Double-sided printing equipment and method for improving alignment precision of front and back patterns in double-sided printing

Abstract

The invention provides a double-sided printing device and a double-sided printing front and back pattern alignment precision improving method, and solves the problem that the front and back pattern alignment precision of a product printed by the printing device is insufficient. The device comprises a feeding roller, an auxiliary vehicle cloth conveying roller, a first printing assembly, a cloth guide roller, a main vehicle cloth conveying roller, a second printing assembly and a discharging roller; the first printing assembly comprises a first printing platform, the second printing assembly comprises a second printing platform, the first printing platform and the second printing platform are obliquely arranged, and the second printing platform is located below the first printing platform; the cloth guide roller is located below the first printing platform, the top end of the main vehicle cloth conveying roller is not lower than the bottom end of the cloth guide roller, and a printing medium printed by the first printing platform can be sequentially wound from the lower surface of the cloth guide roller and the upper surface of the main vehicle cloth conveying roller and conveyed to the second printing platform for printing of the other side. The equipment and the method can reduce errors caused by extension of the cloth cover, so that the alignment precision of double-sided patterns is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of printing devices, and in particular, to a double-sided printing device and a method for improving the alignment accuracy of front and back patterns in double-sided printing. Background Art

[0002] In general, double-sided printing currently uses two printing components to print on both sides of a printing medium respectively. When printing in an existing double-sided printing system, one method is to use two printing platforms with printing nozzles to print on both sides of the printing medium simultaneously; another method is to first use a group of printing nozzles to complete printing on one side and then use another group of printing nozzles to print on the other side. The double-sided printing device can achieve printing on both the front and back sides of a spray-painted cloth. When the front and back printed patterns are accurately aligned, the visual effect of advertising display can be significantly improved; conversely, if the alignment accuracy is insufficient, the quality of advertising display will be seriously affected.

[0003] In the double-sided printing device in the prior art, a plurality of cloth winding rollers are arranged between two printing platforms. After the spray-painted cloth is printed on the first printing platform, it enters the second printing platform for printing through methods such as cloth winding.

[0004] The applicant of the present invention has found that the prior art has at least the following technical problems: In the double-sided printing device in the prior art, due to the influence of various factors, the alignment accuracy of the front and back printed patterns is insufficient, and how to improve the alignment accuracy of the front and back patterns in double-sided printing has always been a technical problem difficult to solve. Among them, in the double-sided printing device in the prior art, the distance between the two printing platforms is too long, which causes serious deformation of the spray-painted cloth surface due to the force on the cloth surface, and the elongation of the cloth surface is too large, seriously affecting the alignment accuracy of the front and back patterns. Summary of the Invention

[0005] The purpose of the present invention is to provide a double-sided printing device and a method for improving the alignment accuracy of front and back patterns in double-sided printing, so as to solve the technical problem of insufficient alignment accuracy of the front and back patterns of the products printed by the double-sided printing device in the prior art. The many technical effects that can be produced by the preferred technical solutions provided by the present invention are described in detail below.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: The double-sided printing device provided by the present invention includes a feeding roller, a secondary vehicle cloth running roller, a first printing component, a cloth guiding roller, a main vehicle cloth running roller, a second printing component, and a discharging roller arranged in sequence along the conveying direction of the printing medium, wherein: At least one of the feeding roller, the auxiliary vehicle fabric guiding roller, the fabric guiding roller, the main vehicle fabric guiding roller, and the discharging roller is a driving roller; the first printing assembly includes a first printing platform, the second printing assembly includes a second printing platform, the first printing platform and the second printing platform are both inclined, and the second printing platform is located below the first printing platform; The fabric guiding roller is located below the first printing platform, the top end of the main vehicle fabric guiding roller is not lower than the bottom end of the fabric guiding roller, and the printed medium printed by the first printing platform can sequentially wind around the lower surface of the fabric guiding roller and the upper surface of the main vehicle fabric guiding roller and be conveyed to the second printing platform for printing on the other side.

[0007] Preferably, the first printing platform extends downward from top to bottom in a direction away from the second printing platform, and the printed medium passing around the auxiliary vehicle fabric guiding roller, the first printing platform, and the fabric guiding roller is in a flat shape; The second printing platform extends downward from top to bottom in a direction away from the first printing platform, and the fabric feeding end of the second printing platform is lower than the main vehicle fabric guiding roller.

[0008] Preferably, the double-sided printing device further includes a frame, a working reel, and a driving device, wherein: The working reel is rotatably connected to the frame, the fabric roll is located on the working reel, and the driving device is in transmission connection with the reel and is used to generate a reverse braking torque so that the fabric surface tension of the fabric roll is at a set value.

[0009] Preferably, the double-sided printing device further includes a roll diameter measuring sensor and a control unit, wherein: The roll diameter measuring sensor is used to measure the roll diameter of the fabric roll in real time; The control unit is electrically connected to both the roll diameter measuring sensor and the driving device and is used to adjust the reverse braking torque of the driving device in real time according to the roll diameter of the fabric roll so as to maintain the constancy of the fabric surface tension.

[0010] Preferably, the last roller body of the feeding roller is a first spiral width expanding roller, and the first spiral width expanding roller is used to expand the fabric surface and then convey it to the auxiliary vehicle fabric guiding roller; The fabric guiding roller is a second spiral width expanding roller, and the second spiral width expanding roller is used to expand the fabric surface and then convey it to the main vehicle fabric guiding roller.

[0011] Preferably, the double-sided printing device further includes a loading device, a transverse movement driving device, and a sewing device. The loading device includes a telescopic driving device, a mounting bracket, and a waiting material reel, wherein: The transverse movement driving device is drivingly connected to the sewing device and is used to drive the sewing device to reciprocate axially along the feeding reel. The telescopic driving device is drivingly connected to the mounting bracket and is used to drive the mounting bracket to move vertically up and down. The mounting bracket is slidably connected to the machine frame. The feeding reel is rotatably connected to the mounting bracket. When the telescopic driving device drives the mounting bracket to rise to the side of the working reel, the sewing device is used to sew the end of the fabric on the working reel and the end of the fabric on the feeding reel.

[0012] Preferably, the double-sided printing device further includes a locking telescopic cylinder. A pin hole is provided on the mounting bracket, and the pin hole is a long strip-shaped hole extending in the vertical direction. The telescopic end of the locking telescopic cylinder is provided with a pin portion, and the pin portion can be inserted into the pin hole to lock the mounting bracket.

[0013] The present invention also provides a method for improving the alignment accuracy of the front and back patterns in double-sided printing. Using the above double-sided printing device, the method includes: Winding the printing medium around the feeding roller and the auxiliary vehicle fabric feeding roller, and transmitting the printing medium to the first printing platform to print the first side. Making the printing medium printed by the first printing platform sequentially wind around the lower surface of the fabric guiding roller and the upper surface of the main vehicle fabric feeding roller, and conveying the printing medium to the second printing platform for printing the other side. By shortening the length of the printing medium between the first printing platform and the second printing platform, reducing the cumulative error caused by the elongation of the printing medium, so as to improve the alignment accuracy of the front and back patterns.

[0014] Preferably, the double-sided printing device further includes a machine frame, a working reel and a driving device. The working reel is rotatably connected to the machine frame. The fabric roll is located on the working reel. The driving device is drivingly connected to the reel and is used to generate a reverse braking torque. The method further includes: Real-time measuring the diameter of the fabric roll on the working reel, and adjusting the magnitude of the reverse braking torque of the driving device according to the diameter of the fabric roll, so as to maintain the fabric tension at a set value.

[0015] Preferably, the method further includes: Before the printing medium enters the first printing platform, using a first spiral spreading roller to perform spreading and widening processing on the printing medium to balance the tension distribution in the width direction of the printing medium. Before the printing medium enters the second printing platform, using a second spiral spreading roller to perform spreading and widening processing on the printing medium to balance the tension distribution in the width direction of the printing medium.

[0016] The double-sided printing device and the method for improving the alignment accuracy of the front and back patterns in double-sided printing provided by the present invention have the following beneficial effects compared with the prior art: The first printing platform and the second printing platform are both inclined, and the second printing platform is located below the first printing platform, which can shorten the cloth length between the two printing platforms as much as possible. The cloth guiding roller is located below the first printing platform, and the top end of the main vehicle cloth running roller is not lower than the bottom end of the cloth guiding roller. The printing medium completed by printing on the first printing platform is wound around the lower surface of the cloth guiding roller and the upper surface of the main vehicle cloth running roller in sequence. This cloth winding method can also effectively shorten the path length of the cloth surface from the reverse printing station to the front printing station. The shorter the cloth surface transmission distance between the two printing stations, the easier it is to control the elongation under the action of tension. By shortening the transmission path, the cumulative error caused by the elongation of the cloth surface can be significantly reduced, thereby improving the alignment accuracy of the double-sided patterns. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 is a schematic diagram of the internal structure of the double-sided printing device; Figure 2 is a schematic diagram of the cloth winding structure; Figure 3 is a schematic diagram of the transmission structure of the working reel and the driving device; Figure 4 is a schematic diagram of the force condition of the cloth; Figure 5 is a schematic diagram of the cloth surface wrinkling condition; Figure 6 is a schematic diagram of the first spiral width-expanding roller or the second spiral width-expanding roller; Figure 7 is a schematic diagram of the force on the cloth surface on the first spiral width-expanding roller or the second spiral width-expanding roller; Figure 8 is a three-dimensional structure schematic diagram of the double-sided printing device; Figure 9 is a schematic diagram of the structure corresponding to the cloth running roller driving device; Figure 10 is a schematic diagram of the structure at the sewing device; Figure 11 is a schematic diagram of the structure of the feeding device; Figure 12 is a partial enlarged schematic diagram at the feeding device.

[0019] In the figure: 100, cloth; 1, cloth roll; 2, first over-roller; 4, second over-roller; 5, first spiral fabric expanding roller; 6, auxiliary vehicle fabric guiding roller; 7, second spiral fabric expanding roller; 8, main vehicle fabric guiding roller; 9, third over-roller; 10, fourth over-roller; 11, fifth over-roller; 12, sixth over-roller; 13, fabric outlet roller; 14, cloth pressing roller; 15, color developing box; 16, first printing carriage; 17, first printing platform; 18, second printing carriage; 19, second printing platform; 20, sewing device; 21, loading device; 211, telescopic driving device; 212, mounting bracket; 213, material waiting reel; 214, slide rail; 215, locking telescopic cylinder; 216, pin hole; 22, AC servo motor; 23, linear guide rail; 24, fabric surface drying device; 25, driving gear; 26, idler wheel; 27, transmission gear; 28, sensor bracket; 29, roll diameter measuring sensor; 30, first cross beam; 31, first linear guide rail; 32, second cross beam; 33, second linear guide rail. Detailed implementation manners

[0020] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope protected by the present invention.

[0021] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "length", "width", "height", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "side", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present invention. In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0022] The embodiment of the present invention provides a double-sided printing device and a method for improving the alignment accuracy of front and back patterns in double-sided printing. By means of the winding method of the cloth, adjusting the reverse braking torque of the driving device, and using the spiral fabric expanding roller, the alignment accuracy of the double-sided patterns is improved.

[0023] The following combines Figures 1 - 12 to elaborate on the technical solutions provided by the present invention in more detail.

[0024] Embodiment 1: Refer to Figure 1 andFigure 2 As shown in the figure, the double-sided printing device provided by the present invention includes a feeding roller, a secondary carriage fabric feeding roller 6, a first printing assembly, a fabric guiding roller (first spiral fabric expanding roller 5), a main carriage fabric feeding roller 8, a second printing assembly, and a discharging roller, which are arranged in sequence along the printing medium conveying direction. Among them: at least one of the feeding roller, the secondary carriage fabric feeding roller 6, the fabric guiding roller (first spiral fabric expanding roller 5), the main carriage fabric feeding roller 8, and the discharging roller is a driving roller, and the driving roller provides forward conveying power for the printing medium; the first printing assembly includes a first printing platform 17, the second printing assembly includes a second printing platform 19, both the first printing platform 17 and the second printing platform 19 are inclined, and the second printing platform 19 is located below the first printing platform 17; the fabric guiding roller (first spiral fabric expanding roller 5) is located below the first printing platform 17, the top end of the main carriage fabric feeding roller 8 is not lower than the bottom end of the fabric guiding roller (first spiral fabric expanding roller 5), and the printed medium completed by the first printing platform 17 can sequentially wind around the lower surface of the fabric guiding roller and the upper surface of the main carriage fabric feeding roller 8, and be conveyed to the second printing platform 19 for printing on the other side.

[0025] The printing medium is described by taking cloth as an example. Refer to Figure 1 and Figure 2 As shown in the figure, the first printing assembly further includes a first printing carriage 16, a first cross beam 30, and a first linear guide rail 31. The first linear guide rail 31 is arranged on the first cross beam 30, and the first printing carriage 16 is slidably connected to the first linear guide rail 31 for spraying the printing medium on the first printing platform 17; the second printing assembly further includes a second printing carriage 18, a second cross beam 32, and a second linear guide rail 33. The second linear guide rail 33 is arranged on the second cross beam 32, and the second printing carriage 18 is slidably connected to the second linear guide rail 33 for spraying the printing medium on the second printing platform 19.

[0026] The spraying cloth roll 1 is wound around the working reel. The feeding roller includes a first idler roller 2 and a second idler roller 4. The discharging roller includes a fifth idler roller 11, a sixth idler roller 12, a cloth discharging roller 13, and a cloth pressing roller 14. The discharging end of the second printing platform 19 is sequentially connected to a third idler roller 9, a color developing box 15, a fourth idler roller 10, a fifth idler roller 11, a sixth idler roller 12, a cloth discharging roller 13, and a cloth pressing roller 14. The raw material of the cloth roll 1 is reversed by the first idler roller 2 and the second idler roller 4, passes through the secondary carriage fabric feeding roller 6 to reach the first printing platform 17, and the first printing carriage 16 prints on the reverse side of the raw material of the cloth roll 1. Subsequently, it passes through the fabric guiding roller and the main carriage fabric feeding roller 8 to reverse the raw material of the cloth roll 1 and reach the second printing platform 19, and the second printing carriage 18 prints on the front side of the raw material of the cloth roll 1. The second printing carriage 18, the second printing platform 19, and the first printing carriage 16, the first printing platform 17 are respectively located on different sides of the raw material of the cloth roll 1. Both the cloth pressing roller 14 and the cloth discharging roller 13 are made of rubber material. The cloth discharging roller is driven by an AC servo motor through a reducer to ensure stable output of the cloth and guarantee the quality of the printed product.

[0027] The printing of the reverse pattern on the fabric surface is completed on the first printing platform 17. Considering that the ink printed on the reverse side of the fabric has not dried yet, in order to prevent the pattern on the fabric from being damaged due to the contact between the fabric and the roller during subsequent transmission, a fabric drying device 24 is specially configured between the fabric guiding roller (the first spiral expanding roller 5) and the main vehicle fabric guiding roller 8. This device can pre-dry the printed pattern on the reverse side of the fabric, effectively preventing the ink from contaminating the roller and avoiding the decline in the pattern quality caused by secondary pollution.

[0028] After double-sided printing is completed, it enters the color developing box 15 for color development. The temperature in the color developing box 15 is generally controlled between 160 - 180 °C. After color development is completed, the fabric is discharged through the sixth guide roller 12, the fabric discharging roller 13 and the fabric pressing roller 14, completing the entire printing process.

[0029] In this embodiment, as shown in Figure 9 Both the second printing carriage 18 and the first printing carriage 16 are driven by independent AC servo motors 22. The advantage of this structure is that it can perform double-sided printing or single-sided printing. The operations of the two printing carriages are independent of each other, solving the problem that only double-sided printing can be performed in existing equipment. At the same time, due to the use of independent servo motors, the problem of affecting the printing accuracy due to the addition of synchronous belts and belt pulleys in the mechanical structure is avoided.

[0030] As an alternative implementation, as shown in Figure 1 and Figure 2 In this embodiment, the first printing platform 17 extends downward from top to bottom in a direction away from the second printing platform 19, and the printing medium bypassing the auxiliary vehicle fabric guiding roller 6, the first printing platform 17, and the fabric guiding roller is in a straight state; the second printing platform 19 extends downward from top to bottom in a direction away from the first printing platform 17, and the fabric feeding end of the second printing platform 19 is lower than the main vehicle fabric guiding roller 8.

[0031] The above-mentioned setting structures of the first printing platform 17 and the second printing platform 19 can minimize the fabric length between the two printing platforms as much as possible and prevent interference between the first printing platform 17, the second printing platform 19, the fabric guiding roller (the first spiral expanding roller 5), and the main vehicle fabric guiding roller.

[0032] The purpose of the above-mentioned setting methods of the first printing platform 17, the second printing platform 19, the auxiliary vehicle fabric guiding roller 6, and the fabric guiding roller is to shorten the fabric length between the two printing platforms as much as possible.

[0033] The principle of improving the double-sided pattern alignment accuracy through the above structure in this embodiment is as follows: According to the formula for the tensile deformation of materials (a deformation of Hooke's law):

[0034] In the formula: --The stretch of the fabric between the two printing platforms ( ); --The tension of the fabric when printing ( ); --The length of the cloth between two dozen platforms ( ); -- Cross-sectional area of printing cloth ( ); --Elastic modulus of printing cloth ( ).

[0035] According to the relevant formula, in a double-sided printing device, the elongation of the advertising cloth between the two printing stations (the first printing platform 17 and the second printing platform 19) is: Fabric tension , proportional to the distance between workstations , which is inversely proportional to the fabric's cross-sectional area (A) and elastic modulus. Excessive fabric stretch can severely affect the alignment accuracy of the patterns on both sides. Therefore, the key to minimizing fabric stretch between workstations lies in precisely controlling fabric tension fluctuations and minimizing the fabric length between workstations.

[0036] In the duplex printing system, only the guide roller (second spiral expansion roller 7) and the main carriage cloth roller 8 are positioned between the first and second printing carriages 16 and 18. Both the first and second printing platforms 17 and 19 are tilted, with the second printing platform 19 positioned below the second printing platform 19. This minimizes the fabric length between the two printing platforms. The guide roller is positioned below the first printing platform 17, and the top of the main carriage cloth roller 8 is no lower than its bottom. Printed media from the first printing platform 17 is wound sequentially from the bottom surface of the guide roller to the top surface of the main carriage cloth roller 8. This fabric winding method also effectively shortens the fabric transport path from the reverse printing station to the front printing station. According to the formula described above, the shorter the fabric transport distance between the two printing stations, the easier it is to control its elongation under tension. This shortened transport path significantly reduces the cumulative error caused by fabric elongation, thus ensuring high-precision alignment of double-sided patterns.

[0037] The above structure shortens the fabric length between the first printing platform 17 and the second printing platform 19 as much as possible from the structural layout of the double-sided printing device, thereby improving the alignment accuracy of the front and back patterns in double-sided printing.

[0038] Example 2: In the prior art, the advertising fabric will undergo elongation deformation under the action of tension. During the operation of the equipment, if the tension fluctuates violently, the tensile deformation amount of the fabric will also change accordingly. Therefore, to ensure the accurate alignment of the front and back images on the double-sided printing equipment, the primary task is to effectively control the tension fluctuation during the operation of the equipment. During the printing process, the fabric tension needs to be maintained within a reasonable range. When the tension is too large, the fabric will be over-stretched and deformed, making it difficult to achieve the expected printing effect; when the tension is too small, the fabric will wrinkle, preventing the printing work from proceeding normally.

[0039] To address the above problems, in this embodiment, the alignment accuracy of the front and back patterns in double-sided printing is improved from a second aspect: Refer to Figures 1 - 3 As shown, the double-sided printing equipment in this embodiment further includes a frame, a working reel, and a driving device, where: the working reel is rotatably connected to the frame, the fabric roll 1 is located on the working reel, and the driving device is in transmission connection with the reel and is used to generate a reverse braking torque, so that the fabric tension of the fabric roll 1 is at a set value.

[0040] Refer to Figure 2 As shown, the driving device can be an AC servo motor, and a driving gear 25 is fixed to the output end of the driving device. As Figure 3 shown, the driving gear 25 meshes with a idler wheel 26, the idler wheel 26 meshes with a transmission gear 27, and the transmission gear 27 is fixedly connected to the working reel (which can be an air shaft). The driving gear 25 drives the working reel to rotate through the meshing of the idler wheel 26 and the transmission gear 27. Refer to Figure 2 As shown, the driving of the driving device provides a reverse braking torque for the fabric roll 1, so that the fabric tension F (as in the direction of the arrow in Figure 2 ) is at a constant set value.

[0041] To solve the above problems, by setting the driving device (AC servo motor) to work in torque mode, a reverse braking torque is generated on the fabric roll 1, thereby imparting an appropriate tension F to the fabric. Refer to Figure 2 As shown, the reverse braking torque is opposite to the conveying direction of the fabric 100.

[0042] As an optional implementation manner, the double-sided printing equipment further includes a roll diameter measurement sensor 29 and a control unit, where: the roll diameter measurement sensor 29 is used to measure the roll diameter of the fabric roll 1 in real time; the control unit is electrically connected to both the roll diameter measurement sensor 29 and the driving device, and is used to adjust the reverse braking torque of the driving device in real time according to the roll diameter of the fabric roll 1, so as to maintain the fabric tension constant.

[0043] Specifically, refer to Figure 2 and Figure 3As shown in the figure, the roll diameter measurement sensor 29 can be an ultrasonic sensor in the prior art, and the roll diameter measurement sensor 29 is fixed by a sensor bracket 28. The ultrasonic sensor is used to monitor the roll diameter of the fabric roll 1 in real time, and the magnitude of the reverse braking torque output by the driving device is dynamically adjusted according to the measurement data, so as to effectively reduce the tension fluctuation of the fabric surface during printing and ensure the stable and high-quality progress of the printing work.

[0044] As Figure 3 shown in the figure, when the driving device (unwinding AC servo motor) operates, the generated reverse braking torque is transmitted through three levels of transmission gears 27, idler wheels 26 and driving gears 25, and finally acts on the fabric roll 1, causing the fabric roll 1 to generate the tension F required for the equipment to work. This tension is the key parameter that needs to be accurately controlled subsequently.

[0045] It can be seen from the following formula

[0046] In the formula: -- Tension of the fabric surface during printing ( ); -- Reverse braking torque of the driving device ( ); -- Radius of the fabric roll 1 ( ); According to the derivation of relevant formulas, it can be known that the fabric surface tension is directly proportional to the reverse braking torque of the driving device and inversely proportional to the roll diameter of the fabric roll 1. During the printing operation process, maintaining the stability of the fabric surface tension F and reducing its fluctuation amplitude are the keys to ensuring the printing quality. However, as the printing process progresses, the roll diameter of the fabric roll 1 is in a continuous decreasing state. To ensure a constant tension, it is necessary to dynamically adjust the magnitude of the reverse braking torque T output by the driving device (unwinding AC servo motor) according to the real-time change of the roll diameter of the fabric roll 1. Since the adjustment of the reverse braking torque directly depends on the roll diameter change data, therefore, achieving real-time and accurate measurement of the roll diameter of the fabric roll 1 becomes a necessary prerequisite for ensuring the stable operation of the system.

[0047] During the operation of the printing device, a roll diameter measurement sensor 29 (ultrasonic sensor) is used to measure the real-time roll diameter of the fabric roll 1. By accurately capturing the time interval from the emission to the reception of ultrasonic waves and combining with the propagation speed of ultrasonic waves in the air, the real-time distance between the sensor and the surface of the fabric roll 1 is obtained through formula conversion, and then the diameter of the fabric roll 1 is calculated through a specific algorithm. In view of the fact that actual measurement is easily affected by factors such as environmental noise and signal interference, in order to ensure the accuracy and stability of measurement data, it is necessary to incorporate a filtering and noise reduction technology into the detection algorithm to effectively remove interference signals, improve the measurement accuracy of the roll diameter of the fabric roll 1, thereby laying a data foundation for accurately regulating the fabric surface tension and reducing quality problems caused by tension fluctuations during the printing process.

[0048] Embodiment 3: Due to production process limitations, during the winding process of the fabric roll 1 produced by the fabric factory, there are often differences in the radial tension distribution. It is difficult to keep the winding tension uniform between the middle and both sides of the fabric roll 1, and there may be a situation where the tension in the middle is large and the tension on both sides is small, or the tension on both sides is large and the tension in the middle is small. This non-uniform distribution of tension along the width direction of the fabric roll 1 will generate an additional pressure F h on the fabric surface, resulting in deformation of the fabric surface, specifically as shown in Figure 4 . Figure 4 In: -- Transverse additional pressure ( ); -- Initial tension of the fabric roll ( ); This additional transverse pressure will cause the fabric surface to wrinkle transversely, that is, the fabric surface undergoes elastic deformation transversely, as shown in Figure 5 . According to the law of generating additional pressure due to uneven transverse tension distribution on the fabric surface, the fabric surface 100 at the part with large tension produces a concave deformation a, and the part with small tension produces a convex deformation b. This result will also affect the alignment accuracy of the printed patterns on the front and back sides of the fabric.

[0049] To address the above problems, in this embodiment, the alignment accuracy of the front and back patterns in double-sided printing is improved from the third aspect: Referring to Figure 1 and Figure 2 shown, the last roller of the feeding roller is the first spiral expanding roller 5, and the first spiral expanding roller 5 is used to expand and convey the fabric surface and then convey it to the auxiliary vehicle fabric guiding roller 6; the fabric guiding roller is the second spiral expanding roller 7, and the second spiral expanding roller 7 is used to expand and convey the fabric surface and then convey it to the main vehicle fabric guiding roller 8.

[0050] To eliminate the problem of uneven tension caused by the winding of the fabric roll 1, the equipment is equipped with a first spiral expanding roller 5 and a second spiral expanding roller 7. Before the fabric enters the printing process, it is first expanded by the spiral expanding rollers. Through this mechanical expanding method, the tension distribution in the width direction of the fabric can be effectively balanced, the negative impact caused by the tension difference can be reduced, and finally the pattern accuracy and quality of the printed product can be improved.

[0051] Among them, the first spiral expanding roller 5 and the second spiral expanding roller 7 are both existing equipment. The principle of the spiral expanding roller to expand and widen mainly depends on its special spiral structure design and movement mode. The core of the principle is to convert the rotational movement of the roller body into the lateral tensile force of the fabric, so as to achieve the effects of anti-wrinkle, wrinkle removal and flattening.

[0052] In this embodiment, the working principle of the first spiral expanding roller 5 and the second spiral expanding roller 7 to improve the pattern alignment accuracy of the front and back sides is as follows: See Figure 6 and Figure 7 As shown, before the fabric enters the printing process, it is first expanded by the first spiral expanding roller 5 and the second spiral expanding roller 7. The expanding force of the first spiral expanding roller 5 and the second spiral expanding roller 7 is:

[0053] In the formula: -- Expanding force ( ); -- Fabric surface tension ( ); -- Contact arc length between the fabric and the roller ( ); -- Friction coefficient; -- Spiral lead angle ( );

[0054] In the formula: -- Pitch ( ); -- Roller diameter ( ); It can be known from the above formula that adjusting the contact arc length between the fabric and the roller, the friction coefficient and the spiral lead angle can all effectively change the magnitude of the expanding force. Among these adjustment methods, adjusting the spiral lead angle is the most convenient, and adjusting the size of the pitch can achieve the adjustment of the size of the spiral lead angle.

[0055] See Figure 6 andFigure 7 As shown, when the duplex printing device is working, a suitable and stable fabric tension F is desired. However, due to the limitations of the fabric mill's manufacturing process, additional tensions will occur in the middle and at both ends of the fabric roll. This tension will cause additional lateral pressure on the fabric in the lateral direction. The lateral additional pressure will cause the fabric surface to wrinkle during the printing process, thus affecting the alignment accuracy of the front and back sides of the fabric. Here, a lateral expanding force is generated by a spiral expanding roller. to offset most of the lateral additional pressure. to prevent the fabric surface from wrinkling during printing and improve the alignment accuracy of the front and back sides of the fabric. By this mechanical expanding method, the tension distribution in the width direction of the fabric surface can be effectively balanced, the negative impact caused by the tension difference can be reduced, and finally the pattern accuracy and quality of the printed product can be improved, as Figure 7 shown.

[0056] As an alternative implementation, the duplex printing device further includes a loading device, a transverse movement driving device, and a sewing device 20. The loading device includes a telescopic driving device, a mounting bracket, and a waiting material reel. Among them: The transverse movement driving device is drivingly connected to the sewing device 20 and is used to drive the sewing device 20 to reciprocate along the axial direction of the waiting material reel; the telescopic driving device is drivingly connected to the mounting bracket and is used to drive the mounting bracket to vertically lift and lower. The mounting bracket is slidably connected to the machine frame, and the waiting material reel is rotatably connected to the mounting bracket. When the telescopic driving device drives the mounting bracket to rise to the side of the working reel, the sewing device 20 is used to sew the fabric head on the working reel and the fabric head on the waiting material reel together.

[0057] As Figures 8 - 12 shown, a sewing device 20 is provided below the fabric roll 1 of the duplex printer. The sewing device 20 is installed on the slider of a linear guide rail, which is convenient for the operator to hold and operate. When the old fabric roll 1 needs to be replaced with a new one after printing, the worker can easily sew the new fabric head and the old fabric head together through the sewing device 20, which is convenient for operation and reduces the waste of advertising fabric heads.

[0058] As Figures 8 - 12As shown in the figure, a feeding device 21 is provided above the sewing device 20. The telescopic driving device can be a large-stroke cylinder. Two large-stroke cylinders are vertically arranged below the input end of the printing medium of the device. The top of the piston rod of the telescopic driving device 211 is connected to the mounting bracket 212 of the cloth roll 1. The mounting bracket 212 of the cloth roll 1 is movably connected to the slide rail 214. Both ends of the waiting material reel 213 are arranged on the mounting bracket 212 of the cloth roll 1. The cloth roll 1 is mounted on the waiting material reel 213 (inflatable shaft). A gear is provided at the end of the waiting material reel 213, and this gear is used to mesh with the gear of the AC servo cloth-releasing motor, so as to drive the waiting material reel 213 to rotate. This feeding device 21 can send the raw material of the cloth roll 1 at a low position to a high position, making it labor-saving and convenient for workers to operate. In addition, the force output by the cylinder can reliably position the gear mounted at the end of the waiting material reel 213 to the gear of the AC servo cloth-releasing motor, ensuring the center distance between the gears during the operation of the device, preventing the position of the waiting material reel 213 from changing, and thus improving the printing accuracy. During operation, the two left and right telescopic driving devices 211 push the mounting bracket 212 of the cloth roll 1 upward to the working position and firmly press it.

[0059] However, since the weight of the cloth roll 1 is relatively large, in order to prevent the cloth roll 1 from dropping at a high position due to the reduction of the air source pressure, which may endanger the personal safety of the operator, as an optional implementation manner, the double-sided printing device further includes a locking telescopic cylinder 215. The locking telescopic cylinder 215 is horizontally arranged. A pin hole 216 is provided on the mounting bracket 212. The pin hole 216 is a long strip-shaped hole extending in the vertical direction; a pin part is provided at the telescopic end of the locking telescopic cylinder 215, and the pin part can be inserted into the pin hole to lock the mounting bracket. The locking telescopic cylinder 215 can adopt a small cylinder, etc. When the mounting bracket 212 is pushed to a high position, the piston rod of the locking telescopic cylinder 215 extends and inserts into the pin hole 216, so as to prevent the cloth roll 1 from suddenly dropping due to various problems during the operation of the device and protect the safety of the operator. In order to facilitate the effective pinning action of the piston rod of the locking telescopic cylinder 215, the pin hole 216 corresponding to the telescopic rod of the locking telescopic cylinder 215 is processed into a strip-shaped hole.

[0060] Embodiment 4: This embodiment provides a method for improving the alignment accuracy of the front and back patterns in double-sided printing. Using the above double-sided printing device, this method includes: winding the printing medium around the feeding roller and the auxiliary vehicle cloth-feeding roller 6, and transmitting the printing medium to the first printing platform 17 to print the first side; making the printing medium printed by the first printing platform 17 sequentially wind around the lower surface of the guide cloth roller and the upper surface of the main vehicle cloth-feeding roller 8, and transporting the printing medium to the second printing platform 19 for printing the other side; by shortening the length of the printing medium between the first printing platform 17 and the second printing platform 19, reducing the cumulative error caused by the elongation of the printing medium, so as to improve the alignment accuracy of the front and back patterns.

[0061] The method for improving the alignment accuracy of front and back patterns in double-sided printing in this embodiment shortens the layout length between the first printing platform 17 and the second printing platform 19 as much as possible from the structural layout of the double-sided printing device, thereby improving the alignment accuracy of front and back patterns in double-sided printing.

[0062] As an alternative implementation, the method further includes: measuring the diameter of the fabric roll 1 on the working reel in real time, and adjusting the magnitude of the reverse braking torque of the driving device according to the diameter of the fabric roll 1, so as to maintain the fabric tension at a set value.

[0063] As the printing process progresses, since the diameter of the fabric roll 1 is continuously decreasing, the fabric tension is prone to fluctuate, affecting the alignment accuracy of front and back patterns. During the printing operation, maintaining the stability of the fabric tension F and reducing its fluctuation amplitude are the keys to ensuring printing quality. The method for improving the alignment accuracy of front and back patterns in double-sided printing in this embodiment needs to dynamically adjust the reverse braking torque of the driving device according to the real-time change of the diameter of the fabric roll 1 to ensure constant tension, thereby improving the alignment accuracy of front and back patterns.

[0064] As an alternative implementation, the method further includes: before the printing medium enters the first printing platform 17, using the first spiral spreading roller 5 to perform spreading and widening treatment on the printing medium to balance the tension distribution in the width direction of the printing medium; before the printing medium enters the second printing platform 19, using the second spiral spreading roller 7 to perform spreading and widening treatment on the printing medium to balance the tension distribution in the width direction of the printing medium.

[0065] The method for improving the alignment accuracy of front and back patterns in double-sided printing in this embodiment first performs spreading treatment on the fabric surface by the spiral spreading roller before the fabric surface enters the printing process. Through this mechanical spreading method, the tension distribution in the width direction of the fabric surface can be effectively balanced, the negative impact caused by the tension difference can be reduced, and finally the pattern accuracy and quality of the printed product can be improved.

[0066] In the description of this specification, specific features, structures or characteristics can be combined in a suitable manner in any one or more embodiments or examples.

[0067] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0068] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, and all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A duplex printing device, characterized in that, It includes a feeding roller, a sub-car fabric feeding roller, a first printing assembly, a fabric guiding roller, a main-car fabric feeding roller, a second printing assembly and a discharging roller which are arranged in sequence along the conveying direction of the printing medium. Among them: Among the feeding roller, the sub-car fabric feeding roller, the fabric guiding roller, the main-car fabric feeding roller and the discharging roller, at least one is a driving roller; the first printing assembly includes a first printing platform, the second printing assembly includes a second printing platform, both the first printing platform and the second printing platform are inclined, and the second printing platform is located below the first printing platform; The fabric guiding roller is located below the first printing platform, the top end of the main-car fabric feeding roller is not lower than the bottom end of the fabric guiding roller, and the printed medium completed by printing on the first printing platform can sequentially wind around the lower surface of the fabric guiding roller and the upper surface of the main-car fabric feeding roller and be conveyed to the second printing platform for printing on the other side.

2. The duplex printing device according to claim 1, characterized in that, The first printing platform extends downward from top to bottom in a direction away from the second printing platform, and the printed medium bypassing the sub-car fabric feeding roller, the first printing platform and the fabric guiding roller is in a straight shape; The second printing platform extends downward from top to bottom in a direction away from the first printing platform, and the fabric feeding end of the second printing platform is lower than the main-car fabric feeding roller.

3. The duplex printing device according to claim 1, wherein The double-sided printing device further includes a frame, a working reel and a driving device. Among them: The working reel is rotatably connected to the frame, the fabric roll is located on the working reel, and the driving device is in transmission connection with the reel and is used for generating a reverse braking torque so that the fabric surface tension of the fabric roll is at a set value.

4. The duplex printing device according to claim 3, wherein, The double-sided printing device further includes a roll diameter measuring sensor and a control unit. Among them: The roll diameter measuring sensor is used for measuring the roll diameter of the fabric roll in real time; The control unit is electrically connected to both the roll diameter measuring sensor and the driving device and is used for adjusting the reverse braking torque of the driving device in real time according to the roll diameter of the fabric roll so as to maintain the constancy of the fabric surface tension.

5. The duplex printing device according to claim 1, characterized in that, The last roller body of the feeding roller is a first spiral width-expanding roller, and the first spiral width-expanding roller is used for expanding and widening the fabric surface and then conveying it to the sub-car fabric feeding roller; The fabric guiding roller is a second spiral width-expanding roller, and the second spiral width-expanding roller is used for expanding and widening the fabric surface and then conveying it to the main-car fabric feeding roller.

6. The duplex printing device according to claim 3, wherein, The double-sided printing device further includes a loading device, a transverse movement driving device and a sewing device. The loading device includes a telescopic driving device, a mounting bracket and a waiting material reel. Among them: The transverse movement driving device is in driving connection with the sewing device and is used for driving the sewing device to reciprocate axially along the waiting material reel; The telescopic driving device is in driving connection with the mounting bracket and is used for driving the mounting bracket to vertically lift and lower. The mounting bracket is slidably connected to the frame, the waiting material reel is rotatably connected to the mounting bracket, and when the telescopic driving device drives the mounting bracket to rise beside the working reel, the sewing device is used for sewing the fabric head on the working reel and the fabric head on the waiting material reel.

7. The duplex printing device according to claim 6, characterized in that, The duplex printing device further includes a locking telescopic cylinder, and a pin hole is provided on the mounting bracket. The pin hole is a long strip hole extending in the vertical direction; A pin portion is provided at the telescopic end of the locking telescopic cylinder. The pin portion can be inserted into the pin hole to lock the mounting bracket.

8. A method for improving the alignment accuracy of front and back patterns in double-sided printing, characterized in that, When using the duplex printing device according to any one of claims 1-7, the method includes: Winding the printing medium around the feeding roller and the auxiliary carriage fabric feeding roller, and transmitting the printing medium to the first printing platform to print the first side; Making the printing medium that has been printed on the first printing platform wind around the lower surface of the fabric guiding roller and the upper surface of the main carriage fabric feeding roller in sequence, and conveying the printing medium to the second printing platform for printing the other side; By shortening the length of the printing medium between the first printing platform and the second printing platform, the cumulative error caused by the elongation of the printing medium is reduced, thereby improving the alignment accuracy of the front and back patterns.

9. The method for improving the alignment accuracy of the front and back patterns in double-sided printing according to claim 8, characterized in that, The duplex printing device further includes a frame, a working reel and a driving device. The working reel is rotatably connected to the frame. A fabric roll is located on the working reel. The driving device is in transmission connection with the reel and is used to generate a reverse braking torque; The method further includes: Measuring the diameter of the fabric roll on the working reel in real time, and adjusting the magnitude of the reverse braking torque of the driving device according to the diameter of the fabric roll, so as to maintain the fabric tension at a set value.

10. The method for improving the alignment accuracy of front and back patterns in double-sided printing according to claim 8, wherein The method further includes: Before the printing medium enters the first printing platform, using a first spiral spreading roller to perform spreading and widening processing on the printing medium to balance the tension distribution in the width direction of the printing medium; Before the printing medium enters the second printing platform, using a second spiral spreading roller to perform spreading and widening processing on the printing medium to balance the tension distribution in the width direction of the printing medium.

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