Plaintiff-appellant is the undisputed owner of the legal title to United States Letters Patent No. 2,520,895, for a 'Sheet Material Spreading Machine.' The machine facilitates the spreading of bolt cloth upon a cutting table in uniform superimposed layers, so that numerous identical pieces can be cut in a single operation. Appellant alleges that appellee, Weatherbee Coats, Inc., has infringed the aforesaid letters patent 'by using or causing to be used' machines embodying the invention set forth therein; and prays that appellee be enjoined from further infringement and that it be required to account for profits. Appellee, by way of counterclaim, prays for judgment dismissing the complaint and for a declaratory judgment that it has not infringed this patent which it asserts is void and invalid with respect to each of its forty-two claims.

The manufacturer of the accused machine, Lion Machine Corp., although not a party to this action, assumed the cost of defending this action and has controlled the defense throughout the proceedings.

In a concise memorandum opinion dated February 3, 1956, District Judge Connell found 'that the evidence adduced at trial clearly and satisfactorily shows that the prior art, as established by the 'Sussman,' 'Regal' and 'Model A' machines, reads on and/or anticipates the claims of the patent in suit. The Court finds that the substitution of mechanical structures made by plaintiff on its 'Gilbert' machine does not amount to invention. * * * The 'Gilbert' machine also operates in exactly the same way; mechanical equivalents being substituted to perform the same operations.' Pursuant to these findings, the district court held the patent in suit invalid as to each of the forty-two claims thereof by virtue of prior arts in public use and sale for more than one year prior to the date of the application for the patent. This holding was based on the authority of Title 35 U.S.C. 102(b); Smith & Griggs Mfg. Co. v. Sprague, 1887, 123 U.S. 249, 8 S. Ct. 122, 31 L. Ed. 141; and National Biscuit Co. v. Crown Baking Co., 1 Cir., 1939, 105 F.2d 422.

Having carefully reviewed the memorandum opinion of the district judge, the detailed record in the case (including physical exhibits in evidence set up for the enlightenment of this court), and the comprehensive briefs of counsel as supplemented by their oral argument, we are unable to find error. Aware of the heavy burden of proof resting upon the assailant of these letters patent, the trial judge has made findings of fact which are decisive of the issues in suit, inasmuch as they are supported by substantial evidence and are not clearly erroneous.

The judgment of the District court is affirmed.