T 1981/07 – How?

This decision deals with the refusal of an application by the Examining Division (ED), on the ground of lack of inventive step. The Board sees an even greater problem.

*** Translated from the German ***

[2] The present application covers an electric motor which differs from a conventional electric motor essentially in that its windings are formed by “band capacitors” that are connected in series. According to claim 1, the band capacitors have the following features:

• their planes of extension (Erstreckungsebenen) are oriented perpendicular to the poles of the magnetic core segments and arranged on them;
• each of them is formed by two ring-shaped metal plates that are interrupted by a gap;
• between their metal plates there is a dielectric.

[2.1] According to the description […] an alternating electric current flows through the windings formed by the band capacitors,

“irrespective of whether the rotor is locked or rotates, rotates slowly or at high speed. This is precisely the physical basis of the newly structured motor, which allows to control the speed of the rotation independently of the current frequency. In order for the motor to turn at the desired speed of rotation, it is necessary, in the embodiment of Fig. 1, to uncouple (abkoppeln) the rotor locking.

Then the rotor turns to the position wherein the magnetic flux is maximised, i.e. the magnetic poles on the stator and on the rotor have to reach a magnetic axis N-S, S-N. Without further action the rotor will remain in this magnetic axis, but the alternating current will continue to flow through the windings 6,7. In this position the locked torque (Anzugsmoment) is zero. The circuit in Fig. 4 shows how to pursue the rotation of the rotor and how to control it. …

 

The windings 7 are directly connected to the AC generator 14 by means of contact brushes 19. A similar electric circuit makes clear that the windings 6 on the magnetic core segments 2 of the stator are also connected to the AC generator via connections 20. Between the windings 6 and the AC generator 14 there is a control unit 21 for controlling the speed of rotation, the function of which is to control the magnetic core system of the stator such that there is always an angle between the axis of the rotating field and the magnetic axis of the rotor. The control unit 21 for controlling the speed of rotation is connected to the rotor by means of a known optical sensor, which provides the precise position of the rotor for the electronic data treatment.” (underlining added)

Moreover, the description […] indicates that the speed of rotation of the rotor can be set with a high precision of about ± 0.3%. 

“Such a precision of the nominal speed of rotation is possible because the torque moment can be controlled within milliseconds by feeding or throttling electric energy. The supply is controlled/throttled by changing the current frequency and/or by changing the amplitude of the alternating current. This can be done very easily because the windings 6,7 each form an electric capacity from the point of view of the underlying physics. In electric motors according to the invention, the well-known characteristic torque/speed curve is completely different from the curves belonging to the state of the art.” (underlining added)

[2.2] The circuit “allowing to pursue the rotation of the rotor and to control it” is not described in more detail in the application. There is only the statement that the motor control is obtained “by feeding or throttling electric energy” and that this is obtained “by changing the current frequency and/or by changing the amplitude of the alternating current”.

[2.3] As shown in Figures 5 and 6, the windings of an electric motor according to the invention consist in a plurality of band capacitors that are connected in series. Each of them comprises two C-shaped metal plates arranged on a magnetic core segment and a dielectric that is provided between the metal plates.

As the electric motor according to the invention has a stator and a rotor of conventional construction, it has to be assumed that the band capacitors are to create a magnetic flux in the corresponding magnetic core segments. As a matter of fact, the application […] mentions

“that the engine power (Leistung) of all electrical machines is directly proportional to the magnetic flux. Moreover, the magnetic flux is proportional to the ampere-turn.”

[2.4] As is generally known, an electric current flowing through a capacitor builds up a positive charge on one of the electrodes and a negative charge on the other. The current flowing between the electrodes is a displacement current; it is an expression of the rate of change of the electrical flux between the electrodes.

Document D4 (see Fig. 3) shows that the displacement current flowing between the electrodes of a plate capacitor generates a magnetic field having circular, concentric magnetic field lines extending parallel to the electrodes. In other words, the displacement current of the band capacitors cannot create an axially oriented magnetic field.

[2.5] Therefore, the question arises of how an arrangement of band capacitors such as the one claimed and depicted in Figures 5 and 6 can serve as winding of a stator or rotor pole and generate a magnetic field that is parallel to the longitudinal axis of the corresponding magnetic core segment.

[2.6] The applicant has pointed out that the particular C-shaped geometry of the metal plates depicted in Figures 5 and 6 results in the current flowing into the band capacitor and out of the band capacitor, respectively, having a circular current path when an alternating current is applied. Moreover, by providing the connections of adjacent metal plates on opposite sides of the gap that interrupts the metal plates, it can be ensured that that the circular currents in the metal plates are aligned (gleichgerichtet).

[2.7] As far as the currents flowing at the C-shaped plate electrodes are concerned, the application does not disclose whether and, if so, under which conditions those currents could generate an axially directed magnetic field in the magnetic core segments that would be sufficient for operating an electric motor.

The application does not explain in detail the arrangement of the connections, which, as emphasized by the applicant, was decisive for giving rise to aligned circular currents generating an axially oriented magnetic field. It could perhaps be derived from Figure 6 only. Also, the application does not establish a link between a current path in the metal plates that is allegedly circular and the C-shaped geometry of the plates.

[2.8] The description […] emphasizes that the type of construction of the electric motor according to the invention has “a completely different structure” “than all electric motors according to the state of the art”.

“In the electric motor that is described here, the interaction between the magnetic fields of stator and rotor are defined in a completely different way, according to the underlying physics, than the interactions in all known electric motors. Figures 1, 2 and 4 show that the magnetic flux is closed only by the magnetic core segments 2 and 5 and also by the slit 15 between the rotor and the stator.” […]

Despite the underlined differences between conventional electric motors and the claimed electric motor the application does not contain any indications concerning the conditions and the technical measures that are required for generating aligned arc-shaped currents in the metal plates of the band capacitors, so that each metal plate would indeed act as a winding of a corresponding coil.

The Board is of the opinion that in the present case the skilled person cannot be expected to complete the incomplete teaching of the application with his knowledge because, as pointed out by the [applicant], the mode of operation of a motor according to the invention is not comparable with the state of the art. […]

[3] To sum up, the Board is of the opinion that the application does not disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (A 83).

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