Research and Analysis on the cylinder crawling phe

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Research and analysis of cylinder crawling phenomenon of automatic liquid filling machine

1 introduction automatic liquid filling machine is a device for filling detergent, chemical agents, beverages, liquid medicine and other liquids into containers. It can not only realize continuous automatic filling, but also carry out manual operation of each process. It can fill containers with different heights and capacities, and solves some inevitable problems in resin production and molding processing. The flow of liquid automatic filling machine is shown in Figure 1. The working procedure is as follows: (1) after pressing the pneumatic signal, the piston rod of the lifting cylinder a of the liquid storage tank returns, and the liquid storage tank and the infusion pipe drop; (2) The infusion pipe is inserted into each container, the piston rod of cylinder B of the filling valve opening and closing cylinder returns, and the outlet valve of each infusion pipe is opened to inject liquid into the container; (3) The piston rod of cylinder B extends and the outlet valve is closed; (4) The piston rod of cylinder a extends, the liquid storage tank and infusion pipe rise, and the liquid storage tank begins to replenish liquid; (5) The liquid storage tank and infusion pipe rise to the highest position, the piston rod of left gear cylinder C extends, the piston rod of right gear cylinder D retracts, and the conveyor belt outputs the filled container; (6) The piston rod of cylinder C retracts and the piston rod of cylinder D extends, and the conveyor belt is input into the empty container. The filling machine completes a working cycle, that is, it realizes one-time filling of containers. In a working cycle, the piston rod of cylinder B is controlled by time delay from returning to extending state, and the filling of containers with different capacities is realized by adjusting the time delay. By adjusting the signal position of the stroke valve of cylinder a, the filling of containers with different heights can be achieved. The time for replenishing the liquid in the liquid storage tank and outputting the container must be controlled within one cycle. The state transition of piston rod of cylinders C and D is also realized by time-delay control

during the operation of the filling machine after the power line is introduced, the force output by the cylinder drives the mechanism to move back and forth in a straight line. In the pneumatic system, the phenomenon that the cylinder piston moves and stops suddenly due to load and air supply is called "crawling" of the cylinder. The filling machine adopts time program control. If one or more of the above cylinders crawl, the action time of the cylinder will be prolonged, resulting in interference and misoperation of the filling machine, such as the filling container is not transported in place, materials are not filled or are filled outside the container, etc. In order to reduce or avoid the occurrence of this situation, this paper analyzes the reasons for the creeping phenomenon of the cylinder of the filling machine one by one, and puts forward the corresponding solutions. 2 reasons for crawling (1) the compressed air of the pneumatic system of the filling machine cannot meet the working requirements

when the air supply pressure and flow of the air source are insufficient, resulting in the working pressure of the cylinder of the filling machine being lower than the minimum operating pressure, the cylinder is prone to crawling; At the same time, water, dust, oil and impurities in the air source accumulate in the working chamber of the cylinder, rusting the working surface of the piston or piston rod, increasing the friction between the cylinder barrel and the piston seal ring, the piston rod and the combined seal ring, and also causing the cylinder to crawl. (2) The internal leakage of the cylinder of the filling machine is large (i.e. gas channeling on both sides of the piston). When the sealing ring is extruded, aged, rotated, surface damaged, expanded, adhered and deformed, it will cause internal leakage of the cylinder, which will make it difficult or slow to boost the pressure of the cylinder, so that the cylinder will crawl. In addition, if the piston mating surface is defective, impurities squeeze into the sealing surface or the piston is stuck, the friction of the sliding parts of the cylinder will increase, and at this time, the cylinder will also crawl. (3) The air consumption and load in the pneumatic circuit of the filling machine change too much. When the regular cleaning of the electromechanical in the pneumatic circuit changes greatly, it will lead to insufficient air supply to the cylinder of the filling machine, resulting in crawling. In addition, the load of containers such as the liquid storage tank of the filling machine changes too much, the cylinder has transverse load, and various problems in the installation process (such as: the installation position of the cylinder is offset, the guide rail or slider is too tightly clamped, the guide rail is not parallel to the cylinder, the piston or piston rod is eccentric in assembly, etc.) will increase the load fluctuation of the cylinder, and the piston is unstable, resulting in crawling. 3 measures to eliminate crawling 3.1 adjust the air supply pressure and flow of the air source. During the design, correctly determine the air source consumption of the filling machine and reasonably select the capacity of the air compressor. The selection of the air compressor is based on the two main parameters of higher test accuracy: the working pressure and flow required by the pneumatic transmission system of the filling machine. When calculating the air consumption, its pressure flow should be converted into free air flow, that is, the flow under an atmospheric pressure. The conversion relationship between the volume flow of compressed air and free air is:

where QZ - volume flow of free air (m3/min); QY -- volume flow of compressed air (m3/min); PC -- output pressure of air compressor (MPA). Assuming that the average air consumption of a single pneumatic equipment (cylinder, air valve, etc.) in the filling machine is Q1, the air supply volume of the air compressor master station is in the formula: QL - the air supply volume of the air compressor master station; φ—— Considering that all pneumatic devices of the filling machine will not use gas at the same time, φ= 0.3~1.0; K1 - coefficient considering wear, K1 = 1.2 ~ 1.5; K2 - consider adding the standby coefficient of new equipment, K2 = 1.2 ~ 1.6; K3 - considering the uneven coefficient of different gas consumption of each shift, K3 = 1.2~1.4. The output pressure PC of the air compressor is PC - the output pressure of the air compressor, MPa

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