Knowles v. Tibbetts (347 F.2d 591, 1965)

ALMOND, Judge.

Hugh S. Knowles appeals from a decision of the Board of Patent Interferences awarding priority of invention to George C. Tibbetts. The interference is between two applications. The board based its award of priority on its holding that the junior party, Knowles, had failed to prove a reduction to practice prior to the senior party’s filing date.

There are three counts in the interference. At oral hearing, Knowles’ attorney abandoned the appeal as to count 1. We thus are concerned only with counts 2 and 3 which read as follows :

2. An electromagnetic transducer comprising a magnet, a pole piece fluxconductively engaging each pole of the magnet, said pole pieces extending laterally of the magnet to form a non-magnetic gap therebetween, an elongated flux-conductive, elastic armature, means clamping one end of said armature in non-magnetic, spaced relationship to the pole pieces in fixed position in said gap so that the other end of said armature may vibrate in another portion of said gap, there being a bending line between the clamped end and the vibratable end of the armature, and means for varying the reluctance between the pole pieces in the air gap at the fixed end of the armature.

3. The electromagnetic transducer of count 2 wherein the reluctance varying means is a T-shaped armature with the clamped portion between the arms of the T which project laterally on both sides into the gap.

It is clear from the applications in interference that the invention relates to a transducer of the type shown in Figure 2 of the Knowles application:

A reed 27 is clamped between washers 28W at one end and is free to vibrate at its other end. When used in a microphone to convert acoustic energy into mechanical energy, the reed is made to vibrate by diaphragm 31 and drive link 32. Vibration of the reed between magnetic poles 22 and 23 causes a variable magnetic flux in the reed. The variable flux causes a current to be set up in coil 20. This output electrical current from the coil varies with the input acoustical energy.

Reduction to Practice

An understanding of the problem solved by the invention is important in determining whether there was a reduction to practice. Both applications in interference indicate that two kind of flux are normally present in the vibrating reed. There is a steady polarizing flux in the region of the gaps between the magnetic poles and a variable signal flux in other regions of the reed. It is desirable that the reed carry as little steady flux as possible in regions outside the gaps. Knowles’ Figure 4 represents a reed positioned between pole pieces:

According to Knowles, circulation of polarizing flux through the reed can be prevented by magnetically balancing the reed. Magnetic balance is obtained when the reluctance across each of the air gaps Gi, G2, G3, and G