Ernő Rubik Needed About a Month to Solve His Own Cube. An American Court Later Found It Infringed an Earlier US Patent.

US4378116 was published on March 29, 1983, naming Ernő Rubik as inventor. The Patent Office title is Spatial Logical Toy. By the time it issued, the Rubik's Cube had already been through a worldwide craze, and it had also run into a patent filed in the United States years earlier by someone else.

A problem in movement

Rubik was a lecturer in design at the Academy of Applied Arts and Crafts in Budapest. In 1974 he built a small cube out of wooden blocks as a way of working through a structural question: how could a set of blocks be made to turn in groups, around several different axes, without the whole thing falling apart?

He built it, turned it, and scrambled it. By his own account, it then took him about a month to get it back to its original state. He had made a puzzle without setting out to.

How it holds together

The mechanism is the real invention, and it is less obvious than the puzzle.

A standard cube has 26 visible pieces: six center pieces, twelve edge pieces, and eight corner pieces. Only the six centers are fastened to anything. They are mounted on a hidden core, a three-axis spindle, and they can rotate in place but never move from their positions.

The edges and corners are not attached to the core or to each other. Each has a hidden extension on its inner side, and those extensions tuck underneath the neighboring pieces. The whole assembly is held together by the pieces pressing on one another, with the centers acting as anchors. Turn a face, and a ring of pieces slides around the core as a group, held in by the pieces around it.

That arrangement allows a very large number of positions. The standard cube can be scrambled into about 43 quintillion distinct configurations, and only one of them is solved.

From Budapest to everywhere

Rubik patented the cube in Hungary, and it went on sale there as the Magic Cube in the late 1970s. The Ideal Toy Company licensed it, renamed it after its inventor, and launched it internationally in 1980. It became one of the best-selling toys ever made.

Rubik's own US patent did not issue until 1983, after the peak of the craze, and the market had long since filled with imitations.

Larry Nichols

In 1972 the US Patent Office had granted US3655201 to Larry D. Nichols, a chemist in Massachusetts, for a pattern-forming puzzle with pieces rotatable in groups. Nichols's puzzle was a two by two by two cube. Its pieces were held together by magnets rather than by an interlocking internal mechanism.

The rights were held by the company Nichols worked for, Moleculon Research Corporation. When the Rubik's Cube became a huge American seller, Moleculon sued CBS, which had acquired Ideal Toy. A federal court found that the Rubik's Cube infringed one of Nichols's claims, and the appeals court upheld that finding in 1986.

Why a different mechanism could infringe

The result surprises people, because the two puzzles work very differently inside. One uses magnets. The other uses interlocking pieces on a spindle.

The answer is in how patent claims work. A patent does not protect the specific object an inventor built. It protects what the claims describe. A claim written broadly, in terms of a cube whose pieces rotate in groups about axes to form patterns, can cover devices that achieve that result by entirely different internal means. If the accused product does everything a claim describes, it infringes that claim, regardless of what holds it together.

It is not a verdict on who was more inventive. Rubik's interlocking mechanism is a brilliant piece of design, and it is the reason the cube could be mass produced cheaply and survive millions of twists. What the court decided was narrower: an earlier American patent already claimed part of what the cube does.

Independent inventors winning against large companies over a patent is a recurring story in this archive. For a longer and more punishing example, see Robert Kearns and the intermittent wiper.

See the original

The full text and figures of US4378116 are on patents.us.