The working principle of offset press deceleration device

4.2 Front flush of printed sheet (reducer)

After the sheet has passed from the impression cylinder to the delivery roller, it cannot stop on the delivery pile without any deceleration device. The following detailed analysis of the working principle of the reduction gear.

1 chain slowdown

When an object is placed on a belt (no relative sliding is allowed), when moving between two wheels (as shown in Figure 4.5), the speed of the object is the same as that of the belt, because they are all in translation. When it runs on the surface of the wheel, the belt is close to the surface of the wheel, its speed is the same as the original, and the speed of each point on the object is not the same, the farther away from the wheel center, the greater the speed; The closer it is, the lower its speed. This can also be seen from the above figure. The arc length of A2 is obviously greater than the arc length of B2, that is, the speed of A2 is greater than the speed of B2. When the object reaches the middle of the next two wheels, it maintains the same speed as the conveyor belt. The speed of A3 is equal to the speed of B3. When the conveyor belt is replaced with a chain and the object is replaced with a chain, the mechanism becomes the delivery chain of the delivery section.

The A1 point is equivalent to the position of the tooth pad. When the tooth row and the impression cylinder are connected, the speed of the tooth pad is consistent with the speed of the tooth pad on the surface of the impression cylinder. Since the mutual transfer can only be performed on the arc, that is, the tooth pad transfer The speed of A2 is the same as the speed of A3 when the tooth row runs to A3 after the transfer. Since the speed of A3 is less than the speed of A2, the speed of the pad is reduced, and the paper moving together with the pad is also decelerated. This is the first level of deceleration for the paper. Since the tooth pad can decelerate, it must also have an accelerating process. As can be seen on the human map, A1 and A2 are the accelerating phases of the dental pad. Therefore, the process of running the dental pad from the upper chain to the lower chain is actually the acceleration and deceleration of the dental pad.

From the point of view of paper deceleration, the greater the difference in speed between A2 and A3, the better, but from the perspective of the flatness of the paper, the smaller the difference in speed between A2 and A3 is, the better. Therefore, the design must be coordinated well between them. Relationships.

Brake roller deceleration

When the paper passes the brake roller, the brake roller starts to suck the air under the paper, causing the paper to produce a downward pressure, thereby increasing the frictional resistance between the paper and the air. After the tooth releases the paper, the resistance acts as a deceleration.

This is the second stage of paper deceleration. Another function of the brake roller suction is to create a pressure differential that causes the paper to rest against the surface of the delivery pile, preventing it from drifting. The amount of air suction on the brake roller can be adjusted. When the speed is high, the suction volume is larger; when the speed is low, the suction volume is smaller. Different models have different adjustment methods. Some equipment is installed on the transmission system of the delivery section, that is, changes with the speed of the transmission system; some machines are equipped with a dedicated speed-regulating motor to control the rotation speed, and the adjustment is convenient. Its position can be adjusted back and forth depending on the width of the paper.
3. Fan deceleration

As the paper passes under the fan, the fan blows air, increasing the friction between the paper and the air. After the tooth releases the paper, this frictional resistance slows down the paper. This is the third stage of paper deceleration. Another function of the fan is to create a pressure difference by blowing air, so that the paper is close to the surface of the pile of paper, so as to facilitate the collection of paper at the same speed. The size of the fan's blow can also be adjusted. The number of fans is different, but their distribution is symmetrical. In essence, the role of the fan and the role of the brake roller is exactly the same.

4 open teeth deceleration

The change of the position of the open tooth plate can change the position of the tooth discharge paper. When the paper speed is too fast, the position of the open tooth plate can be adjusted so that the paper can be discharged in advance so as to achieve the purpose of deceleration. This is the fourth level of paper deceleration.

5. Before the paper board slows down

After the teeth are open, the paper is in an unconstrained state. Due to various factors, the position of each paper on the delivery pile cannot be exactly the same, but at the final delivery pile, it is hoped that they are in the same position. . This process is achieved by the front plate. When the paper is to fall on the delivery pile, the front plate is swayed backwards, and after the plate falls, the front plate is set back again, colliding with the opening of the paper, pushing the paper to make it flush with the front end, when the second When the sheet of paper came over, it began to swing back. This action is repeated, so that all paper fronts can be flush. To some extent, it can be said that the front trim board has a positioning effect, but the positioning requirement is much lower than the positioning requirement of the regulation part. Since the front panel has a positioning effect, all of the upper cardboard strips should be on a flat surface, but this is actually very difficult to do. Two of them are generally selected for positioning, and the rest are for auxiliary positioning.