What’re the purpose and structure of overhead crane(Part I)?
LD electric single girder overhead crane (the following says crane) is a kind of light lifting equipment, used with CD1、MD1 and other electric hoists, lifting capacity 1-20t, span 
7.5-22.5m, working environment -25℃~+40℃, humidity ≤84％. It works under the environment without fire, explosion and corrosive matters and it is prohibited to lift liquid metal, and toxic, flammable and explosive objects. Work duty: intermediate work system（JC25%）
The product is a crane with general purpose, suitable for machinery fabrication, assembly, warehouse and other places. Features of its structures are as follows:
(1) Metal structure
Box type main girder is welded by U type trough plate rolled by steel plate and joist steel group. Cross girder is installed and welded by joist steel rolled by steel plate. For convenient storage and transportation, high tension bolts are used to connect main girder and cross girder.
(2) Lifting system
Be equipped with electric hoist which moves longitudinally along main girder, details of structure features are shown in the electric hoist specification.
（3）Moving system
Adopting independent driving form, the product uses driving device of LD model electric single girder overhead crane, use tapered rotor motor to match with “one open and one closed” gear reducer to finish moving
