CN114055923A

CN114055923A - Plastic film double-sided printing system

Info

Publication number: CN114055923A
Application number: CN202111273651.4A
Authority: CN
Inventors: 汪帝臣; 王洛
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-10-29
Filing date: 2021-10-29
Publication date: 2022-02-18

Abstract

The invention relates to the technical field of plastic film printing, in particular to a plastic film double-sided printing system which comprises a bottom plate, a material receiving frame, a material discharging frame and a first printing box, wherein two first guide roller frames are symmetrically and fixedly arranged on the bottom plate, two second guide roller frames are symmetrically and fixedly arranged on the bottom wall of a top plate, a second printing box is fixedly arranged on the bottom wall of the top plate, two main air pipes are symmetrically and fixedly arranged on a side plate, a hot air drying mechanism is arranged between the two main air pipes and a motor, and evaporation guide mechanisms are arranged on the bottom wall of the top plate. The film coming out of the first printing box is redirected through the first guide roller frame and the second guide roller frame, so that the other surface of the film can be printed by the second printing box above the film, and the purpose of double-sided printing is realized; utilize the motor to drive two fans simultaneously and rotate, air-dry the film, improved the drying rate of film, improved production efficiency, secondly utilize the piston pipe to realize the hot water circulation among a plurality of evaporating pipes, carry out evaporation drying to the film rather than laminating mutually.

Description

Plastic film double-sided printing system

Technical Field

The invention relates to the technical field of plastic film printing, in particular to a plastic film double-sided printing system.

Background

Films made from polyvinyl chloride, polyethylene, polypropylene, polystyrene, and other resins are used for packaging, and as a film coating. Plastic packages and plastic package products occupy more and more share in the market, and particularly, composite plastic flexible packages are widely applied to the fields of food, medicine, chemical industry and the like.

In the prior patent (publication number: CN109532220B), when unwinding a plastic film, an unwinding shaft is placed inside a placing groove, and the plastic film is unwound by pulling the plastic film, so that the plastic film can be conveniently taken and placed, and the unwinding shaft can be effectively prevented from falling; inside circulation water of accessible guide roll cools off plastic film's both sides after the printing is accomplished, draws out plastic film through two guide rolls simultaneously and exposes it with the area increase in the air, and it is convenient for it cools down, avoids the printing ink of printing not dry to cause set-off and set-off.

The invention indeed makes the printing more stable and also improves the cooling efficiency of the plastic film to a certain extent, but still has some problems:

1. the above invention requires two processes for printing both sides of the film, which reduces the production efficiency.

2. After the plastic film is processed, the plastic film needs to be dried, and generally, an air drying mode is adopted, so that a longer production line is needed, and meanwhile, the air drying effect is poorer.

To this end, a plastic film duplex printing system is proposed.

Disclosure of Invention

The invention aims to provide a plastic film double-sided printing system, which is used for carrying out double-sided printing on a film through the reversing action of a first guide roller frame and a second guide roller frame without secondary processing; secondly, the air drying and heating evaporation modes are adopted in the printing reversing process, so that the film is dried quickly, and the problems in the background technology are solved.

In order to achieve the purpose, the invention provides the following technical scheme:

the utility model provides a two-sided printing system of plastic film, includes the bottom plate, receives the work or material rest, goes out work or material rest and first printing box, fixed mounting has the curb plate on the lateral wall of bottom plate, the top fixed mounting of curb plate has the roof, symmetry fixed mounting has two second guide roll framves on the bottom plate, symmetry fixed mounting has two first guide roll framves on the diapire of roof, fixed mounting has second printing box on the diapire of roof, and second printing box is located between two first guide roll framves, fixed mounting has the mounting bracket on the curb plate, fixed mounting has the motor on the mounting bracket, symmetry fixed mounting has two main tuber pipes on the curb plate, two be equipped with hot-blast dry mechanism between main tuber pipe and the motor, fixed mounting has the water tank on the roof of roof, all be equipped with evaporation guiding mechanism on the diapire of roof.

The first guide roller frame and the second guide roller frame are used for guiding the film coming out of the first printing box, so that the other surface of the film enters the second printing box for printing, double-sided printing work is completed at one time, and the processing efficiency is improved; hot air is blown to the outer wall of the film by the hot air drying mechanism, so that the drying speed of the film is accelerated, and the production efficiency and quality are improved; utilize evaporation guiding mechanism to let in hot water in making a plurality of evaporating pipes for film outer wall and a plurality of evaporating pipes fully contact, accelerate the evaporation of moisture in the pigment, further improved production efficiency.

Preferably, the hot air drying mechanism comprises two fans fixedly mounted on a side plate, two first belt pulleys are fixedly mounted on an output shaft of the motor, second belt pulleys are fixedly mounted on rotation shafts of the two fans, a transmission belt is wound between the two first belt pulleys and the two second belt pulleys respectively, the side walls of the two fans are communicated with air guide pipes respectively, the two air guide pipes are communicated with two main air pipes respectively, a plurality of secondary air pipes are connected to the main air pipes at equal distances, each secondary air pipe is provided with a plurality of air blowing nozzles on the side wall, and two first heaters are fixedly mounted in the air guide pipes.

The motor drives two first belt pulleys and rotates, two first belt pulleys drive two second belt pulleys through the drive belt and rotate, thereby drive two fans and rotate, during the outside air enters into the main air pipe through the guide duct, enter into each time tuber pipe respectively by the main air pipe again, blow on the film of upside and downside through the blowing nozzle, owing to be equipped with first heater in the guide duct, so the wind temperature that the blowing nozzle blew off can be than higher, accelerate air-dried speed, the efficiency and the quality of production have been improved.

Preferably, two all be equipped with the air-supply line on the fan, two the port of air-supply line advances to install the filter screen.

The filter screen is additionally arranged at the port of the air inlet pipe, so that dust and sundries can be prevented from entering the air duct, the air outlet cleanliness of the air blowing nozzle is improved, the air drying quality is improved, and the production efficiency and quality are further improved.

Preferably, evaporation guiding mechanism is including reciprocal water delivery subassembly, evaporating pipe and second heater, fixed mounting has four mounts on the roof diapire, and every two aligned mounts all rotate jointly and install a plurality of connecting pipes, two aligned between the connecting pipe be connected with the evaporating pipe jointly, lie in a plurality of with one side the connecting pipe is kept away from evaporating pipe one end and is all rotated jointly and be connected with main water pipe, and the junction of every connecting pipe and main water pipe all is equipped with sealed bearing, every the connecting hole has all been seted up on the main water pipe, be connected with two wet return on the lateral wall of water tank, install two second heaters on the roof of water tank.

Utilize evaporation guiding mechanism to let in hot water in making a plurality of evaporating pipes for film outer wall and a plurality of evaporating pipes fully contact, accelerate the evaporation of moisture in the pigment, further improved production efficiency. After the water tank normal water is heated by the second heater, enter into main water pipe, during main water pipe carried each evaporating pipe with hot water again, adopt connecting pipe and sealed bearing to connect between evaporating pipe and the main water pipe for every evaporating pipe all can rotate, thereby can take the evaporating pipe to rotate together when making the film slide on the evaporating pipe, thereby accelerate the evaporation of the moisture in the pigment on the film, improved the production efficiency and the quality of film.

Preferably, reciprocal water delivery subassembly is including the fixed piston pipe that alternates at the water tank top, and the piston pipe is "U" shape, the piston pipe is kept away from water tank one end activity and is inserted and be equipped with the piston rod, symmetrical connection has two outlet pipes on the lateral wall of piston pipe, symmetrical fixed mounting has two fixed plates on the piston pipe lateral wall, the bottom fixed mounting of piston rod has the driving plate, all be connected with reset spring between driving plate and two fixed plates, fixed mounting has the cam on the output shaft of motor, and sliding contact between cam and the driving plate.

The motor drives the cam to rotate, the cam can push the transmission plate back and forth when rotating, the transmission plate is pushed upwards, two reset springs are compressed, the piston rod is pressed into the piston pipe simultaneously, liquid in the piston pipe is discharged from the two water outlet pipes, the two water outlet pipes are connected with the connecting holes in the two main water pipes positioned on the same side, the two water return pipes on the water tank are connected with the connecting holes in the two main water pipes on the other side, when the cam does not push the transmission plate upwards any more, the transmission plate moves downwards under the elastic action of the two reset springs, so that the transmission plate is driven to move downwards, the piston rod moves downwards, so that hot water in the water tank can be sucked into the piston pipe, the reciprocating operation is carried out, the continuous circulation of the hot water is realized, the efficiency of evaporation drying is improved, and the production efficiency is further improved.

Preferably, one end of the piston pipe close to the water tank is provided with a first one-way valve, and the two water outlet pipes are provided with second one-way valves.

The first check valve on the piston pipe is utilized to ensure that hot water can only flow into the piston pipe from the water tank without backflow, and the second check valve on the water outlet pipe ensures that the hot water can only enter the main water pipe from the water outlet pipe without backflow, so that the efficiency of evaporation drying is further improved, and the production efficiency is further improved.

Compared with the prior art, the invention has the beneficial effects that:

1. the film coming out of the first printing box is redirected by the first guide roller frame and the second guide roller frame, so that the other surface of the film can be printed by the second printing box above the film, the purpose of double-sided printing is realized, and the production efficiency is improved.

2. Utilize the motor to drive two fans simultaneously and rotate, realize blowing of a plurality of time tuber pipes, air-dry the film of upper and lower side, improved the drying rate of film, improved production efficiency, secondly utilize the piston pipe to realize the hot water circulation in a plurality of evaporating pipes, carry out evaporation drying to the film rather than laminating mutually, further improved production efficiency.

Drawings

FIG. 1 is a front view of the present invention;

FIG. 2 is a top view of the present invention;

FIG. 3 is a top view of the airing mechanism of the present invention;

FIG. 4 is a plan view of an evaporating tube according to the present invention;

FIG. 5 is a side view of the reciprocating pressurization mechanism of the present invention;

figure 6 is an enlarged view of subsection A of the present invention.

In the figure: 1. a base plate; 2. a side plate; 3. a top plate; 4. a material receiving frame; 5. a first print cartridge; 6. a second print cartridge; 7. A first guide roller frame; 8. a second guide roller frame; 9. a discharging frame; 10. a main air duct; 11. a secondary air duct; 12. a blowing nozzle; 13. a fan; 14. an air guide pipe; 15. a first heater; 16. a mounting frame; 17. a motor; 18. a first belt pulley; 19. a second belt reel; 20. an air inlet pipe; 21. filtering with a screen; 22. a fixed mount; 23. a connecting pipe; 24. a main water pipe; 25. an evaporation tube; 26. sealing the bearing; 27. a water tank; 28. a water outlet pipe; 29. a water return pipe; 30. connecting holes; 31. a piston tube; 32. a first check valve; 33. a second one-way valve; 34. a second heater; 35. a piston rod; 36. a drive plate; 37. a fixing plate; 38. A return spring; 39. a cam.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise. Furthermore, the terms "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 1 to 6, the present invention provides a plastic film double-sided printing system, which has the following technical scheme:

the utility model provides a two-sided printing system of plastic film, including bottom plate 1, receive material frame 4, go out work or material rest 9 and first printing box 5, fixed mounting has curb plate 2 on the lateral wall of bottom plate 1, the top fixed mounting of curb plate 2 has roof 3, symmetry fixed mounting has two second guide roll framves 8 on bottom plate 1, symmetry fixed mounting has two first guide roll framves 7 on the diapire of roof 3, fixed mounting has second printing box 6 on the diapire of roof 3, and second printing box 6 is located between two first guide roll framves 7.

Referring to fig. 1, a first guide roller frame 7 and a second guide roller frame 8 are used for guiding a film coming out of a first printing box 5, and the other surface of the film enters a second printing box 6 for printing, so that double-sided printing is completed at one time, and the processing efficiency is improved.

An installation frame 16 is fixedly installed on the side plate 2, a motor 17 is fixedly installed on the installation frame 16, two main air pipes 10 are symmetrically and fixedly installed on the side plate 2, and a hot air drying mechanism is arranged between the two main air pipes 10 and the motor 17.

As an embodiment of the present invention, referring to fig. 1 to 3, the hot air drying mechanism includes two fans 13 fixedly mounted on a side plate 2, two first belt pulleys 18 are fixedly mounted on an output shaft of a motor 17, second belt pulleys 19 are fixedly mounted on rotation shafts of the two fans 13, a transmission belt is respectively wound between the two first belt pulleys 18 and the two second belt pulleys 19, air guide pipes 14 are respectively communicated with side walls of the two fans 13, the two air guide pipes 14 are respectively communicated with two main air pipes 10, a plurality of secondary air pipes 11 are connected to the two main air pipes 10 at equal distances, a plurality of air blowing nozzles 12 are respectively mounted on a side wall of each secondary air pipe 11, and first heaters 15 are fixedly mounted in the two air guide pipes 14.

The hot air drying mechanism is used for blowing hot air to and from the outer wall of the film, so that the drying speed of the film is accelerated, and the production efficiency and quality are improved. The motor 17 drives two first belt pulleys 18 and rotates, two first belt pulleys 18 drive two second belt pulleys 19 through the drive belt and rotate, thereby drive two fans 13 and rotate, the outside air enters into main tuber pipe 10 through guide duct 14, enter into each secondary air pipe 11 respectively by main tuber pipe 10 again, blow on the film of upside and downside through blowing nozzle 12, because be equipped with first heater 15 in the guide duct 14, so the wind temperature that blowing nozzle 12 blew out can be than higher, accelerate air-dried speed, the efficiency and the quality of production have been improved.

Referring to fig. 2, an air inlet duct 20 is provided on each of the two fans 13, and a filter screen 21 is installed at a port of each of the two air inlet ducts 20.

The filter screen 21 is additionally arranged at the port of the air inlet pipe 20, so that dust and impurities can be prevented from entering an air duct, the air outlet cleanliness of the air blowing nozzle 12 is improved, the air drying quality is improved, and the production efficiency and quality are further improved.

The top wall of the top plate 3 is fixedly provided with a water tank 27, and the bottom wall of the top plate 3 is provided with an evaporation guide mechanism.

Referring to fig. 1, 2 and 4, the evaporation guide mechanism includes a reciprocating water delivery assembly, an evaporation pipe 25 and a second heater 34, four fixing frames 22 are fixedly installed on the bottom wall of the top plate 3, a plurality of connecting pipes 23 are installed between every two aligned fixing frames 22 in a rotating manner, the evaporation pipe 25 is connected between the two aligned connecting pipes 23 in a rotating manner, one ends of the connecting pipes 23 far away from the evaporation pipe 25 on the same side are connected with a main water pipe 24 in a rotating manner, a sealing bearing 26 is arranged at the connection position of each connecting pipe 23 and the main water pipe 24, a connecting hole 30 is formed in each main water pipe 24, two water return pipes 29 are connected to the side wall of the water tank 27, and two second heaters 34 are installed on the top wall of the water tank 27.

Utilize evaporation guiding mechanism to let in hot water in making a plurality of evaporating pipes 25 for film outer wall and a plurality of evaporating pipes 25 fully contact, accelerate the evaporation of moisture in the pigment, further improved production efficiency. Water in the water tank 27 is heated by the second heater 34 and then enters the main water pipe 24, the main water pipe 24 conveys hot water to each evaporation pipe 25, the evaporation pipes 25 and the main water pipe 24 are connected by the connecting pipes 23 and the sealing bearings 26, each evaporation pipe 25 can rotate, the film can rotate together with the evaporation pipes 25 when sliding on the evaporation pipes 25, evaporation of moisture in the pigment on the film is accelerated, and production efficiency and quality of the film are improved.

Referring to fig. 3 and 5, as an embodiment of the present invention, the reciprocating water delivery assembly includes a piston tube 31 fixedly inserted into the top of the water tank 27, the piston tube 31 is U-shaped, a piston rod 35 is movably inserted into one end of the piston tube 31 away from the water tank 27, two water outlet pipes 28 are symmetrically connected to the side wall of the piston tube 31, two fixing plates 37 are symmetrically and fixedly mounted to the side wall of the piston tube 31, a driving plate 36 is fixedly mounted to the bottom end of the piston rod 35, a return spring 38 is connected between the driving plate 36 and the two fixing plates 37, a cam 39 is fixedly mounted to the output shaft of the motor 17, and the cam 39 is in sliding contact with the driving plate 36.

The motor 17 drives the cam 39 to rotate, the cam 39 pushes the driving plate 36 back and forth when rotating, the driving plate 36 is pushed upwards to compress the two return springs 38, meanwhile, the piston rod 35 is pressed into the piston pipe 31, liquid in the piston pipe 31 is discharged from the two water outlet pipes 28, the two water outlet pipes 28 are connected with the connecting holes 30 on the two main water pipes 24 positioned on the same side, the two water return pipes 29 on the water tank 27 are connected with the connecting holes 30 on the two main water pipes 24 on the other side, when the cam 39 does not push the driving plate 36 upwards any more, the driving plate 36 moves downwards under the elastic force of the two return springs 38 to drive the driving plate 36 to move downwards, the piston rod 35 moves downwards to suck hot water in the piston pipe 31 in the water tank 27 to reciprocate, continuous circulation of the hot water is realized, the efficiency of evaporation drying is improved, and the production efficiency is further improved.

Referring to fig. 5, as an embodiment of the present invention, a first check valve 32 is disposed at one end of the piston tube 31 near the water tank 27, and a second check valve 33 is disposed at both of the water outlet tubes 28.

The first check valve 32 on the piston pipe 31 is used for ensuring that the hot water only flows into the piston pipe 31 from the water tank 27 and does not return, and the second check valve 33 on the water outlet pipe 28 ensures that the hot water only flows into the main water pipe 24 from the water outlet pipe 28 and does not return, so that the efficiency of evaporation drying is further improved, and the production efficiency is further improved.

The working principle is as follows: the first guide roller frame 7 and the second guide roller frame 8 are used for guiding the film coming out of the first printing box 5, the other surface of the film enters the second printing box 6 for printing, double-sided printing work is completed at one time, and processing efficiency is improved.

The motor 17 drives two first belt pulleys 18 and rotates, two first belt pulleys 18 drive two second belt pulleys 19 through the drive belt and rotate, thereby drive two fans 13 and rotate, the outside air enters into main tuber pipe 10 through guide duct 14, enter into each secondary air pipe 11 respectively by main tuber pipe 10 again, blow on the film of upside and downside through blowing nozzle 12, because be equipped with first heater 15 in the guide duct 14, so the wind temperature that blowing nozzle 12 blew out can be than higher, accelerate air-dried speed, the efficiency and the quality of production have been improved.

Water in the water tank 27 is heated by the second heater 34 and then enters the main water pipe 24, the main water pipe 24 conveys hot water to each evaporation pipe 25, the evaporation pipes 25 and the main water pipe 24 are connected by the connecting pipes 23 and the sealing bearings 26, each evaporation pipe 25 can rotate, the film can rotate together with the evaporation pipes 25 when sliding on the evaporation pipes 25, evaporation of moisture in the pigment on the film is accelerated, and production efficiency and quality of the film are improved.

The electric elements in the document are electrically connected with an external main controller and 220V mains supply through a transformer, the main controller can be a conventional known device controlled by a computer and the like, the product model provided by the invention is only used according to the structural characteristics of the product, the product can be adjusted and modified after being purchased, so that the product is more matched with and accords with the technical scheme of the invention, the product model is a technical scheme of the optimal application of the technical scheme, the product model can be replaced and modified according to the required technical parameters, and the product model is familiar to the technical personnel in the field, so that the technical scheme provided by the invention can clearly obtain the corresponding use effect.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a plastic film two-sided printing system, includes bottom plate (1), receives work or material rest (4), goes out work or material rest (9) and first printing box (5), its characterized in that: the hot air drying device is characterized in that a side plate (2) is fixedly mounted on the side wall of the bottom plate (1), a top plate (3) is fixedly mounted at the top of the side plate (2), two second guide roller frames (8) are symmetrically and fixedly mounted on the bottom plate (1), two first guide roller frames (7) are symmetrically and fixedly mounted on the bottom wall of the top plate (3), a second printing box (6) is fixedly mounted on the bottom wall of the top plate (3), the second printing box (6) is located between the two first guide roller frames (7), a mounting frame (16) is fixedly mounted on the side plate (2), a motor (17) is fixedly mounted on the mounting frame (16), two main air pipes (10) are symmetrically and fixedly mounted on the side plate (2), a hot air drying mechanism is arranged between the two main air pipes (10) and the motor (17), and a water tank (27) is fixedly mounted on the top wall of the top plate (3), and evaporation guide mechanisms are arranged on the bottom wall of the top plate (3).

2. A plastic film duplex printing system according to claim 1 wherein: the hot air drying mechanism comprises two fans (13) fixedly mounted on a side plate (2), two first belt discs (18) are fixedly mounted on an output shaft of a motor (17), two second belt discs (19) are fixedly mounted on a rotating shaft of each fan (13), a driving belt is respectively wound between each first belt disc (18) and each second belt disc (19), two air guide pipes (14) are respectively communicated with the side walls of the fans (13), the two air guide pipes (14) are respectively communicated with two main air pipes (10), two auxiliary air pipes (11) are connected to the main air pipes (10) at equal distances, each auxiliary air pipe (11) is provided with a plurality of air blowing nozzles (12) on the side wall, and two first heaters (15) are fixedly mounted in the air guide pipes (14).

3. A plastic film duplex printing system according to claim 2 wherein: two all be equipped with air-supply line (20) on fan (13), two the port of air-supply line (20) advances to install filter screen (21).

4. A plastic film duplex printing system according to claim 1 wherein: the evaporation guide mechanism comprises a reciprocating water delivery component, an evaporation pipe (25) and a second heater (34), four fixing frames (22) are fixedly arranged on the bottom wall of the top plate (3), a plurality of connecting pipes (23) are arranged between every two aligned fixing frames (22) in a rotating mode, an evaporation pipe (25) is connected between every two aligned connecting pipes (23) in a rotating mode, one ends, far away from the evaporation pipe (25), of the connecting pipes (23) on the same side are connected with a main water pipe (24) in a rotating mode, and the joint of each connecting pipe (23) and the main water pipe (24) is provided with a sealing bearing (26), each main water pipe (24) is provided with a connecting hole (30), two water return pipes (29) are connected to the side wall of the water tank (27), and two second heaters (34) are installed on the top wall of the water tank (27).

5. A plastic film duplex printing system according to claim 4 wherein: reciprocal water delivery subassembly is including fixed piston pipe (31) of alternate inserting at water tank (27) top, and piston pipe (31) are "U" shape, water tank (27) one end activity is kept away from in piston pipe (31) and piston rod (35) are inserted and are equipped with, symmetrical connection has two outlet pipes (28) on the lateral wall of piston pipe (31), symmetrical fixed mounting has two fixed plates (37) on piston pipe (31) lateral wall, the bottom fixed mounting of piston rod (35) has driving plate (36), all be connected with reset spring (38) between driving plate (36) and two fixed plates (37), fixed mounting has cam (39) on the output shaft of motor (17), and sliding contact between cam (39) and driving plate (36).

6. A plastic film duplex printing system according to claim 5 wherein: one end of the piston pipe (31) close to the water tank (27) is provided with a first one-way valve (32), and two water outlet pipes (28) are provided with second one-way valves (33).