Grinnell Corp. v. Virginia Electric & Power Co.

CRAVEN, Circuit Judge:

Each of the three patents invalidated below relates to an apparatus for automatically moving steam piping to pre-calculated positions so as to avoid intolerable stress caused by expansion and contraction of the pipe reacting to extremes of temperature. The device is basically a servomechanism employing a motorized jack to position the pipe and various devices to detect erroneous positions and activate the jack. The district judge held each patent invalid on the ground that the difference between its subject matter and the prior art was “such that the subject matter as a…