730 F.2d 753 (Fed. Cir. 1984), 83-1107, Envirotech Corp. v. Al George, Inc.

Docket Nº:Appeal No. 83-1107.
Citation:730 F.2d 753
Party Name:221 U.S.P.Q. 473 ENVIROTECH CORPORATION, Appellant, v. AL GEORGE, INCORPORATED and Monosep, Inc., Appellees.
Case Date:March 19, 1984
Court:United States Courts of Appeals, Court of Appeals for the Federal Circuit

Page 753

730 F.2d 753 (Fed. Cir. 1984)

221 U.S.P.Q. 473



AL GEORGE, INCORPORATED and Monosep, Inc., Appellees.

Appeal No. 83-1107.

United States Court of Appeals, Federal Circuit

March 19, 1984

Page 754

V. Bryan Medlock, Jr., Dallas, Tex., argued for appellant. With him on the brief was Daniel V. Thompson, Dallas, Tex.

Coke Wilson, Houston, Tex., argued for appellees. With him on the brief was Thomas F. Marsteller, Jr., Houston, Tex.

Before DAVIS, BALDWIN and KASHIWA, Circuit Judges.

DAVIS, Circuit Judge.

Envirotech Corporation (Envirotech) appeals from a judgment, after a jury trial, of the United States District Court for the Western District of Louisiana holding that claims 1, 14 and 15 of its U.S. Patent 4,110,210 ('210) ("Dispersed Gas Flotation Process") and claims 1, 10, 11 and 12 of its U.S. Patent 4,226,706 ('706) ("Dispersed Air Flotation Machine") are invalid and not infringed by appellees Al George, Incorporated and Monosep, Inc. (Monosep). We affirm in part, and vacate and remand in part.



  1. The General Technology

    The Envirotech patents involve separation of materials having different densities by ejecting minute gas bubbles into a tank containing a two-component fluid or solid/fluid "slurry". The bubbles attach to the particles to be separated and provide sufficient buoyancy so that both particle and bubble float to the tank surface to form a froth that is skimmed from the surface--thus, the term "flotation separation". Typical flotation separation devices use a nozzle extending beneath the tank's surface in order to introduce bubbles into the tank by ejecting a mixture of air and water as a two-phase (gas and liquid) effluent.

    In order to have successful flotation separation, two principal conditions must exist. First, the surface of the liquid in the tank must be relatively smooth because turbulence will dislodge the particles from their bubbles causing them to sink back into the fluid. Second, the bubbles must be dispersed throughout the tank in order to come into contact with all of the particles to be separated. In the past, dispersion was achieved by using various types of impellers placed at the bottom of the tank,

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    using multiple nozzles in each tank, or using baffles.

  2. The Method of the '210 Patent

    The '210 patent discloses a flotation separation method in which a two-phase effluent is ejected from a single nozzle into a tank in such a fashion that the desired conditions of good bubble distribution and a smooth non-turbulent surface may be obtained throughout a range of tank sizes without the use of baffles, impellers or multiple nozzles. The invention recognized that one could obtain these optimal conditions with a certain effluent density (gas-liquid ratio) and a certain energy rate per tank volume (velocity of the effluent). Figure 2 of the '210 patent graphically illustrates this energy/density relationship for a wide range of tank sizes:


    The curves set forth in Fig. 2, supra, divide the graph into Regions I, II and III. If a nozzle and tank combination are designed to operate within Region I then the two conditions for optimal separation can be obtained. Operation within Region III lacks these two conditions, and Region II is a gray area. Claim 1 of the '210 patent is representative:

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    1. A dispersed gas flotation process wherein hydraulic effects are used to disperse gas bubbles throughout a contained liquid body with a free surface, said process comprising pumping a two-phase fluid into the liquid body through an ejection device with the density and the kinetic energy rate of the ejected fluid per unit volume of the contained body at the point of ejection being defined by a point on the graph of FIG. 2 within the area encompassed by Region 1.

    According to the teachings of the patent, to calculate effluent density the designer need know only the flow rate of gas through the nozzle (QG ) and the flow rate of the liquid through the nozzle (QL ). To calculate the effluent energy rate per tank volume, the designer must know the tank volume (V), the flow rate of the gas through the nozzle (QG ), the flow rate of the liquid through the nozzle (QL ), and the area of the effluent being ejected into the tank at the "point of ejection" (Ae ).

  3. The Apparatus of the '706 Patent

    The '706 patent discloses a flotation separator having a series of tanks arranged in line so that the contaminated fluid can be treated in stages from one tank to another. As shown in Figure 2 of the '706 patent, reproduced below, each flotation tank 13 has one nozzle 20 (extending below the surface of the liquid) which ejects the two-phase effluent. The froth, which is subsequently formed by the bubble-carrying particles, is then skimmed off by paddle wheels 14, 14a.


    The claims of the '706 patent require that each nozzle have a "hollow tubular expansion chamber member" through which the two-phase effluent is discharged. The claimed pipe-within-a-pipe configuration comprises a smaller inner pipe which carries the liquid into a larger outer pipe creating a vacuum which sucks air down the outer pipe into the expansion chamber where it is mixed with the liquid from the inner pipe. The '706 patent expressly incorporates in the specification the types of "converging-diverging" nozzles included in the '210 patent. (Column 4, lines 31-33.)

  4. The Defendants' Alleged Infringing Device

    The defendants' accused device, marketed under the name "Multisep", has a series of tanks, each having a single off-the-shelf nozzle (also called an "eductor") where liquid is pumped and air is drawn in. The resulting two-phase effluent (air and liquid) is then ejected into the tank filling it with small bubbles. Defendants' eductor nozzle, illustrated below, normally used to pump two liquids, is of the converging-diverging type with a cylindrical throat portion and a flared end portion.

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  5. The Parties' Contentions Below

    The defendants stipulated that if their device operated within Region I of the '210 patent graph, they would be infringing that patent. As already mentioned, to ascertain the effluent energy rate, the area (Ae ) at the "point of ejection" from the nozzle must be known. However, the parties disagree about the measurement of the exit diameter of the effluent stream from the defendants' nozzle--a critical difference which affects infringement. Because the defendants' nozzle has a flared end, the diameter in the throat is smaller than the diameter at the end of the nozzle. Defendants say that, if the effluent fills up the flared end due to back pressure, then the larger end diameter should be used, and thus their process would fall completely off the '210 patent graph. The flared end is said to be considered "functional" if the effluent fills up the flare, meeting the tank fluid at the end of the nozzle. Under this construction, the "point of ejection" is at the nozzle's end. On the other hand, if the flared end is not functional, as plaintiff says, the throat diameter is to be used because the effluent exits in a column which does not contact the walls of the flared end, and, thus, defendants' machine falls within Region I of the '210 patent graph. Under this latter construction, plaintiff contends that the flared end is merely non-functional and cosmetic, and the "point of ejection" is at the throat.

    Defendants also stipulated that their machines included many of the elements of the '706 patent. They contend, however, that neither plaintiff's claimed "hollow tubular expansion chamber member" nor the incorporated '210 nozzles...

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