Double-layer plastic film cutting control mechanism

Abstract

A double-layer plastic film slitting knife control mechanism includes a slitting knife support, on which a slitting knife is mounted. The slitting knife support is laterally movable on a transverse slide rail. The cutting edge of the slitting knife has a transverse inner endpoint and a transverse outer endpoint. It also includes a transverse drive mechanism for driving the slitting knife support to move left and right, a central controller, and photoelectric sensors for monitoring the transverse edge position of the double-layer plastic film. Its main feature is that there are two photoelectric sensors mounted on photoelectric sensor supports, with their transverse positions staggered. The one located on the transverse inner side is called the inner photoelectric sensor, and the one located on the transverse outer side is called the outer photoelectric sensor. The photoelectric sensor supports are fixedly connected to the slitting knife support and move synchronously. The transverse inner endpoint of the slitting knife cutting edge is closer to the inner side than the transverse position of the inner photoelectric sensor, and the transverse outer endpoint of the slitting knife cutting edge is closer to the outer side than the transverse position of the outer photoelectric sensor. This invention enables the transverse position of the slitting knife to automatically move with the width fluctuations of the double-layer plastic film, thereby avoiding the problems of "knife dropping" and "knife detachment."

Description

Technical Field

[0001] This utility model belongs to the technical field of plastic film production and processing equipment, and specifically relates to a double-layer plastic film cutting knife control mechanism. Background Technology

[0002] Most plastic films are produced using the blown film method. The resulting plastic film is cylindrical. Before winding, the cylindrical plastic film 8 needs to be flattened to form a double-layered plastic film 9. Figure 1 As shown, the double-layered plastic film 9, viewed in cross-section, still forms a continuous loop, meaning the two layers remain connected at their transverse edges. Since the cylindrical plastic film is obtained through inflation, and the air pressure and thickness inevitably fluctuate slightly during inflation, the diameter of the resulting cylindrical plastic film 8 also fluctuates. Consequently, the transverse width (i.e., width) of the double-layered plastic film 9 also fluctuates, meaning the edges of the double-layered plastic film 9 are not straight but exhibit visible curvature. Figure 2 As shown. In subsequent processing steps, the double-layer plastic film 9 needs to be cut into two single-layer films. Figure 2 As shown, the double-layer plastic film cutting mechanism has cutting blades 1 on both sides of the running trajectory of the double-layer plastic film 9. The cutting edge of the cutting blade 1 faces outward laterally, and the cutting edge line forms an oblique intersection with both the longitudinal and transverse directions. The cutting edge line has a certain length in the transverse direction. During operation, the cutting blade is aligned with the fold line of the edge of the double-layer plastic film. As the double-layer plastic film moves forward (the direction of movement is as shown in the diagram), the cutting blades align with the fold line of the edge of the double-layer plastic film. Figure 2 , Figure 3 As shown by the middle arrow V, the edges of the double-layer plastic film are continuously cut, dividing the double-layer plastic film 9 into two single-layer films. However, since the edges of the double-layer plastic film are not straight, the lateral position of the cutting blade must be able to move with the fluctuations in the lateral endpoints of the double-layer plastic film; otherwise, the blade may fall off.

[0003] The industry term "blade drop" refers to the lateral outward movement of the cutting edge of the cutting blade 1 relative to the edge of the double-layer plastic film 9, until the cutting edge of the cutting blade 1 leaves the horizontal projection range of the double-layer plastic film 9 (e.g., Figure 3(As shown in the right-hand side of the diagram), once the blade falls off, the edge of the double-layer plastic film 9 cannot automatically reattach to the blade of the cutting knife 1, requiring manual intervention to re-cut. To overcome the blade-falling problem, the traditional control method involves fixing a photoelectric sensor in front of each cutting knife. However, the working principle of the photoelectric sensor cannot specifically measure and determine the lateral position of the plastic film edge; it only monitors whether the plastic film has passed through its field of view, and thus roughly judges the lateral position of the plastic film edge. If no plastic film has passed through the photoelectric sensor's field of view, it is determined that the edge of the plastic film has deviated significantly inward, posing a risk of blade fall. Therefore, the lateral drive mechanism is activated to move the cutting knife inward, keeping the lateral position of the cutting knife blade close to the edge of the cylindrical plastic film, thereby avoiding the blade-falling problem.

[0004] In traditional technology, because the diameter of the blown film bubble is small, the absolute value of the bubble diameter fluctuation is small, that is, the lateral position fluctuation of the edge of the double-layer plastic film is small (relative to the lateral length of the cutting blade). Therefore, a single photoelectric sensor is sufficient to avoid the problem of the blade falling off.

[0005] However, with the rapid development of blown film technology in recent years, the diameter of blown film bubbles has been continuously increasing (previously, the diameter of blown film bubbles was generally around two meters, but in recent years it has reached around eight meters). While the proportion of diameter fluctuation remains constant, the absolute value of the diameter fluctuation is becoming increasingly larger. This means that the lateral position fluctuation along the edge of the double-layer plastic film is significant. Therefore, the cutting blade not only experiences outward slippage but also "inward slippage." "Inward slippage" refers to a situation where, although the cutting blade is within the horizontal projection range of the double-layer plastic film, the severe outward fluctuation of the lateral position of the double-layer plastic film 9 causes the cutting blade of the cutting blade to deviate excessively inward and detach from the edge of the double-layer plastic film 9. Figure 3 The cutting tool 1 is shown on the left side of the middle section.

[0006] To simultaneously solve the problems of "inner blade detachment" and "blade drop," the existing solution is to install the blade holder of the slitting blade on a transverse guide rail, and use a suspended weight to pull the slitting blade through a fixed pulley and a steel wire rope. For example, the structure disclosed in Chinese Utility Model Patent No. CN221112118 U. In this way, under the pulling action of the steel wire rope, the blade of the slitting blade 1 will automatically move laterally back and forth as it fluctuates with the edge line of the plastic film. Theoretically, as long as the weight of the suspended weight is appropriate (i.e., basically equal to the resistance of the cutting process), the blade line of the slitting blade can be kept in contact with the fold line of the edge of the plastic film. However, in practice, due to fluctuations in the quality and physical properties of the plastic film, when the resistance of the plastic film to the blade is significantly less than the weight of the suspended object during the cutting process, the plastic film cannot effectively prevent the blade from moving rapidly outward, thus the problem of "blade falling off" still occurs. Conversely, when the resistance of the plastic film to the blade is significantly greater than the weight of the suspended object during the cutting process, the plastic film will quickly drive the blade to move rapidly inward, thus the problem of "blade coming off inward" still occurs. Utility Model Content

[0007] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a double-layer plastic film slitting knife control mechanism, which enables the lateral position of the slitting knife to move automatically with the width fluctuation of the double-layer plastic film, thereby avoiding the problems of "knife falling off" and "inner knife detachment".

[0008] The objective can be achieved as follows: a double-layer plastic film slitting knife control mechanism, including a slitting knife support, a slitting knife mounted on the slitting knife support, the slitting knife support being laterally movable on a transverse slide rail, the slitting knife's cutting edge having a transverse inner endpoint and a transverse outer endpoint; also provided with a transverse drive mechanism for driving the slitting knife support to move left and right, a central controller, and photoelectric sensors for monitoring the transverse edge position of the double-layer plastic film; its main feature is that there are two photoelectric sensors, both mounted on photoelectric sensor supports, the transverse positions of the two photoelectric sensors being staggered, the one located on the transverse inner side being called the inner photoelectric sensor, and the one located on the transverse outer side being called the outer photoelectric sensor, the photoelectric sensor support being fixedly connected to the slitting knife support and moving synchronously; the transverse inner endpoint of the slitting knife's cutting edge is closer to the inner side than the transverse position of the inner photoelectric sensor, and the transverse outer endpoint of the slitting knife's cutting edge is closer to the outer side than the transverse position of the outer photoelectric sensor.

[0009] Preferably, the lateral drive mechanism is a screw mechanism driven by a forward and reverse servo motor.

[0010] The plastic film has a left and right edge, so two cutting blades are needed for cutting, and each cutting blade requires a corresponding cutting blade control mechanism.

[0011] The outer side refers to the side that is laterally away from the center line of the double-layer plastic film; the inner side refers to the side that is laterally closer to the center line of the double-layer plastic film. The center line of the plastic film is the midline between the left and right halves of the double-layer plastic film.

[0012] This utility model has the following advantages and effects: 1. During normal operation, the lateral position of the edge line of the double-layer plastic film is between the inner and outer photoelectric sensors. The edge line of the double-layer plastic film intersects with the cutting edge line of the cutting blade. The inner photoelectric sensor can detect the movement of the plastic film within its monitoring area, while the outer photoelectric sensor can detect the absence of the plastic film within its monitoring area. If both photoelectric sensors detect the absence of the plastic film within their respective monitoring areas, it indicates that the edge line of the double-layer plastic film is very close to the lateral inner end of the cutting edge line, posing a risk of edge breakage. At this time, the central processing unit can command the lateral drive mechanism to move, causing the photoelectric sensor support and the cutting blade support to move inward, bringing the edge line of the double-layer plastic film back close to the lateral middle position of the cutting edge line. Thus, the outer photoelectric sensor continues to detect the absence of the plastic film within its monitoring area, while the inner photoelectric sensor re-detects the movement of the plastic film within its monitoring area; conversely... If both photocells detect the passage of plastic film within their respective monitoring areas, it indicates that the edge of the double-layered plastic film is very close to the outer lateral end of the cutting edge line, posing a risk of internal blade slippage. In this case, the central processing unit can command the lateral drive mechanism to move the photocell support and the cutting edge support outwards, bringing the edge of the double-layered plastic film back close to the middle lateral position of the cutting edge line. The outer photocell will then again detect no plastic film passing through its monitoring area, while the inner photocell will continue to detect plastic film passing through its monitoring area. This control process ensures that the problems of "internal blade slippage" and "edge slippage" will not occur.

[0013] 2. The photoelectric sensor support and the cutting blade support are fixedly connected together and move synchronously. That is, the two photoelectric sensors and the cutting blade move synchronously, so that the lateral position of the two photoelectric sensors is always kept within the lateral position range of the cutting blade line. No matter how much the lateral position of the cutting blade fluctuates with the lateral position of the plastic film edge, the lateral position of the two photoelectric sensors can be kept in close coordination with the lateral position of the cutting blade and the lateral position of the plastic film edge, ensuring that the lateral position of the plastic film edge will not leave or move away from the monitoring range of the two photoelectric sensors. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the cross-sectional shape of a cylindrical membrane that has been flattened to form a double-layered plastic film.

[0015] Figure 2 This is a schematic diagram of the cutting method of double-layer plastic film.

[0016] Figure 3This is a schematic diagram illustrating the states of "inner blade detachment" and "blade drop" that occur during the cutting of double-layer plastic film.

[0017] Figure 4 This is a schematic diagram of the overall structure of a specific embodiment of the present utility model.

[0018] Figure 5 This is a schematic diagram of the normal use state of a specific embodiment of this utility model.

[0019] Figure 6 yes Figure 5 A magnified schematic diagram of the structure of part D.

[0020] Figure 7 yes Figure 6 A schematic diagram of one possible change in the structure shown.

[0021] Figure 8 yes Figure 6 A schematic diagram of another variation of the structure shown. Detailed Implementation

[0022] Figure 4 , Figure 5 The double-layer plastic film slitting knife control mechanism shown includes a slitting knife support 2, on which a slitting knife 1 is mounted. The slitting knife support 2 is laterally movable on a transverse slide rail. The cutting edge 11 of the slitting knife 1 has a transverse inner end point and a transverse outer end point. The transverse inner end point is as follows: Figure 4 , Figure 6 , Figure 7 , Figure 8 As shown by point A in the diagram, the outer horizontal endpoint is as follows: Figure 4 , Figure 6 , Figure 7 , Figure 8 As shown at point B; it also includes a lateral drive mechanism for driving the cutting blade support 2 to move left and right, a central controller, and photoelectric sensors for monitoring the lateral edge position of the double-layer plastic film; the lateral drive mechanism is a screw mechanism 7 driven by a forward and reverse servo motor 6; each cutting blade 1 has two corresponding photoelectric sensors, which are installed on photoelectric sensor supports 5, and the lateral positions of the two photoelectric sensors are staggered, with the one located on the inner side being called the inner photoelectric sensor 3, and the one located on the outer side being called the outer photoelectric sensor 4. The photoelectric sensor support 5 is fixedly connected to the cutting blade support 2 and moves synchronously under the drive of the lateral drive mechanism; the inner lateral endpoint of the cutting edge line 11 of the cutting blade 1 (e.g. Figure 4 , Figure 6 , Figure 7 , Figure 8 Point A in the diagram is closer to the inner side than the lateral position of the corresponding inner photoelectric sensor 3. The outer lateral endpoint of the cutting edge line 11 of the cutting tool (such as...) Figure 4 , Figure 6 , Figure 7 , Figure 8Point B in the diagram is closer to the outer side than the corresponding outer electro-eye 4 in the lateral position.

[0023] The "outer side" refers to the side that is horizontally away from the center line of the double-layer plastic film; the "inner side" refers to the side that is horizontally closer to the center line of the double-layer plastic film. The center line of the plastic film is the midline between the left and right halves of the double-layer plastic film, such as... Figure 5 As shown by the straight line m.

[0024] The working principle of the above embodiments is as follows: The above embodiments are used in pairs, that is, two sets of double-layer plastic film slitting knife control mechanisms are used symmetrically and in pairs. The two sets of double-layer plastic film slitting knife control mechanisms are respectively arranged on the left and right sides of the double-layer film 8, so that the left and right edges of the double-layer plastic film 8 can be slitted simultaneously. Figure 5 As shown.

[0025] During normal operation, the lateral position of the edge line of the double-layer plastic film 8 is located between the inner photocell 3 and the outer photocell 4. The edge line of the double-layer plastic film 8 intersects with the cutting edge line 11 of the cutting blade 1. Therefore, the inner photocell 3 can detect the passage of the plastic film within its monitoring area, while the outer photocell 4 can detect the passage of no plastic film within its monitoring area. Figure 5 , Figure 6 As shown.

[0026] If both the inner photocell 3 and the outer photocell 4 detect that no plastic film has passed through their respective monitoring areas, it indicates that the edge of the double-layer plastic film 8 is very close to the transverse inner end of the cutting edge line 11, posing a risk of edge breakage. Figure 7 As shown, at this time, the central processing unit can command the forward and reverse servo motor 6 to start, drive the screw mechanism 7 to move, and drive the photoelectric support 5 and the cutting tool support 2 (including the cutting tool 1) to move inward ( Figure 7 The image (to the right) is moved, causing the edge of the double-layer plastic film 8 to move closer to the transverse middle position of the cutting edge line 11. Thus, the outer photoelectric sensor 4 continues to detect no plastic film passing through its monitoring area, while the inner photoelectric sensor 3 detects plastic film passing through its monitoring area again. Conversely, if both the inner and outer photoelectric sensors 3 and 4 detect plastic film passing through their respective monitoring areas, it indicates that the edge of the double-layer plastic film 8 is very close to the transverse outer end of the cutting edge line 11, posing a risk of internal blade detachment. Figure 8 As shown, at this time, the central processing unit can command the forward and reverse servo motor 6 to start, driving the screw mechanism 7 to move, causing the photoelectric support 5 and the cutting tool support 2 (including the cutting tool 1) to move outward ( Figure 8The double-layer plastic film 8 moves to the left of the image, causing its edge to reappear near the middle of the cutting edge 11 of the cutting tool. The inner photoelectric sensor 3 continues to detect the movement of the plastic film within its monitoring area, while the outer photoelectric sensor 4 detects no movement of the plastic film within its monitoring area. Through this control process, it is ensured that problems such as "inner tool detachment" and "edge falling off" will not occur.

Claims

1. A double-layer plastic film slitting knife control mechanism, comprising a slitting knife support, a slitting knife mounted on the slitting knife support, the slitting knife support being laterally movably mounted on a transverse slide rail, the cutting edge of the slitting knife having a transverse inner end point and a transverse outer end point; further comprising a transverse drive mechanism for driving the slitting knife support to move left and right, a central controller, and a photoelectric sensor for monitoring the transverse edge position of the double-layer plastic film; characterized in that: There are two photoelectric sensors, which are mounted on photoelectric sensor supports. The two photoelectric sensors are offset laterally. The one located on the inner side is called the inner photoelectric sensor, and the one located on the outer side is called the outer photoelectric sensor. The photoelectric sensor support is fixedly connected to the cutting tool support and moves synchronously. The inner endpoint of the cutting tool's cutting edge is closer to the inner side than the inner photoelectric sensor, and the outer endpoint of the cutting tool's cutting edge is closer to the outer side than the outer photoelectric sensor.

2. The double-layer plastic film slitting knife control mechanism according to claim 1, characterized in that: The lateral drive mechanism is a screw mechanism driven by a forward and reverse servo motor.

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