Plain Talk About Infringement

The U.S. Supreme Court Decision in Festo Corp. v. Shoketsu Kogyo Kabushiki Co., Ltd.

On May 28, 2002, the United States Supreme Court issued a ruling in the case of Festo Corp. v. Shoketsu Kogyo Kabushiki Co., Ltd. ("Festo") (535 U.S. ___ (2002)). In a unanimous decision, the Court held that prosecution history estoppel may apply to any claim amendment made to satisfy the Patent Act's requirements and not just to amendments made to avoid the prior art. The Supreme Court additionally held that estoppel need not bar suit against every equivalent to the amended claim element. The Court remanded the case for further proceedings consistent with its opinion.

Part I of this paper provides the background of the Festo case, particularly focusing on the proceedings before the U.S. Court of Appeals for the Federal Court, the ruling of which shocked inventors and patent practitioners worldwide. Part II discusses the much-anticipated ruling by the U.S. Supreme Court.

PART I: A SURPRISING DECISION BY THE U.S. COURT OF APPEALS FOR THE FEDERAL CIRCUIT

Background The Technology

Petitioner Festo Corporation (hereinafter "Festo") owns two patents, referred to herein as the "Stoll patent" and the "Carroll patent". The two patents are directed to magnetic rodless cylinders, i.e., piston-driven devices that rely on magnets to move objects in a conveying system. Copies of the front pages of the Stoll and Carroll patents are provided in the Appendix hereto. The front pages of the patents contain illustrations of the invention device. Each device contains a piston, a cylinder and a sleeve. The piston is located inside the cylinder and is moved by fluid under pressure. The sleeve is located on the outside of the cylinder and is magnetically coupled to the piston. Magnetic attraction between the sleeve and the piston causes the sleeve to follow the piston when it moves along the inside of the cylinder. The sleeve is used to move objects on a conveying system.

In the magnetic rodless cylinder disclosed in the Stoll patent, the piston includes magnets, two elastomeric sealing rings and a pair of guide rings. The sealing rings prevent any impurities from getting on the piston. The guide rings, which project beyond the piston's surface, pass along the internal cylinder surface in a sliding fit and help prevent impurities from dirtying the piston. The sleeve includes magnets and an outer body made of a magnetizable material.

In the Carroll patent, the sleeve of the magnetic rodless cylinder is a permanent magnet attached to a gripping device and surrounding part of the exterior of the cylinder. Each end of the piston has a sealing ring set in an annular groove. The sealing rings engage the inner wall of the cylinder and form a fluid tight seal that allows compressed air or other pressurized fluid to move the piston in either direction. The polarization of the magnets on the piston and the sleeve causes the sleeve to follow the movement of the piston.

Prosecution History of the Stoll Patent

Originally, the Stoll patent application contained twelve claims. Claim 1, set forth below, initially read:

1. A linear motor for use in a conveying system,

said motor being operable by a pressure medium and comprising a tubular part connectible to a source of the pressure medium,

a piston which is slidable in said tubular part and which has sealing means at each end for [w]iping engagement with an internal surface of the tubular part and so as to form a seal for the pressure medium,

and a driven assembly which is slidable on the tubular part and which has means at each end for [w]iping engagement with an external surface of the tubular part,

the piston and the driven assembly each carrying a drive magnet arrangement in the form of a hollow cylindrical assembly,

each magnet arrangement having radial play relative to the adjacent surface of the tubular part,

and surfaces of the magnet arrangements which face the tubular part being closely adjacent to the respective surfaces of the tubular part [Emphasis Added].

Dependent claims 4 and 8, set forth below, of the Stoll patent application are relevant:

4. A linear motor according to any of claims 1 to 3, wherein the sealing means of the piston comprise sealing rings and the piston is provided with sliding guide rings near the sealing rings [Emphasis Added].

8. A linear motor according to any of the preceding claims wherein the driven assembly is provided with a sleeve made of a magnetisable material, which encircles the hollow cylindrical assembly of the magnet arrangement [Emphasis Added].

All twelve claims of the patent application were rejected in the first Office Action.

Claims 1-12 were rejected under 35 U.S.C. Ã,§ 112, first paragraph, because the "exact method of operation is unclear." The patent examiner asked whether the device was a "true motor or magnetic clutch". Claims 4-12 were further rejected under 35 U.S.C. Ã,§ 112, second paragraph, because they were "improperly multiply dependent."

In response to the Office Action, Stoll amended some claims, including claim 1, and cancelled others, including claims 4 and 8. Claim 1 was amended to recite the following:

"plural guide ring means . . . and first sealing rings located axially outside said guide rings" on the piston

and

"a cylindrical sleeve made of a magnetizable material".

In the remarks accompanying the amendments, Stoll stated that

[e]ach of the claims now present in this application has been reviewed for compliance with the provisions of Title 35 USC 112. Accordingly, further consideration of these claims, particularly with respect to the provisions of Title 35 USC 112, is respectfully solicited.

In the response to the Office Action, Stoll also made two German patents of record in the application. In the remarks section, Stoll stated that the "claims now present in th[e] application" are distinguishable over these references and that "i[t] is clear that neither of these two references discloses the use of structure preventing the interference by impurities located inside the tube and on the outside of the tube while the arrangement is moved along the tube."

The examiner allowed the amended claims and requested that all references to "linear motors" be deleted from the specification because this phrase "connotes a different device having different operational characteristics."

Prosecution History of the Carroll Patent

The relevant portion of the Carroll Patent's prosecution history is its reexamination. Before reexamination, claim 1 of the Carroll patent application read as follows:

1. A device for moving articles comprising

a cylinder of non-ferrous material,

a piston including a permanent magnet having a pole-piece on each axial side thereof,

a body disposed outside and adjacent to said cylinder, said body including a permanent magnet which substantially surrounds the cylinder, there being a pole piece on each axial side of the permanent magnet included in said body, and

means for controlling the admission of pressure fluid into the cylinder and exhaust of fluid from the cylinder for moving the piston in the cylinder,

the attractive forces between the permanent magnets being such that movement of the piston causes corresponding movement of the body below a predetermined load on the body and such that above said predetermined load movement of the piston does not cause corresponding movement of the body.

Claim 1 did not recite the sealing rings disclosed in the specification.

In his request for reexamination, Carroll cited German Patent No. 1,982,379, which was not of record in the Carroll Patent's prosecution history.

During reexamination, Carroll cancelled claim 1 and added claim 9, which explicitly recited " a pair of resilient sealing rings situated near opposite axial ends of the central mounting member and engaging the cylinder to effect a fluid-tight seal therewith." In the remarks accompanying the amendment, Carroll stated that the now-amended claims "more clearly and more specifically" define the "features of the patentee's invention that distinguish over the art of record, including" the German patent cited in the request for reexamination.

Carroll also noted that the structure now described in claim 9 was not disclosed in the art of record. He further pointed out that "the particular structure of the inner piston and outer body now specifically set forth in new claim 9 is not taught or suggested by the German patent." Carroll particularly noted the recitation of the placement and plurality of magnets for both the piston and outer body and the recitation of resilient materials and cushion materials on the ends of the piston.

The examiner allowed the amended claims, stating that "the prior art does not teach or render obvious the claimed combination which includes the plurality of magnets, end members, and cushion members in the claimed relationship."

The Alleged Infringement

After Festo began selling its...