HOISTS MLC300 SERVICE/MAINTENANCE MANUAL
5-22
Published 11-22-17, Control # 257-02
Drum 6 Pawl Control
Pawl Disengagement
When the drum 6 park switch is in the UN-PARK position,
the CCM-10 control module communicates the un-park
command to the IOLC33 control module via the controller
area network bus (CAN Bus).
The IOLC33 control module then sends 24 V
DC
to the pawl-
out solenoid on the pawl valve (10), energizing the solenoid.
The pawl valve shifts to the position that routes hydraulic
fluid from the pump 1 charge pump (5) to the rod side of the
drum pawl cylinder (12). The cylinder retracts, causing a
cam to rotate and disengage the pawl from the ratchet. For
more information, see Drum 6 Pawl on page 5-32
.
The drum 6 pawl limit switch signals the control system when
the pawl is disengaged by sending 0 V
DC
to the IOLC33
control module.
Pawl Engagement
When the drum 6 park switch is in the PARK position, the
CCM-10 control module communicates the park command
to the IOLC33 control module via the CAN Bus.
The IOLC33 control module then sends 24 V
DC
to the pawl-
in solenoid on the pawl valve (10), energizing the solenoid.
The pawl valve shifts to the position that routes hydraulic
fluid from the pump 1 charge pump (5) to the barrel side of
the drum pawl cylinder (12). The cylinder extends, causing
the cam to rotate in the opposite direction, allowing a spring
to engage the pawl with the ratchet. For more information,
see Drum 6 Pawl on page 5-32
.
The drum 6 pawl limit switch signals the control system when
the pawl is engaged by sending 24 V
DC
to the IOLC33
control module.
Drum 6 Hoisting Operation
The following conditions must be met to operate drum 6:
• Seat safety switch must be closed
• Drum 6 must be un-parked
When drum 6 joystick J1 is pulled back to raise the luffing jib,
the CCMC11 control module sends an electrical signal to the
drum 6 system B control valve (7). The control valve shifts to
a position that routes hydraulic fluid to the raise side of the
system.
The CCM-10 control module then sends a pulse-width
modulated (PWM) signal to the electronic displacement
control (EDC) on pump 3 (3). The PWM signal is in
proportion to the speed commanded by the joystick.
Increasing the PWM duty cycle increases the pump’s
swashplate angle, which increases the hydraulic flow from
the pump through the A port of the drum 6 system B control
valve (7), then to the load-holding valve (9) on the B side of
the hydraulic motor (15).
In the load-holding valve, the hydraulic fluid flows through a
check valve, then to the B port on the motor, causing the
motor to attempt to turn the drum.
At the same time, the IOLC33 control module sends 24 V
DC
to the brake release solenoid valve (11), energizing the
solenoid. The brake valve shifts to a position that routes
hydraulic fluid from the pump 1 charge pump (5) to the brake
defeat valve (19). Hydraulic pressure created by the
pressure-reducing valve (20) on the A side of the motor
shifts the brake defeat valve (19). This allows the hydraulic
fluid from the brake release solenoid valve to flow to the
drum brake (14), releasing the brake.
As the motor starts to rotate, pressure on the A side of the
motor opens the sequence valve (22), allowing return
hydraulic fluid to flow back to the tank via the drum 6 system
B control valve. This allows the drum to turn in the direction
that raises the luffing jib.
The CCM-10 control module then sends a signal to the
IOLC32 control module via the CAN Bus to ramp up the
PWM duty cycle to the drum 6 motor controller. Increasing
the PWM duty cycle decreases the swashplate angle in the
motor, which increases the motor flow until the rotational
speed is maximized based on the pump flow.
The following sensors provide feedback to the controllers:
• Drum 6 Motor Speed Sensor
• Pump 3 Pressure Transducer
(pump 3 system B psi)
• Drum 6 Motor Pressure Transducer
(drum 6 motor psi)
• Drum 6 System B Pressure Transducer
(system B manifold psi)
The control system uses this feedback to adjust the pump
and motor flow to maintain the speeds commanded by
drum 6 joystick J1.
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