Dubilier Condenser & Radio Corp. v. Aerovox Wireless Corp.

37 F.2d 657, 4 U.S.P.Q. (BNA) 273, 1930 U.S. App. LEXIS 2611
CourtCourt of Appeals for the Second Circuit
DecidedJanuary 13, 1930
DocketNo. 64
StatusPublished
Cited by5 cases

This text of 37 F.2d 657 (Dubilier Condenser & Radio Corp. v. Aerovox Wireless Corp.) is published on Counsel Stack Legal Research, covering Court of Appeals for the Second Circuit primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Dubilier Condenser & Radio Corp. v. Aerovox Wireless Corp., 37 F.2d 657, 4 U.S.P.Q. (BNA) 273, 1930 U.S. App. LEXIS 2611 (2d Cir. 1930).

Opinion

MACK, Circuit Judge.

Appeal from a decree dismissing a bill for infringement of claims 3 and 8 of United States letters patent No. 1,497,095, issued June 10, 1924, to William Dubilier, and assigned by him to plaintiff, because of invalidity of the claims, and finding, moreover, noninfringement by one of defendant’s devices, type 1350. The District Judge was of the opinion that the other type, No. 1250, would be an infringement, if the claims were valid. The issues of validity and infringement are thus before us on this appeal.

In the early days of radio broadcasting, beginning about 1920, many radio receiving sets were assembled by amateurs, using condensers, transformers, and other individual parts purchased separately; other sets were assembled by manufacturers from separately purchased parts and sold as complete units. With the rapid growth of the business, there grew up from both sources a demand for a fixed condenser of small capacity, ranging from about .0001 to .006 microfarads, which was required for a variety of purposes, unnecessary to be detailed here, in the standard circuits. The device, known as a receiving set condenser, consists principally of tin foil sheets, which serve as the plates or armatures, interleaved with thin mica sheets, which constitute the dielectric or insulating material; the sheets are built up into a stack.

Because of the relatively small capacity required, these stacks are ordinarily quite thin. The amount of electrical energy which a condenser will store, called its capacity and measured in microfarads, depends primarily upon the juxtaposed area of the tin foil plates, the spacing of such plates from each other, and the nature of the insulating medium or dieléetrie interposed between them. If these factors are constant, the capacity of the condenser will remain constant; if the distance between the plates be varied even microscopically, or if a foreign substance, such as moisture or air, gets into the dielectric between the plates, the capacity will vary as much as 40 per cent. Consequently the electrical efficiency of the condenser depends upon the maintenance of the initial spacing and the exclusion of foreign matter.

Mica has long been known as one of the best solid dielectric materials, obtainable in very thin sheets, and is universally used. In ¡order to exclude moisture or air from between the laminas of the condenser, it has been the custom for many years to impregnate the sheets with an insulating compound, which became part of the dielectric. Varnish has frequently been used for this purpose, as it yields a rigid stack after drying; but, where a condenser of low electrical losses is desired, varnish is not suitable because of its poor di.eleetric qualities; therefore paraffin wax is commonly used as an impregnating material, even though it does not impart the same rigidity as varnish. To secure and maintain the rigidity essential both to hold the condenser stack against even microscopic internal movement, and for other purposes, some form of pressure is usually applied; this may be done in the course of the baking during manufacture, or by mechanical means thereafter, or by both.

In addition to the requirement of permanence in capacity and low electrical losses, a receiving set condenser must be small, light weight, and capable of being readily mounted and connected in a circuit. Such condensers are installed between larger instruments, being suspended between wires, or hold against a panel or the terminal posts of other instruments by screws. It is important that the condenser be capable of being interchangeably mounted in any one of the vari[658]*658ous locations in which it might be needed in any particular type of set. Moreover, since electrical connections are usually made by soldering wires or screws to the condenser terminals, and since heat is generated by the vacuum tubes, the condenser must be designed so as not to be affected by this heat; and, for commercial success, it should, of course, be marketable at a low price — an experienced witness said 25 to 30 cents.

The Dubilier patent in suit, No. 1,497,095, does not purport to include, and indeed it expressly disclaims, the structure of the condenser stack as part of the invention; it merely recommends that the condenser be “compressed, evacuated of all air between the plates, and impregnated with melted paraffin, as may be required,” referring, by way of example, to a prior Dubilier patent purporting to cover this impregnating process. The patent ia essentially a structural patent, relating to improvements independent of the stack construction, and specifies a condenser “provided with means whieh will keep the elements constituting the stack or body of the condenser pressed together with firmness, and prevent any loosening or separation of the plates, by whieh the performance of the condenser would be seriously impaired.”

In order to secure this desired pressure, there are applied to opposite faces of the stack, parts whieh the claims define as “relatively heavy and stiff insulating bearing members” (claim 3), and “relatively stiff and thick bearing plates of insulating material disposed on opposite sides of the stack, to build up the condenser to substantial thickness and rigidity (claim 8)”; bakelite being recommended for this purpose. To apply mechanical pressure to these insulated bearing members, the patent prescribes the use of hollow rivets or tubular elements, whieh pass through the stack and insulating bearing members. These rivets are also described as making contact with the two sets of tin foil plates of different polarity, so as to permit terminal connections to be made directly through the rivets. The patent further specifies the interposition of stiff clips or plates between the heads of the hollow rivets and the insulating bearing members, whieh clips are supposed to exert pressure on the bearing members, similar to that exerted by the head of an ordinary carpet taek, over the juxtaposed foil in that portion of the stack known as the “active area.”

The resulting condenser very thoroughly met the requirements of the trgdo; it possessed a constant capacity, a high electrical efficiency, was compact, could be readily and interchangeably mounted in any of the standard sets, and could be supplied within tho price range which satisfied the demand. The record discloses that it enjoyed a huge commercial success, and practically became a trade standard.

The claims relied on are as follows:

“3.

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Bluebook (online)
37 F.2d 657, 4 U.S.P.Q. (BNA) 273, 1930 U.S. App. LEXIS 2611, Counsel Stack Legal Research, https://law.counselstack.com/opinion/dubilier-condenser-radio-corp-v-aerovox-wireless-corp-ca2-1930.