How to design the woven bag opening mechanism by friction break?

21 Dec 2021



The automatic big woven bag packaging machine is widely used in the fields of building materials, chemicals and food products. The packaging objects are mainly liquid, powder, granular materials with strong plasticity and good fluidity. Efficient and reliable realization of opening the woven bag and sending the big bag to the discharge nozzle is a necessary function of the automatic big bag packaging machine. Existing equipment mostly uses vacuum to open the bag directly. According to the leakage coefficient of the vacuum open woven bag, even with the lining woven bag, the suction capacity of the vacuum head is less than one-fifth of the paper-plastic composite bag, and the surface of the woven bag is uneven, Unfavorable factors such as porosity and sticky resistance of the slit of the bag opening will make it difficult to open the bag in a vacuum. Some woven bags can even be opened manually, which increases the production cost. Realizing the reliable and efficient opening of woven bags is a technical problem that urgently needs to be solved in this field. For the problem of opening of woven bags, alternative technologies and solutions are constantly being proposed in the industry. There are many consumables for sticking and removing the bag.

It is difficult to take off the bag after opening the bag with strong adhesiveness; the action of the bionic technology for opening the bag with the clip is tedious and time-consuming. Secondly, the hand on one side may lift both sides of the woven bag at the same time, resulting in the failure of the opening. If one side is fixed, additional parts are required. , Which makes the machine more complicated; the insertion and extraction woven bag is not conducive to maintaining the integrity of the bag and it is easy to lift both sides of the woven bag at the same time. The existing methods for opening bags by friction pre-break or direct friction break lack technical theoretical support, and the mechanism uses a large number of cylinders to cause more motion stops or the broken state of the woven bag is not conducive to subsequent bag opening, bag supporting and bag loading. Therefore, it is necessary to study more reasonable and effective technical methods.

After analysis, the woven bag is made of woven fabric rolls through eagerly cutting. In order to meet the high-speed automatic bag opening requirements of the woven bag packaging machine, the combination technology of pre-breaking the bag opening may improve the bag opening success rate and operating efficiency of the packaging machine. The use of plane friction technology to open the woven bag is one of the possible effective technical solutions. Based on the test results of the friction breaking open bag technology, this study uses the movement characteristics and spring characteristics of the inclined crank slider mechanism to study and analyze the breaking The kinematic law of the mouth actuator and the design of a new friction bag opening mechanism have value and significance for realizing the efficient and reliable woven bag opening of the packaging machine.

1 Mechanism principle and process method

According to the results of pre-experimental research, reasonably applied friction force and expected friction breaking speed law are the main technologies to ensure that through the integrated analysis of the necessary operations of the friction breaking technology, the kinematic characteristics and spring characteristics of the inclined crank slider mechanism can be used to design The mechanism principle of the friction breach actuator is shown in Figure 1. And then further analyze the continuous friction breaking mechanism transmission and execution trajectory.

The movable friction block installed on the spring is driven by the inclined crank slider mechanism, and the spring is compressed with the change of displacement to generate pressure. The friction force increases until the side A of the woven bag can be driven, and the side B of the woven bag is frictionally fixed by the fixed friction block, thereby realizing the rupture of the woven bag. In order to make full use of the advantages of friction break technology and further improve the efficiency of the whole machine, the integrated gripping hand of the bag supporting piece is adopted. Through reasonable arrangement, the continuity of the opening and opening of the bag can be realized.

During the entire process of rubbing and breaking, the gripper (including the bag-holding insert) that completes the bag loading action can immediately lower and stop at the gripper space reserved on the lower fixed plate for standby. After the rupture process is over, a signal can be given, and the bag-supporting and inserting integrated gripping hand can grip the exposed side B, and the initial bag receiving is completed by the bagging hand. After the movable friction block is separated, the woven bag elastically recovers to wrap the insert, and at the same time, the bag is opened and the insert supports the bag. The bagging hand rotates the bagging until the woven bag with the opened mouth of the bag is sent to the spout to complete the bagging process. Compared with the traditional woven bag opening machine, it is necessary to fully open the bag before inserting the bag support insert to improve efficiency.

2 Mechanism Kinematics Analysis

2.1 Kinematic analysis

In view of the proposed break actuator, further analyze the movement characteristics of the mechanism, according to the centripetal crank slider movement formula, substitute the oblique angle a, and remove the item above λ3 after unfolding (input is the ratio of crank to connecting rod length), and get The actual displacement, velocity and acceleration of the sliding friction block. The axis is the β rotation angle (that is, time). Use MATLAB to analyze the time and establish the movement trend. According to the movement trend of the designed mechanism, the change characteristics of the movement can be used to make reasonable arrangements.

2.2 Verification Discussion

It can be seen from the analysis of Fig. 3 that the respective change trends of S, v, and a are in the process, and the forward idle stroke S1, the pressurization process S2, and the working potential are similar under different angles of a. Therefore, the slider crank stroke S3 is used to return to the working stroke S3, the decompression stroke S2, and the return idle stroke S1. Structure movement characteristics, take the range of 0≤B≤2π as the analysis of the work process of the mechanism in a week.

According to the working process of distribution, after the woven bag is in place, the displacement difference will be added. Finally, the larger B can be leaked before the end of S3.

During the compression process, the friction block starts to contact the woven bag and produces a sliding friction surface to facilitate the bag insert and the gripper to clamp the woven bag. In the critical and two break stages, the acceleration is stable, and the design of the approximate plane friction break bag opening mechanism is uniform. Variable speed motion; the limit position speed is 0, that is, return to the working range.

3.1 Modeling the key execution system structure

Do a uniform acceleration motion with an initial speed of 0; the spring reaches the maximum compression at the limit position, and the pressure is the maximum; the process of conveying, breaking and leaving the woven big bag; the above three points are conducive to the continuous work of the drive motor at the end of the stage and reduce the opening of the traditional woven big bag Fully broken, in line with the technological requirements of friction broken bag opening operation.

The bag mechanism has a large amount of start and stop reaction time and impact. At the same time, based on the above research, the pressure required for S to open the bag is S3's different size woven big bags and the opening size requirements, which can be more than 3 times higher, that is, under the same pressure, S3 can open the front stent that is larger than S3, and rotate the back stent; Adjust the spring box bracket and spring displacement. S3 starts with static friction and further increases the relative angle of the box body between S3 and S; it is achieved by adjusting the length of the movable friction plate connecting rod.

Coping with the requirements of different spring pressures can be achieved by adjusting the angle of the spring box to 0, and the internal expansion and contraction of the upper cover of the bag-removing guide with a radius of 30mm at the tail, applying pre-pressure to the spring.

3.2 The design and modeling of the whole machine has a universal overall mechanism that is flexible to different objects. The overall mechanism is shown in Figure 6. In order to facilitate the existing production line, the narrower the friction plate and the closer to the bag opening, the better the bag opening effect. Consider replacement and mechanism The overall shape design and size are consistent with the existing vacuum knitting stability and installation. The friction plate is designed to be 5×375px. The woven bag opening machine is roughly the same, and the acceptable receiving and feeding directions are the same as ensuring the smoothness of the S3 process, improving the S3 bag opening effect and avoiding the existing vacuum woven bag opening machine. The whole machine mainly includes mechanical phenomena that make it difficult to take off the bag at the end of S3. The design of the friction sheet head round frame, the bag loading mechanism, the friction break bag opening mechanism and the bag feeding machine are designed.

The bag loading mechanism is equipped with an integrated gripper for holding the bag and inserting the bag, and the bag opening mechanism can realize the clamping, opening and bag loading actions in conjunction with the friction break bag opening mechanism. The lower fixed plate is equipped with a fixed friction plate and a bag feeding mechanism. Among them, the fixed friction plate is that the center of the openings of the remaining grips is 0m apart, which can be adapted to most woven bags of 25-50kg.

The specific coordination of each part of the friction bag opening mechanism is shown in Figure 7. In the process of S1 and S1 shown in Fig. 3 and Fig. 4, the bag feeding mechanism completes the bag feeding and sends the woven bag to the bag opening station. After finishing the bag loading, the bag loading arm descends, the gripper opens, and waits for the bag to be opened. After the movable friction plate completes the rupture, enter the decompression process S2, the gripper is closed, and the bag is completed. When the friction is reduced, the A side of the woven bag is elastically restored, and the insert is wrapped, and the main arm of the bag loading mechanism rotates the bag.

4 Conclusion

This research mainly focuses on the technical problem of difficult bag opening caused by the eagerly cut woven bag with the opening of the bag. By adopting the principle of flat friction breaking, the friction breaking technology is tested and researched and the motion analysis of the operating actuator is demonstrated. The inclined crank slider mechanism and the design of the pressure spring can meet the continuous, efficient and stable operation requirements of the woven bag for pre-broken bag opening, and meet the technical process of friction broken bag opening. Reflected from the movement characteristic curve diagram of the mechanism, the inclined crank slider mechanism can meet the requirements of the driving speed law, and can improve the operation efficiency and stability, which is of significance for realizing the automatic high-speed opening of the woven bag of the packaging machine.


Design of automatic bagging device for big woven bag packaging machine Packaging and Food Machinery