Appeal from the District Court of the United States for the Eastern District of New York.
Before MANTON, L. HAND, and SWAN, Circuit Judges.
The patent discloses a socket for inclosing the switch mechanism of an electric lamp. It consists of two parts, cap and shell, and is of the so-called "universal" type; that is, in assembling the parts, the end of the shell may be inserted within the cap in twenty different circumferential positions, in any of which the two parts will lock together to prevent longitudinal separation or rotary movement of the shell within the cap. Separation longitudinally is avoided by providing the cap with a series of inwardly extending projections adapted to latch under outwardly extending projections on the shell. Relative rotary movement is avoided by providing the projections on the cap with inclined shoulders parallel to the longitudinal axis of the cap and adapted to nest against the shoulders of longitudinal corrugations on the end of the shell. Sockets of the universal type which accomplished both these objects were old in the art. What Johnson did related only to a change in the form of the locking devices, resulting, as he asserts, in greater strength, improvement in appearance, and economy in manufacture.
In his preferred form, the projections of the cap are formed by making a series of twenty short cuts equally spaced around the flange of the cap and parallel with its edge, the metal below each cut being pressed inwardly to form a projection of which the upper end is a cut edge and the sides are inclined shoulders parallel with the longitudinal axis of the cap. The end of the shell has corresponding longitudinal corrugations into which the projections on the cap will nest when the cap and shell are assembled. In the depressed portion of one or more corrugations adjacent to one side of the key slot of the shell there is an outwardly extending projection having a cut edge on its lower end, and a similar projection or projections are pressed out on the opposite side of the shell. When the cap and shell are assembled, the cut end of a projection on the cap will latch under the ends of the projections on the shell to prevent longitudinal separation. The angular shoulders of the projections on the cap rest against the angular shoulders of the corrugations on the shell, and friction tends to prevent rotary movement of the shell within the cap. Friction does not absolutely prevent relative rotary movement, since it was demonstrated that by a sufficient torque the shell will be deformed so that the shoulders of the projections on the cap will ride up over the shoulders of the corrugations of the shell; but for practical purposes relative rotary movement may be said to be prevented, for the socket is able to withstand the torsional stresses to which it is subjected in customary use.
The first three claims are directed solely to the form of the cap. Claim 1 is the broadest, and reads as follows:
"1. An electric socket cap having a plain annular imperforate flange provided with a series of closely associated equally spaced inwardly extending locking projections having shoulder portions parallel with the longitudinal axis of the cap."
Claim 2 limits the form of the cap as follows:
"2. An electric socket cap having a plain annular imperforate flange provided with a series of equally spaced cuts around the same, portions of the flange adjoining said cuts extending inwardly to constitute locking projections having shoulder portions parallel to the longitudinal axis of the cap."
Claim 3 requires the cuts to be parallel to the edge of the flange, as in the preferred form above described.
Claim 4 covers the combination of the Johnson cap as set forth in claim 1 with the old "universal" type of corrugated shell.
The defendants not only deny the validity of the patent in suit, but assert that in any event their sockets do not infringe. In the view of this court, it will be necessary to consider only the second contention.
The defendants' cap appears to the unaided eye practically identical with the plaintiff's, but the testimony is that the series of incisions in the flange are rectangular, cutting the metal not only at the end, but also along a portion of cach side of the inwardly extending projections. The metal below the incision, being pressed inward, forms a tongue having a cut edge at the sides as well as the end. While the method of latching against longitudinal separation is admitted to be the same as in the socket of the patent in suit, the method of preventing relative rotary movement is claimed to be very different. Instead of relying upon friction between the shoulders of the cap projections and the corrugations of the shell, the defendants cause the cut metal edges of two tongues, which lodge within the key slot of the shell when the two parts are in assembled position, to bear against the edges of the key slot, thereby making a positive lock against rotation of the shell within the cap in either direction -- one which will yield to torsion only when the stress is sufficient to shear off the tongue. It is the contention of the defendants that, because of the file wrapper history of the patent in suit, the plaintiff is precluded from claiming that the caps alleged to infringe have an "imperforate flange" or "projections having shoulder portions" of the sort described in the patent. This requires a consideration of the file wrapper -- a matter not dealt with in the opinion below.
Johnson's original application referred to the projections on the cap as "tongues." The claims were all for the combination of shell and cap, and claim 3 may be ...