Barringer’s motion to stay is therefore denied.
We commence by analyzing the patent in suit:
The nature of the invention claimed is well described in the abstract at the beginning of the patent.
A proximity detector employing a loop or coil positioned in proximity to an electrically conductive object to be detected. The coil is energized with electric current pulses of predetermined width with predetermined intervals between successive pulses. Transients induced in the coil due to decaying eddy currents flowing in the object are detected during the intervals between successive pulses, when the electromagnetic field created by the pulses is absent or is not time varying. The transients are separated from the remainder of the currents flowing in the coil and are converted into a signal suitable for controlling a relay, actuating a counter, etc.
This description is elaborated in the first claim:5
A proximity detector for detecting the presence of electrically conductive objects, comprising:
(a) a coil positioned in proximity to the object to be detected,
(b) a signal generator connected to said coil for energizing said coil with a repetition of electric current primary pulses of predetermined width and with intervals between them during which the electromagnetic field produced by said primary pulses is absent or not time varying,
(c) receiving means for detecting signals induced in said coil including means for separating from said primary pulses any transient signals which are induced in said coil during said intervals, said transient signals being attributable to decaying eddy currents flowing in said object, and
(d) control means connected to said receiving means and responsive to said transient signals for producing a control signal the existence of which is indicative of the presence of said object in proximity with said coil.6
Possible applications of the invention mentioned in the patent include control of traffic lights, counting the number of vehicles passing the point of installation, measuring speed of vehicles or the level of fluid in a tank, counting units in a production line, or monitoring food processing to detect the presence of foreign metallic objects.
Plaintiff contends that the patent in suit is invalid by reason of prior art known to applicant but not presented to the Patent Office, in particular two patents previously granted to Barringer himself.7 These are patents 3,020,471, issued February 6, 1962, and 3,105,934, issued October 1, 1963, and reissued as RE 25,908 on November 16, 1965. Patent ’471 is entitled “Method and Apparatus for the Detection of Ore Bodies.”
It is of course true, as defendant emphasizes, that the outward trappings of the inventions embodied in Patent ’471 and the patent in suit are far different. Patent ’471 seeks to locate “base metal deposits” or ore bodies concealed in non-conductive rocks. The patent in suit ’221 detects metal artifacts such as automobiles (or weapons, as in the challenged device manufactured by plaintiff). Patent ’471 depicts an airborne device with the transmitter located in an airplane and the receiver in a trailing “bird” towed by the aircraft. The patent in suit describes a device buried in the ground underneath a highway over which cars pass.
But these differences, though dramatic, are superficial. The technique for detecting the presence of metal is substantially similar, if not identical. The essential fea
5
Claims 2-5 relate to apparatus.
6
Defendant’s device uses a single coil as both transmitter and receiver of impulses. Plaintiffs accused device has separate coils. Whether this difference is significant with respect to infringement we do not now pause to consider.
7
Dr. Anthony R. Barringer, the inventor in Patents 3,020,471 and 3,105,934, was a co-inventor in Patent 3,430,221, the patent in suit.