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THCHNIDYNE CORP. v. MCPHILBEN-KEATOR

October 6, 1932

THCHNIDYNE CORPORATION et al.
v.
McPHILBEN-KEATOR, Inc.



The opinion of the court was delivered by: GALSTON

GALSTON, District Judge.

This is a patent suit in which infringement is alleged of ten letters patent, all relating to radio receiving apparatus. The inventions described are susceptible of conjoint use.

The following are the patents involved; the first nine listed below were issued on the applications of Lester L. Jones, and the tenth on that of Charles E. Bonine:

 No. 1,673,287 granted June 12, 1928, for an electron discharge tube amplifier system, application filed June 11, 1927.

 No. 1,713,130 granted May 14, 1929, for a method of, and means for, controlling energy feed-back and electron discharge devices, application filed October 8, 1924.

 No. 713,132 granted May 14, 1929, for a radio frequency amplifying system, application filed August 21, 1925.

 Reissue No. 17,915 granted December 30, 1930, for a radio frequency amplifying system, application filed August 21, 1925.

 No. 1,732,937 granted October 22, 1929, for a transformer and coil system, application filed June 1, 1927.

 No. 1,770,525 granted July 15, 1930, for a radio receiving apparatus, application filed July 15, 1927.

 No. 1,779,881 granted October 28, 1930, for an amplifier, application filed October 5, 1929.

 No. 1,788,197 granted January 6, 1931, for radio frequency circuits, application filed October 5, 1929.

 No. 1,791,030 granted February 3, 1931, for a radio receiving system, application filed March 6, 1928.

 No. 1,696,263 granted December 25, 1928, for a radio apparatus, application filed August 12, 1922.

 The alleged infringement consists in the sale by the defendant of radio receiving sets known as the Sparton Equasonne receivers, manufactured by the Sparks-Withington Company of Jackson, Mich.

 The Jones patents all involve highly technical specifications, exceedingly lengthy, oftentimes prolix with needless repetitions, and with numerous claims. To present the issues and keep the opinion within reasonable limits invites a certain grouping of the patents involved.

 The first group, consisting of five patents, may be said to relate to means for coupling a selector to an amplifier; the second group of four patents relates to a fixed tube radio frequency amplifier; and the remaining patent, to a detector and single stage audio frequency amplifier combination. It will add to a logical consideration of these patents in their respective groups to consider them in the order of their application dates.

 The First Group.

 Jones patent No. 1,713,130. This patent relates to electron discharge tube circuits and for means controlling the feed-back from the output circuit to the input circuit due to the capacitive coupling between the grid and the plate of the tube.

 Its particular object is to suppress or eliminate oscillations arising out of such feed-back energy. It was known that such feed-back gave rise to distortion of the input voltage and to oscillations either incipient or sustained in the grid circuit.

 The inventor describes various methods that have been known to the prior art for the control of this feedback. The alleged invention consists in the discovery that the feed-back energy from the plate to the grid circuit may be controlled by suitable resistance means inserted in the plate circuit, such resistance means being associated in a predetermined manner with the characteristics and constants of the electron discharge tube. Such resistance, the inventor found, should preferably be inductance and capacity free, though such condition need not necessarily exist. The resistance should preferably be inserted in the plate circuit lumped at the plate. It is said that such a resistance has the effect of absorbing energy from the preceding input circuit at substantially the same rate, as energy is fed back from the plate to the grid circuit; and hence that the resistance is effective for neutralizing the feed-back reaction.

 Claims 3, 4, and 6 are in issue. It will suffice to consider claim 3. It reads: "3. In combination, an electron discharge tube relay having a filament, a grid and a plate, a variably tuned grid circuit, a plate circuit coupled to the grid circuit through the grid plate capacity of the tube and having a load for producing an energy feed-back through the grid-plate tube capacity, and resistance in said plate circuit for producing a predetermined energy transfer or feed forward from the input circuit to the output circuit through the medium of said coupling and the relay action of the tube for substantially equalizing or neutralizing the energy retransfer or feed-back which takes place from the output circuit to the input circuit due to the capacity coupling of the circuits."

 Means for neutralizing energy feed-back were known prior to the Jones' patent. Generally, they are shown in the Hartley patent No. 1,183,875, Rice patent No. 1,334,118, and the Hazeltine patent No. 1,489,228.

 In Dr. Miller's article in the Bureau of Standards, issue of November 21, 1919, occur the following passages:

 "It will be shown that when the load in the plate circuit is a resistance or capacity the input impedance can be represented as a positive resistance and capacity in series. Thus the tube is not a pure voltage device, but absorbs power."

 "When the load is inductive the input impedance can, in many cases, be represented as a negative resistance and capacity in series. This represents regeneration through the tube itself, and is of importance in the regenerative effects and oscillations in amplifiers."

 With the foregoing as a base, and what the art knew of resistances positioned in the plate circuit, it is hard to see how Jones effected an inventive contribution to the art.

 There was no novelty in introducing a resistance in the plate circuit, for stabilizing an amplifier. It is found, for example, in British patent to Round, No. 149,433.

 In Fig. 1, he shows a radio frequency amplifier having two tubes coupled through a transformer P' S' composed of resistance wire with an air core, which he called a resistance transformer, and arranged so that the ratio of inductance tube capacity is as great as possible.

 The curves in this patent show that the purpose of the resistance is to stop oscillations in the transformers. Round says: "By increasing the number of valves *fn1" and of transformers the magnification of the signals may be increased or until the series begins to self-heterodyne."

 It is true that no teaching is suggested with respect to a difference of the resistance in the primary and the resistance in the secondary of the transformer, but the fundamental disclosure presented is a resistance which operates in accomplishing the same result and in substantially the same way as that of Jones.

 The object of United States patent to Carlson, No. 1,613,741, was to provide an amplifier in which the tendency to oscillate is reduced to a minimum. The inventor says that in radio frequency amplifiers there is a tendency for the individual stages to oscillate locally and for the several stages to oscillate collectively. These oscillations are caused by capacity coupling between the high potential terminals of the circuit, resistance coupling in the common battery circuit, and irregular transformer output voltage characteristics.

 Carlson's invention was to use iron core transformers with primary and secondary windings upon the iron core.The disclosure certainly is of a resistance in the plate circuit for preventing local oscillations of feed-back. Carlson syas: "The primary and secondary windings 8 and 10 are constructed of high resistance wire in order of 10 to 20 times the resistance of an equivalent copper wire construction."

 It may be noted that the value of the resistance resulting from these windings would be, as Mr. Hogan points out, from 1,500 to 3,000 ohms, which is approximately the value suggested by Jones.

 An article in the Radio Digest by H. J. Marx, of January 27, 1923, is referred to by the defendant's expert to show that the writer was aware of the advantages of a resistance in the plate circuit of an amplifier for the purpose of preventing feed-back. The article contains this passage:

 "The variable resistance sometimes added in the plate circuit is used for stabilizing the various stages through which two different frequency currents are passing. * * *

 "High variable resistance such as potentiometers (400 to 1,000 ohms or even more) are inserted in series in the plate circuits of the second and third tubes."

 Jones points out that the use of resistances in the Marx article is for reflex circuits. Though it is probably true that the circuit constants in a reflex circuit and the operational characteristics of the related audio and radio frequency circuit parts are different from that of a circuit in which it is desired to neutralize the feed-back reaction which takes place through the grid-plate capacity of the tube, yet Mr. Hogan seems convincing in contending that the behavior of a radio frequency amplifier in respect to regeneration is not effected by the double use of the tubes.

 In the issue of Q.S.T. of March, 1923, appears the Phelps' article on the Invert Duplex System of Amplification. Fig. 4 shows the employment of an iron core transformer coupling. The receiving set illustrated therein was constructed as a model and offered as defendant's Exhibit F. The measurements on this model clearly indicate its operability in respect to neutralization.

 Generally, on the subject of invention, Jones was not entitled to a patent because he discovered a function in the resistance which was not pointed out in the prior art. He is not entitled to a patent for discovering a particular function of the resistance. In arranging his resistance and determining its magnitude with respect to the characteristics of the particular tube in the circuit of which it is positioned, so as to produce, as claim 3 says, "a predetermined energy transfer * * * from the input circuit to the output circuit through the medium of said coupling and the relay action of the tube," Jones as a skilled engineer took what the art taught and made certain calculations to bring about certain results. It is true that in his specifications he refers to his empirical investigations, which would suggest not the work of a mathematician, but of an experimenter. Despite that reference in the specification, I cannot avoid the conclusion that his work was mathematical rather than inventive.

 Accordingly, I hold this patent to be invalid.

 Jones reissue patent No. 17,915 is for a radio frequency amplifying system. Three groups of claims are involved: 1 and 10; 3 and 5; 7, 13, 14, 15, and 25. The main defense is invalidity.

 The inventor sought here to devise a system in which the number of cascaded radio frequency stages might be increased beyond that found practicable in the prior art.

 A further object was to produce an increased power audion amplifying system with high stability and possessing the characteristics of ease of tuning and high degree of selectivity with the use of a minimum number of control elements.

 The alleged discovery defined in the patent is that there were certain inherent limitations in tuned radio frequency systems, which can be avoided by the cascading of untuned radio frequency stages to tuned radio frequency stages, and that the reactions between the two stages may be so controlled as to produce a suitable radio frequency system having an amplifying power from ten to twenty times greater than the systems of the prior art.

 Jones proposed determining the natural frequency of the output stage with relation to the range of frequencies for which the system is to be designed, so as to prevent production of any damping reaction, and so as to produce only an oscillation-creating feed-back reaction throughout the whole wave length or frequency range for which the system is built. He selects the characteristics of the transformer for the untuned stage, so that the natural frequency of the untuned output circuit is greater than the highest frequency of the predetermined frequency range through which the tuned stage is tunable.In such a selection of the natural frequency or wave length of the untuned stage, the system will oscillate during all changes in tuning of the tuned input circuit in the absence of any feed-back neutralizing means. A definite control may then be introduced to neutralize the feed-back-creating oscillations through the whole range of frequencies which the system is capable of transmitting.

 Jones found empirically that under these conditions the reaction between the output circuit of the transition tube, such as the second radio frequency tube of Fig. 1, to the tuned input circuit, is substantially constant over the whole wave length range.

 As the second step in his invention he provides means associated with the untuned stage for neutralizing or balancing the feed-back reaction.

 Stating the matter as briefly as possible, in view of the involved specification, it would appear that the alleged invention, as shown in Fig. 1 of the drawings, consists in a plate circuit of the tube 2 R.F. having a natural wave length lower than any operating wave length so as to create an inductive reaction to all waves to which the input of 2 R.F. may be turned, and thus having a tendency to oscillate; and secondly, the amplifier is to be provided with some neutralizing means to prevent the oscillation from occurring.

 Claim 3 will serve as well as any other for the purpose of considering the prior art. It reads as follows: "3. An amplifying system comprising an electron discharge device having an input circuit and an output circuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit being untuned and embodying means for coupling the same to a subsequent circuit, the load of said untuned output circuit combined with the load reflected thereinto by the subsequently coupled circuit comprising an impedance having a natural frequency greater than the highest frequency of the whole frequency range through which the input circuit is tunable whereby feed-back reactions from the output circuit to the input circuit are produced for the whole frequency range, and means for controlling the feed-back reactions."

 The text of Dr. Miller's article in the Bureau of Standards publication heretofore referred to is relied upon to show the knowledge of the prior art, that when the plate load is inductive the input impedance can in many cases be represented as a negative resistance and capacity in series. "This represents regeneration through the tube itself, and is of importance in the regenerative effects and oscillations in amplifiers."

 It is also stated that, when the load in the plate circuit is a resistance, the input impedance can be represented as a positive resistance and capacity in series, so that the tube is not a pure voltage device but absorbs power. Mr. Hogan interprets these passages as showing that Miller had expressed exactly what the patentee in this patent asserts, that in order to get away from the transition from a capacitive output to an inductive output, it is necessary to stay on one side of the resonant point. It is the passing of that resonant point which produces the transition. Hogan said: "One may define the transition as that from capacitive to inductive output or as from damping to regeneration or as from shorter to longer wave lengths, it makes no difference."

 It was this knowledge that was used in the practical design of many types of amplifiers prior to the application for the original patent herein on August 21, 1925.

 The fact that in passing through the natural wave length or natural frequency of the circuit, the circuit changes from a capacitive to an inductive phase, was known by others.

 In Principles of Radio Communication, a publication by J. H. Morecroft, of 1921, in Fig. 70 are shown curves drawn between frequency along the resistance and reactance. The curve marked "inductance" at or about the resonant point falls to zero, and the curve marked "capacity" then begins and carries on to the right hand side of the sheet. Mr. Hogan is of opinion that this figure is illustrative at audio frequencies, power frequencies, but that the phenomena are the same as in radio frequency circuits.

 Reference is made to an article by J. Scott-Taggart, published in the Annapolis Radio Station, "The Design of Multi-Stage Vacuum Tube Receiving Circuits," December, 1919. Fig. 1 shows a three stage amplifier with a periodic auto-transformer coupling arrangement. Coils L -- 3 and L -- 4 are the plate coils of this system, and their natural wave length controls the natural wave length of the circuit. The writer says: "The inductances L -- 3 and L -- 4 should have a natural wave length less than the wave length to be received." And adds: "If the range of wave lengths to be received is wide, tappings may be taken from L -- 3 and L -- 4."

 The article in Q.S.T. of March, 1923, by Phelps has been referred to. In Fig. 5 the coil L has a single layer of windings of 100 turns adjusted to have a natural period of about 210 meters. The drawing shows a condenser of .001 mfd. Mr. Hogan says that "when a coil of 210 meters natural period at L (inductance) is connected with another similar coil and a condenser of this size, the effect is to reduce the natural wave length of the entire circuit so that in a specific case the natural wave length of the output circuit of the first tube set up in this way was reduced from 210 meters to 158 meters."

 Mr. Hogan's assumption, however, in this calculation is that the inductance CL is equal to L; and Mr. Jones points out that the inductance CL is a radio frequency choke coil described in the caption and is designed to keep the radio voltages from leaking through the audio-transformer. The author indicates that CL is an inductance similar to L. That hardly justifies the inference that it is equal to L. Mr. Jones was of opinion that this similarity was one of form only; that is, that it should have a single layer winding on a cardboard tube. There seems force in the interpretation that this was merely a suggestion to an amateur to wind his coil single layer. Hogan admitted that the reference to the author's 200 meter experimental work would include a band of from 190 to 220 meters, so far at least as Fig. 5 of the article is concerned.

 I think it clear that the output natural wave length for the circuit shown in Fig. 5 was not below the 200 meters amateur working wave length for which the circuit is suggested, but on the contrary, within the intended wave length band of from 190 to 220 meters.

 The article published April, 1924, in the Bell System Technical Journal by Friis and Jensen on High Frequency Amplifiers, is also referred to, but its pertinency to this patent was not developed by Mr. Hogan and there is nothing but a passing reference to it by name in the defendant's brief.

 Finally, reference is made to Rawsthorne, British patent No. 233,053, for the purpose of showing that the use of small coils tuned to natural frequencies higher than the working range is not limited to circuits in which the inter-tube coupling is invariable. Hogan relies on the following paragraph: "The primary coil P together with the circuit to which it is connected, is in all cases not tuned to resonance with the desired frequency either directly or indirectly, but is arranged to have a natural frequency which is considerably greater than the frequency which it is desired to receive.This is accomplished by making the inductance of the primary coil small and by excluding from its circuit any capacities that would be sufficient to cause its natural frequency to equal or approximate to the frequency which it is desired to receive."

 Jones endeavors to distinguish this reference on the ground that the difference results obtained by him and Rawsthorne indicates difference in invention. Rawsthorne endeavors to prevent self-oscillations; Jones sought to produce these oscillations by means of a coupling between the circuits, and providing means for neutralizing them.

 In Jones' arrangement, the means for coupling together two tubes in untuned; that is, following the tuned stage o, i, the stage which couples together the second and third radio frequency tubes, 2 R.F. and 3 R.F., is an untuned stage. Rawsthorne on the other hand, discloses a tuned stage that couples P and P. In Rawsthorne the primary of the transformer coupling device is untuned, but the secondary is tuned by the condenser C; whereas in Jones, the whole transformer T is the untuned transformer. In Rawsthorne, as appears from the quoted passage, the primary when untuned has a frequency greather than the frequency which it is desired to receive; whereas in Jones, the entire coupling means (i.e., the primary and the secondary of the transformer in connected circuit) and all which follows, has the predetermined natural frequency greater than the range of frequency.

 In his specification, page 3, lines 94 et seq., Jones says:

 "The output circuit o of this tube and the coupled input circuit i of the third radio frequency tube 3 R.F. being non-tunable, these circuits being coupled by the transformer T having a natural frequency in circuit greater than the highest frequency through which the input circuit i is tunable. Viewed from another aspect, the natural wave length of the output transformer T in connected circuit or the natural wave length of the coupled circuits o -- i is smaller than the lowest wave length that can be transmitted through the system by adjustment of the input tuning condenser C."

 For the foregoing reasons I find the combinations of the claims in issue are not disclosed by the cited prior art and are, therefore, valid, showing as they do patentable subject-matter.

 Plaintiffs' Exhibit 5, diagrammatically illustrated as Fig. AB in plaintiffs' Exhibit 8, embodies the combination of these claims. For example, "an amplifying system comprising an electron discharge device having an input circuit and an output circuit" is the tube T with its input and output circuits; "means for tuning the input circuit through a predetermined range of frequencies" is the tuning condenser C; "the output circuit being untuned and embodying means for coupling the same to a subsequent circuit, the load of said untuned output circuit combined with the load reflected thereinto by the subsequently coupled circuit comprising an impedance having a natural frequency greater than the highest frequency of the whole frequency range through which the input circuit is tunable whereby feed-back reactions from the output circuit to the input circuit are produced for the whole frequency range" is the output circuit o' in connected circuit; and "means for controlling the feed-back reactions" is the resistance R'.

 I find, therefore, that this patent is infringed

 Claim 3 is of the same group as claims 5, 7, and 13, and is likewise infringed.

 The other claims involved are sufficiently similar in terms and scope to call for the same finding.

 Patent No. 1,620,661. This patent relates more particularly to the art of cascade amplicification.The object sought is to eliminate distant stage feed-back.Jones says: "A disturbing reaction may take place on the tunable input circuit due to the tuning of a circuit arranged posterior to the untuned or non-tunable stage of the system."

 This disturbing reaction may not be of great magnitude and is to be considered as secondary and distinguished from the primary feed-back reaction. His aim, therefore, is to overcome these secondary disturbing reactions.

 Broadly, the means employed consist in tapping a coupling condenser of the untuned impedance network to different parts of the resistance R'.

 Claims 5, 6, and 7 are in issue. Claim 5 reads as follows: "5. An amplifying system comprising a pair of electron discharge tubes, each having input and output circuits capacitively coupled through the electorstatic coupling of the tube elements, means for tuning the input circuit of the first tube through a predetermined frequency range, the output circuit of the first tube being coupled by non-tunable means to the input circuit of the second tube, said non-tunable coupling means comprising an inductance common to the coupled circuits, means for producing an energy feed-back reaction from the non-tunable coupled circuits to the input circuit of the first tube for the whole predetermined frequency range and means for neutralizing said feed-back reaction."

 From the specification, as well as from Jones' testimony, it would appear that the tapped resistance R', connected at some intermediate point to the coupling condenser K', is the essential means disclosed for eliminating distant stage feed-back.

 Infringement is denied on two grounds: That the defendant's set does not contain a condenser K' tapped into an intermediate point of the resistance R; and because it is without an inductance common to the output circuit of ...


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