Hensley Equipment Company v. Esco Corporation

Decision Date15 September 1967
Docket NumberNo. 23723.,23723.
Citation383 F.2d 252
CourtU.S. Court of Appeals — Fifth Circuit



William A. McKenzie, Henry Baer, Dallas, Tex., Thomas O. Herbert, Donald N. MacIntosh, Flehr, Hohbach, Test, Albritton & Herbert, San Francisco, Cal., for appellant.

Hugh L. Steger, Dallas, Tex., Jerome F. Fallon, Chicago, Ill., John K. DeLay, Jr., Storey, Armstrong & Steger, Dallas, Tex., Dawson, Tilton, Fallon, & Lungmus, Chicago, Ill., of counsel, for appellee.

Before BELL, GODBOLD and DYER, Circuit Judges.

GODBOLD, Circuit Judge:

Hensley Equipment Company, Inc., appeals from an adverse decision in a patent infringement action brought by Esco Corporation, assignee of United States Patent No. 2,919,506 (the "'506 patent").1

The suit concerns excavating teeth to be attached to the digging edge of power shovel buckets and similar excavating equipment. Because of the stress and abrasion to which such a digging edge is subject the teeth must be replaceable. For a number of years two-part teeth have been available, each consisting of an "adapter" affixed to the bucket or digging apparatus and a "wear point" which is the forward or "spike" portion of the tooth. A projection of the adapter fits into a socket in the rear of the wear point. The wear point is held on the adapter by a removable pin. While adapters periodically must be replaced, the wear points bear the brunt of the abrasion and are replaced more frequently.2

Prior to the marketing of teeth produced under the '506 patent most two-piece excavating teeth had a wedge-shaped projection on the adapter with a correspondingly-shaped socket in the rear of the wear point. The horizontal surfaces of wedge-shaped adapter and point were the bearing surfaces at which the two parts came in contact. The bearing surfaces were flat. Under some operating conditions lateral pressure or thrust on the tooth caused sideways movement, producing a pivoting action between adapter and wear point, reducing the full (or substantial) contact or bearing between the two parts, causing instead "point contact" concentrated in a small area of the two bearing surfaces. Under these conditions the teeth were subject to rapid distortion and wear and often broke under the concentrated pressure.

Insofar as can be stated in non-technical terms, the invention which the '506 patent (described as "Excavating Tooth and Base Support Therefor") purports to embody is as follows. A conical bearing surface is employed on the adapter and on a correspondingly shaped socket in the wear point. Both the conical surface of the adapter and the conical surface of the wear point have, as a matter of geometry, a common vertical axis. Each conical surface comprises only a segment of a cone. See Figures 5 and 7 of drawings contained in the patent and made an appendix to this opinion, showing a structure with a complete conical surface (labelled 40) and demonstrating how a segment thereof (labelled 43 in Figure 7) is used to form the bearing surface of the adapter.3

Employing more technical language, the bearing surfaces of adapter and point are described in a number of claims as "surfaces of revolution" around a vertical axis.4 The concept of use of a "surface of revolution," as opposed to surfaces which cannot be created by a single line rotated about a constant axis, is significant, and the creation of the two conical bearing surfaces of wear point and adapter around a common vertical axis likewise is significant.

The invention contemplates that because of the design of the bearing surfaces lateral movement produces little or no change in bearing contact between wear point and adapter. Irrespective of the relative positions of the two members their bearing surfaces remain in substantial contact, and no concentration of pressure develops at one or more points.

The conical tooth enjoyed significant commercial success, and in 1962 Esco received for it an award by a trade magazine, based on selection made by a panel of international mining and metallurgical experts, for "achievement in equipment development by aiding the technological advancement of the mining industry."

In 1965 Hensley began to sell wear points designed, intended, and advertised and held out to the public, as replacement points for Esco adapters. It did so after having supplied a steel company with models of Esco points and an Esco adapter and ordering the points be copied with certain modifications. Hensley publicly referred to its said wear points as "Esco-type points." The points will not fit adapters of any company other than Esco. Later Hensley began to market adapters for one of Esco's smaller conical points. In its catalogs it describes these wear points and adapters as "conical." Since the beginning of this litigation Hensley has acquired a steel foundry and now manufactures as well as sells the products described above.5 Hensley also markets parts corresponding to products manufactured by Esco but not under the patent at issue6 and by other manufacturers.

Esco's complaint alleged that Hensley had infringed the '506 patent by making and selling tooth points. Hensley answered, denying the validity of the '506 patent and infringement and alleging that sale of wear points constitutes legitimate repair. It also alleged that Esco was barred by misuse from enforcing the '506 patent. Several counterclaims were asserted, alleging in substance that Hensley manufactured and sold replacement wear points for those manufactured by Esco under United States Patents No. 3,026,947 and No. 3,079,710 as well as the '506 patent; that these patents were invalid; that Esco had violated the antitrust laws by bringing the present suit and by using the patents on products outside their scope. Hensley asked a declaratory judgment that all three patents are invalid, that Hensley was not infringing any of them, and that Hensley, its supplier and customers, could continue to manufacture, use, and sell the teeth and wear points without interference. Injunctive relief, and triple damages also were demanded.

The district court held that the '506 patent is valid; that Hensley has infringed it; that Esco has not misused the patent, and that Esco is entitled to damages. Hensley was enjoined from further infringement of the '506 patent. The counterclaims were dismissed with prejudice except as related to validity and infringement of the '947 and '710 patents.


Hensley challenges the position of the district court that the patent claims included a conical surface of revolution.

The claims, construed in the light of the specifications and drawings,7 make clear to one familiar with the field involved that the surfaces of revolution — the bearing surfaces — are to be conical, or nearly so, and are not to be flat. We hold that the patent was properly considered as claiming conical surfaces of revolution.

II. Validity.

The district court did not err in finding against Hensley on its defenses of anticipation under 35 U.S.C.A. § 102 and obviousness within the meaning of 35 U.S.C.A. § 103.

We need discuss at length only the closest prior art, the Hensley '601 wear point, marketed by Hensley since 1955 for use on its single-shank "rippers."8 Testimony was produced that as rippers were used with tractors of higher power more breakage was experienced with the wear points, which had rectangular, or flat-surfaced, sockets to receive the wear collars. Therefore, Hensley began experimenting in 1951 or 1952 with a socket containing curved top and bottom, and in 1954 began marketing a wear point with such a feature. Subsequently larger models differing somewhat in the contour of the socket were marketed by Hensley. The 601-H, the model introduced at trial and relied upon by Hensley, was marketed in 1955 or 1956. Conflicting evidence was produced of the nature of the contour of the socket of the 601-H, and the district court found as a fact that it did not constitute a conical surface of revolution. Hensley argues that this is clearly erroneous and that the 601-H tooth literally anticipated the '506 patent or made its subject matter obvious to one skilled in the art.

It is clear that the 601-H point was an attempt to use a rounded socket connection between a wear point and its support to reduce breakage. But Esco's expert, Professor William Tiller of Stanford University's Department of Material Science, testified that the '506 conical point differed significantly in both theory and engineering design from the Hensley 601-H point. The socket shape of the 601-H point, he testified, was approximately an elliptical paraboloid. While it avoided some problems encountered with the rectangular socket models, rotational forces would cause the outer part of the 601-H to "ride up" over the inner part so as to cause "line contact", i. e., contact along a line of limited dimension as opposed to substantial surface-to-surface contact of bearing surfaces. This resulted in wearing of the adapter so as to distort its original shape. The '506 conical design possesses all the advantages of the 601-H shape plus the advantage of accommodating the rotational forces and movement; any wear, he testified, simply makes the cone fit better. He concluded there was little relationship between the '506 conical tooth and the Hensley 601-H.9

The district court did not err in finding that the 601-H tooth (and other prior patents) did not anticipate the '506 patent insofar as that patent claimed a conical surface of revolution about a vertical axis. Nor does the evidence establish that the conical design would have been obvious to one skilled in the art at the time of the invention.10 In this connection the district court gave appropriate recognition to the secondary indicia of commercial success and industry recognition of satisfaction of unsolved needs, referred to in ...

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