is actually why there is more control: too much current will result in a runaway arc, as an arc draws current to replace the resistance  Graver’s method used maganese instead of Linde Air Products magnesium

 Linde Air Products took Graver Tank Manufacturing Company to court  The United States district court found infringement and the Court of Appeals upheld the infringement claim  Was escalated to the Supreme Court in 1950  Chief Justice was Fred M. Vinson  Supreme Court was looking specifically for whether or not the omission of a material not mentioned in the patent could save the defendant from infringement

 Supreme Court upheld the decisions of the lower court  Created the doctrine of equivalents

 “If any party could use a process exactly the same as one that is patented, but escape infringement by making some obvious substitution of materials, it would deprive the patentee of the exclusive control meant to come with a patent.”  When determining equivalents, one must consider qualities it has when combined with other ingredients, its intended function, and if reasonable person would know about the interchangeability  In this case, the equivalency was the substitution of materials in the welding process

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