【疯狂发明家】 今天是《龙门吊》。 dragon door crane also called gate type hoist machine，he is one of the kinds of hoisting machines. Today for everyone to introduce various hoist machines. Among them has tower crane, car crane, track crane etc. Gate type hoist machine has high ground utilization rate, large working range, wide adaptability and strong universality etc. Characteristics, it is widely used in harbor warehouse. dragon door crane can be divided into single main beam and double main beam from main frame. Can be divided into fixed type and mobile type from arm. The main structure of the building mainly has arm, main beam, hook. The main frame and main beam are constructed mainly with mutual locking structure. The installation of hook needs to consider that it can move left and right, as well as bear the goods. We use a short smooth beam and fix it on the main beam.