Gear limit switch:

─     The gear limit switch serves as a hoist limiter in ABUS wire rope hoists at the highest and lowest hook position.

─     It has 3 switching points as standard, which can be used in the range of 92 rotations of the cable drum. Alternatively, the gear limit switch can be delivered with 137, 190 and 280 rotations for larger hook paths and for use with ABUCompact chain hoists.

─     The switching points are implemented as changeover contacts through mechanical microswitches.

─     The adjustable switching points can be covered with a seal and secured.

─     The gear limit switch has an integrated tool holder with an adjusting key with pointer for easier reading of the setting.

─     In addition, the gear limit switch has mounting options for absolute rotary encoders with a ratio of 1:1 to the speed of the cable drum.

─     The gear limit switch can be optionally equipped with the ABUS absolute rotary encoder AWG, which can be used with the intelligent crane electrics ABUControl.

Gear limit switch:

─     The wire rope hoist has a gear limit switch that functions as a mechanical hoist limit switch. 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.

─     The upper switching point is called the “top hoist limiter” (middle adjusting screw); the lower switching point is called the “bottom hoist limiter” (left adjusting screw).

─     When the load hook reaches the switching point of the top or bottom hoist limiter, the hoist motor stops.

─     To additionally increase safety, the gear limit switch has another switching point. It is called the “Backup limiter” (right adjusting screw). 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. The backup limiter has been set in the factory and sealed.

The gear limit switch 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.

─     If the hoist limit switch is incorrectly set or has a technical fault, the backup limiter may nevertheless be activated. The backup limiter must then be bridged so that the crane can be switched on again. In this case, contact your ABUS Service representative. See ABUS Service.

The gear limit switch with normal operative travel to 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.

The absolute rotary encoder (option):

─     In addition to the functions of the gear limit switch, the absolute rotary encoder also serves in measuring the absolute position of the cable drum.

─     The PLC of the ABUControl intelligent crane control then uses this measurement to determine the exact position of the load hook.

─     The absolute rotary encoder registers the rotation by means of three sensors installed in the building, which measure the three mechanically driven axes of the gear limit switch with different gear reductions. The absolute rotary encoder compares the measurements of the three axes with each other for a reliable evaluation and calculation of the position.

─     The absolute rotary encoder communicates with the crane control ABUControl Basic or ABUControl Comfort via CAN bus or Modbus.

─     Additional CAN bus or Modbus devices can be connected (looped through) on the absolute rotary encoder using the second port.

─     1: Switching point of the backup limiter. If this is triggered, the gear limit switch switches off the main contactor and thus the whole crane.

─     2: Switching point of the top hoist limiter. If this is triggered, the hoist motor stops.

─     3: Switching point of the bottom hoist limiter. If this is triggered, the hoist motor stops.