US Patent 6990772 Automatic door closure for double-acting doors

A double-acting door closure device that automatically returns a double-acting door to a preferred center position comprises first and second members each having a helical end surface extending transversely of its center axis. The first member is secured in spaced relation to a door jamb and the second member is mounted on and secured to a door post that extends through and is rotatable in the first member, with the helical end surface of the second member facing and engaging the helical end surface of the first member. The helical end surfaces coact with one another to gravitationally return a door attached to the door post to a closed position automatically after the door has been pushed opened and then released.