Stratoflex, Inc. v. Aeroquip Corporation

713 F.2d 1530, 218 U.S.P.Q. (BNA) 871, 1983 U.S. App. LEXIS 13634
CourtCourt of Appeals for the Federal Circuit
DecidedJuly 25, 1983
DocketAppeal 83-587
StatusPublished
Cited by538 cases

This text of 713 F.2d 1530 (Stratoflex, Inc. v. Aeroquip Corporation) is published on Counsel Stack Legal Research, covering Court of Appeals for the Federal Circuit primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Stratoflex, Inc. v. Aeroquip Corporation, 713 F.2d 1530, 218 U.S.P.Q. (BNA) 871, 1983 U.S. App. LEXIS 13634 (Fed. Cir. 1983).

Opinion

MARKEY, Chief Judge.

Appeal from a judgment of the District Court for the Eastern District of Michigan, 561 F.Supp. 618, declaring Claims 1, 3, 4, 6, and 7 of U.S. Patent No. 3,473,087 to Win-ton Slade (’087 patent) invalid and not infringed. We affirm.

When Stratoflex filed suit seeking a declaration of invalidity and non-infringement of the ’087 patent, Aeroquip, as assignee, counterclaimed for infringement of claims 1, 3, 4, 6, and 7. After a non-jury trial, Judge Boyle declared those claims invalid and found them not infringed. 1

II. Background

A. The Technology

Stratoflex and Aeroquip manufacture electrically conductive polytetrafluoroethylene (PTFE) 2 tubing used in the aircraft and missile industry to convey pressurized fuel, lubricants, and other fluids.

PTFE has replaced organic and synthetic rubbers and plastic in fuel hoses because it has a number of superior characteristics. *1532 Though pure PTFE is dielectric (non-conductive), it can be made with fillers to make it conductive, though the “filled” tubing is more susceptible to leakage when voids form between the PTFE and filler particles.

B. The Invention

The Slade invention relates to a composite PTFE tubing, formed of an inner layer of electrically conductive PTFE having particles such as carbon black uniformly distributed in it and an outer layer of essentially pure non-conductive PTFE. Claims 1 and 7 are representative:

1. A tubular extrudate formed of attached concentric tubular extrusions, the inner tubular extrusion comprising associated particles of unsintered tetrafluoroethylene polymer and pulverulent, inert, electrically conductive particles, and the outer tubular extrusion comprising associated particles of unsintered tetrafluoroethylene polymer.
7. A tube of polytetrafluoroethylene and the like for conducting fluids under pressure and including means for discharge of internal static electricity to the ends of the tube and grounding the same from the tube interior at said ends in order to maintain the polytetrafluoroethylene tubing performance characteristics, said tubing having an integral polytetrafluoroethylene wall structure with an interior liner portion of a substantially annular conformation from end to end and having a uniform dispersion of electrically conductive particles embedded therein, the major portion of said tubing wall completely surrounding said liner portion exteriorly and being relatively nonconductive in character, said surrounding portion together with said liner containing fluid under pressures uniformly within said tubing.

Claims 3, 4, and 6 are similar to claim 1, But specify various percentages of ingredients.

The particles in the inner layer of the claimed tubing dissipate electrostatic charges built up on the inner surface of the tubing, conducting them lengthwise of the tubing to grounded metal fittings at the ends of a hose assembly of which the tubing is part, to prevent arcing or discharging through the tubing wall to the surrounding metal braid. Arcing causes “pin holes” through which fuel can leak. The outer layer.is coextruded or bonded around the inner layer to contain any fuel leaking through the inner layer. The composite tubing has excellent conductivity, while retaining the desirable characteristics of PTFE tubing.

C. Events Leading to the ’087 Patent

Pure PTFE tubing had been used successfully in aircraft engines since at least 1956. In 1959, with the introduction of hydrocarbon jet fuels, leaks were noticed. Aeroquip assigned two staff engineers, Abbey and Upham, to determine the cause. They found the problem to be the arcing of electrostatic charges through the wall of the pure dielectric PTFE tubing to create “pin holes” as described above.

Abbey and Upham found the “pin hole” phenomenon exhibited by all three types of PTFE (White-Titeflex; Pink/Red-Aeroquip; Black-Goodrich) used in aircraft engines. The black tubing appeared superior because the carbon black it contained gave it an intermittent conductivity. The carbon black took the form of discontinuous strings and arcing across the spaces between string ends conveyed charges to the ends of the tubing. Electrical erosion of the strings, however, widened the spaces, destroying conductivity and leading to the “pin hole” phenomenon. Abbey and Upham concluded that susceptibility of PTFE tubing to “pin holing” was proportional to its conductivity, and that carbon black increased the conductivity of PTFE tubing.

In early 1960, having determined the cause of leaking, Aeroquip approached Raybestos-Manhattan (Raybestos), a PTFE hose manufacturer, for a solution. Aeroquip later purchased the hose section of Raybestos, obtaining the Slade patent by mesne assignment.

*1533 Raybestos assigned the project to the inventor, Winton Slade, who prepared several samples of conductive PTFE tubing (powdered lead, copper, chemically etched, and carbon black) and sent them for testing to Aeroquip in the summer of 1960. In the Fall, Aeroquip ordered a small production quantity of carbon black tubing. That tubing was not a composite and the carbon black was not uniformly distributed in it.

Slade conceived of the composite tube of the invention as early as August 5,1960 and reduced it to practice in November of 1961. He filed a patent application on May 22, 1962, with claims directed to the composite tubing and also to various processes for making it.

During prosecution, Slade’s assignee Raybestos sought and was denied declaration of an interference with a patent application assigned to Titeflex. The Titeflex application issued as U.S. Patent 3,166,688 (’688 patent). Raybestos then was granted an interference with claims 1 and 2 of the ’688 patent. An agreement provided that the loser of the interference would receive a royalty free license. Slade was awarded priority and Titeflex was licensed.

When the examiner imposed a restriction requirement on the Slade application, Slade elected to prosecute the product claims, and filed the process claims in a co-pending application which issued as U.S. Patent No. 3,658,976. Slade’s original application issued with its product claims as the ’087 patent on October 1, 1969.

D. Stratoflex Actions

From 1962 to 1970, Stratoflex purchased PTFE tubing containing carbon black from B.F. Goodrich. When Goodrich ceased production, Stratoflex purchased conductive PTFE tubing made by Titeflex under its license. Stratoflex then began manufacturing and selling its own “124” and “127” composite tubing having an inner layer with conductive carbon black uniformly dispersed throughout, and an outer layer that is essentially nonconductive, though that outer layer includes a small amount of carbon black to color the tubing and to aid extrusion.

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Bluebook (online)
713 F.2d 1530, 218 U.S.P.Q. (BNA) 871, 1983 U.S. App. LEXIS 13634, Counsel Stack Legal Research, https://law.counselstack.com/opinion/stratoflex-inc-v-aeroquip-corporation-cafc-1983.