General Radio Co. v. Allen B. Du Mont Laboratories, Inc.

38 F. Supp. 495, 49 U.S.P.Q. (BNA) 300, 1941 U.S. Dist. LEXIS 3502

• Court: District Court, D. Delaware
• Decided: April 11, 1941
• Docket: No. 1214
• Status: Published

Opinion

NIELDS, District Judge,

This is a patent infringement suit. General Radio Company, a corporation of Massachusetts, charges Allen B. DuMont Laboratories, Inc., a corporation of Delaware, with infringement of Bedell Reissue Patient No. 20,945 covering a “Device for Indicating Oscillograph Curves as Stationary”.

The original Bedell Patent No. 1,707,594 was granted April 2, 1929, and was purchased by plaintiff from Frederick Bedell, the patentee, May 29, 1934. The reissue was granted December 13, 1938, on application filed August 18, 1937. November 20, 1939, plaintiff, as assignee, disclaimed claims 1, 2, 3 and 5 of the reissue patent.

Allen B. DuMont, defendant’s predecessor, was a licensee under the original Bedell patent. Thereafter plaintiff brought suit. Application for reissue was filed and was granted with 13 claims. After the grant of the reissue, defendant continued to manufacture and sell its apparatus and was notified of infringement. The pleadings were amended to allege infringement of the claims of the reissue patent. Legg patent No. 1,763,242 was pleaded in anticipation. In view thereof, plaintiff disclaimed claims 1,2, 3 and 5 of the reissue.

An “oscillograph” is a device for picturing the characteristics of electric currents and voltages. Electrical engineers are interested in learning how quickly electric currents vary and how much. The usefulness of the current or voltage for the job at hand depends upon these characteristics. The engineer’s task is to create devices to give to the current the desired characteristics. The oscillograph creates a graph which pictures the characteristics of the current.

At very frequent intervals the engineer is advised as to- the magnitude or the strength of the current. The magnitude is recorded by dots corresponding to the magnitude of the electric quantity at each interval of time. Each dot is placed above a base line and the dots are connected by a line which will show the magnitude of electric current at any instant. The shape of this line or current will be smooth or irregular. Its shape is called the “wave form” of the electric quantity.

The curve in the oscillograph is made by a spot of light which is moved sideways equal distances with equal intervals of time and is moved vertically a distance proportional to the magnitude o.f the electric current at that instant. The spot of light as it sweeps across the face of the tube appears to be a line. This is due to the persistence of human visio'n and in the cathode ray oscillograph is due to the fact that the screen continues to glow after the spot moves on. If the spot traces the same path over and over the line appears brighter. If the variations occur again and again with regularity they are said to have a frequency. If the sweep circuit, which sweeps the spot of light sideways, sweeps it again and again, it has a particular frequency of repetition. If the frequency of the sweep circuit is made the same as the frequency of the periodic quantity under, observation the spot will retrace the same path over and over again. The sweep circuit is then synchronized to the periodic electric quantity under observation. This has always been a necessity in oscillographs not merely to make the graph brighter but to make the image stand still. If the graph is formed in a new place each time it would appear to move or drift. Various ways have been devised for insuring this synchronism so that the image will stand still. Bedell’s invention is concerned with insuring such synchronism in a cathode ray oscillograph using a gas-discharge tube oscillator.

A cathode ray oscillograph uses rays from a cathode to produce the spot of light. These rays are produced in a glass tube having various parts. The rays are composed of electrons. These electrons create a tiny spot of light when they impinge on the screen. They are very light in weight and can change direction of motion very quickly as they have practically no inertia. Also they are charged with a negative charge so that any other negative charge repells them and any positive charge attracts them. This control of motion is accomplished in the cathode ray tube by plates within the tube, one of which is made negative and the other positive, with the result that the electron rays in passing between the plates are deflected toward the positive plate. One pair of plates are called the horizontal deflecting plates; another pair are called the vertical deflecting plates.

If the vertical deflecting plates are appropriately connected to the periodic quantity which is to be studied, the spot of light produced on the screen of the tube will move farther and farther in a vertical direction. Thus there is a mechanism whereby the spot of light takes a vertical position on the screen corresponding at any instant to the magnitude of the periodic voltage under study.

In order to get a graph the spot must move sideways in proportion to time, while the spot is moving vertically in proportion to the varying magnitude of the voltage being studied. This sideways motion is accomplished by connecting to the horizontal plates a gas-discharge tube oscillator. This oscillator builds up a positive potential and then suddenly drops to low value and starts building up again. Being connected with the horizontal plates it gradually makes one of the horizontal plates more positive and the other more negative. Thus it gradually deflects the electron beam and in turn gradually sweeps the spot of light horizontally across the screen of the tube, then suddenly allows it to jump back" to the starting point to begin sweeping to the right again. This whole circuit is usually referred to as the “sweep circuit”.

The gas-discharge oscillator consists of a condenser, a resistance, a battery and a gas-discharge tube. The battery builds up a voltage across the condenser which acts as a reservoir. The resistance keeps it from building up too quickly. The actual speed with which it builds up can be regulated by making the resistance greater or less, also by making the voltage of the battery more or less. The gas-discharge tube remains inert while the voltage is building up. When the condenser has built up a voltage where the gas in the discharge tube begins to conduct current, the gas-discharge tube discharges and current goes through it in a rush from the condenser, thus discharging the condenser. This is accomplished suddenly and when it is accomplished the tube becomes inert again and the condenser begins to charge up again. Such charge is fed to it from the battery through the resistance. A gradual build up and discharge is repeated, and the voltage charge accompanying-it is used to sweep the spot horizontally across the screen of the cathode'ray tube. The frequency at which the gas-discharge tube oscillator oscillates can be controlled by adjusting the amount of resistance, or the battery voltage, or the size of the condenser.

With (1) a cathode ray tube, (2) a timebase oscillator connected to the horizontal plates, and (3) a means for connecting the voltage under observation to the vertical plates of the tube, we have a complete system for making a graph which will show the magnitude at any instant of the periodic voltage which is to be studied. If the graph is always to appear in one place the spot of light must traverse the same path as it moves across the face of the tube, and this means that the relationship between the frequency at which the spot is moved up and down and the frequency with which it is moved, again and again, across the screen, will have to remain exactly the same throughout the study of a particular periodic quantity. This means that the frequency of the gas-discharge oscillator must be synchronized with the frequency of the periodic quantity under study. Expressed differently, the frequency of the gas-discharge oscillator must be stabilized so that it can not vary from exact synchronism.

The adjustable controls in the gas-discharge oscillator may be readjusted if the frequency of the gas-discharge tube oscillator gets out of step with the periodic quantity under observation. Frequent manipulation of the controls is usually required to keep the graph stationary. The problem of locking the gas-discharge oscillator in step with the frequency of the periodic quantity under observation is the problem to which the Bedell invention is directed.

The cathode ray tube was used as an oscillograph as early as 1899. The periodic quantities then being studied were of low frequency. Moving the spot of light horizontally to form a time-base was done mechanically with a rotating mechanism. By 1920 the necessity for observing high radio frequencies was so great that time-base oscillators came into use for supplying the sweep voltage necessary to move the spot of light horizontally. In 1923 Slipping proposed that a gas-discharge tube oscillator be used to provide the sweep voltage because it was made to operate at high frequencies and had the characteristic of slowly building up the voltage to move the spot of light slowly to the right and then quickly dropping the voltage at which time the spot jumps back to the left.

The problem of stabilizing such an oscillator so that, when once tuned to the frequency of the periodic quantity under study, it would stay.at that frequency and •the image would not drift, was one on which neither Kipping nor any other investigator made any suggestion. It was not until years later'that Professor Bedell of Cornell University suggested the system of the patent in suit which is a solution of the problem.

Bedell’s invention consists in an improvement in cathode ray oscillographs whereby the image is made to stand still. The cathode ray oscillograph traces on the screen of a cathode ray tube a graphical reproduction of variations in magnitude of periodic electric quantities such as alternating voltages. The Bedell invention permanently maintains the image stationary on the screen of- the oscillograph without need of continual adjustment of the tuning controls.

Bedell’s invention proposes to stabilize the time-base oscillator by injecting into it a small voltage diverted from the periodic quantity under observation. This small voltage would, of course, be itself periodic. Bedell utilized it to keep the time-base oscillator so it would remain in synchronism with the periodic quantity after it was tuned to synchronism.

In the Bedell patent the means for injecting this small voltage from the periodic quantity under observation into the circuit of the time-base oscillator consists of a connection by means of appropriate wires from the source of the periodic quantity through a transformer and resistances to the circuit of the gas-discharge oscillator. It is thus described: “The means for effecting this stabilization without distortion are shown in Figure 1. The primary of the transformer a' is supplied with periodically varying current from the source A that supplies the circuit under observation through the transformer a. The secondary circuit of the transformer a' is connected, as stated, to the terminals of the resistance 36 in series with the" gas-discharge lamp 35”.

Bedell realized that distortion would result if current from the periodic quantity under observation were allowed to reach the horizontal deflecting plates. He took advantage of the characteristic of the discharge tube that no current passes through it until the instant of discharge. At the instant of discharge the spot of light is rapidly jumping back to one side of the tube to begin another trace of the graph and is not in the process of forming the trace. Bedell explains this arrangement: “Even a small amount of energy, however, if allowed to affect the deflecting plates of the oscillograph would cause objectionable distortion in the resulting wave. By introducing voltage in the manner shown in Figure 1, I have been able to obviate such distortion, making use, for this purpose, of the properties of the gas-discharge lamp itself; for while the gas-discharge lamp is charging, it allows no current to flow; stabilizing current flows through the resistance 36 only and none of it gets through the gas-discharge lamp 35 so as to affect the oscillograph. Should any stabilizing current get through during the instant that the gas-discharge lamp discharges, it would be immaterial and produce no distortion, for the wave-form under observation is produced while the gas-discharge lamp 35 is charging.”

Bedell’s invention made the cathode ray oscillograph a useful and convenient tool. Without his invention it is difficult to tune the oscillator accurately enough to bring the picture momentarily to rest and even then the image drifts over the face of the tube so that the worker must give the device his constant attention to keep the picture still. With Bedell’s invention the local oscillator can be tuned so that the picture stands still and when once tuned will stay there. The invention has gone into wide use and has been employed by defendant in all oscilloscopes it has ever made except for a few special instruments where stabilization was not desired.

In a cathode ray oscillograph using a time-base oscillator, such as a gas-discharge tube oscillator, the fact that the problem of making the image stand still without constant manipulation of the tuning controls existed for a number of years; the fact that a number of leading scientists and men skilled in the art were confronted with that problem between 1920 and 1926 and failed to solve it; the fact that the means for solving it were at all times ready at hand; and the fact that the means employed by Bedell in solving it are simple and effective and have gone into wide use and are employed by defendant — all constitute evidence that what Bedell did was beyond the ordinary skill of a man skilled in the art and amounts to invention.

Defendant admits infringement of claims 4, 6, 8, 10, 11 and 13 but not of 7, 9 and 12. In defendant’s apparatus the stabilizing coupling from the periodic quantity under observation into the circuit of the timebase oscillator whereby the image is made to stand still, consists of a connection by appropriate wires from the source of the periodic quantity through a condenser and resistances to the circuit of the base discharge oscillator. This connection in defendant’s apparatus is put under control of the user by means of a knob on the front panel. It is thus apparent that defendant’s apparatus embodies the Bedell invention.

Defendant does not admit infringement of claims 7 and 12, but asserts that those claims call for the stabilizing voltage to be applied in series with the discharge path. Those claims use the words “in series with” to define the feature of injecting the stabilizing voltage so that it will have to go through the gas discharge path of the oscillator in order to get to the horizontal deflecting plates. This was Bedell’s way of injecting the stabilizing voltage to avoid distortion. In defendant’s apparatus, as in Bedell’s, the gas discharge tube is interposed as a barrier to keep stabilizing voltage off the horizontal plates or, to state it otherwise, that the stabilizing voltage can get to the horizontal deflecting plates only by going through the discharge path of the tube. It is clear from the patent that Bedell uses the term “in series with” in this sense.

The reason defendant does not admit infringement of claim 9 is that, in addition to calling for Bedell’s means for stabilizing, the claim calls for a “distributor” for repeatedly impressing several electrical quantities on the screen in such rapid succession that they can all be seen at once. Its patentability depends upon the fact that the stabilization of the images by Bedell’s invention in a cathode ray oscillograph uses a distributor to give several images simultaneously. This is a particularly valuable embodiment of Bedell’s invention.

Defendant asserts that the invention was anticipated by Hull in his article entitled “The Cathode-Ray Oscillograph and its Application in Radio Work”; by Kipping U. S. Patent No. 1,592,274 granted in 1926; and by Rudenberg German Patent No. 429,926 granted in 1924.

In September, 1920, Hull, a physicist in the United States Bureau of Standards, read a paper before the Institute of Radio Engineers on the use of oscillographs. He mentioned that when an oscillograph is used for tracing wave forms of high frequency current or voltage and a time-base oscillator is used so that quantities of such high frequencies may be observed, the “synchronization of the time deflection with the current or voltage deflection is frequently a difficult matter”, thus recognizing the necessity for making the image stand still and the difficulty of accomplishing it. He says nothing about how to secure synchronization other than by tuning the time-base oscillator. He makes no suggestion that a coupling can be used in securing stabilization of a time-base oscillator. His only suggestion relating to coupling is that it should be avoided.

In 1923 Kipping introduced a gas-discharge tube oscillator into the cathode ray oscillograph in order to provide sweep operation at high frequencies. He recognized the problem of synchronizing the gas-discharge tube oscillator and provided three manual tuning controls consisting of coarse and fine adjustments of the condenser as well as adjustment of the resistance in the oscillator circuit. He recognized that a variation in the power supply voltage would change the frequency of the oscillator even with these three adjustments. Therefore he provided a voltage regulator to reduce this effect. This arrangement made it possible for Kipping to obtain clear images of wave forms by adjustment of the tuning controls. It was demonstrated at the trial that with such tuning controls it is possible to obtain images which temporarily remain stationary and then drift across the screen. They are clear whether stationary or slowly drifting. Slow drifting can be temporarily arrested by manual adjustment of the tuning controls. Also the pattern can be held stationary over long periods by constant attention to the tuning controls.

Neither in the Kipping patent nor in any of his four papers which discuss the timebase oscillator is'there any mention of coupling between the oscillator and the source of .the periodic voltage. There is no mention of a stabilizing effect whereby a stationary image can be secured without constant manipulation of the tuning controls. There existed the need for stabilization so that a stationary image could be secured without constant manipulation of the tuning controls. Both Hull and Kipping failed to solve this need, as did others skilled in the oscillographic art.

Rudenberg discloses an improved means for employing the cathode ray oscillograph for observing transients. Transients are different from periodic quantities in that they are of shorter duration. If they repeat they do not do so with any regularity. Rudenberg was interested in observing .transients of a thousandth of a second. The technique of observing transients is different froim the technique of observing periodic quantities. There is nothing in the Rudenberg patent to suggest that the circuit was an oscillator or that there was any problem of tuning it to the frequency of a periodic wave under observation. This patent does not suggest or teach the Bedell invention.

Before February, 1937, neither plaintiff nor Professor Bedell knew that any claims of the original patent were invalid. In February, 1937, plaintiff was advised by its counsel that certain claims were probably invalid because they defined the problem rather than Bedell’s means for solving the problem. In May, 1937, a reissue application was authorized by plaintiff, This application was diligently prepared and was filed on August 18, 1937.

Original claim 15 was not cancelled but was reissued as claim 4 of the reissue patent. Plaintiff did not retain this claim with any knowledge or belief that it was invalid. It was asserted against defendant before and after reissue. It is still so asserted.

There was no misrepresentation in connection with the application for reissue. The application papers disclose that plaintiff was assignee of the patent. Its representative attended before the examiner in the Patent Office, so that the examiner had ample opportunity to satisfy himself as to when plaintiff .learned of the invalidity of certain Claims of the patent.

Defendant has been making apparatus substantially the same as Model 164 oscillograph employing the use of the Bedell invention since prior to the application for the reissue. There is no evidence that defendant entered upon the manufacture of such apparatus relying on any failure of the original patent to be broad enough to include such apparatus. The apparatus comes within what was claim 15 of the original patent, now claim 4 of .the reissue patent. It also comes within the other claims of the reissue patent. These claims are all more restricted than claims which were can-celled from the original patent by the reissue.

The Bedell reissue patent No. 20,-945 is good and valid as to all claims thereof, namely, claims 4,,6, 7, 8, 9, 10, 11, 12 and 13, and each of those claims has been infringed by defendant.

There was no unreasonable delay in applying for the reissue. There was no necessity for disclaiming claim 15 of the original patent, now claim 4 of the reissue. There was no misrepresentation to the patent office in connection with the reissue. The reissue patent does not claim more than the original patent.

Plaintiff is entitled to an injunction and accounting.

This opinion contains .a statement of the essential facts and of the law applicable thereto in conformity with Rule 52 of the Rules of Civil Procedure, 28 U.S.C. A. following section 723c.