A spreading unit, a spreading roller and a digital printing apparatus
By using a spreading unit with a circumferentially distributed curved section in digital printing equipment, the problem of poor wrinkle removal effect in traditional brush roller structures is solved, achieving full media contact and uniform spreading, thus improving printing accuracy and equipment applicability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN RUNTIANZHI DIGITAL EQUIP
- Filing Date
- 2024-11-25
- Publication Date
- 2026-07-31
AI Technical Summary
In existing digital printing equipment, the traditional brush roller structure results in poor wrinkle removal effect, has blind spots in force application and non-uniform expansion problems, which affect printing accuracy and may damage the printhead.
The expansion unit adopts bending sections evenly distributed around the circumference of the expansion body. The bending sections deform when subjected to radial force. The openings of the bending sections face the same direction and are staggered to form an overlapping area, ensuring full contact of the medium and no blind spots under force. Expansion and wrinkle removal are achieved through the deformation of the medium pressure.
It improves the expansion and wrinkle removal effects, adapts to different media thicknesses, reduces the possibility of wrinkle superposition, and enhances printing accuracy and equipment applicability.
Smart Images
Figure CN119348308B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of digital printing technology, and particularly relates to an expansion unit, an expansion roller, and digital printing equipment. Background Technology
[0002] During the operation of digital printing equipment, wrinkles are generated during media transport and the printing process. If these wrinkles are not removed, the accuracy of the printed pattern will be affected, and severe wrinkles can even scratch the printhead, potentially causing damage. Traditional wrinkle removal methods typically use brush rollers, which have evenly spaced brush strips on the circumference of the roller body. The brush strips extend along the axis of the roller body to both ends, and the brush bundles on the brush strips are angled towards one end of the roller body. When the media passes through the brush roller, the softness of the brushes and the angled texture of the brush bundles amplify the media from one end of the roller body to the other, thus achieving wrinkle removal. However, this structure has the following drawbacks: (1) As a local wrinkle removal unit on the roller, the brush strip has a blank area between the brush strips. When the medium passes through the brush roller, the area between the brush strips does not generate an expansion force on the medium, which means that a force blind zone will be generated; (2) A brush strip spans the entire length of the brush roller in the direction of the roller axis. The contact area between a single brush strip and the medium is too large, and the brush strip cannot guarantee that each local position generates a uniform expansion force on the medium; (3) The brush strip is composed of several individual brush bundles arranged along the direction of the roller axis. The brush bundle contains a large number of fine hairs. When the end of the brush bundle contacts the medium, the fine hairs are also easy to spread outward from the center of the brush bundle when the brush bundle is subjected to the pressure of the medium. This causes the expansion force at the current stress point of the medium to not be concentrated and diffused in the direction of the brush strip's inclination. Therefore, the above problems will all lead to poor wrinkle removal effect. Summary of the Invention
[0003] The expansion unit provided by this invention aims to solve the problem of poor wrinkle removal effect in existing structures.
[0004] This invention is implemented as follows: a widening unit, comprising:
[0005] The expanding body has a ring-shaped structure. The outer wall of the expanding body is evenly distributed with several curved sections at intervals along its circumference. When the expanding body is subjected to radial force, the curved sections can deform towards the center of the expanding body. The openings of the curved sections face the same direction. Two adjacent curved sections are staggered along the axial direction of the expanding body to form two circumferential trajectories. The two staggered curved sections have an overlapping area in the circumferential direction. In the axial direction of the expanding body, the free end of the curved section located on the earlier circumference of the same circle extends out of the expanding body.
[0006] Furthermore, the inner wall of the expanding body is provided with a first limiting part, which is used to limit the circumferential movement when it is installed on the expanding roller.
[0007] Furthermore, the cross-section of the expanded body through its axis is an isosceles trapezoid or a parallelogram.
[0008] The present invention also provides a spreading roller, including a roller body and the aforementioned spreading units. The spreading units are sleeved on the roller body and arranged closely along its axial direction. The spreading units form at least one spreading group. All spreading units in each spreading group are symmetrically arranged and the openings of the curved portions face opposite directions. The axis of symmetry of the spreading group is used to correspond to the center line of the medium.
[0009] Furthermore, the roller body is provided with end caps at both ends, and the end caps protrude from the surface of the roller body and abut against the expansion unit of the expansion unit.
[0010] Furthermore, the expanding roller also includes a first mounting shaft and a second mounting shaft rotatably disposed at both ends of the roller body and extending through the end cover, wherein the first mounting shaft or the second mounting shaft can extend or retract relative to the roller body along its axial direction.
[0011] Furthermore, two first supporting rotating bodies are spaced apart along the axial direction inside one end of the roller body. The first mounting shaft or the second mounting shaft is embedded in the two first supporting rotating bodies. The first mounting shaft or the second mounting shaft can rotate relative to the roller body through the first supporting rotating bodies. Two first limiting members are spaced apart along the axial direction on the first mounting shaft or the second mounting shaft. The two first limiting members are distributed on opposite sides of the first supporting rotating body away from the end of the roller body. When the first mounting shaft or the second mounting shaft extends or retracts along the axial direction of the roller body, the second supporting rotating body can abut against one of the limiting members.
[0012] Furthermore, two second supporting rotating bodies are spaced apart along their axial direction inside the other end of the roller body. The second mounting shaft or the first mounting shaft is embedded in the two second supporting rotating bodies. The second mounting shaft or the first mounting shaft can rotate relative to the roller body through the second supporting rotating bodies. Two second limiting members are spaced apart along their axial direction on the second mounting shaft or the first mounting shaft. The two second limiting members are distributed on opposite sides of the second supporting rotating body away from the end of the roller body and abut against the second supporting rotating body.
[0013] Furthermore, a second limiting part is provided on the outer wall of the roller body, which is used to circumferentially limit the expansion unit when the expansion unit is installed on the expansion roller.
[0014] The present invention also provides a digital printing device, including a machine body, a printing platform disposed on the machine body, and at least one of the aforementioned expanding rollers, wherein one of the expanding rollers is rotatably disposed on one side of the output end of the printing platform, and the medium passes through the printing platform and is wound around the expanding roller before being fed to the next station.
[0015] The beneficial effects achieved by this invention, when applied to a spreading roller, are that there are no blind spots in the force distribution between two adjacent spreading units or on a single spreading unit. The medium can fully contact the spreading unit, and the curved part, as the smallest spreading unit, can form an integral working surface when in contact with the medium, which can avoid pressure dispersion and greatly improve the spreading effect and wrinkle removal effect. Moreover, since the spreading effect is achieved by applying pressure to the curved part through the medium to cause deformation of the curved part, the curved part only needs a small amount of pressure to deform. Therefore, this structure can also be used for spreading of thinner media that do not need to withstand too much tension, and it is suitable for a wide range of media types. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of the expansion unit provided by the present invention;
[0017] Figure 2 yes Figure 1 Cross-sectional view at point AA;
[0018] Figure 3 This is a schematic diagram of the curved section structure of an expansion unit provided by the present invention;
[0019] Figure 4 This is a structural comparison diagram of the bending portion of an expansion unit provided by the present invention before and after being subjected to force;
[0020] Figure 5 This is a schematic diagram of one embodiment of the expansion roller provided by the present invention;
[0021] Figure 6 This is a schematic diagram of the structure of an expansion roller provided by the present invention, in which all the curved parts on the expansion unit are arranged on the same circumference and then arranged on the roller body.
[0022] Figure 7 yes Figure 5 Cross-sectional view at point BB;
[0023] Figure 8 This is a schematic diagram of another embodiment of the expansion roller provided by the present invention;
[0024] Figure 9 yes Figure 5 Cross-sectional view at point C;
[0025] Figure 10 This is a schematic diagram of the structure of a digital printing device provided by the present invention.
[0026] Explanation of icon numbers:
[0027] 1. Expanding body; 11. First limiting part; 2. Bending part; 2a. Free end; 10. Expanding unit; 10a. Expanding group; 20. Roller body; 201. Second limiting part; 30. End cover; 40. First supporting rotating body; 50. Second supporting rotating body; 60. First mounting shaft; 70. Second mounting shaft; 80. First limiting member; 90. Second limiting member; 100. Fixed bushing; 200. Machine body; 300. Printing platform; 400. Expanding roller; 500. Media. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0029] See Figures 1-4This invention provides a widening unit 10, including a widening body 1 in an annular structure. The annular structure of the widening body 1 facilitates the installation of the widening unit 10 on the roller body of the widening roller, enabling modular and rapid assembly of the widening roller. A plurality of curved portions 2 are evenly distributed along the circumference of the outer wall of the widening body 1. When the curved portions 2 are subjected to radial force, they deform towards the center of the widening body 1. When the medium passes through the widening unit 10, the medium contacts the curved portions 2, applying a force towards the center of the widening body 1. The curved portions 2 deform under pressure, causing the opening of the curved portions 2 to contract towards the widening body 1. Therefore, when the folds of the medium pass over the surface of the curved portions 2, the folds diffuse towards the opening of the curved portions 2, thereby achieving... To achieve the desired wrinkle removal effect, the openings of several curved portions 2 face in the same direction, facilitating the assembly of multiple expansion units 10 onto the roller body to achieve the required wrinkle removal amplitude. Adjacent curved portions 2 are staggered along the axial direction of the expansion body 1 to form two circumferential tracks. The staggered curved portions 2 have an overlapping area in the circumferential direction. In the axial direction of the expansion body 1, the free end 2a of the curved portion 2 located on the foremost circumference extends outside the expansion body 1. This ensures that when the expansion units 10 are assembled onto the expansion roller, there are no continuous gaps on the same circumference between adjacent expansion units 10, allowing for full contact with the medium and eliminating blind spots in force distribution. This results in more uniform force distribution and achieves the best wrinkle removal effect (see [link]). Figure 5 When several curved portions 2 are arranged on the same circumference, this structure, when the spreading unit 10 is assembled onto the spreading roller body, results in continuous gaps h between two adjacent circumferentially curved portions 2 when the curved portions 2 are arranged axially. This causes the spreading unit 10 to not fully contact the medium, thus affecting the wrinkle removal effect (see...). Figure 6 ).
[0030] When the expansion unit 10 provided by this invention is applied to an expansion roller, no force blind zone is generated between two adjacent expansion units 10 or on a single expansion unit 10. The medium can fully contact the expansion unit 10. Furthermore, the curved part 2, as the smallest expansion unit 10, can form an integral working surface when in contact with the medium, which can avoid pressure dispersion and greatly improve the expansion effect and wrinkle removal effect. Moreover, since the expansion effect is achieved by applying pressure to the curved part 2 through the medium to deform the curved part 2, the curved part 2 only needs a small pressure to deform. Therefore, this structure can also be used for expansion of thinner media that do not need to withstand too much tension, and it is suitable for a wide range of media types.
[0031] Specifically, both the expansion body 1 and the bending part 2 are made of deformable materials, including but not limited to plastic. The bending part 2 and the expansion body 1 are integrally molded, which facilitates the production and processing of the expansion unit 10 and improves the structural stability of the expansion body 1 and the bending part 2.
[0032] See Figure 1 Furthermore, the inner wall of the expanding body 1 is provided with a first limiting part 11. The first limiting part 11 is used to limit the circumferential position when it is installed on the expanding roller. That is, it can be used to cooperate with the second limiting part 201 described below. In this way, the expanding body 1 can be positioned in the axial direction of the expanding roller, so that the expanding unit 10 can be driven to rotate synchronously when the expanding roller rotates.
[0033] Furthermore, the cross-section of the expanding body 1 along its axis is an isosceles trapezoid or a parallelogram. Thus, when several expanding bodies 1 are installed on the roller body described below, there are no gaps between two adjacent expanding units 10, and their sides can interlock, facilitating installation and improving the compactness and stability of the structure.
[0034] See Figure 2 Furthermore, in this embodiment, the cross-section of the expansion body 1 can preferably be designed as a parallelogram. Compared with the structure of an isosceles trapezoid, which requires the separate production of forward and inverted isosceles trapezoids during production, the parallelogram does not require differentiation and only one type needs to be produced, which facilitates the mass production of the expansion unit 10.
[0035] See Figure 5 , Figure 7 , Figure 8 This invention also provides a widening roller 400, including a roller body 20 and the aforementioned widening units 10. The widening units 10 are sleeved on the roller body 20 and are closely arranged along its axial direction to cover the roller body 20. The widening units 10 form at least one widening group 10a. All widening units 10 in each widening group 10a are symmetrically arranged and the openings of the curved portions 2 face opposite directions. The axis of symmetry of the widening unit group 10 is used to correspond to the center line of the medium. In this way, when the medium passes through the roller surface of the roller body 20, the medium can be widened from the middle to both ends to remove wrinkles. Compared with the prior art where the brush strip is tilted in one direction to remove wrinkles from one end to the other, this design structure can reduce the distance of wrinkle removal in the same direction, reduce the possibility of wrinkle superposition during the wrinkle removal process, and improve the wrinkle removal effect.
[0036] By adopting a separate assembly structure for the roller body 20 and the expansion unit 10, compared with the integrated structure of the expansion roller 400 in the prior art, it is easier to disassemble and reassemble. The position of the symmetry line of the expansion unit 10 on the roller body 20 can be adjusted according to the center line position of the medium so that the symmetry line can be aligned with the center line of the medium. This reduces the positional deviation between the center line of the medium and the symmetry lines of several expansion units 10, thereby allowing the medium to spread more evenly to both ends along the symmetry plane and achieve the best wrinkle removal effect. In addition, the corresponding number of expansion groups 10a can be set according to the current quantity of medium to adapt to different production needs.
[0037] For example, see Figure 5 , Figure 7 When the quantity of media is 1, several expansion units 10 on the roller 20 are symmetrically arranged about the center line of the roller 20 perpendicular to the axis of symmetry to form an expansion group 10a. The openings of the curved portions 2 of all expansion units 10 on each side of the axis of symmetry face the same direction, and the openings of the curved portions 2 of the expansion units 10 on both sides of the axis of symmetry are arranged opposite to each other. When the media passes over the expansion roller 400, the center line of the media corresponds to the axis of symmetry. When the media presses against the expansion units 10, the media can expand from the center to both ends, thereby achieving wrinkle removal; see also Figure 8 When the number of media is 2, the expansion units 10 on the roller body 20 are divided into two expansion groups 10a. Each expansion group 10a is located on both sides of the roller body 20. When the two media pass on the roller body 20 at the same time, the center line of the media corresponds to the axis of symmetry of each expansion group 10a. When the media passes on the expansion unit 10, each media can expand from the center to both ends, thereby realizing the synchronous expansion of the two media.
[0038] It should be noted that the number of expansion groups 10a set on the roller body 20 can be assembled by using the corresponding number of expansion units 10 according to the actual amount of medium, and is not limited to the 1 group or 2 groups exemplified in this example. The length of each expansion group 10a is adapted to the width of the medium, so that it can be used more flexibly and thus adapt to different production needs.
[0039] See Figure 7 Furthermore, end caps 30 are detachably provided at both ends of the roller body 20. The periphery of the end caps 30 protrudes from the surface of the roller body 20 and abuts against the expansion unit 10 of the expansion unit 10. In this way, by assembling and disassembling the end caps 30, the assembly of the expansion unit 10 on the roller body 20 can be facilitated.
[0040] See Figure 7Furthermore, fixed bushings 100 are fixedly installed inside both ends of the roller body 20, and the end cap 30 is connected and fixed to the fixed bushings 100. Setting the fixed bushings 100 to connect to the end cap 30 can increase the connection space between the end cap 30 and the roller body 20. This allows the roller body 20 to adopt a hollow structure and reduce the thickness of the roller body 20, thereby reducing the weight of the roller body 20 to facilitate the installation of the spreading roller 400 and reduce material costs.
[0041] See Figure 5 , Figure 7 Furthermore, the expanding roller 400 also includes a first mounting shaft 60 and a second mounting shaft 70, which are rotatably disposed at both ends of the roller body 20 and extend through the end cover 30. The first mounting shaft 60 or the second mounting shaft 70 can extend and retract relative to the roller body 20 along its axial direction. The expanding roller 400 can be installed through the first mounting shaft 60 and the second mounting shaft 70. Setting one of the mounting shafts to extend and retract can effectively adjust the length of the roller body 20 in the axial direction, making the installation of the roller body 20 easier. That is, during installation, the mounting shaft with the extension function can be retracted to a certain stroke before the mounting shaft is installed with other fixed parts. This can avoid the mounting shaft and the installation parts getting too close to the limit, which would cause installation interference and increase the installation difficulty. At the same time, it can also adapt to the installation in spaces of different lengths.
[0042] See Figure 7 Furthermore, two first supporting rotating bodies 40 are spaced apart along the axial direction inside one end of the roller body 20. A first mounting shaft 60 or a second mounting shaft 70 is embedded within the two first supporting rotating bodies 40. The first mounting shaft 60 or the second mounting shaft 70 can rotate relative to the roller body 20 through the first supporting rotating bodies 40, allowing the medium to drive the roller body 20 to rotate relative to the first mounting shaft 60 or the second mounting shaft 70. The use of two first supporting rotating shafts to mount the first mounting shaft 60 or the second mounting shaft 70 ensures the stability of the first mounting shaft 60 or the second mounting shaft 70 on the roller body 20 and prevents the first mounting shaft 60 or the second mounting shaft 70 from being damaged on the shaft. The first mounting shaft 60 or the second mounting shaft 70 is provided with two first limiting members 80 spaced apart along its axial direction. The two first limiting members 80 are distributed on opposite sides of the first supporting rotating body 40 away from the end of the roller body 20. When the first mounting shaft 60 or the second mounting shaft 70 extends or retracts along the axial direction of the roller body 20, the second supporting rotating body 50 can abut against one of the limiting members. The first limiting member 80 can limit the first mounting shaft 60 or the second mounting shaft 70 in the axial direction, and the distance between the two first limiting members 80 also provides axial extension and retraction space for the first mounting shaft 60 or the second mounting shaft 70.
[0043] See Figure 7Furthermore, two second supporting rotating bodies 50 are spaced apart along the axial direction inside the other end of the roller body 20. A second mounting shaft 70 or a first mounting shaft 60 is embedded within the two second supporting rotating bodies 50. The second mounting shaft 70 or the first mounting shaft 60 can rotate relative to the roller body 20 through the second supporting rotating bodies 50, allowing the medium to drive the roller body 20 to rotate relative to the second mounting shaft 70 or the first mounting shaft 60. The arrangement of two second supporting rotating shafts to mount the second mounting shaft 70 or the first mounting shaft 60 ensures that the second mounting shaft 70... To ensure the stability of the second mounting shaft 70 or the first mounting shaft 60 on the roller body 20 and to prevent the second mounting shaft 70 or the first mounting shaft 60 from wobbling relative to its axis in the axial direction, two second limiting members 90 are provided on the second mounting shaft 70 or the first mounting shaft 60 at intervals along its axial direction. The two second limiting members 90 are distributed on opposite sides of the second support rotating body 50 away from the end of the roller body 20 and abut against the second support rotating body 50, so as to achieve a fixed connection of the second mounting shaft 70 or the first mounting shaft 60 in the axial direction of the roller body 20.
[0044] See Figure 7 Specifically, the first supporting rotating body 40 and the second supporting rotating body 50 are respectively nested and fitted with the corresponding fixed bushings 100 on the roller body 20. The first supporting rotating body 40 and the second supporting rotating body 50 can be selected from, but are not limited to, bearings. The first limiting member 80 and the second limiting member 90 can be selected from, but are not limited to, snap rings.
[0045] See Figure 9 Furthermore, a second limiting part 201 is provided on the outer wall of the roller body 20. The second limiting part 201 is used to limit the expansion unit 10 circumferentially when the expansion unit 10 is installed on the expansion roller. That is, the second limiting part 201 can cooperate with the first limiting part 11 on the expansion body 1, so as to facilitate the limitation of the expansion body 1 in the circumferential direction of the roller body 20.
[0046] See Figure 10 The present invention also provides a digital printing device, including a machine body 200, a printing platform 300 disposed on the machine body 200, and at least one of the aforementioned expanding rollers. One of the expanding rollers is rotatably disposed on the output end side of the printing platform 300. The medium 500 passes through the printing platform 300 and is wound around the expanding roller before being fed to the next station.
[0047] The digital printing equipment provided by this invention has excellent expansion and wrinkle removal effects. It can be used for expansion of relatively thin media 500 that do not require much tension and is suitable for a wide range of media types. The expansion roller 400 can be easily disassembled and reassembled. The position of the symmetry line of the expansion unit 10 on the roller body 20 can be adjusted according to the center line position of the media 500 so that the symmetry line can be aligned with the center line of the media 500. This reduces the positional deviation between the center line of the media 500 and the symmetry lines of several expansion units 10, thereby allowing the media 500 to expand more evenly to both ends along the symmetry plane to achieve the best wrinkle removal effect. In addition, the number of expansion groups 10a can be set according to the current number of media 500 to adapt to different production needs.
[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A widening unit, characterized in that, include: The expanding body has a ring-shaped structure. The outer wall of the expanding body is evenly distributed with several curved portions along its circumference. When the expanding body is subjected to radial force, the curved portions can deform towards the center of the expanding body. The openings of the curved portions face the same direction. Two adjacent curved portions are staggered along the axial direction of the expanding body to form two circumferential trajectories. The two staggered curved portions have an overlapping area in the circumferential direction. In the axial direction of the expanding body, the free end of the curved portion located on the earlier circumference of the same circle extends out of the expanding body. The cross-section of the expanding body through its axis is an isosceles trapezoid or a parallelogram, wherein the interior angles of the parallelogram are not right angles, and the side of the cross-section of the expanding body through its axis is set at an angle with the inner ring side of its axis direction, so that when several expanding bodies are installed on the roller, there is no gap between two adjacent expanding units and the sides interlock with each other. Both the expanded body and the curved portion are made of deformable materials.
2. The widening unit as described in claim 1, characterized in that, The inner wall of the expansion body is provided with a first limiting part, which is used to limit the circumferential movement when it is installed on the expansion roller.
3. A spreading roller, characterized in that, The device includes a roller body and a plurality of expansion units as described in claim 1 or 2. The plurality of expansion units are sleeved on the roller body and arranged closely along its axial direction. The plurality of expansion units form at least one expansion group. All expansion units in each expansion group are symmetrically arranged and the openings of the curved portions face opposite directions. The axis of symmetry of the expansion group is used to correspond to the center line of the medium.
4. The expanding roller as described in claim 3, characterized in that, The roller body is detachably provided with end caps at both ends, and the end caps protrude from the surface of the roller body and abut against the expansion unit of the expansion unit.
5. The spreading roller as described in claim 4, characterized in that, The expanding roller also includes a first mounting shaft and a second mounting shaft that are rotatably disposed at both ends of the roller body and extend through the end cover. The first mounting shaft or the second mounting shaft can extend or retract relative to the roller body along its axial direction.
6. The spreading roller as described in claim 5, characterized in that, Two first supporting rotating bodies are spaced apart along the axial direction inside one end of the roller body. The first mounting shaft or the second mounting shaft is embedded in the two first supporting rotating bodies. The first mounting shaft or the second mounting shaft can rotate relative to the roller body through the first supporting rotating bodies. Two first limiting members are spaced apart along the axial direction on the first mounting shaft or the second mounting shaft. The two first limiting members are distributed on opposite sides of the first supporting rotating bodies away from the end of the roller body. When the first mounting shaft or the second mounting shaft extends or retracts along the axial direction of the roller body, the second supporting rotating body can abut against one of the limiting members.
7. The expanding roller as described in claim 5, characterized in that, Two second supporting rotating bodies are spaced apart along their axial direction inside the other end of the roller body. The second mounting shaft or the first mounting shaft is embedded in the two second supporting rotating bodies. The second mounting shaft or the first mounting shaft can rotate relative to the roller body through the second supporting rotating bodies. Two second limiting members are spaced apart along their axial direction on the second mounting shaft or the first mounting shaft. The two second limiting members are distributed on opposite sides of the second supporting rotating body away from the end of the roller body and abut against the second supporting rotating body.
8. The expanding roller as described in claim 3, characterized in that, The outer wall of the roller is provided with a second limiting part, which is used to circumferentially limit the expansion unit when the expansion unit is installed on the expansion roller.
9. A digital printing device, characterized in that, It includes a machine body, a printing platform disposed on the machine body, and at least one expansion roller as described in any one of claims 3-8. One of the expansion rollers is rotatably disposed on one side of the output end of the printing platform. The medium passes through the printing platform and is wound around the expansion roller before being fed to the next station.