23 F.2d 698 (D.Del. 1928), 589, General Electric Co. v. De Forest Radio Co.

Docket Nº:589, 598.
Citation:23 F.2d 698
Case Date:January 03, 1928
Court:United States District Courts, 3th Circuit, District of Delaware

Page 698

23 F.2d 698 (D.Del. 1928)



DE FOREST RADIO CO. (two cases).

Nos. 589, 598.

United States District Court, D. Delaware.

January 3, 1928

Page 699

Albert G. Davis, of Schenectady, N.Y., Hubert Howson, of New York City, and William G. Mahaffy, of Wilmington, Del., for plaintiff.

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

MORRIS, District Judge.

These two suits, of General Electric Company against De Forest Radio Company, were tried together. In the first suit all the claims of patent No. 1,558,436, granted to Irving Langmuir, assignor to the plaintiff, October 20, 1925, for 'electrical discharge apparatus and process of preparing and using the same, ' upon an application filed October 16, 1913, and renewed March 14, 1916, are in issue. It is known as the high-vacuum tube patent. Infringement is conceded, if the claims are valid. Validity is denied for want of invention and novelty, and because of prior knowledge and use, for double patenting, and upon the ground that Harold D. Arnold, not Langmuir, was the first inventor.

The specification, claims, and testimony are so interwoven with scientific theories, more or less abstruse, that it is somewhat difficult to isolate and keep separate from the principles of physics involved Langmuir's conception and idea of means. Yet an analysis of the Langmuir device and its elements discloses that, apart from its functioning and results, it is nothing more nor less than a Fleming valve or De Forest audion, for example, in which a higher vacuum, maintainable during operation, exists. How much higher the vacuum must be to bring the tube within the patent is not definitely fixed in terms of pressure. The specification states merely that '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. ' A micron is a pressure equal to a millionth of a meter, or a thousandth of a millimeter, of mercury. It corresponds to a barometer reading of that value. The normal barometer reading in the open air is about 760 millimeters.

The justification for the failure to assign definite pressure limits is that the invention 'comprises devices in which the electrical current is carried by negative charges called electrons, emanating from the cathode, independently of gaseous ionization'-- a device in which the residual gases play no part in the operation. The results desired to be obtained are stability and reproducibility of operation and increase of power. The production of these results by the specified manner of functioning is dependent, not on the degree of vacuum alone, but upon four coordinating variables-- geometry or relation of parts of the tube, temperature of cathode, voltage of anode, and degree of vacuum. This fact makes it apparently unavoidable that the claims be functional in form. But they must, of course, be construed to cover the thing. Walker on Patents, Sec. 183.

Claim 26 is comparatively simple. It is:

'A discharge device comprising a sealed-off envelope and electrodes therein, the envelope being shaped and the electrodes located so that the energy of the discharge is delivered mainly upon one or more of the electrodes, the inner wall of the envelope and electrodes being so free from occluded gas and the pressure in the tube being sufficiently low, with respect to the spacing of the electrodes and the energy of the discharge, so that the device is capable of passing a sustained discharge of one-tenth of a milliampere at forty volts, without developing any substantial positive ionization effects.'

The Fleming and De Forest tubes are 'discharge devices comprising a sealed-off envelope and electrodes therein, the envelope being shaped and the electrodes located so that the energy of the discharge is delivered mainly upon one or more of the electrodes. ' The next clause of the claim-- 'the inner wall of the envelope and electrodes being so free from occluded gas and the pressure in the tube being sufficiently low, with respect to the spacing of the electrodes and the energy of the discharge'-- has to do with the manner and degree of evacuation. Underlying this clause are these facts:

The glass wall and the electrodes harbor large volumes of occluded gases. Heat is necessary to expel these gases, so they may be removed by the pump. If not removed before the tube is sealed off, the heat occurring during the operation of the tube expels them, destroying in large degree the vacuum. 'The spacing of the electrodes'-- one illustration of the geometry of the tube-- is a factor, because the permissible gas pressure in the tube increases with the proximity of the electrodes to each other. This varying relation is due to the fact that the opportunity

Page 700

for the electrons to collide with gas molecules varies with the length of the path the electrons have to travel.

'The energy of the discharge' may be interpreted in terms of power, which is the product of the current values and the voltage. The unit of current flow is the ampere, or the current which flows at a pressure of one volt through a closed circuit having a resistance of one ohm. The power of a circuit having a pressure of one volt and a current of one ampere is one watt. The power output of the device of claim 26 is .004 of a watt, or 4 milliwatts. An increase of energy means an increase in the number and velocity of the electrons passing from cathode to anode, and consequently an increase in the number and effect of collisions of electrons with gas molecules. It follows, of course, that, if the maximum voltage at which a given tube will function without ionization is increased, ionization will occur and the tube fail to function in the manner specified in the patent.

'Ionization,' by which is meant the conversion of atoms or molecules into ions, is explained by the 'electron theory.' By this all atoms known to chemistry are deemed to be made up of a nucleus endowed with a permanent positive electrical charge, around which one or more electrons, each of which has mass or weight, and carries, or is, a natural unit of electricity, revolve at inconceivably great speeds in regular orbits in somewhat the same manner as that in which the planets of our solar system revolve about the sun. According to this hypothesis the chief difference between the chemical atoms lies in the number and arrangement of their electrons. Under normal conditions the electrons are maintained within their atoms and in their orbits by the attractive force of the positive nucleus, which, electrically, exactly balances and neutralizes the negative charge of the electrons of the atom. Consequently every atom having its normal complement of electrons exhibits no electrical effects.

If, however, by impact or otherwise, an atom loses an electron and becomes an ion, it is thrown out of electrical balance. The positively charged nucleus predominates, and exhibits a unit positive charge. In thermionic tubes, ions are created by the impact upon the gas atoms or molecules of some of the myriads of electrons constituting the current flowing from the hot cathode to the cold anode-- the Edison effect. See Westinghouse Elec. & Mfg. Co. v. De Forest Radio Tel. & Tel. Co. (C.C.A.) 21 F.2d 918. To dislodge an electron from its atom, the colliding electron must have sufficient momentum. The velocity required for this momentum is given to the electrons mainly by the pull or attractive force of the positively charged anode. The strength of the pull increases, other conditions being stable, with the anode voltage. For the gases with which we are here concerned 15 to 25 or 30 volts constitute the ionizing voltages.

When substantial numbers of atoms or molecules are being converted into positive ions by the electron stream, the 'ionization effects' forbidden by claim 26 occur. One effect of ionization is an increase in the current across the tube over the value it would have at the same voltage in the particular tube, were the vacuum sufficiently high to prevent ionization. Such increase is due to two facts:

First, the electrons, being negative charges of electricity, tend, in the absence of a countervailing force, violently to repel one another, and thus to diminish the number, and so the value of the current, passing to the anode. Positive ions in the field constitute a countervailing force, and consequently expedite the flow of the electrons to the anode. Second, the positively charged ions are drawn with great force to the cathode, the negative electrode, bombard it, and thus increase its temperature. As the electron emissivity of the cathode increases with its temperature, the ion bombardment of the cathode serves to increase the supply of electrons, and consequently the current passing to the anode. This bombardment is so severe that, if continued, it destroys the filamentary cathode.

Another effect to which substantial ionization usually gives rise is a blue glow in the tube. This, as I understand it, is accounted for upon the hypothesis that, as the electrons are shifted in the atom, by impact of the electrons, from one orbit to another, at prodigious speeds, they produce waves or vibrations in the ether, which constitute light. The ultimate effect or result of ionization is an unstable, nonreproducible, and, in a measure, noncontrollable current. As it is necessary, in order to prevent the destruction of the cathode and obtain a stable current, to operate gassy tubes below ionization, their power output-- the product of current and voltage-- was limited. These constitute obvious...

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