Aero Spark Plug Co. v. BG Corporation ( 1942 )

CHASE, Circuit Judge.

The decree was based upon two grounds, non-infringement and invalidity of Claim 2, which is the only claim in issue.

Kasarjian’s patent involves spark plugs for use in airplane engines. The usual aviation spark plug assembly has a core in the center consisting of a metal rod or spindle. The lower end of this spindle constitutes one of the electrodes at the spark gap, and therefore the whole must be insulated from the other electrode known as the ground electrode. Because of the intense heat in aviation engines, mica is used as an insulator. Several thin laminations of mica are first wound around the spindle. This is known as the mica “cigarette.” About midway on this “cigarette” is a tight-fitting brass bushing to hold it in place on the spindle. Above the bushing, and sometimes both above and below it, is placed a stack of mica washers the inner circumference of which fits snugly around the “cigarette.” This constitutes the insulation of the center electrode.

An extremely high voltage is required in aviation engines to create a satisfactory spark in the cylinder because of the high compression of the explosive mixture. It had been found that occasionally a plug would miss fire because there would be a parasitic discharge or flashing within the insulation rather than at the spark gap where resistance was high. This flashing occurred in the slight air space between the mica “cigarette” and the mica washers, and the explanation for it was that in some plugs this air between the “cigarette” and washers became ionized from the leakage of the high voltage electricity and the ionization deprived the air of its usually good insulating properties with the result that there was less resistance offered the discharge through this path than across the spark gap. All this was known to the prior art, and it was while seeking to eliminate this parasitic discharge that Kasarjian invented the new construction which he patented.

Although Kasarjian calls this parasitic discharge or flashing a “corona discharge” which is technically an incorrect term, that is relatively unimportant for there can be no doubt from his specifications that what he means is this jump spark which causes the engine to miss fire. A patentee may use such terms as to him best describe what he means and when he thus makes his meaning plain it will be given effect. Cf. H. J. Wheeler Salvage Co., Inc. v. Rinelli & Guardino, Inc., D.C., 295 F. 717, 727.

Claim 2 of the patent calls for an aviation spark plug of the usual sort “and means for precluding corona discharges through the plug comprising an insulating refractory substance filling the air pockets within the insulating element to exclude residual air from said element.” A reading of this claim leaves no doubt but that Kasarjian’s theory was to exclude all the air so that none could become ionized and afford a path for. the flashing. This was to be done by displacing all the air with a liquid or semi-liquid refractory substance such as liquid porcelain. That the gist of his invention was to exclude all air and prevent the discharge in that way is repeatedly evidenced by his specifications. On page 1 at line 102 says, “I find it essential to the carrying out of this invention that the presence of air pockets within the plug structure be eliminated and thus according to this invention, the presence of air within the plug structure is eliminated by the actual filling of all spaces within the plug structure with a suitable substance of high di-electric value under the temperatures prevailing in the plug during operation.” Page 1, line 91: “I have discovered that by eliminating these air pockets, the silent or coronar discharge within the plug structure is entirely eliminated * * * ” The scope of every patent is limited to the invention which is covered in the claims read in the light of the specifications. Schriber-Schroth Co. v. Cleveland Trust Co., 311 U.S. 211, 217, 312 U.S. 654, 61 S.Ct. 235, 85 L.Ed. 132; Keith v. Charles E. Hires Co., 2 Cir., 116 F.2d 46, 49. And when claim 2 is so read there is no doubt that the only advance from the old to be found in Kasarjian’s construction of the spark plug is that all the air spaces be filled with a refractory insulating substance.

Assuming, without deciding, that claim 2 is valid, we agree that infringement has not been shown. The general structure of the accused plug is that of the conventional aviation spark plug, but in it the parasitic discharge is prevented by placing a refractory substance at only two places, one just above and one just below the brass bushing which holds the mica “cigarette” in place. In actual practice this is done by placing a small amount of the refractory cement in the shape of a doughnut around the “cigarette” at either end of the bushing. The washers are then pressed on and the whole is then compressed as part of the usual assembly method. The theory is that these refractory “doughnuts” will act as an insulating barrier to prevent either the leakage of electricity or parasitic discharge regardless of the presence of air which in the patented construction has been excluded. No effort is made to fill the air spaces completely and that result is not attained. The purpose and the final end of both methods are to prevent flashing, but with that their similarity ends. To eliminate harmful air spaces is one thing and to make the residual air in such spaces harmless is quite another and so different a method that it does not infringe. Westinghouse v. Boyden Power Brake Co., 170 U.S. 537, 568, 18 S.Ct. 707, 42 L.Ed. 1136; E. Van Noorden Co. v. Cheney Co., 1 Cir., 75 F. 2d 298, 302.

The appellant relies on Weiss v. R. Hoe & Co., Inc., 2 Cir., 109 F.2d 722, where the patentee taught the use of an “air-tight” structure in an ink fountain for printing presses, and where this court found infringement in a structure that was not entirely air-tight. But in that case it was said that in the light of the specifications of the patent there “air-tight” meant only as complete a closure as was practicable. The accused fountain took the substance of that invention and copied it imperfectly. There is no analogy in this case where the accused plug has attained the goal not by an imperfect copy, but by a different method; not by eliminating the air spaces but by blocking them off into harmlessness by effective insulation.

Since there is no infringement even if the patent be valid, we do not decide the question of validity. See S. S. Kresge Co. v. Davies, 8 Cir., 112 F.2d 708, 711. But cf. dissent in Exhibit Supply Co. v. Ace Patents Corp., 315 U.S. 126, 137, 62 S.Ct. 513, 86 L.Ed. 736.

Affirmed.