Samsung has won an important battle in its defence against Apple's thermonuclear war against Android. The company has won a preliminary invalidation of a key Apple patent.

Samsung said in a filing late Monday that examiners at the U.S. Patent and Trademark Office (PTO) had taken a second look at an Apple patent and decided that it should not have been granted. The patent allows a user with a touch screen to bounce back to the image on the screen if the user goes beyond the edge.

This was an important one of the six patents that Samsung was found to have infringed by a jury in a California federal court in August. It awarded Apple $1.05 billion in damages. While that case is being appealed, Samsung is pursuing other problems such as requests for the PTO to reexamine the patent.

It is by no means over. The patent remains valid through the appeals process, so in the short term it will not make a difference.  However it comes after a wave of patent wins in Europe.