But the Japanese consumer electronics giant has just paid several million euros to a German inventor who patented the idea in 1977.
After more than 20 years of court battles, 59-year-old Andreas Pavel agreed to a settlement that, in return for the payment, suspends all legal procedures he had set in motion against the company, according to German weekly Der Spiegel, which obtained confirmation from Sony's head office in Tokyo.
In 1977, Pavel, then living in Italy, registered for several patents relating to a portable stereo device named the Stereobelt (literally, the "belt stereo"). In 1979, Sony launched its famous Walkman, which went on to sell more than 200 million units in its first two years.
Pavel sought to take advantage of his patent rights in 1980, starting friendly negotiations with Sony for acceptable royalty payments through a licensing contract. In 1986, the manufacturer paid out royalties, but Sony always rejected Pavel's claim that he had invented the gadget. In 1989, Pavel turned to the British justice system to establish his ownership of the rights.
After more than seven years, Pavel's suit was dismissed, and he found himself near bankruptcy because the court costs--nearly 3 million euros ($3.68 million)--were charged to him.
Pavel threatened to continue his battle in other countries where he held a patent. In 2001, Sony changed its stance and agreed to start new negotiations with Pavel, which led to the settlement.
The contract signed by the two parties is confidential, but sources with knowledge of the deal said Sony agreed to pay Pavel several million euros. (A million euros equals $1.23 million.)
Pavel, extremely proud of his victory, said he now plans to approach other manufacturers of Walkman-like products, including Apple Computer. Apple's white-hot iPod is to some extent the digital successor of the Walkman.
Pavel also has more assets up his sleeve. In 1989, he filed a patent application in the United States for a technology combining the functions of a pocket audio player and a mobile phone. According to Der Spiegel, a decision on that application will be reached soon.
Estelle Dumout of ZDNet France reported from Paris.
