General Electric Co. v. De Forest Radio Co.

• Decision Date: 11 November 1930
• Docket Number: No. 3799-3801.,3799-3801.
• Citation: 44 F.2d 931
• Parties: GENERAL ELECTRIC CO. v. DE FOREST RADIO CO. (two cases). DE FOREST RADIO CO. v. GENERAL ELECTRIC CO.
• Court: U.S. Court of Appeals — Third Circuit

44 F.2d 931 (1930)

GENERAL ELECTRIC CO. v. DE FOREST RADIO CO. (two cases).

DE FOREST RADIO CO. v. GENERAL ELECTRIC CO.

Nos. 3799-3801.

Circuit Court of Appeals, Third Circuit.

November 11, 1930.

Howson & Howson, of New York City, and William G. Mahaffy, of Wilmington, Del. (Ralph B. Evans, of Philadelphia, Pa., Hubert Howson, of New York City, and Albert G. Davis and Charles McClair, both of Schenectady, N. Y., of counsel), for appellant.

Ward Gray, & Ward, of Wilmington, Del. (Thomas G. Haight, of Jersey City, N. J., and Samuel E. Darby, Jr., Carl A. Richmond, and William R. Ballard, all of New York City, of counsel), for appellee.

Before BUFFINGTON, WOOLLEY and DAVIS, Circuit Judges.

BUFFINGTON, Circuit Judge.

In the court below the General Electric Company charged the De Forest Radio Company with the infringement of four patents. On final hearing that court held one of the patents valid and infringed and the other three invalid. By appropriate steps its so holding was brought before this court for review. Without entering into detail, we may say that, save as to patent No. 1,558,436, the reasoning, conclusion, and decree of the court below commend themselves to us, and we affirm the same. In the case of patent No. 1,558,436, we feel the court below committed error in holding the patent invalid and dismissing the bill.

As usual in litigation over a patent of great commercial value, the vast mass of expert speculation, the protracted argument covering days, and with briefs that in the aggregate covered several hundred pages, the case, on reargument, narrowed to the simple question of the patent paternity of what is known commercially as the Langmuir tube. The court below held the tube had no patent paternity, and to that question we now address ourselves. The subject-matter of the patent and the general features of the pertinent art are set forth at length in the comprehensive opinion of the judge below, and by reference thereto we avoid the necessity of present restatement.

Laying aside for the present technical language and scientific discussion, and confining ourselves to simple statement, the Langmuir tube is a tube in which, for example, the gaseous conductor incident to a Fleming valve and a De Forest audion is dispensed with and a vacuum substituted therefor.

In the patent sued on, No. 1,558,436, granted October 20, 1925, to Irving Langmuir, assignor to the General Electric Company for "electrical discharge apparatus and process of preparing and using the same," the specification states:

"The present invention relates to electrical vacuum discharge devices, and it comprises devices in which the electrical current is carried by negative charges called electrons, emanating from the cathode, independently of gaseous ionization such as occurring, for example, in the ordinary Roentgen tube.

"My present invention comprises improvements in electron-discharge apparatus which make possible a high load capacity and operation with the highest voltages, but the invention is also applicable and useful for moderate loads and moderate voltages."

Existing objectionable incidents to the use of gassy tubes and the erratic, nondeterminable action of gas are pointed out as follows:

"In order to distinguish electron discharge devices made in accordance with my invention from the prior art, I will explain briefly the character of a pure electron discharge as distinguished from a discharge through ionized gas. In a Geissler tube, and in a Roentgen or Crookes tube the conduction of current is accompanied by and depends upon gas ionization. Without a certain minimum amount of gas a Roentgen X-ray tube ceases to operate and as this minimum is approached the resistance of the tube steadily increases.

"The passage of an electric current across a tube ordinarily involves the movement of negative charges called electrons which, under the influence of the impressed voltage, pass from the cathode to the anode through the vacuous space. If these electrons when moving above a certain velocity collide with gas molecules they tend to ionize the molecules, splitting them up into electrons and larger and more slowly moving ions. Under these circumstances the phenomena of conduction across the tubes are the result of the action and interaction of the electrons and the ions; these phenomena are in general erratic and non-reproducible. The cathode under these conditions is disintegrated, technically it is `sputtered,' which causes its rapid destruction. As gas ionization continues at higher voltages a blue glow may appear. The bombardment of the cathode by positive ions also causes heating of the cathode. The ionization of gases at low pressures by collision with electrons occurs at definitely determinable voltages, these voltages being known as the ionization voltages. These voltages are different for different gases. In the case of gases such as nitrogen, hydrogen, oxygen, argon, helium and neon, they are of the order of magnitude of fifteen to twenty-five volts."

Describing the De Forest audion, and differentiating it from the alleged invention of the patent, the specification says:

"The phenomena above described as being characteristic of devices involving gas ionization are taken advantage of in an incandescent cathode device with three electrodes known as the `Audion.' This device has been used as a receiver for radio-telegraphy and depends in its operation upon the rapid change of the discharge current when gas ionization begins. This point depends upon various accidental conditions which cause such irregularities in the operation of various devices apparently identical that sometimes only one of a considerable number can be used. Ordinarily the gas ionization in the audion begins to be important somewhere between 20 and 30 volts."

Describing the Fleming valve and its limitations, the specification states:

"Another discharge device previously used to some extent was the Fleming valve. This was a two-electrode tube which, so far as I am aware, was always used at voltages well below the voltages at which positive ionization by collision occurs. It was not evacuated in such a manner as to permit it to be used at voltages materially above these ionization voltages without manifesting substantial positive ionization effects."

Referring to high voltage, the specification makes this statement:

"No prior hot cathode devices are known to me operating with currents as great as above 5 milliamperes with voltages as high as about 200 volts; indeed no prior discharge devices are known to me operating in a practically usable manner and without substantial positive ionization effects with currents as great as about one-tenth of a milliampere with voltages as high as about forty volts."

Specifying some of the differences and advantages of the alleged invention, the specification states:

"In devices made in accordance with my invention gas ionization is either entirely absent or is negligible and a discharge takes place which is distinct in its characteristics from the described discharge taking place in an ionized gas. The cathode is not heated by the discharge itself. Blue glow glass fluorescence and in fact all readily visible indications of a discharge are ordinarily absent."

Referring to the evacuation of the tube, the specification sets forth:

"For the evacuation of the device the glass walls of the tube are carefully heated to as high a temperature as the glass will stand without softening and in general the most approved methods of incandescent lamp exhaust are used. The evacuation of the tube preferably while still heated is carried out by means of a suitable evacuating means, for example, a Gaede molecular pump, which removes vapors as well as gases. * * *

"The evacuation of the device should be preferably carried to a pressure as low as a few hundredths of a micron, or even lower, but no definite limits can be assigned. * * *

"It is also true that when the anode has been carefully freed from gas, residual free gas, even if present in a sufficient amount to cause some gas ionization when the apparatus is first started, does little harm, as it is quickly removed by the gas clean-up effect when the device is operated."

Claim 12, which is, "An electrical discharge device, comprising a gas-tight-envelope, an electronemitting cathode, an anode deprived of ionizable gas and a discharge controlling conductor, the space in the envelope being evacuated to a pressure not substantially in excess of a few hundred thousandths of a millimeter of mercury, said device being characterized by the fact that when operated below saturation and materially above the ionization voltages, the current is controlled by space charge substantially unaffected by positive ionization," is typical in character of the alleged invention.

Does the defendant use a tube answering this general description? We think it does, and that in giving up the old gaseous tube and using one of the "very high vacuum," a change which it announced in its statements to the public, we have a virtual admission of the essential difference between the two tubes. The tube of this disclosure is aptly described as "non gaseous" and "of a very high vacuum" by the defendant when putting it on the market, as follows:

"The tube consists of a highly evacuated vessel, cylindrical, rather than bulbular, in shape enclosing the three elements, grid, plate and filament in the form of the old type T tubular DeForest tube with which amateurs are familiar. The plate is of nickel, cylindrical in shape and surrounds a helical grid also of nickel. The filament is a crimped tungsten wire passing through the center of the grid exactly as it did in the old style type DeForest tube. The chief difference between this tube and the type T tube of similar mechanical construction is in its evacuation. The old style type T was an ionic or gaseous tube very unstable in operation and requiring...