HOISTS MLC300 SERVICE/MAINTENANCE MANUAL
5-30
Published 11-22-17, Control # 257-02
DRUM 4 PAWL
See Figure 5-16 for the following procedures.
Operation
The pawl is controlled by the drum 4 park switch in the
operator cab.
Drum 4 Parked
See View A—Engaged.
The hydraulic cylinder (1) extends and rotates the cam (2)
away from the pawl (3). This allows the spring (4) to rotate
the pawl into engagement with the drum ratchet (7).
Drum 4 Un-Parked
See View B—Disengaged.
The hydraulic cylinder (1) retracts and rotates the cam (2)
against the pawl (3). This action rotates the pawl out of
engagement with the drum ratchet (7). It may be necessary
to operate the drum slightly in the raise direction to fully
disengage the pawl from the ratchet.
Maintenance
Daily
Visually check the pawl for proper operation as described
under Operation.
Weekly
Apply open gear lube to the sliding surfaces between the
cam (2) and pawl (3).
Spring Adjustment
If the spring tension becomes insufficient, perform the
following.
1. Visually check the position of the pawl and make sure it
is fully engaged with the ratchet.
If the pawl is not fully engaged, perform the following.
a. Start the engine and operate the drum slightly in the
up direction, then stop the engine.
b. Check the pawl again and make sure it is fully
engaged with the ratchet.
NOTE: In some cases, the pawl may come to rest on the
top of a ratchet tooth. There must be enough spring
tension to pull the pawl into the root of a ratchet
tooth if the drum starts to turn in the down direction.
2. Lockout-tagout the crane.
3. Adjust the eyebolt adjusting nuts (5) to increase the
spring (4) tension.
4. Start the engine and check the pawl for proper operation
and engagement.
Limit Switch Adjustment
The limit switch (8) signals the crane’s control system when
the drum 4 pawl is fully disengaged.
1. Disengage the pawl by moving the drum 4 park switch to
the UN-PARK position. It may be necessary to boom up
slightly before the pawl will disengage the ratchet.
2. Lockout-tagout the crane.
3. Loosen the setscrew (9) so the limit switch lever (11) is
free to rotate on the limit switch shaft (10).
4. Rotate the limit switch lever up and hold it so the roller is
against the pawl (3).
5. Turn the limit switch shaft counterclockwise until the limit
switch clicks open and hold.
6. Make sure the roller is against the pawl and tighten the
setscrew to lock adjustment.
7. Start the engine and check for proper operation:
• Engage the pawl by moving the drum 4 park switch
to the PARK position and try to boom down. The
drum should not operate in the down direction.
• Disengage the pawl by moving the drum 4 park
switch to the UN-PARK position and try to boom
down. The drum should operate in the down
direction.
8. Readjust the limit switch if required.
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