Rotary color printing plastic mandrel for two-piece cans

Abstract

The present invention relates to the technical field of two-piece can color printing, specifically a rotary color printing plastic mandrel for two-piece cans, which includes a fixed inner tube and a plastic shaft cylinder hermetically sleeved outside the fixed inner tube. A split inner tube capable of rotating relative to the fixed inner tube is coaxially inserted inside the fixed inner tube. An airtight rubber ring with an airtight rotary contact function is arranged between the split inner tube and the fixed inner tube. A support air shaft cooperatively installed with a color printing device is inserted into the split inner tube, and there is airtight contact between the split inner tube and the support air shaft. The rotary color printing plastic mandrel for two-piece cans of the present invention can, after the two-piece can is sleeved onto the mandrel, automatically lock the edge of the two-piece can through the cooperation of the set locking outer ring and the locking driving structure, thereby being able to prevent the two-piece can from rotating relative to the plastic shaft cylinder, and at the same time filling air pressure into the two-piece can through the connecting notch and the air supply end hole.

Description

Technical Field

[0001] The present invention relates to the technical field of two-piece can color printing, and specifically to a rotary color printing plastic mandrel for two-piece cans. Background Art

[0002] A two-piece can refers to a seamless metal container consisting of a can body and a can bottom, which is usually processed by stamping. When packaging, the top of the two-piece can is closed with a can lid. Common two-piece cans include beverage containers such as aluminum cans. When a two-piece can is color printed, a plastic mandrel is inserted into the inside of the two-piece can to support it, and then the two-piece can is driven to rotate at a constant speed in a color printer to complete the color printing. Due to reasons such as wear or dimensional errors of the plastic mandrel, during use, the plastic shaft cylinder of the two-piece can may occasionally rotate relative to the plastic mandrel, which may cause problems such as overlapping printed patterns. Moreover, due to the wear problem of the plastic mandrel, it is difficult to fully support the two-piece can. The aluminum two-piece can has a relatively soft material. When the support is insufficient, the cylindricity of the can body is not enough, which will also affect the pattern distribution of the color printing and reduce the color printing quality. Summary of the Invention

[0003] The purpose of the present invention is to provide a rotary color printing plastic mandrel for two-piece cans to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A rotary color printing plastic mandrel for two-piece cans, including a fixed inner tube and a plastic shaft cylinder hermetically sleeved and fixed outside the fixed inner tube. A split inner tube that can rotate relative to the fixed inner tube is coaxially inserted into the inside of the fixed inner tube. An airtight rubber ring with an airtight rotary contact function is arranged between the split inner tube and the fixed inner tube. A support air shaft cooperatively installed with a color printing device is inserted into the split inner tube, and there is airtight contact between the split inner tube and the support air shaft. An axially penetrating middle ventilation cavity is opened inside the support air shaft. A locking drive structure is arranged at the end of the middle ventilation cavity. A bridge-through branch is arranged in the support air shaft. One end of the bridge-through branch is communicated with the middle ventilation cavity, and the other end is opened at the end position of the support air shaft. A locking outer ring is fixedly arranged on the surface of the plastic shaft cylinder. Uniform oil ring grooves are opened in the locking outer ring. The uniform oil ring grooves are communicated with the locking drive structure. A rubber pressure film is arranged to block the openings of the uniform oil ring grooves. The rubber pressure film can expand and protrude under the oil pressure in the uniform oil ring grooves to lock the edges of the two-piece can body.

[0005] The locking drive structure includes two sets of limit convex rings, a piston body, a piston rod, and a return spring. The two sets of limit convex rings are both fixed on the inner wall surface of the middle ventilation cavity. A piston body in airtight contact with the middle ventilation cavity is arranged between the two sets of limit convex rings. A piston rod is fixedly arranged on the surface of the piston body. A return spring is arranged on one side of the piston body.

[0006] An air supply end hole is provided at the end of the supporting air shaft, and a connecting notch is provided between the air supply end hole and the middle air cavity. The communication port between the connecting notch and the middle air cavity is located between two groups of limiting convex rings.

[0007] A frame side plate is fixedly arranged at the end of the piston rod. A lever pry plate is arranged between the two frame side plates. A moving plate groove is penetrated through the lever pry plate. A plate groove limiting shaft is inserted into the moving plate groove, and both ends of the plate groove limiting shaft are fixedly installed with their corresponding frame side plates respectively.

[0008] An annular sleeve is arranged in the lever pry plate. The distance from one end of the lever pry plate close to the moving plate groove to the annular sleeve is greater than the distance from the other end of the lever pry plate to the annular sleeve. A fulcrum cross shaft is inserted into the annular sleeve, and the fulcrum cross shaft is fixedly installed with the plastic shaft cylinder. When the piston rod axially moves, the lever pry plate can be driven to rotate around the fulcrum cross shaft through the cooperation of the plate groove limiting shaft and the moving plate groove.

[0009] An extrusion top groove is provided on the inner wall surface of the plastic shaft cylinder. A hydraulic chamber is provided on one side of the extrusion top groove. A main hydraulic piston is hermetically inserted into the hydraulic chamber. One end of the lever pry plate far from the moving plate groove is inserted into the extrusion top groove, and when the lever pry plate rotates around the fulcrum cross shaft, the main hydraulic piston can be pushed to axially move. A hydraulic return spring is arranged on the side of the main hydraulic piston far from the lever pry plate. A hydraulic oil path is provided in the plastic shaft cylinder. One end of the hydraulic oil path is connected to the hydraulic chamber, and the other end is connected to the uniformly distributed oil ring groove.

[0010] A pressure reducing air path is provided in the supporting air shaft. One end of the pressure reducing air path is connected to the air supply end hole through a safety solenoid valve, and the other end of the pressure reducing air path is connected to the outside. An outer groove of the shaft cylinder is provided on the surface of the plastic shaft cylinder. An optical displacement sensor is arranged in the outer groove of the shaft cylinder. After two tank bodies are sleeved on the outside of the plastic shaft cylinder, the movement condition of the two tank bodies relative to the plastic shaft cylinder can be detected through the optical displacement sensor, and the safety solenoid valve is automatically connected when the two tank bodies move relative to the plastic shaft cylinder.

[0011] Deep groove ball bearings and cylindrical roller bearings are arranged on the inner wall surface of the fixed inner tube. The fixed inner tube contacts the split inner tube through the deep groove ball bearings, and the fixed inner tube contacts the supporting air shaft through the cylindrical roller bearings.

[0012] A sealing insert ring is embedded on the inner wall surface of the split inner tube. The split inner tube is in airtight contact with the supporting air shaft through the sealing insert ring. A bearing retaining ring is arranged on the surface of the split inner tube, and the bearing retaining ring is used for limiting the deep groove ball bearings.

[0013] The surface of the supporting air shaft is provided with air shaft locking threads, and a locking nut is spirally engaged with the air shaft locking threads. An electromagnetic air valve is arranged in the bridge through branch.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] For the two-piece can rotary color printing plastic core shaft of the present invention, after the two-piece can is sleeved on the core shaft, the edge of the two-piece can can be automatically locked through the cooperation of the set locking outer ring and the locking driving structure, so as to avoid the rotation of the two-piece can relative to the plastic shaft cylinder. At the same time, air pressure is filled into the two-piece can through the connecting notch and the air supply end hole, so that the two-piece can is more round under the support of air pressure, reducing the deformation of the can body, and thus improving the distribution accuracy of the pattern during color printing.

[0016] Through the cooperation of the set pressure reducing air circuit and the optical displacement sensor and other structures, the present invention can perform secondary insurance control to reduce the probability of the two-piece can falling off under the action of air pressure. When the two-piece can body moves relative to the plastic shaft cylinder, the pressure reducing air circuit is quickly and automatically connected to the outside to reduce the air pressure inside the two-piece can body, thereby reducing the probability of the two-piece can falling off. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0018] Figure 2 It is another perspective schematic diagram of the overall structure of the present invention.

[0019] Figure 3 It is a three-dimensional sectional view of the present invention.

[0020] Figure 4 It is Figure 3 The enlarged schematic diagram of area A in

[0021] Figure 5 It is a three-dimensional sectional view of the middle position of the present invention.

[0022] Figure 6 It is Figure 5 The enlarged schematic diagram of area B in

[0023] Figure 7 It is Figure 5 The enlarged schematic diagram of area C in

[0024] Figure 8 It is the front view of the three-dimensional sectional view of the middle position of the present invention.

[0025] Figure 9 It is Figure 8 The enlarged schematic diagram of area D in

[0026] In the figure: 1. Plastic shaft cylinder; 2. Fixed inner tube; 3. Split inner tube; 4. Airtight rubber ring; 5. Support air shaft; 6. Central ventilation cavity; 7. Bridge-through branch; 8. Locking outer ring; 9. Uniform oil ring groove; 10. Rubber pressing film; 601. Limit convex ring; 602. Piston body; 603. Piston rod; 604. Return spring of the reset plug; 605. Air supply end hole; 606. Connecting notch; 607. Side plate of the frame; 608. Lever pry plate; 609. Moving plate groove; 610. Plate groove limit shaft; 611. Fulcrum cross shaft; 612. Extrusion top groove; 613. Hydraulic chamber; 614. Active hydraulic piston; 615. Hydraulic return spring; 616. Hydraulic oil circuit; 501. Pressure-reducing air circuit; 502. Safety solenoid valve; 503. Outer groove of the shaft cylinder; 504. Optical displacement sensor; 201. Deep groove ball bearing; 202. Cylindrical roller bearing; 301. Sealing insert ring; 302. Bearing retaining ring; 505. Air shaft locking thread; 506. Locking nut; 701. Electromagnetic air valve; 11. Two tank bodies. Detailed implementation mode

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] Please refer to Figures 1 to 9 , the present invention provides a technical solution: a two-piece can rotary color printing plastic core shaft, including a fixed inner tube 2 and a plastic shaft cylinder 1 hermetically sleeved and fixed outside the fixed inner tube 2. A split inner tube 3 that can rotate relative to the fixed inner tube 2 is coaxially inserted inside the fixed inner tube 2. An airtight rubber ring 4 with an airtight rotary contact function is arranged between the split inner tube 3 and the fixed inner tube 2. A support air shaft 5 cooperatively installed with the color printing equipment is inserted into the split inner tube 3. An airtight contact is made between the split inner tube 3 and the support air shaft 5. A central ventilation cavity 6 is axially penetrated and opened inside the support air shaft 5. A locking drive structure is arranged at the end of the central ventilation cavity 6. A bridge-through branch 7 is arranged in the support air shaft 5. One end of the bridge-through branch 7 is communicated with the central ventilation cavity 6, and the other end is opened at the end position of the support air shaft 5. A locking outer ring 8 is fixedly arranged on the surface of the plastic shaft cylinder 1. Uniform oil ring grooves 9 are opened in the locking outer ring 8. The uniform oil ring grooves 9 are communicated with the locking drive structure. A rubber pressing film 10 is arranged to block the opening of the uniform oil ring grooves 9. The rubber pressing film 10 is made of rubber and has elasticity. The rubber pressing film 10 can expand and protrude under the oil pressure in the uniform oil ring grooves 9 to lock the edges of the two tank bodies.

[0029] The locking drive structure includes a limit convex ring 601, a piston body 602, a piston rod 603, and a return plug spring 604. There are two sets of limit convex rings 601, and both are fixed on the inner wall surface of the middle ventilation cavity 6. A piston body 602 in airtight contact with the middle ventilation cavity 6 is arranged between the two sets of limit convex rings 601. A piston rod 603 is fixedly arranged on the surface of the piston body 602. A return plug spring 604 is arranged on one side of the piston body 602. An air supply end hole 605 is opened at the end of the support air shaft 5. A connecting notch 606 is communicated between the air supply end hole 605 and the middle ventilation cavity 6. The communication port between the connecting notch 606 and the middle ventilation cavity 6 is located between the two sets of limit convex rings 601.

[0030] A frame side plate 607 is fixedly arranged at the end of the piston rod 603. A lever pry plate 608 is arranged between the two sets of frame side plates 607. A moving plate groove 609 is penetrated through the lever pry plate 608. A plate groove limiting shaft 610 is inserted into the moving plate groove 609. The two ends of the plate groove limiting shaft 610 are respectively fixedly installed on the corresponding frame side plates 607. A ring sleeve is arranged in the lever pry plate 608. The distance from the end of the lever pry plate 608 close to the moving plate groove 609 to the ring sleeve is greater than the distance from the other end of the lever pry plate 608 to the ring sleeve. A fulcrum cross shaft 611 is inserted into the ring sleeve. The fulcrum cross shaft 611 is fixedly installed with the plastic shaft cylinder 1. When the piston rod 603 axially moves, the lever pry plate 608 can be driven to rotate around the fulcrum cross shaft 611 through the cooperation of the plate groove limiting shaft 610 and the moving plate groove 609.

[0031] An extrusion top groove 612 is opened on the inner wall surface of the plastic shaft cylinder 1. A hydraulic chamber 613 is opened on one side of the extrusion top groove 612. A main hydraulic piston 614 is hermetically inserted into the hydraulic chamber 613. The end of the lever pry plate 608 away from the moving plate groove 609 is inserted into the extrusion top groove 612. When the lever pry plate 608 rotates around the fulcrum cross shaft 611, the main hydraulic piston 614 can be pushed to axially move. A hydraulic return spring 615 is arranged on the side of the main hydraulic piston 614 away from the lever pry plate 608. A hydraulic oil path 616 is opened in the plastic shaft cylinder 1. One end of the hydraulic oil path 616 is communicated with the hydraulic chamber 613, and the other end is communicated with the evenly distributed oil ring groove 9. The hydraulic chamber 613, the hydraulic oil path 616, and the evenly distributed oil ring groove 9 are all filled with hydraulic oil.

[0032] A pressure-reducing air passage 501 is provided in the supporting air shaft 5. One end of the pressure-reducing air passage 501 is connected to the air supply end hole 605 through a safety solenoid valve 502, and the other end of the pressure-reducing air passage 501 is connected to the outside. An outer groove 503 of the shaft barrel is provided on the surface of the plastic shaft barrel 1, and an optical displacement sensor 504 is arranged in the outer groove 503 of the shaft barrel. After two tank bodies are sleeved outside the plastic shaft barrel 1, the optical displacement sensor 504 can detect the movement of the two tank bodies relative to the plastic shaft barrel 1. When the two tank bodies move relative to the plastic shaft barrel 1, the safety solenoid valve 502 is automatically turned on; the above-mentioned optical displacement sensor 504 emits laser light to the inner surface of the two tank bodies 11, and captures the reflected laser light through a lens to judge the movement of the two tank bodies 11. Its principle is the same as that of a laser mouse in the prior art and can detect movement.

[0033] Deep groove ball bearings 201 and cylindrical roller bearings 202 are arranged on the inner wall surface of the fixed inner tube 2. The fixed inner tube 2 contacts the split inner tube 3 through the deep groove ball bearings 201, and the fixed inner tube 2 contacts the supporting air shaft 5 through the cylindrical roller bearings 202.

[0034] A sealing ring 301 is embedded on the inner wall surface of the split inner tube 3. The split inner tube 3 is in airtight contact with the supporting air shaft 5 through the sealing ring 301. A bearing retaining ring 302 is arranged on the surface of the split inner tube 3, and the bearing retaining ring 302 is used to limit the deep groove ball bearing 201.

[0035] An air shaft locking thread 505 is provided on the surface of the supporting air shaft 5, and a locking nut 506 is spirally engaged with the air shaft locking thread 505. An electromagnetic air valve 701 is arranged in the bridge connection branch 7. The electromagnetic air valve 701 is a gas valve controlled by electricity and is in a normally closed state and is turned on after being controlled by electricity.

[0036] When the present invention is in use, the supporting air shaft 5 is installed in cooperation with a color printing device, and two tank bodies 11 are sleeved on the plastic shaft barrel 1, as shown in Figure 3 shown; high-pressure air flow is input through the middle air cavity 6, the air pressure acts on the surface of the piston body 602, pushes the piston body 602 to move, so that the piston rod 603 moves synchronously. The piston rod 603 is matched with the moving plate groove 609 through the plate groove limiting shaft 610, drives the lever pry plate 608 to rotate around the fulcrum cross shaft 611, and then enables the lever pry plate 608 to extrude and drive the active hydraulic piston 614. Due to the lever structure of the lever pry plate 608, the axial movement thrust of the piston rod 603 can be amplified, so that the axial movement thrust of the active hydraulic piston 614 is greatly increased.

[0037] When the active hydraulic piston 614 moves axially, the hydraulic oil in the hydraulic chamber 613 can be input into the uniformly distributed oil ring groove 9 through the hydraulic oil path 616, pressing the rubber pressing film 10 to bulge outwards, locking the edges of the two tank bodies 11, so as to avoid the problem of rotation of the two tank bodies 11 relative to the plastic shaft cylinder 1; at the same time, the edges of the two tank bodies 11 are hermetically sealed.

[0038] As Figure 6 shown in the figure, when the piston body 602 moves to the position of the connecting notch 606, the high-pressure air flow in the middle air chamber 6 enters the air supply end hole 605 through the connecting notch 606 and sprays out from the air supply end hole 605 to provide air pressure support for the inside of the two tank bodies 11, making the two tank bodies 11 more round and reducing the collapse of the two tank bodies 11 due to insufficient support.

[0039] At this time, by rotating the two tank bodies 11, color printing patterns are carried out in the color printer. After the color printing is completed, the electromagnetic air valve 701 is controlled to open, and the middle air chamber 6 is directly connected to the inside of the two tank bodies 11 through the bridge connection branch 7, so that the air pressures on both sides of the piston body 602 are balanced, and the piston body 602 loses the thrust of the gas and resets under the elastic force of the return spring 604; then the active hydraulic piston 614 resets and moves, the rubber pressing film 10 releases the lock, and after the two tank bodies 11 lose the lock, they axially move relative to the plastic shaft cylinder 1 under the air pressure and are automatically unloaded.

[0040] In the above process of locking and gas support for the two tank bodies 11, in some cases, when the air pressure input into the middle air chamber 6 is too high, the thrust of the air pressure acting on the bottom surface of the two tank bodies 11 is greater than the locking friction force of the rubber pressing film 10, and the two tank bodies 11 will axially move relative to the plastic shaft cylinder 1; after the displacement of the two tank bodies 11 is detected by the optical displacement sensor 504, the safety solenoid valve 502 is quickly controlled to be connected, so that the high pressure in the air supply end hole 605 and the two tank bodies 11 can be released to the outside through the pressure reducing air path 501, reducing the air pressure in the two tank bodies 11, so as to play a role in protecting against detachment.

[0041] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. The rotary color printing plastic mandrel for two-piece cans comprises a fixed inner tube (2) and a plastic shaft cylinder (1) which is hermetically sleeved and fixed outside the fixed inner tube (2), and is characterized in that: A split inner tube (3) capable of rotating relative to the fixed inner tube (2) is coaxially inserted inside the fixed inner tube (2). An airtight rubber ring (4) with an airtight rotary contact function is provided between the split inner tube (3) and the fixed inner tube (2). A support air shaft (5) cooperatively installed with a color printing device is inserted into the split inner tube (3). An airtight contact is provided between the split inner tube (3) and the support air shaft (5). An axial through middle ventilation cavity (6) is formed inside the support air shaft (5). A locking drive structure is provided at the end of the middle ventilation cavity (6). A bridge-through branch (7) is provided in the support air shaft (5). One end of the bridge-through branch (7) communicates with the middle ventilation cavity (6), and the other end opens at the end position of the support air shaft (5). A locking outer ring (8) is fixedly provided on the surface of the plastic shaft cylinder (1). Uniform oil ring grooves (9) are formed in the locking outer ring (8). The uniform oil ring grooves (9) communicate with the locking drive structure. A rubber pressing film (10) is provided to seal the opening of the uniform oil ring grooves (9). The rubber pressing film (10) can expand and protrude under the oil pressure in the uniform oil ring grooves (9) to lock the edges of the two tank bodies; The locking drive structure includes a limit convex ring (601), a piston body (602), a piston rod (603) and a return plug spring (604). There are two groups of the limit convex rings (601), and both are fixed on the inner wall surface of the middle ventilation cavity (6). A piston body (602) in airtight contact with the middle ventilation cavity (6) is arranged between the two groups of the limit convex rings (601). A piston rod (603) is fixedly arranged on the surface of the piston body (602). A return plug spring (604) is arranged on one side of the piston body (602); An air supply end hole (605) is opened at the end of the support air shaft (5). A connecting notch (606) is communicated between the air supply end hole (605) and the middle ventilation cavity (6). The communication port between the connecting notch (606) and the middle ventilation cavity (6) is located between the two groups of limit convex rings (601); A frame side plate (607) is fixedly arranged at the end of the piston rod (603). A lever pry plate (608) is arranged between the two groups of frame side plates (607). A moving plate groove (609) is penetrated in the lever pry plate (608). A plate groove limit shaft (610) is inserted in the moving plate groove (609). The two ends of the plate groove limit shaft (610) are respectively fixedly installed on the corresponding frame side plates (607); A ring sleeve is arranged in the lever pry plate (608). The distance from the end of the lever pry plate (608) close to the moving plate groove (609) to the ring sleeve is greater than the distance from the other end of the lever pry plate (608) to the ring sleeve. A fulcrum cross shaft (611) is inserted in the ring sleeve. The fulcrum cross shaft (611) is fixedly installed with the plastic shaft cylinder (1). When the piston rod (603) axially moves, the lever pry plate (608) can be driven to rotate around the fulcrum cross shaft (611) through the cooperation of the plate groove limit shaft (610) and the moving plate groove (609); An extrusion top groove (612) is opened on the inner wall surface of the plastic shaft cylinder (1). A hydraulic chamber (613) is opened on one side of the extrusion top groove (612). A main hydraulic piston (614) is hermetically inserted in the hydraulic chamber (613). The end of the lever pry plate (608) far from the moving plate groove (609) is inserted into the extrusion top groove (612). When the lever pry plate (608) rotates around the fulcrum cross shaft (611), the main hydraulic piston (614) can be pushed to axially move. A hydraulic return spring (615) is arranged on the side of the main hydraulic piston (614) far from the lever pry plate (608). A hydraulic oil path (616) is opened in the plastic shaft cylinder (1). One end of the hydraulic oil path (616) is communicated with the hydraulic chamber (613), and the other end is communicated with the uniformly distributed oil ring groove (9).

2. The rotary color printing plastic mandrel for two-piece cans according to claim 1, characterized in that: A pressure-reducing air passage (501) is provided in the supporting air shaft (5). One end of the pressure-reducing air passage (501) is connected to the air supply end hole (605) through a safety solenoid valve (502). The other end of the pressure-reducing air passage (501) is connected to the outside. An outer groove (503) of the shaft cylinder is provided on the surface of the plastic shaft cylinder (1). An optical displacement sensor (504) is arranged in the outer groove (503) of the shaft cylinder. After two tank bodies are sleeved outside the plastic shaft cylinder (1), the movement condition of the two tank bodies relative to the plastic shaft cylinder (1) can be detected by the optical displacement sensor (504). When the two tank bodies move relative to the plastic shaft cylinder (1), the safety solenoid valve (502) is automatically turned on.

3. The rotary color printing plastic mandrel for two-piece cans according to claim 1, characterized in that: Deep groove ball bearings (201) and cylindrical roller bearings (202) are arranged on the inner wall surface of the fixed inner tube (2). The fixed inner tube (2) contacts the split inner tube (3) through the deep groove ball bearings (201). The fixed inner tube (2) contacts the supporting air shaft (5) through the cylindrical roller bearings (202).

4. The rotary color printing plastic mandrel for two-piece cans according to claim 3, characterized in that: A sealing ring (301) is embedded on the inner wall surface of the split inner tube (3). The split inner tube (3) is in airtight contact with the supporting air shaft (5) through the sealing ring (301). A bearing retaining ring (302) is arranged on the surface of the split inner tube (3). The bearing retaining ring (302) is used to limit the deep groove ball bearings (201).

5. The rotary color printing plastic mandrel for two-piece cans according to claim 1, characterized in that: An air shaft locking thread (505) is provided on the surface of the supporting air shaft (5). A locking nut (506) is spirally engaged with the air shaft locking thread (505). An electromagnetic air valve (701) is arranged in the bridge connection branch (7).

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