Inner cooling structure of plastic film blowing machine

Abstract

An internal cooling structure for a plastic blown film machine includes a blown film die, a vertical inner air duct, and a vertical outer air duct. An inner cooling air ring and an annular wall are provided above the blown film die, and the space between the annular wall and the middle section of the inner air duct forms an annular air cavity. A partition plate is provided at the upper end of the upper section of the inner air duct, and an upper air duct is provided above the partition plate. An outer sleeve is fitted over the upper section of the inner air duct. The annular gap between the outer sleeve and the upper section of the inner air duct forms an annular upward air duct. A lower vent is provided between the lower end of the annular upward air duct and the upper end of the annular air cavity, and an upper vent is provided between the upper end of the annular upward air duct and the lower end of the upper air duct cavity. An outer return air port is provided at the upper part of the outer sleeve, and an inner return air port is provided at the upper part of the upper section of the inner air duct. An annular partition plate is welded between the edge of the outer return air port and the edge of the inner return air port, and the space enclosed by the annular partition plate forms a radial return air channel. This invention enables effective cooling of both the upper and lower sections of the film bubble.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plastic film blowing equipment, and particularly relates to an inner cooling structure of a plastic film blowing machine. BACKGROUND

[0002] Plastic film can be produced by a film blowing method. In the production process, plastic melt is extruded upward from a circular annular extrusion port 101 of a film blowing die 10 to form a bubble 8, as shown in the figure. The bubble 8 is continuously pulled upward, and a cooling mechanism located beside the bubble 8 continuously blows cooling air to cool the bubble 8. The cooling method is divided into an outer cooling method and an inner cooling method. The outer cooling method uses an outer cooling air ring 102 located outside the bubble 8 to blow cooling air flow in the centripetal direction to cool the bubble 8 from the outside, as shown in the figure. Figure 1 Figure 1 The air inlet and outlet structure of the inner cooling method is generally as follows: a blower and an air extractor are arranged outside the film blowing die 10, a vertical extending inner air pipe 1 and a vertical extending outer air pipe 2 are arranged, as shown in the figure. The outer air pipe 2 is located at the central position of the film blowing die 10. The inner air pipe 1 includes an inner air pipe lower section 11, an inner air pipe middle section 12 and an inner air pipe upper section 13. The inner air pipe lower section 11 is sleeved in the outer air pipe 2. The inner air pipe middle section 12 and the inner air pipe upper section 13 are located above the film blowing die 10. The cavity of the inner air pipe 1 forms an air outlet channel 14. The lower end of the air outlet channel 14 is connected to the air extractor through an air pipe. The annular space gap between the inner air pipe lower section 1 and the outer air pipe 2 forms an air inlet channel 20. The blower is connected to the lower end of the air inlet channel 20 through an air pipe. Figure 1 The components for implementing the inner cooling method include an inner cooling air ring 3 and an annular wall 4. The inner cooling air ring 3 and the annular wall 4 are located at the periphery of the inner air pipe middle section. The annular wall 4 is located above the inner cooling air ring 3. The inner cooling air ring 3 is provided with a circular annular air outlet 30. The annular wall 4 is provided with a plurality of circular annular air outlet slits 41. The space between the annular wall 4 and the inner air pipe middle section 12 forms an annular air cavity 40. The upper portion of the annular air cavity 40 is provided with a circular air cavity cover plate 42. The inner air pipe 1 passes through the air cavity cover plate 42 upwardly. The inner air pipe upper section 13 is exposed above the air cavity cover plate 42. The air inlet channel 20 is connected to the inner cooling air ring 3 and the annular air cavity 40.

[0003] ​In operation, the bubble 8 is extruded from the annular extrusion port 101 of the film blowing die 10 and runs upwardly and passes the inner cooling air ring 3 and the periphery of the annular wall 4; the cooling air from the air inlet channel 20 flows upwardly into the inner cooling air ring 3 and the annular air cavity 40, wherein the cooling air flowing into the inner cooling air ring 3 is blown out from the annular air outlet 30 to cool the inner surface of the bubble 8, and the cooling air flowing into the annular air cavity 40 is blown out from the plurality of air outlet slits 41 of the annular wall 4 to cool the inner surface of the bubble 8; then, the air flows upwardly to the top of the upper section of the inner air duct 13, is sucked into the air outlet channel 14 from the upper end of the inner air duct 1, and is drawn out from the lower end of the air outlet channel 14.

[0004] However, the above-mentioned inner cooling structure has the following disadvantages: the cooling air blown out from the annular air outlet 30 of the inner cooling air ring 3 and the air outlet slits 41 of the annular wall 4 is heated by the bubble 8 during the upward flow, and the temperature of the cooling air gradually increases, so that the cooling effect of the bubble 8 is basically lost when the cooling air reaches the middle and upper sections of the bubble 8; that is, the bubble 8 can only be cooled at the lower section of the bubble, and the upper section of the bubble cannot be effectively cooled, so that the bubble 8 is cooled for a short time and the cooling process is relatively rapid, and the cooling intensity is not uniform, which is not conducive to the full orientation of the molecules of the plastic material and the stable arrangement of the molecular chains. In addition, according to the existing structure, even if the height of the upper section of the inner air duct 13 is extended upwardly, the above-mentioned problems cannot be solved. SUMMARY

[0005] The present application aims to overcome the above-mentioned disadvantages and provide an inner cooling structure of a plastic film blowing machine, which can effectively cool the upper and lower sections of the bubble, the cooling process is long, the cooling intensity is relatively uniform, and the full orientation of the molecules of the plastic material is facilitated, so that the molecular chains of the plastic material are arranged more stably.

[0006] The purpose can be achieved according to the following scheme: the inner cooling structure of the plastic film blowing machine comprises a film blowing die head, a vertical inner air pipe and a vertical outer air pipe, the inner air pipe is divided into an inner air pipe lower section, an inner air pipe middle section and an inner air pipe upper section, the outer air pipe is located at the central position of the film blowing die head, the inner air pipe lower section is sleeved in the outer air pipe, the inner air pipe middle section and the inner air pipe upper section are located above the film blowing die head, the pipe cavity of the inner air pipe is formed as an air outlet channel, and the annular gap part between the inner air pipe lower section and the outer air pipe is formed as an air inlet channel; an inner cooling air ring and an annular wall are further arranged above the film blowing die head, the inner cooling air ring and the annular wall are sleeved outside the inner air pipe middle section, and the inner cooling air ring is located below the annular wall; the inner cooling air ring is provided with a circular air outlet; the space between the annular wall and the inner air pipe middle section is formed as an annular air cavity, the top of the annular air cavity is provided with a circular air cavity cover plate, and the annular wall is provided with a plurality of circular air outlet slits; the inner air pipe upper section is exposed above the air cavity cover plate; the upper end of the air inlet channel is communicated with the inner cooling air ring, the inner cooling air ring is communicated with the annular air cavity; characterized in that, a partition plate is arranged at the upper end of the inner air pipe upper section, an upper air pipe is further arranged above the partition plate, the pipe cavity of the upper air pipe is separated from the pipe cavity of the inner air pipe by the partition plate, and the upper end of the upper air pipe is open; an outer sleeve pipe is further sleeved outside the inner air pipe upper section; the annular gap part between the outer sleeve pipe and the inner air pipe upper section is formed as an annular upward air duct, a lower air permeable hole is arranged between the lower end of the annular upward air duct and the upper end of the annular air cavity, and an upper air permeable hole is arranged between the upper end of the annular upward air duct and the lower end of the pipe cavity of the upper air pipe; an outer return air outlet is arranged at the upper part of the outer sleeve pipe, an inner return air outlet is arranged at the upper part of the inner air pipe upper section, and a ring-shaped partition piece is connected between the edge of the outer return air outlet and the edge of the inner return air outlet, the space surrounded by the ring-shaped partition piece is formed as a radial return air channel, and the radial return air channel is communicated with the upper part of the air outlet channel.

[0007] A blower and an air extractor are arranged outside the film blowing die head, the blower is connected to the lower end of the air inlet channel through an air pipe, and the lower end of the air outlet channel is connected to the air extractor through an air pipe.

[0008] The radial return air channel has a plurality of radial return air channels, and each radial return air channel is uniformly arranged along the circumferential direction of the outer sleeve pipe and the inner air pipe.

[0009] The radial return air channel is named as "radial" because the flow direction of the air flow in the radial return air channel is the radial direction of the outer sleeve pipe.

[0010] The present application has the following advantages and effects:

[0011] When the present application works, the cooling air flow is divided into two streams in the bubble, and the flow paths of the two streams are different. The flow path of the first stream is the same as that of the conventional structure, and the first stream includes the cooling air flow blown from the annular air outlet of the inner cooling ring and the cooling air flow blown from the multiple air outlet slits of the annular wall; after being blown from the annular air outlet of the inner cooling ring and the multiple air outlet slits of the annular wall, the first stream contacts the inner surface of the bubble and flows upward in the bubble until it turns to enter the radial return air channel when it rises to the height position of the radial return air channel, then flows downward through the air outlet channel, and finally is sucked away; the second stream refers to the air flow that enters the annular upward air duct upward from the lower air-permeable hole of the annular air cavity, passes through the upper air-permeable hole to enter the upper air duct, is then blown out from the upper end of the upper air duct, and then flows downward until it is sucked into the radial return air channel when it falls to the height position of the radial return air channel, then flows downward through the air outlet channel, and finally is sucked away.

[0012] When the second stream reaches the upper end of the upper air duct (i.e. the upper part of the bubble cavity), it still maintains a low temperature state because it has not yet contacted the bubble, so the second stream can effectively cool the upper section of the bubble during the falling process; this further means that the upper and lower parts of the bubble can be effectively cooled, i.e. the cooling intensity of the entire bubble is evenly distributed in space; and for each specific part of the plastic film, the effective cooling time is long (for each specific part, it is cooled when passing through the lower section of the bubble and is cooled again when passing through the upper section of the bubble), the cooling process is prolonged, and the cooling intensity is evenly distributed in the time axis, which is beneficial to the full orientation of the molecules of the plastic material and makes the molecular chain of the plastic material more stable. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic diagram of the cooling structure and cooling mode of a conventional plastic film blowing machine.

[0014] Figure 2 is a schematic diagram of the structure principle and cooling air flow path of a specific embodiment of the present application.

[0015] Figure 3 is Figure 2 is an enlarged schematic diagram of the local air flow path in the bubble.

[0016] Figure 4 is Figure 3 is a local enlarged schematic diagram of the structure shown in the bubble.

[0017] Figure 5 is Figure 2 is a local enlarged schematic diagram of the junction between the upper section of the inner air duct and the upper air duct in the bubble.

[0018] Figure 6 is Figure 5 A-A sectional view of the structure.

[0019] Figure 7 is Figure 6 B-B sectional view of the structure.

[0020] Figure 8 is Figure 2 The internal structure of the air flow channel.

[0021] Figure 9 is Figure 8 C local amplification schematic. DETAILED DESCRIPTION

[0022] Figure 2 , Figure 4 , Figure 3 , Figure 8 , Figure 9 As shown in the figure, the plastic film blowing machine inner cooling structure includes a film blowing die head 10, a vertical inner air pipe 1 and a vertical outer air pipe 2. The film blowing die head 10 is provided with a circular annular extrusion port 101. The inner air pipe 1 is divided into an inner air pipe lower section 11, an inner air pipe middle section 12 and an inner air pipe upper section 13. The outer air pipe 2 is located at the central position of the film blowing die head 10. The inner air pipe lower section 11 is sleeved inside the outer air pipe 2. The inner air pipe middle section 12 and the inner air pipe upper section 13 are located above the film blowing die head 10. The cavity of the inner air pipe 1 is formed into an air outlet channel 14. The annular gap part between the inner air pipe lower section 11 and the outer air pipe 2 is formed into an air inlet channel 20. An inner cooling air ring 3 and an annular wall 4 are further arranged above the film blowing die head 10. The annular wall 4 includes an outer annular wall 46 and an inner annular wall 44. The outer annular wall 46 is located at the periphery of the inner annular wall 44. A transition cavity 45 is formed between the outer annular wall 46 and the inner annular wall 44. The inner cooling air ring 3 and the annular wall 4 are sleeved outside the inner air pipe middle section 12. The inner cooling air ring 3 is located below the annular wall 4. The inner cooling air ring 3 is provided with a circular annular air outlet 30. The space between the inner annular wall 44 and the inner air pipe middle section 12 is formed into an annular air cavity 40. The top of the annular air cavity 40 is provided with a circular air cavity cover plate 42. The inner annular wall 44 is provided with a plurality of air outlet small holes 43. The outer annular wall 46 is provided with a plurality of circular annular air outlet slits 41. The inner air pipe upper section 13 is exposed above the air cavity cover plate 42. The upper end of the air inlet channel 20 is communicated with the inner cooling air ring 3 through a first communication hole 31. The inner cooling air ring 3 is communicated with the annular air cavity 40 through a second communication hole 32.

[0023] Figure 2 , Figure 5 , Figure 6 , Figure 7 , Figure 8As shown, the upper end of the inner air duct upper section 13 is provided with a partition plate 71, and an upper air duct 7 is further provided above the partition plate 71, the lumen 70 of the upper air duct 7 is separated from the lumen of the inner air duct 1 (i.e. the air outlet channel 14) by the partition plate 71, and the upper end of the upper air duct 7 is open; the outer surface of the inner air duct upper section 13 is further sleeved with an outer sleeve 5; the annular gap between the outer sleeve 5 and the inner air duct upper section 13 forms an annular upgoing air channel 6, a lower air permeable hole 61 is provided between the lower end of the annular upgoing air channel 6 and the upper end of the annular air cavity 40, and an upper air permeable hole 62 is provided between the upper end of the annular upgoing air channel 6 and the lower end of the upper air duct lumen 70; the upper part of the outer air return port 50 of the outer sleeve 5 is provided with an outer air return port 50, and the upper part of the inner air duct upper section 13 is provided with an inner air return port 15; the edge of the outer air return port 50 and the edge of the inner air return port 15 are welded with a ring-shaped partition plate 9, and the space surrounded by the ring-shaped partition plate 9 forms a radial air return channel 90; the number of radial air return channels 90 is three, and the three radial air return channels 90 are uniformly arranged along the circumference of the outer sleeve 5 and the inner air duct 1; each radial air return channel 90 communicates with the upper part of the air outlet channel 14, and the radial air return channel 90 and the annular upgoing air channel 6 are separated by the ring-shaped partition plate 9. A blower and an air extractor are provided outside the film blowing die 10, the lower end of the air outlet channel 14 is connected to the air extractor through an air duct, and the blower is connected to the lower end of the air inlet channel 20 through an air duct.

[0024] The working process and principle of the above embodiment are as follows:

[0025] Figure 2 、 Figure 3 、 Figure 8 As shown, the cooling air flow is blown into the air inlet channel 20 by the blower, flows upward from the air inlet channel 20, then enters the inner cooling air ring 3 through the first communication hole 31, and then part of the cooling air flow is blown out of the annular air outlet 30 of the inner cooling air ring and towards the inner surface of the bubble 8, and the other part of the cooling air flow enters the annular air cavity 40 through the second communication hole 32; part of the cooling air flow entering the annular air cavity 40 flows to the transition cavity 45 through the multiple air outlet holes 43 of the inner annular wall 44, then is blown out of the transition cavity 45 through the multiple circular annular air outlet slits 41 of the outer annular wall 46 and towards the inner surface of the bubble 8; the cooling air flow blown out of the annular air outlet 30 of the inner cooling air ring and the cooling air flow blown out of the multiple air outlet slits 41 of the outer annular wall converge to form a first cooling air flow, the first cooling air flow contacts the inner surface of the bubble 8 and flows upward in the bubble 8, and when it rises to the height position near the radial air return channel 90, it turns, enters the air outlet channel 14 through the outer air return port 50, the radial air return channel 90 and the inner air return port 15, then flows downward through the air outlet channel 14, and finally is extracted by the air extractor;

[0026] Figure 2 、 Figure 3 、 Figure 8As shown, another part of the cooling air flow entering the annular air cavity 40 enters the annular upgoing air duct 6 through the lower air-permeable hole 61, then flows upward inside the annular upgoing air duct 6, and flows into the lumen 70 of the upper air duct 7 through the upper air-permeable hole 62, and then blows out of the upper end port of the upper air duct 7 to form a second cooling air flow. After blowing out of the upper end port of the upper air duct 7, the second cooling air flow then flows downward, during which the inner surface of the membrane bubble 8 is cooled, until it turns near the height position of the radial return air passage 90, enters the air outlet passage 14 through the outer return air port 50, the radial return air passage 90 and the inner return air port 15, and then flows downward through the air outlet passage 14, and finally is sucked away by the air suction machine. Figure 2 、 Figure 3 、 Figure 8 The arrows in the above figures represent the flow paths of the first cooling air flow and the second cooling air flow.

[0027] In the above embodiments, the number of radial return air passages 90 can be changed to four or five.

[0028] The ratio of the second cooling air flow to the first cooling air flow can be adjusted according to actual needs to achieve the best cooling effect.

Claims

1. An internal cooling structure for a plastic film blowing machine, comprising a film blowing die, a vertical inner air duct, and a vertical outer air duct. The inner air duct is divided into a lower section, a middle section, and an upper section. The outer air duct is located at the center of the film blowing die. The lower section of the inner air duct is fitted inside the outer air duct. The middle and upper sections of the inner air duct are located above the film blowing die. The cavity of the inner air duct forms an air outlet channel, and the annular gap between the lower section of the inner air duct and the outer air duct forms an air inlet channel. A cooling structure is also provided above the film blowing die. An inner cooling air ring and an annular wall are fitted around the middle section of an inner air duct, with the inner cooling air ring located below the annular wall. The inner cooling air ring has an annular air outlet. The space between the annular wall and the middle section of the inner air duct forms an annular air cavity, with a circular air cavity cover at the top. The annular wall has multiple annular air outlet slits. The upper section of the inner air duct protrudes above the air cavity cover. The upper end of the air inlet channel communicates with the inner cooling air ring, and the inner cooling air ring communicates with the annular air cavity. Its features include: A partition plate is provided at the upper end of the upper section of the inner duct. An upper duct is provided above the partition plate. The cavity of the upper duct is separated from the cavity of the inner duct by the partition plate, and the upper end of the upper duct is open. An outer duct is also provided outside the upper section of the inner duct. The annular gap between the outer duct and the upper section of the inner duct forms an annular upward air duct. A lower vent is provided between the lower end of the annular upward air duct and the upper end of the annular air cavity. An upper vent is provided between the upper end of the annular upward air duct and the lower end of the cavity of the upper duct. An external return air port is provided at the upper part of the outer duct, and an internal return air port is provided at the upper part of the upper section of the inner duct. An annular partition plate is connected between the edge of the external return air port and the edge of the internal return air port. The space surrounded by the annular partition plate forms a radial return air channel, which is connected to the upper part of the air outlet channel.

2. The internal cooling structure of the plastic blown film machine according to claim 1, characterized in that: The blown film die head is equipped with a blower and an exhaust fan. The blower is connected to the lower end of the air inlet channel through an air duct, and the lower end of the air outlet channel is connected to the exhaust fan through an air duct.

3. The internal cooling structure of the plastic blown film machine according to claim 1 or 2, characterized in that: There are multiple radial return air ducts, and each radial return air duct is evenly arranged along the circumference of the outer casing and inner duct.

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