FMC Corporation v. City of Greensboro, 8859.

• Decision Date: 14 January 1964
• Docket Number: No. 8859.,8859.
• Citation: 326 F.2d 581
• Parties: FMC CORPORATION, Appellee, v. The CITY OF GREENSBORO, Appellant.
• Court: U.S. Court of Appeals — Fourth Circuit

326 F.2d 581 (1964)

FMC CORPORATION, Appellee, v. The CITY OF GREENSBORO, Appellant.

No. 8859.

United States Court of Appeals Fourth Circuit.

Reargued September 24, 1963.

Decided January 14, 1964.

Louis Robertson, Arlington Heights, Ill., and Edward A. Haight, Chicago, Ill. (Darbo, Robertson & Vandenburgh, Arlington Heights, Ill., Welch Jordan and H. J. Elam, III, Greensboro, N. C., on brief), for appellant.

R. Howard Goldsmith, Chicago, Ill., (Thornton H. Brooks, Greensboro, N. C., Charles W. Ryan, Schneider, Dressler, Goldsmith & Clement, Chicago, Ill., and McLendon, Brim, Holderness & Brooks, Greensboro, N. C., on brief), for appellee.

Before SOBELOFF, Chief Judge, and HAYNSWORTH and BOREMAN, Circuit Judges.

HAYNSWORTH, Circuit Judge:

Because the defendant departs from the patented process at the very point where novelty is claimed, we find no infringement of the patent. We, therefore, do not consider the question of the validity of this process patent or the defendant's claim of its misuse. The infringement question is not understandable, however, without some reference to the prior art in the treatment of sewage sludge, the subject of the patent.

In plants for the disposal of sewage from municipal systems, the raw sewage is delivered first to settling basins or tanks, in which a large proportion of the water is separated from a remaining sludge which contains volatile solids which are odorous and offensive. Thereafter, the green sludge is usually subjected to treatment to further reduce its water content and to render the remaining solids inoffensive or even to produce useful filter cake. In this further treatment, the green sludge from the preliminary settling tanks is delivered to digesters, and it is the operation of such digesters with which we are concerned.

Under the prevailing practice of the early treatment plants, the sludge was delivered to an unheated digester containing some seed sludge in which there were active anaerobic bacteria which attack the volatile solids, producing as a byproduct a gas containing a high proportion of methane. Such digester gas is combustible and usable as a fuel. In such unheated digestion tanks, the digestion process required two or three months.

It was then found that heating the contents of the digester would speed up the digestion time and shorten the holding period in the digester to approximately thirty days.

Greensboro had such a system in operation from sometime in the 1930's. It had two large digester tanks. Within them, digested solids settled to the bottom leaving above it a layer of comparatively clear, supernatant liquor topped by a scum layer. At appropriate times, the supernatant liquor was drawn off while the digested solids, which were still suspended in enough water to be pumpable, were delivered to an elutriation tank. There, the digested sludge was washed to remove its alkaline contents. The alkaline water from the elutriation tank was pumped off and the remaining, comparatively purified, sludge went to vacuum filters where it was converted into filter cake.

In more recent times, a number of experiments were made with the idea that digestion in the primary digester would be accelerated by stirring the contents. In commercial installations, propellers and other mechanical devices had been employed for that purpose. Two German patents were issued on processes of recirculation of methane containing digester gas for the purpose of accelerating the digestion process, and the second of those patents disclosed gas recirculation for the purpose of turning the contents of the digester, preventing the settling of solids and the separation of supernatant liquor until the mixed sludge entered a second compartment where, quiescent, the digested solids could settle and the supernatant liquor be separated.

Lamb and Klein, employees of Chicago Pump Company, a subsidiary of the plaintiff, filed a patent application disclosing the recirculation of digester gas, they having become convinced that the recirculation of the digester gas had a catalytic effect which accelerated the digestion process. In 1953, they filed a second application for a patent, the specifications of which required the circulation of a larger volume of digester gas in the center of the digestion tank, preferably near the bottom so that the diffused gas rising to the top would turn the contents of the tank, the contents in the center of the tank rising with the diffused gas, spreading outward at and near the surface and descending again near the outer walls of the tank. The result achieved was said to be a very effective mixing of the entire contents of the tank.

The Lamb and Klein applications were rejected on the basis of the German patents mentioned above and, after rejection, were abandoned.

There were other patents with which the District Court was much concerned, but we need not deal with them here since, on the question of infringement, we need only get to the patentee's point of departure. The second Lamb and Klein application was his point of departure.

The patent in suit is that of T. H. Forrest, No. 2,777,815, issued January 15, 1957, for a sewage digestion process. In 1953, Forrest was also an employee of Chicago Pump Company. He knew of the work of Lamb and Klein and worked with them, and his application was processed as copending with that of the second Lamb and Klein application. It disclosed everything that Lamb and Klein disclosed in their second application, but with the addition that the circulation of the diffused gas should be continuous and uninterrupted. Forrest, of course, disclaimed the acknowledged contributions of Lamb and...