Directional Control Valves.
The directional control valves are four-way, three-position valves with either
an open or closed spool. The valves are grouped into valve banks permitting
simultaneous independent control of crane functions. The closed spool type
valve contains an integral load check valve to prevent back sliding of
components which support heavy loads. Each bank contains a main relief
valve, and additionally, certain crane functions are also protected by a circuit
TURNTABLE ASSEMBLY AND SWING MECHANISM.
An anti-friction ball, turntable bearing supports the superstructure on the
carrier and allows 360 degrees stop to stop rotation. Swing is accomplished
by a hydraulically-driven motor driving a gear box which in turn drives the
bearing ring gear through a pinion. A non-free swing, spring actuated and
hydraulically released brake is provided to stop swing and hold the super-
structure in the desired position. The swing speed is reduced with a flow
restrictor to improve swing brake performance and reduce impact with
swing stops. To further secure the superstructure in travel position, a pin-
type swing lock is provided.
The hydraulic swing motor is a low speed, high torque type. The motor
provides indirect drive power for turntable swing through the swing gearbox.
The swing gearbox is a sun and planetary gear type, driven mechanically by
the swing motor. The swing gearbox rotates the turntable at a reduced
operational speed of approximately 2.9 rpm.
The swing brake is a multi-disc brake. Hydraulic pressure, controlled by
movement of the SWING control lever to either left or right, holds the brake
released against spring pressure. Returning the SWING control lever to
neutral causes the hydraulic pressure to be removed and allow the springs to
set the brake.