The steam valve (fig. 4-6) admits and shuts off the
flow of steam to the launching engine cylinders during
catapult operations. With the valve in the CLOSED
position, two plugs in the valve are in full contact with
the valve body seats, providing a tight seal. When the
valve is opened, the plugs are moved away from the
valve body seats and rotated 90 degrees. In the OPEN
position, the circular openings in the plugs are in line
with the valve body passages.
OPERATION CONTROLS ASSEMBLY
The operation controls assembly (fig. 4-7) is
attached to the bottom of the steam valve assembly. The
assembly provides vertical movement needed for
seating and unseating the steam valve plugs and
rotational movement needed for opening and closing
the steam valve. Vertical movement of the plugs is
obtained by the action of the lift nuts. Each lift nut has a
steep angle thread that mates on each steam valve plug
shaft. Each lift nut is connected to the crosshead by a
lifter lever and a lifter link. Movement of the crosshead,
which is connected to the hydraulic cylinder piston rod,
causes the lift nuts to rotate and the plugs to move
toward or away from the steam valve body seats.
Movement of the crosshead also obtains rotational
movement of the plugs. Each plug shaft is connected to
the crosshead by a rotator lever and a rotator link. With
the steam valve in the CLOSED position, the plugs are
fully seated. When the crosshead starts to move to the
OPEN position, the lift nuts move the plugs downward,
and the links and levers begin to rotate. Due to the
geometrical arrangement of the levers, the plugs are
moved away from the body seats before rotation begins.
As the crosshead stroke approaches the FULL OPEN
position, the plugs move toward the valve body seats.
When the valve is fully opened, the plugs are not in
contact with the body seats, because of the unequal
lengths of the links, and the plugs and body parts are in
perfect alignment. As the crosshead moves to the
CLOSED position, the links and levers rotate the plugs
upward to seat the plugs against the seats.
Figure 4-6.Launching valve steam valve.