Comprehensive discussion on the technology of the

Comprehensive discussion on web offset press technology Chapter 12 paper system

5) adjusting roller

● function: when one end of the paper roll is larger and the other end is smaller, or one side is loose and the other side is tight, the length of both sides of the paper tape is actually different. Therefore, the paper tape often deviates. In order to solve this problem, it is generally equipped with adjustment rollers. Adjust the adjusting roller so that it is not parallel to other paper passing rollers to prevent the paper tape from deviation

● structure: as shown in the figure. Roller 9 was fixed on May 5, and the domestic large aircraft C919 made its first flight! What new materials are used? Roller seat 13 and slide 7. The roller seat 13 is fixed on the wallboard through the small shaft 16. The slider 7 can slide because the valve spring is an important part of the valve system of the automobile engine. The seat 6 moves back and forth to achieve the purpose that the roller 9 is not parallel to other rollers

turn the handle 3 and adjust the screw 4 to rotate, thus driving the slider 7 to move forward and backward. The compression spring 5 ensures that there is no relative displacement after the relative position of the sliding block 7 and the sliding seat 6 is adjusted, so as to ensure that the relative position of the adjusting roller and other paper passing rollers remains unchanged and keep the paper tape stable

6) paper passing roller

the function of paper passing roller is to change the paper threading route, and its structure is similar to that in the figure. The difference is that the slide block and adjusting mechanism on the left are all changed to the same roller seat as the right end. Both ends are fixed on the wallboard with roller seats to ensure that the rollers are parallel and fixed

7) paper feeding roller

paper feeding roller is generally the last part of the paper feeder. When the paper belt leaves the paper feeding roller, it will enter the paper feeding mechanism or directly enter the printing unit

the paper feeding roller is generally composed of three rollers, as shown in the figure. There are also two rollers, that is, there is no steel roller 11 in the figure (see the next page). Whether it is composed of three rollers or two rollers, one of them must be rubber rollers, and the other one or two are steel rollers. The steel roll is the active roll, and the speed can be adjusted. The rubber roll is the passive roll, which can rise and fall, and can adjust the pressure between the rubber roll and the steel roll

① effect. The function of the paper feeding roller is firstly to control the speed of the paper belt entering the paper feeding mechanism or directly entering the printing unit through the adjustment of the pressure of the rubber roller and the steel roller and the speed of the steel roller. The purpose of controlling the tension of the paper belt is achieved by controlling the speed of the paper belt; The second is to ensure that the paper tape enters the paper feeding mechanism smoothly and stably or directly into the printing unit. In order to achieve this goal, the parallelism of the center lines of steel roller 15 and rubber roller 12 must be ensured during assembly. The manufacturing accuracy requirements for steel roller 15 and rubber roller 12 are very strict. The circular runout is generally controlled within 0.02mm, and the cylindricity is controlled within 0.025mm. Some also make the rubber roller 12 into a threaded roller with left-right rotation, so that the paper tape sent out is more flat. The steel roller 11 in the figure is not in contact with the rubber roller 12. The function of the steel roller 11 is to increase the wrapping angle of the paper tape on the rubber roller and make the paper tape sent out more stable

② the rise and fall of rubber roller and its pressure adjustment with steel roller. As shown in the figure. The rise and fall of the rubber roller is controlled by the air circuit. When the piston of cylinder 3 extends, the rubber roller falls, otherwise it rises. The position of the adjusting screw 13 can be adjusted. When the rubber roller falls, it is positioned by the adjusting screw 13. Therefore, adjusting the high and low position of screw 13 can change the pressure of rubber roller and steel roller

in addition to ensuring that there is a certain pressure between the rubber roll and the steel roll, it must also ensure that the pressure between the rubber roll and the steel roll is consistent, for which an adjusting mechanism is set. The paper feeding rubber roller is connected with the shaft 9 through two connecting rods 8. On the machine control surface, the connecting rod 8 and the shaft 9 are fixed, while on the transmission surface, the connecting rod 8 and the shaft 9 are sleeved together, and the connecting rod 8 and the shaft 9 are fixed by adjusting screws 5, 10 and their supports. Therefore, adjusting the adjusting screws 5 and 10 can change the relative position of the connecting rod 8 at one end of the transmission surface and the connecting rod 8 at one end of the control surface. Ensure that the pressure between rubber roller and steel roller is consistent. When adjusting the pressure, first adjust the pressure of the operating surface (adjust the position of the adjusting screw 13), and then adjust the pressure of the transmission surface based on the pressure of the operating surface. If it is not appropriate, adjust the position of the adjusting screws 5 and 10. Ensure that the pressure between rubber roller and steel roller is consistent

③ differential cylinder. The rise and fall of the paper feeding rubber roller is completed by the differential cylinder. Its structure is shown in the figure. The so-called differential means that when the piston rod is extended, compressed air is introduced into both ends of it, and the pressure difference is used to push the piston to work. The principle is as follows

to shrink the piston rod, the left end of the cylinder can be filled with compressed air. At this time, the hole 18 at the right end is blocked by the solenoid valve, and the compressed air can only enter the left end of the cylinder. Because the hole 17 is connected with the type gas whose performance greatly exceeds that of the raw fiber itself, the compressed air at the right end is discharged into the atmosphere, so the piston moves to the right, the piston rod shrinks, and the rubber roller is lifted at this time

to extend the piston, use the solenoid valve to open hole 18 and cut off the passage between hole 17 and the atmosphere. At this time, compressed air enters the left end of the cylinder, and at the same time, it enters the right end of the cylinder through the air pipe 14, holes 16, 18 and 17, and compressed air with equal pressure is introduced into both sides at the same time. Because the left compressed air contact surface is the annular surface of the cylinder barrel area minus the piston rod area, while the right surface is the area of the whole cylinder barrel, so there is a difference in the area of the piston rod on both sides. Because the compressed air pressure is the same, the total pressure on the right is greater than that on the left. This pressure difference pushes the piston rod out

④ adjustment of paper feeding steel roller speed. The paper feeding steel roller is the driving roller, and its power comes from the main drive system. A stepless speed changer is set between the paper feeding steel roller and the main drive to adjust the actual linear speed of the paper feeding steel roller. In order to maintain the tension of the paper belt, the linear speed of the paper feeding steel roller should be slightly lower than the linear speed of the printing drum, and the speed of the paper feeding steel roller must be kept stable. Therefore, it is required that the speed regulation of the stepless transmission is accurate, and the speed ratio of the stepless transmission remains unchanged in the process of speed change. Different machines have different requirements for CVT. According to the accuracy of web offset press, the error of CVT is generally within ± 0.3 ~ 1%, and the accuracy of individual requirements is also within 2%

in the experiment of continuously variable transmission, if the value is incorrect, the structural diagram is shown in the figure. There is a silent toothed chain 3 between sprockets 2 and 6. Input shaft 4 will input power, change speed through sprocket 6 and sprocket 2, and output power through output shaft 1. The speed ratio between sprockets 2 and 6 is adjusted by adjusting handwheel 5. Turning the adjusting handwheel 5 can change the distance between the two sprockets of sprocket 2 and sprocket 6. When the distance between sprocket 2 or 6 changes, it means that the pitch diameter of sprocket changes. Because the pitch diameter of its sprocket can be changed continuously, the speed ratio of input and output can be adjusted steplessly. The speed of the input shaft is changed by two sprockets, and the speed of the output shaft can be higher or lower than that of the input shaft. In the figure (a) shows the increase in speed and (b) shows the decrease in speed

when using this stepless transmission, it should be noted that the speed regulation must be adjusted during operation, and the speed regulation cannot be stopped, otherwise the silent toothed chain and sprocket will be damaged

for a web offset press with ordinary accuracy, the speed of the paper feed roller is adjusted manually by experience. The more advanced web offset press adopts electronic technology for automatic control and automatic tracking, so that the speed change of the paper feeding roller is completely synchronized with the printing unit, which greatly improves the accuracy of paper belt tension adjustment

the development of shaftless transmission technology can realize accurate and stable adjustment of synchronous relationship under the condition of canceling the mechanical transmission shafts of printing unit and paper feeding unit