Intelligence Aided Lifting Equipment
9
1.3 Safety protection device
A safety protection device is designed to prevent accidents of intelligence aided lifting
equipment, consisting of limit switches that limit movement, steel cable locking device, overload
prevention device and forced cooling devices.
1.3.1
Limit switch
The intelligence aided lifting equipment is provided with limit switches (Fig. 1. 1) to ensure
reliable operation. A stroke limit switch comprises of an upper and a lower limit switches. When
the equipment operates upward to some 10 cm before the upper limit, it starts to decelerate to
prevent the weight from breaking away from the lifting hook. If the equipment reaches the upper
limit position, the limit switch will be triggered and the equipment can only move downward. The
lower limit switch is designed to ensure at least two turns of steel cable stay on the reel. The
equipment can move upward only if the lower limit switch is triggered.
Fig. 1. 1 Stroke limit switch
1.3.2
Steel cable locking device
The intelligence aided lifting equipment is provided with a micro switch to detect steel cable
looseness (Fig. 1. 2). When a steel cable is loose in operating equipment, the micro switch will
detect such looseness and trigger relevant actions, and then the display on the handle will indicate
“steel cable looseness alert” and the equipment can only move upward.
Fig. 1. 2 Micro switch to detect the looseness of steel cable