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Knowledge collection of offset press mechanism

5 Type and working principle of side gauge

(1) there are generally two kinds of side rules, push rules and pull rules. The push gauge pushes the paper to position horizontally on the opposite side, and the pull gauge pulls the paper to position horizontally on the side of the rule

push gauge can be seen on earlier machines, and now most printing machines use pull gauge. This is because of the flexibility of the paper, it is difficult to maintain the positioning accuracy with the push gauge. Next, we will mainly talk about the side pull gauge

side pull gauges include fan-shaped plate type, roller type, magnetic strip type, etc. The fan-shaped plate puller gauge was used on earlier domestic machines, and now it has been basically eliminated. At present, almost all beiren equipment is roller type. Heidelberg equipment uses magnetic strip type pull gauges. The advantage of the roller type tension gauge is to change the reciprocating motion into rotary motion. Therefore, our company has given a definite suggestion on how to buy a suitable single arm tension tester: the impact is very small, and the disadvantage is that the contact surface with the paper is small. When the vibration is large, it is easy to cause inaccurate overprint

the characteristic of magnetic strip type pull gauge is that it can obtain a large contact area with the paper, and has a relatively small impact on the positioning accuracy of the front gauge, but this structure is relatively complex, and the installation accuracy requirements are also very high. There are the following requirements for the movement of the side gauge:

① the paper can be pulled only after the previous regulation is finished; ② The side gauge must be away from the surface of the paper when taking the paper from the paper delivery tooth; ③ It must be stable during the paper pulling process (the side gauge and the paper must always be in contact)

(2) analysis of the principle of side gauge paper pulling the side fairy paper relies on friction, and the formation principle of friction is basically similar to that of the paper on the paperboard. Therefore, in order to make the paper locate reliably, it is necessary to create the conditions for the stability of the groove condition when the electrolyte of friction is low. The stress analysis of the paper is as follows:

F1 is the friction generated by the driving part, F2 is the friction generated by the driven part (generally refers to the roller), F3 is the friction generated by other parts on the surface of the paper, and F1 = F2 + F3 according to the requirements of motion

f1 and F2 are proportional to the pressure of the side gauge spring. F3 is proportional to the force of other parts on the paper. F3 force includes: friction between paper and paper, resistance of side gauge pressing plate, etc. The relationship between F1, F2 and F3 forces directly affects the positioning accuracy

according to the function of the side gauge, it can be seen that the side gauge should have the following functions:

① according to the change of the paper size, the lateral direction can move relatively

② relative adjustment can be made in the height direction according to the change of paper thickness

③ according to the needs of transmission, the pressure of the roller on the paper should be adjustable

④ according to the needs of position coordination, the included angle between the side gauge baffle and the front gauge can be adjusted mutually (in a right angle state)

⑤ according to the time sequence relationship, the start and end times of side gauge paper pulling should be adjustable; ⑥ Selection of working and non working states

6. The influence of the previous regulation on the positioning of the side gauge. First of all, the front gauge is the benchmark for the positioning of the side gauge. Only when the front gauge is accurately positioned, the positioning of the side gauge is meaningful. Secondly, if the front gauge is too low, there will be greater friction on the paper surface, which will destroy the conditions of friction transmission of the side gauge; If the front gauge is too high, its positioning accuracy is very low, and the side gauge positioning cannot effectively correct the paper. Therefore, the front gauge cannot be too high or too low. Generally, the height of the front gauge is the paper thickness plus 0.20mm, which can basically maintain the positioning accuracy, and at the same time, the friction that hinders the horizontal movement of the paper is relatively small

if the side gauge wants to position accurately, it must overcome all the friction, which should not be paid attention to when adjusting the machine. The height of the side gauge baffle is the paper thickness plus 0.20mm, which can ensure that the resistance of paper entering the side gauge is relatively small. Another is to adjust the pressure of puller, so as to change the conditions of friction transmission. Therefore, we must pay attention to the influence of the front regulation on the positioning of the side gauge, especially for the front gauge with downward pressure

7. Paper delivery teeth. The paper feeding tooth is an extremely important link to make the paper enter the controlled state from the semi free state. The reliability of this state directly affects the overprint accuracy, so the requirements for the paper transfer teeth are very high in terms of design, processing, installation and other aspects. Generally, there are the following requirements for the paper feeding teeth:

(1) its own motion trajectory

① take the paper absolutely still relative to the paper feeding board. This is the key step of paper handover. Only when it is absolutely static, can the stability of handover be guaranteed without damaging the positioning accuracy of the paper

② uniformly accelerate the movement to transfer the paper from the cardboard to the embossing cylinder or the paper transfer cylinder. This requirement ensures the smooth handover of paper and the minimum inertia impact. This is the key to design the paper delivery cam. In fact, the design of paper delivery cam does not necessarily have to be accelerated or decelerated. The key is to ensure smooth movement and minimum inertial impact

③ hand over the paper to the follow-up drum relatively statically. Only when it is relatively static can the paper be handed over. If it slides relatively in the process of handing over, the accuracy of handing over will be destroyed

④ return to the cardboard conveyor from the drum at a uniform speed. This requirement enables the paper to return to the feeding board with the minimum stabilization time and enter the absolute static state as soon as possible. This is also a key part of designing the paper delivery cam

(2) requirements for relative movement

① after the positioning of the front gauge and side gauge is completed, the inner wall of the working cylinder of the paper transfer tooth we universal experimental machine is the guiding surface of the movement of the working piston, and then the paper can be taken out of the paperboard

② when the paper feeding teeth leave the cardboard, the front gauge should leave the cardboard in advance

③ the paper can be handed over only when the tooth pad of the paper delivery tooth is parallel to the tooth pad of the rear paper transfer roller proposed by the German government

④ when there is a paper feeding failure, the paper feeding teeth do not fit on the paper feeding board

(3) requirements for motion trajectory

① the motion trajectory is smooth and the inertial impact is minimum

② do not interfere with any other parts in the motion track

(4) requirements for its own accuracy

① all dental pads are flush and the friction coefficient is evenly distributed

② all dental discs have the same pressure and uniform contact

③ the movements of all dental films are consistent

④ the action of tooth opening and closing mechanism is flexible and reliable

⑤ the string movement and runout of the paper transfer tooth shaft are the smallest

(to be continued)

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