Grapple bucket: types, features, disadvantages and advantages

For moving and loading loose and coarse clastic materials, scrap and wood chips, as well as long timber, a bucket bucket is widely used. It can be represented as a large iron scoop, assembled from two moving identical parts, jaws, which is attached to the crane equipment for moving loads or to an excavator for soil development above or below the parking level. However, the scope of its application is not limited to this.

Lifting capacity of grabs

Grapple is most often used as attachments in excavators and cranes with a mechanical or hydraulic drive. The main parameter that characterizes its work is the carrying capacity. From the ratio of the weight of the load and the bucket itself, its scooping ability depends. Therefore, all materials that move using a clamshell bucket are divided into several groups according to their bulk density. The carrying capacity of the working equipment is determined immediately before the start of the work by test scooping. It is made from a horizontal platform on which freshly spread ground or material is placed. The seized cargo is poured onto a special surface and weighed. During work, the ropes and blocks must be protected against entrapped material.

Cable Grapples

Grapples, depending on the number of working ropes, are divided into one-two-, four-channel and sub-sub-subspecies. The simplest version is a single-clamshell bucket. In it for the movement of cargo in the vertical plane and its capture is responsible for only one cable. The main feature of the bucket of this subspecies is the presence of a lock that connects the traverse with the cage. Its main drawback is the small height of the material and the manual control of the opening of the jaws. Two-rope grabs have lifting and closing rope. The latter is necessary for the opening and closing of the jaws. Such a ladle can be equipped with a pulley, into which the closing rope is packed, if it is necessary to increase the cutting force. The main drawback is that it is not possible to quickly replace the bucket with other lifting equipment.

The four-channel clamshell bucket has two closing and lifting cables, which gives them a greater load-carrying capacity than other types. The paddling type of the working equipment is used for scooping up the material in cramped conditions - from wagons, holds. Often, the rope system in such a grab forms a horizontally oriented pulley.

Drive grabs

In the drive grab, a separate mechanism is responsible for closing and opening the jaws, which is fixed to the hook clip with the winch. They have a greater mass in comparison with rope subspecies, but unloading control is simpler and load capacity is higher. The volume of the clamshell bucket with the drive mechanism depends on its load capacity, which, in turn, is determined by the type of mechanism that closes the jaws. It can be represented by:

  1. Electric hoist with pulley block.
  2. Hydraulic cylinders.
  3. Lever mechanism.

The main advantage of grapples of this type are small dimensions, which allows them to be used on small sites. The main drawback is the displacement of the center of gravity of the bucket, which violates its stability when scooping material from the slope.

Excavator grabs

Grapple buckets for excavators can have a different number of jaws in different shapes. This type of working equipment can be installed on a machine with a mechanical and hydraulic drive. An excavator with a mechanical drive type for the installation of a grab should have a lattice boom of a dragline. The weight of the bucket depends on the density of the soil being developed. In accordance with this, they produce light, medium and heavy equipment. With the increase in the weight of the grapple, its productivity decreases, since the excavator can lift a smaller amount of soil.

To develop dense rocks, use hydraulic grab buckets for excavators. As a rule, this equipment is mounted on the "reverse shovel" technique. The ground is cut by hydraulic cylinders, driven by a special engine.

Magnetic and pneumatic grabs

The construction of pneumatic buckets is no different from the design of hydraulic grabs. But such equipment is driven by compressed air, which is injected into the system by means of a compressor.

The principle of the magnetic grab is based on the occurrence of a magnetic field, which occurs when an electric current is applied to the excitation coils. After applying the current, the magnet approaches the clamshell and closes the jaws. As a rule, magnetic grabs have a large bucket, which not only captures bulk materials, but also attracts ferromagnets (iron, steel), which significantly increases the volume of the material being reloaded.

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