The role of the paper transfer device in the printing process is to hold the paper that has been accurately positioned on the paper feeding platen and hold it in the mouth, and transfer it to the paper transfer cylinder or the impression cylinder to enter the roll printing. This method of paper delivery is called indirect paper delivery. In the direct paper delivery method, the impression roller grips the positioned paper directly.
The accuracy and stability of the paper-handling movement are related to the paper positioning and the normal operation of the machine.
Usually the paper delivery device is called paper delivery tooth or swing tooth in the factory. Paper delivery teeth are generally divided into four categories: upper swing type, lower swing type, roller type and beyond type. The first two forms are commonly used in domestic offset presses. For example: J2108 and J2205 adopt eccentric upper swinging paper delivery teeth. There are many types of paper delivery teeth, but no matter what type of paper delivery teeth, its movement must meet the following four conditions.
(1) When holding paper on the iron table, the movement speed of the delivery tooth is zero, that is, the positioned paper should be picked up at rest.
(2) When the paper is handed over to the impression (or paper transfer) cylinder, the movement speed of the transfer tooth should be equal to the linear speed of the surface of the impression (or transfer) roller, and the junction should be the phase of the transfer tooth and the surface of the roller Cut-off point.
(3) The acceleration movement from the paper receiving point to the paper delivery point has no impact, that is, it requires smooth acceleration.
(4) There should be a period of time for handover and handover. There is a period of rest time on the platen, that is, paper stabilization time. There is a period of time equal to the speed during the handover with the drum, that is, the synchronization time, and the paper is not allowed to run out of control to ensure the accuracy of paper transfer.
Transmission principle and movement track of eccentric upper swinging paper-feeding tooth
1. As shown in Figure 4-8, the up-and-down movement mechanism of the paper delivery tooth is shown in the figure. The two gears 1 installed on the shaft ends of the impression cylinder respectively drive the two eccentric bearing gears 2 of the paper delivery device, the eccentric shaft sleeve and the transmission The two gears are fixed together. The eccentric shaft is set in the frame hole, so the outer circle of the shaft sleeve coincides with the center of the frame hole and the gear. The inner hole of the eccentric shaft sleeve is equipped with a paper delivery device swinging shaft, the center of which is O1. When the gear and the eccentric bearing sleeve rotate, O1 rotates around O, which causes the transfer paper tooth to move up and down.
Figure 4-8 The principle and structure of the eccentric upper swinging paper tooth transmission
2. Swing mechanism for paper-hands
In addition to the gear 1, a cam 3 is installed at the drive shaft end of the impression cylinder, and the swing rod 5, the connecting rod 6, the swing rod 7 and the gripper row swing arm 9 are driven by the roller 4, according to the requirements of the cam curve, the swing arm 9 Swing back and forth between the impression cylinder and the positioning device. The tension spring 8 makes the roller 4 abut against the cam 3. In order to ensure that the two ends of the delivery shaft are evenly stressed, there are two large tension springs 8 installed symmetrically on both ends of the shaft.
3. Positioning of the delivery tooth at the front rule
When the paper feeder swings forward to receive the paper, the stopper 14 on the swing arm contacts the positioning adjustment screw 10 to control the paper feeder and the front gauge to transfer paper, and there is a reliable and still position.
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The contact of the stopper 14 on the transfer arm and the limit screw 10 is usually called the stopper on the transfer arm of the transfer tooth in the domestic offset press, and the limit screw 10 is called the backer, and the overall name is For backers. In practice, the two are often called separately. The brakes are divided into three categories: positioning, limit and protection according to their functions. There are absolutely still, relatively still and various kinds of brakes. For example, the brake on the transfer roller of the paper conveyor can play a very important role in the movement and adjustment of the offset press. It can control the up and down movement range of the delivery roller, and can also control the length of the paper pressing time. When adjusting, pay attention to the coordination of the relationship between the two. The front gauge is positioned by the brake. During the movement of the machine, the tightening nut on the inside of the operating surface should be prevented from loosening and causing the rules to be inaccurate.
The paper delivery mechanism has two brakes. One is that there is a symmetrical brake on the left and right sides of the paper delivery shaft head, which is the benchmark for adjusting the opening and closing width of the paper gripper. The second is the hand brake on the swing arm of the paper tooth, which has the function of positioning and shock absorption. In addition, the water transfer roller shaft, the ink transfer roller shaft, the impression cylinder, the gripper shaft, the delivery shaft, and the clutch pressure are all provided with a brake.
4. Opening and closing of paper tooth
The convex block 12 controls the opening and closing of the delivery tooth when receiving the paper at the front gauge; the convex block 13 controls the opening and closing of the delivery tooth at the drum; the convex fast 11 is a self-locking control device connected with the drum clutch mechanism. When the drum is "off pressure" and the front gauge stops swinging, the bump 11 falls with the clutch mechanism, so that the delivery tooth is opened, and the paper can no longer be picked up at the front gauge. When the front gauge resumes swinging, the bump 11 will automatically move Lift and pass the paper teeth to continue passing the paper.
It can be seen from the transmission process of the paper delivery device that the motion of the eccentric swinging paper delivery tooth is synthesized by two movements. One movement is to drive the gear 2 on the eccentric sleeve of the delivery tooth according to the gear ratio of 1: 1 at the shaft end of the impression cylinder. Gear 1 and gear 2 are one pair each on the side of the operation surface and the transmission surface wall. The two pairs of gears must ensure the concentricity of O1 at both ends during installation and commissioning. The other movement is driven by the cam 3 mounted on the shaft of the impression cylinder, pushing the roller 4, swing rod 5, connecting rod 6, swing rod 7, and the paper delivery swing arm 9 is fixedly connected with the swing rod. Get back and forth.
The cooperation of these two movements makes the delivery tooth obtain the required synthetic movement trajectory.
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