In the mid-20th century the patent expired, and, with it, so did the most important protection.

The critical patents expired in the late 1970s and early 1980s.

The patent has expired and is now available for public use.

The patent on that work expired at the end of 2004.

The patent expired; and several companies are now making similar machines.

This is no longer a problem, because the patents have expired, since then.

The patent expired in 1773, though the partnership continued until 1781 when Need died.

And when the company's patent expired, other companies could simply market the new use under a different name.

It did not come into wide use until his patent expired in 1942.

When his patents expired in 1990, several other companies joined the industry.