Maibohm v. R. C. A. Victor Co.

13 F. Supp. 901, 1936 U.S. Dist. LEXIS 1553
CourtDistrict Court, D. Maryland
DecidedFebruary 26, 1936
DocketNo. 2305
StatusPublished

This text of 13 F. Supp. 901 (Maibohm v. R. C. A. Victor Co.) is published on Counsel Stack Legal Research, covering District Court, D. Maryland primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Maibohm v. R. C. A. Victor Co., 13 F. Supp. 901, 1936 U.S. Dist. LEXIS 1553 (D. Md. 1936).

Opinion

WILLIAM C. COLEMAN, District Judge.

The present suit is one for alleged infringement of patent No. 1,930,980, issued October 17, 1933, to H. C. Maibohm, application filed October 30, 1929, for a variable electrical resistor and switch. The plaintiffs are the present owners of the patent.

By stipulation the issue has been reduced to the question of the validity of the patent. Briefly stated, the patent is for the combination of a standard form of variable resistance or rheostat used as a volume control in radio receiving sets, with a known form of snap switch, for making and breaking the power circuit of such sets. That is to say, both the variable resistor and the snap switch are admittedly old in the art, but it is the combination of the two for which invention is claimed.

When the radio art was in its early stages, batteries were used to operate radio receivers, and the slow make and break switches, well known in the art, were adequate; but when inventions in radio tubes made possible the use of high-voltage house alternating electric current for operating radio receiving sets, this high voltage rendered the slow make and break switches inadequate, because the resulting spark not only corroded the switches, but created a fire hazard.

While there are eight claims in the patent, plaintiffs rely upon only four of these claims, namely, Nos. 5, 6, 7, and 8, and adopt No. 6, which is as follows, as being the more typical, and as adequately embracing the entire invention: “A mono-control variable electrical resistor and switch unit comprising: an electrical resistance element, a frame including means for mounting the unit and for supporting said resistance element, a rotatable shaft jour[902]*902sialcd in said frame, an arm associated with said resistance element and rotatable by said shaft to adjustably vary the electrical resistance of said unit, an instantaneously acting snap switch carried by said frame and having an actuating arm eccentrically disposed with respect to the axis of said shaft and terminating in an open fork, and a trip finger carried by said shaft and freely engageable and disengageable with said fork by rotation of said shaft to non-restrainingly trip said switch to open-circuit or closed-circuit positions irrespective of the rate at which said shaft be rotated.”

Summarizing this claim, we find that the snap switch is mounted on the frame of the variable resistor, and the shaft of the latter, by which the resistance is adjusted by the operator through the means of an outside controller knob, has attached thereto an arm carrying a pin or trip finger, and the operating arm or tumbler of the snap switch has a fork in it. The parts are so arranged that when the radio receiver is to be used, the first movement of the controller knob snaps on the switch, and further movement of the knob cuts out resistance so as to increase the volume. Reversely, when the receiver set is in use and it is desired to discontinue its use, movement of the controller knob cuts in the resistance and snaps the switch to “off” position.

Variations in the construction of the plaintiffs’ device and the device of the defendant we need not consider, because, as already stated, infringement is not now denied, and we are concerned me'rely with the question of the validity of the patent.

In support of its claim that the patent is invalid, the defendant makes the four following defenses: First: That the August, 1927, edition of “Radio News” contains an article which constitutes a publication of the patent device more than two years prior to the filing of the application for it. Second, that the patent device was in public use and on sale in numerous instances more than two years prior to the filing of the application for the patent. Third, that the patent discloses no invention, but merely the exercise of mechanical skill in view of prior patents and publications. Fourth, that the claims of the patent in issue are anticipated by prior patents.

We have concluded that it is unnecessary to consider more than the first two of these four defenses. And, indeed, we believe that the first one is entirely sufficient and conclusive of the invalidity of the patent.

The rule is so well established that citation of authorities is not necessary, to the effect that in order for a prior publication, within the meaning of section 4886 of the Revised Statutes, as amended (35 U.S.C.A. § 31), to invalidate a patent, such publication must describe the invention in such a manner that any person skilled in the art can practice it without further instruction. The precise question, therefore, is: Does the weight of the credible evidence in the present case establish that the article in question, considered as a whole, answers this requirement?

The article consists of the following text, accompanied by a diagrammatic scheme and two photographs:

“Six-Tube Set Operates on Alternating Current.
“A six-tube receiver, operating direct from the 110-volt, 60-cycle house lighting lines, is the latest product of an Ohio radio firm. It employs no battery, or combination of battery and charger; the A.C. being applied in unrectified form to the filaments of the special tubes used and, in rectified and filtered form, to their plates. To place it in operation, one need only connect the aerial and ground wires, screw an attachment plug into the nearest lamp socket, plug in the loud speaker and snap on the switch.
“The set is of the single-control type, the one principal tuning knob operating three separate variable condensers, connected by a pulley-and-string arrangement. The circuit comprises two stages of tuned radio-frequency amplification, a non-regenerative detector, and three stages of straight transformer-coupled audio amplification. The antenna coil, AC, is an auto-transformer, the primary section being adjustable by means of a simple plug-and-jack scheme. Four taps are provided.
“A high-value variable resistor, VR, connected in series with the primaries of the R.F. transformers, acts as a volume and oscillation control. Additional control of the volume is made possible by another resistor, connected across the secondary of the second A.F. transformer.
“The six tubes are arranged in a straight line along the rear edge of the receiver’s subpanel, but their circuit positions do not follow in the usual R.F.-detector-A.F. order. Instead, the first tube on [903]*903the left is the last audio, the second the first R.F.; and the others are as indicated in the schematic diagram shown herewith.
“Combined with the variable resistor VR is a small snap-switch, which is automatically turned on when the resistor knob is disturbed from its ‘off’ position. This switch, it will be noted, is connected in one side of the 110-volt power circuit, and controls the current to the filament-heating transformer, FT, and the ‘B’ supply transformer, PT.”

The defendant introduced the testimony of four witnesses, all persons trained in the art, and in no way related to the parties in suit, who stated that upon the knowledge which they had of radio receiving sets in August, 1927, they could have constructed the patent device with the aid of this article and its accompanying diagram and photographs without further instruction or assistance.

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§ 31
35 U.S.C. § 31

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Bluebook (online)
13 F. Supp. 901, 1936 U.S. Dist. LEXIS 1553, Counsel Stack Legal Research, https://law.counselstack.com/opinion/maibohm-v-r-c-a-victor-co-mdd-1936.