Analysis of the importance of the chain in the offset press

4.6 The importance of the chain

The chain is an important link to ensure that the paper tooth row can accurately pull the paper from the impression cylinder, and its accuracy is very strict. From the point of view of smooth running, it is necessary to make the chain discharge always tightly against the sprocket on both sides of the delivery roller, to prevent it from jumping and causing instability, and the other is to generate noise. The take-up chain row takes the paper from the last impression cylinder, and the same requirements as the other cylinders meet each other.

1. The speed of the tooth pad of the delivery chain is equal to the speed of the impression pad. That is, the transfer is performed in a relatively stationary state.

2. The position of the receiving tooth pad and the position of the impression pad correspond to each other. Can not lead or lag, resulting in unstable handover.

3. The pads of the delivery chain should be on a flat surface. That is, at the time of handover, the preconditions for the positioning of the paper should be ensured, and the surface should have a large coefficient of friction.

4. The action of opening and closing the teeth of the slice of the delivery chain should be the same. That is to prevent the local friction drive from being damaged, causing the footprint to slip or tear.
5. The bite force of the collection teeth should meet the printing requirements. Since the delivery chain is directly involved in the printing process, the bite force must be large enough to remove the paper from the blanket cylinder, otherwise it will stick to the surface of the blanket. However, if the bite force of the pad is too large, a long time impact will cause the position of the pad to change, which will affect the stability of the transfer.

The best way to solve this problem is to leave the blanket completely out of the blanket cylinder and then transfer it from the impression cylinder to the delivery cylinder so that there is little biting force in the delivery chain. At present, some equipment changes the impression cylinder to a double-diameter cylinder, and some devices add two transfer cylinders after the last group of impression cylinders, as shown in Figure 4.8.

From the perspective of the printing process, the printing pressure of the last group is still properly reduced, and the viscosity of the ink is also appropriately reduced, thereby reducing the driving force required for the separation of printed sheets and improving the working environment of the delivery chain.

6. The number of links in the take-up row is a prime number (ie, a number that can only be divisible by "1" or itself). This ensures that all the chain links of the take-up chain are uniformly worn and can increase the overall life of the chain.

7. The operating stability of the delivery chain. In addition to the processing and installation guarantees, the stable operation of the delivery chain line must also be ensured from the design. There is a row of active links between the two chain rows, and one row should be in an auxiliary position. Both ends of the active chain must be absolutely accurate, and the position of the auxiliary chain must be absolutely accurate at the pick-up location, and at the other end it can be in the automatic adjustment state, so as to prevent the existence of internal forces between the two chain rows. . The open jaws should be mounted on the side of the auxiliary chain, which can provide a degree of cushioning.