Patent Publication Number: US-2023140754-A1

Title: Label printer and label printing method for precise positioning thereof

Description:
CROSS REFERENCE TO THE RELATED APPLICATIONS 
     This application is based upon and claims priority to Chinese Patent Application No. 202111266785.3, filed on Oct. 28, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of label printers, and in particular, to a forward and reverse label printer and a label printing method for precise positioning thereof. 
     BACKGROUND 
     At present, in thermal transfer label printers, a carbon ribbon moves with label paper in a same direction, that is, a paper output direction. After printing, the label paper is torn off or cut off. At this time, a certain length of blank label is left between a heating line of a print head and a cutting position of the label paper, and the blank label is not printed. Meanwhile, the carbon ribbon that follows the blank label is not utilized. The label paper with the certain length and the carbon ribbon cannot be utilized in the next printing, thus leading to waste and causing low material utilization and high costs. 
     The label cartridge in the existing label printer is internally equipped with a roll of label paper, mainly including continuous label paper and die-cut label paper. For different types of label stickers, the label paper is wound into rolls in different ways in the industry. The existing label printers have not solved the problem of wrinkling after the label stickers are printed, resulting in the wrinkling and folding of the surface of the label paper output by the printer after printing. This affects the use of the label, and may cause the label itself to wrinkle and stick together to fail to be used. 
     Moreover, in order to realize accurate printing of the die-cut label paper, it is necessary to accurately detect a spacing between die-cut label surface papers. The existing methods for detecting the spacing between die-cut label surface papers generally use a photoelectric sensor. The existing photoelectric sensor includes a transmitting terminal and a receiving terminal respectively arranged on both sides of the label sticker. In this case, the face-to-face arrangement of the transmitting terminal and the receiving terminal requires a large space, and the cost is high, which becomes an obstacle to the miniaturization of the label cartridge. 
     It can be seen that there are still inconveniences and defects in the structure, method and use of the above existing label printers, which need to be further improved. There is an urgent need to create a new label printer and a label printing method for precise positioning thereof in the industry, which can realize forward output of the label paper and take-up of the carbon ribbon, and reverse rollback of the label paper and rollback of the carbon ribbon to reduce waste of the label paper and the carbon ribbon, prevent the label paper from wrinkling and sticking in the process of paper feeding and paper rollback, ensure the label printing effect, and ensure the accuracy of label printing. 
     SUMMARY 
     A technical problem to be solved by the present disclosure is to provide a label printer, such that forward paper output of label paper and take-up of a carbon ribbon can be realized, and reverse rollback of the label paper and rollback of the carbon ribbon can be realized to reduce waste of the label paper and the carbon ribbon, prevent the label paper from wrinkling and sticking in the process of paper feeding and paper rollback, ensure the label printing effect, and ensure the accuracy of label printing, thereby overcoming defects of an existing label printer. 
     In order to solve the above technical problems, the present disclosure provides a label printer, including an outer shell and a label cartridge arranged inside the outer shell, a power mechanism and a control mechanism configured to control paper output of the label cartridge and winding and unwinding of a carbon ribbon, and a print head configured to realize label printing. 
     The label cartridge includes an inner shell and a label paper output channel and a carbon ribbon channel that are arranged inside the inner shell. An interior of the inner shell is divided into a first half area and a second half area. A label paper roll is provided at a lower part of the first half area, and a label rollback release space is reserved at an upper part of the first half area. A carbon ribbon supply roll and a carbon ribbon take-up roll are provided at a lower part of the second half area, and a groove configured to place the print head is provided at an upper part of the second half area. The label paper output channel is arranged along an uppermost end of the second half area, and is in linear correspondence with a paper output port on a side wall of the inner shell and a side wall of the outer shell. The carbon ribbon channel is arranged around the groove, and the carbon ribbon at an open end of the groove is tightly attached to a label paper. 
     The power mechanism includes an electric motor and a gear transmission system. The gear transmission system includes a first gear set in transmission connection with an output shaft of the electric motor. A planetary gear set in transmission connection with the first gear set, a printing rubber roll gear set being in transmission connection with the planetary gear set and configured to drive the label paper to move forward or reversely, and a carbon ribbon winding gear and a carbon ribbon unwinding gear that are selectively in transmission connection with the planetary gear set. The planetary gear set includes a sun gear, a planetary gear meshed with the sun gear, and a planetary carrier connecting the sun gear and the planetary gear. The sun gear is driven by the first gear set to drive the planetary gear to rotate, and under the action of the planetary carrier, the planetary gear is meshed with the carbon ribbon winding gear or the carbon ribbon unwinding gear based on forward rotation or reverse rotation of the sun gear. 
     The printing rubber roll gear set in the gear transmission system is connected to a printing rubber roll. The printing rubber roll drives, through friction with the label paper, the label paper to move. The carbon ribbon winding gear is connected to the carbon ribbon take-up roll, and the carbon ribbon unwinding gear is connected to the carbon ribbon supply roll. When the electric motor rotates to one side, the first gear set transmits power to the planetary gear set, and the planetary gear set drives the printing rubber roll and the carbon ribbon take-up roll to rotate to realize output of the label paper and take-up of the carbon ribbon. When the electric motor rotates to an opposite side, the first gear set transmits reverse power to the planetary gear set, and the planetary gear set drives the printing rubber roll and the carbon ribbon supply roll to rotate to realize rollback of the label paper and recovery of the carbon ribbon. 
     With further improvement, the label paper output channel may be linearly arranged along an inner side of the side wall of the inner shell. The groove may be arranged at an acute angle with the side wall. The print head arranged inside the groove may be in inclined contact with the carbon ribbon. 
     With further improvement, a support baffle configured to separate the first half area and the second half area may be arranged inside the inner shell. An upper part of the support baffle may be set as a concave arc-shaped guide plate with at least two protrusions. Each of the label paper output channel and the carbon ribbon channel may be provided with a plurality of support columns or support rollers. 
     With further improvement, the label paper may use a continuous label paper roll or a die-cut label paper roll, and a label surface paper side of the continuous label paper roll or the die-cut label paper roll may be at least in contact with one of arc-shaped protrusion segments of the concave arc-shaped guide plate. 
     With further improvement, the continuous label paper roll may be wound into a roll with continuous label surface paper facing outward, and a continuous label surface paper side of the continuous label paper roll may be in contact with each of the arc-shaped protrusion segments of the concave arc-shaped guide plate in sequence. 
     The die-cut label paper roll may be wound into a roll with a die-cut label surface paper facing inward, and a die-cut label surface paper side of the die-cut label paper roll may be in contact with one of the arc-shaped protrusion segments of the concave arc-shaped guide plate. 
     With further improvement, the planetary gear set may be further provided with an elastic limit mechanism. The elastic limit mechanism may include an elastic limit member and a limit rod abutting against the elastic limit member. One end of the elastic limit member may be connected to a rear of the planetary carrier, and the other end of the elastic limit member may pop out to an outer side of the planetary carrier to form a certain tension with the planetary carrier. The limit rod may be fixed on the outer shell. When the electric motor is stopped, the elastic limit member may urge the planetary gear to be meshed with the carbon ribbon winding gear under the interference of the limit rod. 
     With further improvement, torsion springs rotating in opposite directions may be respectively arranged inside the carbon ribbon winding gear and the carbon ribbon unwinding gear, and sawteeth configured to control rotation of the roll may be provided inside each of a spindle of the carbon ribbon supply roll and a spindle of the carbon ribbon take-up roll. 
     With further improvement, a photoelectric sensing mechanism configured to detect a label and a cutter configured to cut a label base paper after printing may be arranged inside the outer shell. The photoelectric sensing mechanism, the print head, and the cutter may be arranged on the label paper output channel in sequence. A distance between the photoelectric sensing mechanism and the print head may be less than or equal to a length of a single die-cut label, and a set distance between the print head and the cutter may be a sum of a spacing between die-cut labels and a minimum margin of label printing minus a distance from a label cutting end to a rear end of the die-cut label. 
     With further improvement, the photoelectric sensing mechanism may include a photoelectric sensor with a transmitting terminal and a receiving terminal on a same side of the label paper, and a reflecting prism arranged on the other side of the label paper. After passing through the label paper vertically, a light beam emitted by the transmitting terminal of the photoelectric sensor may be reflected by the reflecting prism, then pass through the label paper vertically, and be received by the receiving terminal to detect a label surface paper. 
     With further improvement, the label printer may be configured for printing of die-cut label paper rolls, continuous label paper rolls, heat shrinkable tube rolls, or labeling strip rolls. 
     As another improvement of the present disclosure, the present disclosure further provides a label printing method for precise positioning of a label printer, using the above label printer, and including the following steps: 
     controlling, by the label printer, the die-cut label to output a paper forward at a constant speed; calculating, by the control mechanism, a time t 1  when a front end of the die-cut label reaches the print head according to a label paper output rate, calculating a time t 2  when a printing starting position of the die-cut label reaches the print head, and calculating a time t 3  required by a sum of a distance from the front end of the die-cut label to the rear end of the die-cut label and a distance from the label cutting end to the rear end of the die-cut label; and 
     when the front end of the die-cut label in a paper output direction is detected by the photoelectric sensing mechanism, starting timing; and at a time t 1 +t 2 , controlling the print head to start a printing action, continuing to output the paper after printing is completed, starting timing when the front end of the die-cut label is detected, and controlling the cutter to perform a cutting action at the time t 3 . 
     The label printing method may further include: in a process of printing the die-cut label by the print head, simultaneously detecting, by the photoelectric sensing mechanism, a front end position of the next die-cut label, and repeating the above printing action and cutting action when the front end position of the next die-cut label is detected. 
     With such a design, the present disclosure has at least the following advantages: 
     1. The present disclosure reasonably plans the inner space of the shell of the label cartridge, arranges a linear label paper output channel inside the shell, and arranges a label rollback release space, which can not only ensure the convenience and smoothness of paper feeding and paper rollback without jamming, but also releases space for the label paper to prevent the label paper from wrinkling or folding in the rollback process. The carbon ribbon supply roll and the carbon ribbon take-up roll are arranged inside the shell, such that the winding and unwinding structure is compact, the carbon ribbon path is compact, and the space utilization is high, which provides the possibility of implementation for small label cartridges. 
     2. Through the setting of the meshing relationship between the gears, the gear transmission system of the label printer of the present disclosure can realize forward and reverse rotation of the gears relying on the same electric motor, and can selectively control the carbon ribbon winding gear or the carbon ribbon unwinding gear to rotate as a driving wheel, which can not only realize the normal printing of the label paper, but also roll back the label paper to the label cartridge, and recover the carbon ribbon into the label cartridge, avoiding the waste of the label paper and the carbon ribbon and improving the material utilization. 
     3. By arranging the internal structure of the label cartridge for different label winding methods, the label sticker can be effectively rolled in the advancing state, and the wrinkling of the label surface paper can be overcome. At the same time, due to the arrangement of the release space in the state of label unwinding, the folding and wrinkling of the label sticker during rollback is also avoided, and the printing quality and printing effect of the label are improved. 
     4. Through the arrangement of the elastic limit mechanism and the interference fit between the elastic limit member and the limit rod, when the electric motor is stopped, the elastic limit member urges the planetary gear to be meshed with the carbon ribbon winding gear to ensure the instantaneity during forward printing. 
     5. The torsion springs rotating in opposite directions are arranged inside the carbon ribbon winding gear and the carbon ribbon unwinding gear to ensure that in the process of taking up the carbon ribbon forward and winding the carbon ribbon reversely, the carbon ribbon can always have a certain tension, such that the carbon ribbon will not wrinkle. 
     6. In the label cartridge of the present disclosure, the photoelectric sensor with its own reflecting prism is arranged, which greatly reduces the occupied space of the photoelectric sensing mechanism on the basis of satisfying the photoelectric detection, provides favorable conditions for arranging a miniaturized and convenient label cartridge, and reduces the cost of the label cartridge. 
     7. By limiting the positions of the photoelectric sensing mechanism, the print head, and the cutter, and by improving the setting of the printing method for precise positioning, the precise positioning of the printing starting position of the die-cut label and the precise positioning of the cutting position of the cutter can be realized, such that the position of the printed content on each die-cut label is precise, and the cutter will not cut the label surface paper when cutting the die-cutting label. The method is simple with convenient and reliable operation and low cost. 
     8. The label printer of the present disclosure has the advantages of simple structure, precise and reliable printing, good effect, and wide application range. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above is only an overview of the technical solutions of the present disclosure. In order to understand the technical means of the present disclosure more clearly, the present disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. 
         FIG.  1    is a schematic structural diagram of a label printer of the present disclosure; 
         FIG.  2    is a schematic diagram of an internal structure of a paper label cartridge of the label printer of the present disclosure; 
         FIG.  3    is a schematic structural diagram of meshing of a planetary gear and a carbon ribbon winding gear in a gear transmission system of the label printer of the present disclosure; 
         FIG.  4    is a schematic structural diagram of meshing of the planetary gear and a carbon ribbon unwinding gear in the gear transmission system of the label printer of the present disclosure; 
         FIG.  5    is a schematic diagram of an internal structure of the carbon ribbon winding gear and the carbon ribbon unwinding gear in the gear transmission system of the label printer of the present disclosure; 
         FIG.  6    is a schematic diagram of an internal structure of the label printer of the present disclosure (a gear  41  and a gear  47  are in a non-meshing state for clear display in the figure); 
         FIG.  7    is a top view of the internal structure of the label printer of the present disclosure (the gear  41 , a gear  42 , and the gear  47  are hidden for clear display in the figure); 
         FIG.  8    is a schematic structural diagram of a continuous label paper roll in the label cartridge of the present disclosure when label paper is guided; 
         FIG.  9    is a schematic structural diagram of a die-cut label paper roll in the label cartridge of the present disclosure when label paper is guided; 
         FIG.  10    is a schematic structural diagram of a photoelectric sensing mechanism of the label cartridge of the present disclosure; and 
         FIG.  11    is a schematic diagram of a label printing method for precise positioning of a label printer of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     With reference to  FIG.  1   , the present embodiment relates to a label printer, including an outer shell  3  and a label cartridge  1  arranged inside the outer shell  3 , a power mechanism and a control mechanism configured to control paper output of the label cartridge and winding and unwinding of a carbon ribbon, and a print head  2  configured to realize label printing. 
     Specifically, as shown in  FIG.  2   , in the present embodiment, the label cartridge  1  includes a shell and a label paper output channel and a carbon ribbon channel that are arranged inside the shell. The label paper output channel is arranged in near linear correspondence with a paper output port  11  of the shell. A groove  12  configured to place the print head  2  is formed in the shell. An open end of the groove  12  is arranged close to the paper output port  11 . The carbon ribbon channel is arranged around the groove  12 , and the carbon ribbon  20  at the open end of the groove is tightly attached to a label paper  10 , such that the print head  2  can print the label by thermal transfer. 
     In the present embodiment, the shell of the label cartridge is a nearly square shell, and an interior of the square shell is divided into a first half area and a second half area that are distributed on left and right. A label paper roll  21  is provided at a lower part of the first half area, and a label rollback release space  22  is reserved at an upper part of the first half area. A carbon ribbon supply roll  23  and a carbon ribbon take-up roll  24  are provided at a lower part of the second half area, and the groove  12  is provided at an upper part of the second half area. The groove  12  is arranged at a certain angle with an upper side wall of the shell, such as the acute angle setting in  FIG.  2   , such that the print head  2  arranged inside the groove  12  is in inclined contact with the carbon ribbon  20 , which is conducive to realizing a linear channel for the label paper output channel. The paper output port  11  is formed at an upper part of a vertical side wall of the second half area. The label paper output channel is arranged along an uppermost end of the second half area and parallel to the upper side wall of the shell, and is in linear correspondence with the paper output port  11 . A printing rubber roll  31  is arranged on an opposite side of the print head  2 , and is configured to drive the label paper through friction with the label paper  10 . In this way, the arrangement of the linear label paper output channel and the label rollback release space provides a reliable guarantee for the rollback of the label paper  10 , which can not only realize smooth rollback of the label paper under the action of the printing rubber roll, but also provide a release space for the rollback of the label paper to prevent the label paper from wrinkling and folding after the rollback to affect the printing effect of the label paper. 
     Each of the label paper output channel and the carbon ribbon channel is provided with a plurality of support columns or support rollers, such that the label paper  10  and the carbon ribbon  20  always have a certain tension in an advancing or rollback process to ensure smooth operation. As shown in  FIG.  2   , the label paper output channel is provided with support columns a 1 , a 2 , a 3 , a 4 , and a 5 , and the carbon ribbon channel is provided with support rollers b 1 , b 2 , b 3 , b 4 , b 5 , b 6 , and b 7 . 
     In the present embodiment, a support baffle  13  configured to separate the first half area and the second half area is arranged inside the shell of the label cartridge. An upper part of the support baffle  13  is set as a concave arc-shaped guide plate configured to roll the label paper  10 . At least two protrusions  14  are formed in the concave arc-shaped guide plate, such as a crescent-shaped plate structure, which can make the label paper  10  continuously rolled by the arc-shaped protrusions  14  for many times in the advancing process to ensure the fit between the label surface paper and base paper, and improve the printing effect. 
     In addition, sawteeth  25  configured to control rotation of the roll are provided inside each of a spindle of the carbon ribbon supply roll  23  and a spindle of the carbon ribbon take-up roll  24 . The sawteeth  25  can realize the rotation of the roll manually and electrically. When the carbon ribbon take-up roll  24  rotates as a driving wheel, the carbon ribbon supply roll  23  acts as an idle wheel, which is conducive to forward take-up of the carbon ribbon  20 . When the carbon ribbon supply roll  23  rotates as a driving wheel, the carbon ribbon take-up roll  24  acts as an idler wheel, which is conducive to reverse take-up of the carbon ribbon  20 . 
     Referring to  FIG.  3    to  FIG.  7   , in the present embodiment, the power mechanism includes an electric motor  4  and a gear transmission system. The gear transmission system includes a first gear set in transmission connection with an output shaft of the electric motor, a planetary gear set in transmission connection with the first gear set, a printing rubber roll gear set being in transmission connection with the planetary gear set and configured to drive the label paper to move forward or reversely, and a carbon ribbon winding gear and a carbon ribbon unwinding gear that are selectively in transmission connection with the planetary gear set. 
     Specifically, as shown in  FIG.  3   , the first gear set includes a first gear  41 , and the first gear  41  uses a duplex gear. An external gear of the duplex gear is meshed with the output shaft of the electric motor, and is driven to rotate by it. At the same time, an internal gear of the duplex gear also rotates accordingly. 
     The duplex gears in the present embodiment can all use two gears on the same central axis, or consist of a plurality of gears that are meshed with each other. 
     In the present embodiment, the planetary gear set includes a sun gear  42 , a planetary gear  43  meshed with the sun gear, and a planetary carrier  44  connecting the sun gear  42  and the planetary gear  43 . The planetary gear  43  is rotatably installed on the planetary carrier  44  and revolves around the sun gear  42 . The sun gear  42  also uses a duplex gear, and includes an external gear meshed with the internal gear of the first gear  41  and an internal gear meshed with the planetary gear  43 , and then the sun gear  42  is driven by the first gear  41  to drive the planetary gear  43  to rotate. The planetary gear  43  also revolves around the sun gear  42 . The planetary gear  43  can be selectively meshed with the carbon ribbon winding gear  45  or the carbon ribbon unwinding gear  46 . When the planetary gear  43  drives the carbon ribbon winding gear  45  to rotate, the carbon ribbon unwinding gear  46  acts as an idle wheel, and the carbon ribbon winding gear  45  drives the carbon ribbon  20  to take up, as shown in  FIG.  3   . When the planetary gear  43  drives the carbon ribbon unwinding gear  46  to rotate, the carbon ribbon winding gear  45  acts as an idle wheel, and the carbon ribbon unwinding gear  46  drives the carbon ribbon  20  to roll back, as shown in  FIG.  4   . 
     In the present embodiment, the printing rubber roll gear set includes a gear  47 , a gear  48 , a gear  49 , and a gear  50  that are meshed in sequence. The gear  47  also uses a duplex gear, and includes an external gear meshed with the external gear of the sun gear  42 , and an internal gear meshed with the gear  48 . The gear  48  is also meshed with the gear  49 , and the gear  49  is meshed with the gear  50 . Then, the gear  47  is driven by the sun gear  42  to drive the gear  48  to rotate, and then drive the gear  49  and the gear  50  to rotate. 
     When the above power mechanism acts on the label cartridge  1 , specific connections are as follows. 
     The printing rubber roll gear set in the gear transmission system is connected to the printing rubber roll  31  inside the outer shell  3 , and the printing rubber roll  31  drives the label paper  10  relying on friction with the label paper  10 . The carbon ribbon winding gear  45  is connected to the sawteeth inside the carbon ribbon take-up roll  24 . The carbon ribbon unwinding gear  46  is connected to the sawteeth inside the carbon ribbon supply roll  23 . When the electric motor  4  rotates to one side, the first gear  41  transmits power to the planetary gear set, and the planetary gear set drives the printing rubber roll  31  to rotate forward through the printing rubber roll gear set, and simultaneously controls the carbon ribbon take-up roll  24  to rotate to realize forward output of the label paper  10  and forward take-up of the carbon ribbon  20 . When the electric motor  4  rotates to an opposite side, the first gear  41  transmits reverse power to the planetary gear set, and the planetary gear set also drives the printing rubber roll  31  to rotate reversely through the printing rubber roll gear set, and simultaneously controls the carbon ribbon supply roll  23  to rotate to realize reverse rollback of the label paper  10  and reverse recovery of the carbon ribbon  20 . The gear transmission system that can drive the label printer to reverse is conducive to rolling back the label paper  10  and the carbon ribbon  20  that have exceeded the heating line of the print head but are not utilized, such that they can be rolled back to the front end of the heating line of the print head, which is conducive to making full use of the unused label paper  10  and carbon ribbon  20  to reduce material waste. 
     In the present embodiment, the planetary gear set is further provided with an elastic limit mechanism, configured to keep the planetary gear  43  meshed with the carbon ribbon winding gear  45  when the electric motor  4  is stopped to ensure the instantaneity of the take-up of the carbon ribbon  20  during forward printing. 
     Specifically, the elastic limit mechanism includes an elastic limit member  51  and a limit rod  52  abutting against the elastic limit member. One end of the elastic limit member  51  is connected to a rear of the planetary carrier  44 , and the other end of the elastic limit member  51  pops out to the outer side of the planetary carrier  44  to form a certain tension with the planetary carrier  44 . The limit rod  52  is fixed on the outer shell  3  of the printer. When the electric motor  4  is stopped, the elastic limit member  51  keeps the planetary gear  43  meshed with the carbon ribbon winding gear  45  under the interference of the limit rod  52 , which can drive the starting of the carbon ribbon winding gear  45  in time to ensure the instantaneity of the take-up of the carbon ribbon. 
     In addition, as shown in  FIG.  5   , torsion springs  53  and  54  rotating in opposite directions are respectively arranged inside the carbon ribbon winding gear  45  and the carbon ribbon unwinding gear  46 . The torsion springs  53  and  54  can ensure that in the process of taking up the carbon ribbon forward and winding the carbon ribbon reversely, the carbon ribbon  20  can always have a certain tension, such that the carbon ribbon  20  will not wrinkle to ensure the smooth operation of the printer. 
     Referring to  FIG.  8   , when the label printer of the present embodiment is configured for printing of a continuous label paper roll, the continuous label paper roll is wound with the continuous label surface paper facing outward to prevent the label surface paper from warping and ensure the fit between the label surface paper and the base paper. The continuous label surface paper side of the continuous label paper roll is guided to contact each of the arc-shaped protrusions  14  of the concave arc-shaped guide plate in sequence, and enter the label paper output channel. In this way, the continuous label surface paper will be rolled by the two arc-shaped protrusions  14  in sequence in the advancing and paper output process, which further ensures the fit between the label surface paper and the base paper, prevents the folding and sticking phenomenon caused by the wrinkling of the label surface paper in the label paper printing process, and improves the label printing effect. 
     Referring to  FIG.  9   , when the label printer is configured for printing of a die-cut label paper roll, the die-cut label paper roll is wound into a roll with a die-cut label surface paper facing inward to prevent the label paper from warping. The die-cut label surface paper side of the die-cut label paper roll is guided to contact with an arc-shaped protrusion  14  of the concave arc-shaped guide plate, and enter the label paper output channel. In this way, the die-cut label surface paper will still be rolled by the arc-shaped protrusion in the advancing and paper output process, which further ensures the fit between the die-cut label surface paper and the base paper, prevents the folding and sticking phenomenon caused by the wrinkling of the die-cut label surface paper in the label sticker printing process, and improves the label printing effect. 
     In order to realize precise positioning of the die-cut label paper, a photoelectric sensing mechanism configured to detect a label is also arranged inside the outer shell  3 . Referring to  FIG.  10   , the photoelectric sensing mechanism in the present embodiment includes a photoelectric sensor  6  with a transmitting terminal  61  and a receiving terminal  62  on a same side of the label paper  10 , and a reflecting prism  63  arranged on the other side of the label paper  10 . After passing through the label paper  10  vertically, a light beam emitted by the transmitting terminal  61  of the photoelectric sensor  6  is reflected by the reflecting prism  63 , then passes through the label paper  10  vertically, and is received by the receiving terminal  62 . Through the change of the detected voltage value, the die-cut label surface paper on the label paper  10  is detected to determine a spacing between the die-cut label surface paper and a starting end of the die-cut label surface paper. 
     Specifically, the reflecting prism  63  is arranged inside the label cartridge  1  and is located on the label surface paper side of the label paper  10 . The photoelectric sensor  6  is arranged at a certain fixed position on the printer outside the side wall of the shell of the label cartridge  1 , and is located on the base paper side of the label paper  10 . The reflecting prism  63  uses a total reflecting prism, which can realize 180-degree reflection of the light beam emitted by the transmitting terminal  61 . 
     Moreover, a distance from a projected position of the light beam emitted by the photoelectric sensor  6  on the label paper  10  to a position of the heating line of the print head  2  should be less than or equal to a length of the shortest die-cut label on the label paper  10  to avoid that the shortest die-cut label cannot be recognized, which is conducive to precisely calculating the moving distance of the die-cut label, and precisely starting the print head. 
     In order to precisely cut the label paper after printing, a cutter is further arranged inside the outer shell  3 . The photoelectric sensing mechanism, the print head  2 , and the cutter are arranged on the label paper output channel in sequence. A distance between the photoelectric sensing mechanism and the print head  2  is less than or equal to the length of a single die-cut label. A set distance between the print head  2  and the cutter is the sum of a spacing between the die-cut labels and a minimum margin of label printing minus a distance from a label cutting end to a rear end of the die-cut label. 
     In order to improve the printing effect of the die-cut label, the minimum margin of the label printing is  2  mm, and the minimum up and down adjustment printing position of the label is 1 mm. The minimum distance from the label cutting end to the rear end of the die-cut label is 1 mm. 
     On the basis of the above structure of the label printer, the label printer can realize the precise positioning of the die-cut label in continuous operation, and the label printing method for precise positioning is as follows. 
     First, the label printer controls the die-cut label to output paper forward at a constant speed. The control mechanism calculates a time t 1  when a front end of the die-cut label reaches the print head according to a label paper output rate, calculates a time t 2  when a printing starting position of the die-cut label reaches the print head, and calculates a time t 3  required by a sum of a distance from the front end of the die-cut label to the rear end of the die-cut label and a distance from the label cutting end to the rear end of the die-cut label. After the above time points are determined, the following printing steps are started. 
     Referring to  FIG.  11   , when the front end of the die-cut label in a paper output direction is detected by the photoelectric sensing mechanism, timing is started, as shown in a state A in  FIG.  11   . When the label continues to advance for time t 1 +t 2 , it is indicated that the printing starting position of the die-cut label is just at the heating line of the print head  2 , and the control mechanism controls the print head  2  to start a printing action, as shown in a state B in  FIG.  11   . In the printing process, the photoelectric sensing mechanism simultaneously detects the front end position of the next die-cut label, as shown in a state C in  FIG.  11   . After the label printing is completed, the paper is output continuously, as shown in a state D in  FIG.  11   . At this time, the timing t 3  is started when the front end of the die-cut label is detected, and the control mechanism can control the cutter to perform a cutting action, such as a state E in  FIG.  11   , to complete the cutting of a label. 
     In the continuous printing process, timing is started with the front end of the next die-cut label detected by the photoelectric sensing mechanism, the above printing action and cutting action are repeated in states A to E, and the continuous automatic printing and cutting of the die-cut label can be realized in sequence. The printing method for precise positioning can realize the precise printing positioning of the die-cut label and the positioning of the cutter, such that the position of the printed content on each die-cut label is precise, and the cutter will not cut the label surface paper when cutting the die-cutting label. The method is simple, stable and reliable. 
     Based on the above structure of the label printer, the working principle of the label printer is as follows: when printing is started, if the heating line of the print head  2  is in the position to be printed, the power mechanism drives the printing rubber roll  31  that is in close contact with the label paper  10  to rotate, and drives the label paper  10  to advance relying on the friction between the rubber roller  31  and the label paper  10 . At the same time, the power mechanism drives the carbon ribbon take-up roll  24  to rotate actively to realize the forward take-up of the carbon ribbon  20 , and controls the printing action of the print head  2  when the label paper  10  and the carbon ribbon  20  advance synchronously. When printing is started, the heating line of the print head  2  is not in the position to be printed, the power mechanism drives the printing rubber roll  31  that is in close contact with the label paper  10  to rotate reversely, and drives the label paper  10  to roll back relying on the friction between the rubber roller  31  and the label paper  10 , and the label paper rolled back is released in the label rollback release space  22 . At the same time, the power mechanism drives the carbon ribbon supply roll  23  to rotate actively to realize the reverse take-up of the carbon ribbon  20  and the synchronous rollback of the label paper  10  and the carbon ribbon  20  until the position to be printed of the label paper  10  is at the heating line of the print head  2 , reversing is stopped, and the normal printing step is started. 
     The label printer of the present disclosure not only is suitable for the die-cut label paper rolls, but also realizes printing and cutting of the die-cut label paper rolls. It can also be configured for printing of continuous label paper rolls, heat shrinkable tube rolls, or labeling strip rolls, which meets the printing and cutting of various label materials, and has a wide range of application and good economy. 
     It should be noted that, in the description of the present disclosure, orientations or position relationships indicated by terms such as “upper”, “lower”, “front”, and “rear” are based on the drawings. These terms are merely used to facilitate description of the present disclosure and simplify the description, rather than to indicate or imply that the mentioned apparatus or elements must have a specific orientation and must be established and operated in a specific orientation. Therefore, these terms should not be understood as a limitation to the present disclosure. 
     In the description of the present disclosure, it should be noted that, unless otherwise clearly specified, meanings of terms “install”, “connected with”, and “connected to” should be understood in a board sense. For example, the connection may be a fixed connection, a removable connection, or an integral connection; may be a mechanical connection or an electrical connection; may be a direct connection or an indirect connection by using an intermediate medium; or may be intercommunication between two components. Those of ordinary skill in the art may understand the specific meanings of the above terms in the present disclosure based on the specific situation. 
     The above are only preferred embodiments of the present disclosure, and are not intended to limit the present disclosure in any form. Simple alterations, equivalent changes or modifications made by those skilled in the art make using the technical contents disclosed above fall within the scope of protection of the present disclosure.