Appeal No. 2003-0749 Page 6
Application No. 09/332,070
that required to lock the reel shaft and reel against rotation for any seated occupant is
contemplated.
Carlson discusses the advantages of using magneto-rheological fluid dampers
as compared with electro-rheological fluid dampers in column 1. Karlow discloses a
variable level seatbelt energy management device comprising a magneto-rheological
fluid resistance mechanism (a piston and cylinder arrangement) and a permanent
magnet having a first magnetic field oriented so as to increase the viscosity of the fluid
and an electromagnet which generates a second magnetic field to cancel the first
magnetic field to decrease the fluid’s viscosity, thereby also reducing the resistance to
seatbelt webbing payout. The controller for controlling the supply of power to the
electromagnet controls the resistance of the cylinder to motion, such that the cylinder
can be controlled to withstand motion, present no resistance to motion or supply a
resistance somewhere in between. In fact, because of the magneto-rheological fluid’s
quick response time to external magnetic fields, the resistance of the cylinder can be
varied at different time intervals during a collision so that a traveler could be “braked” in
a controlled manner during a collision where energy is dissipated by the cylinder in the
manner most protective of the traveler. See column 3, lines 8-28. Karlow also points
out that an advantage of providing a permanent magnet to increase the viscosity and
an electromagnet to cancel the permanent magnet’s field and decrease the viscosity is
that, if the electrical system fails, the permanent magnet will maintain the magneto-
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