Only with wire rope
hoists
The wire rope hoist has a gear limit switch that functions as
a mechanical hoist limiter. It is directly coupled with the cable drum. It
ensures that the load hook does not travel farther than the highest hook
position or the lowest hook position.
─ 1:
Switching point of the top hoist limiter. If this is triggered, the hoist motor
stops.
─ 2:
Switching point of the bottom hoist limiter. If this is triggered, the hoist
motor stops.
─ 3. To
additionally increase safety, the gear limit switch has another switching point.
It is called “backup limiter”. It is located above the top hoist limiter and
serves as an additional switching point when lifting.
If the top hoist limiter is no longer working (e.g. through
faulty contactors, inversely poled rotary field...) and the load hook thus moves
above the switching point of the top hoist limiter, the backup limiter switches
off the main contactor and thus the whole crane.
Only for wire rope hoists
with ABUControl
Shortly before the load hook reaches the switching point of a
hoist limiter, ABUControl slowly brakes the hoist motor. This method means that
the switching points of the hoist limiter are only activated with a slow lifting
speed.
ABUControl individually calculates at which point the brake
phase begins each time, depending on the current lifting speed. If the load hook
travels upwards quickly, the brake phase begins earlier. If the load hook
travels upwards slowly, the brake phase begins later.
Only with wire rope hoist
with ABUS Electrics 3 with ABULiner
The braking behaviour differs from the sequences described
here. See the ABULiner product manual.
However, the operation by the crane operator does not
essentially differ from the sequences described here.
Only with wire rope hoist
without normal operative travel to the top hoist limiter
The top hoist limiter must not be travelled to during normal
operation. If it is travelled to, the load hook stops at the switching point of
the top hoist limiter. The backup limiter switching point is above the top hoist
limiter switching point and can therefore not be activated in a normal case.
Do not intentionally trigger the
top hoist limiter.
The top hoist limiter may not be intentionally triggered during
the normal course of work.
● The load hook stops directly at the
highest / lowest hook position.
Move the load hook in the
opposite direction out of the limit switch range.
Only for wire rope hoist
with normal operative triggering of the top hoist limiter
If the highest hook position must be travelled to in normal
operation, the top hoist limiter is frequently activated and can fail because of
this. In this case, the backup limiter ensures that the crane comes to a safe
stop. So that the backup limiter can be regularly tested, the wire rope hoist
has a toggle switch with which the top hoist limiter can be manually
bridged and the crane can be manually switched on again after the test.
Trigger the top hoist limiter as
required.
The top hoist limiter may be intentionally triggered during the
normal course of work. If the top hoist limiter suddenly stops functioning, the
load hook stops at the switching point of the backup limiter. The switching
point of the backup limiter lies a small distance above the top hoist
limiter.
● The load hook stops directly at the
highest / lowest hook position.
Move the load hook in the
opposite direction out of the limit switch range.
Only with chain hoists
The chain hoist is equipped with an adjustable friction
clutch. This serves as an emergency stop device.
● Do not
intentionally run through the upper or lower end of the hook path.
The friction clutch must not be deliberately triggered during
the normal course of work.
● The
friction clutch is triggered directly at the highest / lowest hook position. The
load hook stops, the hoist motor continues running.
Move the load hook in the
opposite direction out of the end of the hook path.
Note
The friction clutch on the chain hoist GMC cannot be
adjusted!
Only with chain hoists with
a mechanical hoist limit switch
An upper and a lower switching point can be set with the
mechanical hoist limit switch. When the load hook reaches one of the switching
points, the chain hoist brakes and halts.
The switching points may be triggered during normal
operation. If the microswitches of the hoist limit switch wear out due to
regular use, the friction clutch of the chain hoist serves as an emergency end
stop device.
Only with chain hoists with
an electronic hoist limit switch
An upper and a lower switching point can be set with the
electronic hoist limit switch. When the load hook reaches one of the switching
points, the chain hoist brakes and halts.
Setting the intermediate switching point:
With the intermediate switching point function, any hook
position between the upper and lower switching point can be moved to during
normal operation.
See the product manual for the chain hoist.
Moving to the intermediate switching point:
The rotary switch is only required to set the intermediate
switching point.
● In normal
operation, the chain hoist brakes as soon as the load hook approaches the
intermediate switching point and halts there.
The function is optimised for moving to the intermediate
switching point at fast lifting speed. At slow lifting speed, the load hook
stops before the intermediate switching point is reached.
Release the button for
lifting/lowering and press again ("stop and go").
● The chain
hoist continues running and runs over the intermediate switching point.
