Other

International Business Machines Corporation

David L Krimm

Rex D Fathergill

James O Martin

James O Stidham, Deceased

William R Yount

A three-phase stepping motor is automatically tested for excessive friction and winding shorts in less than four seconds. The stepping motor accelerates its rotor at a constant rate to a first predetermined velocity. The level of the current applied to the rotor windings to effect commutation is very low so that the rotor will stop and fail to complete any further steps in the test cycle if there is excessive binding or friction. After the rotor is rotated one revolution, it is accelerated at a constant rate to a second and higher predetermined velocity with the current applied to the rotor windings being increased to a second and higher level at a selected velocity during acceleration. When the rotor reaches the second predetermined velocity, commutation is stopped immediately but current is still applied to at least one phase of the motor. An acceptable motor will continue to turn and generate an AC back electromotive force (EMF) signal in the energized phase of the windings. A motor, which has excessive friction or a winding short, will not produce an AC back EMF signal because it will not be moving. With an acceptable motor, the elapsed time between stopping the application of current to the rotor windings to stop acceleration and when the rotor coasts to a stop is displayed and enables comparison of the degrees of friction between acceptable motors.

Method of testing a stepping motor

A fret assembly for a stringed musical instrument having an elongated neck body, comprising a ladder-like structure including a pair of elongated support rods upon which are fixed a plurality of longitudinally spaced, transverse fret bars, and a clamp member for detachably securing the support rods longitudinally upon the top surface of the neck body.

Guitar neck fret assembly

A guitar assembly including an elongated, channel-shaped, open-top, neck body upon which are mounted a plurality of longitudinally spaced, transversely disposed, free-spanning fret bars.

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Lexington, KY, United States of America

David L Krimm