Trolley Crane Mechanism for Material Handling
The lifting crab of an EOT crane is an independent two motion machine and consists of the hoist machinery built onto a frame, which is mounted on runner wheels, and driven by a motor through suitable gearing. The crab is also known as a trolley.
Various designs of crabs, arranged with C.I. side frames, mild steel side frames are in use. But now a day, preference is given to the built up side frames on which the machinery is mounted.
The function of the crab is to provide cross travel motion to the hoisting machinery along the length of the main bridge of the crane. The entire hoisting machinery is mounted on the crab which moves with runner wheels over rails fitted on the main bridge of the crane.
As standard units is also tailor-made, crab trolley’s can be delivered. They give the greatest benefit when you work freely in open space. Single or twin hoists may be provided with these crane crabs unit. The driving mechanism may be manually operated or motorized. If possible, micro speed arrangements can be made in hoisting.
Trolley Crane Speed Control
Micro-drive fine inching motions of hoists, trolleys or crabs at a pace of between 5% and 20% of the main motor rpm. A separate gear box with a distinctive sun and earth gear system attachment achieves this scheme. It is a positive drive gear mechanism that eliminates external parts of the transmission system, such as clutches.
The straight double-flange cast steel wheels are the trolleys and crane wheels. Heat treated for the achievement of a special mortised structure up to a depth from the surface of 15 to 20 mm and progressively decreases the core properties to the center. The anti-friction ball / roller bearing supports these wheels.
For infinite variable speed control, variable frequency electronic AC drives are available. It saves power from cranes and increases the handling of loads.
Trolley Crane Braking System
In case of failure, the shaft is fitted with protected hydraulic or electromagnetic braking. A second brake is fixed for heavy cranes so that the malfunction is improved.
Trolley Crane Gear Reducer Unit
The transducers are designed to minimize the top speeds by means of robust, wide-faced helicoidal or spur gears that are precision cut from special alloy steel forges and shield the transmission train from shock. Both gears are fully sealed with the lubrication of the oil bath.
Trolley Crane Girder Design:
Box girder are fabricated from mild steel plates or channels. Main girders and carriages are joined by specially made machined bolt to avoid noise and vibration. Bridge is designed for minimum vibrations and deflection.
The motion of the crab is derived from an electric motor. A speed reduction gearbox and a brake are the essential components of a crab gearing. The motion of the motor is transmitted through the reduction gear box via the brake. The HP of motor is calculated by the formula:
HP=W*S*C / 4500
W=total load of the crane including the dead load any payload in tons;
S=Speed of the longitudinal motion in meter per minute;
C=Tractive effort in Kg per ton.
The reduction gear box is designed to obtain a speed ratio which can reduce the motor RPM to the appropriate RPM of the crab runner wheel to produce the desired speed of the crab. The reduction ratio per stage of the gearbox is fixed at 4 to 5 and is the same for all stages.