Thomas Edison of the Edison patent to charge a more reasonable rate for the use of the Edison patent rights and lowering the price of the electric lamp. On October 8, 1883, the US patent office ruled that Edison's patent was based on the work of William E. Sawyer and was, therefore, invalid. Litigation continued for nearly six years, until October 6, 1889, when a judge ruled that Edison's electric light improvement claim for "a filament of carbon of high resistance" was valid. To avoid a possible court battle with Joseph Swan, whose British patent had been awarded a year before Edison's,
World's Columbian Exposition their costs at $554,000 but Westinghouse under bid them by 70 cents per lamp to get the contract. Westinghouse could not use the Edison incandescent lamp since the patent belonged to General Electric and they had successfully sued to stop use of all patent infringing designs. Since Edison specified a sealed globe of glass in his design Westinghouse found a way to sidestep the Edison patent by quickly developing a lamp with a ground glass stopper in one end, based on a Sawyer-Man "stopper" lamp patent they already had. The lamps worked well but were short lived, requiring a small