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Optical Tachometer Using Conductors of PCA as Light Chopper

IP.com Disclosure Number: IPCOM000073943D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Garthwaite, AN: AUTHOR [+3]

Abstract

This printed circuit motor includes an integral digital tachometer whose moving element is a portion of the printed circuit armature (PCA). Printed circuit motor 1, view A, is the capstan motor of a magnetic tape unit and includes low-inertia tubular printed circuit armature 2. The digital optical motor-speed tachometer includes a stationary light source 3, view B, which directs light through the transparent or translucent tube which supports armature winding conductors 4. The light passes between the individual winding conductors and is chopped as the armature rotates. A stationary photocell 5 is positioned on the other side of the armature windings from the light source. The chopped light is viewed by the photocell through stationary mask 6.

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Optical Tachometer Using Conductors of PCA as Light Chopper

This printed circuit motor includes an integral digital tachometer whose moving element is a portion of the printed circuit armature (PCA). Printed circuit motor 1, view A, is the capstan motor of a magnetic tape unit and includes low- inertia tubular printed circuit armature 2. The digital optical motor-speed tachometer includes a stationary light source 3, view B, which directs light through the transparent or translucent tube which supports armature winding conductors 4. The light passes between the individual winding conductors and is chopped as the armature rotates. A stationary photocell 5 is positioned on the other side of the armature windings from the light source. The chopped light is viewed by the photocell through stationary mask 6. The mask carries a slit 7, view C, which is aligned with the direction in which the armature conductors run in the adjacent portion of the armature. The photocell output is connected as an input to electronic circuitry whose output indicates the speed with which the armature is rotating.

Alternatively, the light source and photocell can be positioned to cooperate with the extending interconnect tabs 8 at the extreme end of the armature. To increase the chopping frequency for a given armature speed, each individual interconnecting tab around the armature circumference may be slotted, as shown in enlarged view D.

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