Browse Prior Art Database

Linear Motor with Flexible Magnetic Band Moving Element

IP.com Disclosure Number: IPCOM000107875D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 107K

Publishing Venue

IBM

Related People

Hollis, RL: AUTHOR

Abstract

Using a slotted band as the armature in a linear motor allows distributed stators to be located anywhere along the band, completely eliminating motor inertias by directly generating forces on the band.

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Linear Motor with Flexible Magnetic Band Moving Element

       Using a slotted band as the armature in a linear motor
allows distributed stators to be located anywhere along the band,
completely eliminating motor inertias by directly generating forces
on the band.

      For synchronously transmitting mechanical power over long
distances or tortuous paths, toothed rotary motors, belts and pulleys
may be used to prevent slippage.  The inertia of such a system is the
sum of load, belt, pulley, and motor inertias; the motor inertia may
be dominant, resulting in undesirably large start/stop times.

      This linear motor completely eliminates the motor inertias by
directly generating forces on a magnetic toothed belt.  One or more
motors may be at any point along the belt, independent of the
pulleys.

      U.S. Patent 3,867,676 teaches a linear stepper motor. A feature
is the provision for dual-motor assemblies, which increase the drive
force in the direction of the stator bar long axis, and also provide
balanced forces normal to the stator bar long axis.  This feature
greatly reduces the load requirements of the bearings between the
motors and stator.

      The flux path in the stator bar is normal to the long axis of
the bar.  The stator bar thickness can be greatly reduced without
adversely affecting the magnetic requirements.  In fact, the
magnetics are improved by such a reduction, since the magnetic path
length is re duced.  The bar thickness is reduced until the bar
becomes a thin flexible band of ferro-magnetic material, with
rectangular holes punched in it to form teeth.  The band can be a
continuous loop passing over toothed pulleys which use the punched
holes to provide synchronous motion.

      Fig. 1 shows E-cores 1 (typically of laminated silicon-iron)
with windings A, B, C and A', B', C'.  Fig. 1 shows the flexible
notched band 2 in place over the E-core poles.  A typical flux path
in the top and bottom E-cores has the flux entering and leaving
normal to the band surface.

      Fig. 2 shows the action of the linear motor.  The forces acting
on an isolated tooth of the band 2, as it passes between the teeth of
the E-core pole pairs, tend to move the band 2 along its length, as
shown by the heavy arrow.  The vector sum of two strong, nearly
opposing force vect...