The "Donald Duck as prior art" case

How do you quickly raise a sunken ship full of sheep? The Danish inventor Karl Krøyer came up with a very creative solution: pump buoyant bodies into the ship to achieve sufficient upward lift to bring the ship back to the surface. The solution was so creative he got a patent on it. In a 1949 Donald Duck story, titled The Sunken Yacht a ship is raised by stuffing it full of ping-pong balls. That kind of prior art could kill the patent. But whether the story was actually used by a patent office to refuse the patent (application) remains unclear.

The invention has been used in practice on several occasions. The most famous one, shown in the photograph on the left, was in 1964 in Kuwait. On September 14, 1964, the freighter Al Kuwait capsized at the docks in Kuwait's harbour. The ship was carrying 5,000 sheep that started decomposing in the harbour's water. Since this threatened to contaminate the city of Kuwait's drinking water supply, the ship had to be raised as quickly as possible. Bringing in cranes would have taken too long, and with such methods there is a significant risk that the ship will break.

The Danish inventor Karl Krøyer (sometimes spelled Kroyer or Kroeyer) came up with a method of raising this sunken ship by filling it with buoyant bodies fed through a tube. On December 31, 1964, he filled the ship with 27 million plastic balls made of expandable polystyrene foam and weighing 65 tons. The balls had been airlifted from Berlin to Kuwait.

The total cost to save the ship was $345,000, saving the insurance company most of the $2,000,000 insured value of the ship, according to a contemporary New York Times article (8 March 1965, page 58). Other sources describing the event are magazines "Popular Science", April 1965 (page 118-119); "Die BASF" vol. 15 no. 3, 1965 (page 148-156); and "Chemistry", September 1966.

Figure 1 of Krøyer's patent

Inventor Karl Krøyer received patents for this method in the United Kingdom (GB 1070600) and Germany (DE1247893). Some sources claim that it was company BASF that obtained the patents, but the applicant's name on the patent frontpages is actually Krøyer himself.

According to the patent claim, buoyant bodies 1 are inserted into a sunken vessel 4 through a tube 3 from a salvage ship 2.

The story is usually told as relating to the Dutch patent (NL 6514306) Krøyer applied for. This application was not approved. According to the story, the Dutch Patent Office found an old issue of the Donald Duck magazine which showed the same invention. Since an invention has to be new to be patentable, the application was refused. This story was recently repeated by the Dutch patent office (in Dutch), although surprisingly this confirmation did not give any detail on which patent office or how the Duck story came to its attention.

In 1949 the Donald Duck story The Sunken Yacht (by Carl Barks) shows Donald and the nephews raising a ship by filling it with ping pong balls shoved through a tube, as can be seen below in the images cited from that story.

Images from 'The Sunken Yacht', © 1949 Walt Disney Corporation.

Since ping pong balls are buoyant bodies, and they were fed to the yacht through a tube, the Donald Duck episode discloses the same technique as that which is claimed in the patents. Consequently, the Duck story has to be considered novelty-destroying prior art: given the story, any Patent Office would have rejected Krøyer's patent application.

It remains an open question whether the Dutch patent office in fact used this document as prior art to refuse the patent application. Regrettably the files of the cases have been destroyed by now, and the Dutch patent attorney who represented the inventor has passed away several years ago.

According to some sources, Krøyer himself remembered the Donald Duck story from his youth. This is incorrect as Krøyer (born 21 August 1914) was 35 by the time the Duck story was published.



© 2007 Discovery Communications

In November 2004, the popular Discovery Channel show Mythbusters tried to use the original method (with ping-pong balls) to raise a sunken ship. They succeeded with only 27,000 ping pong balls, although their ship was a lot smaller than the Al Kuwait (see the photo to the right, more photos available). Mythbusters did mention that the technique had been described in the Donald Duck story, but failed to mention that it had been actually used in 1964.

More urban legends relating to comic books are discussed at Comic Book Urban Legends Revealed.