6.3.6 Block Chain (Bar and Pin)
Large conveyance: The steel industry, conveyance of sand and earth, shuttle traction
Block Chain is used for cooling high-temperature steel bars, seamless pipes, or for pushing red-hot slabs and billets, for example (Figure 6.22). In addition to the steel industry, Block Chain is used for vertical conveyance of sand and earth, and for shuttle traction.
Figure 6.22 Block Chain
Construction and Features
This chain is usually composed of three parts: two outer plates and one (or sometimes two) inner plate (block) that are connected with pins. The tensile strength ranges from 309 to 2,720 kN.
In comparison to roller chain, Block Chain has the following features:
- Greater impact resistance due to the strong construction and high rigidity.
- Higher strength considering chain weight.
- All the main parts are heat-treated for greater wear resistance against the guide rails.
- Usually the bottom side of the plate slides on the guide rail; the chain does not have rollers. It's possible to push and carry conveyed objects on the guide rails using special pushers (dogs) attached to the chain (Figure 6.23).
- Solid Pusher
Inner or outer pusher link to push material.
- Tilting Dog
When material on the conveyor runs relatively faster than the chain, the dog is pushed down from behind to enable material to pass over. The dog then resumes its original position.
- Ducking Dog
The dog is supported on the guide rail to convey material. When the guide rail is interrupted, the dog ducks down, leaves the material, and passes beneath it.
- Tilting and Ducking Dog
Both tilting and ducking functions are combined. When the dog comes in contact with the table surface, it lets the material pass over. When the guide rail is discontinued, the dog leaves the material, and passes beneath it.
Figure 6.23 Installation of Pushers on Block Chain
Sprocket teeth engage the inside plate of the chain, entering the area between outer links. The sprocket skips every second tooth to allow for the solid block.
Selection and Handling
- Select a sprocket with more than 12 teeth.
- Use a sprocket with an outer plate support piece (Figure 6.24).
- Install hardened bushings in the inner link for improved wear elongation resistance (Figure 6.25).
Figure 6.24 Sprocket with Outer Plate Support Piece
Figure 6.25 Hardened Bushings Improve Wear Resistance