A printer

Abstract

The present invention discloses a printer, comprising a base, a printing mechanism, an anti-sticking mechanism and a power mechanism. The printing mechanism comprises a print head and a print roller arranged opposite to each other. The anti-sticking mechanism comprises an auxiliary roller and an adjusting roller arranged opposite to each other. The power mechanism comprises a power assembly, a first transmission assembly and a second transmission assembly. The second transmission assembly is connected to the auxiliary roller through a one-way transmission. When paper is retracted, the one-way transmission engages with the auxiliary roller, so that the power assembly can drive the print roller to rotate in the opposite direction through the first transmission assembly. At the same time, the power assembly also drives the auxiliary roller to rotate in the opposite direction through the second transmission assembly, so that the print roller and the auxiliary roller can simultaneously drive the print medium to move along the second direction, thereby increasing the retracting paper feeding power of the print medium, so that the print medium can be peeled off from the print head, preventing the print medium from sticking to the print head, and improving the printing quality.

Description

Technical Field

[0001] The present invention relates to the technical field of printing equipment, and in particular to a printer. Background Art

[0002] In the related art, if a thermal printer encounters printing media made of special materials such as wristbands during the printing process, the following problems are likely to occur during printing: the wristband is likely to become softened due to heat during the printing process, causing the wristband to stick to the print head. If the wristband is not continued after the wristband sticks to the print head, the adhesion strength between the wristband and the print head will increase after cooling, causing the printer's rubber roller to slip against the printing medium during the next printing, resulting in failure to print normally and affecting the printing quality. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a printer that can improve the problem that the print head is easily adhered to the print medium.

[0004] A printer according to an embodiment of the present invention includes:

[0005] The machine base has a paper feeding channel;

[0006] A printing mechanism, disposed at one end of the paper feeding passage, comprising a print head and a print roller disposed opposite to each other;

[0007] an anti-sticking mechanism, arranged at the other end of the paper feeding channel, comprising an auxiliary roller and an adjusting roller arranged opposite to each other;

[0008] The power mechanism includes a power assembly, a first transmission assembly, and a second transmission assembly, wherein the output end of the power assembly is connected to the first transmission assembly and the second transmission assembly, the output end of the first transmission assembly is connected to the printing roller, and the output end of the second transmission assembly is connected to the auxiliary roller;

[0009] The second transmission assembly is connected to the auxiliary roller through a one-way transmission. When the paper is fed forward for printing, the one-way transmission is loosened from the auxiliary roller, and the printing roller drives the auxiliary roller to rotate forward through the printing medium, so that the printing medium moves along the first direction in the paper feeding channel. When the paper is fed backward, the one-way transmission is engaged with the auxiliary roller, and the power assembly drives the printing roller and the auxiliary roller to rotate in opposite directions simultaneously through the first transmission assembly and the second transmission assembly, so that the printing roller and the auxiliary roller can simultaneously drive the printing medium to move along the second direction.

[0010] A printer according to an embodiment of the present invention has at least the following beneficial effects:

[0011] During forward paper feeding, the one-way transmission is disengaged from the auxiliary roller, and the second transmission assembly cannot drive the auxiliary roller via the one-way transmission, while the first transmission assembly can drive the print roller to rotate in the forward direction. In this case, the print roller serves as the active roller and the auxiliary roller serves as the driven roller. The print roller drives the auxiliary roller to rotate in the forward direction through the print medium, so that the print medium moves in the first direction in the paper feed path. At this time, the paper feeding speed of the auxiliary roller is the same as the paper feeding speed of the print roller, which can prevent paper feeding desynchronization and larger paper feeding cumulative errors caused by the front and rear speed difference, thereby achieving forward paper feeding and improving printing quality. During reverse paper feeding, the one-way transmission is engaged with the auxiliary roller, so that the power assembly can drive the print roller to rotate in the reverse direction via the first transmission assembly. At the same time, the power assembly also drives the auxiliary roller to rotate in the reverse direction via the second transmission assembly, so that the print roller and the auxiliary roller can simultaneously drive the print medium to move in the second direction, thereby increasing the reverse paper feeding power of the print medium, allowing the print medium to be separated from the print head, preventing the print medium from sticking to the print head, and improving printing quality.

[0012] According to some embodiments of the present invention, the power assembly includes a motor and a reduction gear set, the output shaft of the motor is connected to the input end of the reduction gear set, and the first transmission assembly and the second transmission assembly are respectively connected to both sides of the output end of the reduction gear set.

[0013] According to some embodiments of the present invention, the first transmission assembly includes a print drive wheel, which is fixedly connected to the print roller and meshes with the output gear of the reduction gear group; the second transmission assembly includes a driven wheel, a changing wheel and an auxiliary drive wheel; the driven wheel is meshed with the output gear of the reduction gear group; the two ends of the changing wheel are respectively meshed with the driven wheel and the auxiliary drive wheel; the one-way transmission is a one-way bearing; the auxiliary drive wheel is fixed to the outer ring of the one-way bearing; and the inner ring of the one-way bearing is fixed to the auxiliary roller.

[0014] According to some embodiments of the present invention, the outer diameter of the printing roller is D1, the rotation speed of the printing drive wheel is N1, the outer diameter of the auxiliary roller is D2, and the rotation speed of the auxiliary drive wheel is N2, satisfying the following relationship: D1*N1 / D2<N2.

[0015] According to some embodiments of the present invention, the outer diameter of the printing roller is equal to the outer diameter of the auxiliary roller, and the rotation speed of the printing drive wheel is lower than the rotation speed of the auxiliary drive wheel.

[0016] According to some embodiments of the present invention, the anti-sticking mechanism further includes an elastic adjusting member, and the adjusting roller is connected to the machine base via the elastic adjusting member.

[0017] According to some embodiments of the present invention, the elastic adjustment member includes an adjustment seat, an elastic member and a connecting block, two ends of the elastic member are respectively connected to the adjustment seat and the connecting block, and the adjustment roller is rotatably mounted on the connecting block.

[0018] According to some embodiments of the present invention, the print head is disposed above the print roller, and an end of the print head close to the auxiliary roller is tilted upward relative to the print roller.

[0019] According to some embodiments of the present invention, the inclination angle of the print head is a, and a satisfies the following relationship: 6°≤a≤10°.

[0020] According to some embodiments of the present invention, the printer is a thermal printer, and the printing medium is a wristband.

[0021] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments with reference to the accompanying drawings, in which:

[0023] Figure 1 Schematic diagram of the three-dimensional structure of a printer according to some embodiments of the present invention (partial cross-section);

[0024] Figure 2 for Figure 1 A is an enlarged schematic diagram;

[0025] Figure 3 A schematic diagram of the power mechanism of a printer in some embodiments of the present invention when paper is being fed and printing;

[0026] Figure 4 A schematic diagram of the printing mechanism and the anti-sticking mechanism of a printer in some embodiments of the present invention when the paper is being fed and printed;

[0027] Figure 5 A schematic diagram of the power mechanism of a printer during paper retraction in some embodiments of the present invention;

[0028] Figure 6 Schematic diagram of the printing mechanism and anti-sticking mechanism of the printer during paper retraction in some embodiments of the present invention;

[0029] Figure 7 Schematic diagram of a print head tilted relative to a print roller in some embodiments of the present invention.

[0030] The accompanying figures are as follows:

[0031] Rack 100;

[0032] Printing mechanism 200; print head 210; print roller 220;

[0033] Anti-sticking mechanism 300; auxiliary roller 310; adjusting roller 320; elastic adjusting member 330; elastic member 331; adjusting seat 332; connecting block 333;

[0034] Power mechanism 400; motor 410; input wheel 420; composite wheel 430; output gear 430; printing drive wheel 440; driven wheel 450; direction-changing wheel 460; auxiliary drive wheel 470; one-way transmission 480;

[0035] Printing medium 500. DETAILED DESCRIPTION

[0036] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0037] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0038] In the description of the present invention, if there is a description of first and second, it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0039] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0040] In the related art, if a thermal printer encounters printing media made of special materials such as wristbands during the printing process, the following problems are likely to occur during printing: the wristband is likely to become softened due to heat during the printing process, causing the wristband to stick to the print head. If the wristband is not continued after the wristband sticks to the print head, the adhesion strength between the wristband and the print head will increase after cooling, causing the printer's rubber roller to slip against the printing medium during the next printing, resulting in failure to print normally and affecting the printing quality.

[0041] To this end, the present invention provides a printer that can improve the problem of easy adhesion between the printing medium and the print head.

[0042] Reference Figures 1 to 7 A printer according to an embodiment of the present invention includes a base, a printing mechanism 200, an anti-sticking structure, and a power mechanism 400. The base is the main frame structure of the printer, and a paper feed path is formed therein, along which the print medium 500 can move. The printing mechanism 200 is disposed at one end of the paper feed path and includes a print head 210 and a print roller 220 disposed opposite each other. The print medium 500 can be printed by passing between the print head 210 and the print roller 220. The anti-sticking mechanism 300 is disposed at the other end of the paper feed path and is located behind the printing mechanism 200 in the normal paper feed direction. The anti-sticking mechanism 300 includes an auxiliary roller 310 and an adjustment roller 320 disposed opposite each other. The adjustment roller 320 can apply a certain pressure to the auxiliary roller 310 to allow the print medium 500 to adhere to the surface of the auxiliary roller 310. The power mechanism 400 includes a power assembly, a first transmission assembly, and a second transmission assembly. The output end of the power assembly is connected to the first and second transmission assemblies. The output end of the first transmission assembly is connected to the print roller 220, while the output end of the second transmission assembly is connected to the auxiliary roller 310. The second transmission assembly is connected to the auxiliary roller 310 via a one-way transmission 480. When the printer is feeding paper forward, the one-way transmission 480 disengages from the auxiliary roller 310, and the print roller 220 drives the auxiliary roller 310 forward through the print medium 500, thereby moving the print medium 500 in a first direction within the paper path. When the printer is feeding paper backward, the one-way transmission 480 engages with the auxiliary roller 310, and the power assembly, through the first and second transmission assemblies, simultaneously drives the print roller 220 and the auxiliary roller 310 in reverse rotation, thereby simultaneously driving the print roller 220 and the auxiliary roller 310 in a second direction. It should be noted that either forward rotation or reverse rotation is clockwise rotation, and the other is counterclockwise rotation. The appropriate rotation direction can be selected based on actual needs. The one-way transmission 480 may be a wedge-type one-way clutch, a roller-type one-way clutch, or a ratchet-type one-way clutch, and may specifically be a one-way bearing or other structure.

[0043] Reference Figure 3 and Figure 4During forward paper feeding, the one-way transmission 480 and the auxiliary roller 310 are disengaged, and the second transmission assembly cannot drive the auxiliary roller 310 through the one-way transmission 480, while the first transmission assembly can drive the printing roller 220 to rotate in the forward direction. At this time, the printing roller 220 is the active roller, and the auxiliary roller 310 is the driven roller. The printing roller 220 drives the auxiliary roller 310 to rotate in the forward direction through the printing medium 500, so that the printing medium 500 moves in the first direction in the paper feeding channel. At this time, the paper feeding speed of the auxiliary roller 310 is the same as the paper feeding speed of the printing roller 220, which can prevent the paper feeding desynchronization caused by the front and rear speed difference and the larger paper feeding cumulative error, thereby achieving forward paper feeding printing and improving the printing quality. Figure 5 and Figure 6 When the paper is retracted, the one-way transmission 480 is engaged with the auxiliary roller 310, so the power assembly can drive the print roller 220 to rotate in the opposite direction through the first transmission assembly. At the same time, the power assembly also drives the auxiliary roller 310 to rotate in the opposite direction through the second transmission assembly, so that the print roller 220 and the auxiliary roller 310 can simultaneously drive the print medium 500 to move in the second direction, thereby increasing the retracting power of the print medium 500, allowing the print medium 500 to be peeled off from the print head 210, preventing the print medium 500 from sticking to the print head 210, and improving the printing quality.

[0044] Reference Figure 1 and Figure 3 It will be appreciated that in some embodiments of the present invention, the power assembly includes a motor 410 and a reduction gear set. The output shaft of the motor 410 is connected to the input end of the reduction gear set, and the first transmission assembly and the second transmission assembly are respectively connected to either side of the output end of the reduction gear set. Of course, the power assembly can also have other structural forms. In this application, the power assembly adopts a combined structure of the motor 410 and the reduction gear set, which allows the power assembly's external dimensions to be kept within a relatively small range, facilitating a reduction in the overall size of the printer while also ensuring more precise and reliable transmission. Specifically, the reduction gear set includes an input wheel 420, a composite wheel 430, and an output gear 430. The input wheel 420 constitutes the input end of the reduction gear set, while the output gear 430 constitutes the output end of the reduction gear set. The input wheel 420 is sleeved and fixed to the output shaft of the motor 410. The composite wheel 430 includes a large gear and a small gear that are fixedly connected. The large gear meshes with the input wheel 420, and the small gear meshes with the output gear 430. This allows the motor 410 to achieve a reduced output after being driven by the reduction gear set. The first transmission assembly and the second transmission assembly are both gear transmission assemblies. The input ends of the two gear transmission assemblies are respectively connected to the two sides of the output gear 430, so that the output gear 430 can drive the first transmission assembly and the second transmission assembly at the same time, making the transmission structure of the printer simpler and helping to reduce the overall size of the printer.

[0045] Reference Figure 3 It will be appreciated that in some embodiments of the present invention, the first transmission assembly includes a print drive wheel 440, which is sleeved and fixed to the end of the print roller 220, thereby enabling synchronous rotation with the print roller 220. The print drive wheel 440 also meshes with the output gear 430 of the reduction gear set. The motor 410 drives the print drive wheel 440 through the reduction gear set, thereby driving the print roller 220. The second transmission assembly includes a driven wheel 450, a direction-changing wheel 460, and an auxiliary drive wheel 470. The driven wheel 450 meshes with the output gear 430 of the reduction gear set. The outer diameter of the direction-changing wheel 460 can be relatively small, thereby reducing the space occupied by the second transmission assembly. The ends of the direction-changing wheel 460 mesh with the driven wheel 450 and the auxiliary drive wheel 470, respectively. The one-way transmission element 480 is a one-way bearing. One-way bearings are compact, provide reliable one-way transmission performance, and are relatively easy to install. The auxiliary drive wheel 470 is fixedly coupled to the outer ring of the one-way bearing, so the auxiliary drive wheel 470 rotates synchronously with the outer ring. The inner ring of the one-way bearing is fixedly coupled to the end of the auxiliary roller 310, so the auxiliary roller 310 rotates synchronously with the inner ring. It should be noted that when the outer ring rotates in the forward direction relative to the inner ring, the inner ring and the outer ring are separated and cannot drive the inner ring to rotate synchronously. In other words, the auxiliary drive wheel 470 cannot drive the auxiliary wheel to rotate synchronously via the one-way bearing. When the outer ring rotates in the reverse direction relative to the inner ring, the inner ring and the outer ring engage, and the outer ring drives the inner ring to rotate synchronously. In other words, the auxiliary drive wheel 470 can drive the auxiliary wheel to rotate synchronously via the one-way bearing.

[0046] It is understood that in some embodiments of the present invention, the outer diameter of the print roller 220 is D1, the rotational speed of the print drive wheel 440 is N1, the outer diameter of the auxiliary roller 310 is D2, and the rotational speed of the auxiliary drive wheel 470 is N2, satisfying the following relationship: D1*N1 / D2<N2. With the above configuration, when the printer is feeding paper forward and printing, the power assembly drives the print roller 220 to rotate via the first transmission assembly. At this time, the print roller 220 rotates synchronously with the print drive wheel 440 in the forward direction. At this time, the paper feeding speed of the print roller 220 is D1*N1. The print roller 220 drives the auxiliary roller 310 to rotate through the printing medium 500. The paper feeding speed of the auxiliary roller 310 is the same as the paper feeding speed of the print roller 220. At this time, the rotational speed of the auxiliary roller 310 is D1*N1 / D2. The auxiliary roller 310 rotates synchronously with the inner ring of the one-way bearing, so the rotational speed of the inner ring is also D1*N1 / D2. The power assembly drives the auxiliary roller 310 to rotate via the second transmission assembly. The outer ring of the one-way bearing is driven to rotate. At this time, the outer ring of the one-way bearing rotates synchronously with the auxiliary drive wheel 470 in the positive direction. Therefore, the speed of the outer ring is N2. Since D1*N1 / D2<N2, that is, the speed of the outer ring is greater than the speed of the inner ring and both rotate in the positive direction, the outer ring rotates positively relative to the inner ring. At this time, the inner ring and the outer ring are separated, and the outer ring cannot drive the inner ring to rotate synchronously. That is, the auxiliary drive wheel 470 cannot drive the auxiliary wheel to rotate synchronously through the one-way bearing, so that the printing roller 220 can drive the auxiliary roller 310 to rotate at the same speed through the printing medium 500, so that the printing medium 500 moves along the first direction to achieve positive paper feeding printing operation.

[0047] Similarly, when the printer retracts the paper, the print drive wheel 440 drives the print roller 220 to rotate synchronously in the opposite direction. At this time, the paper feeding speed of the print roller 220 is D1*N1. The auxiliary drive wheel 470 drives the auxiliary wheel to rotate synchronously in the opposite direction via the one-way bearing. The print roller 220 and the auxiliary roller 310 simultaneously drive the print medium 500 to move in the second direction. At this time, the speed of the outer diameter surface of the auxiliary roller 310 is D2*N2. Since D1*N1 / D2<N2, that is, D1*N1<D2*N2, the outer diameter speed of the auxiliary roller 310 is greater than the outer diameter speed of the print roller 220. At this time, relative sliding occurs between the auxiliary roller 310 and the print medium 500, so that the auxiliary roller 310 can provide additional propulsion force to the print medium 500 in the second direction, thereby increasing the peeling force between the print medium 500 and the print head 210 during retracting the paper, preventing the print medium 500 from sticking to the print head 210 and becoming unable to be peeled off. Compared to the prior art, where only the print roller 220 provides propulsion force to the print medium 500, the printer of the present invention can simultaneously provide propulsion force to the print medium 500 via the print roller 220 and the auxiliary roller 310 during paper retraction. This significantly increases the peeling force between the print medium 500 and the print head 210, effectively preventing the print medium 500 from adhering to the print head 210 and improving print quality. Of course, it should be noted that the additional propulsion force provided by the auxiliary roller 310 in the second direction to the print medium 500 should be less than the sliding friction resistance between the print roller 220 and the print medium 500. This prevents relative slippage between the print medium 500 and the print roller 220 when the additional propulsion force is excessive.

[0048] It is understandable that in order to reduce the difficulty of processing, reduce the cost of accessories and the difficulty of installation, in some embodiments of the present invention, the outer diameter of the printing roller 220 and the outer diameter of the auxiliary roller 310 can be set to be equal, and by setting the transmission ratio of the first transmission assembly and the second transmission assembly, the rotation speed of the printing drive wheel 440 is less than the rotation speed of the auxiliary drive wheel 470, so that D1*N1 / D2<N2 can be achieved.

[0049] It should be noted that when the print medium 500 moves in the first direction, the print roller 220 drives the auxiliary roller 310 to rotate at the same speed through the print medium 500. The print medium 500 moves between the regulating roller 320 and the auxiliary roller 310. If the pressure applied by the regulating roller 320 to the auxiliary roller 310 is too great, the static friction between the print medium 500 and the auxiliary roller 310 will be too great, causing the print roller 220 to be overloaded and slide relative to the print medium 500, resulting in paper feed loss. For this reason, refer to Figure 1 and Figure 2In some embodiments of the present invention, the anti-sticking mechanism 300 further includes an elastic adjustment member 330, through which the adjustment roller 320 is connected to the machine base. The elastic adjustment member 330 can adjust the pressure applied by the adjustment roller 320 to the auxiliary roller 310, thereby preventing excessive pressure from causing paper feed desynchronization.

[0050] Reference Figure 2 It is understood that in some embodiments of the present invention, the elastic adjustment member 330 includes an adjustment seat 332, an elastic member 331 and a connecting block 333, the two ends of the elastic member 331 are respectively connected to the adjustment seat 332 and the connecting block 333, and the adjustment roller 320 is rotatably mounted on the connecting block 333. Specifically, two elastic adjustment members 330 can be provided, and the two elastic adjustment members 330 are connected to the axial ends of the adjustment roller 320, so as to provide a more balanced elastic force adjustment. During adjustment, the deformation of the elastic member 331 can be changed by moving the adjustment seat 332, so that the pressure applied by the elastic member 331 to the auxiliary roller 310 through the connecting block 333 changes. The elastic member 331 can be a structure such as a spring, an elastic metal sheet, or an elastic silicone member, and can be selected according to actual needs.

[0051] Reference Figure 7 It can be understood that in order to allow more installation space for functional components between the print head 210 and the print roller 220, in some embodiments of the present invention, the print head 210 is arranged above the print roller 220, and the end of the print head 210 close to the auxiliary roller 310 is tilted upward relative to the print roller 220, so that the space between the print head 210 and the print roller 220 is increased, thereby enabling the installation of functional components, improving the functional expansion capability of the printer, and meeting more user usage needs.

[0052] It should be noted that when the inclination angle of the print head 210 is too large, while a larger installation space can be created between the print head 210 and the print roller 220, the peeling force between the print medium 500 and the print head 210 increases, increasing the probability of the print medium 500 adhering to the print head 210. When the inclination angle of the print head 210 is too small, while the peeling force between the print medium 500 and the print head 210 can be reduced, the installation space formed between the print head 210 and the print roller 220 becomes smaller, increasing the difficulty of installing functional components. Therefore, after extensive testing, the applicant has found that when the inclination angle a of the print head 210 satisfies the relationship: 6°≤a≤10°, for example, a can be 6°, 8°, 9°, or 10°, etc., a sufficiently large installation space can be created between the print head 210 and the print roller 220 while keeping the peeling force between the print medium 500 and the print head 210 within a relatively small range, thereby enabling the printer to achieve better printing results.

[0053] It is understood that in some embodiments of the present invention, the printer is a thermal printer and the print medium 500 is a wristband. It should be noted that the wristband easily softens when heated and adheres to the print head 210. If the wristband is not in continuous operation, the adhesion strength increases after cooling, which can easily cause slippage between the print roller 220 and the wristband, resulting in the printer being unable to print properly. The printer of the present invention is provided with an auxiliary roller 310 and a second transmission assembly. When the paper is retracted, the auxiliary roller 310 can provide additional propulsion force to the wristband, greatly increasing the peeling force between the wristband and the print head 210, thereby effectively preventing the wristband from adhering to the print head 210 and improving the printing quality. Of course, the print medium 500 can also be other media that easily softens when heated and adheres to the print head 210, and the present invention is not limited to this.

[0054] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the spirit of the present invention.

Claims

1. A printer, characterized in that: include: The machine base has a paper feeding channel; A printing mechanism, disposed at one end of the paper feeding passage, comprising a print head and a print roller disposed opposite to each other; an anti-sticking mechanism, arranged at the other end of the paper feeding channel, comprising an auxiliary roller and an adjusting roller arranged opposite to each other; The power mechanism includes a power assembly, a first transmission assembly, and a second transmission assembly. The output end of the power assembly is connected to the first transmission assembly and the second transmission assembly. The output end of the first transmission assembly is connected to the print roller. The output end of the second transmission assembly is connected to the auxiliary roller. The first transmission assembly includes a print drive wheel, and the print drive wheel is fixedly connected to the print roller. The second transmission assembly is connected to the auxiliary roller through a one-way transmission. During forward paper feeding and printing, the one-way transmission is disengaged from the auxiliary roller, and the printing roller drives the auxiliary roller to rotate forward through the printing medium, so that the printing medium moves along the first direction in the paper feeding path. During reverse paper feeding, the one-way transmission is engaged with the auxiliary roller, and the power assembly drives the printing roller and the auxiliary roller to rotate in opposite directions simultaneously through the first transmission assembly and the second transmission assembly, so that the printing roller and the auxiliary roller can simultaneously drive the printing medium to move along the second direction. The second transmission assembly includes an auxiliary drive wheel, the one-way transmission is a one-way bearing, the auxiliary drive wheel is fixed to the outer ring of the one-way bearing, and the inner ring of the one-way bearing is fixed to the auxiliary roller. The outer diameter of the printing roller is D1, the rotation speed of the printing drive wheel is N1, the outer diameter of the auxiliary roller is D2, and the rotation speed of the auxiliary drive wheel is N2, satisfying the following relationship: D1*N1 / D2<N2.

2. A printer according to claim 1, characterized in that: The power assembly includes a motor and a reduction gear set, the output shaft of the motor is connected to the input end of the reduction gear set, and the first transmission assembly and the second transmission assembly are respectively connected to both sides of the output end of the reduction gear set.

3. A printer according to claim 2, characterized in that: The printing drive wheel is engaged with the output gear of the reduction gear set. The second transmission assembly includes a driven wheel and a changing wheel. The driven wheel is engaged with the output gear of the reduction gear set. The two ends of the changing wheel are respectively engaged with the driven wheel and the auxiliary drive wheel.

4. A printer according to claim 3, characterized in that: The outer diameter of the printing roller is equal to the outer diameter of the auxiliary roller, and the rotation speed of the printing driving wheel is lower than the rotation speed of the auxiliary driving wheel.

5. A printer according to claim 1, characterized in that: The anti-sticking mechanism further includes an elastic adjusting member, and the adjusting roller is connected to the machine base via the elastic adjusting member.

6. A printer according to claim 5, characterized in that: The elastic adjustment member includes an adjustment seat, an elastic member and a connecting block. Two ends of the elastic member are respectively connected to the adjustment seat and the connecting block. The adjustment roller is rotatably mounted on the connecting block.

7. A printer according to claim 1, characterized in that: The print head is arranged above the print roller, and one end of the print head close to the auxiliary roller is tilted upward relative to the print roller.

8. A printer according to claim 7, characterized in that: The inclination angle of the print head is a, and a satisfies the following relationship: 6°≤a≤10°.

9. A printer according to any one of claims 1 to 8, characterized in that: The printer is a thermal printer, and the printing medium is a wristband.

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