8
Types NR, NRV Maintenance Instructions
Figure 14.
Contact engagement adjustment
(stationary contact removed to show measuring
point).
Figure 15.
Contact structure removed from head mechanism.
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Figure 12.
Components of toggle mechanism assembly.
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Figure 13.
Holding back latch lever with screwdriver.
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MOVING CONTACT ARM ASSEMBLY
To replace the moving contact arm assembly proceed as
follows:
1. Detach both opening springs from toggle link (Figure 12).
2. Pull back latch lever assembly and remove C-ring which
secures the toggle link to the bell crank lever.
NOTE: The latch assembly can be held back with a screwdriver
as shown in Figure 13.
COMPLETE CONTACT BOX ASSEMBLY
To replace the complete contact box assembly proceed as fol-
lows:
1. Detach the opening springs and disconnect the toggle link
from the bell crank as described in “Moving Contact Arm
Assembly” section, Steps 1 and 2.
2. Remove the hex nuts, lockwashers and flatwashers that
retain terminal leads to bushing rods.
3. Remove four hex head machine screws with pre-assembled
lockwashers that secure the contact structure to the: head
casting. Contact structure removed from switch is shown in
Figure 15.
3. Remove the pivot pin attaching the contact arm assembly to
the side plates of the contact box.
4. Remove the contact arm assembly.
5. Reassemble the new contact arm assembly, which includes
the moving contact bar, to the contact box.
6. With the mechanism closed, the moving contacts should be
within 1/16-inch of full engagement, as measured between
the top edge of the moving contact insulator and the bottom
edge of the contact box side plate as shown in Figure 14. To
obtain this dimension, adjust the effective length of the insu-
lated operating link by adjusting the attaching point for the
contact arm assembly in the slotted hole of the link. Be sure to
retighten the elastic stop nut when adjustment is completed.
