OP-755 Part 2 Pages 197-401 - Personal Page of GENE SLOVER

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opera ting valve I1KIIin up position, thus preventing
the cam lever from moving into the
path of the rack cam.
(b) with the pilot and shut-off valve "C" at "Ho Lst "
and the cradle control valve moved to "Ra l s e
Cradle il or to IILower Cradle II, (fig. 46) the
25 pound and 400 pound relief valves are blocked
out of the c Lr-cui t (by cr adI e control valve
IM") and pressure will build up to 800 pounds
(depending on cradle load). This pressure extends
throughout the pressure leads, including
the tops of the two pawl operating cylinders,
I1JII and IIHII. .
(C) with the· pilot and shut-off valve at I1Lower
Proj ectiles II and the cradle corrt r-oL valve at
neutral, (fig. 47) the 400 povnd relief maintains
pressure throughout the pressure leads
(including the cradle control valve). This
minimum pressure required to. operate the pawl
and tripping· mechanisms increases to a maximumof
800 pounds when the cradle control valve
is moved f'r-om neutral, blocking off the 400
pound relief. The cradle latch foot pedal
must always be operated to release the latch
prior to such cradle co.ntrol valve movement.
Rack and Tube Pawl Assemblies
27. Projectiles when lifted in the hoist are supported
at the end of each of the first three lifting strokes by tube
pawls which are spring ac tua ted to move beneath the base of the
projectile as the projectile is lifted on the rack pawls. At
the end of the fourth stroke the cradle projectile latch supports
the projectile that has risen into the cradle.
28. Rack pawls are similarly arranged with springs to
move each pawl into. the hoistway. when the rack descends,
after a lifting stroke, the pawls are depressed by any proj ectiles
in the stages below. Thus rack pawls and tube pawls have
conventional f r ee bearing for "hoisting II but are arranged with
operating mechanisms which retract the pawls in reverse cycle
for Illowering li • Rack pawls are seated with pin pivot and spring
plunger in four elements of the rack assembly. These are designa
ted: Upper pawl carrier, upper intermediate pawl carrier,
lower intermediate pawl carrier and lower pawl carrier. Tube
pawls are housed, the lower pawl being mount ed within the upper
projectile handling platform, the intermediate in a housing
integral with a cast tube section and the upper one in an attached
housing.