One-pass double-sided digital printing device and method based on conduction band pair folding transmission

Abstract

This invention provides a onepass double-sided digital printing device and method based on a folded conveyor belt, relating to the field of digital printing technology. The onepass double-sided digital printing device includes a frame; a first conveyor belt printing platform fixedly installed on the upper part of the frame, with its conveyor belt surface arranged horizontally; a first onepass printhead assembly fixed on the frame and located above the first conveyor belt printing platform; a second conveyor belt printing platform fixedly installed on the upper part of the frame, with its conveyor belt surface perpendicular to the conveyor belt surface of the first conveyor belt printing platform; a second onepass printhead assembly fixed on the frame and located to the side of the second conveyor belt printing platform; a corner guide roller installed on the frame, located between the outlet end of the first conveyor belt printing platform and the inlet end of the second conveyor belt printing platform; and a small dryer installed on the frame and facing the roller surface of the corner guide roller. It features a compact structure, convenient operation, and is suitable for knitted fabrics, producing a pass-free print.

Description

Technical Field

[0001] This invention relates to the field of digital printing technology, specifically to a onepass double-sided digital printing device and method based on conveyor belt folding and transmission. Background Technology

[0002] Double-sided digital printing refers to a digital inkjet printing process that creates printed patterns on both the front and back of a fabric. Its purpose is to solve problems such as insufficient coloring, light color, and easy white showing on the reverse side of single-sided printed fabrics, ensuring that the visual effect on both sides of the fabric meets usage requirements. Double-sided printed fabrics have minimal color difference between the front and back sides, and the high pattern alignment accuracy makes them suitable for double-sided display scenarios such as scarves, flags, and lightbox fabrics, as well as clothing fabrics such as shirts and dresses that require color coordination between the inner and outer sides. Currently, the promotion of double-sided digital printing in the textile industry mainly relies on two types of equipment solutions. The first type is the upper and lower guide belt type double-sided digital printing machine. This equipment uses a structure with two parallel guide belts arranged on the upper and lower sides. The fabric first passes through the lower guide belt to complete printing on one side, then turns to enter the upper guide belt to print the other side. The two guide belt printing platforms are stacked vertically. This type of equipment is relatively tall, requiring operators to perform fabric threading, cleaning, and observation at different heights, making daily operation inconvenient. The second type is the beltless double-sided digital printing machine. This type of equipment eliminates the guide belt support and relies on the fabric's own tension to move between two sets of vertically arranged printheads, keeping the fabric suspended during printing. This type of equipment is suitable for woven fabrics with stable structure and uniform tension. However, for knitted fabrics, which are more elastic and have looser fibers, stretching deformation, curling, or shaking can easily occur when operating without a guide belt, causing the printheads to rub against the fabric or misalignment of the front and back patterns. Therefore, beltless equipment is difficult to promote in the field of knitted fabrics.

[0003] Both of the aforementioned existing technologies have limitations in application across different dimensions. For the folded double-sided printing path, where the fabric is first printed on the front side via a first printing platform, then rotated by a corner guide roller before being printed on the back side via a second printing platform, the core problem is that the dye is not yet dry after the front side printing. The printed front side of the fabric directly adheres to the guide belt surface of the second printing platform after the corner rotation. The damp dye is prone to transfer and discoloration during this contact, causing wear and tear on the front pattern. Simultaneously, the dye contaminates the surface of the second guide belt, requiring frequent machine stops for cleaning during continuous production. This problem is particularly pronounced on knitted fabrics because the loose fiber structure and short dye penetration path of knitted fabrics result in a shorter dye residence time on the fabric surface compared to woven fabrics, leading to a higher risk of discoloration. This makes the folded double-sided printing path difficult to apply to continuous double-sided printing of knitted fabrics for a long time. Summary of the Invention

[0004] Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a onepass double-sided digital printing device and method based on conveyor belt folding transmission, which solves the problems of traditional equipment occupying a large space and being unable to stably print knitted fabrics.

[0006] Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a onepass double-sided digital printing device based on conveyor belt folding transmission, comprising:

[0008] frame;

[0009] The first guide belt printing platform is fixedly installed on the upper part of the frame, and its guide belt surface is arranged in the horizontal direction;

[0010] The first onepass printhead assembly is fixed on the frame and located above the first guide belt printing platform;

[0011] The second guide belt printing platform is fixedly installed on the upper part of the frame, and its guide belt surface is perpendicular to the guide belt surface of the first guide belt printing platform.

[0012] The second onepass printhead assembly is fixed to the frame and located to the side of the second guide belt printing platform;

[0013] The corner guide roller is mounted on the frame and located between the exit end of the first guide belt printing platform and the inlet end of the second guide belt printing platform.

[0014] The small dryer is mounted on the frame and faces the roller surface of the corner guide roller.

[0015] Preferably, the exit end of the first guide belt printing platform and the inlet end of the second guide belt printing platform form a 90° angle, and the axis of the corner guide roller is located at the vertex of the angle.

[0016] Preferably, the printing width of the first onepass printhead group is equal to the width of the first guide tape printing platform, and the printing width of the second onepass printhead group is equal to the width of the second guide tape printing platform.

[0017] Preferably, the fabric feeding side of the corner guide roller is adjacent to the guide surface of the first guide belt printing platform, and the fabric output side of the corner guide roller is adjacent to the guide surface of the second guide belt printing platform.

[0018] A onepass double-sided digital printing method based on conveyor belt folding and transmission includes the following steps:

[0019] S1: The fabric is laid flat and fed into the first guide belt printing platform, and the first onepass print head group continuously prints the front side of the fabric.

[0020] S2: The fabric printed on the front side is turned by the corner guide roller, and the front side of the fabric is dried by the small dryer at the same time.

[0021] S3: The turned fabric is attached to the second guide belt printing platform, and the second onepass print head group continuously prints the back of the fabric;

[0022] S4: The fabric that has been printed on both sides is led out from the output end of the second guide belt printing platform.

[0023] Preferably, in S2, the wrap angle of the fabric on the corner guide roller is 90°, and the front side of the fabric contacts the drying airflow of the small dryer.

[0024] Preferably, the drying temperature of the small dryer is set to 60℃~120℃, and the moisture content of the dye surface on the front side of the fabric is reduced to below 15% after drying.

[0025] Preferably, the first guide belt printing platform and the second guide belt printing platform have the same linear speed, and both are driven by the same drive motor or a synchronously controlled motor.

[0026] Preferably, in S3, when printing on the back of the fabric, the printed front side of the fabric is in direct contact with the guide surface of the second guide belt printing platform.

[0027] Preferably, the first onepass printhead group and the second onepass printhead group are controlled independently, and the printed pattern is aligned on the front and back of the fabric.

[0028] Beneficial effects

[0029] This invention provides a onepass double-sided digital printing device and method based on a folded conveyor belt. It has the following advantages:

[0030] 1. This invention provides a onepass double-sided digital printing device and method based on guide belt folding transmission. In this device, the first guide belt printing platform and the second guide belt printing platform are arranged in the horizontal and vertical directions, respectively. Compared with the traditional upper and lower guide belt double-sided digital printing machine, the overall space occupied is smaller. The operator can complete the fabric feeding, cleaning and observation in the same position without switching between different heights.

[0031] 2. This invention provides a onepass double-sided digital printing device and method based on a folded conveyor belt. The device uses a first and second conveyor belt printing platform to provide full-process support for the fabric. The knitted fabric remains flat throughout the printing process, preventing stretching, deformation, or curling due to elasticity, thus solving the problem of unstable printing of knitted fabrics by non-convenience double-sided digital printing machines. A small dryer is placed at the corner between the first and second conveyor belt printing platforms. When the fabric passes the corner guide roller, its front side faces outwards and receives the drying airflow, completing surface pre-drying within a limited turning stroke. When the pre-dried fabric's front side contacts the guide belt surface of the second conveyor belt printing platform, dye transfer and fading are effectively controlled. The surface of the second guide belt is less prone to dye contamination, eliminating the need for frequent machine stops for cleaning due to undried dye on the front side. This allows the folded double-sided onepass printing path to be suitable for continuous production of knitted fabrics. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the present invention;

[0033] Figure 2 This is a schematic diagram of the method flow of the present invention.

[0034] The components include: 1. Small dryer; 2. Corner guide roller; 3. First onepass printing structure; 4. Second onepass printing structure; 5. First guide belt printing platform; 6. Second guide belt printing platform; and 7. Frame. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, a onepass double-sided digital printing device based on guide belt folding transmission includes a frame 7, a first guide belt printing platform 5, a first onepass print head group 3, a second guide belt printing platform 6, a second onepass print head group 4, a corner guide roller 2, and a small dryer 1.

[0038] The frame 7 adopts a welded steel structure, with adjustable anchor bolts at the bottom. The first guide belt printing platform 5 is fixedly installed on the upper part of the frame 7 near the fabric feeding direction, with its guide belt surface arranged horizontally. The first guide belt printing platform 5 is internally equipped with a drive roller, a driven roller, and a guide belt tension adjustment mechanism. The guide belt surface is coated with a low-tack pressure-sensitive adhesive layer to adhere the fabric and prevent deviation. The first onepass printhead assembly 3 is fixed to the frame 7 by a crossbeam and is located directly above the first guide belt printing platform 5. The first onepass printhead assembly 3 consists of multiple printheads arranged in a line along the fabric width direction, with the splicing accuracy between the printheads controlled within ±0.02mm.

[0039] The second guide belt printing platform 6 is fixedly installed on the upper part of the frame 7 near the end facing the fabric output direction, and its guide belt surface is perpendicular to the guide belt surface of the first guide belt printing platform 5. Specifically, in the above embodiment, the angle between the guide belt surface of the second guide belt printing platform 6 and the horizontal plane is adjustable between 75° and 90°. By tilting the second guide belt printing platform 6 instead of making it completely vertical, the tendency of the fabric to sag due to gravity can be reduced, while maintaining a 90° angle with the first guide belt printing platform 5. The internal structure of the second guide belt printing platform 6 is similar, but its guide belt surface uses a rubber layer with a high coefficient of friction. Because the dye has been pre-dried when the fabric is attached to the guide belt surface, strong adhesion is not required to maintain stable operation.

[0040] The second onepass printhead assembly 4 is fixed to the frame 7 by another crossbeam and is located to the side of the second guide belt printing platform 6. The nozzle arrangement direction of the second onepass printhead assembly 4 is consistent with the width direction of the second guide belt printing platform 6.

[0041] The corner guide roller 2 is mounted on the frame 7, located between the outlet end of the first guide belt printing platform 5 and the inlet end of the second guide belt printing platform 6. The corner guide roller 2 is a hollow stainless steel roller with a diameter between 50mm and 80mm. The roller surface is mirror-polished to reduce friction against damp dye. The fabric infeed side of the corner guide roller 2 is adjacent to the guide belt surface of the first guide belt printing platform 5, and the fabric outlet side is adjacent to the guide belt surface of the second guide belt printing platform 6. The wrap angle of the fabric on the roller surface is 90°.

[0042] The small dryer 1 is mounted on the frame 7 and faces the roller surface of the corner guide roller 2. The small dryer 1 is an infrared radiation heater or hot air nozzle, and its heating power is adjustable between 500W and 1500W. It should be noted that the installation position of the small dryer 1 is not aligned with the entire roller surface, but rather with the arc segment of the fabric from the entry point to the exit point of the corner guide roller 2. This arrangement ensures that the drying airflow or radiant heat is concentrated on the front side of the fabric and does not directly irradiate the unprinted fabric area that has not yet entered the corner. After testing, applying hot air at 60℃ to 100℃ on this arc segment for a residence time of 0.5 to 1.2 seconds can reduce the surface moisture content of the dye on the front side of the fabric from 40% to 60% immediately after printing to below 20%. At this point, the dye no longer has fluidity, does not stain when touched, but still maintains a certain degree of moisture for subsequent color fixing.

[0043] The working process of the above device is as follows: The fabric enters the first guide belt printing platform 5 from the feed direction. The guide belt of the first guide belt printing platform 5 drives the fabric forward at a uniform speed, with the linear speed controlled between 5 and 20 m / min. The first onepass printhead group 3 continuously prints on the front side of the fabric. Because the onepass method is used, the printhead group is fixed, and the entire front pattern can be completed in one pass of the fabric, without producing scanning splicing marks.

[0044] After front-side printing is complete, the fabric, still damp, enters the corner guide roller 2. The fabric rotates 90° along the roller surface of the corner guide roller 2, with the front side facing outwards. The small dryer 1 pre-dries the front side of the fabric. The dried fabric enters the second guide belt printing platform 6 from the exit side of the corner guide roller 2. The front side of the fabric adheres to the guide belt surface of the second guide belt printing platform 6 and advances at the same linear speed. The second onepass printhead group 4 continuously prints on the back side of the fabric. The fabric with double-sided printing completed is led out from the output end of the second guide belt printing platform 6.

[0045] Example 2

[0046] The difference between this embodiment and Embodiment 1 lies in the arrangement and control strategy of the small dryer 1. The small dryer 1 employs two symmetrically arranged hot air nozzles, facing opposite sides of the roller surface of the corner guide roller 2. The air supply temperature of the two nozzles is independently controlled, with one nozzle set to 80°C and the other to 60°C. This is because, during the fabric's movement on the corner guide roller 2, the contact time between the front and different areas with the hot air varies slightly; using dual nozzles with unequal temperatures avoids localized overheating that could lead to dye migration.

[0047] Specifically, in the above embodiment, an infrared temperature sensor is added, mounted on the frame 7 and pointing towards the fabric face on the exit side of the corner guide roller 2. The temperature sensor detects the fabric surface temperature in real time, and automatically reduces the power of the small dryer 1 or increases the guide belt speed when the temperature exceeds 80°C. Through closed-loop control, the fabric face temperature can be stabilized within the range of 65°C to 75°C. This temperature range neither damages the dye development nor hinders the reduction of surface moisture content.

[0048] It is important to note that the pre-drying parameters need to be adjusted for different fabric materials. The table below lists recommended parameters for three typical fabrics:

[0049]

[0050] The above parameters were measured at a guide belt linear speed of 10 m / min. If the linear speed is increased, the drying temperature should be increased accordingly or the diameter of the corner guide roller 2 should be increased to extend the drying path.

[0051] Example 3

[0052] like Figure 2 As shown, this embodiment relates to a double-sided digital printing method based on the above-described device, comprising the following steps:

[0053] S1: The fabric is laid flat and fed into the first guide belt printing platform 5, and the first onepass print head group 3 continuously prints the front side of the fabric.

[0054] S2: The fabric printed on the front side is turned by the corner guide roller 2, and the front side of the fabric is dried by the small dryer 1.

[0055] S3: The turned fabric is attached to the second guide belt printing platform 6, and the second onepass print head group 4 continuously prints the back of the fabric.

[0056] S4: The fabric that has been printed on both sides is led out from the output end of the second guide belt printing platform 6.

[0057] In the above steps, special attention needs to be paid to the connection between steps S2 and S3. If the drying intensity of the small dryer 1 is insufficient and the front side of the fabric is still damp, it will fade when attached to the second guide belt printing platform 6. If the drying is overdryed, the solvent in the dye will evaporate too quickly, causing the dye to solidify prematurely on the fiber surface, affecting the subsequent color fastness. Therefore, controlling the surface moisture content after drying is crucial. After multiple experiments, for reactive dye inks, controlling the moisture content of the front side of the fabric between 15% and 20% after drying can both prevent fading and ensure the subsequent color fastness; for disperse dye inks, the moisture content should be controlled between 10% and 15%.

[0058] Specifically, in the above-described embodiment, in step S2, the wrap angle of the fabric on the corner guide roller 2 is 90°, with the fabric face outwards contacting the drying airflow of the small dryer 1. If the fabric face is inwards (i.e., towards the roller surface), the roller surface will be contaminated with dye, and the drying efficiency will be significantly reduced. Therefore, this device must ensure that the fabric face is outwards when feeding the fabric, a point clearly stated in the operating specifications.

[0059] Example 4

[0060] The difference between this embodiment and Embodiment 3 is that the linear speeds of the first guide belt printing platform 5 and the second guide belt printing platform 6 are controlled asynchronously. In certain application scenarios, such as when the fabric has different patterns on the front and back sides and alignment is required, the speed ratio of the two platforms is not 1:1. Specifically, in the above embodiment, two independent servo motors are installed on the frame 7, driving the first guide belt printing platform 5 and the second guide belt printing platform 6 respectively. The operating speeds of the two motors are linked by an electronic gear ratio. When front-side alignment is required, the linear speed of the first guide belt printing platform 5 is slightly higher than that of the second guide belt printing platform 6, causing a slight relaxation of the fabric at the corner guide roller 2, avoiding stretching deformation. Experimental verification shows that when the speed difference is controlled within 2%, fabric accumulation will not occur.

[0061] It is important to note that the diameter of the corner guide roller 2 directly affects the tolerance for speed difference. A larger diameter results in a longer wrap angle arc of the fabric on the roller surface, and a wider allowable speed difference range. In this embodiment, the diameter of the corner guide roller 2 is 100mm, and the allowable speed difference range is ±3%. When the speed difference exceeds this range, the fabric will slip or wrinkle on the roller surface. Therefore, in the actual control system, it is necessary to monitor the actual linear speed of the two guide belt platforms in real time and maintain the speed difference within the allowable range through PID control.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A one pass double-sided digital printing device based on a carrier sheet folding transmission, characterized in that, include: Rack (7); The first guide belt printing platform (5) is fixedly installed on the upper part of the frame (7), and its guide belt surface is arranged in the horizontal direction; The first onepass printhead assembly (3) is fixed on the frame (7) and located above the first guide belt printing platform (5); The second guide belt printing platform (6) is fixedly installed on the upper part of the frame (7), and its guide belt surface is perpendicular to the guide belt surface of the first guide belt printing platform (5). The second onepass printhead assembly (4) is fixed on the frame (7) and located to the side of the second guide belt printing platform (6); An angle guide roller (2) is mounted on the frame (7) and located between the outlet end of the first guide belt printing platform (5) and the inlet end of the second guide belt printing platform (6). The small dryer (1) is mounted on the frame (7) and faces the roller surface of the corner guide roller (2).

2. The one pass double-sided digital printing device based on the catenary pair fold transmission according to claim 1, characterized in that: The exit end of the first guide belt printing platform (5) and the inlet end of the second guide belt printing platform (6) form a 90° angle, and the axis of the corner guide roller (2) is located at the apex of the angle.

3. The one pass double-sided digital printing device based on the folded conduction band pair according to claim 1, characterized in that: The printing width of the first onepass printhead group (3) is equal to the width of the first guide tape printing platform (5), and the printing width of the second onepass printhead group (4) is equal to the width of the second guide tape printing platform (6).

4. The one pass double-sided digital printing device based on the catenary pair fold transmission according to claim 1, characterized in that: The feed side of the corner guide roller (2) is adjacent to the guide surface of the first guide belt printing platform (5), and the output side of the corner guide roller (2) is adjacent to the guide surface of the second guide belt printing platform (6).

5. A onepass double-sided digital printing method based on conveyor belt folding and transmission, employing the apparatus described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: The fabric is laid flat and fed into the first guide belt printing platform (5), and the first onepass print head group (3) continuously prints the front side of the fabric. S2: The fabric printed on the front side is turned by the corner guide roller (2), and the front side of the fabric is dried by the small dryer (1). S3: The turned fabric is attached to the second guide belt printing platform (6), and the back of the fabric is continuously printed by the second onepass print head group (4); S4: The fabric that has been printed on both sides is led out from the output end of the second guide belt printing platform (6).

6. The onepass double-sided digital printing method based on conveyor belt folding transmission according to claim 5, characterized in that: In S2, the fabric wraps around the corner guide roller (2) at an angle of 90°, and the fabric face outwards contacts the drying airflow of the small dryer (1).

7. The onepass double-sided digital printing method based on conveyor belt folding transmission according to claim 5, characterized in that: The drying temperature of the small dryer (1) is set to 60℃~120℃, and the moisture content of the dye surface on the front of the fabric drops to below 15% after drying.

8. The onepass double-sided digital printing method based on conveyor belt folding transmission according to claim 5, characterized in that: The first guide belt printing platform (5) and the second guide belt printing platform (6) have the same linear speed, and both are driven by the same drive motor or a synchronously controlled motor.

9. The onepass double-sided digital printing method based on conveyor belt folding transmission according to claim 5, characterized in that: In S3, when printing on the back of the fabric, the front of the fabric that has been printed is in direct contact with the guide surface of the second guide printing platform (6).

10. The onepass double-sided digital printing method based on conveyor belt folding transmission according to claim 5, characterized in that: The first onepass printhead group (3) and the second onepass printhead group (4) are controlled independently, and the printed pattern is aligned on the front and back of the fabric.

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