Srikanth KondraguntaIEOR 190G2/23/2009

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 2043960

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

http://en.wikipedia.org/wiki/Graver_Tank_%26_Manufacturing_Co._v._Linde_Air_Products_Co.

http://en.wikipedia.org/wiki/The_Linde_Group http://www.netwelding.com/

History_Submerged_Arc%203.htm http://supreme.justia.com/us/336/271/

case.html http://supreme.justia.com/us/339/605/ http://caselaw.lp.findlaw.com/scripts/

getcase.pl?navby=CASE&court=US&vol=339&page=605