Keystone Driller Co. v. Northwest Engineering Corp.,
294 U.S. 42 (1935)

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U.S. Supreme Court

Keystone Driller Co. v. Northwest Engineering Corp., 294 U.S. 42 (1935)

Keystone Driller Co. v. Northwest Engineering Corp.

No. 131

Argued December 5, 1934

Decided January 7, 1935*

294 U.S. 42


1. Claim 4 of Patent 1,317,431, to Clutter, for improvements in excavating machines, held not infringed. P. 294 U. S. 44.

The invention is said to consist in a "pivotal means carried by the boom" of the machine, "and connecting the pulling member therewith and with the scoop-carrying member," or ditcher stick. In machines of this kind, the boom swings on a pivot at its base and is pivoted at its other end to the ditcher stick near the top, or inner end, of the latter. The specifications and drawings of the patent showed a pulley mounted between two links, pivoted to the boom near its upper end, and two cross links extending from the axle of the pulley to the top of the ditcher stick and pivotally attached to it. By tensing or relaxing a cable passed through the pulley, the boom could be raised or lowered and the ditcher stick, bearing the scoop at its outer end, could be advanced or retracted.

Held that, in view of the prior art and of the file wrapper, the claim cannot be construed broadly, and that it is not infringed by devices which, doing away with the links and cross links, run the cable over pulleys in brackets rigidly mounted to the boom and fasten it to the top of the stick; or by devices in which a pulley is attached to the top of the stick firmly or by a link pivoted to the top. P. 294 U. S. 46.

2. Where broad claims are denied in the Patent Office and a narrower one is granted in lieu, the patentee is estopped to read the granted claim as the equivalent of those that were rejected. P. 294 U. S. 48.

3. Claim 6 of Patent No. 1,476,121, to Wagner, claiming means for mounting a sheave at the upper end of the ditcher stick of an excavating machine and a hoisting line passed about the sheave for raising and lowering the boom and stick, and also for moving the

Page 294 U. S. 43

stick outwardly lengthwise of the boom, and Claim 7 of the same patent for a hoisting line connected to the top of the ditcher stick, held void for want of novelty. P. 294 U. S. 49.

4. Claims 6, and 14, of Patent No. 1,511,114, to Downie, for a drop-bottom scoop with side rake teeth, in excavating machines, held void for want of novelty and invention. Pp. 294 U. S. 49-50.

The fixation of the scoop to the ditcher stick, the pivoting of a drop bottom near the front of the scoop, which can be unlatched to drop the contents and closed by checking the momentum of the scoop, and the addition of rake teeth to the sides, were all old in the art, and their combination and adaptation required no more than mechanical skill.

70 F.2d 13 affirmed.

Certiorari, 293 U.S. 539, to review the reversal of three decrees obtained by the petitioner in three suits charging infringements of its patents.

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