AUGUSTUS N. HAND, Circuit Judge.
This is a suit for infringement of U. S. Reissue Process Patent No. 14,816 for a method of regulating or controlling the efficiency of mercury vapor rectifiers, and U. S. Patent No. 1,666,516 for a structure adapted to afford practical regulation and control of such rectifiers. Claims Nos. 4 and 5 of the first patent, and Claims Nos. 17 and 27 of the second patent are relied on.
A mercury arc rectifier to convert alternating current into direct current consists of a cathode (mercury) and a number of anodes located in an evacuated chamber, which may be either of glass or of steel. The conversion from alternating to direct current is accomplished by the valve action of the mercury arc in vacuum, which permits current to flow through the rectifier in only one direction.
The treatise by Marti & Winograd on mercury arc power rectifiers (McGraw Hill Book Co., Inc., 1930) describes their theoretical principles and physical properties and we shall adopt portions of the text found in Chapter II. It tells us that according to the generally accepted theory of matter an atom consists of a positively charged nucleus around which revolve one or more negatively charged electrons. At a high temperature, or under the influence of an electric'field, the force of attraction between the electrons and positive nucleus may be overcome. The ease with which electrons may be dissociated from atoms depends upon the structure of the atom, the pressure, the temperature and the strength of the electric field. An atom from which an electron has been dislodged has an excess of positive charge and is called a positive ion. An atom which has acquired an extra electron has an excess of negative charge and is called a negative ion. The process in which electrons are dissociated from atoms is called ionization and the atoms are said to be ionized. When subjected to the influence of an electric field such as that existing between two electrodes having a difference of potential the free electrons travel along the lines of force of the electric field toward the positive electrode, that is, toward the electrode which [385]*385is at the higher potential. The motion and behavior of the electrons in the electric field are influenced by the voltage gradient of the field, the gas or vapor pressure in their path, and the presence of positively or negatively charged particles. The higher the voltage gradient the greater is the force accelerating the electrons and therefore the higher is their speed. The pressure of a gas or a vapor is due to the density of its molecules and their motion. At higher pressure the number or motion of the molecules is greater which increases the resistance in the path of the electrons on account of more frequent collision and thus reduces their speed. The presence of negatively charged particles, such as electrons, in the space between the electrodes produces a negative space charge which exerts a repelling influence on the stream of electrons and modifies the influence of the field. Similarly, the presence of positively charged particles produces a positive space charge which exerts a force of attraction on the electrons and may compensate for the negative space charge. If an electron, while moving at high speed, collides with a neutral atom of gas or vapor it may liberate an electron by the impact of collision. The electron thus liberated also moves along the lines of force of the electric field toward the positive electrode and the atom from which it has been dislodged becomes a positive ion and moves toward the negative electrode. The movement of electrons toward the positive electrode and of positive ions toward the negative electrode constitutes a flow of current between the electrodes. Since the mass of an electron is much smaller than that of a positive ion (the ratio is 1/370,000 for mercury), the electrons are accelerated more rapidly and travel at higher speed than the positive ions. Practically the entire current in a rectifier is thus carried by the electrons. If the negative electrode is made to emit electrons, by raising its temperature, or by imposing a sufficiently high voltage gradient at its surface, these electrons, together with any electrons liberated as a result of ionization of the gas by collision, will travel toward the positive electrode and thus produce a current flow provided the voltage between the electrodes is sufficiently high. If the voltage becomes zero or is reversed, the movement of electrons and consequently the flow of current ceases. Such an electronic current conduction between two electrodes, one of which is made to emit electrons, has the characteristics of a current valve, since current can flow only when the electron-emitting electrode is at a lower potential than the other electrode.
Every rectifier requires the following necessary parts: A highly evacuated vessel, an electron-emitting cathode, a non-electron-emitting anode, air tight and insulated conductors for the current to the anode and cathode, and an ignition arrangement. If mercury is used as the cathode, a number of advantages accrue. The electrons of the mercury atoms are loosely held by the positive charge, so that a lower temperature and a lower voltage are required to emit electrons than would be the case if another metal was used for the cathode. Mercury vaporized from the cathode offers the means for the production of electrons by collision. Furthermore, the mercury vapor which is not ionized condenses and returns to the cathode, so that the cathode is continually and automatically renovated. The passage of current in a mercury arc rectifier results in a voltage drop. The voltage drop is composed of three portions: The drop at the surface of the cathode, the drop in the arc proper, and the drop at the surface of the anode.
The voltage drop at the cathode represents energy which is consumed in liberating electrons, in evaporating mercury, in heat conducted to the cathode container and in radiation. The voltage drop in the arc represents energy consumed in ionization of mercury vapor by collision. The arc drop has been found to increase with an increase in gas or vapor pressure. The voltage drop at the surface of the anode represents energy used in overcoming the field of electrons crowding around the anode and in collision with the anode surface which energy is converted into heat.
In the specification of Reissue Patent No. 14,816, the patentee states that: “It is the object of my invention to reduce the resistance of a mercury vapor rectifier to the best possible minimum by selecting a particular vapor pressure on which to operate.”
The claims in issue read as follows:
“4..The method of controlling the efficiency of vapor rectifiers receiving alternating currents, which consists in increasing or decreasing the pressure or density of the vapor for the particular current or load being employed, to reduce resistance in the rectifier to a minimum and regulate the watts consumed with said current and load.
[386]*386“5. The method of controlling the rectified current of vapor rectifiers, which consists in delivering an alternating current flow to the rectifier and varying its anode current by increasing or decreasing the pressure or density of the vapor, thereby varying the watts consumed in the rectifier.”
Mercury rectifiers to convert an alternating current into a direct current were known long before the date of the complainant’s inventions.
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AUGUSTUS N. HAND, Circuit Judge.
This is a suit for infringement of U. S. Reissue Process Patent No. 14,816 for a method of regulating or controlling the efficiency of mercury vapor rectifiers, and U. S. Patent No. 1,666,516 for a structure adapted to afford practical regulation and control of such rectifiers. Claims Nos. 4 and 5 of the first patent, and Claims Nos. 17 and 27 of the second patent are relied on.
A mercury arc rectifier to convert alternating current into direct current consists of a cathode (mercury) and a number of anodes located in an evacuated chamber, which may be either of glass or of steel. The conversion from alternating to direct current is accomplished by the valve action of the mercury arc in vacuum, which permits current to flow through the rectifier in only one direction.
The treatise by Marti & Winograd on mercury arc power rectifiers (McGraw Hill Book Co., Inc., 1930) describes their theoretical principles and physical properties and we shall adopt portions of the text found in Chapter II. It tells us that according to the generally accepted theory of matter an atom consists of a positively charged nucleus around which revolve one or more negatively charged electrons. At a high temperature, or under the influence of an electric'field, the force of attraction between the electrons and positive nucleus may be overcome. The ease with which electrons may be dissociated from atoms depends upon the structure of the atom, the pressure, the temperature and the strength of the electric field. An atom from which an electron has been dislodged has an excess of positive charge and is called a positive ion. An atom which has acquired an extra electron has an excess of negative charge and is called a negative ion. The process in which electrons are dissociated from atoms is called ionization and the atoms are said to be ionized. When subjected to the influence of an electric field such as that existing between two electrodes having a difference of potential the free electrons travel along the lines of force of the electric field toward the positive electrode, that is, toward the electrode which [385]*385is at the higher potential. The motion and behavior of the electrons in the electric field are influenced by the voltage gradient of the field, the gas or vapor pressure in their path, and the presence of positively or negatively charged particles. The higher the voltage gradient the greater is the force accelerating the electrons and therefore the higher is their speed. The pressure of a gas or a vapor is due to the density of its molecules and their motion. At higher pressure the number or motion of the molecules is greater which increases the resistance in the path of the electrons on account of more frequent collision and thus reduces their speed. The presence of negatively charged particles, such as electrons, in the space between the electrodes produces a negative space charge which exerts a repelling influence on the stream of electrons and modifies the influence of the field. Similarly, the presence of positively charged particles produces a positive space charge which exerts a force of attraction on the electrons and may compensate for the negative space charge. If an electron, while moving at high speed, collides with a neutral atom of gas or vapor it may liberate an electron by the impact of collision. The electron thus liberated also moves along the lines of force of the electric field toward the positive electrode and the atom from which it has been dislodged becomes a positive ion and moves toward the negative electrode. The movement of electrons toward the positive electrode and of positive ions toward the negative electrode constitutes a flow of current between the electrodes. Since the mass of an electron is much smaller than that of a positive ion (the ratio is 1/370,000 for mercury), the electrons are accelerated more rapidly and travel at higher speed than the positive ions. Practically the entire current in a rectifier is thus carried by the electrons. If the negative electrode is made to emit electrons, by raising its temperature, or by imposing a sufficiently high voltage gradient at its surface, these electrons, together with any electrons liberated as a result of ionization of the gas by collision, will travel toward the positive electrode and thus produce a current flow provided the voltage between the electrodes is sufficiently high. If the voltage becomes zero or is reversed, the movement of electrons and consequently the flow of current ceases. Such an electronic current conduction between two electrodes, one of which is made to emit electrons, has the characteristics of a current valve, since current can flow only when the electron-emitting electrode is at a lower potential than the other electrode.
Every rectifier requires the following necessary parts: A highly evacuated vessel, an electron-emitting cathode, a non-electron-emitting anode, air tight and insulated conductors for the current to the anode and cathode, and an ignition arrangement. If mercury is used as the cathode, a number of advantages accrue. The electrons of the mercury atoms are loosely held by the positive charge, so that a lower temperature and a lower voltage are required to emit electrons than would be the case if another metal was used for the cathode. Mercury vaporized from the cathode offers the means for the production of electrons by collision. Furthermore, the mercury vapor which is not ionized condenses and returns to the cathode, so that the cathode is continually and automatically renovated. The passage of current in a mercury arc rectifier results in a voltage drop. The voltage drop is composed of three portions: The drop at the surface of the cathode, the drop in the arc proper, and the drop at the surface of the anode.
The voltage drop at the cathode represents energy which is consumed in liberating electrons, in evaporating mercury, in heat conducted to the cathode container and in radiation. The voltage drop in the arc represents energy consumed in ionization of mercury vapor by collision. The arc drop has been found to increase with an increase in gas or vapor pressure. The voltage drop at the surface of the anode represents energy used in overcoming the field of electrons crowding around the anode and in collision with the anode surface which energy is converted into heat.
In the specification of Reissue Patent No. 14,816, the patentee states that: “It is the object of my invention to reduce the resistance of a mercury vapor rectifier to the best possible minimum by selecting a particular vapor pressure on which to operate.”
The claims in issue read as follows:
“4..The method of controlling the efficiency of vapor rectifiers receiving alternating currents, which consists in increasing or decreasing the pressure or density of the vapor for the particular current or load being employed, to reduce resistance in the rectifier to a minimum and regulate the watts consumed with said current and load.
[386]*386“5. The method of controlling the rectified current of vapor rectifiers, which consists in delivering an alternating current flow to the rectifier and varying its anode current by increasing or decreasing the pressure or density of the vapor, thereby varying the watts consumed in the rectifier.”
Mercury rectifiers to convert an alternating current into a direct current were known long before the date of the complainant’s inventions. Reducing the resistance in the tube by selecting a particular vapor pressure with which to operate was recognized as a means of insuring continuous operation and avoiding flash backs or short circuits. It gave stability to the arc and a dependable operation to the rectifier. The optimum pressure was obtained by pumping out occluded gases and cooling the appliance by water jackets.
Before large capacity rectifiers were developed the voltage drop of a rectifier was considered practically constant over the whole load range. This was because of the relatively slight variation of the drop in small capacity rectifiers. In large capacity rectifiers the voltage drop was not constant but reached a point where it became important to save the expense due to the consequent loss of energy. It is the complainant’s contention that he was the first to discover that the pressure of the gas and vapor in the rectifier could be regulated so as to obtain the least voltage drop.
In a paper presented by Percy. H. Thomas at the 23rd. Annual Convention of the American Institute of Engineers held at Milwaukee May 28-31, 1906, which dealt with mercury vapor rectifiers, he stated, at page 531, that: “Current passing through the vacuum space in the mercury vapor apparatus experiences a loss of voltage, the numerical value of which tends to remain constant independent of the current strength, except with small currents; * * # »
He stated at subdivision 1, p. 532: “The voltage loss in the vapor increases with increase of vapor pressure, and more or less closely in proportion to this pressure; consequently, since the mercury vápor is saturated and its pressure depends directly upon the temperature of the mercury electrode, the vapor voltage loss is more or less proportional also to the temperature of the mercury electrode or electrodes.” •
At subdivision 5 (on the same page) the author, however, remarked: “The voltage loss is nearly independent of the current strength, but varies slightly in a direction opposite to the current. * * * ”
It may be argued that the first and last statements we have quoted are inconsistent with those in subdivision 1, supra. We think, however, that the references to the voltage drop as constant meant only that it was constant in the small rectifiers of the type then in use. The larger rectifiers had not been developed as early as 1906, when Thomas wrote his article, and no attempt had then been made to deal with the problem of minimizing the loss arising from a voltage drop. But though saving of that loss was not sought and was not important in small rectifiers, when it became important because it was a serious factor in larger rectifiers, the means to lessen it were at hand. It was known to vary with vapor pressure and any one who wished to lessen it might regulate the pressure in standard ways with which those engaged in constructing mercury rectifiers were already familiar. Methods of controlling pressure are shown in British Patent No. 14,171, A. D.1903, where a mercury rectifier was disclosed having a pump for removing occluded gasses and refrigerating coils for cooling the mercury. The patentee said, at page 6, line 25:
“The object of the present invention is to provide a means for keeping a gas or mercury vapour apparatus cool and maintaining the proper purity and density of the gas or vapour within the container chamber and better adapt it to transmit currents of large quantity. In carrying out the invention there is provided a means for withdrawing the gases or vapours from the container by means either of a mercury circulation or by means of an air pump directly connected with the container. Any occluded gases or vapours will, therefore, be withdrawn and the purity of the mercury vapour within 'the chamber will be maintained. * * *
“During the process of circulation, the mercury may be cooled by artificial means, as by one or more refrigerating coils placed at a proper point or points in the cycle; or the cooling effect may be obtained by causing the mercury to enter or re-enter the chamber in the form of spray. These two means may, if desired, be combined, or other cooling devices may be employed.” .
U. S. Patent to Hewitt No. 1,163,664 also disclosed a similar method of removing gases and cooling the rectifier.
[387]*387Whenever it might become desirable to limit voltage loss caused by the pressure of vapors and the heating of the tube it was not difficult to apply the means at hand to remove the gases and cool the apparatus. Tschudy did no more than to apply such means. His contribution to the art cannot be said to have involved skill amounting to invention. He merely used old means to limit the losses occurring in larger rectifiers if pressure was not regulated.
Claims 17 and 27 of U. S. Patent No. 1,666,516 for a vapor rectifier adapted for the method disclosed in U. S. Reissue Patent No. 14,816 certainly cannot sustain complainant’s infringement suit.
Claim 17 sets forth as one element “a tube centrally disposed between said anodes for conducting condensed vapor from said condensing portion to the lower portion of said rectifying chamber and shielding it from the arc.” The defendant’s rectifiers appear to contain no such element, but if Claim 17 be read broadly enough to be infringed by defendant’s apparatus, then the claim would be anticipated by the construction exhibited in the German article in Elektrotechnische Zeitschrift of February 15, 1917 (Book 7, pp. 89-91), which shows shields identical with those in the rectifier defendant is stipulated to have used.
Claim 27 is for a rectifier “including a vapor chamber, a water jacket, means for varying the temperature of said water and a thermostat for controlling said last mentioned means”. In view of the cooling apparatus described in U. S. Patent No. 1,-259,371 to Davis; in British Patent No. 15,076 (A.D. 1914), and in defendant’s Exhibit 7, we can see no invention in Claim 27.
Decree affirmed.