According to the structure, container spreaders can be divided into two categories: non-telescopic fixed spreaders and telescopic spreaders. The fixed spreader can be divided into independent spreader and master-slave spreader (also called mother-child spreader).
1. Fixed spreader
1. Free-standing spreader. From the connection with the crane, it can be divided into fixed connection and separable connection.
A. The fixed connection type spreader is generally suitable for hoisting a single specification container. Generally, the movable pulley is directly installed on the spreader. The turning lock mechanism of this type of spreader is generally driven by power, so the crane needs to have a control circuit for the spreader turning lock. The advantage of this type of spreader is that it can save the lifting height. Because the spreader adopts multi-point connection, it can greatly reduce the shaking of the spreader. At the same time, the spreader has no rotation. The simple guide plate of the spreader itself can greatly improve the work. effectiveness. Since the steel wire rope is directly wound on the pulley of the spreader, it is relatively troublesome to replace the spreader.
B. The separable connecting spreader is generally suitable for occasions where the container type is complicated but the lifting is not very frequent, or where the lifting of the container and other ordinary goods is required. This type of spreader has been connected to the sling before the manufacturer leaves the factory, and the user only needs to hang the ring on the sling on the crane hook when using it. The rotating lock mechanism of this type of spreader generally adopts a heavy hammer type or a ratchet type, no additional power source is required, and the installation and use are very convenient. Because the crane hook is generally unpowered and rotatable, the spreader hanging on the hook will also rotate with it. Therefore, when using this type of spreader, a person must assist in matching the boxes below. This type of spreader is not suitable for use on the second floor.
2. Master-slave spreader (child-mother spreader). The mother-and-child spreader is composed of two spreaders of 20 feet and 40 feet. The 20-foot spreader is a fixed connection spreader used to lift 20-foot containers. When a 40-foot container needs to be lifted, the 20-foot spreader is used to lift 40 feet. The 40-foot spreader is used to lift the 40-foot container. The 20-foot spreader and the 40-foot spreader each have a power source to drive the turn lock mechanism. Due to the large size of the lifting point of the 40-foot spreader, the 40-foot spreader has a large dead weight, generally exceeding 5t, so the lifting weight of the crane must exceed 45t to use this spreader. The advantage is that, compared with the telescopic spreader, the spreader is low in price, simple in structure, and convenient to maintain.
2. Telescopic spreader
The structure of the telescopic spreader is composed of a fixed base frame and a telescopic beam. The telescopic beam is driven by a telescopic drive mechanism to expand and contract, so it can adapt to containers of different specifications. The expansion and rotation of the spreader is generally driven by hydraulic pressure (now there are a few spreaders that are driven by pure electric motors), and they are controlled by the driver in the crane cab. Since multiple sensors are installed on the spreader, which are interlocked with the lifting of the crane, the safety of the spreader for lifting the container can be greatly improved and various risks can be reduced. In order to improve work efficiency and adapt to the lifting requirements of different cranes, manufacturers have installed various mechanisms on the spreader, such as hydraulic guides, tilting devices, rotating mechanisms, center of gravity adjustment mechanisms, etc., making telescopic spreaders more and more complex. More and more functions. Telescopic spreader is suitable for professional container terminals, storage yards and other occasions for frequent lifting of various containers, so telescopic spreader is currently the most widely used spreader for large-scale port container professional terminals. This type of spreader has a complicated structure and a relatively large dead weight, about 8-10t; the maintenance is also more complicated, and generally requires professionals to repair, and the repair cycle is also long.