Browse Prior Art Database

Varied Pitch Force Compensating Voice Coil

IP.com Disclosure Number: IPCOM000096124D
Original Publication Date: 1964-Dec-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Kalhoff, CH: AUTHOR

Abstract

This is a voice coil motor which is designed for use as a long stroke rectilinear prime mover.

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Varied Pitch Force Compensating Voice Coil

This is a voice coil motor which is designed for use as a long stroke rectilinear prime mover.

The motor includes annular permanent magnet 1 which has central core section 2. Field coil 3 is disposed within magnet 1. One end of magnet 1 is interrupted to form gap 4. Cylindrical voice coil 5 fits over core section 2 and moves through gap 4.

The force output of the motor is proportional to the magnetic field density, the length of the conductor in the field, and the current flowing in the conductor. The main concentration of the magnetic field is at gap 4.

Some magnetic flux, however, is present as a leakage field between magnet 1 and core section 2. As voice coil 5 moves out of the leakage flux field within magnet 1, the amount of leakage flux which links coil 5 decreases, with a corresponding decrease in force output per unit of current. With a variable pitch coil, the turns density lying within the gap field increases as the coil moves out of the leakage flux field and the increased force generated by the gap field compensates for the decreased force contribution of the leakage flux field.

A regular close wound voice coil is used to determine the force-gradient versus position-characteristic of the motor. A varied pitch top layer 6 is then laid on the coil to increase the number of turns in the gap field proportionally as the coil is extended out of the motor.

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