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Description
Positive trigger lock-out
Quick make-and-brake contacts, which
directly handle the motor circuit, are
locked in position until tripped. The
roller-type trigger lockouts prevent
positively any operation of the Limit
Switch until the full power of the high-
tensile, oil-tempered, magnafluxed
spring is available to assure extremely
fast operation for either tripping or re-
setting. Operation in any intermediate
position of the operating lever is im-
possible.
Direct contact opening and closing
In the remote possibility of spring fail-
ure, the contacts are operated by the
direct drive action of the tripping and
reset weights. In tripping, as the reset
weight causes the trip pin to engage
the operating pin to operate the con-
tacts. In resetting, the reset-pin does
the job.
One piece movable contacts
The low inertia of these contacts prac-
tically eliminates any contact bounce.
Exclusive arc transfer system
This arc transfer system combined with
the shape of the arc chamber allows
greater arc interrupting in a smaller
space. The arc is confined to a con-
trolled path for more efficient extin-
guishing. No destructive burning of the
contacts can occur as the arc is trans-
ferred to the rearmost part of the mag-
netic blowout coil guards and to the
central rod conductor in the arc shield.
A smaller Limit Switch is made possi-
ble.
Sturdy Housing
Size 4, 5, 6, & 6A cases are of cast
iron. Size 2 and 3 cases are molded
fiberglass. The cover is of tough glass-
reinforced polyester resin. It is easily
removed for ready access to the con-
tacts.
Safety chain
The insulated cover is securely fas-
tened to the case by means of a safety
chain to prevent loss when removed
from the case.
Clearly marked leads
Flexible leads for external connections
extend through snug-fitting neoprene
bushings in the back of the cast-iron
case. They are clearly marked to
speed installation.
Rugged Construction
High-quality materials reduce mainte-
nance. All parts are of non-corrosive
materials. Contacts are hard-drawn
copper, except for sizes 3 & 6A which
use silver faced tips. The shaft is
stainless steel. All current-carrying
parts are copper or brass. Contact and
shunt fastening screws are stainless
steel.
Ball Bearings
Four oversize, double-sealed ball
bearings are permanently lubricated to
minimize friction and reduce mainte-
nance.
Early Break Auxiliary (EBA)
The EBA option is available for crane
hoists that are controlled with AC or
DC drives. The EBA contacts (DPDT)
operate prior to the power contacts,
thus providing a signal to turn off the
drive before motor power interruption.
Installation
Euclid™ Type 4220 Crane Power Limit
Switches are easily field installed.
Mount horizontally on top of the trolley
frame of the hoist, with mounting feet
down. Install the split-sleeve sus-
pended weight guide around the deed-
ended cable. A bracket or striker plate
may be attached to the hook block, if
necessary, to lift the suspended weight
when hoising. Steel cable is furnished
for connection the suspended weight to
the operating lever.
D-C Units Only
The operating lever is adaptable for
either right or left-hand operation. Un-
less otherwise specified, right-hand
operation is furnished. Change in in-
stallation for left-hand operation can be
made either at the Factory or in the
field. Terminal markings only are af-
fected. Refer to wiring diagram for
correct connections.
Resistors For D-C Limit Switches
Euclid™ Type K-exclusive continuous
wound, corrosion resistant, non-
breakable resistors, are specifically
designed for use with Euclid™ Type
4220 Hoist Limit Switches. See Price
List 4220.
