Appeal No. 1999-2781
Application No. 08/656,299
Appellant's invention relates to a speed responsive
coupling device (shown schematically in Figs. 3a and 3b) and
to a fall arrest apparatus that incorporates such a speed
responsive coupling device (e.g., as seen in either Fig. 1 or
Fig. 5). As noted on page 4 of the specification,
at the heart of this invention, lies the concept of using
a ratchet engaging pawl with the pawl being arranged as a
mechanical toggle switch. Such a switch is one in which
the switching member, here the pawl, is spring biased to
remain in one of two stable or quasi-stable conditions.
Switching is effected by causing the switching member,
the pawl, to pass through a metastable position between
those two conditions, whereupon it will flip over to the
other condition. In the instant case, the rocker which
is linked to the pawl, and is preferably an integral part
of the pawl, rocks as the first member, e.g. the drum on
which safety line is wound, rotates. The arrangement is
such that during such rotation at speeds below a
threshold value, for example corresponding to line
withdrawal at rates appropriate to accommodate normal
movements of a worker, this rocking is insufficient to
push the pawl into or past its metastable state, and thus
the pawl remains in the free condition and rotation of
the drum is permitted: in case of rotation at speeds
above the threshold value, however, the rapidity of the
rocking motion imparted gives such momentum and energy to
the pawl and rocker that the pawl is carried into its
metastable position and then flips over into the lock
condition where it engages the ratchet to prevent further
rotation.
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