Application of William J. Popowsky, 351 F.2d 1008 (C.C.P.A. 1965)

Appellant appeals from a decision of the Board of Appeals affirming the examiner's rejection of claims 13 and 14 of appellant's application, serial No. 841,763 filed September 23, 1959 entitled "Measuring Apparatus."

The issue for determination is whether appellant's device is obvious in view of the prior art under 35 USC § 103.¹  The references remaining²  in support of the rejection are as follows:

Geffcken et al., (British) 235,526 June 17, 1926

Jenkins, Voltage-Sensitive Capacitors, Electrical Manufacturing, Dec. 1954, pp. 83-88, 300, 302.

As stated by appellant:

The claims under appeal * * * are drawn to an electrical signal transducer for use in industrial process control applications. The transducer is characterized in that it receives a unidirectional analog voltage signal and, through its unique circuitry, produces a corresponding unidirectional analog current signal which may be economically transmitted and utilized at a distant point with little or no tendency for deterioration in the transmitted signal. * * * [Emphasis by appellant.]

The parties agree that the circuit diagram which comprises Fig. 3 of the drawings of the appealed application best explains the claimed invention.

NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE Appealed claim 13 reads on the circuit shown in Fig. 3 of the application in the following manner, as set forth in the solicitor's brief:³ 

Claim 13. An electrical Figure 3 signal transducer operative in response to an electrical unidirectional-voltage Signal (e in) at terminals input signal 55 and 56 to produce a corresponding Signal across load 39 unidirectional current output signal; said transducer comprising an Transistor 12 amplifier, a positive feedback circuit Tank circuit 17, 50 connected * * *, in Hartley manner between collector 15 (via 20) and base 13 (via 18) a sensing network forming Tank 17, 50 part of said positive feedback circuit and including a variable attenuation means * * *, said variable attenuation Barium titanate capacitor means comprising two serially-connected 51-53 connected in series unidirectional-voltage with barium titanate capacitor sensitive reactance 53-52 elements * * *, an input circuit * * * Input terminals 55 and 56 are connected to variable capacitor 50 directly and through choke coils 57, 58. and an output circuit * * * Choke 35, resistance 36, battery 10, load 39, resistor 30, diode 31, etc.

The board relies in its decision upon certain teachings found in Jenkins, in connection with the circuit diagram shown in Fig. 17 of that article:

NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE

The Jenkins article as it relates to the circuit of Fig. 17 states:

* * * Voltage-sensitive capacitors have been used * * * in circuits for frequency and phase modulation. These systems employ a voltage-sensitive capacitor as one element of an oscillator tank circuit so that variations in capacitance caused by the modulating signal produce corresponding variations of ascillator frequency. Fig. 17 shows a frequency-modulated oscillator using two voltage-sensitive capacitors, C₁ and C₂, as modulating elements. They are connected in series with respect to the r-f potential and in parallel with respect to the modulating potential. A bias battery is used to set the voltage value between the capacitors. Frequency deviations of ± 2 percent in the 50 to 500 mc range have been reported * * *. Under extreme conditions the amplitude modulation is appreciable, but is negligible for smaller deviations.

Comparing the subject matter of claim 13 to Jenkins, the board agreed with the examiner that there was no essential difference in structure except for the output circuit in claim 13 and that it would be obvious to insert a meter as disclosed in Geffcken in the plate circuit of the Jenkins circuitry to satisfy this limitation. The position of the examiner thus affirmed by the board is that it is well known that the variation of the frequency of an oscillator also produces current changes and that the use of the particular capacitors claimed in an oscillator is old as shown by the references.

The Geffcken reference relates specifically to the detection of magnetic bodies. It comments that previous devices acted on the basis of a variation in the effective capacity of a "field-producing condenser" or the self-induction of a "field producing coil," stating that:

For rendering such variation of the alternating current magnitudes noticeable devices sensitive to frequency were hitherto used and connected to an oscillation generator. In order to obtain sufficient sensitiveness for the purpose above referred to, complicated circuit arrangements must be provided.

The reference further comments:

The present invention obviates complicated alternating current arrangements. It converts variations of the alternating current magnitudes directly to direct current fluctuations as it uses variations in the electrode current of a suitably constructed valve generator as a measurement for the variations of its condition of oscillation.

It is already known that in valve generators a variation in the electrode current can occur simultaneously with variations in the generator oscillation. This phenomenon has been used in a scientific measurement for determining the variation of capacities. * * * A vacuum tube oscillator circuit used in Geffcken is shown in Fig. 1 of that reference:

NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE

It is contemplated that the tuned circuit 4 react in response to the presence of a magnetic body to modify the oscillating or tank circuit 2 of the oscillator to cause a variation in anode current which can be observed in a galvanometer 6.

Concerning Fig. 1, Geffcken states, in pertinent part, as follows:

The anode current of the valve generator is observed by means of the galvanometer 6 which is bridged by a condenser 7. The galvanometer may also be replaced by a compensating circuit or the like. * * *

The arrangement shown in Figure 1 corresponds with an intermediate circuit generator. The circuit 4 exerts its greatest action on the generator 1, 2, 5 in the neighbourhood of the resonance position. The action is noticed therein that besides the variations of the amplitudes of the generator oscillation the phase angle of the generator is changed. At the same time the phase of the grid potential is changed as this is induced by the generator current. There is thus positively effected a variation of the anode current which may be observed by the galvanometer 6. * * *

It seems to us that Geffcken, taken as a whole, fairly discloses that variations of the tuning of the tank circuit of an oscillator, including the capacitance in such circuit, can produce variations in the current in the plate circuit. It further discloses that the variations in such current may be shown on a measuring instrument and utilized as an indicator. The Jenkins reference, similarly taken as a whole, teaches that voltage-sensitive capacitors in an oscillator tank circuit will react to a signal input to produce corresponding variations in oscillatory frequency.

Appellant argues that the references do not teach a control device incorporating the following relationships: (1) a unidirectional-voltage input signal which produces variations in the capacitance of the voltage-sensitive capacitors; (2) which, in turn, produce corresponding variations of the magnitudes of oscillations in the tank circuit; (3) which, in turn, produce corresponding variations in the current in the plate circuit of the oscillator; (4) which, in turn, represent a unidirectional-current output signal for control purposes.

Despite appellant's arguments, consideration of the disclosures of Jenkins and Geffcken convince us that they constitute a clear teaching that variations in capacitance of voltage-sensitive capacitors connected in the tank circuit of an oscillator may be utilized to produce corresponding variations in current in the plate circuit of the oscillator.⁴  It is true that the references do not disclose that such arrangement may be used as a means for operating on a unidirectional-voltage signal. However, we think it would have been obvious to a person of ordinary skill in the art that a variable unidirectional-voltage signal might be applied to the terminals of the voltage-sensitive capacitors for the purpose of attaining a corresponding output current signal in accordance with the broad language of the claims. The subject matter in issue thus must be held to be unpatentable under the provisions of 35 U.S.C. § 103.

The decision of the board is affirmed.

Affirmed.

MARTIN, J., took no part in the consideration or decision of this case.